Negative electrode material and battery

Abstract

A negative electrode material and a battery. The negative electrode material comprises a non-carbon matrix and a silicon material, wherein at least part of the silicon material is located inside the particles of the non-carbon matrix. The negative electrode material has pores; and the total pore volume of the negative electrode material is less than or equal to 0.2 cm3 / g, and the surface density β of the negative electrode material is greater than or equal to 80%. The negative electrode material has a high surface density, and can thus reduce the dissolution of the silicon material in the negative electrode material during the cycling of a battery, thereby reducing reactions of the silicon material dissolved out of the negative electrode material with an electrolyte, and effectively reducing the gas evolution amount of the negative electrode material. Moreover, the negative electrode material has a small total pore volume and a more compact structure, and can thus reduce the penetration amount of the electrolyte that directly penetrates into the particles of the negative electrode material via a pore structure during the cycling of the battery, thereby improve the cycling performance of the negative electrode material.

Description

Negative electrode material and battery TECHNICAL FIELD

[0001] The present application relates to the technical field of negative electrode materials, and particularly relates to a negative electrode material and a battery. BACKGROUND

[0002] Lithium ion batteries have advantages of high energy density, long service life and no environmental pollution, and have been widely used in 3C fields. With the development of the market, lithium ion batteries are not only widely used in mobile devices such as smart phones and portable computers, but also applied to large equipment fields such as electric vehicles and electric tools. In order to improve the energy density of the battery, the research and development of silicon-based negative electrode materials are becoming mature. However, the volume expansion of silicon during the process of deintercalation / intercalation of lithium is as high as 420%, and the severe volume effect will cause significant degradation of its electrochemical performance, and the conductivity and liquid absorption capacity will be poor, which will easily lead to problems such as electrode polarization, material pulverization, SEI film reconstruction, low coulombic efficiency and continuous capacity decay, thereby limiting its practical application. In order to alleviate the adverse effects caused by the volume expansion of silicon materials during the charging and discharging process, the silicon material can be compounded with metal, oxide, organic polymer, carbon and other materials to improve its electrochemical stability.

[0003] The silicon-based negative electrode material includes a silicon-based active substance and a coating layer on the surface thereof, but the coating effect of the coating layer of the existing silicon-based negative electrode material is poor. During the preparation of the lithium ion battery, the dissolved silicon particles will contact with the electrolyte, resulting in the problem of gas production.

[0004] Therefore, how to reduce the reaction between the silicon particles and the electrolyte and reduce the gas production value is a problem that needs to be solved at present. SUMMARY

[0005] The negative electrode material and the battery provided by the present application can reduce the reaction between the silicon particles and the electrolyte in the negative electrode material, reduce the gas production value of the negative electrode material, and improve the cycle performance of the battery prepared by the negative electrode material.

[0006] In a first aspect, the present application provides a negative electrode material, comprising a non-carbon matrix and silicon particles, at least part of the silicon particles being located inside the particles of the non-carbon matrix; the negative electrode material has pores, the total pore volume of the negative electrode material is ≤0.2 cm 3 / g, and the surface density β of the negative electrode material is ≥80%;

[0007] The surface density β of the negative electrode material is measured by the following test method:

[0008] The negative electrode material with a mass of m1 g is soaked in a hydrofluoric acid solution with a mass fraction of 20%, and after soaking for 1 hour, m2 g of material is obtained after cleaning and drying, and the surface density β of the negative electrode material is calculated as m2 / m1*100%.

[0009] In a second aspect, the present application provides a battery comprising the negative electrode material according to the first aspect.

[0010] The technical solution of the present application has at least the following technical effects:

[0011] The negative electrode material provided by the present application comprises a non-carbon matrix and silicon particles, and at least part of the silicon particles are located inside the particles of the non-carbon matrix, so that the volume expansion of the silicon particles in the negative electrode material during the lithium intercalation and deintercalation process of the battery prepared from the negative electrode material can be alleviated. The non-carbon matrix has high strength and toughness, which can make the negative electrode material have higher compaction density, thereby improving the structural stability of the negative electrode material, and further reducing the particle breakage and pulverization of the negative electrode material. At the same time, the non-carbon matrix usually has good ionic conductivity, which can play a role similar to an artificial SEI film, can slow down the continuous generation of the solid electrolyte interface film (natural SEI film), reduce the side reaction between the negative electrode material and the electrolyte, and improve the cycle performance of the battery prepared from the negative electrode material. The surface density of the negative electrode material is ≥80%, which can reduce the dissolution of the negative electrode material during the cycle process of the battery prepared from the negative electrode material, thereby reducing the reaction between the dissolved silicon particles in the negative electrode material and the electrolyte, effectively reducing the gas production value of the negative electrode material and improving the powder conductivity of the negative electrode material. And control the total pore volume of the negative electrode material ≤0.2 cm 3 / g, in the charging and discharging process, both the space reserved for the volume expansion of the silicon particles in the negative electrode material during the lithium deintercalation process of the battery prepared from the negative electrode material and the effective reduction of the electrolyte directly penetrating into the particle interior of the negative electrode material through the pore structure can reduce the side reaction between the electrolyte and the silicon particles in the negative electrode material, thereby improving the cycle performance of the lithium ion battery. By controlling the surface density of the negative electrode material and the coordination of the pores in the negative electrode material, the volume expansion of the silicon particles in the negative electrode material during the cycle process of the battery prepared from the negative electrode material is effectively alleviated, the particle breakage of the negative electrode material is reduced, and the cycle performance of the negative electrode material is improved. DETAILED DESCRIPTION

[0012] In order to better understand the technical solutions of the present application, the embodiments of the present application are described in detail below.

[0013] It should be clear that the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0014] The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the description of the application and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0015] It should be understood that the term "and / or" used herein only means an association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " herein generally represents an "or" relationship between the front and rear associated objects.

[0016] Lithium ion batteries have the advantages of high energy density, long service life and no environmental pollution, and have been widely used in 3C fields. With the development of the market, lithium ion batteries are not only widely used in mobile devices such as smart phones and portable computers, but also applied to large equipment fields such as electric vehicles and electric tools. In order to improve the energy density of the battery, the research and development of silicon-based negative electrode materials are becoming mature. The silicon-based negative electrode material includes a silicon-based active substance and a coating layer on the surface thereof, but the existing coating layer needs to use a low-temperature carbon coating process to maintain the silicon grains at a small size. However, when the low-temperature carbon coating is performed, the carbon source cannot be completely cracked, and there are many impurities such as tar, which will affect the quality and integrity of the coating layer, resulting in poor coating effect.

[0017] Therefore, the existing silicon-carbon composite method is difficult to control the contact between the dissolved silicon particles and the electrolyte, and there is a serious problem of gas production, which is not conducive to improving the cycle performance of the negative electrode material.

[0018] In a first aspect, the application provides a negative electrode material, comprising a non-carbon matrix and a silicon material, at least part of the silicon material being located inside the particles of the non-carbon matrix; the negative electrode material has pores, the total pore volume of the negative electrode material is ≤0.2 cm 3 / g, and the surface density β of the negative electrode material is ≥80%;

[0019] The surface density β of the negative electrode material is measured by the following test method:

[0020] A negative electrode material with a mass of m1 g is soaked in a hydrofluoric acid solution with a mass fraction of 20%, and after soaking for 1 hour, m2 g of material is obtained after cleaning and drying. The surface density β of the negative electrode material is calculated as m2 / m1 x 100%.

[0021] In the above scheme, the negative electrode material comprises a non-carbon matrix and a silicon material, and at least part of the silicon material is located inside the particles of the non-carbon matrix, which can alleviate the volume expansion of the silicon material in the negative electrode material during the lithium intercalation and deintercalation process of the battery prepared from the negative electrode material. The non-carbon matrix has high strength and toughness, which can make the negative electrode material have higher compaction density, improve the structural stability of the negative electrode material, and reduce the particle breakage and pulverization of the negative electrode material. At the same time, the non-carbon matrix usually has good ionic conductivity, which can play a role similar to an artificial SEI film, can slow down the continuous generation of the solid electrolyte interface film (natural SEI film), thereby reducing the side reaction between the negative electrode material and the electrolyte, and further improving the cycle performance of the battery prepared from the negative electrode material. The surface density of the negative electrode material is ≥80%, which can reduce the dissolution of the negative electrode material during the cycle process of the battery prepared from the negative electrode material, thereby reducing the reaction between the dissolved silicon material in the negative electrode material and the electrolyte, effectively reducing the gas production value of the negative electrode material and improving the powder conductivity of the negative electrode material. And control the total pore volume of the negative electrode material ≤0.2 cm 3 / g, in the charging and discharging process, both the volume expansion of the silicon particles in the negative electrode material during the lithium deintercalation process of the battery prepared from the negative electrode material can be reserved space by the pores, and the electrolyte can be effectively reduced by the pore structure directly into the inside of the particles of the negative electrode material, thereby reducing the side reaction of the electrolyte and the silicon particles in the negative electrode material, and further improving the cycle performance of the lithium ion battery. The present application controls the surface density of the negative electrode material and the pores in the negative electrode material, effectively alleviates the volume expansion of the silicon material in the negative electrode material during the cycle process of the battery prepared from the negative electrode material, reduces the particle breakage of the negative electrode material, and improves the cycle performance of the negative electrode material.

[0022] In some embodiments, the non-carbon matrix includes at least one of a metal oxide, a silicide, a silicate, a phosphate, a titanate, and an aluminum borate. It can be appreciated that the non-carbon matrix can serve as a support framework using the above-mentioned materials, and compared with the existing conductive carbon matrix, the non-carbon matrix used in the present application has better strength and rigidity, so that the negative electrode material has a higher compaction density during the battery preparation process, which can improve the structural stability of the negative electrode material, reduce the particle breakage and pulverization of the negative electrode material, and thus be beneficial to improving the cycle performance of the negative electrode material. At the same time, the non-carbon matrix has electronic insulation and thus has good ionic conductivity, which can play a role similar to an artificial SEI film, can slow down the generation of a subsequent natural SEI film, thereby reducing the direct contact between the negative electrode material and the electrolyte, and thus reducing the occurrence of side reactions. In addition, the non-carbon matrix has a lower cost advantage compared with the carbon matrix. Due to the complexity of the activation and pore-forming process, the energy consumption and environmental cost involved in the existing carbon matrix are relatively high. If a porous ceramic or other material naturally having a porous pore is used, the complex pore-forming process is omitted, so that the cost can be reduced to 10% or even lower than the cost of the porous carbon matrix.

[0023] It can be appreciated that the non-carbon matrix of the present application is relative to the carbon matrix, which includes one or more of artificial graphite, natural graphite, amorphous carbon, activated carbon, mesocarbon microbeads, carbon nanotubes, carbon nanofibers, and graphene. The non-carbon matrix excludes the above substances.

[0024] In some embodiments, the non-carbon matrix includes a metal oxide, and the metal oxide includes at least one of aluminum oxide, zirconium oxide, germanium dioxide, and manganese dioxide.

[0025] In some embodiments, the non-carbon matrix includes a silicide, and the silicide includes at least one of silicon carbide and silicon nitride.

[0026] In some embodiments, the non-carbon matrix includes a silicate, and the silicate includes at least one of cordierite, mullite, and zeolite. It can be appreciated that the silicate of the present application is mainly a natural silicate mineral, wherein the cordierite (magnesium aluminum silicate) has a chemical formula of Mg2Al4Si5O 18 , which can contain Na, K, Ca, Fe, Mn, and H2O; mullite has a chemical formula of 3Al2O3-2SiO2; and the zeolite (aluminosilicate) has a chemical formula of A m B p O2p.nH2O, wherein A represents a cation, which usually includes Ca, Na, K, Ba, Sr, and other monovalent or divalent metal ions, B represents a basic unit constituting the zeolite framework structure, i.e., Si and Al atoms, p is the valence of the cation, m is the number of cations A, and n is the number of water molecules.

[0027] In some embodiments, the non-carbon matrix comprises a phosphate, the phosphate comprising at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, titanium phosphate, chromium phosphate, cobalt phosphate, nickel phosphate, germanium phosphate, zirconium phosphate, niobium phosphate, molybdenum phosphate, tantalum phosphate, tungsten phosphate, and lanthanum phosphate.

[0028] In some embodiments, the non-carbon matrix comprises a titanate, the titanate comprising at least one of calcium titanate, iron titanate, lithium titanate, and barium titanate.

[0029] In some embodiments, the silicon material comprises silicon particles.

[0030] In some embodiments, the silicon material comprises at least one of silicon element, silicon oxide, and silicon alloy, etc. The type of the non-carbon matrix and the silicon material can be selected according to actual needs, which is not limited herein.

[0031] In some embodiments, the silicon material comprises silicon element, the silicon element comprising one or more of amorphous silicon, crystalline silicon, and a composite of the amorphous silicon and the crystalline silicon. Preferably, the silicon material comprises amorphous silicon, which isotropically expands during lithium intercalation, can reduce the collapse of the pore structure, inhibit the rapid capacity decay of the battery prepared by the negative electrode material, and improve the lithium intercalation cycle performance of the battery prepared by the negative electrode material.

[0032] In some embodiments, the silicon material comprises silicon oxide, the silicon oxide comprising silicon oxide SiO x , wherein 0 , the silicon oxide being a silicon-oxygen composite containing oxygen atoms and silicon atoms, the molar ratio of the oxygen atoms to the silicon atoms being 0 to 2 and not including 0. It can be a substance composed of two or more of Si, SiO 0.2 , SiO 0.5 , SiO 0.8 , SiO, SiO 1.2 , SiO 1.5 , SiO 1.8 , or SiO2, etc., or a compound with the chemical formula of SiO x , and of course, other values within the above range are also possible, which are not limited herein.

[0033] In some embodiments, the silicon material comprises silicon alloy, the silicon alloy can be silicon-lithium alloy, silicon-magnesium alloy, etc. It should be noted that in some cases, the silicon alloy comprises silicon element particles and alloy.

[0034] In some embodiments, the silicon material further comprises silicon particles and a silicon oxide layer on the surface of the silicon particles. The silicon oxide layer comprises silicon oxide with the general formula of SiO x , wherein 0.5 x , and oxygen < 2. Specifically, the SiO0.5 SiO 0.7 SiO 0.9 SiO, SiO 1.2 SiO 1.5 SiO 1.8 SiO 1.9 etc., without limitation.

[0035] In some embodiments, the silicon material further comprises silicon particles and a silicon oxide layer on the surface of the silicon particles. The mass percentage of oxygen atoms in the silicon material is 1% to 18% based on the mass of the silicon material. Specifically, the mass percentage of oxygen atoms in the silicon material can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or any value within the range between any two of the above values. Controlling the mass percentage of oxygen atoms 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 particles and the electrolyte and improving the cycle stability of the negative electrode material. It can also maintain the stability of the silicon particles and improve the specific capacity of the negative electrode material.

[0036] In some embodiments, the average particle size of the silicon material particles is 0.01 nm to 50 nm. Alternatively, the average particle size of the silicon material particles can be 0.01 nm, 0.05 nm, 0.1 nm, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm or 50 nm, etc., or other values within the range, which can be selected according to actual needs, without limitation. The mechanical stress of the silicon material during expansion decreases as the particle size decreases, and the electron and ion transport paths can be shortened after the size is reduced. At the same time, the particle size of the silicon material is reduced, and the gap between adjacent silicon material particles is increased, which can provide space for expansion. It can be understood that the average particle size of the silicon material particles within the above range can ensure the battery capacity of the lithium ion battery and reduce irreversible capacity loss. Preferably, the average particle size of the silicon material particles is 0.05 nm to 5 nm, and more preferably, the average particle size of the silicon material particles is 0.1 nm to 3 nm.

[0037] In some embodiments, the morphology of the silicon material particles includes at least one of a point shape, a spherical shape, an ellipsoidal shape, and a sheet shape, which can be selected according to actual needs, without limitation.

[0038] In some embodiments, the purity of the silicon material is greater than 99%. It can be understood that high-purity silicon material is conducive to Li-Si alloying with lithium and improves the cycle performance of the lithium ion battery.

[0039] In some embodiments, the negative electrode material after removal of the silicon material has pores, including micropores, mesopores, and macropores.

[0040] In some embodiments, the total pore volume of the negative electrode material after removal of the silicon material is 0.3 cm 3 / g to 2 cm 3 / g, specifically 0.3 cm 3 / g, 0.5 cm 3 / g, 0.8 cm 3 / g, 1 cm 3 / g, 1.5 cm 3 / g, 1.8 cm 3 / g, or 2 cm 3 / g, etc., and of course other values within the above ranges are also possible and are not limited herein. Understandably, the negative electrode material after removal of the silicon material has abundant pores that can accommodate the silicon particles and reserve space for the volume expansion of the silicon material. Preferably, the total pore volume of the negative electrode material after removal of the silicon material is 0.5 cm 3 / g to 1.4 cm 3 / g. In the present application, the total pore volume of the negative electrode material containing the silicon material is substantially reduced compared to the negative electrode material after removal of the silicon material, because the silicon material can relatively uniformly fill in the pores of the non-carbon matrix, so that most of the pores of the non-carbon matrix are reduced in pore volume after filling with the silicon material, thereby indicating that the pores of the non-carbon matrix are effectively and relatively uniformly filled with the silicon material, so as to improve the specific capacity of the negative electrode material.

[0041] In some embodiments, the total pore volume of the negative electrode material is ≤ 0.2 cm 3 / g, specifically 0.001 cm 3 / g, 0.002 cm 3 / g, 0.005 cm 3 / g, 0.008 cm 3 / g, 0.01 cm 3 / g, 0.03 cm 3 / g, 0.05 cm 3 / g, 0.08 cm 3 / g, 0.1 cm 3 / g, 0.11 cm 3 / g, 0.15 cm 3 / g, 0.18 cm 3 / g, or 0.2 cm 3etc., and of course can also be other values within the above range, which are not limited herein. After filling the silicon particles, the remaining pores can reserve space for the volume expansion of the silicon particles, alleviate the expansion effect of the negative electrode material, improve the cycle stability of the negative electrode material, and also can adsorb or accommodate a small amount of gas generated by the side reaction of the silicon particles and the electrolyte, and improve the gas generation phenomenon of the negative electrode material.

[0042] In some embodiments, the specific surface area of the negative electrode material after removing the silicon material is 10 m 2 / g to 2500 m 2 / g, specifically can be 10 m 2 , 20 m 2 / g, 50 m 2 / g, 100 m 2 / g, 500 m 2 / g, 1000 m 2 / g, 1500 m 2 / g, 2000 m 2 / g or 2500 m 2 / g, etc., and of course can also be other values within the above range, which are not limited herein. Preferably, the specific surface area of the negative electrode material after removing the silicon material is 1300 m 2 / g to 2200 m 2 / g.

[0043] In some embodiments, the average pore size of all pores in the negative electrode material after removing the silicon material is 0.1 nm to 100 nm, specifically can be 0.1 nm, 0.5 nm, 1 nm, 5 nm, 10 nm, 20 nm, 50 nm, 80 nm or 100 nm, etc., and of course can also be other values within the above range, which are not limited herein.

[0044] In some embodiments, 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, conductive polymer, fluoride and nitride. It can be understood that the coating layer on the surface of the negative electrode material has good conductivity, which can improve the electrical conductivity of the negative electrode material; at the same time, the coating layer can also reduce the exposure oxidation of the silicon particles in the negative electrode material during storage, reduce the direct contact of the silicon particles with the electrolyte, ensure the stability of the SEI film, and thus improve the specific capacity and initial efficiency of the negative electrode material.

[0045] In some embodiments, the material of the coating layer includes conductive polymer, and the conductive polymer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, poly-3-hexylthiophene, poly-p-phenylstyrene, polypyridine and polyphenylvinyl.

[0046] In some embodiments, the material of the coating layer includes fluoride, and the fluoride includes at least one of polyvinyl fluoride, fluoropolymer, lithium fluoride, sodium fluoride, potassium fluoride, fluorocarbon polymer, fluorosilicon polymer, hexafluorobutyl acrylate, polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, perfluoroalkoxy resin, polychlorotrifluoroethylene, ethylene-chlorotrifluoroethylene copolymer, polyvinylidene fluoride, and polyvinyl fluoride.

[0047] In some embodiments, the material of the coating layer includes nitride, and the nitride includes at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride.

[0048] In some embodiments, the material of the coating layer includes carbon material, and the carbon material includes at least one of amorphous carbon and graphitized carbon.

[0049] In some embodiments, the material of the coating layer includes carbon material, and the mass content of carbon element in the negative electrode material is 0.5% to 10%.

[0050] In actual application, the material of the coating layer can be selected according to actual needs, which is not limited herein. The coating layer can be a single-layer coating layer formed by a single material, a coating layer formed by a combination of multiple materials, a multi-layer coating layer formed by a single material, or a multi-layer coating layer formed by multiple materials, and the like. For example, the coating layer can be carbon-coated and then polymer-coated, or carbon-coated and then high-molecular-coated, or polymer-coated and then oxide-coated, and the like. The layer structure of the coating layer can be selected according to actual needs, which is not limited herein. It can be understood that the coating layer has a higher density when it is a multi-layer coating structure.

[0051] In some embodiments, the thickness of the coating layer is 1 nm to 300 nm. Optionally, the thickness of the coating layer can be 1 nm, 50 nm, 150 nm, 200 nm, 250 nm, 300 nm, or other values within the range, which can be selected according to actual needs, which is not limited herein. It can be understood that the coating layer can reduce the solubility of the negative electrode material, and thus reduce the amount of gas generated by the reaction between the dissolved silicon particles in the negative electrode material and the electrolyte. Controlling the thickness of the coating layer in the negative electrode material within the above range is beneficial to maintaining the stability of the particle structure of the negative electrode material during the cycle process, reducing the exposed Si on the surface of the negative electrode material, reducing the large amount of SEI generated during the charge and discharge process due to the exposed Si, and improving the specific capacity and electrochemical performance of the negative electrode material. Preferably, the thickness of the coating layer is 2 nm to 200 nm, and more preferably, the thickness of the coating layer is 5 nm to 100 nm.

[0052] In some embodiments, the mass percentage of the coating layer in the negative electrode material is ≤10%, specifically, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1%, or other values within the above range, which is not limited herein. It can be understood that the coating layer can reduce the solubility of the negative electrode material, thereby reducing the amount of gas generated by the reaction of the dissolved silicon particles with the electrolyte. The mass percentage of the coating layer in the negative electrode material within the above range can ensure the lithium intercalation capacity of the negative electrode material, thereby ensuring the charge and discharge capacity of the lithium ion battery prepared from the negative electrode material.

[0053] In some embodiments, the volume median particle size Dv50 of the negative electrode material is 0.3 μm to 50 μm, specifically, 0.3 μm, 1 μm, 5 μm, 8 μm, 10 μm, 15 μm, 25 μm, 30 μm, 40 μm, 45 μm, or 50 μm, or other values within the above range, which is not limited herein. It can be understood that the volume median particle size of the negative electrode material within the above range is beneficial to the improvement of the cycle performance of the negative electrode material. In some preferred embodiments, the volume median particle size Dv50 of the negative electrode material is 5 μm to 20 μm.

[0054] In some embodiments, the particle size distribution of the negative electrode material satisfies the following relationship: 0.9 ≤ (Dv90-Dv10) / Dv50 ≤ 5, specifically, 0.9, 1, 1.2, 1.5, 2, 2.6, 3, 3.5, 4, 4.3, 4.6, 4.8, or 5, or other values within the above range, which is not limited herein. It indicates that the particle size distribution of the negative electrode material particles is relatively uniform. Such uniform particle size distribution is helpful to improve the electrochemical performance of the negative electrode material, because the material with uniform particle size has more uniform stress distribution during the charge and discharge process, thereby reducing the risk of particle breakage and being beneficial to improve the cycle stability of the battery. If (Dv90-Dv10) / Dv50 is too small, it indicates that there are too many small particles in the negative electrode material, which may lead to too large specific surface area of the negative electrode material, increase the side reaction, and be not beneficial to the electrochemical performance of the negative electrode material. If (Dv90-Dv10) / Dv50 is too large, it indicates that there are too many large particles in the negative electrode material, which may affect the conductivity of the negative electrode material and lead to the increase of the secondary expansion rate of the negative electrode material.

[0055] It should be noted that the volume-based cumulative particle size distribution Dv10 measured by the laser diffraction method indicates the particle size corresponding to the cumulative particle size distribution volume percentage of 10%, Dv50 indicates the particle size corresponding to the cumulative particle size distribution volume percentage of 50%, and Dv90 indicates the particle size corresponding to the cumulative particle size distribution volume percentage of 90%.

[0056] In some embodiments, the specific surface area of the negative electrode material is 0.5 m 2 / g~10m 2 / g, specifically 0.5m 2 / g, 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 or 10m 2 / g, etc., and of course can also be other values within the above range, which are not limited herein. It can be understood that the specific surface area of the negative electrode material will affect the contact area between the negative electrode material and the electrolyte. The specific surface area of the negative electrode material within the above range can reduce the amount of lithium ions consumed by the SEI film formed during the first charge and discharge process of the lithium ion battery, thereby reducing the irreversible capacity loss of the lithium ion battery. A too small specific surface area means that the contact area between the negative electrode material and the electrolyte is insufficient, which can lead to a decrease in the transmission efficiency of lithium ions and a low reaction activity, resulting in poor rate performance. A too large specific surface area will result in a large increase in irreversible capacity, affecting the efficiency (first coulombic efficiency, referred to as "first efficiency") of the battery prepared by the negative electrode material during the first charge and discharge process, resulting in a decrease in the first efficiency.

[0057] In some embodiments, the mass content of silicon in the negative electrode material is 20%~55%, specifically 20%, 25%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50% or 55%, etc., and of course can also be other values within the above range, which are not limited herein. It can be understood that the mass content of silicon within this range can ensure high capacity of the battery prepared by the negative electrode material while controlling the volume change of the material, thereby obtaining stable cycle performance. If the mass content of silicon in the negative electrode material is too low, the high capacity advantage of silicon material cannot be fully utilized. If the mass content of silicon is too high, it will cause excessive volume expansion of the negative electrode material during the cycle process, affecting the stability and reversible charge and discharge performance of the battery.

[0058] Preferably, the mass content of silicon in the negative electrode material is 45%~55%.

[0059] In some embodiments, the mass content of carbon in the negative electrode material is 0~10%, specifically 0, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., and of course can also be other values within the above range, which are not limited herein. It can be understood that the carbon element in the negative electrode material mainly comes from the carbon coating layer.

[0060] In some embodiments, the coating layer comprises a carbon material, and the mass content of carbon element in the negative electrode material is 0.5% to 10%, specifically, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, or other values within the above range, which are not limited herein. If the mass content of carbon element in the negative electrode material is too large, the coating layer formed on the surface of the negative electrode material is too thick, which is not conducive to the improvement of the specific capacity and electrochemical performance of the negative electrode material. If the mass content of carbon element in the negative electrode material is too small, the integrity of the coating layer on the surface of the negative electrode material is poor, which is not conducive to the formation of the negative electrode material with high surface density on the surface of the composite.

[0061] In some embodiments, the average pore size of the negative electrode material is 0.2 nm to 100 nm, specifically, 0.2 nm, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm, or other values within the above range, which are not limited herein. It can be understood that the average pore size of the negative electrode material is related to its surface density. Generally, the lower the surface density, the more micropores on the surface of the negative electrode material, which leads to a decrease in the average pore size. The average pore size of the negative electrode material within the above range indicates that the negative electrode material has a high surface density, which is conducive to reducing the reaction between the dissolved silicon particles and the electrolyte and reducing the gas production value.

[0062] In some embodiments, the negative electrode material of the present application can be subjected to density test. The test principle is as follows: m1 g of negative electrode material is immersed in a 20% mass fraction hydrofluoric acid solution, after immersion for 1 hour, m2 g of material is obtained after cleaning and drying, and the surface density β of the negative electrode material is calculated as m2 / m1 x 100%. In an ideal state, if the density of the coating layer is 100%, the negative electrode material will not dissolve due to the isolation effect of the coating layer, and thus there is no dissolved silicon material in the negative electrode material to react with the solution. However, the coating layer prepared by conventional methods is in a non-ideal state, which makes the negative electrode material have a certain amount of dissolution in the solution, so that the solution contains dissolved silicon material. At this time, the surface density of the negative electrode material can be defined by the amount of dissolved silicon material, i.e., the surface density β = m2 / m1 x 100%.

[0063] Through the above test, the surface density β of the negative electrode material of the present application is ≥80%, and within this range, the high surface density characteristics of the negative electrode material can effectively inhibit the direct contact between the silicon material in the negative electrode material and the water in the slurry, reduce the occurrence of side reactions between the negative electrode material and the aqueous solution in the slurry, and reduce the gas production value of the negative electrode material. In addition, the negative electrode material can also reduce the dissolution amount of the silicon material in the negative electrode material during the charge and discharge cycle, thereby reducing the side reaction between the dissolved silicon material in the negative electrode material and the electrolyte, and also effectively reducing the gas production value of the negative electrode material.

[0064] In some embodiments, the gas production value of the negative electrode material is ≤1 mL / g at room temperature for 24 hours, which can be 1 mL / g, 0.9 mL / g, 0.8 mL / g, 0.7 mL / g, 0.6 mL / g, 0.5 mL / g, 0.4 mL / g, 0.3 mL / g, 0.2 mL / g, 0.1 mL / g or 0.05 mL / g, etc., and of course it can also be other values within the above range, which is not limited herein. The gas production value of the negative electrode material of the present application is controlled within the above range, which shows that the negative electrode material has a high surface density, the coating layer on the surface of the negative electrode material has a high density, the coating effect is good, and thus the direct contact between the silicon material in the negative electrode material and the electrolyte can be effectively reduced, the side reaction between the dissolved silicon material in the negative electrode material and the electrolyte can be reduced, and the gas production value of the negative electrode material can also be effectively reduced.

[0065] In some embodiments, the powder conductivity of the negative electrode material under a pressure of 20 kN is 0.2 S / cm-2 S / cm, which can be 0.2 S / cm, 0.5 S / cm, 0.8 S / cm, 1.0 S / cm, 1.1 S / cm, 1.2 S / cm, 1.5 S / cm, 1.6 S / cm, 1.8 S / cm or 2 S / cm, etc., and of course it can also be other values within the above range, which is not limited herein. It can be understood that the powder conductivity of the negative electrode material is controlled within the above range, which can realize a more complete and effective conductive network, which is conducive to the electron transfer during the charge and discharge process, thereby reducing the polarization of the negative electrode material and improving the cycle stability of the negative electrode material.

[0066] In some embodiments, the tap density of the negative electrode material is 0.5 g / cm 3 -1.5 g / cm 3 , which can be 0.5 g / cm 3 , 0.6 g / cm 3 , 0.8 g / cm 3 , 1.0 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 or 1.5 g / cm 3and other values within the above range, which are not limited herein.

[0067] In a second aspect, the application provides a preparation method of the negative electrode material, comprising the following steps:

[0068] In step S10, a composite containing a non-carbon matrix and a silicon material is prepared, and the composite contains a catalyst.

[0069] In step S20, the composite is coated with a coating material to obtain the negative electrode material; wherein the surface density β of the negative electrode material is greater than or equal to 80%.

[0070] In the above scheme, the composite contains a catalyst, and in the coating process, the catalyst promotes the coating material to coat the surface of the composite to obtain a negative electrode material with high surface density. The problem that the low-temperature carbon coating process in the prior art cannot completely crack the carbon source and thus contains a large amount of impurities such as tar, which affects the quality and integrity of the coating layer and thus cannot guarantee the good coating effect of the coating layer, can be solved. The surface density of the prepared negative electrode material is greater than or equal to 80%, which can reduce the dissolution of the negative electrode material in the cycle process, thereby reducing the reaction between the dissolved silicon material and the electrolyte, effectively reducing the gas production value of the negative electrode material, effectively reducing the direct penetration of the electrolyte into the interior of the negative electrode material particles through the pore structure, reducing the side reaction caused by the contact between the electrolyte and the silicon material, and thus improving the cycle performance of the lithium ion battery.

[0071] The preparation method of the application is specifically described below in combination with examples:

[0072] In step S10, the specific steps of preparing the composite containing the non-carbon matrix and the silicon material include: immersing the non-carbon matrix in a solution containing a catalyst, and depositing silicon particles on the product after solid-liquid separation to obtain the composite.

[0073] In some embodiments, the non-carbon matrix is immersed in a solution containing a catalyst to allow the catalyst to adhere to the surface or interior of the non-carbon matrix. The solution of the catalyst is a salt solution containing at least one of Cu, Ni, Co, Fe, and B. It can be understood that the catalyst contains the above elements, which can reduce the temperature in the coating process and achieve a negative electrode material with high surface density at a lower coating temperature.

[0074] In some embodiments, the infiltrating temperature is 70-220°C, and can be specifically 70°C, 80°C, 100°C, 120°C, 150°C, 160°C, 180°C, 200°C or 220°C, and can also be other values within the above range, which are not limited herein. It can be understood that if the infiltrating temperature is too high, the catalyst particles attached to the surface or inside of the non-carbon matrix are more, and the free catalyst particles on the non-carbon matrix are also more, so that although the obtained negative electrode material has a higher surface density, it can lead to the formation of an over-thick coating layer on the surface of the negative electrode material, thereby being not conducive to the improvement of the specific capacity and electrochemical performance of the negative electrode material. If the infiltrating temperature is too low, the catalyst particles adsorbed on the surface of the non-carbon matrix are less, which can lead to poor integrity of the coating layer on the surface of the negative electrode material, thereby being not conducive to the formation of a negative electrode material with high surface density on the surface of the composite.

[0075] In some embodiments, the mass ratio of the catalyst to the non-carbon matrix is 0.01%-5%, and can be specifically 0.01%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 4.5% or 5%, and can also be other values within the above range, which are not limited herein. It can be understood that if the mass of the catalyst is too small, the coating material is difficult to completely coat on the surface of the composite, thereby leading to poor integrity of the coating layer on the surface of the negative electrode material, and being not conducive to the formation of a negative electrode material with high surface density on the surface of the composite; if the mass of the catalyst is too large, it can lead to the formation of an over-thick coating layer on the surface of the composite, and due to the excessive catalyst, the adsorption force of the non-carbon matrix to the catalyst particles is not enough, thereby possibly leading to the falling off of the physically adsorbed catalyst particles in some areas of the non-carbon matrix, and further leading to poor coating integrity.

[0076] In some embodiments, the non-carbon matrix has pores, and the pores include at least one of micropores, mesopores and macropores.

[0077] In some embodiments, the total pore volume of all pores in the non-carbon matrix is 0.3cm 3 / g-2cm 3 / g, and can be specifically 0.3cm 3 / g, 0.5cm 3 / g, 0.8cm 3 / g, 1.0cm 3 / g, 1.2cm 3 / g, 1.5cm 3 / g or 2cm 3 / g, and can also be other values within the above range, which are not limited herein. It can be understood that the non-carbon matrix has abundant pores, which can accommodate silicon particles and reserve space for the volume expansion of the silicon particles. Preferably, the total pore volume of all pores in the non-carbon matrix is 0.5cm 3 / g~1.4cm 3 / g.

[0078] In some embodiments, the non-carbon matrix has a specific surface area of 10m 2 / g~2500m 2 / g, specifically 10m 2 / g, 50m 2 / g, 100m 2 / g, 500m 2 / g, 1000m 2 / g, 1500m 2 / g, 2000m 2 / g, or 2500m 2 / g, etc., and of course can also be other values within the above range, which are not limited herein. Preferably, the non-carbon matrix has a specific surface area of 1300m 2 / g~2200m 2 / g.

[0079] In some embodiments, the average pore size of all pores in the non-carbon matrix is 0.1nm~100nm, specifically 0.1nm, 1nm, 5nm, 10nm, 20nm, 50nm, 60nm, 80nm, or 100nm, etc., and of course can also be other values within the above range, which are not limited herein.

[0080] In some embodiments, the infiltration time is 10min~1000min, and optionally, the infiltration time specifically can be 10min, 50min, 180min, 240min, 400min, 520min, 600min, 800min, 900min, or 1000min, etc., and can also be other values within the range, which can be selected according to actual needs, and are not limited herein. It can be understood that the infiltration time within the above range can improve the adhesion amount of the catalyst, and is helpful to form the negative electrode material with high surface density on the surface of the composite.

[0081] In some embodiments, the product after solid-liquid separation is further vacuum dried, or the product is directly vacuum dried to remove the solvent to achieve the purpose of solid-liquid separation.

[0082] In some embodiments, the non-carbon matrix includes at least one of a metal oxide, a silicide, a silicate, a phosphate, a titanate, and an aluminum borate. It can be understood that the non-carbon matrix can play a role of supporting the framework by using the above-mentioned materials, and compared with the existing conductive carbon matrix, the non-carbon matrix used in the present application has better strength and rigidity, so that the negative electrode material has a higher compaction density in the battery preparation process, thereby improving the structural stability of the negative electrode material, and further reducing the particle breakage and pulverization of the negative electrode material, which is beneficial to improving the cycle performance of the negative electrode material. At the same time, the non-carbon matrix has good ionic conductivity due to its electronic insulation, and can play a role similar to the artificial SEI film, which can slow down the generation of the subsequent natural SEI film, thereby reducing the direct contact between the negative electrode material and the electrolyte, and further reducing the occurrence of side reactions. In addition, the non-carbon matrix has a lower cost advantage compared with the carbon matrix. Due to the complexity of the activation and pore forming process of the existing carbon matrix, the energy consumption and environmental cost involved are relatively high. If a porous ceramic or other material naturally having porous pores is used, the complex pore forming process is omitted, so that the cost can be reduced to 10% or even lower than the cost of porous carbon.

[0083] In some embodiments, the non-carbon matrix includes a metal oxide, and the metal oxide includes at least one of aluminum oxide, zirconium oxide, germanium dioxide, and manganese dioxide.

[0084] In some embodiments, the non-carbon matrix includes a silicide, and the silicide includes at least one of silicon carbide and silicon nitride.

[0085] In some embodiments, the non-carbon matrix includes a silicate, and the silicate includes at least one of cordierite, mullite, and zeolite. It can be understood that the silicate of the present application is mainly a natural silicate mineral, wherein the cordierite (magnesium aluminum silicate) has a chemical formula of Mg2Al4Si5O 18 , which can contain Na, K, Ca, Fe, Mn, and H2O; mullite has a chemical formula of 3Al2O3-2SiO2; and zeolite (aluminosilicate) has a chemical formula of A m B p O2p·nH2O, wherein A represents a cation, which usually includes Ca, Na, K, Ba, Sr, and other monovalent or divalent metal ions, B represents a basic unit constituting the zeolite framework structure, i.e., Si and Al atoms, p is the valence of the cation, m is the number of cations A, and n is the number of water molecules.

[0086] In some embodiments, the non-carbon matrix includes a phosphate, and the phosphate includes at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, titanium phosphate, chromium phosphate, cobalt phosphate, nickel phosphate, germanium phosphate, zirconium phosphate, niobium phosphate, molybdenum phosphate, tantalum phosphate, tungsten phosphate, and lanthanum phosphate.

[0087] In some embodiments, the non-carbon matrix includes a titanate, which includes at least one of calcium titanate, iron titanate, lithium titanate, and barium titanate.

[0088] In some embodiments, the silicon material includes at least one of crystalline silicon, silicon oxide, amorphous silicon, silicon alloy, and a composite particle of crystalline silicon and amorphous silicon. The type of carbon matrix and silicon material can be selected as desired, and is not limited herein.

[0089] In some embodiments, the silicon oxide includes silicon and oxygen elements, and the atomic ratio of the silicon and oxygen elements is 0-2:1, and does not include 0:1. The atomic ratio of the silicon and oxygen elements can be specifically 0.05:1, 0.11:1, 0.21:1, 0.26:1, 0.31:1, 0.41:1, 0.51:1, 0.59:1, 0.61:1, 0.69:1, 0.71:1, 0.74:1, 0.76:1, 0.79:1, 0.89:1, 0.99:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2:1, and the like, and is not limited herein. Preferably, the atomic ratio of the silicon and oxygen elements is 0-1:1, and does not include 0:1.

[0090] In some embodiments, the silicon oxide has a general chemical formula of SiOx x wherein 0

[0091] In some embodiments, the average particle size of the silicon material particles is 0.01 nm-50 nm. Alternatively, the average particle size of the silicon material particles can be specifically 0.01 nm, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, or 50 nm, and the like, or other values within the range, which can be selected as desired, and is not limited herein. The mechanical stress of the silicon material during expansion decreases as the particle size decreases, and the electronic and ionic transport paths can be shortened after the size is reduced. In addition, the size of the silicon material particles is reduced, and the gap between adjacent silicon material particles is increased, which can reserve space for expansion. It can be understood that the average particle size of the silicon material particles within the above range can ensure the battery capacity of the lithium ion battery, and reduce the irreversible capacity loss. Preferably, the average particle size of the silicon material particles is 0.05 nm-5 nm, and more preferably, the average particle size of the silicon material particles is 0.1 nm-3 nm.

[0092] In some embodiments, the morphology of the silicon material particles includes at least one of a point, a sphere, an ellipsoid, and a sheet, and the morphology of the silicon material particles can be selected as required.

[0093] In some embodiments, the purity of the silicon material particles is greater than 99%, and it can be understood that high-purity silicon material particles are beneficial to Li-Si alloying with lithium and improve the cycle performance of lithium ion batteries.

[0094] In some embodiments, the silicon material particles are deposited by gas-phase chemical deposition, and the step includes: introducing a silicon-containing gas source into a non-carbon substrate to perform a gas-phase chemical deposition reaction.

[0095] In some embodiments, the silicon-containing gas source includes at least one of silane, disilane, trisilane, and tetrasilane, and can be selected as required.

[0096] In an embodiment, the introduced gas includes the silicon-containing gas source and an auxiliary carrier gas, the auxiliary carrier gas can dilute the silicon-containing gas source and help control the residence time of the silicon-containing gas source. The auxiliary carrier gas includes at least one of nitrogen, argon, and helium.

[0097] In some embodiments, the gas flow ratio of the silicon-containing gas source to the auxiliary carrier gas is 1:(0.1-10), and can be 1:0.1, 1:1, 1:2, 1:3, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10, etc., or other values within the range, and can be selected within the above range as required.

[0098] In some embodiments, the concentration of the silicon-containing gas source is 10%-80%, and the concentration of the silicon-containing gas source can be 10%, 13%, 18%, 26%, 35%, 43%, 55%, 68%, 74%, or 80%, etc., or other values within the range, and can be selected within the above range as required, and is not limited herein.

[0099] In some embodiments, the temperature of the gas-phase chemical deposition reaction is 400°C-600°C, and the temperature can be 400°C, 420°C, 450°C, 480°C, 500°C, 550°C, or 600°C, etc., or other values within the range, and can be selected within the above range as required, and is not limited herein. Preferably, the temperature of the gas-phase chemical deposition reaction is 450°C-550°C.

[0100] In some embodiments, the holding time of the gas phase chemical deposition reaction is 1h-20h, and can be 1h, 3h, 4h, 6h, 7h, 8h, 10h, 12h, 15h, 18h or 20h, or other values within the range, which can be selected according to actual needs, and is not limited herein. Preferably, the holding time of the gas phase chemical deposition reaction is 2h-10h.

[0101] By controlling the reaction parameters of the gas phase chemical deposition, the gas phase silicon source can penetrate into the non-carbon matrix and decompose in the pores of the non-carbon matrix to form silicon particles with appropriate particle size.

[0102] In step S20, the composite is coated with the coating material to obtain the negative electrode material; wherein the surface density β of the negative electrode material is ≥80%.

[0103] In step S20, the specific steps of coating the composite with the coating material include: uniformly mixing the composite with the coating material and then performing heat treatment.

[0104] In some embodiments, the coating material includes at least one of carbon material, conductive polymer, fluoride and nitride.

[0105] In some embodiments, the thickness of the coating layer formed by the coating material is 1nm-300nm, and can be 1nm, 50nm, 150nm, 200nm, 250nm or 300nm, or other values within the range, which can be selected according to actual needs, and is not limited herein. It can be understood that the coating layer can reduce the solubility of the negative electrode material, and in turn reduce the gas production amount of the dissolved silicon particles reacting with the electrolyte. Controlling the thickness of the coating layer within the above range is beneficial to maintaining the stability of the particle structure of the negative electrode material during the cycle process, can reduce the exposed Si on the surface of the negative electrode material, reduce the large amount of SEI generated in the charging and discharging process due to the exposed Si, and improve the specific capacity and electrochemical performance of the negative electrode material. Preferably, the thickness of the coating layer is 2nm-200nm, and more preferably, the thickness of the coating layer is 5nm-100nm.

[0106] In some embodiments, the mass fraction of the coating layer formed by the coating material in the negative electrode material is ≤10%, and can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1%, or other values within the range, which is not limited herein. It can be understood that the coating layer can reduce the solubility of the negative electrode material, and in turn reduce the gas production amount of the dissolved silicon particles reacting with the electrolyte. The mass fraction of the coating layer in the negative electrode material within the above range can ensure the lithium intercalation amount of the negative electrode material, and in turn ensure the charging and discharging capacity of the lithium ion battery prepared from the negative electrode material.

[0107] In some embodiments, the coating material includes a carbon material, the carbon material including at least one of amorphous carbon and graphitized carbon.

[0108] In some embodiments, the coating material includes a conductive polymer, the conductive polymer including at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, poly(3-hexylthiophene), poly(p-phenylene vinylene), polypyridine, and polyphenylene vinylene.

[0109] In some embodiments, the coating material includes a fluoride, the fluoride including at least one of fluoroethylene, fluoropolymer, lithium fluoride, sodium fluoride, potassium fluoride, fluorocarbon polymer, fluorosilicon polymer, hexafluorobutyl acrylate, polytetrafluoroethylene (PTFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride.

[0110] In some embodiments, the coating material includes a nitride, the nitride including at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride.

[0111] In some embodiments, the mass ratio of the composite to the coating material is 100:(1-75), and the mass ratio can be specifically 100:1, 100:10, 100:20, 100:40, 100:60, 100:70, or 100:75, or other values within the range, which can be selected according to actual needs, and is not limited herein.

[0112] In some embodiments, the temperature of the heat treatment is 200-600°C, and the holding time of the heat treatment is 0.5-20h, and the temperature can be specifically 200°C, 300°C, 400°C, 500°C, or 600°C, and the time can be specifically 0.5h, 1h, 3h, 5h, 6h, 8h, 10h, 11h, 12h, 15h, 18h, or 20h, or other values within the range, which can be selected according to actual needs, and is not limited herein.

[0113] In some embodiments, the heat treatment is performed under a protective gas, and the protective gas includes at least one of nitrogen, helium, neon, argon, and krypton, which can be selected according to actual needs, and is not limited herein.

[0114] In the above technical solution, the surface of the composite is coated to form a coating layer, which can reduce the entry of electrolyte into the interior of the negative electrode material to cause side reactions, thereby reducing the initial coulombic efficiency and specific capacity, further solving the problem of large volume expansion of the negative electrode material, thereby improving the conductivity of the negative electrode material, and further reducing the volume expansion of the entire composite material and reducing the swelling of the electrode sheet. On the other hand, the coating layer on the surface of the composite can reduce the exposed Si on the surface of the negative electrode material, reduce the generation of a large amount of SEI during the charging and discharging process, and improve the specific capacity and electrochemical performance of the negative electrode material.

[0115] In some embodiments, the coating treatment includes at least one of a gas phase coating treatment, a solid phase coating treatment, and a liquid phase coating treatment.

[0116] In some embodiments, the coating treatment is a gas phase coating treatment, and the steps include: heating the composite, introducing a protective gas and a coating gas, and pyrolyzing the coating gas to obtain the negative electrode material.

[0117] In some embodiments, the coating gas includes a carbon source gas.

[0118] In some embodiments, the carbon source gas is a hydrocarbon.

[0119] In some embodiments, the carbon source gas includes at least one of methane, ethane, propane, ethylene, acetylene, gaseous benzene, gaseous toluene, gaseous xylene, gaseous ethanol, and gaseous acetone.

[0120] In some embodiments, the pyrolysis temperature is 500-900°C, and the temperature can be 500°C, 600°C, 700°C, 800°C, or 900°C, or other values within the range, which can be selected according to actual needs, and is not limited herein. Preferably, the pyrolysis temperature is 550-850°C.

[0121] In some embodiments, the heat preservation time for pyrolysis is 1-20h, and the heat preservation time can be 1h, 3h, 5h, 8h, 10h, 12h, 15h, 18h, or 20h, or other values within the range, which can be selected according to actual needs, and is not limited herein. Preferably, the heat preservation time for pyrolysis is 2-10h.

[0122] In some embodiments, the flow ratio of the coating gas to the protective gas is (0.01-20):1, and the flow ratio can be 0.01:1, 0.05:1, 1:1, 5:1, 10:1, 12:1, 15:1, or 20:1, or other values within the range, which can be selected according to actual needs, and is not limited herein.

[0123] In some embodiments, the flow rate of the carbon source gas is 100-5000 seem, specifically, it can be 100 seem, 500 seem, 1000 seem, 2000 seem, 3000 seem, 4000 seem, 4500 seem or 5000 seem, etc., and of course, it can also be other values within the above range, which are not limited herein. Preferably, the flow rate of the carbon source gas is 200-2000 seem.

[0124] By controlling the volume ratio of the carbon source gas to the protective gas, the gas flow rate, the reaction gas pressure and other parameters, the carbon material obtained by cracking the carbon source gas can be deposited on the surface of the composite.

[0125] In some embodiments, the coating treatment is a solid-phase coating treatment, and the step comprises: mixing the composite with a solid-phase carbon source to obtain a mixture, and performing carbonization treatment on the mixture to obtain the negative electrode material.

[0126] In some embodiments, the carbonization treatment is performed at a temperature of 300-800℃, and the carbonization treatment is performed for 1-20 hours. Optionally, the temperature can be specifically 300℃, 400℃, 500℃, 600℃, 700℃ or 800℃, etc., and the time can be specifically 1 hour, 3 hours, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours or 20 hours, etc., and it can also be other values within the range, which can be selected according to actual needs, and are not limited herein.

[0127] In some embodiments, the solid-phase carbon source comprises at least one of sugars, esters, hydrocarbons, organic acids and high molecular polymers.

[0128] In some embodiments, the solid-phase carbon source comprises at least one of polyvinyl chloride, polyvinyl butyral, polyacrylonitrile, polyacrylic acid, polyethylene glycol, polypyrrole, polyaniline, sucrose, glucose, maltose, citric acid, pitch, furfural resin, epoxy resin and phenolic resin.

[0129] In some embodiments, the mass ratio of the solid-phase carbon source to the composite is 1:(1-10), and optionally, the mass ratio can be specifically 1:1, 1:3, 1:5, 1:6, 1:8, 1:9 or 1:10, etc., and it can also be other values within the range, which can be selected according to actual needs, and are not limited herein.

[0130] In some embodiments, the mixing method of the solid-phase carbon source and the composite can be VC mixing, fusion, ball milling, three-dimensional mixing, fluidized bed mixing, etc.

[0131] In some embodiments, the equipment used for the solid-phase coating treatment is at least one of a rotary furnace, a box furnace, a roller kiln, a tunnel kiln and a push plate kiln.

[0132] In some embodiments, the coating treatment is a liquid-phase coating treatment, and the step comprises: mixing the composite with a liquid-phase carbon source to obtain a mixture, and performing carbonization treatment on the mixture to obtain the negative electrode material.

[0133] In some embodiments, the mass ratio of the liquid-phase carbon source to the composite is 1:(1-10), and the mass ratio can be 1:1, 1:2, 1:5, 1:6, 1:8, 1:9, 1:10, or other values within the range, which can be selected according to actual needs.

[0134] In some embodiments, the liquid-phase carbon source comprises at least one of n-hexane, toluene, benzene, dimethylbenzene, methanol, ethanol, propanol, butanol, pentanol, acetone, butanone, 2-pentanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and pentyl acetate. More preferably, the liquid-phase carbon source comprises at least one of benzene and toluene, and at least one of methanol, ethanol, propanol, butanol, and pentanol.

[0135] In some embodiments, the carbonization treatment is performed at a temperature of 300-800℃ for 1-20 hours. The temperature can be 300℃, 400℃, 500℃, 600℃, 700℃, or 800℃, and the time can be 1 hour, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 16 hours, 18 hours, or 20 hours, or other values within the range, which can be selected according to actual needs.

[0136] In some embodiments, the composite and the liquid-phase carbon source can be mixed by VC mixing, fusion, ball milling, suction filtration, heating reflux, three-dimensional mixing, fluidized bed mixing, or the like, and the equipment for the liquid-phase carbon coating can be at least one of a rotary furnace, a box furnace, a roller kiln, and a tunnel kiln.

[0137] By controlling the mass ratio of the liquid-phase carbon source to the composite, the flow rate of the liquid-phase carbon source, and other parameters, the liquid-phase carbon source and the composite can be fully mixed, the liquid-phase carbon source can be coated on the surface of the composite, and part of the liquid-phase carbon source can penetrate into the composite to form a carbon material coating layer with an appropriate thickness, thereby improving the rate performance of the negative electrode material and reducing the volume expansion of the negative electrode material.

[0138] In some embodiments, the preparation method further comprises: crushing, screening, and then grading the coating product to obtain the negative electrode material.

[0139] In a third aspect, the application provides a battery comprising the negative electrode material or the negative electrode material prepared by the preparation method.

[0140] Those skilled in the art will understand that the preparation method of the battery described above is only an example. Other methods commonly used in the art can be used without departing from the content disclosed in the present application.

[0141] The present application will be further described in the following embodiments. The embodiments of the present application are not limited to the following specific embodiments. Changes can be made as appropriate within the scope of the rights.

[0142] Test method:

[0143] 1. Compactness β test: The negative electrode material with a mass of m1 g is soaked in a 20% mass fraction hydrofluoric acid solution, after soaking for 1 hour, m2 g of material is obtained after cleaning and drying, and the surface compactness β of the negative electrode material is calculated as m2 / m1 x 100%.

[0144] 2. Coating thickness: The material is sectioned by FIB-SEM equipment, 10 particles are randomly taken in SEM, and the coating thickness is measured 3 times for each particle to obtain the average thickness of the coating.

[0145] 3. Test method for pore volume and average pore diameter of non-carbon matrix and negative electrode material after removing silicon material:

[0146] The pore volume of the non-carbon matrix refers to the total pore volume of the unit mass of the non-carbon matrix, and the pore volume of the carbon matrix can be measured by gas adsorption. Nitrogen adsorption is a technique for characterizing the porosity and pore size distribution of materials by condensing gas in the pores of solids. As the pressure increases, the gas first condenses in the pores with the smallest diameter, and the pressure increases until it reaches the saturation point, at which point all the pores are filled with liquid. Then the nitrogen pressure is gradually reduced to evaporate the liquid from the system. Analysis of the adsorption and desorption isotherms enables determination of pore volume and pore size distribution, as well as average pore diameter. Among them, the method for removing silicon material from the negative electrode material is: adding 1M concentration nitric acid solution to the negative electrode material and soaking for 4h, then adding 20% mass fraction HF acid solution dropwise into the negative electrode material, which produces yellow smoke, and the solution is repeatedly added several times until no yellow smoke is produced; Finally, add 1M concentration nitric acid solution to digest the residue, then clean and dry to obtain the negative electrode material after removing the silicon particles.

[0147] 4. Test method for specific surface area of negative electrode material or negative electrode material after removing silicon material:

[0148] The specific surface area is measured using the American Micromeritics TriStar3000 specific surface area and pore size analyzer equipment.

[0149] 5. Gas production test: disperse carboxymethyl cellulose (CMC) in an appropriate amount of water to form a CMC glue solution with a solid content of 1.4%, then mix 10 g of the glue solution with 10 g of the negative electrode material to form a slurry; put the slurry into an aluminum plastic film bag, and record the mass of the slurry; then seal it to form a sealed aluminum plastic film bag; fix the sealed aluminum plastic film bag at the bottom of the container, completely immerse it in water, and record the volume of the aluminum plastic film bag; after 24 hours, record the volume of the aluminum plastic film bag again; calculate the gas production of the silicon negative electrode material according to the volume change of the aluminum plastic film, unit: mL / g.

[0150] 6. Type of silicon material: use an X-ray diffractometer (XRD) to measure the diffraction peak to confirm the type of silicon particles.

[0151] 7. Test of the mass content of silicon in the negative electrode material:

[0152] Use a box-type atmosphere furnace (brand: Nanyang Xiyu, model: SA2-9-17TP) to burn in an oxygen atmosphere, so that the silicon and silicon monoxide in the sample react to form silicon dioxide, and the carbon burns to become carbon dioxide, which is discharged, and the mass content of silicon in the negative electrode material is calculated.

[0153] 8. Test of the powder resistivity:

[0154] Use the MCP-PD51 powder resistance test system of Mitsubishi Chemical, Japan to test the conductivity under 20KN pressure, and use the four-probe method to measure the volume resistivity of the sample. The instrument is used to test the resistance of the powder, and then the computer automatically calculates the conductivity and resistivity of the powder.

[0155] 9. Test of the mass content of carbon elements in the negative electrode material:

[0156] Use the German Bruker / German Elt infrared carbon and sulfur analyzer G4 ICARUS HF / CS-i to burn the sample in a high-temperature oxygen-rich state, and the carbon elements contained therein are oxidized to carbon dioxide and enter the infrared detector with the carrier gas. The content of carbon elements is calculated by quantitatively calculating the change of infrared absorption wavelength intensity of carbon dioxide signal.

[0157] 10. Test method of particle size of negative electrode material:

[0158] The particle size distribution range of the negative electrode material is tested by a Malvern laser particle size analyzer (Mastersizer 3000), the volume-based cumulative particle size distribution of the particle size distribution is measured by a laser diffraction method, Dv10 represents the particle size corresponding to the cumulative particle size distribution volume percentage of 10% of the powder, Dv50 represents the particle size corresponding to the cumulative particle size distribution volume percentage of 50% of the powder, and Dv90 represents the particle size corresponding to the cumulative particle size distribution volume percentage of 90% of the powder, so that the particle size distribution (Dv90-Dv10) / Dv50 of the negative electrode material can be obtained.

[0159] 11. A method for testing the compaction density of a negative electrode material:

[0160] A specified mass m of the sample is placed in a mold and subjected to a pressure of 1.0 T, and after pressure maintaining for 30 s, the pressure is removed to test the thickness, and the compaction density is calculated.

[0161] 12. Electrical performance test:

[0162] The negative electrode material, conductive carbon black, and polyphthalamide (PPA) are mixed in a mass ratio of 70:15:15 to prepare a negative electrode slurry, the negative electrode slurry is coated on a copper foil, and after drying, a negative electrode sheet is prepared. A lithium metal sheet is used as a counter electrode to assemble a button cell in an Ar-filled glove box. The button cell is subjected to charge-discharge test at a current density of 0.1 C in a charge-discharge interval of 0.01 V-5 V to obtain the first reversible specific capacity and the initial coulombic efficiency (ICE) of the button cell.

[0163] The negative electrode material and graphite mixture, conductive carbon black (Super-P), conductive graphite (KS-6), carboxymethyl cellulose (CMC), and butadiene-styrene rubber (SBR) are mixed in a mass ratio of 92:2:2:2:2 to prepare a negative electrode slurry, the negative electrode slurry is coated on a copper foil, and after drying, a negative electrode sheet is prepared. The proportion of the negative electrode material and graphite in the negative electrode material and graphite mixture is determined by the first reversible specific capacity of the two and the capacity required for the two to be prepared. A lithium metal sheet is used as a counter electrode to assemble a button cell in an Ar-filled glove box. The button cell is subjected to repeated 50 times of charge-discharge test at a current density of 1 C in a charge-discharge interval of 0.01 V-5 V to obtain the capacity retention rate and the thickness expansion rate of the electrode sheet after 50 cycles of the battery.

[0164] Example 1

[0165] (1) The non-carbon matrix (alumina, AI2O3) with pores is added to the copper nitrate solution, the soaking temperature is set to 145°C, and the soaking time is 30 min, wherein the mass ratio of copper nitrate to alumina is 0.53%, and then solid-liquid separation is performed, followed by vacuum drying to obtain a non-carbon matrix containing a catalyst.

[0166] (2) The non-carbon matrix containing the catalyst is placed in a chemical vapor deposition (CVD) device, and then a mixed gas of silane (25% concentration) and argon (Ar) is introduced into the CVD device, the gas flow ratio of silane to argon (Ar) is 1:3, the temperature is raised to 500°C, and the vapor deposition reaction is performed for 5 h to obtain a composite.

[0167] (3) The composite is mixed with phenolic resin at a mass ratio of 100:25, and then the mixed material is placed in a high-temperature box furnace, nitrogen is introduced, and heat treatment is performed at 580°C for 2 h.

[0168] (4) After cooling, the obtained sample is crushed, sieved, and then graded to obtain a negative electrode material.

[0169] The negative electrode material prepared in this example includes a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (AI2O3) matrix with pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The surface of the negative electrode material has a coating layer, and the coating layer includes amorphous carbon material.

[0170] Example 2

[0171] The difference from Example 1 is that:

[0172] (1) The non-carbon matrix (silicon carbide, SiC) with pores is added to the iron nitrate solution, the soaking temperature is set to 145°C, and the soaking time is 30 min, wherein the mass ratio of iron nitrate to silicon carbide is 0.53%, and then solid-liquid separation is performed, followed by vacuum drying to obtain a non-carbon matrix containing a catalyst.

[0173] The negative electrode material prepared in this example includes a non-carbon matrix and a silicon material, wherein the non-carbon matrix is a silicon carbide (SiC) matrix with pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The surface of the negative electrode material has a coating layer, and the coating layer includes amorphous carbon material.

[0174] Example 3

[0175] (1) The non-carbon matrix (silicon nitride, Si3N4) with pores is added to the copper nitrate solution, the soaking temperature is set to 145°C, and the soaking time is 30 min, wherein the mass ratio of copper nitrate to silicon nitride is 0.53%, and then solid-liquid separation is performed, followed by vacuum drying to obtain a non-carbon matrix containing a catalyst.

[0176] The negative electrode material prepared in this embodiment includes a non-carbon matrix and a silicon material. The non-carbon matrix is ​​a porous silicon nitride (Si3N4) matrix, and the silicon material is amorphous silicon, with at least a portion of the silicon material located within the pores of the non-carbon matrix. The surface of the negative electrode material has a coating layer comprising an amorphous carbon material.

[0177] Example 4

[0178] The difference from Example 1 is that:

[0179] (1) A porous non-carbon matrix (aluminum phosphate, AlPO4) was added to a nickel carbonate solution, the immersion temperature was set to 145°C, and the immersion time was 30 minutes, wherein the mass ratio of nickel carbonate to aluminum phosphate was 0.53%. The solid-liquid separation was performed, and then vacuum drying was performed to obtain a non-carbon matrix containing a catalyst.

[0180] The negative electrode material prepared in this embodiment includes a non-carbon matrix and a silicon material. The non-carbon matrix is ​​a porous aluminum phosphate (AlPO4) matrix, and the silicon material is amorphous silicon, with at least a portion of the silicon material located within the pores of the non-carbon matrix. The surface of the negative electrode material has a coating layer comprising an amorphous carbon material.

[0181] Example 5

[0182] The difference from Example 1 is that:

[0183] (1) A porous non-carbon matrix (mullite, 3Al2O3-2SiO2) was added to a copper nitrate solution at a soaking temperature of 145°C for 30 minutes, wherein the mass ratio of copper nitrate to mullite was 0.53%. The solid-liquid separation was performed, and the catalyst-containing non-carbon matrix was obtained after vacuum drying.

[0184] The negative electrode material prepared in this embodiment includes a non-carbon matrix and a silicon material. The non-carbon matrix is ​​a porous mullite (3Al2O3-2SiO2) matrix, and the silicon material is amorphous silicon, with at least a portion of the silicon material located within the pores of the non-carbon matrix. The surface of the negative electrode material has a coating layer comprising an amorphous carbon material.

[0185] Example 6

[0186] The difference from Example 1 is that:

[0187] (1) a non-carbon matrix with pores (sodium zeolite, Na2Al2Si3O 10 ·2H2O) was added to a copper nitrate solution, the soaking temperature was set to 145°C, and the soaking time was 30 minutes, wherein the mass ratio of copper nitrate to sodium zeolite was 0.53%, solid-liquid separation was performed, and then vacuum drying was performed to obtain a non-carbon matrix containing the catalyst.

[0188] The negative electrode material prepared in the embodiment comprises a non-carbon matrix and a silicon material, wherein the non-carbon matrix is a sodium zeolite (Na2Al2Si3O 10 ·2H2O) matrix having pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer comprises amorphous carbon material.

[0189] Embodiment 7

[0190] Different from Embodiment 1, the following steps are taken:

[0191] (1) The non-carbon matrix (calcium titanate, CaTiO3) having pores is added into a copper nitrate solution, the soaking temperature is set to 145°C, and the soaking time is 30 min, wherein the mass ratio of the copper nitrate solution to the calcium titanate is 0.53%, then solid-liquid separation is performed, and vacuum drying is performed to obtain the non-carbon matrix containing the catalyst.

[0192] The negative electrode material prepared in the embodiment comprises a non-carbon matrix and a silicon material, wherein the non-carbon matrix is a calcium titanate (CaTiO3) matrix having pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer comprises amorphous carbon material.

[0193] Embodiment 8

[0194] Different from Embodiment 1, the following steps are taken:

[0195] (1) The non-carbon matrix (calcium titanate, CaTiO3) having pores is added into a copper nitrate solution, the soaking temperature is set to 145°C, and the soaking time is 30 min, wherein the mass ratio of the copper nitrate solution to the calcium titanate is 0.53%, then solid-liquid separation is performed, and vacuum drying is performed to obtain the non-carbon matrix containing the catalyst.

[0196] The negative electrode material prepared in the embodiment comprises a non-carbon matrix and a silicon material, wherein the non-carbon matrix is a calcium titanate (CaTiO3) matrix having pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer comprises amorphous carbon material.

[0197] Embodiment 9

[0198] Different from Embodiment 1, the following steps are taken:

[0199] (3) The conductive polymer pyrrole is dissolved in 1.5 mg / L organic acid, and ultrasonic stirring is performed until the mixture is uniform to form a mixed solution A, and the composite obtained in step (2) and the dispersant sodium dodecyl benzene sulfonate are added into the mixed solution A, and after dispersion, a mixed solution B is obtained (in the mixed solution B, the concentration of the composite is 0.1-1 mg / mL, and the concentration of the dispersant is 0.2-1 mg / mL).

[0200] (4) The mixed solution B is placed in a condition of -2℃-5℃ and continuously stirred, and the initiator ferric chloride with a concentration of 20 mg / mL is slowly dropped into the mixed solution B, and after the dropping is completed, the reaction is continuously stirred for 5 hours. After the reaction is completed, the negative electrode material is obtained through filtration, washing, and baking (temperature of 120℃, time of 10 hours).

[0201] The negative electrode material prepared in the embodiment includes a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (Al2O3) matrix with pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer includes polypyrrole.

[0202] Example 10

[0203] Different from the example 1, the following steps are taken:

[0204] (3) The composite and aluminum nitrate are added into 75 mL of anhydrous ethanol according to a mass fraction ratio of 1:0.015, and stirred for 3 hours to obtain a mixed solution A;

[0205] (4) A mixed solution B formed by mixing ammonium fluoride and anhydrous ethanol according to a mass ratio of 1:100 is added dropwise into the mixed solution A, and after the addition is completed, the mixed solution A is stirred for 2 hours, and the solvent is evaporated by stirring at 80℃ for 5 hours. The sample is dried in a vacuum drying oven at 110℃ for 12 hours, and then annealed in a tube furnace filled with argon according to a temperature rising rate of 4℃ / min to 500℃ for 6 hours to obtain the negative electrode material.

[0206] The negative electrode material prepared in the embodiment includes a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (Al2O3) matrix with pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer includes ammonium fluoride.

[0207] Example 11

[0208] Different from the example 1, the following steps are taken:

[0209] (2) The non-carbon matrix containing the catalyst is placed in a chemical vapor deposition (CVD) device, and then a mixed gas of silane (concentration of 14.3%) and nitrogen (N2) is introduced into the CVD device, the gas flow ratio of silane and argon (Ar) is 1:6, the temperature is raised to 500℃, and the vapor deposition reaction is performed for 10 hours to obtain the composite.

[0210] The negative electrode material prepared in the embodiment includes a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (Al2O3) matrix with pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer includes amorphous carbon material.

[0211] Example 12

[0212] Different from Example 1 is that:

[0213] (2) The non-carbon matrix containing the catalyst was placed in a chemical vapor deposition (CVD) device, and then a mixed gas of silane (concentration of 80%) and nitrogen (N2) was introduced into the CVD device, the volume flow ratio of silane and nitrogen (N2) was 4:1, the temperature was raised to 420°C, and a vapor deposition reaction was performed for 20 h to obtain the composite.

[0214] The negative electrode material prepared in this example comprises a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (Al2O3) matrix having pores, and the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer comprises amorphous carbon material.

[0215] Example 13

[0216] Different from Example 1 is that:

[0217] (1) The non-carbon matrix (alumina, Al2O3) having pores was added to a copper nitrate solution, the soaking temperature was set to 145°C, and the soaking time was 30 min, wherein the mass ratio of copper nitrate to alumina was 1%, and then solid-liquid separation was performed, followed by vacuum drying to obtain the non-carbon matrix containing the catalyst.

[0218] The negative electrode material prepared in this example comprises a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (Al2O3) matrix having pores, and the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer comprises amorphous carbon material.

[0219] Example 14

[0220] Different from Example 1 is that:

[0221] (1) The non-carbon matrix (alumina, Al2O3) having pores was added to a copper nitrate solution, the soaking temperature was set to 145°C, and the soaking time was 30 min, wherein the mass ratio of copper nitrate to alumina was 0.01%, and then solid-liquid separation was performed, followed by vacuum drying to obtain the non-carbon matrix containing the catalyst.

[0222] The negative electrode material prepared in this example comprises a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (Al2O3) matrix having pores, and the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer comprises amorphous carbon material.

[0223] Example 15

[0224] Different from Example 1 is that:

[0225] (1) The non-carbon substrate (alumina, AI2O3) with pores was added to the copper nitrate solution, the soaking temperature was set to 75°C, and the soaking time was 30 min, wherein the mass ratio of copper nitrate to alumina was 0.53%, and then solid-liquid separation was performed, followed by vacuum drying to obtain the non-carbon substrate containing the catalyst.

[0226] The negative electrode material prepared in this example comprises a non-carbon substrate and a silicon material, wherein the non-carbon substrate is an alumina (AI2O3) substrate with pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon substrate. The negative electrode material has a coating layer on the surface, and the coating layer comprises amorphous carbon material.

[0227] Example 16:

[0228] Different from Example 1 is that: (1) The non-carbon substrate (alumina, AI2O3) with pores was added to the copper nitrate solution, the soaking temperature was set to 215°C, and the soaking time was 30 min, wherein the mass ratio of copper nitrate to alumina was 0.53%, and then solid-liquid separation was performed, followed by vacuum drying to obtain the non-carbon substrate containing the catalyst.

[0229] The negative electrode material prepared in this example comprises a non-carbon substrate and a silicon material, wherein the non-carbon substrate is an alumina (AI2O3) substrate with pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon substrate. The negative electrode material has a coating layer on the surface, and the coating layer comprises amorphous carbon material.

[0230] Example 17:

[0231] Different from Example 1 is that:

[0232] (1) The non-carbon substrate (alumina, AI2O3) with pores was added to the copper nitrate solution, the soaking temperature was set to 145°C, and the soaking time was 30 min, wherein the mass ratio of copper nitrate to alumina was 4.98%, and then solid-liquid separation was performed, followed by vacuum drying to obtain the non-carbon substrate containing the catalyst.

[0233] The negative electrode material prepared in this example comprises a non-carbon substrate and a silicon material, wherein the non-carbon substrate is an alumina (AI2O3) substrate with pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon substrate. The negative electrode material has a coating layer on the surface, and the coating layer comprises amorphous carbon material.

[0234] Comparative Example 1

[0235] Different from Example 1 is that step (3) is not performed.

[0236] The negative electrode material prepared in the present comparative example comprises a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (Al2O3) matrix having pores, and the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer comprises carbon material amorphous carbon material.

[0237] Comparative Example 2

[0238] Different from Example 1 is that step (1) is not performed.

[0239] The negative electrode material prepared in the present comparative example comprises a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (Al2O3) matrix having pores, and the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer comprises carbon material amorphous carbon material.

[0240] Comparative Example 3

[0241] Different from Example 1 is that:

[0242] (1) The non-carbon matrix (alumina, Al2O3) having pores is added to a copper nitrate solution, the soaking temperature is set to 60°C, and the soaking time is 30 min, wherein the mass ratio of copper nitrate to alumina is 0.53%, and then solid-liquid separation is performed, followed by vacuum drying to obtain a non-carbon matrix containing a catalyst.

[0243] The negative electrode material prepared in the present comparative example comprises a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (Al2O3) matrix having pores, and the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer comprises carbon material amorphous carbon material.

[0244] Comparative Example 4

[0245] Different from Example 1 is that:

[0246] (1) The non-carbon matrix (alumina, Al2O3) having pores is added to a copper nitrate solution, the soaking temperature is set to 145°C, and the soaking time is 30 min, wherein the mass ratio of copper nitrate to alumina is 0.005%, and then solid-liquid separation is performed, followed by vacuum drying to obtain a non-carbon matrix containing a catalyst.

[0247] The negative electrode material prepared in the present comparative example comprises a non-carbon matrix and a silicon material, wherein the non-carbon matrix is an alumina (Al2O3) matrix having pores, and the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon matrix. The negative electrode material has a coating layer on the surface, and the coating layer comprises carbon material amorphous carbon material.

[0248] Comparative Example 5

[0249] Different from Example 1 is that:

[0250] (1) The non-carbon substrate (alumina, AI2O3) with pores is added to the copper nitrate solution, the soaking temperature is set to 145°C, and the soaking time is 30 min, the mass ratio of copper nitrate to alumina is 9.8%, solid-liquid separation is performed, and then vacuum drying is performed to obtain the non-carbon substrate containing the catalyst.

[0251] The negative electrode material prepared in the comparative example includes a non-carbon substrate and a silicon material, wherein the non-carbon substrate is an alumina (AI2O3) substrate with pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon substrate. The negative electrode material has a coating layer on the surface, and the coating layer includes amorphous carbon material.

[0252] Comparative Example 6

[0253] Different from Example 1, the following steps are performed:

[0254] (2) The non-carbon substrate containing the catalyst is placed in a chemical vapor deposition (CVD) device, and then a mixed gas of silane (concentration of 5%) and argon (Ar) is introduced into the CVD device, the gas flow ratio of silane to argon (Ar) is 1:3, the temperature is raised to 500°C, and the vapor deposition reaction is performed for 1 h to obtain the composite.

[0255] The negative electrode material prepared in the comparative example includes a non-carbon substrate and a silicon material, wherein the non-carbon substrate is an alumina (AI2O3) substrate with pores, the silicon material is amorphous silicon, and at least part of the silicon material is located in the pores of the non-carbon substrate. The negative electrode material has a coating layer on the surface, and the coating layer includes amorphous carbon material.

[0256] Test results:

[0257] Table 1 Parameters of the negative electrode material

[0258] Table 2 Parameters of the negative electrode material after removing the silicon material

[0259] Table 3 Performance test results of the examples and comparative examples

[0260] According to the test data of embodiments 1-17, the non-carbon matrix and the silicon material are included, and at least part of the silicon material is located inside the particles of the non-carbon matrix, so as to alleviate the volume expansion of the silicon material in the negative electrode material during the lithium intercalation and deintercalation process of the battery prepared by the negative electrode material. The non-carbon matrix has high strength and toughness, and can make the negative electrode material have higher compaction density, so as to improve the structural stability of the negative electrode material, and further reduce the particle breakage and pulverization of the negative electrode material. At the same time, the non-carbon matrix usually has good ionic conductivity, and can play a role similar to the artificial SEI film, can slow down the continuous generation of the solid electrolyte interface film (natural SEI film), reduce the side reaction between the negative electrode material and the electrolyte, and improve the cycle performance of the battery prepared by the negative electrode material. The surface density of the negative electrode material is ≥80%, which can reduce the dissolution of the negative electrode material during the cycle process of the battery prepared by the negative electrode material, and further reduce the reaction between the dissolved silicon material in the negative electrode material and the electrolyte, effectively reduce the gas production value of the negative electrode material and improve the powder conductivity of the negative electrode material. And control the total pore volume of the negative electrode material ≤0.2 cm 3 / g, in the charging and discharging process, not only can the space be reserved for the volume expansion of the silicon material in the negative electrode material during the lithium intercalation and deintercalation process of the battery prepared by the negative electrode material, but also can effectively reduce the direct infiltration of the electrolyte into the inside of the particles of the negative electrode material through the pore structure, thereby reducing the side reaction between the electrolyte and the silicon material in the negative electrode material, and further improving the cycle performance of the lithium ion battery. The present application controls the surface density of the negative electrode material and the pores in the negative electrode material to effectively alleviate the volume expansion of the silicon material in the negative electrode material during the cycle process of the battery prepared by the negative electrode material, reduce the particle breakage of the negative electrode material, and improve the cycle performance of the negative electrode material.

[0261] According to the test data of embodiments 1-8, different non-carbon matrices can form a dense coating layer after being treated by catalyst infiltration, so as to not only reduce the dissolution of the silicon material, but also improve the cycle performance of the lithium ion battery.

[0262] According to the test data of embodiments 9-10, the coating layer of different materials on the surface of the negative electrode material can achieve a high surface density, but compared with the amorphous carbon material coating layer, the conductive polymer and fluoride coating layer will have a slight effect on the specific capacity of the negative electrode material. Preferably, the coating layer is an amorphous carbon material layer.

[0263] According to the test data of embodiments 11-12, different silicon deposition parameters (time, concentration, etc.) will affect the content of the silicon material deposited in the non-carbon matrix, and further affect the specific capacity of the negative electrode material; and with the increase of the silicon content, the expansion effect of the negative electrode material will increase.

[0264] According to the test data of Examples 13-17, the soaking treatment of the non-carbon matrix affects the surface density of the negative electrode material. When the soaking temperature is high, the soaking time is long, or the mass ratio of the catalyst increases, the surface density of the negative electrode material generally shows an upward trend, which improves the cycle performance of the negative electrode material and reduces the gas production.

[0265] When the soaking temperature is low, the soaking time is short, or the mass ratio of the catalyst decreases, the surface density of the negative electrode material generally shows a downward trend, which reduces the cycle performance of the negative electrode material and increases the gas production.

[0266] According to the test data of Comparative Example 1 and Example 1, Comparative Example 1 does not perform coating treatment on the negative electrode material, the surface density of the negative electrode material decreases, and due to the absence of the coating layer, the conductivity of the negative electrode material decreases, resulting in a decrease in the powder conductivity of the negative electrode material. The exposed silicon material on the surface of the negative electrode material increases significantly, which causes the volume expansion of the silicon material to be unable to be effectively alleviated, and the negative electrode material is prone to particle breakage and pulverization. The exposed silicon material continuously contacts the electrolyte during the cycle process, causing side reactions, repeated destruction and growth of the SEI film, and deterioration of the cycle performance of the negative electrode material.

[0267] According to the test data of Comparative Example 2 and Example 1, since the non-carbon matrix does not contain a catalyst, the surface density of the prepared negative electrode material decreases, the gas production value increases, and the electrochemical performance of the negative electrode material decreases.

[0268] According to the test data of Comparative Example 3 and Example 1, since the temperature for soaking the non-carbon matrix in the catalyst in Comparative Example 3 is too low, the number of catalyst particles adsorbed on the surface of the non-carbon matrix is small, which causes the integrity of the coating layer formed during the subsequent coating process to be poor, resulting in a decrease in the surface density of the negative electrode material. The dissolution of the negative electrode material during the cycle process of the battery prepared from the negative electrode material increases, the amount of dissolved silicon material in the negative electrode material increases, and the amount of exposed silicon material on the surface of the negative electrode material also increases, which causes the volume expansion of the silicon material in the negative electrode material during the lithium intercalation and deintercalation process of the battery prepared from the negative electrode material to be unable to be effectively alleviated, and the negative electrode material is prone to particle breakage and pulverization during the cycle process. The side reactions between the silicon material and the electrolyte increase, the gas production value of the negative electrode material increases, and the initial coulombic efficiency and cycle performance of the negative electrode material decrease.

[0269] According to the test data of Comparative Example 4 and Example 1, it can be known that, since the amount of catalyst added in the process of impregnating the non-carbon matrix into the catalyst is too small in Comparative Example 4, the coating material is difficult to completely coat on the surface of the negative electrode material in the subsequent coating process, resulting in poor integrity of the coating layer on the surface of the negative electrode material, thereby reducing the surface density of the negative electrode material, increasing the dissolution of the negative electrode material in the cycle process of the battery prepared by the negative electrode material, increasing the silicon material dissolved in the negative electrode material, and increasing the exposed silicon material on the surface of the negative electrode material, resulting in that the volume expansion of the silicon material in the negative electrode material in the lithium intercalation and deintercalation process of the battery prepared by the negative electrode material cannot be effectively alleviated, thereby the negative electrode material is prone to particle breakage and pulverization in the cycle process, the side reaction of the silicon material with the electrolyte increases, the gas production value of the negative electrode material increases, and the first coulombic efficiency and cycle performance of the negative electrode material decrease.

[0270] According to the test data of Comparative Example 5 and Example 1, it can be known that, since the amount of catalyst added in the process of impregnating the non-carbon matrix into the catalyst is too large in Comparative Example 5, the thickness of the coating layer formed on the surface of the negative electrode material is too thick, increasing the length of the ion and electron transport path and the diffusion resistance in the negative electrode material, resulting in the decrease of the ion and electron transport in the negative electrode material, thereby causing the decrease of the electrochemical performance of the negative electrode material. At the same time, too much catalyst is difficult to stably adsorb on the non-carbon matrix, resulting in the falling off of the physically adsorbed catalyst in part of the non-carbon matrix, causing the decrease of the subsequent coating integrity, thereby causing the decrease of the surface density of the negative electrode material, the increase of the silicon material dissolved in the negative electrode material, the increase of the side reaction of the silicon material with the electrolyte, the increase of the gas production value of the negative electrode material, and the decrease of the electrochemical performance of the negative electrode material.

[0271] According to the test data of Comparative Example 6 and Example 1, it can be known that, since the concentration of silane introduced in the process of silicon material deposition is too low and the time of gas phase deposition reaction is short in Comparative Example 6, the Si content on the surface of the negative electrode material particles is low, which can make the negative electrode material have a high surface density, and the exposed silicon material on the surface of the negative electrode material is reduced, which can reduce the side reaction of the electrolyte with the silicon material, thereby making the negative electrode material have a low gas production value; and since the silicon content is low and the total pore volume of the negative electrode material increases, space can be reserved for the volume expansion of the silicon material in the negative electrode material in the lithium deintercalation process of the battery prepared by the negative electrode material, thereby reducing the expansion rate of the negative electrode material in the cycle process; but at the same time, the silicon content deposited in the pores of the negative electrode material is low, resulting in the decrease of the specific capacity of the negative electrode material, and since the total pore volume of the negative electrode material increases, part of the electrolyte may directly penetrate into the interior of the negative electrode material particles through the pore structure, thereby increasing the side reaction of the electrolyte with the silicon material in the negative electrode material, resulting in the decrease of the cycle performance of the battery prepared by the negative electrode material.

Claims

1. A negative electrode material, characterized in that The negative electrode material comprises a non-carbon matrix and silicon particles, wherein at least part of the silicon particles are located inside the particles of the non-carbon matrix; the negative electrode material has pores, and the total pore volume of the negative electrode material is ≤0.2 cm 3 / g, and the surface density β of the negative electrode material is ≥80%; The surface density β of the negative electrode material is measured by the following test method: A negative electrode material with a mass of m1 g is immersed in a hydrofluoric acid solution with a mass fraction of 20% for 1 hour, and then washed and dried to obtain m2 g of material. The surface density of the negative electrode material is calculated to be β = m2 / m1×100%.

2. The negative electrode material according to claim 1, characterized in that The non-carbon matrix includes at least one of metal oxides, silicides, silicates, phosphates, titanates and aluminum borates.

3. The negative electrode material according to claim 2, characterized in that The negative electrode material has at least one of the following characteristics: (1) The non-carbon matrix includes a metal oxide, and the metal oxide includes at least one of aluminum oxide, zirconium oxide, germanium dioxide, and manganese dioxide; (2) The non-carbon matrix includes a silicide, and the silicide includes at least one of silicon carbide and silicon nitride; (3) The non-carbon matrix includes a silicate, and the silicate includes at least one of cordierite, mullite, and zeolite; (4) The non-carbon matrix includes a phosphate, and the phosphate includes at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, titanium phosphate, chromium phosphate, cobalt phosphate, nickel phosphate, germanium phosphate, zirconium phosphate, niobium phosphate, molybdenum phosphate, tantalum phosphate, tungsten phosphate, and lanthanum phosphate; (5) The non-carbon matrix includes titanate, and the titanate includes at least one of calcium titanate, iron titanate, lithium titanate, and barium titanate.

4. The negative electrode material according to claim 1, characterized in that The negative electrode material has at least one of the following characteristics: (1) The total pore volume of the negative electrode material after removing the silicon particles is 0.3 cm 3 / g~2cm 3 / g; (2) The specific surface area of ​​the negative electrode material after removing the silicon particles is 10m 2 / g~2500m 2 / g; (3) The average pore size of all pores in the negative electrode material after removing silicon particles is 0.1 nm to 100 nm; (4) The total pore volume of the negative electrode material after removing the silicon particles is 0.5 cm 3 / g~1.4cm 3 / g.

5. The negative electrode material according to any one of claims 1 to 4, characterized in that The silicon particles include at least one of crystalline silicon, silicon oxide, amorphous silicon, silicon alloy, and composite particles of crystalline silicon and amorphous silicon.

6. The negative electrode material according to any one of claims 1 to 4, characterized in that The average particle size of the silicon particles is 0.05 nm to 5 nm, and more preferably, the average particle size of the silicon particles is 0.1 nm to 3 nm.

7. The negative electrode material according to any one of claims 1 to 4, characterized in that The morphology of the silicon particles includes at least one of point-shaped, spherical, ellipsoidal and flake-shaped.

8. The negative electrode material according to any one of claims 1 to 4, characterized in that At least a portion of the surface of the negative electrode material has a coating layer, and the material of the coating layer includes at least one of a carbon material, a conductive polymer, a fluoride, and a nitride.

9. The negative electrode material according to any one of claims 8, characterized in that The coating layer is a single-layer coating layer or a multi-layer coating layer.

10. The negative electrode material according to claim 8, characterized in that The negative electrode material has at least one of the following characteristics: (1) The material of the coating layer includes nitride, and the nitride includes at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride and carbon nitride; (2) The material of the coating layer includes a carbon material, and the carbon material includes at least one of amorphous carbon and graphitized carbon; (3) The material of the coating layer includes a conductive polymer, and the conductive polymer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, poly-3-hexylthiophene, poly(p-phenylene vinylene), polypyridine and poly(styrene vinylene); (4) The material of the coating layer includes a fluoride, and the fluoride includes at least one of polyvinyl fluoride, fluoropolymer, lithium fluoride, sodium fluoride, potassium fluoride, fluorocarbon polymer, fluorosilicone polymer, hexafluorobutyl acrylate, polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, perfluoroalkoxy resin, polychlorotrifluoroethylene, ethylene-chlorotrifluoroethylene copolymer, polyvinylidene fluoride and polyvinyl fluoride; (5) The thickness of the coating layer is 1 nm to 300 nm; (6) The coating layer accounts for ≤10% by mass of the negative electrode material; (7) The thickness of the coating layer is 2 nm to 200 nm; (8) The thickness of the coating layer is 5 nm to 100 nm.

11. The negative electrode material according to any one of claims 1 to 10, characterized in that The gas production value of the negative electrode material at room temperature for 24 hours is ≤1 mL / g.

12. 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 characteristics: (1) The volume median particle size Dv50 of the negative electrode material is 0.3 μm to 50 μm; (2) The particle size distribution of the negative electrode material satisfies the following relationship: 0.9≤(Dv90-Dv10) / Dv50≤5; (3) The specific surface area of ​​the negative electrode material is 0.5 m 2 / g~10m 2 / g; (4) The mass content of silicon in the negative electrode material is 20% to 55%; (5) The average pore size of the negative electrode material is 0.2 nm to 100 nm; (6) The powder conductivity of the negative electrode material under a pressure of 20 kN is 0.2 S / cm to 2 S / cm; (7) The compaction density of the negative electrode material is 0.5 g / cm 3 ~1.5g / cm 3 ; (8) The mass content of silicon in the negative electrode material is 45% to 55%.

13. The negative electrode material according to any one of claims 8, characterized in that The material of the coating layer includes carbon material, and the mass content of carbon element in the negative electrode material is 0.5% to 10%.

14. The negative electrode material according to any one of claims 1 to 12, characterized in that The volume median particle size Dv50 of the negative electrode material is 5 μm to 20 μm.

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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