Method and system for treating waste lithium-ion batteries

Abstract

This treatment method for a waste lithium ion battery is for recovering lithium from a waste lithium ion battery containing phosphorus as a positive electrode active material, the method comprising: a thermal decomposition step in which the waste lithium ion battery is thermally decomposed by roasting to produce a roasted product containing the positive electrode active material; and a recovery step in which the roasted product is immersed in water to elute the lithium, and then the lithium is recovered, wherein the thermal decomposition step includes a roasting step in which the waste lithium ion battery is roasted at a predetermined first temperature, and a mixing step in which an alkali metallic salt other than lithium is mixed with the positive electrode active material of the waste lithium ion battery before the roasting step.

Description

[Technical field]

[0001] The present invention relates to a method and system 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 method and system for treating used lithium-ion batteries that can dissolve and recover lithium from used lithium-ion batteries that contain phosphorus as a positive electrode active material into water without going through complicated processes, and can improve the purity of the lithium. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, a method for treating used lithium ion batteries according to one embodiment of the present invention is a method for recovering lithium from used lithium ion batteries containing phosphorus as a positive electrode active material, the method including: a pyrolysis step of pyrolyzing the used lithium ion batteries by roasting to produce a roasted material containing the positive electrode active material; and a recovery step of immersing the produced roasted material in water to dissolve the lithium and then recovering the lithium, the pyrolysis step including: a roasting step of roasting the used lithium ion batteries at a predetermined first temperature; and a mixing step of mixing an alkali metal salt other than lithium with the positive electrode active material of the used lithium ion batteries prior to the roasting step.

[0010] In addition, a treatment system for used lithium ion batteries according to another aspect of the present invention is a treatment system for used lithium ion batteries for recovering lithium from used lithium ion batteries containing phosphorus as a positive electrode active material, the treatment system including: a pyrolysis system for pyrolyzing the used lithium ion batteries by roasting to generate a roasted material containing the positive electrode active material; and a recovery system for immersing the generated roasted material in water to dissolve the lithium and then recovering the lithium, the pyrolysis system including: a roasting device for roasting the used lithium ion batteries at a predetermined first temperature; and a mixing device for mixing an alkali metal salt other than lithium with the positive electrode active material of the used lithium ion batteries before roasting in the roasting device.

[0011] According to the above method or system, before roasting the used lithium ion battery, the positive electrode active material of the used lithium ion battery is mixed with an alkali metal salt other than lithium. As a result, the positive electrode active material is roasted to decompose the positive electrode active material containing thermally stable phosphorus, and the phosphate ion and the alkali metal ion can be bonded before the phosphate ion and lithium contained in the positive electrode active material are bonded to lithium during elution to generate lithium phosphate (Li3PO4) that is insoluble in water, thereby preventing the insolubilization of lithium. Therefore, lithium can be eluted into water and recovered from the used lithium ion battery containing phosphorus as the positive electrode active material without going through a complicated process. Effect of the Invention

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

[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. 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 as the alkali metal salt with the active material. The mixer 13 is configured, for example, by a roller mill, a paddle mixer, a crusher, or the like.

[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 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] 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. Even if the waste LIB is roasted without mixing with an alkali metal salt, the positive electrode active material containing phosphorus is thermally stable and does not decompose.

[0040] Therefore, as in the present embodiment, 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, so that when the positive electrode active material is roasted, the phosphate ions and the alkali metal ions can be bonded before lithium phosphate is generated, and lithium can be prevented from becoming insoluble. 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 or alkaline solution or going through other complicated processes.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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, in the roasting step P14, roasting was performed in an air atmosphere at a roasting temperature of 700°C for 2 hours. In addition, 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.

[0045] 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 to the amount of phosphorus, i.e., as a molar ratio. In the experiment, a good lithium elution rate was achieved when the A / P ratio was 1.5 or more and 3.0 or less.

[0046] In the present embodiment, magnesium hydroxide or calcium hydroxide is added when the roasted product is immersed in water in the recovery step P2, more specifically, in the first elution step P21. This allows the roasted product containing lithium to be immersed in water, and after the lithium is eluted into the water, the iron, phosphorus, and fluorine contained in the roasted product can be precipitated as insoluble compounds. Therefore, the iron, phosphorus, and fluorine can be easily separated as solids from the aqueous solution containing lithium.

[0047] In addition, in order to remove excess magnesium or calcium from the aqueous solution that has become alkaline due to the addition of magnesium hydroxide or calcium hydroxide, carbon dioxide gas is bubbled into the aqueous solution in the second elution step P23 in the lithium separation step P20. This adjusts the pH of the aqueous solution to weak alkalinity, forming carbonates and removing excess magnesium or calcium from the aqueous solution. In addition, bubbling carbon dioxide gas can supply a carbonate source for precipitating lithium to the aqueous solution.

[0048] Furthermore, in the third separation step P26 in the lithium separation step P20, the slurry containing lithium carbonate is washed with hot water. The hot water used is, for example, water heated to 80° C. or higher.

[0049] During the concentration of the aqueous solution in the concentration step P25, not only the lithium carbonate to be recovered but also the mixed alkali metal salts may precipitate. That is, as the mixed alkali metal salts, one or more of sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate may precipitate. In the concentration step P25, as described above, the aqueous solution is heated to about 80°C. It is known that the solubility of the mixed alkali metal salts in water at 80°C is higher than the solubility of lithium carbonate in water at 80°C, that is, they are easily dissolved in water. For this reason, it is generally considered that in the concentration step P25, when the aqueous solution containing lithium carbonate and the mixed alkali metal salts obtained as the aqueous solution after the treatment in the second separation step P24 is heated to about 80°C and concentrated, lithium carbonate precipitates first and can be separated from the easily soluble mixed alkali metal salts.

[0050] However, when the inventors actually conducted an experiment using the LFP reagent, they found that not only lithium carbonate but also the mixed alkali metal salts may precipitate during concentration. If the mixed alkali metal salts precipitate in the concentration step P25, it becomes difficult to obtain lithium recovered in the lithium separation step P20, more specifically the third separation step P26, with a high purity of, for example, 99.5% or more, which is the purity of a battery. It was also found that if the concentration rate is reduced to increase the purity of lithium carbonate, the precipitation of lithium carbonate also decreases, and the recovery rate of lithium carbonate decreases.

[0051] As a result of intensive research by the inventors into such problems, they have found that, as described above, lithium carbonate can be separated from the mixed alkali metal salt by washing a slurry containing lithium carbonate with hot water. That is, by utilizing the property that lithium carbonate is less soluble the higher the temperature of the aqueous solution, lithium carbonate can be precipitated while dissolving the mixed alkali metal salt by washing the slurry with hot water and performing solid-liquid separation. As a result, it is possible to realize the recovery of high-purity lithium carbonate.

[0052] Instead of introducing hot water into the third separator 26 and washing the concentrated slurry during solid-liquid separation, a dehydrated cake containing lithium carbonate obtained by solid-liquid separation may be washed with hot water. That is, the dehydrated cake after solid-liquid separation in the third separator 26 may be washed with hot water. The amount of hot water to be added may be set to a predetermined amount depending on conditions, such as whether washing is performed during solid-liquid separation or after solid-liquid separation.

[0053] 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.

[0054] For example, 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.

[0055] 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]

[0056] This method enables lithium to be recovered from used lithium-ion batteries that contain phosphorus as a positive electrode active material by dissolving it in water without going through complicated processes, and is useful for improving the recovery rate. [Explanation of symbols]

[0057] 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 method for treating used lithium ion batteries for recovering lithium from used lithium ion batteries containing phosphorus as a positive electrode active material, comprising: a pyrolysis step of pyrolyzing the waste lithium ion batteries by roasting to generate a roasted product containing the positive electrode active material; A recovery step of immersing the produced roasted product in water to dissolve the lithium and then recovering the lithium, The pyrolysis step comprises: A roasting step of roasting the waste lithium ion batteries at a predetermined first temperature; a mixing step of mixing an alkali metal salt other than lithium with the positive electrode active material of the waste lithium ion batteries prior to the roasting step.

2. 2. The method for treating used lithium ion batteries according to claim 1, wherein the mixing step includes mixing the positive electrode active material with one or more of sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate.

3. 3. The method for treating used lithium ion batteries according to claim 1, wherein a ratio of an elemental amount of alkali metal contained in the alkali metal salt to an elemental amount of phosphorus contained in the positive electrode active material is 1.5 or more and 3.0 or less.

4. 4. The method for treating waste lithium ion batteries according to claim 1, wherein in the recovery step, magnesium hydroxide or calcium hydroxide is added when the roasted product is immersed in water.

5. The recovery step includes: A first leaching step of immersing the roasted product in water; a first separation step of performing solid-liquid separation on the aqueous solution treated in the first elution step; a lithium separation step of concentrating the lithium salt aqueous solution from the aqueous solution separated in the first separation step to form a slurry, and separating the slurry into a solid and liquid; The lithium separation step includes: a second elution step of bubbling carbon dioxide gas into the aqueous solution; The method for treating used lithium ion batteries according to claim 1 , further comprising a second separation step of performing solid-liquid separation on the aqueous solution treated in the second elution step.

6. The recovery step includes: A first leaching step of immersing the roasted product in water; a first separation step of performing solid-liquid separation on the aqueous solution treated in the first elution step; a lithium separation step of concentrating the lithium salt aqueous solution from the aqueous solution separated in the first separation step to form a slurry, and separating the slurry into a solid and liquid; 6. The method for treating used lithium ion batteries according to claim 1, wherein in the lithium separation step, the slurry or a dehydrated cake obtained by solid-liquid separation of the slurry is washed with hot water.

7. The pyrolysis step comprises: a pretreatment step of roasting the used lithium ion batteries at a second temperature lower than the first temperature in order to decompose and remove an electrolyte contained in the used lithium ion batteries; a crushing and sorting step of crushing the waste lithium ion batteries treated in the pretreatment step, and separating the positive electrode active material from a positive electrode current collector of the crushed waste lithium ion batteries to select the positive electrode active material, The method for treating used lithium ion batteries according to claim 1 , wherein the mixing step is carried out after the crushing and sorting step.

8. A waste lithium ion battery treatment system for recovering lithium from waste lithium ion batteries containing phosphorus as a positive electrode active material, comprising: A pyrolysis system that pyrolyzes the waste lithium ion batteries by roasting to generate a roasted product containing the positive electrode active material; A recovery system for recovering the lithium after immersing the produced roasted product in water to dissolve the lithium, The pyrolysis system comprises: A roasting device that roasts the waste lithium ion batteries at a predetermined first temperature; a mixing device that mixes an alkali metal salt other than lithium with the positive electrode active material of the waste lithium ion batteries before roasting in the roasting device.

9. The waste lithium ion battery treatment system according to claim 8 , wherein the mixing device mixes the positive electrode active material with at least one of sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate.

10. 10. The waste lithium ion battery treatment system according to claim 8 or 9, wherein the 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 is 1.5 or more and 3.0 or less.

11. The system for treating waste lithium ion batteries according to claim 8 , wherein the recovery system adds magnesium hydroxide or calcium hydroxide when the roasted product is immersed in water.

12. The recovery system comprises: A first leaching machine for immersing the roasted product in water; a first separator for performing solid-liquid separation on the aqueous solution treated in the first elution device; a lithium separation device for concentrating the lithium salt aqueous solution from the aqueous solution separated by the first separator to form a slurry, and separating the slurry into a solid and liquid, The lithium separation device includes: a second elution device for bubbling carbon dioxide gas into the aqueous solution; The waste lithium ion battery treatment system according to claim 8 , further comprising: a second separator that performs solid-liquid separation on the aqueous solution treated in the second elution device.

13. The recovery system comprises: A first leaching machine for immersing the roasted product in water; a first separator for performing solid-liquid separation on the aqueous solution treated in the first elution device; a lithium separation device for concentrating the lithium salt aqueous solution from the aqueous solution separated by the first separator to form a slurry, and separating the slurry into a solid and liquid, The waste lithium ion battery treatment system according to any one of claims 8 to 11, wherein the lithium separation device is configured to wash the slurry or a dehydrated cake obtained by solid-liquid separation of the slurry, using hot water.

14. The pyrolysis system comprises: a pretreatment device for roasting the used lithium ion batteries at a second temperature lower than the first temperature in order to decompose and remove an electrolyte contained in the used lithium ion batteries; a crushing and sorting device that crushes the waste lithium ion batteries treated in the pretreatment device, separates the positive electrode active material from the positive electrode current collector of the crushed waste lithium ion batteries, and sorts the positive electrode active material, The waste lithium ion battery treatment system according to claim 8 , wherein the mixing device mixes the alkali metal salt with the positive electrode active material separated by the crushing and separating device.

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