JP6265079B2 - Method for recovering positive electrode active material of sulfide solid state battery - Google Patents

Description

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

  Metal ion secondary battery having a solid electrolyte layer using a flame retardant solid electrolyte (for example, a lithium ion secondary battery, etc. In the following, a lithium ion secondary battery using a sulfide solid electrolyte is referred to as a “sulfide solid battery”. ”Has the advantage that it is easy to simplify the system for ensuring safety.

  As a technique relating to such a sulfide solid state battery, for example, Patent Document 1 discloses a battery member treatment method including at least a positive electrode active material having Li and a sulfide solid electrolyte material having Li, From the contact process in which Li, which is contained in the sulfide solid electrolyte material, is dissolved in the treatment liquid, and the treatment liquid in which Li is dissolved is generated by bringing hydrogen sulfide into contact with the water that is the member and the treatment liquid. Disclosed is a method for treating a battery member, comprising: a positive electrode active material recovery step for recovering a positive electrode active material, and a Li compound recovery step for recovering a Li compound from a treatment liquid for recovering a positive electrode active material that is an insoluble component. ing. Further, in paragraph 0035 of the specification of Patent Document 2 which discloses a method for recovering an electrode constituent metal from a lithium battery, an impurity metal can be eluted as a hydroxide solution by mixing a strong alkaline solution. It is stated that it can be done. Patent Document 3 discloses a technique for recovering metal from the positive electrode of a sulfide solid state battery.

International Publication No. 2010/106618 JP 2007-323868 A JP 2010-40458 A

  When water is used as the treatment liquid when recovering the positive electrode active material from the sulfide solid state battery, the sulfide solid electrolyte material and water react to generate hydrogen sulfide. When the treatment liquid is water, the generated hydrogen sulfide is released out of the treatment liquid, so that there is a possibility that the workability of the recovery operation is lowered. Further, in the techniques disclosed in Patent Document 1 and Patent Document 3, when collecting the raw material of the sulfide solid electrolyte in addition to the positive electrode active material, the hydrogen sulfide released to the outside of the treatment liquid is recovered. In other words, the process of recovering the raw material is likely to be complicated because of the process of reacting with other substances. These problems are difficult to solve by simply combining the techniques disclosed in Patent Documents 1 and 3 and the technique disclosed in Patent Document 2.

  Accordingly, the present invention provides a method for recovering a positive electrode active material for a sulfide solid state battery capable of recovering the positive electrode active material and the raw material for the sulfide solid electrolyte while suppressing or preventing the release of hydrogen sulfide to the outside of the treatment liquid. It is an issue to provide.

  As a result of intensive studies, the present inventors have used, for example, a Li-based alkaline solution typified by a LiOH aqueous solution or the like as a treatment liquid, while suppressing or preventing the release of hydrogen sulfide to the outside of the treatment liquid. It was found that raw materials for the active material and sulfide solid electrolyte can be recovered. Further, in addition to the treatment using the Li-based alkaline solution, the treatment using a solution that is more alkaline than the Li-based alkaline solution as a treatment solution can be performed from the positive electrode containing the current collector foil. It has been found that the positive electrode active material and the raw material of the sulfide solid electrolyte can be recovered while suppressing or preventing the release of hydrogen sulfide to the outside of the liquid. The present invention has been completed based on these findings.

In order to solve the above problems, the present invention takes the following means. That is,
The present invention is a method for recovering a positive electrode active material from a positive electrode containing at least a sulfide solid electrolyte and a positive electrode active material, and the sulfide is immersed in a first solution that is a Li-based alkaline aqueous solution. A first dissolution step for dissolving the solid electrolyte, a first separation step for separating the solution obtained in the first dissolution step and an insoluble component, and a solution separated in the first separation step A method for recovering a positive electrode active material of a sulfide solid state battery, comprising: a concentration step for concentrating the gas, and a combustion step for burning the insoluble components separated in the first separation step.

Here, the “Li-based alkaline aqueous solution” refers to an alkaline aqueous solution containing Li. For example, an alkaline aqueous solution containing Li and having a pH of 11 or less is included in the Li-based alkaline solution. Examples of such an alkaline aqueous solution include an aqueous lithium hydroxide solution and an aqueous lithium hydrogen carbonate solution.
In the present invention, it is possible to cause a neutralization reaction of hydrogen sulfide generated in the first dissolution step by using a Li-based alkaline aqueous solution. Thereby, it becomes possible to suppress or prevent the release of hydrogen sulfide to the outside of the first solution. Furthermore, Li ₂ S that can be used as a raw material for the sulfide solid electrolyte can be recovered by the concentration step. In addition, the positive electrode active material can be recovered by the combustion process. Therefore, by adopting such a form, the sulfide capable of recovering the positive electrode active material and the raw material of the sulfide solid electrolyte while suppressing or preventing the release of hydrogen sulfide to the outside of the first solution. A positive electrode active material recovery method for a solid state battery can be provided.

  In the present invention, when the positive electrode is further provided with a foil containing aluminum, the insoluble component separated in the first separation step is a second solution that is a stronger alkaline solution than the Li-based alkaline solution. A second dissolving step for dissolving the foil by dipping in a second dissolving step, and a second separating step for separating the solution and the insoluble component obtained in the second dissolving step. The insoluble component separated in the second separation step is burned, and the first solution has a hydroxyl group in the solution of 2 equivalents or more with respect to the amount of sulfur contained in the sulfide solid electrolyte. And the second solution has a hydroxyl group in the solution of 4 equivalents or more with respect to the amount of aluminum contained in the foil. Included in the above foil Substance amount of aluminum is preferably greater than 1/2 with respect to the amount of substance of sulfur contained in the sulfide solid electrolyte. By setting it as such a form, it is possible to melt | dissolve the foil containing aluminum at a 2nd melt | dissolution process, and to isolate | separate the solution which this foil melt | dissolved at the 2nd isolation | separation process. Moreover, when the hydroxyl group in the first solution is 2 equivalents or more with respect to the amount of sulfur contained in the sulfide solid electrolyte and less than 4 equivalents with respect to the amount of aluminum contained in the foil, While preventing the foil from dissolving, it is possible to prevent the release of hydrogen sulfide to the outside of the first solution. Therefore, by adopting such a form, even when the positive electrode includes a foil containing aluminum, the positive electrode active material and the sulfide solid are prevented while preventing the release of hydrogen sulfide to the outside of the treatment liquid. It is possible to provide a method for recovering a positive electrode active material of a sulfide solid state battery capable of recovering an electrolyte raw material.

  ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material collection | recovery of a sulfide solid state battery which can collect | recover the positive electrode active material and the raw material of sulfide solid electrolyte, suppressing or preventing discharge | release of hydrogen sulfide out of a process liquid. A method can be provided.

It is a figure explaining the positive electrode active material collection | recovery method of the sulfide solid state battery of this invention concerning 1st Embodiment. It is a figure explaining the positive electrode active material collection | recovery method of the sulfide solid state battery of this invention concerning 2nd Embodiment. It is a figure explaining the other example of a form of the positive electrode active material collection | recovery method of a sulfide solid battery. It is a figure explaining the other example of a form of the positive electrode active material collection | recovery method of a sulfide solid battery.

  The present invention will be described below with reference to the drawings. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below.

1. First Embodiment FIG. 1 is a diagram for explaining a positive electrode active material recovery method for a sulfide solid state battery according to the first embodiment of the present invention. This 1st Embodiment can be used conveniently, for example, when collect | recovering the positive electrode active material and the raw material of sulfide solid electrolyte from a positive electrode provided with aluminum foil.

  As shown in FIG. 1, the sulfide active battery positive electrode active material recovery method S10 according to the first embodiment of the present invention includes a first dissolution step S11, a first separation step S12, and a concentration step S13. The second dissolution step S14, the second separation step S15, and the combustion step S16.

1.1. 1st melt | dissolution process S11
In the first dissolution step S11, an aluminum foil 11 and a positive electrode mixture layer 12 (a positive electrode active material, a sulfide solid electrolyte, and a conductive material) are added to a first solution 1 that is a Li-based alkaline aqueous solution (LiOH aqueous solution having a pH of 11 or less). This is a step of dissolving the sulfide solid electrolyte contained in the positive electrode mixture layer 12 by immersing the positive electrode 10 including a layer having an auxiliary agent and a binder. Since the first solution 1 is an aqueous solution, when the positive electrode 10 is immersed in the first solution 1, the water contained in the first solution 1 reacts with the sulfide solid electrolyte, so that hydrogen sulfide (H ₂ S ) Occurs. The hydrogen sulfide generated in the first solution 1 reacts with LiOH contained in the first solution 1 (H ₂ S + 2LiOH → Li ₂ S + 2H ₂ O). By causing this reaction, it is possible to suppress the generated hydrogen sulfide from being released out of the first solution 1. Also, for example, the first solution 1 containing LiOH that reacts with all of the generated hydrogen sulfide, that is, contains 2 equivalents or more of lithium hydroxide with respect to the amount of sulfur contained in the sulfide solid electrolyte. By using the first solution 1 (the solution 1 in which the hydroxyl group in the solution is 2 equivalents or more with respect to the amount of sulfur contained in the sulfide solid electrolyte and the pH is 11 or less), It is possible to prevent hydrogen from being released out of the first solution 1 (preventing release of hydrogen sulfide out of the first solution 1). From the viewpoint of making the first solution 1 form a reaction easily, it is preferable that the first dissolution step S11 stirs the first solution 1 after the positive electrode 10 is immersed.
Here, in order to prevent hydrogen sulfide from being released to the first solution 1, it is preferable to contain a large amount of lithium hydroxide in the first solution 1. However, when a large amount of lithium hydroxide is contained in the first solution 1, the aluminum foil 11 is dissolved while forming a hydroxo complex. From the viewpoint of avoiding such a situation, the lithium hydroxide contained in the first solution 1 is less than 4 equivalents with respect to the amount of aluminum in the foil. By using the solution 1 of such first, in the first dissolution step S11, as a reaction of the aluminum foil 11, reaction occurs that _{2Al + 6H 2 O → 2Al (} OH) 3 + 3H 2, as a result, the aluminum foil 11 Becomes foil 11 '. Al (OH) ₃ does not dissolve in the first solution 1. In the present embodiment, the amount of aluminum contained in the aluminum foil 11 is greater than half the amount of sulfur contained in the sulfide solid electrolyte contained in the positive electrode 10. That is, when the amount of aluminum contained in the aluminum foil 11 is M1 (mol) and the amount of sulfur contained in the sulfide solid electrolyte contained in the positive electrode 10 is M2 (mol), M1> 0.5 × M2.

1.2. First separation step S12
The first separation step S12 is a step of separating the solution 1 ′ (solution after reacting hydrogen sulfide and LiOH) obtained in the first dissolution step S11 and the insoluble component 10 ′. The form of the first separation step S12 is not particularly limited as long as the solution 1 ′ and the insoluble component 10 ′ can be separated. The first separation step S12 can be a step of separating the solution 1 ′ and the insoluble component 10 ′ by, for example, filtration or decantation.

1.3. Concentration step S13
The concentration step S13 is a step for obtaining a sulfide solid electrolyte raw material (Li ₂ S) by concentrating the solution 1 ′ separated in the first separation step S12. Concentration process S13 will not be specifically limited if the raw material of sulfide solid electrolyte can be collect | recovered by concentrating solution 1 '. Concentration step S13., For example, by heating the solution by concentrating the solution 1 ', it is possible to process, and to recover the raw material of the sulfide solid electrolyte (Li 2 _S).

1.4. Second dissolution step S14
In the second dissolution step S14, the insoluble component 10 ′ separated in the first separation step S12 is dipped in the second solution 2 which is a stronger alkaline solution than the first solution 1, thereby forming a foil. This is a step of dissolving 11 ′. The 2nd solution 2 should just be able to dissolve foil 11 ', and specifically, a solution (the hydroxyl group in a solution is 4 equivalents or more with respect to the amount of aluminum contained in foil 11' ( An aqueous solution of a metal hydroxide having a pH of 12 or more is used. By using such a solution, a reaction of Al (OH) ₃ + OH ⁻ → [Al (OH) ₄ )] ⁻ can be caused, so that the foil 11 ′ can be dissolved. From the viewpoint of making the second solution 2 form a reaction easily, it is preferable that the second dissolution step S14 stirs the second solution 2 after immersing the insoluble component 10 ′.

1.5. Second separation step S15
The second separation step S15 is a step of separating the solution 2 ′ (solution after dissolving the foil 11 ′) obtained in the second dissolution step S14 and the insoluble component 12 ′. The form of the second separation step S15 is not particularly limited as long as the solution 2 ′ and the insoluble component 12 ′ can be separated. The second separation step S15 can be a step of separating the solution 2 ′ and the insoluble component 12 ′ by, for example, filtration or decantation.

1.6. Combustion process S16
The combustion step S16 is a step of obtaining the positive electrode active material by burning the insoluble component 12 ′ separated in the second separation step S15. The form of the combustion step S16 is not particularly limited as long as the positive electrode active material can be recovered by burning the insoluble component 12 ′.

  According to the first embodiment of the present invention described above, the sulfide solid electrolyte is reduced in the concentration step S13 while suppressing or preventing the release of hydrogen sulfide to the outside of the first solution 1 in the first dissolution step S11. The raw material can be recovered, and the positive electrode active material can be recovered in the combustion step S16. Furthermore, according to the first embodiment of the present invention, the release of hydrogen sulfide to the outside of the first solution 1 is suppressed or prevented without separating the aluminum foil 11 and the positive electrode mixture layer 12 in advance. It is possible to recover the raw materials for the positive electrode active material and the sulfide solid electrolyte. According to the first embodiment of the present invention, since the step of peeling the foil can be omitted, the step of separating and recovering the positive electrode active material and the raw material of the sulfide solid electrolyte can be simplified.

2. 2nd Embodiment FIG. 2: is a figure explaining the positive electrode active material collection | recovery method of the sulfide solid battery of this invention concerning 2nd Embodiment. This 2nd Embodiment can be used conveniently, for example, when collect | recovering the positive electrode active material and the raw material of sulfide solid electrolyte from the positive mix layer peeled from the current collection foil. In FIG. 2, the same components as those shown in FIG. 1 are denoted by the same reference numerals as those used in FIG.

  As shown in FIG. 2, the sulfide active battery positive electrode active material recovery method S20 according to the second embodiment of the present invention includes a first dissolution step S21, a first separation step S22, and a concentration step S23. And a combustion step S24.

2.1. First dissolving step S21
In the first dissolution step S21, a positive electrode mixture layer 12 (a layer having a positive electrode active material, a sulfide solid electrolyte, a conductive assistant, and a binder) is added to the first solution 1 which is a Li-based alkaline aqueous solution (LiOH aqueous solution). Is a step of dissolving the sulfide solid electrolyte contained in the positive electrode mixture layer 12 by immersing. Since the first solution 1 is an aqueous solution, when the positive electrode mixture layer 12 is immersed in the first solution 1, the water contained in the first solution 1 reacts with the sulfide solid electrolyte, so that hydrogen sulfide ( H ₂ S) is generated. The hydrogen sulfide generated in the first solution 1 reacts with LiOH contained in the first solution 1 (H ₂ S + 2LiOH → Li ₂ S + 2H ₂ O). By causing this reaction, it is possible to suppress the generated hydrogen sulfide from being released out of the first solution 1. Also, for example, the first solution 1 containing LiOH that reacts with all of the generated hydrogen sulfide, that is, contains 2 equivalents or more of lithium hydroxide with respect to the amount of sulfur contained in the sulfide solid electrolyte. By using the first solution 1 (the solution 1 in which the hydroxyl group in the solution is 2 equivalents or more with respect to the amount of sulfur contained in the sulfide solid electrolyte and the pH is 11 or less), It is possible to prevent hydrogen from being released out of the first solution 1 (preventing release of hydrogen sulfide out of the first solution 1). From the viewpoint of making the first solution 1 form a reaction easily, it is preferable that the first dissolving step S21 stirs the first solution 1 after the positive electrode mixture layer 12 is immersed.

2.2. First separation step S22
The first separation step S22 is a step of separating the solution 1 ′ (solution after reacting hydrogen sulfide and LiOH) obtained in the first dissolution step S21 and the insoluble component 12 ′. The form of the first separation step S22 is not particularly limited as long as the solution 1 ′ and the insoluble component 12 ′ can be separated. The first separation step S22 can be a step of separating the solution 1 ′ and the insoluble component 12 ′ by, for example, filtration or decantation.

2.3. Concentration step S23
The concentration step S23 is a step of obtaining a sulfide solid electrolyte raw material (Li ₂ S) by concentrating the solution 1 ′ separated in the first separation step S22. Since concentration process S23 is the same process as concentration process S13, description is abbreviate | omitted here.

2.4. Combustion process S24
The combustion step S24 is a step of obtaining a positive electrode active material by burning the insoluble component 12 ′ separated in the first separation step S22. The form of the combustion step S24 is not particularly limited as long as the positive electrode active material can be recovered by burning the insoluble component 12 ′.

  According to the second embodiment of the present invention described above, the sulfide solid electrolyte is reduced in the concentration step S23 while suppressing or preventing the release of hydrogen sulfide to the outside of the first solution 1 in the first dissolution step S21. It is possible to recover the raw material and recover the positive electrode active material in the combustion step S24. Therefore, according to the second embodiment of the present invention, the sulfide capable of recovering the positive electrode active material and the raw material of the sulfide solid electrolyte while suppressing or preventing the release of hydrogen sulfide to the outside of the treatment liquid. A positive electrode active material recovery method for a solid state battery can be provided.

In the present invention, examples of the positive electrode active material used for the positive electrode mixture layer 12 include positive electrode active materials that can be used in solid batteries. Specifically, LiCoO ₂ , LiNiO ₂ , LiFePO ₄ , LiMn ₂ O ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O _{2 and the} like can be exemplified. The shape of the positive electrode active material can be, for example, particulate or thin film. The average particle diameter (D ₅₀ ) of the positive electrode active material is, for example, preferably from 1 nm to 100 μm, and more preferably from 10 nm to 30 μm. Further, the content of the positive electrode active material in the positive electrode layer is not particularly limited, but is preferably 40% or more and 99% or less in mass%, for example.

Moreover, the positive electrode active material contained in the positive electrode mixture layer 12 from the viewpoint of making it easy to prevent an increase in battery resistance by making it difficult for the high resistance layer to be formed at the interface between the positive electrode active material and the solid electrolyte. Is preferably coated with an ion conductive oxide. Examples of the lithium ion conductive oxide that coats the positive electrode active material include a general formula Li _x AO _y (A is B, C, Al, Si, P, S, Ti, Zr, Nb, Mo, Ta, or W). And x and y are positive numbers). Specifically, Li ₃ BO ₃ , LiBO ₂ , Li ₂ CO ₃ , LiAlO ₂ , Li ₄ SiO ₄ , Li ₂ SiO ₃ , Li ₃ PO ₄ , Li ₂ SO ₄ , Li ₂ TiO ₃ , Li ₄ Ti ₅ Examples include O ₁₂ , Li ₂ Ti ₂ O ₅ , Li ₂ ZrO ₃ , LiNbO ₃ , Li ₂ MoO ₄ , Li ₂ WO _{4 and the} like. The lithium ion conductive oxide may be a complex oxide. As the composite oxide covering the positive electrode active material, any combination of the above lithium ion conductive oxides can be employed. For example, Li ₄ SiO ₄ —Li ₃ BO ₃ , Li ₄ SiO ₄ —Li ₃ PO ₄ etc. can be mentioned. Further, when the surface of the positive electrode active material is coated with an ion conductive oxide, the ion conductive oxide only needs to cover at least a part of the positive electrode active material, and covers the entire surface of the positive electrode active material. Also good. In addition, the thickness of the ion conductive oxide covering the positive electrode active material is, for example, preferably from 0.1 nm to 100 nm, and more preferably from 1 nm to 20 nm. The thickness of the ion conductive oxide can be measured using, for example, a transmission electron microscope (TEM).

Moreover, as a sulfide solid electrolyte used for the positive mix layer 12, the sulfide solid electrolyte which can be used for a sulfide solid battery can be illustrated. _{Specifically, 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, Li 2 S-P 2 S ₅ , Li ₃ PS _{4 and the} like.

  Moreover, as a conductive support agent used for the positive mix layer 12, the conductive support agent which can be used for a sulfide solid battery can be illustrated. Specifically, in addition to carbon materials such as vapor-grown carbon fiber, acetylene black (AB), ketjen black (KB), carbon nanotube (CNT), carbon nanofiber (CNF), when using sulfide solid state batteries Examples of the metal material that can withstand this environment can be given.

  Moreover, as a binder used for the positive mix layer 12, the binder which can be used for a sulfide solid state battery can be illustrated. Specific examples include acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), and the like.

  Moreover, in the said description, although aluminum foil 11 was illustrated as a current collection foil used for a positive electrode, the current collection foil used for the positive electrode immersed in the 1st solution in 1st Embodiment is aluminum alloy foil (50 mass). % Aluminum alloy foil containing at least aluminum.

As described above, according to the present invention, a sulfide solid that can recover the raw material of the positive electrode active material and the sulfide solid electrolyte while suppressing or preventing the release of hydrogen sulfide to the outside of the treatment liquid. A positive electrode active material recovery method for a battery can be provided. Here, the sulfide solid electrolyte, by using the Li ₂ S (e.g., using a Li ₂ S and _P 2 _{S 5)} can be produced. In the present invention, since the raw material of the sulfide solid electrolyte is recovered in the state of Li ₂ S, it can be easily recycled.
In addition, for example, even in the form described below, it is considered possible to recover the positive electrode active material while suppressing or preventing the release of hydrogen sulfide to the outside of the treatment liquid.

3. Reference form 3.1. First Reference Embodiment FIG. 3 is a diagram for explaining a positive electrode active material recovery method for a sulfide solid state battery according to the first reference embodiment. This 1st reference form can be used conveniently, for example, when collect | recovering positive electrode active materials from the positive mix layer peeled from the current collection foil. 3, components similar to those illustrated in FIG. 2 are denoted by the same reference numerals as those used in FIG. 2, and description thereof is omitted as appropriate.

  As shown in FIG. 3, the positive electrode active material recovery method S90a for the sulfide solid state battery according to the first reference embodiment includes a first dissolution step S91a, a first separation step S92a, and a combustion step S93a. doing.

In the first dissolution step S91a, the positive electrode mixture layer 12 (a layer having a positive electrode active material, a sulfide solid electrolyte, a conductive additive, and a binder) is immersed in a solution 91a that is an aqueous ammonia solution. In this step, the sulfide solid electrolyte contained in the layer 12 is dissolved. Since the solution 91a is an aqueous solution, when the positive electrode mixture layer 12 is immersed in the solution 91a, water contained in the solution 91a reacts with the sulfide solid electrolyte to generate hydrogen sulfide (H ₂ S). The hydrogen sulfide generated in the solution 91a then reacts with NH ₃ (H ₂ S + 2NH ₃ → (NH ₄ ) ₂ S). By causing this reaction, it is possible to suppress the generated hydrogen sulfide from being released out of the solution 91a. Further, for example, a solution 91a containing NH ₃ that reacts with all of the generated hydrogen sulfide, that is, a solution containing 2 equivalents or more of ammonia with respect to the amount of sulfur contained in the sulfide solid electrolyte. By using 91a, it is possible to prevent hydrogen sulfide from being released out of the solution 91a. From the viewpoint of forming a form in which the reaction is likely to occur in the solution 91a, the first dissolution step S91a preferably stirs the solution 91a after the positive electrode mixture layer 12 is immersed.

The first separation step S92a is a step of separating the solution 91a ′ (solution obtained by reacting hydrogen sulfide and NH ₃ ) obtained in the first dissolution step S91a and the insoluble component 12 ′. The form of the first separation step S92a is not particularly limited as long as the solution 91a ′ and the insoluble component 12 ′ can be separated.

  The combustion step S93a is a step of obtaining the positive electrode active material by burning the insoluble component 12 'separated in the first separation step S92a. The form of the combustion step S93a is not particularly limited as long as the positive electrode active material can be recovered by burning the insoluble component 12 '.

3.2. Second Reference Embodiment FIG. 4 is a diagram for explaining a positive electrode active material recovery method S90b of a sulfide solid state battery according to a second reference embodiment. This 2nd reference form can be used conveniently, for example, when collect | recovering positive electrode active materials from a positive electrode provided with aluminum foil. In FIG. 4, the same components as those shown in FIG. 1 are denoted by the same reference numerals used in FIG. 1, and the description thereof is omitted as appropriate.

  As shown in FIG. 4, the sulfide active battery positive electrode active material recovery method S90b according to the second reference embodiment includes a first dissolution step S91b, a first separation step S92b, and a combustion step S93b. doing.

In the first dissolution step S91b, a sulfide solid contained in the positive electrode mixture layer 12 is obtained by immersing the positive electrode 10 in a solution 91b that is a strong alkaline aqueous solution (aqueous solution of a metal hydroxide that becomes a strong base). In this step, the electrolyte and the aluminum foil 11 are dissolved. Here, in the solution 91b, the hydroxyl group in the solution is 2 equivalents or more with respect to the amount of sulfur contained in the sulfide solid electrolyte, and further, with respect to the amount of aluminum contained in the aluminum foil 11. 4 equivalents or more (the total amount of hydroxyl groups in the solution is 2 equivalents or more with respect to the amount of sulfur contained in the sulfide solid electrolyte and 4 equivalents or more with respect to the amount of aluminum contained in the aluminum foil 11) A lithium hydroxide aqueous solution.
Since the solution 91b is an aqueous solution, when the positive electrode 10 is immersed in the solution 91b, water contained in the solution 91b reacts with the sulfide solid electrolyte to generate hydrogen sulfide (H ₂ S). The hydrogen sulfide generated in the solution 91b then reacts with LiOH (H ₂ S + 2LiOH → Li ₂ S + 2H ₂ O). Therefore, for example, by using the solution 91b containing LiOH that reacts with all of the generated hydrogen sulfide, that is, the lithium hydroxide aqueous solution as the solution 91b, hydrogen sulfide is not released out of the solution 91b. Is possible.
In addition, since the solution 91b is strongly alkaline, when the positive electrode 10 is immersed in the solution 91b, the solution 91b and the aluminum foil 11 react to generate Li [Al (OH) ₄ ]. More specifically, a reaction of Al + 3LiOH → Al (OLi) ₃ + 3 / 2H ₂ occurs as the first stage reaction, and subsequently, Al (OLi) ₃ + 3H ₂ O → Al (OH) ₃ as the second stage reaction. A reaction of + 3LiOH occurs, and subsequently, a reaction of Al (OH) ₃ + LiOH → Li [Al (OH) ₄ ] occurs as a third stage reaction. Summarizing these reactions, the dissolution reaction of the aluminum foil 11 is represented by 2Al + 2LiOH + 6H ₂ O → 2Li [Al (OH) ₄ ] + 3H ₂ . Therefore, for example, the solution 91b containing LiOH that reacts with all of the aluminum constituting the aluminum foil 11 and water, that is, the lithium hydroxide aqueous solution is used as the solution 91b to dissolve the aluminum foil 11. Is possible. From the viewpoint of making the solution 91b likely to cause a reaction, the first dissolution step S91b preferably stirs the solution 91b after the positive electrode 10 is immersed.

In the first separation step S92b, the solution 91b ′ (solution obtained by reacting hydrogen sulfide and LiOH and dissolving the aluminum foil 11) obtained in the first dissolution step S91b and the insoluble component 12 ′. Is a step of separating The form of the first separation step S92b is not particularly limited as long as the solution 91b ′ and the insoluble component 12 ′ can be separated. The solution 91b ′ separated in the first separation step S92b contains Li ₂ S. Therefore, it is possible to recover the raw material of the sulfide solid electrolyte by separating Li [Al (OH) ₄ ] and Li ₂ S contained in the solution 91b ′.

  The combustion step S93b is a step of obtaining a positive electrode active material by burning the insoluble component 12 'separated in the first separation step S92b. The form of the combustion step S93b is not particularly limited as long as the positive electrode active material can be recovered by burning the insoluble component 12 '.

  Thus, even in the first reference form and the second reference form, it is possible to recover the positive electrode active material while suppressing or preventing the release of hydrogen sulfide to the outside of the processing liquid. Compared to these forms, the present invention is superior in that not only the positive electrode active material but also the raw material of the sulfide solid electrolyte can be easily recovered while suppressing or preventing the release of hydrogen sulfide to the outside of the treatment liquid. ing.

DESCRIPTION OF SYMBOLS 1 ... 1st solution 1 ', 2' ... Solution 2 ... 2nd solution 10 ... Positive electrode 10 ', 12' ... Insoluble component 11 ... Aluminum foil 11 '... Foil 12 ... Positive electrode mixture layer 91a, 91a' ... Solution 91b, 91b '... solution

Claims (2)

A method of recovering the positive electrode active material from a positive electrode containing at least a sulfide solid electrolyte and a positive electrode active material,
A first dissolving step of dissolving the sulfide solid electrolyte by immersing the positive electrode in a first solution that is a Li-based alkaline aqueous solution;
A first separation step of separating the solution and insoluble components obtained in the first dissolution step;
A concentration step of concentrating the solution separated in the first separation step;
A combustion step of burning the insoluble component separated in the first separation step;
A method for recovering a positive electrode active material of a sulfide solid state battery. The positive electrode further includes a foil containing aluminum,
A second dissolving step of dissolving the foil by immersing the insoluble component separated in the first separating step in a second solution which is a stronger alkaline solution than the Li-based alkaline solution; ,
A second separation step of separating the solution and insoluble components obtained in the second dissolution step;
The combustion step is a step of burning the insoluble component separated in the second separation step,
In the first solution, the hydroxyl group in the solution is 2 equivalents or more with respect to the amount of sulfur contained in the sulfide solid electrolyte and less than 4 equivalents with respect to the amount of aluminum contained in the foil. Yes,
In the second solution, the hydroxyl group in the solution is 4 equivalents or more with respect to the amount of aluminum contained in the foil,
2. The method for recovering a positive electrode active material of a sulfide solid state battery according to claim 1, wherein the amount of aluminum contained in the foil is more than ½ of the amount of sulfur contained in the sulfide solid electrolyte.