Negative electrode material, preparation method therefor, and lithium-ion battery

Abstract

A negative electrode material, a preparation method therefor, and a lithium-ion battery. The negative electrode material comprises a silicon-based inner core, and a coating layer located on at least part of a surface of the silicon-based inner core. The silicon-based inner core contains a silicon oxide and lithium silicate, and the coating layer contains a carbon material. 20 mg of negative electrode material is dissolved in 10 mL of deionized water to form a slurry, and the slurry is subjected to Zeta potential testing using a nano-particle size and Zeta potential analyzer. In a Zeta potential test distribution diagram of the slurry, the intensity of a first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV is I1, the intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV is I2, the intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV is I3, and the relationship between I1, I2, and I3 satisfies the following: 0≤I2 / I1≤2.0, 0≤I3 / I1≤1.0. Volume expansion of a negative electrode material can be reduced, improving the rate capability and the cycle performance of the negative electrode material.

Description

Negative electrode material and preparation method thereof, and lithium ion battery

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on September 27, 2023, with application number 2023112774159 and application name “Negative electrode material and preparation method thereof, lithium-ion battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of negative electrode materials, and in particular to negative electrode materials and preparation methods thereof, and lithium-ion 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. Anode materials are a crucial component of lithium-ion batteries, directly impacting key battery performance indicators such as energy density, cycle life, and safety. As the range requirements for new energy vehicles continue to increase, power battery materials are also developing towards higher energy density. The graphite anodes of traditional lithium-ion batteries are no longer able to meet current demand, making high-energy-density anode materials a new hotspot for companies.

[0004] Silicon-based anode materials are one of the most critical materials for high-energy-density lithium-ion batteries. However, existing silicon-based anode materials suffer from large volume expansion and poor rate performance, hindering their widespread application in lithium-ion batteries. Currently, coating silicon-based anode materials with a single carbon material is a common coating option. Carbon materials can improve the material's conductivity, but existing carbon coating technologies still have many drawbacks.

[0005] Therefore, developing a negative electrode material with excellent cycle performance and low volume expansion effect and a preparation method thereof remains a technical challenge in the field.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a negative electrode material and a preparation method thereof, and a lithium-ion battery, which aim to reduce the volume expansion of the negative electrode material and improve the rate performance and cycle performance of the negative electrode material.

[0008] In a first aspect, an embodiment of the present application provides a negative electrode material, comprising a silicon-based core and a coating layer located on at least a portion of the surface of the silicon-based core, wherein the silicon-based core contains silicon oxide and lithium silicate, and the coating layer contains a carbon material;

[0009] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV is I1, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV is I2, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV is I3, and the relationship between I1, I2, and I3 satisfies: 0≤I2 / I1≤2.0, 0≤I3 / I1≤1.0.

[0010] In a second aspect, an embodiment of the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0011] A coating agent and a coating gas source containing a gaseous carbon source are simultaneously used to perform vapor deposition on the surface of the silicon-based core to form a coating layer to obtain a negative electrode material, wherein the coating agent is a non-gaseous coating agent containing a benzene ring structure, and the silicon-based core includes silicon oxide and lithium silicate.

[0012] In a third aspect, the present application provides a lithium-ion battery, comprising the negative electrode material described in the first aspect or the negative electrode material prepared by the method for preparing the negative electrode material described in the second aspect.

[0013] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0014] The negative electrode material provided in the present application includes a silicon-based core and a coating layer located on the surface of the silicon-based core, the coating layer includes a carbon material, and the coating layer can effectively isolate the silicon-based core from exposure to the electrolyte, reduce the loss of active silicon and active lithium in the silicon-based core, and improve the cycle performance of the negative electrode material. The silicon-based core includes silicon oxide and lithium silicate; after the negative electrode material is made into a slurry, the slurry is subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, I1, I2 and I3 respectively reflect the existence form and content of the three substances of carbon material, lithium silicate and silicon oxide on the surface of the negative electrode material, that is, the surface of the negative electrode material can have a combination of multiple substances such as lithium silicate, carbon material and silicon oxide, and when the relationship between I1, I2 and I3 satisfies: 0≤I2 / I1≤2.0, 0≤I3 / I1≤1.0, the interface reaction between the negative electrode material and the electrolyte is good, and a high-speed mass transfer and charge transfer interface can be established between the negative electrode material and the electrolyte. Improve the mass-to-charge conduction efficiency of the negative electrode material, thereby improving the rate performance of the negative electrode material. By controlling the solid-liquid reaction between the surface of the negative electrode material and the electrolyte, a stable SEI interface is formed on the surface of the negative electrode material, reducing the degradation of the electrolyte, and inhibiting the cyclic expansion of the negative electrode sheet, thereby improving the cyclic performance of the negative electrode material.

[0015] The negative electrode material preparation method provided in the present application is to prepare the negative electrode material by vapor-phase deposition of a silicon-based core using a gas-phase carbon source, and simultaneously adding a solid-phase coating agent and / or a liquid-phase coating agent for vapor-phase deposition. During the vapor-phase deposition process, since different carbon sources have different dissociation efficiencies at the same temperature, the deposition efficiencies on the surface of the silicon-based core are also different. Different types of carbon sources are deposited on the surface of the silicon-based core in sequence, thereby forming differentiated deposition on the surface of the silicon-based core. The carbon material formed by the dissociation of the gas-phase carbon source is deposited on the surface of the silicon-based core to form a coating layer. At the same time, The carbon material formed by the dissociation of the solid-phase coating agent and / or the liquid-phase coating agent will be deposited into the coating layer and buried in the coating layer. Since the solid-phase coating agent and / or the liquid-phase coating agent contains a benzene ring structure, which is mainly derived from aromatic low-melting and boiling point organic matter, these organic matters can further perform surface modification and functional doping on the coating layer during the carbonization process, thereby optimizing the coating layer surface of the negative electrode material and realizing the regulation of the surface of the negative electrode material, thereby controlling the solid-liquid interface reaction between the negative electrode material and the electrolyte, and improving the processing performance and cycle performance of the negative electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a process flow chart of a method for preparing a negative electrode material according to an embodiment of the present application;

[0017] FIG2 is a Zeta potential test distribution diagram of the negative electrode material provided in Example 1 of the present application;

[0018] FIG3 is a Zeta potential test distribution diagram of the negative electrode material provided in Example 2 of the present application;

[0019] FIG4 is a Zeta potential test distribution diagram of the negative electrode material provided in Example 3 of the present application;

[0020] FIG5 is a Zeta potential test distribution diagram of the negative electrode material provided in Example 4 of the present application;

[0021] FIG6 is a Zeta potential test distribution diagram of the negative electrode material provided in Example 5 of the present application;

[0022] FIG7 is a Zeta potential test distribution diagram of the negative electrode material provided in Comparative Example 1 of the present application;

[0023] FIG8 is a Zeta potential test distribution diagram of the negative electrode material provided in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0024] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0025] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0026] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0027] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0028] In a first aspect, an embodiment of the present application provides a negative electrode material, comprising a silicon-based core and a coating layer located on at least a portion of the surface of the silicon-based core, wherein the silicon-based core contains silicon oxide and lithium silicate, and the coating layer contains a carbon material;

[0029] 20 mg of negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to Zeta potential testing using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the negative electrode slurry, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV is I1, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV is I2, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV is I3, and the relationship between I1, I2, and I3 satisfies: 0≤I2 / I1≤2.0, 0≤I3 / I1≤1.0.

[0030] The negative electrode material provided by the present application includes a silicon-based core and a coating layer located on the surface of the silicon-based core. The material of the coating layer includes a carbon material. The coating layer can effectively isolate the silicon-based core from exposure to the electrolyte, reduce the loss of active silicon and active lithium in the silicon-based core, and improve the cycle performance of the negative electrode material. The silicon-based core includes silicon oxide and lithium silicate. After the negative electrode material is made into a slurry, a nanoparticle size and Zeta potential analyzer is used to perform a Zeta potential test on the slurry. In the Zeta potential test distribution diagram of the slurry, I1, I2 and I3 respectively reflect the existence form and content of the three substances, namely, carbon material, lithium silicate and silicon oxide, on the surface of the negative electrode material. That is, the surface of the negative electrode material can have a combination of various substances such as lithium silicate, carbon material and silicon oxide, and when the relationship between I1, I2 and I3 satisfies: 0≤I2 / I1≤2.0, 0≤I3 / I1≤1.0, the interface reaction between the negative electrode material and the electrolyte is good, and a high-speed mass transfer and charge transfer interface between the negative electrode material and the electrolyte can be built, which can improve the mass-charge conduction efficiency of the negative electrode material, thereby improving the rate performance of the negative electrode material. By controlling the solid-liquid reaction between the surface of the negative electrode material and the electrolyte, a stable SEI interface is formed, the degradation of the electrolyte is reduced, and the cyclic expansion of the negative electrode sheet is inhibited, thereby improving the cyclic performance of the negative electrode material.

[0031] It should be noted that, in the Zeta potential test distribution diagram of the negative electrode material slurry, if a complete peak shape is not formed in the region (the center of the peak is not in the region, and there is no peak in the entire region), the value with the highest intensity (total) is selected and read as the intensity (total) I value of the region;

[0032] Specifically, I2 / I1 can be, for example, 0, 0.1, 0.3, 0.5, 0.7, 0.8, 0.9, 1.0, 1.1, 1.3, 1.5, 1.7, 1.8 or 2.0, etc., without limitation herein. It should be noted that when I2 is 0, that is, the proportion of lithium silicate in the surface of the negative electrode material is 0, indicating that the silicon-based core is basically completely covered by the coating layer. I3 / I1 can specifically be 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0, etc., without limitation herein.

[0033] Understandably, when the I2 / I1 ratio is greater than 2, the rationality of the charge ion distribution on the surface of the negative electrode material decreases, and the surface of the negative electrode material tends to be more uniform instead of diversified. This causes the zeta potential to change during the slurry adjustment process, resulting in reduced dispersion of the slurry and gas production. In the electrochemical reaction, this leads to excessive degradation and deposition of the electrolyte on the negative electrode plate, causing the plate to expand, which in turn affects the safety and cycle performance of the lithium-ion battery. Controlling the I2 / I1 ratio within the above range can make the surface potential distribution of the negative electrode material reasonable, making the surface of the negative electrode material have diversified characteristics. On the one hand, it can achieve solid-liquid control of the negative electrode material during the slurry adjustment process, inhibit gas production, and improve the dispersion of the slurry. On the other hand, in the electrochemical reaction, it can control the degradation reaction and deposition mode with the electrolyte, stabilize the SEI interface, and alleviate the volume expansion of the material, thereby improving the cycle performance of the negative electrode material and maximizing the electrochemical performance of the negative electrode material. In addition, by controlling the I2 / I1 ratio, the surface composition of the negative electrode material can be regulated. By regulating the surface of the negative electrode material, a fast ion electron transmission channel can be established, the conductivity of the negative electrode material can be improved, the material rate performance can be improved, and the loss of active silicon and active lithium can be reduced. When the I3 / I1 ratio is within the range of 0≤I3 / I1≤1.0, the surface of the negative electrode material particles has a certain hydrophilicity, the particles are easy to process and disperse, and the agglomeration and sedimentation of the negative electrode material during processing are reduced. In addition, when the ratios of 0≤I2 / I1≤2.0 and 0≤I3 / I1≤1.0 are simultaneously met, the negative electrode material achieves a balance between hydrophilicity and lipophilicity, further improving the processing performance of the negative electrode material and the electrolyte infiltration efficiency.

[0034] In some embodiments, the carbon material includes at least one of graphite, amorphous carbon, diamond-like carbon, carbon fiber, and carbide.

[0035] In some embodiments, the amorphous carbon includes soft carbon and hard carbon.

[0036] In some embodiments, the carbon material comprises silicon carbide.

[0037] In some embodiments, the material of the coating layer further contains at least one of nitride, metal oxide, phosphate, and silicate.

[0038] In some embodiments, the nitride includes at least one of silicon nitride, pyrrole, and pyridine.

[0039] In some embodiments, the metal oxide includes at least one of titanium oxide, aluminum oxide, magnesium oxide, lithium oxide, zirconium oxide, cobalt oxide, and vanadium oxide.

[0040] In some embodiments, the phosphate includes at least one of lithium phosphate, aluminum phosphate, lithium aluminum phosphate, lithium titanium aluminum phosphate, magnesium phosphate, lithium magnesium phosphate, calcium phosphate, lithium calcium phosphate, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and triammonium phosphate.

[0041] In some embodiments, the silicate comprises at least one of lithium silicate, magnesium silicate, aluminum silicate, magnesium aluminum silicate, lithium magnesium silicate, calcium silicate, magnesium calcium silicate, lithium calcium silicate, or lithium aluminum silicate.

[0042] In some embodiments, the thickness of the coating layer is 20 nm to 700 nm, and specifically can be 20 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, or 700 nm, etc., and of course, other values ​​within the above range can also be used, which is not limited here. If the coating layer is too thick, the lithium ion transmission efficiency is reduced, which is not conducive to high-rate charge and discharge of the material, and reduces the overall performance of the negative electrode material. If the coating layer is too thin, it is not conducive to increasing the conductivity of the negative electrode material and has weak performance in inhibiting the volume expansion of the material, resulting in poor long-cycle performance.

[0043] In some embodiments, silicon oxide comprises oxygen atoms and silicon atoms, with the molar ratio of oxygen atoms to silicon atoms being 0 to 2. Silicon oxide can be represented by the general formula SiOx (0 < x ≤ 2). It can be a material formed by dispersing silicon particles in SiO2, or a material having a tetrahedral structural unit, wherein the silicon atom is located at the center of the tetrahedral structural unit, and the silicon and oxygen atoms are located at the four vertices of the tetrahedral structural unit.

[0044] In some embodiments, the average particle size of the silicon-based core is 2.0 μm to 10.0 μm, specifically 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm or 10.0 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0045] In some embodiments, the lithium content in the silicon-based core is 10 3 ppm~10 5ppm, specifically can be 1000ppm, 2000ppm, 5000ppm, 10000ppm, 30000ppm, 50000ppm, 80000ppm or 100000ppm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0046] In some embodiments, the general formula of the lithium silicate is Li2O-nSiO2, where 0<n≤4. Specifically, the value of n can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, or 4, etc., without limitation herein. For example, when the value of n is 1, the lithium silicate is Li2O·SiO2, and when the value of n is 2, the lithium silicate is Li2O-2SiO2, which are not further described herein.

[0047] In some embodiments, at least a portion of the lithium silicate is located on the surface of the silicon oxide, and the lithium silicate on the surface of the silicon oxide is dispersed.

[0048] In some embodiments, the average particle size of the negative electrode material is 2 μm to 12 μm. Specifically, the average particle size of the negative electrode material can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or 12 μm, etc., without limitation herein. Controlling the average particle size of the negative electrode material within the above range is beneficial to improving the cycle performance of the negative electrode material. Preferably, the average particle size of the negative electrode material is 2.0 μm to 9.0 μm.

[0049] In some embodiments, the specific surface area of ​​the negative electrode material is 0.5 m 2 / g~8.0m 2 / g, specifically 0.5m 2 / g, 1.0m 2 / g, 2.0m 2 / g, 3.0m 2 / g, 4.0m 2 / g, 5.0m 2 / g, 6.0m 2 / g, 7.0m 2 / g or 8.0m 2 / g, of course, it can also be other values ​​within the above range, which is not limited here. The specific surface area of ​​the negative electrode material is within the above range, which ensures the processing performance of the material, is conducive to improving the initial efficiency of the lithium battery made of the negative electrode material, and is conducive to improving the cycle performance of the negative electrode material. Preferably, the specific surface area of ​​the negative electrode material is 1.0m 2 / g~4.0m 2 / g.

[0050] In some embodiments, the tap density of the negative electrode material is 0.5 g / cm 3~2.0g / cm 3 , specifically 0.5g / cm 3 , 0.7g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.2g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 or 2.0g / cm 3 Of course, it can also be other values ​​within the above range, which is not limited here. The tap density of the negative electrode material is within the above range, which is beneficial to improving the energy density of the lithium battery made of the negative electrode material. Preferably, the tap density of the negative electrode material is 0.7g / cm 3 ~1.6g / cm 3 .

[0051] In some embodiments, the mass content of water in the negative electrode material is 0.01% to 0.5%, specifically 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%. Of course, it can also be other values ​​within the above range, which is not limited here.

[0052] In some embodiments, based on the mass of the negative electrode material being 100%, the mass content of the carbon material is 0.5% to 10%, specifically 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, etc., and other values ​​within the above range are also possible and are not limited here. Preferably, the mass content of the carbon material in the negative electrode material is 2.5% to 8%.

[0053] In some embodiments, based on the mass of the negative electrode material as 100%, the lithium content in the negative electrode material is 2% to 15%, specifically 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0054] In some embodiments, the pH value of the negative electrode material is 10.0-12.3, specifically 10.0, 10.3, 10.5, 10.8, 11.0, 11.2, 11.5, 11.7, 11.9, 12.0, 12.1, 12.2 or 12.3. Of course, it can also be other values ​​within the above range, which is not limited here.

[0055] In a second aspect, an embodiment of the present application provides a method for preparing a negative electrode material, as shown in FIG1 , comprising the following steps:

[0056] S100. Simultaneously use a coating agent and a coating gas source containing a gaseous carbon source to perform vapor deposition on the surface of the silicon-based core to form a coating layer to obtain a negative electrode material, wherein the coating agent is a non-gaseous coating agent containing a benzene ring structure, and the silicon-based core includes silicon oxide and lithium silicate.

[0057] In some embodiments, the non-gaseous capping agent includes a solid-phase capping agent and / or a liquid-phase capping agent.

[0058] The negative electrode material preparation method provided in the present application is to prepare the negative electrode material by vapor-phase deposition of a silicon-based core using a gas-phase carbon source, and simultaneously adding a solid-phase coating agent and / or a liquid-phase coating agent for vapor-phase deposition. During the vapor-phase deposition process, since different carbon sources have different dissociation efficiencies at the same temperature, the deposition efficiencies on the surface of the silicon-based core are also different. Different types of carbon sources are deposited on the surface of the silicon-based core in sequence, thereby forming differentiated deposition on the surface of the silicon-based core. The carbon material formed by the dissociation of the gas-phase carbon source is deposited on the surface of the silicon-based core to form a coating layer. At the same time, The carbon material formed by the dissociation of the solid-phase coating agent and / or the liquid-phase coating agent will be deposited into the coating layer and buried in the coating layer. Since the solid-phase coating agent and / or the liquid-phase coating agent contains a benzene ring structure, which is mainly derived from aromatic low-melting and boiling point organic matter, these organic matters can further perform surface modification and functional doping on the coating layer during the carbonization process, thereby optimizing the coating layer surface of the negative electrode material and realizing the regulation of the surface of the negative electrode material, thereby controlling the solid-liquid interface reaction between the negative electrode material and the electrolyte, and improving the processing performance and cycle performance of the negative electrode material.

[0059] The following is a detailed description of the preparation method provided in this scheme:

[0060] In some embodiments, the step of preparing the silicon-based core includes: performing a pre-physical and chemical treatment on a mixture comprising silicon oxide and a lithium source to obtain a pre-lithiated silicon-based core.

[0061] In some embodiments, the silicon oxide is silicon monoxide.

[0062] In some embodiments, the lithium source includes at least one of lithium hydride, alkyl lithium, metallic lithium, lithium aluminum hydride, lithium amide, lithium borohydride, and a silicon-lithium alloy.

[0063] In some embodiments, the mass ratio of silicon oxide to lithium source is (85-99): (1-15), specifically 85:15, 88:12, 90:10, 92:8, 95:5, 96:4, 97:3, 98:2 or 99:1, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0064] In some embodiments, the pretreatment time is 0.5h to 24.0h, specifically 0.5h, 1h, 3h, 5h, 8h, 10h, 12h, 15h, 18h, 20h or 24h, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0065] In some embodiments, the temperature of the pre-treatment is 300°C to 1000°C, specifically 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0066] In some embodiments, the pre-chemical treatment is performed under an inert gas atmosphere, and the inert gas atmosphere includes at least one of helium, neon, argon, krypton, and xenon.

[0067] In some embodiments, before subjecting the mixture comprising silicon oxide and lithium source to a pre-physical and chemical treatment, the method further comprises: mixing the silicon oxide and lithium source and then subjecting the mixture to a shaping treatment to obtain the mixture comprising silicon oxide and lithium source.

[0068] In some embodiments, before subjecting the mixture comprising silicon oxide and a lithium source to a pre-physical and chemical treatment, the method further comprises: mixing the silicon oxide and the lithium source and then subjecting the mixture to a shaping treatment to obtain a mixture comprising silicon oxide and a lithium source, wherein the shaping treatment comprises at least one of crushing, ball milling, grinding, and gas crushing.

[0069] In some embodiments, before vapor-depositing the silicon-based core using a vapor-phase carbon source, the method further comprises: subjecting the silicon-based core to a classification treatment and then a purification treatment.

[0070] It can be understood that grading the silicon-based core can control the particle size range of the silicon-based core. By controlling the particle size of the silicon-based core, the specific surface area and outer surface modification of the silicon-based core can be effectively regulated, which is beneficial to controlling the deposition efficiency of the negative electrode material and controlling the construction of a diversified surface of the material; purifying the silicon-based core can form a differentiated adsorption interface on the outer surface of the silicon-based core, so that the coating layer can form a differentiated deposition during the deposition process, thereby regulating the surface, realizing surface synthesis regulation, and realizing the synthesis of the preferred surface.

[0071] In some embodiments, the fractionation process comprises airflow fractionation process.

[0072] In some embodiments, the average particle size of the silicon-based core is 2.0 μm to 10.0 μm, specifically 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm or 10.0 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0073] In some embodiments, the purification step includes washing and drying the silicon-based core after the classification process in a solvent.

[0074] In some embodiments, the purification step includes washing and drying the graded silicon-based core in a solvent, wherein the solvent includes at least one of ethanol, acetone, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide and ethylene glycol dimethyl ether.

[0075] In some embodiments, the purification step includes washing and drying the fractionated silicon substrate core in a solvent for 2 to 10 hours. The washing time can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, etc., and is not limited here.

[0076] In some embodiments, the purification step includes washing and drying the graded silicon-based core in a solvent, and the drying temperature is 45°C to 80°C, specifically 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0077] In some embodiments, the purification step includes washing and drying the graded silicon-based core in a solvent. The drying time is 3 hours to 48 hours, specifically 3 hours, 5 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours or 48 hours, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0078] In some embodiments, the raw material of the gaseous carbon source includes at least one of methane, ethane, ethylene, acetylene, propyne, propylene, propane, formaldehyde, acetaldehyde, methanol, toluene, benzene, styrene, and phenol.

[0079] In some embodiments, the flow rate of the gaseous carbon source is 200 mL / min to 5000 mL / min, specifically 200 mL / min, 500 mL / min, 800 mL / min, 1000 mL / min, 2000 mL / min, 3000 mL / min, 4000 mL / min, 4500 mL / min or 5000 mL / min, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0080] In some embodiments, the deposition temperature of vapor deposition is 400°C to 1200°C, specifically 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C or 1200°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here. Controlling the deposition temperature within the above range can control the cracking efficiency of the gas-phase carbon source, thereby regulating the deposition efficiency of the carbon material on the surface of the negative electrode active material; at the same time, it can also control the volatilization efficiency of the solid-phase coating agent and the liquid-phase coating agent, as well as the functional group retention efficiency. Controlling the deposition temperature within this temperature range can ensure that the size of the silicon grains is controlled within a certain range, while also ensuring the degree of carbonization of the negative electrode material, reducing the proportion of CH bonds in the negative electrode material, and increasing the conductivity of the carbon coating layer, thereby improving the conductive properties of the negative electrode material.

[0081] In some embodiments, the deposition time of the vapor deposition is 1 hour to 24 hours. Specifically, the deposition time of the vapor deposition can be 1 hour, 3 hours, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours or 24 hours, etc., which are not limited here. It is understandable that if the deposition time of the vapor deposition is too long, it is easy to cause the coating layer to be too thick, and if the deposition time of the vapor deposition is too short, it is easy to cause the coating layer to be too thick. Controlling the deposition time within the above range can control the thickness of the coating layer, which is conducive to controlling the thickness of the coating layer within the ideal range.

[0082] In some embodiments, the deposition pressure of vapor deposition is 10 kPa to 0.1 MPa, and specifically can be 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa, or 0.1 MPa, etc., without limitation herein. Controlling the deposition pressure within the above range can control the compactness of the coating layer, resulting in a good compactness of the coating layer, improving the stability of the negative electrode material, and thereby enhancing the cycling performance of the negative electrode material.

[0083] In some embodiments, an auxiliary carrier gas is added during the vapor deposition process. It is understood that the auxiliary carrier gas can be used to bring the solid-phase coating agent and / or liquid-phase coating agent into the vapor deposition furnace for vapor deposition. At the same time, the solid-phase coating agent and / or liquid-phase coating agent can be deposited into the coating layer during the deposition process, thereby surface modifying and functionally doping the coating layer of the negative electrode material, thereby optimizing the surface interface and achieving material surface regulation. Furthermore, the auxiliary carrier gas can accelerate the cracking of the carbon source, increasing the carbon source cracking rate and vapor deposition rate. The auxiliary carrier gas can increase the carbon chain terminal structure, allowing different types of carbon materials to be deposited on the surface of the negative electrode material, thereby optimizing the pore environment of the negative electrode material.

[0084] In some embodiments, an auxiliary carrier gas is further added during the vapor deposition process, and the auxiliary carrier gas includes at least one of H2, CO2, NH3 and Ar.

[0085] In some embodiments, an auxiliary carrier gas is added during the vapor deposition process, and the flow rate of the auxiliary carrier gas is 100 mL / min to 8000 mL / min, specifically 100 mL / min, 500 mL / min, 1000 mL / min, 2000 mL / min, 3000 mL / min, 4000 mL / min, 5000 mL / min, 6000 mL / min, 7000 mL / min or 8000 mL / min, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0086] In some embodiments, an auxiliary carrier gas is added during the vapor deposition process, and the flow ratio of the gaseous carbon source to the auxiliary carrier gas is (3-9.5): (0.5-7), specifically 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1 or 9.5:0.5, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0087] In some embodiments, an auxiliary carrier gas is also added during the vapor deposition process, and the volume ratio of the gaseous carbon source to the auxiliary carrier gas is (3-9.5): (0.5-7), specifically 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1 or 9.5:0.5, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0088] In some embodiments, vapor deposition is performed in a deposition chamber of a vapor deposition device, and the rotation speed of the deposition chamber is 0.1 r / min to 10 r / min, specifically 0.1 r / min, 0.5 r / min, 1 r / min, 2 r / min, 3 r / min, 4 r / min, 5 r / min, 6 r / min, 7 r / min, 8 r / min, 9 r / min or 10 r / min, etc., and of course other values ​​within the above range are also possible, which are not limited here. Controlling the rotation speed of the deposition chamber within the above range is conducive to improving the uniformity of the deposition coating between the negative electrode material particles.

[0089] In some embodiments, the solid phase coating agent includes tetracarboxylic anhydride, copper phthalocyanine, substituted or unsubstituted naphthalene, substituted or unsubstituted anthracene, substituted or unsubstituted phenanthrene, substituted or unsubstituted pyrene, substituted or unsubstituted biphenyl, substituted or unsubstituted terphenyl, C 60 or at least one of substituted or unsubstituted phenalene.

[0090] In some embodiments, the liquid capping agent includes at least one of toluene, xylene, styrene, ethylene glycol dimethyl ether, or butyltoluene.

[0091] In some embodiments, the method further comprises classifying and drying the vapor-deposited reaction product.

[0092] It is understood that grading the vapor deposition reaction product can break up agglomerates of the negative electrode material powder and help control the average particle size of the negative electrode material within a preferred range. Drying the vapor deposition reaction product can remove moisture from the negative electrode material, thereby improving the electrochemical performance of the negative electrode material.

[0093] In some embodiments, the average particle size of the negative electrode material is 2 μm to 12 μm. Specifically, the average particle size of the negative electrode material can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or 12 μm, etc., without limitation herein. Preferably, the average particle size of the negative electrode material is 2 μm to 9 μm.

[0094] In some embodiments, the drying temperature is 50°C to 120°C, specifically 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 110°C or 120°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0095] In some embodiments, the drying time is 6.0 h to 48.0 h, specifically 6 h, 12 h, 15 h, 18 h, 20 h, 24 h, 30 h, 36 h, 40 h, 45 h or 48 h, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0096] In some embodiments, the method further comprises: solid-phase mixing or liquid-phase mixing the vapor-deposited product with a coating material, wherein the coating material comprises at least one of nitride, metal oxide, phosphate, and silicate.

[0097] In some embodiments, the step of solid-phase mixing the vapor-deposited product and the coating material comprises grinding and heat-treating the mixture comprising the vapor-deposited product and the coating material.

[0098] In some embodiments, the step of solid-phase mixing the vapor-deposited product and the coating material includes: grinding and heat-treating the mixture containing the vapor-deposited product and the coating material, and the grinding time is 0.5h to 48h, specifically 0.5h, 1h, 3h, 8h, 12h, 15h, 18h, 24h, 36h, 40h, 45h or 48h, etc., which is not limited here.

[0099] In some embodiments, the step of solid-phase mixing the vapor-deposited product and the coating material includes: grinding and heat-treating the mixture containing the vapor-deposited product and the coating material, the heat treatment temperature is 400°C to 1000°C, and the heat treatment time is 1.0h to 24.0h.

[0100] Specifically, the heat treatment temperature can be 400°C, 450°C, 500°C, 600°C, 800°C, 900°C or 1000°C, etc., and is not limited here. The heat treatment time can be 1h, 3h, 5h, 8h, 12h, 15h, 18h, 20h or 24h, etc., and is not limited here.

[0101] In some embodiments, the step of solid-phase mixing the vapor-deposited product with the coating material includes: grinding and heat-treating the mixture containing the vapor-deposited product and the coating material, and the heat treatment is carried out under a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, helium, argon, neon, and krypton.

[0102] In some embodiments, the step of mixing the vapor-deposited product with the coating material in liquid phase includes: drying and heat-treating the mixed coating liquid containing the vapor-deposited product and the coating material.

[0103] In some embodiments, the step of liquid-phase mixing the vapor-deposited product and the coating material includes: drying and heat-treating a mixed coating liquid containing the vapor-deposited product and the coating material; wherein the mixed coating liquid includes a polar solvent.

[0104] In some embodiments, the step of liquid-phase mixing the vapor-deposited product with the coating material includes: drying and heat-treating the mixed coating liquid containing the vapor-deposited product and the coating material; wherein the polar solvent includes at least one of water, anhydrous ethanol, methanol and isopropanol.

[0105] In some embodiments, the step of liquid-phase mixing the vapor-deposited product and the coating material includes drying and heat-treating the mixed coating liquid containing the vapor-deposited product and the coating material, the drying temperature is 50° C. to 120° C., and the time is 6 h to 48 h.

[0106] In some embodiments, the step of liquid-phase mixing the vapor-deposited product and the coating material includes drying and heat-treating the mixed coating liquid containing the vapor-deposited product and the coating material, the heat treatment temperature is 80°C to 150°C, and the heat treatment time is 3.0h to 48.0h.

[0107] Specifically, the heat treatment temperature can be 80° C., 90° C., 100° C., 110° C., 120° C., 130° C., 140° C., or 150° C., etc., and is not limited here. The heat treatment time can be 3 h, 5 h, 8 h, 12 h, 15 h, 18 h, 24 h, 30 h, 36 h, 45 h, or 48 h, etc., and is not limited here.

[0108] In some embodiments, the step of liquid-phase mixing the vapor-deposited product with the coating material includes: drying and heat-treating the mixed coating liquid containing the vapor-deposited product and the coating material, and the heat treatment is carried out under a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, helium, argon, neon, and krypton.

[0109] In a third aspect, the present application provides a lithium-ion battery, which includes the negative electrode material described in the first aspect or the negative electrode material prepared by the preparation method of the negative electrode material described in the second aspect.

[0110] Example

[0111] Example 1

[0112] (1) After mixing 200 g of lithium hydride and 1800 g of silicon oxide, the mixture was placed in a vacuum ball mill for vacuum dry ball milling for 60 minutes to obtain a mixture containing lithium hydride and silicon oxide; the mixture was then placed in an atmosphere protection heat treatment equipment, argon gas was introduced, and pre-physical and chemical treatment was performed at 1000°C for 12 hours to obtain a silicon-based core; finally, the silicon-based core was subjected to air flow classification treatment to an average particle size of 5.0 μm.

[0113] (2) Weigh 1000 g of silicon-based core (average particle size 5.0 μm), rinse with deionized water for 30 min, then wash and soak with ethanol for 3 h, and dry in a vacuum drying oven at 80 °C for 24 h;

[0114] (3) The obtained sample was placed in the deposition chamber of a vapor deposition furnace, and methane, acetylene and ethylene gases with a volume ratio of 1:1:1 were introduced into the deposition chamber at a rate of 1000 ml / min as a gaseous carbon source. At the same time, a solid coating agent, tetracarboxylic anhydride (PTCDA), was placed at the front end of the vapor deposition furnace. The pressure in the deposition chamber was regulated by a pressure valve. After the vacuum degree in the reaction chamber was evacuated, Ar was introduced as an auxiliary carrier gas at a rate of 1000 mL / min, and then vapor deposition was carried out at 450 ° C for 10 hours, wherein the flow ratio of the gaseous carbon source to Ar was 1:1, the rotation speed of the deposition chamber was 5 r / min, and the deposition pressure was 0.05 MPa;

[0115] (4) After the vapor deposition product is graded, it is placed in a vacuum drying oven at 100°C for 24 hours to obtain the negative electrode material.

[0116] The negative electrode material prepared in this embodiment includes a silicon-based core and a carbon coating layer located on at least a portion of the surface of the active material, wherein the silicon-based core includes silicon oxide and lithium silicate.

[0117] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, as shown in Figure 2, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV is I1 = 78769, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV is I2 = 98739, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV is I3 = 38278, and I2 / I1 = 1.25, I3 / I1 = 0.486.

[0118] The average particle size of the negative electrode material is 4.92 μm and the specific surface area is 1.57 m 2 / g, and the tap density is 0.98g / cm 3The mass content of carbon element in the negative electrode material is 4.93%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 9.55%, and the mass content of water is 0.21%.

[0119] Example 2

[0120] (1) After mixing 200 g of lithium hydride and 1800 g of silicon oxide, the mixture was placed in a vacuum ball mill for vacuum dry ball milling for 60 minutes to obtain a mixture containing lithium hydride and silicon oxide; the mixture was then placed in an atmosphere protection heat treatment equipment, argon gas was introduced, and pre-physical and chemical treatment was performed at 1000°C for 12 hours to obtain a silicon-based core; finally, the silicon-based core was subjected to air flow classification treatment to an average particle size of 5.0 μm.

[0121] (2) Weigh 1000 g of silicon-based core (average particle size of 5.0 μm), rinse with deionized water for 30 min, then wash and soak with acetone for 3 h, and place in a vacuum drying oven at 80 °C for 24 h.

[0122] (3) The obtained sample was placed in the deposition chamber of a vapor deposition furnace, and methane gas was introduced into the deposition chamber at 1000 mL / min as a gaseous carbon source. At the same time, a solid-phase coating agent, copper phthalocyanine, was placed at the front end of the vapor deposition furnace. The air pressure in the deposition chamber was regulated by an air pressure valve. After the vacuum degree in the reaction chamber was evacuated, Ar and NH3 with a volume ratio of 5:1 were introduced as auxiliary carrier gases at 500 mL / min. Then, vapor deposition was carried out at 500°C for 12 hours. The flow ratio of the gaseous carbon source to the auxiliary carrier gas (Ar and NH3) was 2:1, the rotation speed of the deposition chamber was 5 r / min, and the deposition pressure was 0.03 MPa.

[0123] (4) After the vapor deposition product is graded, it is placed in a vacuum drying oven at 100°C for 24 hours to obtain the negative electrode material.

[0124] The negative electrode material prepared in this embodiment includes a silicon-based core and a carbon coating layer located on at least a portion of the surface of the silicon-based core, wherein the silicon-based core includes silicon oxide and lithium silicate.

[0125] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, as shown in Figure 3, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV is I1 = 179809, the maximum intensity in the Zeta potential range of -65 mV to -50 mV is I2 = 21756, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV is I3 = 36206, and I2 / I1 = 0.121, I3 / I1 = 0.201.

[0126] The average particle size of the negative electrode material is 5.1 μm and the specific surface area is 1.72 m 2 / g, and the tap density is 0.99g / cm 3 The mass content of carbon element in the negative electrode material is 5.12%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 9.13%, and the mass content of water is 0.11%.

[0127] Example 3

[0128] (1) 160 g of lithium hydride and 1840 g of silicon oxide were mixed and placed in a vacuum ball mill for vacuum dry ball milling for 60 min to obtain a mixture containing lithium hydride and silicon oxide; the mixture was then placed in an atmosphere protection heat treatment equipment, argon gas was introduced, and pre-physical and chemical treatment was performed at 1000°C for 12 h to obtain a silicon-based core; finally, the silicon-based core was subjected to air flow classification treatment to an average particle size of 5.0 μm.

[0129] (2) Weigh 1000 g of silicon-based core (average particle size 5.0 μm), rinse with deionized water for 30 min, then wash and soak with N,N-dimethylformamide for 1 h, and dry in a vacuum drying oven at 80 °C for 24 h;

[0130] (3) The obtained sample was placed in the deposition chamber of a vapor deposition furnace, and methane, acetylene, ethylene and propane gases with a volume ratio of 1:1:1:3 were introduced into the deposition chamber at a rate of 1500 mL / min as gaseous carbon sources. At the same time, a liquid coating agent, toluene, was placed at the front end of the vapor deposition furnace. The pressure in the deposition chamber was regulated by a pressure valve. After the vacuum degree in the reaction chamber was evacuated, Ar and NH3 with a volume ratio of 5:1 were introduced as auxiliary carrier gases at a rate of 500 mL / min. Then, vapor deposition was carried out at 800°C for 8 hours, wherein the flow ratio of the gaseous carbon source to the auxiliary carrier gas (Ar and NH3) was 3:1, the rotation speed of the deposition chamber was 5 r / min, and the deposition pressure was normal pressure;

[0131] (4) After the vapor deposition product is graded, it is placed in a vacuum drying oven at 100°C for 24 hours to obtain the negative electrode material.

[0132] The negative electrode material prepared in this embodiment includes an active substance and a carbon coating layer located on at least a portion of the surface of the silicon-based core, and the silicon-based core includes silicon oxide and lithium silicate.

[0133] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, as shown in Figure 4, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV is I1 = 97941, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV is I2 = 44480, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV is I3 = 67448, and I2 / I1 = 0.45, I3 / I1 = 0.689.

[0134] The average particle size of the negative electrode material is 5.1 μm and the specific surface area is 1.29 m 2 / g, and the tap density is 0.97g / cm 3 The mass content of carbon element in the negative electrode material is 4.98%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 7.13%, and the mass content of water is 0.17%.

[0135] Example 4

[0136] Different from Example 1, the deposition temperature during the vapor deposition process is 600°C.

[0137] The negative electrode material prepared in this embodiment includes a silicon-based core and a carbon coating layer located on at least a portion of the surface of the silicon-based core, wherein the silicon-based core includes silicon oxide and lithium silicate.

[0138] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, as shown in Figure 5, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV is I1=159008, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV is I2=50380, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV is I3=64524, and I2 / I1=0.317, I3 / I1=0.406.

[0139] The average particle size of the negative electrode material is 5.12 μm and the specific surface area is 1.58 m 2 / g, and the tap density is 1.02g / cm 3 The mass content of carbon element in the negative electrode material is 4.99%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 9.04%, and the mass content of water is 0.21%.

[0140] Example 5

[0141] Different from Example 1, the deposition temperature during the vapor deposition process is 900°C.

[0142] The negative electrode material prepared in this embodiment includes a silicon-based core and a carbon coating layer located on at least a portion of the surface of the silicon-based core, and the active material includes silicon oxide and lithium silicate.

[0143] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, as shown in Figure 6, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV is I1 = 76042, the maximum intensity in the Zeta potential range of -65 mV to -50 mV is I2 = 32434, and the maximum intensity in the Zeta potential range of -35 mV to -25 mV is I3 = 23691, and I2 / I1 = 0.427, I3 / I1 = 0.312.

[0144] The average particle size of the negative electrode material is 5.0 μm and the specific surface area is 1.49 m 2 / g, and the tap density is 0.98g / cm 3 The mass content of carbon element in the negative electrode material is 5.19%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 9.36%, and the mass content of water is 0.09%.

[0145] Example 6:

[0146] (1) After mixing 200 g of lithium hydride and 1800 g of silicon oxide, the mixture was placed in a vacuum ball mill for vacuum dry ball milling for 60 minutes to obtain a mixture containing lithium hydride and silicon oxide; the mixture was then placed in an atmosphere protection heat treatment equipment, argon gas was introduced, and pre-physical and chemical treatment was performed at 1000°C for 12 hours to obtain a silicon-based core; finally, the silicon-based core was subjected to air flow classification treatment to an average particle size of 5.0 μm.

[0147] (2) Weigh 1000 g of silicon-based core (average particle size of 5.0 μm), rinse with deionized water for 30 min, then wash and soak with acetone for 3 h, and place in a vacuum drying oven at 80 °C for 24 h.

[0148] (3) The obtained sample was placed in the deposition chamber of a vapor deposition furnace. At the same time, a liquid coating agent, liquid asphalt, was placed at the front end of the vapor deposition furnace. The pressure in the deposition chamber was regulated by a pressure valve. After the vacuum in the reaction chamber was evacuated, acetylene gas was introduced into the deposition chamber at a rate of 1000 mL / min as a gaseous carbon source, and Ar and NH3 with a volume ratio of 1:3 were introduced into the deposition chamber at a rate of 3000 mL / min as auxiliary carrier gases. Then, vapor deposition was carried out at 700°C for 12 hours. The flow ratio of the gaseous carbon source to the auxiliary carrier gas (Ar and NH3) was 1:3, the rotation speed of the deposition chamber was 5 r / min, and the deposition pressure was 0.05 MPa.

[0149] (4) After the vapor deposition product is graded, it is placed in a vacuum drying oven at 100°C for 24 hours to obtain the negative electrode material.

[0150] The negative electrode material prepared in this embodiment includes a silicon-based core and a large amount of nitrogen-doped carbon coating layer located on at least a portion of the surface of the silicon-based core, and the silicon-based core includes silicon oxide and lithium silicate.

[0151] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV was I1 = 113024, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV was I2 = 89211, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV was I3 = 21157, and I2 / I1 = 0.789, I3 / I1 = 0.187.

[0152] The average particle size of the negative electrode material is 5.04 μm and the specific surface area is 1.68 m 2 / g, and the tap density is 1.03g / cm 3 The mass content of carbon element in the negative electrode material is 4.87%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 9.02%, and the mass content of water is 0.19%.

[0153] Example 7

[0154] The difference from Example 2 is that:

[0155] Before step (4), the method further includes: weighing 65 g of aluminum chloride and dissolving it in 2000 g of deionized water, stirring for 30 minutes, adding 970 g of the vapor-deposited product after the aluminum chloride is completely dissolved, stirring for 120 minutes, and then centrifuging to remove the solvent; and vacuum drying the centrifuged material at 80° C. for 48 hours.

[0156] (5) The dried sample was placed in an argon atmosphere and heat treated at 600°C for 12 h, and then graded to obtain the negative electrode material.

[0157] The negative electrode material prepared in this embodiment includes a silicon-based core and a coating layer located on at least a portion of the surface of the silicon-based core, the silicon-based core includes silicon oxide and lithium silicate, and the coating layer includes carbon material and aluminum oxide.

[0158] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV was I1 = 121743, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV was I2 = 0, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV was I3 = 57192, and I2 / I1 = 0, I3 / I1 = 0.470.

[0159] The average particle size of the negative electrode material is 4.93 μm and the specific surface area is 2.01 m 2 / g, and the tap density is 1.01g / cm 3 The mass content of carbon element in the negative electrode material is 0.22%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 9.11%, and the mass content of water is 0.08%.

[0160] Example 8

[0161] The difference from Example 2 is that (4) the vapor deposition product is placed in a vacuum drying oven at 100° C. and dried for 24 h.

[0162] After step (4), the method further includes: weighing 970 g of the dried vapor deposition product and uniformly mixing it with 25 g of aluminum oxide and 5 g of lithium fluoride to form a mixture, placing the mixture in a vacuum ball mill for vacuum dry ball milling for 6 hours, placing the ball-milled mixture in an argon atmosphere at 900° C. for 24 hours, and then performing a grading process to obtain a negative electrode material.

[0163] The negative electrode material prepared in this embodiment includes a silicon-based core and a coating layer located on at least a portion of the surface of the silicon-based core, the silicon-based core includes silicon oxide and lithium silicate, and the coating layer includes lithium silicate and aluminum silicate.

[0164] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV was I1 = 102959, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV was I2 = 0, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV was I3 = 23009, and I2 / I1 = 0, I3 / I1 = 0.223.

[0165] The average particle size of the negative electrode material is 5.00 μm and the specific surface area is 1.91 m 2 / g, and the tap density is 0.96g / cm 3 The mass content of carbon element in the negative electrode material is 0.18%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 9.01%, and the mass content of water is 0.07%.

[0166] Example 9

[0167] The difference from Example 1 is that in step (1), the silicon-based core is air flow-pulverized to an average particle size of 2.0 μm, and the subsequent operations are the same as in Example 1.

[0168] The negative electrode material prepared in this embodiment includes a silicon-based core and a carbon coating layer located on at least a portion of the surface of the active material, wherein the silicon-based core includes silicon oxide and lithium silicate.

[0169] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV was I1 = 63788, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV was I2 = 103392, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV was I3 = 29303, and I2 / I1 = 1.62, I3 / I1 = 0.46.

[0170] The average particle size of the negative electrode material is 2.07 μm and the specific surface area is 2.45 m2 / g, and the tap density is 1.18g / cm 3 The mass content of carbon element in the negative electrode material is 5.12%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 9.67%, and the mass content of water is 0.17%.

[0171] Example 10

[0172] The difference from Example 1 is that in step (1), the silicon-based core is air flow-pulverized to an average particle size of 10.0 μm, and the subsequent operations are the same as in Example 1.

[0173] The negative electrode material prepared in this embodiment includes a silicon-based core and a carbon coating layer located on at least a portion of the surface of the active material, wherein the silicon-based core includes silicon oxide and lithium silicate.

[0174] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV was I1 = 72129, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV was I2 = 2309, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV was I3 = 52118, and I2 / I1 = 0.03, I3 / I1 = 0.72.

[0175] The average particle size of the negative electrode material is 9.83 μm and the specific surface area is 1.76 m 2 / g, and the tap density is 0.98g / cm 3 The mass content of carbon element in the negative electrode material is 4.96%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 9.53%, and the mass content of water is 0.05%.

[0176] Example 11

[0177] The difference from Example 1 is that in step (1), 5 g of metallic lithium and 95 g of silicon dioxide are mixed, and the subsequent operations are the same as in Example 1.

[0178] The negative electrode material prepared in this embodiment includes a silicon-based core and a carbon coating layer located on at least a portion of the surface of the active material, wherein the silicon-based core includes silicon oxide and lithium silicate.

[0179] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV was I1 = 55192, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV was I2 = 39180, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV was I3 = 10732, and I2 / I1 = 0.71, I3 / I1 = 0.19.

[0180] The average particle size of the negative electrode material is 4.93 μm and the specific surface area is 1.92 m 2 / g, and the tap density is 0.98g / cm 3 The mass content of carbon element in the negative electrode material is 5.10%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 5.02%, and the mass content of water is 0.02%.

[0181] Comparative Example 1

[0182] (1) After mixing 200 g of lithium hydride and 1800 g of silicon oxide, the mixture was placed in a vacuum ball mill for vacuum dry ball milling for 60 minutes to obtain a mixture containing lithium hydride and silicon oxide; the mixture was then placed in an atmosphere protection heat treatment equipment, argon gas was introduced, and pre-physical and chemical treatment was performed at 1000°C for 12 hours to obtain a silicon-based core; finally, the silicon-based core was subjected to air flow classification treatment to an average particle size of 5.0 μm.

[0183] (2) Weigh 1000 g of silicon-based core (average particle size of 5.0 μm), rinse with deionized water for 30 min, and dry in a vacuum drying oven at 100° C. for 24 h to obtain the negative electrode material.

[0184] The negative electrode material prepared in this comparative example includes a silicon-based core, which includes silicon oxide and lithium silicate located on at least a portion of the surface of the silicon oxide.

[0185] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, as shown in Figure 7, the maximum intensity of the slurry in the Zeta potential range of -50 mV to -40 mV is I1 = 1731, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV is I2 = 112791, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV is I3 = 41337, and I2 / I1 = 65.16, I3 / I1 = 13.27.

[0186] The average particle size of the negative electrode material is 5.0 μm and the specific surface area is 1.31 m 2 / g, and the tap density is 0.98g / cm 3 The mass content of carbon element in the negative electrode material is 0.33%. Based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 10.31%, and the mass content of water is 0.32%.

[0187] Comparative Example 2

[0188] (1) After mixing 200 g of lithium hydride and 1800 g of silicon oxide, the mixture was placed in a vacuum ball mill for vacuum dry ball milling for 60 minutes to obtain a mixture containing lithium hydride and silicon oxide; the mixture was then placed in an atmosphere protection heat treatment equipment, argon gas was introduced, and pre-physical and chemical treatment was performed at 1000°C for 12 hours to obtain a silicon-based core; finally, the silicon-based core was subjected to air flow classification treatment to an average particle size of 5.0 μm.

[0189] (2) Weigh 1000 g of silicon-based core (average particle size of 5.0 μm), rinse with deionized water for 30 min, and dry in a vacuum drying oven at 100°C for 24 h.

[0190] (3) The obtained sample was placed in a deposition chamber of a vapor deposition furnace, methane gas was introduced into the deposition chamber as a gaseous carbon source, and then vapor deposition was performed at 900°C for 4 hours, wherein the rotation speed of the deposition chamber was 5 r / min and the deposition pressure was 0.05 MPa;

[0191] (4) After the vapor deposition product is graded, it is placed in a vacuum drying oven at 100°C for 24 hours to obtain the negative electrode material.

[0192] The negative electrode material prepared in this comparative example includes a silicon-based core and a carbon coating layer located on at least a portion of the surface of the silicon-based core, and the silicon-based core includes silicon oxide and lithium silicate located on at least a portion of the surface of the silicon oxide.

[0193] 20 mg of the negative electrode material was dissolved in 10 ml of deionized water to form a slurry, and the slurry was subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, as shown in Figure 8, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV is I1=43212, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV is I2=132771, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV is I3=34179, and I2 / I1=3.07, I3 / I1=1.26.

[0194] The average particle size of the negative electrode material is 5.0 μm and the tap density is 0.98 g / cm 3 , with a specific surface area of ​​1.59m 2 / g, the mass content of carbon element in the negative electrode material is 4.54%, based on the mass of the negative electrode material being 100%, the mass content of lithium in the negative electrode material is 9.33%, and the mass content of water is 0.21%.

[0195] Test Method

[0196] (1) Test method for particle size of negative electrode material:

[0197] The particle size of the negative electrode material was tested using a Malvern Mastersizer 2000 laser particle size analyzer to obtain the average particle size.

[0198] (2) Testing method for specific surface area of ​​negative electrode material:

[0199] The dynamic specific surface area rapid tester JW-DX of Beijing Jingwei Gaobo Science and Technology Co., Ltd. was used for testing. The unit is m 2 / g.

[0200] (3) Test method for tap density of negative electrode material:

[0201] Using a vibrator, weigh a certain amount of sample and vibrate 3000 times at 300 times / min to test the tap density.

[0202] (4) Test method for the mass content of water in negative electrode materials:

[0203] Thermogravimetry was used to test the water content in the negative electrode material. At 250°C, the proportion of the mass lost by the negative electrode material in the total weight was the water content in the negative electrode material.

[0204] (5) Test method for lithium content in negative electrode materials:

[0205] The lithium content of the negative electrode material is tested using an inductively coupled plasma emission spectrometer (ICP): the negative electrode material is calcined at high temperature to remove the carbon element; the calcined product is treated with nitric acid and hydrofluoric acid in sequence, and then continued to heat to evaporate the acid, and then hydrochloric acid is added and treated until it is completely dissolved. Finally, after the volume is fixed, the product is tested using an inductively coupled plasma emission spectrometer.

[0206] (6) Test method for the mass content of carbon material in negative electrode material:

[0207] Thermogravimetric analysis was used to test the mass content of carbon material in the negative electrode material.

[0208] (7) pH test method:

[0209] pH testing was performed according to GB / T 24533-2019. 5g of negative electrode material was dissolved in 45g of water, stirred thoroughly for 30 minutes, and then tested using a Mettler-Toledo FE20PH. The test was performed following the equipment's user manual, including relevant calibration and other preparations and operating procedures.

[0210] (8) Zeta potential test method of negative electrode material:

[0211] Weigh 20 mg of negative electrode material and dissolve it in deionized water to form a slurry with a pH of 10.5-12. The slurry is then tested for zeta potential using a nanometer particle size analyzer (DLS, Malvern Zetasizer Nano ZS90). In this application, the total number of zeta potential points in a specific differential region is considered the intensity.

[0212] (9) Electrochemical performance test:

[0213] Coin-type batteries were fabricated according to the methods outlined in BTRTC / ZY / 01-020, "Button Cell Method Operating Instructions." PAA was used as a binder to prepare a 5% solids solution. The negative electrode active material and conductive agent were then added in a mass ratio of 75:15:10 (negative electrode active material: conductive agent (SP): binder (PAA). A high-speed disperser was used to evenly disperse the mixture to form a negative electrode slurry. The slurry was then evenly coated onto 10µm thick copper foil, dried, rolled, punched, and dried again to produce the negative electrode. A lithium sheet was used as the positive electrode. The coin-type battery was assembled in the following order: casing, gasket, nickel sheet, lithium sheet, separator, negative electrode, and casing. Battery performance testing was conducted using the methods specified in GB / T 24533-2019. The battery performance test was carried out using a blue electric cabinet: the negative electrode materials prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were assembled into button batteries for testing, wherein a metal lithium sheet was used as the counter electrode, the diaphragm was a PP-PE-PP composite film with a diameter of 19.2 mm, the electrolyte component ratio was EC / EMC / DMC=1:1:1, and the lithium salt (LiPF6) concentration was 1.05 mol / L.

[0214] The specific capacity of the negative electrode material was tested using a button cell battery charging and discharging device, with a 0.1C constant current charge to 10mV, then a 0.02C constant current charge to 5mV, and a 0.1C constant current discharge to 1.5V.

[0215] Half-cell 50-week cycle test: using button cell charging and discharging equipment, in the first week, discharge at 0.1C to 0.01V, then discharge at 0.01C in asymmetric decreasing order to 0.01V, then discharge at 0.01C to 0.005V, and charge at 0.1C to 1.5V; in the second week, discharge at 0.2C to 0.01V, then discharge at 0.02C in asymmetric decreasing order to 0.01V, then discharge at 0.02C to 0.005V, and charge at 0.2C to 1.5V; in the third week, discharge at 0.5C to 0.0 1V, 0.05C discharge in equal steps to 0.01V, 0.05C discharge to 0.005V, 0.5C charge to 1.5V; from the 4th to the 50th week, 1C discharge to 0.01V, 0.1C discharge in equal steps to 0.01V, 0.1C discharge to 0.005V, 1C charge to 1.5V; in the 51st week, 0.1C discharge to 0.01V, 0.01C discharge in equal steps to 0.01V, 0.01C discharge to 0.005V.

[0216] Rate test in full battery performance test: The negative electrode material is mixed with graphite to make the negative electrode material capacity reach the standard 450mAh / g. The material rate performance test is carried out at room temperature (25℃). The battery is charged and discharged at 0.5C (2.75~4.2V) to obtain the discharge capacity. The battery is then charged and discharged at 1.0C / 0.5C, 2.0C / 0.5C, and 3.0C / 0.5C to obtain the respective discharge capacities. The discharge capacity of each group is divided by the 0.5C charge and discharge capacity to obtain the rate charge capacity ratio.

[0217] Table 1 Negative electrode material performance test results

[0218] As shown in Table 1, in the negative electrode materials prepared in Examples 1 to 8, the surface of the silicon-based core has a coating layer, which can effectively isolate the exposure of the silicon-based core in the electrolyte, reduce the loss of active silicon and active lithium in the silicon-based core, and improve the cycle performance of the negative electrode material. The negative electrode material is subjected to a Zeta potential test, and the relationship between the intensities of the characteristic peaks I1, I2, and I3 satisfies 0≤I2 / I1≤2.0 and 0≤I3 / I1≤1.0. The surface of the negative electrode material has a variety of different surface combinations (that is, the surface of the negative electrode material is differentiated and diversified). The negative electrode material has good interfacial reaction, can build a high-speed mass transfer and charge transfer interface between the negative electrode material and the electrolyte, can improve the mass-charge conduction efficiency, thereby improving the rate performance of the negative electrode material, controlling the solid-liquid reaction between the surface of the negative electrode material and the electrolyte, forming a stable SEI interface, reducing the degradation of the electrolyte, and inhibiting cycle expansion, thereby improving the cycle performance of the negative electrode material.

[0219] In the negative electrode material prepared in Comparative Example 1, the negative electrode active material is not coated, resulting in serious loss of negative electrode active material during the cycle process, which greatly reduces the cycle performance of the negative electrode material; the ratios of I2 / I1 and I3 / I1 are greatly increased, so that the surface of the negative electrode material no longer has a variety of different surface combinations. During the electrochemical reaction, it is difficult to regulate the degradation reaction of the electrolyte on the single surface of the negative electrode material. The excessive degradation and deposition of the electrolyte causes the electrode to expand, which greatly increases the expansion rate of the electrode, and further leads to a significant reduction in the cycle performance of the negative electrode material; at the same time, excessive degradation of the electrolyte is not conducive to the rapid transmission of lithium ions, increases the lithium ion transmission path, and reduces the lithium ion transmission efficiency, thereby greatly reducing the rate performance of the negative electrode material.

[0220] In the negative electrode material prepared in Comparative Example 2, no solid-phase coating agent and / or liquid-phase coating agent is added to modify and dope the coating layer. The ratios of I2 / I1 and I3 / I1 in the negative electrode material increase, which reduces the rationality of the surface charge ion distribution of the negative electrode material. The surface of the negative electrode material tends to be single from diversified. It is difficult to establish fast ion electron transmission channels through the single surface composition of the negative electrode material. The ion electron transmission channels in the negative electrode material are reduced, and the ion transmission efficiency is reduced, resulting in reduced conductivity of the negative electrode material and decreased rate performance of the negative electrode material. At the same time, it is difficult to regulate the degradation reaction of the electrolyte in the electrochemical reaction through a single surface, resulting in excessive degradation of the electrolyte, causing expansion of the electrode sheet, and thus reducing the cycle performance of the negative electrode material.

[0221] 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.

Claims

1. A negative electrode material, characterized in that: The negative electrode material comprises a silicon-based core and a coating layer located on at least a portion of the surface of the silicon-based core, wherein the silicon-based core contains silicon oxide and lithium silicate, and the coating layer contains carbon material; 20 mg of the negative electrode material is dissolved in 10 ml of deionized water to form a slurry, and the slurry is subjected to a Zeta potential test using a nanoparticle size and Zeta potential analyzer. In the Zeta potential test distribution diagram of the slurry, the maximum intensity of the first characteristic peak of the slurry in the Zeta potential range of -50 mV to -40 mV is I1, the maximum intensity of the second characteristic peak in the Zeta potential range of -65 mV to -50 mV is I2, and the maximum intensity of the third characteristic peak in the Zeta potential range of -35 mV to -25 mV is I3, and the relationship between I1, I2, and I3 satisfies: 0≤I2 / I1≤2.0, 0≤I3 / I1≤1.

0.

2. The negative electrode material according to claim 1, characterized in that The carbon material includes at least one of graphite, amorphous carbon, diamond-like carbon, carbon fiber and carbide.

3. The negative electrode material according to claim 1, characterized in that The coating layer further contains at least one of nitride, metal oxide, phosphate and silicate.

4. The negative electrode material according to claim 3, characterized in that The negative electrode material includes at least one of the following features (1) to (2): (1) The nitride comprises at least one of silicon nitride, pyrrole and pyridine; (2) The metal oxide includes at least one of titanium oxide, aluminum oxide, magnesium oxide, lithium oxide, zirconium oxide, cobalt oxide and vanadium oxide.

5. The negative electrode material according to claim 3, characterized in that The negative electrode material includes at least one of the following features (1) to (2): (1) The phosphate includes at least one of lithium phosphate, aluminum phosphate, lithium aluminum phosphate, lithium titanium aluminum phosphate, magnesium phosphate, lithium magnesium phosphate, calcium phosphate, lithium calcium phosphate, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate and triammonium phosphate; (2) The silicate includes at least one of lithium silicate, magnesium silicate, aluminum silicate, magnesium aluminum silicate, lithium magnesium silicate, calcium silicate, magnesium calcium silicate, lithium calcium silicate and lithium aluminum silicate.

6. The negative electrode material according to claim 1, characterized in that At least a portion of the lithium silicate is located on the surface of the silicon oxide, and the lithium silicate on the surface of the silicon oxide is dispersedly distributed.

7. The negative electrode material according to claim 1, characterized in that Taking the mass of the negative electrode material as 100%, the mass content of the carbon material is 0.5% to 10%.

8. The negative electrode material according to claim 1, characterized in that Taking the mass of the negative electrode material as 100%, the mass content of lithium in the negative electrode material is 2% to 15%.

9. The negative electrode material according to claim 1, characterized in that The mass content of lithium in the silicon-based core is 10 3 ppm~10 5 ppm.

10. The negative electrode material according to claim 1, characterized in that The general formula of the lithium silicate is Li2O-nSiO2, wherein 0<n≤4.

11. The negative electrode material according to claim 1, characterized in that The pH value of the negative electrode material is 10.0-12.

3.

12. A method for preparing a negative electrode material, characterized in that: The following steps are involved: A coating agent and a coating gas source containing a gas phase carbon source are simultaneously used to perform vapor deposition on the surface of the silicon-based core to form a coating layer to obtain a negative electrode material, wherein the coating agent is a non-gas phase coating agent containing a benzene ring structure, and the silicon-based core includes silicon oxide and lithium silicate.

13. The preparation method according to claim 12, characterized in that: An auxiliary carrier gas is also added during the vapor deposition process.

14. The preparation method according to claim 13, characterized in that: The method comprises at least one of the following features (1) to (3): (1) The auxiliary carrier gas includes at least one of H2, CO2, NH3 and Ar; (2) The flow rate of the auxiliary carrier gas is 100 mL / min to 8000 mL / min; (3) The flow ratio of the gas-phase carbon source to the auxiliary carrier gas is (3-9.5):(0.5-7).

15. A lithium ion battery, characterized in that: The lithium-ion battery comprises the negative electrode material according to any one of claims 1 to 11 or the negative electrode material prepared by the method for preparing the negative electrode material according to any one of claims 12 to 14.

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