CN111261835A - Lithium iron phosphate positive plate and environment-friendly low-temperature-resistant lithium battery comprising same - Google Patents

Lithium iron phosphate positive plate and environment-friendly low-temperature-resistant lithium battery comprising same Download PDF

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CN111261835A
CN111261835A CN202010143321.2A CN202010143321A CN111261835A CN 111261835 A CN111261835 A CN 111261835A CN 202010143321 A CN202010143321 A CN 202010143321A CN 111261835 A CN111261835 A CN 111261835A
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iron phosphate
environment
slurry
lithium iron
temperature
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刘国壮
邓鸿华
许欣凡
黄定东
江利金
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Guangxi Zhuoneng New Energy Science & Technology Co ltd
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Guangxi Zhuoneng New Energy Science & 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
    • H01M4/13—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
    • 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
    • H01M4/139—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
    • 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
    • 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
    • H01M2004/021—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
    • H01M2004/028—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 discloses a lithium iron phosphate positive plate, which comprises an aluminum foil and aqueous positive slurry coated on the aluminum foil, wherein the aqueous positive slurry comprises lithium iron phosphate, a carbon nano tube, graphene, chitosan, styrene butadiene rubber, sodium carboxymethyl cellulose, sodium alginate and amino silicone oil, and the particle size of the lithium iron phosphate is 4-10 mu m; the invention adopts the anode active substance with large particle size and small specific surface area, and has good low-temperature performance; meanwhile, the environment-friendly water-based anode slurry is adopted, so that the anode plate is environment-friendly and nontoxic, has good adaptability to processing environment and stable processing performance, and the obtained anode plate has high compaction density, high specific energy and excellent low temperature property. The invention also discloses an environment-friendly low-temperature-resistant lithium battery which comprises the lithium iron phosphate positive plate and a negative plate with high cost performance, large capacity and strong activity, and the obtained lithium iron phosphate battery has the advantages of good safety performance, high energy density, excellent low-temperature performance, stable processing performance, no pollution in the production process and low battery cost.

Description

Lithium iron phosphate positive plate and environment-friendly low-temperature-resistant lithium battery comprising same
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a lithium iron phosphate positive plate and an environment-friendly low-temperature-resistant lithium battery comprising the same.
Background
With the development of mobile electronic devices, the demand of batteries is increasing, and higher requirements are made on the capacity, voltage, service life and use cost of the batteries. The lithium ion battery is a secondary battery (rechargeable battery) which mainly depends on lithium ions moving between a positive electrode and a negative electrode to work, but the lithium ion batteries on the market often have various defects of poor safety performance, poor low-temperature performance, low capacity, low unit volume capacity, low power and poor cycle performance of a battery core. The lithium iron phosphate lithium ion battery is a lithium ion battery using lithium iron phosphate as a positive electrode material, and a P-O bond in a lithium iron phosphate crystal is stable and difficult to decompose, so that the lithium iron phosphate lithium ion battery does not collapse and generate heat or form a strong oxidizing substance like lithium cobaltate even at high temperature or during overcharge, and therefore the lithium iron phosphate lithium ion battery has good safety; the lithium iron phosphate battery does not contain heavy metals and rare metals, has good environmental protection performance and conforms to the development plan of national green and environment-friendly batteries; the lithium iron phosphate battery also has the advantages of large capacity, good high-temperature performance, stable platform, long cycle life, low material price and the like, and is widely applied to the fields of energy storage, power batteries and the like.
However, the existing lithium iron lithium ion battery has some performance defects, such as low tap density and low compaction density, which results in low energy density of the lithium ion battery; the low-temperature performance is poor, and the electric automobile cannot run at low temperature (below 0 ℃); the processability is unstable: the production and processing of lithium iron phosphate have high requirement on the humidity of the production environment, and the slurry is thickened after water absorption, so that the coating surface density is unstable, and more problems are caused, such as the yield of the produced product is lower than 90%, the consistency of the product is poor, the potential safety hazard ratio is high, the cycle performance of 0.5C/1C is lower than 1000 weeks, the weight ratio energy is low, the volume power density is low, and the like. The wide application of the lithium iron phosphate battery in the fields of new energy automobiles and the like is severely limited by the problems.
Disclosure of Invention
In order to overcome the defects of the prior art, one of the purposes of the invention is to provide a lithium iron phosphate positive plate, which adopts environment-friendly water-based positive slurry, is environment-friendly and nontoxic, has good adaptability to processing environment and stable processing performance; the positive active material with large particle size and small specific surface area is adopted, so that the low-temperature performance is good; the obtained positive plate has high compaction density, high specific energy and excellent low-temperature performance;
the invention also aims to provide an environment-friendly low-temperature-resistant lithium battery containing the positive plate, which is combined with a negative plate with high cost performance, large capacity and strong activity, and the obtained lithium iron phosphate battery has the advantages of good safety performance, high energy density, excellent low-temperature performance, stable processing performance, no pollution in the production process and low battery cost.
One of the purposes of the invention is realized by adopting the following technical scheme:
a lithium iron phosphate positive plate comprises an aluminum foil and water-based positive slurry coated on the aluminum foil; the aqueous positive electrode slurry comprises the following components in percentage by mass:
Figure BDA0002399852600000021
the particle size of the lithium iron phosphate is 4-10 mu m.
Further, the diameter of the carbon nano tube is 3-10nm, and the length is more than 1 μm.
The coating surface density of the aqueous anode slurry is 300-360g/m2(ii) a The compaction density of the positive plate is 2.5-2.8g/mm3。
The positive plate is prepared by the following method, including:
1) adding the components of the aqueous anode slurry and deionized water into a double-planet beater, and stirring for 2h under the conditions that the revolution speed is 40-50 r/min and the rotation speed is 1300-1500 r/min to prepare first aqueous anode slurry;
2) adding the first aqueous anode slurry into a high-speed dispersion machine, and dispersing under the conditions of 3500 and 4500 r/min until the viscosity is 5000 and 8000mPa.s, thus obtaining the aqueous anode slurry;
3) and coating the aqueous anode slurry on an aluminum foil, and sequentially drying, rolling and slitting to obtain the anode sheet.
Preferably, the water content of the positive plate is less than or equal to 1%.
The second purpose of the invention can be achieved by adopting the following technical scheme:
an environment-friendly low-temperature-resistant lithium battery comprises the lithium iron phosphate positive plate, a negative plate and a diaphragm;
the negative plate comprises a copper foil and negative slurry coated on the copper foil; the negative electrode slurry comprises the following components in percentage by mass:
Figure BDA0002399852600000031
further, the graphite is a composition of natural graphite and artificial graphite, and the gram capacity of the graphite is more than 360 mAh/g.
The weight ratio of the natural graphite to the artificial graphite is (1-6): (3-9).
The diaphragm is a compound of one or two of PP and PE with the molecular weight of 80-100 wDa.
The PP and the PE are modified by a pulling-up process.
The coating surface density of the cathode slurry is 140-170g/m2(ii) a The compacted density of the negative plate is 1.6-1.8g/mm3。
Further, the negative plate is prepared by the following method, including:
1) adding the components of the cathode slurry and deionized water into a double-planet beater, and stirring for 2h under the conditions that the revolution speed is 40-50 r/min and the rotation speed is 1400-1600 r/min to prepare first cathode slurry;
2) adding the first negative electrode slurry into a high-speed dispersion machine, and dispersing under the condition of 3000-4000 r/min until the viscosity is 3000-6000mPa.s to obtain the negative electrode slurry;
3) and coating the negative electrode slurry on a copper foil, and sequentially drying, rolling and slitting to obtain the negative electrode sheet.
The water content of the negative plate is less than or equal to 0.15 percent.
Compared with the prior art, the invention has the beneficial effects that:
1. at present, researches on methods for improving the low-temperature use performance of lithium iron phosphate batteries mainly focus on reducing the particle size of positive and negative electrode materials to be in a nanometer level, optimizing low-temperature electrolyte and the like, but the cycle performance in a low-temperature environment is still poor, the use environment is difficult to break through at-20 ℃, and the rate performance is also poor. According to the invention, a proper nano-scale raw material is selected through a unique spheroidization technology, an ultra-fine grinding and sintering process is combined to prepare 50-150nm lithium iron phosphate (LFP) primary particles, and then a high-speed dispersion technology is used to polymerize into 4-10um micron-scale high-compactness LFP secondary spheres, so that the active material has a large particle size and a small specific surface area, and the low-temperature performance of the lithium iron phosphate material can be obviously enhanced; on the basis of not influencing the low-temperature and rate performance of the LFP material, the obtained LFP material has high tap density and good material flowability, and the processing performance of the LFP material is improved; meanwhile, the secondary balls are subjected to compacting treatment, and the large balls and the small balls are mixed and overlapped, so that the compacting density of the LFP pole piece is improved, and the capacity of the battery is improved. The invention is simultaneously matched with the conductive agent carbon nano tube and the graphene, is beneficial to the conduction and the diffusion of lithium ions, can also improve the use ratio of the anode active material, and effectively improves the electric conduction and the heat conduction capability of the anode sheet; the addition of the amino silicone oil can enhance the dispersion efficiency and effect of the slurry, and the double-planet beater and the high-speed disperser in the preparation of the aqueous anode slurry can effectively prevent the secondary agglomeration of the lithium iron phosphate, so that the obtained anode plate has high compaction density, high energy density and excellent low-temperature performance, the discharge capacity retention rate at-20 ℃ is more than 70 percent and is 1 time higher than about 35 percent of the discharge capacity in the existing market.
2. The aqueous anode slurry of the anode plate of the invention removes a polluted N methyl pyrrolidone solvent, and adopts deionized water without any pollution as the solvent; the binder of the aqueous anode slurry removes high-cost fluorine-containing polyvinylidene fluoride, adopts environment-friendly low-cost water-soluble binder comprising chitosan, styrene butadiene rubber, sodium carboxymethylcellulose and sodium alginate, ensures no pollution in the production process of the battery, and simultaneously enhances the dispersion efficiency and effect of the slurry by adding amino silicone oil, so that the prepared battery has high energy density and good safety performance. The solvent and the binder are low in price, low in humidity requirement on production environment, free of toxic and harmful substances during high-temperature drying and vacuum baking, simple, safe and environment-friendly in production process, high in product qualification rate, good in consistency and free of potential safety hazard; the pole piece and the winding core have low water content, and the SEI film of the battery is not easy to damage, so that the lithium battery provided by the invention has the advantages of long service life and safe use.
3. The environment-friendly low-temperature-resistant lithium battery provided by the invention has the advantages of good environment-friendly performance, low processing technology cost, high capacity density and excellent low temperature performance, the safety inspection passing rate reaches 100%, the capacity retention rate of 1000 times of charging and discharging at 0.5C and 1C is more than 90%, and the discharge capacity retention rate at-20 ℃ is more than or equal to 70%.
Detailed Description
The present invention is further described below with reference to specific embodiments, and it should be noted that, without conflict, any combination between the embodiments or technical features described below may form a new embodiment.
A lithium iron phosphate positive plate comprises an aluminum foil and water-based positive slurry coated on the aluminum foil;
the aqueous positive electrode slurry comprises the following components in percentage by mass:
Figure BDA0002399852600000061
the particle size of the lithium iron phosphate is 4-10 mu m, the low temperature property of the lithium iron phosphate is enhanced, and the lithium iron phosphate is prepared by polymerizing 50-150nm LFP primary particles into 4-10 mu m LFP secondary spheres through a unique spheroidization technology, and specifically comprises the following steps: the preparation method comprises the steps of selecting a nano-scale LFP raw material, preparing 50-150nm primary particles through an ultra-fine grinding and sintering process, and carrying out intermolecular mixing polymerization on each raw material substrate through a high-speed dispersion technology to obtain the secondary ball with the high compactness of a micron scale of 4-10 microns. The spheroidization technology can obviously improve the processing performance of the material on the basis of not influencing the low-temperature and rate performance of the LFP material
The carbon nano tube has the diameter of 3-10nm and the length of more than 1 mu m, can effectively improve the electric conduction and heat conduction capability of the positive plate and improve the use proportion of the positive active material.
The coating surface density of the aqueous anode slurry on the aluminum foil is 300-2The obtained positive plate has the compaction density of 2.5-2.8g/mm3。
The positive plate is prepared by the following method, including:
1) adding the aqueous anode slurry and deionized water into a double-planet beater according to the formula ratio, and stirring for 2h under the conditions that the revolution speed is 40-50 r/min and the rotation speed is 1300-1500 r/min to prepare first aqueous anode slurry;
2) adding the first aqueous anode slurry into a high-speed dispersion machine, and dispersing under the conditions of 3500 and 4500 r/min until the viscosity is 5000 and 8000mPa.s, thus obtaining the aqueous anode slurry;
3) coating the water-based anode slurry on an aluminum foil with the thickness of 12-16 mu m, drying until the water content is less than or equal to 1%, then rolling and compacting, and slitting according to the width required by the process to obtain an anode sheet;
an environment-friendly low-temperature-resistant lithium battery comprises the lithium iron phosphate positive plate, a negative plate, a diaphragm, electrolyte, a shell and a sealing piece;
the negative plate comprises a copper foil and negative slurry coated on the copper foil, wherein the negative slurry comprises the following components in percentage by mass:
Figure BDA0002399852600000071
the graphite is a composition of natural graphite and artificial graphite, and the gram volume of the graphite composition is more than 360 mAh/g. The invention adopts the mixed graphite of natural graphite and artificial graphite with high cost performance, wherein the natural graphite has higher capacity and low price, but the liquid absorption and circulation performances are relatively poor, the artificial graphite has relatively higher price, but the circulation and safety performances are better, the weight ratio of the artificial graphite to the mixed graphite can be adjusted according to the requirements on the performances and the price, and preferably, the weight ratio of the natural graphite to the artificial graphite is (1-6): (3-9).
The negative plate also improves the capacity of the negative electrode by introducing silicon carbon, and the styrene butadiene rubber uses small-particle materials to effectively improve the use proportion of the negative active material.
The diaphragm is a diaphragm with high tensile strength and high modulus, and the thickness of the diaphragm is 9-14 mu m; preferably, the separator is a composite of one or both of PP and PE having a molecular weight of 80-100 wDa.
The negative plate is prepared by the following method, including:
1) adding the negative electrode slurry and deionized water into a double-planet beater according to the formula ratio, and stirring for 2h under the conditions that the revolution speed is 40-50 r/min and the rotation speed is 1400-1600 r/min to prepare first negative electrode slurry;
2) adding the first negative electrode slurry into a high-speed dispersion machine, and dispersing under the conditions of 3000-4000 rpm until the viscosity is 3000-6000mPa.s to obtain the negative electrode slurry;
3) coating the negative electrode slurry on a copper foil with the thickness of 8-10 mu m, drying until the water content is less than or equal to 0.15%, then rolling and compacting, and slitting according to the width of the process requirement to obtain a negative electrode sheet;
as a further preferable scheme, the coating surface density of the anode slurry is 140-170g/m2(ii) a The compacted density of the negative plate is 1.6-1.8g/mm3。
The environment-friendly low-temperature-resistant lithium battery is prepared by the following method, including:
1) respectively installing the positive plate and the negative plate on a full-automatic winding machine according to requirements, isolating the positive plate and the negative plate by adopting a diaphragm, welding an aluminum strip positive lug on the positive plate, welding a nickel strip negative lug on the negative plate, and then winding to prepare a winding core;
2) inserting the winding core into a jig, placing the jig into a vacuum oven, vacuumizing to-75-95 MPa, baking at a constant temperature and a constant pressure of 75-95 ℃, and then filling nitrogen to the pressure of-10-45 MPa; circularly performing vacuum pumping, baking and nitrogen filling for 8-14 hours until the content of water in the roll core is less than or equal to 300 PPM;
3) installing a winding core into a steel shell, welding a negative electrode tab and the steel shell, installing a gasket, rolling a groove, testing short circuit, injecting 5.5-5.9g of electrolyte, welding a positive electrode tab and a cap, and buckling and sealing the cap and the steel shell to form a battery cell; cleaning the outer surface of the battery cell;
4) the battery cell is placed in an environment with the temperature of 10-40 ℃ for activation for 24-48 hours, and then is mounted on a formation cabinet for formation, wherein the upper limit voltage of the formation cabinet is 3.65V; the method comprises the steps of firstly aging the battery cell for five days in an environment with the temperature of 25-35 ℃, then screening the voltage and internal resistance of the battery cell, screening the battery cell with the capacity division and single charging voltage of 3.0-3.3V, and then aging for five days in an environment with the room temperature to prepare the finished product environment-friendly low-temperature resistant lithium battery.
The operations in the step 3) are completed in the environment with the environmental temperature of 20-25 ℃ and the dew point of-30 ℃ to-55 ℃.
The water content of the positive plate, the negative plate and the winding core prepared by the method is low, the SEI film of the battery is not easy to damage, and the service life and the use safety of the lithium battery are improved.
Examples 1 to 4
The components were weighed in the ratios in table 1, respectively, and positive electrode sheets were prepared according to the preparation methods of examples 1 to 4.
Table 1 examples 1-4 positive electrode sheet compositions
Figure BDA0002399852600000091
Wherein the particle size of the lithium iron phosphate is 4-10 μm, and the average particle size is 6 μm.
Examples 1-4 the method of making the positive plate was as follows:
example 1
1) Adding the water-based anode slurry and deionized water with the formula amount shown in the table 1 into a double-planet beater, and stirring for 2 hours under the conditions that the revolution speed is 48 revolutions per minute and the rotation speed is 1400 revolutions per minute to prepare first water-based anode slurry;
2) adding the first aqueous anode slurry into a high-speed dispersion machine, and dispersing under the condition of 3500 revolutions per minute until the viscosity is 5000mPa.s to obtain aqueous anode slurry;
3) coating the water-based anode slurry on an aluminum foil with the thickness of 14 mu m according to the surface density of 300 g/square meter, drying until the water content is less than or equal to 1 percent, and then, according to the active matter, 2.6g/mm3Rolling the obtained product with the compacted density, and finally cutting the product into a positive plate with the width of 57 mm.
Example 2
1) Adding the water-based anode slurry and deionized water with the formula amount shown in the table 1 into a double-planet beater, and stirring for 2 hours under the conditions that the revolution speed is 48 revolutions per minute and the rotation speed is 1400 revolutions per minute to prepare first water-based anode slurry;
2) adding the first aqueous anode slurry into a high-speed dispersion machine, and dispersing under the condition of 4500 r/min until the viscosity is 6000mPa.s to obtain aqueous anode slurry;
3) coating the water-based anode slurry on an aluminum foil with the thickness of 12 mu m according to the surface density of 310 g/square meter, drying until the water content is less than or equal to 1 percent, and then, according to the active matter, 2.6g/mm3Rolling the obtained product according to the compacted density, and finally cutting the product into a positive plate with the width of 58 mm.
Example 3
1) Adding the water-based anode slurry and deionized water with the formula amount shown in the table 1 into a double-planet beater, and stirring for 2 hours under the conditions that the revolution speed is 48 revolutions per minute and the rotation speed is 1400 revolutions per minute to prepare first water-based anode slurry;
2) adding the first aqueous anode slurry into a high-speed dispersion machine, and dispersing under the condition of 4000 revolutions per minute until the viscosity is 6000mPa.s to obtain aqueous anode slurry;
3) coating the water-based anode slurry on an aluminum foil with the thickness of 14 mu m according to the surface density of 320 g/square meter, drying until the water content is less than or equal to 1 percent, and then, according to the active matter, 2.65g/mm3Rolling the obtained product with the compacted density, and finally cutting the product into a positive plate with the width of 57.5 mm.
Example 4
1) Adding the water-based anode slurry and deionized water with the formula amount shown in the table 1 into a double-planet beater, and stirring for 2 hours under the conditions that the revolution speed is 48 revolutions per minute and the rotation speed is 1400 revolutions per minute to prepare first water-based anode slurry;
2) adding the first aqueous anode slurry into a high-speed dispersion machine, and dispersing under the condition of 4500 r/min until the viscosity is 6000mPa.s to obtain aqueous anode slurry;
3) coating the water-based anode slurry on an aluminum foil with the thickness of 12 mu m according to the surface density of 330 g/square meter, drying until the water content is less than or equal to 1 percent, and then, according to the active matter, 2.7g/mm3Rolling the obtained product according to the compacted density, and finally cutting the product into a positive plate with the width of 58 mm.
Examples 5 to 8
The components were weighed in the ratios in table 2, respectively, and negative electrode sheets were prepared according to the preparation methods of examples 5 to 8.
Table 2 examples 5-8 negative plate compositions
Figure BDA0002399852600000111
Wherein the gram capacity of the graphite is 360mAh/g, and the weight ratio of the natural graphite to the artificial graphite in the graphite is 1: 1.
The preparation method of the negative plate of the examples 5 to 8 is as follows:
example 5
1) Adding the negative electrode slurry and deionized water in the formula amount shown in the table 2 into a double-planet beater, and stirring for 2h under the conditions that the revolution speed is 48 r/min and the rotation speed is 1500 r/min to prepare first negative electrode slurry;
2) adding the first negative electrode slurry into a high-speed dispersion machine, and dispersing under the condition of 3000 r/min until the viscosity is 5000mPa.s to obtain negative electrode slurry;
3) coating the negative electrode slurry on a copper foil with the thickness of 9 mu m according to the surface density of 140 g/square meter, drying until the water content is less than or equal to 0.15 percent, and then coating the negative electrode slurry on an active substance according to the active substance content of 1.75g/mm3Rolling the obtained product according to the compacted density, and finally cutting the rolled product into cathode sheets with the width of 59 mm.
Example 6
1) Adding the negative electrode slurry and deionized water in the formula amount shown in the table 2 into a double-planet beater, and stirring for 2h under the conditions that the revolution speed is 48 r/min and the rotation speed is 1500 r/min to prepare first negative electrode slurry;
2) adding the first negative electrode slurry into a high-speed dispersion machine, and dispersing the first negative electrode slurry to the viscosity of 4200mPa.s under the condition of 3500 revolutions per minute to obtain negative electrode slurry;
3) coating the negative electrode slurry on a copper foil with the thickness of 8 mu m according to the surface density of 145 g/square meter, drying until the water content is less than or equal to 0.15 percent, and then coating the negative electrode slurry on an active substance according to the active substance content of 1.7g/mm3Rolling the obtained product according to the compaction density, and finally cutting the rolled product into cathode sheets with the width of 59.5 mm.
Example 7
1) Adding the negative electrode slurry and deionized water in the formula amount shown in the table 2 into a double-planet beater, and stirring for 2h under the conditions that the revolution speed is 48 r/min and the rotation speed is 1500 r/min to prepare first negative electrode slurry;
2) adding the first negative electrode slurry into a high-speed dispersion machine, and dispersing under the condition of 3800 revolutions per minute until the viscosity is 5500mPa.s to obtain negative electrode slurry;
3) coating the negative electrode slurry on a copper foil with the thickness of 8 mu m according to the surface density of 150 g/square meter, drying until the water content is less than or equal to 0.15 percent, and then coating the negative electrode slurry on an active substance according to the active substance content of 1.65g/mm3Rolling the obtained product according to the compacted density, and finally cutting the rolled product into cathode sheets with the width of 59 mm.
Example 8
1) Adding the negative electrode slurry and deionized water in the formula amount shown in the table 2 into a double-planet beater, and stirring for 1h under the conditions that the revolution speed is 40 revolutions per minute and the rotation speed is 1200 revolutions per minute to prepare first negative electrode slurry;
2) adding the first negative electrode slurry into a high-speed dispersion machine, and dispersing under the condition of 3000 r/min until the viscosity is 4500mPa.s to obtain negative electrode slurry;
3) coating the negative electrode slurry on a copper foil with the thickness of 9 mu m according to the surface density of 155 g/square meter, drying until the water content is less than or equal to 0.15 percent, and then coating the negative electrode slurry on an active substance according to the active substance content of 1.65g/mm3Rolling the obtained product according to the compaction density, and finally cutting the rolled product into negative plates with the width of 58.5 mm.
Examples 9 to 12
An environment-friendly low-temperature-resistant lithium battery comprises lithium iron phosphate positive plates of examples 1-4, negative plates of examples 5-8, a diaphragm, electrolyte, a shell and a sealing piece; the environment-friendly low-temperature resistant lithium battery is prepared according to the pole piece combination in the table 3 and the preparation methods of the embodiments 9 to 12.
TABLE 3 EXAMPLE 9-12 Pole piece combinations for environmentally friendly low temperature resistant lithium batteries
Item Example 9 Example 10 Example 11 Example 12
Positive plate Example 1 Example 2 Example 3 Example 4
Negative plate Example 5 Example 6 Example 7 Example 8
Examples 9-12 preparation methods of environmentally friendly low temperature resistant lithium batteries are as follows:
example 9
1) Respectively installing the positive plate and the negative plate in the table 3 on a full-automatic winding machine according to requirements, isolating the positive plate and the negative plate by using a diaphragm, welding an aluminum strip positive lug on the positive plate, welding a nickel strip negative lug on the negative plate, and then winding to prepare a winding core; the diaphragm is prepared from a PP/PE composite base material;
2) inserting the winding core into a jig, placing the jig into a vacuum oven, vacuumizing to-90 MPa, baking at the constant temperature and the constant pressure of 85 ℃, and then filling nitrogen to the pressure of-40 MPa; circularly performing vacuum pumping, baking and nitrogen filling for 10 hours until the water content in the roll core is less than or equal to 200 PPM;
3) installing a winding core into a steel shell, welding a negative electrode lug and the steel shell, installing a gasket, rolling a groove, testing short circuit, injecting 5.5g of electrolyte, welding a positive electrode lug and a cap, and buckling and sealing the cap and the steel shell to form a battery cell; cleaning the outer surface of the battery cell; the operations in the step are finished in the environment with the environmental temperature of 23 ℃ and the dew point of-38 ℃ to-42 ℃.
4) Activating the battery cell for 35 hours in an environment with the temperature of 30 ℃, and then installing the battery cell on a formation cabinet to perform formation with the upper limit voltage of 3.65V; the method comprises the steps of firstly aging the battery cell for five days in an environment with the temperature of 35 ℃, then screening the voltage and internal resistance of the battery cell, screening the battery cell with the capacity-dividing single charging voltage of 3.0-3.2V, and then aging for five days in an environment with the temperature of 30 ℃ to prepare the finished product environment-friendly low-temperature resistant lithium battery.
Example 10
1) Respectively installing the positive plate and the negative plate in the table 3 on a full-automatic winding machine according to requirements, isolating the positive plate and the negative plate by using a diaphragm, welding an aluminum strip positive lug on the positive plate, welding a nickel strip negative lug on the negative plate, and then winding to prepare a winding core; the diaphragm is prepared from a PE base material;
2) inserting the winding core into a jig, placing the jig into a vacuum oven, vacuumizing to-85 MPa, baking at a constant temperature and a constant pressure of 75 ℃, and then filling nitrogen to the pressure of-35 MPa; circularly performing vacuum pumping, baking and nitrogen filling for 14 hours until the water content in the roll core is less than or equal to 200 PPM;
3) installing a winding core into a steel shell, welding a negative electrode lug and the steel shell, installing a gasket, rolling a groove, testing short circuit, injecting 5.7g of electrolyte, welding a positive electrode lug and a cap, and buckling and sealing the cap and the steel shell to form a battery cell; cleaning the outer surface of the battery cell; the operations in the step are finished in the environment with the environmental temperature of 20 ℃ and the dew point of-40 ℃ to-43 ℃.
4) The battery cell is placed in an environment with the temperature of 35 ℃ for activation for 30 hours, and then is mounted on a formation cabinet to carry out formation with the upper limit voltage of 3.65V; the method comprises the steps of firstly aging the battery cell for five days in an environment with the temperature of 30 ℃, then screening the voltage and internal resistance of the battery cell, screening the battery cell with the capacity-dividing single charging voltage of 3.0-3.1V, and then aging for five days in an environment with the temperature of 25 ℃ to prepare the finished product environment-friendly low-temperature resistant lithium battery.
Example 11
1) Respectively installing the positive plate and the negative plate in the table 3 on a full-automatic winding machine according to requirements, isolating the positive plate and the negative plate by using a diaphragm, welding an aluminum strip positive lug on the positive plate, welding a nickel strip negative lug on the negative plate, and then winding to prepare a winding core; the diaphragm is prepared from a PP/PE composite base material;
2) inserting the winding core into a jig, placing the jig into a vacuum oven, vacuumizing to-95 MPa, baking at a constant temperature and a constant pressure of 95 ℃, and then filling nitrogen to reach the air pressure of-45 MPa; circularly performing vacuum pumping, baking and nitrogen filling for 9 hours until the content of water in the roll core is less than or equal to 200 PPM;
3) installing a winding core into a steel shell, welding a negative electrode tab and the steel shell, inserting a PIN steel tube, installing a gasket, rolling a groove, testing short circuit, injecting 5.6g of electrolyte, welding a positive electrode tab and a cap, and buckling and sealing the cap and the steel shell to form a battery cell; cleaning the outer surface of the battery cell; the operations in the step are finished in the environment with the ambient temperature of 25 ℃ and the dew point of-38 ℃ to 41 ℃.
4) Activating the battery cell for 40 hours in an environment with the temperature of 35 ℃, and then installing the battery cell on a formation cabinet to carry out formation with the upper limit voltage of 3.65V; the method comprises the steps of firstly aging the battery cell for five days in an environment with the temperature of 30 ℃, then screening the voltage and internal resistance of the battery cell, screening the battery cell with the capacity-dividing single charging voltage of 3.0-3.3V, and then aging for five days in an environment with the temperature of 25 ℃ to prepare the finished product environment-friendly low-temperature resistant lithium battery.
Example 12
1) Respectively installing the positive plate and the negative plate in the table 3 on a full-automatic winding machine according to requirements, isolating the positive plate and the negative plate by using a diaphragm, welding an aluminum strip positive lug on the positive plate, welding a nickel strip negative lug on the negative plate, and then winding to prepare a winding core; the diaphragm is prepared from a PP (polypropylene) base material;
2) inserting the winding core into a jig, placing the jig into a vacuum oven, vacuumizing to-88 MPa, baking at a constant temperature and a constant pressure of 80 ℃, and then filling nitrogen to reach the air pressure of-65 MPa; circularly performing vacuum pumping, baking and nitrogen filling for 12 hours until the water content in the roll core is less than or equal to 200 PPM;
3) installing a winding core into a steel shell, welding a negative electrode tab and the steel shell, inserting a PIN steel tube, installing a gasket, rolling a groove, testing short circuit, injecting 5.4g of electrolyte, welding a positive electrode tab and a cap, and buckling and sealing the cap and the steel shell to form a battery cell; cleaning the outer surface of the battery cell; the operations in the step are finished in the environment with the ambient temperature of 25 ℃ and the dew point of-38 ℃ to 41 ℃.
4) The battery cell is placed in an environment with the temperature of 35 ℃ for activation for 48 hours, and then is mounted on a formation cabinet to carry out formation with the upper limit voltage of 3.65V; the method comprises the steps of firstly aging the battery cell for five days in an environment with the temperature of 30 ℃, then screening the voltage and internal resistance of the battery cell, screening the battery cell with the capacity-dividing single charging voltage of 3.2-3.25V, and then aging for five days in an environment with the temperature of 25 ℃ to prepare the finished product environment-friendly low-temperature resistant lithium battery.
Test example
The environment-friendly low-temperature-resistant lithium batteries of the embodiments 9 to 12 are subjected to the detection of the safety inspection passing rate, the cycle performance (0.5/1C) and the discharge platform (0.5C), wherein the safety inspection passing rate is detected according to the safety requirement and the test method of the power storage battery for the electric automobile GBT 31485 and 2018.
The results are shown in Table 4.
TABLE 4 EXAMPLES 9-12 ENVIRONMENTALLY PROTECTIVE TEST TABLE FOR PERFORMANCE OF LOW-TEMPERATURE RESISTANT LITHIUM BATTERIES
Figure BDA0002399852600000161
As can be seen from Table 4, the environmental-friendly low temperature resistant lithium batteries of examples 9-12 all have better performances than the prior art. The battery has a safety inspection passing rate of 100 percent and excellent cycle performance, the capacity retention rate of 0.5C charging and 1C discharging for 1000 weeks is about 90 percent, the discharge platform is 3.2V, the capacity retention rate of 20 ℃ low-temperature discharging performance is over 70 percent, and is twice higher than that of the prior art about 35 percent, so that the battery can be used as a power storage battery for an electric automobile.
The above embodiments are only preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of the present invention claimed in the present invention.

Claims (10)

1. The lithium iron phosphate positive plate is characterized by comprising an aluminum foil and water-based positive slurry coated on the aluminum foil; the aqueous positive electrode slurry comprises the following components in percentage by mass:
Figure FDA0002399852590000011
the particle size of the lithium iron phosphate is 4-10 mu m.
2. The lithium iron phosphate positive electrode sheet according to claim 1, wherein the carbon nanotubes have a diameter of 3 to 10nm and a length of > 1 μm.
3. The lithium iron phosphate positive electrode sheet according to claim 1, wherein the coating surface density of the aqueous positive electrode slurry is 300-2(ii) a The compaction density of the positive plate is 2.5-2.8g/mm3。
4. The lithium iron phosphate positive electrode sheet according to claim 1, wherein the positive electrode sheet is prepared by a method comprising:
1) adding the components of the aqueous anode slurry and deionized water into a double-planet beater, and stirring for 2h under the conditions that the revolution speed is 40-50 r/min and the rotation speed is 1300-1500 r/min to prepare first aqueous anode slurry;
2) adding the first aqueous anode slurry into a high-speed dispersion machine, and dispersing under the conditions of 3500 and 4500 r/min until the viscosity is 5000 and 8000mPa.s, thus obtaining the aqueous anode slurry;
3) and coating the aqueous anode slurry on an aluminum foil, and sequentially drying, rolling and slitting to obtain the anode sheet.
5. The lithium iron phosphate positive plate according to claim 4, wherein the water content of the positive plate is less than or equal to 1%.
6. An environment-friendly low-temperature resistant lithium battery comprising the lithium iron phosphate positive plate of any one of claims 1 to 5, further comprising a negative plate and a diaphragm;
the negative plate comprises a copper foil and negative slurry coated on the copper foil; the negative electrode slurry comprises the following components in percentage by mass:
Figure FDA0002399852590000021
7. the environmentally friendly low temperature resistant lithium battery of claim 6, wherein the graphite is a combination of natural graphite and artificial graphite, and the gram volume of the graphite is greater than 360 mAh/g.
8. The environment-friendly low temperature resistant lithium battery of claim 6, wherein the separator is a composite of one or both of PP and PE having a molecular weight of 80-100 wDa.
9. The environment-friendly low-temperature-resistant lithium battery as claimed in claim 6, wherein the coating surface density of the negative electrode slurry is 140-170g/m2(ii) a The compacted density of the negative plate is 1.6-1.8g/mm3。
10. The environment-friendly low-temperature-resistant lithium battery as claimed in claim 6, wherein the water content of the negative electrode sheet is less than or equal to 0.15%.
CN202010143321.2A 2020-03-04 2020-03-04 Lithium iron phosphate positive plate and environment-friendly low-temperature-resistant lithium battery comprising same Pending CN111261835A (en)

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