Composite silicon-carbon negative electrode material, preparation method and application thereof, and lithium ion battery

Abstract

The invention provides a composite silicon-carbon negative electrode material, a preparation method and application thereof and a lithium ion battery, and relates to the technical field of lithium ion battery negative electrode materials. Aluminum-containing oxide is anchored to the surface of the silicon-carbon negative electrode material in a dotted enrichment form, and coats the surface of the silicon-carbon negative electrode material in a plaque form at the same time; the technical problems of volume expansion, unstable interface and pulverization corrosion of the existing silicon-carbon negative electrode material are solved, and the technical effects of high specific capacity, low volume expansion rate and stable SEI film characteristics are achieved, and the structural integrity and cycle life of the electrode are remarkably improved.

Description

Technical Field

[0001] This invention relates to the technical field of lithium-ion battery anode materials, and in particular to a composite silicon-carbon anode material, its preparation method, application, and lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles, drones, and the 3C industry, and the main materials affecting the performance of lithium-ion batteries are the positive and negative electrode materials.

[0003] Traditional graphite anode materials are insufficient to meet the demands of high-energy-density batteries, while silicon (Si), with its higher theoretical specific capacity, is considered an ideal candidate anode material for next-generation high-energy-density lithium-ion batteries. Silicon boasts a theoretical specific capacity of up to 4200 mAh / g, approximately ten times that of graphite. Coupled with its abundant natural resources and low cost, silicon has become a key focus of contemporary research in novel anode materials.

[0004] However, the widespread application of silicon anodes still faces many challenges, such as volume expansion caused by alloying with lithium and poor resistance to electrolyte corrosion. Currently, the mainstream strategy is to use porous carbon as a carrier to deposit silicon internally to suppress expansion and deposit a carbon layer to suppress corrosion. In practical applications, especially during high-rate cycling, the porous carbon framework has limited ability to suppress silicon expansion. The solid electrolyte interphase (SEI) film at the interface undergoes repeated rupture and regeneration, continuously thickening. At the same time, when internal stress accumulates to a certain level, structural pulverization and dissolution of carbon and silicon elements occur. The high electrocatalytic activity of deposited nano-carbon and exposed nano-silicon further exacerbates this phenomenon, ultimately leading to rapid capacity decay and a sharp decline in cycle life.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One of the objectives of this invention is to provide a composite silicon-carbon anode material that solves the technical problems of volume expansion, interface instability, and pulverization corrosion in existing silicon-carbon anode materials.

[0007] The second objective of this invention is to provide a method for preparing a composite silicon-carbon anode material.

[0008] The third objective of this invention is to provide an application of a composite silicon-carbon anode material that combines high specific capacity, low volume expansion rate, and stable SEI film characteristics, thereby significantly improving electrode structural integrity and cycle life.

[0009] The fourth objective of this invention is to provide a lithium-ion battery.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, a composite silicon-carbon anode material is provided on the surface of the composite silicon-carbon anode material containing aluminum oxide. The aluminum oxide is anchored to the surface of the silicon-carbon anode material in a dot-like enrichment form, and at the same time, it is coated on the surface of the silicon-carbon anode material in a patch form.

[0011] Furthermore, the chemical formula of the aluminum oxide is as follows: M x Al y O z ; Wherein, M is selected from at least one of Li, Na, K, Ca, Mg and Ti; At the same time, 0≤x≤2, 0<y≤3, 0<z≤4.

[0012] Furthermore, the M x Al y O z The anchored single enrichment region S1 is in the range of 25π–250π nm. 2 between; Preferably, the M x Al y O z The anchoring embedding depth h1 is 0.25-10 nm; Preferably, the M x Al y O z The anchored coverage area S2 satisfies the following condition: 4×π×R 2 ×0.2 μm 2 ≤S2≤4×π×R 2 ×0.8 μm 2 R is half the average of the maximum and minimum lengths of the two-dimensional plane of the silicon-carbon anode material.

[0013] Furthermore, the M x Al y O z The area S3 of a single patch of the morphology satisfies the following condition: S3≤4×π×R 2 ×0.2 μm 2 R is half the average of the maximum and minimum lengths of the two-dimensional plane of the silicon-carbon anode material; Preferably, the M x Al y O z The total area S4 of the patch morphology satisfies the following condition: 4×π×R 2 ×0.05 μm 2≤S4≤4×π×R 2 ×0.5 μm 2 R is half the average of the maximum and minimum lengths of the two-dimensional plane of the silicon-carbon anode material; Preferably, the M x Al y O z The thickness of the plaque morphology ranges from 10 to 100 nm.

[0014] Furthermore, the carbon content in the composite silicon-carbon anode material is 30-60 wt% by mass. Preferably, the silicon content in the composite silicon-carbon anode material is 40-60 wt% by mass. Preferably, in the composite silicon-carbon anode material, M x Al y O z The mass percentage is 0.01-1 wt%.

[0015] Furthermore, the specific surface area of ​​the composite silicon-carbon anode material is 0.1-2 m². 2 / g; Preferably, the particle size of the composite silicon-carbon anode material is 2-30 μm; Preferably, the powder resistivity of the composite silicon-carbon anode material is 5-100 Ω×cm.

[0016] In a second aspect, a method for preparing the composite silicon-carbon anode material according to any one of the above claims includes the following steps: An aluminum oxide-containing material is anchored as a rivet on the surface of a silicon-carbon anode material using an in-situ ion conversion method, while a mottled coating of aluminum oxide-containing material is formed on its surface to form a shell layer, thus obtaining the composite silicon-carbon anode material.

[0017] Furthermore, the preparation method includes the following steps: Porous carbon materials are subjected to silicon infiltration and carbon deposition to obtain silicon-carbon anode materials. The silicon-carbon anode materials are then mixed with metal salts and precipitants and sintered to obtain the composite silicon-carbon anode materials.

[0018] Thirdly, the application of any one of the composite silicon-carbon anode materials described in the invention of a lithium-ion battery anode.

[0019] Fourthly, a lithium-ion battery, wherein the active material used in the negative electrode of the lithium-ion battery includes the composite silicon-carbon negative electrode material described in any one of the above claims.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: The composite silicon-carbon anode material provided by this invention not only maintains the characteristics of porous silicon-carbon materials, but also incorporates aluminum oxide (M...)x Al y O z The anchoring of aluminum oxide (M) enhances structural stability, improves the expansion effect, and also provides good conductivity and corrosion resistance, inhibiting the structural pulverization of silicon-carbon and the dissolution of carbon and silicon elements during electrochemical reactions; simultaneously, aluminum oxide (M) x Al y O z The patches formed on the surface further act as an artificial SEI film, reducing the electrocatalytic activity of the silicon-carbon surface without affecting the lithium-ion diffusion channels. While slowing down SEI cracking, it can replenish inert oxygen salts, inhibit the increase of organic matter and the consumption of lithium ions, and improve cycle performance. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of a composite silicon-carbon anode material provided in one embodiment of the present invention; Figure 2 An electron microscope image of a composite silicon-carbon anode material provided in one embodiment of the present invention; Figure 3 The energy spectrum of aluminum and oxygen in the composite silicon-carbon anode material provided in one embodiment of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] According to a first aspect of the present invention, a composite silicon-carbon anode material is provided, wherein an aluminum oxide-containing material is disposed on its surface; Aluminum oxides are anchored to the surface of silicon-carbon anode material in a dot-like enrichment form, and at the same time, they are coated on the surface of silicon-carbon anode material in a patch form.

[0025] It should be noted that aluminum oxide is a material that is between electrically inert and fast ion conductor. It can be "anchored" and "patch-coated" on the surface of silicon-carbon materials (silicon-carbon materials refer to materials formed by silicon infiltration and carbon deposition inside porous carbon using vapor deposition, and porous carbon can be spherical, near-spherical, or blocky) through in-situ ion conversion methods. Anchoring with aluminum oxide can enhance structural stability, improve expansion, and provide good conductivity and corrosion resistance. Patch coating with aluminum oxide can act as an artificial SEI film. Without affecting the lithium-ion diffusion channels, it can reduce the electrocatalytic activity of the silicon-carbon surface, slow down SEI cracking, and supplement inert oxygen salts, which is beneficial for inhibiting the increase of organic matter and the consumption of lithium ions, thus improving the cycle.

[0026] In this invention, aluminum oxide (M) is used. x Al y O z Anchoring and patch coating of silicon-carbon anode materials form a composite silicon-carbon anode material, the structure of which is shown in [see figure]. Figure 1 Aluminum oxides (M) are anchored on the silicon-carbon surface. x Al y O z As a rivet, the silicon-carbon surface is simultaneously coated with aluminum oxide (M) in a mottled pattern. x Al y O z As a shell, under the dual modification of anchoring and patch coating, the "anchoring" and "patch coating" of aluminum oxide can work together to enhance their respective advantages, effectively make up for and improve defects, and achieve a synergistic effect, effectively solving the technical problems of volume expansion, interface instability and pulverization corrosion of silicon-carbon anode materials.

[0027] In a preferred embodiment, the chemical formula of the aluminum oxide is as follows: M x Al y O z ; Wherein, M is selected from at least one of Li, Na, K, Ca, Mg and Ti; At the same time, 0≤x≤2, 0<y≤3, 0<z≤4, and x, y and z satisfy the chemical valence state rules.

[0028] Compared to other metal oxides, aluminum oxides have certain passivation properties, can adapt to acidic or alkaline environments, and have strong resistance to chemical and electrochemical corrosion, which helps to slow down the occurrence of side reactions during charging and discharging.

[0029] In a preferred embodiment, M x Al y O zThe anchored single enrichment region S1 can be in the range of 25π-250π nm. 2 between.

[0030] In a preferred embodiment, M x Al y O z The anchoring embedding depth h1 can be 0.25-10 nm, with typical but non-limiting depths such as 0.25 nm, 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm.

[0031] At the same time, M x Al y O z The anchored coverage area S2 satisfies the following condition: 4×π×R 2 ×0.2 μm 2 ≤S2≤4×π×R 2 ×0.8 μm 2 R is half the average of the maximum and minimum lengths of the two-dimensional plane of the silicon-carbon anode material.

[0032] In a preferred embodiment, M x Al y O z The area S3 of a single patch of the morphology satisfies the following condition: S3≤4×π×R 2 ×0.2 μm 2 R is half the average of the maximum and minimum lengths of the two-dimensional plane of the silicon-carbon anode material.

[0033] At the same time, M x Al y O z The total area S4 of the patch morphology satisfies the following condition: 4×π×R 2 ×0.05 μm 2 ≤S4≤4×π×R 2 ×0.5 μm 2 R is half the average of the maximum and minimum lengths of the two-dimensional plane of the silicon-carbon anode material.

[0034] In a preferred embodiment, M x Al y O zThe plaque thickness can range from 10 to 100 nm, with typical but not limited plaque thicknesses being, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, and 100 nm.

[0035] M as defined in this invention x Al y O z Anchored single enrichment regions S1, M x Al y O z Anchored coverage areas S2, M x Al y O z The single-patch area S3, M of the patch morphology x Al y O z The total area of ​​the patch morphology S4 and M x Al y O z The thickness of the plaque is more conducive to improving the structural strength of silicon-carbon and the lithium-ion transport capability.

[0036] In a preferred embodiment, the mass percentage of carbon in the composite silicon-carbon anode material can be 30-60 wt%, with typical but non-limiting mass percentages being 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, and 60 wt%.

[0037] In a preferred embodiment, the mass percentage of silicon in the composite silicon-carbon anode material can be 40-60 wt%, with typical but non-limiting mass percentages being 40 wt%, 45 wt%, 50 wt%, 55 wt%, and 60 wt%.

[0038] In a preferred embodiment, M in the composite silicon-carbon anode material x Al y O z The mass percentage can be 0.01-1 wt%, with typical but non-limiting mass percentages being 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, and 1 wt%.

[0039] In a preferred embodiment, the specific surface area of ​​the composite silicon-carbon anode material can be 0.1-2 m². 2 / g, with a typical but not limiting specific surface area of, for example, 0.1 m². 2 / g, 0.5 m 2 / g、1 m 2 / g, 1.5 m 2 / g、2 m 2 / g.

[0040] In a preferred embodiment, the particle size of the composite silicon-carbon anode material can be 2-30 μm, with typical but non-limiting particle sizes such as 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, and 30 μm.

[0041] In a preferred embodiment, the powder resistivity of the composite silicon-carbon anode material can be 5-100 Ω×cm, with typical but non-limiting powder resistivity such as 5 Ω×cm, 10 Ω×cm, 20 Ω×cm, 30 Ω×cm, 40 Ω×cm, 50 Ω×cm, 60 Ω×cm, 70 Ω×cm, 80 Ω×cm, 90 Ω×cm, and 100 Ω×cm.

[0042] According to a second aspect of the present invention, a method for preparing the composite silicon-carbon anode material as described in any one of the preceding claims is provided, comprising the following steps: Anchoring of aluminum oxide (M) on the surface of silicon-carbon anode material using in-situ ion conversion method x Al y O z As a rivet, its surface is treated with aluminum oxide (M) x Al y O z The mottled coating forms a shell layer, resulting in a composite silicon-carbon anode material.

[0043] In this invention, porous carbon materials are subjected to silicon infiltration and carbon deposition to obtain silicon-carbon anode materials. These silicon-carbon anode materials are then mixed with metal salts and a precipitant, and sintered to obtain aluminum oxide (M...) x Al y O z M is anchored to the surface of silicon-carbon material in a dot-like enrichment form, and simultaneously coated on the surface of silicon-carbon material in a patch form, thus obtaining a composite silicon-carbon anode material; by adjusting the process conditions, M can be autonomously controlled. x Al y O z The components and their anchoring quantity and patchy coating area.

[0044] A typical preparation method for a composite silicon-carbon anode material includes the following steps: Step S1: The carbon precursor is sintered in an inert atmosphere at a temperature of 400-900 ℃ for 1-5 h. After crushing and grading, it is activated to obtain porous carbon material. The specific surface area of ​​porous carbon materials can be 1000-2000 m². 2 / g, with a pore volume of 0.6-1.2 cm³. 3 / g, with a particle size of 2-10 μm; Step S2: Place the porous carbon material in a reactor, introduce a mixture of silicon source gas and carrier gas for silicon infiltration, and then introduce carbon source gas for carbon deposition. The reaction temperature is 400-700 ℃ and the deposition time is 2-10 h to obtain silicon-carbon material. The specific surface area of ​​silicon-carbon materials can be 0.1-2 m². 2 / g, particle size can be 2-30 μm, powder resistivity can be 5-100 Ω×cm; Step S3: Mix silicon-carbon material with metal salt and precipitant in liquid phase and then evaporate to dryness, or mix in solid phase to obtain semi-finished product; The solid content of the liquid-phase mixture is 10-60%, and the evaporation temperature is 50-150 ℃; The solid content of the solid-phase mixture is 90-100%. Step S4: The semi-finished product is placed in an inert atmosphere for sintering at a temperature of 400-700 ℃ for 1-5 h to obtain the composite silicon-carbon anode material.

[0045] In a preferred embodiment, the carbon precursor may be selected from one or more combinations of phenolic resin, citric acid, tricarboxylic acid, polyacrylic acid, epoxy resin, urea-formaldehyde resin, glucose, sucrose, fructose, cellulose, starch, asphalt, polyvinyl alcohol, urea, methyl methacrylate, polyvinyl chloride, and polystyrene.

[0046] In a preferred embodiment, the silicon source gas may be selected from one or more combinations of silane, silicon tetrachloride, and dichlorosilane; the carbon source gas may be selected from one or more combinations of methane, ethylene, propylene, and acetylene; and the carrier gas may be selected from one or more combinations of nitrogen, helium, and argon.

[0047] In a preferred embodiment, the metal salt may be selected from one or more combinations of aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum oxalate, lithium chloride, lithium nitrate, lithium sulfate, lithium oxalate, and lithium acetate; the precipitant may be selected from one or more combinations of potassium hydroxide, sodium hydroxide, ammonia, urea, hexamethylenetetramine, sodium carbonate, and sodium bicarbonate.

[0048] According to a third aspect of the present invention, the application of the composite silicon-carbon anode material described in any one of the preceding claims in the anode of a lithium-ion battery is provided.

[0049] The application of the composite silicon-carbon anode material of the present invention is beneficial to have high specific capacity, low volume expansion rate and stable SEI film characteristics, which can significantly improve the integrity of electrode structure and cycle life.

[0050] According to a fourth aspect of the present invention, a lithium-ion battery is provided, wherein the active material used in the negative electrode of the lithium-ion battery comprises the composite silicon-carbon negative electrode material described in any one of the preceding claims.

[0051] The present invention will be further illustrated below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0052] Example 1 A composite silicon-carbon anode material, comprising 46% silicon by mass, 53.8% carbon by mass, and 0.2% Al2O3 (containing aluminum oxide) by mass, is prepared by the following method: First, phenolic resin was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection. After carbonization, it was graded, crushed, and activated to obtain a Dv50 of 12μm and a pore volume of 0.6cm³. 3 / g porous carbon; Then, the porous carbon was placed in a CVD reactor, and a mixture of SiH4 and N2 gas was introduced. The mixture was deposited at 500°C for 6 hours, and then propylene gas was introduced. The mixture was deposited at 500°C for 2 hours, so that silicon and carbon were uniformly deposited in the pores of the porous carbon to obtain silicon-carbon material. Next, silicon carbon material, aluminum nitrate and ammonia water are mixed according to the design ratio and then distilled water is added to control the solid content at 30%. Then, the oil bath is heated to 100°C and stirred at 130°C until the solution is evaporated to dryness to obtain a semi-finished product. Finally, the semi-finished product was placed under nitrogen protection and heated to 500℃ at a rate of 5℃ / min, and held for 2 hours. The aluminum oxides were anchored to the surface of the silicon-carbon material in a dot-like enrichment morphology, and simultaneously coated on the surface of the silicon-carbon material in a patch morphology, thus obtaining the composite silicon-carbon anode material. Its electron micrograph is shown in [image missing]. Figure 2 The energy dispersive spectroscopy (EDS) spectra of aluminum and oxygen are shown below. Figure 3 .

[0053] Example 2 A composite silicon-carbon anode material, comprising 46% silicon by mass, 53.5% carbon by mass, and 0.5% Al2O3 (containing aluminum oxide) by mass, is prepared by the following method: First, phenolic resin was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection. After carbonization, it was graded, crushed, and activated to obtain a Dv50 of 12μm and a pore volume of 0.6cm³. 3 / g porous carbon; Then, the porous carbon was placed in a CVD reactor, and a mixture of SiH4 and N2 gas was introduced. The mixture was deposited at 500°C for 5 hours, and then propylene gas was introduced. The mixture was deposited at 500°C for 3 hours, so that silicon and carbon were uniformly deposited in the pores of the porous carbon to obtain silicon-carbon material. Next, silicon carbon material, aluminum nitrate and ammonia water are mixed according to the design ratio and then distilled water is added to control the solid content at 30%. Then, the oil bath is heated to 110°C and stirred at 130°C until the solution is evaporated to dryness to obtain a semi-finished product. Finally, the semi-finished product was placed under nitrogen protection and heated to 520℃ at 5℃ / min and held for 2 hours. The aluminum oxide was anchored to the surface of the silicon-carbon material in a dot-like enrichment form, and at the same time, it was coated on the surface of the silicon-carbon material in a patch form, thereby obtaining the composite silicon-carbon anode material.

[0054] Example 3 A composite silicon-carbon anode material, comprising 46% silicon by mass, 53% carbon by mass, and 1% Al2O3 (containing aluminum oxide) by mass, is prepared by the following method: First, phenolic resin was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection. After carbonization, it was graded, crushed, and activated to obtain a Dv50 of 12μm and a pore volume of 0.6cm³. 3 / g porous carbon; Then, the porous carbon was placed in a CVD reactor, and a mixture of SiH4 and N2 gas was introduced. The mixture was deposited at 500°C for 7 hours, and then propylene gas was introduced. The mixture was deposited at 500°C for 1 hour, so that silicon and carbon were uniformly deposited in the pores of the porous carbon to obtain silicon-carbon material. Next, silicon carbon material, aluminum sulfate and ammonia water are mixed according to the design ratio and then distilled water is added to control the solid content at 20%. Then, the oil bath is heated to 100°C and stirred at 130°C until the solution is evaporated to dryness to obtain a semi-finished product. Finally, the semi-finished product was placed under nitrogen protection and heated to 500℃ at 5℃ / min and held for 2 hours. The aluminum oxide was anchored to the surface of the silicon-carbon material in a dot-like enrichment form, and at the same time, it was coated on the surface of the silicon-carbon material in a patch form, thereby obtaining the composite silicon-carbon anode material.

[0055] Example 4 A composite silicon-carbon anode material, comprising 46% silicon by mass, 53.8% carbon by mass, and 0.2% LiAlO2 (containing aluminum oxide) by mass, is prepared by the following method: First, phenolic resin was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection. After carbonization, it was graded, crushed, and activated to obtain a Dv50 of 12μm and a pore volume of 0.6cm³. 3 / g porous carbon; Then, the porous carbon was placed in a CVD reactor, and a mixture of SiH4 and N2 gas was introduced. The mixture was deposited at 500°C for 6 hours, and then propylene gas was introduced. The mixture was deposited at 500°C for 2 hours, so that silicon and carbon were uniformly deposited in the pores of the porous carbon to obtain silicon-carbon material. Next, silicon carbide, aluminum chloride, lithium oxalate and ammonia are mixed in the designed ratio and then distilled water is added. The solid content is controlled at 30%. Then, the oil bath is heated to 100°C and stirred at 130°C until the solution is evaporated to dryness to obtain a semi-finished product. Finally, the semi-finished product was placed under nitrogen protection and heated to 500℃ at 5℃ / min and held for 2 hours. The aluminum oxide was anchored to the surface of the silicon-carbon material in a dot-like enrichment form, and at the same time, it was coated on the surface of the silicon-carbon material in a patch form, thereby obtaining the composite silicon-carbon anode material.

[0056] Example 5 A composite silicon-carbon anode material, comprising 46% silicon by mass, 53.5% carbon by mass, and 0.5% LiAlO2 (containing aluminum oxide) by mass, is prepared by the following method: First, phenolic resin was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection. After carbonization, it was graded, crushed, and activated to obtain a Dv50 of 12μm and a pore volume of 0.6cm³. 3 / g porous carbon; Then, the porous carbon was placed in a CVD reactor, and a mixture of SiH4 and N2 gas was introduced. The mixture was deposited at 500°C for 5 hours, and then propylene gas was introduced. The mixture was deposited at 500°C for 3 hours, so that silicon and carbon were uniformly deposited in the pores of the porous carbon to obtain silicon-carbon material. Next, silicon carbon material, aluminum nitrate, lithium oxalate and ammonia water are mixed according to the design ratio and then distilled water is added to control the solid content at 30%. Then, the oil bath is heated to 110°C and stirred at 130°C until the solution is evaporated to dryness to obtain a semi-finished product. Finally, the semi-finished product is placed under nitrogen protection and heated to 500℃ at 5℃ / min and held for 3 hours. The aluminum oxide is anchored to the surface of the silicon-carbon material in a dot-like enrichment form, and at the same time, it is coated on the surface of the silicon-carbon material in a patch form, thereby obtaining the composite silicon-carbon anode material.

[0057] Example 6 A composite silicon-carbon anode material, comprising 46% silicon by mass, 53% carbon by mass, and 1% LiAlO2 (containing aluminum oxide) by mass, is prepared by the following method: First, phenolic resin was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection. After carbonization, it was graded, crushed, and activated to obtain a Dv50 of 12μm and a pore volume of 0.6cm³. 3 / g porous carbon; Then, the porous carbon was placed in a CVD reactor, and a mixture of SiH4 and N2 gas was introduced. The mixture was deposited at 500°C for 6 hours, and then propylene gas was introduced. The mixture was deposited at 500°C for 2 hours, so that silicon and carbon were uniformly deposited in the pores of the porous carbon to obtain silicon-carbon material. Next, silicon carbide material, aluminum chloride, lithium sulfate and ammonia water are mixed according to the design ratio and then distilled water is added to control the solid content at 30%. Then, the oil bath is heated to 100°C and stirred at 130°C until the solution is evaporated to dryness to obtain a semi-finished product. Finally, the semi-finished product was placed under nitrogen protection and heated to 500℃ at 5℃ / min and held for 2 hours. The aluminum oxide was anchored to the surface of the silicon-carbon material in a dot-like enrichment form, and at the same time, it was coated on the surface of the silicon-carbon material in a patch form, thereby obtaining the composite silicon-carbon anode material.

[0058] Example 7 A composite silicon-carbon anode material, comprising 46% silicon by mass, 53.8% carbon by mass, and 0.2% Al2O3 (containing aluminum oxide) by mass, is prepared by the following method: First, phenolic resin was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection. After carbonization, it was graded, crushed, and activated to obtain a Dv50 of 12μm and a pore volume of 0.6cm³. 3 / g porous carbon; Then, the porous carbon was placed in a CVD reactor, and a mixture of SiH4 and N2 gas was introduced. The mixture was deposited at 500°C for 6 hours, and then propylene gas was introduced. The mixture was deposited at 500°C for 2 hours, so that silicon and carbon were uniformly deposited in the pores of the porous carbon to obtain silicon-carbon material. Next, silicon carbide, aluminum nitrate and urea are mixed in the designed ratio, with the solid content controlled at 98%, and the mixture is vibrated and mixed for 5 minutes to obtain a semi-finished product. Finally, the semi-finished product was placed under nitrogen protection and heated to 500℃ at 5℃ / min and held for 2 hours. The aluminum oxide was anchored to the surface of the silicon-carbon material in a dot-like enrichment form, and at the same time, it was coated on the surface of the silicon-carbon material in a patch form, thereby obtaining the composite silicon-carbon anode material.

[0059] Example 8 A composite silicon-carbon anode material, comprising 46% silicon by mass, 53.8% carbon by mass, and 0.2% LiAlO2 (containing aluminum oxide) by mass, is prepared by the following method: First, phenolic resin was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection. After carbonization, it was graded, crushed, and activated to obtain a Dv50 of 12μm and a pore volume of 0.6cm³. 3 / g porous carbon; Then, the porous carbon was placed in a CVD reactor, and a mixture of SiH4 and N2 gas was introduced. The mixture was deposited at 500°C for 6 hours, and then propylene gas was introduced. The mixture was deposited at 500°C for 2 hours, so that silicon and carbon were uniformly deposited in the pores of the porous carbon to obtain silicon-carbon material. Next, silicon carbide, aluminum chloride, lithium oxalate and urea are mixed in the designed ratio, the solid content is controlled at 98%, and the mixture is vibrated for 5 minutes to obtain a semi-finished product. Finally, the semi-finished product was placed under nitrogen protection and heated to 500℃ at 5℃ / min and held for 2 hours. The aluminum oxide was anchored to the surface of the silicon-carbon material in a dot-like enrichment form, and at the same time, it was coated on the surface of the silicon-carbon material in a patch form, thereby obtaining the composite silicon-carbon anode material.

[0060] Example 9 A composite silicon-carbon anode material, comprising 46% silicon by mass, 52% carbon by mass, and 2% LiAlO2 (containing aluminum oxide) by mass, is prepared by the following method: First, phenolic resin was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection. After carbonization, it was graded, crushed, and activated to obtain a Dv50 of 12μm and a pore volume of 0.6cm³. 3 / g porous carbon; Then, the porous carbon was placed in a CVD reactor, and a mixture of SiH4 and N2 gas was introduced. The mixture was deposited at 500°C for 6 hours, and then propylene gas was introduced. The mixture was deposited at 500°C for 2 hours, so that silicon and carbon were uniformly deposited in the pores of the porous carbon to obtain silicon-carbon material. Next, silicon carbide, aluminum chloride, lithium oxalate and ammonia are mixed in the designed ratio and then distilled water is added. The solid content is controlled at 30%. Then, the oil bath is heated to 100°C and stirred at 130°C until the solution is evaporated to dryness to obtain a semi-finished product. Finally, the semi-finished product was placed under nitrogen protection and heated to 500℃ at 5℃ / min and held for 2 hours. The aluminum oxide was anchored to the surface of the silicon-carbon material in a dot-like enrichment form, and at the same time, it was coated on the surface of the silicon-carbon material in a patch form, thereby obtaining the composite silicon-carbon anode material.

[0061] Example 10 The only difference between this embodiment and Embodiment 1 is that the aluminum oxide used is NaAlO2; Everything else is the same as in Example 1; The preparation method is the same as in Example 1, and a composite silicon-carbon anode material is obtained.

[0062] Example 11 The only difference between this embodiment and Embodiment 1 is that the aluminum oxide used is KAlO2; Everything else is the same as in Example 1; The preparation method is the same as in Example 1, and a composite silicon-carbon anode material is obtained.

[0063] Example 12 The only difference between this embodiment and Embodiment 1 is that the aluminum oxide used is CaAl2O4; Everything else is the same as in Example 1; The preparation method is the same as in Example 1, and a composite silicon-carbon anode material is obtained.

[0064] Example 13 The only difference between this embodiment and Embodiment 1 is that the aluminum oxide used is MgAl2O4; Everything else is the same as in Example 1; The preparation method is the same as in Example 1, and a composite silicon-carbon anode material is obtained.

[0065] Example 14 The only difference between this embodiment and Embodiment 1 is that the aluminum oxide used is TiAl2O4; Everything else is the same as in Example 1; The preparation method is the same as in Example 1, and a composite silicon-carbon anode material is obtained.

[0066] Comparative Example 1 A silicon-carbon anode material, comprising 46% silicon and 54% carbon by mass, is prepared by the following method: First, phenolic resin was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection. After carbonization, it was graded, crushed, and activated to obtain a Dv50 of 12μm and a pore volume of 0.6cm³. 3 / g porous carbon; Subsequently, porous carbon was placed in a CVD reactor, and a mixture of SiH4 and N2 gas was introduced. The mixture was deposited at 500°C for 6 hours, followed by the introduction of propylene gas and deposition at 500°C for 2 hours. This process allowed silicon and carbon to be uniformly deposited within the pores of the porous carbon, resulting in silicon-carbon anode material.

[0067] Comparative Example 2 The only difference between this comparative example and Example 1 is that the aluminum oxide is replaced with CaMgO2; Everything else is the same as in Example 1; The preparation method is the same as in Example 1, and the silicon-carbon anode material is obtained.

[0068] Compared with Example 1, the shortcomings of this comparative example are that it reacts very easily with water, has many side reactions, poor electrical conductivity, insufficient interface stability, and poor mechanical properties.

[0069] Comparative Example 3 The only difference between this comparative example and Example 1 is that the aluminum oxide is anchored to the surface of the silicon-carbon material only in a dot-like enrichment form, and is not coated on the surface of the silicon-carbon material in a patch form. Everything else is the same as in Example 1; The preparation method is the same as in Example 1, and the silicon-carbon anode material is obtained.

[0070] Compared with Example 1, the drawback of this comparative example is that the isolation effect on the electrolyte is reduced, there are more side reactions, and thus the stability is reduced.

[0071] Comparative Example 4 The only difference between this comparative example and Example 1 is that the aluminum oxide is not anchored to the surface of the silicon-carbon material in a dot-like enrichment form, but only in a patch form on the surface of the silicon-carbon material. Everything else is the same as in Example 1; The preparation method is the same as in Example 1, and the silicon-carbon anode material is obtained.

[0072] Compared with Example 1, the drawback of this comparative example is that the structural stability is poor, and the silicon-carbon anode is prone to pulverization after the electrochemical reaction, thereby reducing stability.

[0073] Test case The composite silicon-carbon anode materials of each embodiment were tested by SEM, energy dispersive spectroscopy, and slice polishing to obtain aluminum oxide (M) x Al y O z Anchored single enrichment regions S1, M x Al y O z Anchoring embedding depth h1, aluminum oxide (M) x Al y O z Anchored coverage area S2, containing aluminum oxide (M) x Al y O z The patch morphology of the single-piece area S3, containing aluminum oxide (M) x Al y O z The total area S4 of the patch morphology and the aluminum oxide content (M) x Al y O z The plaque thickness was measured, and the results are shown in Table 1 below.

[0074] The button cells made from the negative electrode materials of each embodiment and each comparative example were tested to obtain the capacity, cycle life and electrode expansion rate. The results are shown in Table 1 below.

[0075] Electrode and half-cell preparation and electrochemical performance testing: The negative electrode materials of each embodiment and each comparative example were used as negative electrode active materials to prepare negative electrode sheets. The composition of the electrode sheets was as follows: active material accounted for 90%, binder SBR accounted for 5%, conductive agent SP accounted for 4.9%, and SWCNT accounted for 0.1%. The negative electrode sheets were used to prepare CR2032 coin cells using conventional methods, and the electrical performance of the cells was tested. Electrical performance testing methods: (1) Half-cell assembly: Assemble CR2032 button cells in a glove box, with lithium metal sheet as counter electrode, polypropylene microporous membrane as separator, and LiPF6 dissolved in a mixture of ethyl carbonate (EC) and diethyl carbonate (DEC) (EC and DEC volume ratio of 1:1) as electrolyte, with a LiPF6 concentration of 1 mol / L. The battery was charged and discharged using the LAND battery testing system. (2) Capacity test: After the CR2032 button battery is left to stand for 6 hours, it is discharged at 0.1C to 0.005V, and then discharged at a constant voltage of 0.005V until the current is cut off at 0.01C. After standing for 5 minutes, it is charged at a constant current of 0.1C to 1.5V and the capacity is recorded. (3) Capacity retention rate test: After standing for 5 minutes, repeat the above charging and discharging steps twice; then discharge to 0.005V at 0.5C; after standing for 5 minutes, charge to 1.5V at 0.5C constant current, cycle 50 times; calculate the capacity retention rate by the charge specific capacity of the 50th cycle / the charge capacity of the 1st cycle × 100%. (4) Electrode expansion rate: After the CR2032 type button cell was left to stand for 6 hours, it was discharged to 0.005V at 0.05C and then discharged to 0.005V at 0.01C. Then the button cell was disassembled in the glove box, the electrode was cleaned with DMC and the thickness of the electrode was measured. The expansion rate was calculated as: (thickness of electrode in the first fully charged state - thickness of fresh electrode) / thickness of fresh electrode × 100%.

[0076] Table 1

[0077] As can be seen from the data in Table 1, in this invention, aluminum oxide is anchored to the surface of silicon-carbon anode material in a dot-like enrichment form, and at the same time, it is coated on the surface of silicon-carbon anode material in a patch form. The dual modification of anchoring and patch coating enhances the silicon-carbon structure, reduces the surface carbon activity, and introduces artificial SEI, thereby reducing the volume expansion rate of silicon-carbon anode material, significantly improving the integrity of electrode structure, and increasing specific capacity.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention 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 the present invention.

Claims

1. A composite silicon-carbon anode material, characterized in that, The surface of the composite silicon-carbon anode material is provided with aluminum oxide. The aluminum oxide is anchored to the surface of the silicon-carbon anode material in a dot-like enrichment form, and at the same time, it is coated on the surface of the silicon-carbon anode material in a patch form.

2. The composite silicon-carbon anode material according to claim 1, characterized in that, The chemical formula of the aluminum oxide is as follows: M x Al y O z ; Wherein, M is selected from at least one of Li, Na, K, Ca, Mg and Ti; At the same time, 0≤x≤2, 0<y≤3, 0<z≤4.

3. The composite silicon-carbon anode material according to claim 2, characterized in that, The M x Al y O z The anchored single enrichment region S1 is in the range of 25π–250π nm. 2 between; The M x Al y O z The anchoring embedding depth h1 is 0.25-10 nm; The M x Al y O z The anchored coverage area S2 satisfies the following condition: 4×π×R 2 ×0.2 μm 2 ≤S2≤4×π×R 2 ×0.8 μm 2 R is half the average of the maximum and minimum lengths of the two-dimensional plane of the silicon-carbon anode material.

4. The composite silicon-carbon anode material according to claim 2, characterized in that, The M x Al y O z The area S3 of a single patch of the morphology satisfies the following condition: S3≤4×π×R 2 ×0.2 μm 2 R is half the average of the maximum and minimum lengths of the two-dimensional plane of the silicon-carbon anode material; The M x Al y O z The total area S4 of the patch morphology satisfies the following condition: 4×π×R 2 ×0.05 μm 2 ≤S4≤4×π×R 2 ×0.5 μm 2 R is half the average of the maximum and minimum lengths of the two-dimensional plane of the silicon-carbon anode material; The M x Al y O z The thickness of the plaque morphology ranges from 10 to 100 nm.

5. The composite silicon-carbon anode material according to claim 2, characterized in that, The carbon content in the composite silicon-carbon anode material is 30-60 wt% by mass. The silicon content in the composite silicon-carbon anode material is 40-60 wt% by mass. M in the composite silicon-carbon anode material x Al y O z The mass percentage is 0.01-1 wt%.

6. The composite silicon-carbon anode material according to any one of claims 1-5, characterized in that, The specific surface area of ​​the composite silicon-carbon anode material is 0.1-2 m². 2 / g; The particle size of the composite silicon-carbon anode material is 2-30 μm; The powder resistivity of the composite silicon-carbon anode material is 5-100 Ω×cm.

7. A method for preparing the composite silicon-carbon anode material according to any one of claims 1-6, characterized in that, Includes the following steps: An aluminum oxide-containing material is anchored as a rivet on the surface of a silicon-carbon anode material using an in-situ ion conversion method, while a mottled coating of aluminum oxide-containing material is formed on its surface to form a shell layer, thus obtaining the composite silicon-carbon anode material.

8. The preparation method according to claim 7, characterized in that, The preparation method includes the following steps: Porous carbon materials are subjected to silicon infiltration and carbon deposition to obtain silicon-carbon anode materials. The silicon-carbon anode materials are then mixed with metal salts and precipitants and sintered to obtain the composite silicon-carbon anode materials.

9. The application of the composite silicon-carbon anode material according to any one of claims 1-6 in the anode of a lithium-ion battery.

10. A lithium-ion battery, characterized in that, The active material used in the negative electrode of the lithium-ion battery includes the composite silicon-carbon negative electrode material as described in any one of claims 1-6.

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