Modified silicon-based negative electrode material and preparation method and application thereof

Abstract

The invention provides a modified silicon-based negative electrode material and a preparation method and application thereof, the modified silicon-based negative electrode material comprises a silicon-based core, and a cationic functional layer, a transition carbon layer and a conductive agent network layer which sequentially coat the surface of the silicon-based core, and the transition carbon layer is generated on the surface of the cationic functional layer in situ. The modified silicon-based negative electrode material is of a core-shell structure, the shell is distributed in multiple layers, the layers influence one another and have a synergistic effect, and the electrochemical performance of the silicon-based negative electrode material can be obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of battery materials and relates to a modified silicon-based negative electrode material and a preparation method and application thereof. Background Art

[0002] In recent years, as the market share of new energy vehicles has gradually increased, people have also put forward higher requirements for the various performances of new energy vehicles. The electrode materials in secondary batteries, such as negative electrode materials, have a huge impact on battery performance.

[0003] Silicon-based anode materials are regarded as ideal anode materials for next-generation lithium-ion batteries due to their high energy density, low cost and environmental friendliness. However, the conductivity of silicon-based anode materials is poor, which limits their application in batteries.

[0004] CN117293316A discloses a silicon-carbon particle and a preparation method thereof, a silicon-carbon composite material and a preparation method thereof. The silicon-carbon particle comprises a silicon-based core and a carbon coating layer covering the silicon-based core, and a gap layer is provided between the silicon-based core and the carbon coating layer. The carbon coating layer is formed by carbonizing a photosensitive resin after light curing, and the gap layer is formed by removing the uncured photosensitive resin.

[0005] CN118299550A discloses a negative electrode material, a preparation method thereof and a battery. A negative electrode material comprises: a silicon-based material and a carbon coating layer coated on the surface of the silicon-based material; wherein the silicon-based material comprises an organic siloxane polymer, and the organic siloxane polymer comprises a Si-O group and a Si-R group.

[0006] The coating layer of the negative electrode material obtained by the above scheme has poor bonding strength and cannot give full play to the advantages of each component, and cannot take into account both rate performance and cycle performance, and cannot meet practical applications. Summary of the invention

[0007] The purpose of the present invention is to provide a modified silicon-based negative electrode material and a preparation method and application thereof. The modified silicon-based negative electrode material of the present invention is a core-shell structure, and the outer shell is distributed in multiple layers. The layers influence each other and act synergistically, which can significantly improve the electrochemical performance of the silicon-based negative electrode material.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a modified silicon-based negative electrode material, comprising a silicon-based core and a cationic functionalized layer, a transition carbon layer and a conductive agent network layer sequentially coated on the surface of the silicon-based core, wherein the transition carbon layer is in-situ generated on the surface of the cationic functionalized layer.

[0010] In the modified silicon-based negative electrode material of the present invention, the cation functionalized layer can increase the concentration of local charge carriers, and the conductive agent network layer provides a conductive channel to improve the lithium ion (Li + ) in the electrode material, reducing the diffusion resistance and improving the transmission efficiency of lithium ions, while the presence of the transition carbon layer can improve the bonding strength between the two. At the same time, the cation functionalized layer, transition carbon layer and conductive agent network layer in the modified silicon-based negative electrode material work together to improve the conductivity of the modified silicon-based negative electrode material.

[0011] Preferably, the silicon-based core includes any one of silicon-carbon material, silicon-oxygen material or elemental silicon, or a combination of at least two of them.

[0012] Preferably, the median particle size D50 of the silicon-based core is 1 to 100 nm, for example, 1 nm, 10 nm, 20 nm, 50 nm or 100 nm, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0013] Preferably, the material of the cationic functionalized layer includes polyethyleneimine (PEI), poly(glycidyl methacrylate) (PGMA), poly(ethyleneimine) (PVI), poly(N-vinylimidazole) (PVIm), poly(dimethyldiallyl ammonium chloride) (PDADMAC), poly(N-vinyl pyrrolidone) (PVP), poly(N-vinyl-N-dimethylaminoethyl methacrylate) (PVDMAEMA), poly(N-vinyl-N-dimethylcarbamate) (PVDMA), poly(N-vinyl-N-dimethylaminoethyl chloromethylacrylate) (PVDC), poly(N-vinyl-N-dimethylaminoethyl methacrylamide) (PVDMAM).

[0014] Preferably, the thickness of the cationic functionalized layer is 1 to 100 nm, for example, 1 nm, 10 nm, 20 nm, 50 nm or 100 nm, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0015] Preferably, the thickness of the transition carbon layer is 1 to 200 nm, for example, 1 nm, 10 nm, 50 nm, 100 nm or 200 nm, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] Preferably, the conductive agent network layer comprises a mesh layer constructed of linear conductive agents.

[0017] Preferably, the linear conductive agent includes any one of single-walled carbon nanotubes, silver nanowires or tin oxide nanowires, or a combination of at least two thereof.

[0018] Preferably, the diameter of the linear conductive agent is 1 to 5 nm, for example, 1 nm, 2 nm, 3 nm, 4 nm or 5 nm, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the thickness of the conductive agent network layer is 1 to 100 μm, for example, 1 μm, 10 μm, 20 μm, 50 μm or 100 μm, etc., and is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] In a second aspect, the present invention provides a method for preparing the modified silicon-based negative electrode material as described in the first aspect, the preparation method comprising the following steps:

[0021] (1) mixing a cationic functional material solution with a silicon-based material dispersion to obtain a composite material through a one-step reaction;

[0022] (2) functionalizing the conductive agent and mixing it with a solvent to obtain a suspension, mixing the composite material with the suspension, and obtaining a precursor through a two-step reaction;

[0023] (3) heat-treating the precursor to obtain the modified silicon-based negative electrode material.

[0024] The present invention configures the cation functionalized material and the silicon-based material into a solution, and then mixes the two to react. The two are fully contacted, and the cation functionalized material is adsorbed on the surface of the silicon-based material through electrostatic action to form a cation functionalized outer layer, which is conducive to a further self-assembly process. After the conductive agent is functionalized, it can be attracted by the cationic groups on the cation functionalized outer layer, resulting in orderly spontaneous assembly between the materials to form a conductive agent network. The network structure of the conductive agent can provide additional mechanical support for the negative electrode material, which is conducive to dispersing and buffering the stress generated by silicon nanoparticles during the charging and discharging process. Then, heat treatment is performed at an appropriate temperature, and the outer part of the internal cation functionalized layer is carbonized to generate a transition carbon layer, which further improves the bonding strength between the layers.

[0025] Preferably, the solute of the cationic functionalized material solution in step (1) comprises polyethyleneimine.

[0026] Preferably, the solvent of the cationic functionalized material solution in step (1) comprises deionized water.

[0027] Preferably, the concentration of the cationic functionalized material solution in step (1) is 0.1-1 wt%, for example, 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.8 wt% or 1 wt%, etc., not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0028] Preferably, the solvent of the silicon-based material dispersion in step (1) includes deionized water.

[0029] Preferably, the concentration of the silicon-based material dispersion in step (1) is 0.5 to 10 mg / mL, for example, 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 5 mg / mL or 10 mg / mL, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, stirring is performed during the one-step reaction in step (1), and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] Preferably, the pH of the one-step reaction in step (1) is 6 to 8, for example, 6, 6.5, 7, 7.5 or 8, etc., and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the reaction time of step (1) is 0.5 to 24 h, for example, 0.5 h, 1 h, 5 h, 10 h or 24 h, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the functionalization treatment in step (2) includes hydroxylation treatment and / or carboxylation treatment.

[0034] Preferably, the solvent in step (2) comprises deionized water.

[0035] Preferably, the concentration of the suspension in step (2) is 0.1-1wt%, for example, 0.1wt%, 0.2wt%, 0.5wt%, 0.8wt% or 1wt%, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, stirring is performed during the two-step reaction in step (2).

[0037] Preferably, the functionalization treatment in step (2) is a hydroxylation treatment, and the pH of the two-step reaction is 4 to 7, for example: 4, 4.5, 5, 6 or 7, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, the functionalization treatment in step (2) is a carboxylation treatment, and the pH of the two-step reaction is 3 to 5, for example: 3, 3.5, 4, 4.5 or 5, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the time of the two-step reaction in step (2) is 1 to 4 h, for example, 1 h, 1.5 h, 2 h, 3 h or 4 h, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, the temperature of the heat treatment in step (3) is 250-350°C, for example, 250°C, 280°C, 300°C, 320°C or 350°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] Preferably, the heat treatment time in step (3) is 1 to 4 hours, for example, 1 hour, 1.5 hours, 2 hours, 3 hours or 4 hours, etc., and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0042] In a third aspect, the present invention provides a negative electrode plate, wherein the negative electrode plate comprises the modified silicon-based negative electrode material as described in the first aspect.

[0043] In a fourth aspect, the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the negative electrode sheet as described in the third aspect.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The structure of the modified silicon-based negative electrode material described in the present invention helps to reduce the side reactions between the electrode material and the electrolyte, form a stable solid electrolyte interface (SEI) layer, and thus improve its initial coulombic efficiency, cycle stability and rate performance as a negative electrode material for lithium-ion batteries.

[0046] (2) The initial coulombic efficiency of the battery made of the modified silicon-based negative electrode material of the present invention can reach more than 80%, the capacity retention rate after 500 cycles can reach more than 90%, and the 3C rate performance can reach more than 53%. By adjusting the preparation conditions and the ratio of raw materials, the initial coulombic efficiency of the battery made of the modified silicon-based negative electrode material can reach more than 84%, the capacity retention rate after 500 cycles can reach more than 94%, and the 3C rate performance can reach more than 58%. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0048] Example 1

[0049] This embodiment provides a modified silicon-based negative electrode material, the modified silicon-based negative electrode material comprises a silicon-oxygen core and a PEI layer, a transition carbon layer and a single-walled carbon nanotube network layer sequentially coated on the surface of the silicon-oxygen core, the median particle size D50 of the silicon-oxygen core is 50nm, the thickness of the PEI layer is 60nm, the thickness of the transition carbon layer is 100nm, and the thickness of the single-walled carbon nanotube network layer is 2nm. The modified silicon-based negative electrode material is prepared by the following method:

[0050] (1) adding a 1 wt % PEI solution to a 1 mg / mL silica nanoparticle suspension, stirring while adding to ensure that PEI is in full contact with the surface of the silica nanoparticles, adjusting the pH to 7, reacting for 2 h, and obtaining a composite material by centrifugation, washing, and drying;

[0051] (2) reacting single-walled carbon nanotubes with bromoacetic acid to obtain hydroxylated single-walled carbon nanotubes, mixing the hydroxylated single-walled carbon nanotubes with water to prepare a carbon nanotube suspension with a concentration of 0.5 wt%, mixing the carbon nanotube suspension with the composite material obtained in step (1), stirring and reacting at a pH of 6 for 3 h, and obtaining a precursor through centrifugation, washing and drying;

[0052] (3) The precursor obtained in step (2) is heat treated at 300° C. for 1 h to obtain the modified silicon-based negative electrode material.

[0053] Example 2

[0054] This embodiment provides a modified silicon-based negative electrode material, which includes a silicon-oxygen core and a PVI layer, a transition carbon layer and a single-walled carbon nanotube network layer sequentially coated on the surface of the silicon-oxygen core, the median particle size D50 of the silicon-oxygen core is 1 nm, the thickness of the PVI layer is 1 nm, the thickness of the transition carbon layer is 1 nm, and the thickness of the single-walled carbon nanotube network layer is 1 nm. The modified silicon-based negative electrode material is prepared by the following method:

[0055] (1) adding a 0.1 wt% PVI solution to a 10 mg / mL silica nanoparticle suspension, stirring while adding to ensure that PVI is fully in contact with the surface of the silica nanoparticles, adjusting the pH to 8, reacting for 0.5 h, and obtaining a composite material by centrifugation, washing, and drying;

[0056] (2) treating SWCNTs with potassium permanganate KMnO4 to remove impurities and introduce carboxyl groups to obtain carboxylated single-walled carbon nanotubes, mixing the carboxylated single-walled carbon nanotubes with water to prepare a carbon nanotube suspension with a concentration of 0.1 wt%, mixing the carbon nanotube suspension with the composite material obtained in step (1), stirring for reaction at a pH of 3 for 1 h, and obtaining a precursor through centrifugation, washing and drying;

[0057] (3) The precursor obtained in step (2) is heat treated at 250° C. for 4 hours to obtain the modified silicon-based negative electrode material.

[0058] Example 3

[0059] This embodiment provides a modified silicon-based negative electrode material, which includes a silicon-oxygen core and a PDADMAC layer, a transition carbon layer and a single-walled carbon nanotube network layer sequentially coated on the surface of the silicon-oxygen core, the median particle size D50 of the silicon-oxygen core is 100nm, the thickness of the PDADMAC layer is 100nm, the thickness of the transition carbon layer is 200nm, and the thickness of the single-walled carbon nanotube network layer is 100nm. The modified silicon-based negative electrode material is prepared by the following method:

[0060] (1) adding a 1 wt % PDADMAC solution to a 0.5 mg / mL silica nanoparticle suspension while stirring to ensure that PDADMAC is in full contact with the surface of the silica nanoparticles, adjusting the pH to 6, reacting for 2 h, and obtaining a composite material by centrifugation, washing, and drying;

[0061] (2) reacting single-walled carbon nanotubes with bromoacetic acid to obtain hydroxylated single-walled carbon nanotubes, mixing the hydroxylated single-walled carbon nanotubes with water to prepare a carbon nanotube suspension with a concentration of 1 wt%, mixing the carbon nanotube suspension with the composite material obtained in step (1), stirring and reacting at a pH of 4 for 4 h, and obtaining a precursor through centrifugation, washing and drying;

[0062] (3) The precursor obtained in step (2) is heat treated at 350° C. for 1 h to obtain the modified silicon-based negative electrode material.

[0063] Example 4

[0064] The only difference between this embodiment and embodiment 1 is that the concentration of the cationic functionalized material solution (PEI solution) in step (1) is 0.05 wt %, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0065] Example 5

[0066] The only difference between this embodiment and embodiment 1 is that the concentration of the cationic functionalized material solution (PEI solution) in step (1) is 1.2 wt %, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0067] Example 6

[0068] The only difference between this embodiment and embodiment 1 is that the pH of the one-step reaction in step (1) is 9, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0069] Example 7

[0070] The only difference between this embodiment and embodiment 1 is that the pH of the one-step reaction in step (1) is 5, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0071] Example 8

[0072] The only difference between this embodiment and embodiment 1 is that the pH of the two-step reaction in step (2) is 8, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0073] Example 9

[0074] The only difference between this embodiment and embodiment 1 is that the pH of the two-step reaction in step (2) is 3, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0075] Example 10

[0076] The only difference between this embodiment and embodiment 1 is that the temperature of the heat treatment in step (3) is 200° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0077] Embodiment 11

[0078] The only difference between this embodiment and embodiment 1 is that the temperature of the heat treatment in step (3) is 400° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0079] Comparative Example 1

[0080] The only difference between this comparative example and Example 1 is that no PEI solution is added, and other conditions and parameters are exactly the same as those in Example 1.

[0081] Comparative Example 2

[0082] The only difference between this comparative example and Example 1 is that the carbon nanotubes are not subjected to hydroxylation treatment, and the other conditions and parameters are exactly the same as those in Example 1.

[0083] Button preparation:

[0084] The silicon-based negative electrode materials prepared in the embodiment and the comparative example were weighed according to the mass ratio of active material: SP:CMC:SBR=92:2:2:4, and the silicon-based negative electrode material, SP, CMC, and SBR were respectively weighed and uniformly mixed in deionized water to form a slurry; the uniformly mixed slurry was coated on an aluminum foil current collector, baked in an oven at 80°C for 1h, cooled to room temperature, and assembled into lithium-ion button batteries in a glove box with oxygen and water contents less than 0.01ppm using lithium sheets as counter electrodes and auxiliary electrodes, electrolyte 1MNaPF6 / EC:DMC:DEC=2:2:1, and a glass fiber separator as a separator.

[0085] The assembled button-type lithium-ion battery was left to stand for 12 hours. The electrochemical performance of the button-type lithium-ion battery was tested on the Wuhan Blue Electric Battery Test System with constant current:

[0086] Performance Test:

[0087] Cycle test: Cycle at room temperature with a 1C charge and 1C discharge process to calculate the capacity retention rate

[0088] Rate test: Charge the battery at a rate of 3C and calculate the constant current ratio. The test results are shown in Table 1:

[0089] Table 1

[0090]

[0091]

[0092] As can be seen from Table 1, from Examples 1-11, the initial coulombic efficiency of the battery made of the modified silicon-based negative electrode material of the present invention can reach more than 80%, the capacity retention rate after 500 cycles can reach more than 90%, and the 3C rate performance can reach more than 53%. By adjusting the preparation conditions and the ratio of raw materials, the initial coulombic efficiency of the battery made of the modified silicon-based negative electrode material can reach more than 84%, the capacity retention rate after 500 cycles can reach more than 94%, and the 3C rate performance can reach more than 58%.

[0093] By comparing Example 1 with Examples 4-5, it can be seen that during the preparation process of the modified silicon-based negative electrode material described in the present invention, the concentration of the cationic functionalized material solution will affect its performance. When the concentration of the cationic functionalized material solution is controlled at 0.1-1wt%, the performance of the modified silicon-based negative electrode material is better, resulting in a decrease in conductivity and an increase in ion diffusion resistance. If the concentration of the cationic functionalized material solution is too low, the formed cationic functionalized layer is too thin, resulting in uneven coverage of the functionalized layer and insufficient mechanical stability.

[0094] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation process of the modified silicon-based negative electrode material of the present invention, the pH of the one-step reaction will affect its performance. When the pH of the one-step reaction is controlled at 6-8, the performance of the modified silicon-based negative electrode material is better. If the pH of the one-step reaction is too high, the adsorption of the cationic functionalized layer will be insufficient. If the pH of the one-step reaction is too low, the surface activity of the silicon nanoparticles will be reduced and agglomeration will occur.

[0095] By comparing Example 1 with Examples 8-9, it can be seen that during the preparation of the modified silicon-based negative electrode material of the present invention, the pH of the two-step reaction will affect its performance. When the pH of the two-step reaction is controlled at 3-7 (pH 4-7 for hydroxylation, pH 3-5 for carboxylation), the performance of the modified silicon-based negative electrode material is better. If the pH of the two-step reaction is too high, the generation of functional groups will be reduced. If the pH of the two-step reaction is too low, the activity of the functional groups will be reduced.

[0096] By comparing Example 1 with Examples 10-11, it can be seen that during the preparation process of the modified silicon-based negative electrode material of the present invention, the temperature of heat treatment will affect its performance. When the temperature of heat treatment is controlled at 250-350°C, the performance of the modified silicon-based negative electrode material is better. If the temperature of heat treatment is too high, the cationic functionalized layer is excessively carbonized, resulting in excessive condensation of the structure and a decrease in conductivity. If the temperature of heat treatment is too low, the transition carbon layer cannot be generated, resulting in failure to effectively fix the functional groups and poor battery performance.

[0097] By comparing Example 1 and Comparative Examples 1-2, it can be seen that the present invention configures the cationic functionalized material and the silicon-based material into a solution, and then mixes the two to react. The two are fully in contact, and the cationic functionalized material is adsorbed on the surface of the silicon-based material by electrostatic action to form a cationic functionalized outer layer, which is helpful for further self-assembly process. After functionalization treatment, the conductive agent can be attracted by the cationic groups on the cationic functionalized outer layer, resulting in orderly spontaneous assembly between materials to form a conductive agent network. The network structure of the conductive agent can provide additional mechanical support for the negative electrode material, which helps to disperse and buffer the stress generated by the silicon nanoparticles during the charging and discharging process.

[0098] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A modified silicon-based negative electrode material, characterized in that: The modified silicon-based negative electrode material comprises a silicon-based core and a cationic functionalized layer, a transition carbon layer and a conductive agent network layer which are sequentially coated on the surface of the silicon-based core, wherein the transition carbon layer is in-situ generated on the surface of the cationic functionalized layer.

2. The modified silicon-based negative electrode material according to claim 1, characterized in that: The silicon-based core comprises any one of silicon-carbon material, silicon-oxygen material or elemental silicon, or a combination of at least two thereof; Preferably, the median particle size D50 of the silicon-based core is 1 to 100 nm.

3. The modified silicon-based negative electrode material according to claim 1 or 2, characterized in that: The material of the cationic functional layer includes any one of polyethyleneimine, poly(glycidyl methacrylate), poly(ethyleneimine), poly(N-vinylimidazole), poly(dimethyldiallylammonium chloride), poly(N-vinylpyrrolidone), poly(N-vinyl-N-dimethylaminoethyl methacrylate), poly(N-vinyl-N-dimethylcarbamate), poly(N-vinyl-N-dimethylaminoethyl chloromethylacrylate) or poly(N-vinyl-N-dimethylaminoethyl methacrylamide), or a combination of at least two thereof; Preferably, the thickness of the cationic functionalized layer is 1 to 100 nm; Preferably, the thickness of the transition carbon layer is 1 to 200 nm.

4. The modified silicon-based negative electrode material according to any one of claims 1 to 3, characterized in that: The conductive agent network layer includes a mesh layer constructed by linear conductive agents; Preferably, the linear conductive agent comprises any one of single-walled carbon nanotubes, silver nanowires or tin oxide nanowires, or a combination of at least two thereof; Preferably, the diameter of the linear conductive agent is 1 to 5 nm; Preferably, the thickness of the conductive agent network layer is 1 to 100 μm.

5. A method for preparing the modified silicon-based negative electrode material according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) mixing a cationic functional material solution with a silicon-based material dispersion to obtain a composite material through a one-step reaction; (2) functionalizing the conductive agent and mixing it with a solvent to obtain a suspension, mixing the composite material with the suspension, and obtaining a precursor through a two-step reaction; (3) heat-treating the precursor to obtain the modified silicon-based negative electrode material.

6. The preparation method according to claim 5, characterized in that: The solute of the cationic functionalized material solution in step (1) includes polyethyleneimine; Preferably, the solvent of the cationic functionalized material solution in step (1) comprises deionized water; Preferably, the concentration of the cationic functionalized material solution in step (1) is 0.1 to 1 wt %; Preferably, the solvent of the silicon-based material dispersion in step (1) comprises deionized water; Preferably, the concentration of the silicon-based material dispersion in step (1) is 0.5 to 10 mg / mL; Preferably, stirring is performed during the one-step reaction in step (1); Preferably, the pH of the one-step reaction in step (1) is 6 to 8; Preferably, the one-step reaction time in step (1) is 0.5 to 24 hours.

7. The preparation method according to claim 5 or 6, characterized in that: The functionalization treatment in step (2) includes hydroxylation and / or carboxylation; Preferably, the solvent in step (2) comprises deionized water; Preferably, the concentration of the suspension in step (2) is 0.1 to 1 wt %; Preferably, stirring is performed during the two-step reaction in step (2); Preferably, the pH of the two-step reaction in step (2) is 3 to 7; Preferably, the functionalization treatment in step (2) is hydroxylation treatment, and the pH of the two-step reaction is 4 to 7; Preferably, the functionalization treatment in step (2) is carboxylation treatment, and the pH of the two-step reaction is 3 to 5; Preferably, the time for the two-step reaction in step (2) is 1 to 4 hours.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The temperature of the heat treatment in step (3) is 250-350°C; Preferably, the heat treatment time in step (3) is 1 to 4 hours.

9. A negative electrode plate, characterized in that: The negative electrode plate comprises the modified silicon-based negative electrode material as described in any one of claims 1 to 4.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the negative electrode sheet as claimed in claim 9.

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