A core-shell structure silicon-based negative electrode material, a preparation method thereof and a lithium ion battery

Abstract

The application discloses a kind of core-shell structure silicon-based negative electrode materials and preparation method thereof, lithium ion battery, preparation method includes (1) amorphous silicon oxide layer is deposited on the surface of silicon particle, and first product is obtained;(2) after being coated with first product using carbon source and biomass carbon source, it is calcined, and second product is obtained;(3) carbon layer is deposited on the outer layer of second product, and core-shell structure carbon-coated silicon nanoparticles are obtained;(4) core-shell structure carbon-coated silicon nanoparticles are mixed with carbon source after being dispersed, vacuum drying, calcination, crushing, screening, and core-shell structure silicon-based negative electrode material is obtained;Deposition in step (1) and step (3) is all LPCVD deposition.The application is modified by uniformly coating silicon surface, and good ion passage is constructed, and the comprehensive performance of silicon-based negative electrode material with uniform coating, small volume expansion and strong ion transmission capacity is formed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery, and particularly relates to a core-shell structure silicon-based negative electrode material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] Lithium ion batteries have high working voltage, long cycle life, no memory effect, small self-discharge and environmental friendliness, and thus occupy an increasingly important position in the fields of electric vehicles, wearable devices, mobile communication and large-scale energy storage. As one of the key components of lithium batteries, the negative electrode material directly affects the capacity, power and cycle stability of the battery. The commonly used negative electrode material of lithium ion batteries is graphite-based negative electrode material, which has a low theoretical specific capacity (372 mAh·g -1 ), and cannot meet the needs of the research and development of new generation batteries in the future. Silicon-based negative electrode is considered as one of the most potential negative electrode materials due to its extremely high theoretical specific capacity (4200 mAh·g -1 ) and low delithiation potential platform, and has attracted a large amount of research attention, and gradually becomes a strong competitor to replace the traditional graphite negative electrode, and is considered as a key material of the next generation of high energy density lithium batteries.

[0003] However, although the silicon-based negative electrode has great improvement in energy density, there are still many problems in its large-scale application. Silicon will have a huge volume effect during charging and discharging, which leads to the pulverization and shedding of the electrode material, the loss of effective electrical contact of the active material, and the poor cycle stability. In addition, the direct contact of silicon material with electrolyte leads to the continuous growth of the interface SEI film. In this process, the limited electrolyte in the battery and lithium from the positive electrode are continuously consumed, which eventually leads to the rapid capacity decay of the battery. Due to the low intrinsic conductivity of silicon, it is not conducive to the internal rapid transfer of electrons and high current and large rate charging, which all limit the commercial application of silicon-carbon negative electrode.

[0004] In recent years, scientific researchers have tried to solve a series of problems faced by silicon-based negative electrodes from various aspects, such as surface modification technologies such as surface coating and artificial SEI film; the yolk-eggshell structure, porous structure and loose skeleton structure can effectively improve the electrochemical performance of silicon-based negative electrodes. The patent document with publication number CN115986121B discloses a preparation method of a silicon-based negative electrode material with a two-layer coating layer, a first coating layer of a metal organic framework compound is formed on the surface of the silicon-based material particles, and a second coating layer of carbon material is formed on the first coating layer through ball milling, the structure can inhibit the volume expansion of silicon while increasing the electrical conductivity. The patent document with publication number CN118448608A discloses a hollow structure carbon / aluminum lithium sulfide coated composite material, the outermost shell layer is a uniform carbon layer doped with nitrogen and copper elements, the inner shell is an aluminum lithium sulfide layer, and the core structure is nano silicon. The hollow structure and double-layer shell coating characteristics in the material structure are beneficial to eliminating the huge volume effect of the Si electrode material, thereby effectively improving the electrochemical performance of the electrode material.

[0005] Although many surface modifications of silicon / silicon-carbon composites have achieved certain results, the actual effect is still general. The coating by ball milling / hydrothermal method cannot achieve uniform coating of the silicon surface. The huge volume expansion of the exposed silicon after several cycles is still serious. The ion transport capacity is low, the cycle and rate performance is limited, and it still does not meet the commercialization demand. In view of this, the present patent application is proposed. SUMMARY

[0006] In order to solve the technical problems of the current silicon-based negative electrode material that the coating on the surface of silicon is not uniform, the volume expansion is still serious, and the ion transport capacity is low, the present application provides a preparation method of a core-shell structure silicon-based negative electrode material, provides a negative electrode material prepared by the above preparation method, and further provides a lithium ion battery.

[0007] The present application adopts the following technical solutions:

[0008] The first object of the present application is to provide a preparation method of a core-shell structure silicon-based negative electrode material, comprising the following steps:

[0009] (1) depositing an amorphous silicon oxide layer on the surface of silicon particles to obtain a first product;

[0010] (2) coating the first product with a carbon source and a biomass carbon source, and then calcining to obtain a second product;

[0011] (3) depositing a carbon layer on the outer layer of the second product to obtain a core-shell structure carbon-coated silicon nanoparticle;

[0012] (4) After dispersing and mixing the core-shell structured carbon-coated silicon nanoparticles with the carbon source, vacuum drying, calcination, crushing and sieving are performed to obtain the core-shell structured silicon-based anode material.

[0013] The depositions in steps (1) and (3) are both LPCVD depositions.

[0014] like Figure 1 As shown in the figure, in this invention, an amorphous silicon oxide layer (i.e., ...) is first deposited on the surface of nano-silicon particles using LPCVD technology. Figure 1 The LPCVD amorphous oxide layer in the process exhibits excellent coverage, high deposition uniformity and density, and a high deposition rate. This dense amorphous oxide layer promotes the formation of a stable SEI film at the electrode / electrolyte interface. Then, the first product is coated with a carbon source combined with a biomass carbon source to form a porous carbon-coated silicon particle as the second product. This carbon coating slows down the volume expansion of the silicon anode, and the use of amorphous porous carbon enhances ion transport and reduces impedance, forming a three-dimensional conductive network after calcination. Next, an LPCVD layer of carbon is uniformly deposited on the outer layer of the second product, and finally, it is mixed with a carbon source and calcined to form a coated carbon layer on the outermost layer of the anode material (i.e.,...). Figure 1 The LPCVD carbon coating in this process can significantly reduce the specific surface area of ​​the material, mitigate side reactions between the electrolyte and the material, and enhance the mechanical strength of the entire silicon particle anode, thereby achieving a high compaction density. Furthermore, the core-shell structure possesses a three-dimensional carbon framework, maintaining good ion pathways even at high compaction and tap densities, thus improving the cycle performance of silicon-based anode materials.

[0015] As a preferred design, in step (1), silane and oxygen are used as reaction gases during deposition, and an inert gas is introduced into the deposition chamber to deposit a uniform layer of oxide on the surface of the silicon particles.

[0016] The deposition temperature is 500-1000℃, the silane flow rate is 100-200 sccm, the oxygen flow rate is 50-100 sccm, and the inert gas flow rate is 400-500 sccm. Nitrogen is the preferred inert gas.

[0017] As a preferred design, before deposition in step (1), the silicon particles are cleaned according to the RCA standard (a wet chemical cleaning method), cleaned with deionized water, then soaked in hydrofluoric acid, and then vacuum dried.

[0018] The concentration of hydrofluoric acid is 1-3%, the soaking time is 30-60 seconds, the vacuum drying temperature is 60-90℃, and the drying time is 12-24 hours.

[0019] As a preferred design, the process of step (2) is:

[0020] Mix the monomer solution of quinone with the monomer solution of amine to obtain a quinone amine prepolymer;

[0021] Add biomass carbon cellulose into the quinone amine prepolymer to uniformly disperse to obtain a dispersion solution, and immerse the first product in the dispersion solution;

[0022] Then, stand and dry, and calcine the dried material to obtain a second product.

[0023] As a preferred design, the quinone monomer is any one of benzoquinone, naphthoquinone and anthraquinone, such as p-benzoquinone; the solvent selected in the quinone monomer is any one of ethanol, methanol and diethyl ether, and the mass concentration of the quinone monomer is 4-12 g / L;

[0024] The amine monomer is any one of phenylenediamine, naphthylamine and anthracene amine, such as o-phenylenediamine and p-phenylenediamine; the solvent selected in the amine monomer is any one of ethanol, methanol and diethyl ether, and the mass concentration of the amine monomer is 10-18 g / L;

[0025] The biomass carbon cellulose is one or more of renewable cotton, bamboo pulp, paper pulp and methyl cellulose, and the mass of the biomass carbon cellulose is 0.5-3 g.

[0026] In the application, the quinone amine prepolymer formed by the quinone monomer and the amine monomer is used as a carbon source, has a planar structure, and the biomass carbon cellulose has a linear structure; through the combination of the planar structure and the linear structure, the ion transmission capacity of the material is greatly enhanced; after calcination, a three-dimensional conductive structure can be formed; under high compactness and vibration density, the material still has good ion passage, and the cycle performance of the silicon-based negative electrode material is improved.

[0027] As a preferred design, the temperature during calcination in step (2) is 300-800 DEG C, and after calcination, grinding and crushing are performed to obtain a second product.

[0028] As a preferred design, in step (3), when the carbon layer is deposited on the outer layer of the second product, acetylene gas is used as a reaction gas, and nitrogen is used as an inert gas.

[0029] The flow rate of acetylene is 100-200 sccm, the deposition pressure is 0.2-0.7 Torr, and the deposition time is 30-120 min.

[0030] As a preferred design, in step (4), the time for dispersing and mixing the silicon nanoparticles and the carbon source is 3-8 h, and the temperature for vacuum drying is 60-100 DEG C.

[0031] The baking temperature is 800-1200 DEG C, the heating rate is 2-20 DEG C / min, and the high-temperature holding time is 1-3h.

[0032] The carbon source used in step (4) is any one of natural graphite, artificial graphite, and mesocarbon microbeads.

[0033] The second object of the present application is to provide a core-shell structure silicon-based negative electrode material prepared by the preparation method according to any one of the above.

[0034] The third object of the present application is to provide a lithium ion battery, which comprises the core-shell structure silicon-based negative electrode material according to the above, or the core-shell structure silicon-based negative electrode material prepared by the preparation method according to any one of the above.

[0035] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0036] The silicon-based negative electrode material provided by the present application has a multi-layer core-shell structure, the inner layer is high-capacity micron silicon, a layer of amorphous oxide layer is formed on the surface of the silicon, the electrode / electrolyte interface is promoted to form a stable SEI film, the intermediate layer is coated with silicon by combining the carbon source and the biomass carbon source, the volume expansion is slowed down, and a three-dimensional conductive network is formed, and a carbon layer is uniformly deposited on the outermost layer, which greatly reduces the specific surface area of the material, slows down the side reaction between the electrolyte and the material, and ensures the stability of the material structure. In the application of lithium ion batteries, the expansion degree of the electrode sheet is reduced by 20%, and the cycle performance of the silicon-based negative electrode is improved by 300 cycles (capacity retention rate 80%). BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the example embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0038] Figure 1 The preparation method of the silicon-based negative electrode material provided by the present application is shown in the flowchart. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present application more clear, the following will further illustrate the present application with examples, and the example embodiments of the present application and the description thereof are only used to explain the present application, and should not be regarded as a limitation on the present application.

[0040] Example 1:

[0041] A preparation method of a core-shell structure silicon-based negative electrode material is provided, which adopts the following process:

[0042] (1) The nanometer silicon particles are cleaned using the RCA standard to remove the surface organic matter, inorganic salt, metal ion, etc. After RCA cleaning, the nanometer silicon particles are cleaned thoroughly with deionized water, then soaked in hydrofluoric acid with a concentration of 2% for 60s to remove the surface oxide layer, and then dried in a vacuum oven at 80°C for 24h to obtain the treated nanometer silicon.

[0043] (2) The treated nanometer silicon is placed in a quartz tube in the deposition cavity of an LPCVD device, vacuum is extracted in the furnace cavity, the LPCVD deposition temperature is set to 800°C, silane and oxygen are introduced as the reaction gas, nitrogen is introduced as the inert gas into the cavity for deposition, the silane flow rate is 150sccm, the oxygen flow rate is 80sccm, and the nitrogen flow rate is 400sccm, and the first product is obtained after cooling.

[0044] (3) 100ml of anhydrous ethanol is measured in a beaker, 0.6g of p-benzoquinone powder is weighed and added to the anhydrous ethanol, and stirred uniformly; 30ml of anhydrous ethanol is measured in another beaker, 0.5g of o-phenylenediamine powder is weighed and added to the ethanol, and stirred uniformly. The o-phenylenediamine-ethanol mixed solution is added dropwise to the p-benzoquinone-ethanol solution using a dropper, and stirring is continued. After complete dropwise addition, a black quinone amine prepolymer is formed. Then, 1g of renewable cotton is weighed and added to the quinone amine prepolymer, and ultrasonic dispersion is performed to uniformly disperse the cotton. The first product is placed in the beaker, and the ultrasonically dispersed solution is slowly added dropwise onto the first product material using a dropper, so that the solution completely wets the powdered first product. After standing, the material is placed in a muffle furnace, heated to 700°C under nitrogen protection, calcined for 2-3h, cooled to room temperature, ground, and the second product is obtained.

[0045] (4) The second product is placed in a quartz tube in the deposition cavity of an LPCVD device, vacuum is extracted in the furnace cavity, acetylene gas is introduced as the reaction gas, and nitrogen is introduced as the inert gas into the cavity for deposition. The acetylene flow rate is 150sccm, the deposition pressure is 0.6Torr, and the deposition time is 60min. After deposition is completed and cooling, the core-shell structure carbon-coated nanometer silicon material is obtained.

[0046] (5) The obtained core-shell structure carbon-coated nanometer silicon material is mixed with graphite by fully dispersing in an ethanol solvent, then dried in a vacuum drying oven, and the dried mixture is placed in a muffle furnace and calcined at 1000°C under a nitrogen atmosphere for 2h. After crushing and sieving, the silicon-carbon negative electrode material is obtained.

[0047] Example 2:

[0048] The difference between this example and Example 1 is that in step (4) in which the outer layer of the second product is deposited with a carbon layer, the LPCVD deposition pressure is 0.4 Torr, and the rest is the same as Example 1.

[0049] Example 3:

[0050] The difference between this example and Example 1 is that in step (4) in which the outer layer of the second product is deposited with a carbon layer, the LPCVD deposition time is 120 min, and the rest is the same as Example 1.

[0051] Example 4:

[0052] The difference between this example and Example 1 is that in step (2) in which the surface of the silicon particles is deposited with an amorphous silicon oxide layer, the LPCVD deposition temperature is set to 600°C, and the rest is the same as Example 1.

[0053] Example 5:

[0054] The difference between this example and Example 1 is that in step (2) in which the surface of the silicon particles is deposited with an amorphous silicon oxide layer, the LPCVD deposition temperature is 900°C, and the rest is the same as Example 1.

[0055] Example 6:

[0056] The difference between this example and Example 1 is that the amount of p-benzoquinone powder added is 1.2 g, and the rest is the same as Example 1.

[0057] Example 7:

[0058] The difference between this example and Example 1 is that the amount of o-phenylenediamine powder added is 0.3 g, and the rest is the same as Example 1.

[0059] Example 8:

[0060] The difference between this example and Example 1 is that the amount of p-benzoquinone powder added is 1.2 g, and the amount of cotton added is 3 g, and the rest is the same as Example 1.

[0061] Example 9:

[0062] The difference between this example and Example 1 is that the amount of p-benzoquinone powder added is 1.2 g, the amount of o-phenylenediamine powder added is 0.3 g, and the amount of cotton added is 3 g, and the rest is the same as Example 1.

[0063] Comparative Example 1:

[0064] The difference between this example and Example 1 is that no amorphous silicon oxide layer is deposited on the surface of the silicon particles, i.e. the silicon particles are not oxidized, and the rest is the same as Example 1.

[0065] Comparative Example 2:

[0066] The difference between the present comparative example and Example 1 is that no carbon source and biomass carbon coating is performed, and the rest is the same as Example 1.

[0067] Comparative Example 3:

[0068] The difference between the present comparative example and Example 1 is that after depositing the amorphous silicon oxide layer on the surface of the silicon particles, only carbon source coating is performed, and no biomass carbon cellulose coating is added, and the rest is the same as Example 1.

[0069] Comparative Example 4:

[0070] The difference between the present comparative example and Example 1 is that no carbon deposition is performed on the outer layer of the second product, i.e., steps (4) and (5) in Example 1 are not performed, and the rest is the same as Example 1.

[0071] Comparative Example 5:

[0072] The difference between the present comparative example and Example 1 is that after obtaining the second product, the method used for carbon coating on the outside is fusion coating method.

[0073] Specifically, the second product and pitch are put into a fusion machine for fusion, and the fused material is carbonized at 800℃ for 2h and then cooled to room temperature, and the rest of the process for obtaining the first product and the second product is the same as Example 1.

[0074] Comparative Example 6:

[0075] The difference between the present comparative example and Example 1 is that the RCA standard is used to clean the nano-silicon particles to remove organic matter, inorganic salt, metal ions, etc. on the surface, and after RCA cleaning, the particles are thoroughly washed with deionized water, then soaked in 2% hydrofluoric acid for 60s, and then dried in a vacuum oven at 80℃ for 24h. A certain amount of silicon powder is weighed and loaded into a crucible and transferred to a high-purity argon atmosphere tube furnace, heated to 100℃ at a rate of 2℃ / min, the argon flow rate is kept at 200sccm, and the oxygen valve is opened, the oxygen is introduced at a flow rate of 50sccm for 1h, the oxygen valve is closed and the heating is stopped, and after natural cooling, the first product is obtained, and the rest is the same as Example 1.

[0076] Performance test:

[0077] The materials obtained in each example and comparative example are used as raw materials to prepare negative electrode sheets.

[0078] Specifically: the dried negative plate is cut into a circular plate with a diameter of 12 mm to obtain a silicon-based negative plate suitable for assembling a battery, the weight is measured, the active material mass is calculated, a Si / C half-cell against metal Li is assembled in an inert atmosphere glove box, with a lithium sheet as a counter electrode, LiPF6 as an electrolyte, a solvent being an ethylene carbonate and diethyl carbonate (EC: EMC = 3:7) solution containing 8% of fluoroethylene carbonate (FEC), and polypropylene (PP) as a separator, and electrochemical performance test is performed at 0.1C under charge and discharge after standing for 8h, and the results are shown in Table 1.

[0079] Table 1

[0080]

[0081] As can be seen from Table 1, the deposition temperature, deposition pressure and deposition time in the LPCVD deposition technology have an influence on the performance of the negative electrode material, and the concentration of the carbon source and the biomass carbon is closely related to the battery performance. In Examples 1-5, the preparation technology of the application is used, the temperature, pressure and deposition time in the deposition process are changed, and the negative electrode material obtained has good overall performance in terms of the volume expansion rate of the plate, the first charge and discharge efficiency and the capacity retention rate. In Examples 6-9, the concentration of the carbon source and the biomass carbon is changed, and the negative electrode material also has good performance in terms of the volume expansion rate of the plate, the first charge and discharge efficiency and the capacity retention rate. Among them, the technology of Example 1 has obvious leading advantages in terms of the volume expansion rate of the plate, the first charge and discharge efficiency and the capacity retention rate.

[0082] Compared with Example 1, the inner layer silicon of Comparative Example 1 is not oxidized, and no stable SEI film is formed on the surface, so that the silicon is directly contacted with the electrolyte, resulting in low initial efficiency and poor cycle performance. Compared with Example 1, Comparative Example 2 does not perform carbon source and biomass carbon coating, and the volume expansion is large, and the inner core is not constructed into a three-dimensional ion channel, so that the material has poor conductivity and poor cycle performance. Compared with Example 1, Comparative Example 3 does not add biomass carbon cellulose coating, and the volume expansion is larger than that of the combined coating of carbon source and biomass carbon, which indicates that the combined coating of biomass carbon source and carbon source has a more excellent effect of reducing the volume expansion of the silicon-based material, and the two together form a three-dimensional ion channel, construct a good conductive network through surface lines, enhance the ion transmission capacity, and exhibit excellent cycle performance. Compared with Example 1, Comparative Example 4 does not perform outermost carbon deposition, and exhibits low initial efficiency and cycle performance, which indicates that the outermost carbon deposition can reduce the contact between the electrolyte and the silicon material, avoid the occurrence of side reactions in the cycle, further improve the stability of the material structure, and delay the service life of the battery. Compared with Example 1, Comparative Example 5 performs carbon coating on the outermost layer by using a fusion method, and exhibits low initial efficiency and cycle performance, which indicates that the use of the fusion method causes uneven carbon coating on the outermost layer, and part of the outermost layer is exposed, which is contacted with the electrolyte in the cycle process, resulting in too many side reactions in the cycle process and poor cycle performance. Compared with Example 1, Comparative Example 6 uses a tube furnace to pass a gas to oxidize the surface of silicon, and the silicon powder in the lower layer is not sufficiently oxidized due to the uneven oxidation of the silicon powder caused by the gas passing through the tube furnace. The uneven oxidation leads to the failure to form a stable SEI film, the silicon is directly contacted with the electrolyte, resulting in low initial efficiency and poor cycle performance. At the same time, the silicon powder on the surface is excessively contacted with oxygen, which causes the oxidation layer to be too thick, reduces the activity of the nano-silicon, and affects the overall capacity.

[0083] In summary, the silicon surface is uniformly coated and modified in the present application, and a good ion channel is constructed. The SEI film, the combined coating of carbon source and biomass carbon source, and the outer layer carbon coating are mutually synergistic through the LPCVD deposition technology, so that a silicon-based negative electrode material with uniform coating on the silicon surface, small volume expansion, high ion transmission capacity, and good overall performance is formed. The silicon-based negative electrode material with the structure of the present application reduces the electrode expansion degree by 20% in the application of lithium ion batteries, and the cycle performance of the silicon-based negative electrode is improved by 300 cycles (capacity retention rate of 80%).

[0084] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present application, and it should be understood that the above are only specific embodiments of the present application, and are not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a core-shell structured silicon-based anode material, characterized in that, The method comprises the following steps: (1) depositing an amorphous silicon oxide layer on the surface of silicon particles to obtain a first product; (2) coating the first product with a carbon source 1 and a biomass carbon source, and then calcining to obtain a second product; (3) depositing a carbon layer on the outer layer of the second product to obtain silicon nanoparticles coated with a carbon shell structure; (4) dispersing and mixing the silicon nanoparticles coated with the carbon shell structure with a carbon source 2, and then vacuum drying, calcining, crushing and sieving to obtain a silicon-based negative electrode material with a core-shell structure; The deposition in steps (1) and (3) is LPCVD deposition; The carbon source 1 is a quinone-amine prepolymer formed by a quinone monomer and an amine monomer, and the biomass carbon source is biomass carbon cellulose; The calcining temperature in step (2) is 300-800 DEG C, and the second product is obtained by grinding and crushing after calcining; The calcining temperature in step (4) is 800-1200 DEG C, and the calcining time is 1-3 h; The carbon source 2 used in step (4) is any one of natural graphite, artificial graphite and mesocarbon microbeads; The calcining in step (2) and the calcining in step (4) are both carried out under nitrogen protection.

2. The method for preparing a core-shell structured silicon-based anode material according to claim 1, characterized in that, In step (1), silane and oxygen are used as reaction gases for deposition, and an inert gas is introduced into the deposition chamber for deposition, so that a uniform oxide layer is deposited on the surface of the silicon particles; The deposition temperature is 500-1000 DEG C, the silane flow rate is 100-200 sccm, the oxygen flow rate is 50-100 sccm, and the inert gas flow rate is 400-500 sccm.

3. The method for preparing a core-shell structured silicon-based anode material according to claim 1, characterized in that, Before deposition in step (1), the silicon particles are cleaned according to the RCA standard, deionized water cleaning, then soaked in hydrofluoric acid, and then vacuum dried; The concentration of the hydrofluoric acid is 1-3%, the soaking time is 30-60 s, the vacuum drying temperature is 60-90 DEG C, and the drying time is 12-24 h.

4. The method for preparing a core-shell structured silicon-based anode material according to claim 1, characterized in that, The process of step (2) is as follows: Mix the quinone monomer solution and the amine monomer solution to obtain a quinone-amine prepolymer; Then add biomass carbon cellulose to the quinone-amine prepolymer to obtain a dispersion solution, and immerse the first product in the dispersion solution; Then, dry by standing, and calcine the dried material to obtain the second product.

5. The method for preparing a core-shell structured silicon-based anode material according to claim 4, characterized in that, The quinone monomer is any one of benzoquinone, naphthoquinone and anthraquinone, the solvent selected for the quinone monomer is any one of ethanol, methanol and diethyl ether, and the mass concentration of the quinone monomer is 4-12 g / L; The amine monomer is any one of phenylenediamine, naphthylamine and anthracene amine, the solvent selected for the amine monomer is any one of ethanol, methanol and diethyl ether, and the mass concentration of the amine monomer is 10-18 g / L; The biomass carbon cellulose is one or more of renewable cotton, bamboo pulp and paper pulp, and the mass of the biomass carbon cellulose is 0.5-3 g.

6. The method for preparing a core-shell structured silicon-based anode material according to claim 1, characterized in that, In step (3), acetylene gas is used as the reaction gas for depositing the carbon layer on the outer layer of the second product, and nitrogen is used as the inert gas; The acetylene flow rate is 100-200 sccm, the deposition pressure is 0.2-0.7 Torr, and the deposition time is 30-120 min.

7. The method for preparing a core-shell structured silicon-based anode material according to claim 1, characterized in that, The time for dispersing and mixing the silicon nanoparticles and the carbon source 2 in step (4) is 3-8 h, and the temperature for vacuum drying is 60-100℃; The heating rate during calcination is 2-20℃ / min.

8. A core-shell structure silicon-based negative electrode material prepared by the preparation method of any one of claims 1-7.

9. A lithium-ion battery, characterized by The negative electrode sheet comprises the core-shell structure silicon-based negative electrode material of claim 8, or the core-shell structure silicon-based negative electrode material prepared by the preparation method of any one of claims 1-7.

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