Li3AlF6-coated ultrahigh-nickel ternary lithium ion battery positive electrode material as well as preparation method and application of Li3AlF6-coated ultrahigh-nickel ternary lithium ion battery positive electrode material

Abstract

The invention discloses a Li3AlF6-coated ultrahigh-nickel ternary layered lithium ion battery positive electrode material as well as a preparation method and application of the Li3AlF6-coated ultrahigh-nickel ternary layered lithium ion battery positive electrode material. A nickel-cobalt-manganese ternary precursor is mixed with a lithium source, and the ultrahigh-nickel ternary positive electrode material is obtained through high-temperature calcination. An aluminum source and a fluorine source are added into the positive electrode material by adopting a wet chemical method, secondary high-temperature calcination is completed after drying, and finally the uniform and stable Li3AlF6-coated ultrahigh-nickel ternary layered positive electrode material is obtained. The residual lithium on the surface of the positive electrode is used as the lithium source of the Li3AlF6 coating layer, so that the electrochemical performance of the ultrahigh-nickel ternary positive electrode material is successfully improved while the residual lithium compound is effectively reduced. The uniform and stable Li3AlF6 coating layer prepared in the invention not only can inhibit interface side reaction, relieve degradation of a ternary positive electrode structure and prolong the cycle life of the battery, but also has excellent ionic conductivity, can reduce interface impedance and optimize a lithium ion transmission path, and has a good application prospect. And the cycling stability and the rate capability of the ultrahigh-nickel ternary layered lithium ion battery positive electrode material are synchronously improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material, its preparation method, and its application. Background Technology

[0002] Against the backdrop of accelerated global energy structure transformation, developing efficient and green energy conversion technologies to achieve efficient energy utilization is of significant necessity and practical importance. Lithium-ion batteries, with their advantages of high energy density, long cycle life, environmental friendliness, and wide applicability, have become one of the most promising power battery technologies. As the core component of lithium-ion batteries, the cathode material plays a decisive role in various battery performance indicators. Among various cathode materials, ultra-high nickel ternary layered oxides have become a popular research target for lithium-ion battery cathode materials due to their ultra-high specific capacity. However, the severe interfacial side reactions and other problems associated with this cathode material limit its practical application.

[0003] In pursuit of higher energy density, ternary cathode materials have been continuously developed towards ultra-high nickel content. However, increasing the nickel content exacerbates cation mixing, triggers microcrack propagation, and leads to severe interfacial side reactions. This, in turn, causes HF corrosion of the cathode, surface structure collapse, and accelerated capacity decay; electrolyte decomposition produces gases such as O2 and CO2, causing thermal runaway and significantly reducing battery performance.

[0004] To address these issues, common modification strategies include elemental doping, gradient structure design, and surface coating. Among these, surface coating technology can address key failure problems such as interfacial side reactions, transition metal dissolution, and thermal runaway while maintaining the theoretical capacity of the material. It also boasts advantages such as simple processing, low cost, and strong compatibility, making it one of the core methods for modifying ultra-high nickel ternary cathode materials. However, traditional coatings suffer from the inability to simultaneously achieve ion and electronic conduction and structural stability, thus the development of novel conductive coatings has become a research direction.

[0005] By modifying the surface of the cathode material of ultra-high nickel ternary lithium-ion batteries with an ion-conducting Li3AlF6 coating layer, not only can the electrochemical stability of the battery charging and discharging process be guaranteed, but it also helps to optimize lithium-ion transport and improve rate performance.

[0006] CN113161520A discloses a process for forming a nano-alumina protective layer on the surface of a ternary cathode material using a sol-gel method. This method can obtain a uniform alumina coating layer, thereby preventing direct contact between the electrode and the electrolyte, reducing adverse interfacial reactions, and improving the stability and safety of the ternary cathode in lithium-ion batteries. However, the alumina used in this method is an insulator, which is not conducive to the transport of lithium ions during charging and discharging, affecting the rate performance of the cathode.

[0007] CN117117132A discloses a cathode material with a surface-coated mixture of cobalt hydroxide, aluminum fluoride, and cerium oxide, which effectively improves the cycle performance of modified high-nickel cathode materials. Cobalt hydroxide can react with lithium carbonate on the cathode surface, reducing residual lithium; aluminum fluoride and cerium oxide can inhibit HF corrosion during cycling; and cerium oxide, as a fast ion conductor, can enhance the electrochemical performance of the cathode. However, this method requires numerous materials, has a complex preparation process, and suffers from a low cerium oxide content, resulting in weak ion transport optimization.

[0008] CN114614012B discloses a ternary composite material for in-situ coating fast ion conductors, used to optimize the interfacial performance between the cathode and solid electrolyte in all-solid-state batteries. This method involves constructing Li0 with ionic conductivity... x M y F x+3y The coating layer reduces electrolyte decomposition side reactions while promoting lithium-ion transport, resulting in a stable interface with low impedance. However, this method not only adds a lithium source during the coating process, increasing the possibility of residual lithium compounds on the cathode surface, but also, due to the solid-phase coating method, the thickness and uniformity of the coating layer cannot be controlled, affecting the stability of the cathode material.

[0009] CN118156479A discloses an ultra-high nickel ternary cathode material coated with a fluorine-silicon-cobalt-lithium composite compound, doped with metal ions. This method suppresses lithium-nickel mixing by introducing elements such as Al as dopant, while simultaneously forming a fluorine-silicon-based composite coating layer to consume residual lithium on the surface, thus improving the cycle performance of the cathode material. However, the resulting Li₂Co(SiF₆)₂, Li₂SiF₆, LiCoO₂, and Li₂... x The low ionic conductivity of the CoO2 and Co3O4 composite coating layer limits lithium-ion migration to some extent. More importantly, the introduction of cobalt, a high-priced and low-abundance strategic metal, increases material costs and supply chain risks, which deviates from the current trend of "low-cobalt / cobalt-free" development of high-nickel materials and is not conducive to large-scale commercial applications. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material, its preparation method, and its application.

[0011] To address the problems in the existing technology, the technical solution adopted by this invention is as follows: A method for preparing a Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material involves using a nickel-cobalt-manganese ternary hydroxide precursor as a raw material, mixing it with a lithium source, and then performing high-temperature solid-state sintering under a flowing oxygen atmosphere. After cooling and pulverizing, an ultra-high nickel ternary cathode matrix material is obtained. Subsequently, it is dispersed in an anhydrous ethanol dispersion containing an aluminum source. A fluorine source and a mixed solution of deionized water and anhydrous ethanol are added sequentially. After mixing and drying to remove the solvent, the mixture is calcined again at high temperature, allowing the aluminum source, fluorine source, and residual lithium on the matrix surface to react in situ, generating a fast ion conductor Li3AlF6 coating layer, thus obtaining the Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material.

[0012] The preparation method of the above-mentioned ultra-high nickel ternary lithium-ion battery cathode material includes the following steps: Step 1: Mix the nickel-cobalt-manganese ternary precursor with LiOH·H2O uniformly, and calcine it in a tubular atmosphere furnace with flowing oxygen in stages. First, hold at 450-550°C for 4-6 h, then hold at 700-800°C for 10-15 h, and finally cool down to 80°C at 5°C / min. Then cool to room temperature with the furnace, grind and sieve to obtain ultra-high nickel ternary cathode material. Step 2: Disperse the aluminum source in anhydrous ethanol solution and stir for 1-3 h. Then add the ultra-high nickel ternary cathode material and stir for 0.1-0.5 h. Add the fluorine source and continue stirring for 0.1-0.5 h. Finally, add a mixed solution of deionized water and anhydrous ethanol, heat in a water bath at 60-70°C and stir for 2-3 h. After standing at room temperature for a period of time, place it in a vacuum drying oven and dry at 60-70°C. Then dry at 100-120°C for 10-15 h. After grinding and sieving, the primary ultra-high nickel ternary cathode coating material is obtained. Step 3: The primary ultra-high nickel ternary cathode coating material is refluxed in a tubular atmosphere furnace with a flowing atmosphere and held at 350-450°C for 4-6 h. Finally, the temperature is reduced to 80°C at 5°C / min and then cooled to room temperature with the furnace. After grinding and sieving, the ultra-high nickel ternary lithium-ion battery cathode material coated with Li3AlF6 is obtained.

[0013] Preferably, the chemical formula of the nickel-cobalt-manganese ternary precursor in step 1 is Ni 0.96 Co 0.03 Mn 0.01 (OH)2, Ni 0.96 Co 0.03 Mn 0.01 In (OH)2 and LiOH·H2O, the ratio of nLi : n(Ni + Co + Mn) is 1.05 : 1.

[0014] Preferably, in step 2, the aluminum source is aluminum isopropoxide, and the fluorine source is at least one of lithium fluoride, ammonium fluoride, and aluminum fluoride.

[0015] Preferably, the mass of the ultra-high nickel ternary cathode material mixed with the aluminum source and fluorine source in step 2 is 0.5-1.5 g.

[0016] Preferably, the calcination atmosphere in step 3 is at least one of oxygen, argon, and nitrogen; and the content of the Li3AlF6 coating layer is 0.25-2%.

[0017] Preferably, after grinding in steps 1, 2, and 3, the material is sieved, and the sieve has a mesh size of 300.

[0018] The ultra-high nickel ternary lithium-ion battery cathode material prepared by the above preparation method.

[0019] Preferably, the ultra-high nickel ternary lithium-ion battery cathode material contains Ni ≥ 0.96 mol, and its diffraction peak is [missing information]. α -The characteristic peaks of the layered structure of NaFeO2 indicate that it belongs to the hexagonal crystal system. R-3m Space group.

[0020] The ultra-high nickel ternary cathode material prepared by the above method is used as a cathode in lithium-ion batteries. This application effectively reduces residual lithium compounds on the surface of the ternary cathode material, suppresses interfacial side reactions, and achieves dual optimization of the lithium-ion battery cathode's cycle life and rate performance by constructing a stable, ion-conductive, and uniform coating layer.

[0021] Beneficial effects: Compared with existing technologies, this invention employs a wet chemical method combined with gradient sintering to controllably synthesize Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode materials. Optimizing the coating thickness and sintering process parameters enhances the coating effect, effectively reduces residual lithium on the cathode surface, and improves electrochemical performance. Specific advantages are as follows: First, the coating of fast ion conductor Li3AlF6 can suppress the interfacial side reactions that are prone to occur when ultra-high nickel ternary cathode materials are working, optimize the lithium ion transport channel, and achieve a stable interface with low impedance.

[0022] Second, the Li3AlF6 coating uses lithium compounds on the surface of the ternary cathode material as the lithium source. During burn-back, the coating precursor reacts with the residual lithium compounds, consuming the residual lithium on the cathode surface.

[0023] Third, the preparation process of ultra-high nickel ternary materials coated with Li3AlF6 is controlled, including the precursor calcination temperature, coating thickness, and reheating atmosphere, to obtain a uniform, dense, and high-purity Li3AlF6 coating layer, thereby enhancing the modification effect. This method is simple to operate and has significant effects, achieving a simultaneous improvement in the cycle performance and rate performance of ultra-high nickel ternary lithium-ion battery cathode materials. Attached Figure Description

[0024] Figure 1 The XRD patterns are of Embodiments 1-8 and Comparative Example 2 of the present invention; Figure 2 SEM images of a) Comparative Example 2; b) Example 1; c) Example 2; d) Example 3; e) Example 4; f) Example 5; g) Example 6; h) Example 7; i) Example 8; Figure 3 The cycling performance curves are for Examples 1-8 and Comparative Examples 1-10; Figure 4 The following are the rate performance curves for Examples 1-8 and Comparative Example 2. Detailed Implementation

[0025] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0026] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0027] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0028] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. Specifically, based on existing research, this invention proposes a wet chemical method combined with gradient sintering for the controllable synthesis of Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode materials. First, the fast-ion conductor Li3AlF6 coating can suppress interfacial side reactions that easily occur during the operation of ultra-high nickel ternary cathode materials, optimize lithium-ion transport channels, and achieve a stable interface with low impedance. Second, the Li3AlF6 coating layer uses lithium compounds on the surface of the ternary cathode material as a lithium source; during reheating, the coating layer precursor reacts with residual lithium compounds, consuming residual lithium on the cathode surface. Furthermore, by controlling the preparation process of the Li3AlF6-coated ultra-high nickel ternary material, including the precursor calcination temperature, coating layer thickness, and reheating atmosphere, a uniform, dense, and high-purity Li3AlF6 coating layer is obtained, enhancing the modification effect.

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the equipment and reagents used in the present invention are commercially available products conventional in this technical field. The room temperature mentioned in the present invention refers to 25°C.

[0030] The following will provide a further explanation of the technical solution, its implementation process, and its principles.

[0031] A method for preparing a Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material includes the following steps: Step 1: Mix the nickel-cobalt-manganese ternary precursor with LiOH·H2O uniformly, and calcine it in a tubular atmosphere furnace with flowing oxygen in stages. First, hold at 450-550°C for 4-6 h, then hold at 700-800°C for 10-15 h, and finally cool down to 80°C at 5°C / min. Then cool to room temperature with the furnace, grind and sieve to obtain ultra-high nickel ternary cathode material. Step 2: Disperse the aluminum source in anhydrous ethanol solution and stir for 1-3 h. Then add the ultra-high nickel ternary cathode material and stir for 0.1-0.5 h. Add the fluorine source and continue stirring for 0.1-0.5 h. Finally, add a mixed solution of deionized water and anhydrous ethanol, heat in a water bath at 60-70°C and stir for 2-3 h. After standing at room temperature for a period of time, place it in a vacuum drying oven and dry at 60-70°C. Then dry at 100-120°C for 10-15 h. After grinding and sieving, the primary ultra-high nickel ternary cathode coating material is obtained. Step 3: The primary ultra-high nickel ternary cathode coating material is refluxed in a tubular atmosphere furnace with a flowing atmosphere and held at 350-450°C for 4-6 h. Finally, the temperature is reduced to 80°C at 5°C / min and then cooled to room temperature with the furnace. After grinding and sieving, the ultra-high nickel ternary lithium-ion battery cathode material coated with Li3AlF6 is obtained.

[0032] In this invention, the sintering process in step 1 involves first holding at 500°C for 5 hours, then holding at 725°C for 14 hours. The reheating process is preferably performed at 400°C for 5 hours. The aluminum source is aluminum isopropoxide, and the fluorine source is ammonium fluoride. Aluminum isopropoxide reacts with water added to the final mixed solution (1-3). During hydrolysis, the surface of the nickel-cobalt-manganese ternary material is in direct contact with the aluminum isopropoxide solution, which facilitates the formation of a uniform coating layer on the surface of the ternary material particles by AlOOH in synergy with NH4F.

[0033]

[0034] Finally, the ultra-high nickel ternary cathode powder coated with AlOOH and NH4F was calcined back to react with residual lithium on the surface (4) to generate a Li3AlF6 coating layer: Example 1

[0035] Weigh out 3.6844 g Ni 0.96 Co 0.03 Mn 0.01 (OH)2 powder was uniformly mixed with 1.8239 g LiOH·H2O, where nLi : n(Ni + Co + Mn) = 1.05 : 1 (molar ratio). The mixture was placed in an oxygen-filled tube furnace for segmental sintering. The furnace was first held at 500°C for 5 h, then at 725°C for 14 h, and then cooled to 80°C at a rate of 5°C / min. Finally, the furnace was cooled to room temperature. After grinding and sieving, ultra-high nickel ternary cathode material was obtained.

[0036] Weigh 0.00608 g of aluminum isopropoxide and dissolve it in 5 ml of anhydrous ethanol, stirring for 1.5 h. Then add 1 g of ultra-high nickel ternary cathode material and stir for 0.25 h. Continue to add 0.00338 g of ammonium fluoride and stir for 0.25 h to obtain a slurry. Prepare 4 ml of a mixed solution of deionized water and anhydrous ethanol (where V... 去离子水 V 无水乙醇 = 1 : 2) Add the above slurry, stir in a 65°C water bath for 3 h, and let stand at room temperature for 12 h. Then place it in a vacuum drying oven, first dry at 65°C for 10 h, then dry at 110°C for 12 h, and grind and sieve. Place it in an oxygen-filled tube furnace and reflux at 400°C for 5 h, then cool to 80°C at 5°C / min, and finally cool to room temperature with the furnace. After grinding and sieving, the oxygen-refluxed 0.25% Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material is obtained. The test results of making coin cells using this material are shown in Table 1. Example 2

[0037] Except for placing it in an oxygen-filled tube furnace at 400°C for 5 hours, then cooling it to 80°C at a rate of 5°C / min, and finally cooling it to room temperature with the furnace, the rest of the process was the same as in Example 1, resulting in an argon-filled tube furnace with 0.25% Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material. Example 3

[0038] Weigh out 3.6844 g Ni 0.96 Co 0.03 Mn 0.01(OH)2 powder was uniformly mixed with 1.8239 g LiOH·H2O, where nLi : n(Ni + Co + Mn) = 1.05 : 1 (molar ratio). The mixture was placed in an oxygen-filled tube furnace for segmental sintering. The furnace was first held at 500°C for 5 h, then at 725°C for 14 h, and then cooled to 80°C at a rate of 5°C / min. Finally, the furnace was cooled to room temperature. After grinding and sieving, ultra-high nickel ternary cathode material was obtained.

[0039] Weigh 0.01216 g of aluminum isopropoxide and dissolve it in 5 ml of anhydrous ethanol, stirring for 1.5 h. Then add 1 g of ultra-high nickel ternary cathode material and stir for 0.25 h. Continue to add 0.00675 g of ammonium fluoride and stir for 0.25 h to obtain a slurry. Prepare 4 ml of a mixed solution of deionized water and anhydrous ethanol (where V... 去离子水 V 无水乙醇 = 1 : 2) Add the above slurry, stir in a 65°C water bath for 3 h, and let stand at room temperature for 12 h. Then place it in a vacuum drying oven, first dry at 65°C for 10 h, then dry at 110°C for 12 h, and grind and sieve. Place it in an oxygen-filled tube furnace and reflux at 400°C for 5 h, then cool it down to 80°C at 5°C / min, and finally cool it to room temperature with the furnace. After grinding and sieving, the oxygen-refluxed 0.5% Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material is obtained. Example 4

[0040] Except for placing it in an oxygen-filled tube furnace at 400°C for 5 hours, then cooling it down to 80°C at a rate of 5°C / min, and finally cooling it to room temperature with the furnace, the rest of the process was the same as in Example 3, resulting in an argon-filled tube furnace with 0.5% Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material. Example 5

[0041] Weigh out 3.6844 g Ni 0.96 Co 0.03 Mn 0.01 (OH)2 powder was uniformly mixed with 1.8239 g LiOH·H2O, where nLi : n(Ni + Co + Mn) = 1.05 : 1 (molar ratio). The mixture was placed in an oxygen-filled tube furnace for segmental sintering. The furnace was first held at 500°C for 5 h, then at 725°C for 14 h, and then cooled to 80°C at a rate of 5°C / min. Finally, the furnace was cooled to room temperature. After grinding and sieving, ultra-high nickel ternary cathode material was obtained.

[0042] Weigh 0.01824 g of aluminum isopropoxide and dissolve it in 5 ml of anhydrous ethanol, stirring for 1.5 h. Then add 1 g of ultra-high nickel ternary cathode material and stir for 0.25 h. Continue to add 0.01013 g of ammonium fluoride and stir for 0.25 h to obtain a slurry. Prepare 4 ml of a mixed solution of deionized water and anhydrous ethanol (where V... 去离子水 V 无水乙醇 = 1 : 2) Add the above slurry, stir in a 65°C water bath for 3 h, and let stand at room temperature for 12 h. Then place it in a vacuum drying oven, first dry at 65°C for 10 h, then dry at 110°C for 12 h, and grind and sieve. Place it in an oxygen-filled tube furnace and reflux at 400°C for 5 h, then cool to 80°C at 5°C / min, and finally cool to room temperature with the furnace. After grinding and sieving, the oxygen-refluxed 0.75% Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material is obtained. Example 6

[0043] Except for placing it in an oxygen-filled tube furnace at 400°C for 5 hours, then cooling it to 80°C at a rate of 5°C / min, and finally cooling it to room temperature with the furnace, the rest of the process was the same as in Example 5, resulting in an argon-filled tube furnace with 0.75% Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material. Example 7

[0044] Weigh out 3.6844 g Ni 0.96 Co 0.03 Mn 0.01 (OH)2 powder was uniformly mixed with 1.8239 g LiOH·H2O, where nLi : n(Ni + Co + Mn) = 1.05 : 1 (molar ratio). The mixture was placed in an oxygen-filled tube furnace for segmental sintering. The furnace was first held at 500°C for 5 h, then at 725°C for 14 h, and then cooled to 80°C at a rate of 5°C / min. Finally, the furnace was cooled to room temperature. After grinding and sieving, ultra-high nickel ternary cathode material was obtained.

[0045] Weigh 0.02432 g of aluminum isopropoxide and dissolve it in 5 ml of anhydrous ethanol, stirring for 1.5 h. Then add 1 g of ultra-high nickel ternary cathode material and stir for 0.25 h. Continue to add 0.01351 g of ammonium fluoride and stir for 0.25 h to obtain a slurry. Prepare 4 ml of a mixed solution of deionized water and anhydrous ethanol (where V... 去离子水 V 无水乙醇= 1 : 2) Add the above slurry, stir in a 65°C water bath for 3 h, and let stand at room temperature for 12 h. Then place it in a vacuum drying oven, first dry at 65°C for 10 h, then dry at 110°C for 12 h, and grind and sieve. Place it in an oxygen-filled tube furnace and reflux at 400°C for 5 h, then cool it down to 80°C at 5°C / min, and finally cool it to room temperature with the furnace. After grinding and sieving, the oxygen-refluxed 1.0% Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material is obtained. Example 8

[0046] Except for placing it in an oxygen-filled tube furnace at 400°C for 5 hours, then cooling it to 80°C at a rate of 5°C / min, and finally cooling it to room temperature with the furnace, the rest of the process was the same as in Example 7, resulting in an argon-filled tube furnace with 1.0% Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material.

[0047] Comparative Example 1: Weigh out 3.6844 g Ni 0.96 Co 0.03 Mn 0.01 (OH)2 powder was uniformly mixed with 1.8239 g LiOH·H2O, where nLi : n(Ni + Co + Mn) = 1.05 : 1 (molar ratio). The mixture was placed in an oxygen-filled tube furnace for segmental sintering. The furnace was first held at 500°C for 5 h, then at 700°C for 14 h, and then cooled to 80°C at a rate of 5°C / min. Finally, the furnace was cooled to room temperature. After grinding and sieving, ultra-high nickel ternary cathode material was obtained.

[0048] Comparative Example 2: Except for the segmented sintering process, which was changed from holding at 500°C for 5 hours and then at 700°C for 14 hours to holding at 500°C for 5 hours and then at 725°C for 14 hours, the rest is the same as Comparative Example 1.

[0049] Comparative Example 3: Except for the segmented sintering process, which was changed from holding at 500°C for 5 hours and then at 700°C for 14 hours to holding at 500°C for 5 hours and then at 750°C for 14 hours, the rest is the same as Comparative Example 1.

[0050] Comparative Example 4: Except for the segmented sintering process, which was changed from holding at 500°C for 5 hours and then at 700°C for 14 hours to holding at 500°C for 5 hours and then at 775°C for 14 hours, the rest is the same as Comparative Example 1.

[0051] Comparative Example 5: Weigh out 3.6844 g Ni 0.96 Co 0.03 Mn 0.01 (OH)2 powder was uniformly mixed with 1.8239 g LiOH·H2O, where nLi : n(Ni + Co + Mn) = 1.05 : 1 (molar ratio). The mixture was placed in an oxygen-filled tube furnace for segmental sintering. The furnace was first held at 500°C for 5 h, then at 725°C for 14 h, and then cooled to 80°C at a rate of 5°C / min. Finally, the furnace was cooled to room temperature. After grinding and sieving, ultra-high nickel ternary cathode material was obtained.

[0052] 0.005095 g of sodium fluoride and 1 g of ultra-high nickel ternary cathode material were weighed and dispersed in 5 ml of deionized water. After stirring for 1 h, 0.005145 g of lithium chloride was added and stirred for 6 h. Then, 0.005135 g of aluminum fluoride was added and stirring was continued for 8 h. Subsequently, the mixture was vacuum dried at 110°C for 24 h, ground, and sieved. It was then refluxed at 400°C for 5 h in an argon-filled tube furnace, followed by cooling to 80°C at a rate of 5°C / min. Finally, it was cooled to room temperature with the furnace, ground, and sieved to obtain 0.5% Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material refluxed in oxygen.

[0053] Comparative Example 6: Except for replacing 0.005095 g of sodium fluoride with 0.01019 g of sodium fluoride, 0.005145 g of lithium chloride with 0.01029 g of lithium chloride, and 0.005135 g of aluminum fluoride with 0.01027 g of aluminum fluoride, and replacing vacuum drying at 110°C for 24 h with filtration of the stirred solution, the resulting product was vacuum dried at 110°C for 8 h. The rest was the same as in Comparative Example 5, to obtain an ultra-high nickel ternary lithium-ion battery cathode material coated with 1.0% Li3AlF6 after oxygen reheating.

[0054] Comparative Example 7: Except for replacing 0.005095 g of sodium fluoride with 0.015285 g of sodium fluoride, 0.005145 g of lithium chloride with 0.015435 g of lithium chloride, and 0.005135 g of aluminum fluoride with 0.015405 g of aluminum fluoride, the rest were the same as in Comparative Example 5, to obtain an ultra-high nickel ternary lithium-ion battery cathode material coated with 1.5% Li3AlF6 after oxygen reheating.

[0055] Comparative Example 8: Except for replacing 0.005095 g of sodium fluoride with 0.02038 g of sodium fluoride, 0.005145 g of lithium chloride with 0.020581 g of lithium chloride, and 0.005135 g of aluminum fluoride with 0.020541 g of aluminum fluoride, and replacing vacuum drying at 110°C for 24 h with filtration of the stirred solution, the resulting product was vacuum dried at 110°C for 8 h. The rest was the same as in Comparative Example 5, to obtain an ultra-high nickel ternary lithium-ion battery cathode material coated with 2.0% Li3AlF6 after oxygen reheating.

[0056] Comparative Example 9: Weigh out 3.6844 g Ni 0.96 Co 0.03 Mn 0.01 (OH)2 powder was uniformly mixed with 1.8239 g LiOH·H2O, where nLi : n(Ni + Co + Mn) = 1.05 : 1 (molar ratio). The mixture was placed in an oxygen-filled tube furnace for segmental sintering. The furnace was first held at 500°C for 5 h, then at 725°C for 14 h, and then cooled to 80°C at a rate of 5°C / min. Finally, the furnace was cooled to room temperature. After grinding and sieving, ultra-high nickel ternary cathode material was obtained.

[0057] Weigh 0.00608 g of aluminum isopropoxide and dissolve it in 5 ml of anhydrous ethanol, stirring for 1.5 h. Then add 1 g of ultra-high nickel ternary cathode material and stir for 0.25 h. Continue to add 0.00338 g of ammonium fluoride and stir for 0.25 h to obtain a slurry. Prepare 4 ml of a mixed solution of deionized water and anhydrous ethanol (where V... 去离子水 V 无水乙醇 = 1 : 2) Add the above slurry, stir in a 65°C water bath for 6 h, let stand at room temperature for 12 h, then dry in a vacuum drying oven at 110°C for 12 h, and grind and sieve. Place it in an oxygen-filled tube furnace and reflux at 400°C for 5 h, then cool to 80°C at 5°C / min, and finally cool to room temperature with the furnace. After grinding and sieving, the oxygen-refluxed 0.25% Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material is obtained.

[0058] Comparative Example 10: Except for replacing 0.00608 g of aluminum isopropoxide with 0.01216 g of aluminum isopropoxide and 0.00338 g of ammonium fluoride with 0.00675 g of ammonium fluoride, the rest were the same as in Comparative Example 9, to obtain an ultra-high nickel ternary lithium-ion battery cathode material coated with 0.5% Li3AlF6 after oxygen reheating.

[0059] The positive electrode materials prepared in Examples 1-8 and Comparative Examples 1-10 were used to fabricate 2032 coin cell simulated batteries to test their electrochemical performance. The specific steps are as follows: (1) Weigh the above positive electrode material, conductive acetylene black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1. First, dissolve PVDF in an appropriate amount of N-methylpyrrolidone (NMP). Then, add the uniformly mixed positive electrode material and acetylene black powder to NMP and stir evenly to form a slurry; (2) Coat the slurry evenly on an aluminum foil substrate. Place the wet electrode in a vacuum drying oven and dry at 110°C for 12 h. Cut it into a positive electrode sheet; (3) Assemble the simulated battery in a dry glove box. The above-made positive electrode sheet is used as the positive electrode, the lithium metal sheet is used as the negative electrode, the Celgard 2500 membrane is used as the separator, and the electrolyte is 1 mol·L⁻¹. –1 LiPF6 was dissolved in a solution of ethylene carbonate (EC), methyl ethyl carbonate (EMC), and dimethyl carbonate (DMC) (volume ratio 1:1:1), and its electrochemical performance was tested, as shown in Table 1.

[0060] Table 1. Electrochemical performance of the cathode materials in Examples 1-8 and Comparative Examples 1-10 at 2.70-4.30 V.

[0061] Table 1 shows that among Comparative Examples 1-4, Comparative Example 2 exhibits significantly higher discharge specific capacity and capacity retention after 100 cycles compared to the other samples. This demonstrates that the process in Comparative Example 2 is beneficial for improving the structural stability of the ultra-high nickel ternary cathode material, resulting in superior cycle performance. Examples 1-8 and Comparative Examples 5-10 were all coated on the ultra-high nickel ternary cathode material prepared using the process in Comparative Example 2. The initial discharge specific capacity of Comparative Examples 5-8 was lower than that of the corresponding Comparative Example 2, and the capacity rapidly decayed during cycling, with no modification effect observed from the Li3AlF6 coating layer. The initial cycle performance of Comparative Examples 9-10 was similar to that of Comparative Example 2, and the capacity retention after 100 cycles reached 90%, far exceeding that of Comparative Example 2. This is because the formed Li3AlF6 coating layer can isolate the contact between the cathode and electrolyte interface, suppress interfacial side reactions, and improve cycle stability. Further process improvements yielded Examples 1-8. The initial discharge specific capacity and first-cycle coulombic efficiency of these samples did not show significant differences compared to the original samples; some even exhibited superior performance after modification. This indicates that the uniformly coated and chemically stable Li3AlF6 protective layer effectively reduces interfacial side reactions, contributing to better initial cycle performance. After 100 cycles, the coated samples all showed superior capacity retention compared to the uncoated Comparative Example 2. Furthermore, with increasing coating weight, the cycle performance of Examples 1-8 showed a trend of first increasing and then decreasing. At the same coating weight, the samples reheated in argon performed better than those reheated in oxygen, with Example 4 showing the best performance, still retaining 180.5 mAh·g after 100 cycles. –1 The discharge specific capacity was high, and the capacity retention rate reached 94.2%. It can be seen that different coating thicknesses and sintering atmospheres affect the coating effect. In Example 4, a suitable coating amount resulted in a uniform and dense Li3AlF6 coating layer. At the same time, sintering in argon gas improved the purity of the Li3AlF6 coating layer. The high-quality Li3AlF6 coating significantly improved the cycle stability of the ultra-high nickel ternary cathode material.

[0062] Figure 1 The XRD spectra of Examples 1-8, Comparative Example 2, and Comparative Examples 5-10 were compared. Specific parameters are detailed in Table 2.

[0063] Table 2. Cell parameters and (003) / (104) peak intensity ratio of cathode materials in Examples 1-8 and Comparative Examples 1-10

[0064] These samples exhibit the typical structural characteristics of LiNiO2 cathode materials, with diffraction peaks as follows: α -The characteristic peaks of the layered structure of NaFeO2 indicate that it belongs to the hexagonal crystal system. R-3m Space group. The cell parameters obtained by XRD are shown in Table 2. Examples 1-8 all have...c / a >4.9, and maintains a volume similar to Comparative Example 2. V This indicates that both the modified and unmodified samples possess a complete layered structure, and the Li3AlF6 coating layer does not disrupt the layered structure of the ultra-high nickel ternary cathode material. Comparing the degree of cation mixing, Examples 1-8... I (003) / I (104) The values ​​all exceeded 1.2, indicating a relatively mild degree of cation mixing, which would not reduce the performance of the cathode material.

[0065] Figure 2 The SEM images of Examples 1-8 and Comparative Example 2 show that Examples 1-8 and Comparative Example 2 exhibit consistent particle morphology, proving that the Li3AlF6 coating did not disrupt the crystal structure of the ultra-high nickel ternary cathode material. The particles in Comparative Example 2 have smooth surfaces, while in Examples 1-8, the surface roughness shows a significant gradient change with increasing coating amount. This change in morphology confirms the successful construction of the coating layer. As the coating amount continues to increase, the coated material begins to show obvious aggregation behavior, and the uneven distribution of Li3AlF6 affects the electrochemical performance of the ultra-high nickel ternary cathode material. Comparing the SEM images of samples with the same coating mass ratio reveals that the coating material under an argon-burning atmosphere has a higher coverage density and is more likely to form a dense protective layer.

[0066] Figure 3 The cycling performance curves for Examples 1-8 and Comparative Examples 1-10 are shown. The curves for Examples 1-8 are relatively stable, with a slower decrease in discharge specific capacity, indicating that the ultra-high nickel ternary cathode material coated with Li3AlF6 has superior cycling stability. In Example 4, after 100 cycles at 1 C, the discharge specific capacity still reached 180.5 mAh·g. –1 The capacity retention rate reached 94.2%, with the highest discharge specific capacity and capacity retention rate. This indicates that the Li3AlF6 coating layer effectively suppressed interfacial side reactions, protected the cathode surface structure, and improved the cycle stability of the ultra-high nickel ternary cathode material.

[0067] Figure 4 Examples 1-8 and Comparative Example 2 demonstrate rate performance at different current densities. Example 4 exhibits the highest discharge specific capacity at high rates, which is attributed to the formation of a uniform and high-purity Li3AlF6 coating layer, which consumes residual lithium compounds on the surface of the ultra-high nickel ternary cathode, reduces interfacial impedance during lithium-ion diffusion, and improves the rate performance of the cathode.

[0068] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for preparing a Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material, characterized in that, Using a nickel-cobalt-manganese ternary hydroxide precursor as raw material, it is mixed with a lithium source and then subjected to high-temperature solid-state sintering in a flowing oxygen atmosphere. After cooling and pulverizing, an ultra-high nickel ternary cathode matrix material is obtained. Subsequently, it is dispersed in an anhydrous ethanol dispersion containing an aluminum source. A fluorine source and a mixed solution of deionized water and anhydrous ethanol are added sequentially. After mixing and drying to remove the solvent, it is calcined at high temperature again, so that the aluminum source, fluorine source and residual lithium on the matrix surface can react in situ to generate a fast ion conductor Li3AlF6 coating layer, thus obtaining the Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material.

2. The method for preparing the Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material according to claim 1, characterized in that, Includes the following steps: Step 1: Mix the nickel-cobalt-manganese ternary precursor with LiOH·H2O uniformly, and calcine it in a tubular atmosphere furnace with flowing oxygen in stages. First, hold at 450-550°C for 4-6 h, then hold at 700-800°C for 10-15 h, and finally cool down to 80°C at 5°C / min. Then cool to room temperature with the furnace, grind and sieve to obtain ultra-high nickel ternary cathode material. Step 2: Disperse the aluminum source in anhydrous ethanol solution and stir for 1-3 h. Then add the ultra-high nickel ternary cathode material and stir for 0.1-0.5 h. Add the fluorine source and continue stirring for 0.1-0.5 h. Finally, add a mixed solution of deionized water and anhydrous ethanol, heat in a water bath at 60-70°C and stir for 2-3 h. After standing at room temperature for a period of time, place it in a vacuum drying oven and dry at 60-70°C. Then dry at 100-120°C for 10-15 h. After grinding and sieving, the primary ultra-high nickel ternary cathode coating material is obtained. Step 3: The primary ultra-high nickel ternary cathode coating material is refluxed in a tubular atmosphere furnace with a flowing atmosphere and held at 350-450°C for 4-6 h. Finally, the temperature is reduced to 80°C at 5°C / min and then cooled to room temperature with the furnace. After grinding and sieving, the ultra-high nickel ternary lithium-ion battery cathode material coated with Li3AlF6 is obtained.

3. The method for preparing the Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material according to claim 2, characterized in that, The chemical formula of the nickel-cobalt-manganese ternary precursor in step 1 is Ni 0.96 Co 0.03 Mn 0.01 (OH)2, Ni 0.96 Co 0.03 Mn 0.01 In (OH)2 and LiOH·H2O, the ratio of nLi : n(Ni + Co + Mn) is 1.05 :

1.

4. The method for preparing the Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material according to claim 2, characterized in that, The aluminum source in step 2 is aluminum isopropoxide, and the fluorine source is at least one of lithium fluoride, ammonium fluoride, and aluminum fluoride.

5. The method for preparing the Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material according to claim 2, characterized in that, The mass of the ultra-high nickel ternary cathode material mixed with the aluminum and fluorine sources in step 2 is 0.5-1.5 g.

6. The method for preparing the Li3AlF6-coated ultra-high nickel ternary lithium-ion battery cathode material according to claim 2, characterized in that, In step 3, the atmosphere for reflux is at least one of oxygen, argon, or nitrogen; the content of the Li3AlF6 coating layer is 0.25-2%.

7. The method for preparing the ultra-high nickel ternary lithium-ion battery cathode material according to claim 2, characterized in that, After grinding in steps 1, 2, and 3, the material is sieved through a sieve with a mesh size of 300.

8. The ultra-high nickel ternary lithium-ion battery cathode material prepared by the preparation method described in claim 1.

9. The ultra-high nickel ternary lithium-ion battery cathode material according to claim 8, characterized in that, The ultra-high nickel ternary lithium-ion battery cathode material contains Ni ≥ 0.96 mol, and its diffraction peaks are as follows: α -The characteristic peaks of the layered structure of NaFeO2 indicate that it belongs to the hexagonal crystal system. R-3m Space group.

10. The application of the ultra-high nickel ternary cathode material according to claim 9 as a cathode in lithium-ion batteries.

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