Silicon-carbon negative electrode material with rapid charge-discharge capability and preparation method and application thereof

Abstract

The invention discloses a silicon-carbon negative electrode material with rapid charge-discharge capability and a preparation method and application thereof, the silicon-carbon negative electrode material with rapid charge-discharge capability comprises a silicon-carbon material, and a carbonized polymer and an inorganic component which are at least attached to the surface of the silicon-carbon material, and the diffusion energy barrier of the crystal boundary of the inorganic component is less than 0.6 eV. In the silicon-carbon negative electrode material with the rapid charging and discharging capacity, due to low grain boundary diffusion energy barrier of inorganic components, a large number of lithium ion channels exist in the crystal structure of the inorganic components, the lithium ion transmission resistance can be reduced, rapid diffusion of the lithium ions is assisted, and the rapid charging performance is improved. The carbonized polymer and inorganic component composite coating layer on the surface of the silicon-carbon material can reduce the desolvation energy barrier of lithium ions, increase the diffusion rate and improve the transmission dynamics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery negative electrode material, in particular to a silicon-carbon negative electrode material with fast charging and discharging capacity and a preparation method and application thereof. BACKGROUND

[0002] Silicon (Si) is a potential negative electrode material with a theoretical specific capacity of 4200 mAh / g, which is significantly higher than the 372 mAh / g of traditional graphite negative electrodes, and is considered as an ideal choice for the next generation of high-performance lithium ion battery materials.

[0003] However, the silicon negative electrode faces two key challenges in the process of fast charging and discharging: the lithium ion desolvation energy barrier is high, and the diffusion rate of lithium ions in the solid electrolyte interface (SEI) is slow. These problems are considered to be the core factors restricting the fast charging performance, in which the composition and structure of the SEI play a decisive role.

[0004] The traditional SEI layer presents a typical double-layer structure:

[0005] Porous organic outer layer: mainly composed of electrolyte decomposition products such as alkyl lithium carbonate (ROCO2Li) and alkoxy lithium (ROLi). This type of organic component forms a loose and porous structure, allowing lithium ions to diffuse through liquid channels.

[0006] Dense inorganic inner layer: composed of inorganic materials such as Li2O, Li2CO3, and LiF, forming a dense solid layer, and lithium ions need to migrate through a solid-state diffusion mechanism.

[0007] However, the traditional SEI structure has significant defects: the diffusion rate of lithium ions is limited, and the desolvation ability is insufficient, which greatly limits the fast charging performance of the negative electrode material.

[0008] Previous studies have focused more on electrolyte modification, such as using weakly solvated electrolytes, adding cosolvents, or using high-concentration lithium salts, to weaken the interaction between lithium ions and solvent molecules by adjusting the solvation structure of the electrolyte. Although this method optimizes the interface ion desolvation process to some extent, it does not effectively solve the transmission bottleneck problem of lithium ions in the traditional SEI.

[0009] Therefore, the present application is proposed. SUMMARY

[0010] The purpose of the present application is to provide a silicon-carbon negative electrode material with fast charging and discharging capacity and a preparation method and application thereof, which is beneficial to improve the fast charging performance of lithium batteries using the silicon-carbon negative electrode material.

[0011] The present application is implemented as follows:

[0012] In a first aspect, the present application provides a silicon-carbon negative electrode material with fast charge-discharge capability, comprising a silicon-carbon material and a carbonized polymer and an inorganic component attached to at least part of the surface of the silicon-carbon material, wherein the diffusion energy barrier of the grain boundary of the inorganic component is less than 0.6 eV.

[0013] In an optional embodiment, the mass fraction of the inorganic component in the silicon-carbon negative electrode material is 0.5%-1.5%;

[0014] And / or, the inorganic component is selected from at least one of Li3P, Li3PO4, Li4P2O7, LiF, Li3N;

[0015] And / or, the inorganic component can participate in oxidation reaction as an electron donor under the driving of the electric field of battery charge-discharge;

[0016] And / or, the inorganic component is obtained by calcining an inorganic precursor; and / or, the inorganic component is obtained by a charge-discharge process of an inorganic precursor;

[0017] And / or, the mass fraction of the carbonized polymer in the silicon-carbon negative electrode material is 0.2%-2.5%;

[0018] And / or, the carbonized polymer is obtained by calcining a polymer precursor;

[0019] And / or, the silicon-carbon negative electrode material further comprises a conductive agent.

[0020] In an optional embodiment, the inorganic precursor comprises a first component and a second component, the first component is selected from inorganic substances containing at least one of P, F, and N, and the second component is a lithium salt;

[0021] And / or, the particle size of the inorganic precursor is ≤200 nm;

[0022] And / or, the inorganic component is selected from at least two of Li3P, Li3PO4, Li4P2O7, LiF, and Li3N.

[0023] In an optional embodiment, the polymer precursor has viscosity;

[0024] And / or, the polymer precursor comprises a polar group;

[0025] And / or, the polymer precursor is selected from one or more than two polymers formed by blending or copolymerization of polyacrylic acid, polyvinyl alcohol, polystyrene, polyaniline, polyacrylamide, polyacrylonitrile, sodium carboxymethyl cellulose, and sodium alginate.

[0026] In an optional embodiment, the first component is selected from at least one of hexamethylphosphoramide, ammonium fluoride, black phosphorus, and red phosphorus.

[0027] and / or, the silicon-carbon material comprises a core and a carbon coating layer coated on the core, the core comprises a porous carbon substrate and nano-silicon particles located in the pores of the porous carbon substrate; the silicon-carbon material satisfies at least one of the following characteristics a-k:

[0028] a. the carbon coating layer is amorphous carbon;

[0029] b. the Dv50 of the porous carbon substrate is 6.5 μm-8.5 μm;

[0030] c. the particle size distribution of the porous carbon substrate satisfies: Dv0>2 μm; Dv10>3.7 μm; Dv90<11.5 μm; Dv100<14.5 μm;

[0031] d. the particle size distribution of the porous carbon substrate satisfies: (D90-D10) / D50<1.2;

[0032] e. the average pore size of the porous carbon substrate is 0.5 nm-15 nm;

[0033] f. the thickness of the carbon coating layer is 0.5 nm-15 nm;

[0034] g. the median particle size of the silicon-carbon material is 7 μm-13 μm;

[0035] h. the particle size concentration of the silicon-carbon material is 0.5-1.4;

[0036] i. the carbon content of the silicon-carbon material is 45wt%-55wt%;

[0037] j. the specific surface area of the silicon-carbon material is 0.6 m 2 / g-4.0 m 2 / g;

[0038] k. the resistivity of the silicon-carbon material is 2 Ωcm-6 Ωcm.

[0039] In optional embodiments, the conductive agent is selected from at least one of graphene, acetylene black, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, flake graphite, polyaniline, polypyrrole, polyacetylene, polythiophene, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), and two-dimensional MXene;

[0040] and / or, the mass fraction of the conductive agent in the silicon-carbon negative electrode material is 0.01wt%-0.5wt%.

[0041] In a second aspect, the present application provides a preparation method of the silicon-carbon negative electrode material with fast charge and discharge capability as described in the foregoing embodiments, comprising calcining raw material powder containing silicon-carbon material, polymer precursor and inorganic precursor to obtain the silicon-carbon negative electrode material.

[0042] In an optional embodiment, the mass fraction of the inorganic precursor in the raw material powder is 0.1%-6%;

[0043] And / or, the mass fraction of the polymer precursor in the raw material powder is 0.1%-2%;

[0044] And / or, the calcination temperature is 200-600 DEG C, and the calcination time is 1-5h;

[0045] And / or, the raw material powder is obtained by spray drying slurry containing silicon-carbon material, polymer precursor and inorganic precursor.

[0046] In an optional embodiment, the slurry further contains a conductive agent;

[0047] And / or, the solid content of the slurry is 6wt%-8wt%;

[0048] And / or, the spray drying temperature is 180-200 DEG C, and the feeding speed is 1.5-2.5L / h.

[0049] In a third aspect, the present application provides a lithium ion battery comprising the silicon-carbon negative electrode material as described in any one of the foregoing embodiments.

[0050] The present application has the following beneficial effects:

[0051] In the silicon-carbon negative electrode material with fast charge and discharge capability of the present application, the inorganic component has a low grain boundary diffusion energy barrier, and a large number of lithium ion channels exist in the crystal structure, which can reduce the lithium ion transmission resistance, help its rapid diffusion and improve the fast charging performance. The carbonized polymer and inorganic component composite coating layer on the surface of the silicon-carbon material can reduce the lithium ion desolvation energy barrier, improve the diffusion rate and improve the transmission kinetics. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme of the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0053] This invention provides a silicon-carbon anode material with fast charge-discharge capability, comprising a silicon-carbon material and a carbonized polymer and inorganic components attached to at least a portion of the surface of the silicon-carbon material. The diffusion barrier of the grain boundaries of the inorganic components is less than 0.6 eV, for example, 0.2 eV, 0.25 eV, 0.3 eV, 0.35 eV, 0.4 eV, 0.45 eV, 0.5 eV, 0.55 eV, or 0.6 eV.

[0054] In the silicon-carbon anode material with fast charge / discharge capability described in this application, the inorganic component has a low grain boundary diffusion barrier and a large number of lithium-ion channels in its crystal structure, which can reduce lithium-ion transport resistance, facilitate rapid diffusion, and improve fast charging performance. The composite coating layer of carbonized polymer and inorganic component on the surface of the silicon-carbon material can reduce the lithium-ion desolvation barrier, increase the diffusion rate, and improve transport kinetics.

[0055] The silicon-carbon anode material of this application has inorganic components attached to its surface, which can serve as the initial components of the SEI film. During the charging and discharging process, this facilitates the rapid diffusion of lithium ions in its bulk phase and grain boundaries. Furthermore, it can be further optimized through electrochemical reactions during the charging and discharging process, thereby improving the fast-charging performance of batteries using this material.

[0056] In an optional embodiment, the mass fraction of inorganic components in the silicon-carbon anode material is 0.5%-1.5%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, and 1.5%. This mass fraction range is beneficial because while inorganic components play a role in promoting ion conduction and participating in electrochemical reactions, their content is not too high and will not affect other properties of the silicon-carbon anode material, such as conductivity and volume stability.

[0057] In an optional embodiment, the inorganic component is selected from at least one of Li3P, Li3PO4, Li4P2O7, LiF, and Li3N; these inorganic components have good ionic conductivity or can participate in beneficial electrochemical reactions. For example, phosphorus-containing compounds such as Li3P can provide lithium-ion transport channels, and LiF helps to form a stable SEI film, reducing interface resistance and improving the battery's fast-charging performance.

[0058] Furthermore, these inorganic components will further participate in the formation or modification of the SEI film through electrochemical reactions during the first charge-discharge and subsequent cycles of the battery. Specifically: Li3P can react with components in the electrolyte (such as LiPF6 decomposition products) to generate more stable Li3PO4 or LiF; Li3N can react with H2O or protons in the electrolyte to generate LiOH, Li2O, etc., which will be incorporated into the SEI film to enhance its compactness; the presence of inorganic components can regulate the growth path of the SEI film, making it more inclined to form a stable structure dominated by inorganic components (such as LiF, Li3PO4), reducing the proportion of organic by-products (such as alkyl lithium carbonate), thereby reducing the resistance of the SEI film and improving its stability; when the SEI film breaks due to the volume expansion of silicon-carbon materials, these inorganic components can fill the defects through diffusion or reaction, inhibit the continuous decomposition of the electrolyte, and maintain the integrity of the SEI film.

[0059] In an optional embodiment, the inorganic component, driven by the electric field during battery charging and discharging, can participate in the oxidation reaction as an electron donor. When the inorganic component participates in the oxidation reaction as an electron donor, it possesses a certain electron density and exhibits a high affinity for positively charged lithium ions. This affinity attracts lithium ions, weakens the interaction between lithium ions and solvent molecules, and reduces the number of solvent molecules in the solvation sheath, forming a low solvent coordination number structure. The low coordination number solvation sheath has a lower desolvation energy barrier to overcome when crossing the electrode / electrolyte interface, accelerating the process of lithium ions detaching from the solvent and entering the electrode material, thereby improving lithium ion transport kinetics and contributing to faster charging performance.

[0060] In optional embodiments, the inorganic component is obtained by calcining an inorganic precursor; and / or, the inorganic component is obtained by a charge-discharge process from an inorganic precursor. The calcination process can transform the inorganic precursor into an inorganic component with a specific crystal structure and properties, allowing it to better perform its functions in promoting ion conduction and participating in electrochemical reactions, thus improving the battery's fast-charging performance. Some inorganic components, such as HMPA, generate Li3P during the charge-discharge process.

[0061] In an optional embodiment, the mass fraction of the carbonized polymer in the silicon-carbon anode material is 0.2%-2.5%, for example, 0.2%, 0.45%, 0.7%, 0.95%, 1.2%, 1.45%, 1.7%, 1.95%, 2.2%, and 2.5%. A suitable mass fraction allows the carbonized polymer to form a good coating or network structure on the surface of the silicon-carbon material, improving the interfacial properties and ion transport properties of the material without affecting the main properties of the silicon-carbon material, which is beneficial to improving the fast charging performance of the battery.

[0062] In an optional embodiment, the carbonized polymer is obtained by calcining a polymer precursor; calcination can transform the polymer precursor into a carbonized polymer with specific structure and properties, whose structure is more conducive to the adsorption and diffusion of lithium ions, while enhancing the coating effect on silicon-carbon materials and improving fast charging performance.

[0063] In an optional embodiment, the silicon-carbon anode material further includes a conductive agent to improve the material's electronic conductivity, enabling electrons to move rapidly within the electrode material and improving charging efficiency.

[0064] In an optional embodiment, the inorganic precursor includes a first component and a second component. The first component is selected from inorganic substances containing at least one of P, F, and N, and the second component is a lithium salt. The reaction between the inorganic substance containing P, F, and N and the lithium salt can generate an inorganic component with good ionic conductivity and electrochemical activity, providing a channel for lithium-ion transport or participating in the formation of a stable SEI film, thereby improving fast charging performance.

[0065] In an optional embodiment, the inorganic precursor has a particle size ≤200nm, such as 20nm, 40nm, 60nm, 80nm, 100nm, 120nm, 140nm, 160nm, 180nm, or 200nm. The smaller particle size can increase the specific surface area of ​​the precursor, allowing the inorganic components formed after calcination to be more uniformly distributed on the surface of the silicon-carbon material, thus playing a better role and improving lithium-ion transport efficiency.

[0066] In an optional embodiment, the inorganic component is selected from at least two of Li3P, Li3PO4, Li4P2O7, LiF, and Li3N. Different inorganic components can work synergistically; for example, one inorganic component may provide lithium-ion channels while another helps stabilize the SEI film, thereby more effectively improving the fast-charging performance of the battery.

[0067] In an optional embodiment, the polymer precursor is viscous. The viscous polymer precursor adheres better to the surface of the silicon-carbon material. By limiting the effective contact between inorganic precursors, it prevents chemical reactions or precipitation of the inorganic precursors during the coating stage, which is beneficial for forming a uniform coating layer after calcination. This facilitates the formation of continuous ion transport channels and improves the fast-charging performance of the battery. Furthermore, the viscous polymer precursor is compatible with the inorganic precursor, and the two are bonded together viscously. This allows the polymer precursor to bind the inorganic precursor, uniformly coating the target inorganic precursor onto the silicon-carbon surface. During subsequent calcination, the polymer precursor can also limit the grain size of the inorganic components, preventing excessively large grains and facilitating the obtaining of uniformly dispersed inorganic components and carbonized polymers on the silicon-carbon surface.

[0068] In an optional embodiment, the polymer precursor includes polar groups; the polar groups can improve the bonding strength between the polymer and the silicon-carbon material.

[0069] In an optional embodiment, the polymer precursor is selected from one or more polymers formed by blending or copolymerizing polyacrylic acid, polyvinyl alcohol, polystyrene, polyaniline, polyacrylamide, polyacrylonitrile, sodium carboxymethyl cellulose, and sodium alginate. These polymers, after calcination, can form carbonized polymers with good properties. For example, the carbonaceous layer formed by the carbonized polymer has certain flexibility and mechanical strength, improves interfacial compatibility, assists in the formation of a stable SEI film, and enhances conductivity, thereby helping to improve the battery's fast-charging performance and cycle stability.

[0070] In an optional embodiment, the first component is selected from at least one of hexamethylphosphoric acid triamine, ammonium fluoride, black phosphorus, and red phosphorus;

[0071] In an optional embodiment, the silicon-carbon material includes a core and a carbon coating layer covering the core, the core comprising a porous carbon substrate and nano-silicon particles located within the pores of the porous carbon substrate; the silicon-carbon material satisfies at least one of the following characteristics ak:

[0072] a. The carbon coating layer is amorphous carbon; the carbon layer spacing of amorphous carbon is large, lithium ions can move freely, and the surface porosity is high, which can provide guidance for lithium ion intercalation, prevent co-intercalation of macromolecular organic solvents, inhibit graphite layer peeling and lithium plating, reduce the damage of fast charging to materials, and help improve the fast charging performance of the battery.

[0073] b. The Dv50 of the porous carbon substrate is 6.5μm-8.5μm, for example 6.5μm, 6.7μm, 6.9μm, 7.1μm, 7.3μm, 7.5μm, 7.7μm, 7.9μm, 8.1μm, 8.3μm, 8.5μm;

[0074] c. The particle size distribution of the porous carbon substrate satisfies: Dv0 > 2 μm; Dv10 > 3.7 μm; Dv90 < 11.5 μm; Dv100 < 14.5 μm;

[0075] d. The particle size distribution of the porous carbon substrate satisfies: (D90-D10) / D50<1.2, for example 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2;

[0076] A suitable particle size distribution can give porous carbon substrates good stacking properties, forming more ion transport channels, while ensuring the conductivity of the material, which is conducive to the rapid diffusion of lithium ions and improves fast charging performance.

[0077] e. The average pore size of the porous carbon substrate is 0.5nm-15nm, for example, 0.5nm, 2nm, 3.5nm, 5nm, 6.5nm, 8nm, 9.5nm, 11nm, 12.5nm, 14nm, 15nm; the porous structure increases the specific surface area of ​​the material, providing more insertion sites for lithium ions, and also facilitates the penetration of electrolyte, enabling lithium ions to be transported quickly in the material and improving fast charging performance.

[0078] f. The thickness of the carbon coating layer is 0.5nm-15nm, for example, 0.5nm, 2nm, 3.5nm, 5nm, 6.5nm, 8nm, 9.5nm, 11nm, 12.5nm, 14nm, 15nm; a suitable thickness can ensure good coating of silicon-carbon materials without increasing excessive lithium-ion diffusion resistance, and can also effectively buffer the volume expansion of silicon, which is beneficial to improving the fast charging performance of the battery.

[0079] g. The median particle size of the silicon-carbon material is 7μm-13μm, for example, 7μm, 7.6μm, 8.2μm, 8.8μm, 9.4μm, 10μm, 10.6μm, 11.2μm, 11.8μm, 12.4μm, and 13μm. This particle size range can take into account both the lithium-ion diffusion path and the compaction density of the material, enabling lithium ions to be transported in the material quickly while ensuring a certain lithium storage capacity, which is beneficial to improving the fast charging performance of the battery.

[0080] h. The particle size distribution of the silicon-carbon material is 0.5-1.4, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4. A suitable particle size distribution can make the silicon-carbon material particles more uniformly distributed, avoid the obstruction of lithium-ion diffusion in some areas due to excessive particle size differences, and help improve the overall fast charging performance.

[0081] i. The carbon content of the silicon-carbon material is 45wt%-55wt%, for example, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, and 55wt%. The carbon content within this range ensures that the silicon-carbon material has good conductivity, providing a channel for electron transport. At the same time, the carbon skeleton can buffer the volume expansion of silicon, which is beneficial to improving the fast charging performance and cycle stability of the battery.

[0082] j. The specific surface area of ​​the silicon-carbon material is 0.6 m². 2 / g-4.0m 2 / g, for example 0.6m 2 / g, 1.0m 2 / g, 1.4m 2 / g, 1.8m 2 / g, 2.2m 2 / g, 2.6m 2 / g, 3.0m 2 / g, 3.4m 2 / g, 3.8m 2 / g, 4.0m 2 / g; A suitable specific surface area helps to shorten the diffusion path of lithium ions, improve ionic conductivity, and increase the number of lithium ion insertion sites, thereby improving the fast charging performance of the battery.

[0083] k. The resistivity of the silicon-carbon material is 2Ωcm-6Ωcm, for example, 2Ωcm, 2.4Ωcm, 2.8Ωcm, 3.2Ωcm, 3.6Ωcm, 4.0Ωcm, 4.4Ωcm, 4.8Ωcm, 5.2Ωcm, 5.6Ωcm, and 6Ωcm. The low resistivity indicates good electrical conductivity, which reduces electron transport resistance, allowing for faster charge transfer during fast charging and improving fast charging performance.

[0084] In an optional embodiment, the conductive agent is selected from at least one of graphene, acetylene black, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, flake graphite, polyaniline, polypyrrole, polyacetylene, polythiophene, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate), and two-dimensional MXene.

[0085] In an optional embodiment, the mass fraction of the conductive agent in the silicon-carbon anode material is 0.01wt%-0.5wt%, for example, 0.01wt%, 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, and 0.5wt%. An appropriate amount of conductive agent can form a good conductive network without affecting other properties of the silicon-carbon material, ensuring rapid electron transport. If the content is too low, the conductivity will be poor; if the content is too high, it may occupy too much space, affecting lithium-ion intercalation. A suitable mass fraction is beneficial to improving the fast-charging performance of the battery.

[0086] The present invention also provides a method for preparing the silicon-carbon anode material with fast charge and discharge capability described in the foregoing embodiments, comprising calcining a raw material powder containing silicon-carbon material, a polymer precursor, and an inorganic precursor to obtain the silicon-carbon anode material.

[0087] The preparation method of the silicon-carbon anode material with fast charge-discharge capability in this application is simple and conducive to the commercialization of the product.

[0088] In an optional embodiment, the mass fraction of the inorganic precursor in the raw material powder is 0.1%-6%, for example 0.1%, 0.7%, 1.3%, 1.9%, 2.5%, 3.1%, 3.7%, 4.3%, 4.9%, 5.5%, or 6%.

[0089] And / or, the mass fraction of the polymer precursor in the raw material powder is 0.1%-2%, for example 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9%, or 2%.

[0090] By controlling the mass fraction of inorganic precursors and polymer precursors in the raw materials, the content of inorganic components and carbonized polymers in silicon-carbon anode materials can be controlled within an optimal range, which is beneficial to improving the fast charging performance of the battery.

[0091] In an optional embodiment, the calcination temperature is 200℃-600℃, for example 200℃, 240℃, 280℃, 320℃, 360℃, 400℃, 440℃, 480℃, 520℃, 560℃, 600℃; the calcination time is 1h-5h, for example 1h, 1.4h, 1.8h, 2.2h, 2.6h, 3.0h, 3.4h, 3.8h, 4.2h, 4.6h, 5h; these conditions allow the inorganic precursor and polymer precursor to fully react and transform, forming inorganic components and carbonized polymers with good performance, which is beneficial to improving the fast charging performance of the battery.

[0092] In an optional embodiment, the raw material powder is obtained by spray drying a slurry comprising silicon-carbon materials, polymer precursors, and inorganic precursors. Spray drying can make the raw material powder particles uniform and control the particle size, so that the inorganic components, carbonized polymers, etc. are uniformly distributed on the surface of the silicon-carbon material, which is conducive to the formation of good ion transport channels and conductive networks, and improves fast charging performance.

[0093] In an optional embodiment, the slurry further includes a conductive agent.

[0094] In an optional embodiment, the solid content of the slurry is 6wt%-8wt%, for example, 6wt%, 6.2wt%, 6.4wt%, 6.6wt%, 6.8wt%, 7.0wt%, 7.2wt%, 7.4wt%, 7.6wt%, 7.8wt%, and 8wt%. A suitable solid content in the slurry can ensure the fluidity and stability of the slurry, facilitating spray drying.

[0095] In an optional embodiment, the spray drying temperature is 180℃-200℃, for example 180℃, 182℃, 184℃, 186℃, 188℃, 190℃, 192℃, 194℃, 196℃, 198℃, 200℃; the feed rate is 1.5L / h-2.5L / h, for example 1.5L / h, 1.6L / h, 1.7L / h, 1.8L / h, 1.9L / h, 2.0L / h, 2.1L / h, 2.2L / h, 2.3L / h, 2.4L / h, 2.5L / h.

[0096] Appropriate spray drying temperature and feed rate, combined with slurry solid content, can enable the raw material powder to form particles with suitable size and uniform distribution, resulting in better performance of the subsequently formed silicon-carbon anode material and improving the battery's fast charging performance.

[0097] The present invention also provides a lithium-ion battery comprising the silicon-carbon anode material described in any of the foregoing embodiments.

[0098] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0099] Example 1

[0100] This embodiment provides a method for preparing a silicon-carbon anode material with fast charge-discharge capability, specifically including the following steps:

[0101] 1. Dissolve 19.28 mmol of lithium carbonate (Li2CO3) in 400 g of water, then add 6 g of hexamethylphosphoric triamine (HMPA). After dissolving, add 1 g of polyacrylamide, set the stirring speed to 400 rpm, and stir for 0.5 h.

[0102] 2. Add 38.55 mmol of ammonium fluoride (NH4F, theoretically producing 1 g of LiF) to the slurry obtained in step 1, set the stirring speed to 400 rpm, and stir for 0.5 h;

[0103] 3. Add 0.3g of MXene (3% solids) to the slurry prepared in step 2, set the stirring speed to 600rpm, and stir for 0.5h;

[0104] 4. Slowly add 99g of silicon carbide material to the slurry obtained in step 3, set the stirring speed to 1600rpm, and stir for 1 hour;

[0105] 5. Add 900g of water to the slurry mixed in step 4 to dilute the slurry solid content to approximately 7%;

[0106] 6. The slurry from step 5 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0107] 7. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 200°C for 3 hours to obtain the final modified silicon-carbon product.

[0108] Example 2

[0109] This embodiment provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Embodiment 1 is that the heat treatment temperature in step 7 is 400°C, and the method specifically includes the following steps.

[0110] 1. Dissolve 19.28 mmol of lithium carbonate (Li2CO3) in 400 g of water, then add 6 g of hexamethylphosphoric triamine (HMPA). After dissolving, add 1 g of polyacrylamide, set the stirring speed to 400 rpm, and stir for 0.5 h.

[0111] 2. Add 38.55 mmol of ammonium fluoride (NH4F) to the slurry obtained in step 1, set the stirring speed to 400 rpm, and stir for 0.5 h;

[0112] 3. Add 0.3g of MXene (3% solids) to the slurry prepared in step 2, set the stirring speed to 600rpm, and stir for 0.5h;

[0113] 4. Slowly add 99g of silicon carbide to the slurry obtained in step 3, set the stirring speed to 1600rpm, and stir for 1 hour;

[0114] 5. Add 900g of water to the slurry mixed in step 4 to dilute the slurry solid content to approximately 7%;

[0115] 6. The slurry from step 5 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0116] 7. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 400℃ for 3 hours to obtain the final modified silicon-carbon product.

[0117] Example 3

[0118] This embodiment provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Embodiment 1 is that the heat treatment temperature in step 7 is 600°C, and the method specifically includes the following steps.

[0119] 1. Dissolve 19.28 mmol of lithium carbonate (Li2CO3) in 400 g of water, then add 6 g of hexamethylphosphoric triamine (HMPA). After dissolving, add 1 g of polyacrylamide, set the stirring speed to 400 rpm, and stir for 0.5 h.

[0120] 2. Add 38.55 mmol of ammonium fluoride (NH4F) to the slurry obtained in step 1, set the stirring speed to 400 rpm, and stir for 0.5 h;

[0121] 3. Add 0.3g of MXene (3% solids) to the slurry prepared in step 2, set the stirring speed to 600rpm, and stir for 0.5h;

[0122] 4. Slowly add 99g of silicon carbide to the slurry obtained in step 3, set the stirring speed to 1600rpm, and stir for 1 hour;

[0123] 5. Add 900g of water to the slurry mixed in step 4 to dilute the slurry solid content to approximately 7%;

[0124] 6. The slurry from step 5 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0125] 7. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 600℃ for 3 hours to obtain the final modified silicon-carbon product.

[0126] Example 4

[0127] This embodiment provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Embodiment 1 is that the heat treatment time in step 7 is 1 hour, and the specific steps include the following steps.

[0128] 1. Dissolve 19.28 mmol of lithium carbonate (Li2CO3) in 400 g of water, then add 6 g of hexamethylphosphoric triamine (HMPA). After dissolving, add 1 g of polyacrylamide, set the stirring speed to 400 rpm, and stir for 0.5 h.

[0129] 2. Add 38.55 mmol of ammonium fluoride (NH4F) to the slurry obtained in step 1, set the stirring speed to 400 rpm, and stir for 0.5 h;

[0130] 3. Add 0.3g of MXene (3% solids) to the slurry prepared in step 2, set the stirring speed to 600rpm, and stir for 0.5h;

[0131] 4. Slowly add 99g of silicon carbide to the slurry obtained in step 3, set the stirring speed to 1600rpm, and stir for 1 hour;

[0132] 5. Add 900g of water to the slurry mixed in step 4 to dilute the slurry solid content to approximately 7%;

[0133] 6. The slurry from step 5 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0134] 7. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 400℃ for 1 hour to obtain the final modified silicon-carbon product.

[0135] Example 5

[0136] This embodiment provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Embodiment 1 is that the heat treatment time in step 7 is 5 hours, and the specific steps include the following steps.

[0137] 1. Dissolve 19.28 mmol of lithium carbonate (Li2CO3) in 400 g of water, then add 6 g of hexamethylphosphoric triamine (HMPA). After dissolving, add 1 g of polyacrylamide, set the stirring speed to 400 rpm, and stir for 0.5 h.

[0138] 2. Add 38.55 mmol of ammonium fluoride (NH4F) to the slurry obtained in step 1, set the stirring speed to 400 rpm, and stir for 0.5 h;

[0139] 3. Add 0.3g of MXene (3% solids) to the slurry prepared in step 2, set the stirring speed to 600rpm, and stir for 0.5h;

[0140] 4. Slowly add 99g of silicon carbide to the slurry obtained in step 3, set the stirring speed to 1600rpm, and stir for 1 hour;

[0141] 5. Add 900g of water to the slurry mixed in step 4 to dilute the slurry solid content to approximately 7%;

[0142] 6. The slurry from step 5 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0143] 7. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 400℃ for 5 hours to obtain the final modified silicon-carbon product.

[0144] Example 6

[0145] This embodiment provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Embodiment 2 is that hexamethylphosphoric triamine (HMPA) as a phosphorus source is not added in step 1. The specific method includes the following steps.

[0146] 1. Dissolve 19.28 mmol of lithium carbonate (Li2CO3) in 400 g of water. After dissolving, add 1 g of polyacrylamide, set the stirring speed to 400 rpm, and stir for 0.5 h.

[0147] 2. Add 38.55 mmol of ammonium fluoride (NH4F) to the slurry obtained in step 1, set the stirring speed to 400 rpm, and stir for 0.5 h;

[0148] 3. Add 0.3g of MXene (3% solids) to the slurry prepared in step 2, set the stirring speed to 600rpm, and stir for 0.5h;

[0149] 4. Slowly add 99g of silicon carbide to the slurry obtained in step 3, set the stirring speed to 1600rpm, and stir for 1 hour;

[0150] 5. Add 900g of water to the slurry mixed in step 4 to dilute the slurry solid content to approximately 7%;

[0151] 6. The slurry from step 5 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0152] 7. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 400℃ for 3 hours to obtain the final modified silicon-carbon product.

[0153] Example 7

[0154] This embodiment provides a method for preparing a silicon-carbon anode material with fast charge-discharge capability. The only difference from Embodiment 2 is that lithium carbonate is not added in step 1, step 2 is omitted, and MXene is directly added to the slurry in step 1 in step 3. The specific steps include:

[0155] 1. Dissolve 6g of hexamethylphosphoric acid triamine (HMPA) in 400g of water. After dissolution, add 1g of polyacrylamide, set the stirring speed to 400rpm, and stir for 0.5h.

[0156] 2. Add 0.3g of MXene (3% solids) to the slurry prepared in step 1, set the stirring speed to 600rpm, and stir for 0.5h;

[0157] 3. Slowly add 99g of silicon carbide to the slurry obtained in step 2, set the stirring speed to 1600rpm, and stir for 1 hour;

[0158] 4. Add 900g of water to the slurry mixed in step 3 to dilute the slurry solids content to approximately 7%;

[0159] 5. The slurry from step 4 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0160] 6. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 400℃ for 3 hours to obtain the final modified silicon-carbon product.

[0161] Example 8

[0162] This embodiment provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Embodiment 2 is that the content of inorganic components in the silicon-carbon anode material is too high. The specific method includes the following steps.

[0163] 1. Dissolve 77.12 mmol of lithium carbonate (Li2CO3) in 400 g of water, then add 12 g of hexamethylphosphoric triamine (HMPA). After dissolving, add 1 g of polyacrylamide, set the stirring speed to 400 rpm, and stir for 0.5 h.

[0164] 2. Add 154.20 mmol of ammonium fluoride (NH4F) to the slurry obtained in step 1, set the stirring speed to 400 rpm, and stir for 0.5 h;

[0165] 3. Add 0.3g of MXene (3% solids) to the slurry prepared in step 2, set the stirring speed to 600rpm, and stir for 0.5h;

[0166] 4. Slowly add 99g of silicon carbide to the slurry obtained in step 3, set the stirring speed to 1600rpm, and stir for 1 hour;

[0167] 5. Add 900g of water to the slurry mixed in step 4 to dilute the slurry solid content to approximately 7%;

[0168] 6. The slurry from step 5 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0169] 7. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 400℃ for 3 hours to obtain the final modified silicon-carbon product.

[0170] Example 9

[0171] This embodiment provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Embodiment 2 is that the content of carbonized polymer in the silicon-carbon anode material is too high. The specific method includes the following steps.

[0172] 1. Dissolve 19.28 mmol of lithium carbonate (Li2CO3) in 400 g of water, then add 6 g of hexamethylphosphoric triamine (HMPA). After dissolving, add 5 g of polyacrylamide, set the stirring speed to 400 rpm, and stir for 0.5 h.

[0173] 2. Add 38.55 mmol of ammonium fluoride (NH4F) to the slurry obtained in step 1, set the stirring speed to 400 rpm, and stir for 0.5 h;

[0174] 3. Add 0.3g of MXene (3% solids) to the slurry prepared in step 2, set the stirring speed to 600rpm, and stir for 0.5h;

[0175] 4. Slowly add 99g of silicon carbide to the slurry obtained in step 3, set the stirring speed to 1600rpm, and stir for 1 hour;

[0176] 5. Add 900g of water to the slurry mixed in step 4 to dilute the slurry solid content to approximately 7%;

[0177] 6. The slurry from step 5 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0178] 7. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 400℃ for 3 hours to obtain the final modified silicon-carbon product.

[0179] Example 10

[0180] This embodiment provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Embodiment 2 is that the inorganic components and the types of carbonized polymers have been changed. The specific method includes the following steps.

[0181] 1. Dissolve 25.91 mmol of lithium hydroxide (LiOH) in 400 g of water, then add 4 g of urea. After dissolving, add 1 g of polyacrylic acid, set the stirring speed to 400 rpm, and stir for 0.5 h.

[0182] 2. Add 8.64 mmol of phosphoric acid (H3PO4) to the slurry obtained in step 1, set the stirring speed to 400 rpm, and stir for 0.5 h;

[0183] 3. Add 0.3g of MXene (3% solids) to the slurry prepared in step 2, set the stirring speed to 600rpm, and stir for 0.5h;

[0184] 4. Slowly add 99g of silicon carbide to the slurry obtained in step 3, set the stirring speed to 1600rpm, and stir for 1 hour;

[0185] 5. Add 900g of water to the slurry mixed in step 4 to dilute the slurry solid content to approximately 7%;

[0186] 6. The slurry from step 5 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0187] 7. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 400℃ for 3 hours to obtain the final modified silicon-carbon product.

[0188] Comparative Example 1

[0189] The silicon-carbon material in step 4 of Example 1.

[0190] Comparative Example 2

[0191] This comparative example provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Example 2 is that only a polymer precursor is added to the slurry, and no inorganic precursor is added. The specific steps include the following steps.

[0192] 1. Add 1g of polyacrylamide to 400g of water, set the stirring speed to 400rpm, and stir for 0.5h;

[0193] 2. Add 0.3g of MXene (3% solids) to the slurry prepared in step 1, set the stirring speed to 600rpm, and stir for 0.5h;

[0194] 3. Slowly add 99g of silicon carbide to the slurry obtained in step 2, set the stirring speed to 1600rpm, and stir for 1 hour;

[0195] 4. Add 900g of water to the slurry mixed in step 3 to dilute the slurry solids content to approximately 7%;

[0196] 5. The slurry from step 4 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0197] 6. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 400℃ for 3 hours to obtain the final modified silicon-carbon product.

[0198] Comparative Example 3

[0199] This comparative example provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Example 2 is that only an inorganic precursor is added to the slurry, and no polymer precursor is added. The specific steps include the following steps.

[0200] 1. Dissolve 19.28 mmol of lithium carbonate (Li2CO3) in 400g of water, then add 6g of hexamethylphosphoric triamine (HMPA). After dissolving, add 38.55 mmol of ammonium fluoride (NH4F) to dissolve and obtain a homogeneous and stable slurry.

[0201] 2. Add 0.3g of MXene (3% solids) to the slurry prepared in step 1, set the stirring speed to 600rpm, and stir for 0.5h;

[0202] 3. Slowly add 99g of silicon carbide to the slurry obtained in step 2, set the stirring speed to 1600rpm, and stir for 1 hour;

[0203] 4. Add 900g of water to the slurry mixed in step 3 to dilute the slurry solids content to approximately 7%;

[0204] 5. The slurry obtained in step 4 is dried by spray drying to obtain the modified silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0205] 6. Place the obtained silicon-carbon material in a nitrogen atmosphere and heat-treat it at 400℃ for 3 hours to obtain the final modified silicon-carbon product.

[0206] Comparative Example 4

[0207] This comparative example provides a method for preparing a silicon-carbon anode material with fast charge and discharge capability. The only difference from Example 1 is that the heat treatment temperature in step 7 is 700°C and the heat treatment time is 8 hours. The specific steps include the following steps.

[0208] 1. Dissolve 19.28 mmol of lithium carbonate (Li2CO3) in 400 g of water, then add 6 g of hexamethylphosphoric triamine (HMPA). After dissolving, add 1 g of polyacrylamide, set the stirring speed to 400 rpm, and stir for 0.5 h.

[0209] 2. Add 38.55 mmol of ammonium fluoride (NH4F) to the slurry obtained in step 1, set the stirring speed to 400 rpm, and stir for 0.5 h;

[0210] 3. Add 0.3g of MXene (3% solids) to the slurry prepared in step 2, set the stirring speed to 600rpm, and stir for 0.5h;

[0211] 4. Slowly add 99g of silicon carbide to the slurry obtained in step 2, set the stirring speed to 1600rpm, and stir for 1 hour;

[0212] 5. Add 900g of water to the slurry mixed in step 3 to dilute the slurry solids content to approximately 7%;

[0213] 6. The slurry from step 4 is dried by spray drying to obtain the coated silicon-carbon material. The drying temperature is 190℃ and the feed rate is 2L / h.

[0214] 7. The obtained silicon-carbon material is placed in a nitrogen atmosphere and heat-treated at 700℃ for 8 hours to obtain the final modified silicon-carbon product.

[0215] Physical and chemical performance testing:

[0216] The silicon-carbon finished products obtained in each embodiment and comparative example were tested for powder resistivity (25°C) using a four-probe tester. The test results are shown in Table 1.

[0217] Button cell battery testing:

[0218] The silicon-carbon products obtained in Comparative Examples 1-4 and Examples 1-7 were combined with SP (super carbon black), CMC (sodium carboxymethyl cellulose), and PAALi (lithium polyacrylate) in a ratio of 75:10:5:10 to prepare a negative electrode. Lithium metal was used as the counter electrode. The electrolyte was LiPF6 / EC+DEC, with LiPF6 as the lithium salt at a concentration of 1 mol / L and the volume ratio of EC to DEC being 1:1. The separator was a composite membrane of polyethylene (PE) and polypropylene (PP), i.e., a PE / PP / PE three-layer composite membrane. Finally, a Li / Si half-cell was prepared in a glove box.

[0219] Its charge / discharge specific capacity and initial coulombic efficiency were tested under the following conditions: voltage range: 0.005V-1.5V, charge / discharge rate: 0.1C / 0.1C.

[0220] The capacity retention rate was tested at different charge / discharge rates. The test conditions were: 0.005V-1.5V, and the charge / discharge rates were: 0.1C / 0.1C, 0.3C / 0.3C; 0.1C / 0.1C, 0.5C / 0.5C; 0.1C / 0.1C, 1C / 1C; 0.1C / 0.1C, 1.5C / 1.5C.

[0221] Test its charging DCR (50% SOC). Conditions: Room temperature: 25℃; Procedure: Stand for 2 hours, discharge at 0.1C until voltage < 0.005V, stand for 10 minutes, charge at 0.1C until voltage > 1.5V, stand for 10 minutes, discharge at 0.1C until voltage < 0.175V, stand for 10 minutes, charge at 1C for 30 seconds, stand for 10 minutes. After completing the test, calculate its DC internal resistance (DCR) using the formula: R = U / I.

[0222] Simulation calculation of lithium-ion diffusion barrier:

[0223] This invention employs the climbing elastic band (CI-NEB) method based on density functional theory (DFT) to perform high-precision calculations of the lithium-ion diffusion barrier of inorganic components (Li2CO3, LiF, Li2O, Li3P, etc. and their grain boundary structures) within the SEI film of the anode material.

[0224] First, the grain boundary model was optimized using DFT under PBE+U or HSE06 functionals to obtain the system potential energy surface. Then, the transition state path of lithium ion migration was determined by CI-NEB on the Γ point or high k point density grid. Finally, the activation energy barrier Ea at 0 K was output. Furthermore, the free energy barrier ΔG (i.e. lithium ion diffusion barrier) at 298.15 K was obtained by using phonon correction at finite temperature or ab initio molecular dynamics (AIMD). This provides a theoretical basis for grain boundary modification and fast charging performance prediction.

[0225] The test results are shown in Table 1.

[0226] Table 1

[0227]

[0228] Powder resistivity: As can be seen from Comparative Examples 1-4, the resistivity of the powder slightly increases after the polymer is coated. Only the resistivity of silicon-carbon powder coated with inorganic matter increases slightly. This is because the polymer itself has poor conductivity, and the coating will increase the bulk resistivity of silicon-carbon. Comparing Comparative Example 1 and Examples 1-7, it can also be found that the resistivity of the modified silicon-carbon finished products all increase slightly.

[0229] As can be seen from Comparative Examples 1-4, the modified silicon-carbon products obtained by simply coating with carbonized polymers or inorganic components all exhibit decreased capacity, initial efficiency, capacity retention at different rates, and DCR. In Comparative Example 2, simply coating with polymers easily leads to an increase in powder resistivity and DCR, thereby affecting the lithium-ion transport rate, resulting in an increase in interfacial side reactions, and a decrease in initial efficiency, capacity retention at different rates, and fast-charging performance. In Comparative Example 3, only inorganic matter was coated. On the one hand, the adhesion of inorganic matter is weak, making it easy to fall off, resulting in uneven and incomplete coating. On the other hand, inorganic matter easily forms particles and aggregates, leading to poor contact between silicon-carbon materials and other components, thus affecting initial efficiency, fast-charging performance, and capacity retention. In Comparative Example 4, excessively high heat treatment temperature and excessively long heat treatment time easily lead to a large amount of organic matter decomposition, a reduction in residual carbon, and continuous growth of inorganic particles. Amorphous silicon nanoparticles also gradually transform into crystalline silicon. These problems also lead to an increase in powder resistivity and DCR, thereby deteriorating its initial efficiency, fast-charging performance, and capacity retention.

[0230] As can be seen from Comparative Example 1 and Examples 1-5, the organic-inorganic coating in Examples 1-5 is beneficial to improving the first efficiency and kinetic performance of silicon-carbon. This is because when lithium ions are transported to the surface of silicon-carbon, the inorganic material has a lower desolvation energy barrier and provides a fast lithium ion transport channel (the inorganic material itself and the grain boundaries), which allows lithium ions to be transported quickly and reduces side reactions, thereby improving its first efficiency and capacity retention.

[0231] Examples 1-3 and Examples 1, 4, and 5 demonstrate that heat treatment temperature and time significantly impact performance. Excessively high or low temperatures, and excessively long or short heat treatment times, do not optimally improve the kinetics of silicon-carbon. This is because at excessively low temperatures and short times, the target inorganic material fails to form sufficiently, resulting in limited carbonization of the polymer precursor. Conversely, at excessively high temperatures and long times, the target inorganic material tends to aggregate and grow, leading to severe polymer decomposition and significant coating layer detachment. Furthermore, excessively high temperatures and long times can cause amorphous silicon nanoparticles to crystallize, thus affecting electrochemical performance. Therefore, only within a reasonable range of heat treatment temperature and time can a modified silicon-carbon product with good performance be obtained.

[0232] As can be seen from Comparative Example 1, Example 2, Example 6, and Example 7, coating with a single inorganic component can also improve the kinetic performance of silicon-carbon, but the effect is not as good as the effect of multi-component coating mentioned in Example 2. This is because the grain boundaries between multiple inorganic components can often provide faster lithium-ion transport channels.

[0233] As can be seen from Comparative Example 2, Example 2, and Example 8, when the amount of inorganic component added is too large, the kinetic performance decreases compared to Example 2. This is because excessive inorganic component addition promotes the aggregation of inorganic particles and makes the grains grow larger, resulting in excessively large particle sizes. This phenomenon not only damages the structure of the coating layer but also weakens the adhesion between the coating layer and silicon carbon, causing some of the coating material to lose contact with the silicon carbon. However, compared to pure silicon carbon, its kinetic performance is still improved. This is because the electrode rolling process promotes contact between the coating layer and silicon carbon. Therefore, even with a slightly higher amount of inorganic component added, the modified silicon carbon still has certain advantages in kinetics compared to uncoated silicon carbon.

[0234] As can be seen from Comparative Example 3, Example 2, and Example 9, excessive addition of carbonized polymer precursor will lead to a deterioration in silicon-carbon kinetics. This is because the polymer itself has poor conductivity and ion conductivity. Once the amount added is too much, it will affect the conduction of ions and electrons. The most direct result is that its powder resistivity and DCR both increase significantly, thereby causing its rate performance to decrease.

[0235] As can be seen from Comparative Examples 1, 2, and 10, the kinetic performance of the coating layer is still significantly improved after the carbonized polymer and inorganic material are adjusted within the scope of this application. This indicates that the adjustment of the carbonized polymer and inorganic material in the coating layer within the scope of this application is beneficial to the improvement of its kinetic performance.

[0236] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A silicon-carbon anode material with fast charge-discharge capability, characterized in that, It includes a silicon-carbon material and at least a carbonized polymer and an inorganic component attached to a portion of the surface of the silicon-carbon material, wherein the diffusion barrier of the grain boundaries of the inorganic component is less than 0.6 eV.

2. The silicon-carbon anode material with fast charge-discharge capability according to claim 1, characterized in that, The inorganic component in the silicon-carbon anode material has a mass fraction of 0.5%-1.5%. And / or, the inorganic component is selected from at least one of Li3P, Li3PO4, Li4P2O7, LiF, and Li3N; And / or, the inorganic component can participate in the oxidation reaction as an electron donor under the electric field driven by the charging and discharging of the battery; And / or, the inorganic component is obtained by calcining an inorganic precursor; And / or, the inorganic component is obtained from an inorganic precursor through a charge-discharge process; And / or, the mass fraction of the carbonized polymer in the silicon-carbon anode material is 0.2%-2.5%; And / or, the carbonized polymer is obtained by calcining a polymer precursor; And / or, the silicon-carbon anode material further includes a conductive agent.

3. The silicon-carbon anode material with fast charge-discharge capability according to claim 2, characterized in that, The inorganic precursor includes a first component and a second component, wherein the first component is selected from inorganic substances containing at least one of P, F, and N, and the second component is a lithium salt; And / or, the inorganic precursor has a particle size ≤200nm; And / or, the inorganic component is selected from at least two of Li3P, Li3PO4, Li4P2O7, LiF, and Li3N.

4. The silicon-carbon anode material with fast charge-discharge capability according to claim 2, characterized in that, The polymer precursor is viscous; And / or, the polymer precursor includes polar groups; And / or, the polymer precursor is selected from one or more polymers formed by blending or copolymerizing polyacrylic acid, polyvinyl alcohol, polystyrene, polyaniline, polyacrylamide, polyacrylonitrile, sodium carboxymethyl cellulose, and sodium alginate.

5. The silicon-carbon anode material with fast charge-discharge capability according to claim 3, characterized in that, The first component is selected from at least one of hexamethylphosphoric acid triamine, ammonium fluoride, black phosphorus, and red phosphorus; And / or, the silicon-carbon material comprises a core and a carbon coating layer covering the core, the core comprising a porous carbon substrate and nano-silicon particles located within the pores of the porous carbon substrate; the silicon-carbon material satisfies at least one of the following characteristics ak: a. The carbon coating layer is amorphous carbon; b. The Dv50 of the porous carbon substrate is 6.5 μm-8.5 μm; c. The particle size distribution of the porous carbon substrate satisfies: Dv0 > 2 μm; Dv10 > 3.7 μm; Dv90 < 11.5 μm; Dv100 < 14.5 μm; d. The particle size distribution of the porous carbon substrate satisfies: (D90-D10) / D50<1.2; e. The average pore size of the porous carbon substrate is 0.5 nm to 15 nm; f. The thickness of the carbon coating layer is 0.5 nm-15 nm; g. The median particle size of the silicon-carbon material is 7μm-13μm; h. The particle size distribution of the silicon-carbon material is 0.5-1.4; i. The carbon content of the silicon carbide material is 45wt%-55wt%; j. The specific surface area of ​​the silicon-carbon material is 0.6 m². 2 / g-4.0m 2 / g; k. The resistivity of the silicon-carbon material is 2Ωcm-6Ωcm.

6. The silicon-carbon anode material with fast charge-discharge capability according to claim 2, characterized in that, The conductive agent is selected from at least one of graphene, acetylene black, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, flake graphite, polyaniline, polypyrrole, polyacetylene, polythiophene, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate), and two-dimensional MXene. And / or, the mass fraction of the conductive agent in the silicon-carbon anode material is 0.01wt%-0.5wt%.

7. A method for preparing a silicon-carbon anode material with fast charge-discharge capability as described in claim 1, characterized in that, This includes calcining raw material powder containing silicon-carbon materials, polymer precursors, and inorganic precursors to obtain the silicon-carbon anode material.

8. The method for preparing the silicon-carbon anode material with fast charge-discharge capability according to claim 7, characterized in that, The mass fraction of inorganic precursors in the raw material powder is 0.1%-6%; And / or, the mass fraction of the polymer precursor in the raw material powder is 0.1%-2%; And / or, the calcination temperature is 200℃-600℃, and the calcination time is 1h-5h; And / or, the raw material powder is obtained by spray drying a slurry comprising silicon carbon materials and polymer precursors and inorganic precursors.

9. The method for preparing the silicon-carbon anode material with fast charge-discharge capability according to claim 8, characterized in that, The slurry also includes a conductive agent; And / or, the solid content of the slurry is 6wt%-8wt%; And / or, the spray drying temperature is 180℃-200℃, and the feed rate is 1.5L / h-2.5L / h.

10. A lithium-ion battery, characterized in that, Includes the silicon-carbon anode material as described in any one of claims 1-6.

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