CN118099424A - Adhesive for positive plate, preparation method of adhesive, positive plate and secondary battery - Google Patents

Adhesive for positive plate, preparation method of adhesive, positive plate and secondary battery Download PDF

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Publication number
CN118099424A
CN118099424A CN202211457254.7A CN202211457254A CN118099424A CN 118099424 A CN118099424 A CN 118099424A CN 202211457254 A CN202211457254 A CN 202211457254A CN 118099424 A CN118099424 A CN 118099424A
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China
Prior art keywords
resin
binder
polyolefin resin
adhesive
positive electrode
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Chinese (zh)
Inventor
任鸿烽
李静
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Shenzhen Hongxing Innovative Materials Co ltd
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Shenzhen Hongxing Innovative Materials Co ltd
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Priority to CN202211457254.7A priority Critical patent/CN118099424A/en
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621Binders
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621Binders
    • H01M4/622Binders being polymers
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621Binders
    • H01M4/622Binders being polymers
    • H01M4/623Binders being polymers fluorinated polymers
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

In order to solve the problem that the existing PVDF production raw materials damage an atmospheric layer and NMP is toxic, the application provides a binder for a positive plate, a preparation method thereof, a positive plate and a secondary battery; the application provides a binder for a positive plate, which comprises polyolefin resin, tackifying resin and alkane solvent. The adhesive for the positive plate, provided by the application, has the advantages that the polyolefin resin and the tackifying resin can improve the adhesive force between the adhesive and the metal base material, the adhesive force is strong, the adhesive has lower swelling rate, electrolyte corrosion resistance and good thermal stability and oxidation-reduction resistance in electrolyte. The binder provided by the application can be directly mixed with the anode active material and the conductive agent for coating, replaces the existing PVDF and solvent NMP, has low toxicity and improves the safety performance of personnel.

Description

Adhesive for positive plate, preparation method of adhesive, positive plate and secondary battery
Technical Field
The invention belongs to the technical field of energy storage batteries, and particularly relates to an adhesive for a positive plate, a preparation method of the adhesive, the positive plate and a secondary battery.
Background
Polyvinylidene fluoride (PVDF) is a polymer material with high dielectric constant, has good chemical stability and temperature characteristics, has excellent mechanical properties and processability, has positive effect on improving the bonding performance, and is widely applied to lithium ion batteries as a positive electrode binder. Under the continuous expansion of application requirements in the fields of lithium battery manufacturing, photovoltaic backboard, energy storage and the like, PVDF shows explosive growth, and R142b is used as a main production raw material of a fluoride engineering product PVDF, and only quota production is limited by international agreements due to the fact that the atmosphere can be destroyed, so that the risk of supply shortage exists. Meanwhile, NMP used for PVDF coating has harm such as reproduction toxicity and the like, and belongs to EU REACH limiting substances. Therefore, developing a binder that can replace PVDF and its solvent NMP is of great significance in the lithium battery industry.
Disclosure of Invention
Aiming at the problem that the existing PVDF production raw materials destroy an atmospheric layer and NMP is toxic, the application provides a binder for a positive plate, a preparation method thereof, a positive plate and a secondary battery.
The technical scheme adopted by the invention for solving the technical problems is as follows:
The application provides a binder for a positive electrode sheet, which comprises polyolefin resin, tackifying resin and alkane solvent.
Preferably, the polyolefin resin includes a polyolefin resin a, which is an olefin polymer not modified with a functional group, and a polyolefin resin b, which is a modified olefin polymer;
the polyolefin resin b is obtained by modifying one or more of maleic anhydride, acrylic acid, a compound containing carboxyl and a compound containing hydroxyl;
the mass ratio of the polyolefin resin a to the polyolefin resin b is (0.5-4): 1.
Preferably, the olefin polymer is polymerized from olefin monomers including one or more of alpha olefins, cycloolefins, and aromatic hydrocarbons; the alpha olefin comprises one or more of ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 1, 3-butadiene and isobutene.
Preferably, the polyolefin resin includes one or more of ethylene-vinyl acetate copolymer, polybutadiene rubber, polyisobutylene, amorphous poly-alpha-olefin resin, acrylic modified polyolefin, poly (ethylene-chlorotrifluoroethylene), ethylene-propylene acetate copolymer, ethylene-propylene copolymer, ethylene propylene diene rubber, ethylene propylene rubber, ethylene-propylene-styrene-acrylonitrile copolymer, ethylene propylene terpolymer, vinyl ethyl ether, isobutylene-isoprene rubber, maleic anhydride modified polyolefin, modified polypropylene, modified polyphenylene ether, modified polystyrene, styrene-methyl methacrylate resin, nitrile rubber, hydrogenated nitrile rubber, polybutadiene-acrylonitrile, propylene-butadiene rubber, poly (butadiene-styrene), styrene-ethylene-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, solid styrene-butadiene rubber, styrene-maleic anhydride copolymer, synthetic polyolefin rubber, syndiotactic polystyrene, polyolefin elastomer, olefin block copolymer, and polyolefin copolymer after polymerization.
Preferably, the mass content of the polyolefin resin is 50-95% and the mass content of the tackifying resin is 5-50% based on 100% of the total mass of the polyolefin resin and the tackifying resin;
the mass ratio of the alkane solvent is 60-80% and the mass ratio of the polyolefin resin and the tackifying resin is 20-40% based on 100% of the mass of the binder.
Preferably, the polyolefin resin is 50 to 90% by mass and the tackifying resin is 10 to 50% by mass based on 100% by mass of the total of the polyolefin resin and the tackifying resin.
Preferably, the tackifying resin comprises one or more of a natural resin and a synthetic resin;
the natural resin comprises one or more of rosin resin and rosin derivative resin;
The synthetic resin comprises one or more of hydrogenated rosin resin, terpene resin, petroleum resin, coumarone-indene resin, styrene resin and condensation resin.
Preferably, the alkane solvent comprises one or more of n-heptane, cyclohexane, isooctane, dodecane, white oil, D40 solvent oil, D30 solvent oil, D80 solvent oil, 150# solvent oil, 200# solvent oil, 6# solvent oil;
The boiling point temperature of the alkane solvent is 80-350 ℃.
In a second aspect, the present application provides a method for preparing a binder for a positive electrode sheet, comprising the steps of:
Adding an alkane solvent, polyolefin resin and tackifying resin into a stirring container, gradually heating to 50-200 ℃, stirring for 0.5-4 h, stirring and mixing uniformly, and filtering to obtain the adhesive.
In a third aspect, the application provides a positive plate, which comprises a current collector and a positive electrode material layer, wherein the positive electrode material layer comprises a positive electrode active material, a conductive agent and a binder, and the binder is the binder for the positive plate or the binder for the positive plate, and is prepared by the preparation method.
In a fourth aspect, the application provides a secondary battery, comprising a positive plate, a negative plate, a diaphragm and electrolyte, wherein the positive plate comprises the positive plate.
Advantageous effects
Compared with the prior art, the adhesive for the positive plate, provided by the application, has the advantages that the polyolefin resin and the tackifying resin can improve the adhesive force between the adhesive and the metal substrate, the adhesive force is strong, the adhesive has lower swelling rate, electrolyte corrosion resistance and good thermal stability and oxidation-reduction resistance in the electrolyte. The binder provided by the application can be directly mixed with the anode active material and the conductive agent for coating, replaces the existing PVDF and solvent NMP, has low toxicity and improves the safety performance of personnel. The binder provided by the application also has excellent mechanical property, processability, good chemical stability and temperature characteristics, and does not influence the electrical property and the safety performance of the battery when being applied to the secondary battery.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects solved by the invention more clear, the invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The embodiment of the invention provides a binder for a positive plate, which comprises polyolefin resin, tackifying resin and alkane solvent.
The existing binder for the positive plate of the lithium ion battery is PVDF, but the main production raw material R142b of PVDF can destroy the atmosphere and is limited by international protocols, so that the mass production of PVDF is affected. In the preparation process of the positive plate, positive electrode slurry needs to be prepared, the positive electrode slurry contains solvent NMP, and NMP has harm such as reproduction toxicity and the like and causes a certain harm to human bodies. In view of the above problems, there is a need for a binder that can replace PVDF and a solvent NMP, and the inventors have found through extensive studies that a binder obtained by adding a certain amount of a tackifying resin and a polyolefin resin to an alkane solvent to dissolve can replace PVDF and NMP solvents, and then coating the mixture with a conductive agent and a positive electrode active material without affecting the performance of a battery.
The adhesive for the positive plate, provided by the application, has the advantages that the polyolefin resin and the tackifying resin can improve the adhesive force between the adhesive and the metal base material, the adhesive force is strong, the adhesive has lower swelling rate, electrolyte corrosion resistance and good thermal stability and oxidation-reduction resistance in electrolyte. The binder provided by the application can be directly mixed with the anode active material and the conductive agent for coating, replaces the existing PVDF and solvent NMP, has low toxicity and improves the safety performance of personnel. The binder provided by the application also has excellent mechanical property, processability, good chemical stability and temperature characteristics, and does not influence the electrical property and the safety performance of the battery when being applied to the secondary battery.
In some embodiments, the polyolefin resin includes a polyolefin resin a that is an olefin polymer that is not modified with functional groups and a polyolefin resin b that is a modified olefin polymer;
the polyolefin resin b is obtained by modifying one or more of maleic anhydride, acrylic acid, a compound containing carboxyl and a compound containing hydroxyl;
the mass ratio of the polyolefin resin a to the polyolefin resin b is (0.5-4): 1.
The binding force of the adhesive is enhanced by modifying the olefin polymer by various polar groups such as maleic anhydride, acrylic acid, hydroxyl, carboxyl and the like, because the metal material belongs to the polar material, and the polar groups and the metal base materials (such as copper and aluminum) have strong hydrogen bond and chemical bond action, the binding property of the adhesive is greatly improved, and the binding force of the positive plate is improved.
The polyolefin resin b contains polar groups, and can further improve the adhesion of the adhesive. The mass ratio of the polyolefin resin a to the polyolefin resin b is within the range of (0.5-4): 1, and has the effect of improving the cohesive force of the adhesive, and has good mechanical property, chemical stability and processability.
Specifically, if the mass ratio of the polyolefin resin a to the polyolefin resin b is less than 0.5, the adhesive bonding force is lowered; if the mass ratio of the polyolefin resin a to the polyolefin resin b is higher than 4.0, the swelling ratio of the adhesive increases greatly, the electrolyte corrosion resistance of the adhesive is lowered, and the adhesive strength of the adhesive is lowered. The mass ratio of the specific polyolefin resin a to the polyolefin resin b may be 0.5:1, 0.8:1, 1:1, 1.3:1, 1.5:1, 1.8:1, 2.0:1, 2.2:1, 2.5:1, 3.0:1, 3.4:1, 3.6:1, 4.0:1, etc., as long as the mass ratio of the polyolefin resin a to the polyolefin resin b is in the range of (0.5 to 4): 1.
In some preferred embodiments, the mass ratio of polyolefin resin a to polyolefin resin b is (0.5 to 2.5): 1.
The olefin polymer is polymerized from olefin monomers including one or more of alpha-olefins and cyclic olefins.
For example, alpha-olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 1, 3-butadiene, isobutylene, and the like. The cycloolefin may be an n-membered cycloolefin, n is an integer, and n is not less than 3.
The olefin polymer is polymerized from olefin monomers, and may be, for example, an olefin polymer obtained by polymerizing ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 1, 3-butadiene, isobutylene and other alpha-olefins, and polymerizing or copolymerizing certain cycloolefins and aromatic hydrocarbons alone.
The polyolefin resin b may be prepared by modifying monomers of ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene and other alpha-olefins and cycloolefins with one or more polar groups selected from maleic anhydride, acrylic acid, hydroxyl groups, carboxyl groups and the like, and then polymerizing or copolymerizing the modified monomers alone. It may also be referred to as the polyolefin resin b obtained by first polymerizing or copolymerizing ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene and the like alone and monomers of some cycloolefins, and then modifying the resultant resin with one or more of polar groups such as maleic anhydride, acrylic acid, hydroxyl group and carboxyl group.
In some embodiments, the polyolefin resin comprises ethylene-vinyl acetate copolymer (EVA), polybutadiene rubber (BR), polyisobutylene, amorphous poly-alpha-olefin resin (APAO), acrylic modified polyolefin, poly (ethylene-chlorotrifluoroethylene) (ECTEE), ethylene-propylene acetate copolymer (EEA), ethylene-propylene copolymer (EPM), ethylene Propylene Diene Monomer (EPDM), ethylene Propylene Rubber (EPR), ethylene-propylene-styrene-acrylonitrile copolymer (EPSAN), ethylene Propylene Terpolymer (EPT), vinyl ethyl ether (EVE), isobutylene-isoprene rubber (IIR), isoprene Rubber (IR), maleic anhydride modified polyolefin (Ma-APAO), modified polypropylene (M-PP), modified polyphenylene oxide (MPPO), modified Polystyrene (MPS), styrene-methyl methacrylate resin (MS), nitrile rubber (NBR), hydrogenated nitrile rubber (HNMBR), polybutadiene-acrylonitrile (PBAN), propylene-butadiene rubber (PBR), poly (butadiene-styrene) (PBS), styrene-ethylene-butadiene-styrene copolymer (SEBS), styrene-isoprene-styrene copolymer (SBS), styrene-block copolymer (SBS), solid styrene-butadiene rubber (SBR), styrene-maleic anhydride copolymer (SMA), synthetic Polyolefin Rubber (SPR), syndiotactic polystyrene (SPP), polyolefin elastomer, olefin block copolymer, polymerized polyolefin copolymer such as one or more of ethylene acrylic acid copolymer (EAA), polyvinyl alcohol (PVA).
In some embodiments, the polyolefin resin is present in an amount of 50% to 95% by mass and the tackifying resin is present in an amount of 5% to 50% by mass, based on 100% by mass of the total of the polyolefin resin and the tackifying resin.
The mass content of the polyolefin resin is 50-95%, the content of the polyolefin resin is higher than that of the tackifying resin, the cohesive force of the adhesive can be improved, and the adhesive is ensured to have good mechanical property, electrolyte corrosion resistance and chemical stability. Specifically, the mass content of the polyolefin resin may be 50%, 55%, 60%, 64%, 70%, 75%, 80%, 85%, 90%, 95%, etc., as long as the mass content of the polyolefin resin is in the range of 50% to 95%. If the mass content of the polyolefin resin is higher than 95%, the swelling rate of the adhesive is increased, and the adhesive force of the adhesive is greatly reduced; if the mass content of the polyolefin resin is less than 50%, although the binding power of the binder increases, the swelling ratio of the binder increases greatly, and the electrolyte corrosion resistance of the binder is lowered, thereby lowering the electrical performance of the battery.
The mass content of the tackifying resin is 5-50%, and the addition of the tackifying resin can improve the wettability and initial adhesion performance of the adhesive, has good compatibility with polyolefin resin, and can greatly improve the adhesion of the adhesive to a metal substrate. The mass content of the tackifying resin may be 5%, 10%, 15%, 20%, 25%, 30%, 34%, 36%, 40%, 45%, 50%, etc., as long as the mass content of the tackifying resin is between 5% and 50%.
In some preferred embodiments, the alkane solvent comprises one or more of n-heptane, cyclohexane, isooctane, dodecane, white oil, D40 solvent oil, D30 solvent oil, D80 solvent oil, 150# solvent oil, 200# solvent oil, 6# solvent oil;
The boiling point temperature of the alkane solvent is 80-350 ℃.
The solvent has the function of dissolving the polyolefin resin and the tackifying resin, and simultaneously has the function of dispersing the positive electrode active material and the conductive agent in the preparation process of the positive electrode slurry; and the prepared positive electrode slurry can be well coated on the surface of a current collector to obtain a positive electrode coating layer, the alkane solvent also has the characteristic of easy volatilization in the drying process of the positive electrode coating layer, the alkane solvent is easy to volatilize from the coating layer in the drying process, and the dried positive electrode sheet is rolled and not stuck to a roller, so that the water content of the sheet meets the technological requirement. The alkane solvent provided by the application can replace NMP and can be well coated on the surface of a current collector; the boiling point temperature of the alkane solvent is in the range of 80-350 ℃, the alkane solvent is easy to volatilize when the coating layer is dried, the dried pole piece is not stuck to a roller, and the water content of the pole piece can meet the process requirement.
In some preferred embodiments, the alkane solvent has a boiling temperature of 150 ℃ to 250 ℃.
In some preferred embodiments, the polyolefin resin is present in an amount of 50% to 90% by mass and the tackifying resin is present in an amount of 10% to 50% by mass, based on 100% by mass of the total of the polyolefin resin and the tackifying resin; further preferably, the polyolefin resin has a mass content of 60 to 80% and the tackifying resin has a mass content of 20 to 40%.
In the preferable range, the tackifying resin and the polyolefin resin have good compatibility, the cohesive force of the adhesive is synergistically improved, and the adhesive is ensured to have good mechanical property, electrolyte corrosion resistance and chemical stability.
In some embodiments, the alkane solvent is 60% to 80% by mass and the polyolefin resin and tackifying resin are 20% to 40% by mass, based on 100% by mass of the binder.
The mass ratio of the alkane solvent is between 60% and 80%, and the content of the alkane solvent is high, so that the polyolefin resin and the tackifying resin can be dissolved conveniently. If the mass ratio of the alkane solvent is less than 60%, the viscosity of the binder is greatly increased, which affects the dispersion of particles such as the positive electrode active material and the conductive agent, and reduces the coating quality, thereby affecting the electrical performance of the battery. If the mass ratio of the alkane solvent is higher than 80%, the viscosity of the binder is too low, increasing the transportation cost of the binder.
In some embodiments, the tackifying resin comprises one or more of a natural resin and a synthetic resin;
the natural resin comprises one or more of rosin resin and rosin derivative resin.
The natural resin may be a rosin resin or a rosin derivative resin alone or a mixture of a rosin resin and a rosin derivative resin.
The synthetic resin comprises one or more of hydrogenated rosin resin, terpene resin, petroleum resin, coumarone-indene resin, styrene resin and condensation resin. For example, the petroleum resin may be selected from C5 hydrogenated petroleum resins, C9 hydrogenated petroleum resins, and the like.
The tackifying resin can improve the viscosity, especially the small molecular compound with the surface viscosity, has higher glass transition temperature, and can improve the wetting property and the initial adhesion property. The tackifying resin not only has good compatibility with polyolefin main body resin, but also can greatly improve the adhesion to metal substrates.
In a second aspect, the present application provides a method for preparing a binder for a positive electrode sheet, comprising the steps of:
Adding an alkane solvent, polyolefin resin and tackifying resin into a stirring container, gradually heating to 50-200 ℃, stirring for 0.5-4 h, stirring and mixing uniformly, and filtering to obtain the adhesive.
The stirring temperature is selected appropriately according to the specific type of the alkane solvent to be added, and the stirring temperature is required to be lower than the boiling point temperature of the alkane solvent.
The preparation method of the adhesive for the positive plate provided by the application has the advantages of simple process, no NMP, low toxicity to human body, safety guarantee for workers and capability of industrial production.
In a third aspect, the application provides a positive plate, which comprises a current collector and a positive electrode material layer, wherein the positive electrode material layer comprises a positive electrode active material, a conductive agent and a binder, and the binder is the binder for the positive plate or the binder for the positive plate, and is prepared by the preparation method.
The current collector is made of metal material, such as copper, aluminum, nickel and the like. The positive electrode active material may be lithium cobaltate, lithium manganate, lithium nickel cobalt manganate, lithium iron phosphate, a sodium-containing transition metal material, a sodium-containing oxide, a sodium-containing phosphate, or the like.
The positive plate provided by the application does not use an organic solvent NMP, uses the positive active material, the conductive agent and the binder provided by the application to prepare positive slurry by mixing and stirring, and then coats the positive slurry on the surface of a current collector and dries to obtain the positive plate. Compared with the prior art, the positive plate provided by the application does not use NMP solvent, so that the safety of personnel is improved, the binder has higher binding power, the binding power of the positive active material layer and the current collector can be improved, and the swelling rate is lower. After the positive plate is soaked in the electrolyte, the positive plate basically does not fall off, and the electrical property and the safety property of the battery are ensured.
In a fourth aspect, the application provides a secondary battery, comprising a positive plate, a negative plate, a diaphragm and electrolyte, wherein the positive plate comprises the positive plate.
The secondary battery provided by the application uses the positive plate, so that the binding force between the positive electrode material layer and the current collector is improved, and the electrolyte corrosion resistance is improved, and meanwhile, the electric performance and the safety performance of the battery are not influenced.
The invention is further illustrated by the following examples.
Example 1
The embodiment is used for explaining a preparation method of the adhesive for the positive plate, which comprises the following steps:
700 g of solvent oil D80, 200 g of styrene-ethylene-butadiene-styrene block copolymer (SEBS) and 50g of maleic anhydride modified polyolefin are added into a stirring kettle, 50g of tackifying resin adopts C5 hydrogenated petroleum resin, the temperature is gradually increased to 80 ℃, stirring is carried out for 4 hours, a transparent uniform solution is formed after full stirring, and a binder is obtained after filtering.
Example 2
800 G of n-heptane, 100 g of polyisobutene, 60 g of ethylene acrylic acid copolymer and 40 g of terpene resin are added into a stirring kettle, gradually heated to 80 ℃, stirred for 3 hours, fully stirred to form transparent and uniform solution, and filtered to obtain the adhesive.
Example 3
800 G of 200# solvent oil, 150 g of amorphous poly alpha olefin resin, 60 g of ethylene acrylic acid copolymer and 40 g of terpene resin are added into a stirring kettle, gradually heated to 80 ℃, stirred for 4 hours, fully stirred to form transparent and uniform solution, and filtered to obtain the adhesive.
Example 4
800 G of No. 6 solvent oil, 50g of hydrogenated nitrile rubber, 100 g of ethylene acrylic acid terpolymer and 20 g of hydrogenated C9 petroleum resin are added into a stirring kettle, gradually heated to 80 ℃, stirred for 0.5h, fully stirred to form transparent and uniform solution, and filtered to obtain the adhesive.
Example 5
Example 5 differs from example 4 in that 120 grams of ethylene acrylic acid terpolymer was added; namely, the ratio of polyolefin resin a to polyolefin resin b is 0.417:1; the remainder was the same as the preparation method of example 4.
Example 6
Example 6 example 4 differs in that 12 grams of ethylene acrylic acid terpolymer was added; namely, the ratio of polyolefin resin a to polyolefin resin b is 4.167:1; the remainder was the same as the preparation method of example 4.
Example 7
Example 7 is different from example 1 in that the added tackifying resin C5 hydrogenated petroleum resin has a mass of 15g, the total mass of polyolefin resin and tackifying resin is 100, and the mass ratio of polyolefin resin is 94.34%; the remainder was the same as the preparation method of example 1.
Example 8
Example 8 differs from example 1 in that the added tackifying resin C5 hydrogenated petroleum resin has a mass of 210g; the total mass of the polyolefin resin and the tackifying resin is 100 percent, and the mass ratio of the polyolefin resin is 54.35 percent; the remainder was the same as the preparation method of example 1.
Example 9
Example 9 differs from example 1 in that the added tackifying resin C5 hydrogenated petroleum resin has a mass of 10g; the total mass of the polyolefin resin and the tackifying resin is 100 percent, and the mass ratio of the polyolefin resin is 96.15 percent; the remainder was the same as the preparation method of example 1.
Example 10
Example 10 differs from example 2 in that the mass of the terpene resin of the tackifying resin added is 200g; the total mass of the polyolefin resin and the tackifying resin is 100 percent, and the mass ratio of the polyolefin resin is 44.44 percent; the remainder was the same as the preparation method of example 1.
The adhesive prepared in examples 1 to 10 was used to prepare a positive electrode sheet, and the peel strength of the positive electrode sheet was measured to evaluate the adhesive property of the adhesive.
Preparation of a positive plate: mixing ternary positive active material nickel cobalt lithium manganate, conductive carbon black and the binder prepared in examples 1-10 according to the mass ratio of 94:3:2, dispersing to obtain positive electrode slurry, uniformly coating the positive electrode slurry on two sides of an aluminum foil, drying, calendaring and vacuum drying, welding an aluminum outgoing line by an ultrasonic welding machine to obtain a positive plate, and controlling the compaction density of the positive electrode material through the surface density and the rolling thickness of the positive electrode material to obtain the positive plate with the thickness of 123 mu m. The positive electrode sheets prepared in examples 1 to 10 correspond to the numbers S1 to S10.
Comparative example 1
Preparation of a positive plate: dispersing ternary positive active material nickel cobalt lithium manganate, conductive carbon black and binder PVDF into solvent NMP according to the mass ratio of 94:3:2, stirring and dispersing uniformly to obtain positive slurry, uniformly coating the positive slurry on two sides of an aluminum foil, drying, calendaring and vacuum drying, welding an aluminum outgoing line by an ultrasonic welding machine to obtain a positive plate, and controlling the compaction density of the positive material through the surface density and the rolling thickness of the positive material to obtain the positive plate with the thickness of 123 mu m. The positive electrode sheet prepared in comparative example 1 corresponds to the number D1.
Preparing a negative electrode sheet:
Mixing artificial graphite, conductive carbon black, a binder styrene-butadiene rubber and carboxymethyl cellulose according to the mass ratio of 94:1.2:2.7:2.0, dispersing in deionized water to obtain negative electrode slurry, coating the negative electrode slurry on two sides of a copper foil, drying, calendaring and vacuum drying, welding a nickel lead-out wire by an ultrasonic welder to obtain a negative electrode plate, and controlling the compaction density of a negative electrode material layer through the surface density and the rolling thickness of the negative electrode material to obtain a negative electrode plate with the thickness of 112 mu m.
Preparation of a lithium ion battery:
And respectively winding or laminating the S1-S10 positive plate and the D1 positive plate with the negative plate and the diaphragm to obtain a battery cell, carrying out a hot pressing process at the temperature of more than 80 ℃, packaging the battery cell, putting the battery cell into an aluminum plastic film, and then carrying out a tab welding process and a liquid injection process to prepare the battery. Wherein the electrolyte is vinylene carbonate: diethyl carbonate: the volume ratio of ethylene carbonate is 1:1:1, lithium hexafluorophosphate is 1mol/L, and electrolyte with film forming additives such as carbonic ester and the like is added, and is mainly purchased through the market.
Adhesive evaluation experiment:
1) And (3) testing the peel strength of the positive electrode plate:
Cutting the rolled S1-S10 positive plate and D1 positive plate into test samples with the size of 25 multiplied by 200mm, using a KT-PSA-1056 peeling force tester, and using a VHB adhesive tape as the pressure sensitive adhesive. The adhesive tape was fixed on a test bench in advance, the adhesive tape was stuck on one side of the positive electrode material, then the stress at the time of peeling was measured by stretching one end of the pole piece vertically upward at a stretching speed of 50mm/min, the displacement and the acting force during the process were recorded, the peeling strength was calculated, and the test results were shown in table 1.
2) Battery performance test
Examples and comparative examples the following battery performance tests were performed:
25 ℃ cycle test
The battery was charged to 4.2V at a constant current and constant voltage of 1C, the off current was 0.05C, and then the 1C constant current was discharged to 3.0V, and the charge and discharge cycles were repeated for 400 weeks, and the cycle capacity retention rate was calculated, and the cycle capacity retention rate (%) =400-week discharge capacity per the test cycle/average value of the discharge capacity of the previous 3 cycles×100%.
3) Swelling ratio test
Taking 100g of the positive electrode adhesive prepared in the examples 1-10, respectively placing the positive electrode adhesive in PTFE boxes with 50mm and 100mm sizes, drying the positive electrode adhesive in an oven until the weight is constant to obtain adhesive films, respectively cutting the adhesive films corresponding to the examples 1-10 into at least five samples with the same size and shape, and respectively measuring the average weight W1 of each sample; then, respectively soaking each sample in electrolyte, and placing the electrolyte in an environment of 65 ℃; after 7 days of soaking, the sample was taken out and the electrolyte on the surface of the sample was blotted, and the weight W2 of each sample was measured.
The swelling ratio = (W2-W1)/W1 is calculated as 100%.
Dissolving the binder PVDF of the comparative example 1 in NMP solvent, respectively placing the solvent in PTFE boxes with the size of 50mm and 100mm, drying the solvent in an oven until the weight is constant to obtain adhesive films, respectively cutting the adhesive films corresponding to the comparative example 1 into at least five samples with the same size and shape, and respectively measuring the average weight W3 of each sample; then, respectively soaking each sample in electrolyte, and placing the electrolyte in an environment of 65 ℃; after 7 days of soaking, the sample was taken out and the electrolyte on the surface of the sample was blotted, and the weight W4 of each sample was measured.
The swelling ratio = (W4-W3)/W3 is calculated as 100%.
Wherein the total weight of PVDF and NMP was 100g, and the solid content thereof was the same as that of the positive electrode binder of example 1.
The specific test results are shown in Table 1.
Table 1 results of performance tests of examples and comparative examples
As shown in table 1, compared with the positive plate prepared by the existing PVDF binder in comparative example 1, the positive plates prepared in examples 1-4 and 7-8 have generally higher peel strength and higher swelling rate of the binder than those of comparative example 1 after rolling, and the normal temperature cycle capacity retention rate of the prepared battery is not reduced; the positive plate adhesive provided by the application has the advantages of strong binding power, low swelling rate, electrolyte corrosion resistance, good thermal stability and oxidation-reduction resistance in electrolyte, and no influence on the electrical performance of a battery. In comparison of examples 4 and 5, the mass ratio of polyolefin resin a to polyolefin resin b in example 5 was 0.42, which was lower than 0.5, and the peel strength of the positive electrode sheet prepared was reduced; in comparison of examples 4 and 6, the mass ratio of polyolefin resin a to polyolefin resin b was 4.17, which was higher than 4.0, the swelling ratio of the adhesive was increased and the peel strength was decreased; it is presumed that the mass ratio of the polyolefin resin a to the polyolefin resin b is lower than 0.5, which reduces the adhesive force of the adhesive, and the mass ratio of the polyolefin resin a to the polyolefin resin b is higher than 4.0, which reduces the adhesive force and electrolyte resistance of the adhesive.
When the total mass of the polyolefin resin and the tackifying resin is 100%, compared with the example 1 and the example 9, the polyolefin resin accounts for more than 95%, the peel strength of the pole piece is reduced, the swelling rate is increased, and the cohesive force is greatly reduced; in comparison of example 1 with example 10, the polyolefin resin mass ratio was less than 50%, and the swelling ratio was greatly increased; the adhesive for the positive plate provided by the application has the advantages that when the total mass of the polyolefin resin and the tackifying resin is 100%, the mass ratio of the polyolefin resin is 50% -95%, the tackifying resin is 5% -50%, the swelling rate of the adhesive is low, and the adhesive force is strong.
From the comparison of the data of examples 1-4, polyolefin resin a: the mass ratio of the polyolefin resin b is between 0.5 and 2.5, the swelling rate is lower, the peeling strength is higher, and the cohesive force of the adhesive is stronger.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims (10)

1. A binder for a positive electrode sheet, which comprises a polyolefin resin, a tackifying resin and an alkane solvent.
2. The binder for a positive electrode sheet according to claim 1, wherein the polyolefin resin comprises a polyolefin resin a and a polyolefin resin b, the polyolefin resin a being an olefin polymer not modified with a functional group, the polyolefin resin b being a modified olefin polymer;
the polyolefin resin b is obtained by modifying one or more of maleic anhydride, acrylic acid, a compound containing carboxyl and a compound containing hydroxyl;
the mass ratio of the polyolefin resin a to the polyolefin resin b is (0.5-4): 1.
3. The binder for positive electrode sheet according to claim 2, wherein the olefin polymer is polymerized from olefin monomers including one or more of alpha olefins, cycloolefins, and aromatic hydrocarbons; the alpha olefin comprises one or more of ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 1, 3-butadiene and isobutene.
4. The adhesive for positive electrode sheets according to claim 1, wherein the polyolefin resin comprises one or more of ethylene-vinyl acetate copolymer, polybutadiene rubber, polyisobutylene, amorphous poly- α -olefin resin, acrylic acid modified polyolefin, poly (ethylene-chlorotrifluoroethylene), ethylene-propylene acetate copolymer, ethylene-propylene diene rubber, ethylene propylene rubber, ethylene-propylene-styrene-acrylonitrile copolymer, ethylene propylene terpolymer, vinyl ethyl ether, isobutylene-isoprene rubber, maleic anhydride modified polyolefin, modified polypropylene, modified polyphenylene ether, modified polystyrene, styrene-methyl methacrylate resin, nitrile rubber, hydrogenated nitrile rubber, polybutadiene-acrylonitrile, propylene-butadiene rubber, poly (butadiene-styrene), styrene-ethylene-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, solid styrene-butadiene rubber, styrene-maleic anhydride copolymer, synthetic polyolefin rubber, syndiotactic polystyrene, polyolefin elastomer, olefin block copolymer, and polyolefin-based copolymer after polymerization.
5. The adhesive for positive electrode sheets according to claim 1, wherein the mass content of the polyolefin resin is 50% to 95% and the mass content of the tackifying resin is 5% to 50% based on 100% of the total mass of the polyolefin resin and the tackifying resin;
the mass ratio of the alkane solvent is 60-80% and the mass ratio of the polyolefin resin and the tackifying resin is 20-40% based on 100% of the mass of the binder.
6. The binder for a positive electrode sheet according to claim 1, wherein the tackifying resin comprises one or more of a natural resin and a synthetic resin;
the natural resin comprises one or more of rosin resin and rosin derivative resin;
The synthetic resin comprises one or more of hydrogenated rosin resin, terpene resin, petroleum resin, coumarone-indene resin, styrene resin and condensation resin.
7. The binder for positive electrode sheets according to claim 1, wherein the alkane solvent comprises one or more of n-heptane, cyclohexane, isooctane, dodecane, white oil, D40 solvent oil, D30 solvent oil, D80 solvent oil, 150# solvent oil, 200# solvent oil, 6# solvent oil;
The boiling point temperature of the alkane solvent is 80-350 ℃.
8. A method for preparing the adhesive for a positive electrode sheet according to any one of claims 1 to 7, comprising the steps of:
Adding an alkane solvent, polyolefin resin and tackifying resin into a stirring container, gradually heating to 50-200 ℃, stirring for 0.5-4 h, stirring and mixing uniformly, and filtering to obtain the adhesive.
9. The positive plate is characterized by comprising a current collector and a positive electrode material layer, wherein the positive electrode material layer comprises a positive electrode active material, a conductive agent and a binder, and the binder is prepared by the binder for the positive plate according to any one of claims 1-7 or the binder for the positive plate according to claim 8.
10. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, the positive electrode sheet comprising the positive electrode sheet according to claim 9.
CN202211457254.7A 2022-11-21 2022-11-21 Adhesive for positive plate, preparation method of adhesive, positive plate and secondary battery Pending CN118099424A (en)

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