Lithium recovery agent, lithium recovery method, lithium recovery system, method for producing lithium-containing manganese oxide, and method for producing positive electrode active material for lithium ion battery

Abstract

Lithium can be easily and efficiently recovered from a raw material solution containing lithium by using a lithium recovery agent containing electrogenic bacteria and a lithium intercalation material.

Description

Technical Field

[0001] The invention relates to a lithium recovery agent, a lithium recovery method, a lithium recovery system, a method for producing lithium-containing manganese oxide, and a method for producing a positive electrode active material of a lithium ion battery. Background Art

[0002] Lithium (Li) is a resource with high demand as a raw material for lithium-ion secondary batteries and fusion reactor fuel, and a stable and cheaper method of obtaining it is being sought. As a stable supply source of Li, there are cationic Li + In addition, the technology of cheaply recovering lithium secondary batteries discarded due to battery life etc. is also expected.

[0003] As one of the technologies for recovering Li from seawater, etc., the electrochemical lithium recovery method described below is reported in non-patent documents 1 to 3. First, a coating (mixed product) is prepared by mixing a lithium adsorbent such as spinel-type manganese oxide that can selectively absorb lithium, a conductive additive such as carbon, and a binder such as polyvinylidene fluoride. The coating is applied to an electrode to make a composite electrode. Then, the electrode is energized by using an electrochemical device such as a constant potential / constant current instrument to recover the lithium in the lithium adsorbent.

[0004] Prior art literature

[0005] Non-patent literature

[0006] Non-patent literature 1: S. Kim et al., Environ. Sci. Technol., 2020, 54, 9044-9051

[0007] Non-patent document 2: L. Wang et al., Sustainable Energy Fuels, 2021, 5, 3124-3133

[0008] Non-patent document 3: J. Lee et al., Phys. Chem. Chem. Phys., 2013, 15, 7690-7695 Summary of the invention

[0009] Problems to be solved by the invention

[0010] However, the conventional lithium recovery methods disclosed in non-patent documents 1 to 3 require a coating preparation (kneading) step, a coating step, and further, an electrochemical device for energizing the electrodes. As described above, in the conventional lithium recovery methods, the time and cost required for the complex process and equipment have become issues.

[0011] The present invention solves the above-mentioned problems. That is, one of the objects of the present invention is to provide a lithium recovery agent that can recover lithium simply and efficiently.

[0012] Means for solving problems

[0013] The inventors have conducted intensive studies to achieve the above-mentioned object, and as a result, have found that the above-mentioned object can be achieved by the following configuration.

[0014] [1] A lithium recovery agent for recovering lithium from a raw material solution containing lithium, comprising electrogenic bacteria and a lithium intercalation material.

[0015] [2] The lithium recovery agent according to [1], wherein the electrogenic bacteria are iron-reducing bacteria.

[0016] [3] The lithium recovery agent according to [2] above, wherein the electrogenic bacteria are Shewanella bacteria or Geobacter bacteria.

[0017] [4] The lithium recovery agent according to any one of [1] to [3], wherein the lithium insertion material is a compound containing a first transition metal.

[0018] [5] The lithium recovery agent according to [4], wherein the first transition metal is at least one selected from manganese (Mn), vanadium (V), titanium (Ti) and iron (Fe).

[0019] [6] The lithium recovery agent according to [5], wherein the lithium intercalation material is manganese dioxide with a spinel structure.

[0020] [7] The lithium recovery agent according to any one of [1] to [6], wherein the lithium insertion material is a particle.

[0021] [8] The lithium recovery agent according to any one of [1] to [7], further comprising an electron donor.

[0022] [9] The lithium recovery agent according to [8], wherein the above-mentioned electrogenic bacteria are bacteria of the genus Shewanella, and the above-mentioned electron donor is lactate; or, the above-mentioned electrogenic bacteria are bacteria of the genus Geobacter, and the above-mentioned electron donor is acetate.

[0023]

[10] The lithium recovery agent according to any one of [1] to [9], further comprising an electron mediator.

[0024]

[11] The lithium recovery agent according to

[10] , wherein the electron mediator is a flavin.

[0025]

[12] A lithium recovery method comprising the step of contacting the lithium recovery agent described in any one of [1] to

[11] with the raw material solution.

[0026]

[13] The lithium recovery method according to

[12] , wherein the electrons generated by the above-mentioned electrogenic bacteria are transferred to the above-mentioned lithium intercalation material.

[0027]

[14] The lithium recovery method according to

[12] or

[13] , comprising: preparing a reaction solution comprising the raw material solution and the lithium recovery agent; generating a precipitate containing the lithium recovery agent and the lithium in the reaction solution; and separating the precipitate from the reaction solution.

[0028]

[15] The lithium recovery method according to

[14] , wherein the raw material solution contains lithium ions introduced from the outside via a cation exchange membrane.

[0029]

[16] A lithium recovery system comprising: a reaction container and the lithium recovery agent described in any one of [1] to

[11] disposed in the reaction container, wherein the raw material liquid is in contact with the lithium recovery agent in the reaction container.

[0030]

[17] The lithium recovery system according to

[16] , which does not have a mechanism for supplying electricity to the above-mentioned lithium recovery agent.

[0031]

[18] The lithium recovery system according to

[16] , wherein the reaction container has a cation exchange membrane for introducing lithium ions from the outside of the reaction container into the raw material solution.

[0032]

[19] A method for producing lithium-containing manganese oxide, comprising the lithium recovery method described in any one of

[12] to

[15] , wherein the lithium insertion material is manganese dioxide.

[0033]

[20] A method for producing a positive electrode active material for a lithium ion battery, comprising the lithium recovery method described in any one of

[12] to

[15] .

[0034] Effects of the Invention

[0035] The present invention provides a lithium recovery agent which can recover lithium simply and efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a conceptual diagram for explaining the lithium recovery mechanism of the lithium recovery agent according to the present embodiment.

[0037] Figure 2 1 is a flow chart illustrating the lithium recovery method according to the present embodiment.

[0038] Figure 3 This is a diagram showing the results of X-ray diffraction (XRD) measurements of manganese dioxide (before reaction) and the powder obtained in Experiment 1 (after reaction).

[0039] Figure 4This is a scanning electron microscope (SEM) photograph of the agglomerates recovered in Experiment 1.

[0040] Figure 5 This is a diagram showing the results of X-ray diffraction (XRD) measurements of manganese dioxide (before reaction) and the powder obtained in Experiment 2 (after reaction).

[0041] Fig. 6A This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 3-1.

[0042] Figure 6B This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 3-2.

[0043] Figure 6C This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 3-3.

[0044] Fig.6D This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 3-4.

[0045] Fig. 6E This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 3-5.

[0046] Fig. 6F This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 3-6.

[0047] Fig. 7A This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 4-1.

[0048] Figure 7B This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 4-2.

[0049] Figure 7C This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 4-3.

[0050] Fig.7D This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 4-4.

[0051] Figure 8 This is a conceptual diagram illustrating a lithium recovery system according to another embodiment.

[0052] Fig. 9A is an image showing the apparatus for the demonstration test of the lithium recovery system.

[0053] Fig. 9B The image of the screw bottle before immersion in the LiCl / PBS (10 mM) solution (left) and the image of the screw bottle after immersion and reaction for 24 hours (right) are compared.

[0054] Fig. 10A This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 6-1.

[0055] Fig. 10B This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 6-2.

[0056] Fig. 10C This is a diagram showing the results of X-ray diffraction (XRD) measurement of the powder (after reaction) obtained in Experiment 6-3. DETAILED DESCRIPTION

[0057] Hereinafter, the present invention will be described in detail.

[0058] The description of the constituent elements described below is sometimes based on representative embodiments of the present invention, but the present invention is not limited to such embodiments. It should be noted that in this specification, the numerical range represented by "to" refers to a range including the numerical values ​​described before and after "to" as the lower limit and the upper limit.

[0059] [Lithium recovery agent]

[0060] The lithium recovery agent of this embodiment mainly comprises electrogenic bacteria and lithium intercalation materials. The lithium recovery agent of this embodiment contacts with a raw material solution containing lithium to recover lithium in the raw material solution.

[0061] <Electrogenic bacteria>

[0062] In this specification, "electrogenic bacteria (electric current generating bacteria)" refers to bacteria that have the ability to transfer electrons generated by the decomposition (metabolism) of electron donors (organic matter) in the bacteria to electron acceptors (lithium intercalation materials in this embodiment) outside the bacteria, that is, the ability to perform extracellular electron transfer (EET: Extracellular Electron Transport) (extracellular electron transfer ability).

[0063] As current-generating bacteria, for example, iron-reducing bacteria can be cited. As iron-reducing bacteria, specifically, Shewanella bacteria, Geobacter bacteria, etc. can be cited. These electricity-generating bacteria are safe because they are not pathogenic bacteria. In addition, because they proliferate rapidly, sufficient effects can be obtained even when the initial input amount is small, which is preferred from this point of view. As types of Shewanella bacteria, Oneida Lake Shewanella (S.oneidensis), Photovoltaic Shewanella (S.loihica), Putrefaciens Shewanella (S.putrefaciens), Algae Shewanella (S.algae), etc. can be cited. As types of Geobacter bacteria, G.sulfurreducens, G.metallireducens, etc. can be cited. Electricity-generating bacteria can be known or unknown. These electricity-generating bacteria can be used alone or in combination of two or more within the scope of the effect of the present embodiment.

[0064] <Lithium intercalation materials>

[0065] In this application specification, "lithium intercalation material" refers to a material (host, matrix) into which lithium ions (guests) can be intercalated. Intercalation refers to a reversible chemical reaction in which other elements (lithium ions in this application specification) penetrate into the voids of molecules, molecular groups, or crystals (lithium intercalation materials in this application specification).

[0066] There is no particular limitation on the type (composition, crystal structure, shape, etc.) of the lithium intercalation material, and it can be appropriately selected within the scope of exerting the effect of the present embodiment. For example, the lithium intercalation material can be a compound containing a first transition metal, and as the first transition metal, manganese (Mn), vanadium (V), titanium (Ti) and iron (Fe) can be cited. As specific compounds, for example, manganese oxides such as Mn3O4, Mn2O3, MnO2 (manganese dioxide), MnO3, Mn2O7, iron oxides such as Fe3O4, Fe2O3, vanadium oxides such as V2O5, VO2, titanium oxides such as TiO2, and TiS2, FePO4, etc. can be cited. In addition, as the crystal structure of the lithium intercalation material, for example, layered rock salt type, spinel type, olivine type, etc. can be cited. As a lithium intercalation material, manganese dioxide, especially manganese dioxide with a spinel structure (λ-type MnO2), is preferred due to its high lithium adsorption selectivity. It should be noted that the lithium intercalation material may be used alone or in combination of two or more within the range in which the effects of the present embodiment are exhibited.

[0067] From the perspective of improving lithium recovery efficiency, the lithium insertion material is preferably a powder (particle). The average particle size of the particles is not particularly limited, and may be, for example, 5 nm to 500 μm, 50 nm to 9000 nm, or 100 nm to 300 nm. It should be noted that the “average particle size” can be obtained, for example, by randomly measuring the particle sizes of 100 particles using an electron microscope and averaging (arithmetic mean).

[0068] <Other ingredients>

[0069] The lithium recovery agent of the present embodiment may be formed only of the electrogenic bacteria and the lithium intercalation material, or may contain other components within the range in which the effects of the present embodiment are exerted.

[0070] For example, the lithium recovery agent may further contain an electron donor (electron donor) that can be decomposed by the electrogenic bacteria. As described above, the electrogenic bacteria generate electrons by decomposing (metabolizing) organic matter (electron donors). When the raw material liquid is seawater or other environmental samples, the raw material liquid may already contain organic matter that serves as an electron donor. Even in such a case, the lithium recovery efficiency can be improved by further containing an electron donor in the lithium recovery agent.

[0071] The electron donor (electron donor) is not particularly limited in type and state, as long as it is a substance that is decomposed (metabolized) by the electrogenic bacteria contained in the lithium recovery agent and / or the bacteria contained in the raw material solution and can provide electrons to the electrogenic bacteria. The electron donor can be solid, liquid, gaseous, or a mixture of these, and can be arbitrarily selected according to the specific method of the lithium recovery method.

[0072] For example, when seawater is used as the raw material solution (or when the raw material solution is prepared using seawater as a starting point), the original lithium (ion) content is low, and is approximately 0.2 ppm as an example.

[0073] In this case, supplying a solid or gaseous electron donor can reduce the amount used per unit amount of recovered Li, which is economically more advantageous, compared to supplying the electron donor in liquid (liquid) form to the raw material solution (reaction solution).

[0074] Specifically, if a solid substance or gas that can serve as an electron donor is used near the lithium recovery agent, seawater, microorganisms, and the lithium recovery agent can be separated, and lithium recovery can be performed locally (and continuously) more efficiently.

[0075] As the material of such solid, for example, metals such as magnesium and iron and organic substances such as cellulose and polylactic acid can be enumerated. Its form is not particularly limited, and it can be particulate or blocky. When it is particulate, the reaction is more likely to be carried out efficiently, and when it is blocky, it is easier to be fixed near the lithium recovery agent, which is preferred.

[0076] In addition, when using a gaseous electron donor, the gas can be supplied to the vicinity of the lithium recovery agent. As an example, if it is the above-mentioned secondary cooling system, the electrode is set near the lithium recovery agent, and hydrogen is generated by electrolysis of cooling water. As an example of a gaseous electron donor, hydrogen can be cited.

[0077] It should be noted that among the above-mentioned solid electron donors, metals (such as iron and magnesium) can generate hydrogen in the raw material solution (reaction solution), so they can not only become electron donors themselves, but also become indirect electron donors by releasing hydrogen into the system.

[0078] Among the electron donors, as organic substances, for example, lactates such as sodium lactate, acetates such as sodium acetate, etc. can also be cited. It is preferred to appropriately select an electron donor that improves power generation efficiency based on the type of current-generating bacteria (electrogens). For example, when the electrogenic bacteria are Shewanella bacteria, the electron donor is preferably lactate, and when the electrogenic bacteria are Geobacter bacteria, the electron donor is preferably acetate. In addition, the electron donor may be used alone or in combination of two or more within the range of exerting the effect of the present embodiment.

[0079] The organic substance may be provided in a solid form, a liquid (solution) form, or a mixture thereof. In addition, a polymer gel swollen by a solution in which the organic substance is dissolved may be used as an electron donor. The swollen polymer gel slowly releases the organic substance into the reaction solution, thereby allowing the reaction to proceed more efficiently.

[0080] In addition, for example, the lithium recovery agent may further include an electron mediator. The electrons generated by the electrogenic bacteria are transferred to the electron acceptor (lithium intercalation material) outside the bacteria through the electron transfer protein present in the cell outer membrane. The electron mediator activates the electron transfer protein and further promotes the electron transfer to the lithium intercalation material. As a result, the lithium recovery efficiency is improved, for example, the recovery time (reaction time) can be shortened. As an electron mediator, for example, flavins, quinones, etc. can be cited. Flavins are a general term for derivatives with a substituent at the 10th position of 7,8-dimethylisoxazine, including riboflavin (vitamin B2), FAD, FMN, etc. Quinones are aromatic organic compounds having a cyclic diketone structure with a double bond and containing six carbon atoms, for example, para-benzoquinone, o-quinone, anthraquinone, etc. These electron mediators can be used alone or in combination of two or more within the scope of the effect of the present embodiment.

[0081] In addition, the lithium recovery agent may further contain liquids including various inorganic salt buffers such as boric acid, phosphoric acid, and carbonate, water, physiological saline, cell culture medium, etc. (hereinafter, recorded as "liquid components"). For example, when the lithium recovery agent contains a cell culture medium, the number of electrogenic bacteria can be increased by culturing in the lithium recovery agent. The liquid component can be used alone or in combination of two or more within the scope of exerting the effect of the present embodiment.

[0082] The lithium recovery agent of this embodiment may be composed of a first agent containing electrogenic bacteria and the above-mentioned liquid component, and a second agent containing a lithium intercalation material. The second agent may be composed only of a lithium intercalation material, or may further contain the above-mentioned liquid component. In addition, when the lithium recovery agent contains an electron donor, an electron mediator, etc., these components may be contained in the first agent and / or the second agent, or may be used as other other agents (for example, the third agent and / or the fourth agent). It should be noted that the first agent, the second agent, and the other agents may be stored in different containers, respectively, and the first agent, the second agent, and the other agents may be mixed with the raw material liquid when the lithium recovery agent is used.

[0083] It should be noted that the ratio (proportion) of each component in the lithium recovery agent of the present embodiment is not particularly limited and can be appropriately adjusted within the range in which the effect of the present embodiment is exerted.

[0084] <Raw material liquid>

[0085] For the stock solution, as long as it is a liquid containing lithium, it is not particularly limited, and it can be appropriately selected within the scope of the effect of the present embodiment. As the stock solution, for example, seawater, salt lake brine, geothermal water, lithium-containing aqueous solution obtained by recovering lithium ion batteries, mine drainage, industrial wastewater, etc. can be cited, preferably a stock solution without cytotoxicity to the electrogenic bacteria contained in the lithium recovery agent. The lithium concentration in seawater is low, about 0.025mM, but because it can be obtained in large quantities and easily, it is an important lithium supply source. Since the lithium recovery agent of the present embodiment can also efficiently recover lithium from the stock solution with a low lithium concentration, seawater is suitable for the stock solution of the present embodiment.

[0086] The lithium concentration of the raw material solution is not particularly limited. The lithium recovery agent of the present embodiment can, for example, cope with raw material solutions having a wide range of lithium concentrations of 0.01 mM to 50 mM. For example, lithium can be efficiently recovered from raw material solutions having a low lithium concentration of 0.01 mM to 1 mM. In addition, the raw material solution may contain organic matter that can become an electron donor (electron donor) and can be decomposed by electrogenic bacteria. When the raw material solution contains a sufficient amount of electron donor (organic matter), the lithium recovery agent does not need to contain an electron donor, or the content of the electron donor can be reduced.

[0087] <Mechanism of lithium recovery>

[0088] Figure 1 1 is a schematic diagram showing a lithium recovery agent 100 in contact with a raw material solution 200 containing lithium. First, the electron donor 20 is decomposed (metabolized) in the electrogenic bacteria 10 contained in the lithium recovery agent 100 to generate electrons e - The electrons generated - The electron transfer protein 30 present in the cell membrane of the electrogenic bacteria 10 transfers the electrons to the electron acceptor (lithium insertion material) 40 outside the bacteria. As a result, the electrochemical insertion of lithium ions in the raw material solution into the lithium insertion material 40 is promoted, and lithium (lithium ions Li + ) is recovered from the raw material solution 200. The inventors and others discovered for the first time that the insertion of lithium is significantly promoted by the electrogenic bacteria, thereby completing the present invention. Furthermore, in the lithium recovery agent of this embodiment, when lithium is recovered (during the reaction), there is a tendency for the particles of the lithium-intercalated material to form agglomerates through the components from the electrogenic bacteria. From this, it can be inferred that the conductivity and adhesion between the particles are improved, and the lithium recovery efficiency is further improved.

[0089] The lithium recovery agent of the present embodiment can efficiently recover lithium by a simple method such as contacting with a raw material solution containing lithium (for example, dispersing the lithium recovery agent in the raw material solution). Therefore, compared with the previous methods disclosed in non-patent documents 1 to 3, there is no need for a coating preparation (mixing) process, a coating process, or the equipment required in the process (kneader, coater, dryer, etc.). Furthermore, electrochemical devices such as electrodes, wiring, constant potential / constant current meters are not required. In addition, in the present embodiment, the lithium-embedded lithium material is precipitated by forming an agglomerate from components of electrogenic bacteria, so it is easy to separate from the reaction solution. As described above, the lithium recovery agent of the present embodiment has advantages in time and money, and the environmental burden is low due to the small number of required processes and equipment, and it is highly applicable to mass production equipment.

[0090] For example, when manganese oxide is used as a lithium intercalation material, at least a portion of the manganese oxide is reduced by electrons transferred from the electrogenic bacteria. For example, manganese dioxide (e.g., MnO2) in the lithium recovery agent recovers lithium ions to become a manganese oxide lithium intercalation compound (e.g., Li x Mn2O4, x=0.4 to 2.0). The average oxidation number of manganese (Mn) in the manganese oxide lithium intercalation compound is not particularly limited, and is, for example, +3 to +4. It should be noted that the lithium ions taken into the manganese oxide are not reduced.

[0091] As described above, the metal recovery mechanism of the lithium recovery agent of the present embodiment is very different from that of the recovery agent that directly reduces the metal ions in the raw material solution for recovery. When the metal ions in the raw material solution are directly reduced for recovery, there is the following possibility: the metals other than the target metal contained in the raw material solution are also reduced and recovered at the same time. In contrast, with respect to the lithium recovery agent of the present embodiment, the electrons supplied by the electrogenic bacteria are transferred to the lithium intercalation material, and the lithium ions in the raw material solution are selectively taken into the lithium intercalation material. Therefore, even in the case where the raw material solution contains metal ions other than lithium ions, the lithium recovery agent of the present embodiment can selectively recover lithium ions.

[0092] It should be noted that the mechanism described above is speculative and does not have any impact on the scope of the present invention.

[0093] [Lithium Recovery System]

[0094] right Figure 1 The lithium recovery system 1000 shown in FIG. 1 is described. The lithium recovery system 1000 includes a reaction container 300 and a lithium recovery agent 100 of the present embodiment disposed in the reaction container 300. In the reaction container 300, the raw material solution 200 is in contact with the lithium recovery agent 100. As a result, the lithium ions in the raw material solution are taken in (intercalated) into the lithium insertion material 40, and the lithium (lithium ion Li + ) is recovered from the raw liquid 200.

[0095] The lithium recovery system 1000 does not need to have a power supply mechanism (such as a power supply, wiring, electrodes, etc.) for energizing the lithium recovery agent 100. This is because the sufficient electrons required for the lithium recovery reaction can be supplied to the lithium insertion material through the electrogenic bacteria 10 contained in the lithium recovery agent 100. Since there is no power supply mechanism, the lithium recovery system 1000 can be manufactured and transported at low cost, and the environmental burden is also low.

[0096] [Another embodiment of the lithium recovery system]

[0097] Figure 8 The lithium recovery system 1100 includes a reaction vessel 300 and a lithium recovery agent 100 disposed in the reaction vessel 300 . Furthermore, the reaction vessel 300 includes a cation exchange membrane 400 for introducing lithium ions 130 from the outside into the raw material solution 200 .

[0098] Cation exchange membrane 400 is disposed in a pipe connecting secondary cooling water pipe 110 of the power generation equipment and reaction vessel 300 , and introduces lithium ions 130 contained in cooling water 210 in external pipe 110 to reaction vessel 300 .

[0099] It should be noted that, in this embodiment, the reaction vessel 300 is arranged in the middle of the secondary cooling water pipe 110 of the power generation equipment, but the installation position of the lithium recovery system of this embodiment is not limited to the above position. For example, it can also be immersed in a larger container (such as a water treatment tank, etc.) containing water containing lithium ions, a lake, a swamp, or an ocean, etc. together with the reaction vessel 300.

[0100] The lithium recovery system of this embodiment can easily maintain the reaction container 300 in a state suitable for lithium recovery (eg, an anaerobic state), and can also more efficiently recover lithium from low-concentration lithium ions.

[0101] [Lithium recovery method]

[0102] A lithium recovery method using the lithium recovery agent of this embodiment is described. The lithium recovery method can use the above-mentioned lithium recovery system 1000 (see Figure 1 ) is implemented. The lithium recovery method includes a step of contacting a lithium recovery agent with a raw material solution ( Figure 2 Step S1). Below, according to Figure 2 An example of a lithium recovery method is described with reference to a flow chart of FIG.

[0103] First, a reaction solution ( Figure 2 Step S1). Thus, the lithium recovery agent contacts the raw material solution.

[0104] The reaction solution may consist of only the raw material solution and the lithium recovery agent, or may contain other components within the scope of the effect of the present embodiment. As other components, for example, liquids (the above-mentioned "liquid components") including various inorganic salt buffers such as boric acid, phosphoric acid, and carbonic acid, water, physiological saline, and cell culture medium may be cited.

[0105] The content (concentration) of each component in the reaction solution is not particularly limited and can be appropriately adjusted within the range of exerting the effect of the present embodiment. For example, the initial concentration of the reaction solution can be set to the following range: Electrogenic bacteria (OD value): 0.001 to 1, lithium insertion material: 0.001 to 10 g / L, electron donor: 0 to 100 mM, electron mediator: 0 to 0.1 mM, lithium ion: 0.01 to 100 mM.

[0106] The pH of the reaction solution can be set, for example, to 5 to 8 or 6 to 8. When the pH of the reaction solution is set within the above range, the activity of the electrogenic bacteria is active, and as a result, the lithium recovery efficiency is improved.

[0107] The method for preparing the reaction solution is not particularly limited. For example, the raw material solution, the lithium recovery agent, and other components as required may be uniformly mixed by a known method.

[0108] For example, the reaction solution can be prepared by continuously moving lithium ions from a solution containing relatively low concentrations of lithium ions (ie, from the outside) into the raw material solution via a cation exchange membrane.

[0109] Then, a precipitate ( Figure 2 Step S2). In the reaction solution, a reaction (intercalation) occurs in which lithium ions in the raw material solution are taken into the lithium intercalation material. As a result, a precipitate containing a lithium recovery agent and lithium taken into the lithium recovery agent is generated, and the lithium in the raw material solution is recovered into the precipitate.

[0110] Here, the reaction solution is prepared ( Figure 2 From step S1) to the time of separating the precipitate from the reaction solution described later ( Figure 2 The time from step S3) to step S3) is taken as the "reaction time". The reaction time can be appropriately adjusted within the range of exerting the effect of the present embodiment, for example, it can be set to 10 minutes to 3 days, or 1 hour to 3 hours. If the reaction time is set within the above range, the embedding reaction is fully carried out, and a precipitate containing a sufficient amount of lithium can be obtained. The temperature of the reaction solution during the reaction (reaction temperature) can be set, for example, to 4°C to 40°C, or 25°C to 30°C. If the reaction temperature is set within the above range, the activity of the electrogenic bacteria is active, and as a result, the lithium recovery efficiency is improved. In addition, during the reaction (during the reaction time), the reaction solution can be left to stand, or it can be shaken, stirred, etc.

[0111] Next, the precipitate was separated from the reaction solution ( Figure 2 Step S3). The separation method is not particularly limited, and general methods such as filtration and decantation can be used. In this embodiment, the lithium-intercalated material is aggregated to form a precipitate (aggregate) by the action of the electrogenic bacteria, and the precipitate (aggregate) is easily attached to the bottom of the reaction container. Therefore, the precipitate is easily separated from the supernatant.

[0112] As described above, the lithium recovery method of the present embodiment can efficiently recover lithium by a simple method such as contacting the lithium recovery agent with the raw material liquid. There is no need to energize the lithium recovery agent 100 as in the previous methods (e.g., non-patent documents 1 to 3). The lithium recovery method of the present embodiment has advantages in time and money, and has a low environmental burden due to the small number of required processes and equipment, and is highly applicable to mass production.

[0113] [Application of lithium recovery method]

[0114] In the lithium recovery method of the present embodiment, lithium (lithium ions) in the raw material solution is recovered, and as a result, a lithium intercalation material containing lithium ions is generated. For example, when manganese oxide is used as the lithium intercalation material, the lithium ions in the raw material solution are recovered in the form of lithium-containing manganese oxide (manganese oxide lithium intercalation compound). That is, the lithium recovery method of the present embodiment can be applied to a method for manufacturing lithium-containing manganese oxide. In this manufacturing method, seawater or the like can be used as a lithium source (raw material solution). In addition, by using electricity-producing bacteria, lithium-containing manganese oxide can be manufactured using a low-cost and simple method. As the lithium-containing manganese oxide manufactured, for example, Li x Mn2O4 (x=0.4 to 2.0). The average oxidation number of manganese (Mn) is not particularly limited, and is, for example, +3 to +4.

[0115] In addition, lithium-embedded materials containing lithium ions (such as the above-mentioned lithium-containing manganese oxide) can be used as positive electrode active materials for lithium-ion batteries. That is, the lithium recovery method of this embodiment can be applied to a method for manufacturing positive electrode active materials for lithium-ion batteries. In this manufacturing method, seawater or the like can be used as a lithium source (raw material solution). In addition, by using electricity-producing bacteria, a low-cost and simple method can be used to produce positive electrode active materials for lithium-ion batteries. Among them, compared with Co, Mn is cheaper and has more reserves, and a stable supply in the future can be expected. From this aspect, lithium-containing manganese oxide is attracting attention as a positive electrode material for lithium-ion batteries.

[0116] Example

[0117] Below, the present invention is further described in detail based on embodiment.The material, usage amount, ratio, processing content, processing step etc. shown in the following embodiment can be appropriately changed within the scope not exceeding the gist of the present invention.Therefore, the scope of the present invention should not be limited by the embodiment shown below and be interpreted.

[0118] [Experiment 1]

[0119] Lithium is recovered from the raw material solution (lithium aqueous solution) using a lithium recovery agent containing the following components: It should be noted that the λ-MnO2 particles are produced by acid-treating LiMn2O4 having a spinel structure.

[0120] <Lithium recovery agent composition>

[0121] Electrogenic bacteria: Shewanella

[0122] Electron donor: sodium lactate

[0123] Embedded material: spinel-structured manganese dioxide (λ-MnO2 particles, average particle size: 100-300nm)

[0124] (1) Preparation of reaction solution

[0125] First, an aqueous solution in which lithium chloride and sodium lactate are dissolved in a phosphate buffer solution (lithium chloride concentration: 50 mM, sodium lactate concentration: 50 mM) is prepared. 0.05 g of manganese oxide particles are mixed in 50 mL of the prepared solution. Next, dissolved oxygen in the solution is removed by bubbling with nitrogen, Shewanella is introduced, and the container is sealed to obtain a reaction solution. Shewanella is added in an amount adjusted to the following: when dispersed in 50 mL of the reaction solution, the optical density (OD value) becomes 0.3.

[0126] (2) Formation of precipitate

[0127] The container was placed on an oscillator and shaken at a rotation speed of about 160 rpm for 24 hours in a thermostat set at 30° C. During this time, sheet-like aggregates (precipitates) composed of manganese oxide particles and Shewanella were confirmed to be formed at the bottom of the container.

[0128] (3) Separation of precipitate

[0129] After 24 hours, the container was opened, and the supernatant was removed (decantation) to recover the precipitate. The obtained precipitate was washed with a surfactant to remove the components derived from the microorganisms, and then the water was removed with a dryer to obtain a powder.

[0130] <Evaluation>

[0131] (1) Crystal structure evaluation

[0132] The powder obtained in Experiment 1 was subjected to X-ray diffraction (XRD) measurement. The results were reported in Figure 3 For comparison, the curve of λ-MnO2 is also shown as “before reaction (λ-MnO2)”. Figure 3 . Although the same peaks as before the reaction (λ-MnO2) are observed after the reaction, all peaks after the reaction are shifted to the smaller angle side compared to before the reaction (λ-MnO2). This indicates that the symmetry of the spinel structure is maintained after the reaction, and the lattice size increases. Such an increase in the lattice size suggests that the valence of manganese ions is reduced due to the electrochemical insertion (embedding) of cations such as lithium into the crystal structure. The peak position of the curve after the reaction is shown as a reference. Figure 3 The lower part is consistent with LiMn2O4 (the average valence of manganese is +3.5).

[0133] (2) Composition analysis

[0134] The composition of the powder obtained in Experiment 1 was analyzed by inductively coupled plasma (ICP) emission analysis. The results showed that the molar ratio of manganese to lithium in the powder (sample after reaction) was about Mn:Li=2:0.6, and the amount of lithium was less than that in the case of LiMn2O4 (Mn:Li=2:1) ​​due to the influence of co-doping of protons, but a sufficient amount of lithium was recovered.

[0135] (3) Scanning electron microscopy (SEM) observation and energy dispersive X-ray analysis (EDS)

[0136] The aggregates (precipitates) before washing recovered by decantation in Experiment 1 were subjected to a dehydration and drying treatment of the microorganisms, and then the morphology was observed using a scanning electron microscope (SEM). The results are shown in Figure 4 The majority of the aggregates are composed of manganese oxide particles. Figure 4 The arrow in the figure shows the position where the shape of Shewanella was clearly observed. While performing SEM observation, mapping of manganese and carbon was performed by energy dispersive X-ray analysis (EDS). From this result, Shewanella was also confirmed at the position indicated by the arrow. In addition, carbon was also detected around Shewanella. It is speculated that by covering the aggregate with components from microorganisms, the conductivity and adhesion between manganese oxide particles can be ensured.

[0137] [Experiment 2]

[0138] A powder as a final product was obtained by the same method as in Experiment 1 except that Shewanella was not used (not introduced into the container).

[0139] <Crystal structure evaluation>

[0140] The powder obtained in Experiment 2 was subjected to X-ray diffraction (XRD) measurement in the same manner as in Experiment 1. Figure 5 For comparison, the curve of λ-MnO2 is also shown as “before reaction (λ-MnO2)”. Figure 5 . Compared with the results of Experiment 1 ( Figure 3 ), the peak intensity of the curve after the reaction is greatly attenuated, and a broad peak shape is shown. This suggests that the crystallinity of manganese oxide has decreased, and there is a possibility that a side reaction other than the lithium insertion reaction has occurred while maintaining the skeleton structure of the crystal. In addition, the peak position is also different from that shown in the reference Figure 5 The peak position of LiMn2O4 at the bottom is different, suggesting that the reaction is not complete. Figure 3 ) and Experiment 2 ( Figure 5 ) confirmed that the addition of Shewanella significantly promoted the electrochemical lithium insertion reaction (intercalation).

[0141] [Experiments 3-1 to 3-6]

[0142] Since lithium recovery from an environment with a low lithium concentration is required in practical applications, the lithium recovery characteristics from an aqueous solution with a low lithium concentration were evaluated in Experiments 3-1 to 3-6.

[0143] In Experiments 3-1 to 3-6, the lithium concentration in the reaction solution was set to 20 mM, 10 mM, 5 mM, 2 mM, 1 mM, and 0.5 mM, respectively. A powder as a final product was obtained by the same method as Experiment 1 except for the above.

[0144] <Crystal structure evaluation and composition analysis>

[0145] The powders obtained in Experiments 3-1 to 3-6 were subjected to X-ray diffraction (XRD) measurement and composition analysis in the same manner as in Experiment 1. The X-ray diffraction (XRD) measurement results are shown in Figure 6A to Figure 6F In addition, for comparison, Figure 6A to Figure 6F In the graph, the vertical dotted line with the text "λ-MnO2" indicates the peak position of λ-MnO2.

[0146] like Figure 6A to Figure 6C As shown, in Experiments 3-1 to 3-3 (lithium concentration: 5 to 20 mM), each peak (vertical dashed line without a symbol) maintained its original peak intensity but shifted toward the lower angle side relative to the peak position of λ-MnO2. Figure 3 The results of Experiment 1 (lithium concentration: 50 mM) shown also suggest that lithium ions are electrochemically inserted into the manganese oxide crystal structure (intercalation).

[0147] On the other hand, in the case of Experiments 3-4 to 3-6 (lithium concentration: 0.5 to 2 mM), the amount of the reaction solution was limited to 50 mL, so even if all the lithium in the reaction solution was recovered, the amount of manganese oxide recovered was limited. Fig.6D As shown, the peak shift relative to the peak position of λ-MnO2 is incomplete, which suggests that the amount of lithium insertion is reduced compared with the cases of Experiments 3-1 to 3-3 (lithium concentration: 5 to 20 mM).

[0148] However, the results of composition analysis show that in Experiments 3-5 ( Fig. 6E , lithium concentration: 1 mM) and 3-6 ( Fig. 6FIn the case of a low lithium concentration (lithium concentration: 0.5mM), almost all of the lithium in the prepared reaction solution was recovered by manganese oxide (with an error of less than 5% from the theoretical value). This suggests that lithium recovery can be performed from a reaction solution with an initial lithium concentration of about 1mM, for example, and that even after the reaction advances and the lithium concentration further decreases, the intercalation reaction can also be fully performed to recover lithium. The above content confirms that lithium can be efficiently recovered even from a low-concentration lithium aqueous solution.

[0149] [Experiments 4-1 to 4-4]

[0150] In Experiments 4-1 to 4-4, the lithium recovery characteristics were evaluated when the lithium recovery agent contained an electron mediator.

[0151] In Experiments 4-1 and 4-2, except that the reaction time was shortened to 3 hours, the experiment was conducted under the same conditions as Experiment 3-3 (lithium concentration in the reaction solution: 5 mM) and Experiment 3-2 (lithium concentration in the reaction solution: 10 mM), and a powder was obtained as the final product. In addition, in Experiments 4-3 and 4-4, except that the lithium recovery agent contained riboflavin as an electron mediator, the experiment was conducted under the same conditions as Experiments 4-1 and 4-2, and a powder was obtained as the final product. The riboflavin concentration in the reaction solution was set to 2 μM.

[0152] <Crystal structure evaluation>

[0153] The powders obtained in Experiments 4-1 to 4-4 were subjected to X-ray diffraction (XRD) measurement in the same manner as in Experiment 1. The X-ray diffraction (XRD) measurement results are shown in FIG. 7A to FIG. 7D In addition, for comparison, FIG. 7A to FIG. 7D In the graph, the vertical dotted line with the text "λ-MnO2" indicates the peak position of λ-MnO2.

[0154] like FIG. 7A to FIG. 7D As shown, in Experiment 4-3 ( Figure 7C ) and 4-4 ( Fig.7D ), even though the reaction time was as short as 3 hours, the observed peak (vertical dashed line without label text) still maintained its original peak intensity and clearly shifted to the lower angle side relative to the peak position of λ-MnO2. This suggests that lithium ions were electrochemically inserted into the manganese oxide crystal structure (embedded).

[0155] On the other hand, in Experiment 4-1 ( Fig. 7A ) and 4-2 ( Figure 7B ), the peak shift relative to the peak position of λ-MnO2 is incomplete. This suggests that the amount of lithium insertion is reduced compared to Experiments 4-3 and 4-4 using riboflavin.

[0156] From the above results, it was confirmed that by using the electron mediator (riboflavin), lithium can be recovered from the raw material solution in a shorter time, that is, the lithium recovery efficiency is improved.

[0157] [Experiment 5]

[0158] In Experiment 5, a powder as a final product was obtained by the same method as Experiment 1 except that seawater was used as the reaction liquid.

[0159]

[0160] The Li concentrations of the seawater before the reaction (raw material solution) and the seawater after the reaction (reaction solution after Li recovery) used in Experiment 5 were measured by ICP emission spectrometry. The results are shown below.

[0161] [Table 1]

[0162]

[0163] From the results shown in Table 1, it can be calculated that the lithium recovery rate is about 96 to 98% by weight. From the results of Experiment 5, it can be confirmed that lithium can be recovered at a high recovery rate even when seawater is used as the raw material liquid.

[0164] [Experiment 6]

[0165] conduct Figure 8 Demonstration test of the lithium recovery system shown. Fig. 9A This is an image showing the device. A glass screw sample bottle is immersed in an inverted state in a container (glass beaker) containing a LiCl / PBS (10, 50 mM) solution. It should be noted that for the purpose of explanation, a part of the image has been processed by background removal and the like.

[0166] In a threaded sample bottle, a PBS solution containing a lithium recovery agent and sodium lactate prepared in the same manner as in Experiment 1 except that lithium chloride was not contained was placed. As described above, the PBS solution initially contained no LiCl (w / o LiCl).

[0167] In addition, the opening portion of the screw-thread sample bottle was sealed with a cation exchange membrane instead of the screw-thread cap.

[0168] Fig. 9B Comparison between an image of a screw-threaded vial before immersion in a LiCl / PBS (10 mM) solution (left) and an image of the screw-threaded vial after immersion and reaction for 24 hours (right).

[0169] The solution before immersion was reddish brown, but after the reaction, the solution changed to brown, which was closer to black. This suggests the interaction between lithium and λ-MnO2. Fig. 9BIn fact, the shades of black are used to represent the shades of red.

[0170] Figures 10A to 10C These are the results (diffraction curves) of X-ray diffraction (XRD) measurement of powders performed in the same manner as in Experiment 1. Each figure corresponds to the following experiment.

[0171] · Fig. 10A :Experiment 6-1 (λ-MnO2 curve before impregnation)

[0172] · Fig. 10B :Experiment 6-2 (curve after immersion in 10mM LiCl solution)

[0173] · Fig. 10C :Experiment 6-3 (curve after immersion in 50mM LiCl solution)

[0174] For Experiment 6-2 ( Fig. 10B ) and Experiment 6-3 ( Fig. 10C ) and the results of Experiment 6-1 ( Fig. 10A ) compared, the peak from λ-MnO2 shifted to the small angle side. The peak position after the shift is roughly consistent with the peak position from LiMn2O4. This confirms that the lithium ions introduced from the outside through the cation exchange membrane are recovered.

[0175] Industrial Applicability

[0176] The lithium recovery agent of the present invention can recover lithium simply and efficiently. The recovered lithium can be used as a raw material for lithium-ion secondary batteries, fuel for fusion reactors, etc.

[0177] Description of Reference Numerals

[0178] 10Electrogenic bacteria

[0179] 20 electron donor

[0180] 30 Electron transfer protein

[0181] 40 Embedding Materials

[0182] 100 lithium recovery agent

[0183] 200 Raw material liquid

[0184] 300 reaction vessels

[0185] 1000 Lithium Recovery System

[0186] 110 piping

[0187] 130 Lithium Ion

[0188] 210 Cooling water

[0189] 300 reaction vessels

[0190] 400 cation exchange membrane

[0191] 1100 Lithium Recovery System

Claims

1. A lithium recovery agent, which is a lithium recovery agent for recovering the lithium from a raw material solution containing lithium, comprising: electrogenic bacteria, and Lithium intercalation materials.

2. The lithium recovery agent according to claim 1, wherein The electrogenic bacteria are iron-reducing bacteria.

3. The lithium recovery agent according to claim 2, wherein The electrogenic bacteria are Shewanella bacteria or Geobacter bacteria.

4. The lithium recovery agent according to any one of claims 1 to 3, wherein The lithium insertion material is a compound containing a first transition metal.

5. The lithium recovery agent according to claim 4, wherein The first transition metal is at least one selected from the group consisting of manganese Mn, vanadium V, titanium Ti, and iron Fe.

6. The lithium recovery agent according to claim 5, wherein The lithium-intercalation material is manganese dioxide with a spinel structure.

7. The lithium recovery agent according to any one of claims 1 to 6, wherein The lithium intercalation material is a particle. 8 . The lithium recovery agent according to claim 1 , further comprising an electron donor.

9. The lithium recovery agent according to claim 8, wherein The electrogenic bacteria are Shewanella bacteria, and the electron donor is lactate; or, The exoelectrogenic bacteria are Geobacter bacteria, and the electron donor is acetate. 10 . The lithium recovery agent according to claim 1 , further comprising an electron mediator.

11. The lithium recovery agent according to claim 10, wherein The electron mediator is flavin. 12 . A lithium recovery method, comprising the step of contacting the lithium recovery agent according to claim 1 with the raw material solution.

13. The lithium recovery method according to claim 12, wherein: The electrons generated by the exoelectrogenic bacteria are transferred to the lithium intercalation material.

14. The lithium recovery method according to claim 12 or 13, comprising: preparing a reaction solution comprising the raw material solution and the lithium recovery agent; generating a precipitate containing the lithium recovery agent and the lithium in the reaction solution; and The precipitate is separated from the reaction solution.

15. The lithium recovery method according to claim 14, wherein: The raw material solution contains lithium ions introduced from the outside via a cation exchange membrane.

16. A lithium recovery system comprising: a reaction vessel, and The lithium recovery agent according to any one of claims 1 to 11 disposed in the reaction container, In the reaction container, the raw material solution contacts the lithium recovery agent.

17. The lithium recovery system according to claim 16, which does not have a mechanism for supplying electricity to the lithium recovery agent.

18. The lithium recovery system according to claim 16, wherein: The reaction container has a cation exchange membrane for introducing lithium ions from the outside of the reaction container into the raw material solution.

19. A method for producing lithium-containing manganese oxide, comprising the lithium recovery method according to any one of claims 12 to 15, The lithium insertion material is manganese dioxide.

20. A method for producing a positive electrode active material for a lithium ion battery, comprising the lithium recovery method according to any one of claims 12 to 15.

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