CN118213495A

CN118213495A - Anode materials and batteries

Info

Publication number: CN118213495A
Application number: CN202410205115.8A
Authority: CN
Inventors: 陈曦; 庞春雷; 何鹏; 任建国; 贺雪琴
Original assignee: BTR New Material Group Co Ltd
Current assignee: BTR New Material Group Co Ltd
Priority date: 2023-09-28
Filing date: 2024-02-23
Publication date: 2024-06-18
Also published as: CN119050328A; CN117423823A; CN118867181A

Abstract

本申请涉及负极材料技术领域，尤其涉及一种负极材料及电池。负极材料包括碳基体及硅粒子，所述负极材料具有孔，所述孔包括微孔及介孔，其中，所述微孔的孔体积与所述介孔的孔体积的比值为(1～45)：(55～99)；且所述负极材料的表面致密度β≥80％。本申请的负极材料，负极材料的表面具有高致密度，可减少循环过程中硅粒子的溶出，进而减少溶出的硅粒子与电解液的反应，有效的降低了负极材料的产气值；并且负极材料的孔中体积占比更高的介孔能够给硅粒子的体积膨胀提供空间，提升了负极材料的循环性能。The present application relates to the technical field of negative electrode materials, and in particular to a negative electrode material and a battery. The negative electrode material includes a carbon matrix and silicon particles, and the negative electrode material has pores, and the pores include micropores and mesopores, wherein the ratio of the pore volume of the micropores to the pore volume of the mesopores is (1-45): (55-99); and the surface density β of the negative electrode material is ≥80%. The negative electrode material of the present application has a high density on the surface of the negative electrode material, which can reduce the dissolution of silicon particles during the cycle, thereby reducing the reaction of the dissolved silicon particles with the electrolyte, and effectively reducing the gas production value of the negative electrode material; and the mesopores with a higher volume share in the pores of the negative electrode material can provide space for the volume expansion of the silicon particles, thereby improving the cycle performance of the negative electrode material.

Description

Negative electrode material and battery

Technical Field

The application relates to the technical field of negative electrode materials, in particular to a negative electrode material and a battery.

Background

The lithium ion battery has the advantages of high energy density, long service life, no environmental pollution and the like, and has been widely used in the 3C field. Along with the development of the market, the lithium ion battery is widely applied to mobile equipment such as smart phones and portable computers, and is also applied to the field of large-scale equipment such as electric automobiles and electric tools. In order to improve the energy density of the battery, research and development of silicon-based anode materials are becoming mature. Silicon undergoes large volume changes during lithiation/delithiation, which can lead to breakage, pulverization of materials, exfoliation from current collectors, and continued growth of solid electrolyte membranes, ultimately leading to capacity failure of the cell. In order to relieve adverse effects caused by volume expansion of a silicon material in a charging and discharging process, the silicon material and a carbon material can be compounded, and the silicon-based negative electrode material comprises a silicon-based active substance and a coating layer on the surface of the silicon-based active substance, but the coating layer of the existing silicon-based negative electrode material has poor coating effect, and dissolved silicon particles can be contacted with electrolyte in the process of preparing the silicon-based negative electrode material into a lithium ion battery, so that the problem of gas production exists.

Therefore, how to reduce the side reaction of silicon particles and electrolyte and reduce the gas production value is an urgent problem to be solved at present.

Disclosure of Invention

The application provides a negative electrode material and a battery, wherein the negative electrode material can reduce the reaction of silicon particles and electrolyte, reduce the gas production value and improve the cycle performance of the negative electrode material.

In a first aspect, the present application provides a negative electrode material, including a carbon matrix and silicon particles, the negative electrode material having pores, the pores including micropores and mesopores, wherein a ratio of a pore volume of the micropores to a pore volume of the mesopores is (1 to 45): (55-99);

The surface density beta of the negative electrode material is more than or equal to 80 percent;

the surface compactness beta of the anode material is measured by the following test method:

Soaking a negative electrode material with the mass of m ₁ g in a hydrofluoric acid solution with the mass fraction of 20% for 1 hour, cleaning and drying to obtain a material with the mass of m ₂ g, and calculating to obtain the surface density beta=m ₂/m₁ ×100% of the negative electrode material.

In some embodiments, the total pore volume of the anode material is 0.001cm ³/g～0.1cm³/g, and/or the average pore size of the pores of the anode material is 0.4nm to 50nm.

In some embodiments, the anode material has a micropore volume of 10% or less, a mesopore volume of 80% or more, and a macropore volume of 20% or less.

In some embodiments, the silicon particles comprise at least one of crystalline silicon, silicon oxide, amorphous silicon, silicon alloy, crystalline silicon, and amorphous silicon composite particles.

In some embodiments, the silicon particles have an average particle size of 0.1nm to 50nm.

In some embodiments, at least a portion of the silicon particles are located within particles of the carbon matrix.

In some embodiments, the carbon matrix comprises at least one of amorphous carbon and graphitized carbon.

In some embodiments, the mass content of silicon element in the anode material is 20% -60%; the mass content of the carbon element in the anode material is 20% -80%.

In some embodiments, the negative electrode slurry prepared from the negative electrode material has an average gas yield of less than or equal to 1 mL/g/day for 7 days in an environment of 25 ℃.

In some embodiments, the surface of the anode material has a coating layer, and the material of the coating layer includes at least one of metal oxide, carbon material, conductive polymer, fluoride, phosphate, and nitride.

In some embodiments, the metal oxide includes at least one of Sn, ge, fe, si, cu, ti, na, mg, al, ca and an oxide of Zn.

In some embodiments, the conductive polymer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, poly 3-hexylthiophene, poly-p-styrene, polypyridine, and polystyrene.

In some embodiments, 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.

In some embodiments, the phosphate comprises at least one of magnesium phosphate, calcium phosphate, aluminum phosphate, titanium phosphate, chromium phosphate, cobalt phosphate, nickel phosphate, germanium phosphate, zirconium phosphate, niobium phosphate, molybdenum phosphate, tantalum phosphate, tungsten phosphate, lanthanum phosphate.

In some embodiments, the nitride comprises at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride.

In some embodiments, the carbon material comprises at least one of amorphous carbon and graphitized carbon.

In some embodiments, the coating layer has a thickness of 1nm to 300nm.

In some embodiments, the coating layer accounts for 10% or less of the negative electrode material by mass.

In some embodiments, the median particle diameter D ₅₀ of the negative electrode material is 15 μm or less.

In some embodiments, the particle size distribution of the negative electrode material satisfies: d ₉₀-D₁₀)/D₅₀ is more than or equal to 0.9.

In some embodiments, the specific surface area of the negative electrode material is less than or equal to 10m ²/g.

In some embodiments, the negative electrode material has a compacted density of 0.8g/cm ³～1.3g/cm³.

In some embodiments, the negative electrode material has a tap density of 0.5g/cm ³～1.5g/cm³.

In some embodiments, the negative electrode material has a powder conductivity of 0.5S/cm to 2S/cm at a pressure of 20 kN.

In a second aspect, the present application provides a battery comprising the negative electrode material of the first aspect.

The technical scheme of the application has at least the following beneficial effects:

According to the negative electrode material provided by the application, the surface density of the negative electrode material is more than or equal to 80%, so that the dissolution of the negative electrode material in the circulation process can be reduced, the reaction of dissolved silicon particles and electrolyte is further reduced, the probability of silicate generation by the hydrolysis of the silicon particles is reduced, the gas production value of the negative electrode material is effectively reduced, the electrolyte can be effectively reduced to directly permeate into the inside of particles of the negative electrode material through a pore structure, the side reaction of the electrolyte and the silicon particles is reduced, and the circulation performance of a lithium ion battery is improved. In the application, the ratio of the pore volume of the micropores to the pore volume of the mesopores is controlled to be (1-45): (55-99), the pore volume ratio of micropores in the anode material is effectively reduced, namely, the active sites of side reaction of the anode material and the electrolyte are reduced, so that the thickening of a solid electrolyte membrane caused by continuous invasion of the electrolyte can be reduced, and the cycle performance of the anode material is improved; in addition, the mesoporous with increased volume ratio can reserve sufficient buffer space for the volume expansion of silicon particles, which is beneficial to improving the particle structure stability of the cathode material. According to the application, by controlling the surface density of the anode material and the volume ratio of micropores to mesopores in the anode material, the surface density and the volume ratio of micropores to mesopores in the anode material are synergistic, so that the dissolution of silicon particles is reduced, the side reaction of the anode material and electrolyte is reduced, the volume expansion of the silicon particles in the circulation process is effectively relieved, the particle breakage of the anode material is reduced, and the circulation performance of the anode material is comprehensively improved.

Detailed Description

The present application is explained below by way of examples, which are illustrative only for explaining the present application and are not to be construed as limiting the present application.

In order to improve the energy density of the battery, research and development of silicon-based anode materials are becoming mature. The silicon particles which are difficult to control and dissolve in the existing silicon-carbon composite mode can be contacted with electrolyte, so that the problem of serious gas production exists, and the cycle performance of the cathode material is not improved.

In a first aspect, the present application provides a negative electrode material comprising a carbon matrix and silicon particles; the negative electrode material is provided with holes, wherein the holes comprise micropores, mesopores and macropores, and the ratio of the pore volume of the micropores to the pore volume of the mesopores is (1-45): (55-99);

In the scheme, the surface density of the anode material is more than or equal to 80%, the dissolution of the anode material in the circulating process can be reduced, the reaction of dissolved silicon particles and electrolyte is further reduced, the probability of silicate generation by hydrolysis of the silicon particles is reduced, the gas production value of the anode material is effectively reduced, the electrolyte can be effectively reduced to directly permeate into the inside of particles of the anode material through a pore structure, the side reaction of the electrolyte and the silicon particles is reduced, and the circulating performance of the lithium ion battery is improved. The ratio of the pore volume of the micropores to the pore volume of the mesopores is controlled to be (1-45): (55-99), the pore volume ratio of micropores in the anode material is effectively reduced, namely, the active sites of side reaction of the anode material and the electrolyte are reduced, so that the thickening of a solid electrolyte membrane caused by continuous invasion of the electrolyte can be reduced, and the cycle performance of the anode material is improved; in addition, the mesoporous with increased volume ratio can reserve sufficient buffer space for the volume expansion of silicon particles, which is beneficial to improving the particle structure stability of the cathode material. According to the application, by controlling the surface density of the anode material and the volume ratio of micropores to mesopores in the anode material, the surface density and the volume ratio of micropores to mesopores in the anode material are synergistic, so that the dissolution of silicon particles is reduced, the side reaction of the anode material and electrolyte is reduced, the volume expansion of the silicon particles in the circulation process is effectively relieved, the particle breakage of the anode material is reduced, and the circulation performance of the anode material is comprehensively improved.

In some embodiments, the surface density of the negative electrode material is greater than or equal to 80%, specifically 80%, 82%, 85%, 86%, 89%, 90%, 92%, 95%, 98%, or the like, and of course, may be other values within the above range. It can be understood that, in an ideal state, the surface compactness of the anode material is 100%, and at this time, the surface compactness of the anode material is high, silicon particles in the anode material cannot be dissolved, and then the silicon particles which are not dissolved out are contacted and reacted with the dissolution liquid. However, the surface density of the conventionally prepared anode material is insufficient, the anode material has a certain dissolution amount in a dissolution liquid, the dissolution liquid contains dissolved silicon particles, and the surface density of the anode material can be defined by the dissolution amount of the silicon particles, namely, the surface density beta=m ₂/m₁ ×100%.

The dissolution liquid used in the application is a hydrofluoric acid solution with a mass fraction of 20%, and the dissolution liquid is excessive.

Through the test, the surface density beta of the anode material is more than or equal to 80%, and in the range, the high surface density characteristic of the anode material can effectively inhibit silicon particles from being in direct contact with water in the slurry preparation process, reduce side reaction and reduce the gas production value of the anode material. In addition, the dissolution amount of silicon particles in the charge-discharge cycle process of the anode material can be reduced, so that the side reaction of the dissolved silicon particles and electrolyte is reduced, and the gas production value of the anode material can be effectively reduced.

In some embodiments, the ratio of the pore volume of the micropores to the pore volume of the mesopores is (1-45): (55-99), specifically, it may be 1:99, 5:95, 10:90, 20:80, 30:65, 40:50 or 45:55, etc., but is not limited thereto. In the application, the pore volume ratio of the mesopores is increased, the pore volume ratio of the micropores is reduced, and the molecular size generated by the electrolyte is generally smaller than or equal to the pore diameter of the micropores, so that the adsorption capacity of the anode material is in a proportional relationship with the pore volume of the micropores to a large extent under the action of the strong capillary adsorption capacity of the micropores, namely, the adsorption capacity of the anode material is increased along with the increase of the micropore volume, and then the side reaction of the anode material and the electrolyte is increased. Therefore, the pore volume ratio of micropores of the anode material is controlled, so that the active sites of side reactions of the anode material and the electrolyte can be reduced, and further, the thickening of a solid electrolyte membrane caused by continuous invasion of the electrolyte can be reduced, thereby being beneficial to improving the cycle performance of the anode material; in addition, the mesoporous with increased volume ratio can reserve sufficient buffer space for the volume expansion of silicon particles, which is beneficial to improving the particle structure stability of the cathode material.

In some embodiments, the pore volume of the mesopores in the anode material is greater than or equal to 80%; specifically, the content may be 80%, 82%, 85%, 87%, 90%, 93%, 95%, 99%, or the like, and other values within the above range may be used, without limitation.

In some embodiments, the pore volume of the micropores in the negative electrode material may be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or the like, but may be other values within the above range, and the present invention is not limited thereto.

In some embodiments, the pore volume of macropores in the negative electrode material may be 20%, 18%, 15%, 12%, 10%, 8%, 7%, 5%, 4%, 3%, or 2%, or the like, but may be other values within the above range, and the present invention is not limited thereto.

It can be understood that the volume ratio of the micropores, mesopores and macropores in the anode material is controlled within the above range, so that the uniformity of the distribution of silicon particles in the anode material can be improved, and as most of the pores are mesopores, the volume expansion of the silicon particles can be effectively relieved, the local expansion stress of the anode material caused by the non-uniform volume change of the silicon particles in the circulation process is reduced, the cracking and pulverization of the anode material are caused, and the circulation stability of the anode material is improved.

In some embodiments, the total pore volume of the negative electrode material is 0.001cm ³/g～0.1cm³/g, specifically 0.001cm³/g、0.005cm³/g、0.006cm³/g、0.007cm³/g、0.01cm³/g、0.02cm³/g、0.03cm³/g、0.04cm³/g、0.05cm³/g、0.06cm³/g、0.08cm³/g or 0.1cm ³/g, and the like, but may also be other values within the above range, and is not limited herein. After the silicon particles are filled, the residual pores can reserve space for the volume expansion of the silicon particles, so that the expansion effect of the anode material is relieved, the circulation stability of the anode material is improved, a part of extremely small amount of gas generated by the side reaction of the silicon particles and the electrolyte can be adsorbed or contained, and the gas production phenomenon of the anode material is improved.

In some embodiments, the pores of the negative electrode material have an average pore size of 0.4nm to 50nm; specifically, the wavelength may be 0.4nm, 0.5nm, 1nm, 1.5nm, 2nm, 3nm, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, or the like, but other values within the above range are also possible, and the present invention is not limited thereto.

In some embodiments, the carbon matrix comprises at least one of artificial graphite, natural graphite, amorphous carbon, activated carbon, mesophase carbon microbeads, carbon nanotubes, carbon nanofibers, porous carbon, and graphene. From the viewpoint of production cost, the carbon matrix includes at least one of amorphous carbon and graphitized carbon. It can be understood that the carbon matrix can play a role of a supporting framework by selecting the materials, has good conductivity and ensures the conductivity of the anode material.

In some embodiments, the carbon matrix comprises trace metal elements including at least one of Fe, co, ni, cr, zn, cu and Al.

In some embodiments, the carbon matrix includes trace metal elements at a mass ratio of 200ppm or less; specifically, the concentration may be 200ppm, 180ppm, 160ppm, 150ppm, 140ppm, 130ppm, 120ppm, 100ppm, 50ppm, or the like, but other values within the above range are also possible, and the present invention is not limited thereto.

In some embodiments, the silicon particles include at least one of crystalline silicon, silicon oxide, amorphous silicon, silicon alloy, crystalline silicon and amorphous silicon composite particles, and the kinds of the carbon matrix and the silicon particles may be selected according to actual needs, which are not limited herein.

In some embodiments, the silicon particles comprise amorphous silicon and/or crystalline silicon; preferably, the silicon particles comprise amorphous silicon, and the amorphous silicon expands isotropically in the lithium intercalation process, so that collapse of a pore structure can be reduced, rapid attenuation of specific capacity is inhibited, and the lithium intercalation cycle performance of the anode material is improved.

In some embodiments, at least a portion of the silicon particles are located within the particles of the carbon matrix. The silicon particles are positioned in the carbon matrix, so that the conductivity of the anode material can be improved through the carbon matrix, meanwhile, the direct contact between the silicon particles and electrolyte is reduced, and side reactions are reduced.

In some embodiments, the silicon oxide includes elemental silicon and elemental oxygen, the atomic ratio of elemental silicon to elemental oxygen being from 0 to 2, and excluding 0. The atomic ratio of the silicon element to the oxygen element may be 0.05、0.11、0.21、0.26、0.31、0.41、0.51、0.59、0.61、0.69、0.71、0.74、0.76、0.79、0.89、0.99、1、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9, 2, or the like, and is not limited herein. Preferably, the atomic ratio of the silicon element to the oxygen element is 0 to 1, and 0 is not included.

In some embodiments, the silicon oxide has a chemical formula of SiO _x, wherein 0< x < 2, x may be 0.05、0.11、0.21、0.26、0.31、0.41、0.51、0.59、0.61、0.69、0.71、0.74、0.76、0.79、0.89、0.99、1、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8, 1.9, etc., and is not limited herein. Preferably 0< x <1.

In some embodiments, the silicon particles have an average particle size of 0.1nm to 50nm. Alternatively, the average particle diameter of the silicon particles may be specifically 0.1nm, 1nm, 2nm, 5nm, 10nm, 20nm, 25nm, 30nm, 40nm, 45nm, 50nm, etc., or may be any other value within a range, and may be selected according to actual needs, without limitation. The mechanical stress of the silicon particles during expansion is reduced along with the reduction of the particle size, the electron and ion transmission paths can be shortened after the reduction of the particle size, meanwhile, the silicon particles are reduced in size, the gaps between adjacent silicon particles are increased, and a space can be reserved for expansion. It is understood that the average particle diameter of the silicon particles is within the above range, the battery capacity of the lithium ion battery can be ensured, and the irreversible capacity loss can be reduced. Preferably, the average particle diameter of the silicon particles is 0.1nm to 5nm.

In some embodiments, the morphology of the silicon particles includes at least one of punctiform, spherical, ellipsoidal and lamellar, and the morphology of the silicon particles may be selected according to actual needs, without limitation.

In some embodiments, the silicon particles have a purity greater than 99%, it being understood that high purity silicon particles facilitate Li-Si alloying with lithium, improving the cycling performance of lithium ion batteries.

In some embodiments, the mass content of the silicon element in the anode material is 20% -60%. Specifically, the silicon element content in the negative electrode material is 20%, 25%, 30%, 40%, 45%, 50%, 55% or 60% by mass, and is not limited herein.

In some embodiments, the mass content of the carbon element in the anode material is 20% -80%. Specifically, the mass content of the carbon element in the negative electrode material is 20%, 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%, which is not limited herein.

In some embodiments, the average gas yield of the negative electrode slurry prepared from the negative electrode material is less than or equal to 1 mL/kg/day in an environment of 25 ℃ for 7 days, specifically, 1 mL/kg/day, 0.8 mL/kg/day, 0.6 mL/kg/day, 0.5 mL/kg/day, 0.4 mL/kg/day, 0.3 mL/kg/day, 0.2 mL/kg/day, or 0.1 mL/kg/day, etc., but other values within the above range are also possible, and the present application is not limited thereto. The gas production value of the cathode material is controlled in the range, so that most of silicon particles can be relatively uniformly distributed in the pores of the carbon matrix, and the direct contact between the silicon particles and the electrolyte is reduced, thereby reducing the side reaction (namely, the hydrolysis of silicon into silicate and hydrogen) between the dissolved silicon particles and the electrolyte, and effectively reducing the gas production value of the cathode material. When the surface density of the anode material is insufficient, the gas production value of the anode material can be obviously increased.

In some embodiments, the surface of the anode material has a coating layer, and the material of the coating layer includes at least one of metal oxide, carbon material, amorphous silicon, conductive polymer, fluoride, phosphate, and nitride. It can be appreciated that the coating layer positioned on the outermost layer of the anode material has good conductivity, so that the conductivity of the anode material can be improved, and silicon particles exposed on the surface of the carbon matrix can be coated, so that the continuous oxidation of the exposed silicon particles in the placing process is reduced, and the specific capacity and the first coulombic efficiency (ICE) reduction of the anode material are reduced; the coating layer can also reduce direct contact between silicon particles and electrolyte, and ensure stability of SEI film, thereby improving first coulombic efficiency of the anode material.

In some embodiments, the fluoride includes at least one of vinyl fluoride, fluoropolymer, lithium fluoride, sodium fluoride, potassium fluoride, fluorocarbon polymer, fluorosilicone 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.

In the practical application process, the material of the coating layer can be selected according to practical needs, and the material is not limited herein. The coating layer may be a single layer coating layer formed of the above single material, a coating layer formed of a combination of the above plural materials, a multi-layer coating layer formed of a single material, a multi-layer coating layer formed of a plurality of materials, or the like, and the coating layer may be, for example, a carbon coating layer and then a polymer coating layer, or a polymer coating layer and then an oxide coating layer, or the like. It can be appreciated that the compactness is higher when the cladding layer is a multilayer cladding structure.

In some embodiments, the thickness of the coating layer is 1nm to 300nm, alternatively, the thickness of the coating layer may be specifically 1nm, 50nm, 150nm, 200nm, 250nm, 300nm, or the like, or may be any other value within a range, and may be selected according to actual needs, which is not limited herein. It will be appreciated that the coating may reduce the solubility of the anode material and thus reduce the gas yield of the reaction of the dissolved silicon particles with the electrolyte. The thickness of the coating layer is controlled within the range, so that the stability of the particle structure of the anode material is maintained in the circulation process, the exposed Si on the surface of the anode material can be reduced, a large amount of SEI (solid electrolyte interphase) is generated in the charge and discharge process due to the exposed silicon, and the specific capacity and the electrochemical performance of the anode material are improved. Preferably, the thickness of the coating layer is 1nm to 50nm, more preferably, the thickness of the coating layer is 1nm to 30nm.

In some embodiments, the mass ratio of the coating layer in the anode material is equal to or less than 10%, specifically, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1%, or the like, but other values within the above range are also possible, and the invention is not limited thereto. It can be understood that the coating layer can reduce the solubility of the anode material, so as to reduce the gas production rate of the reaction of the dissolved silicon particles and the electrolyte, and the mass ratio of the coating layer in the anode material is within the above range, so that the lithium intercalation amount of the anode material can be ensured, and the charge and discharge capacity of the lithium ion battery prepared by the anode material can be further ensured.

In some embodiments, the median particle diameter D ₅₀ of the negative electrode material is 15 μm or less, specifically 15 μm, 13 μm, 12 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, or 1 μm, etc., but other values within the above range are also possible, and the present invention is not limited thereto. It can be understood that the median particle diameter refers to the particle size of the anode material located at the middle position after the particles of the anode material are ordered according to the size, and the median particle diameter of the anode material is in the above range, so that the time of lithium ion intercalation and deintercalation can be ensured, the anode material can realize a state of rapidly and fully intercalating lithium, and further the charge and discharge performance of the lithium ion battery can be ensured.

In some embodiments, the particle size distribution of the anode material satisfies: the particle size distribution of the negative electrode material is not limited in the above range, large particles with larger particle size and small particles with smaller particle size of the negative electrode material can be matched with each other, and the small particles fill pores among the large particles, so that the tap density of the negative electrode material can be improved.

In some embodiments, the specific surface area of the negative electrode material is equal to or less than 10m ²/g, specifically 10m²/g、8.9m²/g、6.8m²/g、5.5m²/g、4.2m²/g、4m²/g、3m²/g、2.5m²/g、2m²/g or 1m ²/g, or the like, but may be any other value within the above range, and the specific surface area is not limited thereto. It can be understood that the specific surface area of the anode material affects the contact area between the anode material and the electrolyte, and the specific surface area of the anode material is within the above range, so that the amount of lithium ions consumed by the SEI film formed in the first charge and discharge process of the lithium ion battery can be reduced, and the irreversible capacity loss of the lithium ion battery can be reduced.

In some embodiments, the compacted density of the negative electrode material is 0.8g/cm ³～1.3g/cm³, specifically, may be 0.8g/cm ³、0.9g/cm³、1.0g/cm³、1.1g/cm³、1.2g/cm³ or 1.3g/cm ³, or the like, but may be other values within the above range, which is not limited thereto.

In some embodiments, the tap density of the negative electrode material is 0.5g/cm ³～1.5g/cm³, specifically 0.5g/cm³、0.6g/cm³、0.7g/cm³、0.8g/cm³、0.9g/cm³、1.0g/cm³、1.1g/cm³、1.2g/cm³、1.3g/cm³、1.4g/cm³ or 1.5g/cm ³, but may be other values within the above range, and is not limited thereto.

In some embodiments, the powder conductivity of the negative electrode material under a pressure of 20kN is 0.5S/cm to 2S/cm, specifically, may be 0.5S/cm, 0.8S/cm, 1.0S/cm, 1.2S/cm, 1.5S/cm, 2S/cm, 3S/cm, 4S/cm, or 5.0S/cm, etc., but may be other values within the above range, and is not limited thereto. Because silicon particles have poor electrical conductivity, the worse the coating effect, the lower the electrical conductivity of the negative electrode material in general. The powder conductivity of the anode material is controlled in the range, so that the exposed silicon particles on the surface of the anode material are few, and the silicon particles are embedded in the carbon matrix or covered by the coating material, so that the electrochemical performance of the anode material can be effectively improved.

In a second aspect, the present application provides a method for preparing a negative electrode material, comprising the steps of:

step S10, preparing a compound containing a carbon matrix and silicon particles, wherein the compound contains a metal catalyst;

step S20, coating the compound by using a coating material to obtain a negative electrode material; wherein the surface density beta of the negative electrode material is more than or equal to 80 percent, and the ratio of the pore volume of micropores to the pore volume of mesopores in the negative electrode material is (1-45): (55-99).

In the scheme, the composite comprises the metal catalyst, and the metal catalyst promotes the coating material to be coated on the surface of the composite in the coating treatment process, so that the anode material with high surface density is prepared. The method can solve the problem that when the anode material is prepared by adopting vapor deposition in the prior art, high cracking temperature is adopted to ensure that an air source is completely cracked, so that the reaction of high-activity silicon particles and a carbon matrix is consumed, and the charge and discharge capacity of the lithium ion battery is ensured. The surface density of the prepared anode material is more than or equal to 80%, the dissolution of the anode material in the circulation process can be reduced, the reaction of dissolved silicon particles and electrolyte is further reduced, the gas production value of the anode material is effectively reduced, the electrolyte can be effectively reduced to directly permeate into the inside of particles of the anode material through a pore structure, the side reaction of the electrolyte and the silicon particles is reduced, and the circulation performance of the lithium ion battery is improved. And meanwhile, coating treatment is carried out, and most micropores in the anode material are covered by silicon particles and coating materials, so that the ratio of the pore volume of the micropores to the pore volume of the mesopores is (1-45): (55-99), the pore volume ratio of micropores in the anode material can be effectively reduced, namely, the active sites of side reactions of the anode material and the electrolyte are reduced, and further, the thickening of a solid electrolyte membrane caused by continuous invasion of the electrolyte can be reduced, so that the cycle performance of the anode material is improved; in addition, the mesoporous with increased volume ratio can reserve sufficient buffer space for the volume expansion of silicon particles, which is beneficial to improving the particle structure stability of the cathode material.

The preparation method of the application is specifically described below with reference to examples:

In step S10, the specific steps for preparing a composite of a carbon-containing matrix and silicon particles include: and soaking the carbon matrix in a solution containing a catalyst, and depositing silicon particles on the product after solid-liquid separation to obtain the compound.

In some embodiments, the carbon substrate is immersed in a solution containing a catalyst to adhere the catalyst to the surface or inside of the carbon substrate, the solution of the catalyst is a salt solution containing at least one of Cu, ni, co, fe and B, it is understood that the catalyst contains the above elements, and the temperature during the coating process can be reduced, so that a negative electrode material with high surface density can be obtained at a lower temperature.

In some embodiments, the carbon matrix has pores, including micropores, mesopores, and macropores.

In some embodiments, the volume fraction of pores with a pore diameter below 2nm in the total pore volume in the carbon matrix is ≡70%; specifically, the content may be 70%, 75%, 80%, 85%, 90%, 95%, 99%, or the like, and other values within the above range may be used, without limitation.

In some embodiments, pores with pore diameters below 5nm account for greater than or equal to 85% of the total pore volume in the carbon matrix; specifically, 85%, 87%, 89%, 90%, 92%, 95%, 97% or 99% may be used, and other values within the above range may be used, without limitation.

In some embodiments, the volume fraction of pores with a pore diameter below 10nm in the total pore volume in the carbon matrix is greater than or equal to 95%; specifically, 95%, 96%, 97%, 98%, 99% or the like may be used, and other values within the above range may be used, without limitation.

It can be understood that the pore volume ratio of the carbon matrix is controlled within the above range, and the pores can accommodate most of silicon particles, so that silicon segregation formed by deposition of silicon particles on the surface of the carbon matrix is reduced, the content of silicon particles in the carbon matrix and the uniformity of distribution of silicon particles are improved, and the specific capacity and mechanical properties of the cathode material are further improved.

In some embodiments, the specific surface area of the carbon matrix is 500m ²/g～2000m²/g; the specific surface area may be 500m²/g、800m²/g、1000m²/g、1200m²/g、1400m²/g、1600m²/g、1800m²/g、1900m²/g or 2000m ²/g, or the like, but may be other values within the above range, and is not limited thereto. Preferably, the specific surface area of the carbon matrix is 1200m ²/g～2000m²/g.

In some embodiments, the total pore volume of all pores in the carbon matrix is 0.5cm ³/g～1.5cm³/g; specifically, 0.5cm³/g、0.6cm³/g、0.7cm³/g、0.8cm³/g、0.9cm³/g、1.0cm³/g、1.1cm³/g、1.2cm³/g、1.3cm³/g、1.4cm³/g or 1.5cm ³/g, etc., but other values within the above range are also possible, and the present invention is not limited thereto. It will be appreciated that the carbon matrix has a rich porosity that is capable of accommodating the silicon particles and leaves room for volume expansion of the silicon particles. Preferably, the total pore volume of all pores in the carbon matrix is 0.6cm ³/g～1.0cm³/g.

In some embodiments, the concentration of the catalyst-containing solution is 0.1mol/L to 20mol/L, alternatively, the concentration may be specifically 0.1mol/L, 0.5mol/L, 1.2mol/L, 2.5mol/L, 3.4mol/L, 5.0mol/L, 8mol/L, 10mol/L, 15mol/L, 18mol/L, 20mol/L, etc., and may be other values within a range, and may be selected according to actual needs, without limitation. It will be appreciated that the concentration of the catalyst is within the above range, contributing to the formation of a negative electrode material having high surface density on the surface of the composite.

In some embodiments, the soaking time is 10 min-1000 min, and optionally, the soaking time may specifically be 10min, 50min, 180min, 240min, 400min, 500min, 700min, 800min, 1000min, or other values within a range, and may be selected according to actual needs, which is not limited herein. It is understood that the time of infiltration is within the above range, which can increase the amount of catalyst adhering, and contribute to the formation of a negative electrode material having high surface density on the surface of the composite.

In some embodiments, the carbon matrix comprises at least one of artificial graphite, natural graphite, amorphous carbon, activated carbon, mesophase carbon microbeads, carbon nanotubes, carbon nanofibers, porous carbon, and graphene, and it is understood that the carbon matrix can serve as a supporting framework by selecting the above materials, and has good conductivity, and ensures the conductivity of the anode material.

In some embodiments, the silicon particles include at least one of crystalline silicon, silicon oxide, amorphous silicon, silicon alloy, crystalline silicon and amorphous silicon composite particles, and the kind of the silicon particles may be selected according to actual needs, which is not limited herein. The silicon alloy may be silicon lithium alloy, silicon magnesium alloy, silicon nickel alloy, etc.

In some embodiments, the deposition manner of the silicon particles may be vapor deposition or liquid deposition, and the deposition manner of the silicon particles may be selected according to actual needs, which is not limited herein.

In some embodiments, the silicon particles may also be obtained by rapid decomposition/evaporation of a liquid phase precursor material or a solution containing active silicon particles, the liquid phase precursor material comprising an organoliquid phase silane material.

Preferably, the silicon particles are deposited by vapor phase chemical deposition, and the steps include: introducing a silicon-containing gas source to perform a vapor phase chemical deposition reaction with the carbon matrix.

In some embodiments, the silicon-containing gas source includes at least one of silane, disilane, trisilane, and tetrasilane, and may be selected according to actual needs without limitation.

In one embodiment, the gas feed includes a silicon-containing gas source and an auxiliary carrier gas that is capable of diluting the silicon-containing gas source and helps control the residence time of the silicon-containing gas source. The auxiliary carrier gas comprises at least one of nitrogen, argon and helium.

In some embodiments, the volume ratio of the silicon-containing gas source to the auxiliary carrier gas is 1 (1-10), specifically may be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10, etc., or may be other values within the range, and may be selected according to the actual needs within the above range.

In some embodiments, the gas introduced further comprises a dopant gas, which may be NH ₃、PH₃ in particular.

In some embodiments, the vapor deposition reaction is carried out at a pressure of from 10kPa to normal pressure.

In some embodiments, the temperature of the vapor phase chemical deposition reaction is 400 ℃ to 600 ℃, specifically 400 ℃, 420 ℃, 450 ℃, 480 ℃, 500 ℃, 550 ℃, 600 ℃ and the like, but may be other values within the range, and may be selected within the above range according to actual needs, and the present invention is not limited thereto. Preferably, the temperature of the vapor phase chemical deposition reaction is 400 ℃ to 500 ℃.

In some embodiments, the time of the vapor phase chemical deposition reaction is 1h to 20h, and the time may specifically be 1h, 3h, 4h, 6h, 7h, 8h, 10h, 12h, 15h, 20h, etc., or may be other values within a range, and may be selected according to actual needs, which is not limited herein. Preferably, the temperature holding time of the vapor phase chemical deposition reaction is 2-6 h.

By controlling the reaction parameters of the vapor phase chemical deposition, the vapor phase silicon source can permeate into the carbon matrix and decompose in the pores of the carbon matrix, and silicon particles with proper particle size are formed by deposition.

In some embodiments, a liquid phase silicon source including at least one of monochlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane may also be used in combination with the carbon substrate. .

Step S20, coating the compound by using a coating material to obtain a negative electrode material; wherein, the surface density beta of the anode material is more than or equal to 80 percent.

In some embodiments, the coating material includes at least one of a carbon material, a metal oxide, a conductive polymer, a fluoride, a phosphate, and a nitride.

In some embodiments, the thickness of the coating layer formed by the coating material is 1nm to 300nm, alternatively, the thickness of the coating layer may be specifically 1nm, 50nm, 150nm, 200nm, 250nm, 300nm, etc., and may be any other value within a range, and may be selected according to practical needs, and is not limited herein. It will be appreciated that the coating may reduce the solubility of the anode material and thus reduce the gas yield of the reaction of the dissolved silicon particles with the electrolyte. The thickness of the coating layer is controlled within the range, so that the stability of the particle structure of the anode material in the circulating process is maintained, the dissolution of silicon particles is reduced, the transmission efficiency of lithium ions is improved, and the charge and discharge performance of the anode material is improved. Preferably, the thickness of the coating layer is 1nm to 50nm, more preferably, the thickness of the coating layer is 1nm to 30nm.

In some embodiments, the mass ratio of the coating layer in the anode material is less than or equal to 10%, and it can be understood that the coating layer can reduce the solubility of the anode material, further reduce the gas yield of the reaction of the dissolved silicon particles and the electrolyte, and the mass ratio of the coating layer in the anode material is in the above range, so that the lithium intercalation amount of the anode material can be ensured, and further the charge and discharge capacity of the lithium ion battery prepared by the anode material can be ensured.

In some embodiments, the coating material comprises a carbon material comprising at least one of amorphous carbon and graphitized carbon.

In some embodiments, the cladding material comprises a metal oxide comprising at least one of Sn, ge, fe, si, cu, ti, na, mg, al, ca and an oxide of Zn.

In some embodiments, the coating material comprises a conductive polymer comprising at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, poly 3-hexylthiophene, poly para-styrene, polypyridine, and polystyrene.

In some embodiments, the coating material comprises a fluoride including at least one of vinyl fluoride, fluoropolymer, lithium fluoride, sodium fluoride, potassium fluoride, fluorocarbon polymer, fluorosilicone 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.

In some embodiments, the coating material comprises a phosphate comprising at least one of magnesium phosphate, calcium phosphate, aluminum phosphate, titanium phosphate, chromium phosphate, cobalt phosphate, nickel phosphate, germanium phosphate, zirconium phosphate, niobium phosphate, molybdenum phosphate, tantalum phosphate, tungsten phosphate, lanthanum phosphate.

In some embodiments, the cladding material comprises a nitride comprising at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride.

In some embodiments, the mass content of the coating material is 1% to 75%, specifically 1%, 10%, 20%, 30%, 50%, 55%, 60%, 75%, etc., based on 100% of the total mass of the composite and the coating material, and may be any other value within the range, and may be selected according to practical needs, and is not limited herein.

In some embodiments, the temperature of the heat treatment is 200 ℃ to 600 ℃, the heat preservation time of the heat treatment is 0.5h to 20h, alternatively, the temperature can be 200 ℃, 250 ℃,300 ℃, 400 ℃, 500 ℃, 600 ℃ and the like, the time can be 0.5h, 1h, 3h, 5h, 6h, 8h, 10h, 11h, 15h, 18h, 20h and the like, and other values in the range can be selected according to practical needs, and the heat treatment method is not limited herein.

In some embodiments, the heat treatment is performed under a protective gas, which includes at least one of nitrogen, helium, neon, argon, and krypton, and may be selected according to actual needs, without limitation.

In the technical scheme, the surface of the silicon-carbon composite is coated to form the coating layer, so that on one hand, side reactions caused by the fact that electrolyte enters the cathode material can be reduced, the first coulomb efficiency and the specific capacity are reduced, the problem of volume expansion of the cathode material can be further solved, the conductivity of the cathode material is improved, the volume expansion of the whole composite material is further reduced, and the swelling of electrode plates is reduced. During the coating process, small amounts of coating material may enter the pores of the composite.

The coating process of the application is performed on the premise of reducing the occurrence of crystal transformation of the silicon-carbon anode material. Preferably, in step S20, the composite is subjected to a carbon coating treatment including at least one of solid phase carbon coating, liquid phase carbon coating and gas phase carbon coating.

In some embodiments, the carbon coating process is a gas phase carbon coating, the steps comprising: firstly, vacuumizing, heating the compound, and then, introducing protective gas and carbon source gas, keeping the air pressure within a preset range, and thermally cracking the carbon source gas to obtain the anode material.

In some embodiments, the vacuum degree after the vacuuming treatment is less than or equal to 1600Pa, specifically, 1600Pa, 1500Pa, 1300Pa, 1200Pa, 1000Pa, 800Pa, 500Pa, 100Pa or 10Pa, or other values within the range can be used, and the vacuum degree can be selected according to actual needs, and the vacuum degree is not limited herein.

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

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

In some embodiments, the protective gas and the carbon source gas are introduced and maintained at a gas pressure in the range of 1 to 10 kPa.

In some embodiments, the thermal cracking temperature is 400 ℃ to 800 ℃, alternatively, the temperature may be specifically 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, etc., or may be other values within a range, and may be selected according to actual needs, without limitation. Preferably, the thermal cracking temperature is 500 ℃ to 650 ℃.

In some embodiments, the thermal cracking time is 0.5 h-18 h, and the thermal cracking time may be specifically 0.5h, 1.5h, 3h, 5h, 6h, 7h, 8h, 10h, 18h, etc., or may be other values within a range, and may be selected according to actual needs, which is not limited herein. Preferably, the thermal cracking is carried out for 1-2 hours.

In some embodiments, the volume ratio of protective gas to carbon source gas is 1: (0.01-20), optionally, the volume ratio can be 1:0.01, 1:0.1, 1: 1. 1: 3. 1: 5.1: 8. 1: 10. 1:15 and 1:20, etc., may be any other value within the range, and may be selected according to actual needs, and is not limited thereto.

In some embodiments, the flow rate of the carbon source gas is 100sccm to 500sccm; specifically, the value may be 100sccm, 200sccm, 250sccm, 300sccm, 350sccm, 400sccm, 450sccm, 500sccm, or the like, but other values within the above range are also possible, and the present invention is not limited thereto. Preferably, the flow rate of the carbon source gas is 200sccm to 300sccm.

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

In some embodiments, the deposition coating of the carbon source gas is performed under the condition of rotating the reaction furnace, so as to realize the homogeneous in-situ carbon coating on the surface of the compound.

In some embodiments, the carbon coating treatment is a solid phase carbon coating, the steps comprising: firstly, vacuumizing, and carbonizing a mixture obtained by mixing the compound and a solid-phase carbon source under a preset vacuum degree to obtain the anode material.

In some embodiments, the mixture of the composite and the solid carbon source is carbonized at a predetermined vacuum, the vacuum being controlled in the range of 1 to 10 kPa.

In some embodiments, the carbonization treatment is performed at a temperature of 600 ℃ to 1200 ℃ for a time of 1h to 15h. Alternatively, the temperature may be 600 ℃, 700 ℃, 800 ℃, 900 ℃,1000 ℃, 1200 ℃ and the like, and the time may be 1h, 2h, 4h, 6h, 8h, 9h, 11h, 12h, 15h and the like, or may be other values within a range, and may be selected according to actual needs, and the method is not limited herein.

In some embodiments, the solid phase carbon source comprises at least one of a saccharide, an ester, a hydrocarbon, an organic acid, and a high molecular polymer.

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.

In some embodiments, the mass ratio of solid phase carbon source to complex is 100: (10-200), optionally, the mass ratio may be specifically 100:10, 100:40, 100:60, 100:100, 100:130, 100:160, 100:200, etc., or may be other values within a range, and may be selected according to actual needs, which is not limited herein.

In some embodiments, the solid-phase carbon source and the complex may be mixed in a manner such as VC mixing, fusion, ball milling, three-dimensional mixing, fluidized bed mixing, and the like.

In some embodiments, the apparatus used for solid-phase carbon coating is at least one of a rotary kiln, a box furnace, a roller kiln, a tunnel kiln, and a pusher kiln.

In some embodiments, the carbon coating process is a liquid phase carbon coating, the steps comprising: and (3) carbonizing the mixture obtained by mixing the compound with a liquid-phase carbon source to obtain the anode material.

In some embodiments, the mass ratio of liquid phase carbon source to composite is 100: (5-300), optionally, the mass ratio may be specifically 100:5, 100:10, 100:60, 100:150, 100:200, 100:240, 100:300, etc., or may be other values within a range, and may be selected according to actual needs, which is not limited herein.

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

In some embodiments, the liquid flow rate of the liquid phase carbon source is from 1mL/min to 200mL/min; specifically, the concentration may be 1mL/min, 5mL/min, 8mL/min, 10mL/min, 20mL/min, 30mL/min, 50mL/min, 80mL/min, 100mL/min, 200mL/min, or the like, or may be any other value within a range, and may be selected according to actual needs, without limitation.

In some embodiments, the carbonization treatment is performed at a temperature of 600 ℃ to 1200 ℃ for a time of 1h to 15h. Alternatively, the temperature may be 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1200 ℃ and the like, and the time may be 1h, 3h, 5h, 7h, 9h, 10h, 12h, 13h, 15h and the like, or may be other values within a range, and may be selected according to actual needs, and the method is not limited herein.

In some embodiments, the mixing mode of the compound and the liquid carbon source can be VC mixing, fusion, ball milling, suction filtration, heating reflux, three-dimensional mixing, fluidized bed mixing and the like; the equipment used for coating the liquid-phase carbon is at least one of a rotary furnace, a box furnace, a roller kiln and a tunnel kiln.

By controlling the mass ratio of the liquid-phase carbon source to the compound, the flow rate of the liquid-phase carbon source and other parameters, the liquid-phase carbon source and the compound are fully mixed, the liquid-phase carbon source is coated on the surface of the compound, part of the liquid-phase carbon source permeates into the compound to form a carbon material coating layer with proper thickness, the rate capability of the anode material is improved, and the volume expansion of the anode material is reduced.

In a third aspect, the present application provides a battery comprising the above negative electrode material or the negative electrode material prepared by the above preparation method.

Those skilled in the art will appreciate that the above-described methods of preparing a battery are merely examples. Other methods commonly used in the art may be employed without departing from the present disclosure.

The application is further illustrated in the following examples. The embodiments of the present application are not limited to the following specific embodiments. The modification can be appropriately performed within the scope of the main claim.

The testing method comprises the following steps:

1. And (3) compactness beta test: and (3) soaking the anode material with the mass of m 1g in hydrofluoric acid solution with the mass fraction of 20% for 1 hour, cleaning and drying to obtain m 2g of material, and calculating to obtain the surface compactness beta=m2/m1×100% of the anode material.

2. Thickness of the coating layer: the material was subjected to a section treatment by FIB-SEM equipment, 10 particles were randomly taken in the SEM, each particle was measured 3 times for the thickness of the coating layer, and the average thickness of the coating layer was measured.

3. Pore diameter and pore volume ratio testing method:

The pore volume of the sample refers to the total pore volume per unit mass of the sample, and the pore volume of the carbon matrix can be measured by gas adsorption measurement. Nitrogen adsorption is a technique to characterize the porosity and pore size distribution of a material by condensing a gas in the pores of a solid. As the pressure increases, the gas first condenses in the pores with the smallest diameter and the pressure increases until a saturation point is reached where all pores are filled with liquid. The nitrogen pressure was then gradually reduced to evaporate the liquid from the system. Analysis of adsorption and desorption isotherms enables determination of pore volume and pore size distribution, and the respective pore volume to total pore volume ratio of micropores, mesopores, and macropores.

4. The specific surface area test method of the anode material comprises the following steps:

the specific surface area was measured using a microphone trisar 3000 specific surface area and pore size analyzer device.

5. And (3) gas production test:

Dispersing CMC (carboxymethyl cellulose) in water according to a mass ratio of 1.4% for sizing, and mixing 10g of glue solution with 10g of anode material to obtain slurry after uniform dispersion; filling the slurry into an aluminum plastic film bag, and recording the mass of the slurry; and then sealing to form a sealed aluminum plastic film bag.

Fixing the sealed aluminum-plastic film bag at the bottom of the container, completely immersing the container in water, and recording the volume of the aluminum-plastic film bag; after fixed time (24 h), the volume of the aluminum plastic film bag is recorded again; calculating the gas yield of the silicon anode material according to the volume change of the aluminum-plastic film, wherein the unit is: mL/g.

6. Type of silicon particles: diffraction peaks were measured using an X-ray diffractometer (XRD) to confirm the kind of silicon particles.

7. And testing the mass content of silicon in the anode material:

firing the sample in a box-type atmosphere furnace (model: SA2-9-17 TP) under an oxygen atmosphere to enable silicon and silicon oxide in the sample to react into silicon dioxide, changing carbon into carbon dioxide after burning, discharging, weighing and calculating the mass content of silicon in the anode material.

8. And testing the mass content of carbon in the anode material:

The sample is burnt in a high temperature oxygen-enriched state by using a Blucker/Earthwork infrared carbon-sulfur analyzer G4 ICARUS HF/CS-i in Germany, the carbon element is oxidized into carbon dioxide, and enters an infrared detector along with carrier gas, and the content of the carbon element is calculated by quantitatively counting the change of the infrared absorption wavelength intensity of a carbon dioxide signal.

9. Powder conductivity test:

The conductivity at 20KN pressure point was measured by using an MCP-PD51 powder resistance test system of Mitsubishi chemical in Japan, and the volume resistivity of the sample was measured by using a four-probe method. The resistance of the powder can be measured by the instrument, and then the conductivity and the resistivity of the powder can be automatically calculated by a computer.

10. Tap density test of negative electrode material:

And (3) using a Meikang tower DAT-6-220 tap density instrument, placing a sample with specified mass into a measuring cylinder, vibrating the sample according to specified times (conventional test tap 3000 times), reading the volume of the measuring cylinder after tapping and calculating the tap density.

11. Compaction density test of negative electrode material:

And (3) using a Michael CARVER 4350.22 powder compaction densitometer in the United states, placing a sample with a specified mass m in a die, applying 1.0T pressure, maintaining the pressure for 30 seconds, then removing the pressure, testing the thickness, and calculating to obtain the compaction density.

12. And (3) testing electrical properties:

The button cell test was performed using the following method: preparing negative electrode slurry according to the mass ratio of the negative electrode material, the conductive carbon black and the polyacrylic acid copolymer (PPA) of 70:15:15, coating the negative electrode slurry on a copper foil, and drying the copper foil to prepare the negative electrode plate. The button cell was assembled in a glove box filled with Ar gas using a metallic lithium sheet as a counter electrode. And (3) carrying out charge and discharge test on the button cell in a charge and discharge interval of 0.01-5V at a current density of 0.1C to obtain the first reversible specific capacity and the first coulomb efficiency of the button cell.

And repeating the charge and discharge test for 50 times in a charge and discharge interval of 0.01V-5V at the current density of 1C to obtain the capacity retention rate and the pole piece thickness expansion rate after the battery circulates for 50 circles.

Example 1:

(1) The carbon matrix with holes was added to a 2mol/L copper nitrate solution, immersed for 0.5 hours, and then vacuum-dried to obtain a catalyst-containing carbon matrix.

(2) And (3) placing a carbon matrix containing a catalyst in a CVD reaction cavity, wherein the volume concentration ratio of silane to argon is 1:3 (the concentration of silicon-containing gas is 25%), heating to 500 ℃, preserving heat for 5h, and cooling to room temperature to obtain the compound.

(3) Mixing phenolic resin and the compound according to the mass ratio of 1:4, then placing the mixed materials into a high-temperature box type furnace, vacuumizing to 5kPa, introducing nitrogen, carbonizing at 580 ℃ under 5kPa, preserving heat for 2 hours, reducing the temperature, pulverizing the product, screening, and grading to obtain the anode material.

The anode material prepared in this embodiment includes a carbon matrix and silicon particles, and a part of the silicon particles are located in the pores of the carbon matrix.

Example 2:

Unlike example 1, the following is:

(1) The carbon matrix with holes is added into 1mol/L ferric nitrate solution, soaked for 1 hour, and then vacuum dried, thus obtaining the carbon matrix containing the catalyst.

(2) Placing a carbon matrix containing a catalyst into a CVD reaction cavity, wherein the volume concentration ratio of silane to argon is 1:6 (the silicon-containing gas concentration is 14.3%), vacuumizing to 2.5kPa, heating to 580 ℃, preserving heat for 10 hours under the condition of 2.5kPa, and cooling to room temperature to obtain the compound.

(3) And (3) putting the compound into a rotary CVD furnace, heating to 600 ℃, introducing acetylene and nitrogen, wherein the ratio of the acetylene to the nitrogen is 1:3, preserving heat for 10 hours, crushing and screening the cooled product, and grading to obtain the anode material.

Example 3:

(1) The method comprises the following steps of (1) mixing active carbon and boric acid according to a mass ratio of 100:5, and then drying, and processing at 1000 ℃ to obtain the carbon matrix containing the catalyst.

(2) Placing a carbon matrix containing a catalyst into a CVD reaction cavity, introducing silane, wherein the volume concentration ratio of the silane to H ₂ is 3:2 (the silicon-containing gas concentration is 60%), heating to 600 ℃, reacting for 2H, and cooling to room temperature to obtain the compound.

(3) Placing the compound into a high-temperature box type furnace, introducing mixed gas of 2% oxygen and argon, vacuumizing to 1kPa, heating to 300 ℃ and carbonizing treatment under the condition of 1kPa, preserving heat for 2 hours, crushing and screening the preserved sample, and grading to obtain the negative electrode material.

Example 4:

(1) The method comprises the following steps of (1) mixing active carbon and nickel carbonate according to a mass ratio of 100:2, and then drying, and processing at 950 ℃ to obtain the carbon matrix containing the catalyst.

(2) Placing a carbon matrix containing a catalyst into a CVD reaction cavity, introducing silane, heating to 420 ℃ for reaction for 20 hours, and cooling to room temperature to obtain a compound, wherein the volume concentration ratio of the silane to N ₂ is 4:1 (the silicon-containing gas concentration is 80%).

(3) Mixing sucrose and the compound according to the mass ratio of 1:1, then placing the mixed materials into a high-temperature box-type furnace, vacuumizing to 500Pa, introducing nitrogen, heating to 550 ℃, carbonizing under 500Pa, and preserving heat for 5h; and crushing and screening the heat-preserving sample, and grading to obtain the negative electrode material.

Example 5:

Unlike example 1, the following is:

(2) And (3) placing a carbon matrix containing a catalyst in a CVD reaction cavity, wherein the volume concentration ratio of silane to argon is 1:1 (the concentration of silicon-containing gas is 50%), heating to 500 ℃, preserving heat for 2h, and cooling to room temperature to obtain the compound.

Example 6:

Unlike example 1, the following is:

(2) And (3) placing a carbon matrix containing a catalyst in a CVD reaction cavity, wherein the volume concentration ratio of silane to argon is 1:15 (the concentration of silicon-containing gas is 6.25%), heating to 400 ℃, preserving heat for 5h, and cooling to room temperature to obtain the compound.

(3) Mixing phenolic resin and the compound according to the mass ratio of 4:1, then placing the mixed materials into a high-temperature box-type furnace, introducing nitrogen, performing heat treatment at 580 ℃, preserving heat for 20 hours, reducing the temperature, crushing and screening the product, and grading to obtain the anode material.

Example 7:

unlike example 4, the following is:

(2) Placing a carbon matrix containing a catalyst into a CVD reaction cavity, introducing silane, heating to 420 ℃ for reaction for 10 hours, and cooling to room temperature to obtain a compound, wherein the volume concentration ratio of silane to N ₂ is 4:1 (the silicon-containing gas concentration is 80%).

Example 8:

Unlike example 3, the following is:

(2) Placing a carbon matrix containing a catalyst into a CVD reaction cavity, introducing silane, wherein the volume concentration ratio of the silane to H ₂ is 3:1 (the silicon-containing gas concentration is 75%), heating to 600 ℃, reacting for 1H, and cooling to room temperature to obtain the compound.

Comparative example 1:

Unlike example 1, the following is:

Step (3) is not performed.

Comparative example 2:

Unlike example 1, the following is:

step (1) is not performed.

Comparative example 3:

Unlike example 1, the following is:

(2) And (3) placing a carbon matrix containing a catalyst in a CVD reaction cavity, wherein the volume concentration ratio of silane to argon is 5:1 (the concentration of silicon-containing gas is 83.3 percent), heating to 650 ℃, preserving heat for 22h, and cooling to room temperature to obtain the compound.

(3) Mixing phenolic resin and the compound according to the mass ratio of 1:9, then placing the mixed materials into a high-temperature box-type furnace, introducing nitrogen, performing heat treatment at 580 ℃, preserving heat for 2 hours, reducing the temperature, crushing and screening the product, and grading to obtain the anode material.

The relevant test data of examples and comparative examples were measured according to the above test methods, and specific test results are shown in tables 1 to 3 below:

TABLE 1 parameters of negative electrode materials

TABLE 2 parameters of negative electrode materials

TABLE 3 results of Performance test of examples and comparative examples

According to the test data of examples 1 to 8, after the catalyst is added into the silicon-based active material, the catalyst is beneficial to improving the surface density of the anode material in the process of forming the coating layer, so that the dissolution of the anode material in the circulating process can be reduced, and the reaction of dissolved silicon particles with electrolyte is further reduced.

Compared with example 1, the coating layer thickness of the anode material prepared in example 6 is increased, and the surface density of the anode material is also obviously improved, but the specific capacity of the anode material is slightly reduced due to the reduction of the mass content of silicon particles. The surface density of the anode material is obviously improved, the side reaction of the anode material is reduced, the cycle performance of the battery is also improved, and the expansion rate of the pole piece is reduced.

According to the test data of examples 4 and 7 and the test data of examples 3 and 8, as the volume ratio of micropores in the anode material increases, the adsorption capacity of the anode material increases, the side reaction between the anode material and the electrolyte increases, the volume expansion of the anode material during the cycle increases, and the cycle performance of the anode material slightly decreases.

According to the test data of examples 1 and 8, as the concentration of silane increases and the temperature increases, the size of silicon particles increases, and a part of silane gas is deposited on the surface of the carbon substrate, so that the gas yield increases after the anode material is contacted with the electrolyte, and the cycle performance of the anode material is slightly reduced as compared with example 1.

The negative electrode material prepared in comparative example 1 is not subjected to carbon coating treatment, the surface density of the negative electrode material is greatly reduced, a solid electrolyte membrane formed by side reaction of the negative electrode material and electrolyte is thickened, a large amount of active lithium ions are consumed, the initial coulomb efficiency of the battery is greatly reduced, the volume expansion rate of the battery after circulation is also greatly improved, and the gas production value is increased.

The negative electrode material prepared in comparative example 2, in which no catalyst was added, had decreased surface density and increased gas production.

The negative electrode material prepared in comparative example 3 has the advantages that the silane concentration is higher and the temperature of the temperature rise is higher in comparative example 3, the secondary growth of silicon particles is easy to induce at high temperature, the size of the silicon particles is easy to increase, part of silane gas can not enter the pores of the carbon matrix, the amount of silane gas deposited on the surface of the carbon matrix is increased, a large amount of exposed silicon particles still exist on the surface of the negative electrode material after carbon coating, the surface density of the negative electrode material is greatly reduced, the solid electrolyte film formed by side reaction of the negative electrode material and electrolyte is thickened, a large amount of active lithium ions are consumed, the first coulombic efficiency of the battery is greatly reduced, the volume expansion rate of the battery after circulation is also greatly increased, and the gas production value is increased.

Claims

1. The negative electrode material is characterized by comprising a carbon matrix and silicon particles, wherein the negative electrode material is provided with holes, the holes comprise micropores and mesopores, and the ratio of the pore volume of the micropores to the pore volume of the mesopores is (1-45): (55-99);

2. The anode material according to claim 1, wherein the total pore volume of the anode material is 0.001cm ³/g～0.1cm³/g, and/or the average pore diameter of the pores of the anode material is 0.4nm to 50nm.

3. The negative electrode material according to claim 1, wherein in the negative electrode material, the pore volume of micropores is 10% or less, the pore volume of mesopores is 80% or more, and the pore volume of macropores is 20% or less.

4. The anode material of claim 1, wherein the anode material has at least one of the following characteristics:

(1) The silicon particles comprise at least one of crystalline silicon, silicon oxide, amorphous silicon, silicon alloy, crystalline silicon and amorphous silicon composite particles;

(2) The average grain diameter of the silicon particles is 0.1 nm-50 nm;

(3) At least a portion of the silicon particles are located within the particles of the carbon matrix;

(4) The carbon matrix includes at least one of amorphous carbon and graphitized carbon.

5. The anode material according to claim 1, wherein the mass content of silicon element in the anode material is 20% to 60%; the mass content of the carbon element in the anode material is 20% -80%.

6. The negative electrode material according to claim 1, wherein the negative electrode slurry prepared from the negative electrode material has an average gas yield of 1 mL/g/day or less for 7 days in an environment of 25 ℃.

7. The anode material according to claim 1, wherein a surface of the anode material has a coating layer, and a material of the coating layer includes at least one of a metal oxide, a carbon material, a conductive polymer, a fluoride, a phosphate, and a nitride.

8. The anode material of claim 7, wherein the anode material has at least one of the following characteristics:

(1) The metal oxide includes at least one of Sn, ge, fe, si, cu, ti, na, mg, al, ca and oxides of Zn;

(2) The conductive polymer comprises at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, poly 3-hexylthiophene, poly-p-styrene, polypyridine and polystyrene;

(3) The fluoride comprises at least one of polyvinyl fluoride, fluorine polymer, 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;

(4) The phosphate comprises at least one of magnesium phosphate, calcium phosphate, aluminum 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 nitride includes at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride;

(6) The carbon material comprises at least one of amorphous carbon and graphitized carbon;

(7) The thickness of the coating layer is 1 nm-300 nm;

(8) The mass ratio of the coating layer in the anode material is less than or equal to 10 percent.

9. The anode material according to any one of claims 1 to 8, characterized in that the anode material satisfies at least one of the following characteristics:

(1) The median particle diameter D ₅₀ of the anode material is less than or equal to 15 mu m;

(2) The particle size distribution of the anode material satisfies the following conditions: d ₉₀-D₁₀)/D₅₀ is more than or equal to 0.9;

(3) The specific surface area of the anode material is less than or equal to 10m ²/g;

(4) The compacted density of the negative electrode material is 0.8g/cm ³～1.3g/cm³;

(5) The tap density of the anode material is 0.5g/cm ³～1.5g/cm³;

(6) The powder conductivity of the negative electrode material under the pressure of 20kN is 0.5S/cm-2S/cm.

10. A battery, characterized in that the battery comprises the anode material according to any one of claims 1 to 9.