CN113314694A - High-rate lithium ion battery positive plate and preparation method thereof, and lithium ion battery - Google Patents

High-rate lithium ion battery positive plate and preparation method thereof, and lithium ion battery Download PDF

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Publication number
CN113314694A
CN113314694A CN202110636788.5A CN202110636788A CN113314694A CN 113314694 A CN113314694 A CN 113314694A CN 202110636788 A CN202110636788 A CN 202110636788A CN 113314694 A CN113314694 A CN 113314694A
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positive
lithium ion
coating
ion battery
conductive agent
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汪正兵
孙玉龙
白科
郭娜娜
汪依水
彭小河
陈富源
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Jiangxi ANC New Energy Technology Co Ltd
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Jiangxi ANC New Energy Technology Co Ltd
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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
    • 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
    • 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
    • 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
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • 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
    • H01M2004/028—Positive 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

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a high-rate lithium ion battery positive plate and a preparation method thereof. According to the invention, after two positive active materials are respectively prepared into slurry, a double-layer coating machine is adopted to coat the lower-layer high-solid-content lithium nickel cobalt manganese oxide positive slurry and the upper-layer low-solid-content lithium iron phosphate positive slurry, the porosity of the prepared thick pole piece with the thickness of more than 400 mu m is gradually increased from bottom to top, lithium ion de-intercalation and electrolyte infiltration are facilitated, the positive active material of the lithium nickel cobalt manganese oxide is close to a current collector aluminum foil, and electron transmission is facilitated, so that polarization is reduced. The lithium ion battery provided by the invention has the advantages of high energy density, excellent high rate performance, safety and low cost.

Description

High-rate lithium ion battery positive plate and preparation method thereof, and lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a high-rate lithium ion battery positive plate and a preparation method thereof, and a lithium ion battery.
Background
Under the pressure of energy crisis and environmental pollution problems, safety, environmental protection and energy conservation become the subjects of current automobile development, and new energy automobiles are highly valued and strongly supported by traffic and energy departments due to the advantages of energy conservation, environmental protection and no pollution. The power battery plays a very important role as the key of the new energy automobile. The power battery is used as a power source of the electric automobile and is a key component of the electric automobile. In recent years, power batteries are expensive and have short endurance mileage, which is a constraint point of industry development, and therefore, cost reduction and energy density improvement are required.
The purposes of improving the energy density, the quick charge performance and the safety performance and reducing the cost are targets of the lithium ion battery industry, the loading capacity of the active substances of the pole piece is increased, the use amount of the positive and negative current collectors and the diaphragms with higher weight is reduced, the energy density can be improved, and the purpose of reducing the cost can be achieved; however, a series of problems are also caused by thick pole pieces, the polarization of the battery is large, the pole pieces of the battery are thick, the paths of lithium ions and electrons are increased, and the heterogeneity of the internal and external polarization in the thickness direction of the pole pieces is intensified; if the compaction density of the pole piece is large, the porosity is lower, and the path of lithium ion movement in the thickness direction of the pole piece is longer; in addition, the contact area between the material and the electrolyte is reduced, the electrolyte is difficult to soak, the reaction sites of the electrodes are reduced, the internal resistance of the battery is increased, and the problems of increased temperature of the battery, poor rate capability and cycle performance and the like are caused.
The prior patent CN109148820A discloses a preparation method of a thick pole piece and a high-energy density soft package lithium ion battery thereof, which describe the preparation method and the formula of the thick pole piece, but have the problems of difficult electrolyte infiltration, large battery polarization and the like; another prior patent CN107093701A discloses a method for preparing a thick electrode with excellent electrochemical performance and a lithium ion battery, which describes a method for preparing an electrode with a thickness greater than 300 μm, but still does not solve the problems of large polarization, difficult electrolyte infiltration and the like of the thick electrode under high compaction. In addition, the prior art has the following disadvantages: (1) the addition of substances such as surfactants, porous active substances and the like leads to high cost; (2) the thick electrode is difficult to realize high compaction, and the energy density cannot be further improved under low compaction; (3) the polarization of the thick electrode is large, the electrolyte is difficult to infiltrate, and the electrochemical performance is poor; (4) it is difficult to realize mass production.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a high-rate lithium ion battery positive plate and a preparation method thereof so as to improve the energy density, rate capability and safety of a thick-electrode lithium ion battery.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the utility model provides a high magnification lithium ion battery positive plate, positive plate includes mass flow body and anodal coating, anodal coating includes coating one and coating two, coating one coats in the surface of mass flow body, coating two coats in the surface of coating one.
Preferably, the first coating layer comprises a first positive electrode active material, a conductive agent and a first binder, and the first positive electrode active material is one of NCM111, NCM523 or NCM 811.
More preferably, the first binder is a suspension polymerization type PVDF.
Preferably, the second coating layer comprises a second positive electrode active material, a conductive agent and a second binder, and the second positive electrode active material is lithium iron phosphate.
More preferably, the second binder is emulsion polymerized PVDF.
Preferably, the conductive agent comprises a conductive agent SP, a carbon nano tube and graphene mixed conductive agent, wherein the diameter of the carbon nano tube is 5-10 nm.
The preparation method of the high-rate lithium ion battery positive plate comprises the following steps:
(1) dry-mixing the positive electrode active material I, the conductive agent SP and the binder I, then respectively adding a dispersing agent, a carbon nano tube and graphene mixed conductive agent and a solvent, uniformly mixing and stirring to reach the viscosity of 7000-9000 mPa & s and the solid content of 70-80%, and preparing positive electrode slurry I;
(2) dry-mixing the positive electrode active material II, the conductive agent SP and the binder II, then respectively adding a dispersing agent, a carbon nano tube and graphene mixed conductive agent and a solvent, uniformly mixing and stirring to reach the viscosity of 5000-8000 mPa & s and the solid content of 50-60%, and preparing positive electrode slurry II;
(3) and coating the positive slurry I on the surface of the current collector through a double-layer coating machine, coating the positive slurry II on the surface of the positive slurry I, and drying to obtain the positive plate with the thickness of more than 400 mu m.
Based on a general inventive concept, another object of the present invention is to protect a lithium ion battery, which comprises a positive plate, a negative plate, a diaphragm and an electrolyte, wherein the positive plate adopts the above-mentioned high-rate lithium ion battery positive plate, and the negative plate adopts the prior art, such as artificial graphite as a negative electrode; and selecting a Celgard 2400 membrane as a diaphragm, and assembling into a battery cell according to the prior art to obtain the lithium ion battery.
The nickel cobalt lithium manganate positive electrode material has high energy density, high electronic conductivity and poor safety performance; the lithium iron phosphate anode material has low energy density, low electronic conductivity and excellent safety performance; according to the invention, after two anode active materials are respectively prepared into slurry, a double-layer coating machine is adopted to coat the lower-layer high-solid-content (solid content is 70-80%) nickel cobalt lithium manganate anode slurry and the upper-layer low-solid-content (solid content is 50-60%) lithium iron phosphate anode slurry, the porosity of the prepared thick pole piece with the thickness of more than 400 mu m is gradually increased from bottom to top, lithium ion de-intercalation and electrolyte infiltration are facilitated, and the nickel cobalt lithium manganate anode active material is close to a current collector aluminum foil, so that electron transmission is facilitated, and polarization is reduced. The invention provides the lithium ion battery with high energy density, excellent rate capability, safety and low cost by optimizing the anode formula and improving the coating process.
Detailed Description
The present invention will be further described with reference to specific embodiments for making the objects, technical solutions and advantages of the present invention more apparent, but the present invention is not limited to these examples. It should be noted that, without conflict, any combination between the embodiments or technical features described below may form a new embodiment. In the invention, all parts and percentages are mass units, and the adopted equipment, raw materials and the like can be purchased from the market or are commonly used in the field. The methods in the following examples are conventional in the art unless otherwise specified.
Example 1
The high-rate lithium ion battery positive plate comprises a current collector and a positive coating, wherein the positive coating comprises a first coating and a second coating, the first coating is coated on the surface of the current collector, and the second coating is coated on the surface of the first coating; the thickness of the single side of the first coating coated on the current collector is 280 microns, and the thickness of the single side of the second coating coated on the first coating is 150 microns.
The first coating comprises a first positive electrode active material, a conductive agent and a first binder, wherein the first positive electrode active material is NCM111, and the first binder is suspension polymerization type PVDF.
The second coating comprises a second positive electrode active material, a conductive agent and a second binder, the second positive electrode active material is lithium iron phosphate, and the second binder is emulsion polymerization type PVDF.
The conductive agent comprises a conductive agent SP, a carbon nano tube and graphene mixed conductive agent, and the diameter of the carbon nano tube is 5 nm.
The preparation method of the high-rate lithium ion battery positive plate of the embodiment adopts the following steps:
(1) 97g of NCM111, 0.5g of conductive agent SP, 1g of mixed conductive agent of carbon nano tube and graphene and 1.5g of suspension polymerization type PVDF are subjected to dry mixing, then 1g of dispersing agent-ethanol (the dispersing agent is volatilized after drying), 1g of mixed conductive agent of carbon nano tube and graphene and solvent NMP are added, the mixture is uniformly stirred to reach the viscosity of 8000mPa & s and the solid content of 75 percent, and a positive electrode slurry I is prepared;
(2) firstly, 96g of lithium iron phosphate, 1g of conductive agent SP, 0.5g of mixed conductive agent of carbon nano tube and graphene and 2g of emulsion polymerization type PVDF are dry-mixed, then 1g of dispersing agent-ethanol (the dispersing agent is volatilized after drying), 1g of mixed conductive agent of carbon nano tube and graphene and solvent NMP are added, the mixture is uniformly stirred to reach the viscosity of 6500 mPa.s and the solid content of 55 percent, and a second positive electrode slurry is prepared;
(3) coating positive electrode slurry I on the upper surface of an aluminum foil with the thickness of 13 mu m by using a double-layer coating machine, coating positive electrode slurry II on the surface of the positive electrode slurry I, and drying to obtain a positive plate with the thickness of 450 mu m;
in the lithium ion battery of the embodiment, the positive plate of the embodiment is adopted, the artificial graphite is used as the negative electrode, the Celgard 2400 membrane is used as the diaphragm, the positive plate and the negative plate are rolled and cut by laser, and then the positive plate and the diaphragm are wound, assembled, baked, injected with liquid, formed and subjected to capacity grading to obtain the 25Ah soft-packaged thick electrode lithium ion battery; the electrolyte used for injection is prepared by the following method: mixing LiPF6(concentration of 1.2 mol/L) and an additive VC (1%) were dissolved in a mixed solvent of PC (propylene carbonate)/EC (ethylene carbonate)/DMC (dimethyl carbonate)) ═ 3: 1: 2 (volume ratio) to form an electrolyte.
For convenience, C is the rated capacity (Ah) of the battery, I is the current and I is equal to C (a); the battery in the empty state is charged to an upper limit voltage (V) by a constant current of 1I current (A), and is charged by a constant voltage after reaching the upper limit voltage, the cutoff current (A) is less than or equal to 0.05I, and the obtained charging capacity (Ah) is J; the battery in the empty state is charged to the upper limit voltage (V) by a constant current of 3I current (A), and is charged by the voltage at a constant voltage after reaching the upper limit voltage, the cutoff current (A) is less than or equal to I, and the obtained charging capacity (Ah) is K; the battery in the empty state is charged to the upper limit voltage (V) by a constant current of 1I current (A), is charged at a constant voltage by the voltage after reaching the upper limit voltage, is cut off by the current (A) which is less than or equal to 0.05I, and is discharged to the lower limit voltage (V) by the constant current of 3I current (A), wherein the process is regarded as a cycle;
the test results were as follows:
(1) and the mass energy density of the single battery is 225 Wh/kg.
(2) The temperature probe was placed at the geometric center of the maximum surface of the battery, which was charged from an empty state battery with a constant current of 3I current (a) to an upper limit voltage (V) and then with a constant voltage after reaching the upper limit voltage, during which the difference between the maximum temperature of the probe and the initial temperature recorded at the beginning was 16 ℃.
(3) In cycle 10, K/J >0.994,
(4) in the 100 th cycle, K/J >0.962,
(5) in the 200 th cycle, K/J >0.948,
(6) in the 500 th cycle, K/J >0.902,
(7) in cycle 1000, K/J > 0.805.
Example 2
The high-rate lithium ion battery positive plate comprises a current collector and a positive coating, wherein the positive coating comprises a first coating and a second coating, the first coating is coated on the upper surface of the current collector, and the second coating is coated on the surface of the first coating; the thickness of the single side of the first coating coated on the current collector is 280 microns, and the thickness of the single side of the second coating coated on the first coating is 150 microns.
The first coating comprises a first positive electrode active material, a conductive agent and a first binder, wherein the first positive electrode active material is NCM523, and the first binder is suspension polymerization type PVDF.
The second coating comprises a second positive electrode active material, a conductive agent and a second binder, the second positive electrode active material is lithium iron phosphate, and the second binder is emulsion polymerization type PVDF.
The conductive agent comprises a conductive agent SP, a carbon nano tube and graphene mixed conductive agent, and the diameter of the carbon nano tube is 5 nm.
The preparation method of the high-rate lithium ion battery positive plate of the embodiment adopts the following steps:
(1) 97g of NCM523, 0.5g of conductive agent SP, 0.5g of carbon nano tube and graphene mixed conductive agent and 1.5g of suspension polymerization type PVDF are subjected to dry mixing, then 1g of dispersing agent-ethanol (the dispersing agent is volatilized after drying), 1g of carbon nano tube and graphene mixed conductive agent and solvent NMP are added, the mixture is uniformly stirred to reach the viscosity of 7000mPa & s and the solid content of 80 percent, and a positive electrode slurry I is prepared;
(2) firstly, 96g of lithium iron phosphate, 1g of conductive agent SP, 1g of mixed conductive agent of carbon nano tube and graphene and 2g of emulsion polymerization type PVDF are dry-mixed, then 1g of dispersing agent-ethanol (the dispersing agent is volatilized after drying), 1g of mixed conductive agent of carbon nano tube and graphene and solvent NMP are added, the mixture is uniformly stirred to reach the viscosity of 8000mPa & s and the solid content of 50 percent, and a second positive electrode slurry is prepared;
(3) coating positive electrode slurry I on the upper surface of an aluminum foil with the thickness of 13 mu m by using a double-layer coating machine, coating positive electrode slurry II on the surface of the positive electrode slurry I, and drying to obtain a positive plate with the thickness of 450 mu m;
in the lithium ion battery of the embodiment, the positive plate of the embodiment is adopted, the artificial graphite is used as the negative electrode, the Celgard 2400 membrane is used as the diaphragm, the positive plate and the negative plate are rolled and cut by laser, and then the positive plate and the diaphragm are wound, assembled, baked, injected with liquid, formed and subjected to capacity grading to obtain the 25Ah soft-packaged thick electrode lithium ion battery; the electrolyte used for injection is prepared by the following method: mixing LiPF6(concentration of 1.2 mol/L) and an additive VC (1%) were dissolved in a mixed solvent of PC (propylene carbonate)/EC (ethylene carbonate)/DMC (dimethyl carbonate)) ═ 3: 1: 2 (volume ratio) to form an electrolyte.
For convenience, C is the rated capacity (Ah) of the battery, I is the current and I is equal to C (a); the battery in the empty state is charged to an upper limit voltage (V) by a constant current of 1I current (A), and is charged by a constant voltage after reaching the upper limit voltage, the cutoff current (A) is less than or equal to 0.05I, and the obtained charging capacity (Ah) is J; the battery in the empty state is charged to the upper limit voltage (V) by a constant current of 3I current (A), and is charged by the voltage at a constant voltage after reaching the upper limit voltage, the cutoff current (A) is less than or equal to I, and the obtained charging capacity (Ah) is K; the battery in the empty state is charged to the upper limit voltage (V) by a constant current of 1I current (A), is charged at a constant voltage by the voltage after reaching the upper limit voltage, is cut off by the current (A) which is less than or equal to 0.05I, and is discharged to the lower limit voltage (V) by the constant current of 3I current (A), wherein the process is regarded as a cycle;
the test results were as follows:
(1) the cell mass energy density 234 Wh/kg.
(2) The temperature probe was placed at the geometric center of the maximum surface of the battery, which was charged from an empty state battery at a constant current of 3I current (A) to an upper limit voltage (V) and then at a constant voltage after reaching the upper limit voltage, during which the difference between the maximum temperature of the probe and the initial temperature recorded at the beginning was 18 ℃.
(3) In cycle 10, K/J >0.994,
(4) in the 100 th cycle, K/J >0.969,
(5) in the 200 th cycle, K/J >0.957,
(6) in the 500 th cycle, K/J >0.901,
(7) in the 1000 th cycle, K/J > 0.803.
Example 3
The high-rate lithium ion battery positive plate comprises a current collector and a positive coating, wherein the positive coating comprises a first coating and a second coating, the first coating is coated on the upper surface of the current collector, and the second coating is coated on the surface of the first coating; the thickness of the single side of the first coating coated on the current collector is 280 microns, and the thickness of the single side of the second coating coated on the first coating is 150 microns.
The coating I comprises a positive electrode active material I, a conductive agent and a binder I, wherein the positive electrode active material I is NCM811, and the binder II is suspension polymerization type PVDF.
The second coating comprises a second positive active material, a conductive agent and a second binder, the second positive active material is lithium iron phosphate, and the first binder is emulsion polymerization type PVDF.
The conductive agent comprises a conductive agent SP, a carbon nano tube and graphene mixed conductive agent, and the diameter of the carbon nano tube is 5 nm.
The preparation method of the high-rate lithium ion battery positive plate of the embodiment adopts the following steps:
(1) 97g of NCM811, 0.5g of conductive agent SP, 0.5g of carbon nanotube and graphene mixed conductive agent and 1.5g of suspension polymerization type PVDF are subjected to dry mixing, then 1g of dispersing agent-ethanol (the dispersing agent is volatilized after drying), 1g of carbon nanotube and graphene mixed conductive agent and solvent NMP are added, the mixture is uniformly stirred to reach the viscosity of 9000mPa & s and the solid content of 75 percent, and a first positive electrode slurry is prepared;
(2) firstly, carrying out dry mixing on 96g of lithium iron phosphate, 0.5g of conductive agent SP, 0.5g of mixed conductive agent of carbon nano tube and graphene and 2g of emulsion polymerization type PVDF, then adding 1g of dispersing agent-ethanol (the dispersing agent is volatilized after drying), 1g of mixed conductive agent of carbon nano tube and graphene and solvent NMP, mixing and stirring uniformly to reach the viscosity of 5000mPa & s and the solid content of 60%, and preparing into positive electrode slurry II;
(3) coating positive electrode slurry I on the upper surface of an aluminum foil with the thickness of 13 mu m by using a double-layer coating machine, coating positive electrode slurry II on the surface of the positive electrode slurry I, and drying to obtain a positive plate with the thickness of 450 mu m;
in the lithium ion battery of the embodiment, the positive plate of the embodiment is adopted, the artificial graphite is used as the negative electrode, the Celgard 2400 membrane is used as the diaphragm, the positive plate and the negative plate are rolled and cut by laser, and then the positive plate and the diaphragm are wound, assembled, baked, injected with liquid, formed and subjected to capacity grading to obtain the 25Ah soft-packaged thick electrode lithium ion battery; the electrolyte used for injection is prepared by the following method: mixing LiPF6(concentration of 1.2 mol/L) and an additive VC (1%) were dissolved in a mixed solvent of PC (propylene carbonate)/EC (ethylene carbonate)/DMC (dimethyl carbonate)) ═ 3: 1: 2 (volume ratio) to form an electrolyte.
For convenience, C is the rated capacity (Ah) of the battery, I is the current and I is equal to C (a); the battery in the empty state is charged to an upper limit voltage (V) by a constant current of 1I current (A), and is charged by a constant voltage after reaching the upper limit voltage, the cutoff current (A) is less than or equal to 0.05I, and the obtained charging capacity (Ah) is J; the battery in the empty state is charged to the upper limit voltage (V) by a constant current of 3I current (A), and is charged by the voltage at a constant voltage after reaching the upper limit voltage, the cutoff current (A) is less than or equal to I, and the obtained charging capacity (Ah) is K; the battery in the empty state is charged to the upper limit voltage (V) by a constant current of 1I current (A), is charged at a constant voltage by the voltage after reaching the upper limit voltage, is cut off by the current (A) which is less than or equal to 0.05I, and is discharged to the lower limit voltage (V) by the constant current of 3I current (A), wherein the process is regarded as a cycle;
the test results were as follows:
(1) the mass energy density of the single battery is 246 Wh/kg.
(2) The temperature probe was placed at the geometric center of the maximum surface of the battery, which was charged from an empty state battery with a constant current of 3I current (a) to an upper limit voltage (V) and then with a constant voltage after reaching the upper limit voltage, during which the difference between the maximum temperature of the probe and the initial temperature recorded at the beginning was 20 ℃.
(3) In cycle 10, K/J >0.997,
(4) in the 100 th cycle, K/J >0.962,
(5) in the 200 th cycle, K/J >0.945,
(6) in the 500 th cycle, K/J >0.910,
(7) in the 1000 th cycle, K/J > 0.807.
From the above, it can be seen that: the mass energy density of the single battery is more than 220Wh/kg, and the 3I multiplying power cycle life is more than 1000 times.
Electricity is known from the above: the mass energy density of the single battery in the invention is more than 220 Wh/kg. The electric quantity charged by the battery in a charging state for 20min can reach more than 85% of rated capacity; the battery is charged to an upper limit voltage (V) at a constant current of 3I current (A) from a battery in an empty state, the battery is charged at a constant voltage after the upper limit voltage is reached, the charging process lasts for 20min, and the highest temperature rise of the surface of the battery in the whole process is less than 25 ℃; the battery has a high-rate cycle life of more than 1000 times at 3I current (A). The invention has better high-rate performance and still keeps good cycle stability under the high-rate condition.
The above embodiments are merely preferred embodiments of the present invention, and any simple modification, modification and substitution changes made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.

Claims (8)

1. The positive plate is characterized by comprising a current collector and a positive coating, wherein the positive coating comprises a first coating and a second coating, the first coating is coated on the surface of the current collector, and the second coating is coated on the surface of the first coating.
2. The positive plate of the high-rate lithium ion battery as claimed in claim 1, wherein the first coating layer comprises a first positive active material, a conductive agent and a first binder, and the first positive active material is one of NCM111, NCM523 or NCM 811.
3. The positive plate of the high-rate lithium ion battery as claimed in claim 2, wherein the first binder is emulsion polymerization type PVDF.
4. The positive plate of the high-rate lithium ion battery of claim 1, wherein the second coating layer comprises a second positive active material, a conductive agent and a second binder, and the second positive active material is lithium iron phosphate.
5. The positive plate of the high-rate lithium ion battery according to claim 4, wherein the second binder is a suspension polymerization type PVDF.
6. The positive plate of the high-rate lithium ion battery according to any one of claims 2 to 5, wherein the conductive agent comprises a conductive agent SP, a carbon nanotube and graphene mixed conductive agent, wherein the diameter of the carbon nanotube is 5 to 10 nm.
7. The preparation method of the high-rate lithium ion battery positive plate according to claim 6, characterized by comprising the following steps:
(1) dry-mixing the positive electrode active material I, the conductive agent SP and the binder I, then respectively adding a dispersing agent, a carbon nano tube and graphene mixed conductive agent and a solvent, uniformly mixing and stirring to reach the viscosity of 7000-9000 mPa & s and the solid content of 70-80%, and preparing positive electrode slurry I;
(2) dry-mixing the positive electrode active material II, the conductive agent SP and the binder II, then respectively adding a dispersing agent, a carbon nano tube and graphene mixed conductive agent and a solvent, uniformly mixing and stirring to reach the viscosity of 5000-8000 mPa & s and the solid content of 50-60%, and preparing positive electrode slurry II;
(3) and coating the positive slurry I on the surface of the current collector through a double-layer coating machine, coating the positive slurry II on the surface of the positive slurry I, and drying to obtain the positive plate with the thickness of more than 400 mu m.
8. A lithium ion battery is characterized by comprising a positive plate, a negative plate, a diaphragm and electrolyte, wherein the positive plate adopts the high-rate lithium ion battery positive plate in claim 6.
CN202110636788.5A 2021-06-08 2021-06-08 High-rate lithium ion battery positive plate and preparation method thereof, and lithium ion battery Pending CN113314694A (en)

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Application publication date: 20210827