Separation method of waste lithium ion battery ternary positive electrode material and current collector

Abstract

The invention discloses a method for separating a ternary positive electrode material and a current collector of a waste lithium ion battery, which realizes rapid and efficient separation of the ternary positive electrode material and the current collector through a low-temperature (200-450 DEG C) pyrolysis and electrochemical coupling method under the condition of not damaging the current collector (aluminum foil), the rapid stripping time is 0.5-3 minutes, the separation efficiency is 95-99%, and the method is suitable for industrial production. Meanwhile, chemical substances polluting the environment are prevented from being used or generated, and the environmental protection cost is reduced. The recycled positive electrode material can be used as a raw material precursor of a lithium battery to be recycled through high-temperature calcination lithium supplementation activity recovery, and can also directly enter a subsequent leaching and recycling link; and the recycled current collector (aluminum foil) is complete in separation and smooth in surface, and can be directly recycled and applied. Compared with the prior art, the method has the advantages of simplicity and convenience in operation, mild conditions, low cost, safety, high efficiency, environment friendliness and the like.

Description

Technical Field

[0001] The invention relates to the technical field of battery recycling, and in particular to a method for separating a ternary positive electrode material and a current collector of a waste lithium-ion battery. Background Art

[0002] Lithium-ion batteries dominate the electric vehicle, portable electronics, and stationary storage markets due to their unique advantages of high energy density and long cycle life. Since the content of valuable metals in waste lithium batteries is much higher than that in natural minerals, the recycling of valuable metals (especially lithium, nickel, cobalt, and manganese) in waste lithium batteries is seen as an important way to solve the shortage of strategic resources; at the same time, if waste lithium batteries are not properly recycled, they will bring a series of environmental pollution and safety hazards. Therefore, the recycling of waste lithium batteries is of great significance both from the perspective of resource recycling and environmental protection. It is estimated that between 2021 and 2030, approximately 330 GWh of waste lithium batteries ( EES .2021;14:1461-1468.), it is imperative to quickly and efficiently recycle used lithium batteries.

[0003] When preparing the positive electrode of a ternary lithium-ion battery, it is necessary to mix the ternary positive electrode material (lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide) with a binder into a slurry and evenly coat it on the current collector (aluminum foil) to form a positive electrode sheet. The function of the binder is to bind the active material to the current collector and maintain its activity, which is beneficial to the stability of the lithium battery. However, when recycling waste lithium batteries, it increases the difficulty of separating the ternary positive electrode material from the current collector.

[0004] At present, the separation of waste lithium-ion battery ternary positive electrode materials and current collectors mainly adopts mechanical crushing, alkaline dissolution, acid dissolution, high temperature decomposition and organic dissolution methods ( Sep. Purif. Technol .2024;348:127777.). The mechanical crushing method is to crush the positive electrode sheet by physical means, and then separate it by magnetic separation, gravity separation, nitrogen separator, etc. ( I&EC Res .2024;63:3483-3490.; Sustain. Mater. Technol. 2023;35:e00575; J.Environ.Manage .2024;358:120818.), but this method cannot completely separate the components, and the aluminum content in the recovered ternary positive electrode material is high. The alkaline dissolution method uses an alkaline solution to dissolve the aluminum foil on the positive electrode sheet, and the ternary positive electrode material is collected in a powder state ( J. Mater. Chem. A .2022;10:23905-23914.); The acid dissolution method uses a strong acid solution to leach the ternary cathode material and the current collector together, and then separates the valuable metal elements through extraction, precipitation and other methods ( Waste Management.2018;71:362-371.); Both methods have the disadvantages of complex process, low recovery rate of valuable metals, large amount of chemical reagents used and difficult treatment of waste liquid. The high temperature decomposition method is to decompose the binder at a high temperature of 600-800℃ ( Waste Management .2024;187:244-251.), to achieve the separation of ternary cathode materials and aluminum foil. This method consumes a lot of energy and the binder decomposes at high temperature to produce fluorine-containing toxic gases such as HF and tetrafluoroethylene monomer. It requires a waste gas treatment device to reduce secondary pollution. The organic solvent dissolution method uses organic solvents such as nitrogen methyl pyrrolidone (NMP) to dissolve the binder to achieve the separation of ternary cathode materials and aluminum foil ( I&EC Res. 2021;60:10303-10311.), but NMP is slightly toxic and can cause harm to the ecological environment and human body. Summary of the invention

[0005] The present invention aims to solve the above technical problems existing in the prior art and provides a method for separating ternary positive electrode materials and current collectors of waste lithium-ion batteries.

[0006] The technical solution of the present invention is: a method for separating the ternary positive electrode material and the current collector of waste lithium-ion batteries, which is carried out in the following steps: Step 1. Dismantle the used ternary lithium-ion battery after it is completely discharged, take out the positive electrode sheet, dry it and cut it; Step 2. Place the cut cathode sheet in a tube furnace, gradually heat to 200-450°C and pyrolyze for 20-60 min under a nitrogen atmosphere; Step 3. The pyrolyzed positive electrode sheet is connected to the negative electrode of a DC power supply as the cathode of the electrolytic cell, and the iridium-ruthenium-coated titanium mesh is connected to the positive electrode of the DC power supply as the anode of the electrolytic cell, and the water and ethylene glycol solution of soluble chlorate or the water and ethylene glycol solution of soluble bromate is used as the electrolyte, and the electrolysis is carried out at a voltage of 3-10 V for 0.5-3 min; Step 4. After the electrolysis is completed, the waste electrolyte is filtered to collect the ternary positive electrode material, and the cathode of the electrolytic cell is dried to obtain a current collector.

[0007] The preferred technical solution is that the cutting in step 1 is to cut the dried positive electrode sheet into small pieces of 20 mm×50 mm.

[0008] The preferred technical solution is that the gradual heating in step 2 is 200-450°C at a rate of 5°C / min.

[0009] The preferred technical solution is that the salt concentration in the electrolyte is 2-4 g / L, and the volume ratio of water to ethylene glycol is 2:1.

[0010] The present invention uses a method of coupling low-temperature (200-450°C) pyrolysis and electrochemical phases to achieve a rapid stripping time of 0.5-3 min and a separation efficiency of 95-99% without destroying the current collector (aluminum foil), thereby achieving rapid and efficient separation of the ternary positive electrode material and the current collector, while avoiding the use or production of environmentally polluting chemicals and reducing environmental protection costs. The recovered positive electrode material can be restored to activity by high-temperature calcination and replenishing lithium, and reused as a raw material precursor for lithium batteries, or it can directly enter the subsequent leaching recovery link; the recovered current collector (aluminum foil) is completely separated and has a smooth surface, and can be directly recycled and applied. Compared with the prior art, the present invention has the advantages of simple operation, mild conditions, low cost, safety, high efficiency, and green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the XRD diagram of the positive electrode sheet in the waste lithium-ion battery in Example 1 of the present invention before and after thermal decomposition.

[0012] Figure 2 These are digital photos of the positive electrode sheet of the waste lithium-ion battery in Example 1 of the present invention before and after electrolysis. DETAILED DESCRIPTION Example 1

[0013] A method for separating a waste lithium-ion battery ternary positive electrode material from a current collector is carried out in the following steps: Step 1. Soak the used ternary lithium-ion battery in sodium chloride solution for 24 hours and then manually disassemble it after discharging. Take out the positive electrode sheet, dry it, and cut it into 20mm×50mm. Step 2. Place the cut cathode sheet in a tube furnace and pyrolyze it at 300°C for 30 min at a heating rate of 5°C / min under a nitrogen atmosphere; Step 3. The pyrolyzed positive electrode sheet is used as the cathode of the electrolytic cell and connected to the negative electrode of the DC power supply. The iridium-ruthenium-coated titanium mesh (titanium mesh coated with an iridium-ruthenium layer) is used as the anode of the electrolytic cell and connected to the positive electrode of the DC power supply. The electrolyte is 3 g / L sodium chlorate in water and ethylene glycol solution, and the volume ratio of water to ethylene glycol is 2:1. The electrolysis is carried out at a voltage of 5 V for 2 min. During the electrolysis process, the impact of the gas generated by electrolysis is used to peel off the ternary positive electrode material from the current collector. Step 4. After the electrolysis is completed, the waste electrolyte is filtered to collect the ternary positive electrode material, and the cathode of the electrolytic cell connected to the negative electrode of the power supply is removed and dried at 60°C. Since the ternary positive electrode material on the positive electrode sheet is peeled off, what is obtained is the current collector (aluminum foil).

[0014] The XRD patterns of the positive electrode sheet before and after pyrolysis in Example 1 of the present invention are as follows: Figure 1 As shown, from Figure 1 It can be seen that using N 2Low-temperature pyrolysis in the atmosphere removes the binder in the positive electrode sheet, but the structure of the ternary positive electrode material on the positive electrode sheet does not change before and after pyrolysis.

[0015] Digital photos of the positive electrode sheet of the waste lithium-ion battery before and after electrolysis in Example 1 of the present invention are as follows Figure 2 As shown, Figure 2 Part A is a digital photo of the positive electrode before electrolysis, and Part B is a digital photo of the positive electrode after electrolysis. Figure 2 It can be seen that the current collector obtained after electrolysis of the positive electrode sheet is completely separated and has a smooth surface.

[0016] The recovery rate of ternary positive electrode materials reaches 99.8%. The collected positive electrode materials have complete crystal form and can be restored to activity through high-temperature calcination to replenish lithium and reused as raw material precursors for lithium batteries. They can also directly enter the subsequent leaching recovery link. The collected current collectors are completely separated and have a smooth surface, and can be directly recycled and applied. Example 2

[0017] The difference from Example 1 is that the pyrolysis temperature is 200° C., the pyrolysis time is 60 min, and the other operations are the same as Example 1.

[0018] The recovery rate of ternary positive electrode materials reaches 95.2%. The collected ternary positive electrode materials have complete crystal form and can be restored to activity through high-temperature calcination to replenish lithium and reused as raw material precursors of lithium batteries. They can also directly enter the subsequent leaching recovery link. The collected current collectors are completely separated and have a smooth surface, and can be directly recycled and applied. Example 3

[0019] The difference from Example 1 is that the pyrolysis temperature is 450°C, the pyrolysis time is 20 min, and the other operations are the same as Example 1.

[0020] The recovery rate of ternary positive electrode materials reaches 98.4%. The collected positive electrode materials have complete crystal form and can be restored to activity through high-temperature calcination to replenish lithium and reused as raw material precursors of lithium batteries. They can also directly enter the subsequent leaching recovery link. The collected current collectors are completely separated and have a smooth surface, and can be directly recycled and applied. Example 4

[0021] The difference from Example 1 is that the electrolyte is a water and ethylene glycol solution with a concentration of 4 g / L potassium bromate, the volume ratio of water to ethylene glycol is 2:1, and the remaining operations are the same as Example 1.

[0022] The recovery rate of ternary positive electrode materials reaches 99.1%. The collected positive electrode materials have complete crystal form and can be restored to activity through high-temperature calcination to replenish lithium and reused as raw material precursors for lithium batteries. They can also directly enter the subsequent leaching recovery link. The collected current collectors are completely separated and have a smooth surface, and can be directly recycled and applied. Example 5

[0023] The difference from Example 1 is that the electrolysis voltage is 3 V, the electrolysis time is 3 min, and the other operations are the same as Example 1.

[0024] The recovery rate of ternary positive electrode materials reaches 99.0%. The collected positive electrode materials have complete crystal form and can be restored to activity through high-temperature calcination to replenish lithium and reused as raw material precursors for lithium batteries. They can also directly enter the subsequent leaching recovery link. The collected current collectors are completely separated and have a smooth surface, and can be directly recycled and applied. Example 6

[0025] The difference from Example 1 is that the electrolysis voltage is 10 V, the electrolysis time is 0.5 min, and the other operations are the same as in Example 1.

[0026] The recovery rate of ternary positive electrode materials reaches 98.9%. The collected positive electrode materials have complete crystal form and can be restored to activity through high-temperature calcination to replenish lithium and reused as raw material precursors for lithium batteries. They can also directly enter the subsequent leaching recovery link. The collected current collectors are completely separated and have a smooth surface, and can be directly recycled and applied.

Claims

1. A method for separating waste lithium-ion battery ternary positive electrode materials and current collectors, characterized in that Follow the steps below: Step 1. Dismantle the used ternary lithium-ion battery after it is completely discharged, take out the positive electrode sheet, dry it and cut it; Step 2. Place the cut cathode sheet in a tube furnace, gradually heat to 200-450°C and pyrolyze for 20-60 min under a nitrogen atmosphere; Step 3. The pyrolyzed positive electrode sheet is connected to the negative electrode of a DC power supply as the cathode of the electrolytic cell, and the iridium-ruthenium-coated titanium mesh is connected to the positive electrode of the DC power supply as the anode of the electrolytic cell, and the water and ethylene glycol solution of soluble chlorate or the water and ethylene glycol solution of soluble bromate is used as the electrolyte, and the electrolysis is carried out at a voltage of 3-10 V for 0.5-3 min; Step 4. After the electrolysis is completed, the waste electrolyte is filtered to collect the ternary positive electrode material, and the cathode of the electrolytic cell is dried to obtain a current collector.

2. The method for separating the cathode material and the current collector of waste ternary lithium-ion batteries according to claim 1, characterized in that: The cutting in step 1 is to cut the dried positive electrode sheet into small pieces of 20 mm×50 mm.

3. The method for separating the cathode material and the current collector of waste ternary lithium-ion batteries according to claim 1 or 2, characterized in that: The gradual heating in step 2 is performed at a rate of 5°C / min to a temperature of 200-450°C.

4. The method for separating the cathode material and the current collector of waste ternary lithium-ion batteries according to claim 3, characterized in that: The salt concentration in the electrolyte is 2-4 g / L, and the volume ratio of water to ethylene glycol is 2:1.

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