CN112864383B - Water-soluble power lithium ion battery - Google Patents
Water-soluble power lithium ion battery Download PDFInfo
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- CN112864383B CN112864383B CN202110101880.1A CN202110101880A CN112864383B CN 112864383 B CN112864383 B CN 112864383B CN 202110101880 A CN202110101880 A CN 202110101880A CN 112864383 B CN112864383 B CN 112864383B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—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
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- 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
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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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- 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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- 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
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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
- 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 water-soluble power lithium ion battery which comprises a positive plate, wherein the positive plate comprises a positive current collector and positive slurry, the positive slurry comprises a conductive agent, a water-based binder and deionized water, and the positive current collector is an oily carbon-coated aluminum foil; the conductive agent comprises aqueous conductive slurry and carbon black, and the aqueous binder comprises an aqueous binder A, an aqueous binder B and a binder C. The invention improves the dispersibility and stability of the anode slurry, improves the bonding property of the anode plate and the flexibility of the anode plate, improves the compaction density so as to improve the energy density, and has better flexibility of the pole piece, thereby improving the yield and the production efficiency of rolling, laser cutting, winding and hot pressing; the problems of scratch leakage and pole piece cracking caused by quick drying of the slurry are solved, and the internal resistance of the battery is reduced by the oily carbon-coated aluminum foil.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a water-soluble power lithium ion battery.
Background
Compared with lead-acid batteries, nickel-metal hydride batteries and nickel-cadmium batteries, lithium ion batteries have the advantages of higher energy density, small self-discharge, long cycle life and the like, and are widely applied to the fields of consumer electronics and power batteries at present. Currently, the positive electrode slurry of the lithium ion battery generally adopts a fluorine-containing polymer such as polyvinylidene fluoride as a binder and NMP (N-methyl pyrrolidone) as a solvent. Because the organic solvent is easy to cause environmental pollution and harm to the health of operators, the cost input is increased to recover the organic solvent in the coating and drying process, and meanwhile, the cost of the NMP is higher, so that the production cost of the battery is increased. Therefore, research and development have been conducted on an aqueous positive electrode binder system, which can prevent environmental pollution and reduce production costs.
The water-based anode adopts deionized water as a solvent, and the binder adopts a water-based binder, but the water-based anode also has certain limitation in practical application and has the following problems:
(1) deionized water is used as a solvent, so that the dispersion of the positive electrode is difficult, the dispersion of slurry is difficult, and the stability is poor;
(2) during coating, on one hand, the slurry is dried quickly, so that scratches and foil leakage are caused; on the other hand, cracking powder dropping can be slightly improved by increasing the using amount of the binder and reducing the coating surface density, but the energy density is reduced;
(3) the pole piece is brittle during rolling, and although the flexibility of the pole piece can be slightly improved by reducing the compaction density, the energy density is also reduced;
(4) and the production efficiency is low by adopting a lamination process.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a water-soluble power lithium ion battery.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a water-soluble power lithium ion battery comprises a positive plate, a diaphragm, a negative plate, electrolyte and a shell, wherein the positive plate comprises a positive current collector and positive slurry, the positive slurry comprises a positive active substance, a conductive agent, a water-based binder, a dispersing auxiliary agent, a solvent additive and deionized water, and the positive current collector is an oily carbon-coated aluminum foil;
the weight ratio of the positive electrode active material, the conductive agent, the water-based binder and the dispersing aid is 93-96: 1-1.5: 2.5-3.5: 0.01-0.05; the anode active material is nano lithium iron phosphate with a particle size D500.5 to 2 μm; the conductive agent comprises water-based conductive slurry and carbon black, the water-based conductive slurry is carbon nanotube slurry or graphene conductive slurry, the carbon black is superconducting carbon black, Ketjen black or SP, and the weight ratio of the water-based conductive slurry to the carbon black is 0.5: 1;
the aqueous binder comprises an aqueous binder A, an aqueous binder B and a binder C, wherein the aqueous binder A is modified polyoxyethylene, the aqueous binder B is modified Arabic gum, and the binder C is modified styrene butadiene rubber; the weight ratio of the water-based binder A to the water-based binder B to the binder C is 10-25: 50-70: 10-20; the dispersing aid is a copolymer of butadiene and acrylonitrile.
Preferably, the solvent additive is one or more than two of propylene carbonate, diethyl carbonate, ethyl methyl carbonate, gamma-butyrolactone, methyl butyrate and ethyl butyrate, and the dosage of the solvent additive is 2-10% of that of the positive active material.
Preferably, the thickness of the positive current collector coated on the positive plate is 12-18 μm, and the density of a single-side coating surface is 1.5-2 g/100cm2。
Preferably, the positive electrode sheet is characterized in that the rolled compacted density of the positive electrode sheet is 2.3-2.45 g/cc.
Preferably, the tensile strength of the positive electrode current collector is greater than 200Mpa, and the elongation is greater than 2.0%.
Preferably, the preparation method of the negative electrode sheet is as follows:
uniformly mixing natural graphite, mesocarbon microbeads, conductive carbon black, SBR and CMC in a weight ratio of 90.5:5:1:3.5 with deionized water to prepare negative electrode slurry; and uniformly coating the negative electrode slurry on a copper foil with the thickness of 9 mu m, and then drying, rolling and cutting into strips at the temperature of 110 ℃ to prepare the negative electrode plate.
Preferably, the natural graphite has an average particle size of 12 μm and a tap density of 1.3g/cm3。
Preferably, the average particle size of the mesocarbon microbeads is 9 microns, and the tap density is 1.5g/cm3。
Compared with the prior art, the invention has the following advantages and positive effects:
(1) the dispersibility and stability of the positive slurry are improved through the dispersing auxiliary agent;
(2) the three binders are mixed for use, so that the using amount of the binders can be reduced, the binding property of the pole piece and the flexibility of the positive pole piece can be improved, the problem of cracking and material falling during coating is solved, the compaction density is improved, the energy density is improved, the flexibility of the pole piece is good, and the yield and the production efficiency of rolling, laser cutting, winding and hot pressing can be improved; specifically, the binder A has the function of preventing slurry from settling, the binder B has the main function of bonding, the binder C has the main function of improving flexibility, and the binder C has the secondary function of bonding, so that the bonding effect is far smaller than that of the binder B;
(3) the long-range and short-range conductive network is formed by the aqueous conductive slurry and the carbon black, so that the conductivity is improved, and the consumption of a conductive agent is reduced;
(4) the solvent additive has a higher melting point and has the moisture retention property of the slurry during coating, so that the problem of scratching and foil leakage caused by quick drying of the slurry is solved; when the pole piece is dried, the solvent additive is remained in the pole piece due to the higher melting point of the solvent additive, so that the problem of pole piece cracking is solved, and the flexibility of the pole piece is improved;
(5) the oily carbon-coated aluminum foil reduces the internal resistance of the battery.
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.
The batteries prepared in the following examples and comparative examples were subjected to performance tests in accordance with GB/T31484-2015 and GB/T31486-2015 standards.
The following calculation formula of energy density of the batteries in examples and comparative examples:
energy density is discharge capacity multiplied by plateau voltage/cell weight
Plateau voltage of 3.2V
Example 1
(1) Positive plate
The positive plate comprises a positive current collector and positive slurry, wherein the positive slurry comprises a positive active substance, a conductive agent, a water-based binder, a dispersing auxiliary agent, a solvent additive and deionized water, and the positive current collector is an oily carbon-coated aluminum foil;
the weight ratio of the positive electrode active substance to the conductive agent to the aqueous binder to the dispersing aid is 94.5:1.25:3.0: 0.03; the positive active material is nano lithium iron phosphate;
the conductive agent comprises aqueous conductive slurry and carbon black, the aqueous conductive slurry is carbon nanotube slurry, the carbon black is superconducting carbon black, and the weight ratio of the aqueous conductive slurry to the carbon black is 0.5: 1;
the aqueous binder comprises an aqueous binder A, an aqueous binder B and a binder C, wherein the aqueous binder A is modified polyoxyethylene, the aqueous binder B is modified Arabic gum, and the binder C is modified styrene butadiene rubber; the weight ratio of the water-based binder A to the water-based binder B to the binder C is 17.5:60: 15; the dispersing aid is a copolymer of butadiene and acrylonitrile.
The solvent additive is composed of propylene carbonate, ethyl methyl carbonate and gamma-butyrolactone according to the weight ratio of 2:3:1, and the dosage of the solvent additive is 6% of that of the positive active substance.
The slurry mixing process of the anode slurry comprises the following steps:
uniformly mixing a positive electrode active substance, a conductive agent, a water-based binder, a dispersing aid, a solvent additive and deionized water according to a ratio to prepare a positive electrode slurry, uniformly coating the negative electrode slurry on a positive electrode current collector with the thickness of 15 mu m, and coating the single surface of the positive electrode current collector with the surface density of 1.6g/100cm2And the rolled compaction density of the positive plate is 2.38 g/cc.
(2) Preparation of the negative electrode
Mixing natural graphite (average particle size of 12 μm, tap density of 1.3 g/cm)3) MCMB (average particle size 9 μm, tap density 1.5 g/cm)3) Uniformly mixing the conductive carbon black, SBR and CMC with deionized water according to the weight ratio of 90.5:5:1:3.5 to prepare negative electrode slurry, uniformly coating the negative electrode slurry on a 9-micron copper foil, drying at the temperature of 110 ℃, rolling, slitting and cutting to prepare a negative electrode sheet.
(3) Preparation of roll cores
And (3) winding the positive plate and the negative plate prepared in the steps (1) and (2) and the ceramic coating diaphragm (7+3) into a winding core.
(4) Preparation of the electrolyte
Mixing LiPF6(concentration of 1 mol/l) and an additive VC (1%) were dissolved in a mixed solvent of PC (propylene carbonate)/EC (ethylene carbonate)/DMC (dimethyl carbonate)/EP (ethyl propionate) ═ 3:2:2:3 (volume ratio) to form an electrolytic solution.
(5) Assembly of a battery
And (4) placing the roll core obtained in the step (3) into a shell, and then injecting the electrolyte prepared in the step (4) to prepare the water-soluble power lithium ion battery.
Example 2
(1) Positive plate
The positive plate comprises a positive current collector and positive slurry, wherein the positive slurry comprises a positive active substance, a conductive agent, a water-based binder, a dispersing auxiliary agent, a solvent additive and deionized water, and the positive current collector is an oily carbon-coated aluminum foil;
the weight ratio of the positive electrode active substance to the conductive agent to the aqueous binder to the dispersing aid is 96:1:3.5: 0.01; the positive active material is nano lithium iron phosphate; the conductive agent comprises aqueous conductive slurry and carbon black, wherein the aqueous conductive slurry is graphene conductive slurry, the carbon black is ketjen black ECP600JD, and the weight ratio of the aqueous conductive slurry to the carbon black is 0.5: 1;
the aqueous binder comprises an aqueous binder A, an aqueous binder B and a binder C, wherein the aqueous binder A is modified polyoxyethylene, the aqueous binder B is modified Arabic gum, and the binder C is modified styrene butadiene rubber; the weight ratio of the aqueous binder A to the aqueous binder B to the binder C is 25:50: 20; the dispersing aid is a copolymer of butadiene and acrylonitrile.
The solvent additive is composed of diethyl carbonate, methyl butyrate and ethyl butyrate according to a weight ratio of 4:2:1, and the dosage of the solvent additive is 9.2% of that of the positive active material.
The slurry mixing process of the anode slurry comprises the following steps:
uniformly mixing a positive electrode active substance, a conductive agent, a water-based binder, a dispersing aid, a solvent additive and deionized water according to a ratio to prepare a positive electrode slurry, uniformly coating the negative electrode slurry on a positive electrode current collector with the thickness of 18 mu m, and coating the single surface of the positive electrode current collector with the surface density of 1.5g/100cm2And the rolled compaction density of the positive plate is 2.45 g/cc.
The other preparation steps were the same as in example 1.
Example 3
(1) Positive plate
The positive plate comprises a positive current collector and positive slurry, wherein the positive slurry comprises a positive active substance, a conductive agent, a water-based binder, a dispersing auxiliary agent, a solvent additive and deionized water, and the positive current collector is an oily carbon-coated aluminum foil;
the weight ratio of the positive electrode active substance to the conductive agent to the aqueous binder to the dispersing aid is 93:1.5:2.5: 0.05; the positive active material is nano lithium iron phosphate; the conductive agent comprises aqueous conductive slurry and carbon black, the aqueous conductive slurry is carbon nanotube slurry, the carbon black is SP, and the weight ratio of the aqueous conductive slurry to the carbon black is 0.5: 1;
the aqueous binder comprises an aqueous binder A, an aqueous binder B and a binder C, wherein the aqueous binder A is modified polyoxyethylene, the aqueous binder B is modified Arabic gum, and the binder C is modified styrene butadiene rubber; the weight ratio of the water-based binder A to the water-based binder B to the binder C is 10:70: 10; the dispersing aid is a copolymer of butadiene and acrylonitrile.
The solvent additive is composed of methyl ethyl carbonate, gamma-butyrolactone and methyl butyrate according to the weight ratio of 1:5:2, and the dosage of the solvent additive is 2.1% of that of the positive active material.
The slurry mixing process of the anode slurry comprises the following steps:
uniformly mixing a positive electrode active substance, a conductive agent, a water-based binder, a dispersing aid, a solvent additive and deionized water according to a ratio to prepare a positive electrode slurry, uniformly coating the negative electrode slurry on a positive electrode current collector with the thickness of 12 mu m, and coating the single surface of the positive electrode current collector with the surface density of 2.0g/100cm2And the rolled compaction density of the positive plate is 2.30 g/cc.
The other preparation steps were the same as in example 1.
Comparative example 1
(1) Positive plate
The positive plate comprises a positive current collector and positive slurry, the positive slurry comprises a positive active substance, a conductive agent, a binder and deionized water, and the positive current collector is an aluminum foil;
the weight ratio of the positive electrode active material to the conductive agent to the binder is 92.43:3.96: 3.62; the positive electrode active material is lithium iron phosphate, the conductive agent is conductive carbon black, and the binder is composed of carboxymethyl cellulose and polyacrylic acid according to the weight ratio of 1.14: 2.48;
the slurry mixing process of the anode slurry comprises the following steps:
s1, adding a conductive agent, carboxymethyl cellulose, 46% polyacrylic acid and deionized water into a stirring tank according to a proportion, and stirring for 2 hours at a stirring speed of 3500 rpm;
s2, adding the positive active substances in two times, stirring for 1h at the stirring speed of 2000rpm, and then stirring for 3h at the stirring speed of 3500 rpm;
s3, vacuumizing, and adding 58% of polyacrylic acid and deionized water;
s4, vacuumizing and stirring for 1h at the stirring speed of 1000rpm, wherein the solid content of the slurry is 67.7%, the fineness is 30 microns, and the viscosity is 7600 cps;
s5, the thickness of the positive coating current collector is 15 microns, and the single-side coating surface density is 1.6g/100cm2。
The other preparation steps were the same as in example 1.
Comparative example 2
The amount of the dispersion aid added was adjusted to 0, and other conditions and preparation method were the same as in example 1.
Comparative example 3
The amount of the aqueous binder B added was adjusted to 0, and other conditions and the preparation method were the same as in example 1.
Comparative example 4
The amount of the binder C added was adjusted to 0, and other conditions and the preparation method were the same as in example 1.
Comparative example 5
The solvent additive was propylene carbonate, and the other conditions and preparation method were the same as in example 1.
Comparative example 6
Preparing a positive electrode slurry according to the method of example 1 in patent 201210275706. X;
(1) preparing a premixed solution: weighing 40% of a positive electrode active material (lithium iron phosphate), 10% of a carbon nano tube, 5% of Super-P, 3% of a water-based binder and 42% of deionized water according to mass percentage, wherein the water-based binder comprises the following components in percentage by mass: 30% of methyl cellulose, 30% of sodium polyacrylate and 40% of styrene-butadiene latex, adding deionized water accounting for 60% of the total mass of the deionized water and a water-based binder into a planetary slurry stirrer, and stirring at a low speed of 25r/min for 30min to obtain a premixed solution, wherein the low-speed stirring speed is revolution and 500r/min rotation;
(2) preparing conductive glue solution: adding carbon nano tube and conductive agent into the premixed liquid, and stirring at high speed for 60min to obtain conductive glue solution, wherein the high-speed stirring speed is revolution at 50r/min and rotation at 2500 r/min.
(3) Primary dispersion: and grinding the conductive glue solution in a colloid mill to the fineness of 6 mu m.
(4) And (3) secondary dispersion: and adding the ground conductive glue solution, the positive active substance and the rest deionized water into a planetary slurry stirrer, and stirring at a high speed of revolution of 20r/min and rotation of 1800r/min until the fineness is 30 mu m to obtain a coarse slurry.
(5) Defoaming and standing: and vacuumizing the crude slurry for 30min, wherein the relative vacuum degree of vacuumizing is-92 KPa, and standing for 10min after vacuumizing to obtain the aqueous anode slurry of the lithium ion battery.
Other conditions and preparation method were the same as in example 1.
Comparative example 7
Preparing a positive plate according to the method of example 1 in patent 201510723952.0;
the lithium ion battery aqueous positive electrode composite current collector of the comparative example is prepared by the preparation method comprising the following steps:
1) adding 1kg of adhesive polyvinylidene fluoride (PVDF) into 20kg of solvent N-methyl pyrrolidone, and uniformly mixing to obtain an adhesive solution;
2) adding 9kg of conductive agent Super P into the binder solution prepared in the step 1), uniformly mixing, grinding and emulsifying by adopting grinding balls with the particle size of 0.4mm at the rotating speed of 1000rpm for 2h, defoaming for 8h, and sieving by using a 200-mesh sieve to obtain conductive slurry;
3) uniformly coating the conductive slurry prepared in the step 2) on two surfaces of an aluminum foil of a positive current collector by adopting a gravure printing machine, wherein the thickness of the aluminum foil is 20 mu m, and the coating surface density is 2g/m2And drying at 120 ℃ to obtain the product.
The positive plate comprises the above-mentioned lithium ion battery aqueous positive composite current collector and a positive active material coated on two surfaces of the lithium ion battery aqueous positive composite current collector, the lithium ion battery aqueous positive composite current collector comprises a current collector aluminum and conductive coatings coated on two surfaces of an aluminum foil, and the positive active material comprises the following components in percentage by weight: 95% of lithium iron phosphate, 2% of Super P, 2% of acrylamide-acrylonitrile copolymer and 1% of sodium carboxymethylcellulose.
The preparation method of the positive plate comprises the following steps: dissolving 42g of sodium carboxymethylcellulose in 1500g of water, adding 600g of acrylamide-acrylonitrile copolymer, uniformly mixing, adding 126g of super P, uniformly mixing, adding 4000g of lithium iron phosphate, uniformly mixing, adjusting the viscosity to be 5000mPa & s, defoaming and filtering to obtain anode slurry, wherein the solid content of the obtained anode slurry is 50.8%, and uniformly coating the anode slurry on the aqueous anode composite current collector of the lithium ion battery by using an extrusion coating machine to obtain the anode sheet.
Other conditions and preparation method were the same as in example 1.
Comparative example 8
Preparing a positive plate according to the method of example 1 in patent 201710026337.3;
the preparation of the aqueous positive electrode slurry comprises the following steps:
step one, adding 0.4 part by weight of polyvinylpyrrolidone (PVP), 0.5 part by weight of ethylene carbonate and 10 parts by weight of deionized water into a stirrer, stirring at medium speed of 800rpm for 0.5h, and uniformly stirring to obtain a glue solution A;
step two, adding 5 parts by weight of LA133 and 40 parts by weight of deionized water into a stirrer, stirring at medium speed of 800rpm for 0.5h, and uniformly stirring to obtain a glue solution B;
step three, adding the glue solution A, 2 parts by weight of conductive carbon black and 1 part by weight of conductive graphite into the glue solution B, and stirring at a high speed of 1500rpm for 90 min;
step four, sequentially adding 92 parts by weight of nano lithium iron phosphate into a stirrer in equal amount, wherein the stirring speed is 500rpm when mixing is started, and after the mixture and the glue solution are initially mixed, the stirring speed is increased to high-speed dispersion, wherein the high-speed dispersion speed is 1800 rpm; high-speed dispersion time is 150 min;
step five, adding 25 parts by weight of deionized water to adjust the viscosity of the slurry to 5100 mpas;
and step six, vacuumizing to-0.085 MPa, defoaming, and filtering by using a filter screen to obtain the aqueous anode slurry.
Other conditions and preparation method were the same as in example 1.
Comparative example 9
Preparing a positive plate according to the method of example 1 in patent 201811215720.4;
selecting median particle diameter D50Lithium iron phosphate with the particle size of 3 mu m is taken as a main material of the anode slurry, a conductive agent is conductive carbon black, and a binder is an AB double-component aqueous binder provided by the invention;
wherein the AB two-component aqueous binder comprises a component A and a component B; component A is a mixture of carboxypropylmethylcellulose and polyacrylic acid, and component B is polyacrylic acid.
Firstly, respectively weighing 1722g (solid content is 5%) of glue A (namely the binder of the component A), 1000g of deionized water and 300g of conductive carbon black, and stirring for 2 hours at a stirring speed of 3500 rpm;
then adding 7000g of main material lithium iron phosphate of the positive electrode slurry twice, stirring for 1 hour at the stirring speed of 2000rpm, and then stirring for 3 hours at the speed of 3500 rpm;
then, adding 289g (solid content is 35%) of glue B (namely the binder of the component B) and 750g of deionized water after vacuumizing;
finally, the mixture was stirred under vacuum for 1 hour at a stirring speed of 1000 rpm. The slurry had a solids content of 67.7%, a fineness of 30 μm and a viscosity of 7600 cps.
The single-side coated surface density of the positive electrode slurry coated on the positive electrode current collector (such as aluminum foil) is 1.6g/m2The coating rate was 2m/s and the coating temperatures were 80, 110 and 90 ℃ respectively.
Other conditions and preparation method were the same as in example 1.
The lithium ion batteries of examples 1 to 3 and comparative examples 1 to 6 were each subjected to performance measurement, and the results are shown in table 1.
TABLE 1 measurement results of Performance of lithium ion batteries of examples 1 to 3 and comparative examples 1 to 6
As can be seen from the results in table 1 above, in examples 1 to 3 and comparative examples 1 and 2, the dispersibility and stability of the positive electrode slurry are improved by the dispersion aid, and the cycle life of the battery is further improved; as can be seen from the examples 1-3 and the comparative examples 3 and 4, the invention mixes the three binders for use, solves the problem of cracking and material dropping during coating, improves the compaction density so as to improve the energy density, has good flexibility of the pole piece, and can improve the yield and the production efficiency of rolling, laser cutting, winding and hot pressing; as can be seen from examples 1-3 and comparative example 1, the long-range and short-range conductive network is formed by the aqueous conductive slurry and the carbon black, so that the conductivity is improved, and the consumption of the conductive agent is reduced; as can be seen from examples 1-3 and comparative example 5, the solvent additive has a high melting point, has the moisture retention property of the slurry during coating, and solves the problem of scratch and foil leakage caused by rapid drying of the slurry; when the pole piece is dried, the solvent additive is remained in the pole piece due to the higher melting point of the solvent additive, so that the problem of pole piece cracking is solved, and the flexibility of the pole piece is improved. The invention greatly improves the energy density of the lithium iron phosphate battery through the synergistic effect of the specific formula and the process, and simultaneously improves the discharge capacity, the cycle life and other performances of the battery; as can be seen from examples 1 to 3 and comparative examples 6 to 9, the comprehensive technical effect of the present invention is significantly improved compared to the prior art.
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 (5)
1. A water-soluble power lithium ion battery comprises a positive plate, a diaphragm, a negative plate, electrolyte and a shell, and is characterized in that the positive plate comprises a positive current collector and positive slurry, the positive slurry comprises a positive active substance, a conductive agent, a water-based binder, a dispersing auxiliary agent, a solvent additive and deionized water, and the positive current collector is an oily carbon-coated aluminum foil;
the weight ratio of the positive electrode active material, the conductive agent, the water-based binder and the dispersing aid is 93-96: 1-1.5: 2.5-3.5: 0.01-0.05; the anode active material is nano lithium iron phosphate with a particle size D500.5 to 2 μm; the conductive agent comprises water-based conductive slurry and carbon black, the water-based conductive slurry is carbon nanotube slurry or graphene conductive slurry, the carbon black is superconducting carbon black, and the weight ratio of the water-based conductive slurry to the carbon black is 0.5: 1;
the aqueous binder comprises an aqueous binder A, an aqueous binder B and a binder C, wherein the aqueous binder A is modified polyoxyethylene, the aqueous binder B is modified Arabic gum, and the binder C is modified styrene butadiene rubber; the weight ratio of the water-based binder A to the water-based binder B to the binder C is 10-25: 50-70: 10-20; the dispersing auxiliary agent is a copolymer of butadiene and acrylonitrile;
the solvent additive is selected from one or more of propylene carbonate, diethyl carbonate, ethyl methyl carbonate, gamma-butyrolactone, methyl butyrate and ethyl butyrate, and the dosage of the solvent additive is 2-10% of that of the positive active material;
the thickness of the positive current collector coated on the positive plate is 12-18 mu m, and the density of a single-side coating surface is 1.5-2 g/100cm2；
The rolled compaction density of the positive plate is 2.3-2.45 g/cc.
2. The water-soluble power lithium ion battery of claim 1, wherein the tensile strength of the positive electrode current collector is greater than 200Mpa, and the elongation is greater than 2.0%.
3. The water-soluble power lithium ion battery of claim 1, wherein the preparation method of the negative electrode sheet is as follows:
uniformly mixing natural graphite, mesocarbon microbeads, conductive carbon black, SBR and CMC in a weight ratio of 90.5:5:1:3.5 with deionized water to prepare negative electrode slurry; and uniformly coating the negative electrode slurry on a copper foil with the thickness of 9 mu m, and then drying, rolling and cutting into strips at the temperature of 110 ℃ to prepare the negative electrode plate.
4. The water-soluble power lithium ion battery according to claim 3, wherein the natural graphite has an average particle size of 12 μm and a tap density of 1.3g/cm3。
5. The water-soluble power lithium ion battery of claim 3, wherein the average particle size of the mesocarbon microbeads is 9 μm and the tap density is 1.5g/cm3。
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| CN114678530B (en) * | 2022-03-11 | 2023-09-22 | 厦门海辰储能科技股份有限公司 | Positive electrode slurry, positive electrode plate and lithium battery |
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