Amorphous silicon carbon negative electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of electrode materials, relates to an amorphous silicon carbon negative electrode material and a preparation method and application thereof, and discloses a preparation method of the amorphous silicon carbon negative electrode material, which comprises the following steps: (1) sputtering a silicon layer on the surface of graphite particles to obtain composite particles; (2) dispersing organic matters in an organic solvent, adding the composite particles under a continuous stirring condition, and wrapping the surfaces of the composite particles with the organic matters; then heating and stirring to obtain organic matter coated composite particle powder; and (3) carbonizing the composite particle powder wrapped by the organic matter in an inert gas environment to obtain the amorphous silicon carbon negative electrode material. The amorphous silicon carbon negative electrode material is of a three-layer structure and sequentially comprises graphite inner core particles, an amorphous silicon middle layer and a hard carbon outer layer from inside to outside. The lithium ion battery adopting the amorphous silicon carbon negative electrode material has the advantages of high specific capacity, high first coulombic efficiency, long cycle stability, excellent conductivity and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrode materials, and relates to an amorphous silicon-carbon negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] With the transformation of global energy structure to clean energy, as a high-efficiency energy storage carrier, the performance improvement of lithium ion batteries has become a research hotspot. The current commercial lithium ion battery negative electrode mainly uses graphite material, but its theoretical specific capacity is only 372 mAh / g, which is difficult to meet the needs of new generation electronic devices (such as 5G terminals, wearable devices) and electric vehicles (mileage over 1000 km). Therefore, the development of high specific capacity negative electrode materials has become the key to breaking through the energy density bottleneck of lithium ion batteries.

[0003] Silicon-based materials are considered as the most potential next-generation negative electrode materials due to their ultra-high theoretical specific capacity of 4200 mAh / g (about 11 times that of graphite), low delithiation potential (about 0.4 V vs. Li / Li⁺) and abundant crustal reserves. However, silicon-based materials have three major problems: (1) significant volume effect: the volume expansion rate during lithium ion intercalation / deintercalation is as high as 300~400%, which leads to electrode structure pulverization, active material shedding and rapid cycle life decline; (2) poor electrical conductivity: the intrinsic electrical conductivity is only 10 -4 ~10 - 6 S / cm, which is far lower than that of graphite (10 4 S / cm), and a large amount of conductive additives (such as carbon black) are needed to compensate for it, reducing the volume energy density of the electrode; (3) unstable SEI film: repeated volume expansion will damage the solid electrolyte interface (SEI) film, leading to continuous consumption of electrolyte and low first coulombic efficiency (usually <80 %).

[0004] To solve the above problems, existing research mainly uses material structure design such as nanocrystallization and porosity to alleviate the volume effect, and composite methods such as silicon-carbon composite and silicon-metal composite to improve the electrical conductivity of the material. In addition, amorphization of silicon is also an important design strategy for silicon-based negative electrodes. Due to its disordered amorphous structure, the atomic arrangement structure of amorphous silicon has higher structural elasticity and buffer space. Compared with crystalline silicon materials, its volume expansion rate is significantly reduced during electrochemical cycling, which can effectively release the huge stress generated by lithium ion alloying with silicon, improving the cycle stability; and the high defect density and loose structure can promote the uniform formation of the SEI film, reduce side reactions and significantly improve the first efficiency of the material. On the other hand, amorphous silicon has more natural defects and dangling bonds, and the electronic transmission path is more flexible, so the electrical conductivity is relatively better and does not need to rely too much on conductive additives.

[0005] Currently, the preparation strategies of amorphous silicon mainly include chemical vapor deposition (CVD) method and physical vapor deposition (PVD) method. The amorphous silicon prepared by the CVD method usually uses flammable and explosive silane (SiH4) gas and other raw materials, which are highly dangerous and require harsh reaction conditions, and thus have great safety hazards and extremely high requirements for production and research and development. The reaction conditions of the PVD method are very mild, almost no safety hazards, green and environmentally friendly production process, and no other by-products are generated. However, in the prior art, the PVD method is mainly used for thin film preparation in the photovoltaic industry (such as amorphous silicon solar cells), which is mainly surface plating on the surface of a large-size block, and is not suitable for small particle size substrates, and is difficult to meet the demand as a lithium ion electrode.

[0006] Therefore, it is of great significance to develop a safe, efficient and scalable amorphous silicon carbon negative electrode material to promote the industrialization of high-energy-density lithium ion batteries. SUMMARY

[0007] The purpose of the present application is to solve the above-mentioned problems existing in the prior art, and a preparation method of an amorphous silicon carbon negative electrode material based on magnetron sputtering and organic carbon coating is provided. The uniform deposition of amorphous silicon on the graphite substrate and the carbon coating strategy realize the high cycle stability of the silicon-carbon negative electrode material, so as to realize the advantages of high specific capacity, high initial coulombic efficiency, long cycle stability and excellent conductivity of the amorphous silicon carbon negative electrode material.

[0008] One object of the present application is achieved by the following technical scheme: A preparation method of an amorphous silicon carbon negative electrode material, comprising: (1) sputtering a silicon layer on the surface of graphite particles to obtain composite particles; (2) dispersing organic matter in an organic solvent, adding the composite particles under continuous stirring, and coating the organic matter on the surface of the composite particles; then heating and stirring to obtain organic matter-coated composite particle powder; (3) carbonizing the organic matter-coated composite particle powder at 500-800°C for 1-12h in an inert gas environment to obtain an amorphous silicon carbon negative electrode material; The amorphous silicon carbon negative electrode material has a three-layer structure, and the inner to outer layers are graphite core particles, an amorphous silicon intermediate layer and a hard carbon outer layer.

[0009] Preferably, the graphite particles in (1) are pretreated graphite particles, and the pretreatment includes classification and / or drying.

[0010] Preferably, the particle size D50 of the graphite particles in (1) is 5-75 μm.

[0011] Further preferably, the particle size D50 of the graphite particles in (1) is 5-35 μm.

[0012] Further preferably, the graphite particles in (1) have a particle size D50 of 15 μm.

[0013] Preferably, the graphite particles in (1) comprise natural graphite and / or artificial graphite.

[0014] Preferably, the sputtering process in (1) comprises sputtering a silicon source on the surface of the graphite particles in an inert gas environment of 0.1-20 Pa, at a sputtering power of 100-4500 W, a frequency of 120-360 Hz, and a time of 0.1-100 h.

[0015] Further preferably, the silicon source in (1) is a silicon target, comprising a sheet, a column, and a pie.

[0016] Further preferably, the sputtering process in (1) comprises sputtering a silicon source on the surface of the graphite particles in an inert gas environment of 5 Pa, at a sputtering power of 250-2500 W, a frequency of 250 Hz, and a time of 6-48 h.

[0017] Preferably, the composite particles in (1) have a D50 of 5-75 μm.

[0018] Preferably, the composite particles in (1) comprise a graphite core and a silicon layer.

[0019] Preferably, the silicon layer in the composite particles in (1) has a mass ratio of 1-50 wt%.

[0020] Further preferably, the silicon layer in the composite particles in (1) has a mass ratio of 3-30 wt%.

[0021] Preferably, the sputtering process in (1) comprises placing graphite particles with a D50 of 5-75 μm in a vibrating stirring container of a magnetron sputtering bin, vacuumizing to a vacuum degree in the magnetron sputtering bin lower than 1×10-1 Pa, introducing argon to 0.1-20 Pa, vacuumizing again to a vacuum degree lower than 1×10-1 Pa, repeating three times, until the gas environment is 0.1-20 Pa of argon, and then performing magnetron sputtering at a sputtering power of 100-4500 W, a frequency of 120-360 Hz, and a time of 0.1-100 h, to obtain the composite particles.

[0022] Preferably, the organic matter in (2) comprises one or more of pitch, xylose, glucose, sucrose, cellulose, and phenolic resin.

[0023] Preferably, the organic solvent in (2) comprises one or more of methanol, ethanol, acetone, n-hexane, n-butane, and polyethylene glycol.

[0024] As preferred, the mass ratio of the organic matter in (2) to the composite particle is 1: (2~20).

[0025] Further preferably, the mass ratio of the organic matter in (2) to the composite particle is 1: (4~10).

[0026] As preferred, the structure of the organic matter-wrapped composite particle powder in (2) comprises, in order, a graphite inner core, a silicon intermediate layer, and an organic matter layer.

[0027] Further preferably, the organic matter-wrapped composite particle powder in (2) comprises, in order, a graphite inner core, a silicon intermediate layer, and an organic matter layer, with a mass ratio of 100: (1~90): (5~190).

[0028] More preferably, the organic matter-wrapped composite particle powder in (2) comprises, in order, a graphite inner core, a silicon intermediate layer, and an organic matter layer, with a mass ratio of 100: (1~50): (5~50).

[0029] As preferred, the carbonization temperature in (3) is 600~800℃, and the time is 2~5h.

[0030] As preferred, the amorphous silicon-carbon negative electrode material is further subjected to post-treatment, including ball milling and / or sieving.

[0031] As preferred, the D50 of the amorphous silicon-carbon negative electrode material is 5~50 μm.

[0032] Further preferably, the D50 of the amorphous silicon-carbon negative electrode material is 10~20 μm.

[0033] As preferred, the mass proportion of amorphous silicon in the amorphous silicon-carbon negative electrode material is 4~45wt%.

[0034] Further preferably, the mass proportion of amorphous silicon in the amorphous silicon-carbon negative electrode material is 4.5~25wt%.

[0035] The second object of the present application is achieved by the following technical solution: An amorphous silicon-carbon negative electrode material is prepared by the above method.

[0036] As preferred, the amorphous silicon-carbon negative electrode material is a three-layer structure, comprising, from inside to outside, a graphite inner core particle, an amorphous silicon intermediate layer, and a hard carbon outer layer.

[0037] As preferred, the mass proportion of amorphous silicon in the amorphous silicon-carbon negative electrode material is 4~45wt%.

[0038] Further preferably, the mass proportion of amorphous silicon in the amorphous silicon-carbon negative electrode material is 4.5~25wt%.

[0039] The third object of the present application is achieved by the following technical solutions. A lithium ion battery comprising the amorphous silicon-carbon negative electrode material.

[0040] Preferably, the lithium ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte.

[0041] Further preferably, the negative electrode material of the negative electrode sheet of the lithium ion battery comprises the amorphous silicon-carbon negative electrode material.

[0042] Further preferably, the positive electrode material of the positive electrode sheet of the lithium ion battery comprises one of lithium iron phosphate, a ternary positive electrode material, and lithium cobaltate.

[0043] Preferably, when the positive electrode material is lithium iron phosphate, the lithium ion battery has a capacity retention rate > 95% after 100 cycles at 1C.

[0044] Compared with the prior art, the present application has the following beneficial effects: 1. The present application coats a silicon layer on the surface of a high-conductivity graphite core by magnetron sputtering, uses a high-purity silicon target and inert argon gas, generates no chemical pollutants and has controllable parameters, and can accurately control the thickness of the silicon layer. At the same time, the high-energy argon ions in the magnetron sputtering process can strip impurities on the surface of the graphite by physical bombardment, form a nano-rough structure and generate active sites, and also improve the bonding force between the silicon layer and the graphite matrix.

[0045] 2. The silicon intermediate layer of the amorphous silicon-carbon negative electrode material in the present application reacts with carbon during high-temperature carbonization and is converted into amorphous silicon, which constructs a rapid ion transport channel with the carbon network. The outer organic carbon layer formed by carbonization has high hardness and can constrain the expansion of the silicon layer and provide a buffer space.

[0046] 3. The amorphous silicon-carbon negative electrode material of the present application comprises a graphite core particle, an amorphous silicon intermediate layer, and a hard carbon outer layer, forming a high-efficiency synergistic effect. The graphite core provides stable structural support and a rapid electron transport channel, making up for the conductivity defects of amorphous silicon. The intermediate layer is the main capacity source. The outermost hard carbon layer is a hard carbon layer obtained by carbonization of organic matter, which has high strength characteristics that can inhibit the expansion of the silicon-based material and ensure the stability of the structure. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 The SEM image of the amorphous silicon-carbon negative electrode material in Example 1 of the present application.

[0048] Figure 2 The EDS spectrum of the amorphous silicon-carbon negative electrode material in Example 1 of the present application.

[0049] Figure 3 The XRD image of the amorphous silicon-carbon negative electrode material in Example 1 of the present application.

[0050] Figure 4 The capacity-voltage curve of the 1st, 5th and 10th cycles of the CR2035 button cell assembled by the amorphous silicon-carbon negative electrode material in Example 1 of the present application.

[0051] Figure 5 The cycle curve of the CR2035 button cell assembled by the amorphous silicon-carbon negative electrode material in Example 1 of the present application. DETAILED DESCRIPTION

[0052] The technical solutions of the present application are further described and explained below by specific examples, and it should be understood that the specific examples described herein are only used to help understand the present application, and are not used to limit the present application specifically.

[0053] If not specifically stated, the raw materials used in the examples of the present application are all commonly used raw materials in the art, and the methods used in the examples are all conventional methods in the art.

[0054] In this text, the amorphous silicon is deposited on the surface of graphite by magnetron sputtering to obtain composite particles, so as to regulate the capacity and energy density of the target silicon-carbon negative electrode material; then the organic matter layer is uniformly coated on the surface of the composite particles by liquid phase coating, and the structural strength and cycle stability of the amorphous silicon-carbon negative electrode material are further optimized by the carbonization step. The amorphous silicon-carbon negative electrode material of the present application exhibits excellent electrical conductivity and more stable lithium ion storage characteristics.

[0055] In this text, by adjusting the types and particle sizes of graphite particles, the magnetron sputtering parameters, the types of organic matter, the raw material ratio, etc., amorphous silicon-carbon negative electrode materials with different capacities can be obtained.

[0056] In this text, the CR2035 button cell includes a negative electrode sheet, a positive electrode sheet and an electrolyte; the electrolyte is 1M LiPF6-EC:DEC(1:1), the active material in the positive electrode sheet is lithium iron phosphate, and the specific composition is lithium iron phosphate, acetylene black and PVDF with a mass ratio of 91.5:5.5:3. The active material in the negative electrode sheet is the amorphous silicon-carbon negative electrode material of the present application, and the specific composition is the amorphous silicon-carbon negative electrode material, super P and CMC with a mass ratio of 95:3:2.

[0057] In this text, the test process includes: constant current charge and discharge test.

[0058] Test temperature: 30℃ constant temperature box test, test procedure: after activation for 3 cycles at 0.1C, constant current charge and discharge test is carried out at 1C.

[0059] Example 1 (1) Take 100 g of natural graphite with D50 of 15 μm, vacuum dry at 80 ℃ for 12 h. Place it in the vibration stirring container of the magnetron sputtering bin, vacuumize to a vacuum degree lower than 5 x 10-2 Pa in the magnetron sputtering bin, introduce argon to 0.5 Pa, vacuumize again to a vacuum degree lower than 5 x 10-2 Pa, repeat three times, until the gas environment is 0.5 Pa of argon, then perform magnetron sputtering, sputtering power is 600 W, frequency is 250 Hz, time is 6 h, after sputtering, the composite particles with a mass ratio of graphite core to silicon layer of 19:1 are obtained.

[0060] (2) Add 18.5 g of asphalt into 500 mL of n-hexane, under stirring condition, add the composite particles in step (1), and continuously stir and disperse for 30 min. Then transfer to a heating device for heating and stirring at 70 ℃, remove the solvent, to obtain organic matter wrapped composite particle powder. (3) Place the organic matter wrapped composite particle powder in a tube furnace, carbonize at 600 ℃ for 3 h under argon protective atmosphere, to obtain amorphous silicon-carbon negative electrode material. The amorphous silicon-carbon negative electrode material is a three-layer structure, from inside to outside, it is graphite core particle, amorphous silicon intermediate layer, and hard carbon outer layer.

[0061] The content of amorphous silicon in the amorphous silicon-carbon negative electrode material of the present embodiment is 4.6 wt%.

[0062] The amorphous silicon-carbon negative electrode material is characterized and tested.

[0063] According to Figure 1 , 2 , it can be known that the silicon element in the amorphous silicon-carbon negative electrode material prepared in the present embodiment is uniformly distributed, and highly consistent with the distribution of carbon element, which indicates that the silicon layer and the hard carbon coating layer are uniformly distributed.

[0064] According to Figure 3 , it can be known that the phase composition of the amorphous silicon-carbon negative electrode material prepared in the present embodiment is mainly graphite, and there is no obvious crystalline phase of silicon, which proves that the silicon exists in the form of amorphous silicon.

[0065] The amorphous silicon-carbon negative electrode material is assembled into a CR2035 button cell, and the performance is tested.

[0066] According to Figure 4 , 5 , it can be known that the CR2035 button cell of the present embodiment has a first discharge capacity of 518 mAh / g, a first coulombic efficiency of 88.97%, and a capacity retention rate of 95.77% after 100 cycles.

[0067] Example 2 (1) According to the procedure of Example 1 step (1), except that the D50 of the natural graphite is 35 μm; the composite particles with a mass ratio of graphite core to silicon layer of 19:1 are obtained in this step.

[0068] (2) The same as Example 1 step (2).

[0069] (3) The same as Example 1 step (3).

[0070] The amorphous silicon-carbon negative electrode material of this example is assembled into CR2035 button cells according to the procedure of Example 1, and performance tests are conducted; the performance data are shown in Table 1.

[0071] Example 3 (1) According to the procedure of Example 1 step (1), except that the D50 of the natural graphite is 5 μm; the composite particles with a mass ratio of graphite core to silicon layer of 19:1 are obtained in this step.

[0072] (3) The same as Example 1 step (3).

[0073] The amorphous silicon-carbon negative electrode material of this example is assembled into CR2035 button cells according to the procedure of Example 1, and performance tests are conducted; the performance data are shown in Table 1.

[0074] Example 4 (1) The same as Example 1 step (1).

[0075] (2) 18.5 g of glucose is added to 500 mL of anhydrous ethanol, and the composite particles in step (1) are added under stirring, and the stirring is continued for 30 min. Subsequently, it is transferred to a heating device for heating stirring at 80°C, and the solvent is removed to obtain composite particle powder wrapped with organic matter; (3) The same as Example 1 step (3).

[0076] The amorphous silicon-carbon negative electrode material of this example is assembled into CR2035 button cells according to the procedure of Example 1, and performance tests are conducted; the performance data are shown in Table 1.

[0077] Example 5 (1) The same as Example 1 step (1).

[0078] (2) 18.5 g of xylose is added to 500 mL of anhydrous ethanol, and the composite particles in step (1) are added under stirring, and the stirring is continued for 30 min. Subsequently, it is transferred to a heating device for heating stirring at 80°C, and the solvent is removed to obtain composite particle powder wrapped with organic matter; (3) The same as Example 1 step (3).

[0079] The amorphous silicon-carbon negative electrode material of this example was assembled into CR2035 button cells according to the procedure of Example 1 and tested for performance; performance data are shown in Table 1.

[0080] Example 6 (1) Same as Example 1, step (1).

[0081] (2) 18.5 g of phenol-formaldehyde resin was added to 500 mL of anhydrous ethanol, and the composite particles of step (1) were added under stirring and dispersed for 30 min. Subsequently, it was transferred to a heating device for heating and stirring at 80°C to remove the solvent, and organic matter-coated composite particle powder was obtained.

[0082] (3) Same as Example 1, step (3).

[0083] The amorphous silicon-carbon negative electrode material of this example was assembled into CR2035 button cells according to the procedure of Example 1 and tested for performance; performance data are shown in Table 1.

[0084] Example 7 (1) Same as Example 1, step (1).

[0085] (2) 18.5 g of sucrose was added to 500 mL of anhydrous ethanol, and the composite particles were added under stirring and dispersed for 30 min. Subsequently, it was transferred to a heating device for heating and stirring at 80°C to remove the solvent, and organic matter-coated composite particle powder was obtained. (3) Same as Example 1, step (3).

[0086] The amorphous silicon-carbon negative electrode material of this example was assembled into CR2035 button cells according to the procedure of Example 1 and tested for performance; performance data are shown in Table 1.

[0087] Example 8 (1) Same as Example 1, step (1).

[0088] (2) 18.5 g of cellulose was added to 500 mL of anhydrous ethanol, and the composite particles were added under stirring and dispersed for 30 min. Subsequently, it was transferred to a heating device for heating and stirring at 80°C to remove the solvent, and organic matter-coated composite particle powder was obtained. (3) Same as Example 1, step (3).

[0089] The amorphous silicon-carbon negative electrode material of this example was assembled into CR2035 button cells according to the procedure of Example 1 and tested for performance; performance data are shown in Table 1.

[0090] Example 9 (1) Follow the steps (1) of Example 1, except that artificial graphite with the same particle size is used instead of natural graphite.

[0091] (2) Same as step (2) in Example 1.

[0092] (3) Same as step (3) in Example 1.

[0093] The amorphous silicon-carbon anode material of this embodiment was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data is shown in Table 1.

[0094] Example 10 (1) Follow the steps (1) of Example 1, except that the sputtering power of magnetron sputtering is 2500W, the frequency is 250 Hz, and the time is 6h; the mass ratio of graphite core to silicon layer in the composite particles obtained in this step is 15:1.

[0095] (2) Same as step (2) in Example 1.

[0096] (3) Same as step (3) in Example 1.

[0097] In this embodiment, the amorphous silicon content in the amorphous silicon carbon anode material is 5.8 wt%.

[0098] The amorphous silicon-carbon anode material of this embodiment was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data is shown in Table 1.

[0099] Example 11 (1) Follow the steps (1) of Example 1, except that the sputtering power of magnetron sputtering is 250W, the frequency is 250Hz, and the time is 6h; the mass ratio of graphite core to silicon layer in the composite particles obtained in this step is 22:1.

[0100] (2) Same as step (2) in Example 1.

[0101] (3) Same as step (3) in Example 1.

[0102] In this embodiment, the amorphous silicon content in the amorphous silicon carbon anode material is 4.0 wt%.

[0103] The amorphous silicon-carbon anode material of this embodiment was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data is shown in Table 1.

[0104] Example 12 (1) The process is carried out according to step (1) of Example 1, except that the sputtering power of magnetron sputtering is 600W, the frequency is 250Hz, and the time is 24h; the mass ratio of graphite core to silicon layer in the composite particles obtained in this step is 4.75:1.

[0105] (2) Same as step (2) in Example 1.

[0106] (3) Same as step (3) in Example 1.

[0107] In this embodiment, the amorphous silicon content in the amorphous silicon carbon anode material is 16.15 wt%.

[0108] The amorphous silicon-carbon anode material of this embodiment was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data is shown in Table 1.

[0109] Example 13 (1) The process is carried out according to step (1) of Example 1, except that the sputtering power of magnetron sputtering is 600W, the frequency is 250Hz, and the time is 48h; the mass ratio of graphite core to silicon layer in the composite particles obtained in this step is 2.38:1.

[0110] (2) Same as step (2) in Example 1.

[0111] (3) Same as step (3) in Example 1.

[0112] In this embodiment, the amorphous silicon content in the amorphous silicon carbon anode material is 27.8 wt%.

[0113] The amorphous silicon-carbon anode material of this embodiment was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data is shown in Table 1.

[0114] Example 14 (1) The process is carried out according to step (1) of Example 1, except that the sputtering power of magnetron sputtering is 600W, the frequency is 250Hz, and the time is 100h; the mass ratio of graphite core to silicon layer in the composite particles obtained in this step is 1.14:1.

[0115] (2) Same as step (2) in Example 1.

[0116] (3) Same as step (3) in Example 1.

[0117] In this embodiment, the amorphous silicon content in the amorphous silicon carbon anode material is 44.3 wt%.

[0118] The amorphous silicon-carbon anode material of this embodiment was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data is shown in Table 1.

[0119] Example 15 (1) Same as step (1) in Example 1.

[0120] (2) Same as step (2) in Example 1.

[0121] (3) Proceed according to step (3) of Example 1, except that carbonization is carried out at 800℃ for 3 hours. The amorphous silicon-carbon anode material of this embodiment was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data is shown in Table 1.

[0122] Example 16 (1) Same as step (1) in Example 1.

[0123] (2) Add 9.25 g of asphalt to 500 mL of n-hexane, add the above composite particles under stirring conditions, and continue stirring and dispersing for 30 min. Then transfer to a heating device for heating and stirring at 70°C to remove the solvent and obtain composite particle powder coated with organic matter; (3) Same as step (3) in Example 1.

[0124] In this embodiment, the amorphous silicon content in the amorphous silicon carbon anode material is 4.8 wt%.

[0125] The amorphous silicon-carbon anode material of this embodiment was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data is shown in Table 1.

[0126] Example 17 (1) Same as step (1) in Example 1.

[0127] (2) Add 37 g of asphalt to 500 mL of n-hexane, add the above-mentioned composite particles under stirring conditions, and continue stirring and dispersing for 30 min. Then transfer to a heating device for heating and stirring at 70°C to remove the solvent and obtain composite particle powder coated with organic matter; (3) Same as step (3) in Example 1.

[0128] In this embodiment, the amorphous silicon content in the amorphous silicon carbon anode material is 4.25 wt%.

[0129] The amorphous silicon-carbon anode material of this embodiment was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data is shown in Table 1.

[0130] Comparative Example 1 (1) Take 100g of natural graphite with a D50 of 15μm and dry it under vacuum at 80 ℃ for 12 h. Use CVD method to coat the surface of natural graphite particles with a silicon layer by silane gas. The loading of the silicon layer is the same as in Example 1.

[0131] (2) Same as step (2) in Example 1.

[0132] (3) Same as step (3) in Example 1.

[0133] The amorphous silicon-carbon anode material of this comparative example was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data are shown in Table 1.

[0134] Comparative Example 2 (1) Take 100g of natural graphite with a D50 of 15μm and vacuum dry it at 80℃ for 12h. Mix it with commercially available nano-silicon (average size of 50 nm) by ball milling. The mass ratio of natural graphite to nano-silicon is the same as in Example 1.

[0135] (2) Same as step (2) in Example 1.

[0136] (3) Same as step (3) in Example 1.

[0137] The amorphous silicon-carbon anode material of this comparative example was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data are shown in Table 1.

[0138] Comparative Example 3 (1) Same as step (1) in Example 1.

[0139] (2) Same as step (3) in Example 1.

[0140] The amorphous silicon-carbon anode material of this comparative example was assembled into a CR2035 coin cell according to the steps of Example 1, and its performance was tested; the performance data are shown in Table 1.

[0141] Table 1. Performance Data of CR2035 Button Cells As shown in the table above, the amorphous silicon-carbon anode material prepared in this embodiment exhibits good electrical conductivity and good electrochemical performance when used in batteries.

[0142] As can be seen from Examples 1-3, increasing the particle size of graphite particles can improve the initial coulombic efficiency of the sample, but the cyclic stability will decrease to some extent.

[0143] As shown in Examples 4-8, different coatings of organic matter result in variations in initial efficiency and initial discharge capacity. Sugars such as glucose, xylose, sucrose, and cellulose, containing more oxygen functional groups, exhibit lower residual carbon rates during carbonization and generate more gas, resulting in more surface pores and a relatively thinner carbon layer, thus leading to poorer initial efficiency and cycle performance. Although phenolic resins also produce some gas, their relatively dense carbon layer results in higher structural strength and residual carbon rates, leading to better cycle stability. Asphalt-based organic matter also exhibits relatively high residual carbon rates and overall superior performance.

[0144] As can be seen from Example 9, selecting different types of graphite substrates can regulate the first-efficiency and cycle stability of the product. Artificial graphite has relatively few defects and can improve the electrochemical performance of the final sample to a certain extent.

[0145] According to Examples 10-14, the magnetron sputtering parameters were changed to adjust the ratio of graphite core to silicon interlayer. Changing the sputtering power had no significant effect on performance. However, by increasing the sputtering time, the proportion of silicon interlayer was significantly increased, and the first discharge capacity was significantly improved. However, the first coulombic efficiency showed a slight decreasing trend with the increase of silicon interlayer thickness, and the cycle stability showed a fluctuating and then decreasing trend with the increase of silicon interlayer thickness.

[0146] In summary, the amorphous silicon-carbon anode material prepared by the method of the present invention comprises a three-layer structure consisting of graphite core particles, an amorphous silicon intermediate layer, and a hard carbon outer layer, forming a highly efficient synergistic effect. The graphite core provides stable structural support and a fast electron transport channel, compensating for the conductivity defects of amorphous silicon. The intermediate layer is the main source of capacity. The outermost hard carbon layer is a hard carbon layer obtained by carbonizing organic matter, and its high strength characteristics can both suppress the expansion of silicon-based materials and ensure structural stability, thereby improving the performance of the battery.

[0147] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0148] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0149] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A method for preparing an amorphous silicon-carbon anode material, characterized in that, include: (1) A silicon layer is sputtered onto the surface of graphite particles to obtain composite particles; (2) Disperse the organic matter in an organic solvent, add the composite particles under continuous stirring, and coat the organic matter on the surface of the composite particles; then heat and stir to obtain composite particle powder coated with organic matter. (3) In an inert gas environment, the composite particle powder wrapped with organic matter is carbonized at 500~800℃ for 1~12h to obtain amorphous silicon carbon anode material; The amorphous silicon-carbon anode material has a three-layer structure, consisting of graphite core particles, an amorphous silicon intermediate layer, and a hard carbon outer layer from the inside out.

2. The method for preparing the amorphous silicon-carbon anode material according to claim 1, characterized in that, The particle size D50 of the graphite particles described in (1) is 5~75μm.

3. The method for preparing the amorphous silicon-carbon anode material according to claim 1, characterized in that, The sputtering process described in (1) includes sputtering a silicon source onto the surface of graphite particles in an inert gas environment of 0.1~20 Pa, with a sputtering power of 100~4500W, a frequency of 120~360 Hz, and a time of 0.1~100h.

4. The method for preparing the amorphous silicon-carbon anode material according to claim 1, characterized in that, (1) The composite particles include a graphite core and a silicon layer; the mass percentage of the silicon layer in the composite particles is 1~50wt%.

5. The method for preparing the amorphous silicon-carbon anode material according to claim 1, characterized in that, (2) The organic matter mentioned includes one or more of asphalt, xylose, glucose, sucrose, cellulose, and phenolic resin; the mass ratio of the organic matter to the composite particles is 1:(4~10).

6. The method for preparing the amorphous silicon-carbon anode material according to claim 1, characterized in that, (2) The structure of the composite particle powder encapsulated in organic matter includes, in sequence, a graphite core, a silicon intermediate layer, and an organic matter layer.

7. The method for preparing the amorphous silicon-carbon anode material according to claim 1, characterized in that, (3) The carbonization temperature is 600~800℃ and the time is 2~5h.

8. An amorphous silicon-carbon anode material, characterized in that, It is prepared by the method for preparing amorphous silicon-carbon anode material as described in any one of claims 1 to 7.

9. The amorphous silicon-carbon anode material according to claim 8, characterized in that, The amorphous silicon carbon anode material has a three-layer structure, consisting of graphite core particles, an amorphous silicon intermediate layer, and a hard carbon outer layer from the inside out; the mass percentage of amorphous silicon in the amorphous silicon carbon anode material is 4~45wt%.

10. A lithium-ion battery, characterized in that, It includes the amorphous silicon-carbon anode material prepared by the method of preparing amorphous silicon-carbon anode material as described in any one of claims 1 to 7, or the amorphous silicon-carbon anode material as described in any one of claims 8 to 9.

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