Negative electrode material, negative electrode sheet and battery

Abstract

A negative electrode material, a negative electrode sheet and a battery. The negative electrode material comprises a carbon matrix and a silicon-based active substance. The negative electrode material contains an alkali metal element, an alkaline earth metal element and oxygen, wherein the alkali metal element comprises Na and / or K, and the alkaline earth metal element comprises 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 oxygen is E%; and the negative electrode material satisfies the following relationship: 1×10-5≤(B / A)×E≤5×102. By balancing the mass contents of the alkali metal element, the alkaline earth metal element and oxygen in the negative electrode material, the mechanical strength of the negative electrode material can be improved, the volume expansion of the negative electrode material can be relieved, and the cycling stability of the negative electrode material can be improved, while the specific capacity of the negative electrode material is also improved.

Description

Negative electrode material, negative electrode sheet and battery

[0001] This application claims priority to Chinese patent application No. 202410014552.1, filed on January 5, 2024. This application incorporates the entire text of the aforementioned Chinese patent application. Technical Field

[0002] The present application relates to the technical field of negative electrode materials, and in particular to negative electrode materials, negative electrode sheets and batteries. Background Art

[0003] Lithium-ion batteries are widely used in electric vehicles and consumer electronics due to their high energy density, long cycle life, low environmental pollution, and lack of memory effect. The rapid development of electric vehicles in recent years has led to a growing demand for lithium-ion batteries with higher energy density, prompting researchers to search for battery materials with higher energy density and better cycle performance. Positive and negative electrode materials are the core of the battery and determine its operating efficiency. Currently, the commercialized negative electrode material is graphite, whose capacity is close to its theoretical upper limit, with limited potential for further improvement. Therefore, there is an urgent need to develop a new generation of high-energy-density negative electrode materials. Silicon-based negative electrode materials are widely considered to be the next generation of battery negative electrode materials, offering advantages such as high capacity, abundant sources, and relative safety.

[0004] Silicon anodes are widely considered the next generation of battery negative electrode materials, offering advantages such as high capacity, abundant sources, and relative safety. However, silicon anodes experience dramatic volume expansion during cycling, leading to material pulverization and fragmentation. The repeated volume changes of silicon anode materials during electrochemical cycling also cause the SEI film formed on the silicon material surface to continuously break down and regenerate, resulting in continuous lithium ion consumption and ultimately rapid capacity decay. Summary of the Invention

[0005] The present application provides a negative electrode material, a negative electrode plate and a battery, which can improve the specific capacity of the negative electrode material while increasing the mechanical strength of the particles of the negative electrode material, alleviating the volume expansion of the negative electrode material, and improving the cycle stability of the negative electrode material.

[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 contains an alkali metal element, an alkaline earth metal element, and an oxygen element, wherein the alkali metal element includes Na and / or K, and the alkaline earth metal element includes Mg and / or Ca;

[0007] 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;

[0008] The negative electrode material satisfies the following relationship: 1×10 -5≤(B / A)×E≤5×10 2 .

[0009] In a second aspect, the present application provides a negative electrode plate, which includes the negative electrode material of the first aspect of the present application.

[0010] 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 plate of the second aspect of the present application.

[0011] The technical solution of this application has at least the following beneficial effects:

[0012] The negative electrode material provided in the present application includes a carbon matrix and a silicon-based active material, wherein 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 of the present application satisfies the following requirements: 1×10 -5 ≤(B / A)×E≤5×10 2 , while improving the specific capacity of the negative electrode material, it can also improve the mechanical strength of the particles of the negative electrode material, alleviate the volume expansion of the negative electrode material, and further reduce the gas production phenomenon of the negative electrode material, thereby improving the cycle stability of the negative electrode material. According to the inventors’ speculation, there may be silicates in the negative electrode material. Among them, silicates containing alkaline earth metal elements can enhance the mechanical strength of silicon-based active substances, and have good thermal stability and structural stability, which can effectively alleviate the volume expansion of silicon-based active substances. Silicates of alkali metal elements are water-soluble. Although the mechanical strength of silicates of alkali metal elements themselves is relatively low, they can be used as adhesives to enhance the mechanical strength of silicates containing alkaline earth metal elements, and further alleviate the volume expansion of the negative electrode material. According to the inventors’ speculation, the content of oxygen elements in the negative electrode material can reflect the mass content of silicon oxide in the negative electrode material, and an appropriate amount of silicon oxide on the surface of the silicon-based active material can reduce the direct contact between the silicon-based active material and the electrolyte, reduce the occurrence of side reactions, and reduce gas production. Therefore, the present application controls 1×10 -5 ≤(B / A)×E≤5×10 2 It can balance the mass content of alkali metal silicate, alkaline earth metal silicate and silicon oxide in the negative electrode material. While increasing the specific capacity of the negative electrode material, it can also improve the mechanical strength of the negative electrode material particles, alleviate the volume expansion of the negative electrode material, and further reduce the gas production of the negative electrode material, thereby improving the cycle stability of the negative electrode material. DETAILED DESCRIPTION

[0013] To better illustrate the present application and facilitate understanding of the technical solution of the present application, the present application is further described below. However, the following embodiments are merely simplified examples of the present application and do not represent or limit the scope of protection of the present application. The scope of protection of the present application shall be subject to the claims.

[0014] 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 comprises an alkali metal element, an alkaline earth metal element, and an oxygen element, wherein the alkali metal element comprises Na and / or K, and the alkaline earth metal element comprises Mg and / or Ca;

[0015] 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;

[0016] The negative electrode material satisfies the following relationship: 1×10 -5 ≤(B / A)×E≤5×10 2 .

[0017] The negative electrode material provided in the present application includes a carbon matrix and a silicon-based active material. Specifically, the silicon-based active material is loaded on the carbon matrix. The negative electrode material contains alkali metal elements, alkaline earth metal elements and oxygen elements. The alkali metal elements include Na and / or K, and the alkaline earth metal elements include Mg and / or Ca. The mass content of the alkali metal elements is A ppm, the mass content of the alkaline earth metal elements is B ppm, and the mass content of the oxygen elements is E. The negative electrode material of the present application meets the following requirements: 1×10 -5 ≤(B / A)×E≤5×10 2 While increasing the specific capacity of the negative electrode material, it can also improve the mechanical strength of the negative electrode material particles, alleviate the volume expansion of the negative electrode material, and further reduce the gas production of the negative electrode material, thereby improving the cycle stability of the negative electrode material.

[0018] According to the inventors’ speculation, there may be silicates in the negative electrode material. Among them, silicates containing alkaline earth metal elements can enhance the mechanical strength of silicon-based active materials, and have good thermal stability and structural stability, which can effectively alleviate the volume expansion of silicon-based active materials. Silicates of alkali metal elements are water-soluble. Although the mechanical strength of silicates of alkali metal elements themselves is low, they can be used as adhesives to enhance the mechanical strength of silicates containing alkaline earth metal elements. According to the inventors’ speculation, the content of oxygen elements 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 the direct contact between the silicon-based active material and the electrolyte, reduce the occurrence of side reactions, and reduce gas production. The negative electrode material of this application meets the following requirements: 1×10 -5 ≤(B / A)×E≤5×10 2, can balance the mass content of alkali metal silicate, alkaline earth metal silicate and silicon oxide in the negative electrode material, while increasing the specific capacity of the negative electrode material, it can also improve the mechanical strength of the negative electrode material particles, alleviate the volume expansion of the negative electrode material, and further reduce the gas production of the negative electrode material, thereby improving the cycle stability of the negative electrode material. The above is only a reasonable speculation by the inventor, and there may be other reasons. In short, this application controls 1×10 -5 ≤(B / A)×E≤5×10 2 Within this range, while increasing the specific capacity of the negative electrode material, the mechanical strength of the negative electrode material particles can be improved, the volume expansion of the negative electrode material can be alleviated, the gas production of the negative electrode material can be further reduced, and the cycle stability of the negative electrode material can be improved.

[0019] In some embodiments, the mass content of alkali metal elements in the negative electrode material is A ppm, where 1 ≤ A ≤ 5000. The value of A can be 1, 10, 50, 100, 200, 500, 800, 1000, 2000, 3000, 4000, or 5000, among others, without limitation. The inventors reasonably speculate that, understandably, controlling the mass content of alkali metal elements in the negative electrode material, namely, the mass content of alkali metal silicates, such as sodium silicate and potassium silicate, is water-soluble and can act as a binder to enhance the cracking strength of magnesium silicate and calcium silicate. Preferably, the mass content of alkali metal elements is 5 ppm ≤ A ppm ≤ 3000 ppm.

[0020] In some embodiments, the mass content of the alkaline earth metal element in the negative electrode material is B ppm, 3≤B≤5000; the specific value of B can be 3, 10, 50, 100, 200, 500, 800, 1000, 2000, 3000, 4000 or 5000, etc., without limitation herein. The inventors reasonably speculate that it is understandable that the mass content of the alkaline earth metal element in the negative electrode material, that is, the mass content of the alkaline earth metal silicate, is controlled. Magnesium silicate and calcium silicate have excellent mechanical strength. When magnesium silicate and calcium silicate are located on the surface of the 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 alleviated. Preferably, the mass content of the alkaline earth metal element is 10ppm≤A ppm≤3000ppm. More preferably, the mass content of the alkaline earth metal element is 500ppm≤A ppm≤3000ppm. By optimizing the mass content of alkaline earth metal elements, the negative electrode material has both good mechanical strength and elasticity, is not prone to rupture, and has good cycle stability.

[0021] In some embodiments, in the negative electrode material, the mass content of oxygen is E, 0.005≤E≤0.1; the value of E can be 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, etc., without limitation. Controlling the mass content of oxygen in the negative electrode material can ensure that the silicon oxide layer on the surface of the silicon-based active material is within a suitable range. The inventors reasonably speculate that the silicon oxide layer can synergistically act with the silicate layer to further alleviate 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.

[0022] 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., which are not limited here. Preferably, 1×10 -2 ≤(B / A)×E≤50.

[0023] In some embodiments, the alkaline earth metal element exists in the form of alkaline earth metal silicates and oxides, specifically magnesium silicate and / or calcium silicate, calcium oxide and / or magnesium oxide.

[0024] In some embodiments, the alkali metal element exists in the form of an alkali metal silicate, specifically potassium silicate and / or sodium silicate.

[0025] 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.

[0026] 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 silicon element can be amorphous silicon, crystalline silicon, or a composite of crystalline silicon and amorphous silicon, etc., which is not limited here. The silicon alloy can be a silicon-lithium alloy, a silicon-magnesium alloy, a silicon-nickel alloy, etc., which is not limited here. Silicon oxide includes 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, which is not limited here. The general chemical formula of silicon oxide is SiO x , where 0<x≤2, which is not specifically limited here.

[0027] In some embodiments, the average particle size of the silicon-based active material is 0.1nm to 500nm, and can specifically be 0.1nm, 1nm, 5nm, 10nm, 50nm, 100nm, 150nm, 200nm, 300nm, 350nm, 400nm or 500nm, etc. Of course, it can also be other values ​​within the above range, which is not limited here. Silicon-based active materials of suitable size can improve the distribution uniformity of the silicon-based active material and the carbon matrix, reduce the segregation 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 1nm to 10nm; more preferably, the average particle size of the silicon-based active material is 1nm to 5nm.

[0028] In some embodiments, the mass content of silicon in the silicon-based active material is ≥99%. The mass content of silicon in the silicon-based active material within the above range is beneficial to improving the purity of the silicon-based active material and reducing impurities.

[0029] In some embodiments, the negative electrode material further includes a carbon layer located on the surface of the negative electrode material. It is understood that the carbon layer reduces the volume expansion effect of the negative electrode material to a certain extent while enhancing the conductivity of the negative electrode material. The carbon layer can also reduce direct contact between the silicon-based active material and the electrolyte, inhibit excessive growth of the solid electrolyte interface (SEI) on the surface of the negative electrode material, stabilize the interface of the negative electrode material, and improve the initial coulombic efficiency of the negative electrode material.

[0030] 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 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 improve the rate capability and cycle performance of the negative electrode material.

[0031] In some embodiments, the median particle size D50 of the negative electrode material is ≤15 μm, and specifically can be 0.5 μm, 1 μm, 2 μm, 5 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc. Of course, other values ​​within the above range are also possible and are not limited here. It can be understood that controlling the median particle size of the negative electrode material within the above range is beneficial to improving the cycle performance of the negative electrode material.

[0032] In some embodiments, the specific surface area of ​​the negative electrode material is ≤5m 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、3m2 / 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 here. Controlling the specific surface area of ​​the negative electrode material within the above range is beneficial to improving the initial efficiency and cycle performance of the lithium battery made of the negative electrode material.

[0033] In some embodiments, the negative electrode material includes a carbon matrix and a silicon-based active material, and at least a portion of the surface of the silicon-based active material is coated with a carbon layer. The carbon layer can reduce direct contact between the silicon-based active material and the electrolyte and also help alleviate volume expansion.

[0034] In some embodiments, when at least a portion of the surface of the silicon-based active material is coated with a carbon layer, the mass ratio of silicon to carbon is (0.16-2):1. Controlling the mass ratio of silicon to carbon can improve both the cycle stability and the capacity of the negative electrode material.

[0035] In a second aspect, the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0036] Step S10, compounding the carbon material with the silicon-based material to obtain a composite;

[0037] In step S20 , the mixture comprising the composite, the alkali metal oxide, and the alkaline earth metal oxide is sintered to obtain a negative electrode material, wherein the alkali metal element comprises at least one of Na and K, and the alkaline earth metal element comprises at least one of Mg and Ca.

[0038] The preparation method of the negative electrode material provided in the present application is to compound a carbon material with a silicon-based material, which can improve the electronic conductivity of the negative electrode material with the help of the carbon material, and can also reduce the collapse of the material structure caused by the volume expansion of the negative electrode material during the lithium insertion and extraction process. The composite is then sintered with an alkali metal oxide and an alkaline earth metal oxide. During the sintering process, alkali metal silicates, alkaline earth metal silicates and silicon oxides may be formed. The silicates containing alkaline earth metal elements can enhance the mechanical strength of the negative electrode material, and have good thermal stability and structural stability, which can effectively alleviate the volume expansion of the negative electrode material. In addition, the silicates of alkali metal elements are water-soluble and can be used as an adhesive to enhance the mechanical strength of the silicates containing alkaline earth metal elements. The content of oxygen elements in the negative electrode material can reflect the mass content of silicon oxide in the negative electrode material. By controlling the mass content of silicon oxide, the probability of side reactions between the negative electrode material and the electrolyte can be reduced, and the gas production phenomenon can be reduced.

[0039] In some embodiments, the method for preparing a negative electrode material further includes step S30, using the product after the sintering treatment in S20 as a precursor, and carbon-coating the precursor to obtain a negative electrode material including a carbon matrix, a silicon-based active substance, and at least a portion of the surface of the silicon-based active substance is coated with a carbon layer.

[0040] Carbon coating the precursor can further reduce direct contact between the silicon-based active material and the electrolyte. The negative electrode material prepared by the preparation method of the present application has high mechanical strength of particles, low volume expansion rate, can effectively alleviate gas generation, and has good cycle stability.

[0041] The following is a detailed description with reference to specific embodiments:

[0042] Step S10: Compounding the carbon material with the silicon-based material to obtain a composite.

[0043] In some embodiments, the carbon material includes at least one of hard carbon, soft carbon, graphite, mesocarbon microbeads, activated carbon, porous carbon, mesoporous carbon, and carbon gel.

[0044] In some embodiments, the average particle size of the carbon material is 1 μm to 15 μm, specifically 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 of course other values ​​within the above range are also possible, and are not limited here. It can be understood that controlling the average particle size of the carbon material within the above range is beneficial to improving the cycle performance of the negative electrode material.

[0045] In some embodiments, the carbon material has pores.

[0046] In some embodiments, the average pore size of the carbon material is 2 nm to 100 nm; specifically, it can 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. Of course, it can also be other values ​​within the above range, which is not limited here.

[0047] In some embodiments, the carbon material and the silicon-based material are composited by at least one of vapor deposition, solid-phase fusion, and liquid-phase composite.

[0048] In some embodiments, the step of compounding the carbon material with the silicon-based substance includes: performing vapor deposition on the carbon material using a silicon source gas to obtain the compound.

[0049] In some embodiments, the silicon source gas includes at least one of silane, monochlorosilane, and dichlorosilane.

[0050] In some embodiments, the gas flow rate of the silicon source gas is 50 sccm to 200 sccm; specifically, it can 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 the numerical range are also applicable.

[0051] In some embodiments, the deposition time of vapor deposition is 1 hour to 15 hours. The deposition time can be 1 hour, 3 hours, 5 hours, 6 hours, 8 hours, 10 hours, 12 hours or 15 hours, etc., which is not limited here.

[0052] In some embodiments, the deposition temperature of the vapor deposition is 300°C to 800°C. The deposition temperature can specifically be 300°C, 350°C, 400°C, 500°C, 600°C, 650°C, 700°C, or 800°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here. It can be understood that controlling the temperature of the vapor deposition within the above range is beneficial to 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 thereby reducing the volume expansion of the negative electrode material and improving the cycle performance of the negative electrode material.

[0053] In some embodiments, the step of compounding the carbon material with the silicon-based substance includes: mixing the carbon material, silicon particles, and a solvent, performing a dispersion treatment, and removing the solvent to obtain a composite.

[0054] In some embodiments, the mass ratio of silicon particles to carbon material is (80-200):100. Specifically, it can be 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.

[0055] In some embodiments, the solvent includes at least one of water, methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, pentanol, and ethyl acetate.

[0056] In some embodiments, the mixture further includes a dispersant, and the dispersant includes at least one of stearic acid, sodium stearate, zinc stearate, magnesium stearate, calcium stearate, polyvinyl pyrrolidone, carboxymethyl cellulose, and polyacrylic acid.

[0057] In some embodiments, the mass proportion of the dispersant is 3 wt% to 8 wt% based on 100 wt% of the carbon material, and specifically can be 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, or 8 wt%, etc., without limitation herein. The addition of an appropriate amount of dispersant to the mixture can improve the dispersion of the silicon particles in the mixed solution, reduce the agglomeration of the silicon particles, and thereby improve the dispersion of the silicon particles in the precursor.

[0058] In some embodiments, the dispersion process includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion. Preferably, grinding dispersion is used to disperse the silicon particles, prevent the silicon particles from agglomerating, and disperse the silicon particles into smaller nanoparticles.

[0059] In some embodiments, removing the solvent comprises drying.

[0060] In some embodiments, the drying temperature is 40°C to 200°C, specifically 40°C, 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 190°C or 200°C, etc., and the drying time is 1h to 15h, specifically 1h, 3h, 5h, 7h, 9h, 10h, 12h or 15h, etc. The drying method can be, for example, oven drying, freeze drying, stirring evaporation, spray drying, etc. The drying treatment in this embodiment can remove the solvent in the precursor solution as much as possible.

[0061] In step S20 , the mixture including the composite, the alkali metal oxide, and the alkaline earth metal oxide is sintered to obtain a precursor, 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.

[0062] In some embodiments, the amount of alkali metal oxide added is 1×10 -3 wt%~1.5wt%, specifically 1×10 -3 wt%, 5×10 -3 wt%, 1×10 -2 wt%, 5×10 -2 wt%, 0.1wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.7wt%, 0.8wt%, 1.0wt%, 1.2wt%, 1.4wt% or 1.5wt%, etc., of course, it can also be other values ​​within the above range, which is not limited here.

[0063] In some embodiments, the amount of alkaline earth metal oxide added is 1.5×10 -4wt%~1wt%, specifically 1.5×10 -4 wt%, 1×10 -3 wt%, 5×10 -3 wt%, 1×10 -2 wt%, 5×10 -2 wt%, 0.1wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.7wt%, 0.8wt% or 1wt%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0064] In some embodiments, the sintering temperature is 500°C to 800°C, specifically 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0065] In some embodiments, the holding time of the sintering treatment is 2 hours to 10 hours, and the specific time can be 2 hours, 3 hours, 5 hours, 6 hours, 8 hours, 9 hours or 10 hours, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0066] In some embodiments, the heating rate of the sintering process is 2°C / min to 10°C / min, specifically 2°C / min, 4°C / min, 5°C / min, 6°C / min, 8°C / min, 9°C / min or 10°C / min, etc., which is not limited here.

[0067] In some embodiments, the sintering process is performed under a protective atmosphere comprising at least one of nitrogen, argon, helium, and neon.

[0068] Step S30 , performing carbon coating treatment on the precursor to obtain a negative electrode material.

[0069] In some embodiments, the carbon coating process includes at least one of solid phase carbon coating, liquid phase carbon coating, and gas phase carbon coating.

[0070] It can be understood that carbon coating the precursor to form a carbon layer on the surface of at least part of the silicon-based active material can, on the one hand, reduce the 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 thus improve the electrochemical performance of the negative electrode material; on the other hand, it can also alleviate 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 thus improve the cycle performance of the negative electrode material.

[0071] In some embodiments, the carbon coating treatment step specifically includes: heating the precursor, introducing a protective gas and a carbon source gas, and thermally cracking the carbon source gas to obtain a negative electrode material having a carbon layer on the surface.

[0072] In some embodiments, the carbon source gas is a hydrocarbon.

[0073] In some embodiments, the carbon source gas includes at least one of methane, ethylene, acetylene, propyne, propylene, propane, toluene, benzene, styrene, and phenol.

[0074] In some embodiments, the flow rate of the carbon source gas is 50 sccm to 200 sccm; specifically, it can 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. Other unlisted values ​​within the numerical range are also applicable.

[0075] In some embodiments, the pressure of thermal cracking is 10 Torr to 100 Torr, specifically 10 Torr, 15 Torr, 20 Torr, 30 Torr, 50 Torr, 60 Torr, 70 Torr or 100 Torr, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0076] In some embodiments, the thermal cracking temperature is 600° C. to 1000° C., and the thermal cracking time is 0.5 h to 24 h.

[0077] Specifically, the thermal cracking temperature can be 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., etc., and is not limited here. The thermal cracking time can be 0.5 h, 1 h, 3 h, 5 h, 8 h, 12 h, 15 h, 18 h, 20 h, 22 h, or 24 h, etc., and is not limited here.

[0078] In some embodiments, the heating rate of thermal cracking is 2°C / min to 10°C / min, specifically 2°C / min, 4°C / min, 5°C / min, 6°C / min, 8°C / min, 9°C / min or 10°C / min, etc., which is not limited here.

[0079] In this application, controlling the temperature, time, pressure and other parameters of thermal cracking helps to make the carbon source gas evenly deposited 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 thus improving the electrochemical performance of the negative electrode material.

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

[0081] In some embodiments, the temperature of the carbonization treatment is 500° C. to 1000° C., and the time of the carbonization treatment is 30 minutes to 24 hours.

[0082] Specifically, the temperature of the carbonization treatment can be 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., etc., without limitation herein. The time of the carbonization treatment can be 30 min, 1 h, 3 h, 5 h, 8 h, 12 h, 15 h, 18 h, 20 h, 22 h, or 24 h, etc., without limitation herein.

[0083] In some embodiments, the solid carbon source includes at least one of sugars, esters, hydrocarbons, organic acids, and high molecular weight polymers.

[0084] In some embodiments, the solid carbon source includes 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.

[0085] In some embodiments, the mass ratio of the solid carbon source to the precursor is (1-200):100, specifically 1:100, 2:100, 5:100, 10:100, 50:100, 100:100, 150:100, 180:100 or 200:100, etc., which is not limited here.

[0086] In some embodiments, the carbon coating step specifically includes: carbonizing a mixture obtained by mixing a precursor with a liquid carbon source to obtain a negative electrode material.

[0087] In some embodiments, the mass ratio of the liquid carbon source to the precursor is (1-200):100, specifically 1:100, 2:100, 5:100, 10:100, 50:100, 100:100, 150:100, 180:100 or 200:100, etc., which is not limited here.

[0088] In some embodiments, the liquid carbon source includes 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 pentyl acetate.

[0089] In some embodiments, the temperature of the carbonization treatment is 600° C. to 1200° C., and the time of the carbonization treatment is 2 h to 20 h.

[0090] Specifically, the temperature of the carbonization treatment can be 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., etc., without limitation herein. The time of the carbonization treatment can be 2 h, 3 h, 5 h, 8 h, 12 h, 15 h, 18 h, 20 h, 22 h, 24 h, 25 h, 26 h, 28 h, or 30 h, etc., without limitation herein.

[0091] In some embodiments, the carbon coating process is performed under a protective atmosphere comprising at least one of nitrogen, helium, neon, argon, and krypton.

[0092] In some embodiments, the method for preparing the negative electrode material further includes: shaping, screening and grading the carbon coating product to obtain a negative electrode material with a carbon layer on the surface, and the shaping treatment includes at least one of crushing, grinding, ball milling and gas crushing.

[0093] In a third aspect, the present application provides a negative electrode plate, which includes the negative electrode material of the first aspect or the negative electrode material prepared by the preparation method of the second aspect.

[0094] In a fourth aspect, the present application provides a battery comprising the negative electrode material of the first aspect, the negative electrode material prepared by the preparation method of the second aspect, or the negative electrode sheet of the third aspect. The battery may be a lithium-ion battery or a sodium-ion battery, etc., without limitation herein.

[0095] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0096] Example 1

[0097] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0098] (1) Carbon material is D 50=10μm, porous carbon with a pore size of 2nm to 100nm (the average pore size of the carbon material is 5nm); the carbon material is placed in a CVD reaction chamber, the reaction chamber is repeatedly purged with nitrogen (3-5 times), then the nitrogen is turned off and argon gas is introduced at a flow rate of 400sccm, then the temperature is raised to 500°C, the heating rate is 10°C / min, and after staying at this temperature for 1 hour, the argon gas is turned off and high-purity silane gas (99.9999%) is introduced at a flow rate of 100sccm, the speed is controlled at 10rpm, and the temperature is kept for 3h, then the silane gas is turned off, argon gas is introduced, the temperature is cooled to room temperature, and the material is collected to obtain a composite.

[0099] (2) Based on the mass of the composite being 100 wt%, 1.5 wt% of sodium oxide and 0.0003 wt% of magnesium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 600 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0100] (3) The precursor is placed in a CVD reaction chamber and argon gas is introduced at a flow rate of 400 sccm. The temperature is then raised to 600°C at a heating rate of 10°C / min. After staying at this temperature for 1 hour, the argon gas is turned off and ethylene gas is introduced at a flow rate of 100 sccm. The speed is controlled at 10 rpm and the pressure is 10 Torr. The temperature is kept for 0.5 h. Subsequently, the ethylene gas is turned off and argon gas is introduced. The temperature is lowered to room temperature, and then the material is crushed and sieved to obtain the negative electrode material.

[0101] The negative electrode material prepared in this embodiment includes a carbon matrix and a silicon-based active material supported on the carbon matrix, with at least a portion of the silicon-based active material being 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.

[0102] Example 2

[0103] The difference from Example 1 is that:

[0104] (2) Based on the mass of the composite being 100 wt%, 0.06 wt% of magnesium oxide and 0.03 wt% of sodium oxide were added to the composite and mixed. After the mixture was evenly mixed, the composite was placed in a box furnace, heated to 600 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0105] Example 3

[0106] The difference from Example 1 is that:

[0107] (2) Based on the mass of the composite being 100 wt%, 0.3 wt% of magnesium oxide and 0.0015 wt% of sodium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 600 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0108] Example 4

[0109] The difference from Example 1 is that:

[0110] (2) Based on the mass of the composite being 100 wt%, 0.3 wt% of magnesium oxide and 0.00015 wt% of sodium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 600 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0111] Example 5

[0112] The difference from Example 1 is that:

[0113] (2) Based on the mass of the composite being 100 wt%, 1.4 wt% of magnesium oxide and 0.0007 wt% of sodium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 600 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0114] Example 6

[0115] (1) Carbon material is D 50 =12μm, and artificial graphite with an average pore size of 5nm; artificial graphite and nano-silicon (the mass content of oxygen element in nano-silicon is 0.5%) in a mass ratio of 100:120 are added to a solvent, and 5% by mass of polyacrylic acid (based on the mass of artificial graphite as 100%) is added, and the mixture is fully stirred for 10 minutes, and spray-dried and granulated to obtain a composite.

[0116] (2) Based on the mass of the composite being 100 wt%, 1.5 wt% of potassium oxide and 0.0003 wt% of calcium oxide were added to the composite and mixed. After the mixture was evenly mixed, the composite was placed in a box furnace, heated to 800 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0117] (3) Mix the precursor with asphalt (D 50 =5μm) were mixed in a mass ratio of 3:1 and placed in a box furnace. Nitrogen was introduced and the temperature was increased to 750°C at a heating rate of 10°C / min. The mixture was kept at this temperature for 3h and naturally cooled to room temperature. The negative electrode material was obtained after crushing and screening.

[0118] Example 7

[0119] The difference from Example 6 is that:

[0120] (1) Carbon material is D 50 =12μm, and an average pore size of 10nm artificial graphite; artificial graphite and nano-silicon (the mass content of oxygen element in nano-silicon is 3.5% to 4%) in a mass ratio of 100:120 are added to a solvent, and 5% by mass of polyacrylic acid (based on the mass of artificial graphite as 100%) is added, and the mixture is fully stirred for 10 minutes, and spray-dried and granulated to obtain a composite.

[0121] (2) Based on the mass of the composite being 100 wt%, 0.06 wt% of calcium oxide and 0.03 wt% of potassium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 800 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0122] Example 8

[0123] The difference from Example 6 is that:

[0124] (1) Carbon material is D 50 =12μm, and an average pore size of 20nm artificial graphite; artificial graphite and nano-silicon (the mass content of oxygen element in nano-silicon is 8% to 9%) in a mass ratio of 100:120 are added to a solvent, and 5% by mass of polyacrylic acid (based on the mass of artificial graphite as 100%) is added, and the mixture is fully stirred for 10 minutes, and spray-dried and granulated to obtain a composite.

[0125] (2) Based on the mass of the composite being 100 wt%, 0.3 wt% of calcium oxide and 0.0015 wt% of potassium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 800 ° C at a rate of 10 ° C / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0126] Example 9

[0127] The difference from Example 6 is that:

[0128] (1) Carbon material is D 50 =12μm, and an average pore size of 10nmnm artificial graphite; artificial graphite and nano-silicon (the mass content of oxygen element in nano-silicon is 14% to 15%) in a mass ratio of 100:120 are added to a solvent, and 5% by mass of polyacrylic acid (based on the mass of artificial graphite as 100%) is added, and the mixture is fully stirred for 10 minutes, and spray-dried and granulated to obtain a composite.

[0129] (2) Based on the mass of the composite being 100 wt%, 0.3 wt% of calcium oxide and 0.00015 wt% of potassium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 800 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0130] Example 10

[0131] The difference from Example 6 is that:

[0132] (1) Carbon material is D 50 =12μm, and an average pore size of 10nm artificial graphite; artificial graphite and nano-silicon (the mass content of oxygen element in nano-silicon is 14% to 15%) in a mass ratio of 100:120 are added to a solvent, and 5% by mass of polyacrylic acid (based on the mass of artificial graphite as 100%) is added, and the mixture is fully stirred for 10 minutes, and spray-dried and granulated to obtain a composite.

[0133] (2) Based on the mass of the composite being 100 wt%, 5 wt% of calcium oxide and 0.0005 wt% of potassium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 800 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0134] Example 11

[0135] The difference from Example 1 is that:

[0136] (2) Based on the mass of the composite being 100 wt%, 0.29 wt% of magnesium oxide and 0.0015 wt% of sodium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 600 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0137] Example 12

[0138] The difference from Example 1 is that:

[0139] (2) Based on the mass of the composite being 100 wt%, 1.3 wt% of magnesium oxide and 0.0006 wt% of sodium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 600 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0140] Example 13

[0141] The difference from Example 1 is that:

[0142] (2) Based on the mass of the composite being 100 wt%, 1.5 wt% of sodium oxide and 0.00028 wt% of magnesium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 600 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0143] Comparative Example 1

[0144] The difference from Example 1 is that:

[0145] (2) Based on the mass of the composite being 100 wt%, 5 wt% of sodium oxide and 0.003 wt% of magnesium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 600 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0146] Comparative Example 2

[0147] The difference from Example 1 is that:

[0148] (2) Based on the mass of the composite being 100 wt%, 2.5 wt% of magnesium oxide and 0.00025 wt% of sodium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 600 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0149] Comparative Example 3

[0150] The difference from Example 6 is that:

[0151] (1) Carbon material is D 50 =12μm, and artificial graphite with an average pore size of 10nm; artificial graphite and nano-silicon (the mass content of oxygen element in nano-silicon is 0.4%) in a mass ratio of 100:120 are added to a solvent, and 5% by mass of polyacrylic acid (based on the mass of artificial graphite as 100%) is added, and the mixture is fully stirred for 10 minutes, and spray-dried and granulated to obtain a composite.

[0152] (2) Based on the mass of the composite being 100 wt%, 5 wt% of potassium oxide and 0.003 wt% of calcium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 800 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0153] Comparative Example 4

[0154] The difference from Example 6 is that:

[0155] (1) Carbon material is D 50=12μm, and artificial graphite with an average pore size of 10nm; artificial graphite and nano-silicon (the mass content of oxygen element in nano-silicon is 11%) in a mass ratio of 100:120 are added to a solvent, and 5% by mass of polyacrylic acid (based on the mass of artificial graphite as 100%) is added, and the mixture is fully stirred for 10 minutes, and spray-dried and granulated to obtain a composite.

[0156] (2) Based on the mass of the composite being 100 wt%, 6 wt% of calcium oxide and 0.0006 wt% of potassium oxide were added to the composite and mixed. After mixing evenly, the composite was placed in a box furnace, heated to 800 ℃ at a rate of 10 ℃ / min, and sintered at a constant temperature for 5 hours to obtain a precursor.

[0157] Test method:

[0158] (1) Test method for specific surface area of ​​negative electrode material:

[0159] The specific surface area was measured using a Micromeritics TriStar 3000 surface area and pore size analyzer.

[0160] (2) Test of the mass content of alkaline earth metal elements and alkali metal elements in negative electrode materials:

[0161] The mass contents of sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca) in the negative electrode material were tested using the PEoptima 8000ICP testing equipment and the emission spectrometry method.

[0162] (3) Test of the mass content of oxygen in negative electrode materials:

[0163] The nitrogen and oxygen elements in the material were measured using the hydrogen, oxygen and nitrogen analyzer Airt ONH2000, and the test standard was ISO 17053:2005.

[0164] (4) Test of the mass content of silicon in the negative electrode material:

[0165] The silicon content test method in GBT 38823-2020 of the national standard "Silicon Carbon" is used for measurement;

[0166] (5) Test of carbon content in negative electrode materials:

[0167] Use infrared carbon and sulfur analyzer: Airt CS-i to measure the C element in the material;

[0168] (6) Testing method for particle size of silicon-based active materials:

[0169] The silicon-based active material particles were observed by a field emission scanning electron microscope, and the particle sizes of 50 silicon-based active material particles were directly measured by a scale, and the average value of the particle sizes was taken as the final average particle size of the silicon-based active material particles.

[0170] (7) Test method for particle size of negative electrode material:

[0171] Using the Malvern Laser Particle Sizer MS3000, we can determine the particle size distribution using the scattered light intensity distribution of laser diffraction, based on the principle that the intensity distribution of scattered light generated by particles in all directions depends on the particle size. Large particles have small scattering angles, while small particles have large scattering angles. The test conditions are as follows:

[0172] ① Refractive index: 2.61; Absorption rate: 0.1; Refractive index of pure water and solvent: 1.33;

[0173] ② Select "Continuous" for internal ultrasound intensity mode, internal ultrasound intensity 20%; stirring speed: 2500r / min; background test time: 15s; sample test time: 15s;

[0174] ③ Select "Analysis Model" for data processing and select "General";

[0175] ④The tested shading degree is 8-12%.

[0176] (8) Electrochemical performance test

[0177] The negative electrode materials prepared in the examples and comparative examples were dissolved in N-methylpyrrolidone at a mass ratio of 94:1:5, carboxymethyl cellulose, and styrene-butadiene rubber to a solids content of 50%. The resulting materials were coated onto a copper foil current collector and vacuum-dried to produce negative electrode sheets. 18650 cylindrical cells were assembled using conventional production processes using a ternary positive electrode sheet (NCM523), a 1 mol / L lithium hexafluorophosphate (LiPF6) / (ethylene carbonate (EC) + dimethyl carbonate (DMC) + ethyl methyl carbonate (EMC)) (v / v = 1:1:1) electrolyte, a Celgard 2400 separator, and a casing. Cylindrical cells were tested for charge and discharge at room temperature using a LAND battery test system at a constant current of 0.2C, with the charge and discharge voltage limited to 2.75-4.2V. The first reversible capacity, first-cycle charge capacity, and first-cycle discharge capacity were obtained. First-cycle coulombic efficiency = first-cycle discharge capacity / first-cycle charge capacity.

[0178] Repeat the cycle for 50 cycles and record the discharge capacity as the remaining capacity of the lithium-ion battery; capacity retention rate = remaining capacity / initial capacity*100%.

[0179] The results of the performance tests of 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:

[0180] Table 1

[0181] Table 2

[0182] According to the data in Tables 1 and 2, the mass contents of alkali metal elements, alkaline earth metal elements and oxygen elements in the negative electrode materials satisfy the following relationship: 1×10 -5 ≤(B / A)×E≤5×10 2 It is speculated that the reason may be that silicate and silicon oxide can be effectively controlled within an appropriate range, which can play a synergistic role, thereby alleviating the huge stress impact during the cycle, reducing the volume expansion of the negative electrode material, improving the overall structural stability of the negative electrode material, and improving the cycle stability of the negative electrode material.

[0183] According to the test data of Examples 1 to 5 and Comparative Example 1, it can be seen that the (B / A)×E of the negative electrode material of Comparative Example 1 is too low, indicating that the A value exceeds the upper limit or the B value exceeds the lower limit. The A value exceeding the upper limit indicates that the alkali metal element in the negative electrode material is excessive, and it is speculated that this may cause excessive silicates of the alkali metal elements in the negative electrode material, thereby causing the mechanical strength of the negative electrode material to decrease, the effect of inhibiting expansion to deteriorate, and the cycle performance to deteriorate; the B value exceeding the lower limit indicates that the alkaline earth metal element in the negative electrode material is too little, and it is speculated that this may cause the amount of silicates of the alkaline earth metal elements in the negative electrode material to be too little, thereby causing the mechanical strength of the negative electrode material to be very low, the structure to be unstable, and the effect of inhibiting volume expansion during the cycle to be very small.

[0184] Comparative Example 2 Compared with Examples 1 to 5, the (B / A)×E of the negative electrode material of Comparative Example 2 is too high, indicating that the B value exceeds the upper limit and the alkaline earth metal element in the negative electrode material is excessive. It is speculated that this may lead to an excessive amount of alkaline earth metal silicates in the negative electrode material, thereby making the hardness of the negative electrode material too high and the elasticity reduced, which is also not conducive to alleviating the cyclic expansion stress offset, resulting in poor cycle performance; in addition, excessive alkaline earth metal oxides will lead to a decrease in the content of silicon-based active substances in the negative electrode material, which will reduce the capacity and first coulombic efficiency of the negative electrode material.

[0185] According to the test data of Examples 6 to 10 and Comparative Example 3, it can be seen that the (B / A)×E of the negative electrode material of Comparative Example 3 is too low, indicating that the A value exceeds the upper limit or the E value exceeds the lower limit. The A value exceeding the upper limit indicates that the alkali metal elements in the negative electrode material are excessive, which is speculated to cause excessive silicates of alkali metal elements in the negative electrode material, thereby reducing the mechanical strength of the negative electrode material, deteriorating the expansion inhibition effect, and deteriorating the cycle performance; in addition, the low E value indicates that the oxide layer on the surface of the silicon-based active material is too thin, and the side reaction between the silicon-based active material and the electrolyte increases, which will also cause the material to expand significantly in volume during the cycle and deteriorate the cycle performance.

[0186] According to the test data of Examples 6 to 10 and Comparative Example 4, the (B / A)×E of the negative electrode material of Comparative Example 4 is too high, indicating that the alkaline earth metal elements in the negative electrode material are excessive or the E value exceeds the upper limit. It is speculated that the excess alkaline earth metal elements in the negative electrode material may lead to an excessive amount of alkaline earth metal silicates in the negative electrode material, which in turn leads to excessive hardness of the negative electrode material, reduced elasticity, which is not conducive to relieving stress hedging, and poor cycle and expansion performance. In addition, the E value exceeding the upper limit indicates that the oxygen content of the negative electrode material is too high, the inactive silicon oxide increases, the first reversible capacity of the negative electrode material decreases, and the first coulombic efficiency will decrease.

[0187] The applicant declares that the present invention uses the above-described embodiments to illustrate the detailed process equipment and process flow of the present invention. However, the present invention is not limited to the above-described detailed process equipment and process flow, and does not necessarily rely on the above-described detailed process equipment and process flow in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for the raw materials of the present invention's products, additions of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A negative electrode material, characterized in that: It comprises a carbon matrix and a silicon-based active material; the negative electrode material contains alkali metal elements, alkaline earth metal elements and oxygen elements, the alkali metal elements include Na and / or K, and the alkaline earth metal elements include Mg and / or Ca; The mass content of the alkali metal element is Appm, 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 satisfies the following relationship: 1×10 -5 ≤(B / A)×E≤5×10 2 .

2. The negative electrode material according to claim 1, characterized in that It meets at least one of the following technical features: (1) The mass content of the alkali metal element is A ppm, 1≤A≤5000; (2) The mass content of the alkaline earth metal element is B ppm, 5≤B≤5000; (3) The mass content of the oxygen element is E, 0.005≤E≤0.

1.

3. The negative electrode material according to claim 1 or 2, characterized in that: It meets at least one of the following technical features: (1) The alkali metal element exists in the form of alkali metal silicate; (2) The alkaline earth metal element exists in the form of alkaline earth metal silicates.

4. The negative electrode material according to claim 3, characterized in that The carbon matrix includes at least one of hard carbon, soft carbon, graphite, mesophase carbon microbeads, activated carbon, porous carbon, mesoporous carbon and carbon gel.

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

6. The negative electrode material according to claim 5, characterized in that It meets at least one of the following technical features: (1) The silicon-based active material includes elemental silicon, and the elemental silicon includes crystalline silicon and / or amorphous silicon; (2) The silicon-based active material includes silicon oxide, and the silicon oxide includes silicon and oxygen, and the atomic ratio of the silicon to the oxygen is 0 to 2, excluding 0; (3) The silicon-based active material includes silicon oxide, and the chemical formula of the silicon oxide is SiO x , where 0<x≤2; (4) The silicon-based active material includes a silicon alloy, and the silicon alloy includes at least one of a silicon-lithium alloy, a silicon-magnesium alloy, and a silicon-nickel alloy.

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

8. The negative electrode material according to claim 5, characterized in that The mass content of silicon in the silicon-based active material is ≥99%.

9. The negative electrode material according to claim 1, characterized in that It meets at least one of the following technical features: (1) The median particle size D of the negative electrode material 50 ≤15μm; (2) The specific surface area of ​​the negative electrode material is ≤5m 2 / g.

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

11. The negative electrode material according to claim 10, characterized in that The carbon layer includes at least one of graphite carbon and amorphous carbon.

12. The negative electrode material according to claim 1 or 2, characterized in that: In the negative electrode material, the mass ratio of silicon element to carbon element is (0.16-2):

1.

13. A negative electrode plate, characterized in that: The negative electrode material comprises the negative electrode material according to any one of claims 1 to 12.

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

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