Negative electrode material and battery

Abstract

A negative electrode material and a battery. The negative electrode material comprises an active substance; the active substance comprises a carbon matrix and a silicon material; the negative electrode material comprises an oxygen element and a nitrogen element, the mass content of the oxygen element is A%, and the mass content of the nitrogen element is B%; the powder conductivity of the negative electrode material is P S / m, and the following relationship is satisfied: (A+B) / P≤3. The negative electrode material is conducive to reducing the gas production phenomenon of the negative electrode material while keeping relatively high electronic conductivity.

Description

Anode materials and batteries

[0001] This application claims priority to Chinese Patent Application No. 2023117202419, filed on December 13, 2023, and Chinese Patent Application No. 2024103884968, filed on March 29, 2024. This application incorporates the entirety of the aforementioned Chinese patent applications. Technical Field

[0002] The present application relates to the technical field of negative electrode materials, and in particular, to negative electrode materials 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 resources, and relative safety. However, silicon anodes experience significant volume expansion during cycling, leading to material pulverization and fragmentation, and rapid cyclic degradation. Silicon-carbon composites are commonly used to suppress silicon's volume expansion, but silicon-carbon anode materials suffer from gassing during electrode manufacturing, posing a safety hazard and limiting their application.

[0005] Therefore, how to improve the conductivity of the negative electrode material while reducing the gas production value of the negative electrode material is an urgent problem that needs to be solved. Summary of the Invention

[0006] The present application provides a negative electrode material and a battery, which are beneficial for reducing the gas production of the negative electrode material while maintaining a relatively high electronic conductivity.

[0007] The present application provides a negative electrode material, including an active substance, wherein the active substance includes a carbon matrix and a silicon material; the negative electrode material contains oxygen and nitrogen, the mass content of the oxygen element is A%, and the mass content of the nitrogen element is B%; the powder conductivity of the negative electrode material is PS / m, and satisfies the following relationship: (A+B) / P≤3.

[0008] The technical solution of this application has at least the following beneficial effects:

[0009] The negative electrode material provided by the present application includes an active substance, and the active substance includes a carbon matrix and a silicon material, which helps to improve the capacity of the negative electrode material. Furthermore, the negative electrode material contains a small amount of oxygen and nitrogen elements, and a small amount of nitrogen and oxygen elements can provide lone pairs of electrons. The lone pairs of electrons participate in the π-π conjugated system of the carbon matrix, thereby forming a larger p-π conjugated system and thus increasing the electronic conductivity of the negative electrode material; However, the presence of oxygen and nitrogen elements easily reacts with solvent molecules or hydrogen radicals in the electrolyte to generate some gases (such as CO2, CO, NH2, etc.), and the gas production phenomenon will affect the safety performance of the battery. Therefore, the present application controls (A+B) / P≤3 within this range, controls the relationship between the mass content of oxygen and nitrogen and the electronic conductivity of the negative electrode material, and is conducive to reducing the gas production phenomenon of the negative electrode material while maintaining a higher electronic conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG1 is a process flow chart of the method for preparing the negative electrode material provided in this application.

[0011] FIG2 is an XRD diagram of the negative electrode material prepared in Example 1 of the present application.

[0012] FIG3 is a schematic diagram of the first charge and discharge curve of the negative electrode material prepared in Example 1 of the present application.

[0013] FIG4 is a schematic diagram of the cycle performance curve of the negative electrode material prepared in Example 1 of the present application.

[0014] FIG5 is an XRD diagram of the negative electrode material prepared in Example 10 of the present application.

[0015] FIG6 is the first charge and discharge curve of the negative electrode material prepared in Example 10 of the present application.

[0016] FIG7 is a cycle performance curve of the negative electrode material prepared in Example 10 of the present application. DETAILED DESCRIPTION

[0017] 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.

[0018] In the first aspect, the present application provides a negative electrode material, which includes an active substance, and the active substance includes a carbon matrix and a silicon material; the negative electrode material contains oxygen and nitrogen elements, the mass content of the oxygen element is A%, and the mass content of the nitrogen element is B%; the powder conductivity of the negative electrode material is PS / m, and satisfies the following relationship: (A+B) / P≤3.

[0019] The negative electrode material provided by the present application includes an active substance, and the active substance includes a carbon matrix and a silicon material. The negative electrode material contains oxygen and nitrogen elements. Nitrogen and oxygen elements can provide lone pairs of electrons. The lone pairs of electrons participate in the π-π conjugated system of the carbon matrix, thereby forming a larger p-π conjugated system and thus increasing the electronic conductivity of the negative electrode material. However, the presence of oxygen and nitrogen elements easily reacts with solvent molecules or hydrogen radicals in the electrolyte to generate some gases (such as CO2, CO, NH2, etc.), and the gas production phenomenon will affect the safety performance of the battery. Therefore, the mass content of oxygen and nitrogen elements in the negative electrode material of the present application and the electronic conductivity of the negative electrode material satisfy the relationship of (A+B) / P≤3, which is conducive to reducing the gas production phenomenon of the negative electrode material while maintaining a high electronic conductivity.

[0020] In some embodiments, the silicon material includes silicon particles.

[0021] In some embodiments, the silicon material includes silicon particles and a silicon oxide layer located on the surface of the silicon particles. The silicon oxide layer includes silicon oxide, and the general formula of silicon oxide is SiO x , wherein 0.5≤x<2. Specifically, SiOx can be SiO 0.5 、SiO 0.7 、SiO 0.9 、SiO、SiO 1.2 、SiO 1.5 、SiO 1.8 、SiO 1.9 etc., not limited here.

[0022] In some embodiments, the silicon material includes silicon particles and a silicon oxide layer located on the surface of the silicon particles. The mass percentage of oxygen in the silicon material is 1% to 18%, based on the mass of the silicon material being 100%. Specifically, the mass percentage of oxygen in the silicon material can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, or 18%, etc., without limitation herein. Controlling the mass percentage of oxygen in the silicon material within the above range is conducive to forming a stable silicon oxide layer on the surface of the silicon particles, which can reduce direct contact between the silicon particles and the electrolyte, thereby reducing side reactions between the silicon material and the electrolyte, and improving the cycle stability of the negative electrode material; it can also ensure that the silicon material has stable activity and increase the specific capacity of the negative electrode material.

[0023] In some embodiments, the silicon particles include at least one of silicon, silicon oxide, a silicon alloy, and a silicon-carbon composite. Specifically, the silicon may be amorphous silicon, crystalline silicon, or a composite of crystalline silicon and amorphous silicon, without limitation. The silicon alloy may be a silicon-lithium alloy, a silicon-magnesium alloy, a silicon-nickel alloy, or the like, without limitation.

[0024] In some embodiments, the average particle size of the silicon particles is 0.1nm to 500nm, and can specifically be 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 particles of appropriate size can improve the distribution uniformity of silicon particles and carbon matrix, reduce silicon particle segregation, and improve the cycle performance of negative electrode materials. Preferably, the average particle size of the silicon particles is 1nm to 10nm; more preferably, the average particle size of the silicon particles is 1nm to 5nm.

[0025] In some embodiments, the mass content of silicon in the silicon particles is ≥99%. The mass content of silicon in the silicon particles within the above range is beneficial to improving the purity of the silicon particles and reducing impurities.

[0026] In some embodiments, the morphology of the silicon particles includes at least one of a dot-like shape, a spherical shape, an ellipsoidal shape, and a flake-like shape. The morphology of the silicon particles can be selected according to actual needs and is not limited here.

[0027] In some embodiments, the active material includes a carbon matrix and silicon particles. The carbon matrix has pores, and at least some of the silicon particles are distributed in the pores of the carbon matrix.

[0028] The negative electrode material provided by the present application includes an active substance, and the active substance includes a carbon matrix and silicon particles. The carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix, which can increase the capacity of the negative electrode material. In addition, the negative electrode material contains oxygen and nitrogen elements. Nitrogen and oxygen element doping can provide lone pairs of electrons. The lone pairs of electrons participate in the π-π conjugated system of the carbon matrix, thereby forming a larger p-π conjugated system and thus increasing the electronic conductivity of the negative electrode material. However, the presence of oxygen and nitrogen elements easily reacts with solvent molecules or hydrogen radicals in the electrolyte to generate some gases (such as CO2, CO, NH2, etc.), and the gas production phenomenon will affect the safety performance of the battery. Therefore, the mass content of oxygen and nitrogen elements in the negative electrode material of the present application and the electronic conductivity of the negative electrode material meet the following requirements: (A+B) / P≤3. Controlling the relationship between the mass content of oxygen and nitrogen elements and the electronic conductivity of the negative electrode material is beneficial to reducing the gas production phenomenon of the negative electrode material while maintaining a high electronic conductivity. The pores in the carbon matrix and the distribution of silicon particles in the pores of the carbon matrix are conducive to alleviating the volume expansion of silicon particles in the negative electrode material during the cycle, maintaining the structural stability of the negative electrode material, and reducing the collapse of the material structure caused by volume expansion during the lithium insertion and extraction process of the negative electrode material. The pores in the carbon matrix in the negative electrode material can also absorb a small amount of gas, which can further reduce the gas production of the negative electrode material, thereby improving the cycle performance of the negative electrode material.

[0029] In some embodiments, the oxygen content of the negative electrode material is A%, with a mass content of 0 < A ≤ 3. Specifically, the value of A can be 0.1, 0.2, 0.4, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8, or 3, etc., without limitation. Preferably, the oxygen content is 0 < A % ≤ 1.5%.

[0030] In some embodiments, the nitrogen content of the negative electrode material is B%, with a mass content of 0 < B ≤ 3. The value of B can be 0.1, 0.2, 0.4, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8, or 3, among others, without limitation. Controlling the nitrogen content of the negative electrode material within this range can improve the specific capacity of the negative electrode material. Preferably, the nitrogen content is 0.1% ≤ B% ≤ 0.5%.

[0031] 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.

[0032] In some embodiments, the carbon matrix has functional groups on its surface and / or in its pores, and the functional groups include at least one of hydroxyl, carboxyl, carbonyl, aliphatic, cyclic aliphatic, and amino groups.

[0033] In some embodiments, nitrogen and oxygen elements are present on the surface and / or in the pores of the carbon matrix in the form of atomic doping, specifically in the pores and / or surface defects of the carbon matrix.

[0034] In some embodiments, the total pore volume of the carbon matrix is ​​≥ 0.4 cm 3 / g, specifically 0.4cm 3 / g, 0.5cm 3 / g, 0.8cm 3 / g, 1cm 3 / g, 1.1cm 3 / g, 1.3cm 3 / g, 1.5cm 3 / g or 1.8cm 3 / g, etc., of course, it can also be other values ​​within the above range, which is not limited here. Preferably, the total pore volume of the carbon matrix is ​​≥0.5cm 3 / g; further preferably, the total pore volume of the carbon matrix is ​​≥0.7cm 3 / g.

[0035] In some embodiments, the pores in the carbon matrix include micropores with a pore size of less than 2 nm, and the proportion of micropores is ≥80%. Specifically, the proportion of micropores can be 80%, 82%, 85%, 88%, 90%, 92%, 93%, 95%, 98% or 99%, etc., without limitation herein. It can be understood that the size of the silicon particles deposited in the pores of the carbon matrix is ​​determined by the size of the pores. The higher the proportion of micropores, the smaller the average pore size of the pores of the carbon matrix, and the smaller the particle size of the silicon particles deposited in the pores of the carbon matrix. The silicon particles deposited in the pores of the carbon matrix have a small particle size, and the volume expansion of the negative electrode material during the cycle is small, which is beneficial to improving the cycle performance of the negative electrode material. Preferably, the proportion of micropores is ≥90%; more preferably, the proportion of micropores is ≥95%.

[0036] In some embodiments, the average pore size of the pores in the carbon matrix is ​​≤5nm, and can specifically be 0.1nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm or 5nm, etc., and of course it can also be other values ​​within the above range, which are not limited here. It can be understood that the average pore size of the pores in the carbon matrix will affect the particle size of the silicon particles located in the pores. Controlling the average pore size of the pores in the carbon matrix can adjust the particle size of the silicon particles and reduce the phenomenon of excessive expansion stress caused by the accumulation of local silicon particles. Preferably, the average pore size of the pores in the carbon matrix is ​​≤2nm; more preferably, the average pore size of the pores in the carbon matrix is ​​≤1.8nm.

[0037] In some embodiments, the porosity of the carbon matrix is ​​40% to 60%, specifically 40%, 41%, 43%, 45%, 48%, 50%, 52%, 54%, 56%, 58% or 60%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0038] In some embodiments, under stirring, 150 mL of a 20% mass fraction HF acid solution is added dropwise to 10 g of the negative electrode material, which will generate SiF4 and H2 gases and release heat. After no gas is generated, the supernatant acid solution is removed by centrifugation, and 150 mL of a 20% mass fraction HF acid solution is added to the negative electrode material again. After stirring for 12 hours, the supernatant acid solution is removed by centrifugation again, and then the negative electrode material is washed with pure water until neutral and dried to obtain the negative electrode material after removing the silicon particles, that is, the carbon matrix.

[0039] In some embodiments, the negative electrode material further includes a carbon material located on at least a portion of the surface of the active material. It is understood that the carbon material can act as a buffer layer to reduce the volume expansion effect of the negative electrode material to a certain extent, while enhancing the conductivity of the negative electrode material. The carbon material can also reduce direct contact between the active material and the electrolyte, inhibit excessive growth of the SEI film on the surface of the negative electrode material, stabilize the interface of the negative electrode material, and improve the Coulombic efficiency of the negative electrode material.

[0040] In some embodiments, the carbon material includes at least one of graphitic carbon and amorphous carbon. The presence of the carbon material 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 silicon particles and the electrolyte, reduce the occurrence of side reactions, and improve the rate capability and cycle performance of the negative electrode material.

[0041] In some embodiments, the median particle size D50 of the negative electrode material is ≤10 μm, and specifically can be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 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.

[0042] 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、3m 2 / g, 3.5m 2 / g、4m2 / 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 from the negative electrode material.

[0043] In some embodiments, the 6-day gas production of the negative electrode material is M mL / g, where M≤0.2. The gas production of the negative electrode material can specifically be 0.2 mL / g, 0.18 mL / g, 0.15 mL / g, 0.12 mL / g, 0.10 mL / g, 0.08 mL / g, 0.05 mL / g, or 0.01 mL / g, and other values ​​within the above range are also possible and are not limited herein. Controlling the gas production of the negative electrode material within the above range can improve the cycle stability and safety of the negative electrode material.

[0044] The test method for the gas production of the negative electrode material is as follows: 20g of the negative electrode material is added to 50g of styrene-butadiene rubber solution to obtain a mixed solution, the mixed solution is encapsulated with aluminum-plastic film, and placed in a 2000mL sealed container, and stored at 45°C. The test shows that the 6-day gas production of the negative electrode material is M mL / g.

[0045] In some embodiments, the powder conductivity of the negative electrode material is PS / m, P≥0.01S / m, and the powder conductivity can specifically be 0.01S / m, 0.02S / m, 0.03S / m, 0.05S / m, 0.08S / m, 0.1S / m, 0.2S / m or 1S / m, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0046] In some embodiments, the negative electrode material further contains sulfur, and the content of sulfur in the negative electrode material is S ppm; wherein 0<S≤20ppm.

[0047] First, the above-mentioned negative electrode material contains a small amount of oxygen and nitrogen elements. A small amount of nitrogen and oxygen elements can provide lone pairs of electrons. The lone pairs of electrons participate in the π-π conjugated system of the carbon matrix, thereby forming a larger p-π conjugated system and thus increasing the electronic conductivity of the negative electrode material; however, the presence of oxygen and nitrogen elements makes it easy for the battery prepared with the negative electrode material to react with the solvent molecules or hydrogen radicals in the electrolyte to generate some gases (such as CO2, CO, NH2, etc.). The gas production phenomenon affects the safety performance of the battery. Therefore, the negative electrode material is doped with sulfur at the same time as nitrogen and oxygen, and the content of sulfur in the negative electrode material is 0<S≤20ppm. Since sulfur has a large atomic radius, it can form a CS bond with lithium storage activity with the carbon element in the negative electrode material, so that the carbon layer spacing of the carbon matrix after doping with nitrogen and oxygen elements can be further expanded, and the electrical conductivity of the carbon matrix is ​​better; at the same time, sulfur can combine with oxygen elements to form inactive SO bonds, reducing the gas production problem caused by the reaction between the battery prepared by the negative electrode material and the electrolyte; and after doping with sulfur, the relationship between the oxygen element content A%, the nitrogen element content B% and the powder conductivity P satisfies (A+B) / P≤3, so that nitrogen, oxygen and sulfur doping improves the powder conductivity of the negative electrode material while alleviating the problem of increased gas production caused by the reaction between the battery prepared by the negative electrode material and the electrolyte due to excessive nitrogen and oxygen content, so that the negative electrode material has both excellent electrical conductivity and cycle performance.

[0048] In some embodiments, the sulfur content of the negative electrode material is 0<S≤20ppm. Optionally, the sulfur content of the negative electrode material can be 20ppm, 17ppm, 14ppm, 11ppm, 9ppm, 6ppm, or other values ​​within the range. The above range can be selected based on actual needs and is not limited here. It is understood that when the sulfur content of the negative electrode material is within the above range, the conductivity of the negative electrode material is improved and the gas generation value of the reaction between the battery prepared by the negative electrode material and the electrolyte is reduced, while the structural stability of the carbon matrix is ​​not affected by excessive sulfur doping.

[0049] In some embodiments, the mass content of oxygen element A% is ≤3%. Optionally, the mass content of oxygen element can be 3%, 2.5%, 2%, 1.5%, 1%, 0.5% and 0.3%, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that the mass content of oxygen element within the above range can reduce the amount of gas produced by the reaction between the negative electrode material and the electrolyte during the charge and discharge process of the battery prepared by the negative electrode material, thereby improving the cycle performance of the battery prepared by the negative electrode material. Preferably, the mass content of oxygen element is ≤1%; more preferably, the mass content of oxygen element is ≤0.5%.

[0050] In some embodiments, the mass content of nitrogen element B% ≤ 3%. Optionally, the mass content of nitrogen element can be 3%, 2.5%, 2%, 1.5%, 1%, 0.5% and 0.3%, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. The mass content of nitrogen element in the present application is within the above range, and the nitrogen doping content improves the conductivity and electrocatalytic activity of the negative electrode material. Preferably, the mass content of nitrogen element is ≤ 1%; more preferably, the mass content of nitrogen element is ≤ 0.5%.

[0051] In some embodiments, the powder conductivity P of the negative electrode material satisfies: 10 -1 S / cm≤10 4 S / cm, optionally, the powder conductivity of the negative electrode material can be specifically 10 -1 S / cm、10S / cm、10 2 S / cm, 10 3 S / cm and 10 4 S / cm, etc., and may also be other values ​​within the range, which can be selected according to actual needs and are not limited here. It is understood that when the powder conductivity P of the negative electrode material is within the above range, the negative electrode material can more efficiently transport lithium ions, so that during the initial charge and discharge process of the battery prepared with the negative electrode material, more lithium ions can participate in the reversible charge and discharge reaction, reducing irreversible capacity loss, thereby improving the initial coulombic efficiency of the battery prepared with the negative electrode material.

[0052] In some embodiments, the pores in the negative electrode material include micropores, ie, pores with a pore diameter of less than 2 nm, wherein the volume of the micropores of the negative electrode material accounts for ≤20% of the total pore volume of the negative electrode material.

[0053] In some embodiments, the volume of the micropores of the negative electrode material accounts for ≤5% of the total pore volume of the negative electrode material. Optionally, the volume percentage of the micropores in all pores can be 5%, 4%, 3%, 2%, 1%, etc., or other values ​​within the range, which can be selected according to actual needs and are not limited here. It is understood that when the volume percentage of the micropores of the negative electrode material is within the above range, the specific surface area of ​​the negative electrode material can be increased, providing more active sites for the insertion and deinsertion of lithium ions, thereby improving the reversible capacity of the negative electrode material.

[0054] In some embodiments, the pores in the negative electrode material include mesopores, i.e., pores with a pore diameter of 2 nm to 50 nm, wherein the mesopore volume of the negative electrode material accounts for 87% to 97% of the total pore volume of the negative electrode material. Optionally, the proportion of the mesopore volume in the total pore volume of the negative electrode material can be 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, and 97%, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that the proportion of the mesopore volume in the total pore volume of the negative electrode material within the above range is conducive to the rapid diffusion of lithium ions, and can also provide sufficient space to accommodate the volume change of silicon particles during the charge and discharge process, thereby improving the cycle stability of the negative electrode material.

[0055] In some embodiments, the pores in the negative electrode material include macropores, i.e., pores having a pore diameter greater than 50 nm, wherein the volume ratio of the macropore volume of the negative electrode material to the total pore volume of the negative electrode material is ≤10%. Optionally, the volume ratio of the macropore volume of the negative electrode material to the total pore volume can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, etc., or other values ​​within the range, which can be selected according to actual needs and are not limited herein. It is understood that when the volume ratio of the macropore volume of the negative electrode material to the total pore volume of the negative electrode material is within the above range, the diffusion rate of lithium ions can be increased.

[0056] In some embodiments, the average pore size of the pores in the negative electrode material is 0.5 nm to 20 nm. Optionally, the average pore size of the pores in the negative electrode material can be 0.5 nm, 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm and 20 nm, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0057] In some embodiments, the total pore volume of the negative electrode material is 0.001 cm 3 / g~0.1cm 3 / g, optionally, the total pore volume of the negative electrode material can be specifically 0.001cm 3 / g, 0.01cm 3 / g, 0.02cm 3 / g, 0.03cm 3 / g, 0.04cm 3 / g, 0.05cm 3 / g, 0.06cm 3 / g, 0.07cm 3 / g, 0.08cm 3 / g, 0.09cm 3 / g and 0.1cm 3 / g, etc., and can also be other values ​​within the range, which can be selected according to actual needs and are not limited here. It can be understood that when the total pore volume of the negative electrode material is within the above range, while increasing the specific capacity of the negative electrode material, the negative electrode material also reserves an appropriate amount of pores to alleviate the volume expansion caused by the active material during the lithium insertion and deintercalation process, which is beneficial to improving the cycle performance of the negative electrode material.

[0058] In some embodiments, the pores in the negative electrode material after removing the silicon particles include micropores, and the micropores in the negative electrode material after removing the silicon particles account for ≥80% of the total pore volume of the negative electrode material after removing the silicon particles. Optionally, the micropores after removing the silicon particles account for 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96% and 98% of the total pore volume of the negative electrode material after removing the silicon particles, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0059] In some embodiments, the preparation method of the negative electrode material after removing silicon particles includes: adding a 1M nitric acid solution to the negative electrode material and soaking it for 1 hour, then dripping a 20% mass fraction HF acid solution into the negative electrode material drop by drop, which will produce yellow smoke, and repeating the dripping several times until no yellow smoke is produced in the solution; finally, using a 1M nitric acid solution to digest the residue, and then washing and drying to obtain the negative electrode material after removing the silicon particles, that is, the carbon matrix.

[0060] In some embodiments, the preparation method of the negative electrode material after removing silicon particles includes: under stirring, adding 150mL of 20% mass fraction HF acid solution dropwise into 10g of negative electrode material, which will produce SiF4 and H2 gas and release heat. After no gas is generated, centrifugation is performed to remove the supernatant acid solution, and 150mL of 20% mass fraction HF acid solution is added to the negative electrode material again. After stirring for 12 hours, the supernatant acid solution is removed again by centrifugation, and then the negative electrode material is washed with pure water until it is neutral and dried to obtain the negative electrode material after removing the silicon particles, that is, the carbon matrix.

[0061] Understandably, the size of the silicon particles deposited within the pores of the carbon matrix is ​​affected by the size of the pores. The higher the proportion of micropores, the smaller the average pore size of the carbon matrix's pores, and the smaller the particle size of the silicon particles deposited within the pores of the carbon matrix. The smaller the particle size of the silicon particles deposited within the pores of the carbon matrix, the smaller the volume expansion of the negative electrode material during cycling, which is beneficial for improving the cycling performance of the negative electrode material. Preferably, the proportion of micropores is ≥ 90%; more preferably, the proportion of micropores is ≥ 95%.

[0062] In some embodiments, in the negative electrode material after removing the silicon particles, the pores with a pore size in the range of 2nm to 5nm account for 0% to 10% of the total pore volume of the negative electrode material after removing the silicon particles. Optionally, the pores with a pore size in the range of 2nm to 5nm after removing the silicon particles account for 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% and 10% of the total pore volume of the negative electrode material after removing the silicon particles. It can also be other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0063] In some embodiments, the average pore size of the negative electrode material after removing the silicon particles is ≤5 nm. Optionally, the average pore size of the negative electrode material after removing the silicon particles can be 5 nm, 4 nm, 3 nm, 2 nm, 1 nm, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0064] In some embodiments, the total pore volume of the negative electrode material after removing the silicon particles is 0.2 cm 3 / g~2cm 3 / g, optionally, the total pore volume of the negative electrode material after removing the silicon particles can be specifically 0.2cm 3 / g, 0.4cm 3 / g, 0.6cm 3 / g, 0.8cm 3 / g, 1cm 3 / g, 1.2cm 3 / g, 1.4cm 3 / g, 1.6cm 3 / g, 1.8cm 3 / g and 2cm 3 / g, etc., and can also be other values ​​within the range, which can be selected according to actual needs and are not limited here. It can be understood that the negative electrode material after removing the silicon particles, that is, the carbon matrix, has a total pore volume controlled within the above range, which can not only ensure the structural strength of the carbon matrix, but also reserve sufficient pores for filling silicon particles, so that the negative electrode material after the carbon matrix and silicon particles are composited can have excellent rate performance and cycle performance.

[0065] In some embodiments, the particle size of the negative electrode material satisfies: 2 μm ≤ D 50 ≤20μm, 0.9≤(D 90 -D 10 ) / D 50 ≤5, where the particle size D of the negative electrode material 50 Specifically, it can be 2 μm, 5 μm, 10 μm, 12 μm, 15 μm, 18 μm and 20 μm, etc. (D 90 -D 10 ) / D50 Specifically, it can be 0.9, 1, 2, 3, 4, and 5, etc., or other values ​​within the range, which can be selected according to actual needs and are not limited here. 90 -D 10 ) / D 50 It reflects the particle size distribution span of the negative electrode material. When the particle size distribution span is too small, the screening and preparation costs of the negative electrode material are high. When the particle size distribution span is too large, it means that the particle size distribution of the negative electrode material is wide, resulting in uneven volume changes in the battery prepared from the negative electrode material during the cycle.

[0066] In some embodiments, the specific surface area of ​​the negative electrode material is 1 m 2 / g~10m 2 / g, optionally, the specific surface area of ​​the negative electrode material can be specifically 1m 2 / g, 2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g and 10m 2 / g, etc., and may also be other values ​​within the range, which can be selected according to actual needs and are not limited here. It is understood that when the specific surface area of ​​the negative electrode material is within the above range, it can provide more embedding sites for lithium ions to increase the capacity of the lithium-ion battery, while reducing the contact area between the battery prepared with the negative electrode material and the electrolyte, thereby reducing the occurrence of side reactions and improving the cycle performance of the battery prepared with the negative electrode material.

[0067] In some embodiments, the compacted density of the negative electrode material is 0.80 cm 3 / g~1.30cm 3 / g, optionally, the compaction density of the negative electrode material can be specifically 0.80cm 3 / g, 0.90cm 3 / g, 1cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g and 1.3cm 3 / g, etc., and can also be other values ​​within the range, which can be selected according to actual needs and are not limited here. It can be understood that when the compaction density of the negative electrode material is within the above range, the unit volume of the negative electrode sheet can accommodate more negative electrode material, which helps to improve the volume energy density of the battery.

[0068] In some embodiments, the tap density of the negative electrode material is 0.5 cm3 / g~1.5cm 3 / g, optionally, the tap density of the negative electrode material can be specifically 0.5cm 3 / g, 0.7cm 3 / g, 0.9cm 3 / g, 1.1cm 3 / g, 1.3cm 3 / g and 1.5cm 3 / g, etc., can also be other values ​​within the range, can be selected according to actual needs, and are not limited here.

[0069] In some embodiments, the mass content of carbon element in the negative electrode material is 40% to 60%. Optionally, the mass content of carbon element in the negative electrode material can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58% and 60%, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0070] In some embodiments, the mass content of silicon in the negative electrode material is 35% to 55%. Optionally, the mass content of silicon in the negative electrode material can be 35%, 37%, 39%, 41%, 43%, 45%, 47%, 49%, 51%, 53% and 55%, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0071] In some embodiments, the carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix. The silicon particle active substance fills the pores of the carbon material, ensuring that the silicon particle active substance and the carbon matrix are dispersed. On the one hand, the specific capacity of the negative electrode material can be improved. On the other hand, the pores of the carbon material after filling with the silicon particle active substance are reduced, which can increase the density of the negative electrode material, effectively reduce the occurrence of side reactions between the battery prepared by the negative electrode material and the electrolyte, and further improve the cycle performance of the battery prepared by the negative electrode material.

[0072] In some embodiments, the carbon matrix includes at least one of amorphous carbon, graphitized carbon, mesophase carbon microbeads and carbon gel, wherein the amorphous carbon includes at least one of hard carbon, soft carbon and activated carbon, and the graphitized carbon includes at least one of graphite and graphitized carbon nanotubes. The type of carbon matrix can be selected according to actual needs and is not limited here.

[0073] In some embodiments, at least one of the surface, carbon-carbon skeleton, carbon layer gap and lattice defect of the carbon matrix contains a functional group, and the functional group contains at least one of oxygen, nitrogen and sulfur elements, wherein the functional group includes at least one of hydroxyl, carboxyl, carbonyl, lipid, cyclic lipid, amino, thiol, sulfate, sulfite, thioether and sulfonic acid groups. The type of functional group can be selected according to actual needs and is not limited here.

[0074] In some embodiments, the surface of the negative electrode material has a coating layer, and the material of the coating layer includes at least one of carbon material, titanium nitride, boron nitride, silicon nitride, silicon oxide, magnesium oxide, aluminum oxide, silicon carbide and polyaniline. The type of material of the coating layer can be selected according to actual needs and is not limited here.

[0075] In a second aspect, the present application provides a method for preparing a negative electrode material, which comprises the following steps: subjecting a mixture comprising a carbon source and a modifying substance to a primary carbonization treatment to obtain a precursor, wherein the modifying substance comprises oxygen and nitrogen elements; subjecting the precursor to a secondary carbonization treatment to obtain a carbon matrix; and compounding the carbon matrix with silicon particles or silicon materials to obtain a negative electrode material.

[0076] The preparation method of the negative electrode material provided in the present application utilizes a mixture of a carbon source and a modifying substance containing oxygen and nitrogen elements to perform a primary carbonization treatment and a secondary carbonization treatment to improve the graphitization degree of the carbon matrix. In addition, during the secondary carbonization treatment, more oxygen-containing or nitrogen-containing groups are volatilized, which can control the mass content of nitrogen and oxygen in the carbon matrix. A small amount of nitrogen and oxygen doping can provide lone pairs of electrons, which participate in the π-π conjugated system of the carbon matrix, thereby forming a larger p-π conjugated system and thus increasing the electronic conductivity of the negative electrode material. Finally, the above-mentioned carbon matrix is ​​compounded with silicon particles or silicon materials to increase the capacity of the negative electrode material.

[0077] In some embodiments, a method for preparing a negative electrode material is provided, as shown in FIG1 , comprising the following steps:

[0078] Step S10, subjecting a mixture comprising a carbon source and a modifying substance to a carbonization treatment to obtain a precursor, wherein the modifying substance comprises a nitrogen-containing compound and an oxygen-containing compound;

[0079] Step S20, performing a secondary carbonization treatment on the precursor to obtain a carbon matrix, wherein the temperature of the secondary carbonization treatment is higher than the temperature of the primary carbonization treatment;

[0080] Step S30 , compounding the carbon matrix having pores with silicon particles or silicon material to obtain a negative electrode material, wherein at least part of the silicon particles or silicon material are distributed in the pores of the carbon matrix.

[0081] The preparation method of the above-mentioned negative electrode material uses a mixture of a carbon source and a modifying substance to perform a primary carbonization treatment, so that the modifying substance can be doped into the carbon matrix, and then undergoes a secondary carbonization treatment. The secondary carbonization treatment temperature is controlled to be higher than the primary carbonization treatment temperature, which can increase the graphitization degree of the carbon matrix with the help of high temperature and improve the electronic conductivity of the carbon matrix itself; in addition, during the secondary carbonization treatment, more oxygen-containing or nitrogen-containing groups are volatilized, which can control the mass content of nitrogen and oxygen in the carbon matrix. A small amount of nitrogen and oxygen doping can provide lone pairs of electrons, which participate in the π-π conjugated system of the carbon matrix, thereby forming a larger p-π conjugated system and thus increasing the electronic conductivity of the negative electrode material. Finally, the above-mentioned carbon matrix is ​​compounded with silicon particles or silicon materials to increase the capacity of the negative electrode material; the pores in the carbon matrix are conducive to alleviating the volume expansion of silicon particles or silicon materials during the cycle of the negative electrode material, maintaining structural stability, reducing the collapse of the material structure caused by volume expansion during the lithium insertion and extraction process of the negative electrode material, effectively reducing the occurrence of side reactions between the negative electrode material and the electrolyte, and thus improving the cycle performance of the negative electrode material.

[0082] The preparation method is described in detail below with reference to specific examples:

[0083] In step S10 , a mixture including a carbon source and a modifying substance is subjected to a carbonization treatment to obtain a precursor, wherein the modifying substance includes a nitrogen-containing compound and an oxygen-containing compound.

[0084] In some embodiments, the carbon source includes at least one of bamboo charcoal, fruit shells, starch, coconut shells, rice husks, peanut shells, coal, lignin, sugars, resins, and the like.

[0085] In some embodiments, the temperature of the primary carbonization treatment is 600°C to 900°C, specifically 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C, etc., which is not limited here; the time of the carbonization treatment is 1h to 15h, specifically 1h, 3h, 5h, 8h, 10h, 12h, 13h, 14h or 15h, etc., which is not limited here.

[0086] In some embodiments, the nitrogen-containing compound includes at least one of urea, ammonium acetate, methanolamine, ammonium chloride, ammonium nitrate, and N,N-dimethylformamide. It is understood that urea-based nitrogen-containing compounds inherently contain oxygen and nitrogen, thereby enabling doping and modification of the carbon source. Even if compounds such as ammonium chloride do not contain oxygen, during a primary carbonization process, oxygen in the environment can participate in doping and modification together with the nitrogen in the modifying substance.

[0087] In some embodiments, the mass ratio of the carbon source to the nitrogen-containing compound is 100:(0.5-100), specifically 100:0.5, 100:1, 100:5, 100:10, 100:20, 100:30, 100:50, 100:60, 100:80, 100:90 or 100:100, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0088] In some embodiments, the method further comprises: subjecting the primary carbonization product to an activation treatment in a mixture of nitrogen and water vapor. It is understood that the activation treatment facilitates the directional deposition of silicon particles or silicon material into the pores of the carbon matrix during the subsequent silicon deposition process, thereby reducing the deposition of silicon particles or silicon material on the surface of the carbon matrix.

[0089] The activation treatment method includes at least one of physical activation treatment and chemical activation treatment. Specifically, chemical activation can be performed by treating the primary carbonization product with alkali solution as an activating agent. Physical activation can be performed by using at least two of water vapor, oxygen, and air.

[0090] In some embodiments, the primary carbonization product is placed in a mixed gas of nitrogen and water vapor for activation treatment.

[0091] In some embodiments, the volume concentration of water vapor is 0.1% to 30%, specifically 0.1%, 1%, 2%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25% or 30%, etc., which is not limited here.

[0092] In some embodiments, the activation treatment temperature is 380° C. to 2000° C., and the activation treatment time is 0.5 h to 30 h. Specifically, the activation treatment temperature can be 380° C., 400° C., 500° C., 800° C., 1000° C., 1200° C., 1500° C., 1800° C., or 2000° C., etc., without limitation herein. The activation treatment time can be 0.5 h, 1 h, 3 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 24 h, or 30 h, etc., without limitation herein.

[0093] In the present application, by controlling the volume concentration of water vapor, the temperature and time of the activation treatment, the activation efficiency of the primary carbonization product can be improved, so that the carbon matrix can have a rich pore structure, and the surface and / or pores of the carbon matrix after activation treatment contain oxygen-containing functional groups (such as carboxyl groups, carbonyl groups, etc.), or exist in the form of doped atoms in the skeleton, skeleton gaps, defects and other positions of the carbon matrix. A small amount of oxygen-containing functional groups can provide lone pairs of electrons after subsequent carbonization treatment. The lone pairs of electrons participate in the π-π conjugated system of the carbon matrix, thereby forming a larger p-π conjugated system and thus increasing the electronic conductivity of the negative electrode material.

[0094] 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.

[0095] In some embodiments, the total pore volume of the carbon matrix is ​​≥ 0.4 cm 3 / g, specifically 0.4cm 3 / g, 0.5cm 3 / g, 0.8cm 3 / g, 1cm 3 / g, 1.1cm 3 / g, 1.3cm 3 / g, 1.5cm 3 / g or 1.8cm 3 / g, etc., of course, it can also be other values ​​within the above range, which is not limited here. Preferably, the total pore volume of the carbon matrix is ​​≥0.5cm 3 / g; further preferably, the total pore volume of the carbon matrix is ​​≥0.7cm 3 / g.

[0096] In some embodiments, the pores of the carbon matrix include micropores having a pore size of less than 2 nm, and the proportion of micropores is ≥ 80%. Specifically, the proportion of micropores can be 80%, 82%, 85%, 88%, 90%, 92%, 93%, 95%, 98%, or 99%, etc., without limitation. Preferably, the proportion of micropores is ≥ 90%; more preferably, the proportion of micropores is ≥ 95%.

[0097] In some embodiments, the porosity of the carbon matrix is ​​40% to 60%, specifically 40%, 41%, 43%, 45%, 48%, 50%, 52%, 54%, 56%, 58% or 60%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0098] In some embodiments, the average particle size of the carbon matrix is ​​1 μm to 15 μm, specifically 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0099] In some embodiments, the average pore diameter of the carbon matrix is ​​0.1 nm to 5 nm. Specifically, the average pore diameter of the carbon matrix is ​​0.1 nm, 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm or 5 nm, etc., which is not limited here.

[0100] In step S20 , the precursor is subjected to a secondary carbonization treatment to obtain a carbon matrix, wherein the temperature of the secondary carbonization treatment is higher than the temperature of the primary carbonization treatment.

[0101] In some embodiments, the temperature of the secondary carbonization treatment is 900°C to 2000°C. The temperature of the secondary carbonization treatment can be 900°C, 1000°C, 1050°C, 1200°C, 1300°C, 1400°C, 1500°C, 1800°C, or 2000°C, etc., without limitation. Preferably, the temperature of the secondary carbonization treatment is 900°C to 1800°C, more preferably 900°C to 1300°C.

[0102] In some embodiments, the time of the secondary carbonization treatment is 1 h to 30 h, specifically 1 h, 3 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 24 h or 30 h, etc., which is not limited here.

[0103] Step S30 , compounding the carbon matrix having pores with silicon particles or silicon material to obtain a negative electrode material, wherein at least part of the silicon particles or silicon material are distributed in the pores of the carbon matrix.

[0104] In some embodiments, the step of compounding the porous carbon matrix with silicon particles or silicon material includes: performing vapor deposition on the porous carbon matrix using a silicon source gas to obtain an active material.

[0105] In some embodiments, the silicon source gas includes at least one of monosilane, disilane, monochlorosilane, and dichlorosilane.

[0106] In some embodiments, the volume concentration of the silicon source gas is 1% to 90%. The volume concentration of the silicon source gas can specifically be 1%, 5%, 10%, 15%, 20%, 30%, 50%, 60%, 70%, 80% or 90%, etc., but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable.

[0107] In some embodiments, the deposition time of vapor deposition is 0.1 h to 15 h. The deposition time can be 0.1 h, 0.5 h, 1 h, 3 h, 5 h, 6 h, 8 h, 10 h, 12 h or 15 h, etc., which is not limited here.

[0108] 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 vapor deposition temperature within the above range is beneficial to controlling the crystal form of the silicon particles, reducing the crystallinity of the silicon particles, 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.

[0109] In some embodiments, the method further comprises: performing a carbon coating treatment on the active material to obtain a negative electrode material; the carbon coating treatment comprises at least one of solid-phase carbon coating, liquid-phase carbon coating, and gas-phase carbon coating.

[0110] It can be understood that carbon coating the active material to form a carbon material on at least part of the surface of the 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.

[0111] In some embodiments, the carbon coating treatment step specifically includes: heating the active material, 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 material on the surface.

[0112] In some embodiments, the carbon coating treatment step specifically includes: heating the active material, introducing a protective gas and a carbon source gas, and thermally cracking the carbon source gas to obtain a negative electrode material, wherein the carbon source gas is a hydrocarbon.

[0113] In some embodiments, the carbon source gas includes at least one of methane, ethylene, acetylene, propyne, propylene, propane, toluene, benzene, styrene, and phenol.

[0114] In some embodiments, the thermal cracking temperature is 600° C. to 1000° C., and the thermal cracking time is 30 min to 24 h.

[0115] 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 30 minutes, 1 hour, 3 hours, 5 hours, 8 hours, 12 hours, 15 hours, 18 hours, 20 hours, 22 hours, or 24 hours, etc., and is not limited here.

[0116] In some embodiments, the carbon coating step specifically includes: carbonizing a mixture obtained by mixing the active material with a solid carbon source to obtain a negative electrode material.

[0117] 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.

[0118] 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.

[0119] In some embodiments, the solid carbon source includes at least one of sugars, esters, hydrocarbons, organic acids, and high molecular weight polymers.

[0120] 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.

[0121] In some embodiments, the mass ratio of the solid carbon source to the negative electrode material 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.

[0122] In some embodiments, the carbon coating step specifically includes: carbonizing a mixture obtained by mixing the active material with a liquid carbon source to obtain a negative electrode material.

[0123] In some embodiments, the mass ratio of the liquid carbon source to the negative electrode material 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] In some embodiments, the carbon coating process is performed under a protective atmosphere comprising at least one of nitrogen, helium, neon, argon, and krypton.

[0128] In some embodiments, the method further includes: shaping, screening and grading the carbon-coated product to obtain a negative electrode material having a carbon material on the surface, and the shaping includes at least one of crushing, grinding, ball milling and gas crushing.

[0129] In some embodiments, a method for preparing a negative electrode material is provided, which comprises the following steps: step S10, carbonizing a mixture including a carbon source and a doping material to obtain a precursor, wherein the doping material contains oxygen, nitrogen and sulfur elements; step S20, subjecting the precursor to a high-temperature treatment and a third activation treatment to obtain a carbon matrix; step S30, compounding the carbon matrix with silicon particles to obtain a negative electrode material.

[0130] In the preparation method of the negative electrode material provided in the above scheme, during the preparation of the precursor, the oxygen, nitrogen and sulfur elements in the doping material are doped into the carbon source to obtain a carbon matrix, which is used to prepare the negative electrode material of this application with both excellent conductivity and cycle performance.

[0131] The above-mentioned preparation method is specifically explained below in conjunction with embodiment:

[0132] Step S10, carbonizing the mixture including the carbon source and the modifying substance to obtain a precursor, wherein the modifying substance contains oxygen, nitrogen and sulfur elements;

[0133] In some embodiments, the carbon source includes at least one of resin polymers, lignin, coconut shells, fruit shells, peanut shells, rice husks, and coal-based biomass. The type of carbon source can be selected according to actual needs and is not limited here.

[0134] In some embodiments, the modifying material includes a nitrogen-containing doping material and a sulfur-containing doping material; the nitrogen-containing doping material includes at least one of urea, ammonium acetate, ethanolamine, ammonium methanolate, ammonium chloride, ammonium nitrate and N,N-dimethylformamide, and the sulfur-containing doping material includes at least one of thiol, ammonium bisulfate, thiophenol, sulfide and disulfide. The types of nitrogen-containing doping materials and sulfur-containing doping materials can be selected according to actual needs and are not limited here.

[0135] In some embodiments, the mass ratio of the carbon source, the nitrogen-containing doping material, and the sulfur-containing doping material is 100:(0.01-10):(0.01-5). Optionally, the mass ratio of the carbon source, the nitrogen-containing doping material, and the sulfur-containing doping material can be specifically 100:0.4:0.2, 100:1:0.3, 100:2:0.2, 100:4:4.2, 100:5:0.1, and 100:9:5, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that when the mass ratio of the carbon source, the nitrogen-containing doping material, and the sulfur-containing doping material is within the above range, the structural stability of the carbon matrix is ​​ensured while improving the electrical conductivity of the carbon matrix.

[0136] In some embodiments, the temperature of the primary carbonization treatment is 600°C to 900°C, and the time of the carbonization treatment is 1 hour to 30 hours. Optionally, the temperature of the primary carbonization treatment can be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, and 900°C, and the time of the primary carbonization treatment can be 1 hour, 5 hours, 10 hours, 14 hours, 21 hours, 25 hours, 28 hours, 30 hours, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It is understandable that when the temperature and time of the primary carbonization treatment are within the above range, the carbon content in the obtained carbon matrix is ​​better, so that the conductivity of the carbon matrix is ​​better.

[0137] In step S20 , the precursor is subjected to a secondary carbonization treatment and a third activation treatment to obtain a carbon matrix.

[0138] In some embodiments, the temperature of the secondary carbonization treatment is 900°C to 2500°C, and the time of the secondary carbonization treatment is 1h to 40h. Optionally, the temperature of the secondary carbonization treatment can be 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, 1700°C, 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, 2300°C, 2400°C and 2500°C, etc., and the time of the secondary carbonization treatment can be 1h, 4h, 8h, 12h, 19h, 22h, 28h, 33h, 35h and 40h, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that when the temperature and time of the high temperature treatment are within the above ranges, the content of nitrogen, oxygen and sulfur doped in the carbon matrix can be adjusted, thereby improving the electrochemical performance and structural stability of the negative electrode material.

[0139] In some embodiments, the third activation treatment includes physical activation and / or chemical activation, physical activation includes at least one of steam activation, nitrogen activation, oxygen activation and air activation, and chemical activation includes alkaline solution activation. The type of activation treatment can be selected according to actual needs and is not limited here.

[0140] In some embodiments, the third activation treatment includes at least one activation process, that is, the activation treatment may be performed only once, or may be followed by a second activation process, or may be multiple activation processes. The number of activation treatments may be selected according to actual needs and is not limited here.

[0141] It can be understood that by activating the precursor, the carbon matrix can have a rich pore structure, which is beneficial for the directional deposition of silicon particles into the pores of the carbon matrix during the subsequent silicon deposition process, thereby reducing the deposition of silicon particles on the surface of the carbon matrix.

[0142] Preferably, the activation treatment of the present application includes a primary activation process and a secondary activation process. It can be understood that after the secondary activation process, more and evenly distributed activation pores can be formed in the carbon matrix, which is conducive to the subsequent filling of silicon particles in the activation pores.

[0143] In some embodiments, the temperature of the primary activation process is 400°C to 1000°C, and the time of the primary activation process is 1h to 30h. Optionally, the temperature of the primary activation process can be 400°C, 500°C, 600°C, 700°C, 800°C, 850°C, 900°C, 1000°C, etc., and the time of the primary activation process can be 1h, 4h, 8h, 12h, 19h, 22h, 28h and 30h, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0144] In some embodiments, the temperature of the secondary activation process is 500°C to 900°C, and the time of the secondary activation process is 1h to 30h. Optionally, the temperature of the secondary activation process can be 500°C, 600°C, 700°C, 800°C, 850°C, 900°C, etc., and the time of the secondary activation process can be 1h, 4h, 8h, 12h, 19h, 22h, 28h and 30h, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0145] Step S30 , compounding the porous carbon matrix with silicon particles to obtain a negative electrode material.

[0146] In some embodiments, the preparation method further comprises coating the composite obtained by compounding the carbon matrix and the silicon particles.

[0147] In some embodiments, the coating material includes at least one of a carbon source, titanium nitride, boron nitride, silicon nitride, silicon oxide, magnesium oxide, aluminum oxide, silicon carbide, and polyaniline. The type of coating material can be selected according to actual needs and is not limited here.

[0148] In some embodiments, the mass ratio of the carbon matrix to the coating material is (10-100): (0.1-10). Optionally, the mass ratio of the carbon matrix to the coating material can be specifically 10:0.1, 20:0.5, 40:1, 50:0.1, 70:10, and 100:10, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that when the mass ratio of the carbon matrix to the coating material is within the above range, the resulting coating layer can provide good coating and protection for the carbon matrix without affecting the diffusion of lithium ions during the charge and discharge process, thereby ensuring the cycle performance of the lithium-ion battery.

[0149] In a fourth aspect, the present application provides a battery comprising the negative electrode material of the first aspect or the negative electrode material prepared by the negative electrode material preparation method of the second aspect. The battery may be a lithium-ion battery or a sodium-ion battery, etc., without limitation herein.

[0150] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

[0151] Example 1

[0152] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0153] (1) Bamboo charcoal and urea were mixed in a mass ratio of 100:1, and the mixture was subjected to a primary carbonization treatment at a temperature of 750°C for 5 hours; the primary carbonization product was placed in water vapor and nitrogen for a primary activation treatment at a volume ratio of water vapor to nitrogen of 0.1:90, at a temperature of 650°C for 4 hours, to obtain a primary activation product; the primary activation product was placed in a heat treatment furnace for a secondary activation at a temperature of 950°C for 3 hours, to obtain a precursor.

[0154] (2) The precursor is placed in a heat treatment furnace for secondary carbonization treatment at a temperature of 900° C. for 10 hours to obtain a carbon matrix with an average pore size of 1.8 nm. The carbon matrix has pores.

[0155] (3) The carbon substrate is placed in a chemical vapor deposition (CVD) device, and then silane is introduced into the CVD device, the volume concentration of silane is controlled to be 40%, the temperature is raised to 600° C., and the vapor deposition reaction is carried out for 4 hours to obtain a composite.

[0156] (4) The composite material and asphalt were mixed in a mass ratio of 50:15, and then the mixed material was placed in a high-temperature box furnace, nitrogen was introduced, and solid-phase carbon coating treatment was performed at 520°C and kept warm for 2 hours. The carbon-coated product was crushed, sieved, and then graded to obtain the negative electrode material.

[0157] The negative electrode material prepared in the embodiment of the present application includes an active substance and a carbon material located on the surface of the active substance. The active substance includes a carbon matrix and silicon particles. The carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix.

[0158] Figure 2 is an XRD diagram of the negative electrode material prepared in Example 1 of the present application. As shown in Figure 2, the active material in the negative electrode material is in an amorphous state. Figure 3 is a schematic diagram of the first charge and discharge curve of the negative electrode material prepared in Example 1 of the present application. As shown in Figure 3, the first charge and discharge capacity of the negative electrode material is 1938mAh / g, and the first coulombic efficiency is 93.1%. The negative electrode material has excellent electrochemical performance. Figure 4 is a schematic diagram of the cycle performance curve of the negative electrode material prepared in Example 1 of the present application. As shown in Figure 4, the capacity retention rate of the battery made of the negative electrode material after 50 cycles is 93.1%. It can be seen that the negative electrode material has excellent cycle performance.

[0159] Example 2

[0160] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0161] (1) Commercial porous carbon and ethanolamine were mixed in a mass ratio of 100:1.5, and the mixture was carbonized once at a temperature of 850°C for 8 hours to obtain a precursor.

[0162] (2) The precursor is placed in a heat treatment furnace for secondary carbonization treatment at a temperature of 1900° C. for 12 hours to obtain a carbon matrix with an average pore size of 3.9 nm. The carbon matrix has pores.

[0163] (3) The carbon substrate was placed in a chemical vapor deposition (CVD) device, and then silane was introduced into the CVD device, with the volume concentration of silane controlled at 20%. The temperature was raised to 550° C., and the vapor deposition reaction was carried out for 4 hours to obtain a composite.

[0164] (4) Methane was continuously introduced into the vapor phase chemical deposition apparatus, and the volume concentration of methane was controlled to be 29%. The temperature was raised to 650° C. for vapor phase carbon coating treatment, and the temperature was kept for 4 h. The carbon coating product was crushed, sieved, and then graded to obtain the negative electrode material.

[0165] Example 3

[0166] (1) Coconut shell and ammonium chloride were mixed in a mass ratio of 100:0.5, and the mixture was subjected to a primary carbonization treatment at a temperature of 700°C for 15 hours; the primary carbonization product was placed in water vapor and nitrogen for a primary activation treatment at a volume ratio of 0.5:90, a primary activation temperature of 750°C, and a primary activation time of 4 hours to obtain a primary activation product; the primary activation product was placed in a heat treatment furnace for a secondary activation at a temperature of 850°C and a secondary activation time of 5 hours to obtain a precursor.

[0167] (2) The precursor is placed in a heat treatment furnace for secondary carbonization treatment. The temperature of the secondary carbonization treatment is 1000° C. and the temperature is kept for 6 hours to obtain a carbon matrix with an average pore size of 1.7 nm. The carbon matrix has pores.

[0168] (3) The carbon substrate was placed in a chemical vapor deposition (CVD) device, and then silane was introduced into the CVD device, with the volume concentration of silane controlled at 31%. The temperature was raised to 500° C., and the vapor deposition reaction was carried out for 4 hours to obtain a composite.

[0169] (4) Continue to introduce acetylene into the vapor phase chemical deposition equipment, control the acetylene volume concentration to 45%, raise the temperature to 650°C for vapor phase carbon coating treatment, keep the temperature for 4 hours, crush and screen the carbon coating product, and then grade it to obtain the negative electrode material.

[0170] The negative electrode material prepared in the embodiment of the present application includes an active material, which includes a carbon matrix and silicon particles. The carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix.

[0171] Example 4

[0172] (1) Fruit shells and ammonium bicarbonate were mixed in a mass ratio of 100:3.3, and the mixture was subjected to a primary carbonization treatment at a temperature of 710°C for 6 hours. The primary carbonization product was placed in a steam and nitrogen atmosphere for a primary activation treatment at a volume ratio of 0.9:90, a temperature of 550°C for 5 hours, and a primary activation product was obtained. The primary activation product was placed in a heat treatment furnace for a secondary activation at a temperature of 880°C for 5 hours to obtain a precursor.

[0173] (2) The precursor is placed in a heat treatment furnace for secondary carbonization treatment at a temperature of 1200° C. for 16 hours to obtain a carbon matrix with an average pore size of 2.1 nm. The carbon matrix has pores.

[0174] (3) The carbon substrate was placed in a chemical vapor deposition (CVD) device, and then silane was introduced into the CVD device, with the volume concentration of silane controlled at 11%. The temperature was raised to 560° C., and the vapor deposition reaction was performed for 4 hours to obtain a composite.

[0175] (4) Propylene was continuously introduced into the vapor phase chemical deposition apparatus, and the volume concentration of propylene was controlled to be 45%. The temperature was raised to 690° C. for vapor phase carbon coating treatment, and the temperature was kept for 4 h. The carbon coating product was crushed, sieved, and then graded to obtain the negative electrode material.

[0176] Example 5

[0177] (1) Bamboo charcoal and urea were mixed in a mass ratio of 100:1, and the mixture was subjected to a carbonization treatment at a temperature of 750°C for 5 h. The carbonized product was activated under water vapor and nitrogen at a volume ratio of 0.1:90 at a temperature of 550°C for 24 h to obtain a precursor.

[0178] (2) The precursor is placed in a heat treatment furnace for secondary carbonization treatment at a temperature of 1500° C. for 10 hours to obtain a carbon matrix with an average pore size of 2.1 nm. The carbon matrix has pores.

[0179] (3) The carbon substrate is placed in a chemical vapor deposition (CVD) device, and then silane is introduced into the CVD device, the volume concentration of silane is controlled to be 40%, the temperature is raised to 600° C., and the vapor deposition reaction is carried out for 4 hours to obtain a composite.

[0180] (4) The composite material and asphalt were mixed in a mass ratio of 50:15, and then the mixed material was placed in a high-temperature box furnace, nitrogen was introduced, and solid-phase carbon coating treatment was performed at 520°C and kept warm for 2 hours. The carbon-coated product was crushed, sieved, and then graded to obtain the negative electrode material.

[0181] Example 6

[0182] (1) Commercial porous carbon, ethanolamine, and urea were mixed in a mass ratio of 100:1.0:0.5, and the mixture was carbonized once at a temperature of 600°C for 8 hours to obtain a precursor.

[0183] (2) The precursor is placed in a heat treatment furnace for secondary carbonization treatment at a temperature of 1300° C. for 12 hours to obtain a carbon matrix with an average pore size of 2.2 nm. The carbon matrix has pores.

[0184] (3) The carbon substrate is placed in a chemical vapor deposition (CVD) device, and then silane is introduced into the CVD device, with the volume concentration of silane controlled to be 40%. The temperature is raised to 550° C., and the vapor deposition reaction is performed for 4 hours to obtain a composite.

[0185] (4) Continue to introduce methane into the vapor phase chemical deposition equipment, control the methane volume concentration to 35%, raise the temperature to 800°C for vapor phase carbon coating treatment, keep the temperature for 4 hours, crush and screen the carbon coating product, and then grade it to obtain the negative electrode material.

[0186] Example 7

[0187] The difference from Example 1 is that:

[0188] (2) The precursor is placed in a heat treatment furnace for secondary carbonization treatment at a temperature of 2100° C. for 10 hours to obtain a carbon matrix with an average pore size of 5.8 nm. The carbon matrix has pores.

[0189] Example 8

[0190] The difference from Example 1 is that:

[0191] (1) Bamboo charcoal and urea were mixed in a mass ratio of 100:1, and the mixture was subjected to a primary carbonization treatment at a temperature of 750°C for 5 hours; the primary carbonization product was placed in water vapor and nitrogen for a primary activation treatment at a volume ratio of 2:90 (water vapor:nitrogen), a primary activation temperature of 650°C, and a primary activation time of 4 hours to obtain a primary activation product; the primary activation product was placed in a heat treatment furnace for a secondary activation at a temperature of 950°C and a secondary activation time of 15 hours to obtain a precursor.

[0192] Example 9

[0193] The difference from Example 1 is that:

[0194] (1) Bamboo charcoal and urea were mixed in a mass ratio of 100:2.3, and the mixture was subjected to a primary carbonization treatment at a temperature of 750°C for 5 h. The primary carbonization product was placed in a steam and nitrogen atmosphere for a primary activation treatment at a volume ratio of steam to nitrogen of 0.1:90, at a temperature of 650°C for 4 h, to obtain a primary activation product. The primary activation product was placed in a heat treatment furnace for a secondary activation at a temperature of 950°C for 30 h, to obtain a precursor.

[0195] Comparative Example 1

[0196] The difference from Example 1 is that step (2) is not performed.

[0197] Comparative Example 2

[0198] (1) A carbonization treatment was performed on bamboo charcoal at a temperature of 750°C for 5 h. The carbonized product was then activated under water vapor and nitrogen at a volume ratio of 0.1:90 (volume ratio), at a temperature of 650°C for 4 h to obtain a precursor.

[0199] (2) The precursor is placed in a heat treatment furnace for secondary carbonization treatment at a temperature of 700° C. for 10 hours to obtain a carbon matrix with an average pore size of 1.8 nm. The carbon matrix has pores.

[0200] (3) The carbon substrate is placed in a chemical vapor deposition (CVD) device, and then silane is introduced into the CVD device, the volume concentration of silane is controlled to be 40%, the temperature is raised to 600° C., and the vapor deposition reaction is carried out for 4 hours to obtain a composite.

[0201] (4) The composite material and asphalt were mixed in a mass ratio of 50:15, and then the mixed material was placed in a high-temperature box furnace, nitrogen was introduced, and solid-phase carbon coating treatment was performed at 520°C and kept warm for 2 hours. The carbon-coated product was crushed, sieved, and then graded to obtain the negative electrode material.

[0202] Example 10

[0203] (1) Bamboo charcoal, urea, and mercaptan are mixed in a ratio of 100:1:0.5 to obtain a mixture, and the mixture is carbonized at a temperature of 850°C for 5 hours to obtain a precursor;

[0204] (2) The precursor was placed in a heat treatment furnace for high temperature treatment at 1580°C for 10 hours. After the insulation was completed, the insulation product was pickled, dried, and then introduced into a mixture of water vapor and nitrogen (volume ratio 100:0.4). The activated product was then treated at 800°C for 15 hours to obtain a carbon matrix with an average pore size of 1.8 nm. The volume of micropores in the carbon matrix accounted for 90%, and the total pore volume was 1.6 cm 3 / g;

[0205] (3) placing the carbon substrate in a CVD device, then introducing silane into the CVD device, controlling the silane concentration to 42%, raising the temperature to 600°C, and reacting for 4 hours to obtain a silicon deposition product;

[0206] (4) The silicon deposition product and asphalt were mixed in a mass ratio of 50:15, placed in a high-temperature box furnace, introduced with nitrogen, and heat treated at 700°C for 2 hours to obtain a coated product;

[0207] (5) The coated product is crushed, sieved, and then classified to obtain the negative electrode material.

[0208] Figure 5 shows the XRD pattern of the negative electrode material prepared in this example. As shown in Figure 5, the absence of silicon peaks in the XRD pattern indicates that the silicon particles in the negative electrode material are amorphous. The amorphous structure of amorphous silicon gives it greater tolerance to volume expansion. During the charge and discharge process, the silicon particles can more flexibly undergo lithium ion insertion and extraction without undergoing significant volume changes like crystalline silicon. This reduces the stress and cracking risk of the negative electrode material caused by volume expansion, and improves the mechanical and electrochemical stability of the negative electrode material.

[0209] FIG6 is the first charge and discharge curve of the negative electrode material prepared in this embodiment. As shown in FIG6 , the first charge and discharge capacity of the negative electrode material of the present application is 1908 mAh / g, the first coulombic efficiency is 92.7%, and the negative electrode material has excellent conductive properties.

[0210] FIG7 is a cycle performance curve of the negative electrode material prepared in this embodiment. As shown in FIG7 , the negative electrode material of the present application has excellent cycle performance, and the capacity retention rate after 50 cycles is 92.5%.

[0211] Example 11

[0212] The difference from Example 10 is:

[0213] The bamboo charcoal, urea and mercaptan are mixed in a ratio of 100:1:2.1 to obtain a mixture.

[0214] Example 12

[0215] The difference from Example 10 is:

[0216] The precursor is placed in a heat treatment furnace for high temperature treatment. The temperature of the high temperature treatment is 900° C. and the holding time is 5 hours.

[0217] Example 13

[0218] The difference from Example 10 is:

[0219] The precursor is placed in a heat treatment furnace for high-temperature treatment. The temperature of the high-temperature treatment is 2500° C. and the holding time is 40 hours.

[0220] Example 14

[0221] (1) porous carbon, ethanolamine, and ammonium bisulfate were mixed in a ratio of 100:1.5:1 to obtain a mixture, and the mixture was carbonized at a temperature of 850°C for 8 hours to obtain a precursor;

[0222] (2) The precursor was placed in a heat treatment furnace for high-temperature treatment at a temperature of 1300°C for 12 hours. After the insulation was completed, the insulation product was pickled, and the pickled product was dried and introduced into a mixture of water vapor and nitrogen (volume ratio 100:0.4). It was activated at 850°C for 14.5 hours to obtain a carbon matrix with an average pore size of 1.9 nm. The volume proportion of micropores in the carbon matrix was 86%, and the total pore volume was 1.4 cm 3 / g;

[0223] (3) placing the carbon substrate in a CVD device, then introducing silane into the CVD device, controlling the silane concentration to 26%, raising the temperature to 500° C., and reacting for 4 hours to obtain a silicon deposition product;

[0224] (4) placing the silicon deposited product in a CVD device, then introducing methane into the CVD device, controlling the methane concentration to 29%, raising the temperature to 680°C, and reacting for 4 hours to obtain a coated product;

[0225] (5) The coated product is crushed, sieved, and then classified to obtain the negative electrode material.

[0226] Example 15

[0227] (1) Coconut shell, ammonium chloride and ammonium sulfate were mixed in a ratio of 100:0.5:0.1 to obtain a mixture, and the mixture was carbonized at a temperature of 900°C for 15 hours to obtain a precursor;

[0228] (2) The precursor was placed in a heat treatment furnace for high-temperature treatment at a temperature of 2200°C and a holding time of 6 hours. After the holding was completed, the holding product was pickled, dried, and then introduced into a mixture of water vapor and nitrogen (volume ratio 100:0.4) and activated at 800°C for 14 hours to obtain a carbon matrix with an average pore size of 1.7 nm. The volume proportion of micropores in the carbon matrix was 91%, and the total pore volume was 1.5 cm 3 / g;

[0229] (3) placing the carbon substrate in a CVD device, then introducing silane into the CVD device, controlling the silane concentration to 37%, raising the temperature to 480°C, and reacting for 6 hours to obtain a silicon deposition product;

[0230] (4) placing the silicon deposited product in a CVD device, then introducing acetylene into the CVD device, controlling the acetylene concentration to 45%, raising the temperature to 690° C., and reacting for 3 h to obtain a coated product;

[0231] (5) The coated product is crushed, sieved, and then classified to obtain the negative electrode material.

[0232] Example 16

[0233] (1) The fruit shell and (NH4)2SO4 were mixed in a ratio of 100:2.3, and then subjected to the first step of carbonization treatment at a temperature of 790℃ for 6 hours;

[0234] (2) The precursor was placed in a heat treatment furnace for high-temperature treatment at a temperature of 2400°C for 10 hours. After the insulation was completed, the insulation product was pickled, and the pickled product was dried and introduced into a mixture of water vapor and nitrogen (volume ratio 100:0.4). It was activated at 800°C for 20 hours to obtain a carbon matrix with an average pore size of 2.2 μm. The volume proportion of micropores in the carbon matrix was 85%, and the total pore volume was 1.3 cm 3 / g;

[0235] (3) placing the carbon substrate in a CVD device, then introducing silane into the CVD device, controlling the silane concentration to 17%, raising the temperature to 560°C, and reacting for 7 hours to obtain a silicon deposition product;

[0236] (4) placing the silicon deposited product in a CVD device, then introducing propylene into the CVD device, controlling the propylene concentration to 45%, raising the temperature to 690°C, and reacting for 4 hours to obtain a coated product;

[0237] (5) The coated product is crushed, sieved, and then classified to obtain the negative electrode material.

[0238] Example 17

[0239] The difference from Example 10 is:

[0240] After the acid-washed product was dried, a mixture of water vapor and nitrogen (volume ratio 100:0.4) was introduced, and a primary activation treatment was performed at 800°C for 15 hours, and a secondary activation treatment was performed at 700°C for 15 hours to obtain a carbon matrix with an average pore size of 1.8 nm.

[0241] Example 18

[0242] The difference from Example 10 is:

[0243] The bamboo charcoal, urea and mercaptan are mixed in a ratio of 100:1:6 to obtain a mixture.

[0244] Example 19

[0245] The difference from Example 10 is:

[0246] The bamboo charcoal, urea and mercaptan are mixed in a ratio of 100:15:1 to obtain a mixture.

[0247] Example 20

[0248] (1) Bamboo charcoal and urea were mixed in a ratio of 100:1 to obtain a mixture, and the mixture was carbonized at a temperature of 850°C for 5 hours to obtain a precursor;

[0249] (2) The precursor was placed in a heat treatment furnace for high-temperature treatment at a temperature of 1580°C for 10 hours. After the insulation was completed, the insulation product was pickled, dried, and then introduced into a mixture of water vapor and nitrogen (volume ratio 100:0.4). The product was activated at 800°C for 15 hours to obtain a carbon matrix with an average pore size of 1.9 nm. The volume proportion of micropores in the carbon matrix was 90%, and the total pore volume was 0.91 cm 3 / g;

[0250] (3) placing the carbon substrate in a CVD device, then introducing silane into the CVD device, controlling the silane concentration to 42%, raising the temperature to 600°C, and reacting for 4 hours to obtain a silicon deposition product;

[0251] (4) The silicon deposition product and asphalt were mixed in a mass ratio of 50:15, placed in a high-temperature box furnace, introduced with nitrogen, and heat treated at 700°C for 2 hours to obtain a coated product;

[0252] (5) The coated product is crushed, sieved, and then classified to obtain the negative electrode material.

[0253] Example 21

[0254] (1) Bamboo charcoal, urea and mercaptan are mixed in a ratio of 100:1:0.5 to obtain a mixture, the mixture is carbonized at a temperature of 850°C for 5 hours, the insulation product is pickled after the insulation is completed, the pickled product is dried and then introduced into a mixture of water vapor and nitrogen (volume ratio of 100:0.4), and activated at 800°C for 15 hours to obtain a precursor;

[0255] (2) The precursor was placed in a heat treatment furnace for high temperature treatment at a temperature of 1580°C and a holding time of 10 h. A carbon matrix with an average pore size of 1.93 nm was obtained, the volume proportion of micropores in the carbon matrix was 88%, and the total pore volume was 0.89 cm 3 / g;

[0256] (3) placing the carbon substrate in a CVD device, then introducing silane into the CVD device, controlling the silane concentration to 42%, raising the temperature to 600°C, and reacting for 4 hours to obtain a silicon deposition product;

[0257] (4) The silicon deposition product and asphalt were mixed in a mass ratio of 50:15, placed in a high-temperature box furnace, introduced with nitrogen, and heat treated at 700°C for 2 hours to obtain a coated product;

[0258] (5) The coated product is crushed, sieved, and then classified to obtain the negative electrode material.

[0259] Comparative Example 3

[0260] The difference from Example 10 is that no high-temperature treatment is performed.

[0261] Comparative Example 4

[0262] The difference from Example 10 is that no urea is added to the mixture.

[0263] Test method:

[0264] (1) Test method for specific surface area of ​​negative electrode material:

[0265] The specific surface area was measured using a Micromeritics TriStar 3000 surface area and pore size analyzer.

[0266] (2) Test method for the total pore volume of the negative electrode material, carbon matrix, or the negative electrode material after removing silicon particles:

[0267] The test was conducted using the ASAP2460 equipment from American Micromeritics. The pore volume V was calculated using the BJH Desorption cumulative volume of pores model. Calculated within the pore size range.

[0268] Micropore and mesopore analysis was performed using the Micromeretics ASAP 2460. At liquid nitrogen temperature, the equilibrium amount of nitrogen adsorbed on a surface is correlated with properties such as pore size. By combining the relationship between the amount adsorbed and relative pressure during adsorption, various models can be fitted to calculate pore size. The software generates reports using density functional theory (DFT) to calculate pore size distribution, total pore volume, and pore volume within a specific range.

[0269] (3) Pore size test method for negative electrode materials, carbon substrates, or negative electrode materials after silicon particles are removed:

[0270] An appropriate amount of sample particles was taken and the pore size and porosity were measured under a transmission electron microscope (TEM).

[0271] (4) Testing method of silicon particle size:

[0272] The nano-silicon particles are observed by field emission scanning electron microscopy or transmission electron microscopy, and the particle sizes of 5 to 10 nano-silicon particles are directly measured using a scale. The average value of the particle sizes is taken as the final nano-silicon particle size or the average particle size of silicon particles.

[0273] (5) Test method for particle size of negative electrode material:

[0274] Using the Malvern laser particle size analyzer MS3000, based on the principle that the intensity distribution of scattered light generated by particles in all directions depends on the size of the particles, large particles have small scattering angles, and small particles have large scattering angles, the particle size distribution of the particles can be obtained by using the scattered light intensity distribution of laser diffraction.

[0275] (6) Gas production value test of negative electrode material:

[0276] The negative electrode materials prepared in Examples 1-9 and Comparative Examples 1-2 were added to 50 g of styrene-butadiene rubber solution to obtain a mixed solution. The mixed solution was encapsulated with an aluminum-plastic film and placed in a 2000 mL sealed container. The mixture was stored at 45° C. and the gas production of the negative electrode material over 6 days was tested to be M mL / g.

[0277] (7) Test of the mass content of oxygen atoms and nitrogen atoms in the negative electrode material:

[0278] The nitrogen and oxygen elements in the materials prepared in Examples 1-9 and Comparative Examples 1-2 were measured using a hydrogen, oxygen, and nitrogen analyzer (Alter ONH2000) in accordance with ISO 17053:2005.

[0279] (8) Test method for powder conductivity of negative electrode materials:

[0280] According to the national standard GBT 30835-2014, a resistivity tester (Suzhou Jingge Electronics ST-2255A) was used. 5 g of powder sample was taken and constant pressure was applied to 8000 kg ± 2 kg using an electronic press for 15-25 s. The sample was placed between the tester electrodes. The sample height was h (cm), the voltage across the two terminals was U, the current was I, and the resistance was R (KΩ). The area of ​​the powder after pressing was S = 3.14 cm. 2 The powder conductivity is calculated according to the formula δ = h / (S*R) / 1000, and the unit is S / m.

[0281] (9) Electrochemical performance test

[0282] 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, respectively, 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 housing. Cylindrical cells were tested on a LAND battery test system from Wuhan Jinnuo Electronics Co., Ltd. at room temperature, with a constant current of 0.2C and a voltage limit of 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.

[0283] 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%.

[0284] (10) Etching treatment:

[0285] The negative electrode material is soaked in a 1M nitric acid solution for 1 hour, and then a 20% by mass HF acid solution is dripped dropwise into the negative electrode material, which produces yellow smoke. This dripping is repeated several times until no yellow smoke is produced in the solution. Finally, the residue is digested with a 1M nitric acid solution, and then washed and dried to obtain the negative electrode material after the silicon particles are removed. Alternatively, 150 mL of a 20% by mass HF acid solution is dripped dropwise into 10 g of the negative electrode material while stirring. This produces SiF4 and H2 gases and releases heat. After no gas is generated, the supernatant acid solution is removed by centrifugation. 150 mL of a 20% by mass HF acid solution is added to the negative electrode material again, stirred for 12 hours, and the supernatant acid solution is removed again by centrifugation. The negative electrode material is then washed with pure water until neutral and dried to obtain the negative electrode material after the silicon particles are removed, i.e., the carbon matrix.

[0286] (11) Measurement of hydrogen production of negative electrode materials prepared in Examples 10-21 and Comparative Examples 3-4:

[0287] Apply a 1.4% carboxymethyl cellulose gel to the sample. After uniform dispersion, take 20g of the gel and mix it with 25g of the negative electrode material. Place the gel in a 10cm x 10cm aluminum-plastic bag and seal it. Test the volume of the bag every 24 hours using the water displacement method in a graduated cylinder.

[0288] (12) Test method for the mass content of carbon in negative electrode materials:

[0289] Using Germany's Bruker's G4ICARUSHF infrared carbon and sulfur analyzer: the sample is burned in a high-temperature, oxygen-rich state, and the carbon and sulfur elements it contains are oxidized into carbon dioxide and sulfur dioxide, respectively. The generated gases enter the infrared detector with the carrier gas. By quantitatively analyzing the changes in the carbon dioxide signal and the sulfur dioxide signal, the carbon and sulfur content can be calculated respectively.

[0290] (13) Test method for the mass content of silicon in negative electrode materials:

[0291] Use Nanyang Xinyu SA2-9-17TP box-type atmosphere furnace: burn in an oxygen atmosphere, so that the silicon and silicon oxide in the sample react to form silicon dioxide, and the carbon is burned and converted into carbon dioxide and discharged. The silicon content is calculated by weighing.

[0292] (14) Test method for tap density of negative electrode material:

[0293] The tap density was tested by using a vibrator, weighing 100 g of sample and vibrating 3000 times at 300 times / min.

[0294] (15) Test method for particle size D10, D50 and D90 of negative electrode materials:

[0295] The D50 was measured using a laser particle size analyzer and showed a symmetrical distribution similar to a normal distribution. In the volume-based distribution, the cumulative 50% diameter is D50, and so on, the cumulative 90% diameter is D90, and the cumulative 10% diameter is D10.

[0296] (16) Test method for the mass content of nitrogen, oxygen, and hydrogen elements in the negative electrode materials prepared in Examples 10-21 and Comparative Examples 3-4:

[0297] Using a German Verder ONH2000 oxygen, nitrogen, and hydrogen analyzer, the anode material is melted in an inert atmosphere while surrounded by flux. The oxygen it contains is reduced to carbon dioxide by the carbon in the graphite crucible. The resulting carbon dioxide enters the infrared detector along with the carrier gas. Quantitative statistics of changes in the carbon dioxide signal are used to calculate the oxygen content. The sample is also melted in an inert atmosphere while surrounded by flux. The nitrogen and hydrogen it contains decompose into stable elemental nitrogen and hydrogen gases. The resulting nitrogen and hydrogen gases enter the thermal conductivity detector along with the carrier gas. Quantitative statistics of changes in the thermal conductivity cell heat allow the mass content of the nitrogen and hydrogen to be calculated, respectively.

[0298] (17) Negative electrode material powder resistivity test:

[0299] A Mitsubishi Chemical MCP-PD51 powder conductivity meter was used to measure the sample volume resistivity using the four-probe method. This instrument measures the resistance of the powder, and a computer automatically calculates the powder conductivity and resistivity. Powder conductivity was measured at five pressure points: 4, 8, 12, 16, and 20 kN.

[0300] (18) Negative electrode material compaction density test:

[0301] Using the American McNor CARVER4350.22 powder compaction density tester, a sample of specified mass m is placed in a mold and a pressure of 1.0T is applied. After maintaining the pressure for 30 seconds, the pressure is removed to test its thickness and calculate the compaction density.

[0302] The results of the above performance tests are as follows:

[0303] Table 1. Performance parameters of negative electrode materials prepared in Examples 1-9 and Comparative Examples 1-2

[0304] Table 2. Performance parameters of the batteries of Examples 1-9 and Comparative Examples 1-2

[0305] According to the data in Table 1 and Table 2, the oxygen element mass content A and the nitrogen element mass content B in the negative electrode materials prepared in Examples 1 to 9 and the powder conductivity P of the negative electrode materials all satisfy (A+B) / P≤3. A mixture of a carbon source and a modifying substance is used for a primary carbonization treatment so that the modifying substance can be doped into the carbon matrix, and then subjected to a secondary carbonization treatment. The secondary carbonization treatment temperature is controlled to be higher than the primary carbonization treatment temperature. The graphitization degree of the carbon matrix can be increased with the help of high temperature, thereby improving the electronic conductivity of the carbon matrix itself. In addition, during the secondary carbonization treatment, more oxygen-containing or nitrogen-containing groups are volatilized, which can control the mass content of nitrogen and oxygen in the carbon matrix. A small amount of nitrogen and oxygen doping can provide lone pairs of electrons, and the lone pairs of electrons participate in the π-π conjugated system of the carbon matrix, thereby forming a larger p-π conjugated system and thus increasing the electronic conductivity of the negative electrode material. Finally, the carbon matrix is ​​compounded with silicon particles to increase the capacity of the negative electrode material; the pores in the carbon matrix are beneficial to alleviating the volume expansion of silicon particles during the cycle of the negative electrode material, maintaining structural stability, and reducing the collapse of the material structure caused by volume expansion during the lithium insertion and extraction process of the negative electrode material. The pores in the carbon matrix can also absorb a small amount of gas, which can further reduce the gas production of the negative electrode material, thereby improving the cycle performance of the negative electrode material.

[0306] According to the test data of Examples 1 to 4, as the mass content of nitrogen decreases, the first reversible capacity of the negative electrode material also shows a downward trend. Preferably, the mass content of nitrogen is 0.1% to 0.5%.

[0307] According to the test data of Example 1 and Example 7 in Table 1 and Table 2, it can be seen that the secondary carbonization temperature of Example 7 is too high. Excessively high carbonization temperature will increase the graphitization degree of the carbon matrix. Although the powder conductivity of the negative electrode material is improved, the excessively high carbonization temperature causes the pores of some carbon matrices to collapse, resulting in more silicon being deposited on the surface of the carbon matrix rather than in the pores. The silicon content in the negative electrode material is also reduced. Since part of the silicon is deposited on the surface of the carbon matrix, the volume expansion of the negative electrode material is aggravated, and the first coulombic efficiency and cycle performance of the negative electrode material are reduced compared with Example 1.

[0308] According to the test data of Example 1 and Comparative Example 1 in Table 1 and Table 2, the mass content of oxygen element A and the mass content of nitrogen element B in the negative electrode material of Comparative Example 1 and the powder conductivity P of the negative electrode material do not satisfy (A+B) / P≤3. During the preparation process of the negative electrode material of Comparative Example 1, no secondary carbonization treatment was performed, and more oxygen-containing or nitrogen-containing groups remained in the carbon matrix. The mass content of nitrogen and oxygen in the negative electrode material was greatly increased. The carbon matrix did not undergo secondary carbonization treatment, the degree of graphitization decreased, and the conductivity of the carbon matrix itself decreased significantly. Even if a small amount of nitrogen and oxygen elements are doped with oxygen-containing groups or nitrogen-containing groups to provide lone pairs of electrons, it is difficult to significantly improve the electronic conductivity of the negative electrode material; thereby resulting in capacity decay, first coulombic efficiency and cycle performance of the negative electrode material.

[0309] According to the test data of Example 1 and Comparative Example 2 in Tables 1 and 2, the oxygen element mass content A and the nitrogen element mass content B in the negative electrode material of Comparative Example 2 and the powder conductivity P of the negative electrode material do not satisfy (A+B) / P≤3. During the preparation process of the negative electrode material of Comparative Example 2, no modifying substance is added, and there are not enough nitrogen-containing groups and oxygen-containing groups to cooperate with the carbon matrix to form carbon-carbon conjugation. Moreover, the secondary carbonization temperature is lower than the primary carbonization temperature, and the conductivity of the carbon matrix is ​​greatly reduced, resulting in a significant decrease in the electronic conductivity of the negative electrode material, thereby causing the capacity attenuation, the first coulombic efficiency and the cycle performance of the negative electrode material to decrease.

[0310] Table 3. Performance parameters of negative electrode materials of Examples 10-21 and Comparative Examples 3-4

[0311] Table 4. Performance parameters of negative electrode materials of Examples 10-21 and Comparative Examples 3-4

[0312] Table 5. Battery performance parameters of Examples 10-21 and Comparative Examples 3-4

[0313] The data in Tables 3 to 5 indicate that the negative electrode materials prepared in Examples 10 to 17 contain oxygen and nitrogen. Small amounts of nitrogen and oxygen can provide lone pairs of electrons, which participate in the π-π conjugated system of the carbon matrix, thereby forming a larger p-π conjugated system and thereby increasing the electronic conductivity of the negative electrode material. Furthermore, the negative electrode material is doped with sulfur in addition to nitrogen and oxygen, and the sulfur content of the negative electrode material is 0 < S ≤ 20 ppm. Due to its large atomic radius, sulfur can form lithium-storage-active C-S bonds with the carbon in the negative electrode material, further increasing the interlayer spacing of the carbon matrix after nitrogen and oxygen doping and improving the conductivity of the carbon matrix. Furthermore, sulfur can combine with oxygen to form inactive S-O bonds, reducing gassing caused by the reaction between the negative electrode material and the electrolyte. Moreover, after doping with sulfur, the relationship between the oxygen content, nitrogen content and powder conductivity satisfies (A+B) / P≤3, that is, the mass content A of the oxygen element, the mass content B of the nitrogen element and the powder conductivity P are balanced, so that nitrogen and oxygen doping improves the powder conductivity of the negative electrode material while alleviating the problem of increased gas production in the electrolyte due to excessive nitrogen and oxygen content, so that the negative electrode material has both excellent conductivity and cycle performance.

[0314] Furthermore, during the preparation of the negative electrode material, high-temperature treatment, namely secondary carbonization treatment, is used. On the one hand, high-temperature treatment improves the degree of graphitization of the carbon material, forming more continuous conductive networks to improve the conductivity of the negative electrode material; on the other hand, at high temperatures, more O, N, and S groups volatilize, which can effectively control the content of nitrogen, oxygen, and sulfur elements, thereby reducing the gas production problem of the negative electrode material while maintaining a relatively high conductivity.

[0315] According to the test results of Example 10 and Example 18, the doping amount of sulfur element is too much, and sulfur element can combine with oxygen element to form inactive SO bond, and the gas production value of the negative electrode material is further reduced. However, since the carbon layer spacing of the carbon matrix after doping with sulfur element is further expanded, the structural stability of the carbon matrix is ​​slightly reduced, and the cycle capacity retention rate of the negative electrode material is slightly reduced compared with Example 10.

[0316] According to the test results of Example 10 and Example 19, the doping amounts of nitrogen and oxygen elements are relatively high, the powder conductivity of the negative electrode material increases, and the first coulombic efficiency of the negative electrode material is improved. However, since the sulfur element can combine with the oxygen element to form an inactive SO bond, the gas production value of the negative electrode material increases compared to Example 10.

[0317] According to the test results of Example 10 and Example 20, no thiol was added during the preparation process of Example 20, the sulfur content in the negative electrode material was 0, and the first coulombic efficiency of the negative electrode material was equivalent to that of Example 10. However, due to the preparation method, the total pore volume and specific surface area of ​​the negative electrode material were too large, resulting in a significantly higher gas production value of the negative electrode material than that of Example 10, and a decrease in the cycle performance of the negative electrode material.

[0318] According to the test results of Example 10 and Example 21, it can be seen that in Example 21, since activation is first performed and then high-temperature treatment (i.e., secondary carbonization treatment) is performed during the preparation process, the high-temperature treatment will cause the pores to collapse, the pore volume to decrease, and the deposition to be uneven, resulting in an increase in the gas production value of the negative electrode material and a decrease in the cycle performance.

[0319] According to the test results of Example 10 and Comparative Example 3, the sulfur doping amount of the negative electrode material in Comparative Example 3 that was not subjected to high-temperature treatment significantly exceeded the ideal range, and the nitrogen doping amount was also significantly increased compared to Example 10, resulting in the balance between the mass content A of the oxygen element, the mass content B of the nitrogen element and the powder conductivity P being broken, and the gas production value of the negative electrode material being significantly increased. Since the excessive doping amount of sulfur element affects the structural stability of the carbon matrix, the cycle performance of the negative electrode material is reduced.

[0320] According to the test results of Example 10 and Comparative Example 4, in Comparative Example 4, nitrogen and oxygen doping was not performed during the preparation process, the powder conductivity of the negative electrode material decreased, and the first coulombic efficiency of the negative electrode material decreased significantly.

[0321] The applicant declares that while the above-mentioned embodiments are used to illustrate the detailed process equipment and process flow of the present application, the present application is not limited to the above-mentioned detailed process equipment and process flow, which does not mean that the present application must rely on the above-mentioned detailed process equipment and process flow in order to be implemented. Those skilled in the art should understand that any improvements to the present application, equivalent replacements for the raw materials of the present application's products, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present application.

Claims

1. A negative electrode material, characterized in that: The active material comprises a carbon matrix and a silicon material; The negative electrode material contains oxygen and nitrogen, the mass content of the oxygen is A%, and the mass content of the nitrogen is B%. The powder conductivity of the negative electrode material is PS / m and satisfies the following relationship: (A+B) / P≤3.

2. The negative electrode material according to claim 1, characterized in that It meets at least one of the following technical features: (1) The silicon material includes silicon particles; (2) The silicon material comprises silicon particles and a silicon oxide layer located on the surface of the silicon particles, wherein the silicon oxide layer comprises silicon oxide, and the general formula of the silicon oxide is SiO x ; (3) The silicon material comprises silicon particles and a silicon oxide layer located on the surface of the silicon particles. Taking the mass of the silicon material as 100%, the mass percentage of oxygen element in the silicon material is 1% to 18%.

3. The negative electrode material according to claim 2, characterized in that The carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix.

4. The negative electrode material according to any one of claims 1 to 3, characterized in that The negative electrode material further contains sulfur element, and the content of the sulfur element in the negative electrode material is S ppm; wherein 0<S≤20ppm.

5. The negative electrode material according to any one of claims 1 to 4, characterized in that: It meets at least one of the following technical features: (1) In the negative electrode material, the mass content of the oxygen element is A%, 0<A≤3; (2) In the negative electrode material, the mass content of the nitrogen element is B%, 0<B≤3.

6. The negative electrode material according to any one of claims 2 to 5, characterized in that: It meets at least one of the following technical features: (1) The silicon particles include at least one of elemental silicon, silicon oxide, silicon alloy and silicon-carbon composite; (2) The average particle size of the silicon particles is 0.1 nm to 500 nm; (3) The mass content of silicon in the silicon particles is ≥99%.

7. The negative electrode material according to any one of claims 1 to 6, characterized in that The negative electrode material meets at least one of the following technical characteristics: (1) The median particle size D of the negative electrode material 50 ≤10μm; (2) The specific surface area of ​​the negative electrode material is ≤5m 2 / g; (3) The gas production of the negative electrode material in 6 days is M mL / g, M≤0.2; (4) The powder conductivity of the negative electrode material is PS / m, P≥0.01S / m.

8. The negative electrode material according to any one of claims 1 to 7, characterized in that The negative electrode material has pores, and the negative electrode material has at least one of the following technical features: (1) The pores in the negative electrode material include mesopores, wherein: The volume of the mesopores in the negative electrode material accounts for 87% to 97% of the total pore volume of the negative electrode material; (2) The pores of the negative electrode material further include at least one of micropores or macropores; (3) The pores of the negative electrode material further include at least one of micropores or macropores, the volume of the micropores accounts for ≤20% of the total pore volume of the negative electrode material, and the volume of the macropores accounts for ≤10% of the total pore volume of the negative electrode material; (4) The pores of the negative electrode material further include at least one of micropores or macropores, the volume of the micropores accounts for ≤5% of the total pore volume of the negative electrode material, and the volume of the macropores accounts for ≤10% of the total pore volume of the negative electrode material; (5) The average pore size of the pores in the negative electrode material is 0.5 nm to 20 nm; (6) The total pore volume of the negative electrode material is 0.001 cm 3 / g~0.1cm 3 / g; (7) The powder conductivity of the negative electrode material is 10 -1 S / cm~10 4 S / cm.

9. The negative electrode material according to any one of claims 2 to 8, characterized in that It meets at least one of the following technical features: (1) the pores in the negative electrode material after the silicon particles are removed include micropores, and the volume of the micropores in the negative electrode material after the silicon particles are removed accounts for ≥ 80% of the total pore volume of the negative electrode material after the silicon particles are removed; (2) The average pore size of the negative electrode material after removing the silicon particles is ≤5 nm; (3) The total pore volume of the negative electrode material after removing the silicon particles is 0.2 cm 3 / g~2cm 3 / g; (4) The porosity of the negative electrode material after removing the silicon particles is 40% to 60%.

10. The negative electrode material according to any one of claims 1 to 9, characterized in that: The negative electrode material has at least one of the following technical features: (1) The particle size of the negative electrode material satisfies: 2 μm ≤ D 50 ≤20μm, 0.9≤(D 90 -D 10 ) / D 50 ≤5; (3) The specific surface area of ​​the negative electrode material is 1 m 2 / g~10m 2 / g; (4) The compaction density of the negative electrode material is 0.80 cm 3 / g~1.30cm 3 / g; (5) The tap density of the negative electrode material is 0.50 cm 3 / g~1.50cm 3 / g.

11. The negative electrode material according to any one of claims 1 to 10, characterized in that: The negative electrode material has at least one of the following technical features: (1) The mass content of carbon element in the negative electrode material is 40% to 60%; (2) The mass content of silicon in the negative electrode material is 35% to 55%.

12. The negative electrode material according to any one of claims 1 to 11, characterized in that The carbon matrix has at least one of the following technical features: (1) 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; (2) at least one of the surface, carbon-carbon skeleton, carbon layer gap and lattice defect of the carbon matrix contains a functional group, and the functional group contains at least one of oxygen, nitrogen and sulfur; (3) The carbon matrix has functional groups on its surface and / or in its pores, and the functional groups contain at least one of oxygen, nitrogen and sulfur; wherein the functional groups include at least one of hydroxyl, carboxyl, carbonyl, aliphatic, cycloaliphatic, amino, thiol, sulfate, sulfite, thioether and sulfonic acid groups.

13. The negative electrode material according to any one of claims 2 to 12, characterized in that: The silicon particles have at least one of the following technical features: (1) The silicon particles include at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and a composite of crystalline silicon and amorphous silicon; (2) The morphology of the silicon particles includes at least one of point-shaped, spherical, ellipsoidal and flake-shaped.

14. The negative electrode material according to any one of claims 1 to 13, characterized in that: At least part of the surface of the negative electrode material has a coating layer, and the material of the coating layer includes at least one of carbon material, titanium nitride, boron nitride, silicon nitride, silicon oxide, magnesium oxide, aluminum oxide, silicon carbide and polyaniline.

15. A battery, characterized in that: The battery comprises the negative electrode material according to any one of claims 1 to 14.

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