Method for repairing and improving layered oxide positive electrode material of waste lithium ion battery
Through the methods of pretreatment, primary calcination, water bath ultrasound and secondary calcination, a eutectic lattice perovskite surface structure is constructed, which solves the problems of high energy consumption and poor cycle performance of lithium-ion batteries in recycling, realizes efficient and environmentally friendly positive electrode material repair, and improves the safety performance and cycle stability of lithium-ion batteries.
Patent Information
- Application Number
- CN202510697528.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-28
- Publication Date
- 2025-09-19
AI Technical Summary
Existing lithium-ion battery recycling methods have problems such as high energy consumption, serious pollution, complex processes and high costs, and the recycled positive electrode materials have poor cycle performance at high energy density.
By adopting the methods of pretreatment, primary calcination, water bath ultrasonic treatment and secondary calcination, the positive electrode material is repaired by the synergistic effect of high-temperature molten lithium salt, a stable eutectic lattice perovskite surface structure is constructed, the strain and volume effect during the insertion and extraction of lithium ions are reduced, and alkali metal, alkaline earth metal or rare earth metal ions are doped to capture oxygen escape.
A low-energy, green and environmentally friendly recycling method has been achieved. The repaired positive electrode material shows excellent stability under high-voltage cycles and can be directly used in the positive electrode sheets of lithium-ion batteries without the need for secondary processing.
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Figure CN120674648A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the regeneration and utilization of waste lithium-ion battery resources, in particular to a method for repairing and improving layered oxide positive electrode materials of waste lithium-ion batteries. Background Art
[0002] Since the beginning of the 21st century, the accelerating pace of global development has created enormous energy demands, necessitating an urgent need for more efficient and environmentally friendly energy sources. Lithium-ion batteries, due to their high energy density and fast response time, are widely used in various fields. Demand for lithium-ion batteries has exploded, particularly with the rapid development of electronic devices and electric vehicles. This enormous demand for lithium-ion batteries also poses challenges in the future disposal of discarded batteries. It is estimated that by 2025, approximately one million tons of lithium-ion batteries will be discarded, and this number is projected to reach tens of millions within the next ten to twenty years. The nickel, cobalt, and manganese elements used in high-energy-density battery materials are not only expensive but also in short supply. With the growing demand for high-energy-density batteries in the robotics and low-altitude economy, the demand is increasing, necessitating the development of efficient recycling processes for their effective reuse.
[0003] Currently, the methods for recycling lithium-ion batteries mainly focus on pyrometallurgical recycling and wet recycling methods. Both pyrometallurgical recycling and wet recycling extract key metal elements from discarded positive electrode materials in the form of compounds, and then undergo a series of complex processes to make them into active positive electrode materials that can be used to make new batteries. The pyrometallurgical recycling process consumes a large amount of energy and fuel to meet the temperature required for metal smelting; wet recycling involves the use of a large amount of acid and alkali reagents to selectively leach the relevant metal elements. Although the recovery efficiency of these two methods is relatively high, they are often accompanied by defects such as severe pollution, complex processes, high costs, and difficult to handle emissions. Summary of the Invention
[0004] Purpose of the invention: The purpose of the present invention is to provide a method for repairing and improving waste lithium-ion battery layered oxide positive electrode materials, which has a simple and efficient recovery method with low energy consumption, and the high-voltage cycle performance of the repaired and improved positive electrode materials is excellent and can be directly used.
[0005] Technical solution: The method for repairing and improving the layered oxide positive electrode material of waste lithium-ion batteries described in the present invention comprises the following steps:
[0006] (1) dismantling waste lithium-ion batteries to obtain layered oxide positive electrode materials and performing pretreatment;
[0007] (2) mixing the pretreated positive electrode material with the lithium salt, grinding the mixture, and then calcining the mixture to obtain a primary sintered material;
[0008] (3) placing the primary sintered material in an ion mixed solution containing two ions of alkali metal ions, alkaline earth metal ions and rare earth metal ions for water bath ultrasonic treatment, washing and drying, and then performing a secondary calcination to obtain a repaired and improved layered oxide positive electrode material.
[0009] Furthermore, in step (1), the layered oxide positive electrode material is Li x MO2, M is one or more of the transition metal elements nickel, cobalt or manganese.
[0010] Furthermore, the pretreatment in step (1) is as follows: the waste positive electrode material is soaked in an organic solvent for 18 to 24 hours, calcined at 400°C to 600°C for 1 to 3 hours, soaked in deionized water and ultrasonicated for 1 to 2 minutes, washed and dried, and then calcined at 600°C to 800°C for 2 to 4 hours, and ground to obtain a pretreated positive electrode material. After soaking, the primary calcination and heat preservation are carried out to ensure that the binder polyvinylidene fluoride (PVDF) is completely removed; the positive electrode material is soaked in deionized water and ultrasonicated to separate the positive electrode material from the current collector to obtain a waste positive electrode material suspension, which is then centrifuged, washed, dried, and collected; and the secondary calcination and heat preservation treatment is carried out to ensure that the conductive agent is completely removed.
[0011] Furthermore, the lithium salt in step (2) is one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate or lithium nitrate.
[0012] Furthermore, the primary calcination temperature of step (2) is 700°C to 900°C, and the secondary calcination temperature of step (3) is 400°C to 600°C; the calcination atmosphere of steps (1) and (2) is an oxygen atmosphere, and the calcination heating rate is 3 to 5°C / min.
[0013] Furthermore, the solvent of the ion mixed solution in step (3) is deionized water; the tolerance factor t is calculated based on the ionic radius of two ions among the alkali metal ions, alkaline earth metal ions or rare earth metal ions in the mixed solution, and the tolerance factor t satisfies: 0.8≤t≤1.0.
[0014] Furthermore, the alkali metal ion in step (3) is Cs + or Rb+, alkaline earth metal ions such as Sr 2+ 、Ba 2+ or Ca 2+ and rare earth metal ions such as La 3+ 、Pr 3+ or Nd 3 +.
[0015] Furthermore, the concentration of the ion mixture solution in step (3) is 0.1 to 1.2 mol / L.
[0016] Furthermore, in step (2), the layered oxide positive electrode material is LiCoO2, and the molar ratio of Li / Co of the material before the first sintering is 1.05 to 1.2:1.
[0017] Furthermore, the organic solvent is one of dimethyl carbonate (DMC), diethyl carbonate (DEC), N-methyl-2-pyrrolidone (NMP), and N,N-dimethylformamide (DMF).
[0018] The principle behind this invention is that the structural defects of the positive electrode material are repaired through the synergistic effect of high-temperature molten lithium salts. By utilizing the properties of these structural defects, a stable eutectic perovskite surface structure is constructed on the material's surface. This significantly reduces the strain and volume effects inflicted by lithium ions as they insert and release from the positive electrode material, thereby mitigating the formation of surface cracks in the positive electrode material. Simultaneously, the oxygen vacancies in the perovskite structure effectively capture oxygen released from the positive electrode material during cycling, thereby reducing gas production and enhancing the safety of lithium-ion batteries. A half-cell assembled from recycled positive electrode material maintained a capacity retention rate of 91.04% after 200 cycles at a high voltage of 4.5V and a rate of 0.5C, surpassing batteries that were only repaired with lithium without undergoing doping.
[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant characteristics: the recycling method of the present invention is simple, efficient, and has low energy consumption, no waste is generated, it is green and environmentally friendly, and can be industrialized. At the same time, it can solve the problem of poor effect caused by insufficient purity in the direct recovery method, and provide a new solution for the direct recycling of waste lithium-ion batteries; the repaired and improved positive electrode material has excellent high-voltage cycle stability, which can improve the safety performance of lithium-ion batteries; it can be directly applied to the positive electrode sheets of lithium-ion batteries without the need for secondary processing. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a schematic flow chart of the improved method for repairing the positive electrode material of waste lithium-ion batteries of the present invention;
[0021] Figure 2 This is a SEM image of lithium cobalt oxide S-LCO, a cathode material for waste lithium-ion batteries of the present invention;
[0022] Figure 3 This is a SEM image of lithium cobalt oxide R-LCO, a cathode material for waste lithium-ion batteries of the present invention;
[0023] Figure 4 This is a comparison diagram of the XRD patterns of lithium cobalt oxide, the cathode material of waste lithium-ion batteries, before and after repair and improvement;
[0024] Figure 5 This is a graph showing the electrochemical performance of lithium cobalt oxide, the cathode material of waste lithium-ion batteries, after repair and improvement with different amounts of lithium supplementation;
[0025] Figure 6 This is the voltage-specific capacity cycle curve of the lithium cobalt oxide cathode material of the waste lithium ion battery after repair and improvement of the present invention;
[0026] Figure 7 This is a graph showing the electrochemical performance of lithium cobalt oxide, the cathode material of waste lithium-ion batteries, before and after repair and improvement;
[0027] Figure 8 This is a diagram of the electrochemical performance of lithium cobalt oxide, the cathode material of waste lithium-ion batteries, before and after repair and improvement. DETAILED DESCRIPTION
[0028] The present invention is further described below with reference to specific embodiments.
[0029] Example 1
[0030] A method for repairing and improving layered oxide cathode materials of waste lithium-ion batteries, such as Figure 1 As shown, the following steps are included:
[0031] (1) The waste lithium-ion soft-pack battery was soaked in 10% wt NaCl solution and discharged until the voltage of the waste lithium-ion battery was lower than 2V; the battery after discharge was disassembled in a glove box, the positive electrode was separated and soaked in dimethyl carbonate (DMC) for 18 hours. The soaked electrode was transferred to a muffle furnace, the furnace temperature was raised to 400℃ at a rate of 3℃ / min, and kept at this temperature for 1 hour; after completion, the electrode was soaked in deionized water, ultrasonically treated for 1 minute, cleaned and dried; the electrode was then heated to 600℃ in the muffle furnace at a rate of 3℃ / min and kept at this temperature for 2 hours; then it was ground in a mortar for 30 minutes to obtain the pretreated waste lithium-ion battery positive electrode material lithium cobalt oxide powder, recorded as S-LCO; the Li / Co mass ratio of S-LCO was measured by inductively coupled plasma spectrometer (ICP) to be 1:9.687, and the Li / Co molar ratio was 0.88:1.
[0032] (2) Weigh 2 g of S-LCO and 0.038 g (10% wt excess) of lithium nitrate in a mortar, mix and grind for 30 min, and then calcine in a muffle furnace in an oxygen atmosphere. The temperature is raised to 700 ° C at 5 ° C / min and kept at this temperature for 10 h. Then, the material is annealed to room temperature at 5 ° C / min to obtain a primary sintered material.
[0033] (3) Take 5 mL of a mixed solution of LaCl3 / CaCl2 with a concentration of 0.4 mol / L, place the primary sintered material in the ion mixed solution, ultrasonically stir in an ice-water bath for 30 min, then transfer to a water bath, stir at 960 rpm for 20 h in water temperature below 50 °C, wash with deionized water three times, and then place in a blast drying oven for drying at 80 °C; after drying, heat to 400 °C at 5 °C / min, keep warm in an oxygen atmosphere for 6 h, and anneal to room temperature at 5 °C / min to obtain a repaired and improved lithium cobalt oxide positive electrode material, which is recorded as R-LCO-1.
[0034] Using La 3+ , Ca 2+ The tolerance factor t of the surface doping layer of the material prepared by the ion mixed solution is:
[0035]
[0036] Among them, r A For La 3+ and Ca 2+ The average ionic radius, r Co For Co 3+ The ionic radius, r O O 2+ ionic radius.
[0037] The materials were characterized using scanning electron microscopy (SEM). Figure 2 As shown in Figure 2, there are micropores and particle cracks on the surface of S-LCO, a layered oxide cathode material for waste lithium-ion batteries, before repair and improvement. Figure 3 As shown in the figure, there are no cracks or micropores on the surface of R-LCO-1 after repair and improvement; due to the construction of a stable eutectic lattice perovskite surface structure on the surface, the strain and volume effect brought to the positive electrode material when lithium ions are embedded in and out of the positive electrode material are greatly reduced, thereby reducing the generation of cracks on the surface of the positive electrode material.
[0038] Example 2
[0039] A method for repairing and improving layered oxide positive electrode materials of waste lithium-ion batteries comprises the following steps:
[0040] (1) The waste lithium-ion soft-pack battery was soaked in a 10% wt NaCl solution and discharged until the voltage of the waste lithium-ion battery was lower than 2V; the battery after discharge was disassembled in a glove box, and the positive electrode was separated and soaked in dimethyl carbonate (DMC) for 20 hours. The soaked electrode was transferred to a muffle furnace, and the furnace temperature was raised to 500℃ at a rate of 4℃ / min and kept at this temperature for 2 hours; after completion, the electrode was soaked in deionized water, ultrasonically treated for 2 minutes, cleaned and dried; the electrode was then heated to 700℃ in the muffle furnace at a rate of 4℃ / min and kept at this temperature for 3 hours; then ground in a mortar for 30 minutes to obtain the pretreated waste lithium-ion battery positive electrode material lithium cobalt oxide powder, recorded as S-LCO.
[0041] (2) Take 2 g of S-LCO and mix it with 0.040 g (excess 15% wt) of lithium carbonate, place it in a mortar and grind it for 30 minutes, and then calcine it in a muffle furnace. The calcination atmosphere is an oxygen atmosphere. The temperature is raised to 800 ° C at 3 ° C / min and kept at this temperature for 10 hours. Anneal it to room temperature at 3 ° C / min to obtain a primary sintered material.
[0042] (3) Take 5 mL of a mixed solution of LaCl3 / CaCl2 with a concentration of 0.4 mol / L, place the primary sintered material in the ion mixed solution, ultrasonically stir in an ice-water bath for 30 min, then transfer to a water bath, stir at 960 rpm for 20 h in water temperature below 50 °C, wash with deionized water three times, and then place in a blast drying oven for drying at 80 °C; after drying, heat to 500 °C at 3 °C / min, keep warm in an oxygen atmosphere for 6 h, and anneal to room temperature at 5 °C / min to obtain a repaired and improved lithium cobalt oxide positive electrode material, which is recorded as R-LCO-2.
[0043] Example 3
[0044] A method for repairing and improving layered oxide positive electrode materials of waste lithium-ion batteries comprises the following steps:
[0045] (1) The waste lithium-ion soft-pack battery was soaked in a 10% wt NaCl solution and discharged until the voltage of the waste lithium-ion battery was lower than 2V; the battery after discharge was disassembled in a glove box, and the positive electrode was separated and soaked in dimethyl carbonate (DMC) for 24 hours. The soaked electrode was transferred to a muffle furnace, and the furnace temperature was raised to 600℃ at a rate of 5℃ / min and kept at this temperature for 3 hours; after completion, the electrode was soaked in deionized water, ultrasonically treated for 2 minutes, cleaned and dried; the electrode was then heated to 800℃ in the muffle furnace at a rate of 5℃ / min and kept at this temperature for 4 hours; then ground in a mortar for 30 minutes to obtain the pretreated waste lithium-ion battery positive electrode material lithium cobalt oxide powder, recorded as S-LCO.
[0046] (2) 2 g of S-LCO was mixed with 0.042 g (20% wt excess) of lithium hydroxide in a mortar and ground for 30 min. The mixture was then calcined in a muffle furnace in an oxygen atmosphere. The temperature was raised to 900 °C at a rate of 3 °C / min and kept at that temperature for 10 h. The mixture was then annealed to room temperature at a rate of 3 °C / min to obtain a primary sintered material.
[0047] (3) Take 5 mL of a mixed solution of LaCl3 / CaCl2 with a concentration of 0.4 mol / L, place the primary sintered material in the ion mixed solution, ultrasonically stir in an ice-water bath for 30 min, then transfer to a water bath, stir at 960 rpm for 20 h in water temperature below 50 °C, wash with deionized water three times, and then place in a blast drying oven for drying at 80 °C; after drying, heat to 600 °C at 3 °C / min, keep warm for 6 h in an oxygen atmosphere, and anneal to room temperature at 5 °C / min to obtain a repaired and improved lithium cobalt oxide positive electrode material, which is recorded as R-LCO-3.
[0048] Example 4
[0049] A method for repairing and improving layered oxide positive electrode materials of waste lithium-ion batteries comprises the following steps:
[0050] (1) The waste lithium-ion soft-pack battery was soaked in a 10% wt NaCl solution and discharged until the voltage of the waste lithium-ion battery was lower than 2V; the battery after discharge was disassembled in a glove box, and the positive electrode was separated and soaked in dimethyl carbonate (DMC) for 20 hours. The soaked electrode was transferred to a muffle furnace, and the furnace temperature was raised to 500℃ at a rate of 4℃ / min and kept at this temperature for 2 hours; after completion, the electrode was soaked in deionized water, ultrasonically treated for 2 minutes, cleaned and dried; the electrode was then heated to 700℃ in the muffle furnace at a rate of 4℃ / min and kept at this temperature for 3 hours; then ground in a mortar for 30 minutes to obtain the pretreated waste lithium-ion battery positive electrode material lithium cobalt oxide powder, recorded as S-LCO.
[0051] (2) Take 2 g of S-LCO and mix it with 0.040 g (excess 15% wt) of lithium carbonate, place it in a mortar and grind it for 30 minutes, and then calcine it in a muffle furnace. The calcination atmosphere is an oxygen atmosphere. The temperature is raised to 800 ° C at 3 ° C / min and kept at this temperature for 10 hours. Anneal it to room temperature at 3 ° C / min to obtain a primary sintered material.
[0052] (3) Take 5 mL of a mixed solution of SrCl2 / CaCl2 with a concentration of 0.4 mol / L, place the primary sintered material in the ion mixed solution, ultrasonically stir in an ice-water bath for 30 min, then transfer to a water bath, stir at 960 rpm for 20 h in water temperature below 50 °C, wash with deionized water three times, and then place in a blast drying oven for drying at 80 °C; after drying, heat to 500 °C at 3 °C / min, keep warm for 6 h in an oxygen atmosphere, and anneal to room temperature at 5 °C / min to obtain a repaired and improved lithium cobalt oxide positive electrode material, which is recorded as R-LCO-Sr.
[0053] Using Sr 2+ , Ca 2+ The tolerance factor t of the surface doping layer of the material prepared by the ion mixed solution is:
[0054]
[0055] Among them, r B Sr 2+ and Ca 2+ The average ionic radius, r Co For Co 3+ The ionic radius, r O O 2+ ionic radius.
[0056] Comparative Example 1
[0057] A method for repairing and improving layered oxide positive electrode materials of waste lithium-ion batteries comprises the following steps:
[0058] Unlike Example 2, the primary sintered material was not doped with an ion mixed solution; 2 g of S-LCO was mixed with 0.040 g (15% wt excess) of lithium carbonate in a mortar and ground for 30 min, followed by a primary calcination in a muffle furnace. The temperature was raised to 800 ° C. at 3 ° C. / min and maintained for 10 h. The material was annealed to room temperature at 3 ° C. / min to obtain a repaired and improved lithium cobalt oxide positive electrode material, which was recorded as H-LCO.
[0059] Comparative Example 2
[0060] A method for repairing and improving layered oxide positive electrode materials of waste lithium-ion batteries comprises the following steps:
[0061] The difference from Example 2 is that in step (3), only 0.4 mol / L LaCl3 solution is used to dope the primary sintered material with elements to obtain a repaired and improved lithium cobalt oxide positive electrode material, which is recorded as R-LCO-La.
[0062] Comparative Example 3
[0063] A method for repairing and improving layered oxide positive electrode materials of waste lithium-ion batteries comprises the following steps:
[0064] Different from Example 2, 5 mL of a 1.5 mol / L LaCl3 / CaCl2 ion mixture solution was used to dope the primary sintered material with elements to obtain a repaired and improved lithium cobalt oxide positive electrode material, which was recorded as R-LCO-1.5.
[0065] Material performance testing
[0066] The electrode materials S-LCO, R-LCO-1, R-LCO-2 and R-LCO-3 obtained in Examples 1 to 3 were characterized by X-ray diffraction (XRD). Figure 4 As shown in Figure 2, the position shift of the (003) peak indicates that the interlayer spacing of R-LCO has changed significantly, proving that La and Ca elements have been incorporated into the material.
[0067] The electrochemical performance of the positive electrode materials R-LCO-1, R-LCO-2 and R-LCO-3 obtained in Examples 1 to 3 was tested. Figure 5 As shown, the amount of lithium supplementation has a great influence on the performance of the material. 3+ , Ca 2+ The ion mixed solution is doped, wherein an excess of 15% wt of lithium salt is the optimal lithium replenishment amount, and the material performance is the best. Example 2 is the optimal embodiment; an excess of 10% wt affects the repair effect of the positive electrode material due to the small amount of lithium replenishment, and an excess of 20% wt of lithium replenishment affects the material performance due to the high lithium salt content, which reduces the gram capacity.
[0068] The S-LCO, R-LCO-2 obtained in Example 2, the R-LCO-Sr obtained in Example 4, and the H-LCO, R-LCO-La, and R-LCO-1.5 positive electrode materials obtained in Comparative Examples 1 to 3 were prepared into lithium-ion button batteries, comprising the following steps:
[0069] 0.4 g of S-LCO, R-LCO-2, R-LCO-Sr, H-LCO, R-LCO-La, and R-LCO-1.5 were weighed separately and thoroughly mixed with 0.05 g of acetylene black, placed in a mortar and ground for 30 minutes, 1 g of a 5% wt solution of polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) was added, and then an appropriate amount of NMP was dropped to adjust the slurry to a suitable viscosity. Finally, a slurry mixer was used to mix evenly at 1200 r / min to obtain a positive electrode slurry; the positive electrode slurry was coated on an aluminum foil, and then the aluminum foil was placed in an 80°C blast drying oven for 30 minutes, and then placed in an 80°C vacuum drying oven for 8 hours to obtain a positive electrode sheet.
[0070] The positive electrode sheet was cut into 10 mm diameter discs and assembled into a button-type lithium-ion battery in a glove box using a lithium metal sheet as the negative electrode, a LiPF6 solution with an EC:EMC ratio of 3:7 as the electrolyte, and Celgard 2500 as the separator. The assembled button-type battery was activated at a rate of 0.1C for five cycles within a voltage range of 3-4.5V, followed by charge-discharge cycle performance testing at a rate of 0.5C. The test results are shown in Table 1.
[0071] Table 1 Charge and discharge cycle performance test
[0072]
[0073] As shown in Table 1, the test results show that the capacity and cycle stability of R-LCO-2 and R-LCO-Sr are significantly improved compared with S-LCO and H-LCO, R-LCO-La and R-LCO-1.5 prepared from Comparative Examples 1 to 3.
[0074] Combine Figures 6 to 8 The cycling stability of R-LCO-2 is significantly improved compared to S-LCO and H-LCO. Among them, the capacity retention rate of R-LCO is still 91.04% after 200 cycles. In contrast, the capacity retention rates of H-LCO and S-LCO after 200 cycles are only 86.71% and 61.7%. This shows that the La-doped and repaired LCO material can stabilize the strain and volume effect that occurs when lithium ions are inserted and removed, making the LCO material more robust, thereby improving its cycling stability.
Claims
1. A method for repairing and improving layered oxide cathode materials of waste lithium-ion batteries, characterized in that: The following steps are involved: (1) dismantling waste lithium-ion batteries to obtain layered oxide positive electrode materials and performing pretreatment; (2) mixing the pretreated positive electrode material with the lithium salt, grinding the mixture, and then calcining the mixture to obtain a primary sintered material; (3) placing the primary sintered material in an ion mixed solution containing two ions of alkali metal ions, alkaline earth metal ions and rare earth metal ions for water bath ultrasonic treatment, washing and drying, and then performing a secondary calcination to obtain a repaired and improved layered oxide positive electrode material.
2. The method for repairing and improving the layered oxide positive electrode material of waste lithium-ion batteries according to claim 1, characterized in that: The layered oxide positive electrode material in step (1) is Li x MO2, M is one or more of the transition metal elements nickel, cobalt or manganese.
3. The method for repairing and improving the layered oxide positive electrode material of waste lithium-ion batteries according to claim 1, characterized in that: The pretreatment in step (1) is as follows: the discarded positive electrode material is soaked in an organic solvent for 18 to 24 hours, calcined at 400° C. to 600° C. for 1 to 3 hours, soaked in deionized water and ultrasonicated for 1 to 2 minutes, washed and dried, calcined at 600° C. to 800° C. for 2 to 4 hours, and ground to obtain the pretreated positive electrode material.
4. The method for repairing and improving the layered oxide positive electrode material of waste lithium-ion batteries according to claim 1, characterized in that: The lithium salt in step (2) is one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate or lithium nitrate.
5. The method for repairing and improving the layered oxide positive electrode material of waste lithium-ion batteries according to claim 1, characterized in that: The primary calcination temperature of step (2) is 700°C to 900°C, and the secondary calcination temperature of step (3) is 400°C to 600°C; the calcination atmosphere of steps (1) and (2) is an oxygen atmosphere, and the calcination heating rate is 3 to 5°C / min.
6. The method for repairing and improving the layered oxide positive electrode material of waste lithium-ion batteries according to claim 1, characterized in that: The solvent of the ion mixed solution in step (3) is deionized water; the tolerance factor t is calculated based on the ionic radius of two ions among the alkali metal ions, alkaline earth metal ions or rare earth metal ions in the mixed solution, and the tolerance factor t satisfies: 0.8≤t≤1.
0.
7. The method for repairing and improving layered oxide cathode materials of waste lithium-ion batteries according to claim 1, characterized in that: The alkali metal ion in step (3) is Cs + or Rb+, alkaline earth metal ions such as Sr 2+ 、Ba 2+ or Ca 2+ and rare earth metal ions such as La 3+ 、Pr 3+ or Nd 3 +.
8. The method for repairing and improving layered oxide cathode materials of waste lithium-ion batteries according to claim 1, characterized in that: The concentration of the ion mixed solution in step (3) is 0.1 to 1.2 mol / L.
9. The method for repairing and improving layered oxide cathode materials of waste lithium-ion batteries according to claim 2, characterized in that: In the step (2), the layered oxide positive electrode material is LiCoO2, and the molar ratio of Li / Co of the material before the first sintering is 1.05 to 1.2:
1.
10. The method for repairing and improving layered oxide cathode materials of waste lithium-ion batteries according to claim 3, characterized in that: The organic solvent is one of dimethyl carbonate, diethyl carbonate, N-methyl-2-pyrrolidone and N,N-dimethylformamide.