CN115036492A - Preparation method, product and application of lithium ion battery surface modified silicon negative electrode material - Google Patents

Preparation method, product and application of lithium ion battery surface modified silicon negative electrode material Download PDF

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CN115036492A
CN115036492A CN202210826692.XA CN202210826692A CN115036492A CN 115036492 A CN115036492 A CN 115036492A CN 202210826692 A CN202210826692 A CN 202210826692A CN 115036492 A CN115036492 A CN 115036492A
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powder
pan
lithium ion
ion battery
negative electrode
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CN115036492B (en
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陈伟伦
张五星
薛丽红
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Inner Mongolia Jincheng Green Energy Graphite New Materials 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • 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
    • 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
    • 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
    • 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 invention discloses a preparation method of a surface modified silicon negative electrode material of a lithium ion battery, which is characterized by comprising the following steps of: s1: mixing and dispersing PAN and Si in an N-N dimethylformamide solution, stirring and evaporating to dryness to obtain first powder, namely a PAN @ Si composite material; s2: uniformly mixing the first powder obtained in the step S1 with S powder or Se powder in proportion to obtain second powder; s3: carrying out heat treatment on the second powder in an inert atmosphere to obtain a third powder, namely a PANS/Se @ Si composite material; s4: soaking the third powder in lithium biphenyl-tetrahydrofuran solution for 0.1-10 hr, dryingTo obtain PAN-Li x The material is S/Se @ Si, wherein x = 0.01-2. The invention also provides a corresponding product and application. The invention firstly coats PAN on the surface of Si, the PAN coated on the surface of Si can react with S or Se under the condition of heat treatment to generate PANS or PANSe, and PANS/Se generates PAN-Li after pre-lithiation x And (5) an S/Se artificial SEI film. The composite material can effectively improve the first coulombic efficiency, the cycle performance and the rate capability of the silicon-based cathode lithium ion battery.

Description

Preparation method, product and application of lithium ion battery surface modified silicon negative electrode material
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method, a product and application of a surface modified silicon negative electrode material of a lithium ion battery.
Background
The lithium ion battery has the outstanding advantages of long cycle life, high energy density, environmental protection and the like, so that the lithium ion battery is developed very quickly and is widely applied to the fields of portable electronic products, energy storage equipment, new energy automobiles and the like. At present, the negative electrode of the lithium ion battery is mainly graphite, but the specific capacity of the graphite is low (-372 mAh/g), and the demand of the market on the high-specific-energy lithium ion battery is difficult to meet. Silicon (Li) in contrast to graphite 15 Si 4 ) The material has the theoretical specific capacity of 3579 mAh/g at room temperature, and is expected to make the energy density of the lithium ion battery obtain great breakthrough, so the material is the next generation lithium ion battery cathode material. However, silicon undergoes a volume expansion of 300% during cycling, resulting in instability of a solid electrolyte interface film (SEI film) on the surface and low coulombic efficiency, which in turn greatly reduces the cycle life of the battery.
The common method for improving the interface stability of the silicon cathode is to construct an artificial SEI film on the surface of the silicon, and aims to reduce the direct contact between silicon and electrolyte and reduce the occurrence of side reactions. Li et al passivated the Si/electrolyte interface with a lithium-philic chitosan layer on the surface of the nanosilica, which passivation layer could provide stable and controlled homogeneous Li + To ensure a more uniform lithiation process in most Si (Nano Energy, 2020, 72, 104651). Ai et al coated the COF layer for guiding lithium ions on the surface of the Nano-silicon by a two-step method, which can protect the silicon surface and provide a lithium ion guiding channel, thereby improving the electrochemical performance of the silicon cathode (Nano Energy, 2020, 72, 104657). The artificial SEI film can improve the stability of the silicon cathode to a certain extent, but the ion conductivity and the mechanical strength of the artificial SEI film are required to be improved, and the synthesis process is required to be simplified. Therefore, the artificial SEI film with simple synthesis process and high ionic conductance and mechanical strength aiming at silicon material development has important significance.
Disclosure of Invention
Aiming at the defects in the prior artThe invention provides a preparation method of a lithium ion battery surface modified silicon negative electrode material, and a PAN-Li prepared by the preparation method x S @ Si material or PAN-Li x The Se @ Si material can effectively improve the first coulombic efficiency, the cycle performance and the rate capability of the silicon-based cathode lithium ion battery.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a method for preparing a surface modified silicon negative electrode material for a lithium ion battery, comprising the steps of:
s1: mixing and dispersing PAN powder and Si powder in an N-N dimethylformamide solution according to a ratio, stirring and evaporating to dryness to obtain first powder, namely a PAN @ Si composite material;
s2: uniformly mixing the first powder obtained in the step S1 with S powder or Se powder in proportion to obtain second powder;
s3: heat-treating the second powder in an inert atmosphere to obtain a third powder, namely a PANS/Se @ Si composite material;
s4: soaking the third powder obtained in S3 in a biphenyl lithium-tetrahydrofuran solution for 0.1-10h, and drying to obtain PAN-Li x The S/Se @ Si composite material is characterized in that x = 0.01-2.
In a further improvement of the present invention, in step S1, the mass ratio of the PAN powder to the Si powder is 0.1:1 to 1: 1.
As a further improvement of the present invention, in step S1, the mass-to-volume ratio of the PAN powder and the Si powder to the N-N dimethylformamide solution is 15: 100.
as a further improvement of the invention, in step S1, the temperature for evaporating is 60-100 ℃.
In a further improvement of the present invention, in step S2, the mass ratio of the first powder to the sulfur powder or selenium powder is 2:1 to 0.4: 1.
As a further improvement of the invention, in step S3, the temperature of the heat treatment is 250-350 ℃, and the time is 3-9 h.
As a further improvement of the invention, in step S4, the concentration of the biphenyl lithium-tetrahydrofuran solution is 1-5 mol/L.
As a further improvement of the invention, in step S4, the drying temperature is 50-70 ℃, and the drying time is 10-14 hours.
According to a second aspect of the invention, the invention provides a lithium ion battery surface modified silicon negative electrode material which is prepared by the preparation method.
According to a third aspect of the present invention, an application of a lithium ion battery surface modified silicon negative electrode material as a lithium ion battery negative electrode material is provided, wherein the lithium ion battery surface modified silicon negative electrode material is adopted, and the negative electrode material is obtained by the preparation method.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
the preparation method of the lithium ion battery surface modified silicon negative electrode material comprises the steps of firstly coating PAN on the surface of Si, enabling the PAN coated on the surface of Si to react with S or Se under the heat treatment condition to generate PANS/Se (PANS or PANSe), and enabling the PANS/Se to generate PAN-Li after pre-lithium treatment x And (5) an S/Se artificial SEI film. PAN-Li x PAN in S/Se has good flexibility, and Li is generated x S/Se is a good lithium ion conductor, so PAN-Li x S/Se is an ideal artificial SEI film. PAN-Li x The S/Se artificial SEI film can passivate the interface of Si and electrolyte, reduce side reactions, buffer the volume expansion generated by lithium intercalation of silicon particles due to good flexibility, so that the SEI film is stabilized, and the silicon particles are prevented from falling off from a current collector and losing activity after being crushed. On the other hand, the good lithium ion conductivity of the material is beneficial to lithium ion migration, so that the dynamic performance is improved. Therefore, the artificial SEI film on the Si surface prepared by the invention can greatly improve the cycle performance and the rate capability of the silicon-based negative lithium ion battery.
Drawings
FIG. 1 is a diagram of PAN-Li synthesized in example 1 of the present invention x S @ Si composite material charge-discharge curve;
FIG. 2 is a charge-discharge curve of pure silicon powder;
FIG. 3 shows the PAN-Li synthesized in example 1 of the invention x S @ Si composite and pure silicon circulation curves;
FIG. 4 shows the PAN-Li synthesized in example 1 of the invention x Multiplying power curves of the S @ Si composite material and pure silicon;
FIG. 5 shows the PAN-Li synthesized in example 4 of the invention x A charge-discharge curve diagram of the Se @ Si composite material;
FIG. 6 shows the PAN-Li synthesized in example 4 of the invention x A charge-discharge curve diagram of the Se @ Si composite material.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The preparation method of the surface modified silicon negative electrode material of the lithium ion battery comprises the following steps:
(1) mixing and dispersing PAN powder and Si powder in an N-N dimethylformamide solution in proportion, stirring and evaporating to dryness to obtain first powder, namely PAN @ Si composite material;
(2) uniformly mixing the first powder (PAN @ Si composite material) obtained in the step (1) with S powder or Se powder in proportion to obtain second powder;
(3) carrying out heat treatment on the second powder obtained in the step (2) in an inert atmosphere to obtain a third powder, namely a PANS/Se @ Si composite material;
(4) soaking the third powder (PANS/Se @ Si composite material) obtained in the step (3) in a biphenyl lithium-tetrahydrofuran solution for 0.1-10h, and drying to obtain PAN-Li x The material is S/Se @ Si, wherein x = 0.01-2.
In the PAN @ Si composite material, @ means that PAN is coated on the surface of Si; the PANS/Se @ Si composite material is represented by PANS @ Si composite material or PANSE @ Si composite material, wherein @ represents that the PANS or the PANSE is coated on the surface of Si; PAN-Li x The meaning of S/Se @ Si material is PAN-Li x S @ Si materialMaterial or PAN-Li x Se @ Si material, wherein @ has the meaning PAN-Li x The Si surface is coated with S/Se.
In the step (1), the mass ratio of the PAN powder to the Si powder is preferably 0.1: 1-1: 1, and the mass volume ratio of the whole of the PAN powder and the Si powder to the N-N dimethylformamide solution is 15:100, respectively; in addition, the evaporation temperature is preferably 60-100 ℃, and the stirring time is preferably 8-12 h; the N-N dimethylformamide solution is a pure N-N dimethylformamide solution. In the step, PAN and Si are dispersed in an N-N dimethylformamide solution, PAN can be dissolved in N-N dimethylformamide, and PAN can be uniformly coated on the surface of Si after stirring and evaporation to dryness.
In the step (2), the mass ratio of the first powder obtained after evaporation in the step (1) to the sulfur powder or the selenium powder is 2: 1-0.4: 1, and within the range of the ratio, the sulfur powder or the selenium powder can be ensured to fully react with PAN, the content of sulfur/selenium is too low, part of PAN is not reacted, and if the content of sulfur is too high, excessive polysulfide/selenium residue can be generated, so that the performance is affected. Further inert atmospheres include nitrogen, argon or helium, and the like.
In a preferred embodiment, the first powder obtained by evaporating the step (1) to dryness and the S powder or the Se powder can be ground and mixed in the step, so that the mixing between the two powders is more uniform.
In the step (3), the temperature of the heat treatment is 250-350 ℃, and the time is 3-9 h. At too low a temperature, PAN does not react or reacts insufficiently with sulfur, and at too high a temperature, PAN is pyrolyzed, resulting in a decrease in the amount of PANS produced.
In the step (4), the concentration of the biphenyl lithium-tetrahydrofuran solution is 1-5 mol/L; the drying temperature in the step is preferably 50-70 ℃, and the drying time is preferably 10-14 hours. Meanwhile, when the powder is immersed in the biphenyllithium-tetrahydrofuran solution in this step, the amount of the biphenyllithium-tetrahydrofuran solution to be used is not particularly limited as long as the powder can be immersed. In the step, PANS/Se is subjected to pre-lithiation treatment to prepare the obtained PAN-Li x The S/Se artificial SEI film is characterized in that x = 0.01-2, x =2 in the case of S or Se complete lithium intercalation, and x =0.01 in the case of very little lithium intercalation.
The present invention providesA process for preparing the modified silicon negative electrode composite material on the surface of Li-ion battery includes such steps as coating PAN on silicon surface, reacting with S or Se, coating polyacrylonitrile S or polyacrylonitrile Se (PANS/Se) on the surface of silicon particles to obtain PANS @ Si or PANSE @ Si composite material, pre-lithiation to obtain PAN-Li x S @ Si or PAN-Li x The Se @ Si material (wherein x = 0.01-2) is applied to a lithium ion battery cathode material, and can effectively improve the initial coulomb efficiency, the cycle performance and the rate capability of a silicon-based cathode.
To better illustrate the preparation, product and application of the present invention, the following examples are provided:
example 1
The method comprises the following steps:
(1) taking 30 mg of PAN powder and 270 mg of Si powder, dispersing the powder in 2 mL of N-N dimethylformamide solution, stirring and evaporating to dryness;
(2) uniformly mixing 300 mg of the powder obtained in the step (1) with 150 mg of sulfur powder;
(3) carrying out heat treatment on the powder obtained in the step (2) in an inert atmosphere furnace at 250 ℃ for 6 hours;
(4) soaking the powder obtained in the step (3) in a biphenyl lithium-tetrahydrofuran solution for 1 h, and drying at 60 ℃ for 12h to obtain PAN-Li x S @ Si, wherein x is in the range of 0.01-2.
Preparing the sample obtained in the step (4), conductive carbon and a binder into slurry according to the mass ratio of 70:15:15, uniformly coating the obtained slurry on the surface of the copper foil, and then placing the copper foil in a vacuum drying oven for drying for 12 hours at 80 ℃. And cutting the pole piece into a circular sheet with the diameter of 8 mm, and assembling the circular sheet and a metal lithium sheet with the diameter of 12 mm into the battery.
Example 2
(1) 30 mg of PAN powder and 270 mg of Si powder were dispersed in 2 mL of N-N dimethylformamide solution, and the mixture was stirred and evaporated to dryness.
(2) And (2) uniformly mixing 300 mg of the powder obtained in the step (1) with 150 mg of sulfur powder.
(3) And (3) carrying out heat treatment on the powder obtained in the step (2) in an inert atmosphere furnace at 350 ℃ for 6 h.
(4) Soaking the powder obtained in the step (3) in a biphenyl lithium-tetrahydrofuran solution for 0.1 h, and drying at 60 ℃ for 12h to obtain PAN-Li x S @ Si, wherein x is in the range of 0.01-2.
Preparing the sample obtained in the step (4), conductive carbon and a binder into slurry according to the mass ratio of 70:15:15, uniformly coating the obtained slurry on the surface of the copper foil, and then placing the copper foil in a vacuum drying oven for drying for 12 hours at 80 ℃. And cutting the pole piece into a circular sheet with the diameter of 8 mm, and assembling the circular sheet and a metal lithium sheet with the diameter of 12 mm into the battery.
Example 3
(1) 150 mg of PAN and 150 mg of Si were dispersed in 2 mL of N-N dimethylformamide, and the mixture was stirred and evaporated to dryness.
(2) And (2) uniformly mixing 300 mg of the powder obtained in the step (1) with 750 mg of sulfur powder.
(3) And (3) carrying out heat treatment on the powder obtained in the step (2) in an inert atmosphere furnace at 250 ℃ for 6 hours.
(4) Soaking the powder obtained in the step (3) in a biphenyl lithium-tetrahydrofuran solution for 5 h, and drying at 60 ℃ for 12h to obtain PAN-Li x S @ Si material, wherein x is in the range of 0.01-2.
Preparing the sample obtained in the step (4), conductive carbon and a binder into slurry according to the mass ratio of 70:15:15, uniformly coating the obtained slurry on the surface of the copper foil, and then placing the copper foil in a vacuum drying oven for drying for 12 hours at 80 ℃. And cutting the pole piece into a circular sheet with the diameter of 8 mm, and assembling the circular sheet and a metal lithium sheet with the diameter of 12 mm into the battery.
Example 4
(1) 150 mg of PAN and 150 mg of Si were dispersed in 2 mL of N-N dimethylformamide, and the mixture was stirred and evaporated to dryness.
(2) And (2) uniformly mixing 300 mg of the powder obtained in the step (1) with 750 mg of selenium powder.
(3) And (3) carrying out heat treatment on the powder obtained in the step (2) in an inert atmosphere furnace at 350 ℃ for 6 hours.
(4) Soaking the powder obtained in the step (3) in a biphenyl lithium-tetrahydrofuran solution for 10h, and drying at 60 ℃ for 12h to obtain PAN-Li x Se @ Si material, wherein x is 0.01 to2 in the range of.
Preparing the sample obtained in the step (4), conductive carbon and a binder into slurry according to the mass ratio of 70:15:15, uniformly coating the obtained slurry on the surface of the copper foil, and then placing the copper foil in a vacuum drying oven for drying for 12 hours at 80 ℃. And cutting the pole piece into a circular sheet with the diameter of 8 mm, and assembling the circular sheet and a metal lithium sheet with the diameter of 12 mm into the battery.
Example 5
(1) 150 mg of PAN and 150 mg of Si were dispersed in 2 mL of N-N dimethylformamide solution, and the mixture was evaporated to dryness with stirring.
(2) And (2) uniformly mixing 300 mg of the powder obtained in the step (1) with 300 mg of selenium powder.
(3) And (3) carrying out heat treatment on the powder obtained in the step (2) in an inert atmosphere furnace at 350 ℃ for 6 hours.
(4) Soaking the powder obtained in the step (3) in a biphenyl lithium-tetrahydrofuran solution for 10h, and drying at 60 ℃ for 12h to obtain PAN-Li x Se @ Si material, wherein x is in the range of 0.01-2.
Preparing the sample obtained in the step (4), conductive carbon and a binder into slurry according to the mass ratio of 70:15:15, uniformly coating the obtained slurry on the surface of the copper foil, and then placing the copper foil in a vacuum drying oven for drying for 12 hours at 80 ℃. And cutting the pole piece into a wafer with the diameter of 8 mm, and assembling the wafer and a metal lithium piece with the diameter of 12 mm into the battery.
Comparative example 1:
preparing slurry from non-surface-modified Si, conductive carbon and a binder according to a weight ratio of 70:15:15, uniformly coating the obtained slurry on the surface of a copper foil, and then placing the copper foil in a vacuum drying oven for drying for 12 hours at 80 ℃. And cutting the pole piece into a wafer with the diameter of 8 mm, and assembling the wafer and a metal lithium piece with the diameter of 12 mm into the battery.
The batteries prepared in examples and comparative examples were subjected to performance test, wherein the separator was a polypropylene separator and the electrolyte was 1M LiPF 6 Is EC/DEC (volume ratio 1: 1) solution of electrolyte, and is added with FEC additive with mass fraction of 5%. The test current density is 200 mA/g, and the voltage window is 0.01-1.5V.
The experimental results are as follows:
FIG. 1 and FIG. 2 are respectively a PAN-Li synthesis scheme in accordance with example 1 of the present invention x And a charge-discharge curve diagram of the S @ Si composite material and pure silicon. By comparison, the synthesized PAN-Li of the invention x The initial coulomb efficiency of the S @ Si composite material reaches 90.1 percent, and is obviously improved relative to 79.9 percent of pure silicon.
FIG. 3 shows the synthesis of PAN-Li in example 1 of the invention x Cycle profiles of S @ Si composite and pure silicon. The results show that the synthesized PAN-Li of the invention x The cycle performance of the S @ Si composite material is superior to that of a battery made of pure silicon.
FIG. 4 shows the synthesis of PAN-Li in example 1 of the invention x Rate capability of S @ Si composite and pure silicon. The results show that the synthesized PAN-Li of the invention x The rate capability of the S @ Si composite material is superior to that of a battery made of pure silicon.
FIG. 5 shows the PAN-Li synthesized in example 4 of the invention x Charging and discharging curve diagram of Se @ Si composite material, and PAN-Li synthesized by the method x The first coulombic efficiency of the Se @ Si composite material reaches 89.5 percent, and the reversible specific capacity is 2750 mAh/g.
FIG. 6 shows a PAN-Li synthesized according to an embodiment of the invention x Circulation curve of Se @ Si composite material and PAN-Li synthesized by using method x The specific capacity of the Se @ Si composite material is still 1440 mAh/g after 200 cycles.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A preparation method of a surface modified silicon negative electrode material of a lithium ion battery is characterized by comprising the following steps:
s1: mixing and dispersing PAN powder and Si powder in an N-N dimethylformamide solution according to a ratio, stirring and evaporating to dryness to obtain first powder, namely a PAN @ Si composite material;
s2: uniformly mixing the first powder obtained in the step S1 with S powder or Se powder in proportion to obtain second powder;
s3: heat-treating the second powder in an inert atmosphere to obtain a third powder, namely a PANS/Se @ Si composite material;
s4: soaking the third powder obtained in S3 in a bifendate-tetrahydrofuran solution for 0.1-10h, and drying to obtain PAN-Li x The S/Se @ Si composite material is characterized in that x = 0.01-2.
2. The method for preparing the surface-modified silicon negative electrode material of the lithium ion battery according to claim 1, wherein in step S1, the mass ratio of the PAN powder to the Si powder is 0.1: 1-1: 1.
3. The method for preparing the surface-modified silicon negative electrode material of the lithium ion battery according to claim 1, wherein in step S1, the mass-to-volume ratio of the PAN powder and the Si powder to the N-N dimethylformamide solution is 15: 100.
4. The preparation method of the surface modified silicon negative electrode material of the lithium ion battery according to claim 1, wherein in the step S1, the drying temperature is 60-100 ℃.
5. The preparation method of the surface-modified silicon negative electrode material for the lithium ion battery according to claim 1, wherein in step S2, the mass ratio of the first powder to the sulfur powder or selenium powder is 2: 1-0.4: 1.
6. The method for preparing the surface-modified silicon negative electrode material of the lithium ion battery as claimed in claim 1, wherein the heat treatment temperature in step S3 is 250-350 ℃, and the time is 3-9 h.
7. The method for preparing the surface modified silicon anode material of the lithium ion battery according to claim 1, wherein in the step S4, the concentration of the biphenyl lithium-tetrahydrofuran solution is 1-5 mol/L.
8. The method for preparing the surface modified silicon negative electrode material of the lithium ion battery according to claim 1, wherein in the step S4, the drying temperature is 50-70 ℃ and the drying time is 10-14 hours.
9. A lithium ion battery surface modified silicon negative electrode material prepared by the preparation method of any one of claims 1 to 9.
10. The application of the lithium ion battery surface modified silicon negative electrode material as the lithium ion battery negative electrode material adopts the lithium ion battery surface modified silicon negative electrode material of claim 9, and the negative electrode material is obtained by the preparation method of any one of claims 1 to 8.
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