JP2016058280A - Method for recovering positive electrode active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which a positive electrode active material can be efficiently recovered from a positive electrode of a sulfide solid battery while suppressing the production of a hydrogen sulfide, and a process liquid can be utilized repeatedly.SOLUTION: A method for recovering a positive electrode active material from a positive electrode including the positive electrode active material, a sulfide solid electrolyte and a binder comprises the steps of: obtaining a solid-liquid mixture by immersing the positive electrode in an aprotic solvent to dissolve the sulfide solid electrolyte and the binder in the aprotic solvent while the positive electrode active material is left in the aprotic solvent as a solid content; performing a solid-liquid separation of the resultant solid-liquid mixture; recovering the positive electrode active material from a solid content obtained as a result of the solid-liquid separation of the solid-liquid mixture; and distilling a liquid content obtained as a result of the solid-liquid separation of the solid-liquid mixture thereby obtaining a recovered liquid including the aprotic solvent.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for efficiently recovering a positive electrode active material from a positive electrode of a sulfide solid state battery.

  A sulfide solid state battery is known as one of batteries having excellent safety. The sulfide solid state battery includes an electrode including an active material, a sulfide solid electrolyte, and the like, and a solid electrolyte layer provided between the electrodes. Active materials and sulfide solid electrolytes are composed of valuable components such as rare metals, and it is desirable to recover and reuse these valuable components from waste solid batteries that have passed their useful lives.

For example, Patent Document 1 discloses that a treatment liquid containing water is brought into contact with a positive electrode member containing a sulfide solid electrolyte, so that lithium is dissolved in the treatment liquid. A technique for recovering a lithium treatment liquid containing Li ₃ PO ₄ by recovering a substance and drying the residue is disclosed. Patent Document 2 also discloses a technique for recovering metal from the positive electrode of a sulfide solid state battery. Although not related to a sulfide solid state battery, Patent Document 3 discloses a technique for treating a positive electrode with an aprotic polar solvent.

International Publication No. 2010/106618 Pamphlet JP 2010-040458 A JP 2012-022969 A

  The technique disclosed in Patent Document 1 has a problem that the treatment liquid cannot be repeatedly used because the treatment liquid containing water reacts with the sulfide solid electrolyte. There is also a problem in that hydrogen sulfide is generated by the reaction of water and the sulfide solid electrolyte.

  Therefore, the present invention has an object to provide a method capable of efficiently recovering the positive electrode active material from the positive electrode of the sulfide solid state battery and reusing the treatment liquid while suppressing the generation of hydrogen sulfide. To do.

In order to solve the above problems, the present invention adopts the following configuration. That is,
The present invention is a method for recovering a positive electrode active material from a positive electrode containing a positive electrode active material, a sulfide solid electrolyte, and a binder, wherein the positive electrode is immersed in an aprotic solvent, and the positive electrode active material is immersed in the aprotic solvent. In which the sulfide solid electrolyte and the binder are dissolved in an aprotic solvent to obtain a solid-liquid mixture, the obtained solid-liquid mixture is solid-liquid separated, and the solid-liquid mixture is solidified. A step of recovering the positive electrode active material from the solid content obtained by liquid separation, and a step of obtaining a recovered liquid containing an aprotic solvent by distilling the liquid content obtained by solid-liquid separation of the solid-liquid mixture. It is a method to prepare.

“Solid-liquid separation of the solid-liquid mixture” means that the liquid in the solid-liquid mixture is subjected to solid-liquid separation “while maintaining the state of the liquid”. That is, the form which performs the solid-liquid separation by volatilizing the liquid component in the solid-liquid mixture is not included. Examples of the method for solid-liquid separation of the liquid component in the solid-liquid mixture while maintaining the liquid component state include filtration and centrifugation.

  In the present invention, the method further comprises a step of measuring the electric conductivity or resistance of the recovered liquid. When the electric conductivity or resistance is higher than the threshold value, it is determined that the purity of the aprotic solvent in the recovered liquid is low, and the recovered liquid is Distillation is preferred.

  In the present invention, after the positive electrode is immersed in an aprotic solvent to form a solid-liquid mixture, the positive electrode active material can be efficiently recovered from the solid content obtained by solid-liquid separation of the solid-liquid mixture. Further, by distilling a liquid component obtained by solid-liquid separation of a solid-liquid mixture, a recovered liquid containing an aprotic solvent can be obtained, and the recovered liquid can be reused as an aprotic solvent. . Furthermore, by using an aprotic solvent, the generation of hydrogen sulfide due to the reaction with the sulfide solid electrolyte can be suppressed. That is, according to the present invention, it is possible to provide a method capable of efficiently recovering the positive electrode active material from the positive electrode of the sulfide solid state battery and repeatedly using the treatment liquid while suppressing the generation of hydrogen sulfide. it can.

It is a figure for demonstrating method S10 which concerns on this invention. It is a figure for demonstrating an example of process S3 which collect | recovers positive electrode active materials from solid content. It is a figure for demonstrating process S4 and S5 which raise the purity of a collection | recovery liquid. It is a figure for demonstrating process S4 and S6 which raise the purity of a collection | recovery liquid. It is a figure for demonstrating process S6 and S7 which raise the purity of a collection | recovery liquid. It is a figure for demonstrating process S5 and S6 which raise the purity of a collection | recovery liquid.

  The present invention is a method for recovering a positive electrode active material from a positive electrode including a positive electrode active material, a sulfide solid electrolyte, and a binder. FIG. 1 shows the flow of the method S10 of the present invention according to one embodiment. As shown in FIG. 1, Method S10 includes immersing the positive electrode in an aprotic solvent, leaving the positive electrode active material as a solid content in the aprotic solvent, and removing the sulfide solid electrolyte and binder from the aprotic solvent. Step S1 for obtaining a solid-liquid mixture by dissolving the solid-liquid mixture, Step S2 for solid-liquid separation of the obtained solid-liquid mixture, and Step S3 for recovering the positive electrode active material from the solid content obtained by solid-liquid separation of the solid-liquid mixture And a step S4 of obtaining a recovered liquid containing an aprotic solvent by distilling a liquid component obtained by solid-liquid separation of the solid-liquid mixture.

1. Process S1
In step S1, the positive electrode is immersed in an aprotic solvent, and the positive electrode active material remains as a solid in the aprotic solvent, while the sulfide solid electrolyte and the binder are dissolved in the aprotic solvent to obtain a solid-liquid mixture. It is the process of obtaining. Here, the step S1 may be a step involving stirring and heating in order to efficiently perform the process.

1.1. Positive electrode In the present invention, the positive electrode contains a positive electrode active material, a sulfide solid electrolyte, and a binder. Moreover, a positive electrode current collector, a conductive material, or the like may be included as other positive electrode materials. Such a positive electrode can be easily recovered from the sulfide solid electrolyte, for example, by crushing the sulfide solid state battery.

1.1.1. Positive electrode active material The positive electrode active material is known as a positive electrode active material for sulfide solid state batteries. In particular, a positive electrode active material capable of inserting and extracting lithium ions is preferable. Specifically, LiCoO ₂ , Li (Ni, Co, Al) O ₂ , Li _{1 + x} Ni _1/3 Mn _1/3 Co _1/3 O ₂ (x is a real number of 0 or more), LiNiO ₂ , LiMn ₂ O ₄ , LiCoMnO ₄ , Li ₂ NiMn ₃ O ₈ , Li ₃ Fe ₂ (PO ₄ ) ₃ , Li ₃ V ₂ (PO ₄ ) ₃ , Li _{1 + x} Mn _2−xy M _y O ₄ (M is Al, Heterogeneous element-substituted Li—Mn spinel having a composition represented by Mg, Co, Fe, Ni, and Zn, at least one metal selected from the group consisting of Zn, lithium titanate (Li _x TiO _y ), LiMPO ₄ (M Can be mentioned lithium metal phosphate having a composition represented by Fe, Mn, Co or Ni). Among these, LiCoO ₂ , Li (Ni, Co, Al) O ₂ , and LiNi _1/3 Mn _1/3 Co _1/3 O ₂ are preferable. Although the shape of a positive electrode active material is not specifically limited, A powder form is preferable.

The positive electrode active material may be covered with a coating layer. The coating layer is a layer that can suppress the formation of a high resistance layer at the interface between the positive electrode active material and the sulfide solid electrolyte, has lithium ion conductivity, and has a form of a coating layer on the surface of the active material. It is a layer containing a material that can be maintained. For _{example, LiNbO 3, Li 4 Ti 5} O 12, or include a layer made of _Li 3 PO _4. A layer made of LiNbO _{3 is} particularly preferable. The thickness of the coating layer is not particularly limited.

1.1.2. Sulfide solid electrolyte A sulfide solid electrolyte is a solid electrolyte containing a sulfur atom in its molecular structure or composition. In particular, a glass or glass ceramic solid electrolyte containing sulfide is preferable. For example, a solid electrolyte containing Li, A (A is at least one of P, Si, Ge, Al, and B) and S is preferable, and a solid electrolyte further containing a halogen element is more preferable. _{Specifically, Li 2 S-P 2 S} 5, Li 2 S-P 2 S 3, Li 2 S-P 2 S 3 -P 2 S 5, Li 2 S-SiS 2, LiI-Li 2 S- _{SiS 2, LiI-Li 2 S} -P 2 S 5, LiI-Li 2 S-P 2 O 5, LiI-Li 3 PO 4 -P 2 S 5, LiI-Li 2 S-SiS 2 -P 2 S 5 _{, Li 2 S-SiS 2 -Li} 4 SiO 4, Li 2 S-SiS 2 -Li 3 PO 4, Li 3 PS 4 -Li 4 GeS 4, Li 3.4 P 0.6 Si 0.4 S 4, Examples include Li _3.25 P _0.25 Ge _0.76 S ₄ , Li _4-x Ge _1-x P _x S _{4, and the} like. Among them, a Li ₂ S and _{P 2 S 5, Li 2 S} : P 2 S 5 = 50: 50~100: it is preferable that a proportion of 0. The shape of the solid electrolyte is not particularly limited, but a powder is preferable.

1.1.3. Binder The binder is a known binder used in the positive electrode of a sulfide solid state battery. For example, polyvinylidene fluoride (PVDF), acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE) and the like are preferable.

1.1.4. Other positive electrode materials The positive electrode to be treated by the present invention may include a positive electrode current collector and a conductive material in addition to the above-described materials. The positive electrode current collector is a metal containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. A current collector made of a material can be exemplified. The conductive material is preferably a carbon material such as vapor-grown carbon fiber, acetylene black (AB), ketjen black (KB), carbon nanotube (CNT), or carbon nanofiber (CNF). As will be described later, the positive electrode current collector and the conductive material are present as solids in the solid-liquid mixture.

  In the positive electrode to be treated by the present invention, the content of each material described above is not particularly limited.

1.2. Aprotic solvent In the present invention, the positive electrode described above is immersed in an aprotic solvent. The aprotic solvent is a solvent capable of dissolving the sulfide solid electrolyte and the binder while allowing the positive electrode active material to exist as a solid content when the positive electrode is immersed. Examples of such aprotic solvents include ketones such as acetone and cyclohexanone; lactams such as 1-methyl-2-pyrrolidone and 1-ethyl-2-pyrrolidone; amides such as dimethylacetamide and diethylformamide; preferable. For example, when PVDF is used as the binder, it is preferable to use 1-methyl-2-pyrrolidone (NMP) as the aprotic solvent.

1.3. Solid-liquid mixture In this invention, a solid-liquid mixture is obtained by immersing said positive electrode in said aprotic solvent. The content ratio of the positive electrode and the aprotic solvent in the solid-liquid mixture is not particularly limited. In the solid-liquid mixture, at least the positive electrode active material exists as a solid content, and at least the sulfide solid electrolyte and the binder are dissolved in the aprotic solvent. In the present invention, since the aprotic solvent is used in the solid-liquid mixture, both the sulfide solid electrolyte and the binder can be dissolved, and the positive electrode active material, the conductive material, and the positive electrode current collector, which are solid components, are bound. As a result, the positive electrode active material is easily separated and recovered from the solid content in step S3 described later.

  If a nonpolar solvent such as heptane is used as the solvent in the solid-liquid mixture, the binder can be dissolved but the sulfide solid electrolyte cannot be dissolved. Therefore, as a result that the positive electrode active material and the sulfide solid electrolyte coexist in the solid content in the step S2 to be described later, it becomes difficult to separately collect the positive electrode active material and the sulfide solid electrolyte. Even when a polar solvent is used as the solvent, when the polar solvent is a protic solvent such as alcohol, carboxylic acid, and lower ester, protons are easily released from the solvent. Hydrogen sulfide is easily generated by reaction. Furthermore, when water is used as the solvent, the binder cannot be dissolved, so it is difficult to separate the particles, and the sulfide solid electrolyte tends to remain in the solid content, so that the positive electrode active material and the sulfide solid electrolyte are separated. It becomes difficult to collect. Another problem is that the sulfide solid electrolyte reacts with water to generate hydrogen sulfide. Thus, it can be said that the present invention has one feature in that an aprotic solvent has been found as the most preferable solvent when treating the positive electrode of a sulfide solid state battery among a number of solvents.

2. Process S2
Step S2 is a step of solid-liquid separation of the solid-liquid mixture obtained in step S1. “Solid-liquid separation” in step S2 refers to separating the liquid component in the solid-liquid mixture while “maintaining the state of the liquid component”. That is, the form of performing solid-liquid separation by volatilizing the liquid component (via the gas state) is not included in the “solid-liquid separation” referred to in step S2. If the liquid component is volatilized and solid-liquid separation is performed, the sulfide solid electrolyte and binder remain in the solid content after volatilization, and the meaning of dissolving them in step S1 is lost.
In step S2, the solid content and the liquid content can be easily separated by filtration. For example, a filter press or the like can be used. Alternatively, solid-liquid separation may be performed by recovering the supernatant after the solid is precipitated and solidified by centrifugation or the like and washing the solid. From the viewpoint of efficiently performing solid-liquid separation, it is preferable to perform solid-liquid separation continuously by filtration.

3. Process S3
Step S3 is a step of recovering the positive electrode active material from the solid content obtained by solid-liquid separation of the solid-liquid mixture in step S2. When the positive electrode includes a positive electrode current collector and a conductive material, the solid content includes a positive electrode current collector and a conductive material in addition to the positive electrode active material. In this case, in order to collect a high concentration positive electrode active material, it is preferable to remove the positive electrode current collector and the conductive material from the solid content. FIG. 2 shows an example of step S3. The process shown in FIG. 2 corresponds to the process in the broken line part A in FIG. As shown in FIG. 2, the step S3 includes a step S3a for removing the positive electrode current collector from the solid content obtained in the step S2, a step S3b for drying the solid content residue obtained by removing the positive electrode current collector, A step S3c for removing the carbon content from the dried solid residue by firing or electrolysis and a step S3d for recovering the solid content residue from which the carbon content has been removed as a positive electrode active material are provided.

3.1. Step S3a
Step S3a is a step of removing the positive electrode current collector from the solid content. Specifically, the positive electrode current collector can be removed from the solid content by immersing the solid content in the solution and dissolving the positive electrode current collector. The type of the solution can be appropriately changed depending on the type of the positive electrode current collector. For example, when the positive electrode current collector is made of Al, the positive electrode current collector can be efficiently dissolved from the solid content by using a strong alkaline aqueous solution or sulfuric acid aqueous solution as the solution. When the positive electrode current collector is made of Cu, the positive electrode current collector can be efficiently dissolved from the solid content by using a sulfuric acid aqueous solution, ammonia water, or a potassium cyanide aqueous solution.

3.2. Step S3b
Step S3b is a step of drying the solid residue obtained by removing the positive electrode current collector in step S3a. Drying may be natural drying or rapid drying by heat drying. Here, the step S3b is preferably dried after washing the solid residue. Step S3b includes a form of drying by solid-liquid separation by filtration.

3.3. Step S3c
Step S3c is a step of particularly removing carbon from the solid residue dried in step S3b by firing or electrolysis. Thereby, the carbonaceous conductive material, the binder remaining in the solid content in Step S2 and the like can be removed from the solid content residue. The form of firing or electrolysis is not particularly limited as long as the carbonaceous component can be removed.

3.4. Step S3d
By passing through step S3c, the positive electrode active material can be concentrated in the solid residue. That is, the positive electrode active material can be recovered at a high concentration.

4). Step S4
Step S4 is a step of obtaining a recovered liquid containing an aprotic solvent by distilling the liquid component obtained by solid-liquid separation of the solid-liquid mixture in step S2. Distillation may be performed in one stage or in multiple stages. For example, a form in which the first stage distillation with a high distillation temperature and a second stage distillation with a low distillation temperature are performed, or a form in which the first stage distillation with a low distillation temperature and the second stage distillation with a high distillation temperature are performed. Etc. The distillation temperature may be any temperature at which the aprotic solvent contained in the liquid component volatilizes. Alternatively, the aprotic solvent may be volatilized by reducing the pressure.

  The recovered liquid obtained in step S4 can be used as an aprotic solvent as it is. Or you may perform a predetermined | prescribed process (process S5-S7) with respect to a collection | recovery liquid so that it may mention later, and may raise the purity of an aprotic solvent. On the other hand, the residue obtained in step S4 includes a component (element) derived from the sulfide solid electrolyte and a component (element) derived from the binder. For example, Li, P, S, C, O, Br, I and the like. These components (elements) can also be separated and recovered as appropriate and reused.

  Hereinafter, a method for increasing the purity of the recovered liquid obtained in step S4 will be described. The process shown in FIGS. 3 to 6 described below corresponds to the process in the broken line part B in FIG.

  FIG. 3 shows an example (method S11) of a method for increasing the purity of the recovered liquid. As shown in FIG. 3, the method S11 includes a step S5 of measuring the conductivity or resistance of the recovered liquid, and when the conductivity or resistance is higher than the threshold, the purity of the aprotic solvent in the recovered liquid is It is judged that it is low, and the collected liquid is distilled again.

5. Process S5
Step S5 is a step of measuring the conductivity or resistance of the recovered liquid. The presence or absence of impurities in the recovered liquid can be estimated by measuring the conductivity or resistance of the recovered liquid. As described above, the liquid obtained in step S2 contains a sulfide solid electrolyte and a binder in addition to the aprotic solvent. For this reason, the aprotic solvent containing impurities derived from the sulfide solid electrolyte and the binder tends to have higher conductivity or resistance than the aprotic solvent containing no impurities. In particular, when a halide such as LiI or LiBr is used for the sulfide solid electrolyte, the increase in conductivity or resistance is remarkable. Therefore, using the conductivity or resistance of the recovered liquid as an index, if the conductivity or resistance is greater than or equal to the threshold value, it can be determined that a large amount of impurities remain in the recovered liquid and the purity of the recovered liquid is low. In this case, an aprotic solvent with high purity can be obtained by distilling the recovered liquid again to reduce the amount of impurities.

  The conductivity or resistance of the recovered liquid can be measured inexpensively and easily using a known measuring means. Measurements can also be made in-line. The setting of the conductivity or resistance threshold value is not particularly limited. For example, when the conductivity or resistance of the collected liquid is 1000% or more (10 times or more) based on the conductivity or resistance of the aprotic solvent not containing impurities, the purity of the collected liquid is judged to be low. be able to.

  However, when the conductivity or resistance of the recovered liquid is measured, the presence or absence of impurities can be estimated, but it cannot be specifically identified what impurities remain in the recovered liquid. When it is desired to identify impurities in the recovered liquid, it is preferable to analyze the components of the recovered liquid using an analysis means. FIG. 4 shows another example (method S12) of increasing the purity of the recovered liquid. As shown in FIG. 4, the method S12 includes a step S6 of analyzing the components of the recovered liquid. If it is determined that the amount of impurities in the recovered liquid is large as a result of the analysis, the recovered liquid is distilled again. It has the characteristics. On the other hand, if it is determined as a result of analysis that the amount of impurities in the recovered liquid is small, or even if there are many impurities in the recovered liquid, it is determined that there is no problem in reuse. The recovered liquid can be reused as an aprotic solvent without being distilled again.

6). Step S6
Impurities contained in the collected liquid can be identified using a known analysis means. For example, ICP-MS or GC-MS can be used. By step S6, the impurities contained in the recovered liquid can be identified with high accuracy. Further, as described below, the recovered liquid can be subjected to a separation step other than distillation (step S4) according to the analysis result. Thereby, the energy required to increase the purity of the recovered liquid can be reduced.

  FIG. 5 shows another example (method S13) of increasing the purity of the recovered liquid. As shown in FIG. 5, the method S13 includes a step S6 for analyzing the components of the recovered liquid. If it is determined that the amount of impurities in the recovered liquid is large as a result of the analysis, The recovered liquid is subjected to a separation step S7 other than distillation. On the other hand, as a result of analysis, when it is determined that the amount of impurities in the recovered liquid is small, or even if impurities are present in the recovered liquid, it is determined that there is no problem in reuse, The recovered liquid can be reused as it is as an aprotic solvent without being subjected to a separation step.

7). Step S7
Examples of the separation step S7 other than distillation include, for example, a step of chemically capturing and removing impurities using a reagent, an adsorbent, etc., a step of settling impurities by cooling, a step of depositing impurities by electrolysis, and a step of depositing impurities by electrolysis. Various forms such as a step of generating a gas to be contained can be exemplified. What is necessary is just to select an optimal process suitably according to the kind of impurity. For example, when metal ions or Li ions are included as impurities, they can be deposited and removed by electrolysis. Moreover, when halide ions and moisture are contained as impurities, these can be removed as gas by electrolysis.

  As described above, when measuring the conductivity or resistance of the recovered liquid, there is an advantage that it is possible to estimate the presence or absence of impurities in the recovered liquid easily and inexpensively. When analyzing the components of the recovered liquid, the recovered liquid is accurate. There is an advantage that impurities can be identified. On the other hand, there is a disadvantage that impurities cannot be identified when measuring the conductivity or resistance of the recovered liquid, and when analyzing the components of the recovered liquid, the apparatus is expensive and in-line inspection is difficult. is there. In addition, it may be difficult from the viewpoint of efficiency to analyze and identify impurities for all the recovered liquids sequentially recovered from the recovery line.

8). Combination of Step S5 and Step S6 When considering the advantages and disadvantages of Step S5 and Step S6, (1) First, the conductivity or resistance of the recovered liquid is measured and the conductivity or resistance is greater than or equal to the threshold value. It is preferable to select a recovered liquid with low purity, and (2) analyze an impurity component only for the recovered liquid with low purity. FIG. 6 shows another example (method S14) of increasing the purity of the recovered liquid. As shown in FIG. 6, (1) First, the electric conductivity or resistance of the recovered liquid is measured (step S5), and the recovered liquid whose electric conductivity or resistance is less than the threshold is reused as it is as an aprotic solvent. 2) Analyze the collected liquid with conductivity or resistance equal to or higher than the threshold (step S6). (3) If it is determined that there is no problem even if it is reused as an aprotic solvent as a result of the analysis. If it is determined that it is necessary to remove impurities as a result of (4) analysis, the recovered liquid is again distilled (step S4) to increase the purity. Alternatively, as described above, a separation process other than distillation may be performed.

  As mentioned above, in method S10 provided with process S1-S4, after immersing a positive electrode in an aprotic solvent and making it a solid-liquid mixture (process S1), the solid obtained by carrying out solid-liquid separation of the said solid-liquid mixture The positive electrode active material can be efficiently recovered from the minute (steps S2 and S3). Further, by distilling the liquid component obtained by solid-liquid separation of the solid-liquid mixture, a recovered liquid containing an aprotic solvent can be obtained (steps S2 and S4), and the recovered liquid is used as an aprotic solvent. Can be reused. Furthermore, by using an aprotic solvent, the generation of hydrogen sulfide due to the reaction with the sulfide solid electrolyte can be suppressed. On the other hand, it is easy to increase the purity of the recovered liquid as in steps S5 to S7. That is, according to the method S10, while suppressing generation of hydrogen sulfide, the positive electrode active material can be efficiently recovered from the positive electrode of the sulfide solid state battery, and the treatment liquid can be repeatedly used.

  In the above description, the form of measuring the conductivity or resistance of the recovered liquid has been described. However, it is considered possible to determine the presence or absence of impurities by measuring the ionic conductivity.

  The present invention is useful as a method for recycling a positive electrode of a solid battery. According to the present invention, it is possible to efficiently separate and recover the positive electrode active material, the sulfide solid electrolyte, and the like from the positive electrode of the solid battery using simple means such as solid-liquid separation. It can be recycled.

Claims (2)

A method for recovering a positive electrode active material from a positive electrode comprising a positive electrode active material, a sulfide solid electrolyte and a binder,
The positive electrode is immersed in an aprotic solvent, and the positive electrode active material remains as a solid content in the aprotic solvent, while the sulfide solid electrolyte and the binder are dissolved in the aprotic solvent to form a solid. Obtaining a liquid mixture;
Solid-liquid separation of the obtained solid-liquid mixture;
Recovering the positive electrode active material from a solid content obtained by solid-liquid separation of the solid-liquid mixture;
A step of distilling the liquid obtained by solid-liquid separation of the solid-liquid mixture to obtain a recovered liquid containing the aprotic solvent;
A method comprising: A step of measuring the electric conductivity or resistance of the recovered liquid, and when the electric conductivity or resistance is higher than a threshold value, it is determined that the purity of the aprotic solvent in the recovered liquid is low; The process according to claim 1, wherein the distillation is carried out again.

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