High-nickel single-crystal ternary material, preparation method thereof, positive plate and lithium ion battery

Abstract

The invention provides a high-nickel single-crystal ternary material and a preparation method thereof, a positive plate and a lithium ion battery. The high-nickel single-crystal ternary material comprises a high-nickel single-crystal ternary matrix and an oxygen vacancy modification layer formed on the surface of the high-nickel single-crystal ternary matrix in situ, wherein a metal oxide coating layer is arranged on the surface of the oxygen vacancy modification layer; the high-nickel single crystal ternary matrix has a cation ordered superlattice structure, the chemical formula of the high-nickel single crystal ternary matrix is LimNixCoyMnzO2, m is greater than or equal to 0.6 and less than or equal to 0.95, x is greater than or equal to 0.6, y is greater than or equal to 0, z is greater than or equal to 0, and x + y + z = 1. According to the invention, an oxygen deficiency strategy and an oxygen vacancy strategy are cooperatively matched, so that the problems of bulk phase structure heterogeneity and surface oxygen loss are synchronously solved; and the metal oxide coating layer is introduced, so that the electrolyte corrosion is isolated, the interface stability is improved, the ion conduction is optimized, multiple mechanisms are coordinated and matched, the cycle life of the high-nickel single-crystal ternary material is prolonged, and the rate capability of the high-nickel single-crystal ternary material is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to cathode materials, and more particularly to a high-nickel single-crystal ternary material and its preparation method, cathode sheet and lithium-ion battery. Background Technology

[0002] Nickel-rich layered oxides (such as LiNi) x Co y Mn z O2 (x≥0.6) is a key cathode material for next-generation high-energy-density lithium-ion batteries. To overcome the problem of grain boundary cracking that easily occurs in polycrystalline nickel-rich layered oxides during charge-discharge cycles, monocrystallization has become an important development direction.

[0003] However, the preparation of single-crystal materials faces two major challenges: firstly, the heterogeneity of the bulk structure. To obtain sufficiently dense single-crystal particles, the sintering temperature is usually more than 150°C higher than that of polycrystalline materials (>900°C). However, high temperatures can easily lead to severe lithium volatilization, triggering Ni... 2+ Large-scale migration to Li + Layers cause severe cation mixing and chemical heterogeneity, forming rock salt phase defects and hindering Li + Firstly, oxygen diffusion reduces rate performance and capacity. Secondly, surface structure degradation occurs. At high voltages (>4.3V), the lattice oxygen on the material surface easily becomes unstable, leading to oxygen evolution and side reactions with the electrolyte. This causes the surface to transform from a layered structure to an electrochemically inert rock-salt phase, increasing interfacial impedance and rapidly decaying capacity. Existing technologies mostly use bulk doping or surface coating to address this problem. While bulk doping (such as Al, Mg, Zr) can stabilize the structure, the process is complex and may reduce capacity. Traditional surface coatings are mostly inert barriers, which can suppress side reactions but may sacrifice rate performance and cannot fundamentally solve the problem of surface oxygen loss.

[0004] CN112652771A discloses a multi-anion-doped single-crystal high-nickel cathode material and its preparation method. By introducing two types of doped anions into the oxygen layer through multi-anion doping, the doped anions are evenly distributed and the anion doping does not change the original structure of the material, resulting in a stable structure. This successfully obtains a multi-anion-doped single-crystal high-nickel cathode material. The coupling effect between different ions achieves complementary advantages, reduces the interaction force between the lithium layer and the oxygen layer, increases the distance between the lithium layer and the oxygen layer, and successfully improves the rate performance of the single-crystal high-nickel ternary material.

[0005] CN114212835A discloses an Al and Zr co-doped ultra-high nickel ternary single crystal material. It adopts a low-temperature combustion reaction of a mixed system of nitrate, organic complexing agent and ammonium nitrate to achieve the preparation of ultra-high nickel ternary single crystal material and in-situ co-doping of Al and Zr elements. The invention promotes the combustion reaction by using a large amount of ammonium nitrate as an oxidant, which can avoid the pre-calcination treatment of the precursor at low temperature, save energy consumption, and the intense combustion reaction and high-temperature calcination make the single crystal material grow fully and have strong structural stability, thus comprehensively improving the electrochemical performance of ultra-high nickel ternary cathode material.

[0006] CN116605926A discloses a method for preparing a high-nickel single-crystal cathode material coated with γ-pure-phase alumina. The method uses an organic solvent and pseudoboehmite to coat a high-nickel ternary single-crystal NCM material using a wet coating method. The surface coating layer of the product prepared by this method is pure-phase γ-alumina, which has strong adhesion to the surface of the high-nickel single-crystal NCM material. The coating thickness and composition distribution are very uniform. Moreover, the organic solvent used is relatively inexpensive, such as ethanol and isopropanol, which is conducive to large-scale mass production and promotion.

[0007] Therefore, there is an urgent need to provide a high-nickel single-crystal ternary material and its preparation method that can simultaneously solve the problems of bulk structural heterogeneity and surface oxygen loss in nickel-rich single-crystal materials. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention aims to provide a high-nickel single-crystal ternary material, its preparation method, a cathode sheet, and a lithium-ion battery. This invention utilizes a synergistic "oxygen deficiency" and "oxygen vacancy" strategy to simultaneously solve the problems of bulk structural heterogeneity and surface oxygen loss. Furthermore, by introducing a metal oxide coating layer on the surface of the high-nickel single-crystal ternary material as a physical barrier, it isolates electrolyte corrosion, stabilizes the interface, and optimizes ion conduction, thereby improving the material's structural stability and electrochemical performance. The synergistic effect of these multiple mechanisms collectively enhances the cycle life and rate performance of the high-nickel single-crystal ternary material.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a high-nickel single-crystal ternary material, the high-nickel single-crystal ternary material comprising a high-nickel single-crystal ternary substrate and an oxygen vacancy modification layer formed in situ on the surface of the high-nickel single-crystal ternary substrate, wherein a metal oxide coating layer is further disposed on the surface of the oxygen vacancy modification layer; the high-nickel single-crystal ternary substrate has a cation-ordered superlattice structure, and the chemical formula of the high-nickel single-crystal ternary substrate is Li. m Ni x Co y Mn zO2, 0.6≤m≤0.95, x≥0.6, y>0, z>0, x+y+z=1.

[0011] This invention constructs a high-nickel single-crystal ternary matrix with a cationic ordered superlattice structure by controlling the molar ratio of Li to transition metal TM in the high-nickel single-crystal ternary matrix based on a "lithium deficiency" strategy. This provides a stable diffusion channel and a low migration barrier for lithium ions. Furthermore, an oxygen vacancy modification layer with oxygen vacancies is generated in situ on its surface to regulate the electronic structure of the matrix surface, effectively suppressing lattice oxygen evolution and phase transitions during high-voltage charging, greatly improving interface stability and extending cycle life. This invention utilizes the synergistic combination of the "oxygen deficiency" and "oxygen vacancy" strategies to simultaneously solve the problems of bulk structural heterogeneity and surface oxygen loss. This invention also introduces a metal oxide coating layer on the surface of the high-nickel single-crystal ternary material as a physical barrier, which improves interface stability and optimizes ion conduction while isolating the high-nickel single-crystal ternary matrix from electrolyte corrosion. Through the synergistic effect of these multiple mechanisms, this invention jointly improves the cycle life and rate performance of the high-nickel single-crystal ternary material.

[0012] Preferably, in the high-nickel single-crystal ternary matrix, 0.7 ≤ m ≤ 0.85.

[0013] Preferably, the thickness of the oxygen vacancy modified layer is 3 nm to 20 nm.

[0014] Preferably, the concentration of oxygen vacancies in the oxygen vacancy-modified layer is 0.2 at% to 2 at%.

[0015] Preferably, in the high-nickel single-crystal ternary material, the mass percentage of the metal oxide coating layer is 0.5wt%~3wt%.

[0016] Preferably, the material of the metal oxide coating layer includes any one or a combination of at least two of cerium oxide, zirconium oxide, yttrium oxide, or aluminum oxide.

[0017] In a second aspect, the present invention provides a method for preparing a high-nickel single-crystal ternary material as described in the first aspect, the method comprising:

[0018] The high-nickel ternary precursor and lithium source are mixed according to the molar ratio of total Ni, Co and Mn in lithium to high-nickel ternary precursor (0.6~0.95):1, and sintered in an oxidizing atmosphere to obtain a primary material; the primary material is then liquid-phase coated to obtain a metal oxide precursor coated material; the metal oxide precursor coated material is then heat-treated in a reducing atmosphere to prepare the high-nickel single crystal ternary material.

[0019] In this invention, the high-nickel ternary precursor comprises nickel-cobalt-manganese hydroxide, with the general chemical formula Ni x Coy Mn z (OH)2, where x+y+z=1 and x≥0.6.

[0020] In the preparation method provided by the present invention, a high-nickel ternary precursor and a lithium source are first sintered based on a "lithium deficiency" strategy to obtain a stable bulk primary material with a cationic ordered superlattice structure. Then, a metal oxide precursor is uniformly coated on the surface of the primary phase by liquid phase coating. Finally, heat treatment is performed in a reducing atmosphere to induce oxygen vacancies in the surface lattice of the primary material, forming an oxygen vacancy modification layer. At the same time, the metal oxide precursor decomposes into the corresponding oxides to form a metal oxide coating layer, thus obtaining the high-nickel single-crystal ternary material.

[0021] The preparation method provided by this invention is simple, operates under mild conditions, requires no complex equipment, and is very suitable for large-scale production.

[0022] Preferably, the D50 particle size of the high-nickel ternary precursor is 1.5μm~6μm.

[0023] Preferably, the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium nitrate, lithium oxalate, lithium carbonate, or lithium acetate.

[0024] Preferably, the sintering heating rate is 2℃ / min to 5℃ / min.

[0025] Preferably, the sintering temperature is 750℃~950℃.

[0026] Preferably, the sintering time is 10h to 20h.

[0027] Preferably, the oxidizing atmosphere includes air or oxygen.

[0028] Preferably, the liquid phase coating method includes: dispersing the primary material in water to obtain a primary slurry; mixing the primary slurry with a metal oxide precursor, collecting the precipitate, and drying it to obtain the metal oxide precursor coated material.

[0029] Preferably, the solid-liquid ratio of the primary material to water is 0.05 g / mL to 0.2 g / mL.

[0030] Preferably, the metal oxide precursor includes any one or a combination of at least two of cerium nitrate, cerium sulfate, cerium chloride, zirconium nitrate, zirconium chloride, yttrium nitrate, yttrium chloride, yttrium sulfate, aluminum chloride, aluminum sulfate, or aluminum nitrate.

[0031] Preferably, the mixing method includes stirring.

[0032] Preferably, the stirring time is 1 hour to 4 hours.

[0033] Preferably, the stirring temperature is 40℃~80℃.

[0034] Preferably, the drying temperature is 80℃~120℃.

[0035] Preferably, the heating rate of the heat treatment is 2℃ / min to 5℃ / min.

[0036] Preferably, the temperature of the heat treatment is 500℃~800℃.

[0037] Preferably, the heat treatment time is 2h to 8h.

[0038] Preferably, the reducing atmosphere comprises an H2 / Ar mixture, wherein the volume percentage of H2 in the H2 / Ar mixture is 1 vol% to 10 vol%.

[0039] Thirdly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the high-nickel single-crystal ternary material described in the first aspect.

[0040] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode as described in the third aspect, or comprising a high-nickel single-crystal ternary material as described in the first aspect.

[0041] 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.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) This invention utilizes a synergistic approach of "oxygen deficiency" and "oxygen vacancy" strategies to simultaneously address the issues of bulk structural heterogeneity and surface oxygen loss. By introducing a metal oxide coating layer onto the surface of the high-nickel single-crystal ternary material, which acts as a physical barrier, the interface stability is improved and ion conduction is optimized while isolating the high-nickel single-crystal ternary matrix from electrolyte corrosion. Through the synergistic effect of these multiple mechanisms, this invention enhances the cycle life and rate performance of the high-nickel single-crystal ternary material.

[0044] (2) The preparation method provided by the present invention is simple, mild and does not require complex equipment, making it very suitable for large-scale production. Detailed Implementation

[0045] 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.

[0046] 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 invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. In this invention, "a combination of at least two" means, unless otherwise specified, a quantity greater than or equal to two. For example, "any combination of one or at least two" means one or more of two. It is understood that when referring to "a combination of at least two," it means any suitable combination of multiple items, i.e., a combination of "at least two" items carried out in a manner that does not conflict with and allows for the implementation of the invention.

[0047] In the description of this invention, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0048] 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.

[0049] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0050] In one specific embodiment, the present invention provides a high-nickel single-crystal ternary material, the high-nickel single-crystal ternary material comprising a high-nickel single-crystal ternary substrate and an oxygen vacancy modification layer formed in situ on the surface of the high-nickel single-crystal ternary substrate, wherein a metal oxide coating layer is further disposed on the surface of the oxygen vacancy modification layer; the high-nickel single-crystal ternary substrate has a cation-ordered superlattice structure, and the chemical formula of the high-nickel single-crystal ternary substrate is Li. m Ni x Co y Mn z O2, 0.6≤m≤0.95, for example, can be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or 0.95, x≥0.6, for example, can be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or 0.96, y>0, z>0, y and z are independent, for example, can be 0.1, 0.2, 0.3 or 0.4, x+y+z=1.

[0051] This invention constructs a high-nickel single-crystal ternary matrix with a cationic ordered superlattice structure by controlling the molar ratio of Li to transition metal TM in a high-nickel single-crystal ternary matrix based on a "lithium deficiency" strategy. This provides a stable diffusion channel and a low migration barrier for lithium ions. Furthermore, an oxygen vacancy modification layer with oxygen vacancies is generated in situ on its surface to regulate the electronic structure of the matrix surface, effectively suppressing lattice oxygen evolution and phase transitions during high-voltage charging, greatly improving interface stability and extending cycle life. This invention utilizes the synergistic combination of the "oxygen deficiency" and "oxygen vacancy" strategies to simultaneously solve the problems of bulk structural heterogeneity and surface oxygen loss. This invention also introduces a metal oxide coating layer on the surface of the high-nickel single-crystal ternary material as a physical barrier, which improves interface stability and optimizes ion conduction while isolating the high-nickel single-crystal ternary matrix from electrolyte corrosion, thus enhancing the structural stability and electrochemical performance of the material. Through the synergistic effect of these multiple mechanisms, this invention comprehensively improves the cycle life and rate performance of high-nickel single-crystal ternary materials.

[0052] In some embodiments, in the high-nickel single-crystal ternary matrix, 0.7 ≤ m ≤ 0.85, for example, it can be 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.81, 0.83 or 0.85.

[0053] In some embodiments, the thickness of the oxygen vacancy modified layer is 3nm to 20nm, for example, it can be 3nm, 5nm, 7nm, 9nm, 10nm, 12nm, 14nm, 16nm, 18nm or 20nm.

[0054] In some embodiments, the concentration of oxygen vacancies in the oxygen vacancy-modified layer is 0.2at% to 2at%, for example, it can be 0.2at%, 0.4at%, 0.6at%, 0.8at%, 1at%, 1.2at%, 1.4at%, 1.6at%, 1.8at% or 2at.

[0055] In some embodiments, the metal oxide coating layer in the high-nickel single-crystal ternary material has a mass percentage content of 0.5wt% to 3wt%, for example, it can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt% or 3wt%.

[0056] In some embodiments, the metal oxide coating is made of any one or a combination of at least two of cerium oxide, zirconium oxide, yttrium oxide, or aluminum oxide. Typical but not limited combinations include a combination of cerium oxide and zirconium oxide, or a combination of yttrium oxide and aluminum oxide, or a combination of zirconium oxide and aluminum oxide.

[0057] In another specific embodiment, the present invention provides a method for preparing a high-nickel single-crystal ternary material as described in the foregoing specific embodiment, the preparation method comprising:

[0058] The high-nickel ternary precursor and lithium source are mixed according to the molar ratio of total Ni, Co and Mn in lithium to high-nickel ternary precursor (0.6~0.95):1, and sintered in an oxidizing atmosphere to obtain a primary material; the primary material is then liquid-phase coated to obtain a metal oxide precursor coated material; the metal oxide precursor coated material is then heat-treated in a reducing atmosphere to prepare the high-nickel single crystal ternary material.

[0059] In this invention, the high-nickel ternary precursor comprises nickel-cobalt-manganese hydroxide, with the general chemical formula Ni x Co y Mn z (OH)2, where x+y+z=1 and x≥0.6.

[0060] In the preparation method provided by the present invention, a high-nickel ternary precursor and a lithium source are first sintered based on a "lithium deficiency" strategy to obtain a stable bulk primary material with a cationic ordered superlattice structure. Then, a metal oxide precursor is uniformly coated on the surface of the primary phase by liquid phase coating. Finally, heat treatment is performed in a reducing atmosphere to induce oxygen vacancies in the surface lattice of the primary material, forming an oxygen vacancy modification layer. At the same time, the metal oxide precursor decomposes into the corresponding oxides to form a metal oxide coating layer, thus obtaining the high-nickel single-crystal ternary material.

[0061] The preparation method provided by this invention is simple, operates under mild conditions, requires no complex equipment, and is very suitable for large-scale production.

[0062] In some embodiments, the D50 particle size of the high-nickel ternary precursor is 1.5μm to 6μm, for example, it can be 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm or 6μm.

[0063] In some embodiments, the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium nitrate, lithium oxalate, lithium carbonate, or lithium acetate.

[0064] In some embodiments, the heating rate of the sintering is 2°C / min to 5°C / min, for example, it can be 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min or 5°C / min.

[0065] In some embodiments, the sintering temperature is 750°C to 950°C, for example, it can be 750°C, 800°C, 850°C, 900°C or 950°C.

[0066] In some embodiments, the sintering time is 10h to 20h, for example, it can be 10h, 12h, 14h, 16h, 18h or 20h.

[0067] In some embodiments, the oxidizing atmosphere includes air or oxygen.

[0068] In some embodiments, the liquid-phase coating method includes: dispersing the primary material in water to obtain a primary slurry; mixing the primary slurry with a metal oxide precursor, collecting the precipitate, and drying it to obtain the metal oxide precursor coated material.

[0069] In some embodiments, the solid-liquid ratio of the primary material to water is 0.05 g / mL to 0.2 g / mL, for example, it can be 0.05 g / mL, 0.075 g / mL, 0.1 g / mL, 0.125 g / mL, 0.15 g / mL, 0.175 g / mL or 0.2 g / mL.

[0070] In some embodiments, the metal oxide precursor includes any one or a combination of at least two of cerium nitrate, cerium sulfate, cerium chloride, zirconium nitrate, zirconium chloride, yttrium nitrate, yttrium chloride, yttrium sulfate, aluminum chloride, aluminum sulfate, or aluminum nitrate. Typical but non-limiting combinations include a combination of cerium nitrate and zirconium nitrate, or a combination of yttrium chloride and aluminum nitrate, or a combination of zirconium chloride and aluminum chloride.

[0071] In some embodiments, the mixing method includes stirring.

[0072] In some embodiments, the stirring time is 1 hour to 4 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0073] In some embodiments, the stirring temperature is 40°C to 80°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C.

[0074] In some embodiments, the drying temperature is 80°C to 120°C, for example, it can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C.

[0075] In some embodiments, the heating rate of the heat treatment is 2℃ / min to 5℃ / min, for example, it can be 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min or 5℃ / min.

[0076] In some embodiments, the heat treatment temperature is 500°C to 800°C, for example, it can be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C.

[0077] In some embodiments, the heat treatment time is 2h to 8h, for example, it can be 2h, 3h, 4h, 5h, 6h, 7h or 8h.

[0078] In some embodiments, the reducing atmosphere comprises an H2 / Ar mixture in which the volume percentage of H2 is 1 vol% to 10 vol%, for example, it can be 1 vol%, 2 vol%, 3 vol%, 4 vol%, 5 vol%, 6 vol%, 7 vol%, 8 vol%, 9 vol%, or 10 vol%.

[0079] In yet another embodiment, the present invention provides a positive electrode sheet comprising the high-nickel single-crystal ternary material described in the preceding embodiment.

[0080] In yet another embodiment, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode sheet described in yet another embodiment, or comprising the high-nickel single-crystal ternary material described in one of the preceding embodiments.

[0081] 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.

[0082] Example 1

[0083] This embodiment provides a high-nickel single-crystal ternary material, which includes a high-nickel single-crystal ternary matrix, the chemical formula of which is Li. 0.8 Ni 0.8 Co 0.1 Mn 0.1 O2, an oxygen vacancy modification layer of 12 nm is formed in situ on the surface of the high-nickel single crystal ternary substrate, wherein the concentration of oxygen vacancy is 1.5 at%, and a cerium oxide coating layer is also provided on the surface of the oxygen vacancy layer, wherein the mass percentage of the cerium oxide coating layer is 1 wt%.

[0084] The preparation method of the high-nickel single-crystal ternary material includes the following steps:

[0085] (1) Preparation of primary materials: According to the stoichiometric ratio Li / Me=0.8, high-nickel ternary precursors (Ni 0.8 Co 0.1 Mn 0.1 (OH)2 (D50=2.5μm) and lithium nitrate were heated to 900℃ at a heating rate of 5℃ / min under an oxygen atmosphere and sintered for 15h to obtain the primary material;

[0086] (2) Preparation of metal oxide precursor coating material: The primary material obtained in step (1) is dispersed in water according to the solid-liquid ratio of primary material to water of 0.1 g / mL to obtain primary slurry; cerium nitrate is added to the primary slurry, stirred at 60°C for 2 h, the precipitate is collected, and dried at 100°C to obtain the metal oxide precursor coating material.

[0087] (3) Preparation of the high-nickel single-crystal ternary material: In a H2 / Ar mixed gas of 5 vol% H2, the metal oxide precursor coating material obtained in step (2) is heated to 600°C at a heating rate of 5°C / min and heat-treated for 5 h to obtain the high-nickel single-crystal ternary material.

[0088] Example 2

[0089] This embodiment provides a high-nickel single-crystal ternary material, which includes a high-nickel single-crystal ternary matrix, the chemical formula of which is Li. 0.7 Ni 0.6 Co 0.2 Mn 0.2 O2, an oxygen vacancy modification layer of 3 nm is formed in situ on the surface of the high-nickel single crystal ternary substrate, wherein the concentration of oxygen vacancy is 0.2 at%, and a yttrium oxide coating layer is also provided on the surface of the oxygen vacancy layer, wherein the mass percentage of the yttrium oxide coating layer is 0.5 wt%.

[0090] The preparation method of the high-nickel single-crystal ternary material includes the following steps:

[0091] (1) Preparation of primary materials: According to the stoichiometric ratio Li / Me=0.7, mix high-nickel ternary precursors (Ni 0.6 Co 0.2 Mn 0.2 (OH)2 (D50=1.5μm) and lithium carbonate were heated to 750℃ at a heating rate of 2℃ / min under an oxygen atmosphere and sintered for 10h to obtain the primary material;

[0092] (2) Preparation of metal oxide precursor coating material: The primary material obtained in step (1) is dispersed in water according to the solid-liquid ratio of primary material to water of 0.05 g / mL to obtain primary slurry; Yttrium chloride is added to the primary slurry, and the mixture is stirred at 40°C for 1 h to 4 h. The precipitate is collected and dried at 80°C to obtain the metal oxide precursor coating material.

[0093] (3) Preparation of the high-nickel single-crystal ternary material: In a H2 / Ar mixed gas of 1 vol% H2, the metal oxide precursor coating material obtained in step (2) is heated to 500°C at a heating rate of 3°C / min and heat-treated for 2 hours to obtain the high-nickel single-crystal ternary material.

[0094] Example 3

[0095] This embodiment provides a high-nickel single-crystal ternary material, which includes a high-nickel single-crystal ternary matrix, the chemical formula of which is Li. 0.85 Ni 0.9 Co 0.05 Mn 0.05 O2, an oxygen vacancy modification layer of 20 nm is formed in situ on the surface of the high-nickel single crystal ternary substrate, wherein the concentration of oxygen vacancy is 2 at%, and an alumina coating layer is also provided on the surface of the oxygen vacancy layer, wherein the mass percentage of the alumina coating layer is 3 wt%.

[0096] The preparation method of the high-nickel single-crystal ternary material includes the following steps:

[0097] (1) Preparation of primary materials: Ni was mixed according to the stoichiometric ratio of Li / Me = 0.85. 0.9 Co 0.05 Mn 0.05 (OH)2 high-nickel ternary precursor (Ni 0.9 Co 0.05 Mn 0.05 (OH)2 (D50=3.5μm) was treated with nitric acid and sintered at 950℃ for 20h at a heating rate of 4℃ / min under an oxygen atmosphere to obtain the primary material;

[0098] (2) Preparation of metal oxide precursor coating material: The primary material obtained in step (1) is dispersed in water according to the solid-liquid ratio of primary material to water of 0.2 g / mL to obtain primary slurry; cerium nitrate / zirconium nitrate / yttrium chloride / aluminum nitrate are added to the primary slurry, stirred at 80°C for 4 h, the precipitate is collected, and dried at 120°C to obtain the metal oxide precursor coating material.

[0099] (3) Preparation of the high-nickel single-crystal ternary material: In a H2 / Ar mixed gas of 10 vol% H2, the metal oxide precursor coating material obtained in step (2) is heated to 800°C at a heating rate of 3°C / min and heat-treated for 8 hours to obtain the high-nickel single-crystal ternary material.

[0100] Example 4

[0101] This embodiment provides a high-nickel single-crystal ternary material. Except for the zirconium oxide coating layer on the surface of the oxygen vacancy modification layer, which has a mass percentage content of 1.5 wt%, the rest is the same as in Embodiment 1.

[0102] Example 5

[0103] This embodiment provides a high-nickel single-crystal ternary material, except that the chemical formula of the high-nickel single-crystal ternary matrix is ​​Li. 0.6 Ni 0.8 Co 0.1 Mn 0.1 Except for O2, everything else is the same as in Example 1.

[0104] Example 6

[0105] This embodiment provides a high-nickel single-crystal ternary material, except that the chemical formula of the high-nickel single-crystal ternary matrix is ​​Li. 0.95 Ni 0.8 Co 0.1 Mn 0.1 Except for O2, everything else is the same as in Example 1.

[0106] Example 7

[0107] This embodiment provides a high-nickel single-crystal ternary material, except that the chemical formula of the high-nickel single-crystal ternary matrix is ​​Li. 0.58 Ni 0.8 Co 0.1 Mn 0.1 Except for O2, everything else is the same as in Example 1.

[0108] Example 8

[0109] This embodiment provides a high-nickel single-crystal ternary material, except that the chemical formula of the high-nickel single-crystal ternary matrix is ​​Li. 0.98 Ni 0.8 Co 0.1 Mn 0.1 Except for O2, everything else is the same as in Example 1.

[0110] Example 9

[0111] This embodiment provides a high-nickel single-crystal ternary material, which is the same as that in Embodiment 1 except that the thickness of the oxygen vacancy modification layer is 2 nm.

[0112] Example 10

[0113] This embodiment provides a high-nickel single-crystal ternary material, which is the same as that in Embodiment 1 except that the thickness of the oxygen vacancy modification layer is 22 nm.

[0114] Example 11

[0115] This embodiment provides a high-nickel single-crystal ternary material, which is the same as in Embodiment 1 except that the oxygen vacancy concentration in the oxygen vacancy modification layer is 0.15 at%.

[0116] Example 12

[0117] This embodiment provides a high-nickel single-crystal ternary material, which is the same as that in Embodiment 1 except that the oxygen vacancy concentration in the oxygen vacancy modification layer is 2.5 at%.

[0118] Example 13

[0119] This embodiment provides a high-nickel single-crystal ternary material, which is the same as that in Example 1 except that the cerium oxide coating has a mass percentage content of 0.45 wt%.

[0120] Example 14

[0121] This embodiment provides a high-nickel single-crystal ternary material, which is the same as that in Example 1 except that the cerium oxide coating has a mass percentage content of 3.5 wt%.

[0122] Comparative Example 1

[0123] This comparative example provides a high-nickel single-crystal ternary material, which is a traditional NCM811 material with the chemical formula LiNi. 0.8 Co 0.1 Mn 0.1 O2.

[0124] The preparation method of the high-nickel single-crystal ternary material includes:

[0125] Based on a Li / Me molar ratio of 1:1.05, a high-nickel ternary precursor (Ni...) was mixed... 0.8 Co 0.1 Mn 0.1 (OH)2 (D50=2.5μm) and lithium nitrate were heated to 980℃ at a heating rate of 5℃ / min under an oxygen atmosphere and sintered for 15h to obtain the high-nickel single crystal ternary material.

[0126] Comparative Example 2

[0127] This comparative example provides a high-nickel single-crystal ternary material, except that the chemical formula of the high-nickel single-crystal ternary matrix is ​​LiNi.0.8 Co 0.1 Mn 0.1 Except for O2, everything else is the same as in Example 1.

[0128] The preparation method of the high-nickel single-crystal ternary material, except for step (1) which involves mixing the high-nickel ternary precursor (Ni) according to a Li / Me molar ratio of 1:1.05, is as follows. 0.8 Co 0.1 Mn 0.1 (OH)2 (D50=2.5μm) and lithium nitrate were mixed, and then heated to 980°C at a heating rate of 5°C / min under an oxygen atmosphere and sintered for 15 hours. The rest of the process was the same as in Example 1.

[0129] Comparative Example 3

[0130] This comparative example provides a high-nickel single-crystal ternary material, the chemical formula of which is Li. 0.8 Ni 0.8 Co 0.1 Mn 0.1 O2 is the same as in Example 1, except that it does not include the in-situ oxygen vacancy modification layer and the cerium oxide coating layer.

[0131] The preparation method of the high-nickel single-crystal ternary material is the same as that in Example 1, except that only step (1) is performed.

[0132] Comparative Example 4

[0133] This comparative example provides a high-nickel single-crystal ternary material, which is the same as Example 1 except that it does not include a cerium oxide coating layer.

[0134] Comparative Example 5

[0135] This comparative example provides a high-nickel single-crystal ternary material. Except that step (3) is carried out in an Ar environment, which only forms a cerium oxide coating layer and cannot induce the formation of an oxygen vacancy modification layer, the rest is the same as in Example 1.

[0136] Performance testing:

[0137] The high-nickel single-crystal ternary materials provided in all the above embodiments and comparative examples were dispersed in NMP with PVDF and conductive carbon black at a mass ratio of 94:3:3 to prepare a positive electrode slurry. The positive electrode slurry was coated on the surface of aluminum foil to prepare a positive electrode sheet. Lithium metal was used as the negative electrode, and a 1M LiPF6 EC / DEC (1:1 v / v) solution was used as the electrolyte. A CR2032 coin cell was assembled, and its electrical performance was tested at 25°C and within a voltage range of 2.7V to 4.5V. The specific test methods included:

[0138] First, the button cell was activated by charging and discharging it three times at a rate of 0.1C. Then, it was charged and discharged at 0.1C and 1C respectively to obtain the discharge specific capacity at 0.1C and 1C rates. The 1C / 0.1C discharge capacity ratio was calculated by dividing the 1C discharge specific capacity by the 0.1C discharge specific capacity. Next, it was cycled at a rate of 1C for 100 cycles to test the capacity retention rate after the cycles.

[0139] The test results are shown in Table 1.

[0140] Table 1

[0141]

[0142] Based on the test results of Example 1 and Comparative Example 1 in Table 1, this invention utilizes a synergistic "oxygen deficiency" strategy and an "oxygen vacancy" strategy to simultaneously address the issues of bulk structural heterogeneity and surface oxygen loss. By introducing a metal oxide coating layer as a physical barrier onto the surface of the high-nickel single-crystal ternary material, it isolates the high-nickel single-crystal ternary matrix from electrolyte corrosion, while simultaneously improving interfacial stability and optimizing ion conduction, thereby enhancing the material's structural stability and electrochemical performance. This invention, through the synergistic effect of multiple mechanisms, jointly improves the cycle life and rate performance of the high-nickel single-crystal ternary material.

[0143] According to the test results of Examples 1 and 2 to 5, if any one of "oxygen deficiency", "oxygen vacancy" and "metal oxide coating" is lost, the synergistic cooperation of multiple mechanisms cannot be achieved, and the above strategies do not work alone. For example, in Comparative Example 2, if traditional NCM811 is used as the high-nickel single-crystal ternary matrix without using a lithium-deficient matrix, not only is the lithium-ion migration rate affected and the rate performance reduced, but the capacity and cycle performance also decrease. In Comparative Example 3, if only a lithium-deficient high-nickel single-crystal ternary matrix is ​​used as the positive electrode active material without reduction treatment to form an oxygen vacancy modification layer in situ and without setting a metal oxide coating layer, not only is it impossible to effectively stabilize the interface and improve cycle performance, but the rate performance of the material also cannot be effectively improved. The rate performance decreases simultaneously with the cycle performance. In Example 4, if no oxide coating layer is set, the effects of "lithium deficiency" and "oxygen vacancy" cannot be fully utilized, and the rate performance improvement is not ideal. In Example 5, if a metal oxide coating layer is directly applied to the surface of the lithium-deficient high-nickel single-crystal ternary matrix without generating oxygen vacancies in situ to form an oxygen vacancy modification layer, the rate performance and cycle performance of the material cannot be effectively improved.

[0144] Based on the test results of Examples 1, 7, and 8, the degree of lithium deficiency in the high-nickel single-crystal ternary matrix affects its capacity and stability. Excessive lithium deficiency hinders capacity improvement in the high-nickel single-crystal ternary material, while also causing structural instability and significantly deteriorating rate performance and cycle performance. Conversely, insufficient lithium deficiency fails to fully utilize its effect, resulting in unsatisfactory performance enhancement for the high-nickel single-crystal ternary material.

[0145] Based on the test results of Examples 1 and 9 to 12, the thickness and concentration of the oxygen vacancy modification layer jointly affect the modulation effect on the surface electronic structure of the high-nickel single-crystal ternary substrate. If the thickness of the oxygen vacancy modification layer is too small or the concentration of oxygen vacancies is too small, the precipitation and phase transition of lattice oxygen under high voltage cannot be effectively suppressed, resulting in poor interface stability and poor cycle performance. If the thickness of the oxygen vacancy modification layer is too large or the concentration of oxygen vacancies is too large, excessive oxygen vacancies may induce lattice oxygen rearrangement, exacerbating the transition metal (such as Ni) reaction. 4+ The migration and reduction of ions can form an inactive phase (such as rock salt phase), reducing the reversible capacity. At the same time, it can increase the resistance to interfacial ion transport, thus deteriorating the kinetic performance. Furthermore, in high-pressure cycling, it can lead to problems such as uneven thickening of the CEI film and increased gas production, resulting in a decrease in cycling performance.

[0146] Based on the test results of Examples 1, 13, and 14, if the percentage content of the metal oxide coating layer is too small, the thickness will be too small, and it will be impossible to completely coat the high-nickel single-crystal ternary matrix. This may result in some areas having an excessively thin coating layer, leaving the high-nickel single-crystal ternary matrix exposed in the electrolyte, unable to effectively isolate the electrolyte from corrosion, leading to poor interface stability. On the other hand, if the percentage content of the metal oxide coating layer is too large and the thickness is too large, a dense physical barrier will form on the surface, hindering the diffusion and migration of lithium ions, thereby resulting in poor rate performance of the material. At the same time, the migration path of lithium ions will become longer, leading to increased polarization of the battery and poor cycle performance.

[0147] 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 high-nickel single-crystal ternary material, characterized in that, The high-nickel single-crystal ternary material includes a high-nickel single-crystal ternary matrix and an oxygen vacancy modification layer formed in situ on the surface of the high-nickel single-crystal ternary matrix. The surface of the oxygen vacancy modification layer is further provided with a metal oxide coating layer. The high-nickel single-crystal ternary matrix has a cation-ordered superlattice structure, and the chemical formula of the high-nickel single-crystal ternary matrix is ​​Li. m Ni x Co y Mn z O2, 0.6≤m≤0.95, x≥0.6, y>0, z>0, x+y+z=1.

2. The high-nickel single-crystal ternary material as described in claim 1, characterized in that, The thickness of the oxygen vacancy modified layer is 3 nm to 20 nm. And / or, in the oxygen vacancy modified layer, the concentration of oxygen vacancies is 0.2at%~2at%.

3. The high-nickel single-crystal ternary material as described in claim 1 or 2, characterized in that, In the high-nickel single-crystal ternary material, the mass percentage of the metal oxide coating layer is 0.5wt%~3wt%; And / or, the material of the metal oxide coating layer includes any one or a combination of at least two of cerium oxide, zirconium oxide, yttrium oxide, or aluminum oxide.

4. A method for preparing a high-nickel single-crystal ternary material as described in any one of claims 1 to 3, characterized in that, The preparation method includes: The high-nickel ternary precursor and lithium source are mixed according to the molar ratio of total Ni, Co and Mn in lithium to high-nickel ternary precursor (0.6~0.95):1, and sintered in an oxidizing atmosphere to obtain a primary material; the primary material is then liquid-phase coated to obtain a metal oxide precursor coated material; the metal oxide precursor coated material is then heat-treated in a reducing atmosphere to prepare the high-nickel single crystal ternary material.

5. The preparation method according to claim 4, characterized in that, The heating rate for sintering is 2℃ / min to 5℃ / min; And / or, the sintering temperature is 750℃~950℃; And / or, the sintering time is 10h~20h; And / or, the oxidizing atmosphere includes air or oxygen.

6. The preparation method according to claim 4 or 5, characterized in that, The liquid phase coating method includes: The primary material is dispersed in water to obtain a primary slurry; the primary slurry is mixed with a metal oxide precursor, the precipitate is collected and dried to obtain the metal oxide precursor coated material.

7. The preparation method according to any one of claims 4 to 6, characterized in that, The solid-liquid ratio of the primary material to water is 0.05 g / mL to 0.2 g / mL; And / or, the metal oxide precursor includes any one or a combination of at least two of cerium nitrate, cerium sulfate, cerium chloride, zirconium nitrate, zirconium chloride, yttrium nitrate, yttrium chloride, yttrium sulfate, aluminum chloride, aluminum sulfate, or aluminum nitrate; And / or, the mixing method includes stirring, the stirring time is 1h to 4h, and the stirring temperature is 40℃ to 80℃; And / or, the drying temperature is 80℃~120℃.

8. The preparation method according to any one of claims 4 to 7, characterized in that, The heating rate of the heat treatment is 2℃ / min to 5℃ / min; And / or, the temperature of the heat treatment is 500℃~800℃; And / or, the heat treatment time is 2h~8h; And / or, the reducing atmosphere comprises an H2 / Ar mixture, wherein the volume percentage of H2 in the H2 / Ar mixture is 1 vol% to 10 vol%.

9. A positive electrode plate, characterized in that, The positive electrode comprises the high-nickel single-crystal ternary material as described in any one of claims 1 to 3.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode sheet as described in claim 9, or includes the high-nickel single-crystal ternary material as described in any one of claims 1 to 3.

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