Method for recovering lithium compound

Abstract

To provide a method for efficiently recovering a lithium compound.SOLUTION: A method for recovering a lithium compound includes stirring, in water, particles that are obtained by pulverizing a used positive electrode reaction vessel from which positive electrode material powder and positive electrode material powder precursor have been removed, then separating the particles from an aqueous solution, adding a flocculant to the obtained aqueous solution and stirring the aqueous solution, and further separating aggregates from an aqueous solution containing a lithium compound. It is preferable that the flocculant is one or more selected from the group consisting of ferrous sulfate, polyferric sulfate, ferric chloride, calcium-based metal salt, barium-based metal salt, and cationic polymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for recovering lithium compounds from a used positive electrode reaction vessel of a lithium secondary battery. [Background technology]

[0002] The cathode material for lithium secondary batteries is manufactured in a reaction vessel (also called a reaction crucible). The raw material for the cathode, lithium hydroxide (LiOH·H2O), is used in excess when mixing with the precursor and firing to improve the high capacity performance of lithium secondary batteries. As a result, after manufacturing the cathode material, the excess lithium component must be removed through a water washing process. Furthermore, the corrosion reaction of excess lithium hydroxide, which occurs during the high-temperature manufacturing process of the cathode material, corrodes the reaction vessel used in manufacturing the cathode material, requiring replacement every 30 days or so. Conventionally, used reaction vessels have been discarded, but because the reaction vessels contain a high concentration of lithium hydroxide, the lithium compounds can be recovered and reused as positive electrode material, allowing for effective use of resources.

[0003] Therefore, Patent Document 1 discloses a method for recovering nickel, cobalt, manganese and lithium compounds from a used reaction vessel.

[0004] [Patent Document 1] Korean Publication No. 102408888 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional recovery methods require special equipment because they use highly corrosive hydrochloric acid. In addition, when lithium compounds are extracted from used reactor vessels using acids such as hydrochloric acid, the amount of metals recovered other than lithium (particularly aluminum) increases, which reduces the yield of lithium compounds in the subsequent purification process. There are methods for selectively recovering lithium using electrosorption, which uses a combination of a sorptive medium such as membrane capacitive deionization (MCDI) and an electric field, but this method only processes lithium ions that are attracted to the electrode, which has the problem of low lithium recovery.

[0006] An object of the present invention is to provide a method for efficiently recovering lithium compounds. [Means for solving the problem]

[0007] <1> The method for recovering a lithium compound of the present invention comprises grinding a used cathode reaction vessel from which a cathode material powder and a cathode material powder precursor have been removed, stirring the resulting particles in water, separating the particles from the aqueous solution, adding a flocculant to the resulting aqueous solution and stirring the mixture, and further separating the flocculates from the aqueous solution containing the lithium compound, The flocculant is at least one selected from the group consisting of ferrous sulfate, ferric polysulfate, ferric chloride, calcium-based metal salts, barium-based metal salts, and cationic polymers. <2> The flocculant is at least one selected from the group consisting of polyferric sulfate, ferric chloride, calcium hydroxide, calcium chloride, calcium acetate, barium chloride, and barium acetate. <1> A method for recovering lithium compounds. <3> The pulverized particles are particles that pass through a 0.5 mm mesh. <1> or <2> A method for recovering lithium compounds. <4> <1> ~ <3> A method for recovering lithium carbonate, comprising reacting a lithium compound obtained by any of the recovery methods with sodium carbonate to obtain lithium carbonate. <5> <1> ~ <3> A method for recovering lithium carbonate, comprising reacting a lithium compound obtained by any of the recovery methods with carbon dioxide to obtain lithium carbonate. [Effects of the Invention]

[0008] The present invention as described above can provide a method for efficiently recovering lithium compounds. Also, the present invention can provide a method for recovering lithium carbonate from lithium compounds. DETAILED DESCRIPTION OF THE INVENTION

[0009] The lithium compound recovery method of the present invention involves crushing a used cathode reaction vessel from which the cathode material powder and cathode material powder precursor have been removed, stirring the resulting particles in water, separating the particles from the aqueous solution, adding a flocculant to the resulting aqueous solution and stirring, and again separating the flocculants from the aqueous solution containing the lithium compound, thereby recovering the lithium compound contained in the aqueous solution. The flocculant is at least one selected from the group consisting of ferrous sulfate, polyferric sulfate, ferric chloride, calcium-based metal salts, barium-based metal salts, and cationic polymers.

[0010] The lithium compound recovery method of the present invention involves agitating particles obtained by pulverizing a used cathode reaction vessel from which the cathode material powder and cathode material powder precursor have been removed in water, followed by separating the particles from the aqueous solution to obtain an aqueous solution. The resulting aqueous solution contains not only lithium compounds but also silicon compounds and aluminum compounds originating from the cathode reaction vessel. When one or more flocculants selected from the group consisting of ferrous sulfate, polyferric sulfate, ferric chloride, calcium-based metal salts, barium-based metal salts, and cationic polymers are added to the resulting aqueous solution and stirred, the negatively charged fine particles in the aqueous solution interact with the positively charged flocculant to form flocculants. The flocculants are then separated from the aqueous solution to obtain an aqueous solution containing lithium compounds. Since silicon compound and aluminum compound particles often have a negative charge and form flocculants through interaction with the flocculant, they can be removed by separating the flocculants from the aqueous solution. This separation removes most metal compounds other than lithium, allowing for efficient recovery of lithium compounds.

[0011] <Cathode reaction vessel> The cathode reaction vessel used in the present invention is not particularly limited as long as it is a cathode reaction vessel used in the production of cathode materials for lithium secondary batteries. Generally, a ceramic vessel mainly composed of Al2O3-SiO2-MgO can be used.

[0012] <Pretreatment of used cathode reaction vessel> High concentrations of cathode material powder precursors containing nickel, cobalt, manganese, and lithium are deposited on the surface of used cathode reaction vessels, and these are collected and reused. The collected used cathode reaction vessels contain a large amount of lithium as a metal. It is sufficient to remove as much of the cathode material powder and cathode material powder precursor as possible from the used cathode reaction vessels, and a small amount may remain.

[0013] <Process for crushing used cathode reaction vessels> The process of crushing the used cathode reaction vessel is not particularly limited and can be appropriately selected depending on the purpose. The process of crushing the used cathode reaction vessel can include, for example, a primary crushing process for roughly crushing the used cathode reaction vessel and a secondary crushing process for crushing the used cathode reaction vessel to a particle size of a certain level or less through a screen (a metal plate with holes) or the like. In the primary pulverization step, the positive electrode reaction vessel is roughly pulverized in a crusher or a shredder to a size that can be fed into a fine pulverizer or an ultrafine pulverizer. In the secondary pulverization step, the coarsely pulverized material is preferably pulverized in a fine pulverizer or an ultrafine pulverizer to a size of 0.5 mm or less. Examples of the crusher used in the primary crushing step include an impact crusher, a compression crusher, a cutting / shearing crusher, etc. Examples of the compression crusher include a jaw crusher, a gyratory crusher, a cone crusher, and an impact crusher. Examples of the crusher used in the primary crushing step include a single-shaft crusher, a double-shaft crusher, a hammer crusher, and a mobile crusher.

[0014] Examples of the fine pulverizer used in the secondary pulverization step include a roller mill, a jet mill, a high-speed rotary pulverizer, a container-driven mill, etc. Examples of the high-speed rotary pulverizer include a hammer mill and a pin mill, and examples of the container-driven mill include a rotary mill, a vibration mill, a planetary mill, etc. The secondary pulverization step can be performed using an ultrafine pulverizer, such as a media agitation mill, or an attritor or a bead mill.

[0015] A screen (a metal plate with holes) can be used to remove particles from the crusher used in the secondary crushing process. Only materials smaller than the size of the holes in the screen are discharged. There are no particular restrictions on the size of the screen openings and they can be selected appropriately depending on the purpose. However, by selecting a screen of 0.5 mm or less, the particle size of the particles crushed from the cathode reaction vessel (hereinafter referred to as crushed particles) can be controlled to 0.5 mm or less. This allows the crushed particles to be sorted into particles that pass through a 0.5 mm mesh. When the crushed particles are 0.5 mm or less, the extraction rate of lithium compounds in water improves.

[0016] <Process of stirring crushed particles in water> Water is added to the pulverized particles. The lithium compound is then extracted into the aqueous solution by heating and stirring. The weight of water used is preferably 3 times or more by mass, more preferably 5 to 10 times by mass, in consideration of the extraction efficiency of lithium. When the mass of water is 3 times or more by mass of the pulverized particles, the extraction efficiency of the lithium compound improves. Similarly, when the mass of water is 10 times or less by mass, the separation efficiency by filtration improves.

[0017] The extraction temperature is preferably 30°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher. The efficiency of extraction of lithium compounds into the aqueous solution improves in proportion to the increase in temperature. The extraction time is preferably 10 minutes or longer, more preferably 30 minutes or longer, and even more preferably 1 hour or longer. The longer the extraction time, the higher the extraction rate of lithium compounds. However, the conditions will vary depending on the extraction equipment, etc.

[0018] <First Separation> The pulverized particles are stirred in water, and then the particles and the aqueous solution are separated to obtain an aqueous solution from which the pulverized particles have been removed. It is preferable to remove pulverized products of 0.5 mm or less as much as possible, since this separation can increase the recovery efficiency of the lithium compound. The separation method is not limited as long as it can separate the particles from the aqueous solution. In this specification, examples of separation include filtration, centrifugal filtration, and centrifugation. Among these, filtration and centrifugal filtration are preferred because they use a filter medium and therefore make it easy to control the particle size of the separated particles.

[0019] When performing separation by filtration or centrifugal filtration (hereinafter referred to as the filtration step), various known filter media can be used. Filter media can be broadly classified according to material, structure, shape, and mesh size (also referred to as filtration accuracy). When a filtration step is performed, the pressure or pressure can be appropriately adjusted to accelerate the filtration rate. For example, the filtration step can be performed by filtering stepwise using filter papers ranging from coarse to fine, and then removing the pulverized particles using a membrane filter. Filter media can be broadly classified by material, structure, shape, and mesh size (also known as filtration accuracy).

[0020] Filter media materials can be broadly divided into inorganic compounds and organic compounds. Examples of inorganic compounds include metals such as titanium; alloys such as stainless steel and Hastelloy; metal oxides (ceramics) such as alumina, zirconia, and titanium oxide; silicon dioxide (glass) such as glass fiber, activated carbon, and diatomaceous earth. Examples of organic compounds include polyethylene, polypropylene, polyester, polyolefin, polyethylene terephthalate, polytetrafluoroethylene, polyurethane, polyacrylonitrile, polyvinylidene fluoride, perfluoroalkoxyalkane, cellulose phenol resin, nylon, nylon 66, rayon, acetate, polyphenylene sulfide, polyethersulfone, polysulfone, cotton, wool, and silk.

[0021] The structure of the filter material can be mesh, powder (particles), fiber, etc. The mesh is made by processing the filter material into fibers and weaving them in a regular pattern. The gaps between the fibers are used to capture coarse particles. Examples of weaving methods include plain weave, twill weave, tatami weave, and twill tatami weave. Powder is a form of filter media processed into fine particles. The fine particles are packed together and the gaps between them are used to capture coarse particles. Fiber is a filter material that has been processed into fibers and irregularly intertwined. The gaps between the fibers are used to capture coarse particles. In addition to the above, other methods include a structure in which a void-free resin containing a solvent is made into a thin film and then the solvent is evaporated to create tiny voids in the resin (phase inversion method), and a structure in which a void-free resin is made into a thin film and then stretched to create tiny voids (stretching method).

[0022] Examples of the shape of the filter medium include a disc filter, a membrane filter, a cartridge filter, etc. Examples of the cartridge filter include a depth filter, a pleated filter, a depth-pleated filter, and a thread-wound filter. A depth filter is a filter that uses a thick filter material placed on the outside of the cartridge core to perform filtration. A pleated filter has a thin filter material folded into pleats around the outside of the cartridge core, and utilizes the large surface area of the filter material to perform filtration. Depth-pleated filters have a thick filter material folded into pleats around the outside of the cartridge core, and utilize the thickness and large surface area of the filter material to perform filtration. Depth filters have thick filter media with many voids that can capture coarse particles, making them suitable for filtering low-viscosity liquids with many coarse particles. Pleated filters have thin filter media with few voids that can capture coarse particles, making them suitable for filtering high-viscosity liquids with few coarse particles. Depth pleated filters combine the properties of both.

[0023] The mesh size (filtration accuracy) of the filter medium can be selected arbitrarily within the range of 1 nm to 1 mm depending on the size of the object.

[0024] The mesh size (filtration accuracy) of the filter material can be measured using the following method. If the filter media's mesh size is less than 50 μm, add ACFTD (natural particles with a particle size distribution of 50 μm or less, as specified in ISO 4402) as dust to the purified water, begin filtration at a flow rate of 10 liters / minute, and continue filtration until the manufacturer's specified exchange differential pressure is reached. At this point, collect the aqueous solution. The number of particles in the solution before and after filtration is counted using a particle counter (Beckman Coulter HIAC9703+, measurement range 0.5-600 μm). The β value (filtration ratio) is calculated using the following formula (1). The particle size at which the β value is 1,000 or greater (meaning that 99.9% or more of the particles have been removed) is considered to be the filter media's mesh size (filtration accuracy).

[0025]

number

[0026] The filter medium preferably has a structure with a filtration gradient. A filtration gradient is a structure in which the mesh size of the filter medium gradually decreases. By adopting a structure in which the mesh size of the filter medium on the side that comes into contact with the solution before filtration is the largest and the mesh size of the filter medium on the side from which the solution after filtration is discharged is the smallest, coarse particles are removed in stages from large particles to small particles, which is preferable because coarse particles are efficiently removed and the life of the filter medium is extended.

[0027] The material of the filter medium used in the present invention is preferably, for example, polyethylene, polypropylene, polytetrafluoroethylene, or glass fiber. The filter material preferably has a structure of fiber, a structure obtained by a phase inversion method, or a structure obtained by a drawing method. The filter medium is preferably in the form of a depth filter or a depth pleat filter. The mesh size (filtration accuracy) of the filter medium is preferably 1 to 500 μm, more preferably 10 to 300 μm, and even more preferably 50 to 150 μm. By selecting the above filter media, coarse particles can be removed more efficiently.

[0028] Commercially available filter media include, for example, ROKI TECHNO's SLS series depth filters (material: polypropylene, structure: fiber, shape: depth, with filtration gradient), MPX series (material: polypropylene, structure: fiber, shape: pleated), CTY series (material: polytetrafluoroethylene, structure: structure that generates tiny voids by pulling, shape: membrane), SLP series (material: polypropylene, structure: fiber, shape: depth pleated), DIA-CS series (material: cotton, structure: fiber, shape: spool), SNN series (material: nylon, structure: fiber, shape: depth, with filtration gradient), and MPS series (material: polyester, structure: fiber, shape: pleated);

[0029] The temperature in the filtration step is preferably 5 to 80° C., more preferably 15 to 60° C., and even more preferably 20 to 45° C. The pressure during filtration is preferably 0.01 to 2.00 MPa, more preferably 0.02 to 1.00 MPa, and even more preferably 0.03 to 0.5 MPa.

[0030] <Addition of flocculant and second separation> The resulting aqueous solution contains, in addition to lithium compounds, fine particles containing metal elements such as silicon and aluminum originating from the positive electrode reaction vessel. When a flocculant is added to the resulting aqueous solution and stirred, a neutralization reaction occurs between the negatively charged fine particles in the aqueous solution and the positively charged flocculant, resulting in the formation of flocculants. The flocculants are then separated from the aqueous solution to obtain an aqueous solution containing lithium compounds. Because most of the metal elements other than lithium have been removed from the aqueous solution, lithium compounds can be efficiently recovered from the aqueous solution. The lithium concentration of the second aqueous solution after the second separation is usually 50% or more as determined by ICP analysis.

[0031] The flocculant is a compound selected from the group consisting of ferrous sulfate, polyferric sulfate, ferric chloride, calcium-based metal salts, barium-based metal salts, and cationic polymers. Examples of the cationic polymers include alkylamino methacrylate quaternary salt polymers (DAM), alkylamino acrylate quaternary salt-acrylamide copolymers (DAA), polydiallyldimethylammonium chloride, and polyethyleneimine. Examples of the calcium-based metal salts include calcium hydroxide, calcium chloride, calcium sulfate, calcium acetate, and calcium carbonate. Examples of the barium-based metal salts include barium hydroxide, barium chloride, barium sulfate, barium acetate, and barium carbonate. The flocculant is preferably one or more compounds selected from the group consisting of polyferric sulfate, ferric chloride, calcium hydroxide, calcium chloride, calcium acetate, barium chloride, and barium acetate, in terms of high particle flocculation efficiency.

[0032] The amount of the flocculant used is preferably 0.01 to 5.0 parts by mass, more preferably 0.02 to 3.0 parts by mass, per 100 parts by mass of the aqueous solution. When an appropriate amount is used, the fine particles can be efficiently flocculated, and the lithium compound can be recovered in high yield by removing the flocculants.

[0033] Other polymer flocculants (hereinafter referred to as other polymer flocculants) that can be used in combination with the above flocculants include, for example, anionic polymer flocculants such as acrylamide-sodium acrylate copolymer and acrylamide-sodium 3-methylpropanoate copolymer; nonionic polymer flocculants such as polyacrylamide; and amphoteric polymer flocculants such as acrylamide-acrylic acid-alkylaminoacrylate quaternary salt copolymer.

[0034] The flocculants can be used alone or in combination of two or more.

[0035] The second separation is not limited as long as it can separate the aggregates from the aqueous solution, as in the first separation. In this specification, separation includes, for example, filtration, centrifugal filtration, centrifugation, etc. Among these, filtration and centrifugal filtration are preferred because they use a filter medium and therefore make it easy to control the particle size of the separated particles.

[0036] The filtration method is not limited as long as it can remove the aggregates. Filtration is preferably performed using a filter with a pore size of 100 μm or less. This can prevent the aqueous solution from being contaminated with a flocculant or metal compounds other than lithium. Filtration can be performed multiple times, for example, by using a filter with a smaller pore size or a filter with an even smaller pore size. The filter may be one of the filter media already described above. Preferred examples of the filter include membrane filters, such as a membrane filter, a cellulose mixed ester type membrane filter, a cellulose acetate type membrane filter, a PTFE type membrane filter, a hydrophilic PTFE type membrane filter, a polycarbonate type membrane filter, and a coated type filter.

[0037] The pore size of the filter is preferably 100 μm or less, more preferably 5 μm or less, and even more preferably 0.1 μm or less, and preferably 0.001 μm or more. It is also preferable to perform pretreatment before filtering with the filter. The pretreatment is performed to remove large aggregates using a filter medium with a large filtration size in order to prevent clogging of the filter. Pretreatment can be performed multiple times by preparing multiple filter mediums with large, medium, and small filtration sizes. Examples of filter media used in pretreatment include ROKI TECHNO's SLS series depth filters (material: polypropylene, structure: fiber, shape: depth, with filtration gradient), MPX series (material: polypropylene, structure: fiber, shape: pleated), CTY series (material: polytetrafluoroethylene, structure: structure that generates tiny voids by pulling, shape: membrane), SLP series (material: polypropylene, structure: fiber, shape: depth pleated), DIA-CS series (material: cotton, structure: fiber, shape: spool), SNN series (material: nylon, structure: fiber, shape: depth, with filtration gradient), and MPS series (material: polyester, structure: fiber, shape: pleated).

[0038] <Step of isolating lithium carbonate from the obtained aqueous solution containing the lithium compound> The method for recovering lithium carbonate of the present invention is a method for obtaining lithium carbonate by reacting the lithium compound obtained by the above recovery method with sodium carbonate. The resulting lithium-containing aqueous solution (extract) is reacted with an equivalent or greater amount of hydrochloric acid to produce lithium chloride. Then, an equivalent or greater amount of sodium carbonate solution is added to the hydrochloric acid, causing crystals to precipitate. These crystals are collected by filtration, and lithium carbonate is obtained by removing the water.

[0039] Another method for recovering lithium carbonate according to the present invention is a method for obtaining lithium carbonate by reacting the lithium compound obtained by the above recovery method with carbon dioxide. To the resulting lithium-containing aqueous solution, an equivalent amount or more of hydrochloric acid is added to cause a reaction, producing lithium chloride. Then, carbon dioxide is added to the solution, causing crystals to precipitate. These crystals are collected by filtration, and lithium carbonate is obtained by removing the water. The preferred method for introducing carbon dioxide is to bubble it into the extract, and the reaction temperature is preferably 25°C to 100°C, more preferably 60°C to 100°C. If the temperature is below 25°C, the reaction proceeds slowly. Lithium carbonate can also be obtained by adding hydrochloric acid to the lithium extract to produce lithium chloride, which can then be reacted with sodium carbonate or carbon dioxide.

[0040] Lithium carbonate is easy to handle, so lithium can be efficiently reused as a positive electrode material. [Example]

[0041] The present invention will be specifically described below with reference to examples. However, the present invention is not particularly limited to the examples. In the examples, "parts" means "parts by mass" and "%" means "% by mass."

[0042] Example 1 A used cathode reaction vessel (main component: Al2O3-SiO2-MgO) that had been used for 30 days in the production of nickel, cobalt, and manganese-based cathode materials was tapped, and then the surface was washed with water to remove the cathode material powder and cathode material powder precursor, thereby preparing a used cathode reaction vessel. The used cathode reaction vessel was subjected to primary pulverization using a jaw crusher to obtain a coarsely crushed product. The obtained coarsely crushed product was subjected to secondary pulverization using a Makino type pulverizer (model name: DD-2-3.7, manufactured by Makino Sangyo Co., Ltd.) at a rotation speed of 3500 rpm to obtain a pulverized product. The obtained pulverized product was passed through a stainless steel screen with a mesh size of 0.5 mm to obtain pulverized particles with a particle diameter of 0.5 mm or less. 200 parts of the obtained pulverized particles and 1,000 parts of distilled water were placed in a reaction vessel equipped with a thermometer, a condenser, and a stirrer, and stirred for 1 hour at 90° C. The obtained slurry was filtered through a membrane filter (cellulose mixed ester type, pore size 3 μm, manufactured by ADVANTEC Co., Ltd.) to obtain 950 parts of a first aqueous solution. The first aqueous solution was analyzed by ICP (inductively coupled plasma) and found to contain 43.8% lithium atoms. Next, 1.6 parts of polyferric sulfate was added to 400 parts of the first aqueous solution while stirring, and the mixture was stirred for 1 hour. This solution was filtered through a membrane filter (cellulose mixed ester type, pore size 0.1 μm, manufactured by ADVANTEC) to remove the cationic flocculant aggregates, thereby obtaining a second aqueous solution containing a lithium compound. The main component of the lithium compound was lithium hydroxide.

[0043] <Lithium concentration evaluation> The obtained second aqueous solution was subjected to ICP analysis (apparatus name: ICP-OES (inductively coupled plasma optical emission spectroscopy) manufactured by Agilent 720-ES). As a result of the analysis, the ratio of lithium atoms in the nonvolatile matter was 91.8%. The content of lithium atoms in the second aqueous solution was evaluated in terms of recovery efficiency according to the following criteria.

[0044] <Lithium recovery amount> The amount of recovered lithium was evaluated based on the results of ICP analysis of the second aqueous solution, and scored from 1 to 5 according to the following criteria: The higher the score, the better, and 2 or more is within the practical range. 5 points: The total amount of lithium contained in 1 g of the second aqueous solution obtained by treating crushed particles of used positive electrode reaction vessel powder (hereinafter referred to as particles) is 2500 ppm / 1 g of crucible or more. 4 points: The total amount of lithium contained in 1 g of the second aqueous solution used to treat the particles is 2000 ppm or more per 1 g of crucible and less than 2500 ppm per 1 g of crucible 3 points: The total amount of lithium contained in 1 g of the second aqueous solution used to treat the particles is 1500 ppm / 1 g of crucible or more and less than 2000 ppm / 1 g of crucible 2 points: The total amount of lithium contained in 1 g of the second aqueous solution used to treat the particles is 1000 ppm or more per 1 g of crucible and less than 1500 ppm per 1 g of crucible 1 point: The total amount of lithium contained in 1 g of the second aqueous solution used to treat the particles is less than 1000 ppm / 1 g of crucible

[0045] <Lithium purity> The lithium purity was evaluated based on the ICP analysis results of the second aqueous solution, and scored from 1 to 5 according to the following criteria. The higher the score, the better the lithium purity, and a score of 2 or more is within the practical range. 5 points: Lithium atom ratio is 90% or more 4 points: Lithium atom ratio is between 80% and 90% 3 points: Lithium atom ratio is between 70% and 80% 2 points: Lithium atom ratio is between 60% and 70% 1 point: Lithium atom ratio is less than 60%

[0046] (Examples 2 to 12, Comparative Example 1) The recovery method in Example 1 was changed to the conditions shown in Table 1. In Examples 5, 8, and 9, the obtained slurry was separated using a centrifuge to obtain 900 parts of a first aqueous solution. Examples 5, 8, and 9 were all carried out in the same manner as Example 1, and lithium compounds were recovered by the recovery methods of Examples 2 to 12 and Comparative Example 1, respectively.

[0047] [Table 1] JPEG2025114215000003.jpg114162JPEG2025114215000004.jpg114112

[0048] The flocculants and other polymer flocculants in the table are as follows: P-1000 (Nippon Shokubai Co., Ltd. Epomin P-1000, polyethyleneimine, molecular weight 70,000, non-volatile content 30%) NF-63 (Tomooka Kaken NF-63, a nonionic polymer flocculant)

[0049] From the results in Table 1, it can be seen that in Examples 1 to 12, the use of a flocculant prevents the second aqueous solution from being contaminated with silicon compounds, while allowing lithium compounds to be recovered at high concentrations.

[0050] Example 13 To 300 parts of the second aqueous solution obtained in Example 1, 15.3 parts of 35% hydrochloric acid was added, followed by the addition of a solution of 15.6 parts of sodium carbonate dissolved in 68.0 parts of water. 360 parts of water was removed using a rotary evaporator, and the resulting slurry was filtered through a membrane filter (cellulose mixed ester type, pore size 0.1 μm, manufactured by ADVANTEC). The resulting filter cake was then dried at 200°C for 10 minutes, yielding 1.2 parts of a white solid. XRD analysis confirmed that the white solid was lithium carbonate. ICP analysis revealed a lithium concentration of 98.6%.

[0051] Example 14 15.3 parts of 35% hydrochloric acid was added to 300 parts of the second aqueous solution obtained in Example 1, and the mixture was stirred for 2 hours while blowing in carbon dioxide. 290 parts of water was removed using a rotary evaporator, and the resulting slurry was filtered through a membrane filter (cellulose mixed ester type, pore size 0.1 μm, manufactured by ADVANTEC). The resulting filter cake was then dried at 200°C for 10 minutes, yielding 0.8 parts of a white solid. The white solid was confirmed to be lithium carbonate by XRD analysis (XRD (Rigaku SmartLab)). ICP analysis revealed that the lithium concentration was 96.4%.

[0052] The results of Examples 13 and 14 show that the recovery method described herein can recover lithium carbonate at high concentrations.

Claims

1. A method for recovering a lithium compound, comprising: pulverizing a used cathode reaction vessel from which a cathode material powder and a cathode material powder precursor have been removed; agitating the pulverized particles in water; separating the particles from an aqueous solution; adding a flocculant to the resulting aqueous solution; and agitating the resulting solution; and further separating the flocculates from an aqueous solution containing the lithium compound, The method for recovering a lithium compound, wherein the flocculant is at least one selected from the group consisting of ferrous sulfate, polyferric sulfate, ferric chloride, calcium-based metal salts, barium-based metal salts, and cationic polymers.

2. 2. The method for recovering lithium compounds according to claim 1, wherein the flocculating agent is at least one selected from the group consisting of polyferric sulfate, ferric chloride, calcium hydroxide, calcium chloride, calcium acetate, barium chloride, and barium acetate.

3. 2. The method for recovering a lithium compound according to claim 1, wherein the pulverized particles are particles that pass through a mesh with an opening of 0.5 mm.

4. A method for recovering lithium carbonate, comprising reacting the lithium compound obtained by the method according to any one of claims 1 to 3 with hydrochloric acid, and then reacting the lithium compound with sodium carbonate to obtain lithium carbonate.

5. A method for recovering lithium carbonate, comprising reacting the lithium compound obtained by the recovery method according to any one of claims 1 to 3 with hydrochloric acid, and then reacting with carbon dioxide to obtain lithium carbonate.

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