CN116705988A

CN116705988A - Negative electrode plate and preparation method thereof, battery and preparation method of negative electrode material

Info

Publication number: CN116705988A
Application number: CN202310456477.XA
Authority: CN
Inventors: 金周; 黄学杰; 王丕涛; 胡保平; 闫勇
Original assignee: Institute of Physics of CAS; Songshan Lake Materials Laboratory
Current assignee: Institute of Physics of CAS; Songshan Lake Materials Laboratory
Priority date: 2022-04-26
Filing date: 2023-04-24
Publication date: 2023-09-05
Also published as: CN114944465A; WO2023208058A1

Abstract

The application relates to a negative electrode plate and a preparation method thereof, a battery and a preparation method of a negative electrode material, and belongs to the technical field of secondary batteries. The negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector. The active material in the anode active material layer comprises a flaky silicon-based material, and an included angle between at least 60% of the flaky silicon-based material and the surface of the anode current collector is less than or equal to 20 degrees based on the surface of the anode current collector. The flaky silicon-based materials of the negative electrode plate tend to be parallel to the negative electrode current collector, and the flaky silicon-based materials tend to be arranged in parallel along the thickness direction of the negative electrode plate and form a stacked structure, so that the structure is more stable; in the charge and discharge process, the flaky silicon-based material generates volume change and slides along the thickness direction, so that the gap inside the negative electrode pole piece can be filled, the pole piece has good electrical contact and integrity, and the performance of the battery is better.

Description

Negative electrode plate and preparation method thereof, battery and preparation method of negative electrode material

The application claims the priority of patent application with the application number of 202210446207.6, the application date of 2022, 04 month and 26 days and the patent name of 'negative plate and battery'.

Technical Field

The application relates to the technical field of secondary batteries, in particular to a negative electrode plate and a preparation method thereof, a battery and a preparation method of a negative electrode material.

Background

Due to the rapid development and wide application of portable electronic devices and electric automobiles, the demand for lithium ion batteries with high specific energy and long cycle life is urgent. At present, the commercial lithium ion battery mainly adopts graphite as a negative electrode material, however, the theoretical specific capacity of the graphite is only 372mAh/g, and the further improvement of the specific energy of the lithium ion battery is limited.

While the theoretical specific capacity of silicon can reach 4200mAh/g at maximum, the volume expansion of silicon exceeds 300% in the lithium storage process, resulting in performance degradation.

Disclosure of Invention

Aiming at the defects of the prior art, the embodiment of the application aims at providing a negative electrode plate, a preparation method thereof, a battery and a preparation method of a negative electrode material so as to reduce the influence of expansion of a sheet silicon-based material on the performance of the battery.

In a first aspect, an embodiment of the present application provides a negative electrode tab, including a negative electrode current collector and a negative electrode active material layer disposed on a surface of the negative electrode current collector. The active material in the anode active material layer comprises a flaky silicon-based material, and an included angle between at least 60% of the flaky silicon-based material and the surface of the anode current collector is less than or equal to 20 degrees based on the surface of the anode current collector.

At least 60% of the flaky silicon-based materials and the surface of the negative electrode current collector have an included angle of less than or equal to 20 degrees, the flaky silicon-based materials tend to be parallel to the negative electrode current collector, and the flaky silicon-based materials tend to be arranged in parallel along the thickness direction of the negative electrode plate to form a stacked structure, so that the structure is more stable; in the charge and discharge process, the flaky silicon-based material generates volume change and slides along the thickness direction, so that the gap inside the negative electrode pole piece can be filled, the pole piece has good electrical contact and integrity, and the performance of the battery is better.

In some embodiments of the present application, the sheet-like silicon-based material is one or more of a silicon nano-sheet, a silicon sub-micro-sheet, a silicon alloy nano-sheet, a silicon alloy sub-micro-sheet, a silicon nano-sheet, a silicon sub-micro-sheet, and a surface modified coated material thereof.

In some embodiments of the application, the thickness of the silicon nanoplatelets is 1-200nm; the plane size is 20-5000nm.

In some embodiments of the application, the active material may also include carbon-coated tin nanowires as the synergistic active material.

In some embodiments of the present application, the carbon-coated tin nanowires have a diameter of 100nm or less and an aspect ratio of (5-1000): 1.

In some embodiments of the application, the carbon-coated tin nanowires are formed by in situ reduction of tin oxide nanoparticles and carbon deposition.

In some embodiments of the present application, the graphitization degree γ of the carbon coating layer in the carbon-coated tin nanowire satisfies 0.3+.γ+.1, where γ= (0.344-d) ₀₀₂ )/(0.344-0.3354)，d ₀₀₂ Is the nano-layer spacing of the carbon coating layer in the 002 crystal face.

In some embodiments of the application, the active material further comprises carbon nanotubes as the synergistic active material.

In some embodiments of the present application, the carbon nanotubes have a diameter of 20nm or less and an aspect ratio of (10-1000): 1.

In some embodiments of the application, the carbon nanotubes comprise at least single-walled carbon nanotubes.

In some embodiments of the present application, the sum of the active material, the conductive agent and the binder is taken as the total mass, the active material accounts for 70% -95% of the total mass, the conductive agent accounts for 0% -10% of the total mass, and the binder accounts for 2% -30% of the total mass.

In some embodiments of the present application, the active material comprises 70% -98% silicon by weight, 0.5% -20% tin by weight, and 1.5-20% carbon by weight.

In a second aspect, an embodiment of the present application provides a lithium ion secondary battery, including the above-mentioned negative electrode tab.

In a third aspect, an embodiment of the present application provides a solid-state battery, including the above-mentioned negative electrode tab.

In a fourth aspect, an embodiment of the present application provides a method for preparing a negative electrode material, including: dispersing the carbon nanotube solution, the silicon-based material and the tin oxide nano particles in an organic solvent, grinding, filtering and drying to obtain a composite precursor, placing the composite precursor in a high-temperature sintering furnace, heating to 650-900 ℃ in an inert atmosphere, and then introducing acetylene gas for sintering to obtain the anode material mixed by the carbon nanotube, the carbon-coated tin nanowire and the sheet-shaped silicon-based material. The carbon nano tube, the silicon-based material and the tin oxide nano particles in the solvent are mixed and dispersed in a grinding mode, so that the three materials are mixed more uniformly, and the silicon-based material can be completely converted into a sheet-shaped silicon-based material. In addition, in the subsequent sintering process by introducing acetylene gas, on one hand, tin oxide can be reduced into tin, meanwhile, tin can be used as a catalyst for acetylene gas deposition, carbon coated tin nanowires with carbon layers uniformly deposited on the surfaces of the tin nanowires can be obtained, the carbon layers are more tightly combined with the tin nanowires, the graphitization degree of the carbon layers is high, and the surfaces of the sheet-shaped silicon-based materials can be also deposited with the carbon layers, so that the uniformly mixed anode materials are obtained, and a three-dimensional network structure is formed among the carbon nanotubes, the carbon coated tin nanowires and the sheet-shaped silicon-based materials in the anode materials, so that the anode materials have good ionic conductivity and electronic conductivity, and the performance of the anode materials is better.

In a fifth aspect, the present application provides a method for preparing a negative electrode sheet, comprising mixing a sheet-shaped silicon-based material, a conductive agent, a binder and a solvent in a stirring tank, and then continuously stirring the mixture in the stirring tank at a speed of 200-3000rad/min, wherein the stirring tank itself is continuously rotated at a speed of 200-3000rad/min, so as to obtain a negative electrode active slurry. And then coating the negative electrode active slurry on the surface of a negative electrode current collector, drying and rolling to obtain a negative electrode plate.

By controlling the rotation of the stirrer in the stirring tank and the stirring tank itself at the same time, an included angle between at least 60% of the sheet silicon-based material and the surface of the negative electrode current collector is less than or equal to 20 °. The flaky silicon-based materials tend to be parallel to the negative electrode current collector, and along the thickness direction of the negative electrode plate, the flaky silicon-based materials tend to be arranged in parallel and form a stacked structure, so that the structure is more stable; in the charge and discharge process, the flaky silicon-based material generates volume change and slides along the thickness direction, so that the gap inside the negative electrode pole piece can be filled, the pole piece has good electrical contact and integrity, and the performance of the battery is better.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Fig. 1 is a Scanning Electron Microscope (SEM) image of a negative electrode sheet (original electrode sheet) provided in embodiment 1 of the present application;

Fig. 2 is a Scanning Electron Microscope (SEM) image of the negative electrode tab (fifth week lithium-embedded state) provided in embodiment 1 of the present application;

FIG. 3 is a Scanning Electron Microscope (SEM) image of the negative electrode sheet (original sheet) provided in comparative example 1;

FIG. 4 is a Scanning Electron Microscope (SEM) image of the negative electrode tab (fifth week lithium intercalation state) provided in comparative example 1;

FIG. 5 is an X-ray diffraction (XRD) pattern of the active material provided in example 1 of the present application;

FIG. 6 is an X-ray diffraction (XRD) pattern of the negative electrode sheet provided in example 1 of the present application, before rolling;

FIG. 7 is an X-ray diffraction (XRD) pattern of the negative electrode sheet provided in example 1 of the present application after rolling;

fig. 8 is a charge-discharge curve of a half cell according to embodiment 1 of the present application;

fig. 9 is a Scanning Electron Microscope (SEM) image of the anode active material provided in example 1 of the present application;

fig. 10 is a Scanning Electron Microscope (SEM) image of the anode active material provided in example 9 of the present application;

FIG. 11 is a Scanning Electron Microscope (SEM) image of the negative electrode active material after 5 weeks of cycling of the battery provided in example 1 of the present application;

fig. 12 is a Scanning Electron Microscope (SEM) image of the anode active material provided in comparative example 3;

FIG. 13 is a Transmission Electron Microscope (TEM) image of a carbon-coated tin nanowire provided in example 1 of the present application;

FIG. 14 is a Transmission Electron Microscope (TEM) image of a carbon-coated tin nanowire provided in example 10 of the present application;

Fig. 15 is an impedance diagram of the battery provided in example 1 and example 9 of the present application;

fig. 16 is a graph showing the cycle performance of the battery provided in example 1 of the present application under 2C conditions.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the present application are clearly and completely described below.

The embodiment of the application provides a negative electrode plate, which comprises a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector. The anode active material layer includes an active material, a conductive agent, and a binder. By forming the anode active material layer, the anode piece has good conductivity and battery performance, and the anode active material layer can be well combined on the anode current collector.

Optionally, the sum of the active material, the conductive agent and the binder is taken as the total mass, the active material accounts for 70-95% of the total mass, the conductive agent accounts for 0-10% of the total mass, and the binder accounts for 5-30% of the total mass. The compactness, specific capacity and initial charge of the anode active material layer can be better.

Illustratively, the active material comprises 70%, 75%, 80%, 85%, 90% or 95% by mass of the total mass; the mass percentage of the conductive agent is 0%, 2%, 4%, 6%, 8% or 10% of the total mass; the mass of the binder accounts for 2%, 10%, 15%, 20%, 25% or 30% of the total mass.

The conductive agent can be one or a combination of a plurality of conductive carbon black, conductive graphite, conductive carbon fiber, carbon nano tube and graphene; the binder can be one or a combination of more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, lithium polyacrylate, sodium alginate and polyvinylidene fluoride.

In the present application, the active material includes a sheet-shaped silicon-based material. The flaky silicon-based material refers to: the material contains silicon and can realize the silicon-based material of lithium intercalation; the silicon-based material is sheet-shaped, and the thickness of the sheet-shaped material is nano-scale.

Optionally, the sheet-shaped silicon-based material is a silicon nano-sheet (simple silicon), a silicon submicron sheet (simple silicon), a silicon alloy nano-sheet (silicon alloy), a silicon alloy submicron sheet (silicon alloy), a silicon nanometer sheet (silicon oxygen material SO) _x 0 < x < 2) and submicron sheets of silica (silica material SO) _x 0 < x < 2) and one or more of the surface modified coated materials.

Wherein, the silicon nano-sheet refers to: the simple substance silicon is sheet-shaped, and the thickness of the silicon wafer is nano-scale. Alternatively, the thickness of the silicon nanoplatelets is 1-100nm and the planar dimension is 20-5000nm. Wherein, the thickness of the silicon nano sheet refers to: the maximum distance between the two surfaces of the silicon nanoplatelets; the planar dimensions of the silicon nanoplatelets refer to: the distance between two points farthest from the contour line of the projection of the silicon nano-sheet of the sheet structure on the horizontal plane. For example: the thickness of the silicon nano-sheet is 1nm, 5nm, 10nm, 20nm, 40nm, 60nm, 80nm or 100nm; the planar dimensions of the silicon nanoplatelets are 20nm, 50nm, 100nm, 200nm, 400nm, 600nm, 800nm, 1000nm, 1200nm, 1400nm, 1600nm, 1800nm or 2000nm.

Optionally, the surface of the silicon nano-sheet is further coated with a carbon layer with a nano-scale thickness. On one hand, the carbon layer is thinner, so that the higher specific capacity of the active material can be kept; on the other hand, the coating of the carbon layer can prevent the flaky silicon-based material from being in direct contact with electrolyte to a certain extent, and the circulation stability of the active material is further improved. Optionally, the thickness of the carbon coating layer on the sheet silicon-based material is 2-10nm.

In the application, the surface of the negative electrode current collector is taken as a reference, and the included angle between at least 60% of the flaky silicon-based material and the surface of the negative electrode current collector is less than or equal to 20 degrees; that is, at least 60% of the sheet silicon-based material has an inclination angle of 20 DEG or less with respect to the planar direction of the negative electrode current collector.

The flaky silicon-based materials tend to be parallel to the negative electrode current collector, and along the thickness direction of the negative electrode plate, the flaky silicon-based materials tend to be arranged in parallel and form a stacked structure, so that the structure is more stable; in the charge and discharge process, the flaky silicon-based material generates volume change and slides along the thickness direction, so that the gap inside the negative electrode pole piece can be filled, the pole piece has good electrical contact and integrity, and the performance of the battery is better.

Optionally, along the thickness direction of the negative electrode plate, the included angle between two adjacent sheet silicon-based materials is less than or equal to 10 degrees. The distribution uniformity of the flaky silicon-based materials on the negative electrode current collector is better, so that more flaky silicon-based materials can exist in a stacked mode, and the performance of the battery is improved.

Further, the included angle between at least 90% of the flaky silicon-based material and the surface of the negative electrode current collector is less than or equal to 20 degrees; and the included angle between two adjacent sheet silicon-based materials along the thickness direction of the negative electrode plate is less than or equal to 5 degrees. More sheet silicon-based materials are substantially parallel to the negative current collector and form a stacked structure, which can make the battery perform better.

Further, the included angle between all the flaky silicon-based materials and the surface of the negative electrode current collector is less than or equal to 20 degrees. All sheet-like silicon-based materials tend to be substantially parallel to the negative current collector, resulting in better cell performance.

In the present application, the active material further includes carbon-coated tin nanowires as a synergistic active material. The carbon-coated tin nanowires refer to: the surface of the tin nanowire is coated with a carbon layer, the formed carbon-coated tin nanowire is still in a linear structure, and the size of the carbon-coated tin nanowire is also in a nanoscale. The tin material has good conductivity and ion conductivity, and has rapid charge and discharge capability after being matched with the carbon coating; and the carbon layer is coated to keep the structure of the carbon layer intact in the charge and discharge process, and good electrical contact is realized. Optionally, the carbon coating layer in the carbon-coated tin nanowire has a thickness of nanometer scale. Optionally, the carbon coating on the carbon-coated tin nanowires has a thickness of 2-10nm.

The diameter of the carbon-coated tin nanowire is below 100nm, and the length-diameter ratio is (5-1000): 1. The diameters of different parts of the carbon-coated tin nanowire can be the same or different, the diameter is less than 100nm, the length-diameter ratio is (5-1000): 1, the flexibility is better, the sheet-shaped silicon-based material can form a three-dimensional network structure with the sheet-shaped silicon-based material after being mixed, and the volume expansion of the sheet-shaped silicon-based material can be avoided to a certain extent. Optionally, the carbon-coated tin nanowires have an aspect ratio of 5:1, 10:1, 20:1, 40:1, 80:1, 160:1, 320:1, 480:1, 600:1, or 1000:1.

Optionally, the carbon-coated tin nanowires are formed by in situ reduction of tin oxide nanoparticles and carbon deposition. When reducing gas (such as acetylene gas) is introduced at high temperature, tin oxide is reduced to tin, and tin is used as a catalyst, so that the carbon coated tin nanowire with the carbon layer uniformly deposited on the surface of the tin nanowire can be obtained, the carbon layer is uniformly deposited on the surface of the tin nanowire, the carbon layer is tightly combined with the tin nanowire, the graphitization degree of the carbon layer is high, and the performance of the anode material is improved.

Optionally, the graphitization degree gamma of the carbon coating layer in the carbon-coated tin nanowire satisfies 0.3 +.gamma.ltoreq.1, wherein gamma= (0.344-d) ₀₀₂ )/(0.344-0.3354)，d ₀₀₂ Is the nano-layer spacing of the carbon coating layer in the 002 crystal face. When reducing gas (such as acetylene gas) is introduced at high temperature, tin oxide is reduced to tin, and tin is used as a catalyst, so that the carbon coated tin nanowire with the carbon layer uniformly deposited on the surface of the tin nanowire can be obtained, the carbon layer is uniformly deposited on the surface of the tin nanowire, the carbon layer is tightly combined with the tin nanowire, the graphitization degree of the carbon layer is high, the graphitization degree of the carbon layer in the carbon coated tin nanowire is between 0.3 and 1, the graphitization degree is high, and the performance of the anode material is improved.

Optionally, the graphitization degree gamma of the carbon coating layer in the carbon-coated tin nanowire is 0.3-0.6 or 0.6-1; as an example, the graphitization degree γ of the carbon coating layer in the carbon-coated tin nanowire is 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.

In the present application, the active material further includes carbon nanotubes as a synergistic active material. The carbon nanotubes refer to: the carbon material is tubular, and the outer diameter of the carbon tube is nano-scale. The diameter of the carbon nanotube is below 20nm, and the length-diameter ratio is (10-1000): 1. The diameters of different parts of the carbon nanotubes can be the same or different, the diameter is below 20nm, and the length-diameter ratio is (10-1000): 1. Because the carbon-coated tin nanowires and the carbon nanotubes have certain elasticity and flexibility, after being mixed with the flaky silicon-based material, a better three-dimensional conductive network can be formed, the volume effect of lithium deintercalation of the negative electrode plate can be relieved, and the specific capacity and the cycling stability of the battery are higher; meanwhile, the negative electrode plate has good ionic conductivity and electronic conductivity, and better conductivity.

Alternatively, the carbon nanotubes comprise at least single-walled carbon nanotubes. The performance of the negative electrode plate can be better. Alternatively, the carbon nanotubes may also be a mixture of single-walled carbon nanotubes and multi-walled carbon nanotubes.

In the active material, the weight percentage of silicon is 70% -98%, the weight percentage of tin is 0.5% -20%, and the weight percentage of carbon is 1.5% -20%. Wherein, the weight percentage of silicon, tin and carbon refers to the element content, for example: the weight percentage of carbon is as follows: the sum of the carbon-coated tin nanowire and the carbon of the carbon nanotube in weight percent; the weight percentage of silicon is as follows: the weight percentage of silicon in the flaky silicon-based material; the weight percentage of tin is as follows: the carbon-coated tin nanowires comprise tin in weight percent.

For example: the weight percentage of silicon is 70%, 74%, 78%, 82%, 86%, 90%, 94% or 98%; the weight percentage of tin is 0.5%, 1%, 2%, 4%, 8%, 12%, 16% or 20%; the weight percent of carbon is 1.5%, 3%, 5%, 8%, 10%, 12%, 14%, 16%, 18% or 20%.

The single-sided surface density of the negative pole piece provided by the application is 1-40mg/cm ² . It can be used to prepare secondary batteries, for example: the specific capacity of the battery is 1000-3000mAh/g, and the initial charge-discharge coulomb efficiency is more than or equal to 80%, so as to improve the performance of the battery.

After the structure of the negative electrode plate is introduced above, the preparation method of the negative electrode plate is described below.

In the application, the anode active material (including the sheet silicon-based material), the conductive agent, the binder and the solvent are directly mixed and placed in a stirring tank, then the stirrer in the stirring tank is continuously stirred at a speed of 200-3000rad/min, and the stirring tank is continuously rotated at a speed of 200-3000rad/min, so as to obtain the anode active slurry. And then coating the negative electrode active slurry on the surface of a negative electrode current collector, drying and rolling to obtain a negative electrode plate.

In the technical scheme, the stirrer in the stirring tank and the rotation of the stirring tank are controlled simultaneously, so that the included angle between at least 60% of the flaky silicon-based material and the surface of the negative electrode current collector is less than or equal to 20 degrees. The flaky silicon-based materials tend to be parallel to the negative electrode current collector, and along the thickness direction of the negative electrode plate, the flaky silicon-based materials tend to be arranged in parallel and form a stacked structure, so that the structure is more stable; in the charge and discharge process, the flaky silicon-based material generates volume change and slides along the thickness direction, so that the gap inside the negative electrode pole piece can be filled, the pole piece has good electrical contact and integrity, and the performance of the battery is better.

Alternatively, the rotational speed of the stirrer may be 200-1000rad/min or 1000-3000rad/min, and the rotational speed of the stirring tank itself may be 200-1000rad/min or 1000-3000rad/min. As an example, the rotational speed of the stirrer and the stirring tank may be independently selected from 200rad/min, 500rad/min, 1000rad/min, 1500rad/min, 2000rad/min, 2500rad/min or 3000rad/min.

Further, the preparation method of the anode active material may be: dispersing the carbon nanotube solution, the silicon-based material and the tin oxide nano particles in an organic solvent, grinding (such as ball milling, sand milling and the like), filtering and drying to obtain a composite precursor, placing the composite precursor in a high-temperature sintering furnace, heating to 650-900 ℃ in an inert atmosphere, and then introducing acetylene gas for sintering to obtain the anode material mixed by the carbon nanotube, the carbon-coated tin nanowire and the sheet-shaped silicon-based material.

The carbon nano tube, the silicon-based material and the tin oxide nano particles in the solvent are mixed and dispersed in a grinding mode, so that the three materials are mixed more uniformly, and the silicon-based material can be completely converted into a sheet-shaped silicon-based material. In addition, in the subsequent sintering process by introducing acetylene gas, on one hand, tin oxide can be reduced into tin, meanwhile, tin can be used as a catalyst for acetylene gas deposition, carbon coated tin nanowires with carbon layers uniformly deposited on the surfaces of the tin nanowires can be obtained, the carbon layers are more tightly combined with the tin nanowires, the graphitization degree of the carbon layers is high, and the surfaces of the sheet-shaped silicon-based materials can also be deposited with the carbon layers, so that a uniformly mixed anode material is obtained, and a three-dimensional network structure is formed among the carbon nanotubes, the carbon coated tin nanowires and the carbon coated sheet-shaped silicon-based materials in the anode material, so that the anode material has good ionic conductivity and electronic conductivity, and the performance of the anode material is better.

The preparation method of the anode active material can also be as follows: and (3) putting the tin oxide nano-particles into a high-temperature sintering furnace, heating to 650-900 ℃ in an inert atmosphere, introducing acetylene gas for sintering, and obtaining the carbon-coated tin nano-wire after sintering. Dispersing the carbon nanotube solution, the sheet-shaped silicon-based material and the carbon-coated tin nanowire in an organic solvent, filtering and drying to obtain the anode material mixed by the carbon nanotube, the carbon-coated tin nanowire and the sheet-shaped silicon-based material.

In the sintering process of introducing acetylene gas, on one hand, tin oxide can be reduced into tin, meanwhile, tin can be used as a catalyst for acetylene gas deposition, a carbon layer can be uniformly deposited on the surface of the tin nanowire, the carbon layer is tightly combined with the tin nanowire, and the carbon coated tin nanowire with high graphitization degree of the carbon layer. Mixing the carbon nano tube, the carbon coated tin nano wire and the flaky silicon-based material in a solvent to obtain a uniformly mixed anode material; meanwhile, the three materials form a three-dimensional network structure to a certain extent, so that the anode material has better ionic conductivity and electronic conductivity, and the performance of the anode material is better.

Alternatively, the sintering temperature may be 650-750 ℃ or 750-900 ℃; as an example, the temperature of sintering may be 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, or 900 ℃.

In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1

(1) Preparation of carbon nanotube solution:

dispersing the carbon nano tube in an ethanol solvent to obtain a carbon nano tube solution, wherein the mass ratio of the carbon nano tube to the ethanol is 1:100.

(2) Preparation of active materials:

adding solar silicon wafer cutting waste, tin oxide and polyvinylpyrrolidone (PVP) into the carbon nanotube solution, homogenizing and dispersing in a homogenizer, sanding the homogenized and dispersed suspension in a sand mill for 5 hours, and then filtering, washing and drying to obtain a uniformly dispersed composite precursor. And finally, placing the precursor material into a high-temperature sintering furnace, sintering at the temperature of 700 ℃ from room temperature under the nitrogen atmosphere, and introducing acetylene gas for carbon coating, thus obtaining the active material after sintering.

The active material comprises a silicon nano-sheet, a carbon-coated tin nanowire and a carbon nano-tube, wherein the surface of the silicon nano-sheet is coated with a carbon layer. The thickness of the silicon nano-sheet is 10-80nm, and the plane size is 200-800nm; the diameter of the carbon-coated tin nanowire is 20-80nm, and the length-diameter ratio is (50-500): 1; the diameter of the carbon nano tube is 10-20nm, and the length-diameter ratio is (100-200): 1. Silicon accounts for 86.6wt% of the active material in terms of weight percent; tin represents 4.6wt% of the active material; carbon represents 5.2wt% of the active material; the other materials account for 3.1wt% of the active material.

(3) Preparing a negative electrode plate:

the negative electrode active material prepared by the method is mixed with a conductive agent (SP), sodium carboxymethylcellulose (CMC) and Styrene Butadiene Rubber (SBR) according to the mass ratio of 80:5:5:10 is added in a stirring tank containing water, the stirrer in the stirring tank is continuously stirred at a speed of 500rad/min, and the stirring tank itself is continuously rotated at a speed of 500rad/min to obtain a negative electrode active material slurry. And coating the negative electrode active material slurry on the surface of the copper foil by using a scraper, and drying to obtain the negative electrode plate. And (3) rolling the negative electrode plate, and preparing a small wafer with the diameter of 15mm from the rolled negative electrode plate by using a puncher.

(4) Preparation of half-cell

And matching the negative electrode plate with the lithium plate to form a button type half battery, wherein the battery is assembled in a glove box filled with argon. Wherein Celgard2300 membrane is used as a separation membrane, and the electrolyte is LiPF with the concentration of 1mol/L ₆ Dissolved in EC, DMC, FEC (volume ratio 4.8:4.8:0.4).

Example 2

Example 2 differs from example 1 in that: in the step (2), the solar silicon wafer cutting waste is replaced by silicon oxide with the particle size of 5-10 mu m.

The active material comprises a silicon oxide nano-sheet, a carbon-coated tin nanowire and a carbon nanotube, wherein the surface of the silicon oxide nano-sheet is coated with a carbon layer. The thickness of the silicon oxide nano-sheet is 50-80nm, and the plane size is 200-800nm; the diameter of the carbon-coated tin nanowire is 20-80nm, and the length-diameter ratio is (50-500): 1; the diameter of the carbon nano tube is 10-20nm, and the length-diameter ratio is (100-200): 1. Silicon accounts for 60.8wt% of the active material in terms of weight percent; oxygen represents 29.3wt% of the active material and tin represents 4.6wt% of the active material; carbon represents 4.8wt% of the active material; the other substances account for 0.5wt% of the active material.

Example 3

Example 3 differs from example 1 in that: in the step (2), the solar silicon wafer cutting waste is replaced by ferrosilicon alloy with the grain diameter of 5-10 mu m.

The active material comprises a ferrosilicon nano-sheet, a carbon-coated tin nano-wire and a carbon nano-tube, wherein the surface of the ferrosilicon nano-sheet is coated with a carbon layer. The thickness of the ferrosilicon nano-sheet is 20-60nm, and the plane size is 100-500nm; the diameter of the carbon-coated tin nanowire is 20-80nm, and the length-diameter ratio is (50-500): 1; the diameter of the carbon nano tube is 10-20nm, and the length-diameter ratio is (100-200): 1. Silicon accounts for 76.3wt% of the active material in terms of weight percent; iron represents 12.1wt% of the active material, and tin represents 3.5wt% of the active material; carbon represents 7.6wt% of the active material; the other substances account for 0.5wt% of the active material.

Example 4

Example 4 differs from example 1 in that: in the step (1), the solar silicon wafer cutting waste is replaced by a solar silicon wafer with the thickness of 10-50nm; the silicon nanoplatelets having a planar size of 100-600nm do not require sanding in a sander.

The active material comprises a silicon nano-sheet, a carbon-coated tin nano-wire and a carbon nano-tube. The thickness of the silicon nano-sheet is 10-50nm, and the plane size is 100-600nm; the diameter of the carbon-coated tin nanowire is 20-80nm, and the length-diameter ratio is (50-500): 1; the diameter of the carbon nano tube is 10-20nm, and the length-diameter ratio is (100-200): 1. Silicon accounts for 87.6wt% of the active material in terms of weight percent; tin represents 4.3wt% of the active material; carbon represents 7.8wt% of the active material; the other materials account for 0.3wt% of the active material.

Example 5

Example 5 differs from example 1 in that: in the step (2), the solar silicon wafer cutting waste is replaced with a silicon wafer with the thickness of 50-100nm; the silica nanoplatelets having a planar size of 100-800nm do not require sanding in a sander.

The active material comprises a silicon oxide nano-sheet, a carbon-coated tin nano-wire and a carbon nano-tube. The thickness of the silicon oxide nano-sheet is 50-100nm, and the plane size is 100-800nm; the diameter of the carbon-coated tin nanowire is 20-80nm, and the length-diameter ratio is (50-500): 1; the diameter of the carbon nano tube is 10-20nm, and the length-diameter ratio is (100-200): 1. Silicon accounts for 61.2wt% of the active material in terms of weight percent; oxygen represents 28.5wt% tin of the active material 3.6wt% tin of the active material; carbon represents 4.2wt% of the active material; the other materials account for 3.1wt% of the active material.

Example 6

Example 5 differs from example 1 in that: in the step (2), the solar silicon wafer cutting waste is replaced with a silicon wafer with the thickness of 50-80nm; ferrosilicon nanoplatelets having a planar dimension of 200-600nm do not require sanding in a sander.

The active material comprises a ferrosilicon alloy nano-sheet, a carbon-coated tin nano-wire and a carbon nano-tube. The thickness of the ferrosilicon nano-sheet is 50-80nm, and the plane size is 200-600nm; the diameter of the carbon-coated tin nanowire is 20-80nm, and the length-diameter ratio is (50-500): 1; the diameter of the carbon nano tube is 10-20nm, and the length-diameter ratio is (100-200): 1. Silicon represents 74.6wt% of the active material in weight percent; iron 11.5wt% of the active material and tin 3.2wt% of the active material; carbon represents 7.6wt% of the active material; the other materials account for 2.1wt% of the active material.

Example 7

Example 7 differs from example 1 in that: in the step (2), the solar silicon wafer cutting waste is replaced by monocrystalline silicon with the particle size of 5-10 mu m.

The active material comprises a silicon nano-sheet, a carbon-coated tin nanowire and a carbon nano-tube, wherein the surface of the silicon nano-sheet is coated with a carbon layer. The thickness of the silicon nano-sheet is 50-100nm, and the plane size is 200-1000nm; the diameter of the carbon-coated tin nanowire is 20-80nm, and the length-diameter ratio is (50-500): 1; the diameter of the carbon nano tube is 10-20nm, and the length-diameter ratio is (100-200): 1. Silicon accounts for 84.6wt% of the active material in terms of weight percent; tin comprises 5.1wt% of the active material; carbon represents 6.9wt% of the active material; the other materials account for 3.4wt% of the active material.

Example 8

Example 8 differs from example 1 in that: no carbon nanotubes and no tin oxide were added.

The active material comprises a silicon nano-sheet, and the surface of the silicon nano-sheet is coated with a carbon layer. The thickness of the silicon nano-sheet is 10-80nm, and the plane size is 200-800nm; silicon represents 94.6wt% of the active material in terms of weight percent; tin comprises 0wt% of the active material; carbon represents 4.2wt% of the active material; the other materials account for 1.2wt% of the active material.

Example 9

Example 9 differs from example 1 in that: the preparation method of the anode material comprises the following steps:

(1) And (3) putting the tin oxide nano-particles into a high-temperature sintering furnace, sintering from room temperature to 700 ℃ in a nitrogen atmosphere, introducing acetylene gas for carbon coating, and obtaining the carbon-coated tin nano-wire after sintering.

(2) Preparation of carbon nanotube solution:

(3) Preparation of a negative electrode active material:

adding solar silicon wafer cutting waste, carbon coated tin nanowires and polyvinylpyrrolidone (PVP) into a carbon nanotube solution, uniformly dispersing in a homogenizer, sanding the uniformly dispersed suspension in a sand mill for 5 hours, and then filtering, washing and drying to obtain a uniformly dispersed active material.

Example 10

Example 10 differs from example 9 in that: the preparation method of the carbon-coated tin nanowire comprises the following steps: placing the tin nanowire into an N-methyl pyrrolidone solution containing polytetrafluoroethylene, and dispersing to enable the surface of the tin nanowire to be coated with an adhesive layer; filtering and drying to obtain a precursor. And (3) putting the precursor into a high-temperature sintering furnace, and sintering and carbonizing from room temperature to 700 ℃ in nitrogen atmosphere, so as to obtain the carbon-coated tin nanowire after sintering.

Comparative example 1

Comparative example 1 differs from example 1 in that: in the step (3), the agitation tank itself is not rotated during the agitation to obtain the anode active material slurry.

Comparative example 2

Comparative example 2 differs from example 8 in that: in the step (3), the agitation tank itself is not rotated during the agitation to obtain the anode active material slurry.

Comparative example 3

Comparative example 3 differs from example 1 in that: the solar silicon wafer cutting waste is replaced by silicon powder with the diameter of 80-100nm, and the silicon nano-sheet cannot be formed.

The active material has no silicon nano-sheet, only has silicon nano-particles with the diameter of 80-100nm, and the surface of the silicon is coated with a carbon layer. The carbon-coated tin nanowire has a diameter of 20-80nm and an aspect ratio of (50-500) 1; the diameter of the carbon nano tube is 10-20nm, and the length-diameter ratio is (100-200): 1. Silicon accounts for 84.3wt% of the active material in terms of weight percent; tin represents 5.3wt% of the active material; carbon represents 5.7wt% of the active material; the other materials account for 3.7wt% of the active material.

In summary, the negative electrode tabs provided in examples 1 to 10 and comparative examples 1 to 3 are shown in table 1.

TABLE 1 negative electrode plate

The size of the silicon-based nano-chip, the size of the carbon-coated tin nano-wire, the size of the carbon nano-tube and the arrangement of the silicon-based nano-chip are all obtained through observation of a Scanning Electron Microscope (SEM) image.

The silicon content, the tin content and the carbon content are detected by an inductively coupled plasma spectrometer, a sulfur-carbon analyzer and the like. Fig. 1 is a Scanning Electron Microscope (SEM) image of a negative electrode sheet (original electrode sheet) provided in embodiment 1 of the present application, referring to fig. 1, a portion of the void exists in the original electrode sheet, the electrode sheet has a certain porosity, a linear structure exists between the silicon nano sheets, and the silicon nano sheets tend to be arranged in parallel to form a stacked structure, and also tend to be arranged in parallel to the current collector direction.

Fig. 2 is a Scanning Electron Microscope (SEM) image of a negative electrode sheet (in a fifth peripheral lithium intercalation state) provided in embodiment 1 of the present application, referring to fig. 2, in the lithium intercalation process, the silicon nano sheet undergoes volume change and sliding along the thickness direction, and fills the gap inside the sheet, and the silicon nano sheets are continuously stacked together in a two-dimensional layered structure, so that good electrical contact and integrity of the sheet are maintained.

Fig. 3 is a Scanning Electron Microscope (SEM) image of a negative electrode sheet (original electrode sheet) provided in comparative example 1, referring to fig. 3, a portion of a void exists inside the original electrode sheet, the electrode sheet has a certain porosity, a linear structure exists between the silicon nano sheets, and the silicon nano sheets are randomly arranged.

Fig. 4 is a Scanning Electron Microscope (SEM) image of the negative electrode tab (fifth circumferential lithium intercalation state) provided in comparative example 1, referring to fig. 4, since the silicon nano-sheets are randomly arranged, the silicon nano-sheets undergo volume change and sliding along the thickness direction during the lithium intercalation process, they cannot fill the internal gaps of the tab, and are irregularly distributed in the active material layer.

Fig. 5 is an X-ray diffraction (XRD) pattern of the active material provided in example 1 of the present application, fig. 6 is an X-ray diffraction (XRD) pattern of the negative electrode sheet provided in example 1 of the present application before rolling, and fig. 7 is an X-ray diffraction (XRD) pattern of the negative electrode sheet provided in example 1 of the present application after rolling. In order to avoid the influence of too strong copper peak position in the copper foil, a layer of PVDF is coated on the copper foil in the coating process, and the copper foil is removed when XRD is tested. As can be seen from fig. 5, the (111)/(220) crystal plane peak intensity=2.27, and the (111)/(311) crystal plane peak intensity=3.89; as can be seen from fig. 6, the (111)/(220) crystal plane peak intensity=2.30, and the (111)/(311) crystal plane peak intensity=4.27; as can be seen from fig. 7, the (111)/(220) crystal plane peak intensity=2.39, and the (111)/(311) crystal plane peak intensity=4.35. The values of the (111)/(220) crystal face peak intensity and the (111)/(311) crystal face peak intensity of the rolled pole piece are increased, which shows that the rolled pole piece has better performance, the included angle between the silicon nano-sheet and the negative current collector is smaller, and the silicon nano-sheet tends to be parallel to the negative current collector.

Fig. 8 is a charge-discharge curve of the half cell provided in example 1 of the present application, and as can be seen from fig. 8, the half cell provided in example 1 has a first-week capacity of up to 3000mAh/g and a first-week coulomb efficiency of up to 90%.

Fig. 9 is a Scanning Electron Microscope (SEM) image of the anode active material provided in example 1 of the present application, fig. 10 is a Scanning Electron Microscope (SEM) image of the anode active material provided in example 9 of the present application, fig. 11 is a Scanning Electron Microscope (SEM) image of the anode active material after 5 weeks of battery cycle provided in example 1 of the present application, and fig. 12 is a Scanning Electron Microscope (SEM) image of the anode active material provided in comparative example 3. As can be seen from fig. 9 and 10, the carbon-coated tin nanowires, the silicon nano-sheets and the carbon nano-tubes in the anode active materials of example 1 and example 9 are mixed to form a three-dimensional network structure, and the carbon-coated tin nanowires and the carbon nano-tubes in the anode active materials of fig. 9 can be more uniformly dispersed on the surface of the silicon nano-sheets to form a three-dimensional ion conductive network structure on the surface of the silicon nano-sheets; meanwhile, in the anode active material provided in fig. 9, tin oxide nano particles are uniformly dispersed on the surface of a silicon nano sheet, and then carbon coated tin nano wires are reduced in situ and uniformly grown, so that the particle conductivity of silicon can be compensated, and a three-dimensional conductive network is formed by combining a carbon nano tube and the silicon nano sheet, so that the ion conductivity and the electron conductivity of the anode active material are better. As can be seen from fig. 11, after the battery provided in example 1 circulates for 5 weeks, the tin nanowires on the surface of the silicon nanosheets basically exist, and after the negative electrode material circulates, the tin nanowires can still be well distributed on the surface of the silicon nanosheets. As can be seen from fig. 12, tin particles are easily formed on the surface of the silicon nanoparticles, and tin nanowires are not easily formed.

FIG. 13 is a Transmission Electron Microscope (TEM) image of a carbon-coated tin nanowire provided in example 1 of the present application; fig. 14 is a Transmission Electron Microscope (TEM) image of the carbon-coated tin nanowire provided in example 10 of the present application. As can be seen from FIG. 13, the microstructure of the surface-coated carbon layer of the tin nanowire of example 1 is a parallel linear structure, and the distance between two adjacent linear structures is d ₀₀₂ Is 0.33564 by the formula γ= (0.344-d ₀₀₂ ) The value of graphitization degree γ = (0.344-0.33564)/(0.344-0.3354) =0.972 can be calculated by/(0.344-0.3354) (the unit of parameters in the formula is nm). As can be seen in fig. 14, the microstructure of the surface-coated carbon layer of the tin nanowire in example 10 is irregular, indicating that the graphitization degree is not high.

Fig. 15 is a graph showing the impedance of the battery provided in example 1 and example 9 according to the present application, and it can be seen from fig. 15 that the battery prepared from the negative electrode active material provided in example 9 has an impedance 2.5 times that of the battery prepared from the negative electrode active material provided in example 1, which indicates that the negative electrode active material provided in example 1 has more excellent conductivity.

Fig. 16 is a graph showing the cycle performance of the battery provided in example 1 of the present application under 2C conditions. As can be seen from fig. 16, the battery provided in example 1 of the present application was able to be stably cycled for 1000 weeks, and the capacity was able to be stabilized at 700mAh/g.

Cycle volume retention rate and first week volume expansion rate

And (3) carrying out constant current charge and discharge on the half-cell by using a blue charge and discharge tester, wherein the cut-off voltage is set to be 0.005-1.0V, the multiplying power is set to be 0.2C, and the first-week charge capacity, the first-week coulomb efficiency, the 100-week charge capacity and the 100-week coulomb efficiency of the half-cell are tested.

The cycle capacity retention rate of 100 weeks was calculated by the following formula.

Cycle capacity retention of 100 weeks = charge capacity of 100 th week/charge capacity of first week x 100%.

First week volume expansion rate: the thickness h1 of the original pole piece and the thickness h2 of the first-week completely embedded lithium pole piece are respectively tested by using a micrometer.

First week volume expansion ratio= (h 2-h 1)/h 1

The first week charge specific capacity, first week coulombic efficiency, 100 th week coulombic efficiency, and 100 week cycle capacity retention data for each example and comparative example are shown in table 2.

TABLE 2 electrical Properties of half-cells

As can be seen from the combination of the table 1 and the table 2, the half batteries prepared by using the negative electrode plate provided by the embodiment of the application have the first-week charge capacity of more than 1500mAh/g, the cycle retention rate after 100 weeks of more than 90%, the first-week volume expansion rate of less than 130%, and the comprehensive performance of the half batteries is better. The half batteries prepared by the negative electrode plate provided by the comparative example have very high volume expansion rate and lower cycle retention rate.

As can be seen from comparison between example 1 and example 9, after the battery is prepared from the negative electrode active material provided in example 1, the first-week charge capacity and the cycle retention rate are both high, which means that after the silicon nanosheets, the carbon nanotubes and the tin oxide particles are mixed, acetylene gas is introduced to react under a high temperature condition, so that the carbon-coated tin nanowires with high graphitization degree can be formed, and meanwhile, the three materials are mixed more uniformly, thereby obtaining the negative electrode active material with better performance.

As can be seen from comparison of example 9 and example 10, the negative electrode active material provided in example 9 was higher in both the first-week charge capacity and the cycle retention rate after the battery was prepared. Compared with the embodiment 10, in which the organic binder is directly carbonized on the surface of the tin nanowire to form the carbon layer, the embodiment 9 is filled with acetylene gas under the high temperature condition, so that the carbon-coated tin nanowire with higher graphitization degree can be formed, and the obtained anode active material has better performance after being mixed with the silicon nano-sheet and the carbon nano-tube.

Rate capability

And carrying out constant current charge and discharge on the buckling electricity by using a blue charge and discharge instrument, wherein the cut-off voltage is set to be 0.005-1.0V, and the tests are respectively carried out at 0.1C, 0.2C, 0.5C, 1C and 0.2C multiplying power in sequence.

Capacity retention at different rates was calculated by the following formula.

Rate capacity retention = charge capacity at that rate/0.1C rate charge capacity x 100%.

The capacity retention data for each example and comparative example at different rates are shown in table 3.

TABLE 3 rate capability of half-cells

As can be seen from table 1 and table 3, the half batteries prepared by using the negative electrode sheet provided by the embodiment of the application have capacity retention rate of more than 65% at 1C rate; and the half batteries prepared by the negative electrode plate provided by the comparative example have the capacity retention rate of basically less than 40% at 1C multiplying power.

As can be seen from comparison between example 1 and example 9, the anode active material provided in example 1 has better rate performance after preparing a battery, which means that after mixing silicon nano-sheets and carbon nano-tubes with tin oxide particles, acetylene gas is introduced to react under high temperature conditions, and the carbon coated tin nano-wires with higher graphitization degree can be formed, and meanwhile, the three materials can be mixed more uniformly, so that the anode active material with better performance can be obtained.

As can be seen from comparison of example 9 and example 10, the negative electrode active material provided in example 9 has better rate performance after preparing a battery. Compared with the embodiment 10, in which the organic binder is directly carbonized on the surface of the tin nanowire to form the carbon layer, the embodiment 9 is filled with acetylene gas under the high temperature condition, so that the carbon-coated tin nanowire with higher graphitization degree can be formed, and the obtained anode active material has better performance after being mixed with the silicon nano-sheet and the carbon nano-tube.

Based on the example 1, the proportion of solar silicon and tin, the ball milling time and the silicon type are respectively changed, other conditions are unchanged, an active material is prepared according to the method of the example 1, then the active material is prepared into No. 1-13 batteries according to the method of preparing button half batteries in the example 1, and the batteries are subjected to charge-discharge cycle performance test according to an electrochemical performance test method, and the results are shown in Table 4.

TABLE 4 electrical properties of half-cells

As can be seen from table 4, the effect of the solar silicon wafer cutting waste and the monocrystalline silicon is obviously better than that of other types of silicon, and the result of the electron microscope photo also shows that the solar silicon wafer cutting waste forms a nano sheet structure after being sanded. The silicon accounts for 70-98% of the mass of the material, the silicon has better electrochemical performance, and the sanding time is preferably more than 4 hours.

Table 5 shows the analysis results of XRD patterns of the negative electrode sheet (active material including silicon nano-sheets) and the raw material provided in example 1, and the negative electrode sheet (active material including silicon nano-particles) and the raw material provided in comparative example 3.

TABLE 5 analysis of XRD patterns of negative electrode sheets

The non-rolled and rolled pole pieces of example 1 and comparative example 3 were tested by X-ray diffraction, and the results showed that, in example 1, from the raw material to the production of pole pieces, the rolling was performed,

(111) The ratio of the (111)/(311) crystal plane peak intensities of the (220) crystal plane peak intensities was gradually increased, which means that the nanoplatelets in the pole piece gradually tended to be arranged in parallel, corresponding to the SEM, whereas the ratio of the (111)/(220) crystal plane peak intensities of the (111)/(311) crystal plane peak intensities was substantially unchanged from the raw material to the pole piece manufactured by rolling in comparative example 3.

The embodiments described above are some, but not all embodiments of the application. The detailed description of the embodiments of the application is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Claims

1. The negative electrode plate is characterized by comprising a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector;

the active material in the anode active material layer comprises a flaky silicon-based material, and at least 60% of the flaky silicon-based material has an included angle of less than or equal to 20 degrees with the surface of the anode current collector as a reference.

2. The negative electrode sheet according to claim 1, wherein the sheet-like silicon-based material is one or more of a silicon nano-sheet, a silicon sub-micro-sheet, a silicon alloy nano-sheet, a silicon alloy sub-micro-sheet, a silicon nano-sheet, a silicon sub-micro-sheet and a surface modified coated material thereof;

Or/and the thickness of the silicon nano sheet is 1-200nm; the plane size is 20-5000nm.

3. The negative electrode tab of claim 1, wherein the active material further comprises carbon-coated tin nanowires as a synergistic active material;

or/and the diameter of the carbon-coated tin nanowire is below 100nm, and the length-diameter ratio is (5-1000): 1.

4. The negative electrode sheet of claim 3, wherein the carbon-coated tin nanowires are formed by in situ reduction of tin oxide nanoparticles and carbon deposition.

5. The negative electrode sheet of claim 3, wherein the graphitization degree γ of the carbon coating layer in the carbon-coated tin nanowire satisfies 0.3+.γ+.1, where γ= (0.344-d) ₀₀₂ )/(0.344-0.3354)，d ₀₀₂ Is the nano-layer spacing of the carbon coating layer in the 002 crystal face.

6. The negative electrode sheet of any one of claims 1-5, wherein the active material further comprises carbon nanotubes as a synergistic active material;

or/and the diameter of the carbon nano tube is below 20nm, and the length-diameter ratio is (10-1000): 1;

or/and, the carbon nanotubes at least comprise single-walled carbon nanotubes.

7. The negative electrode sheet according to claim 1, wherein the total mass is the sum of the active material, the conductive agent and the binder, the active material accounts for 70-95% of the total mass, the conductive agent accounts for 0-10% of the total mass, and the binder accounts for 2-30% of the total mass.

8. The negative electrode tab of claim 7, wherein the active material comprises 50-98% silicon by weight, 0.5-20% tin by weight, and 1.5-20% carbon by weight.

9. A lithium ion secondary battery comprising the negative electrode tab of any one of claims 1-8.

10. A solid-state battery comprising the negative electrode tab of any one of claims 1-9.

11. The preparation method of the negative electrode material is characterized in that a carbon nano tube solution, a silicon-based material and tin oxide nano particles are dispersed in an organic solvent, grinding, filtering and drying are carried out to obtain a composite precursor, the composite precursor is placed in a high-temperature sintering furnace, the temperature is increased to 650-900 ℃ in an inert atmosphere, acetylene gas is introduced for sintering, and the negative electrode material obtained by mixing the carbon nano tube, the carbon-coated tin nano wire and the flaky silicon-based material is obtained;

optionally, the diameter of the carbon nano tube is below 20nm, and the length-diameter ratio is (10-1000): 1;

optionally, the carbon nanotubes comprise at least single-walled carbon nanotubes;

optionally, the diameter of the carbon-coated tin nanowire is below 100nm, and the length-diameter ratio is (5-1000): 1;

Optionally, the sheet silicon-based material is one or more of a silicon nano sheet, a silicon submicron sheet, a silicon alloy nano sheet, a silicon alloy submicron sheet, a silicon nanometer sheet, a silicon submicron sheet and a material of which the surface is modified and coated;

optionally, the thickness of the silicon nano-sheet is 1-200nm; the plane size is 20-5000nm;

optionally, in the anode material, the weight percentage of silicon is 50% -98%, the weight percentage of tin is 0.5% -20%, and the weight percentage of carbon is 1.5% -20%.

12. A preparation method of a negative electrode plate is characterized in that a flaky silicon-based material, a conductive agent, a binder and a solvent are mixed and placed in a stirring tank, then a stirrer in the stirring tank is continuously stirred at a speed of 200-3000rad/min, and the stirring tank is continuously rotated at a speed of 200-3000rad/min to obtain a negative electrode active slurry;

then coating the negative electrode active slurry on the surface of a negative electrode current collector, drying and rolling to obtain a negative electrode plate;

Optionally, the thickness of the silicon nano-sheet is 1-200nm; the plane size is 20-5000nm.