Novel silicon-carbon negative electrode material and preparation method and application thereof

Abstract

The invention relates to a novel silicon-carbon negative electrode material as well as a preparation method and application thereof. The novel silicon-carbon negative electrode material comprises an inner core and a shell, the shell covers the surface of the inner core; the inner core is silicon-carbon composite particles; the silicon-carbon composite particle comprises silicon nanoparticles, a carbon material matrix and a primary carbon layer, the shell comprises a first layer and a second layer; the first layer comprises an aluminum oxide layer and a carbon layer; the carbon layer is distributed in a gap of the aluminum oxide layer; the second layer is a carbon coating layer; the chemical general formula of the novel silicon-carbon negative electrode material is AlaSiObCc, a, b and c are the mole numbers of elements Al, O and C respectively, a is more than 0 and less than 25, b is more than 0 and less than 20, and c is more than 0 and less than 30; the novel silicon-carbon negative electrode material is used for preparing a negative electrode plate, so that the gas production behavior in a water system homogenizing process can be reduced, the processing quality of a battery is ensured, and the high-temperature storage stability of the battery is improved.

Description

Technical Field

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

[0002] Currently, silicon-based anode materials possess an ultra-high theoretical capacity of 4200 mAh / g, making them a highly anticipated next-generation anode material for lithium-ion batteries. However, the practical application of silicon in lithium-ion batteries is limited by its low electronic conductivity and large volume change, preventing it from replacing the cycle-stable graphite anode. To address these challenges, miniaturizing silicon materials to the nanoscale is an effective strategy, exemplified by silicon-carbon anodes. This is because the nanostructure of silicon not only shortens the lithium-ion diffusion path but also effectively reduces the strain caused by electrochemical reactions in the active material during cycling, thus maintaining the structural integrity of the electrode.

[0003] The gas generation behavior of silicon-carbon anodes during aqueous slurry preparation poses challenges to the slurrying, coating, and die-cutting processes of the anode sheets, leading to problems such as foil exposure and electrode shedding. Furthermore, it causes irreversible capacity loss during storage. Gas generation during lithium-ion battery storage and application can cause battery expansion, deformation, and even leakage, potentially leading to safety accidents. The increase in battery volume due to gas generation is a crucial indicator for the reliability testing of soft-pack lithium-ion batteries. However, current research on the gas generation behavior of silicon-carbon anodes during storage and cycling is relatively limited.

[0004] For example, Chinese patent CN117525330A (publication date: February 6, 2024) discloses a metal oxide / silicon-carbon composite material, its preparation method and application. By modifying the carbon matrix with nano-metal oxides, the deposition effect of silicon and carbon is enhanced, thereby improving the expansion problem and interface stability of silicon-carbon materials. However, it does not improve the voltage decay during high-temperature storage and the gas generation problem during the slurry coating process. Furthermore, the direct use of nano-metal oxide materials further increases the modification cost. Summary of the Invention

[0005] The purpose of this invention is to address the problems of poor battery storage performance, slurry gas generation, and high modification costs in existing technologies by providing a novel silicon-carbon anode material, its preparation method, and its application.

[0006] To achieve the above objectives, in a first aspect, embodiments of the present invention provide a novel silicon-carbon anode material, the novel silicon-carbon anode material comprising a core and a shell; the shell covering the surface of the core;

[0007] The core is a silicon-carbon composite particle;

[0008] The outer shell includes a first layer and a second layer covering the first layer; the first layer includes an aluminum oxide layer and a carbon layer; the carbon layer is distributed in the gaps of the aluminum oxide layer; the second layer is a carbon coating layer;

[0009] The novel silicon-carbon anode material has the general chemical formula Al. a SiO b C c , where a, b, and c are the number of moles of elements Al, O, and C, respectively, and 0 < a < 25, 0 < b < 20, and 0 < c < 30.

[0010] Preferably, the silicon-carbon composite particles comprise: silicon nanoparticles, a carbon material matrix, and a primary carbon layer; the silicon nanoparticles are attached to the pores of the carbon material matrix, and the primary carbon layer coats the outer surface of the carbon material matrix; the specific surface area of ​​the silicon-carbon composite particles is 0.1 m². 2 / g~800m 2 Between / g;

[0011] The silicon nanoparticles include: silicon nanocrystals and / or silicon oxide;

[0012] The average size of the silicon nanocrystals is between 0.1 nm and 50 nm.

[0013] The general chemical formula of the silicon oxide is SiO2. x And 0 ≤ x < 2;

[0014] The total thickness of the outer shell is between 0.1 nm and 1 μm;

[0015] The alumina layer is distributed in one or more of the following morphologies: island-shaped, dot-shaped, spherical, and rod-shaped; the alumina in the alumina layer is crystalline and / or amorphous.

[0016] The mass of the carbon material matrix accounts for 0.1% to 75% of the total mass of the novel silicon-carbon anode material;

[0017] The percentage of carbon in the outer shell to the total mass of the novel silicon-carbon anode material is 0.1% to 50%.

[0018] The mass percentage of aluminum in the outer shell is less than or equal to 30% of the total mass of the novel silicon-carbon anode material; the aluminum content is between 40 ppm and 40,000 ppm.

[0019] Preferably, the particle size D of the novel silicon-carbon anode material is... v 50 is between 0.1 μm and 100 μm;

[0020] The specific surface area of ​​the novel silicon-carbon anode material is 0.1 m².2 / g~500m 2 Between / g;

[0021] The total carbon content in the novel silicon-carbon anode material is between 1% and 80%.

[0022] In a second aspect, embodiments of the present invention provide a method for preparing the novel silicon-carbon anode material described in the first aspect above, the method comprising:

[0023] An aluminum salt is dissolved in a first solvent and stirred to form a dispersion system; wherein the aluminum-containing compound in the dispersion system includes: an aluminum salt, or an aluminum salt and aluminum oxide;

[0024] The silicon-carbon composite particles are dissolved in the same solvent as the first solvent to form a first silicon-carbon slurry.

[0025] The dispersion system is mixed evenly with the first silicon carbide slurry to form a first mixed slurry;

[0026] The first mixed slurry is spray-dried to load the aluminum-containing compound in the dispersion system onto the surface and pores of the silicon-carbon composite particles, thereby obtaining intermediate particles.

[0027] The intermediate particles are sintered in a protective atmosphere, with water vapor introduced during the sintering process to convert the aluminum salt in the intermediate particles into stable alumina, yielding first precursor particles; wherein the aluminum loading in the first precursor particles is greater than or equal to 50 ppm; and the increase in the specific surface area of ​​the first precursor particles relative to the specific surface area of ​​the silicon-carbon composite particles is greater than 0 and less than or equal to 100 m². 2 / g;

[0028] The first precursor particles are subjected to carbon coating treatment to obtain a novel silicon-carbon anode material.

[0029] Preferably, the specific surface area of ​​the silicon-carbon composite particles is 0.1 m². 2 / g~800m 2 Between / g;

[0030] The aluminum salts include: Al(OH)3, AlOOH, Al2(CO3)3, C9H 21 A l O3, A l(NO3)3, A l(NO3)3·9H2O, A l[OOCH3(OH)2]·yH2O, A l C l3, A l(NO)3, A l2(SO4)3, Al F3, A l F3, Al2H6O 12 S3, Al2H6O9Si3, Al2H6O9Ti3, Al BH3O3, C 54 H105 AlO6, AlCl3H 21 O 21 C2H3Al NO4, C9H 21 AlO3, C 15 H 21 Al O6, C2H5AlO4, C6H5AlO7, C6H8Al O7, C 18 H 15 AlO9, C6H 15 AlO3, C 12 H 27 AlO3, C 12 H 27 Al O3, C 54 H 99 One or more of AlO6, wherein 0.1 ≤ y ≤ 20; the particle size D of the aluminum salt v 50 is between 0.01μm and 20μm;

[0031] The step of uniformly mixing the dispersion system with the first silicon carbide slurry further includes mixing it with a surfactant; the surfactant includes one or more of the following: fatty alcohol polyoxyethylene ether, fatty acid glycol ester, fatty alcohol sulfate, fatty acid salt, sodium α-alkenyl sulfonate, hexadecyltrimethylammonium bromide, hexadecylpyridine chloride, dodecyl imidazoline ammonium salt, cocamidopropyl betaine, lauryl phosphatidyl betaine, sodium dodecyl sulfate, polyoxyethylene stearate, and OP emulsifier;

[0032] The mass ratio of the surfactant to the silicon-carbon composite particles is [0.1-10]:100;

[0033] The first solvent includes: deionized water or an organic solvent; the organic solvent includes: any one of ethanol, dimethylformamide (DMF), DMSO, tetrahydrofuran, isopropanol, polyethylene glycol, methanol, acetone, toluene, ethyl acetate, cyclohexane, chloroform, dichloromethane, and propylene glycol;

[0034] The aluminum content in the intermediate particles ranges from 50 ppm to 50,000 ppm.

[0035] Preferably, the sintering temperature is 300℃~850℃, and the sintering holding time is 2 hours~12 hours;

[0036] The flow rate of the water vapor is greater than or equal to 0 and less than or equal to 70 L / min;

[0037] The inlet temperature range of the spray dryer is 70℃~500℃, and the outlet temperature range is 50℃~350℃.

[0038] The protective atmosphere includes one or more of nitrogen, argon, hydrogen, helium, or neon.

[0039] The carbon coating process employs gas-phase coating; the carbon source gas selected for the gas-phase coating includes one or more of the following: methane, ethane, ethylene, acetylene, propane, propylene, n-butane, isobutane, butene, and 1,3-butadiene.

[0040] Thirdly, embodiments of the present invention provide a method for preparing the novel silicon-carbon anode material described in the first aspect above, the method comprising:

[0041] The silicon-carbon composite particles are dissolved in a second solvent to form a second silicon-carbon slurry;

[0042] Alumina and the second silicon carbide slurry are mixed evenly to obtain a second mixed slurry;

[0043] The second mixed slurry is spray-dried to load the alumina onto the surface and pores of the silicon-carbon composite particles, yielding second precursor particles; wherein the aluminum loading in the second precursor particles is greater than or equal to 50 ppm; and the increase in the specific surface area of ​​the second precursor particles relative to the specific surface area of ​​the silicon-carbon composite particles is greater than 0 and less than or equal to 100 m². 2 / g;

[0044] The second precursor particles are carbon-coated to obtain a novel silicon-carbon anode material.

[0045] Preferably, the specific surface area of ​​the silicon-carbon composite particles is 0.1 m². 2 / g~800m 2 Between / g;

[0046] The alumina includes crystalline alumina and / or amorphous alumina; the particle size Dv50 of the alumina is less than or equal to 20 μm, and the purity is greater than or equal to 95%;

[0047] The second solvent includes: deionized water or an organic solvent; the organic solvent includes: any one of ethanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran, isopropanol, polyethylene glycol, methanol, acetone, toluene, ethyl acetate, cyclohexane, chloroform, dichloromethane, and propylene glycol;

[0048] The molar ratio of aluminum to silicon in the second mixed slurry is (0-1):20;

[0049] The process of uniformly mixing alumina with the second silicon carbide slurry further includes mixing it with a surfactant; the surfactant includes one or more of the following: fatty alcohol polyoxyethylene ether, fatty acid glycol ester, fatty alcohol sulfate, fatty acid salt, sodium α-alkenyl sulfonate, hexadecyltrimethylammonium bromide, hexadecylpyridine chloride, dodecyl imidazoline ammonium salt, cocamidopropyl betaine, lauryl phosphatidyl betaine, sodium dodecyl sulfate, polyoxyethylene stearate, and OP emulsifier;

[0050] The mass ratio of the surfactant to the silicon-carbon composite particles is [0.1-10]:100.

[0051] Preferably, the inlet temperature range of the spray dryer is 70℃~500℃, and the outlet temperature range is 50℃~350℃.

[0052] The carbon coating process employs gas-phase coating; the carbon source gas selected for the gas-phase coating includes one or more of the following: methane, ethane, ethylene, acetylene, propane, propylene, n-butane, isobutane, butene, and 1,3-butadiene.

[0053] Fourthly, embodiments of the present invention provide a secondary battery, the secondary battery comprising the novel silicon-carbon anode material described in the first aspect.

[0054] This invention provides a novel silicon-carbon anode material, its preparation method, and its application. The specific beneficial effects are as follows.

[0055] (1) The present invention provides a method for preparing a novel silicon-carbon anode material. The method of spray granulation loads an aluminum-containing compound onto the surface of silicon-carbon composite particles. The aluminum-containing compound can be an aluminum salt or directly alumina powder. When the aluminum-containing compound is an aluminum salt, it is reduced to alumina in situ at high temperature to achieve a tight bond between the silicon-carbon composite particles and alumina, providing more active sites for small free radical molecules such as methyl groups and forming an alumina layer. Then, gas phase carbon coating is performed to finally obtain the novel silicon-carbon anode material.

[0056] (2) The novel silicon-carbon anode material prepared by the above preparation method of the present invention has a structure in which two coating layers are formed on the outer surface of silicon-carbon composite particles. The first layer is a coating layer formed by an aluminum oxide layer and a carbon layer, and the outermost second layer is a carbon coating layer. The aluminum oxide layer can prevent the corrosion of the electrode material by the HF gas formed by the decomposition of the electrolyte, reduce the occurrence of side reactions, prevent the electrolyte from continuously consuming the solid electrolyte interphase (SEI) film layer on the surface of the silicon-carbon composite particles, and keep the interface between the silicon-carbon composite particles and the electrolyte stable. The carbon coating layer can protect the aluminum oxide layer from falling off and can protect the silicon-carbon composite particles, so that the silicon-carbon composite particles do not react with water during the preparation of the electrode slurry, inhibit the gas generation behavior of the anode slurry, ensure the stability of the material during the homogenization process, thereby ensuring the processing quality of the anode sheet and improving the electrochemical performance of the battery assembled using the anode sheet. At the same time, the carbon coating layer can also reduce the interfacial reaction between the silicon-carbon composite particles and the electrolyte, ensure the interfacial stability, and improve the cycle performance of the battery.

[0057] (3) The novel silicon-carbon anode material provided in this embodiment of the invention has wide applicability and low cost for coating carbon sources. Its application in lithium batteries can suppress gas generation problems in the slurry during lithium battery preparation, ensuring the processing quality of the anode sheet, and is more suitable for large-scale industrial promotion. Furthermore, the novel silicon-carbon anode material provided in this embodiment of the invention can significantly improve the high-temperature storage performance of lithium batteries. For example, the specific capacity of a full battery prepared using the novel silicon-carbon anode material provided in this embodiment of the invention, after being stored at 60°C for 14 days, shows very little decrease compared to the initial capacity, and the voltage decrease is also very small. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the structure of the novel silicon-carbon anode material provided in an embodiment of the present invention.

[0059] Figure 2 This is a flowchart illustrating a method for preparing a novel silicon-carbon anode material according to an embodiment of the present invention.

[0060] Figure 3 A flowchart illustrating a method for preparing another novel silicon-carbon anode material provided in an embodiment of the present invention.

[0061] Figure 4 Scanning electron microscope (SEM) image of the novel silicon-carbon composite material provided in Example 1.

[0062] Figure 5 X-ray diffraction (XRD) pattern of the novel silicon-carbon composite material provided in Example 1.

[0063] Figure 6 The energy dispersive spectroscopy (EDS) diagram of the novel silicon-carbon composite material provided in Example 1.

[0064] Figure 7 The charge-discharge curves of the coin cell prepared from the novel silicon-carbon composite material provided in Example 1 are shown. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0066] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0067] This invention provides a novel silicon-carbon anode material with the general chemical formula Al. a SiO b C c , where a, b, and c are the number of moles of elements Al, O, and C, respectively, and 0 < a < 25, 0 < b < 20, and 0 < c < 30.

[0068] The novel silicon-carbon anode material comprises a core and a shell; the shell covers the outer surface of the core.

[0069] A schematic diagram of the structure of a novel silicon-carbon anode material, as shown below. Figure 1 As shown, the core is a silicon-carbon composite particle, comprising: silicon nanoparticles, a carbon material matrix, and a primary carbon layer, wherein the silicon nanoparticles are attached to the pores of the carbon material matrix, and the primary carbon layer covers the outer surface of the carbon material matrix; the outer shell comprises a first layer and a second layer covering the first layer; the first layer comprises an alumina layer and a carbon layer, wherein the carbon layer covers the surface of the alumina layer and / or the carbon layer is distributed in the gaps of the alumina layer, and the second layer is a carbon coating layer.

[0070] Silicon-carbon composite particles are silicon-carbon composite materials that have undergone initial carbon coating treatment. Based on the degree of carbon coating, they are divided into high specific surface area silicon-carbon composite particles and low specific surface area silicon-carbon composite particles. The specific surface area of ​​silicon-carbon composite particles is less than 0.1 μm. 2 / g~800m 2 Between / g; the silicon-carbon composite particles used in this invention are existing known materials, which can be self-made or commercially available materials.

[0071] Silicon nanoparticles include: silicon nanocrystals and / or silicon oxide; wherein the average size of the silicon nanocrystals is between 0.1 nm and 50 nm; and the general chemical formula of the silicon oxide is SiO₂. x And 0≤x<2.

[0072] The specific surface area of ​​the carbon material matrix is ​​1000 m². 2 / g~3500m 2 / g, the pore size of the carbon material matrix is ​​0.1nm~50nm; the mass ratio of the carbon material matrix in the silicon-carbon composite particles is greater than or equal to 30% and less than 100%; the mass ratio of the carbon material matrix to the total mass of the novel silicon-carbon anode material is 0.1%~75%.

[0073] The total thickness of the outer shell is between 0.1 nm and 1 μm. The alumina layer in the first layer of the outer shell is distributed in one or more of the following forms: island-shaped, dot-shaped, spherical, and rod-shaped; the alumina in the alumina layer is crystalline and / or amorphous; the second carbon coating layer can be one or more of the following forms: dot-shaped, island-shaped, or continuous thin film.

[0074] The carbon element in the outer shell accounts for 0.1% to 50% of the total mass of the novel silicon-carbon anode material.

[0075] The mass percentage of aluminum in the outer shell is less than or equal to 30% of the total mass of the new silicon-carbon anode material; the aluminum content is between 40 ppm and 40,000 ppm.

[0076] The particle size D of the novel silicon-carbon anode material provided in this embodiment of the invention v The value of 50 is between 0.1 μm and 100 μm, preferably between 4 μm and 14 μm.

[0077] The specific surface area of ​​the novel silicon-carbon anode material is 0.1 m². 2 / g~500m 2 Between / g, preferably 0.5m 2 / g~20m 2 / g.

[0078] The total carbon content in the novel silicon-carbon anode material is between 1 wt% and 80 wt%, preferably between 25 wt% and 70 wt%.

[0079] The present invention provides two methods for preparing the above-mentioned novel silicon-carbon anode materials, which are described below.

[0080] This invention provides a method for preparing the above-mentioned novel silicon-carbon anode material, such as... Figure 2 As shown, the specific steps include:

[0081] Step 110: Dissolve the aluminum salt in the first solvent and stir to form a dispersion system;

[0082] The aluminum salts include: Al(OH)3, AlOOH, Al2(CO3)3, C9H 21A l O3, A l(NO3)3, A l(NO3)3·9H2O, A l[OOCH3(OH)2]·yH2O, A l C l3, A l(NO)3, A l2(SO4)3, A l F3, A l F3, Al2H6O 12 S3, A l2H6O9S i3, A l2H6O9T i3, A l BH3O3, C 54 H 105 AlO6, AlCl3H 21 O 21 C2H3AlNO4, C9H 21 AlO3, C 15 H 21 A l O6, C2H5A l O4, C6H5A l O7, C6H8A l O7, C 18 H 15 AlO9, C6H 15 A lO3, C 12 H 27 AlO3, C 12 H 27 AlO3, C 54 H 99 One or more of AlO6, wherein 0.1 ≤ y ≤ 20; the aluminum salt is preferably aluminum isopropoxide (C9H). 21 Aluminum isopropoxide (AlO3) has the following advantages: high alumina conversion rate, low cost, higher safety and environmental protection in the production process, no toxic gases are generated in the process, the alumina coating is uniform and has high purity, and it does not require a harsh reaction environment.

[0083] Particle size D of aluminum salt v 50 is between 0.01μm and 20μm;

[0084] The first solvent includes: deionized water or an organic solvent; the organic solvent includes: any one of ethanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran, isopropanol, polyethylene glycol, methanol, acetone, toluene, ethyl acetate, cyclohexane, chloroform, dichloromethane, and propylene glycol;

[0085] Aluminum-containing compounds in a dispersion system include aluminum salts, or aluminum salts and aluminum oxide; when the solvent is anhydrous, the dispersion system contains only aluminum salts; when the solvent contains water, some aluminum salts will react with the water in the solvent to form aluminum oxide, in which case the dispersion system includes both aluminum salts and aluminum oxide.

[0086] Step 120: Dissolve the silicon-carbon composite particles in the same solvent as the first solvent to form a first silicon-carbon slurry;

[0087] Among them, the specific surface area of ​​silicon-carbon composite particles is 0.1 m². 2 / g~800m 2 Between / g.

[0088] Step 130: Mix the dispersion system with the first silicon carbide slurry evenly to form the first mixed slurry;

[0089] In the first mixed slurry, the molar ratio of aluminum to silicon is (0-1):20.

[0090] In an optional technical solution, this step may further include mixing the dispersion system and the first silicon carbide slurry with a surfactant; wherein the surfactant includes one or more of the following: fatty alcohol polyoxyethylene ether, fatty acid glycol ester, fatty alcohol sulfate, fatty acid salt, sodium α-alkenyl sulfonate, hexadecyltrimethylammonium bromide, hexadecylpyridine chloride, dodecyl imidazoline ammonium salt, cocamidopropyl betaine, lauryl phosphatidyl betaine, sodium dodecyl sulfate, polyoxyethylene stearate, and OP emulsifier;

[0091] The mass ratio of surfactant to silicon-carbon composite particles is [0.1-10]:100, and preferably, the molar ratio of aluminum to silicon is 0.4:20.

[0092] Step 140: Spray dry the first mixed slurry to load the aluminum-containing compound in the dispersion system onto the surface and pores of the silicon-carbon composite particles to obtain intermediate particles.

[0093] The inlet temperature range of the spray dryer is 70℃~500℃, and the outlet temperature range is 50℃~350℃.

[0094] The aluminum content in the intermediate particles ranges from 50 ppm to 50,000 ppm, and preferably, the aluminum content in the intermediate particles ranges from 3,000 ppm to 15,000 ppm.

[0095] Since the silicon-carbon composite particles used in this embodiment of the invention have a primary carbon layer, most of the aluminum-containing compounds in the dispersion system are loaded on the surface of the silicon-carbon composite particles, and very few will enter the large pores of the silicon-carbon composite particles, and will not enter the deeper interior of the pores.

[0096] Step 150: The intermediate particles are sintered in a protective atmosphere. During the sintering process, water vapor is introduced to convert the aluminum salt in the intermediate particles into stable alumina, thus obtaining the first precursor particles.

[0097] Specifically, the aluminum loading in the first precursor particles is greater than or equal to 50 ppm; the increase in the specific surface area of ​​the first precursor particles relative to the specific surface area of ​​the silicon-carbon composite particles is greater than 0 and less than or equal to 100 m². 2 / g;

[0098] The sintering temperature is 300℃~850℃, and the sintering holding time is 2 hours~12 hours;

[0099] The steam flow rate is greater than or equal to 0 and less than or equal to 70 L / min. In this step, steam can be introduced to allow the aluminum salt to undergo a hydrolysis reaction during sintering to obtain alumina. However, when all the aluminum salt in the dispersion system has been converted into alumina, steam can be omitted and sintering can be carried out directly.

[0100] The protective atmosphere includes one or more of the following: nitrogen, argon, hydrogen, helium, or neon.

[0101] Step 160: Carbon coating treatment is performed on the first precursor particles to obtain a novel silicon-carbon anode material.

[0102] Among them, the carbon coating treatment uses gas phase coating;

[0103] The carbon source gases selected for gas phase coating include one or more of the following: methane, ethane, ethylene, acetylene, propane, propylene, n-butane, isobutane, butene, and 1,3-butadiene;

[0104] The coating process is completed using chemical vapor deposition equipment, including one or more of fluidized bed, boiling bed, and rotary furnace. After coating, the material is mixed, demagnetized, and sieved to obtain the final novel silicon-carbon anode material.

[0105] This invention provides another method for preparing the above-mentioned novel silicon-carbon anode material, such as... Figure 3 As shown, the specific steps include:

[0106] Step 210: Dissolve the silicon-carbon composite particles in the second solvent to form a second silicon-carbon slurry;

[0107] Among them, the specific surface area of ​​silicon-carbon composite particles is 0.1 m². 2 / g~800m 2 Between / g;

[0108] The second solvent includes: deionized water or an organic solvent; the organic solvent includes: any one of ethanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran, isopropanol, polyethylene glycol, methanol, acetone, toluene, ethyl acetate, cyclohexane, chloroform, dichloromethane, and propylene glycol.

[0109] Step 220: Mix alumina and the second silicon carbide slurry evenly to obtain the second mixed slurry;

[0110] Among them, alumina includes crystalline alumina and / or amorphous alumina; the particle size of alumina Dv50 is less than or equal to 20 μm and the purity is greater than or equal to 95%;

[0111] The molar ratio of aluminum to silicon in the second mixed slurry is (0-1):20;

[0112] In an optional embodiment, the alumina and second silicon carbide slurry can be uniformly mixed with a surfactant; the surfactant includes one or more of the following: fatty alcohol polyoxyethylene ether, fatty acid glycol ester, fatty alcohol sulfate, fatty acid salt, sodium α-alkenyl sulfonate, hexadecyltrimethylammonium bromide, hexadecylpyridine chloride, dodecyl imidazoline ammonium salt, cocamidopropyl betaine, lauryl phosphatidyl betaine, sodium dodecyl sulfate, polyoxyethylene stearate, and OP emulsifier;

[0113] The mass ratio of surfactant to silicon-carbon composite particles is [0.1-10]:100, and preferably, the molar ratio of aluminum to silicon is 0.4:20.

[0114] Step 230: The second mixed slurry is spray-dried to load alumina onto the surface and pores of the silicon-carbon composite particles, thereby obtaining the second precursor particles.

[0115] The aluminum loading in the second precursor particles is greater than or equal to 50 ppm. The aluminum loading should be within a suitable range because alumina is an inactive substance. Excessive coating will reduce the specific capacity of the material and decrease the first-cycle coulombic efficiency. In this invention, the aluminum loading in the second precursor particles is preferably greater than 50 ppm and less than or equal to 50,000 ppm, and more preferably the aluminum loading range is 3,000 ppm to 15,000 ppm.

[0116] The increase in the specific surface area of ​​the second precursor particles relative to the specific surface area of ​​the silicon-carbon composite particles is greater than 0 and less than or equal to 100 m². 2 / g;

[0117] The inlet temperature range of spray drying is 70℃~500℃, and the outlet temperature range is 50℃~350℃.

[0118] Step 240: Carbon coating treatment is performed on the second precursor particles to obtain the novel silicon-carbon anode material.

[0119] Among them, the carbon coating treatment adopts gas phase coating; the carbon source gas selected for gas phase coating includes one or more of the following: methane, ethane, ethylene, acetylene, propane, propylene, n-butane, isobutane, butene, and 1,3-butadiene.

[0120] The coating process is completed using chemical vapor deposition equipment, including one or more of fluidized bed, boiling bed, and rotary furnace. After coating, the material is mixed, demagnetized, and sieved to obtain the final novel silicon-carbon anode material. In the preparation method provided in this embodiment of the invention, the spray drying process causes the loosely bonded primary carbon layer and alumina on the surface of the silicon-carbon composite particles to fall off, creating voids between the alumina layers. Because alumina has a porous structure, the specific surface area of ​​the silicon-carbon particles slightly increases. Therefore, during the carbon coating process, carbon atoms can continue to bond to the surface of the silicon-carbon particles, forming a carbon layer in the gaps between the alumina layers. This results in the structure of the first layer in the aforementioned outer shell, where a carbon layer coats the surface of the alumina layer and / or the carbon layer is distributed in the gaps between the alumina layers.

[0121] As carbon elements continue to deposit during the carbon coating process, a carbon coating layer is formed on the outermost surface of the alumina layer. Its functions include: First, because the alumina loaded on the surface of the silicon-carbon composite particles is prone to detachment, leading to a decrease in alumina loading, the carbon coating layer protects the alumina layer from detachment, allowing it to better fulfill its function. Second, the carbon coating layer protects the silicon-carbon composite particles, preventing them from reacting with water during electrode slurry preparation, inhibiting gas generation in the negative electrode slurry, ensuring material stability during homogenization, and thus guaranteeing the processing quality of the negative electrode sheet, thereby improving the electrochemical performance of the battery assembled using this negative electrode sheet. Third, the carbon coating layer also reduces the interfacial reaction between the silicon-carbon composite particles and the electrolyte, ensuring interfacial stability and improving the battery's cycle performance.

[0122] The novel silicon-carbon anode material provided in this invention can be used to prepare anode sheets, and these anode sheets containing the novel silicon-carbon anode material can be applied to secondary batteries, including lithium-ion batteries or lithium metal batteries. Full batteries prepared using the novel silicon-carbon anode material provided in this invention exhibit very little capacity and voltage decay after 14 days of storage at 60°C, indicating that batteries prepared using the novel silicon-carbon anode material provided in this invention have better stability. This is because during high-temperature storage, the electrolyte reduction reaction rate increases, producing substances such as HF. HF corrodes the SE I interface, triggering side reactions and continuously consuming active lithium ions in the electrolyte, leading to capacity reduction. The capacity loss after high-temperature storage mainly comes from the loss of active lithium ions caused by side reactions on the anode surface. However, the alumina in the novel silicon-carbon anode material provided in this invention can react with the HF produced by the electrolyte reduction reaction, thereby reducing the corrosion of the SE I interface layer by HF and improving the high-temperature storage stability of the battery.

[0123] To better understand the technical solution provided by this invention, the following examples illustrate the preparation process and characteristics of the novel silicon-carbon anode material of this invention.

[0124] Example 1

[0125] This embodiment provides a preparation process for a novel silicon-carbon anode material, the specific process of which is as follows.

[0126] (1) Dissolve 200g of aluminum isopropoxide in ethanol and stir to form a gel; wherein the concentration of ethanol is 10wt%, the aluminum-containing compounds in the gel include aluminum isopropoxide and aluminum oxide, and the mass of aluminum isopropoxide accounts for 0.01% of the total mass of the gel.

[0127] (2) Dissolve 4 kg of silicon-carbon composite particles in ethanol and stir until homogeneous to form a silicon-carbon slurry with a solid content of 20 wt%, wherein the specific surface area of ​​the silicon-carbon composite particles is 300 m². 2 / g, with a particle size Dv50 of 11μm.

[0128] (3) Mix the gel with the silicon carbide slurry and stir for 2 hours to form a mixed slurry.

[0129] (4) The mixed slurry is spray-dried. The inlet temperature of the spray dryer is 200°C and the outlet temperature is 90°C, so that aluminum isopropoxide and alumina are loaded on the surface and pores of the silicon-carbon composite particles to obtain intermediate particles, wherein the aluminum loading is 6000ppm.

[0130] (5) The intermediate particles are placed in a high-temperature furnace and sintered at 750°C in an argon atmosphere. During the sintering process, 500g of water vapor is introduced and the temperature is maintained for 5 hours to convert aluminum isopropoxide in the intermediate particles into stable alumina, thus obtaining precursor particles. During the sintering process, the high-temperature furnace is kept under positive pressure.

[0131] (6) Carbon coating treatment is performed on the precursor particles to obtain the new silicon-carbon anode material. The specific process is as follows: the precursor particles are placed in a rotary furnace and heated to 750°C under an argon atmosphere. Argon gas mixed with acetylene and propane is introduced in a volume ratio of 1:1 for gas phase coating. The volume ratio of acetylene and propane is 1:1. After holding at the temperature for 1.5 hours, the gas source is turned off. After mixing, demagnetizing and sieving, the new silicon-carbon anode material is obtained.

[0132] The novel silicon-carbon anode material prepared in this embodiment has the chemical formula Al. 0.036 SiO 0.08 C 0.8 The alumina layer in the outer shell of this novel silicon-carbon anode material is distributed in an island-like or dot-like pattern, with local agglomeration. The alumina layer and the encapsulated amorphous carbon layer are interspersed. The particle size increment ΔDv50 of the novel silicon-carbon anode material is 0.5 μm, and the specific surface area is 10 m². 2 / g.

[0133] SEM images of the novel silicon-carbon anode material prepared in this embodiment are shown below. Figure 4 As shown, a small amount of white particles can be seen. These white particles are aluminum oxide, which are formed when a small amount of aluminum oxide coated on the surface of the silicon-carbon composite particles falls off and mixes with the outermost carbon coating layer.

[0134] The XRD pattern of the novel silicon-carbon anode material prepared in this embodiment is shown below. Figure 5 As shown in the figure, the diffraction characteristic peaks are the amorphous characteristics of silicon-carbon composite particles. Since the content of alumina in the new silicon-carbon anode material is relatively low, it is not reflected in the XRD pattern.

[0135] The EDS diagram of the novel silicon-carbon composite material prepared in this embodiment is shown below. Figure 6 As shown in the figure, the novel silicon-carbon composite material prepared in this embodiment contains Si, Al, and C. The local elemental contents of the novel silicon-carbon composite material tested by EDS are shown in Table 1.

[0136] element signal type Element content (Wt%) Wt%Sigma C EDS 71.99 0.28 O EDS 4.05 0.19 Al EDS 0.60 0.04 Si EDS 23.36 0.22 Total / 100 /

[0137] Table 1

[0138] The novel silicon-carbon composite material prepared in this embodiment was used to prepare negative electrode sheets and assembled into coin cells and full cells. The electrochemical performance of the cells was then tested. The specific process is as follows.

[0139] The assembly and testing process for coin cells is as follows: First, the novel silicon-carbon composite material, conductive additive conductive carbon black, and binder polyvinylidene fluoride of this embodiment are homogenized in a mass ratio of 80:10:10. The negative electrode slurry is then coated, and the negative electrode sheet is dried in a vacuum oven at 110°C for 12 hours before being cut into 15mm diameter circles. Finally, the coin cells are assembled in a glove box in the following order: negative electrode shell, negative electrode sheet, separator, lithium sheet, metal gasket, spring sheet, and positive electrode shell. Finally, the cells are encapsulated under a pressure of 50MPa. After the prepared coin cells are left to stand for 12 hours, their electrochemical performance is tested by constant current charge-discharge at a rate of 0.1C under a voltage of 0-2V. The test environment is 25°C. The discharge specific capacity and first-cycle coulombic efficiency data of the coin cells are detailed in Table 2.

[0140] Full-cell high-temperature storage performance test procedure: The negative electrode slurry was prepared by homogenizing the novel silicon-carbon composite material, conductive additive, conductive carbon black, and binder polyvinylidene fluoride (mass ratio) of this embodiment at a mass ratio of 95:2:3. The positive electrode slurry was prepared by homogenizing the positive electrode active material lithium cobalt oxide, conductive additive, conductive carbon black, and binder polyvinylidene fluoride at a mass ratio of 95:2:3. After coating, drying, rolling, slitting, die-cutting, shaping, stacking, liquid injection, formation, aging, and encapsulation, the structure was completed. After standing at 25°C for 24 hours, the 100% SOC (state of charge) battery was stored at 60°C for 48 hours. Then, a discharge-charge cycle was performed at a rate of 0.2C between 2.5V and 4.2V. The fully charged battery was then stored at 60°C for 14 days. After that, a discharge test was performed, and the battery capacity and voltage decay were recorded. The discharge specific capacity and voltage values ​​after 14 days of storage at 60°C are detailed in Table 2.

[0141] Gas generation test procedure: The aluminum-plastic bag containing the negative electrode slurry is suspended in the liquid medium. The gas generation behavior of the slurry is characterized by the volume change of the sealed aluminum-plastic bag using the "drainage method". The gas generation of the slurry is recorded after 48 hours. The test data are detailed in Table 2.

[0142] The charge-discharge curves of the coin cell prepared from the novel silicon-carbon composite material in this embodiment are shown in the figure. Figure 7 As shown.

[0143] Example 2

[0144] This embodiment provides a preparation process for a novel silicon-carbon anode material, the specific process of which is as follows.

[0145] (1) Dissolve 4 kg of silicon-carbon composite particles in ethanol and stir until homogeneous to form a silicon-carbon slurry with a solid content of 20 wt%, wherein the specific surface area of ​​the silicon-carbon composite particles is 260 m². 2 / g, with a particle size Dv50 of 11μm; the silicon-carbon composite particles used in this embodiment have a specific capacity of 2050mAh / g and a coulombic efficiency of 92.5% in the first week, as tested at 2V.

[0146] (2) Mix alumina and silicon carbide slurry evenly to obtain a mixed slurry; wherein the alumina is nano alumina with a particle size Dv50 of 500nm.

[0147] (3) The mixed slurry is spray-dried. The inlet temperature of the spray dryer is 200℃ and the outlet temperature is 90℃, so that alumina is loaded on the surface and pores of the silicon-carbon composite particles to obtain precursor particles. The aluminum loading in the precursor particles is 2800ppm.

[0148] (4) Carbon coating treatment is performed on the precursor particles to obtain the new silicon-carbon anode material. The specific process is as follows: the precursor particles are placed in a rotary furnace and heated to 950°C under an argon atmosphere. Argon gas mixed with acetylene and propane is introduced in a volume ratio of 1:1 for gas phase coating. The volume ratio of acetylene and propane is 1:1. After holding at the temperature for 1.5 hours, the gas source is turned off. After mixing, demagnetizing and sieving, the new silicon-carbon anode material is obtained.

[0149] The novel silicon-carbon anode material prepared in this embodiment has the chemical formula Al. 0.027 SiO 0.04 C 0.83 The particle size increment ΔDv50 of this novel silicon-carbon anode material is 0.8 μm, and its specific surface area is 8.3 m². 2 / g.

[0150] The novel silicon-carbon composite material prepared in this embodiment was used to prepare negative electrode sheets and assembled into coin cells and full cells. The electrochemical performance of the cells was tested, and the gas production of the materials was tested. The specific process was the same as in Example 1. The test results are detailed in Table 2.

[0151] Example 3

[0152] This embodiment provides a novel silicon-carbon anode material preparation process, which differs from Embodiment 1 in step (5). In step (5), the intermediate particles are placed in a high-temperature furnace and sintered at 300°C in a nitrogen atmosphere for 10 hours to allow the C9H atoms in the intermediate particles to precipitate. 21 AlO3 is converted into stable alumina to obtain precursor particles, and no water vapor is introduced during the sintering process. The other processes are the same as in Example 1.

[0153] The novel silicon-carbon anode material prepared in this embodiment has the chemical formula Al. 0.05 SiO 0.04 C 0.88 The particle size increment ΔDv50 of this novel silicon-carbon anode material is 1.2 μm, and its specific surface area is 2 m². 2 / g.

[0154] The novel silicon-carbon composite material prepared in this embodiment was used to prepare negative electrode sheets and assembled into coin cells and full cells. The electrochemical performance of the cells was tested, and the gas production of the materials was tested. The specific process was the same as in Example 1. The test results are detailed in Table 2.

[0155] Example 4

[0156] This embodiment provides a novel preparation process for a silicon-carbon anode material. The difference from Embodiment 1 is that in step (3), a surfactant, hexadecyltrimethylammonium bromide, is added during the mixing of the gel and silicon-carbon slurry to enhance the wettability between the slurries, resulting in a more uniform distribution of aluminum ions on the surface of the silicon-carbon particles during slurry mixing. Furthermore, the carbon source gas used in step (6) for carbon coating is propylene. All other processes are the same as in Embodiment 1.

[0157] The novel silicon-carbon anode material prepared in this embodiment has the chemical formula Al. 0.1 SiO 0.02 C 0.95 The particle size increment ΔDv50 of this novel silicon-carbon anode material is between 1.03 μm and 1.03 μm, and the specific surface area is 4.68 m². 2 / g.

[0158] The novel silicon-carbon composite material prepared in this embodiment was used to prepare negative electrode sheets and assembled into coin cells and full cells. The electrochemical performance of the cells was tested, and the gas production of the materials was tested. The specific process was the same as in Example 1. The test results are detailed in Table 2.

[0159] Example 5

[0160] This embodiment provides a novel silicon-carbon anode material preparation process. The difference from Embodiment 1 is that in step (3), the mixing process of the gel and silicon-carbon slurry uses a circulating pump and an emulsifying pump to enhance the uniformity of slurry dispersion. Furthermore, in step (6), the carbon coating process uses propane as the carbon source gas, and the carbon coating process and the sintering process in step (5) are carried out in the same high-temperature furnace. All other processes are the same as in Embodiment 1.

[0161] The novel silicon-carbon anode material prepared in this embodiment has the chemical formula Al. 0.07 SiO 0.01 C 0.903 The particle size increment ΔDv50 of this novel silicon-carbon anode material is 0.64 μm, and its specific surface area is 1.99 m². 2 / g.

[0162] The novel silicon-carbon composite material prepared in this embodiment was used to prepare negative electrode sheets and assembled into coin cells and full cells. The electrochemical performance of the cells was tested, and the gas production of the materials was tested. The specific process was the same as in Example 1. The test results are detailed in Table 2.

[0163] Example 6

[0164] This embodiment provides a preparation process for a novel silicon-carbon anode material, the specific process of which is as follows.

[0165] (1) Dissolve 4 kg of silicon-carbon composite particles in ethanol, add 200 ml of saturated aqueous solution of aluminum nitrate nonahydrate, and stir until homogeneous to form a silicon-carbon slurry with a solid content of 20 wt%, wherein the specific surface area of ​​the silicon-carbon composite particles is 210 m². 2 / g, with a particle size Dv50 of 12.1μm.

[0166] (2) Stir for 2 hours to mix evenly and form a mixed slurry.

[0167] (3) The mixed slurry is spray-dried. The inlet temperature of the spray dryer is 200℃ and the outlet temperature is 90℃, so that aluminum nitrate nonahydrate and aluminum oxide are loaded on the surface and pores of silicon-carbon composite particles to obtain intermediate particles, wherein the aluminum loading is 6000ppm.

[0168] (4) The intermediate particles are placed in a high-temperature furnace and sintered at 750°C in an argon atmosphere. The temperature is maintained for 5 hours to convert aluminum nitrate in the intermediate particles into stable aluminum oxide, thus obtaining precursor particles. During the sintering process, the high-temperature furnace is kept under positive pressure.

[0169] (5) Carbon coating treatment is performed on the precursor particles to obtain the new silicon-carbon anode material. The specific process is as follows: the precursor particles are placed in a rotary furnace and heated to 750°C under an argon atmosphere. Argon gas mixed with acetylene and propane is introduced in a volume ratio of 1:1 for gas phase coating. The volume ratio of acetylene and propane is 1:1. After holding at the temperature for 1.5 hours, the gas source is turned off. After mixing, demagnetizing and sieving, the new silicon-carbon anode material is obtained.

[0170] The novel silicon-carbon anode material prepared in this embodiment has the chemical formula Al. 0.1 S iO 0.02 C 0.85 The particle size increment ΔDv50 of this novel silicon-carbon anode material is 1.2 μm, and its specific surface area is 1.36 m². 2 / g.

[0171] The novel silicon-carbon composite material prepared in this embodiment was used to prepare negative electrode sheets and assembled into coin cells and full cells. The electrochemical performance of the cells was tested, and the gas production of the materials was tested. The specific process was the same as in Example 1. The test results are detailed in Table 2.

[0172] To better illustrate the effects of the embodiments of the present invention, comparative examples 1-3 are compared with the above embodiments.

[0173] Comparative Example 1

[0174] This comparative example directly uses the silicon-carbon composite particles from Example 1 to prepare coin cells and full cells for testing. Gas production tests were conducted on the materials, and the specific process was the same as in Example 1. The test results are detailed in Table 2.

[0175] Comparative Example 2

[0176] This comparative example provides a preparation process and performance testing of a negative electrode material. This negative electrode material differs from Example 1 in that it has an iron oxide layer and a carbon coating layer coated on the surface of silicon-carbon composite particles. The preparation process is as follows:

[0177] (1) Dissolve 200g of ferric propionate in 70wt% ethanol to form an iron salt solution with a concentration of 0.01%.

[0178] (2) Dissolve 4 kg of silicon-carbon composite particles in ethanol and stir evenly to form a silicon-carbon slurry with a solid content of 20 wt%.

[0179] (3) Stir the iron salt solution and silicon carbide slurry for 2 hours to mix them evenly and form a mixed slurry.

[0180] (4) The mixed slurry is spray-dried. The inlet temperature of the spray dryer is 170°C and the outlet temperature is 85°C, so that ferric propionate is loaded on the surface and pores of the silicon-carbon composite particles to obtain intermediate particles. The iron loading in the intermediate particles is 4100ppm.

[0181] (5) The intermediate particles are placed in a high-temperature furnace and sintered at 700°C in an argon atmosphere. The temperature is maintained for 3 hours to convert the ferric propionate in the intermediate particles into stable iron oxide, thus obtaining the precursor particles. During the sintering process, the high-temperature furnace is kept under positive pressure.

[0182] (6) Carbon coating treatment is performed on the precursor particles to obtain a new type of silicon-carbon anode material. The specific process is as follows: the precursor particles are placed in a rotary furnace and heated to 950°C under an argon atmosphere. Argon gas mixed with ethylene and methane is introduced at a volume ratio of 1:1 for gas phase coating, wherein the volume ratio of ethylene to methane is 2:1. After holding at the temperature for 1.5 hours, the gas source is turned off. After mixing, demagnetizing and sieving, the anode material is obtained.

[0183] The negative electrode material prepared in this comparative example was used to prepare coin cells and full cells for testing. Gas production tests were conducted on the material, and the specific process was the same as in Example 1. The test results are detailed in Table 2.

[0184] Comparative Example 3

[0185] This comparative example provides a preparation process and performance testing of a negative electrode material. This negative electrode material differs from Example 1 in that it only coats the surface of the silicon-carbon composite particles with an alumina layer, without carbon coating. The preparation process is as follows:

[0186] (1) Dissolve 200g of aluminum isopropoxide in ethanol and stir to form a gel; wherein the concentration of ethanol is 10wt%, the aluminum-containing compounds in the gel include aluminum isopropoxide and aluminum oxide, and the mass of aluminum isopropoxide accounts for 0.01% of the total mass of the gel.

[0187] (2) Dissolve 4 kg of silicon-carbon composite particles in ethanol and stir until homogeneous to form a silicon-carbon slurry with a solid content of 20 wt%, wherein the specific surface area of ​​the silicon-carbon composite particles is 300 m². 2 / g, with a particle size Dv50 of 11μm.

[0188] (3) Mix the gel with the silicon carbide slurry and stir for 2 hours to form a mixed slurry.

[0189] (4) The mixed slurry is spray-dried. The inlet temperature of the spray dryer is 200°C and the outlet temperature is 90°C, so that aluminum isopropoxide and alumina are loaded on the surface and pores of the silicon-carbon composite particles to obtain intermediate particles, wherein the aluminum loading is 6000ppm.

[0190] (5) The intermediate particles are placed in a high-temperature furnace and sintered at 750°C in an argon atmosphere. During the sintering process, 500g of water vapor is introduced and the temperature is maintained for 5 hours to convert aluminum isopropoxide in the intermediate particles into stable alumina, thus obtaining precursor particles. During the sintering process, the high-temperature furnace is kept under positive pressure.

[0191] The chemical formula of the negative electrode material prepared in this comparative example is Al. 0.085 Si O 0.02 C 0.95 The particle size increment ΔDv50 of this anode material is 1.01 μm, and its specific surface area is 8.54 m². 2 / g.

[0192] The negative electrode material prepared in this comparative example was used to prepare coin cells and full cells for testing. Gas production tests were conducted on the material, and the specific process was the same as in Example 1. The test results are detailed in Table 2.

[0193] Table 2 summarizes the test data of the button cells (hereinafter referred to as button cells) and full cells assembled in Examples 1-6 and Comparative Examples 1-3.

[0194]

[0195]

[0196] Table 2

[0197] As can be seen from Table 2:

[0198] In the gas generation test, the gas generation of the materials in Examples 1-6 was much smaller than that in Comparative Examples 1-3. This is because the novel silicon-carbon anode materials in Examples 1-6 protect the silicon-carbon composite particles by gas-phase carbon coating, preventing the nano-silicon from reacting with water and inhibiting the gas generation behavior of the anode slurry.

[0199] In the button cell test, the specific capacity of the button cells in Examples 1-6 was greater than that of Comparative Examples 2 and 3, and close to that of Comparative Example 1. The first-week coulombic efficiency of the button cells in Examples 1-6 was greater than that of Comparative Examples 2 and 3.

[0200] In full-cell testing, the discharge specific capacity and voltage values ​​of Examples 1-6 after 14 days of cycling at 60°C were all greater than those of Comparative Examples 1 and 2. This indicates that the full cells assembled using the novel silicon-carbon anode materials of Examples 1-6 of this invention have better storage performance at high temperatures, resulting in better cycling performance at high temperatures. Comparative Example 2, which involved coating iron oxide onto a silicon-carbon composite material, did not improve high-temperature storage. Furthermore, iron, as a magnetic material, would reduce the electrochemical performance of the anode material. Coating iron oxide followed by carbon coating resulted in a loose carbon coating layer structure, which easily led to gas generation during the preparation of the anode slurry.

[0201] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A novel silicon-carbon anode material, characterized in that, The novel silicon-carbon anode material comprises a core and a shell; the shell covers the surface of the core. The core is a silicon-carbon composite particle; The outer shell includes a first layer and a second layer covering the first layer; the first layer includes an aluminum oxide layer and a carbon layer; the carbon layer is distributed in the gaps of the aluminum oxide layer; the second layer is a carbon coating layer; The novel silicon-carbon anode material has the general chemical formula Al. a SiO b C c , where a, b, and c are the number of moles of elements Al, O, and C, respectively, and 0 < a < 25, 0 < b < 20, and 0 < c < 30.

2. The novel silicon-carbon anode material according to claim 1, characterized in that, The silicon-carbon composite particles comprise: silicon nanoparticles, a carbon material matrix, and a primary carbon layer; the silicon nanoparticles are attached to the pores of the carbon material matrix, and the primary carbon layer coats the outer surface of the carbon material matrix; the specific surface area of ​​the silicon-carbon composite particles is 0.1 m². 2 / g~800m 2 Between / g; The silicon nanoparticles include: silicon nanocrystals and / or silicon oxide; The average size of the silicon nanocrystals is between 0.1 nm and 50 nm. The general chemical formula of the silicon oxide is SiO2. x And 0 ≤ x < 2; The total thickness of the outer shell is between 0.1 nm and 1 μm; The alumina layer is distributed in one or more of the following morphologies: island-shaped, dot-shaped, spherical, and rod-shaped; the alumina in the alumina layer is crystalline and / or amorphous. The mass of the carbon material matrix accounts for 0.1% to 75% of the total mass of the novel silicon-carbon anode material; The percentage of carbon in the outer shell to the total mass of the novel silicon-carbon anode material is 0.1% to 50%. The mass percentage of aluminum in the outer shell is less than or equal to 30% of the total mass of the novel silicon-carbon anode material; the aluminum content is between 40 ppm and 40,000 ppm.

3. The novel silicon-carbon anode material according to claim 1, characterized in that, The particle size D of the novel silicon-carbon anode material v 50 is between 0.1 μm and 100 μm; The specific surface area of ​​the novel silicon-carbon anode material is 0.1 m². 2 / g~500m 2 Between / g; The total carbon content in the novel silicon-carbon anode material is between 1% and 80%.

4. A method for preparing the novel silicon-carbon anode material according to any one of claims 1-3, characterized in that, The preparation method includes: An aluminum salt is dissolved in a first solvent and stirred to form a dispersion system; wherein the aluminum-containing compound in the dispersion system includes: an aluminum salt, or an aluminum salt and aluminum oxide; The silicon-carbon composite particles are dissolved in the same solvent as the first solvent to form a first silicon-carbon slurry. The dispersion system is mixed evenly with the first silicon carbide slurry to form a first mixed slurry; The first mixed slurry is spray-dried to load the aluminum-containing compound in the dispersion system onto the surface and pores of the silicon-carbon composite particles, thereby obtaining intermediate particles. The intermediate particles are sintered in a protective atmosphere, with water vapor introduced during the sintering process to convert the aluminum salt in the intermediate particles into stable alumina, yielding first precursor particles; wherein the aluminum loading in the first precursor particles is greater than or equal to 50 ppm; and the increase in the specific surface area of ​​the first precursor particles relative to the specific surface area of ​​the silicon-carbon composite particles is greater than 0 and less than or equal to 100 m². 2 / g; The first precursor particles are subjected to carbon coating treatment to obtain a novel silicon-carbon anode material.

5. The preparation method according to claim 4, characterized in that, The specific surface area of ​​the silicon-carbon composite particles is 0.1 m². 2 / g~800m 2 Between / g; The aluminum salts include: Al(OH)3, AlOOH, Al2(CO3)3, and C9H. 21 AlO3, Al(NO3)3, Al(NO3)3·9H2O, Al[OOCH3(OH)2]·yH2O, AlCl3, Al(NO)3, Al2(SO4)3, AlF3, AlF3, Al2H6O 12 S3, Al2H6O9Si3, Al2H6O9Ti3, AlBH3O3, C 54 H 105 AlO6, AlCl3H 21 O 21 C2H3AlNO4, C9H 21 AlO3, C 15 H 21 AlO6, C2H5AlO4, C6H5AlO7, C6H8AlO7, C 18 H 15 AlO9, C6H 15 AlO3, C 12 H 27 AlO3, C 12 H 27 AlO3, C 54 H 99 One or more of AlO6, wherein 0.1 ≤ y ≤ 20; the particle size D of the aluminum salt v 50 is between 0.01μm and 20μm; The step of uniformly mixing the dispersion system with the first silicon carbide slurry further includes mixing it with a surfactant; the surfactant includes one or more of the following: fatty alcohol polyoxyethylene ether, fatty acid glycol ester, fatty alcohol sulfate, fatty acid salt, sodium α-alkenyl sulfonate, hexadecyltrimethylammonium bromide, hexadecylpyridine chloride, dodecyl imidazoline ammonium salt, cocamidopropyl betaine, lauryl phosphatidyl betaine, sodium dodecyl sulfate, polyoxyethylene stearate, and OP emulsifier; The mass ratio of the surfactant to the silicon-carbon composite particles is [0.1-10]:100; The first solvent includes: deionized water or an organic solvent; the organic solvent includes: any one of ethanol, dimethylformamide (DMF), DMSO, tetrahydrofuran, isopropanol, polyethylene glycol, methanol, acetone, toluene, ethyl acetate, cyclohexane, chloroform, dichloromethane, and propylene glycol; The aluminum content in the intermediate particles ranges from 50 ppm to 50,000 ppm.

6. The preparation method according to claim 4, characterized in that, The sintering temperature is 300℃~850℃, and the sintering holding time is 2 hours~12 hours; The flow rate of the water vapor is greater than or equal to 0 and less than or equal to 70 L / min; The inlet temperature range of the spray dryer is 70℃~500℃, and the outlet temperature range is 50℃~350℃. The protective atmosphere includes one or more of nitrogen, argon, hydrogen, helium, or neon. The carbon coating process employs gas-phase coating; the carbon source gas selected for the gas-phase coating includes one or more of the following: methane, ethane, ethylene, acetylene, propane, propylene, n-butane, isobutane, butene, and 1,3-butadiene.

7. A method for preparing the novel silicon-carbon anode material according to any one of claims 1-3, characterized in that, The preparation method includes: The silicon-carbon composite particles are dissolved in a second solvent to form a second silicon-carbon slurry; Alumina and the second silicon carbide slurry are mixed evenly to obtain a second mixed slurry; The second mixed slurry is spray-dried to load the alumina onto the surface and pores of the silicon-carbon composite particles, yielding second precursor particles; wherein the aluminum loading in the second precursor particles is greater than or equal to 50 ppm; and the increase in the specific surface area of ​​the second precursor particles relative to the specific surface area of ​​the silicon-carbon composite particles is greater than 0 and less than or equal to 100 m². 2 / g; The second precursor particles are carbon-coated to obtain a novel silicon-carbon anode material.

8. The preparation method according to claim 7, characterized in that, The specific surface area of ​​the silicon-carbon composite particles is 0.1 m². 2 / g~800m 2 Between / g; The alumina includes crystalline alumina and / or amorphous alumina; the particle size Dv50 of the alumina is less than or equal to 20 μm, and the purity is greater than or equal to 95%; The second solvent includes: deionized water or an organic solvent; the organic solvent includes: any one of ethanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran, isopropanol, polyethylene glycol, methanol, acetone, toluene, ethyl acetate, cyclohexane, chloroform, dichloromethane, and propylene glycol; The molar ratio of aluminum to silicon in the second mixed slurry is (0-1):20; The process of uniformly mixing alumina with the second silicon carbide slurry further includes mixing it with a surfactant; the surfactant includes one or more of the following: fatty alcohol polyoxyethylene ether, fatty acid glycol ester, fatty alcohol sulfate, fatty acid salt, sodium α-alkenyl sulfonate, hexadecyltrimethylammonium bromide, hexadecylpyridine chloride, dodecyl imidazoline ammonium salt, cocamidopropyl betaine, lauryl phosphatidyl betaine, sodium dodecyl sulfate, polyoxyethylene stearate, and OP emulsifier; The mass ratio of the surfactant to the silicon-carbon composite particles is [0.1-10]:

100.

9. The preparation method according to claim 7, characterized in that, The inlet temperature range of the spray dryer is 70℃~500℃, and the outlet temperature range is 50℃~350℃. The carbon coating process employs gas-phase coating; the carbon source gas selected for the gas-phase coating includes one or more of the following: methane, ethane, ethylene, acetylene, propane, propylene, n-butane, isobutane, butene, and 1,3-butadiene.

10. A secondary battery, characterized in that, The secondary battery includes the novel silicon-carbon anode material as described in any one of claims 1-3.

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