EXTRACTION APPARATUS, EXTRACTION METHOD, AND METHOD OF MANUFACTURING LITHIUM HYDROXIDE

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International Application No. PCT/JP2023/046314, filed on Dec. 25, 2023, which claims priority to Japanese Patent Application No. 2023-019064, filed on Feb. 10, 2023, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present technology relates to an extraction apparatus, an extraction method, and a method of manufacturing lithium hydroxide.

Lithium hydroxide is important in various applications such as industrial applications. Various techniques are therefore known in relation to a method of manufacturing lithium hydroxide.

Specifically, lithium is recovered by performing an electrodialysis using a lithium absorption layer including lanthanum titanate as a separation membrane. A purification process in which an adsorbent is used and an impurity removal process in which an electrodialysis is used are combined with each other. Lithium is purified by causing lithium to be adsorbed in an active alumina porous body under an alkaline condition, and thereafter causing lithium to be desorbed from the active alumina porous body. A negative electrode of an aqueous lithium-ion secondary battery includes anatase-type titanium dioxide.

SUMMARY

The present technology relates to an extraction apparatus, an extraction method, and a method of manufacturing lithium hydroxide.

Although various techniques are known in relation to a method of manufacturing lithium hydroxide, a technique of extracting lithium ions is not sufficient yet. Accordingly, there is still room for improvement in terms of the technique of extracting lithium ions.

It is desirable to provide an extraction apparatus, an extraction method, and a method of manufacturing lithium hydroxide that each make it possible to highly accurately extract lithium ions.

An extraction apparatus according to an embodiment of the present technology includes a first aqueous medium, a second aqueous medium, a first electrode, a second electrode, and a first electric power source. The first aqueous medium includes two or more kinds of metal ions. The second aqueous medium is separated from the first aqueous medium. The first electrode is immersible in the first aqueous medium in a state of not being immersed in the second aqueous medium, and is immersible in the second aqueous medium in a state of not being immersed in the first aqueous medium. The second electrode is immersible in the first aqueous medium. The first electric power source is coupled to the first electrode and the second electrode. The two or more kinds of metal ions include a lithium ion. The first electrode includes a titanium oxide. The first electric power source is configured to energize the first electrode and the second electrode in a state where the first electrode and the second electrode are immersed in the first aqueous medium. The first electrode that has been energized in a state of being immersed in the first aqueous medium is immersible in the second aqueous medium.

An extraction method according to an embodiment of the present technology includes: immersing a first electrode and a second electrode in a first aqueous medium, the first electrode including a titanium oxide, the first aqueous medium including two or more kinds of metal ions including a lithium ion; energizing the first electrode and the second electrode in a state where the first electrode and the second electrode are immersed in the first aqueous medium; and immersing, in a second aqueous medium, the first electrode that has been energized in a state of being immersed in the first aqueous medium, the second aqueous medium being separated from the first aqueous medium.

A method of manufacturing lithium hydroxide according to an embodiment of the present technology includes: immersing a first electrode and a second electrode in a first aqueous medium, the first electrode including a titanium oxide, the first aqueous medium including two or more kinds of metal ions including a lithium ion; energizing the first electrode and the second electrode in a state where the first electrode and the second electrode are immersed in the first aqueous medium; immersing, in a second aqueous medium, the first electrode that has been energized in a state of being immersed in the first aqueous medium and a third electrode, the second aqueous medium including pure water or an aqueous lithium hydroxide solution and being separated from the first aqueous medium; and generating hydrogen at the third electrode by energizing the first electrode and the third electrode in a state where the first electrode and the third electrode are immersed in the second aqueous medium.

According to the extraction apparatus of an embodiment of the present technology, provided are the first aqueous medium, the second aqueous medium, the first electrode, the second electrode, and the first power source that have the respective configurations described above. It is thus possible to highly accurately extract lithium ions.

According to the extraction method of an embodiment of the present technology, the process is performed using the first aqueous medium, the second aqueous medium, the first electrode, and the second electrode described above. It is thus possible to highly accurately extract lithium ions.

According to the method of manufacturing lithium hydroxide of an embodiment of the present technology, the process is performed using the first aqueous medium, the second aqueous medium, the first electrode, and the second electrode described above. It is thus possible to highly accurately extract lithium ions and to thereby manufacture lithium hydroxide with high purity.

Note that effects of the present technology are not necessarily limited to those described above and may include any of a series of effects described below in relation to the present technology.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram illustrating a configuration of an extraction apparatus according to an embodiment of the present technology.

FIG. 2 is a sectional diagram illustrating, in an enlarged manner, a configuration of a capture release electrode illustrated in FIG. 1.

FIG. 3 is a schematic diagram illustrating an electron micrograph of a surface of a capture release layer illustrated in FIG. 2.

FIG. 4 is a block diagram describing an extraction method according to an embodiment of the present technology.

FIG. 5 is a block diagram describing an extraction process after the process illustrated in FIG. 4.

FIG. 6 is a block diagram describing an extraction process after the process illustrated in FIG. 5.

FIG. 7 is a block diagram illustrating a configuration of an extraction apparatus according to an embodiment.

FIG. 8 is a block diagram describing an extraction process according to an embodiment.

DETAILED DESCRIPTION

The present technology is described below in further detail including with reference to the drawings.

A description is given of an extraction apparatus according to an embodiment of the present technology.

Note that an extraction method according to an embodiment of the present technology is described together below, because the extraction method is performed in accordance with a procedure for an extraction process in which the extraction apparatus to be described here is used.

The extraction apparatus to be described here is to be used to perform a process of extracting lithium ions by using a characteristic of a titanium oxide to be described later. The process of extracting lithium ions will be hereinafter simply referred to as an “extraction process”.

First, a description is given of a configuration of the extraction apparatus.

FIG. 1 illustrates a block configuration of an extraction apparatus 100 that is one specific example of the extraction apparatus. FIG. 2 illustrates, in an enlarged manner, a sectional configuration of a capture release electrode 30 illustrated in FIG. 1. FIG. 3 schematically illustrates an electron micrograph of a surface of a capture release layer 30B illustrated in FIG. 2.

As illustrated in FIG. 1, the extraction apparatus 100 includes a feed solution 10, a recovery solution 20, the capture release electrode 30, a counter electrode 41, and an electric power source 51. Here, the extraction apparatus 100 further includes a counter electrode 42, an electric power source 52, a moving mechanism 60, supplying mechanisms 71 and 72, and container chambers 81 and 82. In FIG. 1, the feed solution 10 and the recovery solution 20 are each lightly shaded.

The feed solution 10 is a first aqueous medium to be used in performing the extraction process, and is contained in the container chamber 81, as illustrated in FIG. 1.

The feed solution 10 includes two or more kinds of metal ions, and the two or more kinds of metal ions include lithium ions (Li). In other words, the two or more kinds of metal ions include, together with lithium ions, one or more kinds of metal ions other than lithium ions. Hereinafter, the one or more kinds of metal ions other than lithium ions are each referred to as an “additional metal ion”.

The additional metal ions are not particularly limited in kind, and specific examples thereof include alkali metal ions, alkaline earth metal ions, and transition metal ions. Note that lithium ions are excluded from the alkali metal ions described here, as described above.

Specific examples of the alkali metal ions include sodium ions (Na⁺) and potassium ions (K⁺). Specific examples of the alkaline earth metal ions include magnesium ions (Mg²⁺) and calcium ions (Ca²⁺). Specific examples of the transition metal ions include iron ions (Fe²⁺), manganese ions (Mn²⁺), cobalt ions (Co²⁺), and nickel ions (Ni²⁺).

Specifically, the feed solution 10 includes any one or more of aqueous solvents each including two or more kinds of metal ions. Specific examples of the aqueous solvent to be used as the feed solution 10 include salt water, sea water, brine, and a process waste liquid. Examples of the process waste liquid include a waste liquid produced in a process of synthesizing a material such as a lithium compound, and a waste liquid produced due to a disposal process of an electronic device that includes lithium as a constituent material. Examples of such an electronic device include a lithium-ion secondary battery.

When the two or more kinds of metal ions include lithium ions and one or more kinds of alkali metal ions, it is preferable to perform the extraction process using the extraction apparatus 100. One reason for this is that when the capture release electrode 30 is immersed in the feed solution 10, the capture release electrode 30 selectively captures only lithium ions out of the two or more kinds of metal ions, as will be described later. This allows only lithium ions to be extracted in the extraction process even if lithium ions are mixed with the one or more kinds of alkali metal ions.

The “one or more kinds of alkali metal ions” described above are any one or more kinds of alkali metal ions other than lithium ions, as described above, and are more specifically any one or more kinds of alkali metal ions including, without limitation, sodium ions and potassium ions.

The feed solution 10 is not particularly limited in pH. The feed solution 10 is preferably alkaline, and the feed solution 10 more preferably has a pH of higher than 10, in particular. One reason for this is that this makes it easier for the capture release electrode 30 to capture lithium ions. This increases an amount of lithium ions captured by the capture release electrode 30.

The feed solution 10 may include a pH adjuster to adjust the pH of the feed solution 10. The pH adjuster is not particularly limited in kind, and specifically includes any one or more of hydroxides including, without limitation, sodium hydroxide (NaOH) and potassium hydroxide (KOH). A content of the pH adjuster in the feed solution 10 is not particularly limited, and may be set as desired.

The recovery solution 20 is a second aqueous medium to be used in recovering lithium ions in the extraction process, and is contained in the container chamber 82, as illustrated in FIG. 1.

Here, the recovery solution 20 is contained in the container chamber 82 as described above, unlike the feed solution 10 contained in the container chamber 81. Because the recovery solution 20 is thus contained in the container chamber 82 different from the container chamber 81, the recovery solution 20 is separated from the feed solution 10. In other words, the recovery solution 20 is not mixed with the feed solution 10, and is physically separated away from the feed solution 10.

The recovery solution 20 may include lithium ions. However, the recovery solution 20 preferably includes no additional metal ions. This is to improve efficiency of extracting lithium ions in the extraction process.

Specifically, the recovery solution 20 includes any one or more of aqueous solvents. Specific examples of the aqueous solvent to be used as the recovery solution 20 include pure water and deionized water.

However, the aqueous solvent may be an aqueous solution in which an additive is dissolved. The additive includes, as will be described later, any one or more of materials that accelerate a reduction reaction of a material included in the recovery solution 20 and suppress a side reaction generating the additional metal ions in the recovery solution 20. The material included in the recovery solution 20 is hereinafter referred to as an “existing material”. Examples of the additive include a lithium salt and an acid. Specific examples of the lithium salt include lithium hydroxide. Specific examples of the acid include hydrochloric acid, sulfuric acid, and nitric acid. An aqueous solvent including lithium hydroxide as the additive (the lithium salt) is what is called an aqueous lithium hydroxide solution.

A content of the additive in the aqueous solvent is not particularly limited, and is preferably sufficiently small, in particular. One reason for this is that the amount of the additive that allows lithium ions to be easily released from the capture release electrode 30 is enough. Specifically, when the additive is lithium hydroxide and the aqueous solvent is therefore the aqueous lithium hydroxide solution, a concentration of the aqueous lithium hydroxide solution is preferably 1 M or less, and is more preferably within a range from 0.1 mM to 1 M both inclusive. The unit of concentration “M” described above represents mol/l (=mol/dm³).

Upon the extraction process, lithium ions are released from the capture release electrode 30 into the recovery solution 20, which results in obtainment of an extraction solution 90 including lithium ions that have been released (see FIG. 6), as will be described later. In the extraction solution 90, a lithium compound is newly formed using lithium ions.

Note that a detailed procedure for the extraction process in which the extraction apparatus 100 is used will be described later.

As illustrated in FIG. 1, the capture release electrode 30 is a first electrode that captures and releases lithium ions.

The capture release electrode 30 is immersible in the feed solution 10 in a state of not being immersed in the recovery solution 20 in a first immersion process, and is immersible in the recovery solution 20 in a state of not being immersed in the feed solution 10 in a second immersion process. The first immersion process and the second immersion process will be described later. In other words, the capture release electrode 30 is to be immersed individually in each of the feed solution 10 and the recovery solution 20 and is not to be immersed in both the feed solution 10 and the recovery solution 20 at the same time.

Here, in the extraction process, the capture release electrode 30 is to be immersed in the feed solution 10 together with the counter electrode 41, and is to be immersed in the recovery solution 20 together with the counter electrode 42.

Here, that the capture release electrode 30 captures and releases lithium ions means that lithium ions are taken into an inside of the capture release electrode 30 from an outside (the feed solution 10), which is capturing, and that lithium ions that have been taken into the inside of the capture release electrode 30 are taken out to the outside (the recovery solution 20), which is releasing. Therefore, the capturing and releasing described here excludes a phenomenon in which the additional metal ions are attached to the surface of the capture release electrode 30 in the feed solution 10 and a phenomenon in which the additional metal ions are detached from the surface of the capture release electrode 30 in the recovery solution 20.

In the extraction process, the capture release electrode 30 is energized by the electric power source 51, in a state of being immersed in the feed solution 10. Further, the capture release electrode 30 that has been energized in the state of being immersed in the feed solution 10 is immersible in the recovery solution 20. Here, the capture release electrode 30 is energized by the electric power source 52 in a state of being immersed in the recovery solution 20. That is, the capture release electrode 30 is immersed in the feed solution 10, and is thereafter immersed in the recovery solution 20.

Here, the capture release electrode 30 includes a current collector 30A and a capture release layer 30B, as illustrated in FIG. 2. The current collector 30A has two opposed surfaces. The capture release layer 30B is provided on each of the two opposed surfaces of the current collector 30A. However, the capture release layer 30B may be provided only on one of the two opposed surfaces of the current collector 30A, on a side where the capture release electrode 30 is opposed to the counter electrodes 41 and 42.

Note that the current collector 30A is omittable. More specifically, the capture release electrode 30 may include no current collector 30A and may thus include only the capture release layer 30B.

The capture release electrode 30 is moved to the container chamber 81 by the moving mechanism 60 and is thus immersed in the feed solution 10, as will be described later. In addition, the capture release electrode 30 is moved to the container chamber 82 by the moving mechanism 60 and is thus immersed in the recovery solution 20, as will be described later.

The current collector 30A is an electrically conductive support member that supports the capture release layer 30B. The current collector 30A includes any one or more of electrically conductive materials including, without limitation, a metal material, a carbon material, and an electrically conductive ceramic material. Specific examples of the metal material include stainless steel (SUS), titanium, tin, lead, and an alloy of each of the foregoing materials. Specific examples of the electrically conductive ceramic material include indium tin oxide (ITO).

The stainless steel may be highly corrosion-resistant stainless steel that includes any one or more of additive elements including, without limitation, niobium and molybdenum added thereto. Specifically, the stainless steel may be, for example, SUS444 including molybdenum added thereto as an additive element.

In particular, the current collector 30A is preferably insoluble or sparingly soluble in and resistant to corrosion by the feed solution 10, and preferably has low reactivity to electrode particles 31 to be described later. Therefore, the current collector 30A preferably includes the above-described metal material, and more preferably includes titanium, a titanium alloy, or both. One reason for this is that this prevents the current collector 30A from being easily deteriorated in the extraction process.

Note that the current collector 30A may be an electric conductor having a surface plated with any of the above-described electrically conductive materials. The material included in the electrical conductor is not particularly limited, and may thus be selected as desired.

The capture release layer 30B is an electrode layer that includes an electrode material that captures and releases lithium ions.

Specifically, as illustrated in FIG. 2, the capture release layer 30B includes the electrode particles 31 that are particles of the electrode material. Each of the electrode particles 31 is what is called a primary particle. Each of the electrode particles 31 selectively captures lithium ions out of the two or more kinds of metal ions, and releases lithium ions that have been captured.

Each of the electrode particles 31 includes any one or more of titanium oxides. One reason for this is that it is easy for the titanium oxide to selectively capture and release lithium ions.

The term “titanium oxide” is a generic term for an oxide including titanium as a constituent element. Accordingly, the titanium oxide may include, as a constituent element, only titanium, which is a metal element, or may include two or more metal elements including titanium as constituent elements.

As long as the titanium oxide is able to selectively capture and release lithium ions, the titanium oxide is not particularly limited in kind. Specific examples of the titanium oxide include titanium dioxide (TiO₂) and a titanium composite oxide.

Titanium dioxide is not particularly limited in kind, and is therefore not limited in crystal structure. Accordingly, titanium dioxide may be anatase-type titanium dioxide, rutile-type titanium dioxide, brookite-type titanium dioxide, or a mixture of two or more thereof.

In particular, titanium dioxide is preferably anatase-type titanium dioxide. One reason for this is that anatase-type titanium dioxide easily captures and releases lithium ions, as compared with rutile-type titanium dioxide and brookite-type titanium dioxide.

To check the crystal structure of titanium dioxide, the capture release layer 30B is analyzed by X-ray diffractometry (XRD). The crystal structure (the anatase type, the rutile type, or the brookite type) of titanium dioxide is thus identifiable based on a difference between the crystal structures.

The titanium composite oxide is not particularly limited in kind, and specific examples thereof include a lithium titanium composite oxide including lithium as a constituent element.

The lithium titanium composite oxide is, for example, a compound represented by each of Formulae (1) to (3), i.e., Ramsdellite-type lithium titanate. M1 in Formula (1) is a metal element that is to be a divalent ion. M2 in Formula (2) is a metal element that is to be a trivalent ion. M3 in Formula (3) is a metal element that is to be a tetravalent ion.

Li[Li_xM1_(1-3x)/2Ti_(3+x)/2]O₄  (1)

• • where:
  • M1 includes at least one of Mg, Ca, Cu, Zn, or Sr; and
  • x satisfies 0≤x≤1/3.

Li[Li_yM2_1-3yTi_1+2y]O₄  (2)

• • where:
  • M2 includes at least one of Al, Sc, Cr, Mn, Fe, Ga, or Y; and
  • y satisfies 0≤y≤1/3.

Li[Li_1/3M3_zTi_(5/3)-z]O₄  (3)

• • where:
  • M3 includes at least one of V, Zr, or Nb; and
  • z satisfies 0≤z≤2/3.

The lithium titanium composite oxide is not particularly limited in crystal structure, but preferably has a spinel crystal structure in particular. One reason for this is that the crystal structure does not easily change when lithium ions are captured and released.

Specific examples of the lithium titanium composite oxide represented by Formula (1) include Li_3.75Ti_4.875Mg_0.375O₁₂. Specific examples of the lithium titanium composite oxide represented by Formula (2) include LiCrTiO₄. Specific examples of the lithium titanium composite oxide represented by Formula (3) include Li₄Ti₅O₁₂ and Li₄Ti_4.95N_0.05O₁₂.

In particular, the lithium titanium composite oxide is preferably lithium titanate (Li₄Ti₅O₁₂). One reason for this is that lithium titanate easily captures and releases lithium ions.

Accordingly, the titanium oxide more preferably includes anatase-type titanium dioxide, lithium titanate (Li₄Ti₅O₁₂), or both. One reason for this is that this makes it easier for the titanium oxide to capture and release lithium ions, as described above.

In particular, the capture release layer 30B preferably has a porous structure, as illustrated in FIG. 2. Specifically, the capture release electrode 30 preferably includes the capture release layer 30B having the porous structure.

The porous structure includes the electrode particles 31 that are directly joined to each other. In other words, in the capture release layer 30B, voids (fine pores 32) are present between the electrode particles 31, as a result of the electrode particles 31 being directly joined to each other. The capture release layer 30B thus has the porous structure including the electrode particles 31, as described above.

Specifically, the capture release layer 30B is a sintered body of the electrode particles 31 formed by a firing method. Therefore, the electrode particles 31 are directly joined to each other inside the capture release layer 30B. A method of forming the capture release layer 30B by the firing method will be described in detail later.

The wording “directly joined to each other” means that the capture release layer 30B is the sintered body of the electrode particles 31, as described above. In other words, the electrode particles 31 are not indirectly coupled to each other via a binder, but are directly coupled to each other without the binder therebetween. Further, the electrode particles 31 are not indirectly coupled to each other via a conductor, thus not being electrically coupled to each other via the conductor. Instead, the electrode particles 31 are directly coupled to each other without the conductor therebetween, thus being electrically coupled to each other without the conductor therebetween.

One reason why the capture release layer 30B is the sintered body of the electrode particles 31 and thus has the porous structure is that physical and electrical coupling between the electrode particles 31 allows for easy capturing and releasing of lithium ions in the capture release layer 30B. This makes it easy for the extraction process in which the capture release layer 30B is used to proceed smoothly and efficiently.

Here, the electrode particles 31 preferably have a markedly small average particle size. The average particle size of the electrode particles 31 is calculated based on a result of an observation of the surface of the capture release layer 30B with use of an electron microscope. More specifically, the average particle size of the electrode particles 31 is preferably 100 nm or smaller. In other words, each of the electrode particles 31 is preferably what is called a nanoparticle. One reason for this is that this makes it easy for lithium ions to move inside each of the electrode particles 31 and also makes it easy for the fine pores 32 serving as a movement path for lithium ions to be formed inside the capture release layer 30B. Accordingly, it is easier for each of the electrode particles 31 to capture and release lithium ions.

In particular, the average particle size is preferably 30 nm or smaller. One reason for this is that this makes it even easier for each of the electrode particles 31 to capture and release lithium ions.

Note that although a lower limit of the average particle size is not particularly limited, specifically, the average particle size is preferably 7 nm or larger. One reason for this is that this makes it easy for the electrode particles 31 to be formed stably.

A procedure for calculating the average particle size is as described below. An electron micrograph 200 illustrated in FIG. 3 is used to calculate the average particle size.

Specifically, first, the extraction apparatus 100 is disassembled to thereby take out the capture release electrode 30. Thereafter, the surface of the capture release layer 30B is observed using the electron microscope to thereby acquire the electron micrograph 200. The electron microscope is not particularly limited in kind. Specifically, used are any one or more of electron microscopes including, without limitation, a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Observation conditions are not particularly limited, but specifically, an acceleration voltage is set to 5.0 kV and a magnification is set to 150,000 times.

In this case, the capture release electrode 30 may be cut by, for example, an ion milling apparatus to thereby expose a section of the capture release layer 30B, following which the section of the capture release layer 30B may be observed to thereby acquire the electron micrograph 200. Usable as the ion milling apparatus is, for example, an ion milling apparatus ArBlade (registered trademark) 5000, available from Hitachi High-Tech Corporation.

In the electron micrograph 200, as illustrated in FIG. 3, the porous structure having the fine pores 32 is observed because the electrode particles 31 are directly joined to each other. To simplify the illustration, FIG. 3 illustrates a case where each of the electrode particles 31 has a rectangular plan shape.

Thereafter, 50 electrode particles 31 are selected from the electrode particles 31 visually recognized in the electron micrograph 200, following which a particle size (a maximum outer size) of each of the 50 electrode particles 31 is measured. As a result, 50 particle sizes are obtained.

To select the 50 electrode particles 31, the electrode particles 31 present in the very front among the electrode particles 31 overlapping each other are selected. In other words, an electrode particle 31 (31Y) is not selected whose outer edge (profile) is not entirely visible because the electrode particle 31 and other one or more electrode particles 31 overlap each other. In contrast, an electrode particle 31 (31X) is selected whose outer edge is entirely visible because the electrode particle 31 and other one or more electrode particles 31 do not overlap each other. In FIG. 3, some electrode particles 31X to be selected are shaded.

Lastly, an average value of the 50 particle sizes is calculated to thereby obtain the average value as the average particle size.

The capture release layer 30B is the sintered body of the electrode particles 31, as described above, and thus preferably has characteristic configuration conditions resulting from the sintered body.

Specifically, the capture release layer 30B preferably has a sufficiently great volume density. More specifically, the volume density of the capture release layer 30B is preferably within a range from 1.0 g/cm³ to 3.5 g/cm³ both inclusive. In addition, the capture release layer 30B preferably has a sufficiently great specific surface area. More specifically, the specific surface area of the capture release layer 30B is preferably within a range from 1 m²/g to 500 m²/g both inclusive, and is more preferably within a range from 10 m²/g to 500 m²/g both inclusive. One reason for this is that this makes it easier for each of the electrode particles 31 to capture and release lithium ions.

A procedure for measuring the specific surface area of the capture release layer 30B is as described below. First, the extraction apparatus 100 is disassembled to thereby take out the capture release electrode 30. Thereafter, the capture release electrode 30 is washed with a washing solvent, following which the capture release electrode 30 is sufficiently dried in a vacuum heating furnace. In this case, an aqueous solvent such as pure water is used as the washing solvent, and a heating temperature is set to be within a range from 60° C. to 100° C. both inclusive. Lastly, degassing is performed at 200° C. for 30 minutes, following which the specific surface area of the capture release layer 30B is measured by a BET method with nitrogen gas. Usable as a measurement apparatus is, for example, a fully automated specific surface area measurement apparatus, Macsorb (registered trademark), available from Mountech Co., Ltd.

Note that a void rate of the fine pores 32 is not particularly limited, and specifically, is preferably within a range from 10% to 75% both inclusive. The void rate is calculated based on the following calculation expression: void rate (%)=[1−(volume density of capture release layer 30B/true density of capture release layer 30B)]×100.

Note that the capture release layer 30B may further include any one or more of other electrode materials that capture and release lithium ions.

The other electrode material is not particularly limited in kind, and specific examples thereof include a carbon material and a metal-based material. The metal-based material is a material including, as one or more constituent elements, any one or more of metal elements and metalloid elements that are each able to form an alloy with lithium.

Note that when the capture release layer 30B includes the other electrode material, a procedure described below may be performed to calculate the average particle size. Specifically, when the capture release layer 30B includes the carbon material or the metal-based material as the other electrode material, the capture release layer 30B is analyzed by energy dispersive X-ray spectroscopy (EDX). In this case, it is possible to check presence or absence or a location of each of the carbon material and the metal-based material by elemental mapping.

The capture release layer 30B may further include any one or more of other materials. Specific examples of the other material include a binder, a surfactant, and a sintering aid.

The counter electrode 41 is a second electrode that is immersible in the feed solution 10, as illustrated in FIG. 1, and is to be immersed in the feed solution 10 together with the capture release electrode 30. Here, the counter electrode 41 is already in a state of being immersed in the feed solution 10.

Specifically, the counter electrode 41 includes any one or more of electrically conductive materials including, without limitation, a metal material. The electrically conductive material is not particularly limited in kind, and preferably includes any one or more of metal elements including, without limitation, nickel, manganese, iridium, tantalum, and platinum as one or more constituent elements, in particular. One reason for this is that this makes it easy for the capture release electrode 30 to capture lithium ions in the feed solution 10. Note that the electrically conductive material may be a simple substance, an alloy, or a compound.

The counter electrode 42 is a third electrode that is immersible in the recovery solution 20 together with the capture release electrode 30, as illustrated in FIG. 1. Here, the counter electrode 42 is already in a state of being immersed in the recovery solution 20.

The counter electrode 42 is preferably stable upon a reduction reaction, and more preferably allows the reduction reaction of the existing material included in the recovery solution 20 to easily proceed, as will be described later. One reason for this is that this makes it easy for the capture release electrode 30 to release lithium ions in the recovery solution 20. Another reason is that this makes it easy for the reduction reaction of the existing material to proceed, and thus makes it easy for a sufficient amount of hydrogen to be generated through the reduction reaction even under low voltage.

Specifically, the counter electrode 42 includes any one or more of electrically conductive materials including, without limitation, a metal material. The electrically conductive material is not particularly limited in kind. However, the electrically conductive material preferably includes any one or more of metal elements including, without limitation, titanium, platinum, iridium, nickel, iron, and palladium, as one or more constituent elements, and more preferably includes any one or more of metal elements including, without limitation, platinum, iridium, nickel, iron, and palladium, as one or more constituent elements, in particular. Note that the electrically conductive material may be a simple substance, an alloy, or a compound, as described above.

The electric power source 51 is a first electric power source coupled to the capture release electrode 30 and the counter electrode 41. The electric power source 51 is configured to energize the capture release electrode 30 and the counter electrode 41 by applying a current between the capture release electrode 30 and the counter electrode 41.

Here, the electric power source 51 energizes the capture release electrode 30 and the counter electrode 41 in a state where the capture release electrode 30 and the counter electrode 41 are immersed in the feed solution 10 (the first immersion process to be described later). Note that the electric power source 51 does not energize the capture release electrode 30 and the counter electrode 42 in a state where the capture release electrode 30 and the counter electrode 42 are immersed in the recovery solution 20 (the second immersion process to be described later).

One reason why the electric power source 51 energizes the capture release electrode 30 and the counter electrode 41 in the state where the capture release electrode 30 and the counter electrode 41 are immersed in the feed solution 10 is to cause an electrolytic reaction to proceed between the capture release electrode 30 and the counter electrode 41 through the energization. Lithium ions are thus captured by the capture release electrode 30 from the feed solution 10 through the electrolytic reaction.

The electric power source 52 is a second electric power source coupled to the capture release electrode 30 and the counter electrode 42. The electric power source 52 is configured to energize the capture release electrode 30 and the counter electrode 42 by applying a current between the capture release electrode 30 and the counter electrode 42.

Here, the electric power source 52 energizes the capture release electrode 30 and the counter electrode 42 in a state where the capture release electrode 30 and the counter electrode 42 are immersed in the recovery solution 20 (the second immersion process to be described later). In this case, the electric power source 52 performs the energization in a direction opposite to a direction in which the electric power source 51 performs the energization (a direction in which the electric power source 51 applies a current) in the first immersion process.

One reason why the electric power source 52 energizes the capture release electrode 30 and the counter electrode 42 in the state where the capture release electrode 30 and the counter electrode 42 are immersed in the recovery solution 20 is to cause an electrolytic reaction to proceed between the capture release electrode 30 and the counter electrode 42 through the energization. Lithium ions are thus released from the capture release electrode 30 to the recovery solution 20 through the electrolytic reaction.

The moving mechanism 60 is configured to move the capture release electrode 30 between the feed solution 10 and the recovery solution 20 by moving the capture release electrode 30 between the container chamber 81 and the container chamber 82.

The moving mechanism 60 moves the capture release electrode 30 while holding the capture release electrode 30. The moving mechanism 60 thus immerses the capture release electrode 30 in the feed solution 10 and thus takes the capture release electrode 30 out of the feed solution 10. In addition, the moving mechanism 60 thus immerses the capture release electrode 30 in the recovery solution 20 and thus takes the capture release electrode 30 out of the recovery solution 20.

The supplying mechanism 71 is configured to supply the feed solution 10 to the container chamber 81 to refill the container chamber 81 with the feed solution 10. The supplying mechanism 71 is coupled to the container chamber 81 by an unillustrated supplying pipe, and is thus able to supply the feed solution 10 to the container chamber 81 on an as-needed basis.

Specifically, the supplying mechanism 71 includes, for example, an unillustrated tank and an unillustrated pump. The tank stores the feed solution 10 to be supplied. The pump pushes the feed solution 10 out of the tank to the container chamber 81 by using pressure.

The supplying mechanism 72 is configured to supply the recovery solution 20 to the container chamber 82 to refill the container chamber 82 with the recovery solution 20. The supplying mechanism 72 is coupled to the container chamber 82 by an unillustrated supplying pipe, and is thus able to supply the recovery solution 20 to the container chamber 82 on an as-needed basis.

The supplying mechanism 72 has a configuration similar to the configuration of the supplying mechanism 71 except that the supplying mechanism 72 stores the recovery solution 20 instead of the feed solution 10 and supplies the recovery solution 20 to the container chamber 82 instead of supplying the feed solution 10 to the container chamber 81.

The container chamber 81 is a first container member that contains the feed solution 10, and the container chamber 82 is a second container member that contains the recovery solution 20. The container chambers 81 and 82 are separated from each other to allow the feed solution 10 and the recovery solution 20 to be separated from each other.

Note that the extraction apparatus 100 may further include any one or more of other components.

Specific examples of the other components include a control board. The control board includes, for example, a circuit board for controlling, and is configured to control an overall operation of the extraction apparatus 100.

Next, a description is given of a procedure for the extraction method in which the extraction apparatus 100 is used.

FIGS. 4 to 6 each illustrate a block configuration corresponding to FIG. 1 to describe the extraction process. Note that FIGS. 4 to 6 each illustrate only a main part of the extraction apparatus 100 related to the extraction process, and FIG. 6 applies dark shading to the extraction solution 90.

In the following, a procedure for fabricating the capture release electrode 30 is described, and thereafter, the extraction procedure in which the extraction apparatus 100 is used is described.

To fabricate the capture release electrode 30, first, the electrode particles 31, each of which includes the titanium oxide, and the binder are mixed with each other to thereby obtain a mixture. A composition (a mixture ratio) of the mixture is not particularly limited, and may thus be set as desired. In this case, any one or more of additives may be added to the mixture. The additive is not particularly limited in kind, and specific examples thereof include a surfactant and a sintering aid.

The binder is not particularly limited in kind, as long as the binder includes any one or more of polymer compounds to be mixed with the electrode particles 31 for the purpose of improving strength of a powder molded body to be described later. Specific examples of the polymer compound include polyethylene glycol, polyvinyl alcohol, and polyvinyl butyral. In particular, the binder is preferably a polymer compound to be decomposed and degreased at a temperature lower than or equal to a temperature at which the titanium oxide is fired. Specific examples of the surfactant include stearic acid. Specific examples of the sintering aid include an oxide of boron and an oxide of silicon.

Thus, granulated powder including the electrode particles 31 and the binder is obtained.

Thereafter, the granulated powder is disposed on each of the two opposed surfaces of the current collector 30A, following which the granulated powder is press-molded together with the current collector 30A. A condition such as a pressing pressure may be set as desired. Thus, the granulated powder including the electrode particles 31 is fixed on each of the two opposed surfaces of the current collector 30A. As a result, the powder molded body is obtained.

Lastly, the powder molded body is fired in the atmosphere. Firing conditions including, without limitation, a firing temperature and a firing time may be set as desired depending on, for example, a composition of the powder molded body. In this case, the firing conditions are adjusted to allow the electrode particles 31 including the titanium oxide to be directly joined to each other while remaining in a state of the primary particles. For example, a maximum temperature during firing is within a range from 500° C. to 1200° C. both inclusive. Note that the firing process may be performed in an oxygen atmosphere.

In the firing process, the binder is degreased in accordance with firing. Thus, the electrode particles 31 are directly joined to each other, and the fine pores 32 are formed between the electrode particles 31. This fixes a joined body (the sintered body) of the electrode particles 31 on the surface of the current collector 30A, and thus forms the capture release layer 30B having the porous structure. As a result, the capture release electrode 30 is fabricated.

To fabricate the capture release electrode 30, adjusting the above-described conditions including, without limitation, the pressing pressure, the firing temperature, and the firing time as appropriate makes it possible to adjust the joined state of the electrode particles 31 (the primary particles), and to adjust the volume density and the specific surface area of the capture release layer 30B.

In the extraction process in which the extraction apparatus 100 is used, first, the supplying mechanism 71 supplies the feed solution 10 to the container chamber 81, and the supplying mechanism 72 supplies the recovery solution 20 to the container chamber 82. The feed solution 10 is thus contained in the container chamber 81, and the recovery solution 20 is thus contained in the container chamber 82.

The feed solution 10 includes two or more kinds of metal ions including lithium ions as described above, and the counter electrode 41 is already in the state of being immersed in the feed solution 10 as described above.

In addition, the recovery solution 20 is separated from the feed solution 10 as described above, and the counter electrode 42 is already in the state of being immersed in the recovery solution 20 as described above.

Thereafter, the moving mechanism 60 moves the capture release electrode 30 to the container chamber 81 to thereby immerse the capture release electrode 30 in the feed solution 10, as illustrated in FIG. 4. The capture release electrode 30 is thus immersed in the feed solution 10 together with the counter electrode 41. Hereinafter, the process in which the capture release electrode 30 is immersed in the feed solution 10 together with the counter electrode 41 is referred to as the “first immersion process”.

Thereafter, the electric power source 51 energizes the capture release electrode 30 and the counter electrode 41 in the first immersion process (in the state where the capture release electrode 30 and the counter electrode 41 are immersed in the feed solution 10).

Such energization causes the electrolytic reaction to proceed between the capture release electrode 30 and the counter electrode 41. In this case, the capture release electrode 30 (the electrode particles 31) is reduced in the feed solution 10. This causes each of the electrode particles 31 and lithium ions to react with each other, but does not cause each of the electrode particles 31 and the additional metal ions to react with each other.

Accordingly, each of the electrode particles 31 selectively capture only lithium ions out of the two or more kinds of metal ions in the feed solution 10. As a result, only lithium ions out of the two or more kinds of metal ions are extracted by each of the electrode particles 31.

Note that energization conditions including, without limitation, a current value and an energization time upon the energization are not particularly limited, and may be set as desired.

Thereafter, the moving mechanism 60 takes the capture release electrode 30 out of the container chamber 81. Thereafter, the capture release electrode 30 may be washed with a washing solvent, following which the capture release electrode 30 may be dried, on an as-needed basis. The washing solvent is not particularly limited in kind, and is specifically similar to the kind of the aqueous solvent included in the recovery solution 20. The above-described washing of the capture release electrode 30 removes the additional metal ions unnecessarily attached to the surface of the capture release electrode 30.

Thereafter, the moving mechanism 60 moves the capture release electrode 30 from the container chamber 81 to the container chamber 82, to thereby immerse the capture release electrode 30 in the recovery solution 20, as illustrated in FIG. 5. The capture release electrode 30 that has been energized in the first immersion process is thus immersed in the recovery solution 20 together with the counter electrode 42. Hereinafter, the process in which the capture release electrode 30 is immersed in the recovery solution 20 together with the counter electrode 42 is referred to as the “second immersion process”.

Thereafter, the electric power source 52 energizes the capture release electrode 30 and the counter electrode 42 in the second immersion process (in the state where the capture release electrode 30 and the counter electrode 42 are immersed in the recovery solution 20). An energization direction in the second immersion process is opposite to an energization direction in the first immersion process.

Such energization causes the electrolytic reaction to proceed between the capture release electrode 30 and the counter electrode 42. In this case, the capture release electrode 30 (the electrode particles 31) is oxidized in the recovery solution 20, and the existing material included in the recovery solution 20 is reduced. Each of the electrode particles 31 thus releases lithium ions in the recovery solution 20.

The reduction reaction of the existing material is not particularly limited in kind as long as the reduction reaction generates no metal ions. Here, the recovery solution 20 includes the aqueous solvent such as pure water or deionized water as described above. Therefore, when the aqueous solvent is reduced, hydrogen is generated and hydroxide ions are also generated.

The extraction process is thus performed. As a result, the extraction solution 90 including lithium ions released from the capture release electrode 30 is obtained, as illustrated in FIG. 6. Because the extraction solution 90 includes lithium ions that have been released, when hydroxide ions have been generated, lithium hydroxide is newly formed.

Lastly, the extraction solution 90 is recovered. The recovered extraction solution 90 includes lithium ions obtained by the extraction process. More specifically, the recovered extraction solution 90 includes lithium hydroxide. Lithium ions are thus recovered, and the extraction process in which the extraction apparatus 100 is used is thus completed.

Thereafter, the supplying mechanism 71 supplies the feed solution 10 to the container chamber 81 to refill the container chamber 81 with the feed solution 10 on an as-needed basis. In addition, the supplying mechanism 72 supplies the recovery solution 20 to the container chamber 82 to refill the container chamber 82 with the recovery solution 20 on an as-needed basis.

Note that in the above description of the extraction process, the extraction process in which the extraction apparatus 100 is used is performed only once. However, the extraction process in which the extraction apparatus 100 is used may be repeated multiple times. Repeating the extraction process multiple times increases a recovery amount of lithium ions. In this case, the extraction process in which the capture release electrode 30 is used is repeated by the moving mechanism 60 moving the capture release electrode 30 between the container chamber 81 and the container chamber 82.

According to the extraction apparatus 100, the extraction apparatus 100 includes the feed solution 10, the recovery solution 20, the capture release electrode 30, the counter electrodes 41 and 42, and the electric power sources 51 and 52 that have the respective configurations described above.

In this case, the extraction process is performed using the feed solution 10, the recovery solution 20, the capture release electrode 30, the counter electrodes 41 and 42, and the electric power sources 51 and 52 as described above. Accordingly, lithium ions are extracted using a characteristic of the capture release electrode 30, and the extracted lithium ions are thus recovered.

Specifically, the electric power source 51 energizes the capture release electrode 30 and the counter electrode 41 in the first immersion process (in the state where the capture release electrode 30 and the counter electrode 41 are immersed in the feed solution 10). This allows only lithium ions, out of multiple kinds of metal ions, to be selectively captured by the capture release electrode 30 in the feed solution 10 by using the property of the capture release electrode 30 including the titanium oxide.

In addition, lithium ions are released from the capture release electrode 30 into the recovery solution 20 by using the characteristic of the capture release electrode 30 including the titanium oxide, in the second immersion process (in the state where the capture release electrode 30 and the counter electrode 42 are immersed in the recovery solution 20) after the first immersion process.

The extraction process is thus performed. As a result, the extraction solution 90 including the extracted lithium ions is obtained.

As described above, only lithium ions, out of the multiple kinds of metal ions, are selectively captured by the capture release electrode 30 in the recovery solution 20, and lithium ions are released from the capture release electrode 30 into the recovery solution 20. As a result, only those lithium ions are selectively recovered. It is thus possible to highly accurately extract lithium ions.

In this case, because lithium ions are extracted through the electrolytic reaction in particular, the extraction process is performed without using an absorbent for absorbing lithium ions, as compared with a case where the absorbent is used. This makes it possible to easily and swiftly perform the extraction process, and also makes it possible to improve extraction efficiency of the extraction process.

In addition, it is possible to easily, highly accurately, and selectively extract only lithium ions out of the multiple kinds of metal ions, by using the characteristic of the capture release layer 30B (the electrode particles 31 including the titanium oxide), as compared with a case where an electrodialysis (in which a cation exchange membrane is used) is performed in which it is difficult to selectively extract only lithium ions out of the multiple kinds of metal ions. Accordingly, it is possible to more easily and more swiftly perform the extraction process, and also makes it possible to further improve the extraction efficiency of the extraction process.

In addition, the pH of the feed solution 10 may be higher than 10. This increases an amount of lithium ions captured by the capture release electrode 30. Accordingly, it is possible to achieve higher effects.

Further, the titanium oxide may include anatase-type titanium dioxide, lithium titanate (Li₄Ti₅O₁₂), or both. This makes it easier for the titanium oxide to capture and release lithium ions. Accordingly, it is possible to achieve higher effects.

Further, the capture release electrode 30 may include the electrode particles 31, the electrode particles 31 may each include the titanium oxide, and the capture release electrode 30 may include the porous structure in which the electrode particles 31 are directly joined to each other. This makes it easy for lithium ions to be captured by the capture release electrode 30. Accordingly, it is possible to achieve higher effects.

In this case, the average particle size of the electrode particles 31 may be 100 nm or smaller. This makes it easier for each of the electrode particles 31 to capture and release lithium ions. Accordingly, it is possible to achieve higher effects. In particular, the average particle size may be 30 nm or smaller. This makes it even easier for each of the electrode particles 31 to capture and release lithium ions. Accordingly, it is possible to achieve even higher effects.

Further, the capture release electrode 30 may include the capture release layer 30B having the porous structure, the volume density of the capture release layer 30B may be within the range from 1.0 g/cm³ to 3.5 g/cm³ both inclusive, and the specific surface area of the capture release layer 30B may be within the range from 1 m²/g to 500 m²/g both inclusive. This makes it easy for each of the electrode particles 31 to capture and release lithium ions. Accordingly, it is possible to achieve higher effects.

Further, the recovery solution 20 may include the aqueous lithium hydroxide solution, and the concentration of the aqueous lithium hydroxide solution may be 1 M or lower. This makes it easy for lithium ions to be sufficiently released from the capture release electrode 30 in the recovery solution 20. Accordingly, it is possible to achieve higher effects.

Further, the counter electrode 42 may include one or more of titanium, platinum, iridium, nickel, iron, or palladium as one or more constituent elements. This makes it easy for lithium ions to be released from the capture release electrode 30 in the recovery solution 20. Accordingly, it is possible to achieve higher effects.

Further, the extraction apparatus 100 may further include the moving mechanism 60 that moves the capture release electrode 30 between the feed solution 10 and the recovery solution 20. This allows the process of capturing lithium ions in which the feed solution 10 is used and the process of releasing lithium ions in which the recovery solution 20 is used to be performed automatically and continuously. The extraction process is thus performed efficiently in a short time. Accordingly, it is possible to achieve higher effects.

Further, the extraction apparatus 100 may further include the supplying mechanism 71 that supplies the feed solution 10 to the container chamber 81. This allows the container chamber 81 to be refilled with the feed solution 10 on an as-needed basis. The extraction process is thus performed efficiently in a short time. Accordingly, it is possible to achieve higher effects.

Further, the extraction apparatus 100 may further include the supplying mechanism 72 that supplies the recovery solution 20 to the container chamber 82. This allows the container chamber 82 to be refilled with the recovery solution 20 on an as-needed basis. The extraction process is thus performed efficiently in a short time. Accordingly, it is possible to achieve higher effects.

In addition, according to the extraction method in which the extraction apparatus 100 is used, the extraction process is performed using the feed solution 10, the recovery solution 20, the capture release electrode 30, the counter electrodes 41 and 42, and the electric power sources 51 and 52, by the operation of the extraction apparatus 100 described above. In this case, for some reasons described above, only lithium ions, out of the multiple kinds of metal ions, are selectively captured by the capture release electrode 30 in the recovery solution 20, and lithium ions are released from the capture release electrode 30 in the recovery solution 20. As a result, only those lithium ions are selectively recovered. It is thus possible to highly accurately extract lithium ions.

Here, a description is given of a method of manufacturing lithium hydroxide, which is an application example of the extraction process in which the extraction apparatus 100 is used. Application of the extraction process described above makes it possible to manufacture lithium hydroxide with high purity.

A procedure for manufacturing lithium hydroxide is similar to the above-described extraction procedure except for those described below. In the following, reference will be made to FIGS. 1 to 6 that have already been described.

Specifically, first, the capture release electrode 30, which includes the titanium oxide, and the counter electrode 41 are immersed together in the feed solution 10 that includes two kinds of metal ions including lithium ions (the first immersion process). Details of each of the feed solution 10, the capture release electrode 30, and the counter electrode 41 are as described above.

Thereafter, the capture release electrode 30 and the counter electrode 41 are energized in the first immersion process (in the state where the capture release electrode 30 and the counter electrode 41 are immersed in the feed solution 10). Accordingly, the capture release electrode 30 selectively captures only lithium ions out of the two or more kinds of metal ions in the feed solution 10.

Thereafter, the capture release electrode 30 is taken out of the feed solution 10. Thereafter, the capture release electrode 30 may be washed with a washing solvent, following which the capture release electrode 30 may be dried, on an as-needed basis. Details of the washing solvent are as described above.

Thereafter, the capture release electrode 30 that has been energized in the first immersion process is immersed in the recovery solution 20, which is separated from the feed solution 10, together with the counter electrode 42 (the second immersion process). The recovery solution 20 includes pure water or the aqueous lithium hydroxide solution. Details of each of the counter electrode 42 and the aqueous lithium hydroxide solution are as described above.

Thereafter, hydrogen is generated at the counter electrode 42 by energizing the capture release electrode 30 and the counter electrode 42 in the second immersion process (in the state where the capture release electrode 30 and the counter electrode 42 are immersed in the recovery solution 20). Accordingly, the capture release electrode 30 releases lithium ions in the recovery solution 20, and hydroxide ions are generated in the recovery solution 20. As a result, the extraction solution 90 including lithium hydroxide is obtained.

Lastly, the extraction solution 90 is recovered. Lithium hydroxide is thus obtained.

According to the method of manufacturing lithium hydroxide described above, the extraction method described above is used. Lithium ions are thus extracted highly accurately for some reasons described above. It is therefore possible to manufacture lithium hydroxide with high purity by using the extracted lithium ions.

The configuration of the extraction apparatus 100 and the procedure for the extraction method are appropriately modifiable as described below according to an embodiment. Note that any two or more of the following series of modification examples may be combined with each other. The following series of modification examples may be applied to the method of manufacturing lithium hydroxide.

The extraction apparatus 100 includes two electric power sources, as illustrated in FIG. 1. The two electric power sources are the electric power source 51 that energizes the capture release electrode 30 and the counter electrode 41 in the first immersion process, and the electric power source 52 that energizes the capture release electrode 30 and the counter electrode 42 in the second immersion process.

However, although not specifically illustrated here, the extraction apparatus 100 may include only one electric power source. This electric power source is coupled to the capture release electrode 30 and the counter electrodes 41 and 42. The electric power source thus energizes the capture release electrode 30 and the counter electrode 41 in the first immersion process, and also energizes the capture release electrode 30 and the counter electrode 42 in the second immersion process.

In this case also, because the extraction process is performed using the extraction apparatus 100, it is possible to achieve similar effects.

The extraction apparatus 100 includes two counter electrodes, as illustrated in FIG. 1. The two counter electrodes are the counter electrode 41 to be immersed in the feed solution 10 together with the capture release electrode 30, and the counter electrode 42 to be immersed in the recovery solution 20 together with the capture release electrode 30.

However, although not specifically illustrated here, when a material included in the counter electrode 41 and a material included in the counter electrode 42 are the same as each other, the extraction apparatus 100 may include only one counter electrode. This counter electrode is immersed in the feed solution 10 together with the capture release electrode 30 by being moved to the container chamber 81 together with the capture release electrode 30 by the moving mechanism 60. In addition, the counter electrode is immersed in the recovery solution 20 together with the capture release electrode 30 by being moved to the container chamber 82 together with the capture release electrode 30 by the moving mechanism 60.

In this case also, because the extraction process is performed using the extraction apparatus 100, it is possible to achieve similar effects.

In the process of fabricating the capture release electrode 30, the method (the firing method) of firing the powder molded body including the binder is used to form the capture release layer 30B having the porous structure. However, the procedure for fabricating the capture release electrode 30 is appropriately modifiable as long as the capture release layer 30B is formed as a result of the electrode particles 31 being directly joined to each other through the firing process.

Specifically, a powder molded body may be obtained by press-molding the electrode particles 31 without using the binder, following which the obtained powder molded body may be fired.

Alternatively, a dispersion liquid in which the electrode particles 31 are dispersed may be applied on the current collector 30A, following which the applied dispersion liquid may be dried. In this case, after the dispersion liquid is dried, the current collector 30A with the dispersion liquid applied thereon may be fired.

In these cases also, the capture release layer 30B having the porous structure is formed. Accordingly, it is possible to achieve similar effects.

The capture release layer 30B has the porous structure, as illustrated in FIG. 2. However, although not specifically illustrated here, the capture release layer 30B does not have to have the porous structure.

The capture release layer 30B not having the porous structure includes the electrode particles 31 and the binder. However, the capture release layer 30B may further include another electrode material, as described above. Such a capture release layer 30B includes the electrode particles 31 that are bound to each other via the binder. Details of each of the electrode particles 31 and the binder are as described above.

The capture release layer 30B is formed by a coating method instead of the firing method. To form the capture release layer 30B, first, the electrode particles 31 and the binder are mixed with each other to obtain a mixture. Details of the kinds of the binder are as described above. Note that the binder may be a polymer compound such as polyvinylidene difluoride. Thereafter, the mixture is put into a solvent to thereby prepare a slurry in paste form. The solvent may be an aqueous solvent, or may be an organic solvent. Thereafter, the slurry is applied on the two opposed surfaces of the current collector 30A to thereby form the capture release layer 30B. Thereafter, the capture release layer 30B may be compression-molded by, for example, a roll pressing machine. In this case, the capture release layer 30B may be heated. The capture release layer 30B may be compression-molded multiple times.

In this case also, lithium ions are selectively captured and released in the capture release layer 30B. Accordingly, it is possible to achieve similar effects.

However, the capture release layer 30B having the porous structure is preferable to the capture release layer 30B not having the porous structure. One reason for this is that, with the porous structure, it is easier for the capture release layer 30B to capture and release lithium ions.

In FIG. 1, the extraction apparatus 100 includes the counter electrode 42 and the electric power source 52. Accordingly, as illustrated in FIG. 5, the electric power source 52 energizes the capture release electrode 30 and the counter electrode 42 in the second immersion process.

However, as illustrated in FIG. 7 corresponding to FIG. 1, the extraction apparatus 100 does not have to include the counter electrode 42 and the electric power source 52. In this case, as illustrated in FIG. 8 corresponding to FIG. 5, only the capture release electrode 30 may be immersed in the recovery solution 20 in the second immersion process, and the capture release electrode 30 may not be energized.

In the second immersion process illustrated in FIG. 8, the capture release electrode 30 that has been energized in the first immersion process is solely immersed in the recovery solution 20, and the capture release electrode 30 is not energized, as described above. FIG. 8 illustrates a state where the electric power source 51 used for the energization in the first immersion process has been moved to the container chamber 82 together with the capture release electrode 30. However, the electric power source 51 does not energize the capture release electrode 30 in the second immersion process.

In the second immersion process (in the state where the capture release electrode 30 is immersed in the recovery solution 20), the electrolytic reaction spontaneously proceeds at the capture release electrode 30 even if the capture release electrode 30 is not energized. In this case, the capture release electrode 30 (the electrode particles 31) is oxidized in the recovery solution 20, and the existing material included in the recovery solution 20 is reduced, as in the case where the capture release electrode 30 is energized in the second immersion process. Each of the electrode particles 31 thus releases lithium ions into the recovery solution 20, and when the aqueous solvent included in the recovery solution 20 is reduced, hydroxide ions are generated in accordance with generation of hydrogen.

In this case also, lithium ions are released from the capture release electrode 30 in the recovery solution 20. Accordingly, it is possible to achieve similar effects.

However, energizing the capture release electrode 30 in the second immersion process is preferable to not energizing the capture release electrode 30 in the second immersion process. One reason for this is that this makes it easy for lithium ions to be efficiently released from the capture release electrode 30 in the recovery solution 20.

Here, the capture release electrode 30 is not energized in the second immersion process, and therefore, the extraction apparatus 100 does not include the counter electrode 42 and the electric power source 52, as described above. However, as long as the capture release electrode 30 is not energized in the second immersion process, the extraction apparatus 100 may include the counter electrode 42, the electric power source 52, or both.

EXAMPLES

A description is given of Examples of the present technology according to an embodiment.

Examples 1 to 10 and Comparative Examples 1 and 2

The extraction process described above was performed to evaluate performance of the extraction process, as described below. Here, to simplify the evaluation, the extraction process was performed by hand without using the extraction apparatus.

Note that in Table 1, to simplify the description, Example is simply described as “Ex” and a comparative example is simply described as “Com”. For example, “Ex1” represents Example 1, and “Com1” represents Comparative example 1.

[Extraction Process]

In the following, the capture release electrode 30 was fabricated, following which the extraction process was performed using the capture release electrode 30, in accordance with the following procedure.

[Fabrication of Capture Release Electrode]

Here, the capture release electrode 30 was fabricated by forming the capture release layer 30B by the firing method (Examples 1 to 9). In the “Forming method” column in Table 1, “Firing” represents that the firing method was used as the method of forming the capture release layer 30B.

First, 100 parts by mass of the electrode particles 31 (a titanium oxide in powder form), 10 parts by mass of a binder (polyethylene glycol), and 1 part by mass of a surfactant (a surfactant Triton X (registered trademark), available from Nacalai Tesque, Inc.) were mixed with each other to thereby obtain granulated powder.

Used as the titanium oxide were anatase-type titanium dioxide (TiO₂) and lithium titanate (Li₄Ti₅O₁₂ (LTO)) as a lithium titanium composite oxide. The average particle size (nm) of the electrode particles 31 was as listed in Table 1.

Thereafter, the current collector 30A (a mesh-shaped titanium foil having a thickness of 200 μm) and the granulated powder were press-molded together (at a pressing pressure of 100 MPa) by a pressing machine to thereby obtain a powder molded body.

Lastly, the powder molded body was fired in the atmosphere (at a firing temperature of 750° C.). The electrode particles 31 were thereby directly joined to each other. Thus, the capture release layer 30B that was the sintered body of the electrode particles 31 was formed on each of the two opposed surfaces of the current collector. The capture release electrode 30 was thus fabricated.

The volume density (g/cm³) and the specific surface area (m²/g) of the capture release layer 30B were as described below. When the average particle size was 7 nm, the volume density was 2.0 g/cm³ and the specific surface area was 109 m²/g. When the average particle size was 30 nm, the volume density was 1.9 g/cm³ and the specific surface area was 40 m²/g. When the average particle size was 100 nm, the volume density was 2.0 g/cm³ and the specific surface area was 21 m²/g. When the average particle size was 200 nm, the volume density was 2.0 g/cm³ and the specific surface area was 8 m²/g.

In addition, another capture release electrode 30 was fabricated by a similar procedure except that the capture release layer 30B was formed by the coating method instead of the firing method (Example 10). In the “Forming method” column in Table 1, “Coating” represents that the coating method was used as the method of forming the capture release layer 30B.

A procedure for forming the capture release layer 30B by the coating method was similar to the procedure for forming the capture release layer 30B by the firing method except for those described below. First, 100 parts by mass of the electrode particles 31 (the titanium oxide in powder form) and 4 parts by mass of the binder (polyvinylidene difluoride) were mixed with each other to thereby obtain a mixture. Thereafter, the mixture was put into a solvent (N-methyl-2-pyrrolidone as an organic solvent), following which the solvent was stirred to thereby prepare a slurry in paste form. Lastly, the slurry was applied on the two opposite surfaces of the current collector 30A by a coating apparatus, following which the applied slurry was dried to thereby form the capture release layer 30B.

[Extraction Process in which Capture Release Electrode was Used]

Here, the extraction process was performed by energizing the capture release electrode 30 in the second immersion process (Examples 1 to 7, 9, and 10).

First, the feed solution 10 was placed in the container chamber 81, and the recovery solution 20 was contained in the container chamber 82. Thereafter, the counter electrode 41 (a nickel foil (Ni)) was immersed in the feed solution 10, and the counter electrode 42 (a nickel foil or a titanium foil (Ti)) was immersed in the recovery solution 20.

In the “Kind” under “Counter electrode” column in Table 1, respective materials included in the counter electrodes 41 and 42 are indicated. For example, in the description “Ni/Ni”, “Ni” on the left side represents that a nickel foil was used as the counter electrode 41, and “Ni” on the right side represents that a nickel foil was used as the counter electrode 42.

Used as the feed solution 10 were two kinds of salt water (salt water A and salt water B). The feed solution 10 included lithium ions (Li⁺), sodium ions (Na⁺), potassium ions (K⁺), magnesium ions (Mg²⁺), and calcium ions (Ca²⁺). The pH of the feed solution 10 was as listed in Table 1.

The concentration (g/l (=g/dm³)) of each of the metal ions representing the composition of the salt water A was as follows.

Lithium ⁢ ions = 2.9 g / dm 3 Sodium ⁢ ions = 56 ⁢ g / dm 3 Potassium ⁢ ions = 29 ⁢ g / dm 3 Magnesium ⁢ ions = 0.03 g / dm 3 Calcium ⁢ ions = 0.02 g / dm 3

The concentration (g/dm³) of each of the metal ions representing the composition of the salt water B was as follows.

Lithium ⁢ ions = 3 ⁢ g / dm 3 Sodium ⁢ ions = 10 ⁢ g / dm 3 Potassium ⁢ ions = 10 ⁢ g / dm 3 Magnesium ⁢ ions = 1 ⁢ g / dm 3 Calcium ⁢ ions = 1 ⁢ g / dm 3

Used as the recovery solution 20 were pure water and two kinds of aqueous lithium hydroxide solutions (LiOH). A concentration of a first kind of aqueous lithium hydroxide solution was 10 mM, and a concentration of a second kind of aqueous lithium hydroxide solution was 1 M.

A concentration (g/dm³) of each of the metal ions representing the composition of the first kind of aqueous lithium hydroxide solution (having the concentration of 10 mM) was as follows.

Lithium ⁢ ions = 0.07 g / dm 3 Sodium ⁢ ions = 0 ⁢ g / dm 3 Potassium ⁢ ions = 0 ⁢ g / dm 3 Magnesium ⁢ ions = 0 ⁢ g / dm 3 Calcium ⁢ ions = 0 ⁢ g / dm 3

A concentration (g/dm³) of each of the metal ions representing the composition of the second kind of aqueous lithium hydroxide solution (having the concentration of 1 M) was as follows.

Lithium ⁢ ions = 6.9 g / dm 3 Sodium ⁢ ions = 0 ⁢ g / dm 3 Potassium ⁢ ions = 0 ⁢ g / dm 3 Magnesium ⁢ ions = 0 ⁢ g / dm 3 Calcium ⁢ ions = 0 ⁢ g / dm 3

Thereafter, the capture release electrode 30 and the counter electrode 41 were coupled to the electric power source 51 (an electrochemical measurement system SP-150 available from BioLogic), following which the capture release electrode 30 was immersed in the feed solution 10 (the first immersion process).

In the first immersion process, the capture release electrode 30 and the counter electrode 42 were energized by the electric power source 51 in the state where the capture release electrode 30 and the counter electrode 41 were immersed in the feed solution 10. In this case, energization conditions were set to allow a current per weight of the electrode particles 31 (the titanium oxide) to be constant (=100 mA/g), and an electrolytic reaction was thus caused to proceed (for a reaction time of one hour). Accordingly, only lithium ions, out of the two or more kinds of metal ions, were selectively captured by the capture release electrode 30 in the feed solution 10.

Thereafter, the capture release electrode 30 was taken out of the feed solution 10. Thereafter, the surface of the capture release electrode 30 was washed with a washing solvent (pure water), following which the capture release electrode 30 was dried.

Thereafter, the capture release electrode 30 was moved from the container chamber 81 to the container chamber 82. Thereafter, the capture release electrode 30 and the counter electrode 42 were coupled to the electric power source 52 (the electrochemical measurement system SP-150 available from BioLogic), following which the capture release electrode 30 was immersed in the recovery solution 20 (the second immersion process).

In the second immersion process, the capture release electrode 30 and the counter electrode 42 were energized by the electric power source 52 in the state where the capture release electrode 30 and the counter electrode 42 were immersed in the recovery solution 20. In this case, energization conditions of the second immersion process were set to be similar to the energization conditions of the first immersion process except that the energization direction of the second immersion process was set to be opposite to the energization direction of the first immersion process, and the electrolytic reaction was thus caused to proceed until a potential difference of the counter electrode 42 to the capture release electrode 30 reached −0.5 V. In the recovery solution 20, lithium ions were released from the capture release electrode 30, and hydroxide ions were generated in accordance with generation of hydrogen. As a result, lithium hydroxide was formed.

Accordingly, the extraction process was performed using the feed solution 10, the recovery solution 20, the capture release electrode 30, the counter electrodes 41 and 42, and the electric power sources 51 and 52. As a result, the extraction solution 90 including lithium hydroxide (lithium ions) was obtained.

Lastly, the capture release electrode 30 and the counter electrode 42 were taken out of the extraction solution 90, and the extraction solution 90 was recovered.

In addition, the extraction process was performed by a similar procedure except that the capture release electrode 30 was not energized using the counter electrode 42 in the second immersion process (Example 8).

In the second immersion process, the electrolytic reaction was caused to spontaneously proceed at the capture release electrode 30 by immersing the capture release electrode 30 solely in the recovery solution 20 (for an immersion time of 24 hours). Thus, the extraction process using the feed solution 10, the recovery solution 20, the capture release electrode 30, the counter electrode 41, and the electric power source 51 was performed. As a result, the extraction solution 90 including lithium hydroxide (lithium ions) was obtained.

For comparison, a process was performed by a similar procedure except that the capture release electrode 30 and the counter electrode 41 were not energized in the first immersion process (Comparative example 1).

For comparison, a test electrode (a platinum plate) was used instead of the capture release electrode 30, and an electrodialysis of the feed solution 10 was performed using a cation exchange membrane disposed between the test electrode and a counter electrode (a nickel foil) (Comparative example 2).

In the “Capture release electrode (Electrode particles)” column in Table 1, “* Electrodialysis (Cation exchange membrane)” represents that the electrodialysis was performed in Comparative example 2, instead of performing the extraction process using the capture release electrode 30.

To perform the electrodialysis, the feed solution 10 and the recovery solution 20 separated from each other by the cation exchange membrane (Nafion (registered trademark) 115) were prepared, and the test electrode was immersed in the feed solution 10 and the counter electrode was immersed in the recovery solution 20, following which the test electrode and the counter electrode were energized. In this case, energization conditions were set to be similar to the energization conditions of the first immersion process except that the test electrode was used instead of the capture release electrode 30. The recovery solution 20 after the energization was thus recovered as the extraction solution 90.

[Performance Evaluation of Extraction Process]

The extraction process was evaluated for performance in accordance with the following procedure, and the evaluation revealed the results presented in Table 1.

To examine the performance of the extraction process, first, the recovery solution 20 was analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) prior to the extraction process. The foregoing five kinds of metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, and calcium ions) were thereby quantitatively analyzed, and the concentration (g/dm³) of each of the five kinds of metal ions was thus measured.

Thereafter, the extraction solution 90 was analyzed by the ICP-AES after the extraction process to measure the concentration (g/dm³) of each of the five kinds of metal ions.

Lastly, a concentration increase amount (g/dm³) was calculated by subtracting the concentration after the extraction process from the concentration after the extraction process for each of the five kinds of metal ions. The concentration increase amount was an index for evaluating the performance of the extraction process.

	TABLE 1
	Capture release electrode
	(Electrode particles)

						Average
						particle		Counter

Feed solution

Recovery solution

size

Forming

electrode

	Kind	pH	Kind	Concentration	Kind	(nm)	method	Kind
Ex1	Salt water A	12	LiOH	10 mM	TiO2	30	Firing	Ni/Ni
Ex2	Salt water A	12	LiOH	10 mM	TiO2	7	Firing	Ni/Ni
Ex3	Salt water A	12	LiOH	10 mM	TiO2	100	Firing	Ni/Ni
Ex4	Salt water A	12	LiOH	10 mM	TiO2	200	Firing	Ni/Ni
Ex5	Salt water A	12	LiOH	10 mM	LTO	30	Firing	Ni/Ni
Ex6	Salt water A	12	LiOH	10 mM	TiO2	30	Firing	Ni/Ti
Ex7	Salt water A	12	LiOH	1M	TiO2	30	Firing	Ni/Ni
Ex8	Salt water A	12	Pure water	—	TiO2	30	Firing	Ni/—
Ex9	Salt water B	6	LiOH	10 mM	TiO2	30	Firing	Ni/Ni
Ex10	Salt water A	12	LiOH	10 mM	TiO2	100	Coating	Ni/Ni
Com1	Salt water A	12	LiOH	10 mM	TiO2	7	Firing	Ni/Ni

Com2	Salt water A	12	LiOH	10 mM	*Electrodialysis	—
					(Cation exchange
					membrane)

Electric power source

		First	Second	Concentration increase amount
		immersion	immersion	(g/dm3)

		process	process	Li+	Na+	K+	Mg2+	Ca2+
	Ex1	Energized	Energized	1.9	<0.01	<0.01	<0.01	<0.01
	Ex2	Energized	Energized	2.1	<0.01	<0.01	<0.01	<0.01
	Ex3	Energized	Energized	0.9	<0.01	<0.01	<0.01	<0.01
	Ex4	Energized	Energized	0.3	<0.01	<0.01	<0.01	<0.01
	Ex5	Energized	Energized	1.2	<0.01	<0.01	<0.01	<0.01
	Ex6	Energized	Energized	1.3	<0.01	<0.01	<0.01	<0.01
	Ex7	Energized	Energized	1.6	<0.01	<0.01	<0.01	<0.01
	Ex8	Energized	Not energized	0.8	<0.01	<0.01	<0.01	<0.01
	Ex9	Energized	Energized	0.7	<0.01	<0.01	<0.01	<0.01
	Ex10	Energized	Energized	0.2	<0.01	<0.01	<0.01	<0.01
	Com1	Not energized	Energized	<0.01	<0.01	<0.01	<0.01	<0.01
	Com2	—	—	0.08	5.1	8.1	<0.01	<0.01

As indicated in Table 1, the performance of the extraction process varied greatly depending on the procedure of the extraction process.

Specifically, when the feed solution 10, the recovery solution 20, the capture release electrode 30, and the counter electrode 41 were used but the capture release electrode 30 and the counter electrode 41 were not energized in the first immersion process (Comparative example 1), the concentration of lithium ions did not increase, and lithium ions were therefore not extracted.

When the electrodialysis with the cation exchange membrane was performed without performing the extraction process using the capture release electrode 30 (Comparative example 2), the concentration of lithium ions hardly increased, and lithium ions were therefore hardly extracted.

In contrast, when the feed solution 10, the recovery solution 20, the capture release electrode 30, and the counter electrode 41 were used, and the capture release electrode 30 and the counter electrode 41 were energized in the first immersion process (Examples 1 to 10), only the concentration of lithium ions greatly increased, and a large quantity of lithium ions was therefore extracted.

In this case, in particular, the following tendencies were obtained.

Firstly, when the pH of the feed solution 10 was higher than 10, the concentration of lithium ions further increased. Secondly, when anatase-type titanium dioxide and lithium titanate were used as the titanium oxide, the concentration of lithium ions sufficiently increased. Thirdly, when the firing method was used as the method of forming the capture release layer 30B and the capture release layer 30B thus had the porous structure, the concentration of lithium ions further increased. Fourthly, when the average particle size was 100 nm or smaller, the concentration of lithium ions increased more; and when the average particle size was 30 nm or smaller, the concentration of lithium ions increased even more. Fifthly, when the recovery solution 20 included the aqueous lithium hydroxide solution (having the concentration of 1 M or lower), the concentration of lithium ions increased more. Sixthly, when the capture release electrode 30 was energized in the second immersion process, the concentration of lithium ions increased more. Seventhly, when the nickel foil was used as the counter electrode 42, the concentration of lithium ions increased more.

Based upon the results presented in Table 1, when the extraction process was performed in which the feed solution 10, the recovery solution 20, the capture release electrode 30, and the counter electrode 41 were used and the capture release electrode 30 and the counter electrode 41 were energized in the first immersion process, the concentration of lithium ions greatly increased in the extraction solution 90. As a result, a large quantity of lithium ions was extracted. It was thus possible to highly accurately extract lithium ions.

Although the present technology has been described herein with reference to one or more embodiments including Examples, the configuration of the present technology is not limited thereto, and is therefore modifiable in a variety of ways.

The effects described herein are mere examples, and effects of the present technology are therefore not limited to those described herein. Accordingly, the present technology may achieve any other effect.

Note that the present technology may have any of the following configurations according to an embodiment.

<1>

An extraction apparatus including:

• • a first aqueous medium including two or more kinds of metal ions;
  • a second aqueous medium separated from the first aqueous medium;
  • a first electrode that is immersible in the first aqueous medium in a state of not being immersed in the second aqueous medium, and is immersible in the second aqueous medium in a state of not being immersed in the first aqueous medium;
  • a second electrode that is immersible in the first aqueous medium; and
  • a first electric power source coupled to the first electrode and the second electrode, in which
  • the two or more kinds of metal ions include a lithium ion,
  • the first electrode includes a titanium oxide,
  • the first electric power source is configured to energize the first electrode and the second electrode in a state where the first electrode and the second electrode are immersed in the first aqueous medium, and
  • the first electrode that has been energized in a state of being immersed in the first aqueous medium is immersible in the second aqueous medium.
    <2>

The extraction apparatus according to <1>, in which the titanium oxide selectively captures the lithium ion out of the two or more kinds of metal ions, and releases the lithium ion.

<3>

The extraction apparatus according to <1> or <2>, in which the first aqueous medium has a pH of higher than 10.

<4>

The extraction apparatus according to any one of <1> to <3>, in which the titanium oxide includes anatase-type titanium dioxide, lithium titanate (Li₄Ti₅O₁₂), or both.

<5>

The extraction apparatus according to any one of <1> to <4>, in which

• • the first electrode includes electrode particles,
  • the electrode particles each include the titanium oxide, and
  • the first electrode includes a porous structure in which the electrode particles are directly joined to each other.
    <6>

The extraction apparatus according to <5>, in which the electrode particles have an average particle size of 100 nanometers or smaller.

<7>

The extraction apparatus according to <6>, in which the average particle size is 30 nanometers or smaller.

<8>

The extraction apparatus according to any one of <5> to <7>, in which

• • the first electrode includes an electrode layer having the porous structure,
  • the electrode layer has a volume density of greater than or equal to 1.0 grams per cubic centimeter and less than or equal to 3.5 grams per cubic centimeter, and
  • the electrode layer has a specific surface area of greater than or equal to 1 square meter per gram and less than or equal to 500 square meters per gram.
    <9>

The extraction apparatus according to any one of <1> to <8>, in which

• • the second aqueous medium includes an aqueous lithium hydroxide solution, and
  • the aqueous lithium hydroxide solution has a concentration of 1 mole per cubic decimeter or lower.
    <10>

The extraction apparatus according to any one of <1> to <9>, further including:

• • a third electrode that is immersible in the second aqueous medium; and
  • a second electric power source coupled to the first electrode and the third electrode, in which
  • the second electric power source is configured to energize the first electrode and the third electrode in a state where the first electrode and the third electrode are immersed in the second aqueous medium.
    <11>

The extraction apparatus according to <10>, in which the third electrode includes at least one of titanium, platinum, iridium, nickel, iron, or palladium as a constituent element.

<12>

The extraction apparatus according to any one of <1> to <11>, further including a moving mechanism configured to move the first electrode between the first aqueous medium and the second aqueous medium.

<13>

The extraction apparatus according to any one of <1> to <12>, further including:

• • a first container member that contains the first aqueous medium; and
  • a first supplying mechanism configured to supply the first aqueous medium to the first container member.
    <14>

The extraction apparatus according to any one of <1> to <13>, further including:

• • a second container member that contains the second aqueous medium; and
  • a second supplying mechanism configured to supply the second aqueous medium to the second container member.
    <15>

An extraction method including:

• • immersing a first electrode and a second electrode in a first aqueous medium, the first electrode including a titanium oxide, the first aqueous medium including two or more kinds of metal ions including a lithium ion;
  • energizing the first electrode and the second electrode in a state where the first electrode and the second electrode are immersed in the first aqueous medium; and
  • immersing, in a second aqueous medium, the first electrode that has been energized in a state of being immersed in the first aqueous medium, the second aqueous medium being separated from the first aqueous medium.
    <16>

The extraction method according to <15>, further including:

• • additionally immersing a third electrode in the second aqueous medium; and
  • generating hydrogen at the third electrode by energizing the first electrode and the third electrode in a state where the first electrode and the third electrode are immersed in the second aqueous medium.
    <17>

A method of manufacturing lithium hydroxide, the method including:

• • immersing a first electrode and a second electrode in a first aqueous medium, the first electrode including a titanium oxide, the first aqueous medium including two or more kinds of metal ions including a lithium ion;
  • energizing the first electrode and the second electrode in a state where the first electrode and the second electrode are immersed in the first aqueous medium;
  • immersing, in a second aqueous medium, the first electrode that has been energized in a state of being immersed in the first aqueous medium and a third electrode, the second aqueous medium including pure water or an aqueous lithium hydroxide solution and being separated from the first aqueous medium; and
  • generating hydrogen at the third electrode by energizing the first electrode and the third electrode in a state where the first electrode and the third electrode are immersed in the second aqueous medium.

It should be understood that various changes and modifications to the embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.