Lmo-coated single-crystal nickel-rich positive electrode material, preparation method and battery

Abstract

This invention provides an LMO-coated single-crystal nickel-rich cathode material, its preparation method, and a battery. The preparation method of the LMO-coated single-crystal nickel-rich cathode material includes: dispersing amorphous manganese dioxide nanoparticles in a lithium salt solution to form a precursor solution; then mixing SNCM powder with the precursor solution and performing evaporation-induced self-assembly to obtain a coated precursor; finally, heat-treating the coated precursor in an oxygen-containing atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material. The LMO-coated single-crystal nickel-rich cathode material prepared by the method provided by this invention has a uniform, ultra-thin, and firmly bonded coating layer, which significantly improves the structural stability and cycle performance of the material under high voltage. Furthermore, the preparation method is simple, low-cost, and easy to scale up for mass production.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a modified cathode material, particularly to an LMO-coated single-crystal nickel-rich cathode material, its preparation method, and a battery. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronic devices such as mobile phones and personal computers due to their advantages such as high operating voltage, high energy density, long cycle life, and environmental friendliness. In recent years, with the rapid iteration of electronic technology, the growth of the new energy vehicle industry, and the construction of large-scale electrochemical energy storage systems, the market has placed increasingly stringent requirements on the energy density, cycle stability, safety performance, and overall cost of power storage equipment.

[0003] Ternary lithium batteries, with their adjustable specific capacity and comprehensive performance, have continuously broken through the "energy density-safety-cost" triangle through material innovation and process reform, becoming one of the core technology routes in the power and energy storage fields. With the popularization of monocrystalline technology, the continuous upgrading of battery systems, and the continuous improvement of the industrial chain, ternary materials will continue to occupy a core position in high-end power batteries and other applications with stringent energy density requirements. In the ternary cathode material system, nickel-rich layered oxide cathode materials have attracted much attention due to their high specific capacity exceeding 200 mAh / g. Among them, monocrystalline nickel-rich cathode material LiNi... x Co y Mn 1-x-y O2 (SNCM, x≥0.8) exhibits significant advantages over traditional polycrystalline nickel-rich materials in terms of mechanical integrity, resistance to intergranular cracks, thermal stability, and electrochemical stability. It can effectively alleviate the problems of grain boundary cracking and bulk structure deterioration caused by electrolyte penetration during the cycling process of polycrystalline materials, and has outstanding application potential in high-voltage charge-discharge systems.

[0004] However, SNCMs perform well at high voltages (>4.3 V vs. Li / Li). + During charge / discharge conditions and long-term cycling, interfacial instability and rapid capacity decay remain issues. These problems stem primarily from two aspects: First, irreversible structural phase transitions occur on the material surface during cycling, generating an electrochemically inert NiO rock salt phase, significantly increasing interfacial impedance and hindering rapid lithium-ion transport. Second, during charge / discharge, especially in the H2-H3 phase transition range, the material undergoes significant anisotropic volume changes, leading to intragranular crack formation and causing the material structure to gradually collapse from the surface to the bulk phase. This also exacerbates the irreversible dissolution of transition metal ions and the continuous side reactions in the electrolyte, ultimately resulting in a significant reduction in the material's cycle life and safety performance.

[0005] Surface coating modification is a technical means to suppress interfacial side reactions and improve surface structural stability of cathode materials. Currently, commonly used surface modification methods in the industry, such as atomic layer deposition (ALD), sol-gel method, and multi-step solid-phase coating method, can improve the interfacial stability of materials to a certain extent. However, although ALD can achieve ultra-thin coating, the equipment cost is extremely high and the production efficiency is low, making it unsuitable for large-scale industrial production. Sol-gel method and multi-step coating process generally suffer from uneven coating thickness, incomplete coverage, and easy agglomeration, making it difficult to achieve controllable preparation of ultra-thin continuous coating layers. Excessively thick coating layers can also hinder lithium-ion transport and deteriorate the rate performance of the material. At the same time, the interfacial bonding force between the coating layer prepared by existing processes and the cathode substrate is weak, and it is prone to detachment and failure during long-term charge and discharge volume deformation, failing to achieve long-term stable interfacial protection. In addition, most coating processes are cumbersome, have long preparation cycles, and poor reaction controllability, which can negatively affect the structure and electrochemical performance of the cathode material itself, making it difficult to meet the needs of industrial mass production.

[0006] Therefore, developing a simple and controllable process for surface coating modification of single-crystal nickel-rich ternary cathode materials, characterized by uniform and ultra-thin coating layers, strong bonding with the substrate, low production cost, and ease of large-scale mass production, is of great significance for solving the interface and structural stability problems of SNCMs under high-voltage systems, improving the cycle life and safety performance of materials, and promoting the industrial application of high-energy-density lithium-ion batteries. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an LMO-coated single-crystal nickel-rich cathode material, a preparation method, and a battery. The LMO-coated single-crystal nickel-rich cathode material obtained by this preparation method has a uniform, ultra-thin, and firmly bonded coating layer, which significantly improves the structural stability and cycle performance of the material under high voltage. Furthermore, the preparation method is simple, low-cost, and easy to scale up for mass production, making it suitable for the manufacture of high-energy-density lithium-ion batteries.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing an LMO-coated single-crystal nickel-rich cathode material, the method comprising the following steps:

[0010] Amorphous manganese dioxide nanoparticles are dispersed in a lithium salt solution to form a precursor solution;

[0011] SNCM powder and the precursor solution are mixed and subjected to evaporation-induced self-assembly to obtain a coated precursor.

[0012] The coating precursor is heat-treated in an oxygen-containing atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material.

[0013] This invention employs an evaporation-induced self-assembly method to prepare LMO-coated single-crystal nickel-rich cathode materials. First, amorphous MnO2 nanoparticles are dispersed in a lithium salt solution to obtain a uniform and stable precursor solution. Then, evaporation-induced self-assembly is completed using a centrifugal evaporator to form a uniform precursor coating layer on the surface of SNCM powder. After subsequent heat treatment, it can be transformed into a crystalline LiMnO2 coating layer. This method eliminates the need for stepwise introduction of functional components or multi-step precursor conversion reactions. The process is short, simple to operate, and highly controllable, significantly reducing the preparation difficulty and production cost, and facilitating large-scale industrial production.

[0014] The LMO-coated single-crystal nickel-rich cathode material prepared by the method provided in this invention has a uniform coating layer that is firmly bonded to the substrate. The coating layer can completely cover the surface of the SNCM powder, forming a stable and dense interfacial protective barrier that effectively isolates the direct contact between the electrolyte and the cathode material, and significantly suppresses interfacial side reactions during high-voltage charging and discharging. The uniform and controllable LiMnO2 coating layer can effectively suppress the dissolution of transition metal ions, phase transformation of the cathode material structure, and the generation of intergranular cracks during high-voltage cycling, significantly improving the structural stability, cycle life, and safety performance of the material under high voltage, and can fully meet the manufacturing and application requirements of high-energy-density lithium-ion batteries.

[0015] In some embodiments, the LMO-coated single-crystal nickel-rich cathode material includes an SNCM core and a coating layer covering the SNCM core;

[0016] The thickness of the coating layer is 5nm~20nm.

[0017] This invention does not limit the mass ratio of SNCM powder to precursor solution. As long as a coating layer with a thickness of 5nm to 20nm can be obtained within the process parameters of this invention, it is acceptable. Generally speaking, the mass percentage of the coating layer is 0.5wt% to 3wt% of the SNCM core.

[0018] In some embodiments, the average particle size of the amorphous manganese dioxide nanoparticles is 5 nm to 10 nm.

[0019] In some embodiments, the molar ratio of lithium to manganese in the precursor solution is 1:1 to 2:1.

[0020] In some embodiments, the solvent of the precursor solution is a mixed solvent;

[0021] The mixed solvent comprises anhydrous ethanol and water in a volume ratio of 2.5:1 to 3.5:1.

[0022] In some embodiments, the molar concentration of amorphous manganese dioxide nanoparticles in the precursor solution is 0.3 mol / L to 0.7 mol / L.

[0023] In some embodiments, the lithium salt in the precursor solution includes any one or a combination of at least two of lithium nitrate, lithium carbonate, lithium acetate, or lithium hydroxide.

[0024] In some embodiments, the median particle size of the SNCM powder is 3 μm to 5 μm.

[0025] In some embodiments, the SNCM powder is subjected to a surface cleaning treatment at 280°C to 320°C for 1.5h to 2.5h before being mixed with the precursor solution.

[0026] In this invention, the evaporation-induced self-assembly is carried out in a centrifugal evaporator.

[0027] In some embodiments, the temperature for evaporation-induced self-assembly is 40°C to 70°C.

[0028] In some embodiments, the evaporation-induced self-assembly time is 1 h to 3 h.

[0029] In some embodiments, the centrifugal speed for evaporation-induced self-assembly is 1000 rpm to 3000 rpm.

[0030] In some embodiments, the heat treatment temperature is 400°C to 600°C.

[0031] In some embodiments, the heat treatment time is 2h to 6h.

[0032] In a second aspect, the present invention provides an LMO-coated single-crystal nickel-rich cathode material, wherein the LMO-coated single-crystal nickel-rich cathode material is prepared by the preparation method described in the first aspect.

[0033] Thirdly, the present invention provides a battery comprising a positive electrode material;

[0034] The cathode material includes the LMO-coated single-crystal nickel-rich cathode material prepared by the preparation method described in the first aspect, or the LMO-coated single-crystal nickel-rich cathode material described in the second aspect.

[0035] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention employs an evaporation-induced self-assembly method to prepare LMO-coated single-crystal nickel-rich cathode materials. First, amorphous MnO2 nanoparticles are dispersed in a lithium salt solution to obtain a homogeneous and stable precursor solution. Then, evaporation-induced self-assembly is performed using a centrifugal evaporator to form a uniform precursor coating layer on the surface of SNCM powder. Subsequent heat treatment transforms this into a crystalline LiMnO2 coating layer. This method eliminates the need for stepwise introduction of functional components or multi-step precursor conversion reactions, resulting in a short process flow, simple operation, and strong controllability of the reaction process. It significantly reduces the preparation difficulty and production cost, facilitating large-scale industrial production. This invention provides a method for preparing LMO-coated single-crystal nickel-rich cathode materials. MO-coated single-crystal nickel-rich cathode materials have a uniform coating layer that is firmly bonded to the substrate. The coating layer can completely cover the surface of SNCM powder, forming a stable and dense interfacial protective barrier that effectively isolates the electrolyte from direct contact with the cathode material and significantly suppresses interfacial side reactions during high-voltage charge and discharge. The uniform and controllable LiMnO2 coating layer can effectively suppress the dissolution of transition metal ions, phase transformation of the cathode material structure, and the generation of intergranular cracks during high-voltage cycling, significantly improving the structural stability, cycle life, and safety performance of the material under high voltage, and fully meeting the manufacturing and application requirements of high-energy-density lithium-ion batteries. Detailed Implementation

[0038] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0039] The "range" disclosed in this invention can be defined in the form of 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. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0040] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0042] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0043] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0044] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0045] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0046] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0047] An embodiment of the present invention provides a method for preparing LMO-coated single-crystal nickel-rich cathode material, the method comprising the following steps:

[0048] Amorphous manganese dioxide nanoparticles are dispersed in a lithium salt solution to form a precursor solution;

[0049] SNCM powder and the precursor solution are mixed and subjected to evaporation-induced self-assembly to obtain a coated precursor.

[0050] The coating precursor is heat-treated in an oxygen-containing atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material.

[0051] This invention employs an evaporation-induced self-assembly method to prepare LMO-coated single-crystal nickel-rich cathode materials. First, amorphous MnO2 nanoparticles are dispersed in a lithium salt solution to obtain a uniform and stable precursor solution. Then, evaporation-induced self-assembly is completed using a centrifugal evaporator to form a uniform precursor coating layer on the surface of SNCM powder. After subsequent heat treatment, it can be transformed into a crystalline LiMnO2 coating layer. This method eliminates the need for stepwise introduction of functional components or multi-step precursor conversion reactions. The process is short, simple to operate, and highly controllable, significantly reducing the preparation difficulty and production cost, and facilitating large-scale industrial production.

[0052] The LMO-coated single-crystal nickel-rich cathode material prepared by the method provided in this invention has a uniform coating layer that is firmly bonded to the substrate. The coating layer can completely cover the surface of the SNCM powder, forming a stable and dense interfacial protective barrier that effectively isolates the direct contact between the electrolyte and the cathode material, and significantly suppresses interfacial side reactions during high-voltage charging and discharging. The uniform and controllable LiMnO2 coating layer can effectively suppress the dissolution of transition metal ions, phase transformation of the cathode material structure, and the generation of intergranular cracks during high-voltage cycling, significantly improving the structural stability, cycle life, and safety performance of the material under high voltage, and can fully meet the manufacturing and application requirements of high-energy-density lithium-ion batteries.

[0053] In some embodiments, the LMO-coated single-crystal nickel-rich cathode material includes an SNCM core and a coating layer covering the SNCM core;

[0054] The thickness of the coating layer is 5nm to 20nm, for example, it can be 5nm, 8nm, 10nm, 12nm, 15nm, 16nm, 18nm or 20nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] This invention does not limit the mass ratio of SNCM powder to precursor solution. As long as a coating layer with a thickness of 5nm to 20nm can be obtained within the process parameters of this invention, it is acceptable. Generally speaking, the mass percentage of the coating layer is 0.5wt% to 3wt% of the SNCM core.

[0056] In some embodiments, the average particle size of the amorphous manganese dioxide nanoparticles is 5nm to 10nm, for example, it can be 5nm, 6nm, 7nm, 8nm, 9nm or 10nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] In some embodiments, the molar ratio of lithium to manganese in the precursor solution is 1:1 to 2:1, for example, it can be 1:1, 1.2:1, 1.5:1, 1.6:1, 1.8:1 or 2:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] In some embodiments, the solvent of the precursor solution is a mixed solvent;

[0059] The mixed solvent comprises anhydrous ethanol and water in a volume ratio of 2.5:1 to 3.5:1.

[0060] The volume ratio of anhydrous ethanol to water is 2.5:1 to 3.5:1, for example, it can be 2.5:1, 2.7:1, 2.8:1, 3:1, 3.2:1 or 3.5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] The present invention controls the volume ratio of anhydrous ethanol to water to be 2.5:1 to 3.5:1, which is beneficial to maintaining the stability of the precursor solution, avoiding the aggregation of nanoparticles and the precipitation of lithium salts, and is conducive to achieving a mild and controllable solvent evaporation rate, while reducing the surface erosion of SNCM powder by water.

[0062] In some embodiments, the molar concentration of amorphous manganese dioxide nanoparticles in the precursor solution is 0.3 mol / L to 0.7 mol / L, for example, it can be 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L or 0.7 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0063] In some embodiments, the lithium salt in the precursor solution includes any one or a combination of at least two of lithium nitrate, lithium carbonate, lithium acetate, or lithium hydroxide. Typical but non-limiting combinations include combinations of lithium nitrate and lithium carbonate, combinations of lithium nitrate and lithium acetate, combinations of lithium acetate and lithium hydroxide, or combinations of lithium nitrate, lithium carbonate, lithium acetate, and lithium hydroxide.

[0064] In some embodiments, the median particle size of the SNCM powder is 3μm to 5μm, for example, it can be 3μm, 3.5μm, 4μm, 4.5μm or 5μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0065] In some embodiments, before the SNCM powder is mixed with the precursor solution, a surface cleaning treatment is performed at 280°C to 320°C (e.g., 280°C, 290°C, 300°C, 310°C, or 320°C) for 1.5h to 2.5h (e.g., 1.5h, 1.6h, 1.8h, 2h, 2.1h, 2.4h, or 2.5h) to remove impurities and residual lithium compounds from the surface of the SNCM powder.

[0066] In this invention, the evaporation-induced self-assembly is carried out in a centrifugal evaporator.

[0067] In some embodiments, the temperature for evaporation-induced self-assembly is 40°C to 70°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] In some embodiments, the evaporation-induced self-assembly time is 1h to 3h, for example, it can be 1h, 1.5h, 2h, 2.5h or 3h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] This invention controls the temperature and time of evaporation-induced self-assembly, so that the solvent in the precursor solution is uniformly evaporated, and the precursor is uniformly adsorbed and orderly self-assembled on the surface of SNCM powder. This avoids the decomposition of the precursor caused by high temperature and takes into account both coating quality and coating efficiency.

[0070] In some embodiments, the centrifugation speed for evaporation-induced self-assembly is 1000 rpm to 3000 rpm, for example, it can be 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm or 3000 rpm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0071] In some embodiments, the heat treatment temperature is 400°C to 600°C, for example, 400°C, 420°C, 450°C, 480°C, 500°C, 540°C, 550°C, 560°C, 580°C or 600°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0072] In some embodiments, the heat treatment time is 2h to 6h, for example, it can be 2h, 3h, 4h, 5h or 6h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] As a preferred embodiment of the preparation method provided by the present invention, the preparation method includes the following steps:

[0074] S1. Amorphous manganese dioxide nanoparticles are dispersed in a lithium salt solution to form a precursor solution;

[0075] In the precursor solution, the molar concentration of amorphous manganese dioxide nanoparticles is 0.3 mol / L to 0.7 mol / L, and the average particle size of the amorphous manganese dioxide nanoparticles is 5 nm to 10 nm.

[0076] In the precursor solution, the lithium salt includes any one or a combination of at least two of lithium nitrate, lithium carbonate, lithium acetate or lithium hydroxide, and the molar ratio of lithium to manganese is 1:1 to 2:1.

[0077] The solvent of the precursor solution is a mixed solvent, which includes anhydrous ethanol and water in a volume ratio of 2.5:1 to 3.5:1.

[0078] S2. Mix SNCM powder with the precursor solution and perform evaporation-induced self-assembly in a centrifugal evaporator to form a uniform precursor coating layer by self-assembly of amorphous manganese dioxide nanoparticles and SNCM powder, thereby obtaining a coated precursor.

[0079] The median particle size of the SNCM powder is 3μm~5μm, and the SNCM powder is subjected to a surface cleaning treatment at 280℃~320℃ for 1.5h~2.5h before being mixed with the precursor solution.

[0080] The evaporation-induced self-assembly was performed at a temperature of 40℃ to 70℃ for 1 hour to 3 hours, and at a centrifugation speed of 1000 rpm to 3000 rpm.

[0081] S3. The coating precursor is heat-treated in an oxygen-containing atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material; the heat treatment temperature is 400℃~600℃ and the time is 2h~6h.

[0082] The LMO-coated single-crystal nickel-rich cathode material includes an SNCM core and a coating layer covering the SNCM core; the thickness of the coating layer is 5nm~20nm.

[0083] An embodiment of the present invention provides an LMO-coated single-crystal nickel-rich cathode material, wherein the LMO-coated single-crystal nickel-rich cathode material is prepared by the preparation method described in any embodiment.

[0084] One embodiment of the present invention provides a battery, the battery comprising a positive electrode material;

[0085] The cathode material includes LMO-coated single-crystal nickel-rich cathode material prepared by the preparation method described in any embodiment, or LMO-coated single-crystal nickel-rich cathode material described in any embodiment.

[0086] To clearly illustrate the technical solution of this invention, the chemical formula of the SNCM powder can be LiNi. 0.9 Mn 0.05 Co 0.05 O2.

[0087] Example 1

[0088] This embodiment provides a method for preparing LMO-coated single-crystal nickel-rich cathode material, including the following steps:

[0089] S1. Amorphous manganese dioxide nanoparticles are dispersed in a lithium salt solution to form a precursor solution;

[0090] In the precursor solution, the molar concentration of amorphous manganese dioxide nanoparticles is 0.5 mol / L, and the average particle size of the amorphous manganese dioxide nanoparticles is 8 nm.

[0091] In the precursor solution, the lithium salt is lithium acetate, and the molar ratio of lithium to manganese is 1.5:1.

[0092] The solvent for the precursor solution is a mixed solvent, which includes anhydrous ethanol and water in a volume ratio of 3:1.

[0093] S2, Mixed SNCM powder (LiNi) 0.9 Mn 0.05 Co 0.05 O2) and the precursor solution are subjected to evaporation-induced self-assembly in a centrifugal evaporator, so that the amorphous manganese dioxide nanoparticles and SNCM powder self-assemble to form a uniform precursor coating layer, thereby obtaining a coated precursor.

[0094] The median particle size of the SNCM powder is 4 μm, and the SNCM powder is subjected to a surface cleaning treatment at 300°C for 2 hours before being mixed with the precursor solution.

[0095] The evaporation-induced self-assembly was performed at a temperature of 50°C for 2 hours and a centrifugation speed of 2000 rpm.

[0096] S3. The coating precursor is heat-treated in an air atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material; the heat treatment includes: heating to 500°C at a heating rate of 5°C / min and holding at that temperature for 4 hours.

[0097] The LMO-coated single-crystal nickel-rich cathode material includes an SNCM core and a coating layer covering the SNCM core; the thickness of the coating layer is 10 nm.

[0098] Example 2

[0099] This embodiment provides a method for preparing LMO-coated single-crystal nickel-rich cathode material, including the following steps:

[0100] S1. Amorphous manganese dioxide nanoparticles are dispersed in a lithium salt solution to form a precursor solution;

[0101] In the precursor solution, the molar concentration of amorphous manganese dioxide nanoparticles is 0.5 mol / L, and the average particle size of the amorphous manganese dioxide nanoparticles is 5 nm.

[0102] In the precursor solution, the lithium salt is lithium acetate, and the molar ratio of lithium to manganese is 1.8:1.

[0103] The solvent for the precursor solution is a mixed solvent, which includes anhydrous ethanol and water in a volume ratio of 3:1.

[0104] S2, Mixed SNCM powder (LiNi) 0.9 Mn 0.05 Co 0.05 O2) and the precursor solution are subjected to evaporation-induced self-assembly in a centrifugal evaporator, so that the amorphous manganese dioxide nanoparticles and SNCM powder self-assemble to form a uniform precursor coating layer, thereby obtaining a coated precursor.

[0105] The median particle size of the SNCM powder is 4 μm, and the SNCM powder is subjected to a surface cleaning treatment at 300°C for 2 hours before being mixed with the precursor solution.

[0106] The evaporation-induced self-assembly was performed at a temperature of 60°C for 1.5 hours and a centrifugation speed of 1500 rpm.

[0107] S3. The coating precursor is heat-treated in an air atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material; the heat treatment includes: heating to 550°C at a heating rate of 5°C / min and holding at that temperature for 3 hours.

[0108] The LMO-coated single-crystal nickel-rich cathode material includes an SNCM core and a coating layer covering the SNCM core; the thickness of the coating layer is 8 nm.

[0109] Example 3

[0110] This embodiment provides a method for preparing LMO-coated single-crystal nickel-rich cathode material, including the following steps:

[0111] S1. Amorphous manganese dioxide nanoparticles are dispersed in a lithium salt solution to form a precursor solution;

[0112] In the precursor solution, the molar concentration of amorphous manganese dioxide nanoparticles is 0.5 mol / L, and the average particle size of the amorphous manganese dioxide nanoparticles is 5 nm.

[0113] In the precursor solution, the lithium salt is lithium nitrate, and the molar ratio of lithium to manganese is 2:1.

[0114] The solvent for the precursor solution is a mixed solvent, which includes anhydrous ethanol and water in a volume ratio of 3:1.

[0115] S2, Mixed SNCM powder (LiNi) 0.9 Mn 0.05 Co 0.05 O2) and the precursor solution are subjected to evaporation-induced self-assembly in a centrifugal evaporator, so that the amorphous manganese dioxide nanoparticles and SNCM powder self-assemble to form a uniform precursor coating layer, thereby obtaining a coated precursor.

[0116] The median particle size of the SNCM powder is 4 μm, and the SNCM powder is subjected to a surface cleaning treatment at 300°C for 2 hours before being mixed with the precursor solution.

[0117] The evaporation-induced self-assembly was performed at a temperature of 45°C for 2.5 hours and a centrifugation speed of 2500 rpm.

[0118] S3. The coating precursor is heat-treated in an air atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material; the heat treatment includes: heating to 450°C at a heating rate of 5°C / min and holding at that temperature for 5 hours.

[0119] The LMO-coated single-crystal nickel-rich cathode material includes an SNCM core and a coating layer covering the SNCM core; the thickness of the coating layer is 15 nm.

[0120] Example 4

[0121] This embodiment provides a method for preparing LMO-coated single-crystal nickel-rich cathode material, including the following steps:

[0122] S1. Amorphous manganese dioxide nanoparticles are dispersed in a lithium salt solution to form a precursor solution;

[0123] In the precursor solution, the molar concentration of amorphous manganese dioxide nanoparticles is 0.3 mol / L, and the average particle size of the amorphous manganese dioxide nanoparticles is 5 nm.

[0124] In the precursor solution, the lithium salt is lithium acetate, and the molar ratio of lithium to manganese is 1:1.

[0125] The solvent of the precursor solution is a mixed solvent, which includes anhydrous ethanol and water in a volume ratio of 2.5:1.

[0126] S2, Mixed SNCM powder (LiNi) 0.9 Mn 0.05 Co 0.05 O2) and the precursor solution are subjected to evaporation-induced self-assembly in a centrifugal evaporator, so that the amorphous manganese dioxide nanoparticles and SNCM powder self-assemble to form a uniform precursor coating layer, thereby obtaining a coated precursor.

[0127] The median particle size of the SNCM powder is 3 μm, and the SNCM powder is subjected to a surface cleaning treatment at 280°C for 2.5 h before being mixed with the precursor solution.

[0128] The evaporation-induced self-assembly was performed at a temperature of 40°C for 3 hours and a centrifugation speed of 1000 rpm.

[0129] S3. The coating precursor is heat-treated in an air atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material; the heat treatment includes: heating to 400°C at a heating rate of 5°C / min and holding at that temperature for 6 hours.

[0130] The LMO-coated single-crystal nickel-rich cathode material includes an SNCM core and a coating layer covering the SNCM core; the thickness of the coating layer is 5 nm.

[0131] Example 5

[0132] This embodiment provides a method for preparing LMO-coated single-crystal nickel-rich cathode material, including the following steps:

[0133] S1. Amorphous manganese dioxide nanoparticles are dispersed in a lithium salt solution to form a precursor solution;

[0134] In the precursor solution, the molar concentration of amorphous manganese dioxide nanoparticles is 0.7 mol / L, and the average particle size of the amorphous manganese dioxide nanoparticles is 10 nm.

[0135] In the precursor solution, the lithium salt is lithium acetate, and the molar ratio of lithium to manganese is 2:1.

[0136] The solvent of the precursor solution is a mixed solvent, which includes anhydrous ethanol and water in a volume ratio of 3.5:1;

[0137] S2, Mixed SNCM powder (LiNi) 0.9 Mn 0.05 Co0.05 O2) and the precursor solution are subjected to evaporation-induced self-assembly in a centrifugal evaporator, so that the amorphous manganese dioxide nanoparticles and SNCM powder self-assemble to form a uniform precursor coating layer, thereby obtaining a coated precursor.

[0138] The median particle size of the SNCM powder is 5 μm, and the SNCM powder is subjected to a surface cleaning treatment at 320°C for 1.5 h before being mixed with the precursor solution.

[0139] The evaporation-induced self-assembly was performed at a temperature of 70°C for 1 hour and a centrifugation speed of 3000 rpm.

[0140] S3. The coating precursor is heat-treated in an air atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material; the heat treatment includes: heating to 600°C at a heating rate of 5°C / min and holding at that temperature for 2 hours.

[0141] The LMO-coated single-crystal nickel-rich cathode material includes an SNCM core and a coating layer covering the SNCM core; the thickness of the coating layer is 20 nm.

[0142] Example 6

[0143] This embodiment provides a method for preparing LMO-coated single-crystal nickel-rich cathode material, which is the same as in Example 1 except that the evaporation-induced self-assembly temperature is 80°C.

[0144] Example 7

[0145] This embodiment provides a method for preparing LMO-coated single-crystal nickel-rich cathode material, which is the same as in Example 1 except that the heat treatment temperature is 380°C.

[0146] Example 8

[0147] This embodiment provides a method for preparing LMO-coated single-crystal nickel-rich cathode material, which is the same as in Example 1 except that the heat treatment temperature is 650°C.

[0148] Comparative Example 1

[0149] This comparative example provides a single-crystal nickel-rich cathode material, which is the SNCM powder used in Example 1.

[0150] Comparative Example 2

[0151] This comparative example provides a method for preparing LMO-coated single-crystal nickel-rich cathode material, including the following steps:

[0152] S1. Amorphous manganese dioxide nanoparticles are dispersed in a lithium salt solution to form a precursor solution;

[0153] In the precursor solution, the molar concentration of amorphous manganese dioxide nanoparticles is 0.5 mol / L, and the average particle size of the amorphous manganese dioxide nanoparticles is 8 nm.

[0154] In the precursor solution, the lithium salt is lithium acetate, and the molar ratio of lithium to manganese is 1.5:1.

[0155] The solvent for the precursor solution is a mixed solvent, which includes anhydrous ethanol and water in a volume ratio of 3:1.

[0156] S2, Mixed SNCM powder (LiNi) 0.9 Mn 0.05 Co 0.05 O2) and the precursor solution were dried at 80°C for 12 hours to obtain the coated precursor;

[0157] The median particle size of the SNCM powder is 4 μm, and the SNCM powder is subjected to a surface cleaning treatment at 300°C for 2 hours before being mixed with the precursor solution.

[0158] S3. The coating precursor is heat-treated in an air atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material; the heat treatment includes: heating to 500°C at a heating rate of 5°C / min and holding at that temperature for 4 hours.

[0159] The LMO-coated single-crystal nickel-rich cathode material includes an SNCM core and a coating layer covering the SNCM core; the coating layer is uneven, with some areas having a coating thickness of more than 30 nm and some areas having almost no coating, which affects the electrochemical performance of the cathode material.

[0160] Comparative Example 3

[0161] This comparative example provides a method for preparing LMO-coated nickel-rich cathode material, including the following steps:

[0162] S1, manganese acetate tetrahydrate dissolved in a surfactant (polyvinylpyrrolidone) solution, SNCM powder (LiNi) added. 0.9 Mn 0.05 Co 0.05 O2), stirred at 50℃ for 12h, and then stirred and evaporated at 120℃ to obtain manganese source-coated SNCM powder;

[0163] S2. The manganese source-coated SNCM powder was heated to 450°C in air at a rate of 5°C / min, calcined for 6 hours, and then naturally cooled to room temperature to obtain manganese oxide-coated SNCM powder.

[0164] S3. Mix lithium carbonate and manganese oxide-coated SNCM powder, and then in an oxygen atmosphere, first heat to 480°C at a rate of 5°C / min and sinter for 5 h; then heat to 780°C at a rate of 5°C / min and sinter for 15 h to obtain LMO-coated nickel-rich cathode material.

[0165] TEM analysis showed that the thickness of the LMO-coated nickel-rich cathode material obtained in this comparative example was 10 nm.

[0166] Performance Characterization

[0167] The positive electrode material, conductive carbon black SP, and polyvinylidene fluoride PVDF provided in the above embodiments and comparative examples were mixed in a mass ratio of 90:5:5, with N-methylpyrrolidone as the solvent. The mixture was stirred into a slurry, and the resulting slurry was uniformly coated onto aluminum foil using a doctor blade with a coating gap of 100 μm. After coating, the foil was first dried by blowing air, then rolled and cut into circular electrode sheets, and then vacuum dried at 120°C. The weight of the electrode sheets was then measured to obtain the positive electrode sheet of the button half-cell. The negative electrode was a lithium metal sheet, the separator was a PP microporous membrane, and the electrolyte was a basic lithium battery electrolyte. The positive electrode sheet, lithium metal sheet, separator, and electrolyte were assembled to obtain a CR2032 button cell. The coulombic efficiency of the first charge-discharge at 0.1C and the discharge performance at 5C rate were then tested at room temperature within a voltage range of 2V~4.8V. The cycle capacity retention rate was tested by constant current charge-discharge at 1C rate for 350 cycles at a constant temperature of 55°C. The results are shown in Table 1.

[0168] Table 1

[0169]

[0170] As can be seen from Examples 1 to 5 in Table 1, the LMO-coated single-crystal nickel-rich cathode material provided by the present invention has excellent first charge-discharge coulombic efficiency, rate performance and high-temperature long-cycle stability in the high voltage range of 2V to 4.8V. It can effectively solve the problems of interface degradation and capacity decay of single-crystal nickel-rich cathode materials under high voltage, and is suitable for the application requirements of high energy density lithium-ion batteries.

[0171] A comparison of Comparative Example 1 and Example 1 shows that the electrochemical performance of the unmodified pure SNCM powder is significantly deteriorated. This indicates that during high-voltage charge and discharge, side reactions between the surface and the electrolyte continuously occur in the single-crystal nickel-rich cathode, leading to irreversible dissolution of transition metal ions. This is accompanied by harmful rock salt phase transformation and intergranular crack formation, ultimately resulting in low initial coulombic efficiency, poor rate performance, and rapid capacity decay. The LiMnO2 coating layer constructed in this invention forms a stable interfacial protective barrier, fundamentally suppressing the above problems and significantly improving the overall electrochemical performance of the material.

[0172] A comparison of Examples 1 with Examples 6, 7, and 8 reveals that when the evaporation-induced self-assembly temperature and heat treatment temperature exceed the ranges defined in this invention, the electrochemical performance of the material significantly decreases. This indicates that in Example 6, the excessively high evaporation temperature leads to an excessively rapid solvent evaporation rate, causing precursor components to agglomerate and deposit, preventing the formation of a uniform and continuous coating layer. In Example 7, the excessively low heat treatment temperature prevents sufficient lithiation and crystallization of amorphous MnO2, making it difficult to generate a pure-phase LiMnO2 coating layer, resulting in insufficient interface protection and increased lithium-ion transport impedance. In Example 8, the excessively high heat treatment temperature leads to abnormal growth of coating layer grains, disrupting the ultrathin and continuous coating structure and impairing the structure and electrochemical performance of the cathode material.

[0173] As can be seen from the comparison between Comparative Examples 2 and 3 and Example 1, the one-step evaporation-induced self-assembly process adopted in this invention can achieve a superior modification effect compared with existing conventional evaporation methods and stepwise coating methods. This is because the conventional evaporation method of Comparative Example 2 is difficult to control the uniform deposition of the precursor, and is prone to serious uneven coating thickness. Excessively thick areas will hinder lithium-ion transport, and exposed areas cannot suppress interfacial side reactions, ultimately leading to the deterioration of the material's electrochemical performance. The stepwise coating method of Comparative Example 3 requires multiple precursor conversion reactions, which is not only complex in process and poor in controllability, but also difficult to achieve uniform full coverage and strong interfacial bonding of the coating layer. The modification effect is far inferior to the technical solution of this invention.

[0174] In summary, this invention employs an evaporation-induced self-assembly method to prepare LMO-coated single-crystal nickel-rich cathode materials. First, amorphous MnO2 nanoparticles are dispersed in a lithium salt solution to obtain a homogeneous and stable precursor solution. Then, evaporation-induced self-assembly is performed using a centrifugal evaporator to form a uniform precursor coating layer on the surface of SNCM powder. Subsequent heat treatment transforms this precursor into a crystalline LiMnO2 coating layer. This eliminates the need for stepwise introduction of functional components or multi-step precursor conversion reactions. The process is short, simple to operate, and highly controllable, significantly reducing preparation difficulty and production costs, and facilitating large-scale industrial production. The method provided by this invention yields... The LMO-coated single-crystal nickel-rich cathode material has a uniform coating layer that is firmly bonded to the substrate. The coating layer can completely cover the surface of the SNCM powder, forming a stable and dense interfacial protective barrier that effectively isolates the electrolyte from direct contact with the cathode material and significantly suppresses interfacial side reactions during high-voltage charging and discharging. The uniform and controllable LiMnO2 coating layer can effectively suppress the dissolution of transition metal ions, phase transformation of the cathode material structure, and the generation of intergranular cracks during high-voltage cycling, significantly improving the structural stability, cycle life, and safety performance of the material under high voltage, and fully meeting the manufacturing and application requirements of high-energy-density lithium-ion batteries.

[0175] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing LMO-coated single-crystal nickel-rich cathode material, characterized in that, The preparation method includes the following steps: Amorphous manganese dioxide nanoparticles are dispersed in a lithium salt solution to form a precursor solution; SNCM powder and the precursor solution are mixed and subjected to evaporation-induced self-assembly to obtain a coated precursor. The coating precursor is heat-treated in an oxygen-containing atmosphere to obtain the LMO-coated single-crystal nickel-rich cathode material.

2. The preparation method according to claim 1, characterized in that, The LMO-coated single-crystal nickel-rich cathode material includes an SNCM core and a coating layer covering the SNCM core; The thickness of the coating layer is 5nm~20nm.

3. The preparation method according to claim 1 or 2, characterized in that, The average particle size of the amorphous manganese dioxide nanoparticles is 5 nm to 10 nm. And / or, in the precursor solution, the molar ratio of lithium to manganese is 1:1 to 2:

1.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The solvent for the precursor solution is a mixed solvent; The mixed solvent comprises anhydrous ethanol and water in a volume ratio of 2.5:1 to 3.5:

1.

5. The preparation method according to any one of claims 1 to 4, characterized in that, In the precursor solution, the molar concentration of amorphous manganese dioxide nanoparticles is 0.3 mol / L to 0.7 mol / L; And / or, the lithium salt in the precursor solution includes any one or a combination of at least two of lithium nitrate, lithium carbonate, lithium acetate, or lithium hydroxide.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The median particle size of the SNCM powder is 3μm~5μm; And / or, before the SNCM powder is mixed with the precursor solution, it is subjected to a surface cleaning treatment at 280℃~320℃ for 1.5h~2.5h.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The temperature for evaporation-induced self-assembly is 40℃~70℃; And / or, the evaporation-induced self-assembly time is 1h~3h; And / or, the centrifugal speed for the evaporation-induced self-assembly is 1000 rpm to 3000 rpm.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The heat treatment temperature is 400℃~600℃; And / or, the heat treatment time is 2h to 6h.

9. An LMO-coated single-crystal nickel-rich cathode material, characterized in that, The LMO-coated single-crystal nickel-rich cathode material is prepared by the preparation method described in any one of claims 1 to 8.

10. A battery, characterized in that, The battery includes a positive electrode material; The cathode material includes the LMO-coated single-crystal nickel-rich cathode material prepared by the preparation method according to any one of claims 1 to 8, or includes the LMO-coated single-crystal nickel-rich cathode material according to claim 9.

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