Modified high-nickel ternary positive electrode material, preparation method, positive plate and lithium ion battery

Abstract

The invention provides a modified high-nickel ternary positive electrode material, a preparation method, a positive plate and a lithium ion battery, the preparation method comprises the following steps: mixing a spherical high-nickel ternary positive electrode material matrix and a first coating agent, and carrying out gradient sintering to obtain a first coated high-nickel ternary positive electrode material; and dipping the first coated high-nickel ternary positive electrode material in a second coating agent solution, carrying out spray drying, and carrying out heat treatment to obtain the modified high-nickel ternary positive electrode material, the first coating agent comprises cobalt hydroxide; a second coating agent in the second coating agent solution comprises functional group modified quantum dots and a fluorosilane cross-linking agent. A cobalt hydroxide coating layer and an atomic-scale sealing layer constructed by functional group modified quantum dots and a fluorosilane cross-linking agent through low-temperature covalent cross-linking are sequentially arranged on the surface of a spherical high-nickel ternary positive electrode material matrix, so that a quantum dot-fluorosilane molecule-matrix material multistage bonding system is formed; and the problems of grain boundary instability and interface corrosion of the high-nickel material are systematically solved.

Description

Technical Field

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

[0002] High-nickel ternary cathode materials have become the core choice for high-energy-density lithium-ion batteries due to their theoretical specific capacity exceeding 200 mAh / g. However, during charge-discharge cycling, they suffer from grain boundary oxygen vacancies caused by the H2→H3 phase transition and Ni... 4+ Problems such as catalytic electrolyte decomposition mean that the industrialization process has always been constrained by the dual challenges of grain boundary instability and electrolyte interface corrosion.

[0003] CN119092671A discloses a high-nickel ternary cathode material and its preparation method. The method utilizes a metal carbon oxide coating layer on the surface of the high-nickel ternary cathode material's core to form an effective and stable interface layer. This reduces the interfacial reaction between the electrode and electrolyte, thereby improving the cycle performance of the high-nickel ternary cathode material. Simultaneously, the metal carbon oxide coating layer has excellent moisture-proof properties, reducing the formation of Li2CO3 and LiOH by isolating moisture and carbon dioxide from the air, thus reducing residual alkaline impurities and enhancing the stability of the high-nickel ternary cathode material in the atmosphere.

[0004] CN116022862A discloses a selenium-doped cathode material. Selenium doping not only improves the electronic conductivity and ion diffusion rate of high-nickel ternary cathode materials, but also induces oxygen vacancies that suppress the formation of microcracks within the particles, reducing the dissolution of transition metal ions and thus improving cycle performance. Simultaneously, selenium doping can effectively suppress lattice oxygen evolution, enhancing the safety of the high-nickel ternary cathode electrode.

[0005] CN120109179A discloses a surface modification method for high-nickel ternary cathode materials. This method constructs a functionalized interface layer with a three-dimensional lithium-ion conduction network on the cathode surface using nanoscale in-situ coating technology. A fast-ion conductor material is used as the coating medium, leveraging its high lithium-ion diffusion coefficient to significantly enhance the interfacial lithium-ion transport kinetics. A sol-gel method is employed to form a continuous coating layer with controllable thickness, achieving lithium-ion superconductivity while maintaining the electron tunneling effect. This composite structure layer combines physical barrier and mechanical buffering functions, effectively suppressing electrolyte interfacial side reactions and electrochemical cyclic stress-strain-induced particle crack propagation.

[0006] Therefore, it is of great significance to provide a method for preparing high-nickel ternary cathode materials that is adaptable to low-temperature processes and can effectively suppress grain boundary cracking and interface corrosion. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a modified high-nickel ternary cathode material, its preparation method, cathode sheet, and lithium-ion battery. The present invention involves sequentially depositing a cobalt hydroxide coating layer on the surface of a spherical high-nickel ternary cathode material substrate, followed by an atomic-level sealing layer constructed by low-temperature covalent cross-linking of functionally modified quantum dots with a fluorosilane cross-linking agent. This forms a multi-level bonding system of "quantum dots-fluorosilane molecules-matrix material," systematically solving the problems of grain boundary instability and interface corrosion in high-nickel materials.

[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 a modified high-nickel ternary cathode material, the method comprising:

[0010] A spherical high-nickel ternary cathode material matrix is ​​mixed with a first coating agent and then gradient sintered to obtain a first coated high-nickel ternary cathode material. The first coated high-nickel ternary cathode material is then immersed in a second coating agent solution, spray-dried, and heat-treated to obtain the modified high-nickel ternary cathode material. The first coating agent includes cobalt hydroxide. The second coating agent in the second coating agent solution includes functional group-modified quantum dots and a fluorosilane crosslinking agent.

[0011] In this invention, the high-nickel ternary cathode material refers to a ternary cathode material in which nickel accounts for more than 90% of the total molar amount of all transition metal elements.

[0012] In this invention, cobalt hydroxide is used as the first coating agent. The cobalt hydroxide coating layer is pre-crystallized at a lower temperature and then filled with grain boundary oxygen vacancies at a higher temperature, achieving grain boundary strengthening on the surface of the high-nickel ternary cathode material. Next, functionally modified quantum dots combined with a fluorosilane crosslinking agent are used as the second coating agent. The fluorosilane crosslinking agent bonds with the functional groups modified on the surface of the quantum dots to form an organic-inorganic hybrid structure, enhancing its dispersibility and interfacial activity in the coating system. Simultaneously, the fluorosilane crosslinking agent molecules can hydrolyze and condense under heat treatment conditions, self-… A three-dimensional Si-O-Si covalent cross-linked network is formed, enabling low-temperature bonding without photo / thermal initiators, and forming an atomic-level sealing layer constructed by covalent cross-linking. Finally, quantum dots and fluorosilane cross-linking agents are chemically anchored through Si-O-Ti bonds, and fluorosilane cross-linking agent molecules are cross-linked through Si-O-Si bonds. The coating layer forms Si-OM (M=Ni / Co / Mn) interface bonds with the surface of the high-nickel ternary cathode material, thus constructing a multi-level bonding system of "quantum dots-fluorosilane molecules-matrix material", which together solves the problems of grain boundary instability and interface corrosion of high-nickel materials.

[0013] Preferably, the mass ratio of the spherical high-nickel ternary cathode material matrix to the first coating agent is 1:(0.03~0.1).

[0014] Preferably, in the second coating agent, the mass ratio of functional group-modified quantum dots to fluorosilane crosslinking agent is 1:(2~5).

[0015] Preferably, the functional group-modified quantum dots include MXene quantum dots modified with long-chain fluorosilanes.

[0016] Preferably, the mass fraction of the second coating agent in the second coating agent solution is 3wt% to 10wt%.

[0017] Preferably, the mixing method includes ball milling.

[0018] Preferably, the ball milling speed is 200 rpm to 400 rpm.

[0019] Preferably, the ball milling mixing time is 1h to 4h.

[0020] Preferably, the gradient sintering includes first heating to 350℃~550℃, holding at that temperature for 1h~3h, then further heating to 650℃~850℃, and holding at that temperature for 8h~12h.

[0021] Preferably, the heating rate of the gradient sintering is 3℃ / min to 8℃ / min.

[0022] Preferably, the gradient sintering is carried out in an oxygen-containing atmosphere, wherein the oxygen content in the oxygen-containing atmosphere is 3 vol% to 10 vol.

[0023] Preferably, the impregnation is carried out under stirring.

[0024] Preferably, the immersion time is 15 min to 60 min.

[0025] Preferably, the impregnation temperature is 60°C to 80°C.

[0026] Preferably, the air inlet temperature of the spray dryer is 250℃~400℃.

[0027] Preferably, the outlet temperature of the spray dryer is 85℃~120℃.

[0028] Preferably, the heat treatment temperature is 125℃~150℃.

[0029] Preferably, the heat treatment time is 0.5h to 3h.

[0030] Preferably, the heat treatment is performed under an inert atmosphere.

[0031] Preferably, the method for preparing the functional group-modified quantum dots includes:

[0032] MXene powder was ultrasonically broken down to prepare quantum dots; the quantum dots were then dispersed with long-chain fluorosilanes in a reaction solvent and reacted to obtain functionalized quantum dots.

[0033] Preferably, the reaction solvent includes ethanol.

[0034] Preferably, the mass ratio of the quantum dot to the long-chain fluorosilane is 1:(3~7).

[0035] Preferably, the reaction temperature is 45°C to 75°C.

[0036] Preferably, the reaction time is 1 hour to 3 hours.

[0037] In a second aspect, the present invention provides a modified high-nickel ternary cathode material, which is prepared by the preparation method described in the first aspect.

[0038] Thirdly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the modified high-nickel ternary positive electrode material described in the second aspect.

[0039] Fourthly, the present invention provides a lithium-ion battery comprising a modified high-nickel ternary cathode material as described in the second aspect, or a cathode sheet as described in the third aspect.

[0040] 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.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention involves sequentially depositing a cobalt hydroxide coating layer on the surface of a spherical high-nickel ternary cathode material matrix, and then constructing an atomic-level sealing layer by low-temperature covalent crosslinking of functional group-modified quantum dots and fluorosilane crosslinking agents, forming a multi-level bonding system of "quantum dots-fluorosilane molecules-matrix material", which systematically solves the problems of grain boundary instability and interface corrosion in high-nickel materials. Detailed Implementation

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0048] In one specific embodiment, the present invention provides a method for preparing a modified high-nickel ternary cathode material, the method comprising:

[0049] A spherical high-nickel ternary cathode material matrix is ​​mixed with a first coating agent and then gradient sintered to obtain a first coated high-nickel ternary cathode material. The first coated high-nickel ternary cathode material is then immersed in a second coating agent solution, spray-dried, and heat-treated to obtain the modified high-nickel ternary cathode material. The first coating agent includes cobalt hydroxide. The second coating agent in the second coating agent solution includes functional group-modified quantum dots and a fluorosilane crosslinking agent.

[0050] In this invention, cobalt hydroxide is used as the first coating agent. The cobalt hydroxide coating layer is pre-crystallized at a lower temperature and then filled with oxygen vacancies at grain boundaries at a higher temperature, thereby achieving grain boundary strengthening on the surface of the high-nickel ternary cathode material. Secondly, functionally modified quantum dots combined with a fluorosilane crosslinking agent are used as the second coating agent. The fluorosilane crosslinking agent bonds with the functional groups modified on the surface of the quantum dots to form an organic-inorganic hybrid structure, enhancing its dispersibility and interfacial activity in the coating system. Simultaneously, the fluorosilane crosslinking agent molecules undergo hydrolysis and condensation under heat treatment conditions, spontaneously forming a three-dimensional Si-O-Si covalent structure. Cross-linked networks enable low-temperature bonding without photo / thermal initiators, forming an atomically sealed layer constructed by covalent cross-linking. This layer acts as a physical barrier, preventing the electrolyte from corroding the high-nickel ternary cathode material. Furthermore, quantum dots and fluorosilane cross-linking agents are chemically anchored through Si-O-Ti bonds, while fluorosilane cross-linking agent molecules are cross-linked through Si-O-Si bonds. The coating layer forms Si-OM (M=Ni / Co / Mn) interfacial bonds with the surface of the high-nickel ternary cathode material, constructing a multi-level bonding system of "quantum dots-fluorosilane molecules-matrix material," which together solves the problems of grain boundary instability and interfacial corrosion in high-nickel materials.

[0051] In this invention, the appropriate mass ratio between the spherical high-nickel ternary cathode material matrix and the first coating agent is beneficial for the complete coating of the ternary material matrix by the cobalt hydroxide coating layer, thereby achieving grain boundary strengthening on the surface of the high-nickel ternary cathode material while ensuring the rapid migration and diffusion of lithium ions.

[0052] In some embodiments, the mass ratio of the spherical high-nickel ternary cathode material matrix to the first coating agent is 1:(0.03~0.1), for example, it can be 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09 or 1:0.1.

[0053] In this invention, the appropriate mass ratio between the functional group-modified quantum dots and the fluorosilane crosslinking agent in the second coating agent is beneficial for the fluorosilane crosslinking agent to fully bond with the functional groups modified on the surface of the quantum dots, forming an organic-inorganic hybrid structure. This enhances the dispersibility and interfacial activity of the functional group-modified quantum dots and the fluorosilane crosslinking agent in the coating system, while simultaneously forming an atomically sealed layer constructed by covalent crosslinking, which serves as a physical barrier to prevent the electrolyte from corroding the high-nickel ternary cathode material.

[0054] In some embodiments, the mass ratio of the functional group-modified quantum dots to the fluorosilane crosslinking agent in the second coating agent is 1:(2~5), for example, it can be 1:2, 1:2.25, 1:2.5, 1:2.75, 1:3, 1:3.25, 1:3.5, 1:3.75, 1:4, 1:4.25, 1:4.5, 1:4.75 or 1:5.

[0055] In some embodiments, the functional group-modified quantum dots include MXene quantum dots modified with long-chain fluorosilanes.

[0056] This invention uses long-chain fluorosilanes to modify quantum dots, wherein the chemical formula of the long-chain fluorosilane is C. n F (2n+1) -Si(CH3O)3, n=6~18, the long-chain fluorosilane includes C6F 13 -Si(CH3O)3、C7F 15 -Si(CH3O)3、C8F 17 -Si(CH3O)3、C9F 19 -Si(CH3O)3、C 10 F 21 -Si(CH3O)3、C 11 F 23 -Si(CH3O)3、C 12 F 25 -Si(CH3O)3、C 13 F 27 CH2CH2-Si(CH3O)3、C 14 F 29 -Si(CH3O)3、C 15 F 31 -Si(CH3O)3、C 16 F 33 -Si(CH3O)3、C 17 F 35 -Si(CH3O)3 or C 18 F 37 Any one or at least two combinations of -Si(CH3O)3.

[0057] In this invention, the composition of the fluorosilane crosslinking agent may include the above-mentioned long-chain fluorosilane, or it may include short-chain fluorosilane with n=1~6.

[0058] In some embodiments, the mass fraction of the second coating agent in the second coating agent solution is 3wt% to 10wt%, for example, it can be 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, or 10wt%.

[0059] In some implementations, the mixing method includes ball milling.

[0060] In some implementations, the ball milling speed is 200 rpm to 400 rpm, for example, 200 rpm, 250 rpm, 300 rpm, 350 rpm or 400 rpm.

[0061] In some embodiments, the ball milling mixing time is 1h to 4h, for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h.

[0062] In this invention, gradient sintering is carried out in two temperature ranges from low to high. The pre-crystallization stage is completed first, and then grain boundary strengthening sintering is achieved, which is beneficial to improving the grain boundary stability of high-nickel ternary cathode materials.

[0063] In some embodiments, the gradient sintering includes first heating to 350°C~550°C, for example, 350°C, 400°C, 450°C, 500°C or 550°C, holding at that temperature for 1 hour to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, then further heating to 650°C~850°C, for example, 650°C, 700°C, 750°C, 800°C or 850°C, and holding at that temperature for 8 hours to 12 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours.

[0064] In some embodiments, the heating rate of the gradient sintering is 3°C / min to 8°C / min, for example, it can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min or 8°C / min.

[0065] In some embodiments, the gradient sintering is carried out in an oxygen-containing atmosphere, wherein the oxygen content is 3 vol% to 10 vol%, for example, it can be 3 vol%, 4 vol%, 5 vol%, 6 vol%, 7 vol%, 8 vol%, 9 vol%, or 10 vol%.

[0066] In some embodiments, the impregnation is carried out under stirring.

[0067] In some embodiments, the immersion time is 15 min to 60 min, for example, it can be 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0068] In some embodiments, the impregnation temperature is 60°C to 80°C, for example, it can be 60°C, 65°C, 70°C, 75°C or 80°C.

[0069] In some embodiments, the inlet temperature of the spray dryer is 250°C to 400°C, for example, 250°C, 300°C, 350°C or 400°C.

[0070] In some embodiments, the outlet temperature of the spray dryer is 85°C to 120°C, for example, it can be 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C.

[0071] In this invention, the fluorosilane crosslinking agent undergoes a hydrolysis-condensation reaction below 150°C to spontaneously form a three-dimensional Si-O-Si covalent crosslinking network, achieving low-temperature bonding without the need for photo / thermal initiators.

[0072] In some embodiments, the heat treatment temperature is 125°C to 150°C, for example, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C.

[0073] In some embodiments, the heat treatment time is 0.5h to 3h, for example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h or 3h.

[0074] In some embodiments, the heat treatment is carried out in an inert atmosphere, which includes nitrogen and / or an inert gas.

[0075] In some embodiments, the method for preparing the functional group-modified quantum dots includes:

[0076] MXene powder was ultrasonically broken down to prepare quantum dots; the quantum dots were then dispersed with long-chain fluorosilanes in a reaction solvent and reacted to obtain functionalized quantum dots.

[0077] In some embodiments, the average size of the quantum dots is 5nm to 8nm, for example, it can be 5nm, 6nm, 7nm or 8nm. It should be noted that in this invention, the quantum dots are made of MXene powder, which is a nanosheet material. Therefore, the average size of the quantum dots in this invention refers to the length of the longest side of the broken MXene powder flakes.

[0078] In some embodiments, the MXene powder is made of Ti3C2T. x T includes any one or at least two of the functional groups such as -OH, -F or -O.

[0079] In some embodiments, the reaction solvent includes ethanol.

[0080] In some embodiments, the mass ratio of the quantum dot to the long-chain fluorosilane is 1:(3~7), for example, it can be 1:3, 1:4, 1:5, 1:6 or 1:7.

[0081] In some embodiments, the ultrasonic breaking power is 300W to 500W, for example, it can be 300W, 350W, 400W, 450W or 500W.

[0082] In some embodiments, the ultrasonic fragmentation time is 1 hour to 3 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0083] In some embodiments, the reaction time is 1 hour to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0084] In some embodiments, the reaction temperature is 45°C to 75°C, for example, it can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C or 75°C.

[0085] In this invention, the method for preparing the spherical high-nickel ternary cathode material matrix includes:

[0086] A high-nickel ternary precursor is ball-milled with water, ethylene glycol gel, lithium source, doping coating agent, and defoamer to obtain a slurry. The inlet temperature is set to 250℃~400℃, for example, 250℃, 300℃, 350℃, or 400℃, and the outlet temperature is set to 85℃~120℃, for example, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, or 120℃. The mixture is then spray-granulated and calcined in air at 750℃~900℃, for example, 750℃, 800℃, 850℃, or 900℃, for 2h~6h, for example, 2h, 3h, 4h, 5h, or 6h, to obtain the spherical high-nickel ternary cathode material matrix.

[0087] The mass ratio of the high-nickel ternary precursor, water, and ethylene glycol gel is not particularly limited, and those skilled in the art can adjust it according to the state of the slurry.

[0088] In some embodiments, the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, lithium nitrate, or lithium oxalate; the dopant includes any one or a combination of at least two of aluminum oxide, zirconium oxide, magnesium oxide, or zinc oxide; the defoamer includes a polyether defoamer, specifically a combination of any one or at least two of polyoxyethylene polyoxypropylene propylene glycol ether, polyoxyethylene polyoxypropylene glycerol ether, or polyoxyethylene polyoxypropylene block polyether; and the amount of defoamer added is 0.08 wt% to 0.2 wt% of the total slurry mass, for example, 0.08 wt%, 0.1 wt%, 0.12 wt%, or 0.1 wt%. The content of dopant elements in the doping coating agent is 0.3 mol% to 1 mol% of the high-nickel ternary precursor, for example, 0.3 mol%, 0.4 mol%, 0.5 mol%, 0.6 mol%, 0.7 mol%, 0.8 mol%, 0.9 mol%, or 1 mol%. The molar ratio of the high-nickel ternary precursor to the lithium source is 1:(1.03~1.1), for example, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, or 1:1.1.

[0089] In another specific embodiment, the present invention provides a modified high-nickel ternary cathode material, which is prepared by the preparation method described in one of the aforementioned specific embodiments.

[0090] In yet another embodiment, the present invention provides a positive electrode sheet comprising the modified high-nickel ternary positive electrode material described in the aforementioned other embodiment.

[0091] In another specific embodiment, the present invention provides a lithium-ion battery comprising a modified high-nickel ternary cathode material as described in another specific embodiment above, or comprising a cathode sheet as described in yet another specific embodiment above.

[0092] 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.

[0093] Example 1

[0094] This embodiment provides a modified high-nickel ternary cathode material, the preparation method of which includes:

[0095] (1) Preparation of spherical high-nickel ternary cathode material matrix: High-nickel ternary precursor Ni with a molar ratio of 100:105:0.5 0.9 Co 0.05 Mn 0.05 (OH)2, lithium hydroxide and aluminum oxide, along with water, ethylene glycol gel and polyoxyethylene polyoxypropylene propylene glycol ether, were mixed in a mass ratio of 54:43:2.9:0.1 and refined by high-speed ball milling to D90<5μm to obtain a slurry. The slurry was then transferred to a spray granulator with the inlet temperature set at 300℃ and the outlet temperature at 100℃ for spray granulation. The granules were then sintered at 800℃ for 4 hours in an air atmosphere and sieved to obtain a spherical high-nickel ternary cathode material matrix with a particle size D50 of 8μm.

[0096] (2) Preparation of the second coating agent solution: Set the ultrasonic power to 400W, and add Ti3C2T x MXene powder was ultrasonically crushed for 5 hours to obtain quantum dots with an average size of 7 nm, which were then reacted with C. 13 F 27 -Si(CH3O)3 was dispersed in ethanol at a mass ratio of 1:5 and reacted at 60℃ for 2 h to obtain functionally modified quantum dots; the functionally modified quantum dots and C 13 F 27 -Si(CH3O)3 were mixed in a mass ratio of 1:3 to prepare a 5wt% second coating agent solution;

[0097] (3) Set the ball milling speed to 300 rpm, and mix the spherical high-nickel ternary cathode material matrix prepared in step (1) with cobalt hydroxide at a mass ratio of 1:0.05 for 2 hours. Then, in a nitrogen-oxygen mixed atmosphere containing 5 vol% oxygen, first heat the material to 400°C at 58°C / min and keep it at 400°C for 2 hours, and then heat it to 750°C and keep it at 750°C for 10 hours to obtain the first coated high-nickel ternary cathode material. Immerse the first coated high-nickel ternary cathode material in the second coating agent solution, stir it at 70°C for 30 minutes, set the air inlet temperature to 300°C and the air outlet temperature to 100°C, spray dry it, and then heat treat it at 150°C for 1 hour in a nitrogen atmosphere to obtain the modified high-nickel ternary cathode material.

[0098] Example 2

[0099] This embodiment provides a modified high-nickel ternary cathode material, the preparation method of which includes:

[0100] (1) Preparation of spherical high-nickel ternary cathode material matrix: High-nickel ternary precursor Ni with a molar ratio of 100:103:0.3 0.92 Co 0.04 Mn 0.04(OH)2, lithium nitrate and zirconium oxide, together with water, ethylene glycol gel and polyoxyethylene polyoxypropylene glycol ether, are mixed in a mass ratio of 50:44:5.9:0.1 and refined by high-speed ball milling to D90<5μm to obtain a slurry. The slurry is then transferred to a spray granulator with the inlet temperature set at 250℃ and the outlet temperature at 85℃ for spray granulation. The granules are then sintered at 750℃ for 2 hours in an air atmosphere and sieved to obtain a spherical high-nickel ternary cathode material matrix with a particle size D50 of 6μm.

[0101] (2) Preparation of the second coating agent solution: Set the ultrasonic power to 300W, and add Ti3C2T x MXene powder was ultrasonically crushed for 1 hour to obtain quantum dots with an average size of 5 nm, which were then reacted with C6F. 13 -Si(CH3O)3 was dispersed in ethanol at a mass ratio of 1:3 and reacted at 45℃ for 1 h to obtain functionally modified quantum dots; the functionally modified quantum dots were then reacted with C6F... 13 -Si(CH3O)3 were mixed in a mass ratio of 1:2 to prepare a 3wt% second coating agent solution;

[0102] (3) Set the ball milling speed to 200 rpm, and mix the spherical high-nickel ternary cathode material matrix prepared in step (1) with cobalt hydroxide at a mass ratio of 1:0.03 for 1 h. Then, in a nitrogen-oxygen mixed atmosphere containing 3 vol% oxygen, first heat the material to 350 °C at 3 °C / min and keep it at 3 °C for 1 h, and then heat it to 650 °C and keep it at 650 °C for 8 h to obtain the first coated high-nickel ternary cathode material. Immerse the first coated high-nickel ternary cathode material in the second coating agent solution, stir it at 60 °C for 15 min, set the air inlet temperature to 250 °C and the air outlet temperature to 85 °C, spray dry it, and then heat treat it at 125 °C for 0.5 h in a nitrogen atmosphere to obtain the modified high-nickel ternary cathode material.

[0103] Example 3

[0104] This embodiment provides a modified high-nickel ternary cathode material, the preparation method of which includes:

[0105] (1) Preparation of spherical high-nickel ternary cathode material substrate: Same as in Example 1;

[0106] (2) Preparation of the second coating agent solution: Set the ultrasonic power to 500W, and add Ti3C2T x MXene powder was ultrasonically crushed for 3 hours to obtain quantum dots with an average size of 8 nm, which were then reacted with C. 18 F 37 -Si(CH3O)3 was dispersed in ethanol at a mass ratio of 1:7 and reacted at 75℃ for 3 h to obtain functionally modified quantum dots; the functionally modified quantum dots and C 18 F37 -Si(CH3O)3 were mixed in a mass ratio of 1:5 to prepare a 10wt% second coating agent solution;

[0107] (3) Set the ball milling speed to 400 rpm, and mix the spherical high-nickel ternary cathode material matrix prepared in step (1) with cobalt hydroxide at a mass ratio of 1:0.1 for 4 h. Then, in a nitrogen-oxygen mixed atmosphere containing 10 vol% oxygen, first heat the material to 550 °C at 8 °C / min and keep it at that temperature for 3 h, then heat it to 850 °C and keep it at that temperature for 12 h to obtain the first coated high-nickel ternary cathode material. Immerse the first coated high-nickel ternary cathode material in the second coating agent solution, stir it at 80 °C for 60 min, set the air inlet temperature to 400 °C and the air outlet temperature to 120 °C, spray dry it, and then heat treat it at 150 °C for 3 h in a nitrogen atmosphere to obtain the modified high-nickel ternary cathode material.

[0108] Example 4

[0109] This embodiment provides a modified high-nickel ternary cathode material, which is the same as in Example 1 except that the mass ratio of the spherical high-nickel ternary cathode material matrix to cobalt hydroxide is 1:0.02.

[0110] Example 5

[0111] This embodiment provides a modified high-nickel ternary cathode material. Except for the mass ratio of the spherical high-nickel ternary cathode material matrix to cobalt hydroxide being 1:0.15, everything else is the same as in Example 1.

[0112] Example 6

[0113] This embodiment provides a modified high-nickel ternary cathode material, which is the same as in Example 1 except that the mass ratio of the functional group-modified quantum dots to the fluorosilane crosslinking agent is 1:1.5.

[0114] Example 7

[0115] This embodiment provides a modified high-nickel ternary cathode material, which is the same as in Example 1 except that the mass ratio of the functional group-modified quantum dots to the fluorosilane crosslinking agent is 1:5.5.

[0116] Example 8

[0117] This embodiment provides a modified high-nickel ternary cathode material, which is the same as that in Example 1 except that the impregnation temperature in step (3) is 55°C.

[0118] Example 9

[0119] This embodiment provides a modified high-nickel ternary cathode material, which is the same as that in Example 1 except that the impregnation temperature in step (3) is 85°C.

[0120] Example 10

[0121] This embodiment provides a modified high-nickel ternary cathode material, which is the same as that in Example 1 except that the heat treatment temperature in step (3) is 120°C.

[0122] Example 11

[0123] This embodiment provides a modified high-nickel ternary cathode material, which is the same as that in Example 1 except that the heat treatment temperature in step (3) is 160°C.

[0124] Example 12

[0125] This embodiment provides a modified high-nickel ternary cathode material, except for step (2) quantum dots and C 13 Except for the mass ratio of F27CH2CH2-Si(OMe)3 being 1:2.5, everything else was the same as in Example 1.

[0126] Example 13

[0127] This embodiment provides a modified high-nickel ternary cathode material, except for step (2) quantum dots and C 13 Except for the mass ratio of F27CH2CH2-Si(OMe)3 being 1:7.5, everything else was the same as in Example 1.

[0128] Example 14

[0129] This embodiment provides a modified high-nickel ternary cathode material, except for step (2) quantum dots and C 13 Except for the reaction temperature of F27CH2CH2-Si(OMe)3 being 40°C, everything else was the same as in Example 1.

[0130] Example 15

[0131] This embodiment provides a modified high-nickel ternary cathode material, except for step (2) quantum dots and C 13 Except for the reaction temperature of F27CH2CH2-Si(OMe)3 being 80°C, everything else was the same as in Example 1.

[0132] Comparative Example 1

[0133] This comparative example provides a high-nickel ternary cathode material, which is the same as Example 1 except that only step (1) is performed.

[0134] Comparative Example 2

[0135] This comparative example provides a modified high-nickel ternary cathode material, which is the same as that in Example 1 except that steps (1) and (2) are performed.

[0136] Comparative Example 3

[0137] This comparative example provides a modified high-nickel ternary cathode material, which is the same as that in Example 1 except that steps (1) and (3) are performed.

[0138] Comparative Example 4

[0139] This comparative example provides a modified high-nickel ternary cathode material, which is the same as Example 1 except that the quantum dots are not modified with functional groups in step (2).

[0140] Comparative Example 5

[0141] This comparative example provides a modified high-nickel ternary cathode material, which is the same as in Example 1 except that the second coating agent solution in step (3) is replaced with a glucose solution.

[0142] Performance testing:

[0143] The high-nickel ternary cathode material provided in all the above embodiments and comparative examples was dispersed in NMP with conductive carbon black and PVDF at a mass ratio of 92:4:4, coated onto the surface of aluminum foil to prepare a cathode sheet, matched with a negative electrode, assembled into a lithium-ion battery, and its electrochemical performance was tested. Specifically, this included:

[0144] Hydrophobicity tests were conducted on all the high-nickel ternary cathode materials provided in the above embodiments and comparative examples. The water contact angle of their surfaces was tested, and the test results are shown in Table 1.

[0145] Electrochemical impedance spectroscopy (EIS) tests were performed on the lithium-ion batteries assembled from the high-nickel ternary cathode materials provided in all the above embodiments and comparative examples. The interface impedance was tested, and the test results are shown in Table 1.

[0146] The initial discharge specific capacity and capacity retention rate after 1000 charge-discharge cycles were tested at 0.1C rate within a voltage range of 2.5V to 4.5V at 25℃. The test results are shown in Table 1.

[0147] The battery was disassembled after 1000 cycles, and the Mn content on the negative electrode side (i.e., the amount of Mn dissolved from the positive electrode) was tested. The test results are shown in Table 1.

[0148] Table 1

[0149]

[0150] Based on the test results of Example 1 and Comparative Examples 1 to 5 in Table 1, this invention systematically solves the problems of grain boundary instability and interface corrosion of high-nickel materials by sequentially setting a cobalt hydroxide coating layer and an atomic-level sealing layer constructed by low-temperature covalent cross-linking of functional group-modified quantum dots and fluorosilane cross-linking agents on the surface of a spherical high-nickel ternary cathode material substrate, forming a multi-level bonding system of "quantum dot-fluorosilane molecule-matrix material".

[0151] According to the test results of Examples 1, 4, and 5, if the mass ratio of the spherical high-nickel ternary cathode material matrix to cobalt hydroxide is too small, a complete coating layer cannot be formed, and the grain boundary strengthening on the surface of the high-nickel ternary cathode material cannot be effectively achieved, resulting in an increase in interfacial impedance. If the mass ratio of the spherical high-nickel ternary cathode material matrix to cobalt hydroxide is too large, the coating layer formed is too thick, resulting in an excessively long migration path for lithium ions, which also leads to a significant increase in interfacial impedance, increased polarization, and a significant increase in Mn dissolution.

[0152] Based on the test results of Examples 1, 6, and 7, in the second coating agent, a suitable mass ratio between the functional group-modified quantum dots and the fluorosilane crosslinking agent is beneficial for the fluorosilane crosslinking agent to fully bond with the functional groups modified on the surface of the quantum dots, forming an organic-inorganic hybrid structure. This enhances the dispersibility and interfacial activity of the functional group-modified quantum dots and the fluorosilane crosslinking agent in the coating system. Simultaneously, it forms an atomically sealed layer constructed by covalent crosslinking, improving the hydrophobicity of the modified high-nickel ternary cathode material surface and acting as a physical barrier to prevent the electrolyte from corroding the high-nickel ternary cathode material. If the mass ratio is too large or too small, it will lead to a decrease in the hydrophobicity of the modified high-nickel ternary cathode material surface, a decline in electrical performance, and an increase in Mn dissolution.

[0153] According to the test results of Examples 1, 8 and 9, if the immersion temperature of the first coated high-nickel ternary cathode material in the second coating agent solution is too low or too high, it is not conducive to the construction of the atomic-level sealing layer formed by the low-temperature covalent cross-linking of the functional group modified quantum dots and the fluorosilane cross-linking agent, resulting in a decrease in the electrical performance of the modified high-nickel ternary cathode material.

[0154] According to the test results of Examples 1, 10, and 11, the fluorosilane crosslinking agent undergoes hydrolysis and condensation reaction below 150°C, spontaneously forming a three-dimensional Si-O-Si covalent crosslinking network. If the heat treatment temperature is too low or too high, it is not conducive to the low-temperature covalent crosslinking of the functional group modified quantum dots with the fluorosilane crosslinking agent to form a complete atomic-level sealing layer, effectively forming a physical barrier, inhibiting the corrosion of the substrate by the electrolyte, and leading to a decrease in the electrical performance of the modified high-nickel ternary cathode material.

[0155] Based on the test results of Examples 1, 12, and 13, when preparing functional group-modified quantum dots, the quantum dots and C... 13The mass ratio of F27-Si(CH3O)3 affects the performance of the atomic-level sealing layer obtained by subsequent crosslinking with silane agents. Both excessively high and low mass ratios are detrimental to the improvement of electrical performance.

[0156] Based on the test results of Examples 1, 14, and 15, when modifying quantum dots, both excessively high and excessively low reaction temperatures are not conducive to the effective modification of quantum dots by functional groups, resulting in a decrease in the electrical performance of the subsequently prepared modified high-nickel ternary cathode material.

[0157] 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 a modified high-nickel ternary positive electrode material, characterized in that, The preparation method includes: A spherical high-nickel ternary cathode material matrix is ​​mixed with a first coating agent and then sintered in a gradient to obtain a first coated high-nickel ternary cathode material. The first coated high-nickel ternary cathode material is then immersed in a second coating agent solution, spray-dried, and heat-treated to obtain the modified high-nickel ternary cathode material. The first coating agent includes cobalt hydroxide; The second coating agent in the second coating agent solution includes functional group-modified quantum dots and fluorosilane crosslinking agents.

2. The production method according to claim 1, wherein The mass ratio of the spherical high-nickel ternary cathode material matrix to the first coating agent is 1:(0.03~0.1); And / or, in the second coating agent, the mass ratio of functional group-modified quantum dots to fluorosilane crosslinking agent is 1:(2~5); And / or, the functional group-modified quantum dots include MXene quantum dots modified with long-chain fluorosilanes; And / or, in the second coating agent solution, the mass fraction of the second coating agent is 3wt%~10wt%.

3. The production method according to claim 1 or 2, characterized by, The mixing method includes ball milling; And / or, the gradient sintering includes first heating to 350℃~550℃, holding for 1h~3h, then heating to 650℃~850℃, and holding for 8h~12h. And / or, the heating rate of the gradient sintering is 3℃ / min to 8℃ / min; And / or, the gradient sintering is carried out in an oxygen-containing atmosphere, wherein the oxygen content in the oxygen-containing atmosphere is 3 vol% to 10 vol.

4. The production method according to any one of claims 1 to 3, wherein The impregnation is carried out under stirring; And / or, the immersion time is 15 min to 60 min; And / or, the impregnation temperature is 60°C to 80°C.

5. The production method according to any one of claims 1 to 4, wherein The inlet temperature of the spray dryer is 250℃~400℃; And / or, the outlet temperature of the spray dryer is 85℃~120℃; And / or, the temperature of the heat treatment is 125℃~150℃; And / or, the heat treatment time is 0.5h to 3h; And / or, the heat treatment is performed under an inert atmosphere.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The method for preparing the functional group-modified quantum dots includes: MXene powder was ultrasonically broken down to prepare quantum dots; the quantum dots were then dispersed with long-chain fluorosilanes in a reaction solvent and reacted to obtain functionalized quantum dots.

7. The preparation method according to claim 6, characterized in that, The reaction solvent includes ethanol; And / or, the mass ratio of the quantum dots to the long-chain fluorosilane is 1:(3~7); And / or, the reaction temperature is 45°C to 75°C; And / or, the reaction time is 1h to 3h.

8. A modified high-nickel ternary cathode material, characterized in that, The modified high-nickel ternary cathode material is prepared by the preparation method described in any one of claims 1 to 7.

9. A positive electrode plate, characterized in that, The cathode material comprises the modified high-nickel ternary cathode material as described in claim 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the modified high-nickel ternary cathode material as described in claim 8, or the cathode sheet as described in claim 9.

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