Modified single-crystal ternary positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a modified single-crystal ternary positive electrode material as well as a preparation method and application thereof. The modified single crystal ternary positive electrode material comprises an inner core, a coating layer 1 and a coating layer 2 which are laminated in sequence, the general formula of the inner core is LixNiaCobMncLpO2 + q, x is more than or equal to 1.00 and less than or equal to 1.20, a is more than or equal to 0.10 and less than or equal to 0.60, b is more than or equal to 0.10 and less than or equal to 0.30, c is more than or equal to 0.10 and less than or equal to 0.30, p is more than or equal to 0.0001 and less than or equal to 0.03, q is more than or equal to 0 and less than or equal to 0.03, and L comprises at least one of Mg, Al, Ti, Zr, Y and Sb; the coating layer 1 comprises a fast ion conductor; and the coating layer 2 comprises a conductive polymer. According to the modified single crystal ternary positive electrode material provided by the invention, the rate capability and the cycle life are both considered while the high capacity is maintained.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a modified single-crystal ternary cathode material, its preparation method, and its application. Background Technology

[0002] In recent years, with the continuous increase in demand for extended driving range from mobile terminals, electric vehicles, and energy storage systems, the energy density of lithium-ion batteries has become a core bottleneck restricting their further application. Single-crystal nickel-cobalt-manganese ternary cathode materials are considered an effective way to achieve high energy density due to their high compaction density and excellent mechanical strength. Existing methods to improve energy density include increasing the charging cutoff voltage; however, under high voltage, single-crystal nickel-cobalt-manganese ternary cathode materials face problems such as bulk structure degradation, high surface residual alkali content, severe interfacial side reactions, and decreased lithium-ion migration rate, leading to a significant decrease in battery cycle life and rate performance, making it difficult to meet practical application requirements. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defect that existing modified single-crystal ternary cathode materials cannot take into account rate performance and cycle life while maintaining high capacity, thereby providing a modified single-crystal ternary cathode material, its preparation method and application.

[0004] Therefore, the present invention provides the following technical solution: The first aspect of this invention protects a modified single-crystal ternary cathode material, wherein the modified single-crystal ternary cathode material comprises a core, a coating layer 1 and a coating layer 2 sequentially bonded together; The general formula for the kernel is Li x Ni a Co b Mn c L p O 2+q Wherein, 1.00≤x≤1.20, 0.10≤a≤0.60, 0.10≤b≤0.30, 0.10≤c≤0.30, 0.0001≤p≤0.03, 0≤q≤0.03, and L includes at least one of Mg, Al, Ti, Zr, Y, and Sb; The coating layer 1 includes a fast ion conductor; The coating layer 2 comprises a conductive polymer.

[0005] In one alternative implementation, the kernel's general formula is Li. x Ni a Co b Mn c L p O2, where 0.0001≤p≤0.001, and L includes Zr, Y and Sb.

[0006] In this invention, when L is simultaneously Zr, Y, and Sb, Zr possesses strong Zr-O bonds, which can effectively stabilize the crystal structure, suppress harmful phase transitions, and reduce cation mixing; Y, due to its larger ionic radius, can moderately enlarge the lithium interlayer spacing, promoting Li... + Diffusion enhances lattice oxygen stability; Sb improves intrinsic electronic conductivity by regulating the electronic structure and forms a protective passivation layer on the surface to inhibit electrolyte oxidation and corrosion. The synergistic effect of these three factors maintains high capacity while also improving rate performance and cycle stability.

[0007] In one optional embodiment, the fast ion conductor comprises at least one of lithium titanate, lithium lanthanum zirconium oxide, and lithium aluminum titanium phosphate, with lithium titanate being an option.

[0008] In one alternative embodiment, the conductive polymer comprises polypyrrole and / or polythiophene, optionally polypyrrole.

[0009] A second aspect of this invention protects a method for preparing the aforementioned modified single-crystal ternary cathode material, wherein the preparation method includes the following steps: (1) The lithium source, precursor, dopant source and molten salt are mixed and sintered for the first time to obtain a sintered product; (2) A coating layer 1 is prepared on the surface of a calcined product to obtain an intermediate product; (3) Prepare a coating layer 2 on the surface of the intermediate product and perform a second sintering to obtain a modified single-crystal ternary cathode material.

[0010] In this invention, the lithium source is a conventional lithium source in the art, typically and non-limitingly including lithium carbonate and / or lithium hydroxide; the precursor is a conventional ternary cathode material precursor in the art, which can be prepared by co-precipitation or purchased directly, typically and non-limitingly, the chemical formula of the ternary cathode precursor is LiNi. 0.6 Co 0.1 Mn 0.3 (OH)2 was purchased from GEM Co., Ltd.

[0011] In one alternative implementation, in step (1), the mass ratio of the precursor to the molten salt is (3-10):1.

[0012] In this invention, the molten salt is a conventional molten salt in the art, typically and non-limitingly including LiCl and KCl in a molar ratio of 1:1-3.

[0013] In one optional embodiment, the first sintering conditions include: heating to 850-900℃ at a rate of 1-5℃ / min and holding at that temperature for 8-12 hours.

[0014] In this invention, the first sintering is carried out in an oxygen environment or an air environment.

[0015] In this invention, after obtaining a calcined product, washing, filtering, and drying steps are also performed.

[0016] In an alternative embodiment, in step (2), the coating layer 1 is prepared using atomic layer deposition (ALD).

[0017] In this invention, the raw materials used in the atomic layer deposition method are determined according to the target fast ion conductor, and the types of fast ion conductors have been limited in the first aspect of this invention, and will not be repeated here.

[0018] In one optional embodiment, the conditions for the atomic layer deposition method include: a deposition temperature of 150-180°C and a cycle number of 50-100 times.

[0019] In one optional embodiment, the conditions for the atomic layer deposition method include: a deposition temperature of 170-180°C and a cycle number of 60-80 times.

[0020] In an optional embodiment, step (3) of preparing the coating layer 2 includes the following steps: mixing the intermediate product, the conductive polymer monomer, the solvent and the oxidant, and carrying out a polymerization reaction to obtain the coating layer 2.

[0021] In one optional embodiment, the mass ratio of the intermediate product to the conductive polymer monomer is 100:(1-5), or optionally 100:(3-5).

[0022] In one optional embodiment, the mass ratio of the intermediate product to the oxidant is 100:(1-5), optionally 100:(3-5).

[0023] In this invention, the oxidant is a conventional oxidant in the art, typically and non-limitingly, it can be an inorganic oxidant, such as FeCl3 and / or CuCl2, and further preferably FeCl3.

[0024] In one optional embodiment, the volume ratio of the conductive polymer monomer to the solvent is 1:(10-40).

[0025] In this invention, the solvent is a conventional solvent in the art, typically and non-limitingly including water and / or ethanol.

[0026] In one optional embodiment, the conditions for the second sintering include: heating to 180-300°C at a rate of 1-5°C / min and holding at that temperature for 1-5 hours.

[0027] In this invention, the second sintering is carried out under a nitrogen or inert gas protective environment, which may be argon.

[0028] In one optional embodiment, the conditions for the second sintering include: holding at 200-250°C for 2-4 hours at a rate of 1-3°C / min.

[0029] A third aspect of this invention protects a secondary battery, wherein the secondary battery comprises the aforementioned modified single-crystal ternary cathode material or the modified single-crystal ternary cathode material prepared by the aforementioned preparation method.

[0030] The technical solution of this invention has the following advantages: 1. This invention provides a modified single-crystal ternary cathode material, wherein the modified single-crystal ternary cathode material comprises a core, a coating layer 1, and a coating layer 2 sequentially bonded together; the core has the general formula Li. x Ni a Co b Mn c L p O 2+q Wherein, 1.00≤x≤1.20, 0.10≤a≤0.60, 0.10≤b≤0.30, 0.10≤c≤0.30, 0.0001≤p≤0.03, 0≤q≤0.03, and L includes at least one of Mg, Al, Ti, Zr, Y, and Sb; the coating layer 1 includes a fast ion conductor; the coating layer 2 includes a conductive polymer; wherein, the L doping element can strengthen the lattice oxygen framework, suppress cation mixing, and widen the lithium layer spacing, thereby delaying the phase transition of the material under high voltage; The fast ion conductor of coating layer 1 constructs a low-impedance lithium-ion transport channel, effectively alleviating interfacial lithium depletion and inhibiting electrolyte decomposition; the conductive polymer of coating layer 2 forms a continuous electronic conductive network, reducing interfacial contact resistance, improving rate performance, and physically isolating the active material from the electrolyte, reducing side reactions; it can also prevent cracking of the fast ion conductor layer, ensuring interfacial stability and further extending cycle life; the synergistic effect of the three enables the modified single-crystal ternary cathode material of the present invention to maintain high capacity while taking into account rate performance and cycle life.

[0031] 2. This invention provides a method for preparing a modified single-crystal ternary cathode material, wherein the preparation method includes the following steps: (1) mixing a lithium source, a precursor, a dopant source, and a molten salt, and performing a first sintering to obtain a sintered product; (2) preparing a coating layer 1 on the surface of the sintered product to obtain an intermediate product; (3) preparing a coating layer 2 on the surface of the intermediate product, and performing a second sintering to obtain a modified single-crystal ternary cathode material. In the preparation method of this invention, step (1) uses molten salt to assist the first sintering, which achieves doping uniformity and single-crystal integrity; step (2) forms a uniform, dense, and thickness-controllable fast-ion conductor coating layer on the single-crystal surface; step (3) prepares a conductive polymer coating layer on the outer layer of the fast-ion conductor through an in-situ preparation method; so that the prepared modified single-crystal ternary cathode material maintains high capacity while taking into account rate performance and cycle life.

[0032] 3. In the atomic layer deposition method of this invention, a specific temperature ensures sufficient precursor reaction and coating layer density while avoiding excessive thermal stress that could damage the single-crystal core structure. A specific number of cycles ensures a coating layer thickness sufficient to cover surface defects and block side reactions without excessively hindering lithium-ion diffusion paths. This achieves an optimal balance between interface stability and ionic conductivity, enabling the prepared modified single-crystal ternary cathode material to maintain high capacity while further improving rate performance and cycle life.

[0033] 4. The specific conditions of the second sintering in this invention enhance the interfacial bonding between the conductive polymer and the fast ion conductor, while avoiding carbonization or decomposition of the conductive polymer due to high temperature. This ensures the electronic conductivity and electrochemical stability of the conductive polymer, enabling the prepared modified single-crystal ternary cathode material to further improve rate performance and cycle life while maintaining high capacity. Detailed Implementation

[0034] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having” and any variations thereof in the text of this application are intended to cover non-exclusive inclusion.

[0036] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0037] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0038] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0040] In the description of the embodiments of this application, the term "at least one" refers to one or more (including two).

[0041] 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.

[0042] The chemical formula of the ternary cathode precursor is LiNi 0.6 Co 0.1 Mn 0.3 (OH)2 was purchased from GEM Co., Ltd.

[0043] Example 1 This embodiment provides a modified single-crystal ternary cathode material, the preparation method of which includes the following steps: (1) Lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3, Sb2O3 and molten salt system (LiCl-KCl) are mixed to obtain a mixture; lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3 and Sb2O3 are added according to the stoichiometric ratio of the target product, the mass ratio of ternary cathode precursor to molten salt system is 3:1, and the molar ratio of LiCl and KCl in molten salt system is 1:1; under oxygen environment, the mixture is heated to 850℃ at a rate of 3℃ / min and kept at 850℃ for 8h, cooled, washed, filtered and dried to obtain a calcined product; (2) TiCl4 and LiOC(CH3)3 were mixed, and the molar ratio of Ti:Li was 1:2 based on elemental composition. Atomic layer deposition was performed at a deposition temperature of 180℃ and 60 cycles to deposit a Li2TiO3 layer on the surface of a calcined product to obtain an intermediate product. (3) The intermediate product was dispersed in an ethanol solution containing pyrrole monomer, and FeCl3 was added as an oxidant. The mass ratio of intermediate product:pyrrole monomer:FeCl3 was 100:3:4, and the volume ratio of pyrrole monomer to ethanol was 1:15. The reaction was stirred at room temperature for 12 h. The polypyrrole layer formed was heated to 200 °C at a rate of 2 °C / min and held for 3 h under argon atmosphere to obtain a modified single-crystal ternary cathode material with LiNi as the core. 0.6 Co 0.1 Mn 0.3 Zr 0.0002 Y 0.0001 Sb 0.0001 O 2.0004 .

[0044] Example 2 This embodiment provides a modified single-crystal ternary cathode material, the preparation method of which includes the following steps: (1) Lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3, Sb2O3 and molten salt system (LiCl-KCl) are mixed to obtain a mixture; lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3 and Sb2O3 are added according to the stoichiometric ratio of the target product, the mass ratio of ternary cathode precursor to molten salt system is 3:1, and the molar ratio of LiCl and KCl in molten salt system is 1:1; under oxygen environment, the mixture is heated to 850℃ at a rate of 3℃ / min and kept at 850℃ for 8h, cooled, washed, filtered and dried to obtain a calcined product; (2) TiCl4 and LiOC(CH3)3 were mixed, and the molar ratio of Ti:Li was 1:2 based on elemental composition. Atomic layer deposition (ALD) was used at a deposition temperature of 180℃ and 60 cycles to deposit a Li2TiO3 layer on the surface of a calcined product to obtain an intermediate product. (3) The intermediate product was dispersed in an ethanol solution containing pyrrole monomer, and FeCl3 was added as an oxidant. The mass ratio of intermediate product:pyrrole monomer:FeCl3 was 100:3:4, and the volume ratio of pyrrole monomer to ethanol was 1:15. The reaction was stirred at room temperature for 12 h. The polypyrrole (PPy) layer formed was heated to 200 °C at a rate of 2 °C / min and held for 3 h under argon atmosphere to obtain a modified single-crystal ternary cathode material with LiNi as the core. 0.6 Co 0.1 Mn 0.3 Zr 0.005 Y 0.005 Sb 0.00 3O 2.013 .

[0045] Example 3 This embodiment provides a modified single-crystal ternary cathode material, the preparation method of which includes the following steps: (1) Lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3, Sb2O3 and molten salt system (LiCl-KCl) are mixed to obtain a mixture; lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3 and Sb2O3 are added according to the stoichiometric ratio of the target product, the mass ratio of ternary cathode precursor to molten salt system is 3:1, and the molar ratio of LiCl and KCl in molten salt system is 1:1; under oxygen environment, the mixture is heated to 850℃ at a rate of 3℃ / min and kept at 850℃ for 8h, cooled, washed, filtered and dried to obtain a calcined product; (2) TiCl4 and LiOC(CH3)3 were mixed, and the molar ratio of Ti:Li was 1:2 based on elemental composition. Atomic layer deposition (ALD) was used at a deposition temperature of 150℃ and 50 cycles to deposit a Li2TiO3 layer on the surface of a calcined product to obtain an intermediate product. (3) The intermediate product was dispersed in an ethanol solution containing pyrrole monomer, and FeCl3 was added as an oxidant. The mass ratio of intermediate product:pyrrole monomer:FeCl3 was 100:3:4, and the volume ratio of pyrrole monomer to ethanol was 1:15. The reaction was stirred at room temperature for 12 h. The polypyrrole (PPy) layer formed was heated to 200 °C at a rate of 2 °C / min and held for 3 h under argon atmosphere to obtain a modified single-crystal ternary cathode material with LiNi as the core. 0.6 Co 0.1 Mn 0.3 Zr 0.0002Y 0.0001 Sb 0.000 1O 2.0004 .

[0046] Example 4 This embodiment provides a modified single-crystal ternary cathode material, the preparation method of which includes the following steps: (1) Lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3, Sb2O3 and molten salt system (LiCl-KCl) are mixed to obtain a mixture; lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3 and Sb2O3 are added according to the stoichiometric ratio of the target product, the mass ratio of ternary cathode precursor to molten salt system is 3:1, and the molar ratio of LiCl and KCl in molten salt system is 1:1; under oxygen environment, the mixture is heated to 850℃ at a rate of 3℃ / min and kept at 850℃ for 8h, cooled, washed, filtered and dried to obtain a calcined product; (2) TiCl4 and LiOC(CH3)3 were mixed, and the molar ratio of Ti:Li was 1:2 based on elemental composition. Atomic layer deposition (ALD) was used at a deposition temperature of 180℃ and 60 cycles to deposit a Li2TiO3 layer on the surface of a calcined product to obtain an intermediate product. (3) The intermediate product was dispersed in an ethanol solution containing pyrrole monomer, and FeCl3 was added as an oxidant. The mass ratio of intermediate product:pyrrole monomer:FeCl3 was 100:1:2, and the volume ratio of pyrrole monomer to ethanol was 1:15. The reaction was stirred at room temperature for 12 h to form a polypyrrole layer. Under argon atmosphere, the coated material was heated to 300℃ at a rate of 4℃ / min and held for 2 h to obtain a modified single-crystal ternary cathode material with LiNi as the core. 0.6 Co 0.1 Mn 0.3 Zr 0.0002 Y 0.0001 Sb 0.0001 O 2.0004 .

[0047] Example 5 This embodiment provides a modified single-crystal ternary cathode material, the preparation method of which includes the following steps: (1) Lithium carbonate, ternary cathode precursor, doping source ZrO2, Y2O3 and molten salt system (LiCl-KCl) are mixed to obtain a mixture; lithium carbonate, ternary cathode precursor, doping source ZrO2, Y2O3 are added according to the stoichiometric ratio of the target product, the mass ratio of ternary cathode precursor to molten salt system is 3:1, and the molar ratio of LiCl and KCl in molten salt system is 1:1; under oxygen environment, the mixture is heated to 850℃ at a rate of 3℃ / min and kept at 850℃ for 8h, cooled, washed, filtered and dried to obtain a calcined product; (2) TiCl4 and LiOC(CH3)3 were mixed, and the molar ratio of Ti:Li was 1:2 based on elemental composition. Atomic layer deposition (ALD) was used at a deposition temperature of 180℃ and 60 cycles to deposit a Li2TiO3 layer on the surface of a calcined product to obtain an intermediate product. (3) The intermediate product was dispersed in an ethanol solution containing pyrrole monomer, and FeCl3 was added as an oxidant. The mass ratio of intermediate product:pyrrole monomer:FeCl3 was 100:3:4, and the volume ratio of pyrrole monomer to ethanol was 1:15. The reaction was stirred at room temperature for 12 h. The polypyrrole (PPy) layer formed was heated to 200 °C at a rate of 2 °C / min and held for 3 h under argon atmosphere to obtain a modified single-crystal ternary cathode material with LiNi as the core. 0.6 Co 0.1 Mn 0.3 Zr 0.01 Y 0.011 O2.

[0048] Example 6 This embodiment provides a modified single-crystal ternary cathode material, the preparation method of which includes the following steps: (1) Lithium carbonate, ternary cathode precursor, doping source ZrO2, Sb2O3 and molten salt system (LiCl-KCl) are mixed to obtain a mixture; lithium carbonate, ternary cathode precursor, doping source ZrO2 and Sb2O3 are added according to the stoichiometric ratio of the target product, the mass ratio of ternary cathode precursor to molten salt system is 3:1, and the molar ratio of LiCl and KCl in molten salt system is 1:1; under oxygen environment, the mixture is heated to 850℃ at a rate of 3℃ / min and kept at 8h, cooled, washed, filtered and dried to obtain a calcined product; (2) TiCl4 and LiOC(CH3)3 were mixed, and the molar ratio of Ti:Li was 1:2 based on elemental composition. Atomic layer deposition (ALD) was used at a deposition temperature of 180℃ and 60 cycles to deposit a Li2TiO3 layer on the surface of a calcined product to obtain an intermediate product. (3) The intermediate product was dispersed in an ethanol solution containing pyrrole monomer, and FeCl3 was added as an oxidant. The mass ratio of intermediate product:pyrrole monomer:FeCl3 was 100:3:4, and the volume ratio of pyrrole monomer to ethanol was 1:15. The reaction was stirred at room temperature for 12 h. The polypyrrole (PPy) layer formed was heated to 200 °C at a rate of 2 °C / min and held for 3 h under argon atmosphere to obtain a modified single-crystal ternary cathode material with LiNi as the core. 0.6 Co 0.1 Mn 0.3 Zr 0.01 Sb 0.0105 O 2.0205 .

[0049] Example 7 This embodiment provides a modified single-crystal ternary cathode material, the preparation method of which includes the following steps: (1) Lithium carbonate, ternary cathode precursor, doping source Y2O3, Sb2O3 and molten salt system (LiCl-KCl) are mixed to obtain a mixture; lithium carbonate, ternary cathode precursor, doping source Y2O3 and Sb2O3 are added according to the stoichiometric ratio of the target product, the mass ratio of ternary cathode precursor to molten salt system is 3:1, and the molar ratio of LiCl and KCl in molten salt system is 1:1; under oxygen environment, the mixture is heated to 850℃ at a rate of 3℃ / min and kept at 8h, cooled, washed, filtered and dried to obtain a calcined product; (2) TiCl4 and LiOC(CH3)3 were mixed, and the molar ratio of Ti:Li was 1:2 based on elemental composition. Atomic layer deposition (ALD) was used at a deposition temperature of 180℃ and 60 cycles to deposit a Li2TiO3 layer on the surface of a calcined product to obtain an intermediate product. (3) The intermediate product was dispersed in an ethanol solution containing pyrrole monomer, and FeCl3 was added as an oxidant. The mass ratio of intermediate product:pyrrole monomer:FeCl3 was 100:3:4, and the volume ratio of pyrrole monomer to ethanol was 1:15. The reaction was stirred at room temperature for 12 h. The polypyrrole (PPy) layer formed was heated to 200 °C at a rate of 2 °C / min and held for 3 h under argon atmosphere to obtain a modified single-crystal ternary cathode material with LiNi as the core. 0.6 Co 0.1 Mn 0.3 Y 0.01 Sb 0.0105 O 2.0105 .

[0050] Comparative Example 1 This comparative example provides a modified single-crystal ternary cathode material, the preparation method of which includes the following steps: (1) Lithium carbonate, ternary cathode precursor and molten salt system (LiCl-KCl) are mixed to obtain a mixture; the mass ratio of lithium carbonate, ternary cathode precursor and molten salt system is 3:1, and the molar ratio of LiCl and KCl in molten salt system is 1:1; under oxygen environment, the mixture is heated to 850℃ at a rate of 3℃ / min and kept at 8h for 8h, then cooled, washed, filtered and dried to obtain a calcined product; (2) As in Example 1; (2) Following the method in Example 1, the modified single-crystal ternary cathode material was finally obtained, with LiNi as the core. 0.6 Co 0.1 Mn 0.3 O2.

[0051] Comparative Example 2 This comparative example provides a modified single-crystal ternary cathode material, the preparation method of which includes the following steps: (1) Lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3, Sb2O3 and molten salt system (LiCl-KCl) are mixed to obtain a mixture; lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3 and Sb2O3 are added according to the stoichiometric ratio of the target product, the mass ratio of ternary cathode precursor to molten salt system is 3:1, and the molar ratio of LiCl and KCl in molten salt system is 1:1; under oxygen environment, the mixture is heated to 850℃ at a rate of 3℃ / min and kept at 850℃ for 8h, cooled, washed, filtered and dried to obtain a calcined product; (2) The product of step (1) was dispersed in an ethanol solution containing pyrrole monomer, and FeCl3 was added as an oxidant. The mass ratio of product of step (1):pyrrole monomer:FeCl3 was 100:3:4, and the volume ratio of pyrrole monomer to ethanol was 1:15. The reaction was stirred at room temperature for 12 h. The polypyrrole layer formed was heated to 200 °C at a rate of 2 °C / min and held for 3 h under argon atmosphere to obtain a modified single crystal ternary cathode material with LiNi as the core. 0.6 Co 0.1 Mn 0.3 Zr 0.0002 Y 0.0001 Sb 0.0001 O 2.0004 .

[0052] Comparative Example 3 This comparative example provides a modified single-crystal ternary cathode material, the preparation method of which includes the following steps: (1) Lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3, Sb2O3 and molten salt system (LiCl-KCl) are mixed to obtain a mixture; lithium carbonate, ternary cathode precursor, doping sources ZrO2, Y2O3 and Sb2O3 are added according to the stoichiometric ratio of the target product, the mass ratio of ternary cathode precursor to molten salt system is 3:1, and the molar ratio of LiCl and KCl in molten salt system is 1:1; under oxygen environment, the mixture is heated to 850℃ at a rate of 3℃ / min and kept at 850℃ for 8h, cooled, washed, filtered and dried to obtain a calcined product; (2) TiCl4 and LiOC(CH3)3 were mixed, with a Ti:Li molar ratio of 1:2 based on elemental composition. Atomic layer deposition (ALD) was performed at a deposition temperature of 180℃ for 60 cycles to deposit a Li2TiO3 layer on the surface of a calcined product, thus obtaining a modified single-crystal ternary cathode material with a LiNi core. 0.6 Co 0.1 Mn 0.3 Zr0.0002 Y 0.0001 Sb 0.0001 O 2.0004 .

[0053] Comparative Example 4 This comparative example provides a single-crystal ternary cathode material, the preparation method of which includes the following steps: Lithium carbonate, a ternary cathode precursor, and dopant sources ZrO2, Y2O3, Sb2O3, and a molten salt system (LiCl-KCl) were mixed to obtain a mixture. The lithium carbonate, ternary cathode precursor, and dopant sources ZrO2, Y2O3, and Sb2O3 were added according to the stoichiometric ratio of the target product. The mass ratio of the ternary cathode precursor to the molten salt system was 3:1, and the molar ratio of LiCl to KCl in the molten salt system was 1:1. Under oxygen conditions, the mixture was heated to 850℃ at a rate of 3℃ / min and held for 8 hours. After cooling, washing, filtering, and drying, a calcined product was obtained. This yielded a modified single-crystal ternary cathode material with a LiNi core. 0.6 Co 0.1 Mn 0.3 Zr 0.0002 Y 0.0001 Sb 0.0001 O 2.0004 .

[0054] Test case The materials prepared in the examples and comparative examples were used as positive electrode active materials and mixed with conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) at a mass ratio of 90:5:5. N-methylpyrrolidone (NMP) solvent was added, and the mixture was stirred evenly in a vacuum mixer to obtain a positive electrode slurry with a solid content of 48%. The slurry was uniformly coated onto an aluminum foil current collector, dried, and cold-pressed to obtain a compacted density of 2.2 g / cm³. 3 The positive electrode is a lithium metal sheet. The negative electrode uses a lithium metal sheet as the counter electrode. A glass fiber (such as Whatman GF / D) separator is used. The electrolyte is a 1 mol / L lithium hexafluorophosphate (LiPF6) solution, with the solvent being a mixture of ethylene carbonate (EC), vinylene carbonate (VC), and diethyl carbonate (DEC) in a volume ratio of 31:39:30. In a glove box filled with argon (H2O < 0.1 ppm, O2 < 0.1 ppm), the positive electrode, separator, lithium sheet, gasket, and spring are assembled sequentially into a CR2032 coin cell. After the assembled battery has been left to stand for 12 hours, its electrochemical performance is tested using a Blue Electric testing system.

[0055] Test method for charge / discharge capacity: At 25°C, the battery is charged to 4.5V at a rate of 0.1C. Based on the battery's mass, the initial 0.1C charge specific capacity is obtained. Then, the battery is discharged to 3.0V at a rate of 0.1C. Based on the battery's mass, the initial 0.1C discharge specific capacity is obtained. Initial efficiency = (First 0.1C discharge specific capacity / First 0.1C charge specific capacity) × 100%; Test method for capacity retention: Under 25℃ conditions, charge the battery at a constant current of 0.5C to 4.5V, discharge it at a constant current of 0.5C to 3.0V, and cycle it X times; the capacity retention rate of the Xth cycle = the 0.5C discharge capacity of the Xth cycle / the 0.5C discharge capacity of the first cycle × 100%, where X = 100, 200, 300, 400 or 500; Test method for rate performance: Under 25℃ conditions, the battery is charged to 4.5V at a rate of 0.1C, discharged to 3.0V at a rate of 0.1C, charged to 4.5V at a rate of 0.5C, discharged to 3.0V at a rate of 0.5C, charged to 4.5V at a rate of 1C, discharged to 3.0V at a rate of 1C, charged to 4.5V at a rate of 3C, and discharged to 3.0V at a rate of 3C. The nC capacity retention rate is calculated as: nC discharge specific capacity / first 0.1C discharge specific capacity × 100%. The test results are shown in Tables 1 and 2; Table 1

[0056] Table 2

[0057] A comparison of Example 1 and Comparative Examples 1-4 shows that L doping can strengthen the lattice oxygen framework, suppress cation mixing, and widen the lithium layer spacing, thereby delaying the phase transition of the material under high voltage. The fast ion conductor of coating layer 1 constructs a low-impedance lithium-ion transport channel, effectively alleviating interfacial lithium depletion and suppressing electrolyte decomposition. The conductive polymer of coating layer 2 forms a continuous electronic conductive network, reducing interfacial contact resistance, improving rate performance, and physically isolating the active material from the electrolyte, reducing side reactions. It can also prevent cracking of the fast ion conductor layer, ensuring interfacial stability and further extending cycle life. The synergistic effect of these three elements enables the modified single-crystal ternary cathode material of the present invention to maintain high capacity while taking into account both rate performance and cycle life.

[0058] A comparison of Examples 1 and 3 shows that in atomic layer deposition (ALD), a specific temperature ensures sufficient precursor reaction and coating layer density while avoiding excessive thermal stress that could damage the single-crystal core structure. A specific number of cycles ensures a coating layer thickness sufficient to cover surface defects and block side reactions without excessively hindering lithium-ion diffusion paths. This achieves an optimal balance between interface stability and ionic conductivity, enabling the prepared modified single-crystal ternary cathode material to maintain high capacity while further improving rate performance and cycle life.

[0059] A comparison of Examples 1 and 4 shows that the interfacial bonding between the conductive polymer and the fast ion conductor is enhanced, while avoiding carbonization or decomposition of the conductive polymer due to high temperature. This ensures the electronic conductivity and electrochemical stability of the conductive polymer, enabling the prepared modified single-crystal ternary cathode material to further improve rate performance and cycle life while maintaining high capacity.

[0060] 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 modified single-crystal ternary cathode material, characterized in that, The modified single-crystal ternary cathode material includes a core, a coating layer 1, and a coating layer 2 that are sequentially bonded together. The general formula for the kernel is Li x Ni a Co b Mn c L p O 2+q Wherein, 1.00≤x≤1.20, 0.10≤a≤0.60, 0.10≤b≤0.30, 0.10≤c≤0.30, 0.0001≤p≤0.03, 0≤q≤0.03, and L includes at least one of Mg, Al, Ti, Zr, Y, and Sb; The coating layer 1 includes a fast ion conductor; The coating layer 2 comprises a conductive polymer.

2. The modified single-crystal ternary cathode material according to claim 1, characterized in that, The general formula for the kernel is Li x Ni a Co b Mn c L p O2, wherein 0.0001≤p≤0.001, and L includes Zr, Y and Sb; Optionally, the fast ion conductor includes at least one of lithium titanate, lithium lanthanum zirconium oxide, and lithium aluminum titanium phosphate, and may be lithium titanate; Optionally, the conductive polymer includes polypyrrole and / or polythiophene, with polypyrrole being the preferred choice.

3. A method for preparing the modified single-crystal ternary cathode material according to claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) The lithium source, precursor, dopant source and molten salt are mixed and sintered for the first time to obtain a sintered product; (2) A coating layer 1 is prepared on the surface of a calcined product to obtain an intermediate product; (3) Prepare a coating layer 2 on the surface of the intermediate product and perform a second sintering to obtain a modified single-crystal ternary cathode material.

4. The preparation method according to claim 3, characterized in that, In step (1), the mass ratio of the precursor to the molten salt is (3-10):1; And / or, the first sintering conditions include: heating to 850-900℃ at a rate of 1-5℃ / min and holding for 8-12 hours.

5. The preparation method according to claim 3 or 4, characterized in that, In step (2), the coating layer 1 is prepared by atomic layer deposition. Optionally, the conditions for the atomic layer deposition method include: a deposition temperature of 150-180°C and a cycle number of 50-100 times; Optionally, the conditions for the atomic layer deposition method include: a deposition temperature of 170-180°C and a cycle number of 60-80 times.

6. The preparation method according to any one of claims 3-5, characterized in that, In step (3), the preparation of the coating layer 2 includes the following steps: mixing the intermediate product, conductive polymer monomer, solvent and oxidant, and carrying out a polymerization reaction to obtain the coating layer 2.

7. The preparation method according to claim 6, characterized in that, The mass ratio of the intermediate product to the conductive polymer monomer is 100:(1-5); Optionally, the mass ratio of the intermediate product to the oxidant is 100:(1-5); Optionally, the volume ratio of the conductive polymer monomer to the solvent is 1:(10-40).

8. The preparation method according to claim 7, characterized in that, The mass ratio of the intermediate product to the conductive polymer monomer is 100:(3-5); Optionally, the mass ratio of the intermediate product to the oxidant is 100:(3-5).

9. The preparation method according to any one of claims 3-8, characterized in that, The conditions for the second sintering include: heating to 180-300℃ at a rate of 1-5℃ / min and holding at that temperature for 1-5 hours; Optionally, the conditions for the second sintering include: holding at 200-250°C for 2-4 hours at a rate of 1-3°C / min.

10. A secondary battery, characterized in that, The secondary battery includes the modified single-crystal ternary cathode material as described in claim 1 or 2, or the modified single-crystal ternary cathode material prepared by the preparation method described in any one of claims 3-9.

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