Silicon-carbon negative electrode material with cavity, preparation method of silicon-carbon negative electrode material, lithium ion battery and electric equipment

Abstract

The invention provides a silicon-carbon negative electrode material with a cavity, a preparation method of the silicon-carbon negative electrode material, a lithium ion battery and electric equipment, and relates to the field of lithium ion batteries. The silicon-carbon negative electrode material with the cavity comprises an inner core and a coating layer arranged on the surface of the inner core, the inner core comprises a cavity and a plurality of nano silicon particles; a first carbon layer is arranged on the surface of each nano silicon particle; the cavities are positioned among the nano silicon particles, among the first carbon layers and between the nano silicon particles and the first carbon layers; a catalyst layer is arranged on the inner surface of the cavity, and a carbon nano tube is arranged in the cavity; the coating layer comprises a second carbon layer; the first carbon layer and the second carbon layer include graphitized carbon layers. The silicon-carbon negative electrode material with the cavity has a cavity structure, the cavity has the effect of buffering expansion in the physical and chemical process of a silicon-carbon negative electrode, and the dual effects of the carbon nanotubes and the second carbon layer ensure the stability of the material under the mechanical effects of rolling, expansion and the like, so that the material can exert excellent electrochemical performance.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and more particularly to a silicon-carbon anode material with a cavity, a method for preparing the same, a lithium-ion battery, and an electrical device thereof. Background Technology

[0002] Lithium-ion batteries, with their advantages of high voltage, high energy density, long cycle life, and environmental friendliness, have been widely used in portable electronic products and new energy vehicles. At the same time, the energy density requirements for lithium-ion batteries are becoming increasingly stringent. Traditional lithium-ion battery anode materials are graphite, but graphite's theoretical capacity is only 372 mAh / g, which cannot meet the growing demand for energy density. Among the many anode materials that meet the requirements of high-energy lithium-ion batteries, silicon-based anode materials have advantages such as high theoretical specific capacity, reasonable charge / discharge voltage, good safety performance, and abundant sources, making them a promising candidate to replace graphite as the next-generation lithium-ion battery anode material. However, silicon anodes also have drawbacks. For example, as a semiconductor, silicon has poor conductivity, resulting in poor rate performance when used directly as an anode material. Furthermore, silicon exhibits severe volume expansion during lithium insertion / extraction / deintercalation, leading to a series of adverse consequences, such as rapid capacity decay and poor cycle performance, which seriously hinders the practical application of silicon-based anode materials.

[0003] Based on the issues of volume expansion and low conductivity during the lithium insertion / extraction process of silicon anodes, researchers have found that when the silicon particle size is less than 150nm, the particles will not break due to volume effects. Carbon coating can then significantly improve its conductivity and cycle performance. However, nano-silicon particles have a large specific surface area and low tap density. Therefore, the current process uses a combination of nano-silicon particles and carbon sources for spray granulation followed by high-temperature sintering to form silicon-carbon composite materials. This process can form a simple coating on silicon-based anode materials and reduce their specific surface area while increasing their tap density. However, during the high-temperature sintering process, due to the influence of the volatile components of the coated carbon source, cavities will be generated inside the material particles, and the specific surface area will still be large. Although the presence of cavities can alleviate the volume expansion of silicon-based anode materials during cycling to some extent, it will also cause more side reactions during lithiation, poor conductivity and ion conduction, and material breakage under high-pressure compaction, which cannot meet the application scenarios of silicon-based anode materials in lithium batteries. Therefore, the coating of silicon anode materials must not only alleviate the volume expansion effect of silicon-based materials, but also maintain the ionic / electronic conductivity of the materials. Thus, simple spray coating cannot effectively improve the electrochemical performance of silicon-carbon materials.

[0004] Therefore, there is an urgent need to provide a silicon-carbon anode material to solve the above problems. Summary of the Invention

[0005] The purpose of this application is to provide a silicon-carbon anode material with a cavity, a method for preparing the same, a lithium-ion battery, and an electrical device, in order to solve the above-mentioned problems.

[0006] To achieve the above objectives, the first aspect of this application provides a silicon-carbon anode material with a cavity, comprising a core and a coating layer disposed on the surface of the core; The core includes a cavity and multiple nano-silicon particles; a first carbon layer is disposed on the surface of the nano-silicon particles; the cavity is located between the nano-silicon particles, between the first carbon layers, and between the nano-silicon particles and the first carbon layer. A catalyst layer is disposed on the inner surface of the cavity, and carbon nanotubes are disposed inside the cavity; The coating layer includes a second carbon layer; The first carbon layer includes an amorphous carbon layer; The second carbon layer includes a graphitized carbon layer.

[0007] Optionally, the silicon-carbon anode material with a cavity satisfies at least one of the following conditions: A. The particle size of the silicon-carbon anode material with cavities is 1μm-10μm; B. The specific surface area of ​​the hollow silicon-carbon anode material is 1-200 m². 2 / g; C. The porosity of the silicon-carbon anode material with cavities is greater than 0% and less than or equal to 10%; D. The thickness of the second carbon layer is 2-10 nm; E. The thickness of the first carbon layer is 0.1-2 nm; F. The mass of the carbon nanotubes accounts for 5%-15% of the mass of the hollow silicon-carbon anode material; G. The mass of the nano-silicon particles accounts for more than 0 and less than or equal to 40% of the mass of the cavity-containing silicon-carbon anode material.

[0008] A second aspect of this application provides a method for preparing the cavity-containing silicon-carbon anode material described above, comprising: Nano-silicon particles, a first carbon source, and a second carbon source are first mixed to obtain a first mixture. The first mixture is then spray-dried and first sintered to obtain a first material with a cavity. The first material, catalyst, and first solvent are mixed in a second way to obtain a second mixture. The second mixture is then subjected to a first vacuum impregnation and curing to obtain a second material. The second material, the third carbon source, and the second solvent are mixed in a third way to obtain a third mixture. The third mixture is then subjected to a second vacuum impregnation and drying to obtain a fourth material. Under a protective atmosphere, the fourth material is then subjected to a second sintering to obtain a silicon-carbon anode material with a cavity. The residual carbon rate of the first carbon source is greater than that of the second carbon source.

[0009] Optionally, the method for preparing the cavity-type silicon-carbon anode material satisfies at least one of the following conditions: A. The D50 of the nano-silicon particles is 10nm-200nm; B. The residual carbon content of the first carbon source is ≥40%; C. The residual carbon content of the second carbon source is less than 40%; D. The mass ratio of the first carbon source to the second carbon source is 1:1-5; E. The total mass ratio of the first carbon source and the second carbon source to the mass ratio of the nano-silicon particles is 0.3-1:1; H. The porosity of the first material is 30%-40%.

[0010] Optionally, the method for preparing the cavity-type silicon-carbon anode material satisfies at least one of the following conditions: A. The first carbon source includes one or more of phenolic resin, polypyrrole, polyacrylonitrile, and pitch; B. The second carbon source comprises one or more of polyethylene glycol, polyvinylpyrrolidone, sodium carboxymethyl cellulose, polydopamine, glucose, and sucrose. Optionally, the method for preparing the cavity-shaped silicon-carbon anode material satisfies at least one of the following conditions: A. The catalyst comprises nickel salt compounds and / or iron salt compounds; B. The first solvent, the second solvent, and the third solvent are each independently one or more of water, ethanol, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran; C. The mass of the catalyst is 1%-10% of the mass of the first material; D. The solid content of the second mixture is 10%-50%; E. The mass of the third carbon source is 10%-20% of the mass of the second material; F. The third carbon source includes pitch-based carbon materials and / or soluble polymer materials.

[0011] Optionally, the method for preparing the cavity-type silicon-carbon anode material satisfies at least one of the following conditions: A. The nickel salt compounds include one or more of nickel chloride, nickel sulfate, nickel nitrate, nickel acetate, nickel phosphate, and nickel carbonate; B. The iron salt compounds include one or more of ferric chloride, ferric sulfate, ferric nitrate, and ferric carbonate; C. The third carbon source includes one or more of phenolic resin, epoxy resin, polypropylene pyrrolidone, sodium carboxymethyl cellulose, polyvinyl alcohol, polyethylene oxide, and polyacrylonitrile.

[0012] Optionally, the method for preparing the cavity-type silicon-carbon anode material satisfies at least one of the following conditions: A. The temperature of the first sintering is 600℃-1000℃, and the time is 2h-4h; B. The pressure of the first vacuum impregnation is -0.8 MPa to -1 MPa, and the time is 10 min to 5 h; C. The curing temperature is 600℃-700℃, and the time is 1h-2h; D. The pressure of the second vacuum impregnation is -0.4 MPa to -0.5 MPa, and the time is 10 min to 5 h; E. The second sintering includes sequential low-temperature sintering and high-temperature sintering; The low-temperature sintering temperature is 500℃-700℃, and the time is 1h-4h; The high-temperature sintering temperature is 900℃-1000℃, and the time is 2h-4h.

[0013] A third aspect of this application provides a lithium-ion battery, comprising the aforementioned silicon-carbon anode material with a cavity or the silicon-carbon anode material with a cavity prepared by the aforementioned method for preparing silicon-carbon anode material.

[0014] A fourth aspect of this application provides an electrical device including the aforementioned lithium-ion battery.

[0015] Compared with the prior art, the beneficial effects of this application include: The cavity-based silicon-carbon anode material provided in this application has several key features. First, the core has a cavity structure, which buffers the expansion of the silicon-carbon anode during the physicochemical process. Second, the carbon nanotubes formed inside the cavity effectively enhance the structural stability of the material and provide diffusion channels for electrons and ions. Furthermore, the first carbon layer not only improves the conductivity of the silicon material but also effectively alleviates the volume expansion of silicon during lithium intercalation and provides a carbon source for the catalytic generation of carbon nanotubes. Then, the second carbon layer covering the core surface is graphitized carbon, which effectively reduces the specific surface area of ​​the material, minimizes side reactions, and maintains the overall structural stability of the material. The combined effect of the carbon nanotubes and the second carbon layer ensures the stability of the material under mechanical forces such as rolling and expansion, enabling the material to exhibit excellent electrochemical performance.

[0016] The method for preparing a cavity-based silicon-carbon anode material provided in this application involves adding two different carbon source materials. After a first sintering process, the carbon source with a lower residual carbon rate volatilizes to form a cavity, while the carbon source with a higher carbonization rate coats the surface of the nano-silicon particles, together forming the framework structure of the entire particle. Then, a catalyst is uniformly loaded into the cavity through vacuum impregnation. During the curing process, the catalyst's ability to catalyze the carbon layer is utilized to form interconnected carbon nanotubes inside the cavity, constructing a rapid diffusion channel for ions / electrons, effectively improving the structural stability of the material. Finally, a stable graphitized carbon layer is formed through the coating of a third carbon source.

[0017] The lithium-ion battery and electrical equipment provided in this application have excellent cycle performance and rate performance. Attached Figure Description

[0018] 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.

[0019] Figure 1 This is a schematic diagram of the structure of the silicon-carbon anode material with a cavity provided in Example 1; Figure 2 SEM image of the cavity-containing silicon-carbon anode material provided in Example 1.

[0020] Explanation of key component symbols: 100-nanometer silicon particles; 200-first carbon layer; 300-cavity; 400-catalyst layer; 500-carbon nanotubes; 600-second carbon layer. Detailed Implementation

[0021] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0022] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0023] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0024] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0025] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0026] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0027] The first aspect of this application provides a silicon-carbon anode material with a cavity, including a core and a coating layer disposed on the surface of the core; The core includes a cavity and multiple nano-silicon particles; a first carbon layer is disposed on the surface of the nano-silicon particles; the cavity is located between the nano-silicon particles, between the first carbon layers, and between the nano-silicon particles and the first carbon layer. A catalyst layer is disposed on the inner surface of the cavity, and carbon nanotubes are disposed inside the cavity; The coating layer includes a second carbon layer; The first carbon layer includes an amorphous carbon layer; The second carbon layer comprises a graphitized carbon layer. In some embodiments, the cavity-containing silicon-carbon anode material satisfies at least one of the following conditions: A. The particle size of the silicon-carbon anode material with cavities is 1μm-10μm; Optionally, the particle size of the silicon-carbon anode material with cavities can be any value between 1μm, 2μm, 4μm, 6μm, 8μm, 10μm or 1μm-10μm; B. The specific surface area of ​​the hollow silicon-carbon anode material is 1-200 m². 2 / g; Optionally, the specific surface area of ​​the silicon-carbon anode material with cavities can be 1 m². 2 / g, 10m 2 / g, 50m 2 / g, 100m 2 / g, 150m 2 / g、200m 2 / g or 1-200m 2 Any value between / g; C. The porosity of the silicon-carbon anode material with cavities is greater than 0% and less than or equal to 10%; Optionally, the porosity of the silicon-carbon anode material with cavities can be any value between 0.01%, 0.1%, 1%, 2%, 4%, 6%, 8%, 10%, or greater than 0% and less than or equal to 10%. Preferably, the porosity of the silicon-carbon anode material with cavities is 8%-10%; It should be noted that since silicon-based anode materials undergo a 300% volume expansion during charging and discharging, setting 8%-10% voids in the prepared silicon-carbon anode can serve as a buffer space for expansion, reduce stress concentration during lithium insertion / extraction, prevent material cracking, maintain the overall structural stability of the particles, and improve the cycle performance of the material; D. The thickness of the second carbon layer is 2-10 nm. Optionally, the thickness of the second carbon layer can be any value between 2nm, 4nm, 6nm, 8nm, 10nm, or 2-10nm; It should be noted that the second carbon layer is formed by the first carbon layer and the subsequent carbon source under high temperature catalysis in the presence of a catalyst. Therefore, the overall thickness of the second carbon layer is relatively high. Since the second carbon layer needs to maintain the overall structural stability of the material, it needs to have high strength. In addition, the second carbon layer also plays the role of reducing the overall specific surface area, isolating the penetration of electrolyte, and reducing the occurrence of side reactions in the material. E. The thickness of the first carbon layer is 0.1-2 nm; Optionally, the thickness of the first carbon layer can be any value between 0.1 nm, 0.5 nm, 1 nm, 2 nm, or 0.1-2 nm. It should be noted that the first carbon layer is formed during spray granulation and sintering. Its main function is to improve the conductivity of silicon. Since silicon has poor conductivity, carbon coating can provide a continuous electron transport path and reduce the internal resistance of the electrode. In addition, the presence of the carbon shell can also prevent silicon from oxidizing or agglomerating during cycling, ensuring the dispersion of active materials. F. The mass of the carbon nanotubes accounts for 5%-15% of the mass of the hollow silicon-carbon anode material; Optionally, the mass of carbon nanotubes can be any value between 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or between 5% and 15% of the mass of the hollow silicon-carbon anode material. It is important to note that carbon nanotubes possess excellent electronic and ionic conductivity. Incorporating carbon nanotubes into the material can significantly improve its conductivity, optimize ion migration pathways, and enhance its mechanical properties (tensile strength ~50-200 GPa). This reduces volume changes of the active material during charging and discharging, thus improving the material's cycle life. Furthermore, because the carbon nanotubes are located within the cavity, they enhance the structural stability of the material under mechanical forces such as rolling expansion. G. The mass of the nano-silicon particles accounts for a greater than 0 and less than or equal to 40% of the mass of the cavity-containing silicon-carbon anode material.

[0028] Optionally, the mass of the nano-silicon particles can be any value between 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or greater than 0 and less than or equal to 40% of the mass of the silicon-carbon anode material with cavities.

[0029] Preferably, the mass of the nano-silicon particles accounts for 30%-40% of the mass of the silicon-carbon anode material with cavities.

[0030] A second aspect of this application provides a method for preparing the cavity-containing silicon-carbon anode material described above, comprising: Nano-silicon particles, a first carbon source, and a second carbon source are first mixed to obtain a first mixture. The first mixture is then spray-dried and first sintered to obtain a first material with a cavity. The first material, catalyst, and first solvent are mixed in a second way to obtain a second mixture. The second mixture is then subjected to a first vacuum impregnation and curing to obtain a second material. It is important to note that the catalyst catalyzes the carbon in the first material. Catalytic graphitization is a complex multi-stage catalytic reaction and transport process. When the catalyst is located on the surface of the carbon material, it dissolves and rearranges the carbon material during catalysis, forming carbon nanotubes. When the catalyst is located inside the carbon material, it also dissolves and rearranges the carbon material, but forms a dense graphitized carbon layer. When the catalyst solution enters the particle through impregnation, the solvent is removed by evaporation, and the catalyst is loaded onto the carbon surface within the pores. During high-temperature catalysis, interconnected carbon nanotubes are generated within the pores. It is also important to note that the curing process is specifically for curing the catalyst. The silicon-carbon anode material with cavities undergoes a total of three sintering processes (the first sintering...). The process involves three stages: solidification, sintering, and second sintering. The primary purpose of the second sintering is to solidify the catalyst. When loading the catalyst, the catalyst-formed metal salt is loaded. For example, nickel acetate is used as a catalyst, but the actual active component is the nickel atoms in the nickel acetate. Nickel acetate dissolves in water, but at high temperatures, it decomposes to form nickel oxide. Elemental nickel does not dissolve in solvents such as water. Therefore, low-temperature sintering at 500℃-700℃ decomposes and solidifies the catalyst on the surface of the carbon layer, preventing it from dissolving and falling off during the third impregnation of the outermost carbon source. Carbon catalysis (high-temperature sintering) occurs at 900℃-1000℃, so the second sintering at a lower temperature allows the catalyst to decompose into a form insoluble in solvents without catalyzing the carbon layer. In some embodiments, prior to curing, the mixture obtained from the first vacuum impregnation is further evaporated at a temperature of 50°C-100°C; The second material, the third carbon source, and the second solvent are mixed in a third way to obtain a third mixture. The third mixture is then subjected to a second vacuum impregnation and drying to obtain a fourth material. Under a protective atmosphere, the fourth material is then subjected to a second sintering to obtain a silicon-carbon anode material with a cavity. In some embodiments, the drying temperature is 50°C-100°C; The residual carbon rate of the first carbon source is greater than that of the second carbon source.

[0031] It is important to note that different carbon sources have different proportions of hydrogen (H) and oxygen (O) atoms. Carbon sources with higher residual carbon content have lower proportions of hydrogen and oxygen atoms, resulting in a higher carbonization rate. Therefore, when two carbon sources with different residual carbon content are mixed together, at the same sintering temperature, the carbon source with lower residual carbon content will release more space, while the carbon source with higher residual carbon content will form the framework of the entire particle together with the silicon particles, supporting the overall structure.

[0032] In some embodiments, the method for preparing the cavity-containing silicon-carbon anode material satisfies at least one of the following conditions: A. The D50 of the nano-silicon particles is 10nm-200nm; Optionally, the D50 of the silicon nanoparticles can be any value between 10nm, 50nm, 100nm, 150nm, 200nm, or 10nm-200nm. In some embodiments, the raw materials for the nano-silicon particles include metallic silicon powder and / or flake metallic silicon sludge. For example, the metallic silicon powder and / or flake metallic silicon sludge are sand-milled to obtain nano-silicon particles with a D50 of 10nm-200nm. B. The residual carbon content of the first carbon source is ≥40%; Optionally, the residual carbon rate of the first carbon source can be any value of 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or ≥50%. C. The residual carbon content of the second carbon source is less than 40%; Optionally, the residual carbon rate of the second carbon source can be any value of 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 39% or less than 40%. D. The mass ratio of the first carbon source to the second carbon source is 1:1-5; Optionally, the mass ratio of the first carbon source to the second carbon source can be any value between 1:1, 1:2, 1:3, 1:4, 1:5, or 1:1-5; E. The total mass ratio of the first carbon source and the second carbon source to the mass ratio of the nano-silicon particles is 0.3-1:1; Optionally, the mass ratio of the total mass of the first carbon source and the second carbon source to the mass of the nano-silicon particles can be any value between 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, or 0.3:1. H. The porosity of the first material is 30%-40%.

[0033] Optionally, the porosity of the first material can be any value between 30%, 35%, 40%, or 30%-40%.

[0034] In some embodiments, the method for preparing the cavity-containing silicon-carbon anode material satisfies at least one of the following conditions: A. The first carbon source includes one or more of phenolic resin, polypyrrole, polyacrylonitrile, and pitch; B. The second carbon source includes one or more of polyethylene glycol, polyvinylpyrrolidone, sodium carboxymethyl cellulose, polydopamine, glucose, and sucrose.

[0035] In some embodiments, the method for preparing the cavity-containing silicon-carbon anode material satisfies at least one of the following conditions: A. The catalyst comprises nickel salt compounds and / or iron salt compounds; B. The first solvent, the second solvent, and the third solvent are each independently one or more of water, ethanol, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran; C. The mass of the catalyst is 1%-10% of the mass of the first material; Optionally, the mass of the catalyst can be any value between 1%, 2%, 4%, 6%, 8%, 10% or 1%-10% of the mass of the first material; D. The solid content of the second mixture is 10%-50%; Optionally, the solid content of the second mixture can be any value between 10%, 20%, 30%, 40%, 50%, or 10%-50%. E. The mass of the third carbon source is 10%-20% of the mass of the second material; Optionally, the mass of the third carbon source can be any value between 10%, 15%, 20%, or 10%-20% of the mass of the second material; F. The third carbon source includes pitch-based carbon materials and / or soluble polymer materials.

[0036] In some embodiments, the method for preparing the cavity-containing silicon-carbon anode material satisfies at least one of the following conditions: A. The nickel salt compounds include one or more of nickel chloride, nickel sulfate, nickel nitrate, nickel acetate, nickel phosphate, and nickel carbonate; It is worth noting that introducing nickel salts as catalysts during the graphitization of amorphous carbon can significantly reduce the graphitization temperature, increase the degree of graphitization, and optimize the performance of carbon materials. Traditional graphitization requires high temperatures (usually above 2500°C), while nickel-catalyzed graphitization can reduce the temperature to 800°C-1500°C. Furthermore, the graphitized carbon layer formed by the catalyst has higher conductivity and better mechanical strength. The graphitized carbon layer is more stable at high temperatures or in electrolytes, with fewer side reactions, thus avoiding excessive growth of the SEI. B. The iron salt compounds include one or more of ferric chloride, ferric sulfate, ferric nitrate, and ferric carbonate; It should be noted that iron salts have similar catalytic effects to nickel salts, but are cheaper and have lower costs, and their catalytic effect is slightly weaker than that of nickel salt catalysts. C. The third carbon source includes one or more of the following: pitch-based carbon materials, phenolic resin, polypropylene pyrrolidone, sodium carboxymethyl cellulose, polyvinyl alcohol, polyethylene oxide, and polyacrylonitrile.

[0037] It is important to note that the third carbon source needs to be soluble in water or other organic solvents so that it can be loaded by the impregnation method. As the outermost layer of the hollow silicon-carbon material, it needs to have a high residual carbon rate to completely cover the material surface, so that the material has a low specific surface area and reduces the occurrence of side reactions. As a carbon layer covering the catalyst surface, the coating layer prevents the catalyst from forming carbon nanotubes.

[0038] In some embodiments, the method for preparing the cavity-containing silicon-carbon anode material satisfies at least one of the following conditions: A. The temperature of the first sintering is 600℃-1000℃, and the time is 2h-4h; Optionally, the temperature of the first sintering can be any value between 600℃, 700℃, 800℃, 900℃, 1000℃ or 600℃-1000℃, and the time can be any value between 2h, 3h, 4h or 2h-4h. It is important to note that the primary purpose of the first sintering is to form a porous structure. The carbon source is carbonized through sintering. It is important to note that the sintering temperature should not be too high. If the sintering temperature is too high, it will make the subsequent catalyst catalysis more difficult. If the temperature is too low, it will be difficult to completely carbonize. Therefore, the temperature and time of the first sintering are set to ensure the carbonization temperature is guaranteed, and the time is extended to ensure that the carbon source is completely carbonized to form a porous structure. B. The pressure of the first vacuum impregnation is -0.8 MPa to -1 MPa, and the time is 10 min to 5 h; Optionally, the pressure of the first vacuum impregnation can be any value between -0.8 MPa, -9 MPa, -1 MPa, or -0.8 MPa and -1 MPa, and the time can be any value between 10 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, or 10 min to 5 h. It should be noted that -0.8 MPa to -1 MPa are gauge pressures, with -1 MPa being the lowest value displayed. In some embodiments, the first vacuum impregnation is carried out in a vacuum oven. With electric stirring, the vacuum pump is turned on to evacuate the air, and the reaction state of the second mixture is observed during the evacuation process. The vacuum pipeline switch is adjusted according to the bubble size and boiling degree to ensure that the organic solvent does not boil over or splash. It should also be noted that different vacuum levels result in different impregnation depths. When impregnating the catalyst, the vacuum pressure drop must be below -0.8 MPa, because the catalyst solution needs to penetrate deep into the pores to carry the catalyst atoms to the depths of the pores. When loading the catalyst, since it is impossible to completely load the catalyst into the pores, there will also be catalyst loading on the particle surface when the solvent evaporates. To prevent this part of the catalyst from catalyzing the original carbon to form carbon nanotubes, a final carbon coating is needed to press it down, and the whole is coated in the center of the carbon layer, so that it catalyzes the surface carbon to form a uniform and dense graphitized carbon layer (first carbon layer), changing the open pores into closed pores, reducing the overall specific surface area of ​​the particles, and improving the uniformity of its coating. C. The curing temperature is 600℃-700℃, and the time is 1h-2h; Optionally, the curing temperature can be any value between 600℃, 650℃, 700℃ or 600℃-700℃, and the time can be any value between 1h, 1.5h, 2h or 1h-2h. It should be noted that when the curing temperature is 600℃-700℃, it will promote the decomposition of the catalyst but will not catalyze the carbon layer. D. The pressure of the second vacuum impregnation is -0.4 MPa to -0.5 MPa, and the time is 10 min to 5 h; Optionally, the pressure of the second vacuum impregnation can be any value between -0.4 MPa, -0.45 MPa, -0.5 MPa, or -0.4 MPa and -0.5 MPa, and the time can be any value between 10 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, or 10 min to 5 h. It should be noted that when the third carbon source is used for carbon coating, the vacuum pressure is only required to drop from -0.4 MPa to -0.5 MPa. The main purpose is to allow the third carbon source solution to slightly wet the particles so that a certain amount of carbon source will remain on the surface of the open pores when the solution evaporates. It is not required to wet the particles to the depth of the pores. It should also be noted that -0.4 MPa to -0.5 MPa is the gauge pressure. In some embodiments, the second vacuum impregnation is carried out in a vacuum oven. With electric stirring, the vacuum pump is turned on to draw a vacuum. The reaction state of the third mixture is observed during the vacuuming process. The vacuuming pipeline switch is adjusted according to the bubble size and boiling degree to ensure that the organic solvent does not boil or splash. E. The second sintering includes sequential low-temperature sintering and high-temperature sintering; The low-temperature sintering temperature is 500℃-700℃, and the time is 1h-4h; Optionally, the temperature for low-temperature sintering can be any value between 500℃, 600℃, 700℃ or 500℃-700℃, and the time can be any value between 1h, 2h, 3h, 4h or 1h-4h. The high-temperature sintering temperature is 900℃-1000℃, and the time is 2h-4h.

[0039] Optionally, the high-temperature sintering temperature can be any value between 900℃, 950℃, 1000℃ or 900℃-1000℃, and the time can be any value between 2h, 3h, 4h or 2h-4h.

[0040] It should be noted that the two-stage sintering is divided into two phases. The temperature and time settings in the low-temperature sintering phase are mainly to promote catalyst decomposition and surface carbon source carbonization. The temperature and time settings in the high-temperature phase are beneficial to the internal amorphous carbon catalytic generation of carbon nanotubes and the graphitization of the surface amorphous carbon layer.

[0041] A third aspect of this application provides a lithium-ion battery, comprising the aforementioned silicon-carbon anode material with a cavity or the silicon-carbon anode material with a cavity prepared by the aforementioned method for preparing silicon-carbon anode material.

[0042] A fourth aspect of this application provides an electrical device including the aforementioned lithium-ion battery.

[0043] It should be noted that electrical equipment may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc.; among them, mobile devices may include, but are not limited to, at least one of mobile phones, laptops, etc.; electric vehicles may include, but are not limited to, at least one of pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0044] 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.

[0045] Example 1 This embodiment provides a silicon-carbon anode material with a cavity and its preparation method. The specific preparation steps are as follows: S1: Weigh 500g of silicon powder with a particle size of 3μm, and disperse it evenly in 5L of ethanol solution under electric stirring. Then, feed it into a sand mill using a feed pump and grind for 4 hours. When the particle size D50 is approximately 0.05μm, stop grinding and transfer the silicon slurry to a mixing tank. Continue electric stirring to prevent the silicon from settling and agglomerating. Weigh 100g of phenolic resin powder and add it to the ethanol solution. Stir until completely dissolved. Then, weigh 150g of polyethylene glycol and add it to the slurry. After it is completely dissolved, a mixed slurry containing phenolic resin and polyethylene glycol is obtained. S2: The mixed slurry obtained in step S1 above is fed into a closed-loop centrifugal spray granulation dryer by a feed pump for spray drying to obtain nano-silicon materials coated with polyethylene glycol and phenolic resin. S3: The above-mentioned polyethylene glycol and phenolic resin coated nano-silicon material is transferred to a tube furnace and heated to 600°C at a rate of 3°C / min. After holding at this temperature for 4 hours, a first material with cavities (porosity of 35%) is obtained. S4: Weigh 63.56g of nickel acetate and dissolve it in 1000g of ethanol. With electric stirring, after the nickel acetate is completely dissolved, a green and transparent solution is formed. Weigh 500g of the first material with cavities collected in S3 above and evenly disperse it in the ethanol solution containing nickel acetate. Transfer the mixed solution to a vacuum oven with electric stirring. Turn on the vacuum pump to evacuate the vacuum. Observe the reaction state of the mixture during the vacuuming process. Adjust the vacuum pipeline switch according to the bubble size and boiling degree to ensure that the ethanol solution does not boil over or splash. After the vacuum pressure drops below -0.8Mpa, turn off the vacuum pump switch and maintain the vacuum environment. Set the temperature to 25℃ and maintain room temperature. Stir for 24h. The first 2h is the time for the carbon source solution to impregnate the material, and the remaining 22h is the solvent evaporation time. The solution is blackish-green. Turn on the heating function of the vacuum oven and set the temperature to 80℃. Evaporate the ethanol solvent while stirring to obtain a dry material with catalyst coating. S5: The catalyst-coated material produced in S4 is collected, screened, and transferred to a tube furnace for solidification treatment. The temperature is increased to 600℃ at a rate of 3℃ / min and held for 2 hours to obtain the second material. S6: Weigh 100g of asphalt material with a soft point of 280 and a particle size of about 1μm, add it to 1L of tetrahydrofuran solvent, stir, and after the asphalt is completely dissolved, weigh 500g of the second material obtained in S5, add it to the tetrahydrofuran solution containing asphalt, transfer the mixed solution to a vacuum oven under electric stirring, turn on the vacuum pump to evacuate, observe the reaction state of the mixture during the vacuuming process, adjust the vacuum pipeline switch according to the bubble size and boiling degree to ensure that the ethanol solution does not boil over or splash, after the vacuum pressure drops below -0.4Mpa, turn off the vacuum pump switch, maintain the vacuum environment and stir for 1h, transfer the mixture outside the vacuum oven, heat the mixture under electric stirring until the tetrahydrofuran is completely volatilized, and obtain dry asphalt and catalyst-coated hollow nano-silicon carbon material; S7: The material produced in S6 is sieved and transferred to a tube furnace. It is heated to 600℃ at a rate of 33℃ / min and held for 2 hours. Then it is heated to 1000℃ and held for 4 hours to obtain a silicon-carbon anode material with a cavity.

[0046] The cavity-based silicon-carbon anode material includes a core and a coating layer disposed on the surface of the core; the core includes a cavity and multiple nano-silicon particles; a first carbon layer 200 is disposed on the surface of the nano-silicon particles 100; cavities 300 are located between the nano-silicon particles 100, between the first carbon layers 200, and between the nano-silicon particles 100 and the first carbon layer 200; a catalyst layer 400 is disposed on the inner surface of the cavity 300, and interlaced carbon nanotubes 500 are disposed inside the cavity 300; The coating layer includes a second carbon layer 600.

[0047] The structural diagram of this cavity-type silicon-carbon anode material is shown below. Figure 1 As shown.

[0048] SEM images of the cavity-type silicon-carbon anode material are shown below. Figure 2 As shown.

[0049] Example 2 The difference from Example 1 is that in step S1 of this example, the carbon source phenolic resin powder and polyethylene glycol are replaced with asphalt and polyvinylpyrrolidone (PVP) with a softening point of 280°C, respectively.

[0050] Comparative Example 1 The difference from Example 1 is that in step S1, all the phenolic resin powder is replaced with polyethylene glycol.

[0051] Comparative Example 2 The difference from Example 1 is that in step S1, all polyethylene glycol is replaced with phenolic resin powder.

[0052] Comparative Example 3 The difference from Example 1 is that phenolic resin powder and polyethylene glycol are not added in step S1.

[0053] Comparative Example 4 The difference from Example 1 is that nickel acetate is not added in step S4.

[0054] Comparative Example 5 The difference from Example 1 is that in step S4, vacuum impregnation is not performed, but instead atmospheric pressure immersion is performed.

[0055] Comparative Example 6 The difference from Example 1 is that no calcination and curing treatment is performed in step S5.

[0056] Comparative Example 7 The difference from Example 1 is that no asphalt material is added in step S6.

[0057] The relevant parameters of the negative electrode materials prepared in the above embodiments and comparative examples are shown in Table 1.

[0058] Table 1 Product Parameters

[0059] The silicon-carbon anode materials prepared in the above embodiments and comparative examples were coated on copper foil to form electrode sheets. In the latter case, silicon-carbon anode materials, conductive carbon, carbon nanotubes, and polyacrylic acid were prepared into a slurry by a high-speed disperser in a ratio of 82:10:1:7. The separator was PP2400, and a lithium metal sheet was used as the counter electrode to assemble a 2032 coin cell.

[0060] The electrochemical performance of the 2032 coin cells prepared in the above examples and comparative examples was tested in the Blue Battery Testing System, and the results are shown in Table 2.

[0061] Table 2 Electrochemical Performance Tests

[0062] analyze: Based on the above tests, comparing Example 1 and Comparative Example 1.2, it can be seen that when all the core carbon sources are converted to low or high residual carbon sources, the most significant change is in the porosity of the material. When all the core carbon sources are low residual carbon sources, the porosity is larger than that of Example 1. Although the larger porosity provides more space for carbon nanotube growth, the insufficient carbon source results in a lower proportion of generated carbon nanotubes. Combined with the overall increased porosity of the material, this leads to a decrease in the overall conductivity of the material. The larger porosity also makes the overall structure of the material unstable and the cycling performance worse. When all the core carbon sources are converted to high residual carbon sources, the porosity of the material becomes smaller, and there is no space for carbon nanotube growth, resulting in a decrease in the conductivity of the material. Furthermore, because the smaller porosity does not provide sufficient expansion space for the silicon material, the material will be subjected to greater stress during cycling, so the cycling stability is worse than that of Example 1. Comparative Example 3 has no added carbon source in the core, so the core is made of pure silicon. The catalyst is loaded on the surface of the silicon material and has no catalytic effect on silicon. No carbon nanotubes are generated, and the overall conductivity of the material is poor. Although there is a graphitized carbon layer on the surface, a single carbon layer is not enough to withstand the expansion stress of the material during cycling. The overall structural stability of the material is poor, and the cycling performance is poor. Comparative Example 4 was without a catalyst. No carbon nanotubes were generated inside the material, so there were large gaps inside the material, resulting in poor electrical conductivity. Since no catalysis was performed, the surface of the material was covered with amorphous carbon material. Amorphous carbon cannot limit the volume expansion of silicon material, so the overall structural stability of the material is poor during cycling. Comparative Example 5 uses a catalyst impregnated at atmospheric pressure. Compared to catalyst loading at negative pressure, catalyst loading at atmospheric pressure results in the catalyst remaining on the surface of the material and not entering the pores. Therefore, the catalytic effect on the carbon source in the pores is poor, the proportion of carbon nanotubes generated is low, and the material is not filled with carbon nanotubes, which leads to a decrease in conductivity. Furthermore, due to the large number of pores, the mechanical strength of the material deteriorates, and the cycle stability is poor. Comparative Example 6 shows that the catalyst is not calcined and solidified, which causes the salt compound formed by the catalyst to redissolve during the outermost carbon coating. As a result, the catalyst is not sandwiched in the middle of the carbon layer. Some of the catalyst will be loaded on the material surface when the outermost carbon source is loaded. During the final high-temperature sintering, this part of the catalyst will catalyze the carbon layer to form a carbon nanotube structure, resulting in an increase in the overall specific surface area of ​​the material and a decrease in the first efficiency. Comparative Example 7, which did not have an outermost coating, showed that due to the porous structure of the core, the carbon nanotubes generated by the superimposed catalytic load at high temperatures would lead to a significant increase in the specific surface area of ​​the material, a significant decrease in the material's first efficiency, structural instability, and a deterioration in cycle performance.

[0063] In summary, the combined effect of the interstitial voids, carbon nanotubes, and graphitized carbon layers is what enables the material to possess excellent electrochemical performance. Finally, it should be noted that the above embodiments are merely illustrative of the technical solutions of this application and are not intended to limit it. 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; and these 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.

[0064] 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, in the foregoing claims, 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 silicon-carbon anode material with a cavity, characterized in that, Includes a core and a covering layer disposed on the surface of the core; The core includes a cavity and multiple nano-silicon particles; a first carbon layer is disposed on the surface of the nano-silicon particles; the cavity is located between the nano-silicon particles, between the first carbon layers, and between the nano-silicon particles and the first carbon layer. A catalyst layer is disposed on the inner surface of the cavity, and carbon nanotubes are disposed inside the cavity; The coating layer includes a second carbon layer; The first carbon layer includes an amorphous carbon layer; The second carbon layer includes a graphitized carbon layer.

2. The silicon-carbon anode material with a cavity according to claim 1, characterized in that, At least one of the following conditions must be met: A. The particle size of the silicon-carbon anode material with cavities is 1μm-10μm; B. The specific surface area of ​​the hollow silicon-carbon anode material is 1-200 m². 2 / g; C. The porosity of the silicon-carbon anode material with cavities is greater than 0% and less than or equal to 10%; D. The thickness of the second carbon layer is 2-10 nm; E. The thickness of the first carbon layer is 0.1-2 nm; F. The mass of the carbon nanotubes accounts for 5%-15% of the mass of the hollow silicon-carbon anode material; G. The mass of the nano-silicon particles accounts for more than 0 and less than or equal to 40% of the mass of the cavity-containing silicon-carbon anode material.

3. A method for preparing a cavity-containing silicon-carbon anode material as described in claim 1 or 2, characterized in that, include: Nano-silicon particles, a first carbon source, and a second carbon source are first mixed to obtain a first mixture. The first mixture is then spray-dried and first sintered to obtain a first material with a cavity. The first material, catalyst, and first solvent are mixed in a second way to obtain a second mixture. The second mixture is then subjected to a first vacuum impregnation and curing to obtain a second material. The second material, the third carbon source, and the second solvent are mixed in a third way to obtain a third mixture. The third mixture is then subjected to a second vacuum impregnation and drying to obtain a fourth material. Under a protective atmosphere, the fourth material is then subjected to a second sintering to obtain a silicon-carbon anode material with a cavity. The residual carbon rate of the first carbon source is greater than that of the second carbon source.

4. The method for preparing the cavity-containing silicon-carbon anode material according to claim 3, characterized in that, At least one of the following conditions must be met: A. The D50 of the nano-silicon particles is 10nm-200nm; B. The residual carbon content of the first carbon source is ≥40%; C. The residual carbon content of the second carbon source is less than 40%; D. The mass ratio of the first carbon source to the second carbon source is 1:1-5; E. The total mass ratio of the first carbon source and the second carbon source to the mass ratio of the nano-silicon particles is 0.3-1:1; H. The porosity of the first material is 30%-40%.

5. The method for preparing the cavity-containing silicon-carbon anode material according to claim 4, characterized in that, At least one of the following conditions must be met: A. The first carbon source includes one or more of phenolic resin, polypyrrole, polyacrylonitrile, and pitch; B. The second carbon source includes one or more of polyethylene glycol, polyvinylpyrrolidone, sodium carboxymethyl cellulose, polydopamine, glucose, and sucrose.

6. The method for preparing the cavity-containing silicon-carbon anode material according to claim 3, characterized in that, At least one of the following conditions must be met: A. The catalyst comprises nickel salt compounds and / or iron salt compounds; B. The first solvent, the second solvent, and the third solvent are each independently one or more of water, ethanol, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran; C. The mass of the catalyst is 1%-10% of the mass of the first material; D. The solid content of the second mixture is 10%-50%; E. The mass of the third carbon source is 10%-20% of the mass of the second material; F. The third carbon source includes pitch-based carbon materials and / or soluble polymer materials.

7. The method for preparing the cavity-containing silicon-carbon anode material according to claim 6, characterized in that, At least one of the following conditions must be met: A. The nickel salt compounds include one or more of nickel chloride, nickel sulfate, nickel nitrate, nickel acetate, nickel phosphate, and nickel carbonate; B. The iron salt compounds include one or more of ferric chloride, ferric sulfate, ferric nitrate, and ferric carbonate; C. The third carbon source includes one or more of phenolic resin, epoxy resin, polypropylene pyrrolidone, sodium carboxymethyl cellulose, polyvinyl alcohol, polyethylene oxide, and polyacrylonitrile.

8. The method for preparing a cavity-containing silicon-carbon anode material according to any one of claims 3-7, characterized in that, At least one of the following conditions must be met: A. The temperature of the first sintering is 600℃-1000℃, and the time is 2h-4h; B. The pressure of the first vacuum impregnation is -0.8 MPa to -1 MPa, and the time is 10 min to 5 h; C. The curing temperature is 600℃-700℃, and the time is 1h-2h; D. The pressure of the second vacuum impregnation is -0.4 MPa to -0.5 MPa, and the time is 10 min to 5 h; E. The second sintering includes sequential low-temperature sintering and high-temperature sintering; The low-temperature sintering temperature is 500℃-700℃, and the time is 1h-4h; The high-temperature sintering temperature is 900℃-1000℃, and the time is 2h-4h.

9. A lithium-ion battery, characterized in that, This includes the cavity-containing silicon-carbon anode material as described in claim 1 or 2, or the cavity-containing silicon-carbon anode material prepared by the method for preparing the silicon-carbon anode material as described in any one of claims 3-8.

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

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