CN108511689B - Lithium ion battery positive plate containing conductive coating and preparation method thereof - Google Patents
Lithium ion battery positive plate containing conductive coating and preparation method thereof Download PDFInfo
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- CN108511689B CN108511689B CN201710218859.3A CN201710218859A CN108511689B CN 108511689 B CN108511689 B CN 108511689B CN 201710218859 A CN201710218859 A CN 201710218859A CN 108511689 B CN108511689 B CN 108511689B
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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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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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
- 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
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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
- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0404—Methods of deposition of the material by coating on electrode collectors
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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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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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
- H01M4/64—Carriers or collectors
- H01M4/66—Selection of materials
- H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
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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
- H01M4/64—Carriers or collectors
- H01M4/66—Selection of materials
- H01M4/665—Composites
- H01M4/667—Composites in the form of layers, e.g. coatings
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- 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
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- 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
Abstract
The invention relates to the field of lithium batteries, and discloses a lithium ion battery positive plate containing a conductive coating and a preparation method thereof. This positive plate includes aluminium foil mass flow body, conductive coating and anodal active material layer, and anodal active material layer is formed by anodal thick liquids solidification, and anodal thick liquids include: 91-95 parts of lithium iron phosphate, 1-3 parts of conductive carbon black SP, 0.5-1.5 parts of vapor grown carbon fiber, 3-5 parts of polyvinylidene fluoride and 60-80 parts of N-N-dimethyl pyrrolidone; the conductive coating is formed by curing conductive paste, and the conductive paste comprises: 10-95 parts of composite carbon source, 5-50 parts of binder, 5-40 parts of dispersant and 550 parts of organic solvent. According to the invention, the current collector is coated with the special conductive slurry, so that the specific surface area is large, the impedance is small, the pole piece binding power can be greatly improved, the conductivity is enhanced, the addition amount of the binding agent and the conductive agent is reduced, and the energy density of the battery is improved.
Description
Technical Field
The invention relates to the field of lithium batteries, in particular to a lithium ion battery positive plate containing a conductive coating and a preparation method thereof.
Background
At present, the positive plate of the lithium ion battery generally comprises a current collector and a positive active material coated on the current collector. The current collector of the positive electrode mainly adopts aluminum foil plain foil. The smooth surface of the optical foil is smooth, so that the interface binding force of the positive active material and a current collector is weak when the positive active material is coated, the binding force of the positive active material is poor, and the problems of pole piece falling and the like are easily caused in the later-stage process. Therefore, the amount of the conductive agent added must not be increased, and in order to secure the electrode binding force, it is necessary to add more binder to the slurry of the positive electrode active material, eventually resulting in a decrease in the energy density of the battery.
In order to solve the technical problems, chinese patent application No. CN201610395112.0 discloses a conductive coating material for a lithium ion battery, which comprises the following components in parts by weight: 100 parts of conductive agent, 20-150 parts of binder, 0-30 parts of polyvinylpyrrolidone and 500-10000 parts of water; wherein, based on 100 weight portions of conductive agent, 70 to 100 weight portions of conductive carbon black and 0 to 30 weight portions of carbon nano tube. The invention also provides a preparation method of the conductive coating material and a lithium ion battery adopting the conductive coating material. The conductive coating material is safe and environment-friendly, has good stability after dispersion, and can obviously improve the electrochemical performance of the lithium ion battery. Chinese patent with application number CN201610530167.8 discloses an environment-friendly battery conductive coating material, which is composed of the following raw materials in parts by weight: 40-60 parts of a base material, 15-25 parts of a conductive additive, 10-18 parts of an inorganic filler and 8-15 parts of a modified additive. The environment-friendly battery conductive coating material provided by the invention is proved to have good adhesive force and lower contact resistance through reasonable raw material proportion and a large number of experiments, the dosage of an adhesive can be effectively reduced, and the environment-friendly property of battery manufacture is improved; the conductive coating does not contain toluene and xylene with high toxicity, and has good sealing effect.
In the above patent, before coating the active material, a layer of conductive coating is attached to the current collector, so as to solve the technical problem of poor adhesion between the current collector and the active material. However, the above-mentioned conductive coatings also have some problems: 1. because a layer of conductive coating is added, and the specific surface area of the material in the conductive coating is not large enough, the impedance of the pole piece is increased; 2. its adhesion to the current collector still remains to be further improved.
Disclosure of Invention
In order to solve the technical problems, the invention provides a lithium ion battery positive plate containing a conductive coating and a preparation method thereof. According to the invention, the current collector is coated with the special conductive slurry, so that the specific surface area is large, the impedance is small, the pole piece binding power can be greatly improved, the conductivity is enhanced, the addition amount of the binding agent and the conductive agent is reduced, and the energy density of the battery is improved.
The specific technical scheme of the invention is as follows: the lithium ion battery positive plate comprises an aluminum foil current collector, a conductive coating coated on the aluminum foil current collector, and a positive active material layer coated on the conductive coating. The positive active material layer is formed by solidifying positive slurry, and the positive slurry comprises the following substances in parts by weight: 91-95 parts of lithium iron phosphate, 1-3 parts of conductive carbon black SP, 0.5-1.5 parts of vapor grown carbon fiber, 3-5 parts of polyvinylidene fluoride and 60-80 parts of N-N-dimethyl pyrrolidone; the conductive coating is formed by curing conductive slurry, and the conductive slurry comprises the following substances in parts by weight: 10-95 parts of composite carbon source, 5-50 parts of binder, 5-40 parts of dispersant and 550 parts of organic solvent.
According to the invention, the special conductive coating is coated on the surface of the optical foil in advance, and after the special conductive coating is matched with the specific positive electrode slurry, the conductivity of the electrode plate can be enhanced, the binding force between the coated active substance and a current collector can be obviously improved, the content of a binding agent and a conductive agent in the positive electrode slurry can be reduced, and the energy density of the battery can be improved.
Preferably, the conductive paste comprises the following substances in parts by weight: 50-90 parts of composite carbon source, 5-20 parts of binder, 5-20 parts of dispersant and 550 parts of organic solvent.
Preferably, the composite carbon source comprises a particle size of 40-600nm and a specific surface area of 100-300m2The pipe diameter of the carbon black aggregate is 0.4-5nm, the pipe length is more than 30um, and the specific surface area is 300-2A single-wall carbon nanotube of less than 10 layers and a specific surface area of more than 500m2The graphene has the porosity of 90-98 percent and the specific surface area of 600-900m2Carbon aerogel in g and a particle size d50At least two kinds of coated carbon particles with the particle size less than or equal to 6 mu m.
In the composite carbon source, more than two materials can be selected for compounding, and after the materials are compounded, the specific surface area is large, so that the material has strong infiltration capacity on electrolyte, and the interface resistance cannot be obviously increased; and the adhesive force with the current collector is strong, and the current collector is not easy to fall off.
Preferably, the binder is polyvinylidene fluoride or polyacrylic acid; the dispersing agent is polyvinyl chloride; the organic solvent is N-N-dimethyl pyrrolidone.
Preferably, the conductive coating has a thickness of 1 to 5 microns.
Preferably, the coated carbon particles have a core-shell structure in which the core material is artificial graphite and the shell material is amorphous carbon.
The coated carbon particles with the core-shell structure have small particle size, good adhesion and uniformity on an aluminum foil, and low contact internal resistance with the aluminum foil.
Preferably, the preparation method of the coated carbon particles comprises the following steps:
1) mixing coal tar and pitch at a mass ratio of 5-50:1 at 75-85 ℃, heating to 400-430 ℃ after uniform mixing, and carrying out thermal polymerization for 2-4 h;
2) carrying out low-temperature treatment on the product obtained in the step 1) to remove light components, wherein the temperature is 350-420 ℃, the vacuum degree is-0.10 to-0.08 MPa, and the time is 0.5 to 1.5 h;
3) graphitizing the product obtained in the step 2) at 2800-3000 ℃ for 4-8h to obtain artificial graphite;
4) adding soft carbon or hard carbon into the artificial graphite, adding the artificial graphite into a water-soluble phenolic resin solution under an inert gas atmosphere to carry out organic liquid phase coating treatment to obtain a carbon polymer coated organic compound, then carrying out high-temperature calcination treatment at the temperature of 600-1700 ℃, and keeping the constant temperature for 0.5-48h to obtain a carbon coated material;
5) carbonizing the carbon-coated material in an inert gas atmosphere at 800-1200 ℃ for 4-6 h; and then crushing the carbonized product, and grading according to the particle size after crushing to obtain the coated carbon particles.
The invention selects raw materials with good multiplying power performance and excellent cycle performance, carries out thermal polymerization, then carries out low-temperature modification treatment, and then carries out high-temperature heat treatment to obtain the single-particle structure artificial graphite with specific particle size, the large-current charging and discharging performance of the artificial graphite is good, and the compact small-particle size artificial graphite substrate is prepared, and has good large-current charging and discharging performance and cycle life. The coated carbon particles have the following functions:
1. the small-particle coated carbon particles can shorten the diffusion distance of lithium ions, increase the infiltration area of electrolyte and reduce the OI value of a pole piece, thereby effectively improving the multiplying power and power performance of the material.
2. The surface of the graphite has rough surface with pure artificial graphite, the electrochemical reaction activity is higher, the consumption of electrolyte is increased, after the amorphous carbon is coated on the artificial graphite, the coated surface is smoother, the surface forms amorphous carbon coating, and the active points are reduced; meanwhile, the electrochemical reaction impedance of the material can be greatly reduced, so that the power and the low-temperature performance of the material are improved.
3. After the pure artificial graphite is circulated, the internal structure of the pure artificial graphite becomes loose and not compact, the situation can be avoided after the pure artificial graphite is coated, and the cycle life of the lithium battery can be effectively prolonged due to the compact internal structure and the smooth surface structure.
The particle modification is carried out on the basis of single-particle artificial graphite, and amorphous carbon is coated on the surface of the artificial graphite through a liquid phase, so that the artificial graphite has a core-shell structure, and the aims of further improving the interface resistance and improving the low-temperature performance and the power characteristic are fulfilled. Liquid phase coating is adopted, so that the coating is uniform and the residual carbon is low.
Preferably, in the step 4), the mass ratio of the artificial graphite to the soft carbon or the hard carbon is 1:0.01-15, the temperature of the high-temperature calcination treatment is 1200 ℃, and the constant-temperature holding time is 24 hours.
Preferably, the preparation method of the carbon aerogel comprises the following steps: uniformly mixing formaldehyde, m-diphenol, toluene and water according to the mass ratio of 2-4:1:0.1-0.2:100 to prepare a mixed solution; then dropwise adding ammonia water and sodium bicarbonate with the mass of 0.01-0.03 time of that of the mixed solution into the mixed solution while stirring, and when the pH value of the mixed solution is 7-8; reacting at 60-80 deg.C for 10-20h to obtain carbon precursor sol solution; standing and aging the carbon precursor sol solution for 1-2 days, and then sequentially carrying out solvent replacement on the carbon precursor sol solution by using absolute ethyl alcohol and normal hexane to obtain a carbon precursor gel solution; then, taking carbon dioxide as a medium, and performing supercritical fluid drying on the carbon precursor gel liquid; and carbonizing the dried carbon precursor gel liquid at the temperature of 600-1000 ℃ to obtain the carbon aerogel.
The carbon aerogel prepared by the method is subjected to auxiliary hole making by using toluene and sodium bicarbonate in the preparation process, is aged and carbonized to form a three-dimensional network framework with high porosity, has a large number of loose pore passages, has an ultrahigh specific surface area, is favorable for infiltration of electrolyte, enhances conductivity, reduces internal resistance, is not easy to crack or fall off after being cured, and has high bonding fastness with a current collector.
The preparation method of the lithium ion battery positive plate containing the conductive coating comprises the following steps:
A) coating of the conductive paste: uniformly coating the conductive slurry on a positive current collector, drying, and rolling by using a common mirror rolling machine to form a conductive coating;
B) coating of positive electrode slurry: and uniformly coating the positive electrode slurry on the conductive coating, drying, and rolling by using a common mirror rolling machine to prepare the positive electrode piece.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, the current collector is coated with the special conductive slurry, so that the specific surface area is large, the impedance is small, the pole piece binding power can be greatly improved, the conductivity is enhanced, the addition amount of the binding agent and the conductive agent is reduced, and the energy density of the battery is improved.
Detailed Description
The present invention will be further described with reference to the following examples.
Example 1
The lithium ion battery positive plate comprises an aluminum foil current collector, a conductive coating coated on the aluminum foil current collector, and a positive active material layer coated on the conductive coating.
The positive active material layer is formed by solidifying positive slurry, and the positive slurry comprises the following substances in parts by weight: 92 parts of lithium iron phosphate, 3 parts of conductive carbon black SP, 1 part of vapor grown carbon fiber, 4 parts of polyvinylidene fluoride and 70 parts of N-N-dimethylpyrrolidone; the conductive coating is formed by curing conductive slurryThe material comprises the following substances in parts by weight: 70 parts of composite carbon source (particle size of 40-600nm, specific surface area of 100-220 parts of carbon black aggregate/g, the pipe diameter is 0.4-5nm, the pipe length is more than 30um, and the specific surface area is 300-220 parts of single-walled carbon nanotubes per gram, less than 10 layers, and specific surface area greater than 500m230 parts of graphene per gram), 15 parts of polyvinylidene fluoride, 15 parts of polyvinyl chloride and 500 parts of N-N-dimethyl pyrrolidone.
The preparation method of the lithium ion battery positive plate containing the conductive coating comprises the following steps:
A) coating of the conductive paste: uniformly coating the conductive slurry on a positive current collector, drying, and rolling by using a common mirror rolling machine to form a conductive coating with the thickness of 3 microns;
B) coating of positive electrode slurry: and uniformly coating the positive electrode slurry on the conductive coating, drying, and rolling by using a common mirror rolling machine to prepare the positive electrode piece.
Example 2
The lithium ion battery positive plate comprises an aluminum foil current collector, a conductive coating coated on the aluminum foil current collector, and a positive active material layer coated on the conductive coating.
The positive active material layer is formed by solidifying positive slurry, and the positive slurry comprises the following substances in parts by weight: 94 parts of lithium iron phosphate, 3 parts of conductive carbon black SP, 1 part of vapor grown carbon fiber, 4 parts of polyvinylidene fluoride and 60 parts of N-N-dimethyl pyrrolidone; the conductive coating is formed by curing conductive slurry, and the conductive slurry comprises the following substances in parts by weight: 90 parts of composite carbon source (particle size of 40-600nm, specific surface area of 100-230 parts of carbon black aggregate/g, the pipe diameter is 0.4-5nm, the pipe length is more than 30um, and the specific surface area is 300-230 parts of single-walled carbon nanotubes per gram, less than 10 layers, and specific surface area greater than 500m230 parts of graphene per gram), 5 parts of polyacrylic acid, 5 parts of polyvinyl chloride and 450 parts of N-N-dimethyl pyrrolidone.
The preparation method of the lithium ion battery positive plate containing the conductive coating comprises the following steps:
A) coating of the conductive paste: uniformly coating the conductive slurry on a positive current collector, drying, and rolling by using a common mirror rolling machine to form a conductive coating with the thickness of 3 microns;
B) coating of positive electrode slurry: and uniformly coating the positive electrode slurry on the conductive coating, drying, and rolling by using a common mirror rolling machine to prepare the positive electrode piece.
Example 3
The lithium ion battery positive plate comprises an aluminum foil current collector, a conductive coating coated on the aluminum foil current collector, and a positive active material layer coated on the conductive coating.
The positive active material layer is formed by solidifying positive slurry, and the positive slurry comprises the following substances in parts by weight: 95 parts of lithium iron phosphate, 1 part of conductive carbon black SP, 1 part of vapor grown carbon fiber, 3 parts of polyvinylidene fluoride and 80 parts of N-N-dimethyl pyrrolidone; the conductive coating is formed by curing conductive slurry, and the conductive slurry comprises the following substances in parts by weight: 50 parts of composite carbon source (particle size of 40-600nm, specific surface area of 100-220 parts of carbon black aggregate/g, the pipe diameter is 0.4-5nm, the pipe length is more than 30um, and the specific surface area is 300-220 parts of single-walled carbon nanotubes per gram, less than 10 layers, and specific surface area greater than 500m210 parts of graphene per gram), 20 parts of polyvinylidene fluoride, 20 parts of polyvinyl chloride and 550 parts of N-N-dimethyl pyrrolidone.
The preparation method of the lithium ion battery positive plate containing the conductive coating comprises the following steps:
A) coating of the conductive paste: uniformly coating the conductive slurry on a positive current collector, drying, and rolling by using a common mirror rolling machine to form a conductive coating with the thickness of 3 microns;
B) coating of positive electrode slurry: and uniformly coating the positive electrode slurry on the conductive coating, drying, and rolling by using a common mirror rolling machine to prepare the positive electrode piece.
Example 4
The lithium ion battery positive plate comprises an aluminum foil current collector, a conductive coating coated on the aluminum foil current collector, and a positive active material layer coated on the conductive coating.
The positive active material layer is formed by solidifying positive slurry, and the positive slurry comprises the following substances in parts by weight: 93 parts of lithium iron phosphate, 2 parts of conductive carbon black SP, 0.5 part of vapor grown carbon fiber, 4.5 parts of polyvinylidene fluoride and 70 parts of N-N-dimethyl pyrrolidone; the conductive coating is formed by curing conductive slurry, and the conductive slurry comprises the following substances in parts by weight: 90 parts of composite carbon source (particle size of 40-600nm, specific surface area of 100-220 parts of carbon black aggregate/g, the pipe diameter is 0.4-5nm, the pipe length is more than 30um, and the specific surface area is 300-220 parts of single-walled carbon nanotubes per gram, less than 10 layers, and specific surface area greater than 500m210 parts of graphene/g, the porosity of 90-98%, and the specific surface area of 600-220 parts of carbon aerogel per gram, and the particle diameter is d5020 parts of coated carbon particles with the particle size less than or equal to 6 mu m), 5 parts of polyvinylidene fluoride, 5 parts of polyvinyl chloride and 500 parts of N-N-dimethyl pyrrolidone.
The coated carbon particles have a core-shell structure, wherein the core material is artificial graphite and the shell material is amorphous carbon. The preparation method of the coated carbon particles comprises the following steps:
1) mixing coal tar and pitch at a mass ratio of 30: 1 at 80 ℃, heating to 415 ℃ after uniformly mixing, and carrying out thermal polymerization for 3 h;
2) carrying out low-temperature treatment on the product obtained in the step 1) to remove light components, wherein the temperature is 385 ℃, the vacuum degree is-0.10 to-0.08 MPa, and the time is 1 h;
3) graphitizing the product of the step 2) at 2900 ℃ for 5h to obtain artificial graphite;
4) adding soft carbon with the mass 8 times of that of the artificial graphite into the artificial graphite, adding the artificial graphite into a water-soluble phenolic resin solution under an inert gas atmosphere to carry out organic liquid phase coating treatment to obtain a carbon polymer coated organic compound, then carrying out high-temperature calcination treatment at 1200 ℃, and keeping the constant temperature for 24 hours to obtain a carbon coated material;
5) carbonizing the carbon-coated material in an inert gas atmosphere at 1000 ℃ for 5 h; and then crushing the carbonized product, and grading according to the particle size after crushing to obtain the coated carbon particles.
The preparation method of the carbon aerogel comprises the following steps: uniformly mixing formaldehyde, m-diphenol, toluene and water according to the mass ratio of 3: 1: 0.15: 100 to prepare a mixed solution; then dropwise adding ammonia water and sodium bicarbonate with the mass being 0.02 time of that of the mixed solution into the mixed solution while stirring, and when the pH value of the mixed solution is 7-8; reacting for 15h at 70 ℃ to obtain a carbon precursor sol solution; standing and aging the carbon precursor sol solution for 1.5 days, and then sequentially carrying out solvent replacement on the carbon precursor sol solution by using absolute ethyl alcohol and normal hexane to obtain a carbon precursor gel solution; then, taking carbon dioxide as a medium, and performing supercritical fluid drying on the carbon precursor gel liquid; and carbonizing the dried carbon precursor gel liquid at 800 ℃ to obtain the carbon aerogel.
The preparation method of the lithium ion battery positive plate containing the conductive coating comprises the following steps:
A) coating of the conductive paste: uniformly coating the conductive slurry on a positive current collector, drying, and rolling by using a common mirror rolling machine to form a conductive coating with the thickness of 3 microns;
B) coating of positive electrode slurry: and uniformly coating the positive electrode slurry on the conductive coating, drying, and rolling by using a common mirror rolling machine to prepare the positive electrode piece.
Example 5
The lithium ion battery positive plate comprises an aluminum foil current collector, a conductive coating coated on the aluminum foil current collector, and a positive active material layer coated on the conductive coating.
The positive active material layer is formed by solidifying positive slurry, and the positive slurry comprises the following substances in parts by weight: 91.5 parts of lithium iron phosphate, 2 parts of conductive carbon black SP, 1.5 parts of vapor grown carbon fiber, 5 parts of polyvinylidene fluoride and 70 parts of N-N-dimethyl pyrrolidone; the conductive coating is formed by curing conductive slurry, and the conductive slurry comprises the following substances in parts by weight: 90 parts of composite carbon source (particle size of 40-600nm, specific surface area of 100-220 parts of carbon black aggregate/gThe tube diameter is 0.4-5nm, the tube length is more than 30um, and the specific surface area is 300-220 parts of single-walled carbon nanotubes per gram, less than 10 layers, and specific surface area greater than 500m210 parts of graphene/g, the porosity of 90-98%, and the specific surface area of 600-220 parts of carbon aerogel per gram, and the particle diameter is d5020 parts of coated carbon particles with the particle size less than or equal to 6 mu m), 5 parts of polyvinylidene fluoride, 5 parts of polyvinyl chloride and 500 parts of N-N-dimethyl pyrrolidone.
The coated carbon particles have a core-shell structure, wherein the core material is artificial graphite and the shell material is amorphous carbon. The preparation method of the coated carbon particles comprises the following steps:
1) mixing coal tar and pitch at a mass ratio of 25: 1 at 75 ℃, heating to 430 ℃ after uniformly mixing, and carrying out thermal polymerization for 2 h;
2) carrying out low-temperature treatment on the product obtained in the step 1) to remove light components, wherein the temperature is 350 ℃, the vacuum degree is-0.10 to-0.08 MPa, and the time is 1.5 h;
3) graphitizing the product obtained in the step 2) at 2800 ℃ for 8h to obtain artificial graphite;
4) adding hard carbon which is 5 times of the mass of the artificial graphite into the artificial graphite, adding the artificial graphite into a water-soluble phenolic resin solution under an inert gas atmosphere to carry out organic liquid phase coating treatment to obtain a carbon polymer coated organic compound, then carrying out high-temperature calcination treatment at 600 ℃, and keeping constant temperature for 48 hours to obtain a carbon coated material;
5) carbonizing the carbon-coated material in an inert gas atmosphere at 1200 ℃ for 4 h; and then crushing the carbonized product, and grading according to the particle size after crushing to obtain the coated carbon particles.
The preparation method of the carbon aerogel comprises the following steps: uniformly mixing formaldehyde, m-diphenol, toluene and water according to the mass ratio of 2: 1: 0.1: 100 to prepare a mixed solution; then dropwise adding ammonia water and sodium bicarbonate with the mass being 0.01 time of that of the mixed solution into the mixed solution while stirring, and when the pH value of the mixed solution is 7-8; reacting for 20h at 60 ℃ to obtain a carbon precursor sol solution; standing and aging the carbon precursor sol solution for 1 day, and sequentially carrying out solvent replacement on the carbon precursor sol solution by using absolute ethyl alcohol and normal hexane to obtain a carbon precursor gel solution; then, taking carbon dioxide as a medium, and performing supercritical fluid drying on the carbon precursor gel liquid; and carbonizing the dried carbon precursor gel liquid at 1000 ℃ to obtain the carbon aerogel.
The preparation method of the lithium ion battery positive plate containing the conductive coating comprises the following steps:
A) coating of the conductive paste: uniformly coating the conductive slurry on a positive current collector, drying, and rolling by using a common mirror rolling machine to form a conductive coating with the thickness of 3 microns;
B) coating of positive electrode slurry: and uniformly coating the positive electrode slurry on the conductive coating, drying, and rolling by using a common mirror rolling machine to prepare the positive electrode piece.
Comparative example
The positive plate of the lithium ion battery comprises an aluminum foil current collector and a positive active material layer coated on the aluminum foil current collector.
The positive active material layer is formed by solidifying positive slurry, and the positive slurry comprises the following substances in parts by weight: 91 parts of lithium iron phosphate, 3.5 parts of conductive carbon black SP, 1 part of vapor grown carbon fiber, 4.5 parts of polyvinylidene fluoride and 70 parts of N-N-dimethyl pyrrolidone.
The positive electrode sheets of examples 1 to 5 and comparative example were subjected to performance tests as shown in the following table:
| impedance/m omega | Adhesive force/N | |
| Comparative example | 1.68 | 0.6 |
| Example 1 | 0.54 | 7.6 |
| Example 2 | 0.86 | 6.8 |
| Example 3 | 1.11 | 6.5 |
| Example 4 | 0.49 | 7.5 |
| Example 5 | 0.57 | 7.3 |
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (6)
1. The utility model provides a lithium ion battery positive plate that contains conductive coating, include the aluminium foil mass flow body, coat in conductive coating on the aluminium foil mass flow body coat in the anodal active material layer on the conductive coating, its characterized in that: the positive active material layer is formed by solidifying positive slurry, and the positive slurry comprises the following substances in parts by weight: 91-95 parts of lithium iron phosphate, 1-3 parts of conductive carbon black SP, 0.5-1.5 parts of vapor grown carbon fiber, 3-5 parts of polyvinylidene fluoride and 60-80 parts of N-N-dimethyl pyrrolidone; the conductive coating is formed by curing conductive slurry, and the conductive slurry comprises the following substances in parts by weight: 10-95 parts of a composite carbon source, 5-50 parts of a binder, 5-40 parts of a dispersant and 550 parts of an organic solvent;
the composite carbon source has a particle size of 40-600nm and a specific surface area of 100-2The pipe diameter of the carbon black aggregate is 0.4-5nm, the pipe length is more than 30um, and the specific surface area is 300-2A single-wall carbon nanotube of less than 10 layers and a specific surface area of more than 500m2Graphene/g, the porosity of the graphene is 90-98%, and the specific surface area is 600-2At least one carbon aerogel in g, and a particle diameter d50Coated carbon particles with the particle size less than or equal to 6 mu m;
the coated carbon particles have a core-shell structure, wherein the core material is artificial graphite, and the shell material is amorphous carbon, and the preparation method comprises the following steps:
1) mixing coal tar and pitch at a mass ratio of 5-50:1 at 75-85 ℃, heating to 400-430 ℃ after uniform mixing, and carrying out thermal polymerization for 2-4 h;
2) carrying out low-temperature treatment on the product obtained in the step 1) to remove light components, wherein the temperature is 350-420 ℃, the vacuum degree is-0.10 to-0.08 MPa, and the time is 0.5 to 1.5 h;
3) graphitizing the product obtained in the step 2) at 2800-3000 ℃ for 4-8h to obtain artificial graphite;
4) adding soft carbon or hard carbon into the artificial graphite, adding the artificial graphite into a water-soluble phenolic resin solution under an inert gas atmosphere to carry out organic liquid phase coating treatment to obtain a carbon polymer coated organic compound, then carrying out high-temperature calcination treatment at the temperature of 600-1700 ℃, and keeping the constant temperature for 0.5-48h to obtain a carbon coated material;
5) carbonizing the carbon-coated material in an inert gas atmosphere at 800-1200 ℃ for 4-6 h; then crushing the carbonized product, and grading according to the particle size after crushing to obtain coated carbon particles;
the preparation method of the carbon aerogel comprises the following steps: uniformly mixing formaldehyde, m-diphenol, toluene and water according to the mass ratio of 2-4:1:0.1-0.2:100 to prepare a mixed solution; then dropwise adding ammonia water and sodium bicarbonate with the mass of 0.01-0.03 time of that of the mixed solution into the mixed solution while stirring, and when the pH value of the mixed solution is 7-8; reacting at 60-80 deg.C for 10-20h to obtain carbon precursor sol solution; standing and aging the carbon precursor sol solution for 1-2 days, and then sequentially carrying out solvent replacement on the carbon precursor sol solution by using absolute ethyl alcohol and normal hexane to obtain a carbon precursor gel solution; then, taking carbon dioxide as a medium, and performing supercritical fluid drying on the carbon precursor gel liquid; and carbonizing the dried carbon precursor gel liquid at the temperature of 600-1000 ℃ to obtain the carbon aerogel.
2. The positive plate of the lithium ion battery with the conductive coating, according to claim 1, wherein the conductive paste comprises the following materials in parts by weight: 50-90 parts of composite carbon source, 5-20 parts of binder, 5-20 parts of dispersant and 550 parts of organic solvent.
3. The positive plate of the lithium ion battery with the conductive coating as claimed in claim 1, wherein the binder is polyvinylidene fluoride or polyacrylic acid; the dispersing agent is polyvinyl chloride; the organic solvent is N-N-dimethyl pyrrolidone.
4. The positive electrode sheet for a lithium ion battery comprising a conductive coating according to claim 1, wherein the conductive coating has a thickness of 1 to 5 μm.
5. The positive plate of the lithium ion battery with the conductive coating, according to claim 1, wherein in the step 4), the mass ratio of the artificial graphite to the soft carbon or the hard carbon is 1:0.01-15, the temperature of the high-temperature calcination treatment is 1200 ℃, and the constant-temperature holding time is 24 h.
6. A method for preparing a positive plate of a lithium ion battery containing a conductive coating according to any one of claims 1 to 5, which comprises the following steps:
A) coating of the conductive paste: uniformly coating the conductive slurry on a positive current collector, drying, and rolling by using a mirror rolling machine to form a conductive coating;
B) coating of positive electrode slurry: and uniformly coating the positive electrode slurry on the conductive coating, drying, and rolling by using a mirror rolling machine to prepare the positive electrode piece.
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