Anode material, anode sheet and battery

Abstract

The present application provides a negative electrode material, a negative electrode sheet, and a battery, the negative electrode material comprising a carbon matrix and a silicon-based active material, the negative electrode material containing an alkali metal element, an alkaline earth metal element, and an oxygen element, the alkali metal element including Na and / or K, the alkaline earth metal element including Mg and / or Ca, the mass content of the alkali metal element being Appm, the mass content of the alkaline earth metal element being B ppm, and the mass content of the oxygen element being E%, and the negative electrode material being 1×10 -5 ≦(B / A)×E≦5×10 2 The negative electrode material provided in the present application not only improves the specific capacity of the negative electrode material, but also improves the mechanical strength of the particles of the negative electrode material, reduces the volume expansion of the negative electrode material, and improves the cycle stability of the negative electrode material.

Description

[Technical Field]

[0001] This application claims priority from Chinese Patent Application No. 202410014552.1, filed on January 5, 2024. The entire text of the above Chinese patent application is incorporated herein by reference.

[0002] The present application relates to the technical field of negative electrode materials, and more particularly to negative electrode materials, negative electrode sheets, and batteries. [Background technology]

[0003] Lithium-ion batteries are widely used in electric vehicles and consumer electronics due to their advantages of high energy density, long cycle life, minimal environmental pollution, and no memory effect. In recent years, the rapid development of electric vehicles has driven increasing demand for higher energy density lithium-ion batteries, prompting researchers to explore battery materials with higher energy density and better cycle performance. Cathode and anode materials are the core components of batteries and determine their operating efficiency. Currently, commercially available anode materials are graphite, whose capacity is close to its theoretical upper limit, limiting further improvement. Therefore, the development of a new generation of anode materials with higher energy density is urgently needed. Silicon-based anode materials are generally considered to be next-generation battery anode materials, offering the advantages of high capacity, abundant supply, and relative safety.

[0004] Silicon anodes are generally considered to be next-generation battery anode materials, with the advantages of high capacity, abundant supply, and relative safety. However, the intense volume expansion effect of silicon anodes during cycling leads to material pulverization and crushing, and the repeated volume changes of silicon anode materials during electrochemical cycling also lead to the continuous destruction and regeneration of the SEI film formed on the surface of the silicon material, which results in the continuous consumption of lithium ions and ultimately leads to rapid capacity decay. Summary of the Invention [Problem to be solved by the invention]

[0005] The present application provides an anode material, an anode sheet, and a battery that improve the specific capacity of the anode material, improve the mechanical strength of the particles of the anode material, mitigate the volume expansion of the anode material, and improve the cycle stability of the anode material. [Means for solving the problem]

[0006] In a first aspect, the present application provides a negative electrode material comprising a carbon matrix and a silicon-based active material, the negative electrode material containing an alkali metal element, an alkaline earth metal element, and an oxygen element, the alkali metal element comprising Na and / or K, and the alkaline earth metal element comprising Mg and / or Ca; The mass content of the alkali metal element is A p m, the mass content of the alkaline earth metal element is B ppm, and the mass content of the oxygen element is E; The negative electrode material is 1×10 -5 ≦(B / A)×E≦5×10 2 Satisfy the relationship.

[0007] In a second aspect, the present application provides a negative electrode sheet comprising the negative electrode material of the first aspect of the present application.

[0008] In a third aspect, the present application provides a battery comprising the negative electrode material of the first aspect of the present application or the negative electrode sheet of the second aspect of the present application. [Effects of the Invention]

[0009] The technical solution of the present application has at least the following beneficial effects:

[0010] The present application provides a negative electrode material comprising a carbon matrix and a silicon-based active material, the negative electrode material containing an alkali metal element, an alkaline earth metal element, and an oxygen element, the alkali metal element including Na and / or K, the alkaline earth metal element including Mg and / or Ca, the mass content of the alkali metal element being A p m, the mass content of the alkaline earth metal element being B ppm, and the mass content of the oxygen element being E, and the negative electrode material of the present application has a mass of 1×10 -5 ≦(B / A)×E≦5×10 2 This satisfies the above requirements, improving the specific capacity of the negative electrode material while also improving the mechanical strength of the particles of the negative electrode material, alleviating the volumetric expansion of the negative electrode material, further reducing the gas generation phenomenon of the negative electrode material, and improving the cycle stability of the negative electrode material. The inventors speculate that silicates may be present in the negative electrode material. However, alkaline earth metal element-containing silicates can enhance the mechanical strength of the silicon-based active material and have good thermal and structural stability, effectively alleviating the volumetric expansion of the silicon-based active material. Alkali metal element silicates are water-soluble. Although they have low mechanical strength themselves, they can act as adhesives to enhance the mechanical strength of alkaline earth metal element-containing silicates and further alleviate the volumetric expansion of the negative electrode material. The inventors speculate that the content of oxygen in the negative electrode material can reflect the mass content of silicon oxide in the negative electrode material. An appropriate amount of silicon oxide on the surface of the silicon-based active material can reduce direct contact between the silicon-based active material and the electrolyte, thereby reducing side reactions and gas generation. Therefore, the present application proposes a 1×10 -5 ≦(B / A)×E≦5×10 2 By controlling the mass content of the alkali metal silicate, alkaline earth metal silicate, and silicon oxide in the negative electrode material, it is possible to balance the mass content of the alkali metal silicate, alkaline earth metal silicate, and silicon oxide in the negative electrode material, thereby improving the specific capacity of the negative electrode material, improving the mechanical strength of the particles of the negative electrode material, mitigating the volume expansion of the negative electrode material, further reducing the gas generation phenomenon of the negative electrode material, and improving the cycle stability of the negative electrode material. DETAILED DESCRIPTION OF THE INVENTION

[0011] In order to better explain the present application and facilitate understanding of the technical solution of the present application, the present application will be described in more detail below. However, the following examples are merely simple examples of the present application and do not limit the protection scope of the rights of the present application, which is governed by the claims.

[0012] In a first aspect, the present application provides a negative electrode material comprising a carbon matrix and a silicon-based active material, the negative electrode material containing an alkali metal element, an alkaline earth metal element, and an oxygen element, the alkali metal element comprising Na and / or K, and the alkaline earth metal element comprising Mg and / or Ca; The mass content of the alkali metal element is A p m, the mass content of the alkaline earth metal element is B ppm, and the mass content of the oxygen element is E; The negative electrode material is 1×10 -5 ≦(B / A)×E≦5×10 2 Satisfy the relationship.

[0013] The present application provides a negative electrode material comprising a carbon matrix and a silicon-based active material. Specifically, the silicon-based active material is supported on a carbon matrix. The negative electrode material contains an alkali metal element, an alkaline earth metal element, and an oxygen element. The alkali metal element includes Na and / or K, and the alkaline earth metal element includes Mg and / or Ca. The mass content of the alkali metal element is A p m, the mass content of the alkaline earth metal element is B ppm, and the mass content of the oxygen element is E. The negative electrode material of the present application has a mass of 1×10 -5 ≦(B / A)×E≦5×10 2 This satisfies the above requirement, thereby improving the specific capacity of the negative electrode material, and also improving the mechanical strength of the particles of the negative electrode material, thereby mitigating the volume expansion of the negative electrode material, further reducing the gas generation phenomenon of the negative electrode material, and improving the cycle stability of the negative electrode material.

[0014] The inventors speculate that silicates may be present in the negative electrode material. However, alkaline earth metal element-containing silicates can enhance the mechanical strength of silicon-based active materials and have good thermal and structural stability, effectively mitigating the volume expansion of silicon-based active materials. Alkali metal element silicates are water-soluble, and although they have low mechanical strength themselves, they can act as adhesives to enhance the mechanical strength of alkaline earth metal element-containing silicates. The inventors speculate that the oxygen content in the negative electrode material can reflect the mass content of silicon oxide in the negative electrode material. An appropriate amount of silicon oxide on the surface of the silicon-based active material reduces direct contact between the silicon-based active material and the electrolyte, reducing the occurrence of side reactions and gas generation. The negative electrode material of the present application has a 1×10 -5 ≦(B / A)×E≦5×10 2 and the mass contents of alkali metal silicate, alkaline earth metal silicate, and silicon oxide in the negative electrode material are balanced, which improves the specific capacity of the negative electrode material, improves the mechanical strength of the particles of the negative electrode material, reduces the volume expansion of the negative electrode material, further reduces the gas generation phenomenon of the negative electrode material, and improves the cycle stability of the negative electrode material. The above is merely the inventor's reasonable speculation, and there may be other reasons. In short, in this application, -5 ≦(B / A)×E≦5×10 2 By controlling the specific capacity of the negative electrode material within this range, it is possible to improve the specific capacity of the negative electrode material, as well as to improve the mechanical strength of the particles of the negative electrode material, mitigate the volume expansion of the negative electrode material, further reduce the gas generation phenomenon of the negative electrode material, and improve the cycle stability of the negative electrode material.

[0015] In some embodiments, the mass content of alkali metal elements in the negative electrode material is 1≦A≦5000 in Appm, where A may be, for example, 1, 10, 50, 100, 200, 500, 800, 1000, 2000, 3000, 4000, or 5000, and is not limited thereto. The inventors reasonably conjecture that it is possible to control the mass content of alkali metal elements in the negative electrode material, i.e., the mass content of alkali metal silicates. Alkali metal silicates such as sodium silicate and potassium silicate are water-soluble and can enhance the crack resistance of magnesium silicate and calcium silicate as adhesives. Preferably, the mass content of alkali metal elements is 5 ppm≦Appm≦3000 ppm.

[0016] In some embodiments, the mass content of alkaline earth metal elements in the negative electrode material is B ppm, where B is 3≦B≦5000, and the value of B may be, for example, 3, 10, 50, 100, 200, 500, 800, 1000, 2000, 3000, 4000, or 5000, etc., and is not limited thereto. The inventors reasonably conjecture that controlling the mass content of alkaline earth metal elements, i.e., the mass content of alkaline earth metal silicates, in the negative electrode material is understood to be understood. Magnesium silicate and calcium silicate have excellent mechanical strength, and when magnesium silicate and calcium silicate are located on the surface of a silicon-based active material, the mechanical strength of the silicon-based active material can be improved and the volume expansion of the silicon-based active material can be reduced. Preferably, the mass content of alkaline earth metal elements is 10 ppm≦A p m ≦3000 ppm. More preferably, the mass content of alkaline earth metal elements is 500 ppm≦A p m ≦3000 ppm. By optimizing the mass content of alkaline earth metal elements, the negative electrode material has both good mechanical strength and elasticity, and the negative electrode material is not easy to burst and has good cycle stability.

[0017] In some embodiments, the mass content of oxygen in the negative electrode material is E, where E is 0.005≦E≦0.1. The value of E may be, for example, 0.005 (i.e., 0.5%), 0.008, 0.01, 0.012, 0.015, 0.018, 0.02, 0.025, 0.03, 0.04, 0.05, 0.06, 0.08, or 0.1, but is not limited thereto. By controlling the mass content of oxygen in the negative electrode material, the silicon oxide layer on the surface of the silicon-based active material can be within an appropriate range. The inventors reasonably speculate that the silicon oxide layer and the silicate layer can act synergistically to further mitigate the volume expansion of the silicon-based active material during cycling, thereby improving the cycling performance of the negative electrode material. Preferably, the mass content of oxygen is 0.01≦E≦0.08.

[0018] In some embodiments, 1×10 -5 ≦(B / A)×E≦5×10 2 Specifically, 1×10 -5 , 1×10 -4 , 1×10 -3 , 1×10 -2 , 1×10 -1 , 1, 10, 20, 50, 100, 5×10 2 etc., but are not limited thereto. Preferably, 1×10 -2 ≦(B / A)×E≦50.

[0019] In some embodiments, the alkaline earth metal element is present in the form of an alkaline earth metal silicate or oxide, such as magnesium silicate and / or calcium silicate, calcium oxide and / or magnesium oxide.

[0020] In some embodiments, the alkali metal element may be present in the form of an alkali metal silicate, specifically potassium silicate and / or sodium silicate.

[0021] In some embodiments, the carbon matrix includes at least one of hard carbon, soft carbon, graphite, mesocarbon microbeads, activated carbon, porous carbon, mesoporous carbon, and carbon gel.

[0022] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, silicon alloy, and silicon-carbon composite. Specifically, the elemental silicon may be amorphous silicon, crystalline silicon, or a composite of crystalline silicon and amorphous silicon, etc., and is not limited herein. The silicon alloy may be a silicon-lithium alloy, a silicon-magnesium alloy, a silicon-nickel alloy, etc., and is not limited herein. The silicon oxide contains silicon element and oxygen element, and the atomic ratio of the silicon element to the oxygen element is 0 to 2 and does not include 0, and is not limited herein. The chemical formula of the silicon oxide is SiO x where 0 < x ≦ 2, and is not specifically limited herein.

[0023] In some embodiments, the average particle size of the silicon-based active material is 0.1 nm to 500 nm. Specifically, it may be 0.1 nm, 1 nm, 5 nm, 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, 350 nm, 400 nm, or 500 nm, etc. Naturally, it may be other values within the above range and is not limited herein. The silicon-based active material with an appropriate size can improve the uniformity of the distribution of the silicon-based active material and the carbon matrix, reduce the agglomeration phenomenon of the silicon-based active material, and improve the cycle performance of the negative electrode material. Preferably, the average particle size of the silicon-based active material is 1 nm to 10 nm, and more preferably, the average particle size of the silicon-based active material is 1 nm to 5 nm.

[0024] In some embodiments, the mass content of silicon element in the silicon-based active material is ≧ 99%. The mass content of silicon element in the silicon-based active material being within the above range is advantageous for improving the purity of the silicon-based active material and reducing impurities.

[0025] In some embodiments, the negative electrode material further comprises a carbon layer located on the surface of the negative electrode material, which can reduce the volume expansion effect of the negative electrode material to some extent and increase the conductivity of the negative electrode material, and the carbon layer can also reduce direct contact between the silicon-based active material and the electrolyte, inhibit excessive growth of a solid electrolyte interlayer (SEI) on the surface of the negative electrode material, stabilize the interface of the negative electrode material, and improve the first coulomb efficiency of the negative electrode material.

[0026] In some embodiments, the carbon layer comprises at least one of graphitic carbon and amorphous carbon. The presence of the carbon layer on the surface of the active material can improve the electrical conductivity of the negative electrode material, stabilize the interface of the negative electrode material, reduce direct contact between the silicon-based active material and the electrolyte, reduce the occurrence of side reactions, and also improve the rate capability and cycle performance of the negative electrode material.

[0027] In some embodiments, the median particle size D50 of the negative electrode material is ≦15 μm, and may be, specifically, 0.5 μm, 1 μm, 2 μm, 5 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., and of course, may be other values ​​within the above range, and is not limited thereto. It can be understood that controlling the median particle size of the negative electrode material within the above range is advantageous for improving the cycling performance of the negative electrode material.

[0028] In some embodiments, the specific surface area of ​​the negative electrode material is ≦5 m 2 / g, specifically, 0.1m 2 / g, 0.5m 2 / g, 1m 2 / g, 1.5m 2 / g, 2m 2 / g, 2.5m 2 / g, 3m 2 / g, 3.5m 2 / g, 4m 2 / g, 4.5m 2 / g or 5m 2 / g, etc., and of course, other values ​​within the above range are also possible, and are not limited thereto. Controlling the specific surface area of ​​the negative electrode material within the above range is advantageous in improving the initial effect and cycle performance of a lithium battery made of the negative electrode material.

[0029] In some embodiments, the negative electrode material includes a carbon matrix and a silicon-based active material, and a carbon layer is coated on at least a portion of the silicon-based active material, which can reduce direct contact between the silicon-based active material and the electrolyte and also help alleviate volume expansion.

[0030] In some embodiments, when at least a portion of the silicon-based active material is coated with a carbon layer, the mass ratio of elemental silicon to elemental carbon is (0.16-2): 1. Adjusting the mass ratio of elemental silicon to elemental carbon not only helps to improve the cycling stability of the negative electrode material, but also helps to improve the capacity of the negative electrode material.

[0031] In a second aspect, the present application provides a method for producing a negative electrode material, the method comprising: Step S10 of compounding the carbon material with the silicon-based substance to obtain a compound; and step S20 of calcining the mixture containing the composite, an alkali metal oxide, and an alkaline earth metal oxide to obtain a negative electrode material, wherein the alkali metal element includes at least one of Na and K, and the alkaline earth metal element includes at least one of Mg and Ca.

[0032] The method for manufacturing an anode material provided herein involves compositeizing a carbon material with a silicon-based material. The carbon material can be used to improve the electronic conductivity of the anode material and reduce the collapse of the material structure due to volume expansion during the lithium absorption and desorption process. The composite is then calcined with an alkali metal oxide and an alkaline earth metal oxide. During the calcination process, alkali metal silicates, alkaline earth metal silicates, and silicon oxides can be formed. The alkaline earth metal silicates can enhance the mechanical strength of the anode material and have good thermal and structural stability, effectively mitigating the volume expansion of the anode material. Furthermore, the alkali metal silicates are water-soluble and can act as an adhesive to enhance the mechanical strength of the alkaline earth metal silicates. The oxygen content in the anode material can reflect the mass content of silicon oxide in the anode material. Controlling the mass content of silicon oxide can reduce the probability of side reactions between the anode material and the electrolyte, thereby reducing gas generation.

[0033] In some embodiments, the method for producing a negative electrode material further includes step S30 of using the product obtained after the calcination treatment in S20 as a precursor and performing a carbon coating treatment on the precursor to obtain a negative electrode material including a carbon matrix and a silicon-based active material, wherein a carbon layer is coated on a surface of at least a portion of the silicon-based active material.

[0034] By subjecting the precursor to a carbon coating treatment, direct contact between the silicon-based active material and the electrolyte can be further reduced. The negative electrode material produced by the present method has high particle mechanical strength, a low volume expansion coefficient, effectively mitigated gas generation, and good cycle stability.

[0035] Hereinafter, a detailed description will be given with reference to specific examples.

[0036] In step S10, the carbon material and the silicon-based substance are combined to obtain a composite.

[0037] In some embodiments, the carbon material comprises at least one of hard carbon, soft carbon, graphite, mesocarbon microbeads, activated carbon, porous carbon, mesoporous carbon, and carbon gel.

[0038] In some embodiments, the average particle size of the carbon material is 1 μm to 15 μm, and specifically may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 10 μm, 12 μm, or 15 μm, etc., and may of course be other values ​​within the above range, and is not limited thereto. It can be understood that controlling the average particle size of the carbon material within the above range is advantageous for improving the cycle performance of the negative electrode material.

[0039] In some embodiments, the carbon material is porous.

[0040] In some embodiments, the average pore size of the carbon material is 2 nm to 100 nm, and specifically may be 2 nm, 4 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 80 nm, or 100 nm, etc., and of course may be other values ​​within the above ranges and are not limited herein.

[0041] In some embodiments, the method of compositing the carbon material with the silicon-based substance comprises at least one of vapor deposition, solid state fusion, and liquid state compositing.

[0042] In some embodiments, the step of combining the carbon material with the silicon-based substance comprises vapor deposition of the carbon material using a silicon source gas to obtain the composite.

[0043] In some embodiments, the silicon source gas comprises at least one of silane, monochlorosilane, and dichlorosilane.

[0044] In some embodiments, the gas flow rate of the silicon source gas is 50 sccm to 200 sccm, and specifically may be 50 sccm, 80 sccm, 90 sccm, 100 sccm, 120 sccm, 150 sccm, 180 sccm, or 200 sccm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] In some embodiments, the growth time of the vapor phase epitaxy is 1 hour to 15 hours, and the growth time may be specifically 1 hour, 3 hours, 5 hours, 6 hours, 8 hours, 10 hours, 12 hours, or 15 hours, etc., and is not limited thereto.

[0046] In some embodiments, the growth temperature for vapor deposition is 300°C to 800°C, and the growth temperature may be, for example, 300°C, 350°C, 400°C, 500°C, 600°C, 650°C, 700°C, or 800°C, and may be other values ​​within the above range, without limitation. It can be appreciated that controlling the vapor deposition temperature within the above range is advantageous for controlling the crystal form of the silicon-based active material, reducing the crystallinity of the silicon-based active material, reducing the conversion of amorphous silicon to crystalline silicon, and further reducing the volume expansion of the negative electrode material, thereby improving the cycle performance of the negative electrode material.

[0047] In some embodiments, the step of compounding the carbon material with the silicon-based substance comprises mixing the carbon material, silicon particles, and a solvent, followed by a dispersion process, and removing the solvent to obtain the compound.

[0048] In some embodiments, the mass ratio of the silicon particles to the carbon material is (80-200):100. Specifically, the mass ratio is 80:100, 100:100, 120:100, 140:100, 150:100, 180:100, or 200:100, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0049] In some embodiments, the solvent comprises at least one of water, methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, pentanol, and ethyl acetate.

[0050] In some embodiments, the mixture further comprises a dispersing agent, the dispersing agent comprising at least one of stearic acid, sodium stearate, zinc stearate, magnesium stearate, calcium stearate, polyvinylpyrrolidone, carboxymethylcellulose, and polyacrylic acid.

[0051] In some embodiments, the mass ratio of the dispersant is 3 wt% to 8 wt%, specifically, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, or 8 wt%, etc., relative to 100 wt% of the carbon material. Adding an appropriate amount of dispersant to the mixture can improve the dispersion of silicon particles in the mixture, reduce the aggregation of silicon particles, and further improve the dispersion of silicon particles in the precursor.

[0052] In some embodiments, the dispersion treatment includes at least one of mechanical stirring, ultrasonic dispersion, and abrasive dispersion. Preferably, abrasive dispersion is employed to disperse the silicon particles, avoid agglomeration of the silicon particles, and disperse the silicon particles into smaller nanoparticles.

[0053] In some embodiments, the method of removing the solvent comprises a drying process.

[0054] In some embodiments, the drying temperature is 40°C to 200°C, and more specifically, 40°C, 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 190°C, or 200°C, and the drying time is 1 hour to 15 hours, and more specifically, 1 hour, 3 hours, 5 hours, 7 hours, 9 hours, 10 hours, 12 hours, or 15 hours, and the drying method may be, for example, oven drying, freeze drying, stirring evaporation drying, spray drying, or the like. The drying process in this embodiment can remove as much of the solvent in the precursor solution as possible.

[0055] In step S20, the mixture containing the composite, alkali metal oxides, and alkaline earth metal oxides is calcined to obtain a precursor, where the alkali metal elements include at least one of Na and K, and the alkaline earth metal elements include at least one of Mg and Ca.

[0056] In some embodiments, the amount of alkali metal oxide added is 1×10 -3 wt% to 1.5 wt%, specifically, 1 × 10 -3 wt%, 5 × 10 -3 wt%, 1×10 -2 wt%, 5 × 10 -2 wt%, 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.5 wt%, 0.7 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.4 wt%, or 1.5 wt%, etc., and of course other values ​​within the above ranges are also possible and are not limited herein.

[0057] In some embodiments, the amount of alkaline earth metal oxide added is 1.5×10 -4 wt% to 1 wt%, specifically, 1.5 × 10 -4 wt%, 1×10 -3 wt%, 5 × 10 -3 wt%, 1×10 -2 wt%, 5 × 10 -2wt%, 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.5 wt%, 0.7 wt%, 0.8 wt%, or 1 wt%, etc., and of course, other values ​​within the above ranges are also possible and are not limited herein.

[0058] In some embodiments, the temperature of the calcination treatment is 500°C to 800°C, and specifically may be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, or 800°C, etc., and of course may be other values ​​within the above range and are not limited thereto.

[0059] In some embodiments, the incubation time for the baking treatment is 2 hours to 10 hours, and the time may be specifically 2 hours, 3 hours, 5 hours, 6 hours, 8 hours, 9 hours, or 10 hours, etc., and of course, may be other values ​​within the above range and is not limited here.

[0060] In some embodiments, the heating rate in the baking treatment is 2°C / min to 10°C / min, and specifically may be 2°C / min, 4°C / min, 5°C / min, 6°C / min, 8°C / min, 9°C / min, 10°C / min, etc., but is not limited thereto.

[0061] In some embodiments, the calcination is carried out under a protective atmosphere, the protective atmosphere comprising at least one of nitrogen gas, argon gas, helium gas, and neon gas.

[0062] In step S30, the precursor is subjected to a carbon coating process to obtain a negative electrode material.

[0063] In some embodiments, the carbon coating process includes at least one of solid phase carbon coating, liquid phase carbon coating, and vapor phase carbon coating.

[0064] By performing a carbon coating treatment on the precursor to form a carbon layer on the surface of at least a portion of the silicon-based active material, on the one hand, it can reduce direct contact between the negative electrode material and the electrolyte, reduce the occurrence of side reactions between the negative electrode material and the electrolyte, and further improve the electrochemical performance of the negative electrode material, and on the other hand, it can relieve the mechanical stress caused by the volume expansion of the negative electrode material, improve the structural stability of the negative electrode material, improve the interface stability, and further improve the cycle performance of the negative electrode material.

[0065] In some embodiments, the carbon coating step specifically includes heating the precursor, introducing a protective gas and a carbon source gas, and pyrolyzing the carbon source gas to obtain an anode material having a carbon layer on its surface.

[0066] In some embodiments, the carbon source gas is hydrocarbon-based.

[0067] In some embodiments, the carbon source gas comprises at least one of methane, ethylene, acetylene, propyne, propylene, propane, toluene, benzene, styrene, and phenol.

[0068] In some embodiments, the flow rate of the carbon source gas is 50 sccm to 200 sccm, and may be, for example, 50 sccm, 80 sccm, 90 sccm, 100 sccm, 120 sccm, 150 sccm, 180 sccm, or 200 sccm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0069] In some embodiments, the pressure of the pyrolysis is between 10 Torr and 100 Torr, and may be, for example, 10 Torr, 15 Torr, 20 Torr, 30 Torr, 50 Torr, 60 Torr, 70 Torr, or 100 Torr, but is not limited to the listed values; other unlisted values ​​within this range are equally applicable.

[0070] In some embodiments, the pyrolysis temperature is 600° C. to 1000° C., and the pyrolysis time is 0.5 hours to 24 hours.

[0071] Specifically, the pyrolysis temperature may be, but is not limited to, 600°C, 620°C, 650°C, 680°C, 700°C, 760°C, 870°C, 900°C, 920°C, 950°C, 980°C, or 1000°C.Specifically, the pyrolysis time may be, but is not limited to, 0.5 hours, 1 hour, 3 hours, 5 hours, 8 hours, 12 hours, 15 hours, 18 hours, 20 hours, 22 hours, or 24 hours.

[0072] In some embodiments, the heating rate for pyrolysis is 2°C / min to 10°C / min, and specifically may be 2°C / min, 4°C / min, 5°C / min, 6°C / min, 8°C / min, 9°C / min, or 10°C / min, etc., but is not limited thereto.

[0073] In this application, the parameters of pyrolysis, such as temperature, time, and pressure, are controlled, which allows the carbon source gas to grow uniformly on the surface of the precursor, further reducing the direct contact between the silicon-based active material and the electrolyte, reducing the probability of side reactions between the negative electrode material and the electrolyte, and further improving the electrochemical performance of the negative electrode material.

[0074] In some embodiments, the carbon coating step specifically includes a step of carbonizing a mixture obtained by mixing the precursor with a solid-phase carbon source to obtain a negative electrode material.

[0075] In some embodiments, the carbonization temperature is 500° C. to 1000° C., and the carbonization time is 30 minutes to 24 hours.

[0076] Specifically, the carbonization temperature may be, but is not limited to, 500°C, 540°C, 580°C, 600°C, 620°C, 650°C, 680°C, 700°C, 760°C, 870°C, 900°C, 920°C, 950°C, 980°C, or 1000°C.Specifically, the carbonization time may be, but is not limited to, 30 min, 1 h, 3 h, 5 h, 8 h, 12 h, 15 h, 18 h, 20 h, 22 h, or 24 h.

[0077] In some embodiments, the solid phase carbon source comprises at least one of a sugar-based, an ester-based, a hydrocarbon-based, an organic acid, and a high molecular weight polymer.

[0078] In some embodiments, the solid phase carbon source comprises at least one of polyvinyl chloride, polyvinyl butyral, polyacrylonitrile, polyacrylic acid, polyethylene glycol, polypyrrole, polyaniline, sucrose, glucose, maltose, citric acid, asphalt, furfural resin, epoxy resin, and phenolic resin.

[0079] In some embodiments, the mass ratio of the solid-phase carbon source to the precursor is (1 to 200):100, and specifically may be 1:100, 2:100, 5:100, 10:100, 50:100, 100:100, 150:100, 180:100, or 200:100, etc., but is not limited thereto.

[0080] In some embodiments, the carbon coating step specifically includes a step of carbonizing a mixture obtained by mixing the precursor with a liquid-phase carbon source to obtain a negative electrode material.

[0081] In some embodiments, the mass ratio of the liquid-phase carbon source to the precursor is (1 to 200):100, and specifically may be 1:100, 2:100, 5:100, 10:100, 50:100, 100:100, 150:100, 180:100, or 200:100, etc., but is not limited thereto.

[0082] In some embodiments, the liquid phase carbon source comprises at least one of n-hexane, toluene, benzene, xylene, methanol, ethanol, propanol, butanol, pentanol, acetone, butanone, 2-pentanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and amyl acetate.

[0083] In some embodiments, the carbonization temperature is 600° C. to 1200° C., and the carbonization time is 2 hours to 20 hours.

[0084] Specifically, the carbonization temperature may be, but is not limited to, 600°C, 620°C, 650°C, 680°C, 700°C, 760°C, 870°C, 900°C, 920°C, 950°C, 980°C, 1000°C, 1020°C, 1080°C, 1100°C, 1160°C, or 1200°C.Specifically, the carbonization time may be, but is not limited to, 2 hours, 3 hours, 5 hours, 8 hours, 12 hours, 15 hours, 18 hours, 20 hours, 22 hours, 24 hours, 25 hours, 26 hours, 28 hours, or 30 hours.

[0085] In some embodiments, the carbon coating process is performed in a protective atmosphere, which includes at least one of nitrogen gas, helium gas, neodymium gas, argon gas, and krypton gas.

[0086] In some embodiments, the method for producing an anode material further includes shaping, screening, and classifying the product of the carbon coating process to obtain an anode material having a carbon layer on its surface, wherein the shaping process includes at least one of crushing, grinding, ball milling, and jet milling.

[0087] In a third aspect, the present application provides a negative electrode sheet comprising the negative electrode material of the first aspect or the negative electrode material produced by the production method of the second aspect.

[0088] In a fourth aspect, the present application provides a battery including the negative electrode material of the first aspect, the negative electrode material produced by the production method of the second aspect, or the negative electrode sheet of the third aspect. The battery may be a lithium ion battery, a sodium ion battery, or the like, but is not limited thereto.

[0089] The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

[0090] Example 1 The method for producing the negative electrode material of this example includes the following steps.

[0091] (1) Carbon materials are D 50 The carbon material was placed in a CVD reaction chamber, which was repeatedly purged with nitrogen gas (3-5 times). The nitrogen gas was then turned off and argon gas was introduced at a flow rate of 400 sccm. The temperature was then increased to 500°C at a rate of 10°C / min. After dwelling at this temperature for 1 hour, the argon gas was turned off and high-purity silane gas (99.9999%) was introduced at a flow rate of 100 sccm. The rotation speed was controlled to 10 rpm, and the temperature was maintained for 3 hours. After this, the silane gas was turned off and argon was introduced. The temperature was then lowered to room temperature, and the material was recovered to obtain a composite.

[0092] (2) When the mass of the composite is 100 wt%, sodium oxide with a mass ratio of 1.5 wt% and magnesium oxide with a mass ratio of 0.0003 wt% are added and mixed with the composite. After uniform mixing, the mixture is placed in a box furnace, heated to 600°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0093] (3) The precursor was placed in a CVD reaction chamber, and argon gas was introduced at a flow rate of 400 sccm. The temperature was then increased to 600°C at a rate of 10°C / min. After remaining at this temperature for 1 hour, the argon was stopped, and ethylene gas was introduced at a flow rate of 100 sccm. The rotation speed was controlled to 10 rpm, and the pressure was 10 Torr. After maintaining the temperature for 0.5 hours, the ethylene gas was stopped, argon was introduced, and the temperature was reduced to room temperature. The material was then crushed and screened to obtain the negative electrode material.

[0094] The negative electrode material prepared in the examples of the present application includes a carbon matrix and a silicon-based active material supported on the carbon matrix, and at least a portion of the silicon-based active material is coated with a carbon layer. The silicon-based active material includes amorphous silicon. Other parameters of the negative electrode material are detailed in Table 1.

[0095] Example 2 The difference from the first embodiment is as follows.

[0096] (2) When the mass of the composite is 100 wt%, magnesium oxide with a mass ratio of 0.06 wt% and sodium oxide with a mass ratio of 0.03 wt% are added and mixed with the composite. After uniform mixing, the mixture is placed in a box furnace, heated to 600°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0097] Example 3 The difference from the first embodiment is as follows.

[0098] (2) When the mass of the composite is 100 wt%, magnesium oxide with a mass ratio of 0.3 wt% and sodium oxide with a mass ratio of 0.0015 wt% are added and mixed with the composite. After mixing uniformly, the mixture is placed in a box furnace, heated to 600°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0099] Example 4 The difference from the first embodiment is as follows.

[0100] (2) When the mass of the composite is 100 wt%, magnesium oxide with a mass ratio of 0.3 wt% and sodium oxide with a mass ratio of 0.00015 wt% are added and mixed with the composite. After mixing uniformly, the mixture is placed in a box furnace, heated to 600°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0101] Example 5 The difference from the first embodiment is as follows.

[0102] (2) When the mass of the composite is 100 wt%, magnesium oxide with a mass ratio of 1.4 wt% and sodium oxide with a mass ratio of 0.0007 wt% are added and mixed with the composite. After mixing uniformly, the mixture is placed in a box furnace, heated to 600°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0103] Example 6

[0104] (1) Carbon materials are D 50 The artificial graphite has a pore size of 12 μm and an average pore size of 5 nm. A mass ratio of 100:120 of artificial graphite and nanosilicon (the mass content of oxygen element in nanosilicon is 0.5%) was added to a solvent, and a mass ratio of 5% of polyacrylic acid (the mass of artificial graphite is 100%) was added. The mixture was thoroughly stirred for 10 minutes, spray-dried, and granulated to obtain a composite.

[0105] (2) When the mass of the composite is 100 wt%, potassium oxide with a mass ratio of 1.5 wt% and calcium oxide with a mass ratio of 0.0003 wt% are added and mixed with the composite. After uniform mixing, the mixture is placed in a box furnace, heated to 800°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0106] (3) Precursor and Asphalt (D 50= 5 μm) in a mass ratio of 3:1, then placed in a box furnace, nitrogen gas was introduced, and the temperature was raised to 750 °C at a rate of 10 °C / min. The temperature was maintained for 3 hours, and the material was allowed to cool to room temperature. After pulverization and screening, the negative electrode material was obtained.

[0107] Example 7 The difference from Example 6 is as follows.

[0108] (1) Carbon materials are D 50 The artificial graphite has a pore size of 12 μm and an average pore size of 10 nm. A mass ratio of 100:120 of artificial graphite and nanosilicon (the mass content of oxygen element in nanosilicon is 3.5% to 4%) was added to a solvent, and 5% mass of polyacrylic acid (the mass of artificial graphite is taken as 100%) was added. The mixture was thoroughly stirred for 10 minutes, spray-dried, and granulated to obtain a composite.

[0109] (2) When the mass of the composite is 100 wt%, calcium oxide with a mass ratio of 0.06 wt% and potassium oxide with a mass ratio of 0.03 wt% are added and mixed with the composite. After uniform mixing, the mixture is placed in a box furnace, heated to 800°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0110] Example 8 The difference from Example 6 is as follows.

[0111] (1) Carbon materials are D 50 The artificial graphite has a pore size of 12 μm and an average pore size of 20 nm. A mass ratio of 100:120 of artificial graphite and nanosilicon (the mass content of oxygen element in nanosilicon is 8% to 9%) was added to a solvent, and 5% mass of polyacrylic acid (the mass of artificial graphite is taken as 100%) was added. The mixture was thoroughly stirred for 10 minutes, spray-dried, and granulated to obtain a composite.

[0112] (2) When the mass of the composite is 100 wt%, calcium oxide with a mass ratio of 0.3 wt% and potassium oxide with a mass ratio of 0.0015 wt% are added and mixed with the composite. After mixing uniformly, the mixture is placed in a box furnace, heated to 800°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0113] Example 9 The difference from Example 6 is as follows.

[0114] (1) Carbon materials are D 50 The artificial graphite has a pore size of 12 μm and an average pore size of 10 nm. A mass ratio of 100:120 of artificial graphite and nanosilicon (the mass content of oxygen element in nanosilicon is 14% to 15%) was added to a solvent, and a mass ratio of 5% of polyacrylic acid (the mass of the artificial graphite is taken as 100%) was added. The mixture was thoroughly stirred for 10 minutes, spray-dried, and granulated to obtain a composite.

[0115] (2) When the mass of the composite is 100 wt%, calcium oxide with a mass ratio of 0.3 wt% and potassium oxide with a mass ratio of 0.00015 wt% are added and mixed with the composite. After mixing uniformly, the mixture is placed in a box furnace, heated to 800°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0116] Example 10 The difference from Example 6 is as follows.

[0117] (1) Carbon materials are D 50 The artificial graphite has a pore size of 12 μm and an average pore size of 10 nm. A mass ratio of 100:120 of artificial graphite and nanosilicon (the mass content of oxygen element in nanosilicon is 14% to 15%) was added to a solvent, and a mass ratio of 5% of polyacrylic acid (the mass of the artificial graphite is taken as 100%) was added. The mixture was thoroughly stirred for 10 minutes, spray-dried, and granulated to obtain a composite.

[0118] (2) When the mass of the composite is 100 wt%, calcium oxide with a mass ratio of 5 wt% and potassium oxide with a mass ratio of 0.0005 wt% are added and mixed with the composite. After mixing uniformly, the mixture is placed in a box furnace, heated to 800°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0119] Example 11 The difference from the first embodiment is as follows.

[0120] (2) When the mass of the composite is 100 wt%, magnesium oxide with a mass ratio of 0.29 wt% and sodium oxide with a mass ratio of 0.0015 wt% are added and mixed with the composite. After mixing uniformly, the mixture is placed in a box furnace, heated to 600°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0121] Example 12 The difference from the first embodiment is as follows.

[0122] (2) When the mass of the composite is 100 wt%, magnesium oxide with a mass ratio of 1.3 wt% and sodium oxide with a mass ratio of 0.0006 wt% are added and mixed with the composite. After mixing uniformly, the mixture is placed in a box furnace, heated to 600°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0123] Example 13 The difference from the first embodiment is as follows.

[0124] (2) When the mass of the composite is 100 wt%, sodium oxide with a mass ratio of 1.5 wt% and magnesium oxide with a mass ratio of 0.00028 wt% are added and mixed with the composite. After uniform mixing, the mixture is placed in a box furnace, heated to 600°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0125] (Comparative Example 1) The difference from the first embodiment is as follows.

[0126] (2) When the mass of the composite is 100 wt%, sodium oxide with a mass ratio of 5 wt% and magnesium oxide with a mass ratio of 0.003 wt% are added and mixed with the composite. After uniform mixing, the mixture is placed in a box furnace, heated to 600°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0127] (Comparative Example 2) The difference from the first embodiment is as follows.

[0128] (2) When the mass of the composite is 100 wt%, magnesium oxide with a mass ratio of 2.5 wt% and sodium oxide with a mass ratio of 0.00025 wt% are added and mixed with the composite. After mixing uniformly, the mixture is placed in a box furnace, heated to 600°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0129] (Comparative Example 3) The difference from Example 6 is as follows.

[0130] (1) Carbon materials are D 50 The artificial graphite had a pore size of 12 μm and an average pore size of 10 nm. A mass ratio of 100:120 of artificial graphite and nanosilicon (the mass content of oxygen element in nanosilicon was 0.4%) was added to a solvent, and a mass ratio of 5% of polyacrylic acid (the mass of artificial graphite was taken as 100%) was added. The mixture was thoroughly stirred for 10 minutes, spray-dried, and granulated to obtain a composite.

[0131] (2) When the mass of the composite is 100 wt%, potassium oxide with a mass ratio of 5 wt% and calcium oxide with a mass ratio of 0.003 wt% are added and mixed with the composite. After uniform mixing, the mixture is placed in a box furnace, heated to 800°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0132] Comparative Example 4 The difference from Example 6 is as follows.

[0133] (1) Carbon materials are D 50 The artificial graphite had a pore size of 12 μm and an average pore size of 10 nm. A mass ratio of 100:120 of artificial graphite and nanosilicon (the mass content of oxygen element in nanosilicon was 11%) was added to a solvent, and a mass ratio of 5% of polyacrylic acid (the mass of artificial graphite was taken as 100%) was added. The mixture was thoroughly stirred for 10 minutes, spray-dried, and granulated to obtain a composite.

[0134] (2) When the mass of the composite is 100 wt%, calcium oxide with a mass ratio of 6 wt% and potassium oxide with a mass ratio of 0.0006 wt% are added and mixed with the composite. After uniform mixing, the mixture is placed in a box furnace, heated to 800°C at a rate of 10°C / min, and calcined at a constant temperature for 5 hours to obtain a precursor.

[0135] Measurement method:

[0136] (1) Measurement method for the specific surface area of ​​negative electrode material: The specific surface area is measured using a TriStar 3000 specific surface area and pore size analysis instrument manufactured by Micromeritics, Inc., USA.

[0137] (2) Measurement of the mass content of alkaline earth metal elements and alkali metal elements in the negative electrode material: The model number of the measuring instrument used was PEoptima8000ICP, and the mass contents of sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca) in the negative electrode material were measured using emission spectroscopy.

[0138] (3) Measurement of the mass content of oxygen element in the negative electrode material: The hydrogen, oxygen and nitrogen analyzer Eltra ONH2000 is used to measure N and O elements in materials, and the measurement standard is ISO17053:2005.

[0139] (4) Measurement of the mass content of silicon element in the negative electrode material: The silicon content was measured using the method for determining silicon content in the Chinese national standard GBT38823-2020 for "silicon carbon."

[0140] (5) Measurement of the mass content of carbon element in the negative electrode material: The carbon element in the material was measured using an infrared carbon and sulfur analyzer, Eltra CS-i.

[0141] (6) Method for measuring particle size of silicon-based active materials: The silicon-based active material particles are observed using a field emission scanning electron microscope, the particle sizes of 50 silicon-based active material particles are directly measured on a reduced scale, and the average particle size is calculated as the final average particle size of the silicon-based active material particles.

[0142] (7) Measurement method for particle size of negative electrode material: Using Malvern's laser particle size analyzer MS3000, based on the principle that the intensity distribution of scattered light generated in each direction by particles depends on the particle size, large particles have a small scattering angle and small particles have a large scattering angle, so the particle size distribution is obtained by using the intensity distribution of scattered light caused by laser diffraction. The measurement conditions are as follows:

[0143] 1. Refractive index: 2.61, absorption index: 0.1, pure water, solvent refractive index: 1.33, 2. The internal ultrasonic intensity mode is selected as "continuous", the internal ultrasonic intensity is 20%, the stirring speed is 2500 r / min, the background measurement time is 15 s, and the sample measurement time is 15 s. 3. For data processing, select "Analysis Model" and then "General". 4. The measured light blocking rate is 8 to 12%.

[0144] (8) Measurement of electrochemical performance The negative electrode materials prepared in the examples and comparative examples were dissolved in N-methylpyrrolidone in a mass ratio of 94:1:5 between the negative electrode material, carboxymethyl cellulose, and styrene-butadiene rubber, adjusting the solid content to 50%. The solution was applied to a copper foil current collector and vacuum-dried to produce a negative electrode sheet. This was then assembled into an 18650 cylindrical cell using a standard manufacturing process using a ternary positive electrode sheet (NCM523), a 1 mol / L lithium hexafluorophosphate (LiPF6) / (ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC)) (v / v = 1:1:1) electrolyte, a Celgard 2400 separator, and a shell. Charge and discharge measurements of the cylindrical cells were performed using a LAND battery measurement system. Charge and discharge were performed at room temperature with a constant current of 0.2 C, and the charge and discharge voltage was limited to 2.75 to 4.2 V. The initial reversible capacity, first cycle charge capacity, and first cycle discharge capacity were measured. First coulombic efficiency = first cycle discharge capacity / first cycle charge capacity.

[0145] The cycle was repeated 50 times, and the discharge capacity was recorded as the remaining capacity of the lithium-ion battery. The capacity retention rate = remaining capacity / initial capacity * 100%.

[0146] The results of performance measurements of the above Examples 1 to 13 (abbreviated as S1 to S13) and Comparative Examples 1 to 4 (abbreviated as D1 to D4) are shown in Tables 1 and 2.

[0147] [Table 1]

[0148] [Table 2] As can be seen from the data in Tables 1 and 2, the mass content of alkali metal elements, alkaline earth metal elements, and oxygen elements in the negative electrode material is 1 × 10 -5 ≦(B / A)×E≦5×10 2The reason for this is believed to be that the silicate and silicon oxide can be effectively controlled within an appropriate range to produce a synergistic effect, thereby mitigating the collision of huge stresses generated during cycling, reducing the volume expansion of the negative electrode material, improving the overall structural stability of the negative electrode material, and improving the cycling stability of the negative electrode material.

[0149] As can be seen from the measurement data of Examples 1 to 5 and Comparative Example 1, when the (B / A)×E of the negative electrode material of Comparative Example 1 is too low, it indicates that the A value exceeds the upper limit or the B value exceeds the lower limit. An A value exceeding the upper limit indicates that there is an excess of alkali metal elements in the negative electrode material, which leads to an excess of alkali metal silicates in the negative electrode material, which may further reduce the mechanical strength of the negative electrode material, worsen the expansion suppression effect, and possibly worsen the cycle performance. A B value exceeding the lower limit indicates that there is too little alkaline earth metal elements in the negative electrode material, which leads to an insufficient amount of alkaline earth metal silicates in the negative electrode material, which may further reduce the mechanical strength of the negative electrode material, cause an unstable structure, and greatly reduce the suppression effect against volume expansion during cycling.

[0150] Comparing Comparative Example 2 with Examples 1 to 5, the (B / A)×E ratio of the negative electrode material in Comparative Example 2 is too high, which means that the B value exceeds the upper limit and there is an excess of alkaline earth metal elements in the negative electrode material. This results in too much alkaline earth metal silicate in the negative electrode material, which in turn results in too much hardness and reduced elasticity of the negative electrode material, which is also unfavorable for mitigating the impact of cycle expansion stress and may result in poor cycle performance. In addition, the amount of alkaline earth metal oxide is too high, which reduces the content of silicon-based active material in the negative electrode material, which reduces the capacity and initial coulombic efficiency of the negative electrode material.

[0151] As can be seen from the measurement data of Examples 6 to 10 and Comparative Example 3, the (B / A) × E ratio of the negative electrode material of Comparative Example 3 is too low, which means that the A value exceeds the upper limit or the E value exceeds the lower limit. An A value exceeding the upper limit means that there is an excess of alkali metal elements in the negative electrode material, which is presumably due to the excess silicate of alkali metal elements in the negative electrode material, which may further reduce the mechanical strength of the negative electrode material, reduce the expansion suppression effect, and potentially result in poor cycle performance. In addition, a low E value indicates that the oxide layer on the surface of the silicon-based active material is too thin, which increases side reactions between the silicon-based active material and the electrolyte, resulting in large volume expansion of the material during cycling and poor cycle performance.

[0152] As can be seen from the measurement data of Examples 6 to 10 and Comparative Example 4, the (B / A)×E ratio of the negative electrode material of Comparative Example 4 is too high, indicating that there is an excess of alkaline earth metal elements in the negative electrode material or that the E value exceeds the upper limit. It is presumed that an excess of alkaline earth metal elements in the negative electrode material results in too much alkaline earth metal silicate in the negative electrode material, which in turn results in the negative electrode material being too hard and reducing its elasticity, which is unfavorable for mitigating stress collisions and may result in poor cycle and expansion performance. Furthermore, an E value exceeding the upper limit indicates that the oxygen content of the negative electrode material is too high, increasing inactive silicon oxide, reducing the initial reversible capacity of the negative electrode material and reducing the initial coulombic efficiency.

[0153] The applicant declares that although the present invention describes the detailed process equipment and process flow of the present invention in the above examples, the present invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that the present invention cannot be implemented without relying on the above detailed process equipment and process flow. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions and addition of auxiliary components for each raw material of the product of the present invention, selection of specific methods, etc., are all within the protection scope and disclosure scope of the present invention.

Claims

1. A negative electrode material, a carbon matrix and a silicon-based active material; the negative electrode material contains an alkali metal element, an alkaline earth metal element, and an oxygen element, the alkali metal element includes Na and / or K, and the alkaline earth metal element includes Mg and / or Ca; the mass content of the alkali metal element is A ppm, the mass content of the alkaline earth metal element is B ppm, and the mass content of the oxygen element is E; The negative electrode material is 1×10 －５ ≦(B / A)×E≦5×10 ２ Satisfy the relationship of A negative electrode material characterized by:

2. (1) The mass content of the alkali metal element is A ppm, and 1≦A≦5000; (2) The mass content of the alkaline earth metal element is B ppm, and 5≦B≦5000; and (3) The mass content of the oxygen element, E, satisfies at least one of the following conditions: 0.005≦E≦0.1; The negative electrode material according to claim 1 .

3. (1) The form of the alkali metal element includes a silicate of the alkali metal; and (2) The alkaline earth metal element is present in a form that satisfies at least one of the following conditions: a silicate of an alkaline earth metal is included; 3. The negative electrode material according to claim 1 or 2.

4. The carbon matrix comprises at least one of hard carbon, soft carbon, graphite, mesocarbon microbeads, activated carbon, porous carbon, mesoporous carbon, and carbon gel; The negative electrode material according to claim 3 .

5. The silicon-based active material comprises at least one of elemental silicon, silicon oxide, silicon alloy, and silicon-carbon composite. The negative electrode material according to claim 3 .

6. (1) The silicon-based active material comprises elemental silicon, including crystalline silicon and / or amorphous silicon; (2) The silicon-based active material includes a silicon oxide containing silicon element and oxygen element, and the atomic ratio of the silicon element to the oxygen element is 0 to 2 and does not include 0; (3) The silicon-based active material has the chemical formula SiO ｘ wherein 0<x≦2, and (4) The silicon-based active material satisfies at least one of the following requirements: a silicon alloy including at least one of a silicon-lithium alloy, a silicon-magnesium alloy, and a silicon-nickel alloy; The negative electrode material according to claim 5 .

7. The average particle size of the silicon-based active material is 0.1 nm to 500 nm; The negative electrode material according to claim 5 .

8. The mass content of silicon element in the silicon-based active material is ≧99%; The negative electrode material according to claim 5 .

9. (1) Median particle size D of the negative electrode material ５０ is ≦15 μm, and (2) The specific surface area of ​​the negative electrode material is ≦5 m ２ / g, The negative electrode material according to claim 1 .

10. In the negative electrode material, a carbon layer is coated on the surface of at least a portion of the silicon-based active material. The negative electrode material according to claim 9 .

11. the carbon layer contains at least one of graphitic carbon and amorphous carbon; The negative electrode material according to claim 10 .

12. In the negative electrode material, the mass ratio of silicon element to carbon element is (0.16 to 2):

1.

3. The negative electrode material according to claim 1 or 2.

13. The negative electrode material according to any one of claims 1 to 12, A negative electrode sheet characterized by:

14. The negative electrode material according to any one of claims 1 to 12 or the negative electrode sheet according to claim 13, A battery characterized by:

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