Three-dimensional structure repairing method for positive material of waste lithium nickel battery

Abstract

The application provides a three-dimensional structure repairing method for waste lithium nickel oxide battery positive electrode material, and relates to the technical field of secondary battery regeneration, and comprises the following steps: S1, after waste lithium nickel oxide battery positive electrode material is crushed and sieved, the waste lithium nickel oxide battery positive electrode material after acid washing is obtained by immersing in an acid solution and filtering; S2, a first mixture is obtained by adding organic lithium to the waste lithium nickel oxide battery positive electrode material after acid washing and ball milling; S3, the first mixture is sintered in an oxygen atmosphere in sections to obtain a second mixture; S4, a gradient coating layer is formed by passing the second mixture into an aluminum source through atomic layer deposition; the waste lithium nickel oxide positive electrode material is treated by acid to dissolve Ni in the halite phase 2+ , organic lithium is added to make it uniformly adhere to the surface of the waste lithium nickel oxide positive electrode material through ball milling, and the lithium supplement uniformity is ensured; the lithium loss in the crystal lattice is repaired by section calcination, and the layered structure is restored; the aluminum source is passed in to form a gradient coating layer by using atomic deposition technology, and the interface bonding stability is enhanced.

Description

Technical Field

[0001] This application relates to the field of secondary battery regeneration technology, specifically to a method for repairing the three-dimensional structure of cathode materials from waste lithium nickel oxide batteries. Background Technology

[0002] In the global transition to a green and low-carbon energy structure, lithium nickel oxide (LiNiO2) batteries have become a core power source for new energy vehicles, energy storage power stations, and other fields due to their advantages such as high specific capacity and low cost. Lithium nickel oxide (LiNiO2) cathode materials have seen their market share steadily increase in recent years due to their theoretical specific capacity of up to 274 mAh / g, far exceeding that of traditional lithium cobalt oxide materials. However, the service life of LiNiO2 batteries is typically only 5-8 years. If these used batteries are not effectively disposed of, it will not only waste key resources such as lithium and nickel, but also pose a potential threat to the ecological environment due to the residual fluoride electrolyte, organic carbonate solvents, and heavy metal elements in the cathode materials.

[0003] Therefore, the effective recycling and utilization of cathode materials from spent lithium nickel oxide batteries is of great significance. Currently, the recycling of cathode materials from spent lithium nickel oxide batteries faces multiple technical bottlenecks. Regarding structural stability, Chinese patent CN105870408A discloses a lithium-ion battery cathode material and its preparation method. During long-term charge and discharge, lithium ions and nickel ions within the lithium nickel oxide lattice exhibit similar radii (Li... + Radius 0.76 Å, Ni 2+ With a radius of 0.69 Å, it is highly susceptible to cation mixing, leading to the collapse of the material's layered structure and blockage of lithium-ion diffusion channels. From the perspective of ion diffusion kinetics, as disclosed in Chinese patent application CN118136797A regarding self-healing polycrystalline cathode materials and their preparation methods, during the cycling process of waste cathode materials, the crystal lattice repeatedly undergoes volume expansion and contraction caused by lithium insertion and extraction, resulting in microcracks at the grain boundaries and hindering lithium-ion transport efficiency. These technical challenges make it difficult for existing recycling processes to effectively restore the electrochemical performance of the materials, necessitating the development of a repair technology for waste lithium nickel oxide battery cathode materials to achieve high-value recycling of these materials. Summary of the Invention

[0004] To address the above technical issues, this application provides a method for repairing the three-dimensional structure of waste lithium nickel oxide battery cathode materials. First, the waste lithium nickel oxide battery cathode materials are acid-washed and then mixed with organic lithium and ball-milled. Second, lithium is replenished through segmented sintering of bulk phases. Finally, the three-dimensional structure of the waste lithium nickel oxide battery cathode materials is regenerated through an atomic layer deposition gradient coating process.

[0005] To achieve the above objectives, one technical solution adopted by the present invention is:

[0006] In a first aspect, this application provides a method for repairing the three-dimensional structure of cathode materials from waste lithium nickel oxide batteries, comprising the following steps:

[0007] S1. After crushing and sieving the waste lithium nickelate cathode material, it is immersed in an acid solution and filtered to obtain the acid-washed waste lithium nickelate cathode material.

[0008] S2. Add organic lithium to the acid-washed waste lithium nickelate cathode material and ball-mill to obtain the first mixture;

[0009] S3. The first mixture is sintered in sections in an oxygen atmosphere to obtain the second mixture;

[0010] S4. The second mixture is passed into an aluminum source to form a gradient coating layer through atomic layer deposition.

[0011] In this application, the waste lithium nickelate (LiNiO2) cathode material undergoes charge-discharge cycling, resulting in the formation of an electrochemically inert rock salt phase (NiO) on its surface due to oxygen loss and transition metal (Ni) migration. The waste lithium nickelate cathode material is then treated with an acid solution (such as dilute sulfuric acid / citric acid) to dissolve the Ni in the rock salt phase. 2+ It retains its internal layered structure. The reaction formula is: NiO + 2H₂O + →Ni 2+ +H2O. Simultaneously, it dissolves impurities (such as Li2CO3, LiF, etc.) remaining in the electrolyte after surface charge-discharge cycles. Organic lithium and waste LiNiO2 cathode material are uniformly dispersed at the micron level through ball milling mechanical force. Electrostatic adsorption ensures that organic lithium is uniformly attached to the surface of the waste LiNiO2 cathode material, guaranteeing uniform lithium replenishment. The C-Li bonds in the organic lithium break at low temperatures, decomposing into lithium oxide. The lithium oxide melts at high temperatures, releasing Li+, thereby repairing lithium deficiencies in the crystal lattice. Simultaneously, high-temperature calcination allows Ni... 2+ Oxidized to Ni 3+ This process allows the lithium to migrate from the Li layer (octahedral position) back to the transition metal layer, eliminating lattice distortion and restoring the layered structure. The high-temperature repaired lithium-containing mixture is then passed through an aluminum source precursor and other reactive gases, and atomic deposition is used to deposit these gases on its surface. By precisely controlling the number of cycles or process parameters, a gradient coating layer with varying thickness or composition is formed. The gradient structure, due to the dense coating layer formed by alumina on the material surface, helps alleviate stress between the coating layer and the host material, enhancing interfacial bonding stability.

[0012] Preferably, in step S1, the waste nickel-lithium battery cathode material is crushed and sieved to a particle size of 5~50μm.

[0013] Preferably, the acid solution in S1 includes at least one of oxalic acid, citric acid, malic acid and tartaric acid; the concentration of the acid solution is 0.1-2 mol / L; and the mass ratio of the crushed and sieved waste nickel-lithium battery cathode material to the acid solution in S1 is 1:(5-20).

[0014] Preferably, the organic lithium in S2 includes at least one of lithium acetate, lithium propionate, lithium lactate and lithium acetate; the mass ratio of the acid-washed waste nickel-lithium battery cathode material to the organic lithium in S2 is 1:(0.05-0.2).

[0015] Preferably, in step S2, the ball milling speed is 200-600 r / min and the time is 2-10 h; during the ball milling process, 0.5-2 wt% lithium phosphate is added as a grain boundary stabilizer.

[0016] Preferably, the oxygen flow rate in S3 is 100~500 mL / min.

[0017] Preferably, the segmented sintering in S3 includes a first-stage sintering and a second-stage sintering; the first-stage sintering involves heating to 300-500°C at a heating rate of 5-20°C / min and holding at that temperature for 1-3 hours; the second-stage sintering involves heating to 700-900°C at a heating rate of 3-10°C / min and holding at that temperature for 2-6 hours.

[0018] Preferably, the aluminum source includes at least one of trimethylaluminum, triisopropoxide aluminum, and methylaluminoxane; the atomic layer deposition temperature is 80-300°C, the deposition cycle is 50-500 times, and a single deposition step includes an aluminum source pulse, a first inert gas purging, an oxygen source pulse, and a second inert gas purging.

[0019] Preferably, the gradient coating layer is aluminum oxide, aluminum hydroxide, or lithium aluminate, the thickness of the gradient coating layer is 5-50 nm, and the aluminum content gradient from the inside to the outside ranges from 10% to 90%.

[0020] Preferably, before step S1, the method further includes a pretreatment step: disassembling the waste lithium battery, separating the positive electrode sheet, removing the current collector aluminum foil, and collecting the positive electrode active material; after step S4, a post-treatment step is included: sieving the second mixture that forms the gradient coating layer.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This application provides a method for repairing the three-dimensional structure of spent lithium nickelate battery cathode materials. During charge-discharge cycles, the spent lithium nickelate cathode materials experience oxygen loss and transition metal (Ni) migration, resulting in the formation of an electrochemically inert rock salt phase (NiO) on their surface. The spent lithium nickelate cathode materials are then treated with acid, which dissolves the Ni²⁺ in the rock salt phase. + It retains its internal layered structure. The reaction formula is: NiO + 2H₂O + →Ni 2+ +H2O. Simultaneously, it dissolves impurities (such as Li2CO3, LiF, etc.) remaining in the electrolyte after surface charge-discharge cycles. Organic lithium and waste LiNiO2 cathode material are uniformly dispersed at the micron level through ball milling mechanical force. Electrostatic adsorption ensures that organic lithium is uniformly attached to the surface of the waste LiNiO2 cathode material, guaranteeing uniform lithium replenishment. The C-Li bonds in the organic lithium break at low temperatures, decomposing into lithium oxide. The lithium oxide melts at high temperatures, releasing Li+, thereby repairing lithium deficiencies in the crystal lattice. Simultaneously, high-temperature calcination allows Ni... 2+ Oxidized to Ni 3+ This process allows the lithium oxide to migrate from the Li layer back to the transition metal layer, eliminating lattice distortion and restoring the layered structure, thus achieving three-dimensional structural regeneration of spent lithium nickel oxide battery cathode materials. The high-temperature repaired lithium-containing mixture is then passed through an aluminum source precursor and other reactive gases, and atomic deposition technology is used to deposit these gases on its surface. By precisely controlling the number of cycles or process parameters, a gradient coating layer with varying thickness or composition is formed. The gradient structure, due to the dense coating layer formed by alumina on the material surface, helps alleviate stress between the coating layer and the host material, enhancing interfacial bonding stability. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of a three-dimensional structure repair method for waste lithium nickel oxide battery cathode materials;

[0024] Figure 2 The graph shows the cycle life curves of the batteries prepared in Example 1 and Comparative Examples 1-3. Detailed Implementation

[0025] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] In this application, the terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0027] The singular forms “for,” “or,” “a,” “any,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0028] Furthermore, the terms "first" and "second" appearing in this application are for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] Example 1

[0030] like Figure 1 As shown in the figure, this embodiment provides a method for repairing the three-dimensional structure of cathode material from waste lithium nickel oxide batteries, including the following steps:

[0031] S1: Disassemble the waste LiNiO2 power battery, separate the positive electrode sheet, remove the current collector aluminum foil, and collect the positive electrode material. Crush the positive electrode material to a particle size of 40μm, sieve it through a 400-mesh sieve, and then immerse it in a 0.6mol / L citric acid solution. The mass ratio of the crushed and sieved waste nickel-lithium battery positive electrode material to the citric acid solution is 1:5. Filter and dry.

[0032] S2: Add lithium lactate to the acid-washed waste lithium nickel oxide battery cathode material and ball mill at 300 r / min for 3 h. The mass ratio of acid-washed waste lithium nickel oxide battery cathode material to lithium lactate is 1:0.1 to obtain the first mixture.

[0033] S3: The first mixture is placed in an oxygen atmosphere with an oxygen flow rate of 350 mL / min, heated to 350℃ and held for 2 hours, then heated to 850℃ and held for 3.5 hours, and then sintered in stages to obtain the second mixture.

[0034] S4: The second mixture is placed in a fluidized bed, evacuated and heated to 220°C. Trimethylaluminum is used as the aluminum source precursor and high-purity oxygen plasma is used as the reaction gas for gradient coating. The deposition cycle is 250 times. Each deposition step includes aluminum source pulse, first inert gas purging, oxygen source pulse and second inert gas purging to form an aluminum hydroxide gradient coating layer with a thickness of 25nm and an aluminum element content gradient ranging from 20% to 80% from the inside to the outside. The second mixture that forms the aluminum hydroxide gradient coating layer is sieved to obtain the three-dimensional structure repaired waste nickel-lithium battery cathode material.

[0035] Example 2

[0036] like Figure 1 As shown in the figure, this embodiment provides a method for repairing the three-dimensional structure of cathode material from waste lithium nickel oxide batteries, including the following steps:

[0037] S1: Disassemble the waste LiNiO2 power battery, separate the positive electrode sheet, remove the current collector aluminum foil, and collect the positive electrode material. Crush the positive electrode material to a particle size of 50μm, sieve it through a 300-mesh sieve, and then immerse it in a 1.5 mol / L oxalic acid solution. The mass ratio of the crushed and sieved waste nickel-lithium battery positive electrode material to the oxalic acid solution is 1:12. Filter and dry.

[0038] S2: Add lithium acetate to the acid-washed waste lithium nickel oxide battery cathode material and ball mill at 600 r / min for 2 h. The mass ratio of the acid-washed waste lithium nickel oxide battery cathode material to lithium acetate is 1:0.08, and the first mixture is obtained.

[0039] S3: The first mixture is placed in an oxygen atmosphere with an oxygen flow rate of 250 mL / min, heated to 500℃ and held for 2 hours, then heated to 850℃ and held for 4 hours, and then sintered in stages to obtain the second mixture.

[0040] S4: The second mixture is placed in a fluidized bed, evacuated and heated to 200°C. Using aluminum triisopropoxide as the aluminum source precursor and high-purity oxygen plasma as the reactant gas, gradient coating is performed. The deposition cycle is 350 times. Each deposition step includes an aluminum source pulse, a first inert gas purging, an oxygen source pulse, and a second inert gas purging to form an aluminum hydroxide gradient coating layer with a thickness of 35 nm and an aluminum content gradient ranging from 18% to 82% from the inside to the outside. The second mixture that forms the aluminum hydroxide gradient coating layer is sieved to obtain the three-dimensional structure repaired waste nickel-lithium battery cathode material.

[0041] Example 3

[0042] like Figure 1 As shown, a method for repairing the three-dimensional structure of cathode material from waste lithium nickel oxide batteries includes the following steps:

[0043] S1: Disassemble the waste LiNiO2 power battery, separate the positive electrode sheet, remove the current collector aluminum foil, and collect the positive electrode material. Crush the positive electrode material to a particle size of 35μm, sieve it through a 300-mesh sieve, and then immerse it in a 2 mol / L tartaric acid solution. The mass ratio of the crushed and sieved waste nickel-lithium battery positive electrode material to the tartaric acid solution is 1:18. Filter and dry.

[0044] S2: Add lithium acetate to the acid-washed waste lithium nickel oxide battery cathode material and ball mill at 500 r / min for 5 h. The mass ratio of the acid-washed waste lithium nickel oxide battery cathode material to lithium acetate is 1:0.16, and the first mixture is obtained.

[0045] S3: The first mixture was placed in an oxygen atmosphere with an oxygen flow rate of 450 mL / min, heated to 470℃ and held for 2 hours, then heated to 880℃ and held for 4 hours, and sintered in stages to obtain the second mixture. S4: The second mixture was placed in a fluidized bed, evacuated and heated to 250℃, using methylaluminoxane as the aluminum source precursor and high-purity oxygen plasma as the reactant gas, and gradient coating was performed. The deposition cycle was 450 times. Each deposition step included an aluminum source pulse, a first inert gas purging, an oxygen source pulse and a second inert gas purging, forming an aluminum hydroxide gradient coating layer with a thickness of 33 nm and an aluminum element content gradient ranging from 17% to 86% from the inside to the outside. The second mixture with the aluminum hydroxide gradient coating layer was sieved to obtain the three-dimensional structure repaired waste nickel-lithium battery cathode material.

[0046] Comparative Example 1

[0047] This comparative example provides a method for repairing the three-dimensional structure of waste lithium nickel oxide battery cathode material. The difference between this method and Example 1 is that the comparative example uses a traditional direct regeneration method. The waste lithium nickel oxide cathode material after crushing and sieving is mixed with lithium carbonate (Li2CO3) at a mass ratio of 1:0.1. After ball milling at 300 r / min for 3 h, the mixture is heated to 850 °C and sintered for 12 h to obtain the waste lithium nickel oxide battery cathode material with three-dimensional structure repair. Compared with Example 1, the method does not include the S1 acid washing step or the S4 gradient coating step.

[0048] Comparative Example 2

[0049] This comparative example provides a method for repairing the three-dimensional structure of waste lithium nickel oxide battery cathode material. The difference between this method and Example 1 is that after the waste lithium nickel oxide battery cathode material is crushed and sieved in S1, it is not immersed in citric acid solution for acid washing, so as to obtain the waste lithium nickel oxide battery cathode material with three-dimensional structure repair.

[0050] Comparative Example 3

[0051] This comparative example provides a method for repairing the three-dimensional structure of waste lithium nickel oxide battery cathode material. The difference between this method and Example 1 is that the traditional impregnation method is used in S4: the sintered second mixture is immersed in a 0.1 mol / L Al(NO3)3 solution, soaked for 12 hours, and then sintered at 600°C for 2 hours. A uniform aluminum hydroxide coating layer is formed by the traditional impregnation method, which replaces the atomic layer deposition to form an aluminum hydroxide gradient coating layer in S4 of Example 1, thus obtaining the waste lithium nickel oxide battery cathode material with three-dimensional structure repair.

[0052] Performance testing:

[0053] 1. Lithium Concentration Standard Deviation Test: Secondary ion mass spectrometry was used to analyze the lithium elemental distribution of the repaired cathode materials in Examples 1-3 and Comparative Examples 1-3. Multiple different areas on the material surface were selected for testing, and the standard deviation of the lithium elemental concentration was calculated to evaluate the uniformity of lithium crystal distribution. The smaller the standard deviation of lithium concentration, the more uniform the lithium crystal distribution.

[0054] 2. Crystal Structure Integrity Test: The crystal structure of the repaired cathode materials in Examples 1-3 and Comparative Examples 1-3 was analyzed using X-ray diffraction (XRD). The full width at half maximum (FWHM) of the main peak in the XRD patterns was calculated, and the grain size was estimated using the Scherrer equation. The crystal structure integrity was assessed by combining the symmetry and intensity of the peaks in the patterns. Higher crystal structure integrity indicates better structural stability of the material. The test results are shown in Table 1.

[0055] 3. Initial Coulombic Efficiency Test: The repaired cathode materials from Examples 1-3 and Comparative Examples 1-3 were fabricated into coin cells and subjected to an initial charge-discharge test on a charge-discharge testing device. The charging voltage range was 2.5-4.3V, the charging current was 0.1C, and the discharging current was also 0.1C. Initial Coulombic Efficiency = Initial Discharge Capacity / Initial Charge Capacity × 100%.

[0056] 4. Cycle life test: The batteries assembled from the repaired positive electrode materials of Examples 1-3 and Comparative Examples 1-3 were cycled 100 times at a current density of 1C. The charge and discharge data were recorded once every 10 cycles, the capacity retention rate was calculated, and the capacity retention rate and stability in long-term cycling were tested.

[0057] 5. Rate Performance Test: Batteries assembled from the repaired cathode materials of Examples 1-3 and Comparative Examples 1-3 were first subjected to three charge-discharge cycles at a 1C current density, then three charge-discharge cycles at a 5C current density, and finally three charge-discharge cycles at a 1C current density. The ratio of the discharge capacity at 5C current density to the discharge capacity at 1C current density was calculated as the rate performance indicator. The higher this ratio, the better the material's performance at high rates. The test results are shown in Table 2.

[0058] Table 1. Results of lithium concentration standard deviation test and crystal structure integrity test in Examples 1-3 and Comparative Examples 1-3

[0059]

[0060] As shown in Table 1, the example group achieved efficient and uniform diffusion of lithium through acid washing and segmented sintering with added organic lithium. Acid washing removes impurities, exposes transition metal active sites, and preserves the layered structure of lithium phosphate. Segmented sintering with organic lithium provides a sufficient lithium source for the cathode material, increases the concentration of free lithium ions, and improves lattice repair of lithium ions in the lithium nickel oxide cathode material, thereby reducing the standard deviation of lithium concentration. The standard deviations of lithium concentration in Examples 1-3 were 2.8%, 3.2%, and 3.5%, respectively, while the lowest in the comparative group was 6.1%. On the other hand, the segmented sintering step further promotes the homogenization of lithium elements and crystal reconstruction, eliminates lattice defects, and improves the integrity of the crystal structure (reaching 85%, 83%, and 82% in Examples 1-3, respectively). Taking Example 1 as an example, by exposing the transition metal active sites after acid washing, segmented sintering with organic lithium ensures a stable distribution of lithium elements in the lattice, effectively reducing cation mixing and maintaining the stability of the layered structure. Comparative Example 1 uses a traditional direct regeneration method, which has low lithium replenishment efficiency, resulting in a lithium concentration standard deviation as high as 8.7%. The crystal structure suffers from localized stress due to uneven lithium distribution, and its integrity is only 65%. Comparative Example 2, without acid washing, cannot remove the inert layer on the surface of the original waste material, and the transition metal active sites are not fully exposed. Therefore, the lithium concentration standard deviation is 7.6%, and the crystal structure integrity is only 68%. Comparative Example 3, although post-processed, has poor coating density, and electrolyte penetration leads to interfacial side reactions, resulting in insufficient initial lithium distribution and structural repair. The lithium concentration standard deviation is 6.1%, and the crystal structure integrity is 72%, still lower than the data disclosed in Examples 1-3.

[0061] Table 2. Initial coulombic efficiency, cycle life, and rate performance test data for Examples 1-3 and Comparative Examples 1-3

[0062]

[0063] like Figure 2The figure shows the cycle life curves of Example 1 and Comparative Examples 1-3. According to Table 2, the initial coulombic efficiencies of Examples 1-3 were 94.5%, 93.8%, and 92.7%, respectively, while the initial coulombic efficiency of Comparative Example 2 without acid washing was 89.5%. In the examples, acid washing dissolves residual impurities such as Li₂CO₃ and LiOH on the surface of the cathode material, reducing side reactions with the electrolyte during the first charge and discharge (such as the formation of an impedance layer like LiF), thereby improving the reversible capacity. In the 1C 100-cycle test, the stable crystal structure of lithium nickelate after repair reduced structural changes and capacity loss during charge and discharge, resulting in capacity retention rates of 92.3%, 90.1%, and 89.7% for Examples 1-3, respectively. This is compared to 78.5% for the traditional regeneration method in Comparative Example 1, and only 75.2% for Comparative Example 2 without acid washing. The gradient coating effectively isolates the electrolyte, buffers volume changes, reduces interfacial impedance, and improves the ion transport efficiency of the material at high rates. Therefore, the 5C / 1C rate performance of Examples 1-3 are 85.2%, 82.7%, and 80.5%, respectively. Taking Example 1 as an example, the alumina gradient coating effectively inhibits electrolyte erosion of the material during high-rate charge and discharge, maintains structural stability, and ensures rapid lithium-ion transport. In Comparative Example 1, due to uneven lithium distribution, some lithium ions cannot participate in the reaction during the first charge and discharge, resulting in a rate performance of only 68.3%. Although Comparative Example 3 shows some improvement, its overall performance is still inferior to the examples, with a rate performance of 72.1%.

[0064] In summary, the example group systematically regenerated waste lithium nickel oxide battery cathode materials by acid washing, adding organic lithium and ball milling, then supplementing lithium through segmented sintering of bulk phase, and finally using atomic layer deposition gradient coating process. From lithium element supplementation, diffusion optimization, crystal structure repair to surface protection, the process demonstrated performance advantages compared to the comparative example.

[0065] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0066] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A method for repairing a three-dimensional structure of a positive electrode material of a waste lithium nickel battery, characterized by, Includes the following steps: S1. After crushing and sieving the waste nickel-lithium battery cathode material, it is immersed in an acid solution and filtered to obtain acid-washed waste nickel-lithium battery cathode material; the acid solution includes at least one of oxalic acid, citric acid, malic acid and tartaric acid. S2. Organic lithium is added to the acid-washed waste nickel-lithium battery cathode material and ball-milled to obtain a first mixture; during the ball-milling process, lithium phosphate with a mass fraction of 0.5-2wt% is added as a grain boundary stabilizer; S3. The first mixture is sintered in segments in an oxygen atmosphere to obtain the second mixture; the segmented sintering includes a first stage sintering and a second stage sintering; the first stage sintering is to heat to 300-500℃ at a heating rate of 5-20℃ / min and hold for 1-3 hours; the second stage sintering is to heat to 700-900℃ at a heating rate of 3-10℃ / min and hold for 2-6 hours. S4. The second mixture is introduced into an aluminum source to form a gradient coating layer through atomic layer deposition; the thickness of the gradient coating layer is 5-50 nm, and the content of aluminum element from the inside to the outside varies from 10% to 90%; the gradient coating layer is aluminum oxide, aluminum hydroxide or lithium aluminate.

2. The method according to claim 1, wherein the method is characterized by, In S1, the waste nickel-lithium battery cathode material is crushed and sieved to a particle size of 5~50μm.

3. The method according to claim 1, wherein the method is characterized by, In S1, the concentration of the acid solution is 0.1-2 mol / L; the mass ratio of the crushed and sieved waste nickel-lithium battery cathode material to the acid solution in S1 is 1:(5-20).

4. The method according to claim 1, wherein the method is characterized by, The organic lithium in S2 includes at least one of lithium acetate, lithium propionate, lithium lactate and lithium acetate; the mass ratio of the acid-washed waste nickel-lithium battery cathode material to organic lithium in S2 is 1:(0.05-0.2).

5. The method according to claim 1, wherein the method is characterized by, The ball milling speed in S2 is 200-600 r / min, and the time is 2-10 h.

6. The method according to claim 1, wherein the method is characterized by, The oxygen flow rate in S3 is 100~500 mL / min.

7. The method for repairing the three-dimensional structure of waste lithium nickel oxide battery cathode material according to claim 1, characterized in that, The aluminum source includes at least one of trimethylaluminum, triisopropoxide aluminum, and methylaluminoxane; the atomic layer deposition temperature is 80-300℃, the deposition cycle is 50-500 times, and a single deposition step includes an aluminum source pulse, a first inert gas purging, an oxygen source pulse, and a second inert gas purging.

8. The method for repairing the three-dimensional structure of the positive electrode material of a waste lithium nickel oxide battery according to claim 1, characterized in that, Before S1, the method further includes a pretreatment step: disassembling the waste lithium battery, separating the positive electrode sheet, removing the current collector aluminum foil, and collecting the positive electrode active material; after S4, a post-treatment step is included: sieving the second mixture that forms the gradient coating layer.

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