Silicon-carbon-graphite negative electrode active material, negative electrode material and application thereof

Abstract

The application provides a silicon-carbon-graphite negative electrode active material, a negative electrode material and application thereof, and the silicon-carbon-graphite negative electrode active material comprises spherical silicon-carbon material and fast-charging artificial graphite. The silicon-carbon-graphite negative electrode active material contains the spherical silicon-carbon material, on the one hand, the spherical silicon-carbon material improves the energy density of the negative electrode active material, and on the other hand, the spherical silicon-carbon material has a spherical shape, the spherical silicon-carbon material can improve the compression resistance, and the spherical silicon-carbon material and the fast-charging artificial graphite have a synergistic effect, so that the silicon-carbon-graphite negative electrode active material composed of the spherical silicon-carbon material and the fast-charging artificial graphite has high compression resistance, thereby greatly improving the compaction density of the negative electrode sheet prepared from the silicon-carbon-graphite negative electrode active material, and enabling the negative electrode sheet to exhibit more excellent long-cycle low-expansion performance under the same compaction; therefore, the silicon-carbon-graphite negative electrode active material has excellent expansion inhibition performance while improving the energy density.

Description

A silicon-carbon-graphite anode active material, the anode material and its application Technical Field

[0001] This invention belongs to the field of battery technology and relates to a silicon-carbon-graphite anode active material, particularly to a silicon-carbon-graphite anode active material, an anode material, and its applications. Background Technology

[0002] Lithium-ion batteries are widely used in smartphones, laptops, bicycles, and automobiles. With the development of technology, the requirements for energy density are gradually increasing, and silicon-based anode materials have emerged. The advantages of silicon anode materials are mainly reflected in their high theoretical specific capacity and excellent performance on lithium voltage. The theoretical specific capacity of silicon materials is significantly higher than that of graphite, which is approaching its performance limit. This makes silicon materials a promising candidate for anode materials in high-energy-density lithium batteries. Secondly, the voltage platform of silicon materials is slightly higher than that of graphite, and it is difficult to cause surface lithium deposition during charging. Therefore, its safety performance is also better than that of graphite anode materials.

[0003] However, whether it is silicon-oxygen or silicon-carbon material, it will undergo severe volume expansion and contraction (up to 300%) during battery charging and discharging. During battery charging and discharging, the high expansion rate makes the material very prone to cracking and falling off, resulting in battery capacity loss and battery failure.

[0004] Therefore, the application of silicon-oxygen and / or silicon-carbon materials in existing technologies is primarily focused on mixing them into graphite anodes to improve energy density. Based on this, the formulation of the anode material is crucial to mitigating volume expansion during charging and discharging of silicon-based anodes. Currently, most commercially available silicon-carbon materials are amorphous, and the selection of graphite is largely based on rate capability and expansion considerations. For binders, polyacrylic acid compounds, carboxymethyl cellulose, and styrene-butadiene rubber are commonly chosen. However, the expansion suppression effect of the anode active materials disclosed in existing technologies is quite limited.

[0005] CN116314605A discloses a lithium-ion battery negative electrode sheet, its preparation method, and a lithium-ion battery. The lithium-ion battery negative electrode sheet has a composite layer structure, including a first, second, and third layer. The first layer is close to the current collector side, and the third layer is far away from the current collector. The first layer includes a graphite negative electrode active material and a silicon-based active negative electrode material; the second layer includes a graphite negative electrode active material, a silicon-based active negative electrode material, and conductive carbon; and the third layer is composed of a graphite negative electrode material.

[0006] CN104810506A discloses a high-energy-density lithium-ion battery, including a positive electrode, a negative electrode, a separator, an electrolyte, and an outer packaging. The positive and negative electrode are respectively composed of positive and negative current collectors and positive and negative electrode materials coated on the positive and negative current collectors. The positive electrode material includes a positive active material, a positive conductive agent, and a positive binder. The negative electrode material includes a negative active material, a negative conductive agent, a thickener, and a negative binder. The positive active material is a nickel-cobalt-aluminum ternary positive electrode material or a nickel-cobalt-manganese ternary positive electrode material, and the negative active material is a silicon-carbon material with a carbon source coated on a silicon source.

[0007] Existing silicon-based anode active materials all have certain drawbacks, including the inability to achieve both high energy density and good expansion suppression performance. Therefore, it is crucial to develop and design a novel silicon-carbon-graphite anode active material, anode material, and its applications. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a silicon-carbon-graphite anode active material, an anode material, and its applications. The silicon-carbon-graphite anode active material provided by the present invention includes spherical silicon-carbon material. On the one hand, the spherical silicon-carbon material improves the energy density of the anode active material; on the other hand, the spherical shape of the silicon-carbon material enhances its compressive strength. Furthermore, the spherical silicon-carbon material has a synergistic effect with fast-charging artificial graphite. Therefore, the silicon-carbon-graphite anode active material composed of spherical silicon-carbon material and fast-charging artificial graphite exhibits high compressive strength, thereby significantly improving the compaction density of the anode sheet prepared from the silicon-carbon-graphite anode active material. This results in the anode sheet exhibiting superior long-cycle low-expansion performance under the same compaction conditions. Therefore, the silicon-carbon-graphite anode active material, while improving energy density, also possesses excellent expansion suppression performance.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a silicon-carbon-graphite anode active material, wherein the silicon-carbon-graphite anode active material comprises spherical silicon-carbon material and fast-charging artificial graphite.

[0011] The silicon-carbon-graphite anode active material provided by this invention includes spherical silicon-carbon material. On the one hand, the spherical silicon-carbon material improves the energy density of the anode active material; on the other hand, the spherical shape of the silicon-carbon material improves its compressive strength. Moreover, the spherical silicon-carbon material has a synergistic effect with fast-charging artificial graphite. Therefore, the silicon-carbon-graphite anode active material composed of spherical silicon-carbon material and fast-charging artificial graphite has high compressive strength, which can greatly improve the compaction density of the anode sheet prepared with silicon-carbon-graphite anode active material, so that the anode sheet exhibits better long-cycle low-expansion performance under the same compaction. Therefore, the silicon-carbon-graphite anode active material not only improves the energy density but also has excellent expansion suppression performance.

[0012] Preferably, the D50 particle size of the spherical silicon-carbon material is smaller than that of fast-charging artificial graphite.

[0013] Because of the crosstalk effect between lithium ions in silicon and graphite, lithium ions gradually accumulate inside silicon during cycling. Under the repeated compression of the huge expansion stress of silicon particles, the capacity of graphite decreases. Therefore, in this invention, by limiting the D50 particle size of the spherical silicon-carbon material to be smaller than that of the fast-charging artificial graphite, the pores formed between the fast-charging artificial graphite particles are made comparable to the size of the expanded spherical silicon-carbon material. The pores formed between the fast-charging artificial graphite particles are used to accommodate the volume change of the spherical silicon-carbon material, thereby improving the expansion suppression performance of the silicon-carbon-graphite anode active material.

[0014] Preferably, the D50 particle size of the spherical silicon carbide material is 9 to 10 μm, for example, it can be 9 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm, 9.9 μm or 10 μm, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0015] Preferably, the silicon content in the spherical silicon-carbon material is 47.5% to 55%, for example, it can be 47.5%, 48%, 48.5%, 49%, 49.5%, 50%, 51%, 52% or 55%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, the compaction density of the spherical silicon carbide material is 1.2–1.7 g / cm³. 3 For example, it could be 1.7 g / cm³ 3 1.68g / cm 3 1.66 g / cm 3 1.64 g / cm 3 1.62g / cm 3 1.6g / cm3 1.55g / cm 3 1.5g / cm 3 1.45g / cm 3 1.4g / cm 3 1.3g / cm 3 Or 1.2g / cm 3 However, this does not apply to all values ​​listed; other unlisted values ​​within this range also apply.

[0017] Preferably, the spherical silicon-carbon material has a coin cell capacity of 1650-1850mAh at 1.5V, for example, it can be 1650mAh, 1660mAh, 1665mAh, 1670mAh, 1680mAh, 1690mAh, 1700mAh, 1720mAh, 1750mAh, 1800mAh or 1850mAh, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0018] The capacitance of the spherical silicon carbon material described in this invention is defined as follows: using a button cell manufacturing method, the formulation of the button cell manufacturing method contains polyacrylic acid (PAA), carbon nanotubes (CNT), conductive carbon black (SP), spherical silicon carbon material and water. After thorough mixing, it is coated on copper foil, dried, rolled and sliced ​​using a mold to obtain a circular piece with a diameter of 14mm. It is then assembled according to conventional button cell manufacturing steps. After the button cell assembly is completed, it is left to stand for 6 hours, and then the specific capacitance and first-time efficiency are tested.

[0019] The specific capacity test method is as follows: discharge to 0.005V with a current of 0.05C, let stand for 5 minutes, then discharge to 0.005V with a current of 0.01C, let stand for 5 minutes, and then charge to 1.5V with a current of 0.05C. The charging capacity is obtained by dividing the effective active material mass by the charging capacity, which is the specific capacity of the material (1.5V).

[0020] Preferably, the spherical silicon-carbon material has an initial efficiency of 82-84% at 0.8V. The initial efficiency can be, for example, 82%, 82.5%, 83%, 83.5% or 84%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] The test method for the first efficiency is as follows: discharge the button cell to 0.005V with a current of 0.05C, let it stand for 5 minutes, then discharge it to 0.005V with a current of 0.01C, let it stand for 5 minutes, and then charge it to 0.8V with a current of 0.05C. The ratio of the charging capacity to the discharging capacity of the button cell is the first efficiency of the button cell at 0.8V.

[0022] Preferably, the spherical silicon-carbon material is prepared by a gas-phase method.

[0023] Preferably, the vapor phase method includes: using a resin-based material as a carbon matrix, and preparing spherical silicon-carbon material by vapor phase deposition.

[0024] Preferably, the pore volume of the carbon matrix is ​​≥0.8 cm³. 3 / g, and the proportion of pores with a pore size greater than 2nm is ≥93%.

[0025] The carbon matrix described in this invention has a pore volume ≥ 0.8 cm³. 3 / g, for example, could be 0.8cm 3 / g, 0.85cm 3 / g, 0.9cm 3 / g, 0.95cm 3 / g, 1cm 3 / g, 1.05cm 3 / g, 1.1cm 3 / g, 1.15cm 3 / g or 1.2cm 3 / g, but not limited to the listed values; other unlisted values ​​within this range also apply.

[0026] In this invention, the proportion of carbon matrix with a pore size greater than 2 nm is ≥93%, for example, it can be 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5% or 98%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the D50 particle size of the fast-charging artificial graphite is 12-14 μm, for example, it can be 12 μm, 12.2 μm, 12.4 μm, 12.6 μm, 12.8 μm, 13 μm, 13.2 μm, 13.4 μm, 13.6 μm, 13.8 μm or 14 μm, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0028] Preferably, the compacted density of the fast-charging artificial graphite is 1.73–1.78 g / cm³. 3 For example, it could be 1.73 g / cm³ 3 1.74 g / cm 3 1.75g / cm 3 1.76 g / cm 3 1.77g / cm 3 Or 1.78g / cm 3 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0029] Preferably, the specific capacity of the fast-charging artificial graphite is 356-360 mAh / g, for example, it can be 356 mAh / g, 357 mAh / g, 358 mAh / g, 359 mAh / g or 360 mAh / g, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, the orientation degree OI value of the fast-charging artificial graphite is 6.0 to 9.0, for example, it can be 9.0, 8.8, 8.6, 8.2, 8.0, 7.8, 7.5, 7.2, 7.0, 6.5 or 6.0, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the fast-charging artificial graphite can meet the high-rate fast charging performance of 3C and above.

[0032] Preferably, the method for preparing the fast-charging artificial graphite includes:

[0033] Petroleum coke raw coke is crushed and shaped, and then granulated to obtain semi-finished secondary particles. The obtained semi-finished secondary particles are subjected to graphitization heat treatment, coated with a coating agent, and then subjected to carbonization heat treatment to obtain fast-charging artificial graphite.

[0034] Preferably, the raw petroleum coke has a particle size of 6–7 μm and a tap density greater than 0.68 g / cm³. 3 .

[0035] The particle size of the petroleum coke raw coke described in this invention is 6-7 μm, for example, it can be 6 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm or 7 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the pulverization and shaping yields pulverized particles with a D50 particle size of 7–9 μm, for example, 7 μm, 7.2 μm, 7.4 μm, 7.6 μm, 7.8 μm, 8 μm, 8.2 μm, 8.4 μm, 8.6 μm, 8.8 μm, or 9 μm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0037] Preferably, the granulation includes: mixing the asphalt binder with the crushed particles and granulating at 800-950°C for less than 9 hours.

[0038] In this invention, granulation is carried out at 800 to 950°C, for example, 800°C, 820°C, 850°C, 870°C, 890°C, 910°C, 930°C or 950°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] In this invention, granulation time of less than 9 hours is used, for example, 8.9 hours, 8.7 hours, 8.5 hours, 8 hours, 7.5 hours, 7 hours, 6.5 hours, 6 hours, 5.5 hours, or 5 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] Preferably, the granulation is carried out in a granulation axe.

[0041] Preferably, the D50 particle size of the semi-finished secondary particles obtained after granulation is 12-13.5 μm, for example, it can be 12 μm, 12.2 μm, 12.4 μm, 12.6 μm, 12.8 μm, 13 μm, 13.2 μm, 13.4 μm or 13.5 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the graphitization heat treatment is performed at a temperature of 2850–3200°C for 9–12 hours, and the graphitized material is obtained after the graphitization heat treatment.

[0043] The temperature of the graphitization heat treatment described in this invention is 2850 to 3200℃, for example, it can be 2850℃, 2900℃, 2950℃, 3000℃, 3050℃, 3100℃, 3150℃ or 3200℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] The graphitization heat treatment time described in this invention is 9 to 12 hours, for example, it can be 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours or 12 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, the coating agent comprises a combination of at least two of phenolic resin, epoxy resin and tubular conductive agent. Typical but non-limiting combinations include a combination of phenolic resin and epoxy resin, a combination of epoxy resin and tubular conductive agent, or a combination of phenolic resin, epoxy resin and tubular conductive agent.

[0046] Preferably, the coating method includes mixing the coating agent with the graphitized material by stirring.

[0047] Preferably, the stirring is carried out in a horizontal reactor.

[0048] Preferably, the mass fraction of the coating agent is not less than 8 wt%, based on the total mass of the coating agent and the graphitized material. For example, it can be 8 wt%, 8.2 wt%, 8.5 wt%, 8.8 wt%, 9 wt%, 9.2 wt%, 9.5 wt%, 9.8 wt%, or 10 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] Preferably, the carbonization heat treatment is performed at a temperature of 900–1100°C for 7–9 hours.

[0050] The carbonization heat treatment temperature described in this invention is 900 to 1100°C, for example, it can be 900°C, 920°C, 940°C, 960°C, 980°C, 1000°C, 1020°C, 1040°C, 1060°C, 1080°C or 1100°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] The carbonization heat treatment time described in this invention is 7 to 9 hours, for example, it can be 7.2 hours, 7.5 hours, 7.8 hours, 8 hours, 8.2 hours, 8.5 hours, 8.8 hours or 9 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, based on the mass of the silicon-carbon-graphite anode active material, the mass fraction of spherical silicon-carbon material in the silicon-carbon-graphite anode active material is 3-15 wt%, and the mass fraction of fast-charging artificial graphite is 85-97 wt%.

[0053] In this invention, the mass of the silicon-carbon-graphite anode active material is taken as 100%. The mass fraction of spherical silicon-carbon material in the silicon-carbon-graphite anode active material is 3 to 15 wt%, for example, it can be 3 wt%, 5 wt%, 7 wt%, 10 wt%, 12 wt%, 14 wt%, or 15 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] In this invention, the mass of the silicon-carbon-graphite anode active material is taken as 100%, and the mass fraction of fast-charging artificial graphite is 85-97 wt%, for example, it can be 85 wt%, 86 wt%, 87 wt%, 88 wt%, 90 wt%, 92 wt%, 95 wt%, or 97 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] In a second aspect, the present invention provides a negative electrode material, the negative electrode material comprising a conductive agent, a binder, and the silicon-carbon-graphite negative electrode active material described in the first aspect.

[0056] Preferably, the adhesive comprises lithium-ionized polyacrylic acid and styrene-butadiene rubber.

[0057] The lithium-ionized polyacrylic acid in the binder of this invention contains hydrophilic side chains and lipophilic groups, achieving a combination of multiple functions. It can change the molecular chain conformation according to pH, and the viscosity of the system increases rapidly after the molecular chain extends. It can replace carboxymethyl cellulose and play the roles of thickening, suspending, binding and dispersing. In addition, as a macromolecular lithium salt thickener, lithium-ionized polyacrylic acid has better dispersibility for graphite. Lithium carboxylate can provide lithium ion channels, which is conducive to lithium ion transport, reduces the internal resistance of the battery and improves the kinetic performance.

[0058] The binder in this invention includes styrene-butadiene rubber (SBR). SBR emulsion can be directly prepared into slurry by adding alkali using a wet process. It is not prone to gelling, which simplifies the process and improves efficiency.

[0059] Preferably, the solid content of the lithium-ionized polyacrylic acid is 0.5 to 2.5 wt%, for example, it can be 0.5 wt%, 0.7 wt%, 0.9 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.7 wt%, 1.9 wt%, 2 wt%, 2.2 wt%, or 2.5 wt%, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0060] Preferably, the conductive agent comprises any one or a combination of at least two of carbon black, carbon nanotubes, carbon nanofibers, or graphene. Typical but non-limiting combinations include a combination of carbon black and carbon nanotubes, a combination of carbon nanotubes and carbon nanofibers, a combination of carbon nanofibers and graphene, or a combination of carbon nanotubes, carbon nanofibers, and graphene.

[0061] Preferably, the adhesive has a viscosity of 10,000 to 20,000 mPa·s, a glass transition temperature of 90 to 95°C, and a mass ratio of lithium-ionized polyacrylic acid to styrene-butadiene rubber in the adhesive is (2 to 4):(1 to 3).

[0062] The viscosity of the adhesive described in this invention is 10,000 to 2,000 mPa·s, for example, it can be 10,000 mPa·s, 11,000 mPa·s, 12,000 mPa·s, 13,000 mPa·s, 14,000 mPa·s, 15,000 mPa·s, 16,000 mPa·s, 17,000 mPa·s, 18,000 mPa·s, 19,000 mPa·s or 20,000 mPa·s, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] The glass transition temperature of the adhesive described in this invention is 90 to 95°C, for example, it can be 90°C, 91°C, 92°C, 93°C, 94°C or 95°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0064] In the adhesive described in this invention, the mass ratio of lithium-ionized polyacrylic acid to styrene-butadiene rubber is (2-4):(1-3), for example, it can be 2:1, 2:1.3, 2:1.7, 2:1.9, 2:2.3, 2:2.7, 2:2.9, 2:3, 4:1, 4:1.3, 4:1.7, 4:1.9, 4:2.3, 4:2.7, 4:2.9 or 4:3, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0065] Preferably, based on the mass of the negative electrode material, the mass fraction of the conductive agent in the negative electrode material is 1-2 wt%, the mass fraction of the binder is 3-4 wt%, and the mass fraction of the silicon-carbon-graphite negative electrode active material is 94-96 wt%.

[0066] In this invention, the mass of the negative electrode material is taken as 100%. The mass fraction of the conductive agent in the negative electrode material is 1 to 2 wt%, for example, it can be 1 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, or 2 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0067] In this invention, the mass of the negative electrode material is taken as 100%. The mass fraction of the binder in the negative electrode material is 3 to 4 wt%, for example, it can be 3 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt%, or 4 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0068] In this invention, the mass of the negative electrode material is taken as 100%. The mass fraction of silicon-carbon-graphite negative electrode active material in the negative electrode material is 94-96 wt%, for example, it can be 94 wt%, 94.2 wt%, 94.6 wt%, 94.8 wt%, 95 wt%, 95.2 wt%, 95.4 wt%, 95.6 wt%, 95.8 wt%, or 96 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0069] Thirdly, the present invention provides a negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative electrode material layer covering the surface of the negative current collector, the negative electrode material layer being composed of the negative electrode material described in the second aspect.

[0070] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the negative electrode sheet described in the third aspect.

[0071] Preferably, the positive electrode of the lithium-ion battery includes a positive current collector and a positive electrode material layer covering the surface of the positive current collector. The positive electrode active material in the positive electrode material layer includes any one or a combination of at least two of ternary positive electrode materials, lithium cobalt oxide, or lithium iron phosphate.

[0072] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] (1) The silicon-carbon-graphite anode active material provided by the present invention contains spherical silicon-carbon material. On the one hand, the spherical silicon-carbon material improves the energy density of the anode active material. On the other hand, the spherical silicon-carbon material has a spherical shape, which can improve the compressive strength. Moreover, the spherical silicon-carbon material has a synergistic effect with fast-charging artificial graphite. Therefore, the silicon-carbon-graphite anode active material composed of spherical silicon-carbon material and fast-charging artificial graphite has a high compressive strength, which can greatly improve the compaction density of the anode sheet prepared with silicon-carbon-graphite anode active material, so that the anode sheet exhibits better long-cycle low expansion performance under the same compaction. Therefore, the silicon-carbon-graphite anode active material improves the energy density and also has excellent expansion suppression performance.

[0075] (2) In this invention, by limiting the D50 particle size of the spherical silicon carbon material to be smaller than that of the fast-charging artificial graphite, the pores formed between the fast-charging artificial graphite particles are comparable to the size of the spherical silicon carbon material after expansion. The pores formed between the fast-charging artificial graphite particles are used to accommodate the volume change of the spherical silicon carbon material, thereby improving the expansion suppression performance of the silicon carbon-graphite negative electrode active material.

[0076] (3) The lithium-ionized polyacrylic acid in the binder of the present invention contains hydrophilic side chains and lipophilic groups, achieving a combination of multiple functions; it can change the molecular chain conformation according to pH, and the viscosity of the system increases rapidly after the molecular chain is extended, which can replace carboxymethyl cellulose and play the roles of thickening, suspending, binding and dispersing; in addition, as a macromolecular lithium salt thickener, lithium-ionized polyacrylic acid has better dispersibility for graphite, and lithium carboxylic acid can provide lithium ion channels, which is conducive to the transport of lithium ions, reduces the internal resistance of the battery, and improves the dynamic performance;

[0077] (4) The binder in this invention includes styrene-butadiene rubber. The styrene-butadiene rubber emulsion can be directly prepared by adding alkali to the wet process to make slurry. It is not easy to gel, which can simplify the process and improve efficiency. Attached Figure Description

[0078] Figure 1 shows the concentration at 1.2 g / cm³. 3 SEM images of spherical silicon-carbon materials at the compaction density.

[0079] Figure 2 shows the concentration at 1.2 g / cm³. 3 SEM images of amorphous silicon-carbon materials at the compaction density. Detailed Implementation

[0080] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0081] Example 1

[0082] This embodiment provides a silicon-carbon-graphite anode active material, which includes spherical silicon-carbon material and fast-charging artificial graphite;

[0083] Based on the mass of the silicon-carbon-graphite anode active material, the mass fraction of spherical silicon-carbon material in the silicon-carbon-graphite anode active material is 10 wt%, and the mass fraction of fast-charging artificial graphite is 90 wt%.

[0084] The spherical silicon-carbon material has a D50 particle size of 9.5 μm, a silicon content of 50%, and a compaction density of 1.2 g / cm³. 3 The coin cell capacity is 1700mAh at 1.5V and the first-efficiency is 83% at 0.8V.

[0085] The method for preparing spherical silicon-carbon materials is as follows:

[0086] With a pore volume of 0.9 cm 3 Spherical silicon-carbon materials were prepared by vapor deposition using phenolic resin with a pore size greater than 2nm as the carbon matrix and 95% of the resin being phenolic resin.

[0087] The fast-charging artificial graphite has a D50 particle size of 13μm and a compaction density of 1.76g / cm³. 3 It has a specific capacity of 358 mAh / g and an orientation OI value of 8.0;

[0088] The method for preparing the fast-charging artificial graphite is as follows:

[0089] With a particle size of 6.5 μm and a tap density of 0.7 g / cm³, 3Petroleum coke raw coke is used as raw material and is crushed and shaped to obtain crushed particles with a D50 particle size of 7.5 μm. Asphalt binder is mixed with the obtained crushed particles and granulated in a granulator at 880℃ for 6 hours to obtain semi-finished secondary particles with a D50 particle size of 12.5 μm. The obtained semi-finished secondary particles are subjected to graphitization heat treatment at 3000℃ for 10 hours to obtain graphitized material. Then, phenolic resin and the obtained graphitized material (based on the total mass of the phenolic resin and graphitized material as 10% and the mass fraction of the phenolic resin as 10 wt%) are mixed in a horizontal reactor by stirring, and then subjected to carbonization heat treatment at 1000℃ for 7 hours to obtain fast-charging artificial graphite.

[0090] This embodiment also provides a negative electrode material, which includes carbon black, a binder, and the silicon-carbon-graphite negative electrode active material provided in this embodiment;

[0091] The negative electrode material contains 1.5 wt% carbon black, 3.5 wt% binder, and 95 wt% silicon-carbon-graphite negative electrode active material.

[0092] The adhesive comprises lithium-ionized polyacrylic acid and styrene-butadiene rubber in a mass ratio of 3:2, and has a viscosity of 15000 mPa·s and a glass transition temperature of 92°C.

[0093] This embodiment also provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode material layer covering the surface of the negative electrode current collector. The negative electrode material layer is composed of the negative electrode material provided in this embodiment.

[0094] Example 2

[0095] This embodiment provides a silicon-carbon-graphite anode active material, which includes spherical silicon-carbon material and fast-charging artificial graphite;

[0096] Based on the mass of the silicon-carbon-graphite anode active material, the mass fraction of spherical silicon-carbon material in the silicon-carbon-graphite anode active material is 3 wt%, and the mass fraction of fast-charging artificial graphite is 97 wt%.

[0097] The spherical silicon-carbon material has a D50 particle size of 10 μm, a silicon content of 47.5%, and a compaction density of 1.2 g / cm³. 3 The coin cell capacity is 1850mAh at 1.5V and the first-efficiency rating is 84% ​​at 0.8V.

[0098] The method for preparing spherical silicon-carbon materials is as follows:

[0099] With a pore volume of 0.8cm 3Spherical silicon-carbon materials were prepared by vapor deposition using phenolic resin with a pore size greater than 2nm as the carbon matrix and 93% of the resin being phenolic resin.

[0100] The fast-charging artificial graphite has a D50 particle size of 14 μm and a compaction density of 1.78 g / cm³. 3 It has a specific capacity of 360mAh / g and an orientation OI value of 9.0;

[0101] The method for preparing the fast-charging artificial graphite is as follows:

[0102] With a particle size of 7 μm and a tap density of 0.88 g / cm³ 3 Petroleum coke raw coke is used as raw material and is crushed and shaped to obtain crushed particles with a D50 particle size of 9μm. Asphalt binder is mixed with the obtained crushed particles and granulated in a granulator at 800℃ for 8.5h to obtain semi-finished secondary particles with a D50 particle size of 13.5μm. The obtained semi-finished secondary particles are subjected to graphitization heat treatment at 3200℃ for 9h to obtain graphitized material. Then, epoxy resin and the obtained graphitized material (based on the total mass of the epoxy resin and graphitized material as 100%, and the mass fraction of the epoxy resin is 8wt%) are mixed in a horizontal reactor by stirring, and then subjected to carbonization heat treatment at 900℃ for 9h to obtain fast-charging artificial graphite.

[0103] This embodiment also provides a negative electrode material, which includes carbon nanotubes, a binder, and the silicon-carbon-graphite negative electrode active material provided in this embodiment;

[0104] The anode material contains 2 wt% carbon nanotubes, 4 wt% binder, and 94 wt% silicon-carbon-graphite anode active material.

[0105] The adhesive comprises lithium-ionized polyacrylic acid and styrene-butadiene rubber in a mass ratio of 2:3, and the adhesive has a viscosity of 10000 mPa·s and a glass transition temperature of 90°C.

[0106] This embodiment also provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode material layer covering the surface of the negative electrode current collector. The negative electrode material layer is composed of the negative electrode material provided in this embodiment.

[0107] Example 3

[0108] This embodiment provides a silicon-carbon-graphite anode active material, which includes spherical silicon-carbon material and fast-charging artificial graphite;

[0109] Based on the mass of the silicon-carbon-graphite anode active material, the mass fraction of spherical silicon-carbon material in the silicon-carbon-graphite anode active material is 15 wt%, and the mass fraction of fast-charging artificial graphite is 85 wt%.

[0110] The spherical silicon-carbon material has a D50 particle size of 9 μm, a silicon content of 55%, and a compaction density of 1.2 g / cm³. 3 At 1.5V, the coin cell capacity is 1650mAh, and at 0.8V, the first-efficiency is 82%.

[0111] The method for preparing spherical silicon-carbon materials is as follows:

[0112] With a pore volume of 1.0 cm 3 Spherical silicon-carbon materials were prepared by vapor deposition using phenolic resin with a pore size greater than 2nm as the carbon matrix and 97% of the resin being phenolic resin.

[0113] The fast-charging artificial graphite has a D50 particle size of 12μm and a compaction density of 1.73g / cm³. 3 It has a specific capacity of 356 mAh / g and an orientation OI value of 6.0;

[0114] The method for preparing the fast-charging artificial graphite is as follows:

[0115] With a particle size of 6 μm and a tap density of 0.7 g / cm³ 3 Petroleum coke raw coke is used as raw material and is crushed and shaped to obtain crushed particles with a D50 particle size of 7μm. Asphalt binder is mixed with the obtained crushed particles and granulated in a granulator at 950℃ for 6 hours to obtain semi-finished secondary particles with a D50 particle size of 12μm. The obtained semi-finished secondary particles are subjected to graphitization heat treatment at 2850℃ for 12 hours to obtain graphitized material. Then, phenolic resin and the obtained graphitized material (based on the total mass of the phenolic resin and graphitized material as 100%, and the mass fraction of the phenolic resin is 12wt%) are mixed in a horizontal reactor by stirring, and then subjected to carbonization heat treatment at 1100℃ for 7 hours to obtain fast-charging artificial graphite.

[0116] This embodiment also provides a negative electrode material, which includes graphene, a binder, and the silicon-carbon-graphite negative electrode active material provided in this embodiment;

[0117] The negative electrode material contains 1 wt% graphene, 3 wt% binder, and 96 wt% silicon-carbon-graphite negative electrode active material.

[0118] The adhesive comprises lithium-ionized polyacrylic acid and styrene-butadiene rubber in a mass ratio of 4:1, and has a viscosity of 20,000 mPa·s and a glass transition temperature of 95°C.

[0119] This embodiment also provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode material layer covering the surface of the negative electrode current collector. The negative electrode material layer is composed of the negative electrode material provided in this embodiment.

[0120] Example 4

[0121] This embodiment provides a silicon-carbon-graphite anode active material, which is the same as that in Embodiment 1.

[0122] This embodiment provides a negative electrode material, except that the binder in the negative electrode material is replaced with an equal mass of a binder composed of carboxymethyl cellulose, polyacrylic acid (solid content of 5%, viscosity of 15000 mpa.s) and styrene-butadiene rubber in a mass ratio of 1:1:1, and otherwise it is the same as in Example 1.

[0123] This embodiment also provides a negative electrode sheet, which is the same as that in Embodiment 1 except for the composition of the negative electrode material layer provided in this embodiment.

[0124] Example 5

[0125] This embodiment provides a silicon-carbon-graphite anode active material, which is the same as that in Embodiment 1.

[0126] This embodiment provides a negative electrode material, which is the same as in Example 1 except that the lithium-ionized polyacrylic acid in the binder of the negative electrode material is replaced with an equal mass of carboxymethyl cellulose.

[0127] This embodiment also provides a negative electrode sheet, which is the same as that in Embodiment 1 except for the composition of the negative electrode material layer provided in this embodiment.

[0128] Example 6

[0129] This embodiment provides a silicon-carbon-graphite anode active material, which is the same as in Example 1 except that the D50 particle size of the fast-charging artificial graphite in the silicon-carbon-graphite anode active material is 8 μm.

[0130] This embodiment also provides a negative electrode material, except that the silicon-carbon-graphite negative electrode active material in the negative electrode material is the silicon-carbon-graphite negative electrode active material provided in this embodiment, and the rest are the same as in embodiment 1.

[0131] This embodiment also provides a negative electrode sheet, which is the same as that in Embodiment 1 except for the composition of the negative electrode material layer provided in this embodiment.

[0132] Example 7

[0133] This embodiment provides a silicon-carbon-graphite anode active material, which is the same as in Example 1 except that the D50 particle size of the fast-charging artificial graphite in the silicon-carbon-graphite anode active material is 16μm.

[0134] This embodiment also provides a negative electrode material, except that the silicon-carbon-graphite negative electrode active material in the negative electrode material is the silicon-carbon-graphite negative electrode active material provided in this embodiment, and the rest are the same as in embodiment 1.

[0135] This embodiment also provides a negative electrode sheet, which is the same as that in Embodiment 1 except for the composition of the negative electrode material layer provided in this embodiment.

[0136] Example 8

[0137] This embodiment provides a silicon-carbon-graphite anode active material, which is the same as in Example 1 except that the D50 particle size of the spherical silicon-carbon material in the silicon-carbon-graphite anode active material is 7 μm.

[0138] This embodiment also provides a negative electrode material, except that the silicon-carbon-graphite negative electrode active material in the negative electrode material is the silicon-carbon-graphite negative electrode active material provided in this embodiment, and the rest are the same as in embodiment 1.

[0139] This embodiment also provides a negative electrode sheet, which is the same as that in Embodiment 1 except for the composition of the negative electrode material layer provided in this embodiment.

[0140] Example 9

[0141] This embodiment provides a silicon-carbon-graphite anode active material, which is the same as in Example 1 except that the D50 particle size of the spherical silicon-carbon material in the silicon-carbon-graphite anode active material is 12 μm.

[0142] This embodiment also provides a negative electrode material, except that the silicon-carbon-graphite negative electrode active material in the negative electrode material is the silicon-carbon-graphite negative electrode active material provided in this embodiment, and the rest are the same as in embodiment 1.

[0143] This embodiment also provides a negative electrode sheet, which is the same as that in Embodiment 1 except for the composition of the negative electrode material layer provided in this embodiment.

[0144] Comparative Example 1

[0145] This comparative example provides a silicon-carbon-graphite anode active material, except that the spherical silicon-carbon material is replaced with an amorphous silicon-carbon material. The amorphous silicon-carbon material has a D50 particle size of 9.5 μm, a silicon content of 50%, and a compaction density of 1.5 g / cm³. 3Except for the coin cell capacity of 1750mAh at 1.5V and the first-efficiency of 83% at 0.8V, all other aspects are the same as in Example 1.

[0146] This comparative example also provides a negative electrode material, except that the silicon-carbon-graphite negative electrode active material in the negative electrode material is the silicon-carbon-graphite negative electrode active material provided in this comparative example, and the rest are the same as in Example 1.

[0147] This comparative example also provides a negative electrode sheet, which is the same as that in Example 1, except for the negative electrode material layer of the negative electrode sheet and the composition of the negative electrode material provided in this comparative example.

[0148] Comparative Example 2

[0149] This comparative example provides a silicon-carbon-graphite anode active material, except that the spherical silicon-carbon material is replaced with an amorphous silicon-carbon material. The amorphous silicon-carbon material has a D50 particle size of 9.5 μm, a silicon content of 50%, and a compaction density of 1.5 g / cm³. 3 Except for the coin cell capacity of 1750mAh at 1.5V and the first-efficiency of 83% at 0.8V, all other aspects are the same as in Example 1.

[0150] This comparative example provides a negative electrode material, except that the silicon-carbon-graphite negative electrode active material is replaced with the silicon-carbon-graphite negative electrode active material in this comparative example, and the binder in the negative electrode material is replaced with an equal mass of a binder composed of polyacrylic acid (solid content of 5%, viscosity of 15000 mpa.s), carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:1:1. All other aspects are the same as in Example 1.

[0151] This comparative example also provides a negative electrode sheet, which is the same as that in Example 1, except for the negative electrode material layer of the negative electrode sheet and the composition of the negative electrode material provided in this comparative example.

[0152] At 1.2 g / cm 3 At a compaction density of 1.2 g / cm³, the morphology of spherical and amorphous silicon carbon materials was tested using scanning electron microscopy. The SEM images of the spherical silicon carbon materials are shown in Figure 1, and those of the amorphous silicon carbon materials are shown in Figure 2. A comparison between Figure 1 and Figure 2 shows that at a compaction density of 1.2 g / cm³, the morphology of the spherical silicon carbon materials and amorphous silicon carbon materials is significantly different. 3 At the specified compaction density, amorphous silicon-carbon materials exhibited cracked particles, while spherical silicon-carbon materials showed no cracked particles. The spherical silicon-carbon materials, with their spherical shape, demonstrated improved compressive strength. Therefore, the silicon-carbon-graphite anode active material composed of spherical silicon-carbon materials and fast-charging artificial graphite possesses high compressive strength, thereby significantly increasing the compaction density of the anode sheet prepared using this material. This results in superior long-cycle, low-expansion performance of the anode sheet under the same compaction conditions.

[0153] The negative electrode sheet provided in the above embodiments and comparative examples is used to prepare a lithium-ion battery. The method for preparing the lithium-ion battery is as follows: the obtained lithium cobalt oxide positive electrode material, conductive carbon black SP and polyvinylidene fluoride PVDF are mixed in a mass ratio of 90:5:5, and N-methylpyrrolidone is used as the solvent. The mixture is stirred into a slurry. The slurry is uniformly coated on aluminum foil with a coating gap of 100 μm using a doctor blade. After coating, it is first dried by blowing air, and then rolled and pressed to form a sheet. The negative electrode sheet provided in the embodiments and comparative examples of the present invention is used. The separator is a ceramic coated microporous membrane. The electrolyte is a high-voltage silicon-based electrolyte. The positive electrode sheet, negative electrode sheet, separator and electrolyte are assembled to obtain a lithium-ion battery.

[0154] The 3C charging current ratio, energy density, full charge expansion rate and cycle performance of the obtained lithium-ion batteries were tested.

[0155] The test method for 3C charging constant current ratio is as follows: the battery cell is tested in the Xinwei cabinet, and constant current fast charging is performed under 3C current. The charging capacity during the constant current stage and the total charging capacity are obtained. 3C charging constant current ratio = constant current stage charging capacity / total charging capacity. The test results are shown in Table 1.

[0156] The energy density test method is as follows: the total energy density of a lithium battery = battery discharge energy / battery weight; the discharge energy test method is as follows: charge at 0.2C constant current and constant voltage to 4.5V, then discharge at 0.2C to 2.5V, cycle for 3 weeks, and obtain the discharge energy. The total energy density is calculated as shown in Table 1. The test results are shown in Table 1.

[0157] The test method for the full charge expansion rate is as follows: the initial thickness of the negative electrode before charging and the full charge thickness after charging are obtained by testing. The full charge expansion rate = (full charge thickness of the negative electrode - initial thickness of the negative electrode) / initial thickness of the negative electrode. The test results are shown in Table 1.

[0158] The cycle performance test method is as follows: At an ambient temperature of 25℃, constant current and constant voltage charging is performed at the same rate of 3C, with a cutoff voltage of 3.65V and a cutoff current of 0.05C. After resting for 30 minutes, constant current discharge is performed at 1C, with a cutoff voltage of 2.5V. The battery is cycled for 600 cycles according to the above test method, and the battery capacity retention rate and expansion rate are shown in Table 2. Then, at an ambient temperature of 45℃, constant current and constant voltage charging is performed at the same rate of 3C, with a cutoff voltage of 3.65V and a cutoff current of 0.05C. After resting for 30 minutes, constant current discharge is performed at 1C, with a cutoff voltage of 2.5V. The battery is cycled for 600 cycles according to the above test method, and the battery capacity retention rate and expansion rate are shown in Table 2.

[0159] Table 1

[0160]

[0161] Table 2

[0162]

[0163]

[0164] From Table 1, we can obtain:

[0165] (1) The lithium-ion batteries prepared with the negative electrode materials provided in Examples 1 to 3 have a higher 3C charging current ratio, higher energy density and lower full-charge expansion rate; in addition, the lithium-ion batteries prepared with the negative electrode materials provided in Examples 1 to 3 show a higher capacity retention rate and a lower expansion rate in the cycle performance test.

[0166] (2) By comparing Example 1 with Examples 4 and 5, it can be seen that the binder in the negative electrode material provided by the present invention affects the performance of lithium-ion batteries. When the binder is composed of lithium-ion polyacrylic acid and styrene-butadiene rubber, the lithium-ion battery exhibits superior performance. This is because: Firstly, the lithium-ion polyacrylic acid in the binder contains hydrophilic side chains and lipophilic groups, achieving a combination of multiple functions. It can change the molecular chain conformation according to pH, and the viscosity of the system increases rapidly after the molecular chain is extended. It can replace carboxymethyl cellulose and play the roles of thickening, suspending, binding and dispersing. In addition, lithium-ion polyacrylic acid, as a macromolecular lithium salt thickener, has better dispersibility for graphite. Lithium carboxylate can provide lithium-ion channels, which is beneficial to the transport of lithium-ions, reduces the internal resistance of the battery, and improves the dynamic performance. Secondly, the binder in the present invention includes styrene-butadiene rubber. The styrene-butadiene rubber emulsion can be directly prepared by adding alkali in a wet process. It is not easy to gel, which can simplify the process and improve efficiency. Thirdly, replacing the traditional carboxymethyl cellulose with a binder composed of lithium-ion polyacrylic acid and styrene-butadiene rubber effectively inhibits anode expansion.

[0167] (3) By comparing Example 1 with Examples 6 and 7, it can be seen that the D50 particle size of the fast-charging artificial graphite in the silicon-carbon-graphite anode active material described in this invention will affect the performance of the lithium-ion battery. When the D50 particle size of the fast-charging artificial graphite is 12-14 μm, the lithium-ion battery exhibits better performance. This is because when the D50 particle size of the fast-charging artificial graphite is too small, it is not conducive to the utilization of the specific capacity of the fast-charging artificial graphite, and the pressure resistance is weak, which leads to a deterioration in the performance of the lithium-ion battery. When the D50 particle size of the fast-charging artificial graphite is too large, it will lead to an increase in the lithium-ion transport path, and a deterioration in rate performance and fast-charging performance.

[0168] (4) By comparing Example 1 with Examples 8 and 9, it can be seen that the D50 particle size of the spherical silicon carbon material in the silicon-carbon-graphite anode active material described in this invention affects the performance of lithium-ion batteries. When the D50 particle size of the spherical silicon carbon material is 9 to 10 μm, the lithium-ion battery exhibits better performance. This is because if the D50 particle size of the spherical silicon carbon material is too small, it will affect the first efficiency of the lithium-ion battery and is not conducive to the improvement of energy density. If the D50 particle size of the spherical silicon carbon material is too large, it is not conducive to the transport of lithium ions, and the expansion rate after lithium intercalation is relatively large.

[0169] (5) By comparing Example 1 and Comparative Example 1, it can be seen that the silicon-carbon-graphite anode active material provided by the present invention contains spherical silicon-carbon material. On the one hand, the spherical silicon-carbon material improves the energy density of the anode active material. On the other hand, the spherical silicon-carbon material has a spherical shape, which can improve the compressive strength. Moreover, the spherical silicon-carbon material has a synergistic effect with fast-charging artificial graphite. Therefore, the silicon-carbon-graphite anode active material composed of spherical silicon-carbon material and fast-charging artificial graphite has a high compressive strength, which can greatly improve the compaction density of the anode sheet prepared with silicon-carbon-graphite anode active material, so that the anode sheet exhibits better long-cycle low expansion performance under the same compaction. Therefore, the silicon-carbon-graphite anode active material improves the energy density and also has excellent expansion suppression performance.

[0170] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A silicon-carbon-graphite anode active material, characterized in that, The silicon-carbon-graphite anode active material comprises only spherical silicon-carbon material and fast-charging artificial graphite; the D50 particle size of the spherical silicon-carbon material is 9~10μm; The spherical silicon-carbon material is prepared by a vapor phase method; the vapor phase method includes: using a resin-based material as a carbon matrix, and obtaining the spherical silicon-carbon material through vapor phase deposition; the pore volume of the carbon matrix is ​​≥0.8 cm³. 3 / g, and the proportion of particles with a pore size greater than 2nm is ≥93%; the D50 particle size of the fast-charging artificial graphite is 12~14μm, and the compaction density is 1.73~1.78g / cm³. 3 The specific capacity is 356~360mAh / g, and the orientation degree OI value is 6.0~9.

0. The method for preparing the fast-charging artificial graphite includes: using petroleum coke as raw material, crushing and shaping it, then granulating it to obtain semi-finished secondary particles, subjecting the obtained semi-finished secondary particles to graphitization heat treatment, coating them with a coating agent, and then subjecting them to carbonization heat treatment to obtain fast-charging artificial graphite; the crushing and shaping process yields crushed particles; the granulation process includes: mixing asphalt binder with the crushed particles and granulating them at 800~950℃ for less than 9 hours; the coating agent includes phenolic resin or epoxy resin; the carbonization heat treatment temperature is 900~1100℃, and the time is 7~9 hours.

2. The silicon-carbon-graphite anode active material according to claim 1, characterized in that, The silicon content in the spherical silicon-carbon material is 47.5% to 55%.

3. The silicon-carbon-graphite anode active material according to claim 1, characterized in that, The compaction density of the spherical silicon carbide material is 1.2~1.7 g / cm³. 3 .

4. The silicon-carbon-graphite anode active material according to claim 1, characterized in that, The spherical silicon-carbon material has a coin cell capacity of 1650~1850mAh at 1.5V.

5. The silicon-carbon-graphite anode active material according to claim 1, characterized in that, The spherical silicon-carbon material has an initial efficiency of 82-84% at 0.8V.

6. The silicon-carbon-graphite anode active material according to any one of claims 1 to 5, characterized in that, The raw petroleum coke has a particle size of 6-7 μm and a tap density of 0.68-1 g / cm³. 3 .

7. The silicon-carbon-graphite anode active material according to any one of claims 1 to 5, characterized in that, The pulverization and shaping process yields pulverized particles with a D50 particle size of 7~9μm.

8. The silicon-carbon-graphite anode active material according to any one of claims 1 to 5, characterized in that, The D50 particle size of the semi-finished secondary particles obtained after granulation is 12~13.5μm.

9. The silicon-carbon-graphite anode active material according to any one of claims 1 to 5, characterized in that, The graphitization heat treatment is performed at a temperature of 2850~3200℃ for 9~12 hours, and graphitized material is obtained after the graphitization heat treatment.

10. The silicon-carbon-graphite anode active material according to claim 1, characterized in that, Based on the mass of the silicon-carbon-graphite anode active material, the mass fraction of spherical silicon-carbon material in the silicon-carbon-graphite anode active material is 3~15wt%, and the mass fraction of fast-charging artificial graphite is 85~97wt%.

11. A negative electrode material, characterized in that, The negative electrode material includes a conductive agent, a binder, and the silicon-carbon-graphite negative electrode active material as described in any one of claims 1 to 10.

12. The negative electrode material according to claim 11, characterized in that, The adhesive comprises lithium-ionized polyacrylic acid and styrene-butadiene rubber.

13. The negative electrode material according to claim 11, characterized in that, The adhesive has a viscosity of 10,000 to 20,000 mPa·s, a glass transition temperature of 90 to 95°C, and a mass ratio of lithium-ionized polyacrylic acid to styrene-butadiene rubber of (2 to 4):(1 to 3).

14. The negative electrode material according to any one of claims 11 to 13, characterized in that, Based on the mass of the negative electrode material, the mass fraction of the conductive agent in the negative electrode material is 1~2wt%, the mass fraction of the binder is 3~4wt%, and the mass fraction of the silicon-carbon-graphite negative electrode active material is 94~96wt%.

15. A negative electrode sheet, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode material layer covering the surface of the negative current collector, wherein the negative electrode material layer is composed of the negative electrode material according to any one of claims 11 to 14.

16. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode sheet as described in claim 15.

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