CN111900360B - Quick-charging type high-specific-capacity negative plate and lithium ion battery comprising same - Google Patents
Quick-charging type high-specific-capacity negative plate and lithium ion battery comprising same Download PDFInfo
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- CN111900360B CN111900360B CN202010851773.6A CN202010851773A CN111900360B CN 111900360 B CN111900360 B CN 111900360B CN 202010851773 A CN202010851773 A CN 202010851773A CN 111900360 B CN111900360 B CN 111900360B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/364—Composites as mixtures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
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- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a quick-charging type high-specific-capacity negative plate and a lithium ion battery comprising the same. The invention firstly provides a composite material of silicon oxide coated by porous carbon spheres and a conductive carbon tube, wherein in the composite material of the silicon oxide coated by graphite and the conductive carbon tube, the conductive carbon tube is positioned between silicon oxide particles and the porous carbon spheres, so that the conductivity between the silicon oxide particles and between the particles and the porous carbon spheres coated on the surface of the particles can be increased, the collapse of a conductive network on the surface of silicon caused by the volume expansion in the charging and discharging process of a silicon cathode can be relieved, the polarization internal resistance of a battery cell can be reduced, the problems of lowest graphite potential and high lithium ion concentration near the silicon oxide and lithium precipitation caused by the lowest graphite potential and high lithium ion concentration after the silicon is doped into the graphite cathode can be effectively solved, and the cycle performance is improved.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a quick-charging type high-specific-capacity negative plate and a lithium ion battery comprising the same.
Background
In recent years, consumer portable electronic products have seen explosive growth in sales. The lithium ion battery is used as a core component of a consumer portable electronic product, and the long service life is used as an important index of the lithium ion battery, so that the lithium ion battery has important significance for energy conservation, emission reduction and environmental protection. Meanwhile, in order to solve the problems of 'endurance and charging anxiety' of products, the continuous improvement of the energy density and the rapid charging of the battery are one of the main development directions at present. The specific capacity of graphite as the most mature anode material at present is basically fully exerted, the theoretical specific capacity of the emerging silicon anode material is up to 4200mAh/g, and silicon and a carbon material are combined to be a better mode for increasing the energy density on the existing chemical system and material. However, since the volume of the silicon material is easy to expand in the charging and discharging processes, the application range of the silicon material is limited due to the poor rate capability and cycle performance in the practical application process. Meanwhile, the problems of the quick charging capability and the safety of the lithium ion battery are also key factors and technical problems influencing the large-scale popularization and application of the lithium ion battery.
Disclosure of Invention
At present, methods for improving high energy density, quick charging performance and long cycle performance of a lithium ion battery mainly comprise the following steps: reducing the particle size of positive and negative active materials, and reducing the coating thickness of positive and negative pole pieces so as to reduce the diffusion path and concentration polarization of lithium ions; (II) using a composite conductive agent system to improve the electronic conductivity among particles; and (III) silicon and silicon oxide are directly mixed in the negative electrode, so that the gram capacity of the negative electrode is improved, and the energy density of the battery cell is increased. However, the above-mentioned technology has some disadvantages, such as reducing the particle size of the positive and negative electrode active materials and reducing the coating thickness of the positive and negative electrode sheets, and this measure can reduce the diffusion path and concentration polarization of lithium ions and improve the fast charging capability of the lithium ion battery, but this measure inevitably leads to the reduction of the energy density of the lithium ion battery. Although the energy density of the lithium ion battery can be improved by the negative electrode doped silicon and silicon oxide, the potential and polarization degree of the silicon, silicon oxide and graphite materials are different due to the difference of the conductivity and lithium storage amount of the two materials during charging, so that the potential of silicon and silicon oxide particles is high, the graphite potential near the doped silicon and silicon oxide is the lowest, the lithium ion concentration distribution in the negative electrode plate is uneven, and lithium precipitation is caused. Meanwhile, the volume expansion of silicon and silicon oxide in the charging and discharging process causes the electrode material to collapse in structure and the particle differentiation in the circulating process, so that the electron conductivity between active materials and between the active materials and a current collector is lost, and the problem of poor conductivity of the silicon negative electrode and the like finally causes the reversible capacity loss, so that the dynamic performance of the mixed negative electrode plate is reduced, the quick charging capacity of the lithium ion battery is reduced, and the charging and discharging performance of the lithium ion battery under the large-current charging and discharging is influenced.
The problems that lithium is separated out from the surface of the negative plate and the volume is expanded and the like in the high-rate charge and discharge process due to the fact that the dynamic performance of the negative plate is reduced after the negative electrode of the lithium ion battery is doped with silicon and silicon oxide are solved. The invention provides a quick-charging type high-specific-capacity negative plate and a lithium ion battery comprising the same. The negative plate can well solve the problems of lithium precipitation, volume expansion and the like on the surface of the negative plate in the high-rate charge and discharge process.
The purpose of the invention is realized by the following technical scheme:
a composite comprising silicon oxide, conductive carbon tubes, and porous carbon spheres; the conductive carbon tube is coated on the surface of the silicon oxide to form a first coating layer, and the silicon oxide coated by the conductive carbon tube is formed and marked as silicon oxide @ conductive carbon tube; and coating the porous carbon spheres on the surface of the silicon oxide @ conductive carbon tube to form a second coating layer, and forming the composite material, namely the silicon oxide @ conductive carbon tube coated by the porous carbon spheres.
According to the invention, the silicon oxide is in the form of particles, the median particle diameter D of which 50 Is 10nm-7 μm.
According to the invention, the length of the conductive carbon tube is 20-100 μm, and the diameter is 5-30nm.
According to the invention, the porous carbon spheres are in the form of particles having a median particle diameter D 50 500nm-1200nm, and 2.5nm of pore diameter<D meso <6nm。
According to the invention, the thickness of the first coating layer is 30nm-100nm and the thickness of the second coating layer is 1-5 μm.
According to the invention, the mass of the conductive carbon tubes is 0.5-2wt% of the total mass of the core material.
According to the invention, the mass ratio of the porous carbon spheres to the silicon oxide coated by the conductive carbon tubes is 10-50.
According to the invention, the composite material is in the form of particles, the median particle diameter D of which 50 Is 5-12 μm.
The invention also provides a negative plate, which comprises a negative current collector and an active substance layer arranged on the surface of the negative current collector, wherein the active substance layer comprises a negative active substance, and the negative active substance comprises the composite material.
According to the present invention, the anode active material includes a carbon anode active material and a silicon anode active material selected from the above-described composite materials.
According to the invention, the mass ratio of the carbon negative electrode active material to the silicon negative electrode active material is (80-99): (20-1).
The invention also provides a negative plate, which comprises a negative current collector, a first negative active material layer, a second negative active material layer and a third negative active material layer, wherein the first negative active material layer is arranged on the surface of the negative current collector, the second negative active material layer is arranged on the surface of the first negative active material layer, and the third negative active material layer is arranged on the surface of the second negative active material layer; wherein the first anode active material layer includes a first anode active material; the second anode active material layer includes a second anode active material selected from the composite materials described above; the third anode active material layer includes a third anode active material.
According to the present invention, the first negative electrode active material is in the form of particles having a particle size distribution satisfying: d is not less than 5 mu m 10 ≤8μm，12μm≤D 50 ≤18μm，24μm≤D 90 ≤29μm。
According to the present invention, the third negative electrode active material is in the form of particles having a particle size distribution satisfying: 3 μm<D 10 <4μm，8μm<D 50 <12μm，18μm<D 90 <25μm。
According to the invention, the first negative electrode active material layer further contains a first conductive agent and a first binder, and the first negative electrode active material layer comprises the following components in percentage by mass: 75-99wt% of a first negative electrode active material, 0.5-15wt% of a first conductive agent, and 0.5-10wt% of a first binder.
According to the invention, the second negative electrode active material layer further contains a second conductive agent and a second binder, and the second negative electrode active material layer comprises the following components in percentage by mass: 75-99wt% of a second negative electrode active material, 0.5-15wt% of a second conductive agent, and 0.5-10wt% of a second binder.
According to the invention, the third negative electrode active material layer further contains a third conductive agent and a third binder, and the third negative electrode active material layer comprises the following components in percentage by mass: 75-99wt% of a third negative electrode active material, 0.5-15wt% of a third conductive agent, and 0.5-10wt% of a third binder.
The invention also provides a lithium ion battery which comprises the negative plate.
The invention has the beneficial effects that:
the invention firstly provides a composite material of silicon oxide coated by porous carbon spheres and a conductive carbon tube, wherein the conductive carbon tube is positioned between silicon oxide particles and the porous carbon spheres in the composite material of the silicon oxide coated by the porous carbon spheres and the conductive carbon tube, so that the electrical conductivity between the silicon oxide particles and between the particles and the porous carbon spheres coated on the surfaces of the silicon oxide particles can be increased, the collapse of a conductive network on the silicon surface caused by the volume expansion in the charge-discharge process of a silicon cathode can be relieved, the polarization internal resistance of a battery cell can be reduced, the problems of lowest graphite potential near the silicon oxide, high lithium ion concentration and lithium precipitation caused by the doped silicon on the graphite cathode can be effectively solved, and the cycle performance is improved.
Drawings
Fig. 1 is a schematic structural diagram of a porous carbon sphere coated silicon oxide @ conductive carbon tube composite material according to the present invention; reference numerals are as follows: 1 is silicon oxide; 2 is a porous carbon sphere; and 3 is a conductive carbon tube.
FIG. 2 is a schematic structural diagram of a blended fast-charging high-specific-capacity negative electrode sheet; reference numerals: 4 is a composite material; 5 is carbon material, 6 is current collector.
FIG. 3 is a schematic structural diagram of a sandwich-type fast-charging high-specific-capacity negative electrode sheet; reference numerals: 4 is a composite material; 5 is carbon material, 6 is current collector.
Detailed Description
< composite Material >
As previously described, the present invention provides a composite material comprising silicon oxide, conductive carbon tubes, and porous carbon spheres; wherein, a plurality of silicon oxides are coated by the conductive carbon tube to form the silicon oxide coated by the conductive carbon tube, which is marked as silicon oxide @ conductive carbon tube; and a plurality of silicon oxides @ conductive carbon tubes are coated by the porous carbon spheres to form the composite material, namely the porous carbon sphere coated silicon oxides @ conductive carbon tubes.
In the present invention, the "plurality" may be one silicon oxide particle or a plurality of silicon oxide particles.
In a specific embodiment of the invention, the conductive carbon tube forms a first coating layer on the surfaces of a plurality of silicon oxides; and the porous carbon spheres form a second coating layer on the surfaces of the silicon oxide @ conductive carbon tubes.
In one embodiment of the invention, the silicon oxide is in the form of particles, the median particle diameter D being the diameter of the particles 50 Is 10nm-7 μm.
In one embodiment of the present invention, the silicon oxide has a chemical formula SiOx, and x is a number between 0.5 and 2.0, preferably a number between 1.0 and 1.5.
In a specific embodiment of the present invention, the conductive carbon tube is coated on the outer surface of one or more silicon oxide particles in a disordered and three-dimensional network shape; for example, the carbon conductive tubes are coated on the outer surface of one or more silicon oxide particles in a disordered, three-dimensional network.
In one embodiment of the present invention, the first coating layer formed on the surfaces of the silicon oxides by the conductive carbon tubes has a thickness of 30nm to 100nm, preferably 40nm to 70nm.
In one embodiment of the invention, the length of the conductive carbon tubes is 20-100 μm, preferably 30-80 μm; the diameter is 5-30nm, preferably 8-20nm.
In one embodiment of the invention, the mass of the conductive carbon tubes is 0.5 to 2wt%, preferably 0.7 to 1.2wt%, of the total mass of the silicon oxide.
In one embodiment of the present invention, the porous carbon spheres are in the form of particles having a median particle diameter D 50 500nm-1200nm, and 2.5nm of pore diameter<D meso <6nm。
In one embodiment of the present invention, the thickness of the second coating layer formed on the surface of the silicon oxide @ conductive carbon tubes by the porous carbon spheres is 1 to 5 μm, preferably 1.5 to 4 μm.
In one embodiment of the invention, the mass ratio of the porous carbon spheres to the silicon oxide @ conductive carbon tubes is 10-50, preferably 20-40.
In one embodiment of the invention, the composite material is in the form of particles, the median particle diameter D of which 50 Is 5-12 μm, preferably 6-10 μm.
< preparation method of composite Material >
The invention also provides a preparation method of the composite material, which comprises the following steps:
(1) Preparing silicon oxide, and preparing the silicon oxide coated by the conductive carbon tube by adopting a chemical deposition method, wherein the silicon oxide is marked as silicon oxide @ conductive carbon tube;
(2) And mixing the silicon oxide @ conductive carbon tube, the binder and the porous carbon spheres, and coating the porous carbon spheres on the surface of the silicon oxide @ conductive carbon tube by using the binder to prepare the composite material, which is marked as the silicon oxide @ conductive carbon tube coated by the porous carbon spheres.
In a specific embodiment of the present invention, the step (1) specifically includes the following steps:
(1-1) mixing and grinding silicon oxide and a catalyst;
and (1-2) placing the material obtained in the step (1-1) in a tubular furnace, introducing carbon source gas and protective gas, and performing chemical vapor deposition to prepare the silicon oxide @ conductive carbon tube.
Wherein, the step (1-1) may specifically be:
mixing silicon oxide, a catalyst and a solvent, and evaporating the solvent under the stirring condition to obtain a physically mixed mixture of the silicon oxide and the catalyst;
grinding, drying, ball-milling and other post-treatments are carried out on the mixture of the silicon oxide and the catalyst which are physically mixed to prepare the mixture with the median diameter D 50 Is a mixed material with the particle size of 2-6 mu m.
Wherein, the catalyst is selected from one or a combination of two of ferric nitrate, cobalt nitrate, nickel nitrate, ferric sulfate, cobalt sulfate and nickel sulfate, and cobalt nitrate is preferred. The catalyst can be dispersed in the silicon oxide more uniformly when being physically mixed, and the generation of the catalytic carbon tube during the chemical vapor deposition is further improved.
Wherein the solvent is selected from absolute ethyl alcohol. The addition amount of the solvent is 5-17 times of the total mass of the solid components (silicon oxide and catalyst).
Wherein the mass ratio of the silicon oxide to the catalyst is 90-98.
Wherein the milling is, for example, primary milling using an agate mortar, followed by drying at 100 to 120 ℃, followed by ball milling in a ball mill.
Wherein, in the step (1-2), the carbon source gas is selected from at least one of carbon monoxide, methane, ethylene, propylene and benzene.
And the protective gas is at least one of argon, helium or a mixed gas of hydrogen and helium.
The gas flow of the carbon source gas is 1-7L/min, and the gas flow of the protective gas is 1-8L/min
The temperature of the chemical vapor deposition is 600-1000 ℃, and the time of the chemical vapor deposition is 6-10h.
After the chemical vapor deposition is finished, the temperature in the furnace is reduced to the room temperature, the materials are taken out, ground, crushed and sieved to prepare the medium particle size D 50 Silicon oxide @ conductive carbon of 3.5 μm to 8 μmA tube.
In a specific embodiment of the present invention, the step (2) specifically includes the following steps:
(2-1) mixing the silicon oxide @ conductive carbon tubes with a surfactant;
(2-2) spraying a binder solution on the surface of the material in the step (2-1);
(2-3) mixing the porous carbon balls with the material obtained in the step (2-2), performing heat treatment, and performing ball-milling and sieving treatment;
and (2-4) carbonizing the material obtained in the step (2-3) to prepare the composite material.
Wherein, in the step (2-1), the surfactant is selected from polyvinylpyrrolidone PVP.
The mass ratio of the surfactant to the silicon oxide @ conductive carbon tubes is 1-3.
The mixing is, for example, rapid stirring at elevated temperature.
Wherein, in the step (2-2), the binder is selected from at least one of petroleum asphalt, coal asphalt, phenolic resin, polyvinyl chloride and polystyrene.
The temperature of the spray is 100-130 ℃.
The mass ratio of the binder to the silicon oxide @ conductive carbon tubes is 5-15, such as 10.
In the step (2-3), the porous carbon spheres are prepared by the following method:
(2-3-1) mixing ellagic acid, zinc acetate and an organic solvent, reacting, and collecting a precipitate;
and (2-3-2) roasting the precipitate obtained in the step (2-3-1) to prepare the porous carbon spheres.
In the step (2-3-1), the mass ratio of the ellagic acid to the zinc acetate is 2-5.
In the step (2-3-1), the organic solvent is selected from NMP, and the amount of the solvent is determined according to the total mass of ellagic acid and zinc acetate, so that the concentration of the solid substance dissolved in NMP is 5 to 10g/L, such as 8.68g/L.
In the step (2-3-2), the roasting temperature is 900-1100 ℃, and the roasting time is 3-6h.
Illustratively, the method includes the steps of:
dissolving ellagic acid in NMP, continuously stirring until the powder is fully dissolved, slowly adding zinc acetate into the solution, and stirring at room temperature for 3-12 h to obtain yellow powder precipitate. The obtained product is centrifugally washed, dried and ground to obtain yellow powder with the grain diameter of 1-3 mu m. And (3) putting the yellow powder into a tubular furnace, introducing high-purity nitrogen into the tubular furnace, and carbonizing the yellow powder for 4 hours at the temperature of 1000 ℃ to obtain the porous carbon spheres with the particle size of 500 nm-1.2 microns.
The temperature of the heat treatment is 800-950 ℃, for example 900 ℃, and the time of the heat treatment is 5-10 hours.
The median particle diameter D is obtained after ball milling and sieving 50 Is 5-12 μm.
The mass ratio of the silicon oxide @ conductive carbon tube to the porous carbon sphere is 50-90, such as 60-80.
Wherein, in the step (2-4), the temperature of the carbonization treatment is 1000-1150 ℃, for example 1000 ℃, and the time of the carbonization treatment is 2-6 hours, for example 4 hours.
< negative electrode sheet >
The invention also provides a negative plate, which comprises a negative current collector and an active substance layer arranged on the surface of the negative current collector, wherein the active substance layer comprises a negative active substance, and the negative active substance comprises the composite material.
< blend type negative electrode sheet >
In a specific embodiment, there is provided a negative electrode sheet comprising a negative electrode current collector and an active material layer disposed on a surface of the negative electrode current collector; wherein the active material layer includes an anode active material including a carbon anode active material and a silicon anode active material selected from the above-described composite materials.
Specifically, as shown in fig. 2, the carbon negative electrode active material and the silicon negative electrode active material are uniformly mixed and coated on the surface of the negative electrode current collector to form an active material layer.
Specifically, the carbon negative electrode active material includes at least one of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, and organic polymer compound carbon.
Specifically, the mass ratio of the carbon negative electrode active material to the silicon negative electrode active material (g: g) = (80-99): (20-1); further (90-99) is, for example, 90.
In one embodiment of the present invention, the carbon negative electrode active material is in the form of particles having a median particle diameter D 50 Is 11-18 μm, preferably 12-16 μm.
In one embodiment of the present invention, the active material layer further contains a conductive agent and a binder.
In a specific embodiment of the invention, the active material layer comprises the following components in percentage by mass: 75-99wt% of negative active material, 0.5-15wt% of conductive agent and 0.5-10wt% of binder; wherein the negative electrode active material comprises a carbon negative electrode active material and a silicon negative electrode active material selected from the above-mentioned composite materials.
In a specific embodiment of the invention, the active material layer comprises the following components in percentage by mass: 80-98wt% of negative active material, 1-10wt% of conductive agent and 1-10wt% of binder; wherein the active material comprises a carbon anode active material and a silicon anode active material, and the silicon anode active material is selected from the composite material.
In one embodiment of the present invention, the conductive agent is at least one selected from conductive carbon black, acetylene black, ketjen black, conductive carbon fiber, carbon nanotube, graphene, and carbon fiber.
In one embodiment of the present invention, the binder is at least one selected from sodium carboxymethylcellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.
In one embodiment of the invention, the thickness of the active substance layer is 80 to 150. Mu.m, preferably 90 to 135. Mu.m.
In a specific embodiment of the present invention, the length of the negative electrode sheet is not particularly limited, preferably 80-170cm, and the width of the negative electrode sheet may be determined according to the width of the battery cell, and may be 10-150mm, preferably 50-100mm.
< preparation of blend type negative electrode sheet >
The invention also provides a preparation method of the blended negative plate, which comprises the following steps:
a1 Preparing a slurry for forming an active material layer;
a2 The negative electrode sheet is prepared by coating the active material layer-forming slurry on the surface of a negative electrode current collector using a coater.
In one embodiment of the present invention, in the step A1), the solid content of the slurry for forming an active material layer is 40wt% to 45wt%.
< Sandwich type negative electrode sheet >
As described above, the present invention provides a negative electrode sheet including a negative electrode current collector, a first negative electrode active material layer provided on a surface of the negative electrode current collector, a second negative electrode active material layer provided on a surface of the first negative electrode active material layer, and a third negative electrode active material layer provided on a surface of the second negative electrode active material layer; wherein the first anode active material layer includes a first anode active material; the second anode active material layer includes a second anode active material selected from the composite materials described above; the third anode active material layer includes a third anode active material.
In one embodiment of the present invention, the first negative active material and the third negative active material are the same or different and are independently selected from at least one of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, and organic polymer compound carbon.
In one embodiment of the present invention, the first negative electrode active material is in the form of particles having a particle size distribution of: d is not less than 5 mu m 10 ≤8μm，12μm≤D 50 ≤18μm，24μm≤D 90 Less than or equal to 29 mu m; the third negative electrode active material is in the form of particles, and has a particle size distribution of: 3 μm<D 10 <4μm，8μm<D 50 <12μm，18μm<D 90 <25μm。
Specifically, as shown in fig. 3, the bottom layer is a first negative electrode active material layer which is a coating layer made of a carbon material having a relatively large particle size, the intermediate layer is a second negative electrode active material layer which is a coating layer made of a composite material, and the surface layer is a third negative electrode active material layer which is a coating layer made of a carbon material having a relatively small particle size.
In one embodiment of the present invention, the first negative electrode active material layer further contains a first conductive agent and a first binder.
In one embodiment of the present invention, the first negative electrode active material layer includes the following components by mass: 75-99wt% of a first negative electrode active material, 0.5-15wt% of a first conductive agent, and 0.5-10wt% of a first binder.
In one embodiment of the present invention, the first negative electrode active material layer includes the following components by mass: 80-98wt% of a first negative electrode active material, 1-10wt% of a first conductive agent, and 1-10wt% of a first binder.
In one embodiment of the present invention, the second anode active material layer further contains a second conductive agent and a second binder.
In one embodiment of the present invention, the second negative electrode active material layer includes the following components by mass: 75-99wt% of a second negative electrode active material, 0.5-15wt% of a second conductive agent, and 0.5-10wt% of a second binder.
In one embodiment of the present invention, the second negative electrode active material layer includes the following components by mass: 80-98wt% of a second negative electrode active material, 1-10wt% of a second conductive agent, and 1-10wt% of a second binder.
In one embodiment of the present invention, the third negative electrode active material layer further contains a third conductive agent and a third binder.
In one embodiment of the present invention, the third negative electrode active material layer includes the following components by mass: 75-99wt% of a third negative electrode active material, 0.5-15wt% of a third conductive agent, and 0.5-10wt% of a third binder.
In one embodiment of the present invention, the third anode active material layer includes the following components by mass: 80-98wt% of a third negative electrode active material, 1-10wt% of a third conductive agent, and 1-10wt% of a third binder.
In one embodiment of the present invention, the first conductive agent, the second conductive agent, and the third conductive agent forming the first anode active material layer, the second anode active material layer, and the third anode active material layer are the same or different, and the first binder, the second binder, and the third binder are the same or different.
In a specific embodiment of the present invention, the first conductive agent, the second conductive agent and the third conductive agent are the same or different and are independently selected from at least one of conductive carbon black, acetylene black, ketjen black, conductive carbon fiber, carbon nanotube, graphene and carbon fiber.
In one embodiment of the present invention, the first binder, the second binder and the third binder are the same or different and are independently selected from at least one of sodium carboxymethylcellulose, styrene-butadiene latex, polytetrafluoroethylene and polyethylene oxide.
In one embodiment of the present invention, the sum of the thicknesses of the first negative electrode active material layer, the second negative electrode active material layer, and the third negative electrode active material layer is 100 to 150 μm, preferably 100 to 135 μm.
In one embodiment of the present invention, the first negative electrode active material layer has a thickness of 50 to 70 μm, preferably 50 to 60 μm, the second negative electrode active material layer has a thickness of 20 to 40 μm, preferably 20 to 30 μm, and the third negative electrode active material layer has a thickness of 30 to 70 μm, preferably 30 to 40 μm.
In a specific embodiment of the present invention, the length of the negative electrode sheet is not particularly limited, preferably 80-170cm, and the width of the negative electrode sheet may be determined according to the width of the battery cell, and may be 10-150mm, preferably 50-100mm.
< preparation of Sandwich type negative electrode sheet >
The invention also provides a preparation method of the sandwich type negative plate, which comprises the following steps:
1) Preparing a slurry for forming a first negative electrode active material layer, a slurry for forming a second negative electrode active material layer, and a slurry for forming a third negative electrode active material layer, respectively;
2) And coating the slurry for forming the first negative electrode active material layer, the slurry for forming the second negative electrode active material layer and the slurry for forming the third negative electrode active material layer on the surface of a negative electrode current collector by using a coating machine to prepare the negative electrode sheet.
In one embodiment of the present invention, in step 1), the solid contents of the slurry for forming the first anode active material layer, the slurry for forming the second anode active material layer, and the slurry for forming the third anode active material layer are 40wt% to 45wt%.
In one embodiment of the present invention, in step 2), the slurry for forming the first negative electrode active material layer is coated on the surface of the negative electrode current collector to form the first negative electrode active material layer, then the slurry for forming the second negative electrode active material layer is coated on the surface of the first negative electrode active material layer to form the second negative electrode active material layer, and then the slurry for forming the third negative electrode active material layer is coated on the surface of the second negative electrode active material layer to form the third negative electrode active material layer.
< lithium ion Battery >
As described above, the present invention also provides a lithium ion battery, which includes the above negative electrode sheet.
The present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
In the description of the present invention, it should be noted that the terms "first", "second", etc. are used for descriptive purposes only and do not indicate or imply relative importance.
The silicon oxide used in the following examples was a general silicon material having a particle diameter D as obtained from beidou corporation, which was a silicon oxide obtained in preparation example 1 50 Is 5-7 μm.
Preparation example 1
(1) Mixing silicon oxide (chemical formula is SiOx, x is 1.5) and a cobalt nitrate catalyst according to a mass ratio of 98;
(2) mixing the mixture with absolute ethyl alcohol according to a mass ratio of 1.
(3) Sieving the above powder material with 2000-6000 mesh sieve to obtain particle diameter D 50 Particles between 2 and 6 μm;
(4) placing the substances in a tube furnace, introducing carbon monoxide and methane mixed gas (mixed gas volume ratio is 3.
(5) Grinding and crushing the silicon oxide @ conductive carbon tube, and screening the crushed material through a 1800-4000-mesh screen to obtain a material with a median particle size D 50 Silicon oxide @ conductive carbon tubes of 3.5 μm to 8 μm.
(6) The median diameter D is measured 50 Putting 3.5-8 mu m of silicon oxide @ conductive carbon tube into a reaction kettle, adding 1% of PVP surfactant, stirring at a speed of 45rmp, and rapidly heating to 120 ℃; petroleum is mixed at 120 deg.CSpraying an asphalt solution binder to the surface of a material in the reaction kettle, wherein the mass ratio of the silicon oxide @ conductive carbon tube to the liquid binder is 90; the process keeps continuous stirring, and the liquid adhesive is ensured to uniformly coat the silicon oxide @ conductive carbon tubes;
(7) 3.5g of ellagic acid was dissolved in NMP, stirring was continued until the powder was sufficiently dissolved, and 1g of zinc acetate was slowly added to the above solution, followed by stirring at room temperature for 3 hours to obtain a yellow powder precipitate. The obtained product is centrifugally washed, dried and ground to obtain yellow powder with the grain diameter of 1-1.8 mu m. And (3) putting the yellow powder in a tube furnace, introducing high-purity nitrogen, and carbonizing at 1000 ℃ for 4h to obtain the porous carbon spheres with the particle size of 500-700 nm.
(8) At a stirring speed of 100rmp, the median particle diameter D is added 50 Fully stirring the porous carbon spheres with the particle size of 500nm-700nm, wherein the mass ratio of the silicon oxide @ conductive carbon tube uniformly coated by the liquid adhesive to the porous carbon spheres is 60; then quickly heating to 900 ℃ and keeping the temperature for 10 hours, ball-milling the product after cooling through a 1600-2500 mesh screen to prepare the product with the median particle diameter D 50 And (3) putting the precursor with the particle size of 6-8 microns into a tubular furnace, and carbonizing the precursor at the high temperature of 1000 ℃ for 4 hours to obtain the silicon oxide @ conductive carbon tube coated by the porous carbon ball, namely the composite material.
Preparation examples 2 to 9
The preparation examples 2 to 9 were prepared in the same manner as in preparation example 1, the preparation examples 2 to 3 were different in the chemical vapor deposition time, the preparation examples 4 to 5 were different in the particle size of the porous carbon spheres, the preparation examples 6 to 7 were different in the mass ratio of the silicon oxide @ conductive carbon tubes uniformly coated with the liquid binder to the porous carbon spheres, and the preparation examples 8 to 9 were different in the selection of screens of different mesh numbers after the final heat treatment to obtain composite materials of different particle sizes, specifically different as shown in table 1 below.
TABLE 1 working procedures for the preparation of composites and parameters for the preparation of the resulting composites in preparation examples 1 to 9
Example 1
(1) Preparing a negative plate:
the graphite (D) was taken in a mass ratio of 99 50 =15 μm) and the composite material prepared in the preparation example 1 are placed in a ball mill to be ball-milled for 2-5min, and are fully mixed to obtain a negative electrode active material;
the obtained negative electrode active material, a conductive agent (conductive carbon black) and a binder (sodium carboxymethyl cellulose) were mixed in a proportion of 97.0%:1.5%: adding 1.5% of the mixture into a stirring tank, and adding deionized water according to a known batching process to prepare cathode active substance slurry, wherein the solid content of the cathode active substance slurry is 40% -45%;
coating the slurry on a copper foil by using a coating machine, and drying at the temperature of 100 ℃ to prepare a blended fast-charging type high-specific-capacity negative plate;
the length of the negative pole piece is 883 +/-2 mm, the thickness of the negative active material layer is 100 microns, the width of the pole piece can be determined according to the width of a battery cell and the model of the battery cell, for example, the model of 386383 is used in the patent, and the width of the selected pole piece is 79mm +/-0.5 mm.
(2) Preparing a positive plate:
lithium cobaltate is used as a positive electrode active material, then the lithium cobaltate, a conductive agent (conductive carbon black) and a binder (polyvinylidene fluoride) are added into a stirring tank according to the mass ratio of 97.2;
(3) Assembling the battery cell:
and (3) winding the negative plate prepared in the step (1), the positive plate prepared in the step (2) and the diaphragm together to form a winding core, packaging the winding core by using an aluminum plastic film, baking the winding core to remove moisture, injecting electrolyte, and forming the winding core by adopting a hot pressing formation process to obtain the battery core.
Examples 2 to 10
Examples 2 to 10 were prepared as in example 1 with respect to the cells of example 1, except that:
the mass ratio of graphite to the composite material in the negative electrode active material layer was different, the carbon material in the negative electrode active material layer was different, and the content of the conductive agent in the negative electrode active material layer was different, as specifically described in table 2.
Examples 11 to 18
Examples 11-18 were prepared as in example 1, except that: in examples 11 to 18, the composite materials prepared in preparation examples 2 to 9 were used, and the details are shown in Table 2.
Comparative examples 1 to 7
The cells of comparative examples 1 to 7 and example 1 were prepared as in example 1, except that: the composite material is replaced by a common silicon material in the negative active material, and the material ratio is different, which is specifically shown in table 3.
The negative electrode sheets prepared in the above examples and comparative examples were compacted in the same manner, and assembled into a pouch cell type 386283, and subjected to 0.2C/0.2C charging/discharging at 25 ℃ to test the energy density, and each of the pouch cells was subjected to 1.8C charging/0.7C discharging at 25 ℃, and disassembled at different cycles to confirm the lithium precipitation on the surface of the negative electrode of the battery, and the disassembly results and the energy density are shown in tables 2 and 3.
TABLE 2 negative electrode sheets of examples 1-18 and cases of lithium deposition from the surfaces of the negative electrode sheets during cycling
TABLE 3 negative electrode sheets of comparative examples 1 to 7 and cases of lithium deposition from the surfaces of the negative electrode sheets during cycling
Example 19
(1) Preparing a negative plate:
(1) preparing a first negative electrode active material slurry: the first negative electrode active material (graphite), the first conductive agent (conductive carbon black), and the first binder (sodium carboxymethyl cellulose) were mixed in a mass ratio of 97.0%:1.5%:1.5 percent of the mixture is added into a stirring tank, deionized water is added according to a known batching process to prepare first cathode active material slurry, and the solid content of the cathode active material slurry is 40 to 45 percent;
(2) preparing a second negative electrode active material slurry: the mass ratio of the second negative electrode active material (the composite material of preparation example 1), the second conductive agent (carbon nanotubes) and the second binder (styrene-butadiene rubber) was 97.0%:1.5%:1.5 percent of the mixture is added into a stirring tank, deionized water is added according to a known batching process to prepare a second negative electrode active substance slurry, and the solid content of the negative electrode slurry is 40 to 45 percent;
(3) preparing a third active material slurry: adding 97.0% of a third negative electrode active material (graphite), a third conductive agent (conductive carbon black) and a third binder (sodium carboxymethyl cellulose) according to the mass ratio: 1.5%:1.5 percent of the mixture is put into a stirring tank, deionized water is added according to the known batching process to prepare second cathode active material slurry, and the solid content of the cathode slurry is 40 to 45 percent;
coating the first negative electrode active material slurry on a copper foil current collector by using a coating machine, coating the second negative electrode active material slurry on the surface of the first negative electrode active material slurry, coating the third negative electrode active material slurry on the surface of the second negative electrode active material slurry, and drying the coated negative electrode piece at the temperature of 100 ℃ to obtain a negative electrode piece; the length of the negative electrode piece is 883 +/-2 mm, the thickness of the first negative electrode active material layer is 60 mu m, the thickness of the second negative electrode active material layer is 20 mu m, the thickness of the third negative electrode active material layer is 50 mu m, and the width of the negative electrode piece is 79mm +/-0.5 mm.
(2) Preparing a positive plate:
lithium cobaltate is used as a positive electrode active material, then the lithium cobaltate, a conductive agent (conductive carbon black) and a binder (polyvinylidene fluoride) are added into a stirring tank according to the mass ratio of 97.2;
(3) Assembling the battery cell:
and (3) winding the negative plate prepared in the step (1), the positive plate prepared in the step (2) and the diaphragm together to form a winding core, packaging the winding core by using an aluminum plastic film, baking the winding core to remove moisture, injecting electrolyte, and forming the winding core by adopting a hot pressing formation process to obtain the battery core.
Examples 20 to 32
The cells of examples 20-32 were prepared as in example 19, except that: the particle size of graphite in the negative electrode active material layer was different, the composite material was different, the amount of the composite material added was different, the thickness of the negative electrode active material layer was different, and the content of the conductive agent in the negative electrode active material layer was different, as specifically shown in table 4.
Examples 33 to 40
The cells of examples 33-40 were prepared as in example 19, except that: the composite materials prepared in preparation examples 2 to 9 were used in examples 33 to 40, respectively, and the details are shown in Table 4.
Comparative examples 8 to 13
Comparative examples 8-13 and example 19 cells were prepared as in example 19, except that: the particle size of graphite in the negative electrode active material layer, the composite material, the thickness of the negative electrode active material layer, and the content of the conductive agent in the negative electrode active material layer were different, and specific examples thereof are shown in table 4.
The negative electrode sheets prepared in the above examples and comparative examples were compacted in the same manner, and assembled into a soft packaging cell of model 386283, and subjected to a 0.2C/0.2C charge-discharge test at 25 ℃ for energy density, and subjected to a 1.8C charge/0.7C discharge at 25 ℃ for each soft packaging cell, and disassembled at different cycle times to confirm the lithium precipitation on the surface of the negative electrode of the battery, and the disassembly results and energy density are shown in table 5.
TABLE 4 compositions of negative electrode sheets of examples 19 to 40 and comparative examples 8 to 13
TABLE 5 negative electrode sheets of examples 19-40 and comparative examples 8-13 exhibit lithium precipitation from the surface of the negative electrode sheet during cycling
From tables 1 to 5, it can be seen that under the conditions of the same coating thickness, graphite particle size and formula, the energy density and charging speed of the lithium ion battery can be greatly improved by doping the composite material prepared by the method of the present invention into the negative electrode material compared with the common silicon negative electrode material, and the problems of lithium precipitation and volume expansion on the surface of the negative electrode sheet in the process of high-rate charge and discharge caused by the reduced dynamic performance of the negative electrode sheet after the lithium ion battery negative electrode is doped with the common silicon can be fully solved after the specific composite material is doped, so that the cycle life and the rapid charging capability of the lithium ion battery can be improved.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (17)
1. A composite comprising silicon oxide, electrically conductive carbon tubes, and porous carbon spheres; the conductive carbon tube is coated on the surface of the silicon oxide to form a first coating layer, and the silicon oxide coated by the conductive carbon tube is formed and marked as silicon oxide @ conductive carbon tube; coating the porous carbon spheres on the surface of the silicon oxide @ conductive carbon tube to form a second coating layer and forming the composite material, which is marked as the silicon oxide @ conductive carbon tube coated by the porous carbon spheres;
the silicon oxide is granular, and the median grain diameter D 50 2-6 μm;
the porous carbon spheres are granular, and the median particle diameter D 50 Is 500nm-1200nm;
the conductive carbon tube is coated on the outer surface of one or more silicon oxide particles in a disordered and three-dimensional network shape.
2. Composite according to claim 1, characterized in that the conductive carbon tubes have a length of 20-100 μm and a diameter of 5-30nm.
3. The composite material of claim 1, wherein the porous carbon spheres have a pore size of 2.5nm<D meso <6nm。
4. The composite material of claim 1, wherein the first cladding layer has a thickness of 30nm to 100nm and the second cladding layer has a thickness of 1 to 5 μm.
5. Composite according to claim 1, characterized in that the mass of the conductive carbon tubes is 0.5-2wt% of the total mass of the core material.
6. The composite material according to claim 1, wherein the mass ratio of the porous carbon spheres to the silicon oxide coated by the conductive carbon tubes is 1.
7. Composite material according to claim 1, characterized in that it is in the form of particles with a median particle diameter D 50 Is 5-12 μm.
8. A negative electrode sheet comprising a negative electrode current collector and an active material layer provided on a surface of the negative electrode current collector, the active material layer comprising a negative electrode active material, the negative electrode active material comprising the composite material according to any one of claims 1 to 7.
9. The negative electrode sheet according to claim 8, wherein the negative electrode active material comprises a carbon negative electrode active material and a silicon negative electrode active material selected from the composite material according to any one of claims 1 to 7.
10. The negative electrode sheet of claim 9, wherein the mass ratio of the carbon negative electrode active material to the silicon negative electrode active material is (80-99): (20-1).
11. The negative plate is characterized by comprising a negative current collector, a first negative active material layer, a second negative active material layer and a third negative active material layer, wherein the first negative active material layer is arranged on the surface of the negative current collector, the second negative active material layer is arranged on the surface of the first negative active material layer, and the third negative active material layer is arranged on the surface of the second negative active material layer; wherein the first anode active material layer includes a first anode active material; the second anode active material layer includes a second anode active material selected from the composite material according to any one of claims 1 to 7; the third anode active material layer includes a third anode active material.
12. The negative electrode sheet according to claim 11, wherein the third negative electrode active material is in a granular form having a particle size distribution of: d is more than 3 mu m 10 ＜4μm，8μm＜D 50 ＜12μm，18μm＜D 90 ＜25μm。
13. The negative electrode sheet according to claim 11, wherein the first negative electrode active material is in a particulate form having a particle size distribution of: d is more than 5 mu m 10 ＜8μm，12μm＜D 50 ＜18μm，24μm＜D 90 ＜29μm。
14. The negative electrode sheet according to claim 11, wherein the first negative electrode active material layer further contains a first conductive agent and a first binder, and the first negative electrode active material layer contains the following components in percentage by mass: 75-99wt% of a first negative electrode active material, 0.5-15wt% of a first conductive agent, and 0.5-10wt% of a first binder.
15. The negative electrode sheet according to claim 11, wherein the second negative electrode active material layer further contains a second conductive agent and a second binder, and the second negative electrode active material layer contains the following components in percentage by mass: 75-99wt% of a second negative electrode active material, 0.5-15wt% of a second conductive agent, and 0.5-10wt% of a second binder.
16. The negative electrode sheet according to claim 11, wherein the third negative electrode active material layer further contains a third conductive agent and a third binder, and the third negative electrode active material layer contains the following components in percentage by mass: 75-99wt% of a third negative electrode active material, 0.5-15wt% of a third conductive agent, and 0.5-10wt% of a third binder.
17. A lithium ion battery, characterized in that the battery comprises the composite material according to any one of claims 1 to 7 or the negative electrode sheet according to any one of claims 8 to 16.
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| CN112436104B (en) * | 2020-12-30 | 2022-09-06 | 兰溪致德新能源材料有限公司 | Negative pole piece and preparation method thereof |
| CN113130869B (en) * | 2021-04-09 | 2022-11-08 | 珠海冠宇电池股份有限公司 | Negative plate and lithium ion battery |
| CN113161528A (en) * | 2021-04-25 | 2021-07-23 | 天津市捷威动力工业有限公司 | Preparation method of double-layer composite silicon-coated material and lithium ion battery thereof |
| CN113488637B (en) * | 2021-06-18 | 2023-04-07 | 江苏正力新能电池技术有限公司 | Composite negative electrode material, negative plate and lithium ion battery |
| CN114050234B (en) * | 2021-11-15 | 2023-02-28 | 珠海冠宇电池股份有限公司 | Negative plate and lithium ion battery comprising same |
| CN114447292B (en) * | 2021-12-23 | 2023-12-01 | 东莞市鸿德电池有限公司 | Lithium ion battery negative electrode material and preparation method thereof |
| CN115995546B (en) * | 2023-03-22 | 2023-07-25 | 江苏正力新能电池技术有限公司 | Vanadium sodium phosphate material with three-dimensional carbon framework, and preparation method and application thereof |
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| CN102983317A (en) * | 2012-12-05 | 2013-03-20 | 奇瑞汽车股份有限公司 | Silicon-based composite material and preparation method thereof, silicon-carbon composite material and lithium ion battery |
| CN105161695A (en) * | 2015-06-12 | 2015-12-16 | 南通彩都新能源科技有限公司 | Spherical active material particles for lithium ion battery negative electrode, preparation method and application of spherical active material particles |
| CN109037636A (en) * | 2018-08-03 | 2018-12-18 | 深圳市斯诺实业发展有限公司 | A kind of preparation method of SiO/ carbon graphite composite negative pole material |
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