CN111435732A - Negative electrode material of lithium ion battery, preparation method of negative electrode material and lithium ion battery - Google Patents

Negative electrode material of lithium ion battery, preparation method of negative electrode material and lithium ion battery Download PDF

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CN111435732A
CN111435732A CN201911335660.4A CN201911335660A CN111435732A CN 111435732 A CN111435732 A CN 111435732A CN 201911335660 A CN201911335660 A CN 201911335660A CN 111435732 A CN111435732 A CN 111435732A
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negative electrode
electrode material
silicon composite
graphene
composite particles
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CN111435732B (en
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赵晓锋
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Svolt Energy Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides a negative electrode material of a lithium ion battery, a preparation method of the negative electrode material and the lithium ion battery. The anode material includes: graphene silicon composite particles; a carbon layer coated on the surface of the graphene-silicon composite particle; and the lithium salt layer is coated on the surface of the carbon layer far away from the graphene-silicon composite particles. Therefore, the graphene silicon composite particles have better conductivity and lower expansion rate, and the stability of the cathode material can be effectively ensured; the coating of the carbon layer can reduce the specific surface area of the negative electrode material and improve the first efficiency (first charge and discharge efficiency) of the lithium ion battery, and the gram capacity of the negative electrode material cannot be influenced by the coating of the carbon layer; the lithium salt layer is coated to realize the transmission of lithium ions of the lithium ion battery under the condition of high multiplying power, so that the cycle performance of the lithium ion battery can be improved, and meanwhile, the lithium salt layer has good compatibility with electrolyte, so that the stability of the lithium ion battery is improved.

Description

Negative electrode material of lithium ion battery, preparation method of negative electrode material and lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a negative electrode material of a lithium ion battery, a preparation method of the negative electrode material and the lithium ion battery.
Background
With the improvement of the energy density requirement of the electric automobile on the lithium ion battery, the negative electrode material used by the lithium ion battery is required to have high specific capacity and long cycle life. However, the current commercial lithium ion battery generally adopts graphite carbon materials as the negative electrode material, and the demand of the high specific capacity lithium ion battery is difficult to meet due to the lower theoretical electrochemical capacity (the theoretical capacity is 372 mAh/g). The silicon-carbon negative electrode material is a novel energy storage negative electrode material developed in recent years, but the silicon-carbon negative electrode material has high expansion rate and poor conductivity, and in addition, the serious volume effect generated during electrochemical lithium intercalation and deintercalation causes the damage and mechanical pulverization of the material structure, so that the separation between electrode materials and the separation between the electrode materials and a current collector is caused, and further the electrical contact is lost, so that the cycle performance of the electrode is sharply reduced.
Therefore, research on the negative electrode material of the lithium ion battery is awaited.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, an object of the present invention is to provide a negative electrode material for a lithium ion battery, which has better conductivity or stability.
In one aspect of the invention, the invention provides a negative electrode material for a lithium ion battery. According to an embodiment of the present invention, the anode material includes: graphene silicon composite particles; a carbon layer coated on the surface of the graphene-silicon composite particle; and the lithium salt layer is coated on the surface of the carbon layer far away from the graphene-silicon composite particles. Therefore, the graphene silicon composite particles have better conductivity and lower expansion rate, and the stability of the cathode material can be effectively ensured; the carbon layer coating can reduce the surface area of the negative electrode material and improve the first efficiency (first charge and discharge efficiency) of the lithium ion battery, and the gram capacity of the negative electrode material cannot be influenced by the carbon layer coating; the lithium salt layer is coated to realize the transmission of lithium ions of the lithium ion battery under the condition of high multiplying power, so that the cycle performance of the lithium ion battery can be improved, and meanwhile, the lithium salt layer has good compatibility with electrolyte, so that the stability of the lithium ion battery is improved.
According to an embodiment of the present invention, a ratio of a particle diameter of the graphene-silicon composite particle, a thickness of the carbon layer, and a thickness of the lithium salt layer is 100: (1-10): (1-10), and optionally, the thickness of the lithium salt layer is 5-100 nm.
According to the embodiment of the invention, the material of the lithium salt layer is L i1+(x+y)AxByTi2-(x+y)(PO4)3Wherein A is a tetravalent element, B is a divalent element, 0<x is less than or equal to 1 and 0<y is less than or equal to 1, wherein A is selected from at least one of Zr, Nb, Mo, Ce, Cr, Ge, Ru, Se, Sn, Ta, Tb, V and W, and B is selected from at least one of Mg, Zn, Cu, Ca, Sr, Ba, Cd, Fe, Mn, Nd and Yb.
According to the embodiment of the invention, the particle size of the negative electrode material is 5-20 micrometers, and optionally, the graphene silicon composite particles are nitrogen-doped graphene silicon composite particles.
In another aspect of the present invention, the present invention provides a method of preparing a negative electrode material for a lithium ion battery. According to an embodiment of the present invention, a method of preparing an anode material for a lithium ion battery includes: dispersing and mixing graphene silicon composite particles and an organic carbon source solution, and performing carbonization treatment to obtain a first composite material of the graphene silicon composite particles coated by a carbon layer; and forming a lithium salt layer on the surface of the first composite material through physical vapor deposition so as to obtain the negative electrode material. Therefore, the graphene silicon composite particles have better conductivity and lower expansion rate, and the stability of the cathode material can be effectively ensured; the coating of the carbon layer can reduce the specific surface area of the negative electrode material and improve the first efficiency (first charge and discharge efficiency) of the lithium ion battery, and the gram capacity of the negative electrode material cannot be influenced by the coating of the carbon layer; the coating of the lithium salt layer can realize the transmission of lithium ions of the lithium ion battery under the condition of high multiplying power, so that the cycle performance of the lithium ion battery can be improved, and meanwhile, the lithium salt layer has better compatibility with the electrolyte; in addition, the lithium salt layer is prepared through physical vapor deposition, the lithium salt layer which is controllable in thickness, high in density and uniformly coated on the surface of the carbon layer can be obtained, and the risk that the carbon layer or the graphene silicon composite particles are contacted with the electrolyte due to nonuniform coating of the lithium salt layer is avoided.
According to an embodiment of the invention, the physical vapor deposition conditions are: the temperature is 100-300 ℃, and the vacuum degree is 1 x 10-4～10*10-4Pa for 10-120 minutes, and the distance between the target lithium salt and the first composite material is 1-1000 mm.
According to the embodiment of the invention, the mass ratio of the graphene silicon composite particles to the organic carbon source is 1-5: 10 to 30.
According to the embodiment of the invention, the graphene silicon composite particles are nitrogen-doped graphene silicon composite particles.
According to the embodiment of the invention, the graphene oxide dispersion liquid, the cuprammonium solution, the nitrogen source and the aqueous nano-silicon solution are mixed, the mixed solution is reacted for 2-12 hours in a high-pressure reaction kettle at the temperature of 150-200 ℃ so as to obtain the nitrogen-doped graphene silicon composite particles,
optionally, the graphene oxide dispersion liquid is 1000m L with the concentration of 1-10 mg/m L, the copper ammonia solution is 100m L with the concentration of 0.1-0.5 mol/L, the nitrogen source is 1-5 m L, and the aqueous nano silicon solution is 100m L with the mass concentration of 1-10%.
In yet another aspect of the present invention, a lithium ion battery is provided. According to an embodiment of the present invention, the lithium ion battery comprises the foregoing negative electrode material. Therefore, the lithium ion battery has better battery performances such as cycle performance, gram capacity, charge and discharge performance, capacitance retention rate and the like. Those skilled in the art will appreciate that the lithium ion battery has all of the features and advantages of the foregoing negative electrode material, and will not be redundantly described here.
Drawings
Fig. 1 is a schematic structural diagram of an anode material of a lithium ion battery according to an embodiment of the present invention.
Fig. 2 is a flow chart of a method of preparing a negative electrode material for a lithium ion battery in another embodiment of the invention.
FIG. 3 is a schematic structural view of a first composite material according to yet another embodiment of the present invention.
Fig. 4 is a scanning electron micrograph of the anode material prepared in example 1.
Detailed Description
The following describes embodiments of the present invention in detail. The following examples are illustrative only and are not to be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
In one aspect of the invention, the invention provides a negative electrode material for a lithium ion battery. According to an embodiment of the present invention, referring to fig. 1, the anode material 100 includes: graphene silicon composite particles 10; a carbon layer 20, wherein the carbon layer 20 is coated on the surface of the graphene silicon composite particle 10; the lithium salt layer 30 is coated on the surface of the carbon layer 20 far away from the graphene-silicon composite particle 10 by the lithium salt layer 30. Therefore, the graphene silicon composite particles 10 have better conductivity and lower expansion rate, and further can effectively ensure the stability of the cathode material; the carbon layer 20 can reduce the specific surface area of the negative electrode material, improve the first efficiency (first charge-discharge efficiency) of the lithium ion battery, and the gram capacity of the negative electrode material cannot be influenced by the coating of the carbon layer 20; the coating of the lithium salt layer 30 can realize the transmission of lithium ions of the lithium ion battery under the condition of high multiplying power, so that the cycle performance of the lithium ion battery can be improved, and meanwhile, the lithium salt layer 30 has good compatibility with the electrolyte, so that the stability of the lithium ion battery is improved.
According to an embodiment of the present invention, the graphene silicon composite particles are nitrogen-doped graphene silicon composite particles. Therefore, by doping nitrogen, the specific capacity of graphene and the conductivity of the negative electrode material can be effectively improved, and the specific capacity (namely gram capacity) of the negative electrode material is further improved.
According to the embodiment of the present invention, the carbon layer is amorphous carbon, and thus, the battery performance of the lithium ion battery can be improved.
According to the embodiment of the invention, the material of the lithium salt layer is L i1+(x+y)AxByTi2-(x+y)(PO4)3Wherein A is a tetravalent element, B is a divalent element, 0<x is less than or equal to 1 and 0<y is less than or equal to 1, wherein A is selected from Zr, Nb, Mo, Ce, Cr, Ge, Ru, Se, Sn, Ta, Tb, V and WB is selected from at least one of Mg, Zn, Cu, Ca, Sr, Ba, Cd, Fe, Mn, Nd and Yb. Therefore, the lithium salt layer is a composite lithium salt, so that the transmission of lithium ions of the lithium ion battery under a high-rate condition can be realized, the compatibility of the lithium salt layer 30 made of the material with the electrolyte is better, the cycle performance of the lithium ion battery can be improved, and furthermore, various metal elements in the composite lithium salt have certain synergistic effect, so that the conductivity of the lithium ions in the lithium salt layer and the structural stability of the lithium salt layer can be better improved.
According to an embodiment of the present invention, referring to fig. 1, a ratio of a particle diameter D1 of the graphene-silicon composite particles, a thickness D2 of the carbon layer, and a thickness D3 of the lithium salt layer is 100: (1-10): (1-10), for example, 100:1:1, 100:1:2, 100:1:4, 100:1:6, 100:1:8, 100:1:10, 100:2:10, 100:5:10, 100:10:10, 100:2:4, 100:4:6, 100:2:8, etc. The negative electrode material in the proportion range can ensure that the carbon layer and the lithium salt layer are relatively thin, and further the gram capacity of the negative electrode material is favorably improved.
According to the embodiment of the invention, the thickness of the lithium salt layer is 5-100 nm, such as 5 nm, 10nm, 15 nm, 20 nm, 25 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm. Therefore, the lithium salt layer with the thickness can completely and uniformly coat the carbon layer, and the thinner lithium salt layer can not influence the battery performance such as gram capacity of the negative electrode material; if the thickness is less than 30 nm, the carbon layer may not be completely and uniformly coated; if the thickness is greater than 100nm, the gram capacity of the lithium ion battery is relatively low.
According to the embodiment of the invention, the particle size of the negative electrode material is 5-20 micrometers, such as 5 micrometers, 6 micrometers, 8 micrometers, 10 micrometers, 12 micrometers, 14 micrometers, 16 micrometers, 18 micrometers and 20 micrometers. Therefore, the cathode material has a proper specific surface area, so that the cathode material has better activity; if the particle size is less than 5 microns, the processing difficulty is high, the specific surface area of the negative electrode material is large, and the primary efficiency of the negative electrode material is low; if the particle size is larger than 20 micrometers, the dynamic performance of the material is deviated, the compacted density is low, and the specific surface area of the negative electrode material is small, so that the improvement of the activity and the rate capability of the negative electrode material are not facilitated.
In another aspect of the present invention, the present invention provides a method of preparing a negative electrode material for a lithium ion battery. According to an embodiment of the present invention, referring to fig. 2, a method of preparing an anode material for a lithium ion battery includes:
s100: the graphene silicon composite particles 10 and an organic carbon source solution are dispersed and mixed, and a first composite material of the graphene silicon composite particles 10 coated with the carbon layer 20 is obtained through carbonization treatment, and a schematic structural diagram refers to fig. 3. Therefore, the graphene silicon composite particles 10 have better conductivity and lower expansion rate, and further can effectively ensure the stability of the cathode material; the carbon layer 20 can reduce the surface area of the negative electrode material, improve the first efficiency (first charge-discharge efficiency) of the lithium ion battery, and the gram volume of the negative electrode material is not affected by the coating of the carbon layer 20.
Wherein, after the carbonization treatment, the method further comprises the step of crushing the first composite material so as to obtain the first composite material with proper particle size, so that the lithium salt can be uniformly and completely coated on the surface of the first composite material (namely the surface of the carbon layer).
According to an embodiment of the present invention, the organic carbon source in the organic carbon source solution is at least one of sucrose, glucose, phenolic resin, epoxy resin, polyacrylonitrile, polyvinyl chloride, polyurethane, polypropylene, melamine, asphalt, tar, cellulose, lignin, starch, and husk. Therefore, the material and the graphene silicon composite particles do not generate side reaction, a layer of uniform carbon layer can be formed on the surfaces of the graphene silicon composite particles through carbonization treatment, and the material is wide in source and low in cost. The solvent in the organic carbon source solution is not particularly limited, as long as the organic carbon source can be dissolved well.
According to an embodiment of the present invention, the graphene silicon composite particles are nitrogen-doped graphene silicon composite particles. Therefore, by doping nitrogen, the specific capacity of graphene and the conductivity of the negative electrode material can be effectively improved, and the specific capacity (namely gram capacity) of the negative electrode material is further improved.
According to the embodiment of the invention, the mass ratio of the graphene silicon composite particles (or the nitrogen-doped graphene silicon composite particles) to the organic carbon source is 1-5: 10-30, such as 1:10, 1:15, 1:20, 1:25, 1:30, 3:10, 3:15, 3:20, 3:25, 3:30, 5:10, 5:15, 5:20, 5:25, 5: 30. Therefore, a carbon layer can be formed on the surface of the graphene-silicon composite particle completely and uniformly, the thickness of the carbon layer is appropriate, the thickness of the carbon layer is not too thick (otherwise, the gram capacity of the negative electrode material is affected), and if the mass ratio of the organic carbon source is too low, the carbon layer may not completely coat the surface of the graphene-silicon composite particle.
According to the embodiment of the invention, the graphene oxide dispersion liquid, the copper ammonia solution, the nitrogen source and the aqueous nano silicon solution are mixed, and the mixed solution is reacted in a high-pressure reaction kettle (with the pressure of 1-5 Mpa) at 150-200 ℃ (such as 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃ or 200 ℃) for 2-12 hours, so as to obtain the nitrogen-doped graphene silicon composite particles. The raw materials are gasified at high pressure and high temperature, so that uniform doping of a solid raw material (graphene oxide) and a liquid raw material can be realized, meanwhile, an oxidant copper ammonia solution oxidizes the graphene oxide, hydroxyl/carboxyl on the surface of the graphene is combined, then the temperature and the pressure are reduced, dehydration is carried out, and a hydrogel material is left (the nitrogen-doped graphene silicon composite particles are obtained after drying and dehydration are carried out later). Therefore, graphene oxide and nano silicon can be uniformly dispersed and mixed in a high-pressure reaction kettle by a hydrothermal method, and then high-density nitrogen-doped graphene silicon composite particles are prepared, so that the expansion rate of the nitrogen-doped graphene silicon composite particles is reduced, and the conductivity of the nitrogen-doped graphene silicon composite particles is improved; the copper ammonia solution is adopted, the surface of the graphene oxide can be oxidized to form carboxyl/hydroxyl groups, so that the material can be conveniently dehydrated to form hydrogel, and meanwhile, the copper ammonia solution oxidant has weak oxidizability, does not damage the structure of the material, contains copper substances, and can be used as a negative electrode material to improve the capacity and conductivity; furthermore, water is evaporated in the subsequent vacuum drying process, so that the nitrogen-doped graphene silicon composite particles have nano/micron pores, that is, the purpose of forming pores in the nitrogen-doped graphene silicon composite particles is realized, an expansion space is provided for silicon in the nitrogen-doped graphene silicon composite particles, and the expansion rate of the whole size of the nitrogen-doped graphene silicon composite particles is reduced; and when the nitrogen-doped graphene silicon composite particles are subjected to hydrothermal method, the raw materials are gasified and then cooled to form the nitrogen-doped graphene silicon composite particles with higher density, so that the negative electrode material has higher tap density and smaller pore diameter, lithium storage of the negative electrode material is facilitated, and the specific capacity of the negative electrode material is improved.
In the preparation of the nitrogen-doped graphene silicon composite particles, the dosage of the graphene oxide dispersion liquid is 1000m L, the concentration is 1-10 mg/m L (such as 1mg/m L0, 2mg/m L1, 4mg/m L2, 6mg/m L3, 8mg/m L4, 10mg/m L5), the dosage of the copper ammonia solution is 100m L6, the concentration is 0.1-0.5 mol/L7 (such as 0.1 mol/L8, 0.2 mol/L9, 0.3 mol/L, 0.4 mol/L0, 0.5 mol/L1), the dosage of the nitrogen source is 1-5 m L, such as 1m L, 2m L, 3m L, 4m L, 5m L, the dosage of the aqueous nano silicon solution is 100m L, the mass concentration is 1-10%, the content of the nitrogen-doped graphene silicon composite particles is 2%, 4% and the expansion rate of the lithium ion battery is improved, and the capacity of the battery is improved.
According to the embodiment of the present invention, the specific type of the nitrogen source has no special requirement, and those skilled in the art can flexibly select the nitrogen source according to the actual situation. In some embodiments, the carbon source is selected from at least one of pyrrole, aniline, urea, pyridine, and thiophene. Therefore, the material has wide sources and low cost, and is favorable for preparing the nitrogen-doped graphene silicon composite particles with good performance.
According to the embodiment of the invention, after the reaction in the high-pressure reaction kettle is finished, the nitrogen-doped graphene silicon composite particles obtained by the reaction are naturally cooled to room temperature, then filtered, and vacuum-dried at 50 ℃ for 24-96 hours. After the nitrogen-doped graphene silicon composite particles are prepared by the method, a plurality of nitrogen-doped graphene silicon composite particles may be bonded together, so that the method further comprises the step of crushing the nitrogen-doped graphene silicon composite particles so as to obtain the nitrogen-doped graphene silicon composite particles with proper particle size.
S200: a lithium salt layer 30 is formed on the surface of the first composite material by physical vapor deposition, so as to obtain the anode material 100, and the structural schematic diagram refers to fig. 1. The coating of the lithium salt layer can realize the transmission of lithium ions of the lithium ion battery under the condition of high multiplying power, and meanwhile, the lithium salt layer has better compatibility with the electrolyte, so that the cycle performance of the lithium ion battery can be improved; in addition, the lithium salt layer is prepared through physical vapor deposition, the lithium salt layer which is controllable in thickness, high in density and uniformly coated on the surface of the carbon layer can be obtained, and the risk that the carbon layer or the graphene silicon composite particles are contacted with the electrolyte due to nonuniform coating of the lithium salt layer is avoided.
According to the embodiment of the invention, the material of the lithium salt layer is L i1+(x+y)AxByTi2-(x+y)(PO4)3Wherein A is a tetravalent element, B is a divalent element, 0<x is less than or equal to 1 and 0<y is less than or equal to 1, wherein A is selected from at least one of Zr, Nb, Mo, Ce, Cr, Ge, Ru, Se, Sn, Ta, Tb, V and W, and B is selected from at least one of Mg, Zn, Cu, Ca, Sr, Ba, Cd, Fe, Mn, Nd and Yb. Therefore, the lithium salt layer is a composite lithium salt, so that the transmission of lithium ions of the lithium ion battery under a high-rate condition can be realized, the compatibility of the lithium salt layer 30 made of the material with the electrolyte is better, the cycle performance of the lithium ion battery can be improved, and furthermore, various metal elements in the composite lithium salt have certain synergistic effect, so that the conductivity of the lithium ions in the lithium salt layer and the structural stability of the lithium salt layer can be better improved.
According to an embodiment of the invention, the physical vapor deposition conditions are: the temperature is 100-300 ℃, and the vacuum degree is 1 x 10-4～10*10-4Pa, the time is 10-120 minutes, and the distance between the target lithium salt and the first composite material is 1-1000 mm. Thus, a lithium salt layer having a suitable thickness can be prepared under the above conditions.
According to the embodiment of the invention, the graphene silicon composite particles have better conductivity and lower expansion rate, so that the stability of the cathode material can be effectively ensured; the carbon layer coating can reduce the surface area of the negative electrode material and improve the first efficiency (first charge and discharge efficiency) of the lithium ion battery, and the gram capacity of the negative electrode material cannot be influenced by the carbon layer coating; the coating of the lithium salt layer can realize the transmission of lithium ions of the lithium ion battery under the condition of high multiplying power, so that the cycle performance of the lithium ion battery can be improved, and meanwhile, the lithium salt layer has better compatibility with electrolyte so as to improve the stability of the lithium ion battery; in addition, the lithium salt layer is prepared through physical vapor deposition, the lithium salt layer which is controllable in thickness, high in density and uniformly coated on the surface of the carbon layer can be obtained, and the risk that the carbon layer or the graphene silicon composite particles are contacted with the electrolyte due to nonuniform coating of the lithium salt layer is avoided.
According to an embodiment of the present invention, the above method for preparing a negative electrode material of a lithium ion battery may be used to prepare the negative electrode material of the lithium ion battery, wherein the requirements for the size and the material of the structure, such as the negative electrode material, the graphene silicon composite particles, the carbon layer, and the lithium salt layer, in the preparation method are consistent with the requirements in the negative electrode material, and are not repeated here.
In yet another aspect of the present invention, a lithium ion battery is provided. According to an embodiment of the present invention, the lithium ion battery comprises the foregoing negative electrode material. Therefore, the lithium ion battery has better battery performances such as cycle performance, gram capacity, charge and discharge performance, capacitance retention rate and the like. Those skilled in the art will appreciate that the lithium ion battery has all of the features and advantages of the foregoing negative electrode material, and will not be redundantly described here.
Examples
Example 1
The preparation method of the anode material comprises the following steps:
weighing 1000m L graphene oxide solution with the concentration of 5mg/m L, then adding 100m L copper ammonia solution with the concentration of 0.3 mol/L, stirring uniformly, then adding 3m L pyrrole, stirring uniformly, then adding 100m L aqueous nano silicon solution with the concentration of 5%, then transferring the solution into a high-pressure reaction kettle, reacting for 6 hours at the pressure of 3Mpa and the temperature of 180 ℃, then naturally cooling to room temperature, filtering, drying in vacuum for 48 hours at the temperature of 50 ℃, and crushing to obtain high-density nitrogen-doped graphene silicon composite particles;
adding 20g of phenolic resin into 500m of L g of acetone solvent, dissolving and dispersing uniformly, adding 3g of nitrogen-doped graphene silicon composite particles, ultrasonically dispersing uniformly, filtering, carbonizing and crushing to obtain a first composite material of the carbon-layer-coated nitrogen-doped graphene silicon composite particles;
l i1.4Cr0.2Mg0.2Ti1.6(PO4)3Transferring the composite material to vacuum coating equipment, depositing a multi-element lithium salt on the surface of the first composite material by a magnetron sputtering method to obtain a lithium salt layer with the thickness of 100nm, and then crushing and grading to obtain a negative electrode material, wherein the magnetron sputtering conditions are as follows: temperature 150 ℃ and vacuum degree 3 x 10-4Pa, the time is 60min, and the distance between the target lithium salt and the base material (namely the first composite material) is 10 mm.
The negative electrode material prepared in example 1 was subjected to electron microscope scanning, and an electron microscope scanning image thereof refers to fig. 4, and as can be seen from fig. 4, the particle size of the negative electrode material was 5 to 20 μm, and the size distribution was relatively uniform.
Example 2
The preparation method of the anode material comprises the following steps:
weighing 1000m L and graphene oxide solution with the concentration of 1mg/m L, then adding 100m L and copper ammonia solution with the concentration of 0.1 mol/L, stirring uniformly, then adding 1m L urea, stirring uniformly, then adding 100m L aqueous nano silicon solution with the concentration of 1%, then transferring the solution into a high-pressure reaction kettle, reacting for 12 hours at the pressure of 3Mpa and the temperature of 150 ℃, then naturally cooling to room temperature, filtering, drying for 24 hours in vacuum at the temperature of 50 ℃, and crushing to obtain high-density nitrogen-doped graphene silicon composite particles;
adding 10g of epoxy resin into 500m L of N, N-dimethylacetamide solvent, dissolving and dispersing uniformly, adding 1g of nitrogen-doped graphene silicon composite particles, ultrasonically dispersing uniformly, filtering, carbonizing and crushing to obtain a first composite material of the carbon-layer-coated nitrogen-doped graphene silicon composite particles;
l i1.2Cr0.1Sr0.1Ti1.8(PO4)3Transferring the mixture into vacuum coating equipment, and depositing a multi-element lithium salt on the surface of the first composite material by a magnetron sputtering method to obtain a lithium salt with the thickness of 10nmAnd (3) crushing and grading to obtain the negative electrode material, wherein the magnetron sputtering conditions are as follows: temperature 100 ℃, vacuum degree 1 x 10-4Pa, time 10min, distance of the target lithium salt and the substrate (i.e. the first composite material) 1 mm.
Example 3
The preparation method of the anode material comprises the following steps:
weighing 1000m L graphene oxide solution with the concentration of 10mg/m L, then adding 100m L copper ammonia solution with the concentration of 0.5 mol/L, stirring uniformly, then adding 5m L aniline, stirring uniformly, then adding 100m L aqueous nano silicon solution with the concentration of 10%, then transferring the solution into a high-pressure reaction kettle, reacting for 2 hours at the pressure of 3Mpa and the temperature of 200 ℃, then naturally cooling to room temperature, filtering, vacuum drying for 96 hours at the temperature of 50 ℃, and crushing to obtain high-density nitrogen-doped graphene silicon composite particles;
adding 30g of melamine into 500m L of n-hexane solvent, dissolving and dispersing uniformly, adding 5g of nitrogen-doped graphene silicon composite particles, ultrasonically dispersing uniformly, filtering, carbonizing and crushing to obtain a first composite material of the carbon-layer-coated nitrogen-doped graphene silicon composite particles;
l i2.6Mo0.8Mn0.8Ti0.4(PO4)3Transferring the lithium salt to vacuum coating equipment, depositing a multi-element lithium salt on the surface of the first composite material by a magnetron sputtering method to obtain a lithium salt layer with the thickness of 10nm, and then crushing and grading to obtain a negative electrode material, wherein the magnetron sputtering conditions are as follows: temperature 300 deg.C, vacuum degree 10 x 10-4Pa, the time is 120min, and the distance between the target lithium salt and the base material (namely the first composite material) is 100 mm.
Comparative example 1
Weighing 1000ml of graphene oxide solution with the concentration of 5mg/m L, adding aqueous nano silicon solution with the concentration of 5% of 100m L, transferring the solution into a high-pressure reaction kettle, reacting at the temperature of 180 ℃ for 6 hours, naturally cooling to room temperature, filtering, vacuum drying at the temperature of 50 ℃ for 48 hours, and crushing to obtain the high-density nitrogen-doped graphene silicon composite particles.
Comparative example 2
The nitrogen-doped graphene silicon composite particles in example 1 were used as a negative electrode material.
Comparative example 3
The first composite material of the carbon-layer-coated nitrogen-doped graphene silicon composite particles in example 1 was used as a negative electrode material.
And (4) testing results:
1. the specific surface area, tap density, specific capacity and pore diameter of the negative electrode material obtained in the above examples and comparative examples are tested according to the national standard GBT _245332009 graphite negative electrode material of lithium ion battery, and the rate capability and cycle performance of the button cell of each negative electrode material are also tested, and the test results are shown in table 1.
The method for testing the rate capability comprises the following steps: charging at multiplying power of 1C, 3℃, 5C, 7C and 10C, respectively, discharging at 1C, with voltage range of 0.005-2V and temperature of 25 + -3 deg.C;
and (3) testing the cycle performance: 1C charging and 1C discharging, wherein the voltage range is 0.005-2V, and the temperature is 25 +/-3 ℃; the number of cycles was 100.
The negative electrode materials obtained in examples 1 to 3 and comparative examples 1 to 3 were used to prepare negative electrodes (in the formulation, the negative electrode material, CMC (sodium carboxymethylcellulose), SBR (styrene butadiene rubber), SP (super carbon black) and H2The mass ratio of O is 95:2.5:1.5:1:150), a lithium sheet is used as a positive electrode, and L iPF is adopted as an electrolyte6The battery is characterized in that the battery is prepared by adopting a composite membrane of Polyethylene (PE), polypropylene (PP) and polyethylene propylene (PEP), the volume ratio of an electrolyte solvent to DEC is 1:1, the diaphragm is a composite membrane of Polyethylene (PE), polypropylene (PP) and polyethylene propylene (PEP), the button cell is assembled in a glove box filled with hydrogen, the electrochemical performance is carried out on a Wuhan blue electricity CT2001A type battery tester, the charging and discharging voltage range is controlled to be 0.005-2.0V, and the charging and discharging speed is 0.1C, and finally the button cell is assembled into A1, A2, A3, B1, B2 and B3.
TABLE 1
Figure BDA0002330859850000091
As can be seen from Table 1, the tap densities of the materials prepared in examples 1-3 are significantly higher than those of comparative examples 1-3, for the reason that: the hydrothermal method is used for gasifying the material and then cooling the gasified material to form the material with high density, and the first efficiency and the conductivity of the material are improved by depositing lithium salt on the surface of the material, and the specific capacity of the material is improved. Meanwhile, materials such as oxidant graphene oxide are adopted, the specific surface area of the nitrogen-doped graphene silicon composite particles is increased, and the liquid absorption and retention capacity of the negative electrode material is facilitated. Meanwhile, the cathode material has the advantages of high density, strong structural stability and the like, so that the rate capability of the lithium ion battery is improved.
2. Manufacturing a soft package battery:
electrochemical performance test, the negative electrode materials prepared in examples 1 to 3 and comparative examples 1 to 3 were used as negative electrodes, NCM811 was used as positive electrode, the solvent was EC/DEC/PC (propylene carbonate) (wherein EC: DEC: PC: 1:1:1) + 0.5% vinylene carbonate + 1% cyclic Ethyl Methyl Carbonate (EMC) + 0.5% lithium fluoride was used as electrolyte, and the solute was L iPF6And the Celgard 2400 membrane is used as a separator, and 5Ah soft package batteries C1, C2, C3 and D1, D2 and D3 are respectively prepared.
The negative electrode was then tested for its liquid absorption capacity, as well as the cycling performance of the cell (2.0C/2.0C), with the results shown in tables 2 and 3.
TABLE 2 imbibition Capacity of negative plate
Figure BDA0002330859850000092
Figure BDA0002330859850000101
As can be seen from Table 2, the liquid absorbing and retaining capabilities of the negative electrodes in examples 1 to 3 are obviously superior to those of comparative examples 1 to 3, and the analysis reasons are as follows: the lithium salt layer on the outer surface of the negative electrode material prepared in the embodiment has good compatibility with the electrolyte, so that the liquid absorption and retention capacity of the negative electrode material can be improved.
TABLE 3 cycling performance of pouch cells
Figure BDA0002330859850000102
As can be seen from Table 3, the cycle performance of the soft package batteries in examples 1 to 3 is obviously superior to that of comparative examples 1 to 3, and the analysis reason is as follows: the outer layer of the negative electrode material is coated with a layer of high-density multi-element composite lithium salt, so that the quantity of lithium ions in the lithium ion battery is increased, and the cycle performance of the battery is improved.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (10)

1. An anode material for a lithium ion battery, comprising:
graphene silicon composite particles;
a carbon layer coated on the surface of the graphene-silicon composite particle;
and the lithium salt layer is coated on the surface of the carbon layer far away from the graphene-silicon composite particles.
2. The negative electrode material according to claim 1, wherein a ratio of a particle diameter of the graphene-silicon composite particle to a thickness of the carbon layer to a thickness of the lithium salt layer is 100: (1-10): (1-10) of a first step,
optionally, the thickness of the lithium salt layer is 5-100 nanometers.
3. The negative electrode material of claim 1, wherein the material of the lithium salt layer is L i1+(x+y)AxByTi2-(x+y)(PO4)3Wherein A is a tetravalent element, B is a divalent element, 0<x is less than or equal to 1 and 0<y is less than or equal to 1, wherein A is selected from at least one of Zr, Nb, Mo, Ce, Cr, Ge, Ru, Se, Sn, Ta, Tb, V and W, and B is selected from at least one of Mg, Zn, Cu, Ca, Sr, Ba, Cd, Fe, Mn, Nd and Yb.
4. The negative electrode material of claim 1, wherein the particle size of the negative electrode material is 5-20 microns, and optionally, the graphene silicon composite particles are nitrogen-doped graphene silicon composite particles.
5. A method of making a negative electrode material for a lithium ion battery, comprising:
dispersing and mixing graphene silicon composite particles and an organic carbon source solution, and performing carbonization treatment to obtain a first composite material of the graphene silicon composite particles coated by a carbon layer;
and forming a lithium salt layer on the surface of the first composite material through physical vapor deposition so as to obtain the negative electrode material.
6. The method of claim 5, wherein the physical vapor deposition conditions are: the temperature is 100-300 ℃, and the vacuum degree is 1 x 10-4～10*10-4Pa for 10-120 minutes, and the distance between the target lithium salt and the first composite material is 1-1000 mm.
7. The method according to claim 5, wherein the mass ratio of the graphene silicon composite particles to the organic carbon source is 1-5: 10 to 30.
8. The method according to claim 5 or 7, wherein the graphene silicon composite particles are nitrogen-doped graphene silicon composite particles.
9. The method according to claim 8, wherein the graphene oxide dispersion liquid, the cuprammonium solution, the nitrogen source and the aqueous nano-silicon solution are mixed, and the mixed solution is reacted in a high-pressure reaction kettle at 150-200 ℃ for 2-12 hours to obtain the nitrogen-doped graphene-silicon composite particles,
optionally, the dosage of the graphene oxide dispersion liquid is 1000m L, and the concentration is 1-10 mg/m L;
the dosage of the copper ammonia solution is 100m L, and the concentration is 0.1-0.5 mol/L;
the dosage of the nitrogen source is 1-5 m L;
the dosage of the aqueous nano silicon solution is 100m L, and the mass concentration is 1-10%.
10. A lithium ion battery comprising the negative electrode material according to any one of claims 1 to 4.
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