Method for recovering positive electrode active material

Abstract

The method for recovering positive electrode active material includes a lithium recovery step, a displacement step, and a binder removal step. In the lithium recovery step, a battery slurry containing positive electrode active material and binder, taken from a lithium-ion secondary battery, is filtered to recover lithium. In the displacement step, the positive electrode composite material slurry obtained in the lithium recovery step is displaced with a compatible solvent and then filtered. In the binder removal step, the positive electrode composite material slurry treated in the displacement step is displaced with a hydrophobic solvent and then filtered, and the binder in the positive electrode composite material slurry is dissolved to obtain a binder-removed slurry. Accordingly, the binder can be effectively dissolved using a hydrophobic solvent.

Description

Technical Field

[0001] This invention relates to a method for recovering positive electrode active materials. Background Technology

[0002] In lithium-ion rechargeable batteries and all-solid-state batteries, there exist batteries with stacked electrodes consisting of a positive electrode and a negative electrode separated by a separator. The positive electrode active material in the positive electrode composite material of such batteries is a ternary cathode material (NCM) composed of nickel-based, cobalt-based, and manganese-based materials. When lithium-ion rechargeable batteries and the like are disposed of, it is desirable to remove the binder from the positive electrode composite material and recover the positive electrode active material.

[0003] In the prior art, there is a known technique that uses a solvent to dissolve the binder contained in the positive electrode composite material, thereby recovering valuable metals (for example, see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 2014-207192 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] However, when using hydrophobic solvents to remove the binder of the cathode composite material, the binder sometimes repels the hydrophobic solvent.

[0009] The present invention was made in view of the above circumstances, and its object is to effectively dissolve adhesives using hydrophobic solvents.

[0010] Technical solutions for solving technical problems

[0011] To solve the above-mentioned technical problems, the method for recovering positive electrode active material of the present invention includes a lithium recovery step, a replacement step, and a binder removal step. In the lithium recovery step, the battery slurry containing positive electrode active material and binder, taken from a lithium-ion secondary battery, is filtered to recover lithium. In the replacement step, the positive electrode composite material slurry obtained in the lithium recovery step is replaced with a compatible solvent and then filtered. In the binder removal step, the positive electrode composite material slurry after the replacement step is replaced with a hydrophobic solvent and then filtered. The binder in the positive electrode composite material slurry is dissolved to obtain a slurry with the binder removed.

[0012] Invention Effects

[0013] In this invention, the adhesive can be effectively dissolved using a hydrophobic solvent. Furthermore, it simplifies the recycling process of lithium-ion secondary batteries, reduces environmental impact, and lowers recycling costs. Attached Figure Description

[0014] Figure 1 This is a diagram showing a device for recovering positive electrode active material.

[0015] Figure 2 This is a flowchart illustrating the method for recovering positive electrode active material. Detailed Implementation

[0016] (Implementation Method)

[0017] [1. Recycling device]

[0018] Figure 1 This is a diagram showing a positive electrode active material recovery device 100.

[0019] The recycling device 100 has a main tank 101.

[0020] A positive electrode composite slurry containing positive electrode composite material separated from a lithium-ion secondary battery and a battery dissolution slurry containing lithium ions dissolved from the positive electrode composite material into water are added to the main tank 101.

[0021] The cathode composite material includes a cathode active material and a resin-based binder. Furthermore, the cathode composite material separated from a lithium-ion secondary battery contains lithium. The cathode active material contains valuable metals such as nickel, cobalt, and manganese, and is recycled from used lithium-ion secondary batteries.

[0022] Positive electrode composite slurry is a slurry containing positive electrode active material and binder.

[0023] A filter section 102 is connected to the main tank 101. The path from the main tank 101 to the filter section 102 is connected by opening the first valve 111, and the path from the filter section 102 to the main tank 101 is connected by opening the second valve 112. The filter section 102 filters the mixture of solids and liquids supplied from the main tank 101, achieving solid-liquid separation.

[0024] In the filtration section 102, a lithium recovery section 103 is connected via a third valve 113, and a drain tank 104 is connected via a fourth valve 114. Opening the third valve 113 and closing the fourth valve 114 connects the path from the filtration section 102 to the lithium recovery section 103. Closing the third valve 113 and opening the fourth valve 114 connects the path from the filtration section 102 to the drain tank 104.

[0025] A water tank 105, a compatible solvent tank 106, and a hydrophobic solvent tank 107 are connected to the main tank 101.

[0026] By opening valve 5 115, the path from water tank 105 to main tank 101 is connected. Water is stored in water tank 105, and by opening valve 5 115, water can be supplied to main tank 101.

[0027] By opening valve 116, the path from the compatible solvent tank 106 to the main tank 101 is connected. The compatible solvent tank 106 stores compatible solvent, and opening valve 116 allows the supply of compatible solvent to the main tank 101. The compatible solvent is a liquid that readily mixes with both water and hydrophobic solvents, such as ethanol.

[0028] By opening valve 7 117, the path from the hydrophobic solvent tank 107 to the main tank 101 is connected. The hydrophobic solvent tank 107 stores a hydrophobic solvent, which can be supplied to the main tank 101 by opening valve 7 117. The hydrophobic solvent is, for example, anisole. The hydrophobic solvent dissolves the binder contained in the cathode composite material.

[0029] The upstream side of the distillation section 108 is connected to the drain tank 104, and the downstream side is connected to the water tank 105, the compatible solvent tank 106, and the hydrophobic solvent tank 107.

[0030] The distillation section 108 separates water, compatible solvents, and hydrophobic solvents discharged from the main tank 101 to the discharge tank 104 using a distillation method. Distillation is a method of separating liquids according to their types by utilizing the differences in their boiling points.

[0031] Water from the distillation section 108 is supplied to the water tank 105, a compatible solvent is supplied to the compatible solvent tank 106, and a hydrophobic solvent is supplied to the hydrophobic solvent tank 107. The water, compatible solvent, and hydrophobic solvent can be recycled and reused through the distillation section 108.

[0032] The recycling unit 109 is connected to the main tank 101. By opening the 8th valve 118, the path from the main tank 101 to the recycling unit 109 can be connected.

[0033] [2. Actions and Effects]

[0034] Next, a highly efficient method for recovering positive electrode active material is disclosed.

[0035] Figure 2 This is a flowchart illustrating the method for recovering positive electrode active material.

[0036] In preparation step S1, battery dissolution slurry is added to the main tank 101. As described above, the battery dissolution slurry contains a positive electrode composite material slurry that has been separated from a lithium-ion secondary battery and mixed with a liquid to form a slurry.

[0037] In the lithium recovery process S2, battery dissolution slurry is fed into the filtration section 102. In the filtration section 102, the positive electrode composite material slurry and water-soluble components in the battery dissolution components are filtered.

[0038] The water-soluble component discharged from the filter section 102 contains lithium ions, which is stored in the lithium recovery section 103. Lithium is recovered by recycling the liquid stored in the lithium recovery section 103.

[0039] In the replacement process S3, the positive electrode composite material slurry is replaced with a compatible solvent and then filtered. This operation is repeated until the concentration of the compatible solvent reaches or exceeds the specified threshold.

[0040] Specifically, a compatible solvent is added from the compatible solvent tank 106 to the main tank 101 to replace the cathode composite material slurry. The cathode composite material slurry and the compatible solvent are then filtered through the filter section 102. This operation is repeated until the concentration of the compatible solvent reaches a predetermined threshold. The compatible solvent discharged from the filter section 102 is stored in the drain tank 104.

[0041] The so-called specified threshold refers to a quality percentage of 90%.

[0042] Since the compatible solvent mixes with water, it is easy to replace the water and compatible solvent contained in the cathode composite slurry. By using this replacement to reduce the proportion of water contained in the cathode composite slurry, the cathode composite slurry and the hydrophobic solvent can be mixed more easily. In the subsequent binder removal process S4, the cathode composite slurry and the hydrophobic solvent can easily react.

[0043] In the binder removal step S4, the operation of replacing the cathode composite slurry with a hydrophobic solvent and then filtering is repeated. This operation is repeated until the concentration of the hydrophobic solvent reaches a predetermined threshold. Accordingly, the binder in the cathode composite slurry is dissolved.

[0044] Specifically, a hydrophobic solvent is added from the hydrophobic solvent tank 107 to the main tank 101. Then, the positive electrode composite slurry and the hydrophobic solvent are filtered through the filter section 102. This process is expected to be repeated until the concentration of the hydrophobic solvent reaches a threshold value. The hydrophobic solvent discharged from the filter section 102 is stored in the drain tank 104.

[0045] The so-called specified threshold refers to a quality percentage of 90%.

[0046] Through the binder removal process S4, a cathode composite material slurry with the binder removed is obtained. Hereinafter, the cathode composite material slurry with the binder removed is appropriately referred to as the removed slurry. The removed slurry refers to a slurry containing the cathode active material and a hydrophobic solvent or a compatible solvent.

[0047] By performing the adhesive removal step S4 after the replacement step S3, even water-based adhesives such as styrene-butadiene rubber, which are prone to repelling hydrophobic solvents, can be effectively removed.

[0048] Furthermore, by performing a wet process for recovering lithium ions (lithium recovery process S2), even when the cathode composite slurry is mixed with water, the binder can be removed using a hydrophobic solvent.

[0049] In the hydrophilization step S5, the removed slurry is repeatedly replaced with a compatible solvent and then filtered. This process is repeated until the concentration of the compatible solvent reaches a predetermined threshold. Accordingly, the hydrophobic solvent remaining in the adhesive removal step S4 can be removed from the removed slurry.

[0050] The so-called specified threshold refers to a quality percentage of 90%.

[0051] In the water replacement step S6, water is introduced from water tank 105 into main tank 101. Water is introduced into the removed slurry, thereby removing the compatibility solvent remaining in the hydrophilization step S5 from the removed slurry. Based on this, a concentrated slurry is obtained. The concentrated slurry is a slurry containing a positive electrode active material and water at a predetermined concentration or higher. The concentrated slurry is an example of the slurry processed in the water replacement step.

[0052] In the water replacement process S6, the slurry that has been removed is repeatedly replaced with water and filtered until the water concentration reaches or exceeds a specified threshold. The specified threshold refers to a mass percentage of 90%.

[0053] In addition, the concentrations of the compatible solvent, the hydrophobic solvent, and water are measured using known concentration measurement methods.

[0054] In the recycling process S7, the concentrated slurry processed in the water replacement process S6 is recycled from the main tank 101 to the recycling section 109.

[0055] According to this embodiment, since there is a displacement step S3 between the lithium recovery step S2 and the adhesive removal step S4, the adhesive can be effectively dissolved by a hydrophobic solvent.

[0056] According to this embodiment, since the positive electrode active material is recovered in a non-destructive state after processes S1 to S7, it can be directly used as a positive electrode composite material for lithium-ion secondary batteries by adding adhesives, conductive materials, etc.

[0057] According to this embodiment, the positive electrode composite material slurry separated from the discarded lithium-ion secondary battery can be recycled as a new positive electrode composite material for lithium-ion secondary batteries through processes S1 to S7, thus enabling effective recycling.

[0058] Furthermore, although the specified concentration is given as a mass percentage of 90%, it is not limited to this.

[0059] [Structure supported by the above embodiments]

[0060] The above implementation supports the following structures.

[0061] (Structure 1) A method for recovering positive electrode active material, comprising a lithium recovery step, a displacement step, and a binder removal step, wherein, in the lithium recovery step, a battery slurry containing positive electrode active material and binder, taken from a lithium-ion secondary battery, is filtered to recover lithium; in the displacement step, a compatible solvent is used to displace the positive electrode composite material slurry obtained in the lithium recovery step, and the slurry is filtered; in the binder removal step, a hydrophobic solvent is used to displace the positive electrode composite material slurry after the displacement step, the slurry is filtered, and the binder in the positive electrode composite material slurry is dissolved to obtain a slurry with the binder removed.

[0062] According to Structure 1, since there is a displacement step between the lithium recovery step and the adhesive removal step, the adhesive can be effectively dissolved by a hydrophobic solvent.

[0063] (Structure 2) The method for recovering positive electrode active material according to Structure 1, wherein in the replacement step, a step of replacing with the compatible solvent and filtering is performed until the concentration of the compatible solvent reaches or exceeds a predetermined threshold.

[0064] According to structure 2, the miscibility of the cathode composite slurry with hydrophobic solvents can be further improved.

[0065] (Structure 3) The method for recovering positive electrode active material according to Structure 1 or 2, comprising a hydrophilization step, a water replacement step, and a recovery step, wherein, in the hydrophilization step, the removed slurry after treatment in the adhesive removal step is replaced with a compatible solvent and filtered to remove the hydrophobic solvent remaining in the adhesive removal step from the removed slurry; in the water replacement step, water is added to the removed slurry to remove the compatible solvent remaining in the hydrophilization step from the removed slurry; and in the recovery step, the positive electrode active material is recovered from the slurry after treatment in the water replacement step.

[0066] According to structure 3, it is possible to recover slurry containing positive electrode active material in a state where hydrophobic solvents and compatible solvents have been removed.

[0067] (Structure 4) The method for recovering the positive electrode active material according to Structure 3, wherein in the hydrophilization process, a process of replacing and filtering with the compatible solvent is performed until the concentration of the compatible solvent reaches a predetermined threshold or above.

[0068] According to structure 4, hydrophobic solvents and compatible solvents can be effectively removed.

[0069] (Structure 5) The method for recovering the positive electrode active material according to Structure 4, wherein the specified threshold refers to a mass percentage of 90%.

[0070] According to structure 5, since the removal of both hydrophobic and compatible solvents can be carried out after the concentration of the compatible solvent has been confirmed to increase, sufficient removal is possible.

[0071] (Structure 6) The method for recovering positive electrode active material according to Structure 1, wherein in the adhesive removal step, a step of replacing and filtering with the hydrophobic solvent is performed until the concentration of the hydrophobic solvent reaches or exceeds a predetermined threshold.

[0072] According to structure 6, water can be effectively removed. Furthermore, according to structure 6, compatible solvents can be effectively removed.

[0073] (Structure 7) The method for recovering the positive electrode active material according to Structure 2 or 6, wherein the specified threshold refers to a mass percentage of 90%.

[0074] According to structure 7, since water removal can be performed after the concentration of the compatible solvent has increased, sufficient removal is possible. Furthermore, according to structure 7, the compatible solvent can be removed after the concentration of the hydrophobic solvent has increased, thus ensuring sufficient removal.

[0075] Explanation of reference numerals in the attached figures

[0076] 100: Recovery device; 101: Main tank; 102: Filtration section; 103: Lithium recovery section; 104: Drainage tank; 105: Water tank; 106: Compatible solvent tank; 107: Hydrophobic solvent tank; 108: Distillation section; 109: Recovery section; 111: Valve 1; 112: Valve 2; 113: Valve 3; 114: Valve 4; 115: Valve 5; 116: Valve 6; 117: Valve 7; 118: Valve 8; S1: Preparation process; S2: Lithium recovery process; S3: Replacement process; S4: Adhesive removal process; S5: Hydrophilization process; S6: Water replacement process; S7: Recovery process.

Claims

1. A method for recovering positive electrode active material, characterized in that, It has lithium recovery process, displacement process and binder removal process, among which, In the lithium recovery process, lithium is recovered by filtering the battery slurry, which is taken from a lithium-ion secondary battery and contains positive electrode active material and binder. In the replacement process, the cathode composite material slurry obtained in the lithium recovery process is replaced with a compatible solvent and then filtered. In the adhesive removal process, the cathode composite material slurry treated in the replacement process is replaced with a hydrophobic solvent, filtered, and the adhesive in the cathode composite material slurry is dissolved to obtain a slurry with the adhesive removed.

2. The method for recovering the positive electrode active material according to claim 1, characterized in that, In the replacement process, the process of replacing with the compatible solvent and filtering is performed until the concentration of the compatible solvent reaches or exceeds a predetermined threshold.

3. The method for recovering the positive electrode active material according to claim 1 or 2, characterized in that, It has hydrophilization process, water replacement process and recycling process. In the hydrophilization step, the removed slurry after the adhesive removal step is replaced with a compatible solvent and filtered to remove the hydrophobic solvent remaining in the adhesive removal step from the removed slurry. In the water replacement process, water is added to the removed slurry to remove the compatibility solvent remaining in the hydrophilization process from the removed slurry; In the recycling process, the positive electrode active material is recovered from the slurry treated in the water replacement process.

4. The method for recovering the positive electrode active material according to claim 3, characterized in that, In the hydrophilization process, a process of replacing and filtering with the compatible solvent is performed until the concentration of the compatible solvent reaches or exceeds a specified threshold.

5. The method for recovering the positive electrode active material according to claim 4, characterized in that, The specified threshold refers to a mass percentage of 90%.

6. The method for recovering the positive electrode active material according to claim 1, characterized in that, In the adhesive removal process, a process of replacing and filtering with the hydrophobic solvent is performed until the concentration of the hydrophobic solvent reaches or exceeds a predetermined threshold.

7. The method for recovering the positive electrode active material according to claim 2 or 6, characterized in that, The specified threshold refers to a mass percentage of 90%.

Images