Extraction apparatus, extraction method, and method for producing lithium hydroxide

Abstract

The present invention provides an extraction apparatus which is capable of extracting lithium ions with high accuracy. This extraction apparatus is provided with: a first aqueous medium which contains two or more kinds of metal ions; a second aqueous medium which is separated from the first aqueous medium; a first electrode which can be immersed in the first aqueous medium without being immersed in the second aqueous medium, and can be immersed in the second aqueous medium without being immersed in the first aqueous medium; a second electrode which can be immersed in the first aqueous medium; and a first power supply which is connected to the first electrode and the second electrode. The two or more kinds of metal ions include lithium ions, and the first electrode contains titanium oxide. The first power supply can energize the first electrode and the second electrode in the state where the first electrode and the second electrode are immersed in the first aqueous medium, and the first electrode that is energized while being immersed in the first aqueous medium can be immersed in the second aqueous medium.

Description

Extraction apparatus, extraction method, and method for producing lithium hydroxide

[0001] The present technology relates to an extraction apparatus, an extraction method, and a method for producing lithium hydroxide.

[0002] Since lithium hydroxide is important in various applications, including industrial applications, various techniques related to methods for producing lithium hydroxide are known.

[0003] Specifically, lithium is recovered by electrodialysis using a lithium adsorption layer containing lanthanum titanate as a separation membrane (see, for example, Patent Document 1). A purification process using an adsorbent and an impurity removal process using electrodialysis are combined (see, for example, Patent Document 2). Lithium is adsorbed onto an activated alumina porous body under alkaline conditions, and then desorbed from the activated alumina porous body to purify the lithium (see, for example, Patent Document 3). The negative electrode of an aqueous lithium-ion secondary battery contains anatase-type titanium oxide (see, for example, Patent Document 4).

[0004] Japanese Patent Application Publication No. 2017-131863 Japanese Patent Application Publication No. 2020-193130 Special Publication No. 2017-534563 International Publication No. 2020 / 218456 Pamphlet

[0005] Although various techniques related to the production of lithium hydroxide are known, there is still room for improvement as the extraction techniques for lithium ions are still insufficient.

[0006] There is a demand for an extraction device, an extraction method, and a method for producing lithium hydroxide that are capable of extracting lithium ions with high precision.

[0007] According to one embodiment of the present technology, an extraction device includes: a first aqueous medium containing two or more types of metal ions; a second aqueous medium separated from the first aqueous medium; a first electrode that can be immersed in the first aqueous medium without being immersed in the second aqueous medium and can be immersed in the second aqueous medium without being immersed in the first aqueous medium; a second electrode that can be immersed in the first aqueous medium; and a first power source connected to the first electrode and the second electrode. The two or more types of metal ions include lithium ions, and the first electrode contains titanium oxide. The first power source is capable of passing electricity through the first electrode and the second electrode while the first electrode and the second electrode are immersed in the first aqueous medium, and the first electrode, when immersed in the first aqueous medium, is immersable in the second aqueous medium.

[0008] In one embodiment of the present technology, an extraction method involves immersing a first electrode containing titanium oxide and a second electrode in a first aqueous medium containing two or more types of metal ions including lithium ions, passing a current through the first electrode and the second electrode while the first electrode and the second electrode are immersed in the first aqueous medium, and immersing the first electrode, to which a current is passed, while the first electrode is immersed in the first aqueous medium in a second aqueous medium separated from the first aqueous medium.

[0009] A method for producing lithium hydroxide in one embodiment of the present technology includes immersing a first electrode containing titanium oxide and a second electrode in a first aqueous medium containing two or more types of metal ions including titanium ions, and applying a current to the first and second electrodes while the first and second electrodes are immersed in the first aqueous medium; immersing the first electrode and a third electrode, which are immersed in the first aqueous medium, in a second aqueous medium containing pure water or a lithium hydroxide aqueous solution separated from the first aqueous medium; and applying a current to the first and third electrodes while the first and third electrodes are immersed in the second aqueous medium, thereby generating hydrogen at the third electrode.

[0010] According to one embodiment of the present technology, the extraction device is equipped with the first aqueous medium, the second aqueous medium, the first electrode, the second electrode, and the first power source having the above-mentioned configurations, and therefore can extract lithium ions with high precision.

[0011] According to the extraction method of one embodiment of the present technology, the treatment is performed using the first aqueous medium, the second aqueous medium, the first electrode, and the second electrode described above, so that lithium ions can be extracted with high precision.

[0012] According to the method for producing lithium hydroxide in one embodiment of the present technology, the treatment is performed using the first aqueous medium, the second aqueous medium, the first electrode, and the second electrode described above, and therefore, lithium ions can be extracted with high precision, thereby producing high-purity lithium hydroxide.

[0013] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below.

[0014] Fig. 1 is a block diagram showing the configuration of an extraction device in an embodiment of the present technology. Fig. 2 is an enlarged cross-sectional view showing the configuration of the occlusion-release electrode shown in Fig. 1. Fig. 3 is a schematic diagram showing an electron microscope photograph of the surface of the occlusion-release layer shown in Fig. 2. Fig. 4 is a block diagram for explaining an extraction method in an embodiment of the present technology. Fig. 5 is a block diagram for explaining an extraction step following Fig. 4. Fig. 6 is a block diagram for explaining an extraction step following Fig. 5. Fig. 7 is a block diagram showing the configuration of an extraction device in Modification 5. Fig. 8 is a block diagram for explaining the extraction step in Modification 5.

[0015] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be made in the following order: 1. Extraction device and extraction method 1-1. Configuration of extraction device 1-2. Procedure of extraction method 1-3. Actions and effects 2. Method for producing lithium hydroxide 3. Modified examples

[0016] 1. Extraction Device and Extraction Method An extraction device according to an embodiment of the present technology will be described.

[0017] Note that the extraction method according to an embodiment of the present technology is realized by an extraction processing procedure using the extraction device described here, and therefore the extraction method will also be described below.

[0018] The extraction device described here is used to perform a lithium ion extraction process (hereinafter simply referred to as "extraction process") by utilizing the properties of titanium oxide, which will be described later.

[0019] <1-1. Configuration of Extraction Device> First, the configuration of the extraction device will be described.

[0020] Fig. 1 shows a block diagram of an extraction device 100, which is a specific example of an extraction device. Fig. 2 shows an enlarged cross-sectional configuration of the absorption / emission electrode 30 shown in Fig. 1, and Fig. 3 shows a schematic electron microscope photograph of the surface of the absorption / emission layer 30B shown in Fig. 2.

[0021] 1, the extraction device 100 includes a raw material liquid 10, a recovery liquid 20, an occlusion / desorption electrode 30, a counter electrode 41, and a power supply 51. Here, the extraction device 100 further includes a counter electrode 42, a power supply 52, a moving mechanism 60, supply mechanisms 71 and 72, and storage tanks 81 and 82. In FIG. 1, the raw material liquid 10 and the recovery liquid 20 are each lightly shaded.

[0022] [Raw Material Liquid] As shown in FIG. 1, the raw material liquid 10 is a first aqueous medium used for performing the extraction treatment, and is contained in a container 81 .

[0023] The raw material solution 10 contains two or more kinds of metal ions, and the two or more kinds of metal ions are lithium ions (Li + That is, the two or more types of metal ions include lithium ions as well as one or more types of metal ions other than the lithium ions (hereinafter referred to as "additional metal ions").

[0024] The type of additional metal ion is not particularly limited, but specific examples include alkali metal ions, alkaline earth metal ions, and transition metal ions, although as mentioned above, lithium ions are excluded from the alkali metal ions described here.

[0025] Specific examples of alkali metal ions include sodium ions (Na + ) and potassium ions (K + ) and the like. Specific examples of alkaline earth metal ions include magnesium ions (Mg 2+ ) and calcium ions (Ca 2+ ) and the like. Specific examples of transition metal ions include iron ions (Fe 2+ ), manganese ions (Mn 2+ ), cobalt ions (Co 2+ ) and nickel ions (Ni 2+ ) etc.

[0026] Specifically, the raw material solution 10 contains one or more aqueous solvents containing two or more types of metal ions. Specific examples of aqueous solvents used as the raw material solution 10 include salt water, seawater, brine, and process waste liquid. Examples of process waste liquid include waste liquid generated in the synthesis of lithium compounds and waste liquid generated during the disposal of electronic devices containing lithium as a constituent material, such as lithium-ion secondary batteries.

[0027] In addition, when two or more types of metal ions contain one or more types of alkali metal ions together with lithium ions, it is preferable to use an extraction process using the extraction device 100. As will be described later, this is because when the occlusion / release electrode 30 is immersed in the raw material solution 10, the occlusion / release electrode 30 selectively occludes only lithium ions from among the two or more types of metal ions. As a result, even if lithium ions are mixed with one or more types of alkali metal ions, only lithium ions are extracted in the extraction process.

[0028] The "one or more types of alkali metal ions" described here refers to, as described above, any one or more types of alkali metal ions other than lithium ions, and more specifically, any one or more types of alkali metal ions such as sodium ions and potassium ions.

[0029] The pH of the raw material liquid 10 is not particularly limited. In particular, the raw material liquid 10 is preferably alkaline, and the pH of the raw material liquid 10 is more preferably higher than 10. This is because the absorption / desorption electrode 30 can more easily absorb lithium ions. This increases the amount of lithium ions absorbed in the absorption / desorption electrode 30.

[0030] In order to adjust the pH of the raw material solution 10, the raw material solution 10 may contain a pH adjuster. The type of pH adjuster is not particularly limited, but specifically, it is any one or more hydroxides such as sodium hydroxide (NaOH) and potassium hydroxide (KOH). The content of the pH adjuster in the raw material solution 10 is not particularly limited and can be set as desired.

[0031] [Recovery Liquid] As shown in FIG. 1, the recovery liquid 20 is a second aqueous medium used to recover lithium ions in the extraction process, and is contained in a storage tank 82.

[0032] Here, the recovery liquid 20 is different from the raw material liquid 10 contained in the storage tank 81, and is contained in the storage tank 82 as described above. As a result, the recovery liquid 20 is contained in the storage tank 82 which is different from the storage tank 81, and is therefore separated from the raw material liquid 10. In other words, the recovery liquid 20 is not mixed with the raw material liquid 10, but is physically separated from the raw material liquid 10.

[0033] The recovery solution 20 may contain lithium ions, but preferably does not contain additional metal ions, in order to improve the extraction efficiency of lithium ions in the extraction process.

[0034] Specifically, the recovery liquid 20 contains one or more aqueous solvents. Specific examples of aqueous solvents used as the recovery liquid 20 include pure water and deionized water.

[0035] However, the aqueous solvent may also be an aqueous solution in which an additive is dissolved. As will be described later, this additive is one or more of materials that promote the reduction reaction of substances contained in the recovery solution 20 (hereinafter referred to as "existing substances") and suppress side reactions that generate additional metal ions in the recovery solution 20. This additive is, for example, a lithium salt or an acid. A specific example of a lithium salt is lithium hydroxide, and specific examples of acids are hydrochloric acid, sulfuric acid, and nitric acid. An aqueous solvent containing lithium hydroxide as an additive (lithium salt) is a so-called lithium hydroxide aqueous solution.

[0036] The content of the additive in the aqueous solvent is not particularly limited, but it is preferable that it is sufficiently small. This is because the amount of additive is sufficient as long as it is an amount that facilitates the release of lithium ions from the storage / release electrode 30. Specifically, since the additive is lithium hydroxide, when the aqueous solvent is an aqueous solution of lithium hydroxide, the concentration of the aqueous solution of lithium hydroxide is preferably 1 M or less, and more preferably 0.1 mM to 1 M. The unit of concentration "M" explained here is mol / l (= mol / dm 3 )

[0037] In the extraction process, as will be described later, lithium ions are released from the storage / release electrode 30 into the recovery liquid 20, and an extract 90 containing the lithium ions is obtained (see FIG. 6 ). In the extract 90, new lithium compounds are formed using the lithium ions.

[0038] The detailed procedure of the extraction process using the extraction device 100 will be described later.

[0039] [Storage-release electrode] As shown in FIG. 1, the storage-release electrode 30 is a first electrode that stores and releases lithium ions.

[0040] The occlusion / release electrode 30 can be immersed in the raw material liquid 10 without being immersed in the recovery liquid 20 in a first immersion step described below, and can be immersed in the recovery liquid 20 without being immersed in the raw material liquid 10 in a second immersion step described below. In other words, the occlusion / release electrode 30 is not immersed in both the raw material liquid 10 and the recovery liquid 20 at the same time, but is immersed in each of the raw material liquid 10 and the recovery liquid 20 separately.

[0041] Here, the occlusion / release electrode 30 is immersed in the raw material liquid 10 together with the counter electrode 41 and in the recovery liquid 20 together with the counter electrode 42 during the extraction process.

[0042] Here, the absorption and desorption of lithium ions by the absorption and desorption electrode 30 means that lithium ions are taken into the absorption and desorption electrode 30 from the outside (raw material liquid 10) (= absorption), and that the lithium ions taken into the absorption and desorption electrode 30 are released to the outside (recovery liquid 20) (= desorption). For this reason, the phenomenon in which additional metal ions adhere to the surface of the absorption and desorption electrode 30 in the raw material liquid 10 and the additional metal ions are desorbed from the surface of the absorption and desorption electrode 30 in the recovery liquid 20 does not fall under the category of absorption and desorption described here.

[0043] In the extraction process, the occlusion / release electrode 30 is energized via a power source 51 while immersed in the raw material liquid 10. The occlusion / release electrode 30 energized while immersed in the raw material liquid 10 can be immersed in the recovery liquid 20. Here, the occlusion / release electrode 30 is energized via a power source 52 while immersed in the recovery liquid 20. That is, the occlusion / release electrode 30 is immersed in the raw material liquid 10, and then immersed in the recovery liquid 20.

[0044] 2, the occlusion / release electrode 30 includes a current collector 30A having a pair of surfaces and an occlusion / release layer 30B provided on both surfaces of the current collector 30A. However, the occlusion / release layer 30B may be provided on only one surface of the current collector 30A on the side where the occlusion / release electrode 30 faces the counter electrodes 41 and 42.

[0045] The current collector 30A may be omitted. That is, the occlusion / release electrode 30 does not include the current collector 30A, and may include only the occlusion / release layer 30B.

[0046] As will be described later, the occlusion / release electrode 30 is moved to a storage tank 81 via a moving mechanism 60, whereby it is immersed in the raw material liquid 10. Furthermore, as will be described later, the occlusion / release electrode 30 is moved to a storage tank 82 via the moving mechanism 60, whereby it is immersed in the recovery liquid 20.

[0047] (Current Collector) The current collector 30A is a conductive support member that supports the absorption / release layer 30B and includes one or more conductive materials such as metal materials, carbon materials, and conductive ceramic materials. Specific examples of metal materials include stainless steel (SUS), titanium, tin, lead, and alloys thereof. Specific examples of conductive ceramic materials include indium tin oxide (ITO).

[0048] The stainless steel may be a highly corrosion-resistant stainless steel to which one or more of the additive elements such as niobium and molybdenum have been added. Specifically, the stainless steel may be SUS444 or the like to which molybdenum has been added as an additive element.

[0049] In particular, it is preferable that the current collector 30A is insoluble or hardly soluble in the raw material liquid 10 and has corrosion resistance, and also has low reactivity with the plurality of electrode particles 31 described below. For this reason, it is preferable that the current collector 30A contains the above-mentioned metal material, and more preferably contains one or both of titanium and its alloy, because this makes the current collector 30A less susceptible to deterioration during the extraction process.

[0050] The current collector 30A may be a conductor whose surface is plated with the above-mentioned conductive material. The material for forming the conductor is not particularly limited and can be selected arbitrarily.

[0051] (Storage-release layer) The storage-release layer 30B is an electrode layer containing an electrode material, and the electrode material stores and releases lithium ions.

[0052] Specifically, as shown in Fig. 2, the occlusion / release layer 30B includes a plurality of electrode particles 31, which are a plurality of particulate electrode materials. Each of the plurality of electrode particles 31 is a so-called primary particle, and selectively occludes lithium ions from among two or more types of metal ions and releases the lithium ions.

[0053] Each of the plurality of electrode particles 31 contains one or more types of titanium oxides, because titanium oxides tend to selectively absorb and release lithium ions.

[0054] Titanium oxide is a general term for oxides containing titanium as a constituent element, and therefore titanium oxide may contain only titanium as a constituent element, or may contain two or more metal elements including titanium as constituent elements.

[0055] The type of titanium oxide is not particularly limited as long as the titanium oxide is capable of selectively absorbing and releasing lithium ions. Specific examples of titanium oxide include titanium oxide (TiO 2 ) and titanium composite oxides.

[0056] The type of titanium oxide is not particularly limited, and therefore the crystal structure of the titanium oxide is not particularly limited either. Thus, the titanium oxide may be anatase type titanium oxide, rutile type titanium oxide, brookite type titanium oxide, or a mixture of two or more of these types.

[0057] Among these, the titanium oxide is preferably anatase type titanium oxide, because anatase type titanium oxide is more likely to absorb and release lithium ions than rutile type titanium oxide and brookite type titanium oxide.

[0058] When examining the crystal structure of titanium oxide, the occlusion-release layer 30B is analyzed using X-ray diffraction (XRD), which makes it possible to identify the crystal structure (anatase, rutile, or brookite) of titanium oxide based on the difference in crystal structure.

[0059] The type of titanium composite oxide is not particularly limited, but specifically includes lithium titanium composite oxide containing lithium as a constituent element.

[0060] This lithium-titanium composite oxide is a compound represented by each of formulas (1) to (3), i.e., a ramsdellite-type lithium titanate. Here, M1 in formula (1) is a metal element that can become a divalent ion. M2 in formula (2) is a metal element that can become a trivalent ion. M3 in formula (3) is a metal element that can become a tetravalent ion.

[0061] Li [Li x M1 (1-3x) / 2 Ti (3+x) / 2 ]O 4 ...(1) (M1 is at least one of Mg, Ca, Cu, Zn, and Sr. x satisfies 0≦x≦1 / 3.)

[0062] Li [Li y M2 1-3y Ti 1+2y ]O 4 ...(2) (M2 is at least one of Al, Sc, Cr, Mn, Fe, Ga, and Y, and y satisfies 0≦y≦1 / 3.)

[0063] Li [Li 1 / 3 M3 z Ti (5 / 3)-z ]O 4 ... (3) (M3 is at least one of V, Zr, and Nb. z satisfies 0≦z≦2 / 3.)

[0064] The crystal structure of the lithium-titanium composite oxide is not particularly limited, but is preferably a spinel type, because the crystal structure is less likely to change when absorbing and releasing lithium ions.

[0065] Specific examples of the lithium titanium composite oxide shown in formula (1) include Li 3.75 Ti 4.875 Mg 0.375 O 12 Specific examples of the lithium titanium composite oxide shown in formula (2) include LiCrTiO 4 Specific examples of the lithium titanium composite oxide shown in formula (3) include Li 4 Ti 5 O 12 and Li 4 Ti 4.95 Nb 0.05 O 12 And so on.

[0066] Among them, lithium titanium composite oxide is lithium titanate (Li 4 Ti 5 O 12 ) is preferable because lithium titanate easily absorbs and releases lithium ions.

[0067] As a result, the titanium oxide is converted into anatase-type titanium oxide and lithium titanate (Li 4 Ti 5 O 12 ) is more preferably contained, because, as described above, titanium oxide can more easily absorb and release lithium ions.

[0068] In particular, it is preferable that the occlusion-release layer 30B has a porous structure as shown in Fig. 2. That is, it is preferable that the occlusion-release electrode 30 includes the occlusion-release layer 30B having a porous structure.

[0069] This porous structure is formed by directly bonding a plurality of electrode particles 31 to one another. That is, in the occlusion-release layer 30B, the plurality of electrode particles 31 are directly bonded to one another, thereby forming a plurality of voids (pores 32) between the plurality of electrode particles 31. As a result, the occlusion-release layer 30B has a porous structure formed by the plurality of electrode particles 31, as described above.

[0070] More specifically, the occlusion-release layer 30B is a sintered body of a plurality of electrode particles 31 formed by a firing method, and therefore the plurality of electrode particles 31 are directly bonded to one another inside the occlusion-release layer 30B. Details of the method for forming the occlusion-release layer 30B using this firing method will be described later.

[0071] As described above, "directly bonded to each other" means that the occlusion-release layer 30B is a sintered body of a plurality of electrode particles 31. That is, the plurality of electrode particles 31 are not indirectly bonded to each other via a binder, but are directly bonded to each other without the binder. Furthermore, since the plurality of electrode particles 31 are indirectly bonded to each other via a conductive agent, they are not electrically connected to each other via the conductive agent, but are directly bonded to each other without the conductive agent, and are therefore electrically connected to each other without the conductive agent.

[0072] The reason why the occlusion-release layer 30B is a sintered body of a plurality of electrode particles 31 and has a porous structure is that the plurality of electrode particles 31 are physically and electrically connected to one another, and thus lithium ions are easily absorbed and released in the occlusion-release layer 30B. This makes it easier for the extraction process using the occlusion-release electrode 30 to proceed smoothly and efficiently.

[0073] Here, the average particle size of the plurality of electrode particles 31 calculated based on the results of observation of the surface of the occlusion-release layer 30B using an electron microscope is preferably extremely small, more specifically, preferably 100 nm or less. That is, each of the plurality of electrode particles 31 is preferably so-called nanoparticles. This is because lithium ions can easily move inside each electrode particle 31 and multiple pores 32 that serve as lithium ion migration paths can easily be formed inside the occlusion-release layer 30B. This makes it easier for each of the plurality of electrode particles 31 to occlude and release lithium ions.

[0074] In particular, the average particle size is preferably 30 nm or less, because this allows each of the plurality of electrode particles 31 to more easily absorb and release lithium ions.

[0075] The lower limit of the average particle size is not particularly limited, but specifically, it is preferably 7 nm or more, because this makes it easier to form a plurality of electrode particles 31 stably.

[0076] The procedure for calculating the average particle size is as follows: To calculate this average particle size, an electron microscope photograph 200 shown in FIG.

[0077] Specifically, first, the extraction device 100 is disassembled to recover the absorption / release electrode 30. Next, the surface of the absorption / release layer 30B is observed using an electron microscope to obtain an electron microscope photograph 200. The type of electron microscope is not particularly limited, but specifically, it is any one or more of a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The observation conditions are not particularly limited, but specifically, an acceleration voltage of 5.0 kV and a magnification of 150,000 times are used.

[0078] In this case, the storage / release electrode 30 may be cut using an ion milling device or the like to expose a cross section of the storage / release layer 30B, and then the cross section of the storage / release layer 30B may be observed to obtain the electron microscope photograph 200. As this ion milling device, an ion milling device such as ArBlade (registered trademark) 5000 manufactured by Hitachi High-Tech Corporation may be used.

[0079] In the electron microscope photograph 200, as shown in Fig. 3, a porous structure having a plurality of pores 32 is observed because a plurality of electrode particles 31 are directly bonded to one another. In Fig. 3, in order to simplify the illustration, the planar shape of each of the plurality of electrode particles 31 is shown as a rectangle.

[0080] Next, 50 electrode particles 31 are selected from the plurality of electrode particles 31 visible in the electron microscope photograph 200, and then the particle size (maximum outer diameter) of each electrode particle 31 is measured. In this way, the particle sizes of the 50 electrode particles are obtained.

[0081] When selecting 50 electrode particles 31, the electrode particle 31 located closest to the front of the multiple overlapping electrode particles 31 is selected. That is, the electrode particle 31 (31Y) whose entire outer edge (outline) is not visible because it overlaps with one or more other electrode particles 31 is not selected. In contrast, the electrode particle 31 (31X) whose entire outer edge is visible because it does not overlap with one or more other electrode particles 31 is selected. In Figure 3, some of the electrode particles 31X to be selected are shaded.

[0082] Finally, the average value of the particle diameters of the 50 particles is calculated, and this average value is set as the average particle diameter.

[0083] As described above, the storage / release layer 30B is a sintered body of a plurality of electrode particles 31, and therefore preferably has characteristic structural conditions resulting from the sintered body.

[0084] That is, it is preferable that the volume density of the storage-release layer 30B is sufficiently large, more specifically, 1.0 g / cm 3 ~3.5g / cm 3 It is preferable that the specific surface area of ​​the storage / release layer 30B is sufficiently large, more specifically, 1 m 2 / g~500m 2 / g, and 10m 2 / g~500m 2 / g is more preferable because each of the plurality of electrode particles 31 can more easily absorb and release lithium ions.

[0085] The procedure for measuring the specific surface area of ​​the storage-release layer 30B is as follows. First, the extraction device 100 is disassembled to recover the storage-release electrode 30. Next, the storage-release electrode 30 is washed using a cleaning solvent, and then the storage-release electrode 30 is thoroughly dried using a vacuum heating furnace. In this case, an aqueous solvent such as pure water is used as the cleaning solvent, and the heating temperature is set to 60°C to 100°C. Finally, after degassing (200°C x 30 minutes), the specific surface area of ​​the storage-release layer 30B is measured using the BET method (nitrogen gas). As a measuring device, a fully automatic specific surface area measuring device such as Macsorb (registered trademark) manufactured by Mountech Co., Ltd. can be used.

[0086] The porosity of the plurality of pores 32 is not particularly limited, but is preferably 10% to 75%. The porosity is calculated based on the following formula: porosity (%) = [1 - (volume density of the occlusion-release layer 30B / true density of the occlusion-release layer 30B)] x 100.

[0087] The occlusion / release layer 30B may further contain one or more of other electrode materials that occlude and release lithium ions.

[0088] The type of other electrode material is not particularly limited, but specific examples include carbon materials and metal-based materials, etc. The metal-based material is a material that contains, as a constituent element, one or more of metal elements and semimetal elements that can form an alloy with lithium.

[0089] If the storage-release layer 30B contains other electrode materials, the following procedures may be taken to calculate the average particle size. Specifically, if the storage-release layer 30B contains a carbon material or a metal-based material as the other electrode material, the storage-release layer 30B is analyzed using energy dispersive X-ray analysis (EDX). In this case, the presence or location of the carbon material and the metal-based material can be confirmed using element mapping.

[0090] The storage-release layer 30B may further contain one or more of other materials, such as a binder, a surfactant, and a sintering aid.

[0091] 1 , the counter electrode 41 is a second electrode that can be immersed in the raw material liquid 10, and is immersed in the raw material liquid 10 together with the occlusion / desorption electrode 30. Here, the counter electrode 41 is immersed in the raw material liquid 10 in advance.

[0092] Specifically, the counter electrode 41 contains one or more types of conductive materials such as metal materials. The type of conductive material is not particularly limited, but it is preferable that the conductive material contains one or more types of metal elements such as nickel, manganese, iridium, tantalum, and platinum as constituent elements. This is because the occlusion / release electrode 30 can easily occlude lithium ions in the raw material solution 10. The conductive material may be a simple substance, an alloy, or a compound.

[0093] 1, the counter electrode 42 is a third electrode that can be immersed in the recovery liquid 20 together with the storage / desorption electrode 30. Here, the counter electrode 42 is immersed in the recovery liquid 20 in advance.

[0094] As will be described later, the counter electrode 42 is preferably stable in the reduction reaction, and more preferably facilitates the progress of the reduction reaction of the existing substances contained in the recovery liquid 20. This is because the absorption / desorption electrode 30 is more likely to release lithium ions in the recovery liquid 20. In addition, since the reduction reaction of the existing substances is more likely to progress, a sufficient amount of hydrogen is more likely to be generated in the reduction reaction even at a low voltage.

[0095] Specifically, the counter electrode 42 contains one or more types of conductive materials such as metal materials. The type of conductive material is not particularly limited, but it is preferable that the conductive material contains one or more types of metal elements such as titanium, platinum, iridium, nickel, iron, and palladium as constituent elements, and it is more preferable that the conductive material contains one or more types of metal elements such as platinum, iridium, nickel, iron, and palladium. As described above, the conductive material may be a simple substance, an alloy, or a compound.

[0096] [Power Supply] The power supply 51 is a first power supply connected to the occlusion / emission electrode 30 and the counter electrode 41. This power supply 51 can energize the occlusion / emission electrode 30 and the counter electrode 41 by passing a current between the occlusion / emission electrode 30 and the counter electrode 41.

[0097] Here, the power supply 51 supplies current to the occlusion / release electrode 30 and the counter electrode 41 in a state where the occlusion / release electrode 30 and the counter electrode 41 are immersed in the raw material liquid 10 (a first immersion step described later). Note that the power supply 51 does not supply current to the occlusion / release electrode 30 and the counter electrode 42 in a state where the occlusion / release electrode 30 and the counter electrode 42 are immersed in the recovery liquid 20 (a second immersion step described later).

[0098] The reason why the power source 51 is energized while the occlusion / release electrode 30 and the counter electrode 41 are immersed in the raw material solution 10 is to cause an electrolytic reaction to proceed between the occlusion / release electrode 30 and the counter electrode 41 in response to the energization. As a result, lithium ions are absorbed from the raw material solution 10 into the occlusion / release electrode 30 by utilizing the electrolytic reaction.

[0099] The power supply 52 is a second power supply connected to the occlusion / emission electrode 30 and the counter electrode 42. This power supply 52 can energize the occlusion / emission electrode 30 and the counter electrode 42 by passing a current between the occlusion / emission electrode 30 and the counter electrode 42.

[0100] Here, the power supply 52 supplies current to the occlusion / release electrode 30 and the counter electrode 42 in a state where the occlusion / release electrode 30 and the counter electrode 42 are immersed in the recovery liquid 20 (a second immersion step described later). In this case, the power supply 52 supplies current in a direction opposite to the direction in which the power supply 51 supplies current (direction in which current flows) in the first immersion step.

[0101] The reason why the power source 52 is energized while the occlusion / release electrode 30 and the counter electrode 42 are immersed in the recovery liquid 20 is to cause an electrolytic reaction to proceed between the occlusion / release electrode 30 and the counter electrode 42 in response to the energization. As a result, lithium ions are released from the occlusion / release electrode 30 into the recovery liquid 20 by utilizing the electrolytic reaction.

[0102] [Moving Mechanism] The moving mechanism 60 is a mechanism that can move the occlusion / release electrode 30 between the storage tank 81 and the storage tank 82, thereby moving the occlusion / release electrode 30 between the raw material liquid 10 and the recovery liquid 20.

[0103] The moving mechanism 60 moves while holding the occlusion / release electrode 30. In this way, the moving mechanism 60 immerses the occlusion / release electrode 30 in the raw material liquid 10 and removes the occlusion / release electrode 30 from the raw material liquid 10. The moving mechanism 60 also immerses the occlusion / release electrode 30 in the recovery liquid 20 and removes the occlusion / release electrode 30 from the recovery liquid 20.

[0104] [Supply Mechanism] The supply mechanism 71 is a mechanism capable of supplying the raw material liquid 10 to the storage tank 81 in order to replenish the raw material liquid 10. The supply mechanism 71 is connected to the storage tank 81 via a supply pipe (not shown), and is therefore capable of supplying the raw material liquid 10 to the storage tank 81 as needed.

[0105] Specifically, the supply mechanism 71 includes a tank, a pump, etc. (not shown). The tank stores the raw material liquid 10 to be supplied, and the pump uses pressure to push the raw material liquid 10 from the tank into the storage tank 81.

[0106] The supply mechanism 72 is a mechanism that can supply the recovery liquid 20 to the storage tank 82 in order to replenish the recovery liquid 20. The supply mechanism 72 is connected to the storage tank 82 via a supply pipe (not shown), and is therefore able to supply the recovery liquid 20 to the storage tank 82 as needed.

[0107] The configuration of the supply mechanism 72 is similar to that of the supply mechanism 71, except that it stores the recovery liquid 20 instead of the raw material liquid 10, and supplies the recovery liquid 20 to the storage tank 82 instead of supplying the raw material liquid 10 to the storage tank 81.

[0108] [Storage Tank] The storage tank 81 is a first storage member that stores the raw material liquid 10, and the storage tank 82 is a second storage member that stores the recovery liquid 20. The storage tanks 81 and 82 are separated from each other in order to separate the raw material liquid 10 and the recovery liquid 20 from each other.

[0109] [Others] The extraction device 100 may further include one or more of the other components.

[0110] A specific example of the other components is a control board, etc. This control board includes a control circuit board, etc., and is capable of controlling the overall operation of the extraction device 100.

[0111] <1-2. Procedure of Extraction Method> Next, the procedure of the extraction method using the extraction device 100 will be described.

[0112] 4 to 6 each show a block diagram corresponding to Fig. 1 in order to explain the extraction process. However, in each of Fig. 4 to 6, only the main parts of the extraction device 100 involved in the extraction process are shown, and in Fig. 6, the extraction liquid 90 is shaded darkly.

[0113] In the following, a procedure for producing the storage / release electrode 30 will be described, and then an extraction procedure using the extraction device 100 will be described.

[0114] [Procedure for Producing the Storage and Release Electrode] When producing the storage and release electrode 30, first, a mixture is obtained by mixing a plurality of electrode particles 31 containing titanium oxide with a binder. The composition (mixing ratio) of the mixture is not particularly limited and can be set as desired. In this case, one or more types of additives may be added to the mixture. The type of additive is not particularly limited, but specific examples include a surfactant and a sintering aid.

[0115] The type of binder is not particularly limited, as long as it is one or more of the polymer compounds mixed with the plurality of electrode particles 31 for the purpose of improving the strength of the powder compact described below. Specific examples of the polymer compounds include polyethylene glycol, polyvinyl alcohol, and polyvinyl butyral. Of these, the binder is preferably a polymer compound that is decomposed and degreased at a temperature equal to or lower than the temperature at which titanium oxide is fired. Specific examples of surfactants include stearic acid, and specific examples of sintering aids include boron oxide and silicon oxide.

[0116] As a result, a granulated powder containing the plurality of electrode particles 31 and the binder is obtained.

[0117] Next, the granulated powder is placed on both sides of the current collector 30A, and then the granulated powder is press-molded together with the current collector 30A. Conditions such as the pressing pressure can be set as desired. As a result, the granulated powder containing the plurality of electrode particles 31 is fixed to both sides of the current collector 30A, thereby obtaining a powder compact.

[0118] Finally, the powder compact is sintered in the atmosphere. The sintering conditions, such as the sintering temperature and sintering time, can be set as desired depending on the composition of the powder compact. In this case, the sintering conditions are adjusted so that the plurality of electrode particles 31 containing titanium oxide are directly bonded to each other while maintaining the primary particle state. As an example, the maximum temperature during sintering is 500°C to 1200°C. The sintering process may also be performed in an oxygen atmosphere.

[0119] In this firing process, the binder is degreased during firing, so that the plurality of electrode particles 31 are directly bonded to one another and a plurality of pores 32 are formed between the plurality of electrode particles 31. As a result, a bonded body (sintered body) of the plurality of electrode particles 31 is fixed to the surface of the current collector 30A, so that the storage-release layer 30B having a porous structure is formed. Thus, the storage-release electrode 30 is produced.

[0120] When manufacturing this occlusion / release electrode 30, by appropriately adjusting the conditions such as the pressing pressure, firing temperature, and firing time described above, it is possible to adjust the bonding state of the multiple electrode particles 31 (multiple primary particles) and also to adjust the volume density and specific surface area of ​​the occlusion / release layer 30B.

[0121] [Extraction Procedure Using Extraction Apparatus] In the extraction process using the extraction apparatus 100, first, the supply mechanism 71 supplies the raw material liquid 10 to the storage tank 81, and the supply mechanism 72 supplies the recovery liquid 20 to the storage tank 82. As a result, the raw material liquid 10 is stored in the storage tank 81, and the recovery liquid 20 is stored in the storage tank 82.

[0122] As described above, the raw material solution 10 contains two or more types of metal ions including lithium ions, and the counter electrode 41 is immersed in the raw material solution 10 in advance, as described above.

[0123] As described above, the recovery liquid 20 is separated from the raw material liquid 10, and the counter electrode 42 is immersed in the recovery liquid 20 in advance.

[0124] Next, the moving mechanism 60 moves the occlusion / release electrode 30 to the storage tank 81, thereby immersing the occlusion / release electrode 30 in the raw material liquid 10, as shown in Fig. 4. As a result, the occlusion / release electrode 30 is immersed in the raw material liquid 10 together with the counter electrode 41. Hereinafter, the step of immersing the occlusion / release electrode 30 in the raw material liquid 10 together with the counter electrode 41 will be referred to as a "first immersion step."

[0125] Subsequently, in a first immersion step (a state in which the occlusion / release electrode 30 and the counter electrode 41 are immersed in the raw material liquid 10 ), the power source 51 applies electricity to the occlusion / release electrode 30 and the counter electrode 41 .

[0126] In response to this current flow, an electrolytic reaction proceeds between the occlusion / release electrode 30 and the counter electrode 41. In this case, the occlusion / release electrode 30 (plurality of electrode particles 31) is reduced in the raw material solution 10. As a result, each of the plurality of electrode particles 31 reacts with the lithium ions, but each of the plurality of electrode particles 31 does not react with the additional metal ions.

[0127] Therefore, each of the plurality of electrode particles 31 selectively occludes only lithium ions from among two or more types of metal ions in the raw material liquid 10. As a result, only lithium ions from among the two or more types of metal ions are extracted by each of the plurality of electrode particles 31.

[0128] The current flow conditions, such as the current value and the time for which the current is applied, are not particularly limited and can be set arbitrarily.

[0129] Next, the moving mechanism 60 removes the occlusion / release electrode 30 from the storage tank 81. Next, if necessary, the occlusion / release electrode 30 may be washed with a washing solvent, and then the occlusion / release electrode 30 may be dried. The type of washing solvent is not particularly limited, but specifically, it is the same as the type of aqueous solvent contained in the recovery liquid 20. By washing the occlusion / release electrode 30 in this way, unnecessary additional metal ions attached to the surface of the occlusion / release electrode 30 are removed.

[0130] Next, the moving mechanism 60 moves the occlusion / release electrode 30 from the storage tank 81 to the storage tank 82, thereby immersing the occlusion / release electrode 30 in the recovery liquid 20, as shown in Fig. 5. As a result, the occlusion / release electrode 30 to which electricity has been applied in the first immersion step is immersed in the recovery liquid 20 together with the counter electrode 42. Hereinafter, the step of immersing the occlusion / release electrode 30 together with the counter electrode 42 in the recovery liquid 20 will be referred to as the "second immersion step."

[0131] Subsequently, in a second immersion step (a state in which the occlusion / release electrode 30 and the counter electrode 42 are immersed in the recovery liquid 20), the power source 52 applies current to the occlusion / release electrode 30 and the counter electrode 42. The current application direction in the second immersion step is opposite to the current application direction in the first immersion step.

[0132] In response to this current flow, an electrolytic reaction proceeds between the occlusion / release electrode 30 and the counter electrode 42. In this case, the occlusion / release electrode 30 (the plurality of electrode particles 31) is oxidized in the recovery liquid 20, and the existing substances contained in the recovery liquid 20 are reduced. As a result, each of the plurality of electrode particles 31 releases lithium ions in the recovery liquid 20.

[0133] The type of reduction reaction of the existing substance is not particularly limited as long as it is a reaction that does not generate metal ions. Here, as described above, since the recovery liquid 20 contains an aqueous solvent such as pure water or deionized water, when the aqueous solvent is reduced, hydrogen and hydroxide ions are generated.

[0134] 6, an extract 90 containing lithium ions released from the occlusion / release electrode 30 is obtained. Since lithium ions have been released into the extract 90, if hydroxide ions have been generated, new lithium hydroxide is formed.

[0135] Finally, the extract 90 is collected. The extract 90 contains the lithium ions obtained by the extraction process, and more specifically, lithium hydroxide. This completes the extraction process using the extraction device 100, as the lithium ions are collected.

[0136] Thereafter, the supply mechanism 71 supplies the raw material liquid 10 to the storage tank 81 as needed to replenish the raw material liquid 10. Furthermore, the supply mechanism 72 supplies the recovery liquid 20 to the storage tank 82 as needed to replenish the recovery liquid 20.

[0137] In the above description of the extraction process, the extraction process using the extraction device 100 is performed only once. However, the extraction process using the extraction device 100 may be repeated multiple times. By repeating the extraction process multiple times, the amount of recovered lithium ions increases. In this case, the movement mechanism 60 moves the occlusion / release electrode 30 between the storage tank 81 and the storage tank 82, and the extraction process using the occlusion / release electrode 30 is repeated.

[0138] <1-3. Actions and Effects> According to the extraction device 100, the extraction device 100 comprises the raw material liquid 10, the recovery liquid 20, the occlusion / release electrode 30, the counter electrodes 41, 42, and the power sources 51, 52 having the above-described configurations.

[0139] In this case, as described above, the extraction process is carried out using the raw material liquid 10, the recovery liquid 20, the occlusion / release electrode 30, the counter electrodes 41, 42, and the power sources 51, 52, and the lithium ions are extracted and recovered by utilizing the characteristics of the occlusion / release electrode 30.

[0140] Specifically, in the first immersion step (a state in which the occlusion / release electrode 30 and the counter electrode 41 are immersed in the raw material solution 10), the power source 51 supplies electricity to the occlusion / release electrode 30 and the counter electrode 41. As a result, by utilizing the properties of the occlusion / release electrode 30 containing titanium oxide, only lithium ions are selectively occluded by the occlusion / release electrode 30 from among the plurality of metal ions in the raw material solution 10.

[0141] Furthermore, in the second immersion step following the first immersion step (in which the occlusion / release electrode 30 and the counter electrode 42 are immersed in the recovery liquid 20), lithium ions are released from the occlusion / release electrode 30 into the recovery liquid 20 by utilizing the characteristics of the occlusion / release electrode 30 containing titanium oxide.

[0142] As a result, the extraction process is carried out, and an extract 90 containing extracted lithium ions is obtained.

[0143] For these reasons, only lithium ions from among the multiple metal ions in the recovery liquid 20 are selectively absorbed by the absorption / desorption electrode 30, and the lithium ions are released from the absorption / desorption electrode 30 into the recovery liquid 20, so that only the lithium ions are selectively recovered. Therefore, lithium ions can be extracted with high precision.

[0144] In this case, lithium ions are extracted using an electrolytic reaction, and therefore, compared to the case where an adsorbent for adsorbing lithium ions is used, the extraction process can be performed without using the adsorbent, which makes it possible to easily and quickly perform the extraction process and also improve the extraction efficiency of the extraction process.

[0145] Furthermore, by utilizing the characteristics of the occlusion-release layer 30B (the plurality of electrode particles 31 containing titanium oxide), it is possible to selectively extract only lithium ions from the plurality of metal ions easily and with high precision, compared to the case of using electrodialysis (cation exchange membrane), which has difficulty in selectively extracting only lithium ions from the plurality of metal ions. Therefore, the extraction process can be performed more easily and quickly, and the extraction efficiency of the extraction process can also be improved.

[0146] In addition, if the pH of the raw material solution 10 is higher than 10, the amount of lithium ions absorbed in the absorption / desorption electrode 30 increases, and therefore a greater effect can be obtained.

[0147] In addition, titanium oxide is anatase type titanium oxide and lithium titanate (Li 4 Ti 5 O 12 ) the titanium oxide can more easily absorb and release lithium ions, thereby achieving a higher effect.

[0148] Furthermore, if the occlusion / release electrode 30 contains a plurality of electrode particles 31, each of which contains titanium oxide, and the occlusion / release electrode 30 has a porous structure in which the plurality of electrode particles 31 are directly bonded to each other, lithium ions can be more easily absorbed and released in the occlusion / release electrode 30, thereby achieving a greater effect.

[0149] In this case, if the average particle size of the plurality of electrode particles 31 is 100 nm or less, each of the plurality of electrode particles 31 can more easily absorb and release lithium ions, thereby achieving a higher effect. In particular, if the average particle size is 30 nm or less, each of the plurality of electrode particles 31 can more easily absorb and release lithium ions, thereby achieving an even higher effect.

[0150] The storage / release electrode 30 includes a storage / release layer 30B having a porous structure, and the volume density of the storage / release layer 30B is 1.0 g / cm 3 ~3.5g / cm3 and the specific surface area of ​​the occlusion / release layer 30B is 1 m 2 / g to 500m 2 / g, each of the plurality of electrode particles 31 can easily absorb and release lithium ions, and therefore a higher effect can be obtained.

[0151] Furthermore, if the recovery liquid 20 contains a lithium hydroxide aqueous solution and the concentration of the lithium hydroxide aqueous solution is 1 M or less, lithium ions are more easily released from the occlusion / release electrode 30 in the recovery liquid 20, thereby achieving a greater effect.

[0152] Furthermore, if the counter electrode 42 contains one or more of platinum, iridium, nickel, iron, and palladium as constituent elements, lithium ions are more easily released from the occlusion / release electrode 30 in the recovery liquid 20, thereby achieving a greater effect.

[0153] Furthermore, if the extraction device 100 further includes a moving mechanism 60 that moves the occlusion / release electrode 30 between the raw material liquid 10 and the recovery liquid 20, the lithium ion occlusion process using the raw material liquid 10 and the lithium ion release process using the recovery liquid 20 are automatically and continuously performed. Therefore, the extraction process can be performed efficiently in a short time, and a higher effect can be obtained.

[0154] Furthermore, if the extraction apparatus 100 further includes a supply mechanism 71 for supplying the raw material liquid 10 to the storage tank 81, the raw material liquid 10 can be replenished to the storage tank 81 as needed. Therefore, the extraction process can be carried out efficiently in a short time, and a higher effect can be obtained.

[0155] Furthermore, if the extraction device 100 further includes a supply mechanism 72 for supplying the recovery liquid 20 to the storage tank 82, the recovery liquid 20 can be replenished to the storage tank 82 as needed. Therefore, the extraction process can be carried out efficiently in a short time, thereby achieving a higher effect.

[0156] Furthermore, according to the extraction method using the extraction apparatus 100, an extraction process is performed using the raw material solution 10, the recovery solution 20, the occlusion / release electrode 30, the counter electrodes 41, 42, and the power sources 51, 52, as realized by the operation of the extraction apparatus 100 described above. In this case, for the reasons described above, only lithium ions from among the multiple metal ions in the recovery solution 20 are selectively occluded by the occlusion / release electrode 30, and lithium ions are released from the occlusion / release electrode 30 in the recovery solution 20, so that only those lithium ions are selectively recovered. Therefore, lithium ions can be extracted with high precision.

[0157] 2. Method for Producing Lithium Hydroxide Here, a description will be given of a method for producing lithium hydroxide, which is an application example of the extraction process using the extraction apparatus 100. By applying this extraction process, high-purity lithium hydroxide can be produced.

[0158] The procedure for producing lithium hydroxide is generally similar to the extraction procedure already described, except as follows: Reference is made below to Figures 1 to 6 already described.

[0159] Specifically, first, the absorption / desorption electrode 30 containing titanium oxide is immersed together with the counter electrode 41 in the raw material solution 10 containing two types of metal ions, including lithium ions (first immersion step). Details of the raw material solution 10, the absorption / desorption electrode 30, and the counter electrode 41 are as described above.

[0160] Subsequently, in a first immersion step (a state in which the occlusion / release electrode 30 and the counter electrode 41 are immersed in the raw material liquid 10), a current is applied to the occlusion / release electrode 30 and the counter electrode 41. As a result, the occlusion / release electrode 30 selectively occludes only lithium ions from among two or more types of metal ions in the raw material liquid 10.

[0161] Next, the occlusion / release electrode 30 is taken out from the raw material liquid 10. Next, if necessary, the occlusion / release electrode 30 may be washed with a washing solvent, and then dried. Details regarding the washing solvent are as described above.

[0162] Next, the absorption / desorption electrode 30 to which electricity has been applied in the first immersion step is immersed together with the counter electrode 42 in the recovery liquid 20 separated from the raw material liquid 10 (second immersion step). This recovery liquid 20 contains pure water or a lithium hydroxide aqueous solution. Details regarding the counter electrode 42 and the lithium hydroxide aqueous solution are as described above.

[0163] Subsequently, in a second immersion step (a state in which the occlusion / release electrode 30 and the counter electrode 42 are immersed in the recovery liquid 20), current is applied to the occlusion / release electrode 30 and the counter electrode 42 to generate hydrogen at the counter electrode 42. As a result, the occlusion / release electrode 30 releases lithium ions in the recovery liquid 20 and hydroxide ions are generated, thereby obtaining an extract 90 containing lithium hydroxide.

[0164] Finally, the extract 90 is collected, thereby obtaining lithium hydroxide.

[0165] This method for producing lithium hydroxide utilizes the extraction method described above. Therefore, for the reasons described above, lithium ions are extracted with high precision, and high-purity lithium hydroxide can be produced using the lithium ions.

[0166] 3. Modifications The configuration of the extraction apparatus 100 and the procedure of the extraction method can be modified as appropriate, as described below. However, any two or more of the series of modifications described below may be combined with each other. Furthermore, the series of modifications described below may be applied to a method for producing lithium hydroxide.

[0167] 1, the extraction device 100 includes two types of power supplies: a power supply 51 that supplies current to the occlusion / release electrode 30 and the counter electrode 41 in the first immersion step, and a power supply 52 that supplies current to the occlusion / release electrode 30 and the counter electrode 42 in the second immersion step.

[0168] However, although not specifically illustrated here, the extraction device 100 may be provided with only one type of power supply. This power supply is connected to the storage / release electrode 30 and the counter electrodes 41 and 42, and therefore energizes the storage / release electrode 30 and the counter electrode 41 in the first immersion step, and energizes the storage / release electrode 30 and the counter electrode 42 in the second immersion step.

[0169] In this case, the extraction process is performed using the extraction device 100, and therefore the same effect can be obtained.

[0170] 1, the extraction device 100 includes two types of counter electrodes: a counter electrode 41 that is immersed in the raw material liquid 10 together with the occlusion / release electrode 30, and a counter electrode 42 that is immersed in the recovery liquid 20 together with the occlusion / release electrode 30.

[0171] However, although not specifically shown here, if the counter electrode 41 and the counter electrode 42 are made of the same material, the extraction device 100 may be provided with only one type of counter electrode. This counter electrode is moved together with the occlusion / release electrode 30 to the storage tank 81 via the moving mechanism 60, and is immersed together with the occlusion / release electrode 30 in the raw material liquid 10, and is moved together with the occlusion / release electrode 30 to the storage tank 82 via the moving mechanism 60, and is immersed together with the occlusion / release electrode 30 in the recovery liquid 20.

[0172] In this case, the extraction process is performed using the extraction device 100, and therefore the same effect can be obtained.

[0173] [Variation 3] In the manufacturing process of the storage / release electrode 30, a method of firing a powder compact containing a binder (firing method) was used to form the storage / release layer 30B having a porous structure. However, the manufacturing procedure of the storage / release electrode 30 can be changed as appropriate as long as the storage / release layer 30B is formed by directly bonding a plurality of electrode particles 31 to each other using the firing process.

[0174] Specifically, a plurality of electrode particles 31 may be press-molded without using a binder to obtain a powder compact, and then the powder compact may be fired.

[0175] Alternatively, a dispersion liquid in which a plurality of electrode particles 31 are dispersed may be applied to the current collector 30A, and then the dispersion liquid may be dried. In this case, after the dispersion liquid is dried, the current collector 30A to which the dispersion liquid is applied may be fired.

[0176] In these cases, the occlusion / release layer 30B having a porous structure is formed, and therefore the same effect can be obtained.

[0177] [Modification 4] The occlusion-release layer 30B has a porous structure as shown in Fig. 2. However, although not specifically shown here, the occlusion-release layer 30B does not have to have a porous structure.

[0178] The occlusion-release layer 30B, which does not have a porous structure, contains a plurality of electrode particles 31 and a binder. However, as described above, the occlusion-release layer 30B may further contain other electrode materials. In this occlusion-release layer 30B, the plurality of electrode particles 31 are bound to one another via the binder. Details regarding the electrode particles 31 and the binder are as described above.

[0179] The occlusion-release layer 30B is formed using a coating method instead of a firing method. To form the occlusion-release layer 30B, first, a mixture is obtained by mixing a plurality of electrode particles 31 with a binder. Details regarding the type of binder are as described above. However, the binder may be a polymer compound such as polyvinylidene fluoride. Next, a paste-like slurry is prepared by adding the mixture to a solvent. This solvent may be an aqueous solvent or an organic solvent. The slurry is then applied to both sides of the current collector 30A to form the occlusion-release layer 30B. The occlusion-release layer 30B may then be compression-molded using a roll press or the like. In this case, the occlusion-release layer 30B may be heated, or the occlusion-release layer 30B may be compression-molded multiple times.

[0180] In this case, the same effect can be obtained because lithium ions are selectively absorbed and released in the absorption / release layer 30B.

[0181] However, it is preferable that the occlusion / release layer 30B has a porous structure rather than not having a porous structure, because this allows the occlusion / release layer 30B to more easily occlude and release lithium ions.

[0182] [Variation 5] In FIG. 1, the extraction device 100 includes the counter electrode 42 and the power supply 52, and therefore, as shown in FIG. 5, the power supply 52 applies electricity to the storage / release electrode 30 and the counter electrode 42 in the second immersion step.

[0183] However, as shown in FIG. 7 corresponding to FIG. 1, the extraction device 100 does not include the counter electrode 42 and the power supply 52. ​​Therefore, as shown in FIG. 8 corresponding to FIG. 5, in the second immersion step, only the occlusion / release electrode 30 is immersed in the recovery liquid 20, and no current is required to be applied to the occlusion / release electrode 30.

[0184] 8, as described above, the occlusion / release electrode 30 that was energized in the first immersion step is immersed alone in the recovery liquid 20, and no current is applied to the occlusion / release electrode 30. In Fig. 8, the power source 51 used for energizing the occlusion / release electrode 30 in the first immersion step is shown moved to the storage tank 82 together with the occlusion / release electrode 30, but the power source 51 does not apply current to the occlusion / release electrode 30 in the second immersion step.

[0185] In this second immersion step (a state in which the occlusion / release electrode 30 is immersed in the recovery liquid 20), even if no current is applied to the occlusion / release electrode 30, an electrolytic reaction proceeds spontaneously in the occlusion / release electrode 30. In this case, similar to the case in which current is applied to the occlusion / release electrode 30 in the second immersion step, the occlusion / release electrode 30 (the plurality of electrode particles 31) is oxidized in the recovery liquid 20, and existing substances contained in the recovery liquid 20 are reduced. As a result, each of the plurality of electrode particles 31 releases lithium ions into the recovery liquid 20, and when the aqueous solvent contained in the recovery liquid 20 is reduced, hydroxide ions are generated in response to the generation of hydrogen.

[0186] In this case, the same effect can be obtained because lithium ions are released from the occlusion / release electrode 30 in the recovery liquid 20.

[0187] However, it is preferable to pass a current through the occlusion-release electrode 30 in the second immersion step rather than not passing a current through the occlusion-release electrode 30 in the second immersion step, because this makes it easier for lithium ions to be efficiently released from the occlusion-release electrode 30 in the recovery liquid 20.

[0188] Here, since no current is applied to the occlusion / release electrode 30 in the second immersion step, as described above, the extraction device 100 does not include the counter electrode 42 or the power supply 52. ​​However, if no current is applied to the occlusion / release electrode 30 in the second immersion step, the extraction device 100 may include one or both of the counter electrode 42 and the power supply 52.

[0189] An embodiment of the present technology will be described.

[0190] Examples 1 to 10 and Comparative Examples 1 and 2 As described below, the performance of the extraction process was evaluated by carrying out the above-mentioned extraction process. Here, in order to perform a simple evaluation, the extraction process was carried out manually without using an extraction device.

[0191] In Table 1, for the sake of simplicity, examples are simply referred to as "Example" and comparative examples are simply referred to as "Comparative." For example, "Example 1" means Example 1, and "Comparative 1" means Comparative Example 1.

[0192] [Extraction Process] Here, the occlusion / emission electrode 30 was fabricated according to the procedure described below, and then the extraction process was carried out using the occlusion / emission electrode 30 .

[0193] (Fabrication of Storage and Release Electrode) Here, the storage and release layer 30B was formed by a firing method to fabricate the storage and release electrode 30 (Examples 1 to 9). "Firing" shown in the "Forming method" column in Table 1 indicates that the firing method was used as the method for forming the storage and release layer 30B.

[0194] First, 100 parts by mass of a plurality of electrode particles 31 (powdered titanium oxide), 10 parts by mass of a binder (polyethylene glycol), and 1 part by mass of a surfactant (Triton X (registered trademark) surfactant manufactured by Nacalai Tesque, Inc.) were mixed together to obtain a granulated powder.

[0195] Titanium oxides include anatase-type titanium oxide (TiO 2 ) and lithium titanium composite oxide lithium titanate (Li 4 Ti 5 O 12 The average particle size (nm) of the plurality of electrode particles 31 was as shown in Table 1.

[0196] Next, the current collector 30A (mesh-like titanium foil having a thickness of 200 μm) and the granulated powder were press-molded together using a press (pressing pressure: 100 MPa) to obtain a powder molded body.

[0197] Finally, the powder molded body was fired in the atmosphere (firing temperature = 750°C). As a result, the plurality of electrode particles 31 were directly bonded to each other, and therefore, occlusion / release layers 30B, which were sintered bodies of the plurality of electrode particles 31, were formed on both sides of the current collector. In this way, the occlusion / release electrode 30 was produced.

[0198] Volume density (g / cm 3 ) and specific surface area (m 2 / g) was as explained below. When the average particle size was 7 nm, the volume density was 2.0 g / cm 3 and specific surface area = 109 m 2 When the average particle size was 30 nm, the volume density was 1.9 g / cm 3 and specific surface area = 40 m 2 When the average particle size was 100 nm, the volume density was 2.0 g / cm 3 and specific surface area = 21 m 2 When the average particle size was 200 nm, the volume density was 2.0 g / cm 3 and specific surface area = 8 m 2 / g.

[0199] In addition, an occlusion / release electrode 30 was fabricated by the same procedure except that the occlusion / release layer 30B was formed by a coating method instead of a firing method (Example 10). "Coating" shown in the "Formation method" column in Table 1 indicates that the coating method was used as the method for forming the occlusion / release layer 30B.

[0200] The procedure for forming the storage-release layer 30B using the coating method is the same as the procedure for forming the storage-release layer 30B using the firing method, except as described below. First, 100 parts by mass of a plurality of electrode particles 31 (powdered titanium oxide) and 4 parts by mass of a binder (polyvinylidene fluoride) were mixed together to obtain a mixture. Next, the mixture was poured into a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the solvent was stirred to prepare a paste-like slurry. Finally, the slurry was applied to both sides of the current collector 30A using a coating device, and the slurry was dried to form the storage-release layer 30B.

[0201] (Extraction Treatment Using the Storage and Release Electrode) Here, the extraction treatment was carried out by passing a current through the storage and release electrode 30 in the second immersion step (Examples 1 to 7, 9, and 10).

[0202] First, raw material liquid 10 was stored in storage tank 81, and recovery liquid 20 was stored in storage tank 82. Subsequently, counter electrode 41 (nickel foil (Ni)) was immersed in raw material liquid 10, and counter electrode 42 (nickel foil or titanium foil (Ti)) was immersed in recovery liquid 20.

[0203] The column "Counter electrode (type)" in Table 1 indicates the material of the counter electrode 41 and the material of the counter electrode 42. For example, in the notation "Ni / Ni", the "Ni" on the left side indicates that nickel foil was used as the counter electrode 41, and the "Ni" on the right side indicates that nickel foil was used as the counter electrode 42.

[0204] Two types of salt water (salt water A and salt water B) were used as the raw material solution 10. The raw material solution 10 contains lithium ions (Li + ) and sodium ions (Na + ) and potassium ions (K + ) and magnesium ions (Mg 2+ ) and calcium ions (Ca 2+ The pH of the raw material solution 10 was as shown in Table 1.

[0205] The concentration of each metal ion (g / l (= g / dm 3 ) was as follows: Lithium ion = 2.9 g / dm 3 Sodium ion = 56 g / dm 3 Potassium ion = 29 g / dm 3 Magnesium ion = 0.03 g / dm 3 Calcium ion = 0.02 g / dm 3

[0206] The concentration of each metal ion (g / dm 3 ) was as follows: Lithium ion = 3 g / dm 3 Sodium ion = 10 g / dm 3 Potassium ion = 10 g / dm 3 Magnesium ion = 1 g / dm 3 Calcium ion = 1 g / dm 3

[0207] Pure water and two kinds of lithium hydroxide aqueous solutions (LiOH) were used as the recovery liquid 20. The concentration of the first lithium hydroxide aqueous solution was 10 mM, and the concentration of the second lithium hydroxide aqueous solution was 1 M.

[0208] The concentration of each metal ion (g / dm) representing the composition of the first lithium hydroxide aqueous solution (concentration = 10 mM) 3 ) was as follows: Lithium ion = 0.07 g / dm 3 Sodium ion = 0 g / dm 3 Potassium ion = 0 g / dm 3 Magnesium ion = 0 g / dm 3 Calcium ion = 0 g / dm 3

[0209] The concentration of each metal ion (g / dm) representing the composition of the second lithium hydroxide (concentration = 1 M) 3 ) was as follows: Lithium ion = 6.9 g / dm 3 Sodium ion = 0 g / dm 3 Potassium ion = 0 g / dm 3 Magnesium ion = 0 g / dm 3 Calcium ion = 0 g / dm 3

[0210] Subsequently, the occlusion / release electrode 30 and the counter electrode 41 were connected to a power source 51 (electrochemical measurement system SP-150 manufactured by Biologic Co., Ltd.), and then the occlusion / release electrode 30 was immersed in the raw material liquid 10 (first immersion step).

[0211] In this first immersion step, while the occlusion / release electrode 30 and the counter electrode 41 were immersed in the raw material solution 10, a current was applied to the occlusion / release electrode 30 and the counter electrode 42 using a power source 51. In this case, the current application conditions were set so that the current per weight of the plurality of electrode particles 31 (titanium oxide) was constant (=100 mA / g), thereby allowing the electrolytic reaction (reaction time=1 hour) to proceed. As a result, only lithium ions were selectively occluded by the occlusion / release electrode 30 from among the two or more types of metal ions in the raw material solution 10.

[0212] Subsequently, the occlusion / emission electrode 30 was taken out from the raw material liquid 10. Subsequently, the surface of the occlusion / emission electrode 30 was washed with a washing solvent (pure water), and then the occlusion / emission electrode 30 was dried.

[0213] Next, the occlusion / release electrode 30 was moved from the storage tank 81 to the storage tank 82. Next, the occlusion / release electrode 30 and the counter electrode 42 were connected to a power source 52 (an electrochemical measurement system SP-150 manufactured by Biologic Corporation), and then the occlusion / release electrode 30 was immersed in the recovery liquid 20 (second immersion step).

[0214] In this second immersion step, while the occlusion / release electrode 30 and the counter electrode 42 were immersed in the recovery liquid 20, a current was applied to the occlusion / release electrode 30 and the counter electrode 42 using the power source 52. In this case, the current application conditions in the second immersion step were set to be the same as those in the first immersion step, except that the current application direction in the second immersion step was set to be opposite to that in the first immersion step, thereby allowing the electrolysis reaction to proceed until the potential difference between the occlusion / release electrode 30 and the counter electrode 42 reached −0.5 V. As a result, lithium ions were released from the occlusion / release electrode 30 in the recovery liquid 20, and hydroxide ions were generated in response to the generation of hydrogen, resulting in the formation of lithium hydroxide.

[0215] Therefore, an extraction process was carried out using the raw material liquid 10, the recovery liquid 20, the occlusion / release electrode 30, the counter electrodes 41, 42, and the power sources 51, 52, and an extract 90 containing lithium hydroxide (lithium ions) was obtained.

[0216] Finally, the occlusion / release electrode 30 and the counter electrode 42 were removed from the extract 90, and the extract 90 was then recovered.

[0217] In addition, an extraction treatment was carried out in the same manner except that the counter electrode 42 was used and no current was applied to the occlusion / desorption electrode 30 in the second immersion step (Example 8).

[0218] In the second immersion step, the occlusion / release electrode 30 was immersed alone in the recovery liquid 20 (immersion time = 24 hours), thereby allowing the electrolysis reaction to proceed spontaneously in the occlusion / release electrode 30. Thus, an extraction process was performed using the raw material liquid 10, the recovery liquid 20, the occlusion / release electrode 30, the counter electrode 41, and the power source 51, and an extract 90 containing lithium hydroxide (lithium ions) was obtained.

[0219] For comparison, a treatment was carried out in the same manner except that no current was applied to the occlusion / desorption electrode 30 and the counter electrode 41 in the first immersion step (Comparative Example 1).

[0220] For comparison, a test electrode (platinum plate) was used instead of the storage / release electrode 30, and electrodialysis of the raw material solution 10 was performed using a cation exchange membrane placed between the test electrode and a counter electrode (nickel foil) (Comparative Example 2).

[0221] In Table 1, the entry "*Electrodialysis (cation exchange membrane)" in the "Storage-release electrode (multiple electrode particles)" column indicates that in Comparative Example 2, electrodialysis was performed instead of performing extraction processing using the storage-release electrode 30.

[0222] When performing this electrodialysis, a raw material solution 10 and a recovery solution 20 separated from each other by a cation exchange membrane (Nafion (registered trademark) 115) were prepared, and a test electrode was immersed in the raw material solution 10 and a counter electrode was immersed in the recovery solution 20, and then a current was applied to the test electrode and the counter electrode. In this case, the current application conditions were set to be the same as those in the first immersion step, except that the test electrode was used instead of the storage / release electrode 30. As a result, the recovery solution 20 after application of current was recovered as the extraction solution 90.

[0223] [Evaluation of Extraction Process Performance] The performance of the extraction process was evaluated according to the procedure described below, and the results shown in Table 1 were obtained.

[0224] When examining the performance of the extraction treatment, first, the recovery liquid 20 was analyzed using inductively coupled plasma atomic emission spectroscopy (ICP-AES) before the extraction treatment was performed. This resulted in quantitative analysis of the five types of metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, and calcium ions), and the concentrations (g / dm 3 ) was measured.

[0225] Subsequently, after the extraction process, the extract 90 was analyzed using ICP-AES to determine the concentrations (g / dm 3 ) was measured.

[0226] Finally, for each of the five metal ions, the concentration increase (g / dm ), which is an index for evaluating the performance of the extraction treatment, was calculated by subtracting the concentration after the extraction treatment from the concentration after the extraction treatment. 3 ) was calculated.

[0227]

[0228] [Discussion] As shown in Table 1, the performance of the extraction process varied greatly depending on the procedure of the extraction process.

[0229] Specifically, even when raw material liquid 10, recovery liquid 20, occlusion / release electrode 30, and counter electrode 41 were used, when no current was applied to occlusion / release electrode 30 and counter electrode 41 in the first immersion step (Comparative Example 1), the concentration of lithium ions did not increase, and therefore the lithium ions were not extracted.

[0230] Furthermore, when electrodialysis using a cation exchange membrane was performed without performing the extraction process using the absorption / desorption electrode 30 (Comparative Example 2), the concentration of lithium ions hardly increased, and therefore almost no lithium ions were extracted.

[0231] In contrast, when raw material liquid 10, recovery liquid 20, occlusion / release electrode 30, and counter electrode 41 were used and a current was passed through occlusion / release electrode 30 and counter electrode 41 in the first immersion step (Examples 1 to 10), only the concentration of lithium ions increased significantly, and therefore a large amount of lithium ions was extracted.

[0232] In this case, the following trends were observed.

[0233] First, the lithium ion concentration increased more when the pH of the raw material solution 10 was higher than 10. Second, the lithium ion concentration increased sufficiently when anatase-type titanium oxide and lithium titanate were used as titanium oxides. Third, the occlusion-release layer 30B was formed by a calcination method, and therefore the occlusion-release layer 30B had a porous structure, which increased the lithium ion concentration more. Fourth, the lithium ion concentration increased more when the average particle size was 100 nm or less, and further increased when the average particle size was 30 nm or less. Fifth, the lithium ion concentration increased more when the recovery solution 20 contained a lithium hydroxide aqueous solution (concentration = 1 M or less). Sixth, the lithium ion concentration increased more when current was applied to the occlusion-release electrode 30 in the second immersion step. Seventh, the lithium ion concentration increased more when nickel foil was used as the counter electrode 42.

[0234] [Summary] From the results shown in Table 1, when the extraction process was performed using the raw material liquid 10, the recovery liquid 20, the occlusion / release electrode 30, and the counter electrode 41 in the first immersion step by passing a current through the occlusion / release electrode 30 and the counter electrode 41, the concentration of lithium ions in the extraction liquid 90 increased significantly. Therefore, a large amount of lithium ions was extracted, and the lithium ions could be extracted with high precision.

[0235] The present technology has been described above with reference to an embodiment and examples. However, the configuration of the present technology is not limited to the configuration described in the embodiment and examples, and can be modified in various ways.

[0236] The effects described in this specification are merely examples, and the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

[0237] The present technology may also be configured as follows: <1> An extraction device comprising: a first aqueous medium containing two or more types of metal ions; a second aqueous medium separated from the first aqueous medium; a first electrode that can be immersed in the first aqueous medium without being immersed in the second aqueous medium and can be immersed in the second aqueous medium without being immersed in the first aqueous medium; a second electrode that can be immersed in the first aqueous medium; and a first power source connected to the first electrode and the second electrode, wherein the two or more types of metal ions include lithium ions, the first electrode includes titanium oxide, and the first power source is capable of applying electricity to 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, when energized while immersed in the first aqueous medium, can be immersed in the second aqueous medium. <2> The extraction device described in <1>, wherein the titanium oxide selectively occludes the lithium ions from among the two or more types of metal ions and releases the lithium ions. <3> The extraction apparatus according to <1> or <2>, wherein the pH of the first aqueous medium is greater than 10. <4> The titanium oxide is selected from the group consisting of anatase-type titanium oxide and lithium titanate (Li 4 Ti 5 O12 <5> The extraction device according to any one of <1> to <3>, wherein the first electrode includes a plurality of electrode particles, each of the plurality of electrode particles including the titanium oxide, and the first electrode includes a porous structure in which the plurality of electrode particles are directly bonded to one another. <6> The extraction device according to <5>, wherein the average particle size of the plurality of electrode particles is 100 nm or less. <7> The extraction device according to <6>, wherein the average particle size is 30 nm or less. <8> The first electrode includes an electrode layer having the porous structure, and the volume density of the electrode layer is 1.0 g / cm 3 3.5g / cm or more 3 the specific surface area of ​​the electrode layer is 1 m or less 2 / g or more 500m 2 <9> The extraction apparatus according to any one of <5> to <7>, wherein the second aqueous medium contains an aqueous lithium hydroxide solution, and the concentration of the aqueous lithium hydroxide solution is 1 mol / dm 3 The extraction apparatus according to any one of <1> to <8>, which is as follows: <10> The extraction apparatus according to any one of <1> to <9>, further comprising: a third electrode immersable in the second aqueous medium; and a second power source connected to the first electrode and the third electrode, wherein the second power source is capable of passing electricity through the first electrode and the third electrode when the first electrode and the third electrode are immersed in the second aqueous medium. <11> The extraction apparatus according to <10>, wherein the third electrode contains at least one of titanium, platinum, iridium, nickel, iron, and palladium as a constituent element. <12> The extraction apparatus according to any one of <1> to <11>, further comprising: a movement mechanism capable of moving 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 comprising: a first storage member that stores the first aqueous medium; and a first supply mechanism capable of supplying the first aqueous medium to the first storage member. <14> The extraction device according to any one of <1> to <13>, further comprising: a second storage member for storing the second aqueous medium; and a second supply mechanism capable of supplying the second aqueous medium to the second storage member. <15> An extraction method comprising: immersing a first electrode containing titanium oxide and a second electrode in a first aqueous medium containing two or more types of metal ions including lithium ions; applying current to the first electrode and the second electrode while the first electrode and the second electrode are immersed in the first aqueous medium; and immersing the first electrode, to which current is applied while immersed in the first aqueous medium, in a second aqueous medium separated from the first aqueous medium. <16> The extraction method according to <15>, further comprising: immersing a third electrode in the second aqueous medium; and generating hydrogen at the third electrode by applying current to the first electrode and the third electrode while the first electrode and the third electrode are immersed in the second aqueous medium.<17> A method for producing lithium hydroxide, comprising: immersing a first electrode containing titanium oxide and a second electrode in a first aqueous medium containing two or more types of metal ions including lithium ions; applying current to the first electrode and the second electrode while the first electrode and the second electrode are immersed in the first aqueous medium; immersing the first electrode, to which current is applied while the first electrode and the third electrode are immersed in the first aqueous medium, in a second aqueous medium containing pure water or a lithium hydroxide aqueous solution separated from the first aqueous medium; and generating hydrogen at the third electrode by applying current to the first electrode and the third electrode while the first electrode and the third electrode are immersed in the second aqueous medium.

Claims

1. a first aqueous medium containing two or more types of metal ions; a second aqueous medium separated from the first aqueous medium; a first electrode that can be immersed in the first aqueous medium without being immersed in the second aqueous medium, and can be immersed in the second aqueous medium without being immersed in the first aqueous medium; a second electrode that is immersible in the first aqueous medium; a first power source connected to the first electrode and the second electrode; Equipped with the two or more types of metal ions include lithium ions, the first electrode includes titanium oxide; the first power source is capable of supplying electricity to the first electrode and the second electrode in a state in which the first electrode and the second electrode are immersed in the first aqueous medium; The first electrode, which is energized while immersed in the first aqueous medium, can be immersed in the second aqueous medium. Extraction device.

2. the titanium oxide selectively occludes the lithium ions from among the two or more types of metal ions and releases the lithium ions; The extraction device of claim 1 .

3. The pH of the first aqueous medium is greater than 10; The extraction device of claim 1 .

4. The titanium oxide is an anatase type titanium oxide and lithium titanate (Li 4 Ti 5 O 12 ) The extraction device of claim 1 .

5. the first electrode includes a plurality of electrode particles; each of the plurality of electrode particles contains the titanium oxide; the first electrode includes a porous structure in which the plurality of electrode particles are directly bonded to each other; The extraction device of claim 1 .

6. The average particle size of the plurality of electrode particles is 100 nm or less.

6. The extraction device of claim 5.

7. The average particle size is 30 nm or less.

7. The extraction device of claim 6.

8. the first electrode includes an electrode layer having the porous structure, The volume density of the electrode layer is 1.0 g / cm 3 3.5g / cm or more 3 is as follows: The specific surface area of ​​the electrode layer is 1 m 2 / g or more 500m 2 / g or less, 6. The extraction device of claim 5.

9. the second aqueous medium contains an aqueous lithium hydroxide solution, The concentration of the lithium hydroxide aqueous solution is 1 mol / dm 3 Below is the The extraction device of claim 1 .

10. moreover, a third electrode that is immersible in the second aqueous medium; a second power source connected to the first electrode and the third electrode; Equipped with the second power source is capable of supplying electricity to the first electrode and the third electrode in a state in which the first electrode and the third electrode are immersed in the second aqueous medium. The extraction device of claim 1 .

11. the third electrode contains at least one of titanium, platinum, iridium, nickel, iron, and palladium as a constituent element; 11. The extraction device of claim 10.

12. The liquid ejection device further includes a moving mechanism capable of moving the first electrode between the first aqueous medium and the second aqueous medium. The extraction device of claim 1 .

13. moreover, a first containing member that contains the first aqueous medium; a first supply mechanism capable of supplying the first aqueous medium to the first storage member; The extraction device of claim 1 , comprising:

14. moreover, a second containing member that contains the second aqueous medium; a second supply mechanism capable of supplying the second aqueous medium to the second storage member; and 14. The extraction device according to any one of claims 1 to 13, comprising:

15. immersing a first electrode containing titanium oxide and a second electrode in a first aqueous medium containing two or more types of metal ions including lithium ions; energizing the first electrode and the second electrode while the first electrode and the second electrode are immersed in the first aqueous medium; immersing the first electrode, which is immersed in the first aqueous medium and to which a current is applied, in a second aqueous medium separated from the first aqueous medium; Extraction method.

16. a third electrode is further immersed in the second aqueous medium; Furthermore, in a state where the first electrode and the third electrode are immersed in the second aqueous medium, a current is applied to the first electrode and the third electrode, thereby generating hydrogen at the third electrode. The extraction method according to claim 15.

17. immersing a first electrode containing titanium oxide and a second electrode in a first aqueous medium containing two or more types of metal ions including lithium ions; energizing the first electrode and the second electrode while the first electrode and the second electrode are immersed in the first aqueous medium; immersing the first electrode and a third electrode, which are energized while immersed in the first aqueous medium, in a second aqueous medium containing pure water or a lithium hydroxide aqueous solution, which is separated from the first aqueous medium; a second aqueous medium that is immersed in the first electrode and the third electrode; and a second aqueous medium that is immersed in the second aqueous medium. The first electrode and the third electrode are electrically connected to each other to generate hydrogen. How to make lithium hydroxide.