Recycling process of positive electrode materials for lithium-ion batteries

Abstract

The present invention provides a recycling process for positive electrode materials of lithium-ion batteries, comprising the following steps: disassembling a module battery into a single battery, disassembling the battery after discharge, separating the positive and negative electrode sheets from the disassembled winding core, and then soaking the separated electrode sheets in an organic solution respectively to achieve preliminary separation of the foil and the electrode sheets, selecting the positive electrode sheet, cutting it into small pieces and then crushing it into powder, then sieving to remove impurities to obtain a raw material powder, and using a physical sintering method to treat the raw material powder of the lithium source to obtain qualified lithium source recycled materials. The present invention first removes impurities such as moisture and free carbon by high-temperature baking, and also causes the organic adhesive between the aluminum foil and the electrode sheet to evaporate at high temperature, so that the aluminum foil and the electrode sheet are dispersed, and then a vibrating screen is used to screen out the lithium source electrode sheet material with large mass and smaller particle size, thereby separating it from the lighter and larger aluminum foil. High-temperature baking will also cause the surface of the aluminum foil to expand, the density becomes lower, and it is also more conducive to screening.

Description

Technical Field

[0001] The present invention relates to the technical field of battery recycling, and in particular to a recycling process for positive electrode materials of lithium-ion batteries. Background Art

[0002] Lithium-ion batteries have been used extensively for automotive propulsion over the past few decades as they provide many years of reliable service and are expected to last about 10 years under normal driving conditions. These lithium-ion batteries can then be used for utility energy storage until the end of their useful life.

[0003] Environmental issues caused by waste lithium-ion batteries have attracted widespread public attention. If usable materials can be recovered from used batteries, the need to extract raw materials from the limited supply of land will be reduced. In addition, if used lithium-ion batteries can be recycled, the significant negative impact on the environment caused by mining and processing ore can be avoided.

[0004] In December 2016, the Ministry of Industry and Information Technology issued the "Interim Measures for the Management of Recycling and Utilization of Power Batteries for New Energy Vehicles", which clearly stated that automobile manufacturers bear the main responsibility for the recycling and utilization of power batteries, and required producers to take responsibility throughout the product life cycle, linking production and recycling to improve the recycling rate. In December 2020, the European Commission announced the new European battery policy, which aims to ensure that batteries put on the EU market are sustainable and safe throughout their life cycle. In this environment, battery manufacturers such as CATL, BYD, AVIC Lithium Battery, Guoxuan High-tech, and Chaowei Power are actively deploying lithium battery recycling.

[0005] There are roughly the following methods for recycling lithium battery materials on the market: physical methods (including crushing and sorting processes), chemical methods (including pyrometallurgy, hydrometallurgy recovery processes), biometallurgy technology and other methods. These methods can relatively effectively recycle lithium, cobalt, phosphorus, iron and other materials in lithium-ion batteries, but these methods also have a common problem, that is, the purity of the recycled materials is not enough. Because the pole pieces of lithium-ion batteries need to be combined with foil materials to achieve good functions, and aluminum foil is the most cost-effective foil material currently, most lithium-ion battery pole pieces are tightly attached with aluminum foil. However, the current recycling methods are difficult to effectively separate the pole pieces from the foil materials, resulting in a high content of aluminum impurities in the recycled materials, which affects the purity of the lithium-ion materials and hinders subsequent reuse. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a process for recycling positive electrode materials of lithium-ion batteries, which solves the problem that the methods for recycling positive electrode materials of lithium-ion batteries in the prior art are difficult to separate the electrode sheets and foils, resulting in a high level of aluminum impurities in the recycled materials.

[0007] According to an embodiment of the present invention, a process for recycling positive electrode materials of lithium-ion batteries comprises the following steps:

[0008] S1. Disassemble the module battery into individual batteries, and then select the batteries that are obviously severely damaged by appearance screening as the batteries to be disassembled; the remaining batteries are graded after charge and discharge aging treatment, and some batteries that can be downgraded are downgraded according to the battery grade, and some batteries that cannot be downgraded are used as batteries to be disassembled;

[0009] S2. Discharge the battery to be disassembled to ≤2.5V, then disassemble the battery, separate the positive and negative electrode sheets from the disassembled winding core, and then soak the separated electrode sheets in an organic solution respectively to achieve preliminary separation of the foil and the electrode sheets, while partially eliminating the electrolyte and adhesive;

[0010] S3. Select positive electrode plates, classify them according to the type of positive electrode materials, cut each type of classified plates into small pieces, crush them into powder, and then sieve out impurities to obtain raw material powder, use physical sintering method to process the raw material powder of lithium source, and obtain qualified lithium source recovery material.

[0011] Furthermore, for the raw material powder obtained in step S3, the Li content is first detected. If the Li content is ≤4.0%, a lithium supplement is added and mixed evenly to make the Li content greater than 4.0%.

[0012] Furthermore, for the raw material powder whose Li content has been detected, its Al content is detected again. If the Al content is ≤350ppm, physical sintering method is directly used for treatment; if the Al content is in the range of 350-600ppm, lithium source material of the corresponding type of positive electrode material is added, and the ratio of raw material powder to added material is between 8:2 and 3:7, and then physical sintering method is used for treatment.

[0013] Furthermore, the processing steps of the physical sintering method are as follows: the raw material powder is baked in an atmosphere roller furnace to remove moisture, adhesives, free carbon and other impurities in the material, and then a 50-mesh screen is used to separate the electrode foil and the powder through high-frequency vibration in a dehumidified environment. The aluminum foil is then recovered and packaged, and the powder is graded with a 100-mesh vibrating screen, and qualified products are selected and then refined and mixed.

[0014] Furthermore, the baking temperature in the atmosphere roller furnace is 400-800°C, the time is 3-10 hours, and the final discharge temperature is ≤60°C.

[0015] Preferably, the organic solution comprises a mixture of one or more of phenylbenzoic acid, N-methylpyrrolidone, acetone, ethanol, liquid ammonia, methyl butyl ketone, isopropanol, phenol, and propylene oxide.

[0016] Preferably, the lithium supplement includes a mixture of one or more of lithium phosphate, lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate or lithium sulfate and lithium oxide.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention first uses high-temperature baking to not only remove impurities such as moisture and free carbon, but also evaporates the organic adhesive between the aluminum foil and the pole piece at high temperature, so that the aluminum foil and the pole piece are dispersed, and then a vibrating screen is used to screen out the lithium source pole piece material with large mass and smaller particle size, thereby separating it from the lighter and larger aluminum foil;

[0019] 2. The high temperature baking in the present invention will also cause the surface of the aluminum foil of the small particles to expand and crack, making its surface morphology more irregular, so it can be more easily peeled off from the tightly adhered pole pieces. At the same time, its density becomes lower after expansion, which is also more conducive to screening. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below in conjunction with embodiments.

[0021] The waste lithium-ion batteries used in the embodiments of the present invention are all 280Ah square aluminum shell batteries produced by CATL.

[0022] Since steps S1 and S2 in the process of the present invention are basically the same, the following embodiments all adopt the following steps:

[0023] S1. Disassemble the module battery into individual batteries, and then select the batteries that are obviously severely damaged by appearance screening as the batteries to be disassembled; the remaining batteries are graded after charge and discharge aging treatment, and some batteries that can be downgraded are downgraded according to the battery grade, and some batteries that cannot be downgraded are used as batteries to be disassembled;

[0024] S2. Discharge the battery to be disassembled to ≤2.5V, and then disassemble the battery. Separate the positive and negative electrode plates of the disassembled winding core, and then soak the separated electrode plates in an organic solution, wherein the organic solution is phenylbenzoic acid, to achieve preliminary separation of the foil and the electrode plates, and partially eliminate the electrolyte and adhesive.

[0025] The positive electrode sheets separated through the above steps are respectively prepared into final lithium source recovery materials through different S3 steps according to different embodiments.

[0026] Embodiment 1:

[0027] Take 20kg of the positive electrode sheet material obtained in the previous step, cut it into small pieces, grind it into powder, and then pass it through a multi-level vibrating screen with a mesh size of 50 to 200, where each vibrating screen has a mesh size difference of 50, to screen out lithium source material powders of different fineness levels, and then sieve the powder materials of different levels to remove impurities to obtain raw material powder. Test the Li and Al contents of the raw material powder, first detect the Li content of 3.6% and the Al content of 278ppm, then add 1.0% lithium phosphate and mix evenly to make the Li content reach 4.6%.

[0028] The raw material powder was baked in an atmosphere roller furnace at a specific baking temperature of 500°C for 10 hours, and the final discharge temperature was 52°C. The moisture, adhesive, free carbon and other impurities in the material were removed, and then sieved with a 100-mesh sieve in a dehumidified environment and refined and mixed. The tested Li content was 4.0%, and the Al content was 278ppm, and the required lithium source recovery material was obtained.

[0029] Embodiment 2:

[0030] Take 20kg of the positive electrode sheet material obtained in the previous step, cut it into small pieces, grind it into powder, and then pass it through a multi-stage vibrating screen with a mesh size of 50 to 200, where each vibrating screen has a mesh size difference of 50, to screen out lithium source material powders of different fineness levels, and then sieve the powder materials of different levels to remove impurities to obtain raw material powder. Test the Li and Al content of the raw material powder, first detect the Li content of 4.0%, and then detect the Al content of 325ppm, add 0.3% lithium carbonate and 0.3% lithium hydroxide and mix them evenly.

[0031] The raw material powder was baked in an atmosphere roller furnace at a specific baking temperature of 800°C for 3 hours and a final discharge temperature of 60°C. The material was free of moisture, adhesives, free carbon and other impurities, and then sieved with a 300-mesh sieve in a dehumidified environment and refined and mixed. The tested Li content was 4.6% and the Al content was 325ppm, and the required lithium source recovery material was obtained.

[0032] Embodiment 3:

[0033] Take 20 kg of the positive electrode sheet material obtained in the previous step, cut it into small pieces, grind it into powder, and then pass it through a multi-stage vibrating screen with a mesh size of 50 to 200, where the mesh size difference between each vibrating screen is 50, to screen out lithium source material powders of different fineness levels, and then sieve the powder materials of different levels to remove impurities to obtain raw material powders, test the Li and Al contents of the raw material powders, and the Li content is 3.5% and the Al content is 460 ppm. Add 0.4% lithium phosphate, 0.4% lithium dihydrogen phosphate and 0.4% lithium oxide and mix them evenly.

[0034] The raw material powder was baked in an atmosphere roller furnace at a specific baking temperature of 650°C for 6 hours, and the final discharge temperature was 44°C. The material was free of moisture, adhesives, free carbon and other impurities, and then sieved with a 200-mesh sieve in a dehumidified environment and refined and mixed. The tested Li content was 4.3% and the Al content was 460ppm, and the required lithium source recovery material was obtained.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A process for recycling positive electrode materials of lithium-ion batteries, characterized in that: The steps include: S1. Disassemble the module battery into individual batteries, and then select the batteries that are obviously severely damaged by appearance screening as the batteries to be disassembled; the remaining batteries are graded after charge and discharge aging treatment, and some batteries that can be downgraded are downgraded according to the battery grade, and some batteries that cannot be downgraded are used as batteries to be disassembled; S2. Discharge the battery to be disassembled to ≤2.5V, then disassemble the battery, separate the positive and negative electrode sheets from the disassembled winding core, and then soak the separated electrode sheets in an organic solution respectively to achieve preliminary separation of the foil and the electrode sheets, while partially eliminating the electrolyte and adhesive; S3, selecting positive electrode sheets, classifying them according to the types of positive electrode materials, cutting each of the classified sheets into small pieces, crushing them into powder, then sieving them to remove impurities to obtain raw material powders, and using physical sintering method to process the raw material powders of lithium source to obtain qualified lithium source recovery materials; The processing steps of the physical sintering method are as follows: the raw material powder is baked in an atmosphere roller furnace to remove moisture, adhesives, free carbon and other impurities in the material, and then the pole piece foil and powder are separated by high-frequency vibration using a 50-mesh screen in a dehumidified environment. The aluminum foil is then recovered and packaged, and the powder is graded using a 100-mesh vibration screen to select qualified products and then refine and mix; The baking temperature in the atmosphere roller furnace is 400-800°C, the time is 3-10h, and the final discharge temperature is ≤60°C; For the raw material powder obtained in step S3, first detect its Li content. If the Li content is ≤4.0%, add a lithium supplement and mix evenly to make the Li content greater than 4.0%; For the raw material powder after the Li content is detected, its Al content is then detected. If the Al content is ≤350ppm, physical sintering method is directly used for treatment; if the Al content is in the range of 350-600ppm, lithium source material of the corresponding positive electrode material type is added, and the ratio of raw material powder to added material is between 8:2 and 3:7, and then physical sintering method is used for treatment.

2. The process for recycling positive electrode materials of lithium-ion batteries according to claim 1, characterized in that: The organic solution includes a mixture of one or more of phenyl benzoic acid, N-methyl pyrrolidone, acetone, ethanol, liquid ammonia, methyl butyl ketone, isopropanol, phenol, and propylene oxide.

3. The process for recycling positive electrode materials of lithium-ion batteries according to claim 1, characterized in that: The lithium supplement includes a mixture of one or more of lithium phosphate, lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate or lithium sulfate and lithium oxide.