CN112467115A - Silicon-carbon composite material, preparation method thereof and lithium battery cathode - Google Patents

Silicon-carbon composite material, preparation method thereof and lithium battery cathode Download PDF

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CN112467115A
CN112467115A CN202011383816.9A CN202011383816A CN112467115A CN 112467115 A CN112467115 A CN 112467115A CN 202011383816 A CN202011383816 A CN 202011383816A CN 112467115 A CN112467115 A CN 112467115A
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silicon
lithium
composite material
carbon composite
solid electrolyte
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陈松
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Hunan Shinzoom Technology Co ltd
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Hunan Shinzoom 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The application relates to the field of battery materials, in particular to a silicon-carbon composite material, a preparation method thereof and a lithium battery cathode. A silicon-carbon composite material comprises an inner core and a shell coated outside the inner core; the inner core comprises nano silicon material, and the particle size of nano silicon is 10-500 nm; the material of the housing includes carbon and a lithium-containing solid electrolyte. The silicon-carbon composite material has the electronic conductivity of carbon and also has a higher lithium ion transmission rate of a lithium-containing solid electrolyte, and the lithium-containing solid electrolyte can reduce the consumption of lithium ions in the first charge-discharge process, so that the first efficiency is improved; the shell and the inner core formed by the carbon material and the solid electrolyte have strong binding force, and the expansion of the silicon-carbon composite material in the charging and discharging processes can be effectively inhibited.

Description

Silicon-carbon composite material, preparation method thereof and lithium battery cathode
Technical Field
The application relates to the field of battery materials, in particular to a silicon-carbon composite material, a preparation method thereof and a lithium battery cathode.
Background
With the improvement of the energy density requirement of the lithium ion battery, the energy density and the electrochemical performance of the cathode material are correspondingly improved. Although the silicon-carbon material has high specific capacity, the silicon-carbon material has limited application due to the defects of large self expansion rate, poor rate capability and the like.
Disclosure of Invention
An object of the embodiments of the present application is to provide a silicon-carbon composite material, a preparation method thereof, and a lithium battery negative electrode, which aim to solve the problems of a large expansion rate and poor rate capability of the existing silicon-carbon material.
The first aspect of the application provides a silicon-carbon composite material, which comprises an inner core and a shell coated outside the inner core;
the inner core comprises a nano silicon material, and the particle size of the nano silicon is 10-500 nm;
the material of the housing includes carbon and a lithium-containing solid electrolyte.
The lithium-containing sulfide solid electrolyte with high ion transmission rate and carbon with high conductivity are coated on the surface of the nano silicon material, so that the electronic conductivity and the ion transmission rate of the silicon-carbon composite material can be improved. The silicon-carbon composite material has the electronic conductivity of carbon and also has a higher lithium ion transmission rate of a lithium-containing solid electrolyte, and the lithium-containing solid electrolyte can reduce the consumption of lithium ions in the first charge-discharge process, so that the first efficiency is improved; the expansion of the silicon-carbon composite material in the charging and discharging process can be effectively inhibited.
In some embodiments of the first aspect of the present application, the mass ratio of the nano-silicon material, the lithium-containing solid electrolyte and the carbon is (20-70): (1-10): (20-79).
In some embodiments of the first aspect of the present application, the lithium-containing solid electrolyte is a sulfide electrolyte;
optionally, the sulfide electrolyte comprises 5Li2S-GeS2-P2S5、70Li2S-30P2S5And 80Li2S-20P2S5At least one of (1).
In a second aspect of the present application, a method for preparing the silicon-carbon composite material includes:
mixing lithium-containing solid electrolyte, nano silicon material and a binder, and then carrying out first carbonization to obtain a precursor;
and mixing the precursor, the high molecular polymer and the solvent, drying to remove the solvent, and performing secondary carbonization to obtain the silicon-carbon composite material.
In some embodiments of the second aspect of the present application, the step of mixing the lithium-containing solid electrolyte, the nano-silicon material, and the binder comprises:
firstly, mixing the lithium-containing solid electrolyte and the binding agent to obtain a mixture, and then mixing the nano silicon material with the mixture through particle beam bombardment.
In some embodiments of the second aspect of the present application, the conditions of the particle beam bombardment are: under an oxygen atmosphere, the gas flow rate is (1-10) sccm, the gas pressure is (1-10) × 10-4The injection temperature is 100-500 ℃ under Pa, and the time is 10 min-120.
In some embodiments of the second aspect of the present application, the mass ratio of the nano-silicon material, the lithium-containing solid electrolyte, the high molecular polymer, and the binder is (20-70): (1-10): (19.5-78.9): (0.1-0.5).
In some embodiments of the second aspect of the present application, the binder comprises at least one of polytetrafluoroethylene powder, ethylene-tetrafluoroethylene copolymer, and polyperfluoroethylpropylene.
In some embodiments of the second aspect of the present application, the high molecular weight polymer comprises at least one of a phenolic resin, a furfural resin, and an epoxy resin;
optionally, the mass ratio of the high molecular polymer to the solvent is (1-5): 50.
in a third aspect, the present application provides a negative electrode for a lithium battery, which includes the silicon-carbon composite material provided in the first aspect.
The lithium battery cathode provided by the application contains the lithium-containing solid electrolyte, so that the lithium ions of the anode have higher transmission rate in the charging and discharging processes of the lithium battery. The lithium battery cathode provided by the application has all the advantages of the silicon-carbon composite material. It has the advantages of excellent cycle performance and capability of effectively inhibiting the expansion of materials in the cycle process.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
Fig. 1 is an SEM image of a silicon carbon composite material prepared in example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The following specifically describes the silicon-carbon composite material, the preparation method thereof, and the lithium battery negative electrode in the embodiments of the present application.
A silicon-carbon composite material comprises an inner core and a shell coated outside the inner core; the material of the inner core comprises nano silicon material, and the particle size of the nano silicon is 10-500 nm;
the material of the housing includes carbon and a lithium-containing solid electrolyte.
As an example, the lithium-containing solid electrolyte is a sulfide electrolyte; for example, the sulfide electrolyte includes 5Li2S-GeS2-P2S5、70Li2S-30P2S5And 80Li2S-20P2S5At least one of (1).
Wherein, 5Li2S-GeS2-P2S5Is prepared from Li in a molar ratio of 5:1:12S、GeS2And P2S5Formed by complexation, i.e. Li10GeP2S12. Accordingly, 70Li2S-30P2S5Is prepared from Li in a molar ratio of 70:302S and P2S5And compounding. 80Li2S-20P2S5Is prepared from Li in a molar ratio of 80:202S and P2S5And compounding.
The sulfide electrolyte has high lithium ion transmission characteristic, and the preparation process of the material is simple and the cost is low.
In other embodiments of the present application, the lithium-containing solid electrolyte may also be an oxide solid electrolyte or the like.
Illustratively, the mass ratio of the nano silicon material to the lithium-containing solid electrolyte to the carbon is (20-70): (1-10): (20-79). For example, the mass ratio of the nano silicon material, the lithium-containing solid electrolyte and the carbon may be 20:1: 20. 20: 10: 70. 50: 1: 49. 60: 5: 35. 70: 10: 20. 20:1:79, and so forth.
In some embodiments of the present application, the material of the core is a nano-silicon material and the material of the shell is composed of a lithium-containing solid electrolyte and carbon. For example, the percentage by mass of the nano silicon material is 20-70%, the percentage by mass of the lithium-containing solid electrolyte is 1-10%, and the balance is carbon.
In some embodiments of the application, the expansion rate of the negative pole piece prepared from the silicon-carbon composite material is 30% -35% after 100 cycles; the expansion rate is the ratio of the difference between the thickness of the pole piece after 100 cycles and the thickness of the pole piece before no cycle to the thickness of the pole piece before no cycle.
The silicon-carbon composite material provided by the embodiment of the application has at least the following advantages:
the surface of the nano silicon material is coated with the solid electrolyte with high ion transmission rate and the carbon with high conductivity, so that the electronic conductivity and the ion transmission rate of the silicon-carbon composite material can be improved. The silicon-carbon composite material provided by the embodiment of the application has the electronic conductivity of carbon and also has a higher lithium ion transmission rate of a lithium-containing solid electrolyte, and the lithium-containing solid electrolyte can reduce the consumption of lithium ions in the first charge-discharge process, so that the first efficiency is improved; the expansion of the silicon-carbon composite material in the charging and discharging process can be effectively inhibited.
The application also provides a preparation method of the silicon-carbon composite material, which mainly comprises the following steps:
mixing lithium-containing solid electrolyte, nano silicon material and a binder, and then carrying out first carbonization to obtain a precursor; and mixing the precursor, the high molecular polymer and the solvent, drying to remove the solvent, and performing secondary carbonization to obtain the silicon-carbon composite material.
As mentioned above, the lithium-containing solid electrolyte is a sulfide electrolyte; for example, it may be Li2S-GeS2-P2S5、70Li2S-30P2S5And 80Li2S-20P2S5At least one of (1).
Illustratively, the binder includes at least one of polytetrafluoroethylene powder, ethylene-tetrafluoroethylene copolymer, and polyperfluoroethylpropylene.
Illustratively, the high molecular polymer includes at least one of a phenol resin, a furfural resin, and an epoxy resin; in other embodiments of the present application, the high molecular polymer may be other substances that can be carbonized into a carbon material.
The main function of the solvent is to fully mix the high molecular polymer and the precursor; the solvent is not mixed with the precursor and the high molecular polymer, and the solvent is volatile in the subsequent drying process.
The solvent may be organic or aqueous, and may be, for example, N-methylpyrrolidone, carbon tetrachloride, cyclohexane, dimethylformamide, tetrahydrofuran, or the like.
In the embodiment of the application, the carbonization conditions of the first carbonization and the second carbonization are kept for 1h to 12h at 700 ℃ to 1100 ℃ in a protective atmosphere. For example, the protective atmosphere may be nitrogen, argon, helium, and the like.
The binding agent makes the lithium-containing solid electrolyte and the nano silicon material mutually bound, the binding agent is carbonized through the first carbonization, the carbon formed after the binder is carbonized is coated on the surface of the nano silicon material, and meanwhile, the falling of the lithium-containing solid electrolyte can be avoided. The second carbonization is to carbonize the high molecular polymer to form carbon on the surface of the nano silicon material.
In some embodiments of the present application, the drying to remove the solvent is spray drying, and it is understood that in other embodiments of the present application, other drying methods such as freeze drying may be used.
In some embodiments of the present application, the nano silicon material is mixed with the lithium-containing solid electrolyte and the binder by using a particle beam bombardment method.
Illustratively, the lithium-containing solid electrolyte and the binder are mixed uniformly to obtain a mixture, and then the nano silicon material is mixed with the mixture through particle beam bombardment.
Mixing the nano silicon material with lithium-containing solid electrolyte and adhesive by particle beam bombardment. The nano silicon material is injected into the mixture through particle beam bombardment, so that the nano silicon material has the advantages of high uniformity, strong binding force and the like; in addition, in the ion beam bombardment process, parameters such as the implantation depth of the material and the like can be controlled, the quantity, the depth and the like of the nano silicon material are easy to control, and the preparation process is simple. The risk of stripping between the nano silicon material and carbon in the cyclic expansion process due to the fact that the nano silicon material is combined into a whole through a mechanical and physical method is overcome.
By way of example, in the present application, the conditions of the particle beam bombardment are: under oxygen atmosphere, the gas flow rate is (1-10) sccm (standard cubic center) per minute, and the gas pressure is (1-10) × 10-4And (3) under Pa, the injection temperature is 100-500 ℃, and the time is 10-120 min.
For example, the gas flow rate for the particle beam bombardment can be 1sccm, 2sccm, 4sccm, 5sccm, 8sccm, or 10sccm, among others.
The air pressure can be 1 x 10-4Pa、2×10-4Pa、3×10-4Pa、7×10-4Pa、9×10-4Pa or 10X 10- 4Pa, and the like.
The injection temperature may be 100 deg.C, 200 deg.C, 260 deg.C, 320 deg.C, 410 deg.C, 480 deg.C or 500 deg.C, etc.
The time of particle beam bombardment may be 10min, 20min, 32min, 43min, 57min, 67min, 85min, 93min, 101min, or 120min, and so on.
Further, in some embodiments of the present application, the lithium-containing solid electrolyte and the additive are milled into a powder prior to particle beam bombardment.
By adopting the particle injection method, the coating uniformity of the nano silicon material can be improved, the binding force between the solid electrolyte and the amorphous carbon and the core nano silicon material is improved, the cycle performance of the material is improved, and the expansion of the material in the cycle process is reduced.
It should be noted that, in other embodiments of the present application, the nano silicon material may be mixed with the mixture by vapor deposition or the like.
The application also provides a lithium battery cathode which comprises the silicon-carbon composite material.
In summary, the lithium battery cathode provided by the present application has all the advantages of the above silicon-carbon composite material. It has the advantages of excellent cycle performance and capability of effectively inhibiting the expansion of materials in the cycle process.
The features and properties of the present application are described in further detail below with reference to examples.
Example 1
The embodiment provides a silicon-carbon composite material which is mainly prepared by the following steps:
5g of 5Li2S-GeS2-P2S5Mixing sulfide electrolyte and 0.3g of polytetrafluoroethylene powder raw material, fully grinding the mixture into viscous powder at 100 ℃, performing compression molding to obtain a lithium-containing solid electrolyte composite material A, and implanting 60g of nano silicon with the particle size of 50nm into the surface layer of the lithium-containing solid electrolyte composite material A through high-speed particle beam bombardment. Wherein, the particle beam bombardment conditions are as follows: gas flow 5sccm, gas pressure 5X 10-4Pa, the injection temperature is 200 ℃, and the time is 60 min.
Carbonizing at 800 deg.C for 48h to obtain material B; and then adding the prepared material B into an N-methyl pyrrolidone solution containing 30g of phenolic resin, stirring at a high speed to obtain a mixed solution, and then carbonizing at 800 ℃ for 48 hours by spray drying to obtain the silicon-carbon composite material.
Fig. 1 is an SEM image of the silicon-carbon composite material prepared in example 1, and it can be seen from fig. 1 that the silicon-carbon composite material of example 1 has a particle size of 5 to 10 μm and a uniform and reasonable size distribution.
Example 2
The embodiment provides a silicon-carbon composite material which is mainly prepared by the following steps:
1g of 70Li2S-30P2S5Mixing sulfide electrolyte and 0.1g of ethylene-tetrafluoroethylene copolymer raw materials, fully grinding the mixture into viscous powder at the temperature of 100 ℃, performing compression molding to obtain a lithium-containing solid electrolyte composite material A, and then implanting 20g of nano silicon particles with the particle size of 100nm into the surface layer of the lithium-containing solid electrolyte composite material A through high-speed particle beam bombardment. Wherein: the conditions of the particle beam bombardment were: the gas flow is 1sccm, and the gas pressure is 1 × 10-4Pa, the injection temperature is 100 ℃, and the time is 120 min.
Carbonizing at 800 deg.C for 48h to obtain material B; and then adding the prepared material B into N-methyl pyrrolidone containing 79g of phenolic resin, stirring at a high speed to obtain a mixed solution, and carbonizing at 800 ℃ for 48 hours by spray drying to prepare the silicon-carbon composite material.
Example 3
The embodiment provides a silicon-carbon composite material which is mainly prepared by the following steps:
mixing 10g of 5Li2S-GeS2-P2S5Mixing sulfide electrolyte and 0.5g of ethylene-tetrafluoroethylene copolymer raw material, fully grinding the mixture into viscous powder at the temperature of 100 ℃, performing compression molding to obtain a lithium-containing solid electrolyte composite material A, and then implanting 70g of nano silicon particles with the particle size of 100nm into the surface layer of the lithium-containing solid electrolyte composite material A through high-speed particle beam bombardment; wherein, the particle beam bombardment conditions are as follows: the gas flow is 10sccm, and the gas pressure is 10 multiplied by 10-4PaThe injection temperature is 500 ℃ and the time is 10 min.
Carbonizing at 800 deg.C for 48h to obtain material B; and then adding the prepared material B into an aqueous solution containing 19.5g of phenolic resin, stirring at a high speed to obtain a mixed solution, and then carbonizing at 800 ℃ for 48 hours by spray drying to prepare the silicon-carbon composite material.
Example 4
The embodiment provides a silicon-carbon composite material which is mainly prepared by the following steps:
mixing 5g of lithium lanthanum zirconium oxygen lithium-containing solid electrolyte and 0.3g of polytetrafluoroethylene powder, fully grinding the mixture into viscous powder at the temperature of 100 ℃, performing compression molding to obtain a lithium-containing solid electrolyte composite material A, and then implanting 60g of nano silicon with the particle size of 50nm into the surface layer of the lithium-containing solid electrolyte composite material A through high-speed particle beam bombardment; wherein, the particle beam bombardment conditions are as follows: gas flow 5sccm, gas pressure 5X 10-4Pa, the injection temperature is 200 ℃, and the time is 60 min.
Carbonizing at 800 deg.C for 48h to obtain material B; and then adding the prepared material B into an aqueous solution containing 30g of epoxy resin, stirring at a high speed to obtain a mixed solution, and then performing spray drying and carbonization at 800 ℃ for 48 hours to prepare the silicon-carbon composite material.
Example 5
The embodiment provides a silicon-carbon composite material which is mainly prepared by the following steps:
70g of nano-silicon particles having a particle size of 100nm, 10g of 5Li2S-GeS2-P2S5And 0.5g of ethylene-tetrafluoroethylene copolymer, grinding the mixture for 24 hours at the temperature of 200 ℃ by a grinding machine, cooling the mixture, adding the mixture into 19.5g of phenolic resin aqueous solution, stirring the mixture at a high speed to obtain a mixed solution, and then performing spray drying and carbonization for 48 hours at the temperature of 800 ℃ to prepare the silicon-carbon composite material.
Comparative example 1
The comparative example provides a silicon carbon composite material, which is mainly prepared by the following steps:
uniformly mixing 60g of nano silicon particles with the particle size of 50nm and 0.5g of ethylene-tetrafluoroethylene copolymer, grinding the mixture for 24 hours at the temperature of 200 ℃ by a grinding machine, cooling the mixture, adding the cooled mixture into an aqueous solution containing 19.5g of phenolic resin, stirring the mixture at a high speed to obtain a mixed solution, and then carbonizing the mixed solution for 48 hours at the temperature of 800 ℃ by spray drying to obtain the silicon-carbon composite material.
Test example 1
The specific surface area, tap density and powder conductivity of the silicon-carbon composite materials provided in examples 1 to 5 and comparative example 1 were tested according to the national standard GBT-245332009 graphite-based anode material for lithium ion batteries, and the results are shown in table 1.
The preparation of the pole piece by the silicon-carbon composite material provided in the examples 1-5 and the comparative example 1 comprises the following steps: weighing 9g of negative electrode material, 0.5g of conductive agent SP and 0.5g of LA132 binder, adding the materials into 220ml of deionized water, uniformly stirring, coating on a copper foil to prepare a membrane, and then using a LiPF with a lithium sheet as a negative electrode, a celegard2400 as a membrane and an electrolyte solute of 1mol/L to prepare the LiPF6The solvent is Ethylene Carbonate (EC) and diethyl carbonate (DMC) in a weight ratio of 1: 1; assembling the button cell in a glove box with oxygen and water contents lower than 0.1ppm to obtain a button cell, then loading the button cell on a blue tester, charging and discharging at a rate of 0.1C, wherein the voltage range is 0.05V-2.0V, and stopping after circulating for 3 weeks. The results of the button cell performance tests are shown in table 1.
TABLE 1 physicochemical Properties test and button cell Performance test results
Figure BDA0002808142860000101
As can be seen from table 1, examples 1 to 5 provide silicon carbon composites superior to comparative example 1 in terms of first efficiency and gram capacity thereof because the lithium-containing solid electrolyte reduces the loss of irreversible capacity thereof to improve first efficiency thereof. Examples 1-4 provide silicon carbon composites having tap densities superior to those of example 5, probably because the tap densities can be increased by combining silicon with lithium-containing solid electrolytes tightly by particle implantation.
Test example 2
Examples 1 to 5 and comparative example 1The carbon composite material is doped with 90% of artificial graphite as a negative electrode material, and a negative electrode plate is prepared. With ternary materials (LiNi)1/3Co1/3Mn1/3O2) As the positive electrode, LiPF6The solution (the solvent is EC + DEC with the volume ratio of 1:1, and the concentration is 1.3mol/l) is used as an electrolyte, and the celegard2400 is used as a diaphragm to prepare the 5Ah flexible package battery. And then testing the cycle performance and the rate capability of each soft package battery and the expansion rate of the pole piece of each soft package battery.
Testing the expansion rate of the pole piece: the method comprises the steps of firstly testing the thickness D1 of a negative pole piece of the soft package battery after constant volume, then circulating for 100 times and fully charging the soft package battery, then testing the thickness D2 of the negative pole piece of the soft package battery after the soft package battery is dissected, and then calculating the expansion rate (D2-D1)/D1.
TABLE 2 comparison of pole piece thickness for examples and comparative examples
D1/μm D2/μm Expansion ratio (D2-D1)/D1
Example 1 105 137 30.5％
Example 2 104 137 31.5％
Example 3 106 140 32.5％
Example 4 105 138 31.4％
Example 5 106 146 37.7％
Comparative example 1 104 153 47.1％
As can be seen from table 2, the expansion rate of the negative electrode plate made of the silicon-carbon composite materials of examples 1 to 5 is significantly lower than that of comparative example 1, because the pores between the materials can be reduced by the particle injection method of the examples, and the density and tap density of the materials can be improved, thereby reducing the expansion in the charging and discharging processes.
The soft package lithium ion battery is subjected to cycle test under the conditions that the charge-discharge voltage range is 2.5-4.2V, the temperature is 25 +/-3.0 ℃ and the charge-discharge multiplying power is 0.5C/0.5C, and the test results are shown in a table 3.
TABLE 3 comparison of the cycles of the examples and comparative examples
Initial capacity retention (%) Capacity retention rate (%). about 500 times
Example 1 100 93.3
Example 2 100 93.0
Example 3 100 92.7
Example 4 100 92.8
Example 5 100 89.3％
Comparative example 1 100 81.1％
As can be seen from table 3, the cycle performance of the soft package lithium ion battery prepared by using the silicon-carbon composite materials of examples 1 to 5 is better than that of comparative example 1 at each stage of the cycle, because the cycle performance of the silicon-carbon composite materials of examples 1 to 5 is improved by virtue of the structural stability of the prepared materials, and sufficient lithium ions are provided by virtue of the characteristic that the lithium-containing solid electrolyte has high lithium ion conductivity, thereby improving the cycle performance.
Conditions of rate performance test: the charging and discharging voltage range is 2.5-4.2V, the temperature is 25 +/-3.0 ℃, the charging and discharging multiplying power is 1.0C, and the discharging multiplying power is 1.0C, 2.0C, 3.0C and 5.0C. The results of the rate performance test are shown in table 4.
TABLE 4 comparison of Rate Properties of examples and comparative examples
Figure BDA0002808142860000121
As can be seen from table 4, the rate performance of the soft-packed lithium ion battery using the silicon-carbon composite materials of examples 1 to 5 is obviously improved in comparison with that of comparative example 1, because the silicon-carbon composite materials coated with the lithium-containing solid electrolyte of examples 1 to 5 contain lithium-containing solid electrolyte to provide sufficient lithium ions during charging and discharging, thereby improving the high rate performance.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. The silicon-carbon composite material is characterized by comprising an inner core and an outer shell coated outside the inner core;
the inner core comprises a nano silicon material, and the particle size of the nano silicon is 10-500 nm;
the material of the housing includes carbon and a lithium-containing solid electrolyte.
2. The silicon-carbon composite material according to claim 1,
the mass ratio of the nano silicon material, the lithium-containing solid electrolyte and the carbon is (20-70): (1-10): (20-79).
3. The silicon-carbon composite material according to claim 1 or 2, wherein the lithium-containing solid electrolyte is a sulfide electrolyte;
optionally, the sulfide electrolyte comprises 5Li2S-GeS2-P2S5、70Li2S-30P2S5And 80Li2S-20P2S5At least one of (1).
4. A method of preparing a silicon carbon composite material according to any one of claims 1 to 3, comprising:
uniformly mixing a lithium-containing solid electrolyte, a nano silicon material and a binder, and then carrying out primary carbonization to obtain a precursor;
and mixing the precursor, the high molecular polymer and a solvent, drying to remove the solvent, and performing secondary carbonization to obtain the silicon-carbon composite material.
5. The method of claim 4, wherein the step of mixing the lithium-containing solid electrolyte, the nano-silicon material, and the binder comprises:
firstly, mixing the lithium-containing solid electrolyte and a bonding agent to obtain a mixture, and then mixing the nano silicon material with the mixture through particle beam bombardment.
6. The method for preparing the silicon-carbon composite material according to claim 5, wherein the conditions of the particle beam bombardment are as follows: under an oxygen atmosphere, the gas flow rate is (1-10) sccm, the gas pressure is (1-10) × 10-4The injection temperature is 100-500 ℃ under Pa, and the time is 10-120 min.
7. The method for preparing the silicon-carbon composite material according to any one of claims 4 to 6, wherein the mass ratio of the nano silicon material, the lithium-containing solid electrolyte, the high molecular polymer and the binder is (20-70): (1-10): (19.5-78.9): (0.1-0.5).
8. The method of any one of claims 4-6, wherein the binder comprises at least one of polytetrafluoroethylene powder, ethylene-tetrafluoroethylene copolymer, and fluorinated ethylene propylene.
9. The method for producing a silicon-carbon composite material according to any one of claims 4 to 6, wherein the high molecular polymer comprises at least one of a phenol resin, a furfural resin, and an epoxy resin;
optionally, the mass ratio of the high molecular polymer to the solvent is (1-5): 50.
10. a negative electrode for a lithium battery comprising the silicon-carbon composite material according to any one of claims 1 to 3.
CN202011383816.9A 2020-11-30 2020-11-30 Silicon-carbon composite material, preparation method thereof and lithium battery cathode Pending CN112467115A (en)

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