Modified high-nickel ternary positive electrode material, and preparation method therefor and use thereof

Abstract

The present application belongs to the technical field of battery materials, and specifically relates to a modified high-nickel ternary positive electrode material, and a preparation method therefor and the use thereof. The preparation method for a modified high-nickel ternary positive electrode material provided by the present application comprises the following steps: 1) mixing a lithium source, a precursor, a tellurium source and a divalent metal compound, and subjecting same to first calcination, so as to obtain a first calcined product; (2) dissolving a tellurate in an organic solvent, mixing and grinding the resulting tellurate organic solvent solution and the first calcined product obtained in step (1), and then subjecting same to second calcination to obtain a second calcined product, wherein the tellurate is selected from at least one of potassium tellurite and sodium tellurite; and (3) washing the second calcined product obtained in step (2) with water, mixing same with boric acid, and subjecting the mixture to third calcination, so as to obtain the modified high-nickel ternary positive electrode material. Through the specific preparation method and the synergistic effect among the steps in the present application, the resulting modified high-nickel ternary positive electrode material has a good specific capacity, initial Coulombic efficiency and cycling performance.

Description

A modified high-nickel ternary cathode material, its preparation method and application Technical Field

[0001] This application belongs to the field of battery materials technology, specifically relating to a modified high-nickel ternary cathode material, its preparation method, and its application. Background Technology

[0002] Existing high-nickel layered oxide cathode materials (high-nickel ternary cathode materials) have high theoretical specific capacity and are considered the most promising cathode materials for next-generation high-energy-density lithium-ion batteries. However, due to the reduced manganese and cobalt content, existing high-nickel layered oxide cathode materials are more prone to irreversible mechanical damage and have poor chemical stability during storage or use, resulting in capacity decay. Furthermore, with increasing nickel content, high-nickel layered oxide cathode materials readily react with water and CO2 in the air to generate LiOH and Li2CO3, leading to high residual alkali on the surface. All these factors contribute to the poor specific capacity, initial efficiency, and cycle performance of high-nickel layered oxide cathode materials.

[0003] Existing modification methods include bulk doping to improve the structural stability of high-nickel layered oxide cathode materials, surface coating to suppress surface side reactions, and the preparation of gradient materials and single crystals to improve stress-strain stability. However, the effects of existing modification methods on improving the specific capacity, first-efficiency performance, and cycle performance of high-nickel layered oxide cathode materials remain limited. Summary of the Invention

[0004] This application provides a modified high-nickel ternary cathode material, its preparation method, and its application, which solves the problem that the improvement effect of existing high-nickel layered oxide cathode materials on specific capacity, first efficiency, and cycle performance is limited.

[0005] In a first aspect, this application provides a method for preparing a modified high-nickel ternary cathode material, comprising the following steps:

[0006] (1) A lithium source, a precursor, a tellurium source and a divalent metal compound are mixed and calcined for the first time to obtain a calcined product;

[0007] (2) Dissolve the tellurate in an organic solvent, and then mix and grind the resulting tellurate organic solvent solution with the first calcined product obtained in step (1), and then calcine it a second time to obtain the second calcined product;

[0008] The tellurite is selected from at least one of potassium tellurite or sodium tellurite.

[0009] (3) The calcined product obtained in step (2) is washed with water and mixed with boric acid, and then calcined for the third time to obtain the modified high-nickel ternary cathode material.

[0010] In one embodiment, the divalent metal compound in step (1) is selected from at least one of cobalt hydroxide, strontium carbonate, magnesium oxide, or calcium oxide;

[0011] The tellurite is potassium tellurite and sodium tellurite;

[0012] Optionally, the mass ratio of potassium tellurite to sodium tellurite is (0.1-1):(0.1-1);

[0013] The molar amount of nickel in the precursor accounts for more than 90% of the total molar amount of metal elements in the precursor.

[0014] The lithium source is selected from at least one of lithium hydroxide or lithium carbonate;

[0015] The tellurium source mentioned in step (1) is selected from tellurium dioxide.

[0016] In one embodiment, the precursor described in step (1) has the general chemical formula Ni. x Co y Mn z O2, and 0.9≤x≤0.99, 0.01≤y≤0.09, 0.01≤z≤0.09, x+y+z=1;

[0017] The ratio of the total molar amount of metal elements in the precursor, the molar amount of tellurium in the tellurium source, and the molar amount of divalent metal elements in the divalent metal compound in step (1) is (0.975-1):(0.0001-0.015):(0.0001-0.01).

[0018] It is understandable that the total molar amount of metal elements in the precursor is expressed in terms of the general formula Ni. x Co y Mn z Taking O2 as an example, it includes the total molar amounts of the metal elements nickel, cobalt, and manganese.

[0019] The sum of the total molar amount of metal elements in the precursor, the molar amount of tellurium in the tellurium source, and the molar amount of divalent metal elements in the divalent metal compound mentioned in step (1) is denoted as a, and the molar amount of lithium in the lithium source is denoted as b, where b:a is (1.01-1.06):1.

[0020] In one embodiment, the first calcination temperature in step (1) is 700-850°C and the first calcination time is 8-16h;

[0021] In step (1), the calcination atmosphere of the first calcination includes an oxygen-containing atmosphere.

[0022] Optionally, the oxygen-containing atmosphere includes at least one of an oxygen atmosphere or an air atmosphere;

[0023] Optionally, after the first calcination step is completed, the process may further include crushing and sieving steps.

[0024] In one embodiment, the organic solvent in step (2) is selected from ethanol;

[0025] In step (2), the tellurate is dissolved in an organic solvent, and the mass concentration of tellurium in the resulting tellurate organic solvent solution is 0.01-0.1 wt%.

[0026] The mass ratio of the tellurate organic solvent solution in step (2) to the calcined product obtained in step (1) is (1-2):2;

[0027] In one embodiment, the grinding speed is 300-600 rpm and the grinding time is 0.5-1 h;

[0028] Optionally, the grinding includes ball milling;

[0029] The second calcination temperature is 500-700℃, and the second calcination time is 6-12h;

[0030] The second calcination atmosphere includes an oxygen-containing atmosphere;

[0031] Optionally, the oxygen-containing atmosphere includes at least one of an oxygen atmosphere or an air atmosphere.

[0032] In one embodiment, the calcined product described in step (3) is mixed with water and washed with water. After washing, it is dried to obtain the washed calcined product, which is then mixed with boric acid and calcined a third time to obtain the modified high-nickel ternary cathode material.

[0033] In one embodiment, the mass ratio of the distilled product to water is 1:(0.5-1.0);

[0034] The mass ratio of the water-washed dicalcined product to boric acid is 700:(2-10);

[0035] The third calcination temperature is 200-400℃, and the third calcination time is 5-11h.

[0036] Secondly, this application provides a modified high-nickel ternary cathode material, which is prepared by the preparation method of the modified high-nickel ternary cathode material described in the first aspect.

[0037] Thirdly, this application also provides an application of the modified high-nickel ternary cathode material described in the second aspect in lithium-ion batteries.

[0038] The technical solution of this application has the following advantages:

[0039] 1. The method for preparing the modified high-nickel ternary cathode material provided in this application includes the following steps: (1) mixing a lithium source, a precursor, a tellurium source and a divalent metal compound, and calcining the mixture to obtain a calcined product; (2) dissolving a tellurate in an organic solvent, and then mixing and grinding the resulting tellurate organic solvent solution with the calcined product obtained in step (1), and then calcining the mixture to obtain a calcined product; wherein the tellurate is selected from at least one of potassium tellurite and sodium tellurite; (3) washing the calcined product obtained in step (2) with water and mixing it with boric acid, and then calcining the mixture to obtain the modified high-nickel ternary cathode material. This application utilizes tellurium source doping in the bulk phase to refine the grains, followed by wet surface coating with potassium tellurite and / or sodium tellurite to form an ordered Te-Ni-Ni-Te superstructure in the cathode material. This suppresses the thermodynamically irreversible phase transition and improves the material's stability, thereby enhancing its specific capacity, first-efficiency performance, and cycle life. Simultaneously, by introducing low-valence elements through divalent metal compounds during the first calcination, the lithium-nickel mixing caused by tellurium introduction is mitigated, further synergistically improving the electrochemical performance of the cathode material with the tellurium source. The wet coating with potassium tellurite and / or sodium tellurite not only provides tellurium (including the formed nano-lithium tellurite), sodium, and / or... The surface coating of potassium or sodium ions, along with wet coating, promotes shallow doping of sodium and / or potassium ions at the interface between the coating layer and the cathode material. After penetrating into the shallow layer, sodium and potassium ions occupy some lithium ion sites. Since the ionic radii of sodium and potassium ions are larger than those of lithium ions, this increases the interlayer spacing of the cathode material, improving lithium ion throughput and thus enhancing the specific capacity, initial efficiency, and cycle performance of the cathode material. The uniform and smooth coating layer formed by wet coating effectively isolates the electrolyte, preventing its influence on the cathode material and significantly improving its structural stability, thereby enhancing its initial efficiency and cycle performance. This application, through a specific preparation method and the synergistic effect of each step, yields a modified high-nickel ternary cathode material with excellent specific capacity, initial efficiency, and cycle performance.

[0040] 2. The method for preparing the modified high-nickel ternary cathode material provided in this application preferably uses potassium tellurite and sodium tellurite as tellurates. This application achieves sodium and potassium ion doping on the surface by simultaneously wet-coating potassium tellurite and sodium tellurite, occupying lithium ion sites. While the radius of sodium ions is smaller than that of potassium ions, both are larger than the radius of lithium ions. The synergistic effect of potassium and sodium ions on the surface increases the interlayer spacing of the crystal, generating abundant lattice defects, broadening the Li transport path, and improving the Li diffusion coefficient. Simultaneously, lithium tellurite forms in situ on the surface, promoting the transport and migration of lithium ions and, consequently, electrons. The coating effect of nano-lithium tellurite also helps to improve the interfacial stability between the electrode material and the electrolyte, reducing the corrosion of the active material by the electrolyte. The synergistic coating of potassium tellurite and sodium tellurite further enhances the structural stability of the cathode material, resulting in a modified high-nickel ternary cathode material with higher specific capacity, first-time efficiency, and cycle performance. Detailed Implementation

[0041] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0042] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0043] Example 1

[0044] This embodiment provides a method for preparing a modified high-nickel ternary cathode material, including the following steps:

[0045] (1) Ni 0.92 Co 0.05 Mn 0.03 (OH)₂ ternary precursor, lithium hydroxide, tellurium dioxide and cobalt hydroxide according to Ni 0.92 Co 0.05 Mn 0.03 The ratio of the total molar amounts of nickel, cobalt, and manganese in the (OH)2 ternary precursor, the molar amounts of lithium in lithium hydroxide, the molar amounts of tellurium in tellurium dioxide, and the molar amounts of cobalt in cobalt(OH)2 ternary precursor is 1.04:0.999:0.0008:0.0002. The mixture is then mixed in a high-speed mixer, placed in a muffle furnace, and calcined at 780°C for 10 hours in an oxygen atmosphere. After pulverization and sieving, a calcined product is obtained.

[0046] (2) Dissolve potassium tellurite in ethanol to form a potassium tellurite ethanol solution with a tellurium element mass concentration of 0.05wt%. The potassium tellurite ethanol solution is then mixed with the first calcined product obtained in step (1) at a mass ratio of 1:2. The mixture is placed in a ball mill and ball-milled at a speed of 400rpm for 0.5h. Then it is dried and calcined at 650℃ in an oxygen atmosphere for 10h to obtain the second calcined product.

[0047] (3) The calcined product obtained in step (2) is mixed with water at a mass ratio of 1:0.5 and washed. After washing, it is dried to obtain the washed calcined product. Then, 700g of the washed calcined product and 4g of boric acid are mixed in a high-speed mixer and calcined at 300℃ for 6h to obtain the modified high-nickel ternary cathode material.

[0048] Example 2

[0049] This embodiment provides a method for preparing a modified high-nickel ternary cathode material, including the following steps:

[0050] (1) Ni 0.92 Co 0.05 Mn 0.03 (OH)₂ ternary precursor, lithium hydroxide, tellurium dioxide and cobalt hydroxide according to Ni 0.92 Co 0.05 Mn 0.03 The ratio of the total molar amounts of nickel, cobalt, and manganese in the (OH)2 ternary precursor, the molar amounts of lithium in lithium hydroxide, the molar amounts of tellurium in tellurium dioxide, and the molar amounts of cobalt in cobalt(OH)2 ternary precursor is 1.04:0.999:0.0008:0.0002. The mixture is then mixed in a high-speed mixer, placed in a muffle furnace, and calcined at 780°C for 10 hours in an oxygen atmosphere. After pulverization and sieving, a calcined product is obtained.

[0051] (2) Dissolve potassium tellurite in ethanol to form a potassium tellurite ethanol solution with a tellurium element mass concentration of 0.01wt%. The potassium tellurite ethanol solution is then mixed with the first calcined product obtained in step (1) at a mass ratio of 1.5:2. The mixture is placed in a ball mill and ball-milled at 400 rpm for 0.5 h. After drying, it is calcined at 650 °C in an oxygen atmosphere for 10 h to obtain the second calcined product.

[0052] (3) The calcined product obtained in step (2) is mixed with water at a mass ratio of 1:0.5 and washed. After washing, it is dried to obtain the washed calcined product. Then, 700g of the washed calcined product and 4g of boric acid are mixed in a high-speed mixer and calcined at 300℃ for 6h to obtain the modified high-nickel ternary cathode material.

[0053] Example 3

[0054] This embodiment provides a method for preparing a modified high-nickel ternary cathode material, including the following steps:

[0055] (1) Ni 0.92 Co 0.05 Mn 0.03 (OH)₂ ternary precursor, lithium hydroxide, tellurium dioxide and cobalt hydroxide according to Ni 0.92 Co 0.05 Mn 0.03 The ratio of the total molar amounts of nickel, cobalt, and manganese in the (OH)2 ternary precursor, the molar amounts of lithium in lithium hydroxide, the molar amounts of tellurium in tellurium dioxide, and the molar amounts of cobalt in cobalt(OH)2 ternary precursor is 1.04:0.999:0.0008:0.0002. The mixture is then mixed in a high-speed mixer, placed in a muffle furnace, and calcined at 780°C for 10 hours in an oxygen atmosphere. After pulverization and sieving, a calcined product is obtained.

[0056] (2) Sodium tellurite is dissolved in ethanol to form a sodium tellurite ethanol solution with a tellurium element mass concentration of 0.05wt%. The sodium tellurite ethanol solution is then mixed with the first calcined product obtained in step (1) at a mass ratio of 1:2. The mixture is placed in a ball mill and ball-milled at 400rpm for 0.5h. Then it is dried and calcined at 650℃ in an oxygen atmosphere for 10h to obtain the second calcined product.

[0057] (3) The calcined product obtained in step (2) is mixed with water at a mass ratio of 1:0.5 and washed. After washing, it is dried to obtain the washed calcined product. Then, 700g of the washed calcined product and 4g of boric acid are mixed in a high-speed mixer and calcined at 300℃ for 6h to obtain the modified high-nickel ternary cathode material.

[0058] Example 4

[0059] This embodiment provides a method for preparing a modified high-nickel ternary cathode material, including the following steps:

[0060] (1) Ni 0.92 Co 0.05 Mn 0.03 (OH)₂ ternary precursor, lithium hydroxide, tellurium dioxide and cobalt hydroxide according to Ni 0.92 Co 0.05 Mn 0.03 The ratio of the total molar amounts of nickel, cobalt, and manganese in the (OH)2 ternary precursor, the molar amounts of lithium in lithium hydroxide, the molar amounts of tellurium in tellurium dioxide, and the molar amounts of cobalt in cobalt(OH)2 ternary precursor is 1.04:0.999:0.0008:0.0002. The mixture is then mixed in a high-speed mixer, placed in a muffle furnace, and calcined at 780°C for 10 hours in an oxygen atmosphere. After pulverization and sieving, a calcined product is obtained.

[0061] (2) Dissolve potassium tellurite in ethanol to form a potassium tellurite ethanol solution with a tellurium element mass concentration of 0.05wt%. Dissolve sodium tellurite in ethanol to form a sodium tellurite ethanol solution with a tellurium element mass concentration of 0.05wt%. Mix the potassium tellurite ethanol solution, sodium tellurite ethanol solution and the first calcined product obtained in step (1) in a mass ratio of 0.5:0.5:2, place them in a ball mill, ball mill at 400 rpm for 0.5 h, then dry them, and then calcine them at 650℃ in an oxygen atmosphere for 10 h to obtain the second calcined product.

[0062] (3) The calcined product obtained in step (2) is mixed with water at a mass ratio of 1:0.5 and washed. After washing, it is dried to obtain the washed calcined product. Then, 700g of the washed calcined product and 4g of boric acid are mixed in a high-speed mixer and calcined at 300℃ for 6h to obtain the modified high-nickel ternary cathode material.

[0063] Example 5

[0064] This embodiment provides a method for preparing a modified high-nickel ternary cathode material, including the following steps:

[0065] (1) Ni 0.92 Co 0.05 Mn 0.03 (OH)₂ ternary precursor, lithium hydroxide, tellurium dioxide and cobalt hydroxide according to Ni 0.92 Co 0.05 Mn 0.03 The ratio of the total molar amounts of nickel, cobalt, and manganese in the (OH)2 ternary precursor, the molar amounts of lithium in lithium hydroxide, the molar amounts of tellurium in tellurium dioxide, and the molar amounts of cobalt in cobalt(OH)2 ternary precursor is 1.04:0.999:0.0008:0.0002. The mixture is mixed in a high-speed mixer, placed in a muffle furnace, and calcined at 850°C for 8 hours in an oxygen atmosphere. After pulverization and sieving, a calcined product is obtained.

[0066] (2) Dissolve potassium tellurite in ethanol to form a potassium tellurite ethanol solution with a tellurium element mass concentration of 0.03wt%. The potassium tellurite ethanol solution is then mixed with the first calcined product obtained in step (1) at a mass ratio of 1.8:2. The mixture is placed in a ball mill and ball-milled at 400 rpm for 0.5 h. After drying, it is calcined at 500 °C in an oxygen atmosphere for 12 h to obtain the second calcined product.

[0067] (3) The calcined product obtained in step (2) is mixed with water at a mass ratio of 1:0.5 and washed. After washing, it is dried to obtain the washed calcined product. Then, 700g of the washed calcined product and 3g of boric acid are mixed in a high-speed mixer and calcined at 200℃ for 10h to obtain the modified high-nickel ternary cathode material.

[0068] Example 6

[0069] This embodiment provides a method for preparing a modified high-nickel ternary cathode material, including the following steps:

[0070] (1) Ni 0.92 Co 0.05 Mn 0.03 (OH)₂ ternary precursor, lithium carbonate, tellurium dioxide and cobalt hydroxide according to Ni 0.92 Co 0.05 Mn 0.03The ratio of the total molar amounts of nickel, cobalt, and manganese in the (OH)2 ternary precursor, the molar amounts of lithium in lithium carbonate, the molar amounts of tellurium in tellurium dioxide, and the molar amounts of cobalt in cobalt hydroxide is 1.04:0.998:0.001:0.001. The mixture is mixed in a high-speed mixer, placed in a muffle furnace, and calcined at 700°C for 16 hours in an oxygen atmosphere. After pulverization and sieving, a calcined product is obtained.

[0071] (2) Dissolve potassium tellurite in ethanol to form a potassium tellurite ethanol solution with a tellurium element mass concentration of 0.1wt%. The potassium tellurite ethanol solution is then mixed with the first calcined product obtained in step (1) at a mass ratio of 1:2. The mixture is placed in a ball mill and ball-milled at 400 rpm for 0.5 h. After drying, it is calcined at 700 °C in an oxygen atmosphere for 6 h to obtain the second calcined product.

[0072] (3) The calcined product obtained in step (2) is mixed with water at a mass ratio of 1:1.0 and washed. After washing, it is dried to obtain the washed calcined product. Then, 700g of the washed calcined product and 5g of boric acid are mixed in a high-speed mixer and calcined at 400℃ for 6h to obtain the modified high-nickel ternary cathode material.

[0073] Comparative Example 1

[0074] This comparative example provides a method for preparing a modified high-nickel ternary cathode material, including the following steps:

[0075] (1) Ni 0.92 Co 0.05 Mn 0.03 (OH)₂ ternary precursor, lithium hydroxide, tellurium dioxide and cobalt hydroxide according to Ni 0.92 Co 0.05 Mn 0.03 The ratio of the total molar amounts of nickel, cobalt, and manganese in the (OH)2 ternary precursor, the molar amounts of lithium in lithium hydroxide, the molar amounts of tellurium in tellurium dioxide, and the molar amounts of cobalt in cobalt(OH)2 ternary precursor is 1.04:0.999:0.0008:0.0002. The mixture is then mixed in a high-speed mixer, placed in a muffle furnace, and calcined at 780°C for 10 hours in an oxygen atmosphere. After pulverization and sieving, a calcined product is obtained.

[0076] (2) Dissolve telluric acid in ethanol to form a telluric acid ethanol solution with a telluric acid element mass concentration of 0.05wt%. The telluric acid ethanol solution is then mixed with the first calcined product obtained in step (1) at a mass ratio of 1:2. The mixture is placed in a ball mill and ball-milled at 400rpm for 0.5h. Then it is dried and calcined at 650℃ in an oxygen atmosphere for 10h to obtain the second calcined product.

[0077] (3) The calcined product obtained in step (2) is mixed with water at a mass ratio of 1:0.5 and washed. After washing, it is dried to obtain the washed calcined product. Then, 700g of the washed calcined product and 4g of boric acid are mixed in a high-speed mixer and calcined at 300℃ for 6h to obtain the modified high-nickel ternary cathode material.

[0078] Comparative Example 2

[0079] This comparative example provides a method for preparing a modified high-nickel ternary cathode material, including the following steps:

[0080] (1) Ni 0.92 Co 0.05 Mn 0.03 (OH)₂ ternary precursor, lithium hydroxide, tellurium dioxide and cobalt hydroxide according to Ni 0.92 Co 0.05 Mn 0.03 The ratio of the total molar amounts of nickel, cobalt, and manganese in the (OH)2 ternary precursor, the molar amounts of lithium in lithium hydroxide, the molar amounts of tellurium in tellurium dioxide, and the molar amounts of cobalt in cobalt(OH)2 ternary precursor is 1.04:0.999:0.0008:0.0002. The mixture is then mixed in a high-speed mixer, placed in a muffle furnace, and calcined at 780°C for 10 hours in an oxygen atmosphere. After pulverization and sieving, a calcined product is obtained.

[0081] (2) The first calcined product obtained in step (1) is placed in a ball mill and ball milled at 400 rpm for 0.5 h, and then calcined at 650 °C in an oxygen atmosphere for 10 h to obtain the second calcined product.

[0082] (3) The calcined product obtained in step (2) is mixed with water at a mass ratio of 1:0.5 and washed. After washing, it is dried to obtain the washed calcined product. Then, 700g of the washed calcined product and 4g of boric acid are mixed in a high-speed mixer and calcined at 300℃ for 6h to obtain the modified high-nickel ternary cathode material.

[0083] Comparative Example 3

[0084] This comparative example provides a method for preparing a modified high-nickel ternary cathode material, including the following steps:

[0085] (1) Ni 0.92 Co 0.05 Mn 0.03 (OH)₂ ternary precursor, lithium hydroxide, tellurium dioxide and cobalt hydroxide according to Ni 0.92 Co 0.05 Mn 0.03The ratio of the total molar amounts of nickel, cobalt, and manganese in the (OH)2 ternary precursor, the molar amounts of lithium in lithium hydroxide, the molar amounts of tellurium in tellurium dioxide, and the molar amounts of cobalt in cobalt(OH)2 ternary precursor is 1.04:0.999:0.0008:0.0002. The mixture is then mixed in a high-speed mixer, placed in a muffle furnace, and calcined at 780°C for 10 hours in an oxygen atmosphere. After pulverization and sieving, a calcined product is obtained.

[0086] (2) Potassium tellurite is mixed with the calcined product obtained in step (1), placed in a ball mill, and ball-milled at 400 rpm for 0.5 h. The mass ratio of tellurium element in potassium tellurite to the mass of the calcined product is 0.05:2. The product is then calcined at 650 °C in an oxygen atmosphere for 10 h to obtain the calcined product.

[0087] (3) The calcined product obtained in step (2) is mixed with water at a mass ratio of 1:0.5 and washed. After washing, it is dried to obtain the washed calcined product. Then, 700g of the washed calcined product and 4g of boric acid are mixed in a high-speed mixer and calcined at 300℃ for 6h to obtain the modified high-nickel ternary cathode material.

[0088] Comparative Example 4

[0089] This comparative example provides a method for preparing a modified high-nickel ternary cathode material, including the following steps:

[0090] (1) Ni 0.92 Co 0.05 Mn 0.03 (OH)₂ ternary precursor, lithium hydroxide and tellurium dioxide according to Ni 0.92 Co 0.05 Mn 0.03 The ratio of the total molar amounts of nickel, cobalt, and manganese in the (OH)2 ternary precursor, the molar amounts of lithium in lithium hydroxide, and the molar amounts of tellurium in tellurium dioxide is 1.04:0.999:0.001. The mixture is prepared in a high-speed mixer, placed in a muffle furnace, and calcined at 780°C for 10 hours in an oxygen atmosphere. After pulverization and sieving, a calcined product is obtained.

[0091] (2) Dissolve potassium tellurite in ethanol to form a potassium tellurite ethanol solution with a tellurium element mass concentration of 0.05wt%. The potassium tellurite ethanol solution is then mixed with the first calcined product obtained in step (1) at a mass ratio of 1:2. The mixture is placed in a ball mill and ball-milled at 400 rpm for 0.5 h. Then it is dried and calcined at 650 °C in an oxygen atmosphere for 10 h to obtain the second calcined product.

[0092] (3) The calcined product obtained in step (2) is mixed with water at a mass ratio of 1:0.5 and washed. After washing, it is dried to obtain the washed calcined product. Then, 700g of the washed calcined product and 4g of boric acid are mixed in a high-speed mixer and calcined at 300℃ for 6h to obtain the modified high-nickel ternary cathode material.

[0093] Test case

[0094] The modified high-nickel ternary cathode materials prepared in Examples 1-6 and Comparative Examples 1-4 were used as the main materials for preparing cathode sheets, and then lithium-ion batteries were assembled. The specific steps were as follows: Cathode sheets were prepared by mixing the main material, carbon black, polyvinylidene fluoride (PVDF), and dispersant at a mass ratio of 90:5:5:100 using N-methylpyrrolidone as a dispersant to obtain a cathode slurry. The cathode slurry was then uniformly coated onto carbon-coated aluminum foil with a coating density of 12 cm³. 2 / mg, dried in an oven at 80℃ for 2h to obtain the positive electrode; in an argon atmosphere in a glove box, using a Celgard 2500 type separator, lithium metal sheet as the negative electrode, and a 1mol / L lithium hexafluorophosphate (LiPF6) ethylene carbonate (EC) / dimethyl carbonate (DMC) solution, with a volume ratio of ethylene carbonate (EC) / dimethyl carbonate (DMC) of 1:1; CR2032 type button half cell was assembled in the order of negative electrode, electrolyte, separator, electrolyte and positive electrode.

[0095] Using the Blue Electric system, at 25℃, the voltage was charged to 4.25V at a rate of 0.2C, and then discharged to 2.5V at a rate of 0.2C. This constitutes one cycle. The charge / discharge capacity of this cycle is the initial charge / discharge specific capacity. The value of the first cycle is the ratio of the discharge specific capacity to the charge specific capacity multiplied by 100%. After two cycles, the voltage was charged at 1C and discharged at 1C for 50 cycles. The charge / discharge capacity of the third cycle and the charge / discharge capacity of the 52nd cycle were recorded. The cycle capacity retention rate is the ratio of the discharge capacity of the 52nd cycle to that of the third cycle multiplied by 100%. The test results are shown in Table 1.

[0096] Table 1

[0097] As shown in Table 1, the modified high-nickel ternary cathode material prepared by the method of this application has significantly better specific capacity, first-efficiency, and cycle performance than the comparative example. In particular, the modified high-nickel ternary cathode material obtained by the synergistic coating of potassium tellurite and sodium tellurite in Example 3 has even better specific capacity, first-efficiency, and cycle performance.

[0098] 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 application.

Claims

1. A method for preparing a modified high-nickel ternary cathode material, comprising the following steps: (1) A lithium source, a precursor, a tellurium source and a divalent metal compound are mixed and calcined for the first time to obtain a calcined product; (2) Dissolve the tellurate in an organic solvent, and then mix and grind the resulting tellurate organic solvent solution with the first calcined product obtained in step 1), and then calcine it a second time to obtain the second calcined product; The tellurite is selected from at least one of potassium tellurite or sodium tellurite. (3) The calcined product obtained in step (2) is washed with water and mixed with boric acid, and then calcined for the third time to obtain the modified high-nickel ternary cathode material.

2. The method for preparing the modified high-nickel ternary cathode material according to claim 1, wherein, The divalent metal compound mentioned in step (1) is selected from at least one of cobalt hydroxide, strontium carbonate, magnesium oxide, or calcium oxide; The tellurite is potassium tellurite and sodium tellurite; The molar amount of nickel in the precursor accounts for more than 90% of the total molar amount of metal elements in the precursor. The lithium source is selected from at least one of lithium hydroxide or lithium carbonate; The tellurium source mentioned in step (1) is selected from tellurium dioxide.

3. The method for preparing the modified high-nickel ternary cathode material according to claim 1 or 2, wherein, The general chemical formula of the precursor mentioned in step (1) is NixCoyMnzO2, and 0.9≤x≤0.99, 0.01≤y≤0.09, 0.01≤z≤0.09, x+y+z=1; The ratio of the total molar amount of metal elements in the precursor, the molar amount of tellurium in the tellurium source, and the molar amount of divalent metal elements in the divalent metal compound in step (1) is (0.975-1):(0.0001-0.015):(0.0001-0.01). The sum of the total molar amount of metal elements in the precursor, the molar amount of tellurium in the tellurium source, and the molar amount of divalent metal elements in the divalent metal compound mentioned in step (1) is denoted as a, and the molar amount of lithium in the lithium source is denoted as b, where b:a is (1.01-1.06):

1.

4. The method for preparing the modified high-nickel ternary cathode material according to any one of claims 1-3, wherein, In step (1), the first calcination temperature is 700-850℃ and the first calcination time is 8-16h; In step (1), the calcination atmosphere of the first calcination includes an oxygen-containing atmosphere.

5. The method for preparing the modified high-nickel ternary cathode material according to any one of claims 1-4, wherein, The organic solvent mentioned in step (2) is selected from ethanol; In step (2), the tellurate is dissolved in an organic solvent, and the mass concentration of tellurium in the resulting tellurate organic solvent solution is 0.01-0.1 wt%. The mass ratio of the tellurate organic solvent solution in step (2) to the calcined product obtained in step (1) is (1-2):

2.

6. The method for preparing the modified high-nickel ternary cathode material according to any one of claims 1-5, wherein, The grinding speed is 300-600 rpm, and the grinding time is 0.5-1 h; Optionally, the grinding includes ball milling; The second calcination temperature is 500-700℃, and the second calcination time is 6-12h; The second calcination atmosphere includes an oxygen-containing atmosphere.

7. The method for preparing the modified high-nickel ternary cathode material according to any one of claims 1-6, wherein, The calcined product described in step (3) is mixed with water and washed. After washing, it is dried to obtain the washed calcined product, which is then mixed with boric acid and calcined a third time to obtain the modified high-nickel ternary cathode material.

8. The method for preparing the modified high-nickel ternary cathode material according to claim 7, wherein, The mass ratio of the distilled product to water is 1:(0.5-1.0); The mass ratio of the water-washed dicalcined product to boric acid is 700:(2-10); The third calcination temperature is 200-400℃, and the third calcination time is 5-11h.

9. A modified high-nickel ternary cathode material, which is prepared by the preparation method of the modified high-nickel ternary cathode material according to any one of claims 1-8.

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

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