Method for removing residual alkali on surface of high-nickel ternary positive electrode material, positive electrode material and lithium ion battery

Abstract

The application discloses a method for removing residual alkali on the surface of high-nickel ternary positive electrode material, a positive electrode material and a lithium ion battery. The method comprises the following steps: 1) adding lithium salt into a green organic solvent to mix, stirring until clear and free of precipitate, and preparing a lithium salt solution; 2) adding air failure high-nickel ternary positive electrode material into the lithium salt solution, stirring and then drying to obtain a powder; and 3) centrifugally washing, drying and sintering the powder to obtain a repaired high-nickel ternary positive electrode material. According to the application, the air failure high-nickel ternary positive electrode material is reacted in the lithium salt solution, residual alkali on the surface of the positive electrode material is effectively removed, and a stable and fast lithium-conducting modification layer is formed on the surface of the positive electrode material. Compared with the prior art, the application has the advantages of simple operation, short technological process and significant improvement of the stability of the high-nickel ternary positive electrode material in air.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, specifically relating to a method for removing residual alkali from the surface of high-nickel ternary cathode material, the cathode material, and the lithium-ion battery. Background Technology

[0002] Against the backdrop of continuously increasing fossil fuel consumption, lithium-ion batteries, as a clean energy source used in portable electronic devices, have become an indispensable part of human life. With the growing demand for portable energy storage devices, long-distance electric vehicles, and hybrid electric vehicles, the development of cathode materials with high capacity and high voltage has become particularly important. Therefore, a key direction in lithium-ion battery research is to develop cathode materials that combine high energy density and excellent stability at a reasonable cost. High-nickel ternary cathode materials have attracted considerable attention due to their high theoretical capacity and relatively low nickel cost.

[0003] High nickel content can improve the energy density of ternary materials, but it also affects their industrialization. During the synthesis of high-nickel ternary cathode materials, an excess of lithium precursors is typically added to compensate for lithium loss during high-temperature calcination and to suppress cation disorder in the crystal structure. However, this results in residual lithium compounds (such as LiOH and Li₂CO₃) remaining on the material surface. Lithium compounds have an electrochemical passivation effect, severely affecting the lithium conduction kinetics on the cathode material surface, leading to cathode material failure. The synthesis process of high-nickel ternary materials is not the only source of lithium compounds. Compared with other cathode materials, high-nickel ternary materials are extremely sensitive to ambient air; during long-term storage or transportation, they are prone to generating surface alkaline substances, leading to decreased electrochemical performance and material failure. Furthermore, during the preparation of the cathode sheet, alkaline products increase the pH of the slurry, causing gelation and making slurry preparation difficult, resulting in a significant reduction in the processing performance of the cathode sheet.

[0004] Residual alkali on the surface of high-nickel ternary cathode materials is usually removed by washing with water. However, this process can easily cause the dissolution of lattice lithium, damaging the material's structure. Currently, the main methods for removing residual alkali from the surface of high-nickel ternary cathode materials are doping the bulk phase to stabilize the structure and surface modification to stabilize the interface.

[0005] Currently, researchers mainly employ the following techniques to remove residual alkali from the surface of high-nickel ternary cathode materials. For example, patent CN113666431A discloses a method for removing residual alkali from high-nickel ternary cathode materials. This method uses a solvent to ultrasonically wash the high-nickel ternary cathode material, followed by spray drying of the washed system to obtain alkali-free high-nickel ternary cathode material. This method is simple to operate, thoroughly cleans the residual alkali in the high-nickel ternary cathode material, and reduces washing time; however, the washing process still causes damage to the surface structure of the material. CN116072876A discloses a high-nickel ternary cathode material and a method for removing residual alkali from its surface. This method mixes the precursor and lithium source primary sintering material with an organic solvent, performs solid-liquid separation, and dries the solid phase. The dried material is then mixed with a coating material for secondary sintering to generate a coating layer on the material surface. This method removes alkali while generating a coating layer on the material surface, improving the electrochemical performance of the material. However, it requires multiple high-temperature sintering processes, resulting in high energy consumption and environmental pollution. CN115332471A discloses a method for removing residual alkali and coating high-nickel ternary cathode materials. This method utilizes the strong oxidizing properties of ozone to oxidize residual lithium to lithium peroxide, which then reacts with titanium tetrachloride to generate lithium titanate, neutralizing the surface residual lithium. Finally, titanium tetrachloride is reacted with oxygen via vapor deposition to obtain a titanium dioxide coating layer. This method uses vapor deposition to process the material and generate the coating layer. However, this method requires not only controlling the amount of reactant gas but also specifying pressure requirements for the equipment.

[0006] Therefore, there is an urgent need for a low-cost, simple-to-operate, and low-energy-consumption method to remove residual alkali from the surface of high-nickel ternary cathode materials without damaging their structure. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a method for removing residual alkali from the surface of high-nickel ternary cathode materials, the cathode material itself, and a lithium-ion battery. The method of this invention converts the residual alkali on the surface of failed high-nickel ternary cathode materials into a stable, fast-conducting lithium-ion modification layer, significantly reducing the residual alkali content on the material surface and effectively solving the problem of instability of high-nickel materials in air. Furthermore, this method converts surface residual alkali into a fast-conducting lithium-ion modification layer, further improving the electrochemical performance and structural stability of the high-nickel ternary cathode material. Simultaneously, this invention has advantages such as low cost, simple operation, and low energy consumption.

[0008] The technical solution adopted in this invention is as follows:

[0009] A method for removing residual alkali from the surface of a high-nickel ternary cathode material includes the following steps:

[0010] (1) Add lithium salt to a green organic solvent and mix and stir to prepare a lithium salt solution;

[0011] (2) Add the air-failed high-nickel ternary cathode material to the lithium salt solution, stir and dry to obtain powder;

[0012] (3) The powder is centrifuged, washed, dried and sintered to obtain the repaired high-nickel ternary cathode material.

[0013] Furthermore, the lithium salt is one or more of lithium difluorophosphate, lithium hexafluorophosphate, lithium trifluorophosphate, and lithium monofluorophosphate.

[0014] Furthermore, in step (1), the green organic solvent is one or more of ethanol, methanol, ethylene glycol, propylene glycol, and isopropanol, with ethanol being preferred.

[0015] Furthermore, the lithium salt in the lithium salt solution has a mass fraction of 1% to 5%.

[0016] Furthermore, the high-nickel ternary cathode material is a nickel-cobalt-manganese ternary cathode material or a nickel-cobalt-aluminum ternary cathode material.

[0017] Furthermore, in step (2), the mass ratio of the high-nickel ternary cathode material to the lithium salt solution is 1:10 to 50.

[0018] Furthermore, in step (1), the stirring time is 2 to 6 hours and the stirring speed is 200-1000 r / min; in step (2), the stirring time is 5 to 48 hours and the stirring speed is not less than 400 r / min.

[0019] Furthermore, in step (3), the washing process uses one or more of ethanol, methanol, ethylene glycol, propylene glycol, and isopropanol; the sintering temperature is 500–1000°C, and the time is 5–12 h.

[0020] A high-nickel ternary cathode material was prepared using the method described above.

[0021] A lithium-ion battery, wherein the positive electrode material of the lithium-ion battery is prepared by the above method.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The method of the present invention uses a specific lithium salt to react with the residual alkali on the surface of the high-nickel ternary cathode material under certain conditions, thereby effectively removing the residual alkali on the surface of the cathode material. The residual alkali on the surface of the cathode material is removed by reacting the lithium salt with the residual alkali lithium hydroxide or lithium carbonate.

[0024] (2) This invention not only reduces the residual alkali on the surface of the cathode material, but also converts the residual alkali in situ into a stable, fast-conducting lithium interface layer. Compared with commercial ternary cathode materials, the repaired ternary cathode material exhibits higher air stability and enhanced electrochemical performance due to the presence of the fast-conducting lithium interface layer.

[0025] (3) The raw materials used in the process of removing residual alkali in this invention are inexpensive, providing an economical and feasible solution for large-scale production. The equipment requirements are low, and the process conditions are easy to implement, making it suitable for large-scale production. It has advantages such as simple operation, high speed and efficiency, and low energy consumption, which is conducive to future large-scale application.

[0026] (4) The process for removing residual alkali in this invention is green and environmentally friendly. It does not use any acid, alkali or toxic solvents. The reaction can be completed at room temperature and in an open environment using green solvents, and it does not produce any toxic byproducts or other secondary pollution. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the repaired high-nickel ternary cathode material in an embodiment of the present invention.

[0028] Figure 2 The high-nickel ternary cathode material (LiNi) repaired in Example 1 0.82 Co 0.15 Mn 0.03 Scanning electron microscope (SEM) image and energy dispersive spectroscopy (EDS) analysis diagram of O2; where (a) is the SEM image of the repaired high-nickel ternary cathode material; (b) is the P element distribution diagram; and (c) is the F element distribution diagram.

[0029] Figure 3 The high-nickel ternary cathode material (LiNi) repaired in Example 1 0.82 Co 0.15 Mn 0.03 X-ray photoelectron spectra of O2; where (a) is the X-ray photoelectron spectrum of P 2p; and (b) is the X-ray photoelectron spectrum of F1s.

[0030] Figure 4 The high-nickel ternary cathode material (LiNi) before and after repair in Example 1 0.82 Co 0.15 Mn 0.03 Surface residual alkali content diagram (O2).

[0031] Figure 5 The high-nickel ternary cathode material (LiNi) before and after repair in Example 1 0.82 Co 0.15 Mn 0.03 X-ray diffraction pattern of O2.

[0032] Figure 6 The high-nickel ternary cathode material (LiNi) before and after repair in Example 1 0.82 Co 0.15 Mn 0.03 Raman spectrum of O2.

[0033] Figure 7 The high-nickel ternary cathode material (LiNi) before and after repair in Example 1 0.82 Co 0.15 Mn 0.03 Infrared spectrum of O2.

[0034] Figure 8 The high-nickel ternary cathode material (LiNi) before and after repair in Example 1 0.82 Co 0.15 Mn 0.03 Thermogravimetric-differential scanning calorimetry (TGC) of O2.

[0035] Figure 9 The high-nickel ternary cathode material (LiNi) before and after repair in Example 1 0.82 Co 0.15 Mn 0.03 O2) Cyclic performance diagram of lithium batteries.

[0036] Figure 10 The high-nickel ternary cathode material (LiNi) before and after repair in Example 1 0.82 Co 0.15 Mn 0.03 The rate performance of lithium batteries (O2).

[0037] Figure 11 The high-nickel ternary cathode material (LiNi) before and after repair in Example 1 0.82 Co 0.15 Mn 0.03 Cyclic performance of graphite full cells (O2). Detailed Implementation

[0038] The technical solution of the present invention will be further described clearly and in detail below with reference to specific examples and accompanying drawings.

[0039] A method for removing residual alkali from the surface of a high-nickel ternary cathode material includes the following steps:

[0040] (1) Add lithium salt to a green organic solvent and mix. Stir at room temperature for 2-6 hours at a stirring speed of 200-1000 r / min to prepare a lithium salt solution. The lithium salt is one or more of lithium difluorophosphate, lithium hexafluorophosphate, lithium trifluorophosphate, and lithium monofluorophosphate. The green organic solvent is one or more of ethanol, methanol, ethylene glycol, propylene glycol, and isopropanol. The mass fraction of lithium salt in the lithium salt solution is 1%-5%.

[0041] (2) Add the air-failed high-nickel ternary cathode material to the lithium salt solution, stir for 5 to 48 hours at a stirring speed of not less than 400 r / min, and then dry to obtain powder; the high-nickel ternary cathode material is a nickel-cobalt-manganese ternary cathode material or a nickel-cobalt-aluminum ternary cathode material; the mass ratio of the high-nickel ternary cathode material to the lithium salt solution is 1:10 to 50.

[0042] This step involves placing the cathode powder in a lithium salt solution and stirring it at room temperature. This reaction involves the lithium salt reacting with lithium carbonate and lithium hydroxide, allowing the residual alkali on the surface of the high-nickel ternary cathode material to fully react.

[0043] (3) The powder is centrifuged and washed to remove the residual lithium salt after multiple washes, and then dried and sintered. The sintering temperature is 500-1000℃ and the time is 5-12h to obtain the repaired high-nickel ternary cathode material. The washing process uses one or more of ethanol, methanol, ethylene glycol, propylene glycol, and isopropanol.

[0044] The use of green organic solvents in this step for washing dissolves residual lithium salts, thus preventing the impact of lithium salt residues on the cathode powder. Furthermore, simple chemical reactions and sintering facilitate structural repair of the material, transforming the rock salt structure into a layered structure.

[0045] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used in the examples are commercially available unless otherwise specified.

[0046] Example 1

[0047] 1) Add a certain proportion of lithium difluorophosphate to ethanol and mix to form a 1% lithium difluorophosphate solution. Stir at room temperature for 3 hours at a stirring speed of 400 r / min.

[0048] 2) Air-depleted high-nickel ternary cathode material (LiNi) 0.82 Co 0.15 Mn 0.03 O2) was added to the lithium difluorophosphate solution in step 1), with a mass ratio of high-nickel ternary cathode material to lithium difluorophosphate solution of 1:20. The mixture was stirred at room temperature for 6 hours at a stirring speed of 500 r / min. The high-nickel ternary cathode material treated with lithium difluorophosphate solution was then placed in a vacuum drying oven at 70℃ for 10 hours to obtain powder.

[0049] This step involves placing the high-nickel ternary cathode material in a lithium salt solution and stirring it at room temperature. This reaction involves lithium difluorophosphate reacting with lithium carbonate and lithium hydroxide, ensuring that any residual alkali on the surface of the high-nickel ternary cathode material reacts fully.

[0050] 3) Add the powder obtained in step 2) to ethanol, centrifuge at 9000 r / min for 3 min, centrifuge twice, and then place it in an 80℃ vacuum drying oven for 12 h. Place the dried powder in a tube furnace under an oxygen atmosphere and sinter at a heating rate of 5℃ / min for 5 h at a sintering temperature of 600℃. After natural cooling, the repaired high-nickel ternary cathode material is obtained.

[0051] The addition of ethanol in this step dissolves the residual lithium difluorophosphate, thus minimizing the impact of residual lithium difluorophosphate on the resulting high-nickel ternary cathode material. Furthermore, the simple chemical reaction and sintering process facilitates structural repair, transforming the rock salt structure into a layered structure.

[0052] 4) Assemble the high-nickel ternary cathode material obtained in step 3) into a lithium battery.

[0053] A schematic diagram of the repaired high-nickel ternary cathode material in this embodiment is shown below. Figure 1 As shown. Figure 2 These are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) analyses of the high-nickel ternary cathode material after repair in Example 1. The images show that P and F elements are uniformly distributed on the surface of the high-nickel material.

[0054] like Figure 3 The figure shows the X-ray photoelectron spectrum of the high-nickel ternary cathode material after repair in Example 1. As can be seen from the figure, peaks for Li3PO4 and LiF appear on the repaired material, further indicating that a Li3PO4-LiF coating has formed on the material surface.

[0055] like Figure 4 The figure shows the surface residual alkali content of the high-nickel ternary cathode material before and after repair in Example 1. Automated potentiometric titration showed that the residual alkali content of the original sample was 0.106 wt% LiOH and 4.7017 wt% Li₂CO₃. The residual alkali content of the repaired sample was 0.0198 wt% LiOH and 0.1202 wt% Li₂CO₃. This indicates a significant reduction in the residual alkali content of the original sample.

[0056] like Figure 5 The figure shows the X-ray diffraction patterns of the high-nickel ternary cathode material before and after repair in Example 1. From bottom to top, the figures show the spectral lines of the lithium carbonate PDF card, the high-nickel ternary cathode material, and the repaired high-nickel ternary cathode material. It can be seen from the figure that lithium carbonate impurity peaks appeared on the surface of the high-nickel ternary cathode material after residual alkali formed. The repaired high-nickel ternary cathode material did not have any additional impurity peaks, indicating that the crystal phase of the repaired material was somewhat restored.

[0057] like Figure 6The figure shows the Raman spectra of the high-nickel ternary cathode material before and after repair in Example 1. As can be seen from the figure, the peaks of LiOH and Li₂CO₃ weakened after repair, indicating that the residual alkali on the surface of the original sample was significantly reduced after repair.

[0058] like Figure 7 The image shows the infrared spectra of the high-nickel ternary cathode material before and after repair in Example 1. Analysis revealed a significant reduction in the residual alkali absorption peak on the repaired sample surface, indicating a marked improvement in the residual alkali concentration.

[0059] like Figure 8 The figure shows thermogravimetric-differential scanning calorimetry (TGC-DSC) images of the high-nickel ternary cathode material before and after repair in Example 1. Compared with the original sample, the repaired sample (mass loss caused by self-decomposition at 700℃) showed improvement in two additional mass losses (removal of surface adsorbed impurities at 200-500℃ and decomposition of surface impurities at 500-700℃).

[0060] like Figure 9 The diagram shows the cycle performance of the cathode materials before and after repair, after assembling lithium anodes into batteries. The cathode materials were tested for cycle stability at 1C within a voltage range of 2.8–4.3V at room temperature. The original electrode had an initial discharge specific capacity of 164.9 mAh / g at 0.2C, which decreased to 1.02 mAh / g after 300 cycles, with almost zero capacity retention. In contrast, the repaired electrode had an initial discharge specific capacity of 184.4 mAh / g at 0.2C, which decreased to 95.5 mAh / g after 300 cycles, with a capacity retention of 58.5%. This indicates that the high-nickel ternary cathode material obtained in this invention has improved cycle stability and some capacity recovery.

[0061] like Figure 10 The graph shows the rate performance of the lithium anode battery assembled with the cathode materials before and after repair. The battery current density was increased from 0.2C to 10C. The discharge specific capacities of the original electrode were 157.5, 116.1, 86.8, 52.2, 0.57, and 0.5 mAh / g, respectively; while the discharge specific capacities of the repaired electrode were 181.9, 164.4, 146.5, 127.1, 92.5, and 45.6 mAh / g, respectively. This demonstrates that the repaired electrode consistently exhibits superior cycle performance at all current densities.

[0062] like Figure 11The diagram shows the cycle performance of the reassembled graphite anode battery after using the cathode materials before and after repair. The cathode materials were tested for cycle stability at 1C within a voltage range of 2.8–4.3V at room temperature. The original electrode had a discharge specific capacity of 22.3 mAh / g after 500 cycles, with a capacity retention of 22.8%. The repaired electrode had a discharge specific capacity of 87.3 mAh / g after 500 cycles, with a capacity retention of 55.6%. This further demonstrates that the high-nickel ternary cathode material obtained in this application has improved cycle performance.

[0063] Example 2

[0064] 1) Add a certain proportion of lithium difluorophosphate to ethanol and mix to form a 2% lithium difluorophosphate solution. Stir at room temperature for 2 hours at a stirring speed of 500 r / min.

[0065] 2) Air-depleted high-nickel ternary cathode material (LiNi) 0.80 Co 0.15 Al 0.05 O2) was added to the lithium difluorophosphate solution in step 1), with a mass ratio of high-nickel ternary cathode material to lithium difluorophosphate solution of 1:15. The mixture was stirred at room temperature for 8 hours at a stirring speed of 450 r / min. The high-nickel ternary cathode material treated with lithium difluorophosphate solution was then placed in a vacuum drying oven at 70℃ for 12 hours to obtain powder.

[0066] This step involves placing the high-nickel ternary cathode material in a lithium salt solution and stirring it at room temperature. This reaction involves lithium difluorophosphate reacting with lithium carbonate and lithium hydroxide, ensuring that any residual alkali on the surface of the high-nickel ternary cathode material reacts fully.

[0067] 3) Add the powder obtained after the reaction treatment in step 2) to ethanol, centrifuge at 9000 r / min for 3 min, centrifuge twice, and then place it in an 80℃ vacuum drying oven for 10 h. Place the dried cathode powder in a tube furnace under an oxygen atmosphere and sinter at a heating rate of 5℃ / min for 8 h at a sintering temperature of 700℃. After natural cooling, the repaired high-nickel ternary cathode material is obtained.

[0068] The addition of ethanol in this step dissolves the residual lithium difluorophosphate, thus minimizing the impact of residual lithium difluorophosphate on the resulting high-nickel ternary cathode material. Furthermore, the simple chemical reaction and sintering process facilitates structural repair, transforming the rock salt structure into a layered structure.

[0069] 4) Assemble the high-nickel ternary cathode material obtained in step 3) into a lithium battery.

[0070] Electrochemical tests were conducted on the batteries assembled with the repaired cathode material. It was found that the initial specific capacity of the repaired battery was nearly 30 mAh / g higher than that of the original battery, indicating that the method of the present invention is also effective in repairing nickel-cobalt-aluminum ternary cathode materials.

[0071] Example 3

[0072] 1) Add a certain proportion of lithium hexafluorophosphate to ethanol and mix to form a 1% lithium hexafluorophosphate solution. Stir at room temperature for 5 hours at a stirring speed of 500 r / min.

[0073] 2) Air-depleted high-nickel ternary cathode material (LiNi) 0.82 Co 0.15 Mn 0.03 O2) was added to the lithium hexafluorophosphate solution in step 1), with a mass ratio of high-nickel ternary cathode material to lithium hexafluorophosphate solution of 1:20. The mixture was stirred at room temperature for 6 hours at a stirring speed of 600 r / min. The high-nickel ternary cathode material treated with lithium hexafluorophosphate solution was then placed in a vacuum drying oven at 70℃ for 10 hours to obtain powder.

[0074] This step involves placing the high-nickel ternary cathode material in a lithium salt solution and stirring it at room temperature. This reaction involves lithium hexafluorophosphate reacting with lithium carbonate and lithium hydroxide, allowing the residual alkali on the surface of the high-nickel ternary cathode material to fully react.

[0075] 3) Add the powder obtained after the reaction treatment in step 2) to ethanol, centrifuge at 9000 r / min for 3 min, centrifuge twice, and then place it in a vacuum drying oven at 90℃ for 11 h. Place the dried cathode powder in a tube furnace under an oxygen atmosphere and sinter at a heating rate of 5℃ / min for 8 h at a sintering temperature of 650℃. After natural cooling, the repaired high-nickel ternary cathode material is obtained.

[0076] The addition of ethanol in this step dissolves the residual lithium hexafluorophosphate, thus minimizing the impact of residual lithium hexafluorophosphate on the resulting high-nickel ternary cathode material. Furthermore, the simple chemical reaction and sintering process facilitate structural repair, transforming the rock salt structure into a layered structure.

[0077] 4) Assemble the high-nickel ternary cathode material obtained in step 3) into a lithium battery.

[0078] Electrochemical tests were conducted on the batteries assembled with the repaired cathode material. The results showed that the initial specific capacity of the repaired batteries recovered to 190 mAh / g, an increase of nearly 30 mAh / g compared to the original batteries. Furthermore, the crystal phase of the repaired material also returned to normal, indicating that the method of this invention is effective for repairing high-nickel ternary cathode materials.

[0079] Example 4

[0080] 1) Add a certain proportion of lithium trifluorophosphate to ethanol and mix to form a 1% lithium trifluorophosphate solution. Stir at room temperature for 4 hours at a stirring speed of 450 r / min.

[0081] 2) Air-depleted high-nickel ternary cathode material (LiNi) 0.60 Co 0.20 Mn 0.20 O2) was added to the lithium trifluorophosphate solution in step 1), with a mass ratio of high-nickel ternary cathode material to lithium trifluorophosphate solution of 1:20. The mixture was stirred at room temperature for 7 hours at a stirring speed of 500 r / min. The high-nickel ternary cathode material treated with lithium trifluorophosphate solution was then placed in an 80℃ vacuum drying oven for 10 hours to obtain powder.

[0082] This step involves placing the high-nickel ternary cathode material in a lithium salt solution and stirring it at room temperature. This reaction involves lithium trifluorophosphate reacting with lithium carbonate and lithium hydroxide, allowing the residual alkali on the surface of the high-nickel ternary cathode material to react fully.

[0083] 3) Add the powder obtained after the reaction treatment in step 2) to ethanol, centrifuge at 9000 r / min for 3 min, centrifuge twice, and then place it in an 80℃ vacuum drying oven for 12 h. Place the dried cathode powder in a tube furnace under an oxygen atmosphere and sinter at a heating rate of 5℃ / min for 5 h at a sintering temperature of 700℃. After natural cooling, the repaired high-nickel ternary cathode material is obtained.

[0084] The addition of ethanol in this step dissolves the residual lithium trifluorophosphate, thus minimizing the impact of residual lithium trifluorophosphate on the resulting high-nickel ternary cathode material. Furthermore, the simple chemical reaction and sintering process facilitates structural repair, transforming the rock salt structure into a layered structure.

[0085] 4) Assemble the high-nickel ternary cathode material obtained in step 3) into a lithium battery.

[0086] Electrochemical tests were conducted on the batteries assembled with the repaired cathode material. The results showed that the initial specific capacity of the repaired batteries recovered to 180 mAh / g, an increase of nearly 20 mAh / g compared to the original batteries. Furthermore, the crystal phase of the repaired material also returned to normal, indicating that the method is effective.

[0087] Example 5

[0088] 1) Add a certain proportion of lithium monofluorophosphate to ethanol and mix to form a 1% lithium monofluorophosphate solution. Stir at room temperature for 3 hours at a stirring speed of 500 r / min.

[0089] 2) Air-depleted high-nickel ternary cathode material (LiNi) 0.80 Co 0.10 Mn 0.10 O2) was added to the lithium monofluorophosphate solution in step 1), with a mass ratio of high-nickel ternary cathode material to lithium monofluorophosphate solution of 1:20. The mixture was stirred at room temperature for 7 hours at a stirring speed of 600 r / min. Afterward, the high-nickel ternary cathode material treated with the lithium monofluorophosphate solution was placed in a vacuum drying oven at 100℃ for 10 hours.

[0090] This step involves placing the high-nickel ternary cathode material in a lithium salt solution and stirring it at room temperature. This reaction involves lithium monofluorophosphate reacting with lithium carbonate and lithium hydroxide, allowing the residual alkali on the surface of the high-nickel ternary cathode material to fully react.

[0091] 3) Add the powder obtained after the reaction treatment in step 2) to ethanol, centrifuge at 9000 r / min for 3 min, centrifuge twice, and then place it in an 80℃ vacuum drying oven for 10 h. Place the dried cathode powder in a tube furnace under an oxygen atmosphere and sinter at a heating rate of 5℃ / min for 7 h at a sintering temperature of 650℃. After natural cooling, the repaired high-nickel ternary cathode material is obtained.

[0092] The addition of ethanol in this step dissolves the residual lithium monofluorophosphate, thus minimizing the impact of residual lithium monofluorophosphate on the resulting high-nickel ternary cathode material. Furthermore, the simple chemical reaction and sintering process facilitate structural repair, transforming the rock salt structure into a layered structure.

[0093] 4) Assemble the high-nickel ternary cathode material obtained in step 3) into a lithium battery.

[0094] Electrochemical tests were conducted on the batteries assembled with the repaired cathode material. The results showed that the initial specific capacity of the repaired batteries recovered to 180 mAh / g, an increase of nearly 20 mAh / g compared to the original batteries. Furthermore, the crystal phase of the repaired material also returned to normal, indicating that the method is effective.

[0095] Nickel-rich cathode materials are sensitive to trace amounts of moisture in the atmosphere and require extremely dry conditions for long-term storage. Once the surface of the nickel-rich cathode material is exposed to air, LiOH / Li₂CO₃ impurities form, hindering Li insertion and extraction, and leading to Li source loss. This invention addresses this by combining an air-depleted high-nickel ternary cathode material with green LiPO₄. x F yThe solution is mixed and stirred at room temperature to transform the LiOH / Li2CO3 failure layer in situ into a Li3PO4 / LiF fast lithium-conducting interface. This conformal interface not only improves the air stability of the high-nickel ternary cathode material during storage, but also significantly enhances the interfacial lithium-conducting kinetics, improves electrochemical rate performance, and isolates the cathode material from electrolyte corrosion, thus improving cycle stability. The process for removing residual alkali from the surface of high-nickel ternary cathode materials involved in this invention is green and environmentally friendly, with a mild reaction that does not cause secondary pollution. Moreover, the equipment is simple, requiring only room temperature stirring and centrifugation. The process is simple, low-cost, and can be quickly deployed industrially.

[0096] The above-described specific embodiments are preferred examples of this application. Although they are quite detailed, they do not limit the claims of this application. Any changes, modifications, substitutions, combinations, or simplifications made using the technical content disclosed in this invention should be considered equivalent embodiments and should not depart from the technical features of this application. They should all fall within the scope of the technical features of this application and should be included within the protection scope of this application.

[0097] Obviously, the above embodiments of this application are merely examples for clear illustration and are not intended to limit the implementation of this application. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of the claims of this application.

Claims

1. A method for removing residual alkali from the surface of air-failed high-nickel ternary cathode material, characterized in that, Includes the following steps: (1) Add lithium salt to green organic solvent and mix, stir until clear and free of precipitate to prepare lithium salt solution; wherein, the stirring time is 2-6h and the stirring speed is 200-1000r / min; the lithium salt is one or more of lithium difluorophosphate, lithium hexafluorophosphate, lithium trifluorophosphate and lithium monofluorophosphate. (2) Add the air-failed high-nickel ternary cathode material to the lithium salt solution, stir and dry to obtain powder; wherein, the mass ratio of the high-nickel ternary cathode material to the lithium salt solution is 1:10~50, the stirring time is 5~48 hours, and the stirring speed is not less than 400r / min; (3) The powder is centrifuged, washed, dried and sintered to transform the rock salt structure into a layered structure to obtain the repaired high-nickel ternary cathode material; wherein the sintering temperature is 500~1000℃ and the time is 5~12h.

2. The method for removing residual alkali from the surface of air-failed high-nickel ternary cathode material according to claim 1, characterized in that, In step (1), the green organic solvent is one or more of ethanol, methanol, ethylene glycol, propylene glycol, and isopropanol.

3. The method for removing residual alkali from the surface of air-failed high-nickel ternary cathode material according to claim 1, characterized in that, The lithium salt solution contains 1% to 5% by mass of lithium salt.

4. The method for removing residual alkali from the surface of air-failed high-nickel ternary cathode material according to claim 1, characterized in that, The high-nickel ternary cathode material is either a nickel-cobalt-manganese ternary cathode material or a nickel-cobalt-aluminum ternary cathode material.

5. The method for removing residual alkali from the surface of air-failed high-nickel ternary cathode material according to claim 1, characterized in that, In step (3), the washing process uses one or more of ethanol, methanol, ethylene glycol, propylene glycol, and isopropanol.

6. A high-nickel ternary cathode material, characterized in that, It is prepared by the method described in any one of claims 1-5.

7. A lithium-ion battery, characterized in that, The positive electrode material of the lithium-ion battery is prepared by the method described in any one of claims 1-5.

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