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

Abstract

The invention discloses a modified silicon-based negative electrode material and a preparation method and application thereof. The preparation method of the modified silicon-based negative electrode material comprises the following steps: carrying out spray drying on a mixture of a silicon-based material, lithium difluoro (oxalato) borate and lithium tetrafluoroborate to prepare an intermediate; and sequentially carrying out first heat treatment and second heat treatment on the intermediate to prepare the modified silicon-based negative electrode material. The modified silicon-based negative electrode material disclosed by the invention has a self-repairing function, can reduce full-charge expansion of a pole piece, can improve the fast charge performance and the cycle stability of a battery, and can enable the battery to have excellent first coulombic efficiency and self-adaptive capability.

Description

Technical Field

[0001] This invention relates to a modified silicon-based anode material, its preparation method, and its application. Background Technology

[0002] Based on the current anode market, silicon-based anode materials have been recognized and are gradually increasing in volume. The market penetration rate of silicon-based anode materials is expected to grow explosively in the future, mainly due to the increasing use of silicon doping in the 3C and power consumer electronics sectors. However, the market's requirements for silicon-based anode materials have never decreased, primarily focusing on: long cycle life, super-fast charging, and low expansion performance.

[0003] Regarding fast-charging performance, existing technologies include improvements such as controlling porous carbon precursors, enhancing the intrinsic conductivity of silicon and its deposition state, adjusting carbon deposition state, and back-end modification, but none have achieved significant progress. Controlling porous carbon precursors mainly focuses on eliminating micropores and introducing mesopores; the deposition state mainly focuses on controlling silicon / carbon deposition uniformity, deposition amount, and interface stability. However, these improvements are all at the early stages of the process, and their impact on the later stages and overall performance still needs further exploration and improvement. Currently, there is a lack of silicon-based anode materials that can simultaneously achieve excellent cycle performance, fast-charging performance, and low expansion performance; this problem urgently needs to be solved. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the deficiency of existing silicon-based anode materials that combine fast charging performance, cycle stability, and low expansion performance, and to provide a modified silicon-based anode material, its preparation method, and its applications. The modified silicon-based anode material prepared by this invention has a self-healing function, which can reduce the full-charge expansion of the electrode, improve the fast charging performance and cycle stability of the battery, and enable the battery to have excellent first coulombic efficiency and self-adaptive capability.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0006] This invention provides a method for preparing a modified silicon-based anode material, comprising the following steps:

[0007] S1. A mixture of silicon-based material, lithium difluorooxalate borate, and lithium tetrafluoroborate is spray-dried to obtain an intermediate.

[0008] S2. The intermediate is subjected to a first heat treatment and a second heat treatment in sequence to obtain the modified silicon-based anode material.

[0009] In step S1, the silicon-based material may be one or more of pure silicon, silicon suboxide, modified silicon suboxide, lithium silicon alloy, and silicon-carbon materials.

[0010] The pure silicon can be silicon material with a silicon content of 98% or more, which is common in the art.

[0011] The modified silicon suboxide generally refers to a material obtained by treating silicon suboxide through physical or chemical methods.

[0012] The lithium-silicon alloy generally refers to a metal compound formed by lithium and silicon elements through a certain process.

[0013] The silicon-carbon material is generally a material obtained by mixing silicon and carbon. The silicon material is generally one or more of pure silicon, silicon suboxide, modified silicon suboxide, and lithium-silicon alloy.

[0014] In step S1, the percentage of lithium difluorooxalate borate in the total mass of the raw materials can be 0.1%-5%, preferably 0.5%-2%, for example 0.5%, 0.7%, 1%, 1.5%, 1.8%, or 2%. The total mass of the raw materials refers to the sum of the masses of the silicon-based material, lithium difluorooxalate borate, and lithium tetrafluoroborate.

[0015] In step S1, the percentage of lithium tetrafluoroborate by mass of the raw materials can be 0.1%-5%, preferably 0.5%-2%, for example 0.5%, 0.7%, 1%, 1.5%, 1.8% or 2%. The total mass of the raw materials refers to the sum of the masses of the silicon-based material, lithium difluorooxalate borate, and lithium tetrafluoroborate.

[0016] In step S1, the mass ratio of lithium difluorooxalate borate to lithium tetrafluoroborate can be 1:(0.1-5), preferably 1:(0.5-2), for example 1:0.2, 1:0.5, 1:0.8, 1:1, 1:1.5, 1:1.8 or 1:2.

[0017] In step S1, the lithium difluorooxalate borate accounts for 0.1%-5% of the mass percentage of the silicon-based material, preferably 0.5%-2.1%, for example 0.51%, 0.7%, 1.02%, 1.5%, 1.8% or 2.04%.

[0018] In step S1, the lithium tetrafluoroborate accounts for 0.1%-5% of the mass percentage of the silicon-based material, preferably 0.5%-2.1%, for example 0.51%, 0.7%, 1.02%, 1.5%, 1.8% or 2.04%.

[0019] In step S1, the mixture can be prepared according to conventional methods and conditions in the art, preferably including the following steps: mixing a first suspension containing the silicon-based material with a second suspension containing "the lithium difluorooxalate borate and the lithium tetrafluoroborate"; more preferably, adding the second suspension to the first suspension in batches under stirring conditions (for example, adding it in 3 batches respectively).

[0020] In the preparation method of the mixture, the preparation method of the first suspension can be conventional in the art, generally obtained by mixing the solvent and the silicon-based material under stirring conditions.

[0021] In some preferred embodiments, the mixing speed may be 1500 rpm. The mixing time may be 2 hours.

[0022] In the method for preparing the mixture, the solvent in the first suspension can be a solvent conventional in the art capable of dispersing silicon-based materials, such as water and / or alcohols. The alcohol is preferably ethanol.

[0023] When the solvent is a combination of water and ethanol, the mass ratio of water to ethanol is preferably 1:(0.8-1.2), for example 1:1.

[0024] In the preparation method of the mixture, the mass ratio of the solvent in the first suspension to the silicon-based material can be 0.1-3, preferably 0.2-2.1, for example 2.041.

[0025] In the preparation method of the mixture, the preparation method of the second suspension can be conventional in the art, generally obtained by mixing the solvent with the lithium difluorooxalate borate and the lithium tetrafluoroborate under stirring conditions.

[0026] In some preferred embodiments, the mixing speed may be 1500 rpm. The mixing time may be 2 hours.

[0027] In the preparation method of the mixture, the solvent in the second suspension can be a conventional solvent in the art capable of dispersing "lithium difluorooxalate borate and lithium tetrafluoroborate", such as N,N-dimethylformamide.

[0028] In the preparation method of the mixture, the mass ratio of the solvent in the second suspension to the lithium difluorooxalate borate can be 1:(0.01-2), preferably 1:(0.02-0.1), for example 1:0.025, 1:0.05 or 1:0.1.

[0029] In the preparation method of the mixture, the mass ratio of the solvent in the second suspension to the lithium tetrafluoroborate can be 1:(0.01-2), preferably 1:(0.02-0.1), for example 1:0.025, 1:0.05 or 1:0.1.

[0030] In the method for preparing the mixture, the mixing speed can be 2000 rpm.

[0031] In the preparation method of the mixture, the mixing time can be 3 hours.

[0032] In step S1, the inlet air temperature of the spray dryer can be 140-180°C, for example, 150°C or 165°C.

[0033] In step S1, the feed rate of the spray dryer can be 10-16 Hz, for example 13 Hz.

[0034] In step S1, the spray drying process generally includes a drying step as well.

[0035] The drying temperature can be 100-140℃, for example 120℃.

[0036] The drying time can be 24 hours.

[0037] In step S2, the first heat treatment or the second heat treatment is generally performed in an inert atmosphere. The inert atmosphere can be conventional in the art, such as a nitrogen atmosphere.

[0038] In step S2, the rate of heating to the temperature of the first heat treatment can be 2-10℃ / min, for example 5℃ / min.

[0039] In step S2, the temperature of the first heat treatment can be 150-250℃, for example, 200℃.

[0040] In step S2, the duration of the first heat treatment can be 1-8 hours, for example, 4 hours.

[0041] In step S2, the rate of heating to the temperature of the second heat treatment can be 2-10℃ / min, for example 5℃ / min.

[0042] In step S2, the temperature of the second heat treatment can be 300-600℃, preferably 320℃-580℃, for example 320℃, 350℃, 380℃, 400℃, 450℃, 500℃, 520℃, 550℃ or 580℃.

[0043] In step S2, the duration of the second heat treatment can be 1-4 hours, for example, 2 hours.

[0044] The present invention also provides a modified silicon-based anode material, which is prepared by the above-described method for preparing modified silicon-based anode materials.

[0045] The present invention also provides a modified silicon-based anode material, comprising a core and a composite layer coated on the surface of the core, wherein the composite layer comprises a three-dimensional interwoven network formed by LiF, LixByOz and BmOn, and the core comprises a silicon-based material;

[0046] Wherein, x is 1-2; y is 1-4; z is 1-7; m is 1-4; and n is 1-3.

[0047] In this invention, x can be 1 or 2.

[0048] In this invention, y can be 1, 2, 3 or 4, preferably 2-4, for example 2 or 4.

[0049] In this invention, z can be 1, 2, 3, 4, 5, 6 or 7, preferably 2-7, for example 2 or 7.

[0050] In this invention, m can be 1, 2, 3 or 4, preferably 2.

[0051] In this invention, n can be 1, 2 or 3, preferably 3.

[0052] In this invention, the LixByOz is preferably LiBO2 and / or Li2B4O7.

[0053] In this invention, BmOn is preferably B2O3.

[0054] In this invention, the mass ratio of LiF to LixByOz can be 1-5, for example, 1, 2 or 4.

[0055] In this invention, the mass ratio of LiF to BmOn can be 1-10, for example 2, 4 or 8.

[0056] In this invention, the mass ratio of the core to the composite layer can be 9-100, preferably 50-90, for example 90.

[0057] Preferably, the three-dimensional interwoven network formed by LiF, LixByOz and BmOn is formed by a chemical reaction.

[0058] In this invention, the composite layer preferably does not contain polymeric monomers or polymers. The polymeric monomers generally refer to small molecule compounds conventional in the art that can polymerize with the same or other molecules; the polymers generally refer to high molecular weight polymers generated by polymerizing conventional polymeric monomers in the art.

[0059] The present invention also provides an application of the above-mentioned modified silicon-based anode material in a battery.

[0060] The battery may be a lithium battery and / or a solid-state battery.

[0061] The present invention also provides a negative electrode for a battery, comprising the modified silicon-based negative electrode material as described above.

[0062] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0063] The reagents and raw materials used in this invention are all commercially available.

[0064] The positive and progressive effects of this invention are as follows:

[0065] The present invention provides a method for preparing modified silicon-based anode materials using silicon-based materials, lithium difluorooxalate borate (LiDFOB), and lithium tetrafluoroborate (LiBF4) as raw materials. Through spray drying and two different heat treatments, the decomposition of LiDFOB and LiBF4 is controlled, forming an in-situ self-healing LiF cycle: LiBF4 decomposes into LiF and BF3 gases. BF3 promotes the decomposition of LiDFOB to generate LiBO2, LiF, Li2B4O7, B2O3, and other products. Simultaneously, BF3 reacts with LiBO2 to form LiBF4. In a preferred embodiment, LiF, Li2B4O7, LiBO2, and B2O3 form a three-dimensional interwoven network, resulting in more uniform shell coating and improved product performance. For example, this product can prevent or inhibit cracking of the battery SEI film, and can self-repair after SEI film cracking, thereby suppressing the decline in fast-charging performance. The preparation method of this invention is simple, operable, and practical.

[0066] The anode prepared using the modified silicon-based anode material of the present invention can be used in batteries to enable the batteries to have excellent electrochemical performance: for example, the 4C rate ratio can reach more than 68%, and in some preferred embodiments it can reach more than 85%; the capacity retention rate after 100 cycles can reach more than 90.6%, and in some preferred embodiments it can reach more than 92%; it also has excellent electrode full charge expansion rate, first charge specific capacity and first coulombic efficiency.

[0067] The modified silicon-based anode material of the present invention also has self-adaptability; the soft-hard interface can expand and then contract with the expansion of silicon-carbon particles, thus possessing better anti-expansion properties.

[0068] The modified silicon-based anode material of the present invention exhibits a certain degree of roughness on the shell surface, which makes the material easier to process and has good application prospects in the field of batteries. Detailed Implementation

[0069] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0070] The sources of the main raw materials used in the following examples and comparative examples are as follows:

[0071] (1) Silicon carbide material: purchased from Shanshan New Materials Co., Ltd., model GT8 (this model is spherical silicon carbide material).

[0072] (2) Lithium difluorooxalate borate (LiDFOB) and lithium tetrafluoroborate (LiBF4): purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of 99%.

[0073] Example 1

[0074] Preparation of modified silicon-based anode materials:

[0075] Weigh 4.9 kg of silicon carbide material and disperse it in a mixed solution of 5 kg of water and 5 kg of ethanol. Stir at 1500 rpm for 2 h to obtain a first suspension. Weigh 50 g of LiDFOB and 50 g of LiBF4 and dissolve them in 1 kg of DMF. Stir at 1500 rpm for 2 h to obtain a second suspension. Add the second suspension to the first suspension in three portions and stir at 2000 rpm for 3 h to obtain a mixture.

[0076] The mixture was spray-dried at an inlet air temperature of 165°C and a feed rate of 13 Hz. The material was collected and dried in an oven at 120°C for 24 hours. After drying, an intermediate was obtained.

[0077] Heat treatment: The intermediate is put into a rotary kiln and heated to 200℃ at 5℃ / min under N2 atmosphere for 4 hours for the first heat treatment; then heated to 350℃ at 5℃ / min for 2 hours for the second heat treatment, and then discharged to obtain the modified silicon-based anode material.

[0078] The obtained modified silicon-based anode material includes a core and a composite layer coated on the surface of the core. The core includes silicon-based materials, and the composite layer includes a three-dimensional interwoven network formed by LiF, LiBO2, Li2B4O7, and B2O3.

[0079] The mass ratio of the core to the composite layer is 90, the mass ratio of LiF to "LiBO2 and Li2B4O7" is 2, and the mass ratio of LiF to B2O3 is 4.

[0080] Example 2

[0081] The amount of LiBF4 used was 25g, and the other raw materials, amounts, and preparation methods were the same as in Example 1.

[0082] The obtained modified silicon-based anode material includes a core and a composite layer coated on the surface of the core. The core includes silicon-based materials, and the composite layer includes a three-dimensional interwoven network formed by LiF, LiBO2, Li2B4O7, and B2O3.

[0083] The mass ratio of the core to the composite layer is 90, the mass ratio of LiF to "LiBO2 and Li2B4O7" is 1, and the mass ratio of LiF to B2O3 is 4.

[0084] Example 3

[0085] The amount of LiDFOB used was 25g, and the other raw materials, amounts, and preparation methods were the same as in Example 1.

[0086] The obtained modified silicon-based anode material includes a core and a composite layer coated on the surface of the core. The core includes silicon-based materials, and the composite layer includes a three-dimensional interwoven network formed by LiF, LiBO2, Li2B4O7, and B2O3.

[0087] The mass ratio of the core to the composite layer is 90, the mass ratio of LiF to "LiBO2 and Li2B4O7" is 2, and the mass ratio of LiF to B2O3 is 2.

[0088] Example 4

[0089] The amount of LiBF4 used was 100g, and the other raw materials, amounts, and preparation methods were the same as in Example 1.

[0090] The obtained modified silicon-based anode material includes a core and a composite layer coated on the surface of the core. The core includes silicon-based materials, and the composite layer includes a three-dimensional interwoven network formed by LiF, LiBO2, Li2B4O7, and B2O3.

[0091] The mass ratio of the core to the composite layer is 90, the mass ratio of LiF to "LiBO2 and Li2B4O7" is 4, and the mass ratio of LiF to B2O3 is 4.

[0092] Example 5

[0093] The amount of LiDFOB used was 100g, and the other raw materials, amounts, and preparation methods were the same as in Example 1.

[0094] The obtained modified silicon-based anode material includes a core and a composite layer coated on the surface of the core. The core includes silicon-based materials, and the composite layer includes a three-dimensional interwoven network formed by LiF, LiBO2, Li2B4O7, and B2O3.

[0095] The mass ratio of the core to the composite layer is 90, the mass ratio of LiF to "LiBO2 and Li2B4O7" is 2, and the mass ratio of LiF to B2O3 is 8.

[0096] Example 6

[0097] The heat treatment steps are as follows: under N2 atmosphere, the temperature is increased to 200℃ at a rate of 5℃ / min and held at that temperature for 4 hours, then increased to 550℃ and held at that temperature for 2 hours, and then discharged. The raw materials, dosages, and other preparation methods are the same as in Example 1.

[0098] The obtained modified silicon-based anode material includes a core and a composite layer coated on the surface of the core. The core includes silicon-based materials, and the composite layer includes a three-dimensional interwoven network formed by LiF, LiBO2, Li2B4O7, and B2O3.

[0099] The mass ratio of the core to the composite layer is 90, the mass ratio of LiF to "LiBO2 and Li2B4O7" is 2, and the mass ratio of LiF to B2O3 is 4.

[0100] Comparative Example 1

[0101] The mixture was directly mixed and dried without spray drying. The raw materials, dosages, and other preparation methods were the same as in Example 1.

[0102] Comparative Example 2

[0103] The raw materials and dosages were the same as in Example 1. The mixture was coated by atomic layer deposition (ALD) to obtain a modified silicon-based anode material. The ALD coating method was as follows: 100g of silicon-carbon powder was placed in a vacuum oven and dried at 120℃ for 4 hours. The dried powder was then uniformly loaded into the ALD powder module, ensuring that the powder layer was loose and not compacted. The chamber was then closed, and a vacuum was drawn until the base pressure was ≤5×10⁻³Pa. Subsequently, the sample was heated to the deposition temperature of 450℃ and stabilized for 30 minutes under continuous argon purging. Then, acetylene (20 sccm) pulse: 8s, argon purging (20 sccm): 50s, argon plasma pulse (50 sccm): 20s, argon purging 50s, and the deposition cycle was repeated 100 times. After cooling, the material was discharged.

[0104] Comparative Example 3

[0105] The amount of LiDFOB and LiBF4 used was 0g, and the other raw materials, amounts, and preparation methods were the same as in Example 1.

[0106] Comparative Example 4

[0107] The amount of LiBF4 used was 0g, and the other raw materials, amounts, and preparation methods were the same as in Example 1.

[0108] Comparative Example 5

[0109] The amount of LiDFOB used was 0g, and the other raw materials, amounts, and preparation methods were the same as in Example 1.

[0110] Comparative Example 6

[0111] In the heat treatment operation, the temperature was directly increased to 200℃ at 5℃ / min under N2 atmosphere and kept constant for 6 hours. The material was then discharged. The remaining raw materials, dosages and preparation methods were the same as in Example 1.

[0112] Effect Example

[0113] 1. Battery manufacturing

[0114] Preparation of the negative electrode: Accurately weigh the modified silicon-based negative electrode material, Super P conductive additive, and polyacrylic acid (PAA) binder prepared in each example and comparative example. According to the mass ratio of silicon carbon: Super P: PAA = 85:7:8, place these materials in a deionized water solvent and stir thoroughly for 4 hours using a magnetic stirrer to ensure uniform mixing and form a uniform slurry. Use a transfer coating machine to uniformly coat the prepared slurry onto the Cu current collector. Place the coated current collector in a constant temperature environment of 100°C to dry for 24 hours to ensure that the moisture in the slurry is completely evaporated and to enhance the stability of the electrode. Cut the dried electrode into circular electrode sheets with a diameter of 16 mm as negative electrode sheets.

[0115] Battery assembly: LiPF6 dissolved in a mixed solvent of EC and DEC (mass ratio of EC to DEC 1:1) was selected as the electrolyte. In an argon-filled glove box, lithium sheets, separator (polypropylene membrane), negative electrode and electrolyte were assembled to obtain a coin cell.

[0116] 2. Electrical performance testing

[0117] (1) Charge-discharge cycle test

[0118] At 25℃, the assembled lithium-ion battery was subjected to charge-discharge cycle tests using a Blue Electric testing instrument to obtain data on its capacity, initial coulombic efficiency, and cycle stability. The thickness change of the electrode was measured in situ to obtain the electrode expansion rate. The charge-discharge cycle test procedure was as follows: 0.1C discharge to 5mV, 0.05C discharge to 5mV, 0.1C charge to 2V; 0.5C discharge to 5mV, 0.05C discharge to 5mV, 0.5C charge to 1V.

[0119] (2) 4C ratio test

[0120] The discharge specific capacity of the coin cells assembled by the above method was tested at 25°C and a voltage range of 0.005-2V at 4C.

[0121] The test results are recorded in Table 1.

[0122] Table 1. Effect data of each embodiment and comparative example.

[0123]

[0124] Here, % refers to the percentage of the mass of LiDFOB and LiBF4 relative to the total mass of the raw materials (excluding solvent).

[0125] The results of Examples 1 and 2 show that when the amount of LiDFOB remains unchanged, the amount of LiBF4 decreases, the full charge expansion rate of the battery prepared by the modified silicon-based anode material increases, the 4C rate ratio decreases, the first charge specific capacity and the first coulombic efficiency increase, and the capacity retention rate after 100 cycles decreases.

[0126] The results of Examples 1 and 4 show that when the amount of LiDFOB remains unchanged, increasing the amount of LiBF4 increases the full-charge expansion rate of the electrode in the battery prepared by the modified silicon-based anode material, and reduces the 4C rate ratio, first-charge specific capacity, first-charge coulombic efficiency, and 100-cycle capacity retention rate.

[0127] The results of Examples 1 and 3 show that when the amount of LiBF4 remains unchanged, the amount of LiDFOB decreases, the full charge expansion rate of the battery prepared by the modified silicon-based anode material increases, the 4C rate ratio decreases, the first charge specific capacity and the first coulombic efficiency increase, and the capacity retention rate after 100 cycles decreases.

[0128] The results of Examples 1 and 5 show that when the amount of LiBF4 remains unchanged, increasing the amount of LiDFOB increases the full-charge expansion rate of the battery prepared by the modified silicon-based anode material, and reduces the 4C rate ratio, first-charge specific capacity, first-charge coulombic efficiency, and 100-cycle capacity retention rate.

[0129] The results of Examples 1 and 6 show that when the temperature of the second heat treatment increases from 350°C to 550°C, the full charge expansion rate of the battery prepared by the modified silicon-based anode material increases, and the 4C rate ratio, first charge specific capacity, first coulombic efficiency, and 100-cycle capacity retention rate decrease.

[0130] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A method for preparing a modified silicon-based anode material, characterized in that, It includes the following steps: S1. A mixture of silicon-based material, lithium difluorooxalate borate, and lithium tetrafluoroborate is spray-dried to obtain an intermediate. S2. The intermediate is subjected to a first heat treatment and a second heat treatment in sequence to obtain the modified silicon-based anode material.

2. The method for preparing the modified silicon-based anode material as described in claim 1, characterized in that, It satisfies one or more of the following conditions ac: a. In step S1, the mass of lithium difluorooxalate borate accounts for 0.1%-5% of the total mass of the raw materials, where the total mass of the raw materials refers to the sum of the masses of the silicon-based material, lithium difluorooxalate borate, and lithium tetrafluoroborate. b. In step S1, the mass of lithium tetrafluoroborate accounts for 0.1%-5% of the total mass of the raw materials, and the total mass of the raw materials refers to the sum of the masses of silicon-based materials, lithium difluorooxalate borate, and lithium tetrafluoroborate. Preferably, in step S1, the mass ratio of lithium difluorooxalate borate to lithium tetrafluoroborate is 1:(0.1-5), more preferably 1:(0.5-2), for example 1:0.2, 1:0.5, 1:0.8, 1:1, 1:1.5, 1:1.8 or 1:2; c. In step S1, the silicon-based material is one or more of pure silicon, silicon suboxide, modified silicon suboxide, lithium silicon alloy, and silicon-carbon material; the pure silicon is a silicon material with a silicon content of 98% or more.

3. The method for preparing the modified silicon-based anode material as described in claim 1, characterized in that, In step S1, the mass of lithium difluorooxalate borate accounts for 0.5%-2% of the total mass of the raw materials, for example, 0.5%, 0.7%, 1%, 1.5%, 1.8% or 2%. The total mass of the raw materials refers to the sum of the masses of the silicon-based material, lithium difluorooxalate borate and lithium tetrafluoroborate. And / or, in step S1, the mass of lithium tetrafluoroborate accounts for 0.5%-2% of the total mass of the raw materials, for example, 0.5%, 0.7%, 1%, 1.5%, 1.8% or 2%, where the total mass of the raw materials refers to the sum of the masses of the silicon-based material, lithium difluorooxalate borate and lithium tetrafluoroborate.

4. The method for preparing the modified silicon-based anode material as described in claim 1, characterized in that, It satisfies one or more of the following conditions: a. In step S1, the inlet air temperature of the spray dryer is 140-180℃, for example, 150℃ or 165℃; b. In step S1, the feed rate of the spray dryer is 10-16 Hz, for example 13 Hz; c. In step S1, the spray drying process further includes a drying step; d. In step S2, the rate of heating to the temperature of the first heat treatment is 2-10℃ / min, for example, 5℃ / min; e. In step S2, the temperature of the first heat treatment is 150-250℃, for example, 200℃; f. In step S2, the duration of the first heat treatment is 1-8 hours, for example, 4 hours; g. In step S2, the rate of heating to the temperature of the second heat treatment is 2-10℃ / min, for example 5℃ / min; h. In step S2, the temperature of the second heat treatment is 300-600℃, preferably 320℃-580℃, for example 320℃, 350℃, 380℃, 400℃, 450℃, 500℃, 520℃, 550℃ or 580℃. i. In step S2, the duration of the second heat treatment is 1-4 hours, for example, 2 hours; and, j. In step S2, the first heat treatment or the second heat treatment is carried out in an inert atmosphere; the inert atmosphere is preferably a nitrogen atmosphere.

5. The method for preparing the modified silicon-based anode material as described in claim 1, characterized in that, In step S1, the preparation method of the mixture includes the following steps: mixing a first suspension containing the silicon-based material with a second suspension containing "lithium difluorooxalate borate and lithium tetrafluoroborate"; preferably, the second suspension is added to the first suspension in batches under stirring conditions.

6. A modified silicon-based anode material, characterized in that, It is prepared by the method for preparing the modified silicon-based anode material according to any one of claims 1-5.

7. A modified silicon-based anode material, characterized in that, It includes a core and a composite layer covering the surface of the core, the composite layer comprising a three-dimensional interwoven network formed by LiF, LixByOz and BmOn, and the core comprising a silicon-based material; Wherein, x is 1-2; y is 1-4; z is 1-7; m is 1-4; and n is 1-3.

8. The modified silicon-based anode material as described in claim 7, characterized in that, It satisfies any one of the following conditions ah: a. The x is 1 or 2; b. The value of y is 1, 2, 3 or 4, preferably 2-4, for example 2 or 4; c. The z is 1, 2, 3, 4, 5, 6 or 7, preferably 2-7, for example 2 or 7; d. The value of m is 1, 2, 3 or 4, preferably 2; e. The n is 1, 2 or 3, preferably 3; f. The mass ratio of LiF to LixByOz is 1-5, for example, 1, 2 or 4; g. The mass ratio of LiF to BmOn is 1-10, for example 2, 4 or 8; and, h. The mass ratio of the core to the composite layer is 9-100, preferably 50-90, for example 90; Preferably, the LixByOz is LiBO2 and / or Li2B4O7; Preferably, BmOn is B2O3.

9. The application of a modified silicon-based anode material as described in any one of claims 6-8 in a battery, wherein the battery is preferably a lithium battery and / or a solid-state battery.

10. A negative electrode of a battery, characterized in that, It includes the modified silicon-based anode material as described in any one of claims 6-8.

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