Preparation method of borate-coated high-nickel positive electrode material

Abstract

The application provides a preparation method of a borate-coated high-nickel positive electrode material, comprising the following steps: step one, uniformly mixing a high-nickel positive electrode material matrix, a borate and a surface modifier in a solvent to obtain a precursor solution; step two, performing spray drying treatment on the precursor solution to uniformly attach the borate on the surface of the high-nickel positive electrode material matrix to obtain a precursor; and step three, performing heating treatment on the precursor to make the borate react with residual lithium on the surface of the high-nickel positive electrode material matrix to obtain the borate-coated high-nickel positive electrode material. The material prepared by the preparation method has the advantages of low surface residual lithium content, small interface impedance, good cycle stability and the like, and can still maintain excellent electrochemical performance under high-temperature conditions. Meanwhile, the preparation method is simple in process, friendly to the environment, suitable for industrial production, and important for the development of high-performance, high-safety and long-life lithium ion batteries.

Description

Invention Field This invention belongs to the field of battery materials, specifically relating to a method for preparing a borate-coated high-nickel cathode material. Background Technology

[0001] High-nickel layered oxides (such as LiNi) 1-x-y Co x Mn y O2 (where 1-xy≥0.6) has become a research hotspot in the field of power batteries due to its advantages of high energy density and low cost as a cathode material for lithium-ion batteries. However, with the increase of nickel content, the material faces a series of challenges: First, high surface lithium residue (mainly in the form of Li2CO3 and LiOH) is a problem. Surface lithium residue originates from the synthesis process of high-nickel layered oxide cathode materials and their subsequent storage in the air. Surface lithium residue seriously affects the transport of lithium ions between the electrode material surface and the organic electrolyte, resulting in a decrease in rate performance. During the preparation of high-nickel layered oxide cathode materials, excess lithium needs to be added to suppress cation mixing and achieve the ideal design capacity. After the material is synthesized, the remaining lithium residue on the material surface easily reacts with water vapor and CO2 in the air to generate LiOH and Li2CO3. In addition, lithium in the inner layer of high-nickel layered cathode materials can also react with CO2 and H2O to generate LiOH / Li2CO3 lithium residue. Lithium residue on the electrode material surface primarily exists in the form of LiOH / Li₂CO₃. However, LiOH / Li₂CO₃ has very low ionic conductivity, severely impacting lithium-ion transport between the active material surface and the organic electrolyte, leading to a decrease in rate performance. During long-term electrochemical cycling, lithium residue can react with the organic electrolyte to generate gases such as CO₂, CO, and N₂, causing battery "bloating" and significantly affecting battery performance. Furthermore, LiOH / Li₂CO₃ is highly alkaline and can react with binders, leading to binder failure and difficulties in slurry mixing, thus affecting electrode preparation. Therefore, eliminating surface lithium residue is crucial for the industrial application of high-nickel layered oxide cathode materials.

[0002] Secondly, the volume of high-nickel layered oxide cathode materials shrinks / expands during cycling, resulting in poor cycle stability. This is particularly problematic at high temperatures, where it easily leads to mechanical degradation or void formation at the solid-solid interface, affecting interfacial mechanical stability. Furthermore, due to the high surface oxidation state of high-nickel layered oxide materials, especially at high charging potentials, the solid electrolyte is prone to chemical and electrochemical interfacial side reactions with the cathode material, impacting interfacial chemical and electrochemical stability. These shortcomings severely restrict their commercial application.

[0003] Currently, surface coating is one of the effective means to improve the performance of high-nickel cathode materials. For example, coating with metal fluorides (such as AlF3 coating) can improve the interfacial stability of the material.

[0004] However, existing coating technologies still have the following limitations: First, the coating layer is not firmly bonded to the substrate and is prone to falling off during long-term cycling; second, the lithium-ion conductivity of the coating layer is insufficient, affecting high-rate performance; in addition, the coating process is complex and often requires multiple steps, which is not conducive to industrial production. Summary of the Invention

[0005] The purpose of this invention is to address the problems of poor surface stability, high residual lithium content, and complex and unsatisfactory coating effects of existing high-nickel cathode materials, by providing a novel method for preparing borate-coated high-nickel cathode materials with a core-shell structure. This invention is specifically achieved through the following technical solution: A method for preparing a borate-coated high-nickel cathode material includes: Step 1: Add the high-nickel cathode material matrix, borate, and surface modifier to a solvent and mix thoroughly to obtain the precursor solution; Step 2: The precursor solution is spray-dried to allow the borate to adhere uniformly to the surface of the high-nickel cathode material substrate, thus obtaining the precursor. Step 3: Heat the precursor to allow the borate to react with the residual lithium on the surface of the high-nickel cathode material matrix, thus obtaining the borate-coated high-nickel cathode material.

[0006] Optionally, the chemical formula of the high-nickel cathode material in step one is: LiNi 1-x-y Co x Mn y O2, where 0.6 ≤ 1 - xy ≤ 0.95. Preferably, 0.03 ≤ x ≤ 0.3 and 0.02 ≤ y ≤ 0.2.

[0007] Optionally, in step one, the high-nickel cathode material is prepared using the following method: Nickel-cobalt-manganese hydroxide was synthesized by co-precipitation, and then the nickel-cobalt-manganese hydroxide was mixed with a lithium source and sintered at 700-850℃ to obtain a high-nickel cathode material matrix.

[0008] Optionally, the co-precipitation method for synthesizing nickel cobalt manganese hydroxide includes: adding a precipitant to a mixed solution containing nickel salt, cobalt salt, and manganese salt, controlling the reaction system temperature at 50-60℃, the pH value at 11.0-12.0, and the stirring speed at 500-1000 rpm to obtain nickel cobalt manganese hydroxide precipitate.

[0009] Optionally, the lithium source is lithium hydroxide or lithium carbonate, and the molar ratio of lithium to transition metal is (1.02-1.08):1; Preferably, the boric acid is selected from one or more of boric acid, lithium metaborate, and boron trioxide, and the amount added is 1%-5% of the mass of the high-nickel cathode material matrix.

[0010] Optionally, the surface modifier is selected from polyethylene glycol, polyvinylpyrrolidone, and hexadecyltrimethylammonium bromide; Preferably, the solvent is water, ethanol, or acetone.

[0011] Optionally, the material inlet temperature during the spray drying process is 160-200℃, and the outlet temperature is 80-120℃.

[0012] Optionally, the heat treatment is performed by heating at 300-600°C for 2-6 hours in an oxygen atmosphere.

[0013] The present invention also proposes a borate-coated high-nickel cathode material obtained by the above preparation method.

[0014] This invention also proposes the application of the above-mentioned borate-coated high-nickel cathode material in lithium batteries.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The material prepared by this invention has a unique coating structure. Through surface-modified spray coating and subsequent heat treatment, an amorphous metaborate coating layer is formed. This coating layer is continuous, uniform, and firmly bonded to the substrate, effectively preventing the electrolyte from eroding the cathode material particles. The material prepared by this invention exhibits high interfacial stability; the boron atoms in the metaborate coating layer are in an electron-unsaturated state, readily adsorbing OH groups. - This promotes electrochemical reaction kinetics, while the coating layer, as a good lithium-ion conductor, reduces interfacial impedance and improves the rate performance of the material.

[0016] The material prepared by this invention completely eliminates residual lithium. The borate source reacts with residual lithium compounds such as Li₂CO₃ and LiOH on the surface of the high-nickel cathode material to generate stable metaborate, significantly reducing the risk of surface alkalinity and slurry gelation, and improving battery processing performance. The material prepared by this invention exhibits excellent electrochemical performance. The coated high-nickel cathode material maintains high capacity while significantly improving cycle stability (especially high-temperature cycle stability) and storage performance. Experimental results show that after 50 cycles at 45°C, the capacity retention rate can be increased from 88.3% of the uncoated material to over 95.8%.

[0017] The preparation method of this invention is simple and environmentally friendly. The spray coating method used in this invention is simple, produces uniform coating, requires no complex equipment, and uses environmentally friendly reagents, making it suitable for industrial production. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 These are SEM images of the materials prepared in Example 1; Figure 2 These are SEM images of the materials prepared in Comparative Example 2; Figure 3 These are the performance test results of the material prepared in Example 1. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0021] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] Example 1 Synthesis of high-nickel precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were added to deionized water in a molar ratio of Ni:Co:Mn = 0.83:0.12:0.05 to prepare a mixed salt solution with a total metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L NaOH solution and a 0.5 mol / L NH3·H2O solution were prepared as precipitating and complexing agents, respectively. The above mixed salt solution, precipitating agent, and complexing agent were added to a reactor, and the reaction was carried out at a controlled temperature of 50℃, pH = 11.5, and stirring speed of 800 rpm for 20 hours with continuous feeding to obtain Ni. 0.83 Co 0.12 Mn 0.05 (OH)2 precursor.

[0025] Lithification sintering: The precursor and LiOH·H2O were mixed uniformly at a molar ratio of Li:TM = 1.05:1 (TM is a transition metal). The mixture was then sintered in an oxygen atmosphere at a heating rate of 5℃ / min to 780℃ for 12 hours to obtain LiNi. 0.83 Co 0.12 Mn 0.05 O2 matrix material.

[0026] Borate coating: 5g of the above matrix material was dispersed in 100mL of deionized water, and then 0.15g of H3BO3 (3% of the matrix material mass) and 0.05g of polyvinylpyrrolidone (PVP) were added. The mixture was ultrasonically dispersed for 30 minutes to obtain a precursor solution. Subsequently, the precursor solution was spray-dried using a spray dryer to ensure that the borate was uniformly attached to the surface of the high-nickel cathode material matrix. The inlet temperature of the spray dryer was 180℃ and the outlet temperature was 100℃, resulting in precursor particles.

[0027] Heat treatment: The spray-coated precursor particles are heated at 450°C for 4 hours in an oxygen atmosphere to allow the borate to react with the residual lithium on the surface of the high-nickel cathode material matrix, resulting in a borate-coated high-nickel cathode material product, denoted as B-NCM-1.

[0028] Example 2 Synthesis of high-nickel precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were added to deionized water in a molar ratio of Ni:Co:Mn = 0.83:0.12:0.05 to prepare a mixed salt solution with a total metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L NaOH solution and a 0.5 mol / L NH3·H2O solution were prepared as precipitants and complexing agents, respectively. The above mixed salt solution, precipitants, and complexing agents were added to a reactor, and the reaction was carried out at a controlled temperature of 55℃, pH = 11, and stirring speed of 800 rpm for 18 hours with continuous feeding to obtain Ni. 0.83 Co 0.12 Mn 0.05(OH)2 precursor.

[0029] Lithification sintering: The precursor and LiOH·H2O were mixed uniformly at a molar ratio of Li:TM = 1.02:1 (TM is a transition metal). The mixture was then sintered at 750℃ for 12 hours in an oxygen atmosphere at a heating rate of 5℃ / min to obtain LiNi. 0.83 Co 0.12 Mn 0.05 O2 matrix material.

[0030] Borate coating: 5g of the above matrix material was dispersed in 100mL of deionized water, then 0.15g of H3BO3 (3% of the matrix material mass) and 0.05g of polyethylene glycol were added, and the mixture was ultrasonically dispersed for 30 minutes to obtain a precursor solution. The precursor solution was then spray-dried using a spray dryer to ensure uniform adhesion of borate to the surface of the high-nickel cathode material matrix. The spray dryer inlet temperature was 200℃ and the outlet temperature was 120℃, yielding precursor particles.

[0031] Heat treatment: The spray-coated precursor particles are heated at 300°C for 3 hours in an oxygen atmosphere to allow the borate to react with the residual lithium on the surface of the high-nickel cathode material matrix, resulting in a borate-coated high-nickel cathode material product, denoted as B-NCM-2.

[0032] Example 3 Synthesis of high-nickel precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were added to deionized water in a molar ratio of Ni:Co:Mn = 0.83:0.12:0.05 to prepare a mixed salt solution with a total metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L NaOH solution and a 0.5 mol / L NH3·H2O solution were prepared as precipitants and complexing agents, respectively. The above mixed salt solution, precipitants, and complexing agents were added to a reactor, and the reaction was carried out at a controlled temperature of 60℃, pH = 11.5, and stirring speed of 850 rpm for 22 hours with continuous feeding to obtain Ni. 0.83 Co 0.12 Mn 0.05 (OH)2 precursor.

[0033] Lithification sintering: The precursor and LiOH·H2O were mixed uniformly at a molar ratio of Li:TM = 1.06:1 (TM is a transition metal). The mixture was then sintered at 750℃ for 12 hours in an oxygen atmosphere at a heating rate of 5℃ / min to obtain LiNi. 0.83 Co 0.12 Mn 0.05 O2 matrix material.

[0034] Borate coating: 5g of the above matrix material was dispersed in 100mL of deionized water, and then 0.15g of H3BO3 (3% of the matrix material mass) and 0.05g of hexadecyltrimethylammonium bromide were added. The mixture was ultrasonically dispersed for 30 minutes to obtain a precursor solution. Subsequently, the precursor solution was spray-dried using a spray dryer to ensure that the borate was uniformly attached to the surface of the high-nickel cathode material matrix. The inlet temperature of the spray dryer was 160℃ and the outlet temperature was 90℃, resulting in precursor particles.

[0035] Heat treatment: The spray-coated precursor particles are heated at 300°C for 6 hours in an oxygen atmosphere to allow the borate to react with the residual lithium on the surface of the high-nickel cathode material matrix, resulting in a borate-coated high-nickel cathode material product, denoted as B-NCM-3.

[0036] Example 4 Synthesis of high-nickel precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were added to deionized water in a molar ratio of Ni:Co:Mn = 0.83:0.12:0.05 to prepare a mixed salt solution with a total metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L NaOH solution and a 0.5 mol / L NH3·H2O solution were prepared as precipitants and complexing agents, respectively. The above mixed salt solution, precipitants, and complexing agents were added to a reactor, and the reaction was carried out at a controlled temperature of 52℃, pH = 12, and stirring speed of 1000 rpm for 20 hours with continuous feeding to obtain Ni. 0.83 Co 0.12 Mn 0.05 (OH)2 precursor.

[0037] Lithification sintering: The precursor and LiOH·H2O were mixed uniformly at a molar ratio of Li:TM = 1.07:1 (TM is a transition metal). The mixture was then sintered in an oxygen atmosphere at a heating rate of 5℃ / min to 850℃ for 11 hours to obtain LiNi. 0.83 Co 0.12 Mn 0.05 O2 matrix material.

[0038] Borate coating: 5g of the above matrix material was dispersed in 100mL of deionized water, then 0.2g of boron trioxide (4% of the matrix material mass) and 0.05g of hexadecyltrimethylammonium bromide were added, and the mixture was ultrasonically dispersed for 30 minutes to obtain a precursor solution. The precursor solution was then spray-dried using a spray dryer to ensure uniform adhesion of borate to the surface of the high-nickel cathode material matrix. The inlet temperature of the spray dryer was 170℃, and the outlet temperature was 110℃, yielding precursor particles.

[0039] Heat treatment: The spray-coated precursor particles are heated at 600°C for 2 hours in an oxygen atmosphere to allow the borate to react with the residual lithium on the surface of the high-nickel cathode material matrix, resulting in a borate-coated high-nickel cathode material product, denoted as B-NCM-4.

[0040] Example 5 Synthesis of high-nickel precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were added to deionized water in a molar ratio of Ni:Co:Mn = 0.83:0.12:0.05 to prepare a mixed salt solution with a total metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L NaOH solution and a 0.5 mol / L NH3·H2O solution were prepared as precipitants and complexing agents, respectively. The above mixed salt solution, precipitants, and complexing agents were added to a reactor, and the reaction was carried out at a controlled temperature of 60℃, pH = 11, and stirring speed of 1000 rpm for 20 hours with continuous feeding to obtain Ni. 0.83 Co 0.12 Mn 0.05 (OH)2 precursor.

[0041] Lithification sintering: The precursor and LiOH·H2O were mixed uniformly at a molar ratio of Li:TM = 1.08:1 (TM is a transition metal). The mixture was then sintered in an oxygen atmosphere at a heating rate of 5℃ / min to 800℃ for 11 hours to obtain LiNi. 0.83 Co 0.12 Mn 0.05 O2 matrix material.

[0042] Borate coating: 5g of the above matrix material was dispersed in 100mL of deionized water, and then 0.25g of lithium metaborate (5% of the matrix material mass) and 0.05g of hexadecyltrimethylammonium bromide were added. The mixture was ultrasonically dispersed for 30 minutes to obtain a precursor solution. Subsequently, the precursor solution was spray-dried using a spray dryer to ensure that the borate was uniformly attached to the surface of the high-nickel cathode material matrix. The inlet temperature of the spray dryer was 160℃ and the outlet temperature was 100℃, resulting in precursor particles.

[0043] Heat treatment: The spray-coated precursor particles are heated at 400°C for 3 hours in an oxygen atmosphere to allow the borate to react with the residual lithium on the surface of the high-nickel cathode material matrix, resulting in a borate-coated high-nickel cathode material product, denoted as B-NCM-5.

[0044] Example 6 Synthesis of high-nickel precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were added to deionized water in a molar ratio of Ni:Co:Mn = 0.9:0.05:0.05 to prepare a mixed salt solution with a total metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L NaOH solution and a 0.5 mol / L NH3·H2O solution were prepared as precipitants and complexing agents, respectively. The above mixed salt solution, precipitants, and complexing agents were added to a reactor, and the reaction was carried out at a controlled temperature of 50℃, pH = 11.5, and stirring speed of 800 rpm for 20 hours with continuous feeding to obtain Ni. 0.9 Co 0.05 Mn 0.05 (OH)2 precursor.

[0045] Lithification sintering: The precursor and LiOH·H2O were mixed uniformly at a molar ratio of Li:TM = 1.03:1 (TM is a transition metal). The mixture was then sintered at 750℃ for 12 hours in an oxygen atmosphere at a heating rate of 5℃ / min to obtain LiNi. 0.9 Co 0.05 Mn 0.05 O2 matrix material.

[0046] Borate coating: 5g of the above matrix material was dispersed in 100mL of deionized water, and then 0.1g of lithium metaborate (LiBO2) (2% of the matrix material mass) and 0.05g of polyvinylpyrrolidone (PVP) were added. The mixture was ultrasonically dispersed for 30 minutes to obtain a precursor solution. Subsequently, the precursor solution was spray-dried using a spray dryer to ensure that the borate was uniformly attached to the surface of the high-nickel cathode material matrix. The inlet temperature of the spray dryer was 180℃ and the outlet temperature was 100℃, resulting in precursor particles.

[0047] Heat treatment: The spray-coated precursor particles are heated at 500°C for 3 hours in an oxygen atmosphere to allow the borate to react with the residual lithium on the surface of the high-nickel cathode material matrix, resulting in a borate-coated high-nickel cathode material product, denoted as B-NCM-6.

[0048] Example 7 Synthesis of high-nickel precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were added to deionized water in a molar ratio of Ni:Co:Mn = 0.6:0.2:0.2 to prepare a mixed salt solution with a total metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L NaOH solution and a 0.5 mol / L NH3·H2O solution were prepared as precipitants and complexing agents, respectively. The above mixed salt solution, precipitants, and complexing agents were added to a reactor, and the reaction was carried out at a controlled temperature of 50℃, pH = 11.5, and stirring speed of 800 rpm for 20 hours with continuous feeding to obtain Ni. 0.6 Co 0.2 Mn 0.2(OH)2 precursor.

[0049] Lithification sintering: The precursor and LiOH·H2O were mixed uniformly at a molar ratio of Li:TM = 1.06:1 (TM is a transition metal). The mixture was then sintered in an oxygen atmosphere at a heating rate of 5℃ / min to 780℃ for 12 hours to obtain LiNi. 0.6 Co 0.2 Mn 0.2 O2 matrix material.

[0050] Borate coating: 5g of the above matrix material was dispersed in 100mL of deionized water, then 0.2g of boron trioxide (4% of the matrix material mass) and 0.05g of polyethylene glycol (PEG-400) were added, and the mixture was ultrasonically dispersed for 30 minutes to obtain a precursor solution. The precursor solution was then spray-dried using a spray dryer to ensure uniform adhesion of borate to the surface of the high-nickel cathode material matrix. The inlet temperature of the spray dryer was 180℃, and the outlet temperature was 100℃, resulting in precursor particles.

[0051] Heat treatment: The spray-coated precursor particles are heated at 400°C for 5 hours in an oxygen atmosphere to allow the borate to react with the residual lithium on the surface of the high-nickel cathode material matrix, resulting in a borate-coated high-nickel cathode material product, denoted as B-NCM-7.

[0052] Comparative Example 1 Take the same mass of LiNi prepared in Example 1 0.83 Co 0.12 Mn 0.05 O2-based materials without borate coating are denoted as NCM.

[0053] Comparative Example 2 The steps are the same as in Example 1, except that PVP is not added during the borate coating process. Then, spray drying is performed, and after heat treatment, it is designated as B-NCM-8.

[0054] Test example: Morphology and structure: SEM of the material in Example 1 ( Figure 1 The results show that the B-NCM-1 particles have a smooth surface and a uniform and complete coating layer.

[0055] Control group without added surfactant, such as Figure 2 As shown, the electron micrograph of the material in Comparative Example 2 shows particle agglomeration, which prevents it from dispersing well and results in poor particle size distribution uniformity.

[0056] Electrochemical performance testing: The positive electrode material (the positive electrode material prepared in Examples 1-5 and Comparative Example 1), the binder being polyvinylidene fluoride (PVDF), and the conductive agent being conductive carbon black (SP) were mixed in a mass ratio of 8:1:1, and an appropriate amount of NMP was added. The mixture was stirred to form a slurry, coated onto copper foil, and then dried and rolled to obtain a positive electrode sheet. Lithium hexafluorophosphate (LiPF6) was used as the electrolyte, and a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 was used as the solvent to prepare an electrolyte solution with a concentration of 1 mol / L. A lithium metal sheet was used as the counter electrode, and a polypropylene (PP) membrane was used as the separator. The cells were assembled into a coin cell in an argon-filled glove box. The tests were conducted using a Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 3.0-4.3V. The test process was as follows: 0.2C charge / 0.2C discharge for 1 week, and 0.2C charge / 1C discharge for 200 weeks. The initial coulombic efficiency at 0.2C and the cycle capacity retention after 200 cycles were recorded. Furthermore, the test temperature was increased, and the capacity retention after 50 cycles at 45℃ was also tested. The test results are shown in Table 1. Table 1

[0057] In half-cell testing, B-NCM-1 achieved a discharge specific capacity of 206.4 mAh / g at 0.2C rate, higher than the comparative NCM (200.6 mAh / g). After 200 cycles at 1C rate, B-NCM-1 retained 92.5% of its capacity. Figure 3 The capacity retention of B-NCM-1 was significantly higher than that of the comparative NCM (84.6%). After 50 cycles at 45°C, the capacity retention of B-NCM-1 reached 95.8%, which was significantly better than that of the comparative NCM (88.3%). This is mainly because the material prepared by this invention has a low surface residual lithium content, thus exhibiting advantages such as low interfacial impedance and good cycle stability, especially maintaining excellent electrochemical performance under high temperature conditions.

[0058] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a borate-coated high-nickel cathode material, characterized in that, Includes the following steps: Step 1: Add the high-nickel cathode material matrix, borate, and surface modifier to a solvent and mix thoroughly to obtain the precursor solution; Step 2: The precursor solution is spray-dried to allow the borate to adhere uniformly to the surface of the high-nickel cathode material substrate, thus obtaining the precursor. Step 3: Heat the precursor to allow the borate to react with the residual lithium on the surface of the high-nickel cathode material matrix, thus obtaining the borate-coated high-nickel cathode material.

2. The method for preparing borate-coated high-nickel cathode material according to claim 1, characterized in that, The chemical formula of the high-nickel cathode material in step one is: LiNi 1-x-y Co x Mn y O2, where 0.6≤1-xy≤0.

95.

3. The method for preparing borate-coated high-nickel cathode material according to claim 1, characterized in that, In step one, the high-nickel cathode material is prepared using the following method: Nickel-cobalt-manganese hydroxide was synthesized by co-precipitation, and then the nickel-cobalt-manganese hydroxide was mixed with a lithium source and sintered at 700-850℃ to obtain a high-nickel cathode material matrix.

4. The method for preparing borate-coated high-nickel cathode material according to claim 3, characterized in that, The co-precipitation method for synthesizing nickel cobalt manganese hydroxide includes: adding a precipitant to a mixed solution containing nickel salt, cobalt salt, and manganese salt; controlling the reaction system temperature at 50-60℃, the pH value at 11.0-12.0, and the stirring speed at 500-1000 rpm to obtain nickel cobalt manganese hydroxide precipitate.

5. The method for preparing borate-coated high-nickel cathode material according to claim 3, characterized in that, The lithium source is lithium hydroxide or lithium carbonate; In step two, the molar ratio of lithium to the transition metal in nickel-cobalt-manganese hydroxide is (1.02-1.08):1; Preferably, the borate is selected from one or more of boric acid, lithium metaborate, and boron trioxide, and the weight of the borate is 1%-5% of the mass of the high-nickel cathode material matrix.

6. The method for preparing borate-coated high-nickel cathode material according to claim 1, characterized in that, The surface modifier is selected from one of polyethylene glycol, polyvinylpyrrolidone, and hexadecyltrimethylammonium bromide; Preferably, the solvent is water, ethanol, or acetone.

7. The method for preparing borate-coated high-nickel cathode material according to claim 1, characterized in that, The material inlet temperature during the spray drying process is 160-200℃, and the outlet temperature is 80-120℃.

8. The method for preparing borate-coated high-nickel cathode material according to claim 1, characterized in that, The heat treatment is performed by heating at 300-600°C for 2-6 hours in an oxygen atmosphere.

9. The borate-coated high-nickel cathode material obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the borate-coated high-nickel cathode material according to claim 9 in lithium batteries.

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