WO2021056266A1

WO2021056266A1 - Lithium ion battery pre-lithiated silicon-carbon multilayer composite negative electrode material and preparation method therefor

Info

Publication number: WO2021056266A1
Application number: PCT/CN2019/107858
Authority: WO
Inventors: 赵东辉; 周鹏伟; 白宇; 霍振翔
Original assignee: 福建翔丰华新能源材料有限公司
Priority date: 2019-09-25
Filing date: 2019-09-25
Publication date: 2021-04-01

Abstract

A lithium ion battery pre-lithiated silicon-carbon multilayer composite negative electrode material and a preparation method therefor. The composite negative electrode material comprises an amorphous carbon matrix (1), pre-lithiated silicon oxide particles (3) and a graphene material (2). The graphene material (2) evenly wraps the outer surface of the pre-lithiated silicon oxide to form composite particles. The composite particles are evenly dispersed in the amorphous carbon matrix (1). The silicon oxide particles after pre-lithiation greatly increase the coulombic efficiency of the silicon-based negative electrode material, and the graphene material is lightweight and high in strength, and the excellent conductivity thereof greatly enhances the mechanical performance and conductivity of the composite material. The amorphous carbon matrix has the function of isolating an electrolyte solution, and preventing the silicon from coming into contact with the electrolyte solution and producing a large, unstable SEI film. Experiments show that the prepared composite negative electrode material has the advantages of a good mechanical performance, high conductivity, high first coulombic efficiency, and a stable cycle performance.

Description

Pre-lithiated silicon carbon multilayer composite negative electrode material for lithium ion battery and preparation method thereof

Technical field

The invention relates to the electrochemical field technology, in particular to a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries and a preparation method thereof.

Background technique

Lithium-ion batteries have many advantages such as high volume and mass energy density, high power density, long cycle life, high discharge voltage, low self-discharge rate, no memory effect, low environmental pollution, low cost, and wide operating temperature range. The most promising secondary energy storage battery. In the field of portable consumer electronics, new energy vehicles, aerospace and large-scale energy storage in daily life, lithium-ion batteries have shown a wide range of application prospects. With the development of lightweight and highly integrated equipment, the energy density, cycle life, and safety performance of lithium-ion batteries need to be improved urgently. One of the important starting points for improving its performance is to improve the performance of the negative electrode material.

At present, the most widely used negative electrode material in lithium-ion batteries is graphite-based materials. The capacity of some high-end graphite anodes on the market can reach 360～365mAh/g, which is very close to the theoretical capacity of 372mAh/g. Therefore, graphite is used as a lithium-ion battery anode, and its energy density has little room for improvement. This forces the academic and industrial circles to find new A new type of anode material with high energy density.

There are many types of new anode materials that have been explored. According to different lithium storage mechanisms, they can be divided into three categories: embedded, alloy, and conversion. Among them, the silicon anode material is an alloy-based anode material for lithium storage, which has attracted widespread attention due to its extremely high theoretical specific capacity. Silicon stores lithium at room temperature (25～85℃) to form Li15Si4 alloy phase, the theoretical mass specific capacity is as high as 3579mAh/g, and at high temperature (100～120℃) lithium stores form Li22Si5 alloy phase, and the theoretical mass specific capacity is as high as 4212mAh/g. The theoretical volumetric capacity of silicon at room temperature is 2081mAh·cm-3, which is also much higher than the theoretical volumetric capacity of graphite (779mAh·cm-3). At the same time, the lithium insertion potential of silicon is slightly higher than that of graphite, about 0.2V vs. Li/Li+, which can reduce lithium evolution to a certain extent and improve the safety performance of the battery. In addition, silicon has abundant reserves, low production costs, and is environmentally friendly. However, there are two key problems in the development of silicon anode materials: the volume change during the cycle is as high as 300% to 400%, causing the electrode to powder and fall off, and at the same time, a fresh surface is created, which leads to the continuous growth of the SEI film, resulting in the continuous consumption of electrolyte. In addition, the electronic conductivity and ion conductivity of intrinsic silicon are not high, and the rate performance is poor.

To solve the above problems, the nanometer method can be used to reserve space for the volume expansion of silicon, such as silicon particles, silicon nanowires, or to construct porous nanostructures, such as silicon thin films. It can also be combined with some matrix materials with high elastic modulus. It forms a coated or embedded composite structure to reduce the contact area between silicon and electrolyte and buffer the volume expansion of silicon. For example, silicon is compounded with mesoporous carbon spheres. If the conductivity of the matrix material is better, the internal resistance of the electrode can also be reduced. This type of composite matrix includes conductive polymers, carbon materials, and metals. Among them, the silicon-carbon composite form can effectively improve the electrochemical performance of the silicon anode. At the same time, the silicon-carbon composite can make full use of the existing carbon anode production line, and the electrolyte system of the silicon-carbon anode and the existing graphite anode are relatively matched, so the use of this silicon-carbon composite method is also conducive to the gradual transition of the lithium-ion battery industry . Therefore, it is a general trend that silicon carbon anodes become the next-generation anode materials for lithium-ion batteries.

According to reports, the common methods of silicon-carbon composite in the industry mainly include the following five types: 1. Carbon-coated nano-Si@C: low cost, high first-time coulombic efficiency, but large volume expansion, long The cycle stability is poor, and the monomer capacity is generally 400-2000mAh/g. 2. Carbon-coated silicon oxide (SiO@C): higher cost, lower volume expansion, very good long-cycle stability, and generally lower first-time coulombic efficiency. The monomer capacity is generally 1300～1700mAh/g. 3. Carbon-coated silicon nanowire (Si nanowire/SS): Both the specific capacity and the first coulombic efficiency are high, but it needs to cooperate with mature pre-physical technology to ensure long cycle stability, and there are certain difficulties in the process. 4. Carbon-coated metamorphic silicon oxide (SiOx@C): Improve the first Coulomb efficiency or improve the cycle performance of the material by changing the content of oxygen. For the first time, the Coulombic efficiency is high, and the long-cycle stability is good. It is currently one of the higher-end silicon carbon anode materials. The monomer capacity is generally 1300～1700mAh/g. 5. Carbon-coated amorphous silicon alloy (amorphous-SiM@C): First, nano-silicon and metal element (such as Fe, Cu) are composited at high temperature, and then the carbon layer is coated. The first-time coulombic efficiency is generally high, but there are certain difficulties in the process, the preparation cost is high, and crystalline silicon is easy to precipitate during the carbonization process, which is not suitable for large-scale production at present.

Summary of the invention

technical problem

The solution to the problem

Technical solutions

In view of this, the main purpose of the present invention is to provide a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries and a preparation method thereof, which has good mechanical properties, high conductivity, and is the first The characteristics of high coulombic efficiency and stable cycle performance.

In order to achieve the above objectives, the present invention adopts the following technical solutions:

A pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries, comprising an amorphous carbon matrix, pre-lithiated silicon oxide particles and a graphene material; the graphene material is uniformly coated on the pre-lithiated silicon oxide The outer surface forms composite particles, which are uniformly dispersed in the amorphous carbon matrix.

A method for preparing the aforementioned pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries. Firstly, using silicon oxide as a raw material, the silicon oxide and the lithium-containing ionic liquid are mixed and sintered to achieve pre-lithiation to obtain pre-lithiation The silicon oxide particles are then loaded with a catalyst precursor, and graphene material is grown on the surface of the pre-lithiated silicon oxide by chemical vapor deposition, and finally it is homogeneously fused with the carbon source and subjected to heat treatment to obtain the final lithium-ion battery pre-lithiated silicon Carbon multilayer composite anode material.

As a preferred solution, it includes the following specific steps:

(1) Mix a certain particle size of silicon oxide with a lithium-containing ionic liquid, and then place it in a high-temperature tube furnace for sintering, so that the silicon oxide can fully react with the lithium-containing ionic liquid to obtain pre-lithiated silicon oxide Particles

(2) Disperse a certain proportion of pre-lithiated silica particles uniformly in the solution of the catalyst precursor through ultrasonic treatment, and then perform stirring treatment at a certain temperature to volatilize the solvent, so that the catalyst precursor is uniformly supported on the pre-lithiation The surface of the silicon oxide particles;

(3) Put the pre-lithiated silicon oxide particles that have supported the catalyst precursor into a high-temperature furnace, and heat it for a period of time in the mixed gas of inert gas and reducing gas to fully reduce the catalyst precursor; then keep the inert gas The volume ratio of the reducing gas remains unchanged, and the gaseous carbon source is introduced, the carbon source is decomposed and reconstructed at a higher temperature, and the graphene material is deposited on the outer surface of the pre-lithiated silicon oxide particles;

(4) Mix the pre-lithiated silicon oxide particles coated with the graphene material and the solid carbon source uniformly and then add them to the fusion machine for homogeneous fusion, and then put the mixture into a high-temperature furnace for high-temperature carbonization in an inert atmosphere. The final pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries is obtained.

As a preferred solution, the particle size of the silicon oxide in the step (1) is 10 nm-10 μm.

As a preferred solution, the lithium-containing ionic liquid in the step (1) is LiMIM-TFSI, LiEMI M-BF4, LiEMIM-PF6, LiEMIM-TFSI, LiPMMIM-TFSI, LiBMIM-TFSI, LiAAIM-Cl, LiAMIM- One or more of Br, LiAEIM-Br, LiAAIM-Br, LiAAIM-I, LiAAIM-TFSI, LiAMIM-TFSA, LiAMIM-BF4, LiEMIMBF4, LiEMIMTFSI, LiEMIMTFSI, LiBMIMBF, LiBMIMPF6, LiBMIMPF6, and LiPMMIMTFSI.

As a preferred solution, the mass ratio of silicon oxide to lithium-containing ionic liquid in the step (1) is (10-35):1.

As a preferred solution, the gas introduced into the high-temperature tube furnace in the step (1) is one of the inert gases nitrogen, argon, and helium, and the sintering temperature is 500-1000°C.

As a preferred solution, the mass ratio of the pre-lithiated silicon oxide particles to the catalyst precursor in the step (2) is (20-1):1.

As a preferred solution, the catalyst precursor used in the step (2) is a transition metal salt, which includes ferric chloride, ferrous chloride, ferric nitrate, ferrous nitrate, ferric acetate, ferrous acetate, and sulfuric acid Iron, ferrous sulfate, ferric oxalate, ferrous oxalate, ferric citrate, ferrous gluconate, ferrocene, cobalt chloride, cobalt nitrate, cobalt acetate, cobalt sulfate, cobalt oxalate, cobalt citrate, cobalt gluconate, Cobalt dicene, nickel chloride, nickel nitrate, nickel acetate, nickel sulfate, nickel oxalate, nickel citrate, nickel gluconate, nickel dicene, copper chloride, copper nitrate, copper acetate, copper sulfate, copper oxalate, citric acid Copper, copper gluconate, etc.; the solvent is one or more of water, methanol, ethanol, ethylene glycol, isopropanol, glycerol, ether, acetone, benzene or toluene.

As a preferred solution, the temperature of the stirring treatment in the step (2) is 25-200°C.

As a preferred solution, in the step (3), the inert gas is one of nitrogen, argon, and helium, and the reducing gas is one or more of hydrogen, ammonia, methane, and nitric oxide. The volume percentage of the reducing gas is 10-40%, the gas carbon source accounts for 5-25% of the total volume, and the gas carbon source used is one of acetylene, methane, ethane, ethylene, and butene.

As a preferred solution, the precursor reduction temperature in the step (3) is 300-600° C., the temperature is maintained for 1-10 h, and the graphene deposition temperature is 500-1000° C., and the temperature is maintained for 5 min-1 h.

As a preferred solution, the solid carbon source used in the step (4) is one or more of sucrose, petroleum pitch, coal tar, epoxy resin, phenolic resin, polyvinyl alcohol, and polyvinyl chloride, During the fusion process, the speed of the fusion machine is 1000～2000rpm, and the fusion time is 1～4h.

As a preferred solution, the carbonization temperature in the step (4) is 700-1000°C, and the holding time is 1-8h.

The beneficial effects of the invention

Beneficial effect

The silicon oxide in the present invention greatly improves the first effect of the silicon-based negative electrode material after pre-lithiation, and the light weight, high strength, and excellent electrical conductivity of the graphene material greatly improve the mechanical properties and electrical conductivity of the composite material. Amorphous carbon The matrix plays the role of isolating the electrolyte and avoiding the contact between silicon and the electrolyte to produce a large number of unstable SEI films. Experiments show that the composite anode material prepared by the invention has good mechanical properties, high conductivity, high first-time coulombic efficiency and stable cycle performance. specialty.

Brief description of the drawings

Description of the drawings

Fig. 1 is a schematic diagram of the structure of the composite negative electrode material of the present invention.

Description of the drawing identification:

1. Amorphous carbon matrix 2. Graphene material

3. Pre-lithiated silicon oxide particles.

The best embodiment for implementing the invention

The best mode of the present invention

The present invention discloses a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries, as shown in Figure 1, comprising an amorphous carbon matrix 1, pre-lithiated silicon oxide particles 3 and graphene material 2; the graphene The material 2 is evenly coated on the outer surface of the pre-lithiated silicon oxide 3 to form composite particles. The graphene material 2 plays a role in enhancing mechanical properties and conductivity. The composite particles are uniformly dispersed in the amorphous carbon matrix 1. The amorphous carbon matrix 1 plays a role of isolating the electrolyte, thereby avoiding the contact between silicon and the electrolyte to produce a large number of unstable SEI films.

The present invention also discloses a method for preparing the foregoing pre-lithiation silicon-carbon multilayer composite negative electrode material for lithium ion batteries. Firstly, using silicon oxide as a raw material, the silicon oxide and the lithium-containing ionic liquid are mixed and sintered to achieve pre-lithiation. , To obtain pre-lithiated silicon oxide particles, and then support the catalyst precursor, grow graphene material on the surface of the pre-lithiated silicon oxide by chemical vapor deposition, and finally homogenously fuse with the carbon source and heat treatment to obtain the final lithium ion Battery pre-lithiated silicon carbon multilayer composite anode material.

It includes the following specific steps:

(1) Mix a certain particle size of silicon oxide with a lithium-containing ionic liquid, and then place it in a high-temperature tube furnace for sintering, so that the silicon oxide can fully react with the lithium-containing ionic liquid to obtain pre-lithiated silicon oxide Particles; silicon oxide particle size is 10nm～10μm; lithium-containing ionic liquids are LiMIM-TFSI, LiEMIM-BF4, LiEMIM-PF6, LiEMIM-TFSI, LiPMMIM-TFSI, LiBMIM-TFSI, LiAAIM-Cl, LiAMIM-Br, One or more of LiAEIM-Br, LiAAIM-Br, LiAAIM-I, LiAAIM-TFSI, LiAMIM-TFSA, LiAMIM-BF4, LiEMIMBF4, LiEMIMTFSI, LiEMIMTFSI, LiBMIMBF, LiBMIMPF6, LiBMIMPF6 and LiPMMIMTFSI; silicon oxide and containing The mass ratio of the ionic liquid of lithium is (10-35):1; the gas introduced into the high-temperature tube furnace is one of the inert gases nitrogen, argon, and helium, and the sintering temperature is 500-1000°C.

(2) Disperse a certain proportion of pre-lithiated silica particles uniformly in the solution of the catalyst precursor through ultrasonic treatment, and then perform stirring treatment at a certain temperature to volatilize the solvent, so that the catalyst precursor is uniformly supported on the pre-lithiation The surface of the silicon oxide particles; the mass ratio of the pre-lithiated silicon oxide particles to the catalyst precursor is (20-1):1; the catalyst precursor used is a transition metal salt, which includes ferric chloride and sodium chloride Iron, ferric nitrate, ferrous nitrate, ferric acetate, ferrous acetate, ferric sulfate, ferrous sulfate, ferric oxalate, ferrous oxalate, ferric citrate, ferrous gluconate, ferrocene, cobalt chloride, cobalt nitrate, Cobalt acetate, cobalt sulfate, cobalt oxalate, cobalt citrate, cobalt gluconate, cobalt diocene, nickel chloride, nickel nitrate, nickel acetate, nickel sulfate, nickel oxalate, nickel citrate, nickel gluconate, nickel diocene, chlorine Copper, copper nitrate, copper acetate, copper sulfate, copper oxalate, copper citrate, copper gluconate, etc.; solvents are water, methanol, ethanol, ethylene glycol, isopropanol, glycerol, ether, acetone, benzene or One or more of toluene; the temperature of the stirring treatment is 25-200°C.

(3) Put the pre-lithiated silicon oxide particles that have supported the catalyst precursor into a high-temperature furnace, and heat it for a period of time in the mixed gas of inert gas and reducing gas to fully reduce the catalyst precursor; then keep the inert gas The volume ratio of the reducing gas remains unchanged, and the gas carbon source is introduced. The carbon source is decomposed and reconstructed at a higher temperature, and the graphene material is deposited on the outer surface of the pre-lithiated silicon oxide particles; the inert gas is nitrogen, One of argon and helium, the reducing gas is one or more of hydrogen, ammonia, methane, and nitric oxide. The volume percentage of the reducing gas is 10-40%, and the gas carbon source accounts for the total 5-25% of the volume, the gas carbon source used is one of acetylene, methane, ethane, ethylene, and butene; the precursor reduction temperature is 300-600℃, and the heat preservation time is 1-10h. The temperature is 500～1000℃, and the heat preservation is 5min～1h.

(4) Mix the pre-lithiated silicon oxide particles coated with the graphene material and the solid carbon source uniformly and then add them to the fusion machine for homogeneous fusion, and then put the mixture into a high-temperature furnace for high-temperature carbonization in an inert atmosphere. The final pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries is obtained. The solid carbon source used is one or more of sucrose, petroleum pitch, coal tar, epoxy resin, phenolic resin, polyvinyl alcohol, and polyvinyl chloride. During the fusion process, the speed of the fusion machine is 1000～2000rpm, and the fusion time It is 1～4h; the temperature of carbonization is 700～1000℃, and the holding time is 1～8h.

Hereinafter, the present invention will be further described in detail with a number of embodiments:

Example 1:

A preparation method of pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion battery includes the following specific steps:

(1) The silicon oxide particles are placed in a high-energy ball mill for ball milling, the rotation speed of the ball mill is set to 500 rpm, the mass ratio of the ball to the particles is set to 100:1, and the ball milling time is 24 hours.

(2) Put the ball-milled silica particles in a fusion machine, add lithium-containing ionic liquid LiMIM-TFSI, the mass ratio of the silica particles to the lithium-containing ionic liquid is 20:1, and the fusion time is 3h.

(3) Put the mixed silica particles in a high-temperature tube furnace for sintering, pass argon gas for protection, raise the temperature to 600°C for 2 hours, and make the silica particles and the lithium-containing ionic liquid carry out After sufficient reaction, the temperature is automatically lowered to obtain pre-lithiated silicon oxide particles.

(4) Disperse the pre-lithiated silicon oxide particles in an aqueous solution of nickel citrate ultrasonically, wherein the mass ratio of the pre-lithiated silicon oxide particles to nickel citrate is 10:1, and then perform agitation treatment at 80°C to make The solvent volatilizes, so that the catalyst precursor is uniformly supported on the outer surface of the pre-lithiated silica, and the pre-lithiated silica particles with the catalyst precursor are obtained.

(5) Put the silicon-carbon particles loaded with the catalyst precursor into a high-temperature furnace, and at the same time pass in a mixed gas of hydrogen and argon, where the volume ratio of hydrogen to argon is 1:5, and the furnace is heated to 300°C for heat preservation After 2 hours, the catalyst precursor was fully reduced and activated, and then keeping the volume ratio of hydrogen and argon constant, the gaseous carbon source was introduced, which accounted for 10% of the total volume. At this time, the furnace temperature was raised to 500℃ and the temperature was kept 0.5 h. Depositing the graphene material on the outer surface of the pre-lithiated silicon oxide particles under the action of a catalyst.

(6) The pre-lithiated silicon oxide particles coated with the graphene material and the solid carbon source are mixed uniformly and then added to the fusion machine for homogeneous fusion, the speed of the fusion machine is 1000 rpm, and the fusion time is 2 h. After fusion, the mixture is put into a high-temperature furnace under an inert atmosphere at 1000°C for high-temperature carbonization, and the holding time is 2h, to obtain the final pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries.

Example 2:

(1) Place the silicon oxide particles in a jet mill for pulverization.

(2) Put the pulverized silica in a fusion machine, add LiBMIM-TFSI, the mass ratio of silica particles to LiBMIM-TFSI is 20:1, the speed of the fusion machine is 800rpm, and the fusion time is 5h.

(3) Put the silicon oxide particles fused with LiBMIM-TFSI in a high-temperature tube furnace for sintering, pass in nitrogen for protection, and raise the temperature to 800°C for 2 hours to keep the silicon oxide particles and lithium-containing ions The liquid undergoes a sufficient reaction, and then the temperature is automatically lowered to obtain pre-lithiated silicon oxide particles.

(4) Disperse the pre-lithiated silicon oxide ultrasonically in an aqueous solution of nickel citrate, where the mass ratio of silicon oxide particles to nickel citrate is 5:1, and then stir at 90°C to volatilize the solvent, thereby The catalyst precursor is uniformly supported on the outer surface of the pre-lithiated silicon oxide particles to obtain the pre-lithiated silicon oxide particles that have been loaded with the catalyst precursor.

(5) Put the pre-lithiated silicon oxide particles that have supported the catalyst precursor into a high temperature furnace, and at the same time pass in a mixed gas of ammonia and argon, of which the volume of ammonia accounts for 20%, and the furnace is heated to 300°C Keep the temperature for 3 hours to fully reduce and activate the catalyst precursor; then, keeping the volume ratio of ammonia and argon unchanged, start to pass in the gas carbon source, which accounts for 14.29% of the total volume, and raise the furnace temperature to 800°C. After keeping the temperature for 15 minutes, the graphene material is deposited on the outer surface of the pre-lithiated silicon oxide particles under the action of the catalyst.

(6) The pre-lithiated silicon oxide particles coated with the graphene material and the solid carbon source are uniformly mixed and then added to the fusion machine for homogeneous fusion, the speed of the fusion machine is 1000 rpm, and the fusion time is 1 h. After fusion, the mixture is put into a high-temperature furnace under an argon atmosphere at 1000°C for high-temperature carbonization, and the holding time is 2h, to obtain the final pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries.

Example 3:

(1) Place the silicon oxide particles in a mechanical mill for pulverization.

(2) The pulverized silica particles are placed in a fusion machine, and lithium-containing ionic liquid LiEMIM-PF6 is added. The mass ratio of the silica particles to the lithium-containing ionic liquid is 30:1, and the speed of the fusion machine is 1000 rpm. , The fusion time is 3h.

(3) Put the mixed silicon oxide particles in a high-temperature tube furnace for sintering, pass argon gas for protection, raise the temperature to 500°C for 2h, and make the silicon oxide particles and the lithium-containing ionic liquid carry out After sufficient reaction, the temperature is automatically lowered to obtain pre-lithiated silicon oxide particles.

(4) Disperse the pre-lithiated silica particles in an aqueous solution of nickel citrate ultrasonically, wherein the mass ratio of the pre-lithiated silica particles to nickel citrate is 10:1, and then stir at 100°C to volatilize the solvent Therefore, the catalyst precursor is uniformly supported on the outer surface of the pre-lithiated silica particles, and the pre-lithiated silica particles with the catalyst precursor are obtained.

(5) Put the pre-lithiated silicon oxide particles loaded with the catalyst precursor into a high-temperature furnace, and at the same time pass in a mixed gas of hydrogen and argon, where the volume ratio of hydrogen to argon is 2:5, and the furnace is heated up Keep the temperature at 500°C for 3 hours to fully reduce the catalyst precursor, then keep the volume ratio of hydrogen and argon unchanged, and start to pass in the gaseous carbon source, which accounts for 18% of the total volume. At this time, the furnace temperature is increased to 800 The temperature is kept for 10 minutes, and the graphene material is deposited on the outer surface of the pre-lithiated silicon oxide particles under the action of a catalyst.

(6) The pre-lithiated silicon oxide particles coated with the graphene material and the solid carbon source are mixed uniformly and then added to the fusion machine for homogeneous fusion, the speed of the fusion machine is 1000 rpm, and the fusion time is 2 h. After the fusion, the mixture is put into a high-temperature furnace under an inert atmosphere at 1000° C. for high-temperature carbonization, and the holding time is 3 hours to obtain the final pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries.

The lithium-ion battery pre-lithiated silicon-carbon multilayer composite negative electrode material obtained in each of the above embodiments was mixed with the conductive agent carbon black and sodium alginate in a mass ratio of 6:2:2, the solvent was deionized water, and the mixture was stirred to form a uniform After coating the slurry on the copper foil current collector, drying and slicing to obtain battery pole pieces. Using the metal lithium sheet as the counter electrode, the CR2032 button cell was assembled for electrochemical performance test, and the constant current charging and discharging were performed under normal temperature conditions. The current density was 100mA/g and the cut-off voltage was 0.005-2V. The results are as follows:

The test results show that the lithium ion battery pre-lithiated silicon-carbon multilayer composite negative electrode material prepared by the invention has the characteristics of high conductivity, high first-time coulombic efficiency and stable cycle performance.

The above are only preferred embodiments of the present invention, and do not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention are still valid. It belongs to the scope of the technical solution of the present invention.

Claims

A pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries, which is characterized in that it comprises an amorphous carbon matrix, pre-lithiated silicon oxide particles and a graphene material; the graphene material is evenly coated on the pre-lithiated The outer surface of the silicon oxide forms composite particles, which are uniformly dispersed in the amorphous carbon matrix.
A method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium-ion batteries according to claim 1, characterized in that: firstly, using silicon oxide as a raw material, the silicon oxide and the lithium-containing ionic liquid are mixed Sintering to achieve pre-lithiation to obtain pre-lithiated silicon oxide particles, then support the catalyst precursor, and grow graphene material on the surface of the pre-lithiated silicon oxide by chemical vapor deposition, and finally homogenously fuse with the carbon source and perform heat treatment, that is, The final pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries is obtained.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium-ion batteries according to claim 2, characterized in that it comprises the following specific steps:

(1) Mix a certain particle size of silicon oxide with a lithium-containing ionic liquid, and then place it in a high-temperature tube furnace for sintering, so that the silicon oxide can fully react with the lithium-containing ionic liquid to obtain pre-lithiated silicon oxide Particles

(2) Disperse a certain proportion of pre-lithiated silica particles uniformly in the solution of the catalyst precursor through ultrasonic treatment, and then perform stirring treatment at a certain temperature to volatilize the solvent, so that the catalyst precursor is uniformly supported on the pre-lithiation The surface of the silicon oxide particles;

(3) Put the pre-lithiated silicon oxide particles that have supported the catalyst precursor into a high-temperature furnace, and heat it for a period of time in the mixed gas of inert gas and reducing gas to fully reduce the catalyst precursor; then keep the inert gas The volume ratio of the reducing gas remains unchanged, and the gaseous carbon source is introduced, the carbon source is decomposed and reconstructed at a higher temperature, and the graphene material is deposited on the outer surface of the pre-lithiated silicon oxide particles;

(4) Mix the pre-lithiated silicon oxide particles coated with the graphene material and the solid carbon source uniformly and then add them to the fusion machine for homogeneous fusion, and then put the mixture into a high-temperature furnace for high-temperature carbonization in an inert atmosphere. The final pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries is obtained.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries according to claim 3, wherein the particle size of the silicon oxide in the step (1) is 10 nm-10 μm.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium-ion batteries according to claim 3, wherein the lithium-containing ionic liquid in the step (1) is LiMIM-TFSI, LiEMIM-BF4 , LiEMIM-PF6, LiEMIM-TFSI, LiPMMIM-TFSI, LiBMIM-TFSI, LiAAIM-Cl, LiAMIM-Br, LiAEIM-Br, LiAAIM-Br, LiAAIM-I, LiAAIM-TFSI, LiAMIM-TFSA, LiAMIM-BF4, LiEMIMBF4 One or more of, LiEMIMTFSI, LiEMIMTFSI, LiBMIMBF, LiBMIMPF6, LiBMIMPF6 and LiPMMIMTFSI.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium-ion batteries according to claim 3, wherein the mass ratio of the silicon oxide to the lithium-containing ionic liquid in the step (1) is (10～35):1.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium-ion batteries according to claim 3, wherein the gas introduced into the high-temperature tube furnace in the step (1) is inert gas nitrogen. One of argon and helium, the sintering temperature is 500～1000℃.
The method for preparing pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries according to claim 3, characterized in that: the quality of the pre-lithiated silicon oxide particles and the catalyst precursor in the step (2) The ratio is (20-1):1.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium-ion batteries according to claim 3, wherein the catalyst precursor used in the step (2) is a transition metal salt, which comprises Ferric chloride, ferrous chloride, ferric nitrate, ferrous nitrate, ferric acetate, ferrous acetate, ferric sulfate, ferrous sulfate, ferric oxalate, ferrous oxalate, ferric citrate, ferrous gluconate, ferrocene, Cobalt chloride, cobalt nitrate, cobalt acetate, cobalt sulfate, cobalt oxalate, cobalt citrate, cobalt gluconate, cobalt diocene, nickel chloride, nickel nitrate, nickel acetate, nickel sulfate, nickel oxalate, nickel citrate, gluconic acid Nickel, nickelocene, copper chloride, copper nitrate, copper acetate, copper sulfate, copper oxalate, copper citrate, copper gluconate, etc.; solvents are water, methanol, ethanol, ethylene glycol, isopropanol, glycerol One or more of, ether, acetone, benzene or toluene.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries according to claim 3, wherein the temperature of the stirring treatment in the step (2) is 25-200°C.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium-ion batteries according to claim 3, wherein the inert gas in step (3) is one of nitrogen, argon, and helium. The reducing gas is one or more of hydrogen, ammonia, methane, and nitric oxide. The volume percentage of the reducing gas is 10-40%, and the gas carbon source accounts for 5-25% of the total volume. The gas carbon source used is one of acetylene, methane, ethane, ethylene, and butene.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries according to claim 3, wherein the precursor reduction temperature in the step (3) is 300-600°C, and the temperature is kept at 1 ～10h, the temperature of graphene deposition is 500～1000℃, and the temperature is kept for 5min～1h.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium-ion batteries according to claim 3, wherein the solid carbon source used in the step (4) is sucrose, petroleum pitch, coal One or more of tar, epoxy resin, phenolic resin, polyvinyl alcohol, and polyvinyl chloride. During the fusion process, the speed of the fusion machine is 1000 to 2000 rpm, and the fusion time is 1 to 4 hours.
The method for preparing a pre-lithiated silicon-carbon multilayer composite negative electrode material for lithium ion batteries according to claim 3, wherein the carbonization temperature in step (4) is 700-1000°C, and the holding time is 1 ～8h