System and method for processing waste lithium-ion batteries

Abstract

This system for treating a waste lithium ion battery is for recovering lithium from a waste lithium ion battery through the elution of lithium by immersing, in water, a calcinated product that can be obtained by calcinating a waste lithium ion battery containing phosphorus as a positive electrode active material. The system comprises: a mixing device for mixing an alkali metal salt other than lithium with a positive electrode active material contained in a waste lithium ion battery; and a calcinating device for calcinating, at a predetermined first temperature, the mixture obtained by the mixing device at a predetermined first temperature, wherein the mixing device is configured such that an alkali metal salt is ground and kneaded into the positive electrode active material.

Description

[Technical field]

[0001] The present invention relates to a system and method for treating waste lithium-ion batteries. [Background technology]

[0002] Lithium-ion batteries (LIBs) are widely used in electric vehicles, mobile phones, laptops, etc. Lithium-ion batteries consist of positive electrode active materials, negative electrode active materials, electrolyte, separators, current collectors, etc. There are two types of lithium-ion batteries: NCM, which contains nickel, cobalt, manganese, and lithium as positive electrode active materials, and LFP, which contains iron, phosphorus, and lithium as positive electrode active materials.

[0003] Since the lithium contained in such lithium ion batteries is a rare metal, it is desirable to recover lithium from lithium ion batteries that have been discarded after use (waste lithium batteries). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-191143 A [Patent Document 2] JP 2012-229481 A Summary of the Invention [Problem to be solved by the invention]

[0005] When recovering lithium from used lithium-ion batteries, it is possible to recover lithium after immersing the positive electrode active material obtained by thermally decomposing the used lithium-ion batteries by roasting or the like in water to dissolve the lithium.

[0006] However, it has been found that it is difficult to extract lithium from LFP by immersing it in water. In the above cited document 1, lithium is extracted by hydrothermal treatment in which an aqueous solution of an alkali metal salt is added to powder obtained by roasting lithium-ion batteries, the powder is charged into a pressure vessel, mixed, and then heated. This hydrothermal treatment is performed by heating in a sealed pressure vessel. Therefore, there are problems such as difficulty in increasing the processing capacity, i.e., the processing amount per unit time, complexity of the equipment, and difficulty in operation and management.

[0007] Patent Document 2 also discloses the addition of an alkaline earth metal hydroxide to turn fluorine and phosphorus into solid compounds during oxidation roasting. However, alkaline earth metals are less reactive than alkali metals, so there is a risk that lithium, an alkali metal, will combine with phosphate ions to form lithium phosphate (Li3PO4), which is insoluble in water. In addition, when a used lithium battery uses a positive electrode active material containing phosphorus, there is a concern that the addition of an alkaline earth metal will not advance the decomposition of the positive electrode active material itself by roasting, making it difficult to dissolve lithium into water.

[0008] The present invention has been made to solve the above-mentioned problems, and aims to provide a treatment system and a treatment method for used lithium-ion batteries that can dissolve lithium into water and recover it from used lithium-ion batteries that contain phosphorus as a positive electrode active material without going through complicated processes, and that can improve the dissolution rate. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, a processing system for used lithium ion batteries according to one embodiment of the present invention is a processing system for used lithium ion batteries for recovering lithium from used lithium ion batteries by roasting used lithium ion batteries containing phosphorus as a positive electrode active material, immersing the roasted material obtained by roasting the used lithium ion batteries in water to dissolve the lithium, the processing system comprising: a mixing device that mixes an alkali metal salt other than lithium with the positive electrode active material contained in the used lithium ion batteries; and a roasting device that roasts the mixture mixed in the mixing device at a predetermined first temperature, and the mixing device is configured to grind the alkali metal salt and knead it into the positive electrode active material.

[0010] In addition, a method for treating used lithium ion batteries according to another aspect of the present invention is a method for treating used lithium ion batteries, which comprises roasting used lithium ion batteries containing phosphorus as a positive electrode active material, immersing the roasted product obtained by roasting the used lithium ion batteries in water to dissolve the lithium, thereby recovering the lithium from the used lithium ion batteries. The method includes a mixing step of mixing an alkali metal salt other than lithium with the positive electrode active material contained in the used lithium ion batteries, and a roasting step of roasting the mixed mixture at a predetermined first temperature, and in the mixing step, the alkali metal salt is mixed with the positive electrode active material so as to be kneaded into the positive electrode active material while grinding the alkali metal salt.

[0011] According to the above system or method, before roasting the waste lithium ion battery, the positive electrode active material of the waste lithium ion battery is mixed with an alkali metal salt other than lithium. At this time, by mixing the alkali metal salt with the positive electrode active material while grinding it, the decomposition of the positive electrode active material containing thermally stable phosphorus is promoted when the positive electrode active material is roasted. In addition, since the phosphate ion and the alkali metal ion can be bonded, the generation of lithium phosphate (Li3PO4) which is insoluble in water due to the combination of the phosphate ion and lithium contained in the positive electrode active material is suppressed. In this way, according to the above system and method, it is possible to prevent the insolubilization of lithium during elution. Therefore, it is possible to dissolve lithium into water and recover it from the waste lithium ion battery containing phosphorus as the positive electrode active material without going through a complicated process, and the elution rate can be improved. Effect of the Invention

[0012] The present invention has the effect of being able to dissolve lithium into water and recover it from used lithium ion batteries that contain phosphorus as a positive electrode active material without going through complicated processes, and of being able to improve the dissolution rate.

[0013] The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic process diagram showing the processing steps in a processing system for used lithium ion batteries in one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of a pyrolysis system for carrying out the pyrolysis step shown in FIG. [Diagram 3] FIG. 3 is a schematic diagram of a recovery system that performs the recovery process shown in FIG. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of a mixing device in the processing system of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a processing step in a processing system for used lithium ion batteries according to an embodiment of the present invention.

[0016] The waste lithium ion batteries (waste LIBs) to be treated by the treatment system in this embodiment are LFP type lithium ion batteries that contain phosphorus in the positive electrode active material. More specifically, LFPs are batteries that contain iron phosphate (LiFePO4) as the positive electrode active material, graphite as the negative electrode active material, aluminum foil as the positive electrode current collector, and copper foil as the negative electrode current collector.

[0017] This processing system is intended for large waste LIBs, i.e., battery modules made up of multiple battery cells of waste lithium-ion batteries, and battery units made up of multiple battery modules. The battery unit is configured, for example, by housing multiple electrically connected battery modules, a control device, and a cooling device in a housing. This processing system is intended, for example, to remove a waste LIB installed in an electric vehicle or hybrid vehicle, and process the waste LIB in the removed state, i.e., the battery unit or battery module, without dismantling it.

[0018] As shown in Figure 1, the processing system of this embodiment includes a pyrolysis process P1 in which waste LIBs are pyrolyzed and the resulting powder containing active material is roasted, and a recovery process P2 in which the roasted active material is immersed in water to dissolve the lithium and then the lithium is recovered.

[0019] First, the pyrolysis process P1 will be described. The pyrolysis process P1 includes a pretreatment process P11, a crushing and sorting process P12, a mixing process P13, and a roasting process P14. Figure 2 is a schematic diagram of a pyrolysis system that performs the pyrolysis process shown in Figure 1. The pyrolysis system 1 includes a supply device 10, a pretreatment device 11, a crushing and sorting device 12, a mixing device 13, and a roasting device 14.

[0020] In the pretreatment process P11, the waste LIBs are roasted, i.e., pre-roasted, at a second temperature lower than the first temperature in the roasting process P14 described below in order to decompose and remove the electrolyte contained in the waste LIBs. For this purpose, the waste LIBs are supplied from a supply device 10 to a pretreatment device 11. The supply device 10 is, for example, configured by a belt conveyor or the like. The pretreatment device 11 is, for example, configured by a grate preheater.

[0021] The second temperature in the pretreatment step P11 is set to a temperature at which the electrolyte contained in the waste LIB can be decomposed and removed. For example, the second temperature is 150° C. or higher and lower than 400° C., and may be 150° C. or higher and 250° C. or lower.

[0022] In the crushing and sorting process P12, the waste LIBs processed in the pretreatment process P11 are crushed, and the active material is separated from the current collectors of the crushed waste LIBs to sort the active material. For this purpose, the crushing and sorting device 12 includes a crusher 12a and a sorter 12b. The crusher 12a is, for example, a roll crusher. The crusher 12a crushes large waste LIBs (battery units or battery modules) into battery cells or smaller.

[0023] The sorter 12b is configured to separate active material from current collectors of the waste LIBs crushed by the crusher 12a, and to select and extract the active material. The sorter 12b is configured, for example, by a sieve shaker or the like. In reality, the sorter 12b extracts not only the positive electrode active material, but also a small amount of impurities other than the active material, such as the negative electrode active material, and supplies them to the mixer 13. Other than these, the exterior materials of the waste LIBs, current collectors, etc. are sent to a separate processing facility.

[0024] In the mixing step P13, an alkali metal salt is mixed with the active material of the waste LIBs sorted in the crushing and sorting step P12, i.e., the positive electrode active material. The mixer 13 is configured to mix an alkali metal salt with the active material and the like removed by the sorter 12b. In this embodiment, at least one selected from the group consisting of sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate is mixed with the active material as the alkali metal salt. A more detailed configuration of the mixer 13 will be described later.

[0025] In the roasting process P14, the mixed waste LIBs are roasted at a predetermined first temperature. The mixed waste LIBs are a mixture containing the active material of the waste LIBs and an alkali metal salt. The roasting device 14 is, for example, an externally heated rotary kiln. The externally heated rotary kiln includes a cylinder 14a that rotates around the central axis and a heating jacket 14b that is provided to surround the outer periphery of the cylinder 14a.

[0026] The cylindrical body 14a has an inlet 14c at one end and an outlet 14d at the other end, and is supported rotatably about its central axis with the central axis inclined at a predetermined angle so as to slope downward from the inlet 14c to the outlet 14d. The waste LIBs supplied from the mixer 13 to the inlet 14c of the cylindrical body 14a are transported toward the outlet 14d by the rotation of the cylindrical body 14a.

[0027] The inside of the cylinder 14a is an air atmosphere. Alternatively, the inside of the cylinder 14a may be a reducing atmosphere or a low-oxygen atmosphere with an oxygen concentration of, for example, 10% or less. By supplying a heating gas to a heating jacket 14b surrounding the outer periphery of the cylinder 14a, the outer wall of the cylinder 14a is heated, and the waste LIBs transported inside the cylinder 14a are heated and discharged as roasted material from the discharge port 14d. The first temperature, which is the roasting temperature in the roasting process P14, is 400°C or higher, and may be, for example, 700°C.

[0028] By mixing an alkali metal salt with the positive electrode active material of a waste LIB containing lithium and phosphorus and then roasting it, the alkali metal ions in the mixture are combined with phosphate ions to form a phosphate. As described above, the alkali metal salt includes one or more of sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate.

[0029] Next, the recovery process P2 will be described. The recovery process P2 includes a first elution process P21, a first separation process P22, and a lithium separation process P20. Fig. 3 is a schematic diagram of a recovery system that performs the recovery process shown in Fig. 1. The recovery system 2 includes a first elution machine 21, a first separator 22, and a lithium separation device 20.

[0030] In the first elution step P21, the roasted material is immersed in water. For this purpose, the first elution machine 21 is configured so that the roasted material is introduced into an immersion tank in which water is stored. The roasted material is supplied to the immersion tank of the first elution machine 21 at a predetermined amount via a hopper 27. As a result, the aqueous solution in the immersion tank becomes a mixture of water and the roasted material. The first elution machine 21 is provided with a stirring mechanism (not shown) that stirs the aqueous solution in the immersion tank.

[0031] In the first elution step P21, magnesium hydroxide (Mg(OH)2) or calcium hydroxide (Ca(OH)2) is added when the roasted product is immersed in water. By adding magnesium hydroxide or calcium hydroxide to the aqueous solution in the immersion tank, the iron, phosphorus, and fluorine in the aqueous solution each produce a compound that is insoluble in water.

[0032] In the first separation step P22, solid-liquid separation is performed on the aqueous solution treated in the first elution step P21. For this purpose, the first separator 22 is configured as a solid-liquid separator. By performing solid-liquid separation by the first separator 22, the iron, phosphorus and fluorine components are removed from the aqueous solution as solid residues.

[0033] The lithium separation process P20 concentrates lithium salts such as Li2O and Li2CO3 from the aqueous solution separated in the first separation process to form a slurry, and separates the slurry into solid and liquid. The lithium separation process P20 includes a second elution process P23, a second separation process P24, a concentration process P25, and a third separation process P26. The lithium separation device 20 includes a second elution machine 23, a second separator 24, a concentrator 25, and a third separator 26 to carry out each process.

[0034] The second eluter 23 includes an immersion tank and a stirring mechanism, similar to the first eluter 21. The aqueous solution after solid-liquid separation in the first separator 22 is introduced into the second eluter 23. Furthermore, carbon dioxide gas is introduced into the aqueous solution in the immersion tank of the second eluter 23. In the second elution step P23, the aqueous solution stored in the immersion tank of the second eluter 23 is bubbled with carbon dioxide gas.

[0035] The pH of the aqueous solution is adjusted to a weak alkaline level by bubbling with carbon dioxide gas, causing the excess magnesium hydroxide or calcium hydroxide added in the first elution step P21 to precipitate as magnesium carbonate (MgCO3) or calcium carbonate (CaCO3).

[0036] In the second separation step P24, solid-liquid separation is performed on the aqueous solution treated in the second elution step P23. By performing solid-liquid separation using the second separator 24, solid impurities including magnesium carbonate or calcium carbonate precipitated in the second elution step P23 are removed from the aqueous solution.

[0037] In the concentration step P25, the aqueous solution obtained by solid-liquid separation in the second separation step P24 is concentrated. The concentrator 25 for this purpose is composed of, for example, an evaporative concentration device that heats the aqueous solution to about 80°C and evaporates the water content of the aqueous solution, or a crystallization device. By concentrating the aqueous solution, the concentration of lithium contained in the aqueous solution increases, and a slurry containing lithium carbonate (Li2CO3) is produced.

[0038] In the third separation step P26, the slurry is subjected to solid-liquid separation. By performing solid-liquid separation using the third separator 26, lithium carbonate is precipitated from the slurry. As a result, lithium is recovered as lithium carbonate. The remaining aqueous solution is subjected to waste liquid treatment. The remaining aqueous solution may be returned to the first eluter 21 or the second eluter 23 again.

[0039] Here, the mixing device 13 in this embodiment will be described in more detail. FIG. 4 is a schematic diagram showing the mixing device in the processing system of this embodiment. FIG. 4 shows a cross-sectional view in a virtual plane including central axes S31 and S32 described later. The mixing device 13 in this embodiment is configured as a so-called crushing machine. The mixing device 13 is configured to crush the alkali metal salt and knead it into the active material and the like taken out by the sorting machine 12b. A more detailed description will be given below.

[0040] The mixing device 13 includes a receiving container 31 and a mixer 32. The receiving container 31 has a cone-shaped inner surface 31b that defines a storage section 31a on the inside. An alkali metal salt is fed into the receiving container 31 from a first input section 33, and the active material, etc. removed by the sorter 12b is fed into the receiving container 31 from a second input section 34. As a result, the alkali metal salt and the active material, etc. are stored in the storage section 31a of the receiving container 31.

[0041] The receiving container 31 is supported by a base 35 so as to be rotatable around a central axis S31 of the inner surface 31b of the storage section 31a. A driving source such as a motor for driving the receiving container 31 to rotate is provided on the base 35, and drives the receiving container 31 to rotate. The central axis S31 extends in the vertical direction.

[0042] The mixer 32 is supported by a support part 36 whose base end part extends upward from a base 35. In the example of Fig. 4, the support part 36 is fixed integrally to the base 35, but instead, the support part 36 may be configured by an articulated robot having a predetermined number of degrees of freedom. In other words, the mixer 32 may be held at the tip part of the articulated robot.

[0043] The mixer 32 has an extension portion 32a extending from a base end in a first direction D1 close to the inner surface 31b of the receiving container 31, and an action portion 32b provided at a tip end of the extension portion 32a. The action portion 32b has a plurality of tips branching out and extending from the extension portion 32a.

[0044] The central axis S32 of the mixer 32 is inclined with respect to the central axis S31 of the receiving container 31. The central axis S32 of the mixer 32 intersects with the inner surface 31b of the receiving container 31 at a position radially outward from the central axis S31 of the inner surface 31b of the receiving container 31 in a plan view. The mixer 32 is biased in a first direction D1 approaching the inner surface 31b of the receiving container 31, i.e., in a direction along the central axis S32 of the mixer 32, by a biasing means such as a spring. This keeps the mixer 32 in contact with the inner surface 31b of the receiving container 31 or the input material contained in the storage section 31a.

[0045] The mixer 32 is configured to be rotatable around the central axis S32 of the extension portion 32a while being biased in the first direction D1. The extension portion 32a rotates around the central axis S32, i.e., rotates on its axis, causing the multiple tips of the action portion 32b to revolve around the central axis S32. That is, the action portion 32b of the mixer 32 moves, i.e., revolves, within a virtual plane VP intersecting the first direction D1 relative to the receiving container 31 within the receiving container 31, as the mixer 32 rotates around the central axis S32. A drive source such as a motor that drives the mixer 32 to rotate is provided on the support portion 36, and drives the mixer 32 to rotate.

[0046] With this configuration, the mixer 32 moves within the receiving container 31 in a virtual plane VP intersecting the first direction D1 relative to the receiving container 31 while being biased in the first direction D1 approaching the inner surface 31b of the receiving container 31. Furthermore, in addition to the above-mentioned operation of the mixer 32, the receiving container 31 itself rotates around the central axis S31, so that the range in which the mixer 32 moves on the inner surface 31b of the receiving container 31 changes relatively in the circumferential direction.

[0047] When the alkali metal salt and active material are placed in the storage section 31a of the receiving container 31, the mixer 32 and the receiving container 31 are operated, and the alkali metal salt between the tip of the action section 32b of the mixer 32 and the inner surface 31b of the receiving container 31 is ground up by the sliding of the mixer 32 due to the biasing force of the mixer 32 toward the receiving container 31 and its relative movement with respect to the receiving container 31, and the ground alkali metal salt is kneaded into the active material.

[0048] If the alkali metal salt is simply stirred, it is likely to absorb moisture in the air and become lumpy. Therefore, by kneading the alkali metal salt with the active material while grinding it, that is, by performing the grinding step and the kneading step simultaneously, the alkali metal salt can be uniformly attached to the active material.

[0049] Furthermore, the mixer 13 is configured so that the alkali metal salt and the active material are simultaneously charged into the receiving vessel 31. This facilitates more homogeneous mixing of the alkali metal salt and the active material.

[0050] The biasing force of the mixer 32 in the first direction D1 is appropriately set depending on the input amount of the alkali metal salt and the active material, the mixing time, the required lithium elution rate, and the like. As a result of intensive research, the inventors of the present invention have obtained the following findings regarding the relationship between the input amount, the biasing force, the mixing time, and the lithium elution rate. That is, the lithium elution rate tends to increase as the biasing force increases, but if the mixing time is extended, the magnitude of the biasing force becomes unimportant. In other words, the mixing time contributes more to the lithium elution rate than the magnitude of the biasing force, in other words, it has a higher setting priority. Also, the lithium elution rate tends to decrease as the input amount increases.

[0051] In addition, in the mixing step P13 in the mixer 13, when the input materials are concentrated on the periphery of the receiving container 31, a consolidation step may be performed to scrape or gather the input materials in the center of the receiving container 31. Alternatively, the consolidation step may be performed periodically in the mixing step P13. The consolidation step may be performed manually, or the mixer 13 may be capable of performing the consolidation operation.

[0052] For example, the support part 36 that supports the mixer 32 may be configured by an articulated robot having a predetermined number of degrees of freedom, and in the collecting step, the articulated robot may be controlled so that the action part 32b of the mixer 32 moves from the periphery toward the center on the inner surface 31b of the receiving container 31. Note that the collecting step may be performed by a robot device or the like other than the mixer 13.

[0053] As described above, according to the above method, the positive electrode active material containing phosphorus and lithium of the waste LIB is mixed with an alkali metal salt other than lithium before the waste LIB is roasted. At this time, by mixing the alkali metal salt with the positive electrode active material while grinding it, the decomposition of the positive electrode active material containing thermally stable phosphorus is promoted when the positive electrode active material is roasted. In addition, since the bond between phosphorus and the alkali metal can be promoted before lithium phosphate is generated, the generation of lithium phosphate (Li3PO4) that is insoluble in water due to the bond between the phosphate ion contained in the positive electrode active material and lithium is suppressed. In this way, according to the above method, it is possible to prevent lithium from becoming insoluble when the roasted product is immersed in water. Therefore, it is possible to dissolve lithium into water and recover it from the waste LIB containing phosphorus and lithium as the positive electrode active material without using an acidic solution or an alkaline solution or going through other complicated processes, and the dissolution rate can be improved.

[0054] Furthermore, the waste LIBs are pretreated to decompose and remove the electrolyte, the pretreated waste LIBs are crushed, the positive electrode active material is selected, and then an alkali metal salt is mixed with the positive electrode active material, which makes it easier to mix the positive electrode active material with the alkali metal salt and to promote bonding between phosphorus and the alkali metal contained in the positive electrode active material.

[0055] In addition, the positive electrode active material is mixed with the alkali metal salt as an independent step separate from the pretreatment step P11, the crushing and sorting step P12, or the roasting step P14. This allows the positive electrode active material to be sufficiently mixed with the alkali metal salt, and effectively prevents lithium from bonding with phosphorus during roasting.

[0056] Furthermore, in this embodiment, the alkali metal salt is charged as a carbonate into the mixer 13. Carbonates are easy to obtain, less dangerous than hydroxides, and easier to handle. Therefore, the mixing step P13 can be introduced inexpensively and easily into the pyrolysis step.

[0057] For example, the ratio (A / P ratio) of the amount of alkali metal contained in the alkali metal salt to the amount of phosphorus contained in the positive electrode active material (P) is 1.5 or more and 3.0 or less. In the experiment, the roasting step P14 was performed in an air atmosphere at a roasting temperature of 700°C for 2 hours. The weight ratio of the roasted material to water in the first elution step P21 was set to roasted material:water=1:100. The first elution step P21 was performed at room temperature.

[0058] As mentioned above, the A / P ratio is the mixing ratio of the alkali metal salt to the positive electrode active material, expressed as the ratio of the amount of alkali metal (A) to the amount of phosphorus (P), i.e., as a molar ratio. In experiments, a good lithium elution rate was achieved when the A / P ratio was 1.5 or more and 3.0 or less.

[0059] (Example) The results of a mixing test using the above-mentioned mixer 13 are shown below. A predetermined crusher was used as the mixer 13, and a predetermined alkali metal salt and active material were charged into the receiving container 31 at a predetermined A / P ratio, and the mixer 13 was operated to mix them. The total amount of the alkali metal salt and active material charged was 6 g. The operation time of the mixer 13, i.e., the mixing time, was 5 minutes for the total amount.

[0060] As Comparative Example 1, the same amount of alkali metal salt and active material as in the Example were put into a specified bottle, and the bottle was shaken for the same 5 minutes as in the Example. Also, as Comparative Example 2, a simple ball mill was made. The simple ball mill is configured to rotate a specified cylindrical body made of stainless steel in a circumferential direction with a specified amount of alumina balls with a diameter of 3 mm put into the cylindrical body. The rotation axis of the cylindrical body extends horizontally. The same amount of alkali metal salt and active material as in the Example were put into the cylindrical body of such a simple ball mill, and the ball was rotated for 2 hours.

[0061] Thereafter, the recovery step P2 was carried out for each mixture, and the elution rate of lithium into water was examined. As a result, in the example using the above-mentioned mixer 13, the elution rate of lithium was 87.5%, which was a good result. On the other hand, in the comparative example 1, the elution rate of lithium was 24.0%, which showed that a good elution rate of lithium could not be obtained by simply stirring.

[0062] In Comparative Example 2, the lithium elution rate was 70.9%. Although Comparative Example 2 took a much longer time than the Examples, a sufficient lithium elution rate could not be obtained. From this, it is presumed that the mixing method using a ball mill does not sufficiently grind the alkali metal salt.

[0063] From the above, it can be seen that in the mixing step P13 of mixing the active material and the alkali metal salt, it is important to knead the alkali metal salt into the positive electrode active material while grinding it in order to improve the elution rate of lithium.

[0064] From the above description, many improvements and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the above description should be construed as merely illustrative and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function thereof may be substantially changed without departing from the spirit of the present invention.

[0065] For example, in the above embodiment, a grinder is exemplified as the mixer 13, but the present invention is not limited to this, and the mixer may be configured to grind the alkali metal salt while kneading it into the positive electrode active material.

[0066] For example, in the above embodiment, the mixer 13 has a configuration in which the central axis S32 of the mixer 32 is inclined with respect to the central axis S31 of the receiving container 31, but the present invention is not limited to this, and the central axis S32 of the mixer 32 may extend in the vertical direction. In addition, in the above embodiment, the receiving container 31 rotates around the central axis S31, but the receiving container 31 may be fixed to the base 35.

[0067] In the above embodiment, the mixer 32 rotates around the central axis S32. However, the present invention is not limited to this. The mixer 32 may reciprocate in a direction intersecting the central axis S32, i.e., the first direction D1. The action portion at the tip of the mixer 32 may move three-dimensionally. That is, the mixer 32 may not be constantly biased in the first direction D1 during mixing. The force of biasing the mixer 32 in the first direction D1 may be changed stepwise or continuously.

[0068] For example, the receiving container 31 may be formed in a mortar shape as in the above embodiment, or may have a horizontal or convex bottom surface like the lower member of a mill called a lower mill or a fixed mill. The mixer 32 may be configured as a rod-shaped body having an action part at the tip as in the above embodiment. Specifically, the mixer 32 may have a pestle-shaped tip or a spatula-shaped tip. The mixer 32 may have a shape corresponding to the receiving container 31 like the upper member of a mill called an upper mill or a rotary mill.

[0069] In this way, the mixing device 13 may be configured with a mortar and pestle, or may be configured as a mill. When the mixing device 13 is configured as a mill, a groove may be formed on the facing surface, i.e., the mill surface, of at least one of the receiving container 31 configured as the lower member of the mill and the mixer 32 configured as the upper member of the mill.

[0070] In addition, in the above embodiment, a processing system in which one or more devices or equipment correspond to each process is exemplified, but the processing system may be configured to realize multiple processes using one device or equipment.

[0071] In addition, in the above embodiment, an example was given of a form in which a carbonate of an alkali metal other than lithium, including one or more of sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate, is mixed with the positive electrode active material of a waste LIB, but a hydroxide of an alkali metal other than lithium may also be mixed. [Industrial Applicability]

[0072] INDUSTRIAL APPLICABILITY The present invention is useful for enabling the recovery of lithium from used lithium ion batteries containing phosphorus as a positive electrode active material by dissolving it into water without going through complicated steps, and for improving the dissolution rate. [Explanation of symbols]

[0073] 1. Pyrolysis System 2. Collection System 11 Pretreatment device 12 Crushing and sorting equipment 13 Mixing device 14 Roasting equipment 20 Lithium Separation Device 21 1st eluator 22 1st separator 23 Second eluator 24 Second separator

Claims

1. A waste lithium ion battery treatment system for recovering lithium from waste lithium ion batteries by immersing a roasted product obtained by roasting waste lithium ion batteries containing phosphorus as a positive electrode active material in water to dissolve lithium, comprising: A mixing device for mixing an alkali metal salt other than lithium with a positive electrode active material contained in waste lithium ion batteries; A roasting device that roasts the mixture mixed in the mixing device at a predetermined first temperature, The mixing device is configured to grind the alkali metal salt while kneading it into the positive electrode active material.

2. The mixing device comprises: a receiving vessel into which the alkali metal salt and the positive electrode active material are placed; 2. The waste lithium ion battery processing system of claim 1, further comprising: a mixer that is biased in a first direction adjacent to the inner surface of the receiving container and moves relative to the receiving container in a second direction intersecting the first direction within the receiving container.

3. The mixing device comprises: a first input section for inputting the alkali metal salt into the receiving container; A second input unit that inputs the positive electrode active material into the receiving container, The waste lithium ion battery treatment system according to claim 2 , wherein the alkali metal salt and the positive electrode active material are simultaneously introduced into the receiving container.

4. The waste lithium ion battery processing system according to claim 1 , wherein the mixing device is a crusher.

5. A method for treating used lithium ion batteries, comprising: roasting a used lithium ion battery containing phosphorus as a positive electrode active material; immersing a roasted product obtained by roasting the used lithium ion battery in water to dissolve lithium; and recovering the lithium from the used lithium ion battery, A mixing step of mixing an alkali metal salt other than lithium with a positive electrode active material contained in the waste lithium ion batteries; and a roasting step of roasting the mixed mixture at a predetermined first temperature, The mixing step comprises mixing the alkali metal salt with the positive electrode active material in such a manner that the alkali metal salt is ground and kneaded into the positive electrode active material.

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