A fast-charging type gas-phase silicon-carbon composite material, a preparation method thereof, a lithium ion battery and an electric device

Abstract

The application provides a fast-charging type gas-phase silicon-carbon composite material, a preparation method thereof, a lithium ion battery and an electric device, and relates to the field of lithium ion batteries. The fast-charging type gas-phase silicon-carbon composite material comprises a core and a first fast-ion conductor layer, a carbon-coated layer and an interface modification layer arranged on the surface of the core in sequence; the core comprises a porous carbon framework, a second fast-ion conductor layer is arranged in the cavity of the porous carbon framework, and the second fast-ion conductor layer contains silicon particles and fast-ion conductor particles. The second fast-ion conductor layer and the fast-ion conductor particles are loaded in the interior of the porous carbon framework, a fast ion channel is constructed, the conduction performance of lithium ions in the interior of the porous carbon material is improved, and mechanical properties such as the compression resistance of the fast-charging type gas-phase silicon-carbon composite material are improved; the interface modification layer improves the lithium ion conductivity of the carbon phase material and the overall particle strength, forms a fast lithium ion conducting network with the internal fast-ion conductor, shortens the diffusion distance of lithium ions, and improves the rate performance of the fast-charging type gas-phase silicon-carbon composite material.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and more particularly to a fast-charging fumed silicon-carbon composite material and its preparation method, a lithium-ion battery, and an electrical device thereof. Background Technology

[0002] With the rapid development of emerging industries such as portable electronic devices and electric vehicles, lithium-ion batteries have become the mainstream power source in these fields due to their high energy density and long cycle life. At the same time, the continuous upgrading of the new energy industry has placed higher demands on power supply performance, and the market demand for the energy density of lithium-ion batteries is also increasing. Currently, the theoretical capacity of graphite anode materials, which are most widely used in industrial applications, is only 372 mAh / g, which is insufficient to meet the development needs of high-energy-density batteries. Therefore, finding high-capacity anode materials to replace graphite has become a research hotspot in this field.

[0003] Among numerous candidate materials, silicon stands out due to its extremely high theoretical capacity (approximately 4200 mAh / g, far exceeding graphite's 372 mAh / g) and low lithium potential (<0.5 V vs Li / Li). + Silicon is considered one of the most promising next-generation lithium-ion battery anode materials. However, the practical application of silicon-based anode materials is constrained by two key issues. First, during the lithium insertion / extraction process, silicon undergoes dramatic volume expansion and contraction (volume change rate can reach over 300%). This repeated volume change easily leads to silicon particle breakage and electrode structure collapse, resulting in rapid capacity decay and shortened cycle life. Second, silicon is a semiconductor material with low intrinsic electronic conductivity, which limits electrode reaction kinetics and affects the battery's output power and rate performance.

[0004] To alleviate these problems, researchers have attempted to nanoscale silicon materials, fabricating various nanostructures such as nanoparticles, nanowires, and nanotubes to reduce material failure caused by volume expansion. However, simple nanoscale fabrication cannot completely solve the expansion problem of silicon. Therefore, constructing silicon-carbon composites by combining silicon with carbon materials has become a more reasonable and effective strategy. Silicon-carbon composite methods mainly include coating, embedding, and doping types. The core idea is to use carbon layers or a carbon matrix to provide mechanical confinement and buffering for silicon particles, suppressing volume expansion, while simultaneously leveraging the high conductivity of carbon materials to enhance the overall electronic conductivity of the composite material, thus achieving both high capacity and cycling stability.

[0005] Currently, the mainstream preparation method for embedded silicon-carbon materials is chemical vapor deposition (CVD). The process involves pyrolyzing a gaseous silicon source (such as silane) on the surface of a carbon matrix at high temperatures to generate nano-silicon, which is then deposited into the pores or surface of the carbon material. A dense carbon layer is then formed through a vapor-phase carbon coating process. However, this technique has inherent drawbacks. On the one hand, the extremely dense carbon layer obtained by CVD effectively buffers the volume expansion of silicon and prevents direct contact between the electrolyte and silicon, but it also severely restricts the diffusion channels of lithium ions in the solid phase, leading to a decrease in ion transport efficiency. On the other hand, while the inherent cavity structure within porous carbon materials provides space for silicon volume expansion, excessive cavities prolong the lithium ion diffusion path, and the cavity structure is prone to rupture during high-voltage electrode fabrication, further deteriorating the electrochemical performance of the material. These factors collectively result in poor rate performance of silicon-carbon materials prepared by CVD, especially with significant capacity decay under high-current charge-discharge conditions.

[0006] Therefore, in the design of silicon-carbon materials, it is necessary not only to effectively mitigate the volume expansion effect of silicon, but also to consider the internal ion and electron conduction efficiency of the material. Simple chemical vapor deposition processes are insufficient to simultaneously meet these requirements, necessitating the development of a novel silicon-carbon material preparation method that can achieve synergistic optimization of volume expansion suppression and ion / electron conduction. Summary of the Invention

[0007] The purpose of this application is to provide a fast-charging fumed silicon-carbon composite material, its preparation method, a lithium-ion battery, and an electrical device to solve the above-mentioned problems.

[0008] To achieve the above objectives, the first aspect of this application provides a fast-charging fumed silicon-carbon composite material, comprising a core and a first fast ion conductor layer, a carbon coating layer, and an interface modification layer sequentially disposed on the surface of the core; The core includes a porous carbon skeleton, and a second fast ion conductor layer is disposed within the cavity of the porous carbon skeleton. The second fast ion conductor layer contains silicon particles and fast ion conductor particles. The interface modification layer comprises organic polymers and / or inorganic compounds.

[0009] Optionally, the fast-charging fumed silicon-carbon composite material satisfies at least one of the following conditions: (1) The raw materials for the first fast ion conductor layer, the second fast ion conductor layer and the fast ion conductor particles include fast ion conductor reactants and lithium sources; the fast ion conductor reactants include at least one of lithium hydroxide, tetrabutyl titanate, ammonium dihydrogen phosphate, aluminum nitrate nonahydrate and ammonium fluoride; the lithium sources include at least one of lithium carbonate, aluminum hydroxide, lithium titanate, lithium phosphate, β-alumina, lithium aluminate and lithium fluoride; (2) The interface modification layer includes at least one of polyacrylic acid, graphene oxide, carbon nanotubes, lithium salt, aluminum salt, titanate, titanium dioxide and alumina; (3) The thickness of the first fast ion conductor layer is 0.1-5 nm; (4) The thickness of the second fast ion conductor layer is 0.1-2 nm; (5) The thickness of the carbon coating layer is 5-20 nm; (6) The thickness of the interface modification layer is 1-200 nm; (7) The particle size of the fast-charging fumed silicon-carbon composite material is 5-20 μm, and the specific surface area is 1-10 m². 2 / g, pore volume 0.5-1.2cm 3 / g; (8) The silicon mass content of the fast-charging gas phase silicon-carbon composite material is 40%-60%.

[0010] A second aspect of this application provides a method for preparing the fast-charging fumed silicon-carbon composite material, comprising: Porous carbon material and solvent are mixed to obtain a porous carbon material dispersion; under vacuum, an aqueous solution of fast ion conductor reactant and the porous carbon material dispersion are mixed to obtain a mixed solution; an aqueous solution of lithium source is added dropwise to the mixed solution for reaction, solid-liquid separation, and drying to obtain the dried material; Under a nitrogen atmosphere, the dried material is subjected to a first heat treatment to obtain a porous carbon material containing a fast ion conductor layer inside. A fluidized bed chemical vapor deposition process is used to deposit silane gas in the pores of a porous carbon material containing a fast ion conductor layer under a nitrogen atmosphere, thereby obtaining a deposited porous carbon material. Acetylene is then introduced to coat the surface of the deposited porous carbon material, resulting in a carbon-coated porous carbon material. The interface-modifying compound and the carbon-coated porous carbon material are mixed and spray-granulated to obtain the granulated porous carbon material; the granulated porous carbon material is then subjected to a second heat treatment under an inert atmosphere to obtain a fast-charging fumed silicon-carbon composite material.

[0011] Optionally, the preparation method of the fast-charging fumed silicon-carbon composite material satisfies at least one of the following conditions: (1) The particle size of the porous carbon material is 1-20 μm; (2) The porous carbon material includes biomass-based porous carbon material and / or petroleum coke-based porous carbon material; (3) The total pore volume of the porous carbon material is 0.6-1.5 cm³. 3 / g, specific surface area is 1500-3000m² 2 / g; (4) The solvent includes at least one of water, ethanol, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone and tetrahydrofuran; (5) The solid content of the porous carbon material dispersion is 1-10%.

[0012] Optionally, the preparation method of the fast-charging fumed silicon-carbon composite material satisfies at least one of the following conditions: (1) The mass of the fast ion conductor reactant accounts for 1%-5% of the mass of the porous carbon material; (2) The mass ratio of the fast ion conductor reactant to the lithium source is 1:1-5; (3) The vacuum degree of the vacuum environment is 0 MPa to -1 MPa; (4) The dropping rate of the aqueous solution of the lithium source is 1-2 mL / min; (5) The reaction temperature is 25-60℃, the time is 5-12h, and the vacuum degree is ≤ -0.08MPa.

[0013] Optionally, the preparation method of the fast-charging fumed silicon-carbon composite material satisfies at least one of the following conditions: (1) The temperature of the first heat treatment is 400-1000℃ and the time is 2-6h; (2) The specific surface area of ​​the internal fast ion conductor layer is 1500-2500 m². 2 / g.

[0014] Optionally, the particle size of the carbon-coated porous carbon material is 5-20 μm, and the specific surface area is 1-5 m². 2 / g.

[0015] Optionally, the preparation method of the fast-charging fumed silicon-carbon composite material satisfies at least one of the following conditions: (1) The mass of the interface-modifying compound accounts for less than 5% of the total mass of the carbon-coated porous carbon material; (2) The inlet air temperature of the spray granulation is 100-300℃, the outlet air temperature is 60-150℃, the atomization pressure is 0.1-1 MPa, and the solid content of the slurry is 5%-30%; (3) The temperature of the second heat treatment is 100-600℃ and the time is 1-10h.

[0016] A third aspect of this application provides a lithium-ion battery comprising the aforementioned fast-charging fumed silicon-carbon composite material.

[0017] A fourth aspect of this application provides an electrical device including the aforementioned lithium-ion battery.

[0018] Compared with the prior art, the beneficial effects of this application include: The fast-charging fumed silicon-carbon composite material provided in this application firstly loads a second fast ion conductor layer and fast ion conductor particles inside a porous carbon skeleton, filling part of the cavity in the porous carbon skeleton, constructing a fast ion channel, improving the conductivity of lithium ions inside the porous carbon material, solving the problem of low ion diffusion rate inside the material, and providing support for the entire particle, improving its mechanical properties such as compressive strength; secondly, the first fast ion conductor layer can also form a fast ion channel with the core and the outside, shortening the ion diffusion path, and together with the porous carbon material, achieving efficient and coordinated electron and ion transport. Finally, a carbon coating layer and an interface modification layer are set on the core surface. The interface modification layer modifies the carbon coating layer, optimizes its material surface, improves the lithium-ion conductivity and overall particle strength of the carbon phase material, and also provides a rigid outer shell support for the fast-charging fumed silicon-carbon composite material. By reducing side reactions, it guides the formation of a thinner and more stable solid electrolyte membrane during charging and discharging, improves the lithium-ion transport capability of the carbon coating layer, forms a fast lithium-conducting network with the internal fast-ion conductor, shortens the lithium-ion diffusion distance, and improves the rate performance of the fast-charging fumed silicon-carbon composite material.

[0019] The method for preparing fast-charging fumed silicon-carbon composite material provided in this application employs wetting and in-situ reaction. It prioritizes wetting the raw material inside the cavity of a porous carbon material, and then, through reaction under negative pressure and calcination, generates a first fast-ion conductor layer, a second fast-ion conductor layer, and fast-ion conductor particles inside the porous carbon material. This constructs a fast lithium-ion channel within the fast-charging fumed silicon-carbon composite material and enhances the material's internal stability before silicon deposition. Furthermore, during surface coating, in addition to the acetylene carbon coating layer, a surface interface modifier is applied to the surface to improve the lithium conductivity of the carbon phase coating layer and guide the construction of a more stable and thinner solid electrolyte interface film. The lithium-ion batteries and electrical devices provided in this application have good rate performance and long cycle life. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0021] Figure 1 This is a schematic diagram of the structure of the fast-charging fumed silicon-carbon composite material provided in Example 1; Figure 2 The image shows a SEM image of the fast-charging vapor phase silicon-carbon composite material provided in Example 1.

[0022] Explanation of key component symbols: 100 - Core; 110 - Porous carbon framework; 120 - Second fast ion conductor layer; 130 - Silicon particles; 140 - Fast ion conductor particles; 200 - First fast ion conductor layer; 300 - Carbon coating layer; 400 - Interface modification layer. Detailed Implementation

[0023] First, the solution provided in this application will be explained in more detail as follows: The first aspect of this application provides a fast-charging fumed silicon-carbon composite material, comprising a core and a first fast ion conductor layer, a carbon coating layer and an interface modification layer sequentially disposed on the surface of the core; The core includes a porous carbon skeleton, and a second fast ion conductor layer is disposed within the cavity of the porous carbon skeleton. The second fast ion conductor layer contains silicon particles and fast ion conductor particles. The interface modification layer comprises organic polymers and / or inorganic compounds.

[0024] In some embodiments, the fast-charging fumed silicon-carbon composite material satisfies at least one of the following conditions: (1) The raw materials for the first fast ion conductor layer, the second fast ion conductor layer and the fast ion conductor particles include fast ion conductor reactants and lithium sources; the fast ion conductor reactants include at least one of lithium hydroxide, tetrabutyl titanate, ammonium dihydrogen phosphate, aluminum nitrate nonahydrate and ammonium fluoride; the lithium sources include at least one of lithium carbonate, aluminum hydroxide, lithium titanate, lithium phosphate, β-alumina, lithium aluminate and lithium fluoride; It should be noted that fast ion conductors and fast ion conductor reactants are different. Lithium carbonate and lithium hydroxide are both lithium sources and fast ion conductor reactants. Tetrabutyl titanate, ammonium dihydrogen phosphate, aluminum nitrate nonahydrate and ammonium fluoride are fast ion conductor reactants. Lithium titanate, lithium phosphate, lithium aluminate and lithium fluoride are fast ion conductors themselves. The lithium source and fast ion conductor reactants of this application can generate fast ion conductors. It should also be noted that in the existing technology, a carbon layer is set in the cavity. However, since the porous carbon material itself is a carbon material, filling the interior with carbon material is useless and may even have negative effects such as blockage of the deposition channels. In the overall material design, the pore structure of the porous carbon material serves as a container for silicon particles. The conductivity of the porous carbon itself is responsible for providing a fast transport network for electrons, while the fast ion conductor is a fast channel for ion conduction, specifically responsible for providing a fast channel for the migration of lithium ions. (2) The interface modification layer includes at least one of polyacrylic acid, graphene oxide, carbon nanotubes, lithium salt, aluminum salt, titanate, titanium dioxide and alumina; It is important to note that the inorganic salts in the interface modification layer are responsible for optimizing the ion pathways on the material surface, improving the ionic conductivity of the material, and enhancing the rate performance of the material. Some inorganic salts, such as titanium dioxide and alumina, are also rigid materials that can improve the structural strength of the material, reduce the overall expansion of the material, and maintain particle stability. However, inorganic salts have poor conductivity, and highly conductive materials such as carbon nanotubes and graphene are needed to build an electronic conductive network to provide electron transport channels. Preferably, the interface modification layer includes titanium dioxide and carbon nanotubes. (3) The thickness of the first fast ion conductor layer is 0.1-5 nm; Optionally, the thickness of the first fast ion conductor layer can be any value between 0.1 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, or 0.1-5 nm. (4) The thickness of the second fast ion conductor layer is 0.1-2 nm; Optionally, the thickness of the second fast ion conductor layer can be any value between 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, or 0.1-2 nm. (5) The thickness of the carbon coating layer is 5-20 nm; Optionally, the thickness of the carbon coating can be any value between 5 nm, 10 nm, 15 nm, 20 nm, or 5-20 nm. (6) The thickness of the interface modification layer is 1-200 nm; Optionally, the thickness of the interface modification layer can be any value between 1 nm, 10 nm, 50 nm, 100 nm, 150 nm, 200 nm or 1-200 nm. (7) The particle size of the fast-charging fumed silicon-carbon composite material is 5-20 μm, and the specific surface area is 1-10 m². 2 / g, pore volume 0.5-1.2cm 3 / g; Optionally, the particle size of the fast-charging fumed silicon-carbon composite material can be any value between 5μm, 10μm, 15μm, 20μm, or 5-20μm, and the specific surface area can be 1 m². 2 / g、5 m 2 / g、10 m 2 / g or 1-10 mg 2 For any value between / g, the pore volume can be 0.5 cm³. 3 / g, 0.6 cm 3 / g, 0.7 cm 3 / g, 0.8 cm 3 / g, 0.9 cm 3 / g, 1 cm3 / g, 1.1 cm 3 / g, 1.2cm 3 / g or 0.5-1.2 cm 3 Any value between / g; (8) The silicon mass content of the fast-charging gas phase silicon-carbon composite material is 40%-60%.

[0025] Optionally, the silicon mass content of the fast-charging fumed silicon-carbon composite material can be any value between 40%, 45%, 50%, 55%, 60%, or 40-60%. A second aspect of this application provides a method for preparing the fast-charging fumed silicon-carbon composite material, comprising: Porous carbon material and solvent are mixed to obtain a porous carbon material dispersion; under vacuum, an aqueous solution of fast ion conductor reactant and the porous carbon material dispersion are mixed to obtain a mixed solution; an aqueous solution of lithium source is added dropwise to the mixed solution for reaction, solid-liquid separation, and drying to obtain the dried material; It should be noted that the precursor of the existing gas phase silicon-carbon material is a porous carbon material, which contains a large number of pore cavities. Although some of the cavities are filled during silane deposition and provide cavities for the expansion of silicon material, the presence of pore cavities still results in poor overall lithium conductivity of the material. Under a nitrogen atmosphere, the dried material is subjected to a first heat treatment to obtain a porous carbon material containing a fast ion conductor layer inside. A fluidized bed chemical vapor deposition process is used to deposit silane gas in the pores of a porous carbon material containing a fast ion conductor layer under a nitrogen atmosphere, thereby obtaining a deposited porous carbon material. Acetylene is then introduced to coat the surface of the deposited porous carbon material, resulting in a carbon-coated porous carbon material. In some embodiments, the thickness of the carbon coating layer in the carbon-coated porous carbon material is 5-20 nm. This thickness can prevent the carbon layer from breaking down and causing side reactions during the next surface modification process. The interface-modifying compound and the carbon-coated porous carbon material are mixed and spray-granulated to obtain the granulated porous carbon material; the granulated porous carbon material is then subjected to a second heat treatment under an inert atmosphere to obtain a fast-charging fumed silicon-carbon composite material.

[0026] In some embodiments, the preparation method of the fast-charging fumed silicon-carbon composite material satisfies at least one of the following conditions: (1) The particle size of the porous carbon material is 1-20 μm; Optionally, the particle size of the porous carbon material can be any value between 1 μm, 5 μm, 10 μm, 15 μm, 20 μm or 1-20 μm; (2) The porous carbon material includes biomass-based porous carbon material and / or petroleum coke-based porous carbon material; (3) The total pore volume of the porous carbon material is 0.6-1.5 cm³. 3 / g, specific surface area is 1500-3000m² 2 / g; Optionally, the total pore volume of the porous carbon material can be 0.6 cm³. 3 / g, 1 cm 3 / g, 1.5 cm 3 / g or 0.6-1.5 cm 3 For any value between / g, the specific surface area can be 1500 m². 2 / g、2000 m 2 / g、2500 m 2 / g、3000 m 2 / g or 1500-3000 m 2 Any value between / g; (4) The solvent includes at least one of water, ethanol, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone and tetrahydrofuran; (5) The solid content of the porous carbon material dispersion is 1-10%.

[0027] Optionally, the solid content of the porous carbon material dispersion can be any value between 1%, 5%, 10%, or 1-10%.

[0028] In some embodiments, the preparation method of the fast-charging fumed silicon-carbon composite material satisfies at least one of the following conditions: (1) The mass of the fast ion conductor reactant accounts for 1%-5% of the mass of the porous carbon material; Optionally, the mass of the fast ion conductor reactant can be any value between 1%, 2%, 3%, 4%, 5% or 1-5% of the mass of the porous carbon material; (2) The mass ratio of the fast ion conductor reactant to the lithium source is 1:1-5; Optionally, the mass ratio of the fast ion conductor reactant to the lithium source can be any value between 1:1, 1:2, 1:3, 1:4, 1:5, or 1:1-5; (3) The vacuum degree of the vacuum environment is 0 MPa to -1 MPa; Optionally, the vacuum level of the vacuum environment can be 0 MPa, -0.5 MPa, -1 MPa, or any value between 0 MPa and -1 MPa; It should be noted that a vacuum level of 0 MPa to -1 MPa in the vacuum environment allows the synthesis solution of the fast ion conductor to fully wet the interior of the porous carbon material. (4) The dropping rate of the aqueous solution of the lithium source is 1-2 mL / min; Optionally, the dropping rate of the lithium source aqueous solution can be any value between 1 mL / min, 1.5 mL / min, 2 mL / min, or 1-2 mL / min; (5) The reaction temperature is 25-60℃, the time is 5-12h, and the vacuum degree is ≤ -0.08MPa.

[0029] Optionally, the reaction temperature can be any value between 25℃, 30℃, 40℃, 50℃, 60℃ or 25-60℃, the reaction time can be any value between 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or 5-12h, and the vacuum degree can be any value between -1MPa, -0.09MPa, -0.08MPa or ≤ -0.08MPa.

[0030] In some embodiments, the preparation method of the fast-charging fumed silicon-carbon composite material satisfies at least one of the following conditions: (1) The temperature of the first heat treatment is 400-1000℃ and the time is 2-6h; Optionally, the temperature of the first heat treatment can be any value between 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃ or 400-1000℃, and the time can be any value between 2h, 3h, 4h, 5h, 6h or 2-6h. (2) The specific surface area of ​​the internal fast ion conductor layer is 1500-2500 m². 2 / g.

[0031] Optionally, the specific surface area of ​​the internal fast ion conductor layer can be 1500 m². 2 / g、2000 m 2 / g、2500m 2 / g or 1500-2500 m 2 Any value between / g.

[0032] In some embodiments, the carbon-coated porous carbon material has a particle size of 5-20 μm and a specific surface area of ​​1-5 m². 2 / g.

[0033] Optionally, the particle size of the carbon-coated porous carbon material can be any value between 5 μm, 10 μm, 15 μm, 20 μm, or 5-20 μm, and the specific surface area can be 1 m². 2 / g、2 m 2 / g、3 m 2 / g、4 m 2 / g、5 m 2 / g or 1-5m 2 Any value between / g.

[0034] In some embodiments, the preparation method of the fast-charging fumed silicon-carbon composite material satisfies at least one of the following conditions: (1) The mass of the interface-modifying compound accounts for less than 5% of the total mass of the carbon-coated porous carbon material; Optionally, the mass of the interface-modifying compound can be any value of 1%, 2%, 3%, 4%, 5% or less of the total mass of the carbon-coated porous carbon material. (2) The inlet air temperature of the spray granulation is 100-300℃, the outlet air temperature is 60-150℃, the atomization pressure is 0.1-1 MPa, and the solid content of the slurry is 5%-30%; Optionally, the inlet air temperature of the spray granulation can be any value between 100℃, 200℃, 300℃ or 100-300℃, the outlet air temperature can be any value between 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or 60-150℃, the atomization pressure can be any value between 0.1 MPa, 0.5 MPa, 1 MPa or 0.1-1 MPa, and the slurry solid content can be any value between 5%, 10%, 15%, 20%, 25%, 30% or 5-30%. (3) The temperature of the second heat treatment is 100-600℃ and the time is 1-10h.

[0035] Optionally, the temperature of the second heat treatment can be any value between 100℃, 200℃, 300℃, 400℃, 500℃, 600℃ or 100-600℃, and the time can be any value between 1h, 5h, 10h or 1-10h.

[0036] A third aspect of this application provides a lithium-ion battery comprising the aforementioned fast-charging fumed silicon-carbon composite material.

[0037] A fourth aspect of this application provides an electrical device including the aforementioned lithium-ion battery.

[0038] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0039] Example 1 This embodiment provides a fast-charging fumed silicon-carbon composite material, comprising a core 100 and a first fast ion conductor layer 200, a carbon coating layer 300, and an interface modification layer 400 sequentially disposed on the surface of the core 100; a specific structural diagram is shown below. Figure 1 As shown.

[0040] The core includes a porous carbon skeleton 110, and a second fast ion conductor layer 120 is disposed in the cavity of the porous carbon skeleton 110. The second fast ion conductor layer 120 contains silicon particles 130 and fast ion conductor particles 140. The raw materials for the first fast ion conductor layer 200, the second fast ion conductor layer 120, and the fast ion conductor particles 140 include fast ion conductor reactants and a lithium source; the fast ion conductor reactant is ammonium dihydrogen phosphate; and the lithium source is lithium carbonate. The interface modification layer 400 consists of single-walled carbon nanotubes and titanium dioxide; The thickness of the first fast ion conductor layer 200 is 0.1-5 nm; The thickness of the second fast ion conductor layer 120 is 0.5-1.5 nm; The carbon coating 300 has a thickness of 10 nm; The thickness of the interface modification layer 400 is 2-5 nm; among them, single-walled carbon nanotubes are uniformly embedded and interwoven in the titanium dioxide interface modification layer (thickness of about 2-5 nm) (the mass content of single-walled carbon nanotubes is about 0.5% of the total mass of the fast-charging fumed silicon-carbon composite material), and the single-walled carbon nanotubes form a local three-dimensional conductive network structure.

[0041] The fast-charging fumed silicon-carbon composite material has a silicon content of 50% by mass, a particle size of 8-18 μm, and a specific surface area of ​​2-5 m². 2 / g, pore volume 0.5-1.2cm 3 / g, tap density is approximately 0.8-1.0 g / cm³. 3 .

[0042] The second aspect of this embodiment provides a method for preparing a fast-charging fumed silicon-carbon composite material, the specific preparation steps of which are as follows: S1. Spherical porous carbon material powder was selected as the carbon substrate, with a particle size D50 of 8 μm and a total pore volume of 1.2 cm³. 3 / g, specific surface area is 2200m² 2 / g, weigh 100g of porous carbon material and disperse it in 1000mL of anhydrous ethanol (solid content about 10%), and stir to form a homogeneous mixed solution; use lithium carbonate as the lithium source and ammonium dihydrogen phosphate as the phosphorus source to synthesize lithium phosphate according to the stoichiometric ratio. The amount of lithium phosphate synthesized is 3% of the mass of porous carbon material (i.e., the theoretical amount of lithium phosphate produced is 3g). Weigh about 1.11g of lithium carbonate and dissolve it in 50mL of deionized water, and stir until completely dissolved to obtain the lithium source solution; weigh about 3.45g of ammonium dihydrogen phosphate and dissolve it in 50mL of deionized water, and stir until completely dissolved to obtain the phosphorus source solution; S2. Vacuum Impregnation and Reaction: Transfer the ethanol mixture solution of porous carbon material to a reactor equipped with a vacuum feeder and a stirring device. Turn on the electric stirrer and maintain a stirring speed of 200-400 rpm. Transfer the prepared phosphorus source solution to the first vacuum feeder and the lithium source solution to the second vacuum feeder. Turn on the vacuum pump for vacuum impregnation. Adjust the vacuum line switch according to the bubble size and boiling degree to ensure that the mixed solution does not boil violently or splash. After the vacuum pressure drops below -0.08 MPa, turn off the vacuum pump switch and maintain a vacuum environment. After the mixed solution no longer produces bubbles or boils, turn on the first vacuum feeder and slowly add ammonium dihydrogen phosphate solution. Maintain stirring for 2 hours to ensure that the phosphorus source and porous carbon material are fully mixed and homogeneous. After the phosphorus source and porous carbon material are homogeneous, turn on the second vacuum feeder containing the lithium source solution and slowly add lithium carbonate solution, controlling the dropping rate to about 1-2 mL / min. S3: After all the lithium source solution has been added, maintain a vacuum (below -0.08 MPa) and continue the reaction for 12 hours at 60°C to ensure the lithium phosphate precursor fully infiltrates the pores of the porous carbon material. After the reaction, filter the mixture, collect the filter cake, and dry it in an 80°C vacuum oven for 12 hours. Place the dried material in a tube furnace and heat-treat it under a nitrogen atmosphere, raising the temperature to 600°C at a rate of 5°C / min and holding it for 4 hours to fully convert the precursor into a fast-ion conductor of lithium phosphate. After the heat treatment, allow it to cool naturally to room temperature and pass the product through a 200-mesh sieve to obtain a porous carbon material containing a fast-ion conductor of lithium phosphate. S4: The porous carbon material containing lithium phosphate obtained through the above steps has a lithium phosphate layer coated on its surface, and lithium phosphate layers and lithium phosphate particles are disposed in the cavity. The overall particle size of the porous carbon material containing lithium phosphate is 5-15 μm, and the pore volume is 1.0 cm³. 3 / g, specific surface area is 2100m² 2 / g, the thickness of the lithium phosphate layer in the cavity is about 0.5-1.5nm, and it is uniformly distributed on the inner wall of the pores of the porous carbon material; S5. Preparation of porous carbon material containing lithium phosphate in vapor phase deposition: The porous carbon material containing lithium phosphate obtained in S4 is transferred to a fluidized bed reactor. First, high-purity nitrogen (purity ≥99.999%) is introduced as a carrier gas at a flow rate of 2-5 L / min for 30 minutes to completely replace the air in the equipment and bring the porous carbon material to a stable fluidized state. The fluidized bed reactor is then heated to 500℃ at a heating rate of 5℃ / min. After the temperature stabilizes, silane gas is introduced to cause the silane to decompose and deposit within the pores of the porous carbon material, completing the internal silicon loading. After deposition, the silane gas supply is immediately stopped, and nitrogen carrier gas is continuously introduced to purge any remaining silane gas for 30 minutes. S6. Adjust the temperature of the fluidized bed reactor to 550℃. After the temperature stabilizes, introduce acetylene (C2H2) gas to form a carbon coating layer on the material surface. This prevents the carbon layer from breaking down and causing side reactions during the subsequent liquid-phase coating process. After coating is completed, stop introducing acetylene gas and continue introducing nitrogen carrier gas. Cool down to room temperature under a protective atmosphere. Remove the prepared vapor-deposited silicon-carbon material from the fluidized bed reactor to obtain a vapor-phase silicon-carbon material containing lithium phosphate fast ion conductors. The silicon-carbon material containing lithium phosphate obtained through the above steps has a silicon content of approximately 50%, a particle size of 8-18 μm, and a specific surface area of ​​1 m². 2 / g, with a surface acetylene carbon coating thickness of approximately 15nm; S7. Interfacial modification and coating of titanium dioxide and single-walled carbon nanotube composites via liquid-phase method: Take 1.0 g of single-walled carbon nanotubes (SWCNTs, approximately 0.8-1.2 nm in diameter and 5-20 μm in length) (weighed as 1% of the mass of the fumed silicon-carbon material in S6), disperse it in 200 mL of anhydrous ethanol, and place the mixture in an ultrasonic dispersion device. Ultrasonic dispersion is performed for 30 minutes at a power of 500 W and a frequency of 40 kHz to obtain a uniform and stable pre-dispersion of single-walled carbon nanotubes; add 100 g of the fumed silicon-carbon material containing lithium phosphate obtained in S6 to 1000 mL of anhydrous ethanol. In a mixed solvent of anhydrous ethanol and deionized water (volume ratio of anhydrous ethanol to deionized water = 9:1), turn on the electric stirrer and stir at a speed of 300-500 rpm to disperse the gaseous silicon-carbon material evenly and form a suspension. Slowly add the pre-dispersed single-walled carbon nanotubes to the above suspension, maintain the stirring speed of 300-500 rpm, and stir for 30 minutes to ensure that the single-walled carbon nanotubes and silicon-carbon material are fully mixed evenly. Weigh 3.0 g of tetrabutyl titanate (Ti(OC4H9)4) (weighed as 5% of the mass of the gaseous silicon-carbon material in step 2), dilute it with 50 mL of anhydrous ethanol, and slowly add it dropwise to the above mixture. Meanwhile, 2.0 mL of deionized water was slowly added dropwise using a constant pressure dropping funnel to promote the hydrolysis and polycondensation reaction of tetrabutyl titanate. After the tetrabutyl titanate was completely added, stirring was continued for 2 hours to allow the titanium dioxide precursor sol and single-walled carbon nanotubes to uniformly coat the surface of the silicon-carbon material, forming a TiO2 / SWCNT composite precursor coating layer. S8. Transfer the above materials to the liquid storage tank of the closed-loop two-fluid spray granulation equipment, start the closed-loop two-fluid spray granulation equipment, and let hot nitrogen enter the drying chamber for preheating. Set the inlet temperature to 180℃, the outlet temperature to 120℃, the atomization pressure to 0.1MPa, and the liquid feed rate to 50mL / min. After the relevant parameters reach the set values, the pre-prepared liquid is transported to the atomizer through the liquid feed system. After the material is atomized, it enters the drying chamber. The droplets are instantly dried in the hot air flow to form spherical particles, which enter the collection hopper with the air flow. S9. The material collected in the hopper is taken out and transferred to a tube furnace. Under nitrogen atmosphere protection, it is heat-treated to 400°C at a heating rate of 5°C / min and held for 3 hours to completely convert the tetrabutyl titanate precursor into anatase titanium dioxide coating. The single-walled carbon nanotubes maintain structural integrity during the inert atmosphere heat treatment and form a three-dimensional conductive network with the TiO2 coating. After the heat treatment is completed, it is naturally cooled to room temperature and the product is passed through a 200-mesh sieve to obtain a fast-charging fumed silicon-carbon composite material with an internal lithium phosphate fast ion conductor, a surface composite coating fast ion conductor layer, a carbon layer, titanium dioxide, and a single-walled carbon nanotube interface modification layer.

[0043] SEM images of this fast-charging fumed silicon-carbon composite material are shown below. Figure 2As shown.

[0044] Example 2 The difference from Example 1 is that in the preparation process of S1, lithium carbonate is used as the lithium source and tetrabutyl titanate is used as the fast ion conductor reactant.

[0045] Example 3 The difference from Example 1 is that in step S7, the graphene and titanate composite interface modification coating is performed by liquid phase method.

[0046] Comparative Example 1 The difference from Example 1 is that steps S1-S4 are omitted, and the porous carbon material is directly subjected to step S5 for silicon deposition.

[0047] Comparative Example 2 The difference from Example 1 is that no fast ion conductor reactant is added in steps S1-S4.

[0048] Comparative Example 3 The difference from Example 1 is that no lithium source is added in steps S1-S4.

[0049] Comparative Example 4 The difference from Example 1 is that step S6 is not performed, that is, no carbon coating layer is provided.

[0050] Comparative Example 5 The difference from Example 1 is that step S7 is not performed, that is, the interface modification layer is not set.

[0051] The fast-charging fumed silicon-carbon composite materials provided in the above embodiments and comparative examples were coated on copper foil to form electrode sheets. Specifically, silicon-carbon anode material, conductive carbon, carbon nanotubes, and polyacrylic acid were mixed in a ratio of 82:10:1:7 and prepared into a slurry using a high-speed disperser. A PP2400 separator was used, and a lithium metal sheet was used as the counter electrode. The resulting 2032 coin cell batteries were assembled. The electrochemical performance of the batteries was tested, and the specific electrochemical performance test results are shown in Table 1.

[0052] Electrochemical performance testing method: The first, second, and third cycles are performed using a 0.05C charge-discharge rate to fully activate the coin cells. Subsequent cycles are performed using one cycle each at 0.25C, 0.5C, 0.75C, 1C, 1.25C, 1.5C, 1.75C, and 2C. The voltage range for the re-discharge cycle test is 0.005V-1.5V.

[0053] Table 1 Electrochemical Performance Tests

[0054] analyze: As can be seen from the above tests, the capacity difference of all samples is very small at a low magnification of 0.05C. Examples 1-3 are slightly lower than Comparative Example 5. This is because a fast ion conductor layer and an interface modification layer were introduced into the material, which increased the mass ratio of inactive substances and slightly diluted the unit mass capacity. At a high magnification, the examples are significantly higher than the comparative example. At 1C, the retention rate of the examples was approximately 70%-71%, while that of the comparative examples was only 64%-66%, indicating a significant difference. At 2C, the difference widened further, with the retention rate of the examples still at 42%-43%, while that of the comparative examples was only 29%-34%. This demonstrates that examples 1-3 exhibit superior rate performance, reflecting the fast charging effect of this application. The fast ion conductor layer provides an efficient ion transport channel, while the carbon coating layer and interface modification layer suppress side reactions and structural degradation at high rates. The synergistic effect of these two layers effectively improves the transport kinetics and interface stability of the material, achieving excellent rate performance.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0056] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A fast-charging fumed silicon-carbon composite material, characterized in that, It includes a core and a first fast ion conductor layer, a carbon coating layer, and an interface modification layer sequentially disposed on the surface of the core; The core includes a porous carbon skeleton, and a second fast ion conductor layer is disposed within the cavity of the porous carbon skeleton. The second fast ion conductor layer contains silicon particles and fast ion conductor particles. The interface modification layer comprises organic polymers and / or inorganic compounds.

2. The fast-charging fumed silicon-carbon composite material according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The raw materials for the first fast ion conductor layer, the second fast ion conductor layer and the fast ion conductor particles include fast ion conductor reactants and lithium sources; the fast ion conductor reactants include at least one of lithium hydroxide, tetrabutyl titanate, ammonium dihydrogen phosphate, aluminum nitrate nonahydrate and ammonium fluoride; the lithium sources include at least one of lithium carbonate, aluminum hydroxide, lithium titanate, lithium phosphate, β-alumina, lithium aluminate and lithium fluoride; (2) The interface modification layer includes at least one of polyacrylic acid, graphene oxide, carbon nanotubes, lithium salt, aluminum salt, titanate, titanium dioxide and alumina; (3) The thickness of the first fast ion conductor layer is 0.1-5 nm; (4) The thickness of the second fast ion conductor layer is 0.1-2 nm; (5) The thickness of the carbon coating layer is 5-20 nm; (6) The thickness of the interface modification layer is 1-200 nm; (7) The particle size of the fast-charging fumed silicon-carbon composite material is 5-20 μm, and the specific surface area is 1-10 m². 2 / g, pore volume 0.5-1.2cm 3 / g; (8) The silicon mass content of the fast-charging fumed silicon-carbon composite material is 40%-60%.

3. A method for preparing a fast-charging fumed silicon-carbon composite material as described in claim 1 or 2, characterized in that, include: Porous carbon material and solvent are mixed to obtain a porous carbon material dispersion; In a vacuum environment, an aqueous solution of the fast ion conductor reactant and a dispersion of the porous carbon material are mixed to obtain a mixture; an aqueous solution of the lithium source is added dropwise to the mixture, and the mixture is reacted, separated into solid and liquid, and dried to obtain the dried material. Under a nitrogen atmosphere, the dried material is subjected to a first heat treatment to obtain a porous carbon material containing a fast ion conductor layer inside. A fluidized bed chemical vapor deposition process is used to deposit silane gas in a nitrogen atmosphere into the pores of a porous carbon material containing a fast ion conductor layer, thereby obtaining a deposited porous carbon material. Acetylene is introduced to coat the surface of the deposited porous carbon material, thereby obtaining a carbon-coated porous carbon material. The interface modification compound and the carbon-coated porous carbon material are mixed and spray-granulated to obtain the granulated porous carbon material. Under an inert atmosphere, the granulated porous carbon material is subjected to a second heat treatment to obtain a fast-charging fumed silicon-carbon composite material.

4. The method for preparing the fast-charging fumed silicon-carbon composite material according to claim 3, characterized in that, At least one of the following conditions must be met: (1) The particle size of the porous carbon material is 1-20 μm; (2) The porous carbon material includes biomass-based porous carbon material and / or petroleum coke-based porous carbon material; (3) The total pore volume of the porous carbon material is 0.6-1.5 cm³. 3 / g, specific surface area is 1500-3000m² 2 / g; (4) The solvent includes at least one of water, ethanol, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone and tetrahydrofuran; (5) The solid content of the porous carbon material dispersion is 1-10%.

5. The method for preparing the fast-charging fumed silicon-carbon composite material according to claim 3, characterized in that, At least one of the following conditions must be met: (1) The mass of the fast ion conductor reactant accounts for 1%-5% of the mass of the porous carbon material; (2) The mass ratio of the fast ion conductor reactant to the lithium source is 1:1-5; (3) The vacuum level of the vacuum environment is 0 MPa to -1 MPa; (4) The dropping rate of the aqueous solution of the lithium source is 1-2 mL / min; (5) The reaction temperature is 25-60℃, the time is 6-12h, and the vacuum degree is ≤ -0.08MPa.

6. The method for preparing the fast-charging fumed silicon-carbon composite material according to claim 3, characterized in that, At least one of the following conditions must be met: (1) The temperature of the first heat treatment is 400-1000℃ and the time is 2-6h; (2) The specific surface area of ​​the internal fast ion conductor layer is 1500-2500 m². 2 / g.

7. The method for preparing the fast-charging fumed silicon-carbon composite material according to claim 3, characterized in that, The carbon-coated porous carbon material has a particle size of 5-20 μm and a specific surface area of ​​1-5 m². 2 / g.

8. The method for preparing the fast-charging fumed silicon-carbon composite material according to claim 3, characterized in that, At least one of the following conditions must be met: (1) The mass of the interface-modifying compound accounts for less than 5% of the total mass of the carbon-coated porous carbon material; (2) The inlet air temperature of the spray granulation is 100-300℃, the outlet air temperature is 60-150℃, the atomization pressure is 0.1-1 MPa, and the solid content of the slurry is 5%-30%; (3) The temperature of the second heat treatment is 100-600℃ and the time is 1-10h.

9. A lithium-ion battery, characterized in that, Including the fast-charging fumed silicon-carbon composite material as described in claim 1 or 2.

10. An electrical appliance, characterized in that, Including the lithium-ion battery as described in claim 9.

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