CN115216245A - Binder, battery pole piece, preparation method of battery pole piece and secondary battery - Google Patents

Binder, battery pole piece, preparation method of battery pole piece and secondary battery Download PDF

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Publication number
CN115216245A
CN115216245A CN202110404761.3A CN202110404761A CN115216245A CN 115216245 A CN115216245 A CN 115216245A CN 202110404761 A CN202110404761 A CN 202110404761A CN 115216245 A CN115216245 A CN 115216245A
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pole piece
conductive
binder
battery pole
polymer
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占莎
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Evergrande New Energy Technology Shenzhen Co Ltd
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Evergrande New Energy Technology Shenzhen Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J9/00—Adhesives characterised by their physical nature or the effects produced, e.g. glue sticks
    • C09J9/02—Electrically-conducting adhesives
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J127/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers
    • C09J127/02—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers not modified by chemical after-treatment
    • C09J127/12—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
    • C09J127/16—Homopolymers or copolymers of vinylidene fluoride
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J165/00—Adhesives based on macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain; Adhesives based on derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J179/00—Adhesives based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen, with or without oxygen, or carbon only, not provided for in groups C09J161/00 - C09J177/00
    • C09J179/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • C09J179/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2201/00—Properties
    • C08L2201/04—Antistatic
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2203/00—Applications
    • C08L2203/20—Applications use in electrical or conductive gadgets
    • C08L2203/206—Applications use in electrical or conductive gadgets use in coating or encapsulating of electronic parts
    • 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 batteries, and particularly relates to a binder, a battery pole piece and a preparation method thereof, and a secondary battery. Wherein, the binder includes: a polymer binder and a conductive polymer, wherein the conductive polymerAt least one substance selected from formula I and formula II:

Description

Binder, battery pole piece, preparation method of battery pole piece and secondary battery
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a binder, a battery pole piece and a preparation method thereof, and a secondary battery.
Background
Lithium ion batteries have become the main power source of electric vehicles due to their performance advantages, and as an energy storage device, they are mainly composed of an anode, a cathode, a separator, an electrolyte, and the like. The improvement of the endurance mileage of the electric automobile drives the improvement of the energy density of the battery core, and the positive and negative electrode materials play a vital role in the energy density and other electrical properties of the battery core. The theoretical specific capacity of the current commercialized negative electrode graphite material is 372mAh/g, which hinders the improvement of the cell energy density. Therefore, the silicon negative electrode material enters the visual field of people, the theoretical specific capacity of the silicon negative electrode material is up to 4200mAh/g, and the silicon negative electrode material is considered as an alternative product of the graphite negative electrode material and has important application prospect. However, in the process of lithium ion intercalation and deintercalation of the silicon negative electrode, the volume expansion of the silicon negative electrode reaches 100% -300%, so that material particles are crushed and pole pieces are pulverized, and the pole pieces cause the rapid reduction of electrical property, so that the cycle performance is poor. At present, one of the important methods for inhibiting the volume expansion of the silicon-based material is to reduce the deformation of a pole piece through the bonding performance of an adhesive and prevent powder falling and the like. The common binders include polyacrylic acid, CMC/SBR, sodium alginate, chitosan, polyimide and the like, the adhesion performance of the binders needs to be further improved, the binders are easy to be separated from a system in the repeated expansion and contraction process of silicon, the integrity of the whole conductive system is damaged, the problems of disconnection of a conductive path, pole piece differentiation and the like are caused, and the cycle performance of the silicon-based battery is greatly reduced.
Therefore, a proper adhesive needs to be developed to solve the problems of the disconnection of a conductive path and the differentiation of a pole piece caused by the cyclic expansion and contraction process of the silicon negative electrode and improve the cycle performance of the silicon negative electrode.
Disclosure of Invention
The invention aims to provide a binder, a battery pole piece and a preparation method thereof, and a secondary battery, aiming at solving the problems that the traditional battery pole piece such as a silicon-based negative electrode is easy to cause the disconnection of a conductive path and the differentiation of the pole piece in the cyclic expansion and shrinkage process.
In order to achieve the purpose of the application, the technical scheme adopted by the invention is as follows:
in a first aspect, the present invention provides an adhesive, comprising: the conductive polymer is selected from at least one of the substances in the formulas I and II:
Figure BDA0003021815220000021
wherein Ar1 and Ar2 are respectively and independently selected from aromatic groups, R1 and R2 are respectively and independently selected from: H. one of alkyl and alkoxy, n is an integer of 100 to 1000, and m is an integer of 100 to 1000.
The adhesive provided by the first aspect of the invention comprises a high-molecular adhesive material and a conductive polymer, wherein the conductive polymer is a polymer of which the main chain contains aromatic rings such as pyrrolidine dione or fluorene, so that the conductive polymer has certain adhesive property, and the aromatic rings on the main chain have conjugated large pi bonds, so that the polymer has conductive property. On one hand, the electronic conductivity among active materials in the electrode plate is improved, and on the other hand, the influence of volume expansion and contraction of electrode active materials such as silicon on the integrity of a conductive path of the electrode plate in the cyclic charge-discharge process is improved, so that the cyclic stability of the battery electrode plate is improved. In addition, the polymer binding material has excellent binding performance, has strong binding force with an electrode active substance and a current collector, can improve the stability of the pole piece, and can reduce the phenomena of pulverization, powder falling and the like of the pole piece in the cyclic charge-discharge process.
Further, ar1 and Ar2 are respectively and independently selected from the group consisting of: the aromatic groups all have large conjugated pi bonds, so that the conductivity of the polymer can be better improved.
Further, in the substituted phenyl, substituted biphenyl and substituted diphenyl ether, the substituents are respectively and independently selected from: at least one of alkyl and alkoxy. Further, in substituted phenyl, substituted biphenyl, substituted diphenyl ether, the substitution pattern includes mono-substitution or poly-substitution. The substituent groups such as alkyl, alkoxy and the like can be mono-substituted or polysubstituted at any position of Ar1 and Ar2, and the bonding property of the conductive polymer is improved by the substitution of the alkyl or the alkoxy, so that the volume expansion of the active substance in the electrode slice is better inhibited
Further, the conductive polymer is selected from: at least one of a copolyimide polymer of pyromellitic dianhydride and p-phenylenediamine, a copolyimide polymer of pyromellitic dianhydride and oxydianiline, and a polyfluorene polymer, and the conductive polymers simultaneously have good adhesive property and excellent electric conductivity.
Further, the polymeric binder material is selected from: the adhesive is at least one of polyvinylidene fluoride, sodium methylcellulose, styrene butadiene rubber, ethyl cellulose, polyacrylic acid, polyacrylonitrile, polyacrylate and sodium alginate, and the high-molecular adhesives have excellent adhesive property and stable viscosity and can provide stable viscosity and adhesive force for adhesion.
Further, the mass ratio of the high-molecular binding material to the conductive polymer is 1: (1-4), the proportion integrates the bonding strength and the conductivity of the binder.
In a second aspect, the present invention provides a battery plate, comprising: a positive electrode active material or a negative electrode active material, a conductive agent, and the above binder.
The battery pole piece provided by the second aspect of the invention comprises a positive electrode active material or a negative electrode active material, a conductive agent and the binder which has excellent adhesive property and conductive property, wherein the binder has good adhesive property, can perform dispersing, thickening and anti-settling effects on the electrode active material and the conductive agent, can improve the electronic conductivity between the active materials in the pole piece, and can improve the influence of volume expansion and shrinkage of the electrode active material such as silicon on the integrity of a conductive path of the pole piece in the cyclic charge-discharge process. Therefore, the battery pole piece and the current collector in the embodiment of the invention have strong bonding force and good pole piece circulation stability.
Furthermore, in the battery pole piece, the content of the binder is 1-10%; the content of the conductive agent is 0.5 to 10 percent; if the content of the conductive agent is too small, the resistance of the electrode plate is too large; if the content of the conductive agent is too large, the capacity of the pole piece is reduced, and the capacity of the battery cell is influenced.
Further, the conductive agent includes: the conductive agent is at least one of conductive carbon black, ketjen black, conductive carbon nanotube and conductive carbon fiber, and the conductive agent has excellent conductivity, so that the conductivity of the pole piece can be remarkably improved.
Further, the battery pole piece is a positive pole piece, and comprises: the cathode material comprises at least one cathode active material selected from nickel-cobalt-manganese ternary material, nickel-cobalt-manganese-aluminum quaternary material, nickel-cobalt-aluminum ternary material, lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate and lithium manganate, and the cathode materials have good electrochemical performance.
Further, the battery pole piece is a negative pole piece, and comprises: si, siO 2 At least one silicon-based anode active material, the silicon-based active material having a high gram capacity.
Further, the compaction density of the negative plate is 1.50-1.85g/cm 3 (ii) a The compacted density of the positive plate is 3.2-3.8 g/cm 3 The compaction density of the battery pole piece not only ensures the energy density of the pole piece, but also avoids the overlarge volume expansion rebound of the pole piece during charging and discharging caused by overlarge pole piece compaction.
Further, the negative plate also comprises a carbon material, and the mass ratio of the carbon material to the silicon-based negative active material is (80-95): (5-20), the graphite material with small volume expansion and the silicon-based negative electrode material are compounded in the proportion, so that the volume expansion of the pole piece is reduced, and the stability of the pole piece is improved.
In a third aspect, the present invention provides a method for preparing the battery pole piece, including the steps of: and dispersing the positive electrode active material or the negative electrode active material, the conductive agent and the binder in a solvent to form electrode slurry, coating or depositing the electrode slurry on a current collector, and drying to obtain the battery pole piece.
According to the preparation method of the battery pole piece provided by the third aspect of the invention, the positive pole active material or the negative pole active material, the conductive agent and the binder are dispersed in the solvent to form the electrode slurry, and then the electrode slurry is coated or deposited on the current collector, and the negative pole piece or the positive pole piece can be obtained through drying and rolling. And the prepared battery pole piece contains the binder with excellent adhesive property and conductivity, so that the adhesive force between the electrode slurry and the current collector is strong, the electronic conductivity between active materials in the electrode piece can be improved, and the integrity of a conductive path is improved.
In a fourth aspect, the invention provides a secondary battery, which comprises the battery pole piece, or comprises the battery pole piece prepared by the method.
The secondary battery provided by the fourth aspect of the present invention has a long service life and high safety because it includes the positive electrode sheet or the negative electrode sheet having a high gram capacity, good cycle stability, and excellent conductivity.
Detailed Description
In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the present invention, the term "and/or" describes the association relationship of the associated objects, which means that there may be three relationships, for example, a and/or B, which may mean: a is present alone, A and B are present simultaneously, and B is present alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.
In the present invention, "at least one" means one or more, "a plurality" means two or more. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, "at least one (one) of a, b, or c," or "at least one (one) of a, b, and c," may each represent: a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple respectively.
It should be understood that, in various embodiments of the present invention, the sequence numbers of the above-mentioned processes do not mean the execution sequence, some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The weight of the related components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present invention as long as it is in accordance with the description of the embodiments of the present invention. Specifically, the mass described in the description of the embodiments of the present invention may be a mass unit known in the chemical industry field, such as μ g, mg, g, and kg.
The terms "first" and "second" are used for descriptive purposes only and are used for distinguishing purposes such as substances from one another and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the invention. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.
A first aspect of embodiments of the present invention provides an adhesive, including: the conductive polymer is selected from at least one of the substances in the formula I and the formula II:
Figure BDA0003021815220000061
wherein Ar1 and Ar2 are respectively and independently selected from aromatic groups, and R1 and R2 are respectively and independently selected from aromatic groupsFrom: H. one of alkyl and alkoxy, n is an integer of 100 to 1000, and m is an integer of 100 to 1000.
The binder provided by the first aspect of the embodiment of the present invention includes a polymer binder material and a conductive polymer, wherein the conductive polymer is a polymer whose main chain contains aromatic rings such as pyrrolidinone or fluorene, so that the conductive polymer has a certain binding property, and the aromatic rings on the main chain have conjugated large pi bonds, so that the polymer has conductivity at the same time. On one hand, the electronic conductivity among active materials in the electrode plate is improved, and on the other hand, the influence of volume expansion and contraction of electrode active materials such as silicon on the integrity of a conductive path of the electrode plate in the cyclic charge-discharge process is improved, so that the cyclic stability of the battery electrode plate is improved. In addition, the polymer binding material has excellent binding performance, has strong binding force with an electrode active substance and a current collector, can improve the stability of the pole piece, and can reduce the phenomena of pulverization, powder falling and the like of the pole piece in the cyclic charge-discharge process.
In the formula I and the formula II of the conductive polymer in the embodiment of the invention, n is an integer of 100-1000, m is an integer of 100-1000, if n or m is too small, the polymerization degree of the conductive polymer is insufficient, and the bonding capability of the conductive polymer is influenced, and if n or m is too large, the molecular weight of the conductive polymer is too large, and the bonding performance is too large, so that the conductivity of the conductive adhesive is influenced, and the conductive adhesive is not favorable for being applied in the adhesive.
In some embodiments, the polymer binder and the conductive polymer in the binder according to embodiments of the present invention are mixed uniformly and applied to the electrode material.
In some embodiments, the conductive polymer is selected from at least one of formula I, formula II:
Figure BDA0003021815220000071
wherein Ar1 and Ar2 are respectively and independently selected from aromatic groups, and the aromatic groups are further introduced into the main chain of the formula I, so that the conductive polymer of the formula I has more conjugated pi bonds, and the conductivity of the polymer can be further improved. In addition, theIn formula II, R1 and R2 are independently selected from: H. the substituent can increase the molecular weight of the polymer, and the bonding performance of the polymer can be regulated and controlled by controlling the chain length of the introduced side chain alkyl or alkoxy. In some embodiments, the greater the molecular weight of the conductive polymer, the greater the adhesion properties.
In some embodiments, ar1, ar2 in the backbone of formula I are each independently selected from: the aromatic groups all have large conjugated pi bonds, so that the conductivity of the polymer can be better improved. When the adhesive is applied to the electrode plate, the influence of volume expansion and contraction on the integrity of a conductive path of the electrode plate caused by the electrode active materials such as silicon and the like in the cyclic charge-discharge process can be better improved, and a conductive path is formed among the electrode active materials.
In some embodiments, in the substituted phenyl, the substituted biphenyl, the substituted diphenyl ether, the substituents are each independently selected from: at least one of alkyl and alkoxy. In some embodiments, the substituted phenyl group, the substituted biphenyl group, and the substituted diphenyl ether have a single substitution or multiple substitutions, and the substitution position is not specifically limited in the embodiments of the present invention. When Ar1 and Ar2 aromatic groups are connected to the main chain of the formula I, substituent groups such as alkyl, alkoxy and the like can be subjected to single substitution or multiple substitution at any positions of Ar1 and Ar2, and the bonding property of the conductive polymer is improved through the substitution of the alkyl or the alkoxy, so that the volume expansion of active substances in the electrode slice is better inhibited.
In some embodiments, the carbon chain length of the substituent groups such as alkyl and alkoxy is preferably 1-8, and the substituent groups with the chain length can effectively improve the adhesive property of the conductive polymer and avoid the problems of excessive polymer molecular weight, excessive viscosity and difficult dispersion, which are not beneficial to the application in the electrode plate.
In some embodiments, the conductive polymer is selected from the group consisting of: the conductive polymer has good adhesion performance and excellent conductivity performance at the same time.
In some embodiments, the polymeric binder material is selected from: the adhesive is at least one of polyvinylidene fluoride, sodium methylcellulose, styrene butadiene rubber, ethyl cellulose, polyacrylic acid, polyacrylonitrile, polyacrylate and sodium alginate, and the high-molecular adhesives have excellent adhesive property and stable viscosity and can provide stable viscosity and adhesive force for adhesion. Meanwhile, when the binder is applied to the electrode plate, the high polymer binding materials also have the functions of dispersing, thickening and preventing sedimentation on the electrode active materials and the conductive agent; the processing performance of the electrode slurry is stabilized, the peel strength of the electrode plate is improved, and the like, so that the cycle performance of the battery is improved.
In some embodiments, in the binder, the mass ratio of the high molecular binder material to the conductive polymer is 1: (1-4), if the content of the high-molecular binding material in the binding agent is too low, the binding force of the binding agent is not enough, the binding performance of the binding agent on active substances and a conductive agent in a pole piece is not good after the binding agent is applied to the pole piece, the flexibility of the pole piece is poor, and the pole piece is too brittle; if the content of the conductive polymer in the binder is too low, the conductivity of the binder is poor, and after the binder is applied to an electrode plate, a conductive path is difficult to form between electrode active materials, so that the effect of improving the differentiation of the electrode plate caused by volume expansion and shrinkage is poor. In some embodiments, the mass ratio of the polymeric binder material to the conductive polymer may be 1: 1. 1.
A second aspect of the embodiments of the present invention provides a battery pole piece, which is characterized in that the battery pole piece includes: a positive electrode active material or a negative electrode active material, a conductive agent, and the above binder.
The battery pole piece provided by the second aspect of the embodiment of the invention comprises a positive electrode active material or a negative electrode active material, a conductive agent and the binder which has excellent adhesive property and conductive property, wherein the binder has good adhesive property, can perform dispersing action, thickening action and anti-settling action on the electrode active material and the conductive agent, can improve electronic conductivity among the active materials in the pole piece, and can improve the influence of volume expansion and shrinkage of the electrode active material such as silicon on the integrity of a conductive path of the pole piece in the cyclic charge-discharge process. Therefore, the battery pole piece and the current collector in the embodiment of the invention have strong bonding force and good pole piece circulation stability.
In some embodiments, the content of the binder in the battery pole piece is 1-10%; the content of the conductive agent is 0.5-10%. In the battery pole piece provided by the embodiment of the invention, the conductive agent can obviously improve the conductivity of the pole piece, and if the content of the conductive agent is too small, the resistance of the pole piece is too large; if the content of the conductive agent is too large, the capacity of the pole piece is reduced, and the capacity of the battery cell is influenced. The content of the binder in the battery pole piece effectively ensures the stability and the conductivity of the pole piece, and if the content of the binder is too small, the binding strength is too low, and the effect of inhibiting the volume expansion of the pole piece is poor; if the content of the binder is too large, lithium ion transmission and electrical property in the pole piece are affected. In some embodiments, the binder content in the battery pole piece may be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or the like, and the conductive agent content may be 0.5%, 2%, 4%, 6%, 8%, 10%, or the like.
In some embodiments, the conductive agent comprises: the conductive agent is at least one of conductive carbon black, ketjen black, conductive carbon nanotube and conductive carbon fiber, and the conductive agent has excellent conductivity, so that the conductivity of the pole piece can be remarkably improved.
In some embodiments, the battery pole piece is a positive pole piece, comprising: the cathode material comprises at least one cathode active material of cathode materials such as Nickel Cobalt Manganese (NCM) ternary material, nickel Cobalt Manganese Aluminum (NCMA) quaternary material, nickel Cobalt Aluminum (NCA) ternary material, lithium iron phosphate (LFP) lithium manganese phosphate (LFMP), lithium Cobaltate (LCO), lithium Manganate (LMO) and the like, and the cathode materials have good electrochemical performance. The battery pole piece in the embodiment of the invention is a positive pole piece, and the binder in the pole piece can effectively solve the problem that the capacity is rapidly reduced due to particle breakage in the cyclic charge-discharge process of nickel-cobalt-manganese ternary polycrystal and other positive pole materials. In some embodiments, the ratio of nickel, cobalt and manganese in the nickel, cobalt and manganese ternary material may be 424, 333, 523, 701, 515, etc.
In some embodiments, the battery pole piece is a negative pole piece, comprising: si, siO 2 The adhesive in the battery pole piece can effectively improve the influence of the volume expansion and contraction of the silicon-based active material on the integrity of a conductive path of the electrode piece in the cyclic charge-discharge process, and improve the electronic conductivity between the silicon-based active materials in the electrode piece.
In some embodiments, the negative electrode sheet has a compacted density of 1.50 to 1.85g/cm 3 (ii) a The compacted density of the positive plate is 3.2-3.8 g/cm 3 . The compaction density of the battery pole piece in the embodiment of the invention not only ensures the energy density of the pole piece, but also avoids the overlarge volume expansion rebound of the pole piece during charging and discharging caused by overlarge pole piece compaction. If the compaction density is too low, the thickness and the energy density of the battery cell are influenced, and the electrical property is not facilitated; if the compaction density is too high, the pole piece is over-pressed to cause low porosity, the electrical property and the cycle performance are influenced, and the volume expansion rebound is too large during charging and discharging.
In some embodiments, the negative electrode sheet further comprises a carbon material, and the mass ratio of the carbon material to the silicon-based negative electrode active material is (80-95): (5-20). In some embodiments, the carbon material includes graphite materials such as artificial graphite, natural graphite, and the like. In the negative plate of the embodiment of the invention, as the silicon-based negative active material has larger volume expansion compared with graphite materials, the thickness of the battery plate exceeds the standard, the volume energy density is reduced, and meanwhile, the negative active material is more easily dropped from a current collector due to the large volume expansion, so that the cycle performance of the battery is rapidly reduced, and the safety performance of the battery is not favorable. Therefore, the graphite material with small volume expansion and the silicon-based negative electrode material are used in a compounding way according to the proportion, so that the volume expansion of the pole piece is reduced, and the stability of the pole piece is improved. If the content of the silicon-based material in the negative plate is too low, the capacity of the negative plate is too low, and if the content of the silicon-based material is too high, the volume expansion rate of the negative plate is high, and the circulation stability is poor.
The electrode sheet of the embodiment of the present application can be manufactured by the following embodiment method.
The third aspect of the embodiments of the present invention provides a method for manufacturing the battery pole piece, including the steps of: and dispersing the positive electrode active material or the negative electrode active material, the conductive agent and the binder in a solvent to form electrode slurry, coating or depositing the electrode slurry on a current collector, and drying to obtain the battery pole piece.
According to the preparation method of the battery pole piece provided by the third aspect of the embodiment of the invention, the positive pole active material or the negative pole active material, the conductive agent and the binder are dispersed in the solvent to form the electrode slurry, and then the electrode slurry is coated or deposited on the current collector, and the negative pole piece or the positive pole piece can be obtained through drying and rolling. And the prepared battery pole piece contains the binder with excellent adhesive property and conductivity, so that the adhesive force between the electrode slurry and the current collector is strong, the electronic conductivity between active materials in the electrode piece can be improved, and the integrity of a conductive path is improved.
In some embodiments, the step of dispersing the positive or negative electrode active material, the conductive agent, and the binder in a solvent to form an electrode slurry includes:
dissolving a high-molecular adhesive material in a solvent, stirring at the rotating speed of 1000-3000rpm, adding a conductive polymer after uniformly stirring, controlling the solid content of a glue solution to be 10wt% (facilitating subsequent stirring and mixing), continuously stirring at the rotating speed of 2000-4000rpm for 30-60 minutes to uniformly disperse a conductive adhesive, and vacuumizing to remove bubbles to obtain the adhesive slurry. Then, the conductive agent is added and stirred at 2000-4000rpm for 1-2 hours. Then adding electrode active materials such as silicon-based powder and the like, stirring for 10-20 minutes at the rotating speed of 500-1000 rpm, then adding graphite powder material, and stirring for 10-30 minutes at the rotating speed of 500-1000 rpm. Then adding a proper amount of solvent, controlling the solid content of the slurry to be 50-70wt% (beneficial to subsequent stirring and mixing), continuously stirring for 1-2 hours at the rotating speed of 2000-4000rpm, adjusting the solid content to be 35-50wt%, and then stirring for 10-30 minutes at 500-1000 rpm, controlling the viscosity of the electrode slurry to be 3000-9000cps, wherein the excessive or insufficient viscosity of the slurry is not beneficial to the control of coating. The fineness of the slurry is controlled to be below 40um, the dispersion is insufficient due to the overlarge fineness, the coating is easy to block, and the coating precision is not easy to control. Vacuumizing to remove bubbles, and filtering by using a 150-mesh screen to obtain the electrode slurry.
In some embodiments, the electrode slurry which is uniformly and stably dispersed is deposited on the current collector by coating or the like, the coating speed can be 1-3 m/min, the moisture content in a coating workshop is lower than 10%, and the influence of moisture on the electrode plate slurry is avoided. And then drying the electrode plate at the temperature of 80-110 ℃, and rolling the dried electrode plate to obtain the stable battery electrode plate. The rolled pole piece can be manufactured into the size required by the design according to a set punching die.
In some embodiments, the solvent may be N-methylpyrrolidine (NMP), ketols, acetone, water, and the like. In the actual preparation process, a solvent with good solubility can be selected to prepare the electrode slurry according to the physical and chemical properties of the binder.
The fourth aspect of the embodiments of the present invention provides a secondary battery, where the secondary battery includes the above battery pole piece, or includes the battery pole piece prepared by the above method.
The secondary battery provided by the fourth aspect of the embodiment of the present invention includes the positive electrode tab or the negative electrode tab having a high gram capacity, good cycle stability, and excellent conductivity, and thus has a long service life and high safety.
In order to make the above implementation details and operations of the present invention clearly understood by those skilled in the art and obviously embody the advanced performance of the adhesive, the battery pole piece, the preparation method thereof and the secondary battery according to the embodiments of the present invention, the above technical solutions are exemplified by a plurality of embodiments below.
Example 1
Adhesive and bagThe mass ratio of the components is 1:1 PVDF high-molecular binder and copolyimide polymer conductive polymer:
Figure BDA0003021815220000121
wherein Ar1 and Ar2 have the structure
Figure BDA0003021815220000122
n is an integer of 100 to 1000.
A negative electrode sheet is prepared by the steps of:
(1) adding 2 parts of PVDF into a solvent NMP, stirring at the rotating speed of 2000rpm, adding 2 parts of conductive polymer after uniformly stirring, controlling the solid content of a glue solution to be 10wt%, continuously stirring at the rotating speed of 3000rpm for 40 minutes to uniformly disperse a conductive adhesive, and vacuumizing to remove bubbles to obtain an adhesive slurry.
(2) 2 parts of acetylene black is added into the adhesive slurry and stirred for 2 hours at the rotating speed of 3000rpm to obtain a conductive glue solution.
(3) Adding 14 parts of silicon powder material into the conductive glue solution, stirring for 10 minutes at the rotating speed of 500rpm, adding 80 parts of graphite powder material, stirring for 10 minutes at the rotating speed of 500rpm, then adding a proper amount of NMP solvent, controlling the solid content of the slurry to be 60wt%, continuously stirring for 2 hours at the rotating speed of 3000rpm, adding NMP to adjust the solid content to be 42wt%, stirring for 10 minutes at 500rpm, and controlling the viscosity of the negative electrode slurry to be 6000cps.
(4) And coating the slurry passing through the screen on a copper foil current collector for drying, wherein the temperature of an oven is 100 ℃, the coating speed is 2m/min, and the water content in a coating workshop is lower than 10%.
(5) Rolling the coated negative pole piece, and controlling the rolling density of the pole piece to be 1.70g/cm 3 And manufacturing the rolled pole piece into the size required by design according to a set punching die to obtain the negative pole piece.
A secondary battery is prepared by the procedures of laminating, packaging, injecting liquid, forming, aging, grading and the like of a negative plate, an NCM ternary positive material and a diaphragm together to obtain a soft package battery core. Wherein diaphragm thickness is 16um, and the thickness of encapsulation plastic-aluminum membrane is 152um.
Example 2
A binder comprising, in a mass ratio of 1:2 PVDF high-molecular binder material and copolyimide polymer conductive polymer:
Figure BDA0003021815220000131
wherein Ar1 has the structure
Figure BDA0003021815220000132
Ar2 has the structure
Figure BDA0003021815220000133
n is an integer of 100 to 1000.
A negative electrode sheet is prepared by the steps of:
(1) adding 1 part of PVDF into NMP (N-methyl pyrrolidone) as a solvent, stirring at the rotating speed of 2000rpm, adding 2 parts of conductive polymer after uniform stirring, controlling the solid content of glue solution to be 10wt%, continuously stirring at the rotating speed of 4000rpm for 30 minutes to uniformly disperse the conductive adhesive, and vacuumizing to remove bubbles to obtain adhesive slurry.
(2) 2 parts of acetylene black is added into the adhesive slurry and stirred for 1 hour at the rotating speed of 4000rpm, so as to obtain a conductive glue solution.
(3) Adding 15 parts of silicon powder material into the conductive glue solution, stirring for 10 minutes at the rotating speed of 500rpm, adding 80 parts of graphite powder material, stirring for 10 minutes at the rotating speed of 500rpm, then adding a proper amount of NMP solvent, controlling the solid content of the slurry to be 50wt%, continuously stirring for 1 hour at the rotating speed of 4000rpm, adding NMP to adjust the solid content to be 35wt%, stirring for 10 minutes at 500rpm, and controlling the viscosity of the negative electrode slurry to be 3000cps.
(4) And coating the slurry after passing through the screen on a copper foil current collector for drying, wherein the temperature of an oven is 80 ℃, the coating speed is 2m/min, and the water content in a coating workshop is lower than 10%.
(5) Rolling the coated negative pole piece, and controlling the rolling density of the pole piece to be 1.65g/cm 3 Manufacturing the rolled pole piece into the size required by the design according to a set punching die to obtain the negative pole piece。
A secondary battery is prepared by the steps of laminating a negative plate, an NCM ternary positive electrode material and a diaphragm, packaging, injecting liquid, forming, aging, grading and the like to obtain a soft package battery cell. Wherein diaphragm thickness is 16um, and the thickness of encapsulation plastic-aluminum membrane is 152um.
Example 3
A binder comprising, in a mass ratio of 1:4 of PVDF high-molecular binding material and copolyimide polymer conductive polymer:
Figure BDA0003021815220000141
wherein Ar1 has the structure
Figure BDA0003021815220000142
Ar2 has the structure
Figure BDA0003021815220000143
n is an integer of 100 to 1000.
A negative electrode sheet, the preparation of which comprises the steps of:
(1) adding 1 part of PVDF into NMP (N-methyl pyrrolidone) as a solvent, stirring at the rotating speed of 1000rpm, adding 4 parts of conductive polymer after uniform stirring, controlling the solid content of the glue solution to be 10wt%, continuously stirring at the rotating speed of 2000rpm for 60 minutes to uniformly disperse the conductive adhesive, and vacuumizing to remove bubbles to obtain the adhesive slurry.
(2) 2 parts of acetylene black is added into the adhesive slurry and stirred for 2 hours at the rotating speed of 2000rpm to obtain a conductive glue solution.
(3) Adding 14 parts of silicon powder material into the conductive glue solution, stirring for 10 minutes at the rotating speed of 500rpm, adding 79 parts of graphite powder material, stirring for 10 minutes at the rotating speed of 500rpm, then adding a proper amount of NMP solvent, controlling the solid content of the slurry to be 70wt%, continuing stirring for 2 hours at the rotating speed of 2000rpm, adding NMP to adjust the solid content to be 50wt%, stirring for 10 minutes at 500rpm, and controlling the viscosity of the negative electrode slurry to be 9000cps.
(4) And coating the slurry after passing through the screen on a copper foil current collector for drying, wherein the temperature of an oven is 110 ℃, the coating speed is 2m/min, and the water content in a coating workshop is lower than 10%.
(5) Rolling the coated negative pole piece, and controlling the rolling density of the pole piece to be 1.60g/cm 3 And manufacturing the rolled pole piece into the size required by design according to a set punching die to obtain the negative pole piece.
A secondary battery is prepared by the steps of laminating a negative plate, an NCM ternary positive electrode material and a diaphragm, packaging, injecting liquid, forming, aging, grading and the like to obtain a soft package battery cell. Wherein diaphragm thickness is 16um, and the thickness of encapsulation plastic-aluminum membrane is 152um.
Example 4
A binder comprising, in a mass ratio of 1:1 of PVDF polymer binding material and polyfluorene polymer conductive polymer:
Figure BDA0003021815220000151
wherein R1 is-CH 3 R2 is-CH 3 And m is an integer of 100 to 1000.
A negative electrode sheet is prepared by the steps of:
(1) adding 2 parts of PVDF into NMP (N-methyl pyrrolidone) serving as a solvent, stirring at the rotating speed of 2000rpm, adding 2 parts of conductive polymer after uniform stirring, controlling the solid content of glue solution to be 10wt%, continuously stirring at the rotating speed of 3000rpm for 40 minutes to uniformly disperse the conductive adhesive, and vacuumizing to remove bubbles to obtain adhesive slurry.
(2) 2 parts of acetylene black is added into the adhesive slurry and stirred for 2 hours at the rotating speed of 3000rpm to obtain a conductive glue solution.
(3) Adding 14 parts of silicon powder material into the conductive glue solution, stirring for 10 minutes at the rotating speed of 500rpm, adding 80 parts of graphite powder material, stirring for 10 minutes at the rotating speed of 500rpm, then adding a proper amount of NMP solvent, controlling the solid content of the slurry to be 60wt%, continuously stirring for 2 hours at the rotating speed of 3000rpm, adding NMP to adjust the solid content to be 42wt%, stirring for 10 minutes at 500rpm, and controlling the viscosity of the negative electrode slurry to be 6000cps.
(4) And coating the slurry after passing through the screen on a copper foil current collector for drying, wherein the temperature of an oven is 100 ℃, the coating speed is 2m/min, and the water content of a coating workshop is lower than 10%.
(5) Rolling the coated negative pole piece, and controlling the rolling density of the pole piece to be 1.70g/cm 3 And manufacturing the rolled pole piece into the size required by design according to a set punching die to obtain the negative pole piece.
A secondary battery is prepared by the procedures of laminating, packaging, injecting liquid, forming, aging, grading and the like of a negative plate, an NCM ternary positive material and a diaphragm together to obtain a soft package battery core. Wherein diaphragm thickness is 16um, and the thickness of encapsulation plastic-aluminum membrane is 152um.
Example 5
A binder comprising, by mass, 1:2 PVDF high-molecular binder material and polyfluorene polymer conductive polymer:
Figure BDA0003021815220000161
wherein R1 is-CH 3 R2 is-CH 2 H 3 And m is an integer of 100 to 1000.
A negative electrode sheet, the preparation of which comprises the steps of:
(1) adding 1 part of PVDF into a solvent NMP, stirring at the rotating speed of 2000rpm, adding 2 parts of conductive polymer after uniformly stirring, controlling the solid content of a glue solution to be 10wt%, continuously stirring at the rotating speed of 4000rpm for 30 minutes to uniformly disperse a conductive adhesive, and vacuumizing to remove bubbles to obtain an adhesive slurry.
(2) 2 parts of acetylene black is added into the adhesive slurry and stirred for 1 hour at the rotating speed of 4000rpm, so as to obtain a conductive glue solution.
(3) Adding 15 parts of silicon powder material into the conductive glue solution, stirring for 10 minutes at the rotating speed of 500rpm, adding 80 parts of graphite powder material, stirring for 10 minutes at the rotating speed of 500rpm, then adding a proper amount of NMP solvent, controlling the solid content of the slurry to be 50wt%, continuing stirring for 1 hour at the rotating speed of 4000rpm, adding NMP to adjust the solid content to be 35wt%, then stirring for 10 minutes at 500rpm, and controlling the viscosity of the negative electrode slurry to be 3000cps.
(4) And coating the slurry after passing through the screen on a copper foil current collector for drying, wherein the temperature of an oven is 80 ℃, the coating speed is 2m/min, and the water content of a coating workshop is lower than 10%.
(5) Rolling the coated negative pole piece, and controlling the rolling density of the pole piece to be 1.65g/cm 3 And manufacturing the rolled pole piece into the size required by design according to a set punching die to obtain the negative pole piece.
A secondary battery is prepared by the steps of laminating a negative plate, an NCM ternary positive electrode material and a diaphragm, packaging, injecting liquid, forming, aging, grading and the like to obtain a soft package battery cell. Wherein diaphragm thickness is 16um, and the thickness of encapsulation plastic-aluminum membrane is 152um.
Example 6
A binder comprising, in a mass ratio of 1:4 of PVDF high-molecular binding material and polyfluorene polymer conductive polymer:
Figure BDA0003021815220000171
wherein R1 is-CH 2 H 3 R2 is-CH 2 H 3 And m is an integer of 100 to 1000.
A negative electrode sheet is prepared by the steps of:
(1) adding 1 part of PVDF into a solvent NMP, stirring at the rotating speed of 1000rpm, adding 4 parts of conductive polymer after uniformly stirring, controlling the solid content of a glue solution to be 10wt%, continuously stirring at the rotating speed of 2000rpm for 60 minutes to uniformly disperse a conductive adhesive, and vacuumizing to remove bubbles to obtain an adhesive slurry.
(2) 2 parts of acetylene black is added into the adhesive slurry and stirred for 2 hours at the rotating speed of 2000rpm to obtain a conductive glue solution.
(3) Adding 14 parts of silicon powder material into the conductive glue solution, stirring for 10 minutes at the rotating speed of 500rpm, adding 79 parts of graphite powder material, stirring for 10 minutes at the rotating speed of 500rpm, then adding a proper amount of NMP solvent, controlling the solid content of the slurry to be 70wt%, continuing stirring for 2 hours at the rotating speed of 2000rpm, adding NMP to adjust the solid content to be 50wt%, stirring for 10 minutes at 500rpm, and controlling the viscosity of the negative electrode slurry to be 9000cps.
(4) And coating the slurry after passing through the screen on a copper foil current collector for drying, wherein the temperature of an oven is 110 ℃, the coating speed is 2m/min, and the water content of a coating workshop is lower than 10%.
(5) Rolling the coated negative pole piece, and controlling the rolling density of the pole piece to be 1.60g/cm 3 And manufacturing the rolled pole piece into the size required by design according to a set punching die to obtain the negative pole piece.
A secondary battery is prepared by the procedures of laminating, packaging, injecting liquid, forming, aging, grading and the like of a negative plate, an NCM ternary positive material and a diaphragm together to obtain a soft package battery core. Wherein diaphragm thickness is 16um, and the thickness of encapsulation plastic-aluminum membrane is 152um.
Example 7
A binder comprising, by mass, 1:1 of PVDF polymer binding material and copolyimide polymer conductive polymer:
Figure BDA0003021815220000181
wherein Ar1 and Ar2 have the structure
Figure BDA0003021815220000182
n is an integer of 100 to 1000.
A positive electrode sheet is prepared by the steps of:
(1) adding 2 parts of PVDF into a solvent NMP, stirring at the rotating speed of 2000rpm, adding 2 parts of conductive polymer after uniformly stirring, controlling the solid content of a glue solution to be 10wt%, continuously stirring at the rotating speed of 3000rpm for 40 minutes to uniformly disperse a conductive adhesive, and vacuumizing to remove bubbles to obtain an adhesive slurry.
(2) 2 parts of acetylene black is added into the adhesive slurry and stirred for 2 hours at the rotating speed of 3000rpm to obtain a conductive glue solution.
(3) 94 parts of NCM811 ternary polycrystalline material is added into the conductive glue solution, the mixture is stirred for 10 minutes at the rotating speed of 500rpm, then a proper amount of NMP solvent is added, the solid content of the slurry is controlled to be 80wt%, the stirring is continued for 2 hours at the rotating speed of 3000rpm, NMP is added to adjust the solid content to be 70wt%, the stirring is carried out for 10 minutes at 500rpm, and the viscosity of the anode slurry is controlled to be 6000cps.
(4) And coating the slurry after passing through the screen on an aluminum foil current collector for drying, wherein the temperature of an oven is 100 ℃, the coating speed is 2m/min, and the water content of a coating workshop is lower than 10%.
(5) Rolling the coated positive plate, and controlling the rolling density of the plate to be 3.50g/cm 3 And manufacturing the rolled pole piece into the size required by the design according to a set punching die to obtain the positive pole piece.
A secondary battery is prepared through stacking positive plate, negative plate made of silicon-base material mixed with graphite, and diaphragm, sealing, injecting liquid, shaping, ageing and grading. Wherein diaphragm thickness is 16um, and the thickness of encapsulation plastic-aluminum membrane is 152um.
Comparative example 1
Comparative example 1 differs from example 1 in that: the binder only contains PVDF polymer binding material; the negative plate contains 3 parts of PVDF polymer binding material, 2 parts of conductive agent and 15 parts of silicon powder material.
Comparative example 2
Comparative example 2 differs from example 1 in that: the binder only contains PVDF polymer binder; the negative plate contains 12 parts of PVDF polymer binding material, 2 parts of conductive agent and 6 parts of silicon powder material.
Comparative example 3
Comparative example 3 differs from example 1 in that: the negative plate contains 4 parts of PVDF high-molecular binding material, 8 parts of conductive polymer, 2 parts of conductive agent and 6 parts of silicon powder material.
Comparative example 4
Comparative example 4 differs from example 3 in that: the mass ratio of the PVDF to the polyimide polymer conductive polymer in the binder is 1:8; the negative electrode sheet contains 0.5 parts of PVDF,4 parts of conductive polymer, 2 parts of conductive agent and 14 parts of silicon powder material.
Comparative example 5
Comparative example 5 differs from example 3 in that: the mass ratio of PVDF to the polyimide polymer conductive polymer in the binder is 3; the negative plate contains 3 parts of PVDF,1 part of conductive polymer, 2 parts of conductive agent and 14 parts of silicon powder material.
Comparative example 6
Comparative example 6 differs from example 1 in that: n is an integer of 1100 to 2000.
Further, in order to verify the improvement of the embodiments of the present invention, the battery pole pieces and the secondary batteries prepared in the above embodiments and comparative examples were subjected to the following performance test in table 1, and the ohmic resistance and the peel strength of the battery pole pieces in each of embodiments 1 to 7, and the cycle performance and DCR (direct current resistance) increase of 1/3C of the finished soft package battery under room temperature were counted, and the cycle voltage range was 2.5 to 4.25V.
TABLE 1
Figure BDA0003021815220000201
From the test results in table 1 above, it can be seen that the negative electrode sheets and the positive electrode sheets prepared in examples 1 to 7 both have high peel strength, small sheet resistance, high battery capacity retention rate, good cycle stability, small DCR dc impedance increase rate, and excellent comprehensive properties. The positive electrode sheet of example 7 had better adhesiveness than the negative electrode sheets of examples 1 to 6, and the sheet resistance of the positive electrode sheet was generally much higher than that of the negative electrode sheet, because the negative electrode sheet contained a larger amount of graphite material in the negative electrode material, the conductivity was better.
As can be seen from comparison between examples 1 to 6 and comparative example 1, the peel strength of the silicon-based negative electrode plate made of the binder of comparative example 1 without the conductive polymer is obviously lower than that of the silicon-based negative electrode plate made of the conductive polymer in the binders of examples 1 to 6. Meanwhile, the sheet resistance of the electrode sheet of comparative example 1 is higher than that of the example; the cycle performance test result shows that after the comparative example 1 is cycled for 300 cycles at 1/3C, the capacity retention rate is 71% -73%, the capacity retention rate is smaller than that of the embodiment, and the DCR growth rate of the soft package cell is larger than that of the embodiment. The conductive polymer in the binder of the embodiments 1 to 6 of the invention has conductive property and binding effect, so that on one hand, the electronic conductivity between silicon and graphite is improved, and simultaneously, the integrity of a conductive path of silicon in the cyclic expansion and contraction process is improved, and thus, the cycle performance of a silicon cathode battery is improved.
As can be seen from comparison of examples 1 to 6 with comparative examples 2 to 3, when the binder content in the battery electrode sheet is too high, the peel strength of the electrode sheet can be increased to some extent, but the sheet resistance of the electrode sheet increases, the capacity retention ratio of the battery decreases, and the DCR increase rate increases.
As can be seen from comparison between examples 1 to 6 and comparative examples 4 to 5, when the content of the polymer binder in the binder is too high or the content of the conductive polymer is too high, the capacity retention ratio of the battery is decreased, the DCR increase rate is increased, and it is also not advantageous to improve the cycle stability of the battery.
As can be seen from comparison of examples 1 to 6 with comparative example 6, when the molecular weight of the conductive polymer in the binder is too large, the capacity retention rate of the battery is reduced, the DCR increase rate is increased, and the improvement of the cycle stability of the battery is also not facilitated.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. An adhesive, characterized in that the adhesive comprises: the conductive polymer is selected from at least one substance in a formula I and a formula II:
Figure FDA0003021815210000011
wherein Ar1 and Ar2 are respectively and independently selected from aromatic groups, R1 and R2 are respectively and independently selected from: H. one of alkyl and alkoxy, n is an integer of 100 to 1000, and m is an integer of 100 to 1000.
2. The binder of claim 1 wherein Ar1, ar2 are each independently selected from the group consisting of: at least one of phenyl, substituted phenyl, biphenyl, substituted biphenyl, diphenyl ether and substituted diphenyl ether.
3. The binder of claim 2 wherein the substituted phenyl group, the substituted biphenyl group, and the substituted diphenyl ether each independently comprise a substituent selected from the group consisting of: at least one of alkyl and alkoxy;
and/or, in the substituted phenyl, the substituted biphenyl and the substituted diphenyl ether, the substitution form comprises single substitution or multiple substitution.
4. The adhesive of claim 3, wherein the conductive polymer is selected from the group consisting of: at least one of a copolyimide polymer of pyromellitic dianhydride and p-phenylenediamine, a copolyimide polymer of pyromellitic dianhydride and oxydianiline, and a polyfluorene polymer;
and/or the polymer binding material is selected from: at least one of polyvinylidene fluoride, sodium methylcellulose, styrene-butadiene rubber, ethyl cellulose, polyacrylic acid, polyacrylonitrile, polyacrylate and sodium alginate;
and/or the mass ratio of the high-molecular binding material to the conductive polymer is 1: (1-4).
5. A battery pole piece, comprising: a positive electrode active material or a negative electrode active material, a conductive agent and the binder according to any one of claims 1 to 4.
6. The battery pole piece of claim 5, wherein the content of the binder in the battery pole piece is 1-10%; the content of the conductive agent is 0.5-10%;
and/or, the conductive agent comprises: at least one of conductive carbon black, ketjen black, conductive carbon nanotube and conductive carbon fiber.
7. The battery pole piece of claim 5 or 6, wherein the battery pole piece is a positive pole piece comprising: at least one positive electrode active material selected from nickel cobalt manganese ternary material, nickel cobalt manganese aluminum quaternary material, nickel cobalt aluminum ternary material, lithium iron phosphate, lithium iron manganese phosphate, lithium cobaltate and lithium manganate;
or, the battery pole piece is a negative pole piece, and comprises: si, siO 2 At least one silicon-based anode active material.
8. The battery pole piece of claim 7, wherein the compacted density of the negative pole piece is 1.50 to 1.85g/cm 3 (ii) a The compaction density of the positive plate is 3.2-3.8 g/cm 3 ；
And/or the negative plate further comprises a carbon material, and the mass ratio of the carbon material to the silicon-based negative active material is (80-95): (5-20).
9. A method for preparing a battery pole piece according to any one of claims 5 to 8, comprising the steps of: and dispersing the positive electrode active material or the negative electrode active material, the conductive agent and the binder in a solvent to form electrode slurry, coating or depositing the electrode slurry on a current collector, and drying to obtain the battery pole piece.
10. A secondary battery comprising a battery pole piece according to any one of claims 5 to 8, or a battery pole piece prepared by the method of claim 9.
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CN109411761A (en) * 2018-12-03 2019-03-01 中南民族大学 The multifunctional unit combination electrode slurry and preparation method of the polymer containing active carbonyl group
CN112563511A (en) * 2020-12-10 2021-03-26 深圳中科瑞能实业有限公司 Aluminum-containing negative electrode material, negative electrode plate and lithium ion secondary battery

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117050689A (en) * 2023-07-28 2023-11-14 江苏理工学院 Preparation method and application of conductive polymer adhesive
CN117050689B (en) * 2023-07-28 2024-03-19 江苏理工学院 Preparation method and application of conductive polymer adhesive

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