CN112909252B - Polymer binder, its preparation and use - Google Patents
Polymer binder, its preparation and use Download PDFInfo
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- CN112909252B CN112909252B CN202110067789.2A CN202110067789A CN112909252B CN 112909252 B CN112909252 B CN 112909252B CN 202110067789 A CN202110067789 A CN 202110067789A CN 112909252 B CN112909252 B CN 112909252B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/42—Nitriles
- C08F220/44—Acrylonitrile
- C08F220/46—Acrylonitrile with carboxylic acids, sulfonic acids or salts thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F212/00—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 an aromatic carbocyclic ring
- C08F212/34—Monomers containing two or more unsaturated aliphatic radicals
- C08F212/36—Divinylbenzene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/04—Acids; Metal salts or ammonium salts thereof
- C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention discloses a polymer binder and preparation and application thereof. The polymer binder comprises a first polymer binder and a second polymer binder, wherein molecular chains of the first polymer binder and the second polymer binder respectively form a grid structure, and the grid structure of the first polymer binder and the grid structure of the second polymer binder mutually penetrate to form an interpenetrating network structure. The polymer binder can act and connect with an electrode active material, particularly a silicon-based active material, and can coat the electrode active material, particularly the silicon-based active material, to form a coating layer, so that the dispersion uniformity of the electrode active material in an electrode active layer and the stability of the electrode active material in a circulation process are improved; the adhesive force between the active layer and the current collector is strong, so that the bonding strength between the active layer and the current collector is effectively enhanced. It can be applied in electrodes and lithium ion batteries.
Description
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a polymer binder and preparation and application thereof.
Background
Along with the enhancement of awareness of environmental protection and energy crisis, the lithium ion battery is more and more popular as an environment-friendly energy storage technology. Lithium ion batteries are widely used due to their high energy density, long cycle, and high stability. With the wide application of electronic products and the vigorous development of electric automobiles, the market of lithium ion batteries is increasingly wide, but higher requirements on the safety of the lithium ion batteries are provided.
At present, the silicon-based negative electrode material has high theoretical specific capacity and a suitable lithium embedding platform, and is an ideal high-capacity negative electrode material for a lithium ion battery. However, in the process of charging and discharging, the volume change of silicon reaches more than 300%, and the internal stress generated by the violent volume change easily causes electrode pulverization and peeling, thereby influencing the cycle stability.
In order to effectively overcome the disadvantage caused by the volume expansion of silicon in the charging and discharging processes, attention is focused on the development of composite silicon materials, such as a cladding structure for buffering the volume expansion of silicon. However, electrochemical properties such as specific capacity, cycle performance, etc. of the silicon-containing electrode are affected by properties of other materials contained in the electrode active layer, such as a binder, etc., in addition to properties related to the silicon active material.
Currently, in lithium ion batteries with negative electrodes containing silicon-based materials, binders commonly used for negative electrodes are Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), and the like. However, the surface of SBR lacks enough functional groups, cannot form effective bonding effect on silicon materials, and is difficult to inhibit huge volume expansion of the silicon materials. When the PAA is used as the binder, the PAA has low mechanical strength, large deformation and excessive swelling, and low glass transition temperature, so that poor adhesion is easily caused, the pole piece is brittle, even powder falling and the like occur, and the yield of the production process of the negative pole piece and the performance of the lithium ion battery are greatly influenced. And SBR and PAA binder molecules are straight-chain, and are easy to fall off from the surface of silicon particles when used as a binder, so that the irreversible capacity of the silicon-based negative electrode in the later cycle period is increased.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a polymer binder, a preparation method thereof, an electrode containing the polymer binder and a lithium ion battery, so as to solve the technical problem that the electrochemical performance of the electrode and the lithium ion battery is unstable due to the unsatisfactory bonding performance of the binder used by the conventional electrode.
In order to achieve the above object, according to one aspect of the present invention, there is provided a polymer binder. The polymer binder comprises a first polymer binder and a second polymer binder, wherein molecular chains of the first polymer binder and the second polymer binder respectively form a grid structure, and the grid structure of the first polymer binder and the grid structure of the second polymer binder mutually penetrate to form an interpenetrating network structure.
Thus, the polymer binder can act and connect with the electrode active material, particularly the silicon-based active material, on one hand, and can coat the electrode active material, particularly the silicon-based active material to form a coating layer by virtue of the synergistic effect of the contained first polymer binder and the second polymer binder, so that the dispersion uniformity of the electrode active material in the electrode active layer and the stability of the electrode active material in the circulating process are improved; on the other hand, strong bonding force can be formed between the active layer and the current collector, so that the bonding strength between the active layer and the current collector is effectively enhanced. And the molecular chains of the contained first polymer binder and the second polymer binder are respectively arranged into a grid structure, and the grid structures contained in the two polymer binders are mutually penetrated and arranged to form an interpenetrating network structure, so that the molecular chains of the two polymer binders form a network structure whole, the two polymer binders can play a synergistic interaction role, the bonding strength between the two polymer binders and the electrode active material, between the current collectors and between the two polymer binders and the materials contained in the active layer is effectively enhanced, the using amount of the polymer binders is reduced, and the structural stability and the electrochemical performance stability of the electrode in the circulating process are effectively improved.
Preferably, the first polymeric binder comprises-COOH、-OH、-NH2At least one polar functional group.
Specifically, the first polymeric binder includes at least one of poly (acrylic acid-acrylonitrile), poly (acrylic acid-acrylonitrile) salt type binders, and poly (vinyl alcohol).
The adhesive strength of the first polymer binder to the electrode active material is further enhanced by optimizing the functional groups contained in the first polymer binder. Specifically, the contained polar functional group can generate hydrogen bonds with the surface of an electrode active material, particularly a silicon-based active material, so that the silicon-based active material is firmly bonded and coated, and the dispersibility and the dispersion stability in an active layer are improved.
Preferably, the second polymeric binder comprises at least one of a poly (styrene-butadiene) polymer, polybutylacrylate. The adhesive strength between the second polymer binder and the electrode active material and the current collector is further enhanced by optimizing the functional groups contained in the second polymer binder. Specifically, the water-based group can be effectively combined with the group contained on the surface of a current collector such as a negative electrode current collector to form adhesive force, and the non-water-based group can be effectively combined with an electrode material in an adhesive way.
Preferably, the mass ratio of the first polymeric binder to the second polymeric binder is 1: 2-1: 10. by optimizing the first polymer binder and the second polymer binder, the synergistic effect between the two polymer binders is improved, the stability of an interpenetrating network structure formed by the two polymer binders is enhanced, the bonding strength between the polymer binders and an electrode active material, between the polymer binders and a current collector and between materials contained in an active layer is enhanced, and the using amount of the polymer binders is reduced, so that the structural stability and the stability of electrochemical performance of the electrode in the circulating process are effectively improved.
In another aspect of the present invention, a method of preparing a polymeric binder is provided. The preparation method of the polymer binder comprises the following steps:
preparing a monomer of a first polymer binder, a cross-linking agent, an emulsifier and water into a pre-emulsion;
providing an emulsion of a second polymeric binder and heat treating to swell the second polymeric binder molecules; molecular chains of the second polymer binder form a grid structure;
and mixing the pre-emulsion and the emulsion of the second polymer binder after the heat treatment to form a mixed emulsion, heating the mixed emulsion to the polymerization reaction temperature range of the monomer, adding an initiator into the mixed emulsion to perform polymerization reaction on the monomer, and generating the first polymer binder in situ in a grid structure contained in the second polymer binder.
In this way, the preparation method of the polymer binder takes the grid structure contained in the second polymer binder as a template to carry out in-situ polymerization reaction on the monomers of the first polymer binder to generate the first polymer binder, so that the generated first polymer binder also has a network structure, and the network structures contained in the two polymer binders can mutually penetrate and set to form an interpenetrating network structure, so that the prepared polymer binder has the excellent binding performance of the polymer binder, and the preparation method of the polymer binder has the advantages of easily controlled process conditions, stable performance and high efficiency.
Preferably, the crosslinking agent accounts for 2-10 wt% of the total monomer; and/or
The proportion of the emulsifier in the total amount of the monomers is 0.5-5 wt%; and/or
In the mixed emulsion, the mass ratio of the emulsion to the pre-emulsion is 1: 2-1: 10; wherein the concentration of the second polymer binder in the emulsion is 10-50 wt%, and the mass ratio of water to the total amount of monomers in the pre-emulsion is 1: 1-5: 1; and/or
A buffering agent is further added into the pre-emulsion, and the buffering agent accounts for 2-10 wt% of the total amount of the monomers;
and the total amount of the initiator added into the mixed emulsion accounts for 1-5 wt% of the total amount of the monomers.
By controlling and optimizing the addition proportion of the components contained in the pre-emulsion and the second polymer binder, the generated first polymer binder can fully form a network structure in the polymerization reaction, and can mutually penetrate through the network structure of the second polymer binder to form an interpenetrating network structure, so that the bonding property of the prepared polymer binder is improved.
Specifically, the monomer comprises at least one of a mixed monomer of acrylic acid and acrylonitrile and a vinyl alcohol monomer;
the cross-linking agent comprises at least one of divinylbenzene, acrylic acid, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, methacrylic acid, N-methylolacrylamide and diacetone acrylamide;
the emulsifier comprises at least one of sodium dodecyl sulfate, sodium stearate and oleate;
the buffer comprises at least one of ammonium bicarbonate, ammonium acetate and sodium bicarbonate;
the second polymeric binder comprises at least one of poly (styrene-butadiene), polybutylacrylate;
the initiator comprises at least one of ammonium persulfate, sodium persulfate and potassium persulfate.
Through the selection and optimization of the types of the reactants and the second polymer binder, the dispersion uniformity of each component in the mixed emulsion can be improved, and the yield of the first polymer binder and the efficiency of polymerization reaction can be improved, so that the generated first polymer binder has a stable network structure, and can be mutually penetrated and arranged with the grid structure of the second polymer binder to form an interpenetrating network structure, thereby improving the bonding performance of the prepared polymer binder.
In yet another aspect of the present invention, an electrode is provided. The electrode comprises a current collector and an electrode active layer combined on the surface of the current collector, wherein the electrode active layer contains a binder, and the binder is the polymer binder. The electrode contains the polymer binder, so the polymer binder can be uniformly coated on the surface of the electrode active material, components in an electrode active layer, particularly the electrode active material, can be uniformly dispersed, and the electrode active layer has a stable structure and high bonding strength with a current collector, so that the electrode has stable structure and electrochemical performance in the charge-discharge cycle process. In addition, the polymer binder has high binding performance and low content, so that the electrode has high conductivity.
Preferably, the electrode is a negative electrode, and the active layer containing the electrode active material is a silicon-based negative electrode material. Therefore, the polymer binder contained in the active layer can effectively coat the silicon-based negative electrode material and form hydrogen bonds with the surface of the silicon-based negative electrode material, so that the bonding strength of the polymer binder to the silicon-based negative electrode material is improved, the stability of the structure and the electrochemical performance of the electrode can be effectively improved due to the network structure of the polymer binder, and the phenomenon that the structure and the electrochemical performance of the electrode are unstable due to the volume expansion of the silicon-based negative electrode material in the circulation process is avoided.
In yet another aspect of the present invention, a lithium ion battery is provided. The lithium ion battery comprises a positive electrode, a negative electrode and a diaphragm which is stacked between the positive electrode and the negative electrode, wherein the positive electrode or/and the negative electrode is/are the electrode. The electrode of the lithium ion battery is the electrode of the invention, so the lithium ion battery of the invention has good cycle performance, long service life and stable electrochemical performance.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic diagram of the molecular chain structure of a polymer binder according to an embodiment of the present invention;
FIG. 2 is a schematic process flow diagram of a method for preparing a polymer binder according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described, and the embodiments described below are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art without any inventive step in connection with the embodiments of the present invention shall fall within the scope of protection of the present invention. Those whose specific conditions are not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer; the reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
In the description of the present invention, the term "and/or" describing an association relationship of associated objects means that there may be three relationships, for example, a and/or B, 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 description of 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 (a), b, or c", or "at least one (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 may be single or plural, respectively.
It should be understood that the weight of the related components mentioned in 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, it is within the scope of the disclosure that the content of the related components is scaled up or down according to the embodiments of the present invention. Specifically, the weight described in the embodiments of the present invention may be a unit of mass known in the chemical field such as μ g, mg, g, kg, etc.
In addition, unless the context clearly uses otherwise, an expression of a word in the singular is to be understood as including the plural of the word. The terms "comprises" or "comprising" are intended to specify the presence of stated features, quantities, steps, operations, elements, portions, or combinations thereof, but are not intended to preclude the presence or addition of one or more other features, quantities, steps, operations, elements, portions, or combinations thereof.
The following relates to the description of the names:
poly (acrylic acid-acrylonitrile): represents a polymer of an acrylic monomer and an acrylonitrile monomer.
Poly (styrene-butadiene): represents a polymer of a styrene monomer and a butadiene monomer.
In one aspect, embodiments of the present invention provide a polymeric binder. The molecular chain structure of the polymer binder is shown in fig. 1, the polymer binder comprises a first polymer binder 10 and a second polymer binder 20, wherein the molecular chain of the first polymer binder 10 is formed with a grid structure 11, as shown in fig. 1 (a); the molecular chains of the second polymeric binder 20 form a lattice structure 21, as shown in fig. 1 (B). The grid structure 11 and the grid structure 21 are mutually penetrated and arranged to form an interpenetrating network structure, as shown in fig. 1 (C). In the interpenetrating network structure, the molecular chain segments contained in the lattice structure 11 and the molecular chain segments contained in the lattice structure 21 are physically arranged in a penetrating manner, that is, no chemical bond is formed between the molecular chain segments contained in the lattice structure 11 and the molecular chain segments contained in the lattice structure 21, and the two are mainly subjected to mutual cross permeation and mechanical entanglement to play the roles of forced mutual compatibility and synergistic effect. Thus, the polymer binder of the embodiment of the present invention can act and connect with the electrode active material on the one hand, and can coat the electrode active material, particularly, the silicon-based active material to form a coating layer, by the action of the two polymer binders included in the first polymer binder 10 and the second polymer binder 20, limit the movement and separation between the electrode active material and other components such as the conductive agent during the cycle, suppress the huge volume expansion of the electrode active material such as the silicon-based active material during the charge and discharge, and improve the uniformity of the dispersion of the electrode active material in the electrode active layer and the stability during the cycle; on the other hand, strong bonding force can be formed between the active layer and the current collector, so that the bonding strength between the active layer and the current collector is effectively enhanced. And the contained first polymer binder 10 and the second polymer binder 20 form an interpenetrating network structure, so that the two polymer binders can play a role in synergy, molecular chains of the two polymer binders form a network structure whole, the bonding strength between the two polymer binders and electrode active materials, current collectors and materials contained in an active layer is effectively enhanced, the using amount of the polymer binders is reduced, and the structural stability and the electrochemical performance stability of the electrode in the circulating process are effectively improved.
In one embodiment, the first polymeric binder 10 contains polar functional groups, wherein the polar functional groups preferably include-COOH, -OH, -NH2At least one of (1). Thus, in particular embodiments, the first polymeric binder 10 includes at least one of poly (acrylic-acrylonitrile), poly (acrylic-acrylonitrile) salt-based binders, and poly (vinyl alcohol). When the first polymeric binder 10 is a poly (acrylic-acrylonitrile) polymer, the molar ratio of acrylic groups to acrylonitrile groups in the poly (acrylic-acrylonitrile) is 1: 0.1-1: 10. the adhesive strength of the first polymer binder 10 to the electrode active material is further enhanced by optimizing the functional groups contained in the first polymer binder and the selection of a specific species. Specifically, the contained polar functional group can generate hydrogen bonds with the surface of an electrode active material, particularly a silicon-based active material, so that the electrode active material, particularly the silicon-based active material, is firmly bonded and coated, the dispersibility of the electrode active material, particularly the silicon-based active material, and the dispersion stability in an active layer are improved, the movement and separation between the electrode active material and other components, such as a conductive agent, in a circulation process are limited, and the huge volume expansion of the electrode active material, particularly the silicon-based active material, in a charging and discharging process is inhibited.
In another embodiment, the second polymeric binder 20 contains aqueous groups, wherein the aqueous groups (i.e., hydrophilic groups) preferably include at least one of-COOH, -OH. Thus, in particular embodiments, the second polymeric binder 20 includes at least one of poly (styrene-butadiene), polybutylacrylate. When the second polymeric binder 20 is poly (styrene-butadiene), the molar ratio of styrene groups to butadiene groups in the poly (styrene-butadiene) is 2: 1. The adhesive strength of the second polymer binder 20 to the electrode active material and the current collector is further enhanced by optimizing the functional groups contained in the second polymer binder 20 and the selection of a specific species. Specifically, the contained water-based group can be effectively combined with the group contained on the surface of a current collector such as a negative electrode current collector to form binding force, and the contained oil-based group can be effectively combined with an electrode material in a binding way.
In one embodiment, the polymer binder includes a first polymer binder 10 and a second polymer binder 20 in a mass ratio of 1: 2-1: 10. by optimizing the ratio of the first polymer binder 10 to the second polymer binder 20, the synergy between the two polymer binders is improved, the stability of an interpenetrating network structure formed by the two polymer binders is enhanced, the bonding strength between the polymer binders and the electrode active material, the current collector and the materials contained in the active layer is enhanced, the movement and separation between the electrode active material and other components such as a conductive agent in the circulating process are further limited, the huge volume expansion of the electrode active material such as a silicon-based active material in the charging and discharging process is inhibited, and the dispersion uniformity of the electrode active material in the electrode active layer and the stability in the circulating process are improved. Meanwhile, the dosage of the polymer binder is reduced, so that the structural stability and the electrochemical performance stability of the electrode in the circulating process are effectively improved.
Correspondingly, the embodiment of the invention also provides a preparation method of the polymer binder. The polymer binder described in conjunction with fig. 1, the process flow of the preparation method of the polymer binder is shown in fig. 2, and comprises the following steps:
s01: preparing a pre-emulsion from a monomer of a first polymer binder, a cross-linking agent, an emulsifier and water;
s02: providing an emulsion of second polymeric binder 20 and heat treating to swell the molecules of second polymeric binder 20; molecular chains of the second polymer binder form a grid structure;
s03: mixing the pre-emulsion in the step S01 with the emulsion of the second polymer binder 20 in the step S02 to form a mixed emulsion, heating the mixed emulsion to a polymerization temperature range of the monomers, adding an initiator to the mixed emulsion to perform a polymerization reaction of the monomers, and generating the first polymer binder 10 in situ in the lattice structure 21 included in the second polymer binder 20.
Thus, in the method for preparing the polymer binder according to the embodiment of the present invention, the monomers of the first polymer binder 10 are subjected to an in-situ polymerization reaction with the lattice structure 21 contained in the second polymer binder 20 as a template to generate the first polymer binder 10, so that the generated first polymer binder 10 also has the network structure 11, and the network structure 11 and the network structure 21 contained in the two polymer binders can be mutually arranged in a penetrating manner to form an interpenetrating network structure, so that the prepared polymer binder has the excellent binding performance of the polymer binder according to the embodiment of the present invention.
In the pre-emulsion prepared in step S01, the monomers, the cross-linking agent, the emulsifier, and the like constitute a polymerization system for forming the first polymer binder 10, so that the polymerization reaction is performed in step S03 to form the first polymer binder 10. In one embodiment, the crosslinking agent accounts for 2-10 wt% of the total amount of the monomers. In a specific embodiment, the crosslinking agent comprises at least one of Divinylbenzene (DVB), acrylic acid, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, methacrylic acid, N-methylolacrylamide, diacetone acrylamide, and the monomer may be a monomer forming the first polymeric binder 10 contained in the polymeric binders above, such as at least one mixed monomer comprising a mixed monomer of acrylic acid and acrylonitrile, and a vinyl alcohol monomer. When the monomer is a mixed monomer of acrylic acid and acrylonitrile, the acrylic acid accounts for 10-90 wt% of the total mass of the mixed monomer of acrylic acid and acrylonitrile. By optimizing the mixing ratio of the cross-linking agent and the monomer and the types of the cross-linking agent and the monomer, the monomer can be ensured to be fully subjected to polymerization reaction to generate the first polymer binder 10, and the efficiency of the polymerization reaction and the yield of the first polymer binder 10 are improved.
In another embodiment, the proportion of the emulsifier in the total amount of the monomers is 0.5-5 wt%, and the mass ratio of the water in the pre-emulsion to the total amount of the monomers is 1: 1-5: 1. in particular embodiments, the emulsifier comprises at least one of Sodium Dodecyl Sulfate (SDS), sodium dodecyl sulfate, sodium stearate, oleate. By optimizing the mixing ratio of the emulsifier and the water and the selection of the emulsifier type, the emulsion forms a stable polymerization reaction system, so that the polymerization reaction efficiency and the yield of the first polymer binder 10 are improved, and meanwhile, the solvent of the generated polymer binder is finally formed, and the stability of the polymer binder system is improved.
In a further embodiment, a buffering agent is further added to the pre-emulsion, and the proportion of the buffering agent in the total amount of the monomers is controlled to be 2-10 wt%. In particular embodiments, the buffer comprises at least one of ammonium bicarbonate, ammonium acetate, sodium bicarbonate. The buffer may be mixed with water together with the monomer, the crosslinking agent, the emulsifier, and the like, or may be mixed by adding the buffer after the monomer, the crosslinking agent, the emulsifier, and water are preliminarily emulsified. By adding the buffering agent to the pre-emulsion, the change of the pH value in the emulsion is prevented, and the stability of the pre-emulsion system is improved, so that the efficiency of the polymerization reaction and the yield of the first polymer binder 10 are improved, and the stability of the polymer binder system is improved.
The second polymer binder 20 in step S02 is the second polymer binder 20 contained in the polymer binders described above, so that the molecular chains of the second polymer binder 20 form a lattice structure 21 as shown in fig. 1 (B). Thus, the second polymer binder 20 may specifically be at least one binder including a poly (styrene-butadiene) polymer, an acrylate polymer. Additionally, the emulsion of the second polymeric binder 20 may be conventional emulsions of such binders. Specifically, the concentration of the second polymer binder 20 in the emulsion of the second polymer binder may be 10 to 50 wt%.
The second polymeric binder 20 is subjected to a heat treatment, whereby the second polymeric binder 20 molecules swell. In this way, the stretching of the lattice structure 21 contained in the second polymer binder 20 is facilitated, so that the monomers contained in the pre-emulsion in the step S01 can be sufficiently dispersed and taken into the lattice structure 21 contained in the second polymer binder 20 in the mixing process of the step S03.
In step S03, after the pre-emulsion is mixed with the emulsion of the second polymer binder 20 heat-treated in step S02, since the molecules of the second polymer binder 20 swell during the heat treatment, the lattice structure 21 contained therein also swells and expands, so that the monomers, crosslinking agents, etc. in the pre-emulsion can enter the lattice structure 21, and can be uniformly dispersed, so that when an initiator is added, polymerization can be started, and the monomers can be polymerized in situ in the grid structure 21 to generate the network structure 11 shown in figure 1(A), and the network structure 11 can be interpenetrated with the network structure 21 to form an interpenetrating network structure as shown in figure 1(C), so that the prepared polymer binder has excellent binding performance of the polymer binder of the embodiment of the invention.
In one embodiment, the pre-emulsion is first partially mixed with the emulsion of the second polymer binder 20, and the mixed emulsion is heated to the polymerization temperature range of the monomer, and then the initiator and the rest of the pre-emulsion are added dropwise to perform the polymerization. Thus, through the addition control of reactants, the monomers in the pre-emulsion can be fully polymerized, and in-situ polymerization occurs in the grid structure 21 to generate the network structure 11 shown in fig. 1(a), so that the mutual penetration and mechanical winding arrangement between the grid structure 11 and the grid structure 21 are more sufficient, and the interpenetrating network structure is more stable.
In one embodiment, when the concentration of the second polymer binder 20 in the emulsion is 10 to 50 wt%, the mass ratio of water to the total amount of monomers in the pre-emulsion is 1: 1-5: 1, time; the emulsion in the step S02 and the pre-emulsion in the step S01 are mixed according to the mass ratio of 1: 2-1: 10, a mixing process is performed. By optimizing the mixing ratio of the two emulsions, the ratio of the first polymer binder 10 and the second polymer binder 20 generated by the polymerization reaction is controlled, so that the synergistic effect between the two polymer binders is improved, and the bonding strength of the prepared polymer binders is improved.
Wherein the total amount of the initiator added to the mixed emulsion accounts for 1-5 wt% of the total amount of the monomers. In particular embodiments, the initiator comprises ammonium persulfate ((NH)4)2S2O8) Sodium persulfate and potassium persulfate. By optimizing the addition amount and the type of the initiator, the monomers in the mixed emulsion can be sufficiently polymerized to generate the first polymer binder 10, and form the network structure 11. In addition, the initiator is preferably added in the form of an initiator solution, for example, the initiator solution with the concentration of 5-10 wt% is added into the mixed emulsion.
In addition, the polymerization temperature can be flexibly controlled according to the polymerization characteristics of the monomers contained in the specific pre-emulsion, so that the polymerization of the monomers is started after the initiator is added.
On the other hand, the embodiment of the invention also provides an electrode. The electrode includes a current collector and an electrode active layer bonded on a surface of the current collector.
The current collector can be a common electrode current collector, and when the electrode is a positive electrode, the current collector is a positive electrode current collector, and the common positive electrode current collector can be selected; when the electrode is a negative electrode, then the current collector is a negative electrode current collector, then a commonly used negative electrode current collector may be selected.
The electrode active layer may be, for example, an electrode active layer included in a conventional electrode, which includes components such as an electrode active material, a binder, and a conductive agent, but may also include other additives that are advantageous to electrochemical performance of the electrode. In this embodiment, the binder is an embodiment of the present invention polymer binder described above. Thus, in the electrode active layer, the polymer binder can be uniformly coated on the surface including the electrode active material, thereby restricting the movement and separation between the electrode active material and other components such as a conductive agent during the cycle, inhibiting the huge volume expansion of the electrode active material such as a silicon-based active material during the charge and discharge processes, simultaneously enabling the components such as the electrode active material, the conductive agent and the like in the electrode active layer to be uniformly dispersed, and the electrode active layer has a stable structure and high bonding strength with a current collector, thereby enabling the electrode to have stable structure and electrochemical performance during the charge and discharge cycles. In addition, since the polymer binder has high binding properties as described above, it is contained in a low amount in the electrode, so that the electrode is high in conductivity.
In one embodiment, the electrode active material contained in the electrode active layer is a silicon-based negative electrode material. Then, the electrode of the present example is a negative electrode. Therefore, the polymer binder in the electrode active layer can be uniformly coated on the surface of the silicon-based negative electrode material, so that the movement and separation of the silicon-based negative electrode material and other components such as a conductive agent in the circulation process are limited, huge volume expansion of the silicon-based active material in the charge-discharge process is inhibited, the components such as the silicon-based negative electrode material and the conductive agent are uniformly dispersed in the electrode active layer, the structure of the electrode active layer is stable, the bonding strength between the electrode active layer and a current collector is high, and the structure and the electrochemical performance of the electrode are stable and the conductivity is high in the charge-discharge circulation process.
On the other hand, the embodiment of the invention also provides a lithium ion battery. The lithium ion battery includes a positive electrode, a negative electrode, and a separator stacked between the positive electrode and the negative electrode, and certainly includes other components necessary for the lithium ion battery, such as an electrolyte solution. Wherein, the positive electrode or/and the negative electrode is/are the electrode of the embodiment of the invention. In a preferred embodiment, the negative electrode of the lithium ion battery is the electrode of the embodiment of the present invention, and the electrode active material contained in the electrode active layer is a silicon-based negative electrode material. Therefore, the lithium ion battery has good cycle performance, long service life and stable electrochemical performance.
The polymer binder, the method for preparing the same, the lithium metal battery, and the like according to the embodiments of the present invention will be illustrated by examples.
Polymer binder and preparation method embodiment thereof
Example A1
The embodiment provides a polymer binder and a preparation method thereof. The polymer binder comprises poly (acrylic acid-acrylonitrile) and poly (styrene-butadiene), molecular chains of the poly (acrylic acid-acrylonitrile) and the poly (styrene-butadiene) respectively form a grid structure, and the grid structure of the poly (acrylic acid-acrylonitrile) and the grid structure of the poly (styrene-butadiene) mutually penetrate through to form an interpenetrating network structure.
The preparation method of the polymer binder comprises the following steps:
s1: in a reactor equipped with stirring means, network I polymerization monomers (50.0g of acrylic acid and 55.2g of acrylonitrile), 5.3g of the crosslinking agent Divinylbenzene (DVB), 5.3g of a 10% strength by weight buffer (NaHCO) were introduced3) The solution, 3.2g of emulsifier Sodium Dodecyl Sulfate (SDS) and 105.2g of deionized water are stirred at a high speed for pre-emulsification for 1 hour to prepare a network I pre-emulsion;
s2: adding 525.8g of poly (styrene-butadiene) polymer emulsion with the concentration of 40 wt% into a reactor provided with a stirring device, a reflux condenser tube, a thermometer and a constant pressure dropping device, and heating to 60 ℃ and stirring for 60min to swell poly (styrene-butadiene) polymer molecules;
s3: 55.2g of the network I pre-emulsion was added to step S2, stirred at 60 ℃ for 30min and warmed to 75 ℃, and 2.1g of ammonium persulfate ((NH) having a concentration of 5 wt.%was added dropwise4)2S2O8) Continuously heating the solution of the initiator to 79 ℃, keeping the temperature for 30min, controlling the dropping speed, and simultaneously dropping the rest pre-emulsion of the network I and the initiator;
s4: after the dropwise addition, the temperature is kept for 6h until the reaction is complete, and the poly (acrylic acid-acrylonitrile)/poly (styrene-butadiene) interpenetrating network polymer emulsion is obtained after cooling to room temperature and pumping filtration.
Example A2
The embodiment provides a polymer binder and a preparation method thereof. The polymeric binder contains the ingredients as in example a 1.
The preparation method of the polymer binder comprises the following steps:
s1: in a reactor equipped with stirring means, network I polymerization monomers (50.0g of acrylic acid and 147.1g of acrylonitrile), 9.9g of the crosslinking agent Divinylbenzene (DVB), 9.9g of a buffer (NaHCO) having a concentration of 10% by weight are introduced3) The solution, 5.9g of emulsifier Sodium Dodecyl Sulfate (SDS) and 197.1g of deionized water are stirred at a high speed for pre-emulsification for 1 hour to prepare a network I pre-emulsion;
s2: 492.7g of poly (styrene-butadiene) polymer emulsion with the concentration of 40 wt% is added into a reactor provided with a stirring device, a reflux condenser tube, a thermometer and a constant pressure dropping device, and the temperature is raised to 60 ℃ to be stirred for 60min, so that the poly (styrene-butadiene) polymer molecules are swelled;
s3: adding 103.5g of the pre-emulsion of the network I into the step S2, and stirring for 30min at 60 ℃; the temperature was raised to 75 ℃ and 3.9g of ammonium persulfate ((NH) having a concentration of 5 wt.% was added dropwise4)2S2O8) Continuously heating the solution of the initiator to 79 ℃, keeping the temperature for 30min, controlling the dropping speed, and simultaneously dropping the rest pre-emulsion of the network I and the initiator;
s4: after the dropwise addition, the temperature is kept for 6 hours until the reaction is complete. Cooling to room temperature, and filtering to obtain the poly (acrylic acid-acrylonitrile)/poly (styrene-butadiene) interpenetrating network polymer emulsion.
Example A3
The embodiment provides a polymer binder and a preparation method thereof. The polymeric binder contains the ingredients as in example a 1.
The preparation method of the polymer binder comprises the following steps:
s1: in a reactor equipped with stirring means, network I polymerization monomers (20.0g of acrylic acid and 132.4g of acrylonitrile), 7.6g of the crosslinking agent Divinylbenzene (DVB), 7.6g of a buffer (NaHCO) having a concentration of 10% by weight, were charged3) Solution, 4.6g of emulsifier Sodium Dodecyl Sulfate (SDS) and 152.4gIonized water, and stirring at a high speed for pre-emulsification for 1h to prepare a pre-emulsion of a network I;
s2: adding 114.3g of poly (styrene-butadiene) polymer emulsion with the concentration of 40 wt% into a reactor provided with a stirring device, a reflux condenser tube, a thermometer and a constant pressure dropping device, and heating to 60 ℃ and stirring for 60min to swell poly (styrene-butadiene) polymer molecules;
s3: adding 80.0g of the pre-emulsion of the network I into the step S2, and stirring for 30min at 60 ℃; the temperature was raised to 75 ℃ and 3.0g of ammonium persulfate ((NH) having a concentration of 5 wt.% was added dropwise4)2S2O8) Continuously heating the solution of the initiator to 79 ℃, keeping the temperature for 30min, controlling the dropping speed, and simultaneously dropping the rest pre-emulsion of the network I and the initiator;
s4: after the dropwise addition, the temperature is kept for 6 hours until the reaction is complete. Cooling to room temperature, and filtering to obtain the poly (acrylic acid-acrylonitrile)/poly (styrene-butadiene) interpenetrating network polymer emulsion.
And applying 1.5 wt% of the binder to artificial graphite negative electrode slurry containing 15 wt% of SiOx, coating the artificial graphite negative electrode slurry on copper foil, and drying to obtain a negative electrode sheet. And laminating the lithium ion battery core with an anode plate containing NCM811 anode material and a 16 mu mPE diaphragm to obtain a battery core, packaging the battery core through an aluminum plastic film, and sequentially performing the working procedures of baking, injecting electrolyte, forming, final sealing and the like to obtain the lithium ion battery.
Example A4
The embodiment provides a polymer binder and a preparation method thereof. The polymeric binder contains the ingredients as in example a 1.
The preparation method of the polymer binder comprises the following steps:
s1: adding network I polymerization monomers (20.0g of acrylic acid and 34.3g of acrylonitrile), 2.7g of cross-linking agent Divinylbenzene (DVB), 2.7g of a 10 wt% buffer (NaHCO3) solution, 1.6g of emulsifier Sodium Dodecyl Sulfate (SDS) and 54.3g of deionized water into a reactor provided with a stirring device, and stirring at a high speed for pre-emulsification for 1 hour to prepare network I pre-emulsion;
s2: 407.4g of poly (styrene-butadiene) polymer emulsion with the concentration of 40 wt% is added into a reactor provided with a stirring device, a reflux condenser tube, a thermometer and a constant pressure dropping device, and the temperature is raised to 60 ℃ to be stirred for 60min, so that the poly (styrene-butadiene) polymer molecules are swelled;
s3: adding 28.5g of the pre-emulsion of the network I into the step S2, and stirring for 30min at 60 ℃; heating to 75 ℃, dropwise adding 1.1g of ammonium persulfate ((NH4)2S2O8) solution initiator solution with the concentration of 5 wt%, continuously heating to 79 ℃, keeping the temperature for 30min, controlling the dropwise adding speed, and dropwise adding the rest network I pre-emulsion and the initiator;
s4: after the dropwise addition is finished, the temperature is kept for 6 hours until the reaction is full. Cooling to room temperature, and filtering to obtain the poly (acrylic acid-acrylonitrile)/poly (styrene-butadiene) interpenetrating network polymer emulsion.
Example A5
The embodiment provides a polymer binder and a preparation method thereof. The polymeric binder contains the ingredients as in example a 1.
The preparation method of the polymer binder comprises the following steps:
s1: adding network I polymerization monomers (20.0g of acrylic acid and 132.4g of acrylonitrile), 7.6g of cross-linking agent Divinylbenzene (DVB), 7.6g of a buffering agent (NaHCO3) solution with the concentration of 10 wt%, 4.6g of emulsifier Sodium Dodecyl Sulfate (SDS) and 152.4g of deionized water into a reactor provided with a stirring device, and stirring and pre-emulsifying at a high speed for 1 hour to prepare a network I pre-emulsion;
s2: adding 152.4g of poly (styrene-butadiene) polymer emulsion with the concentration of 40 wt% into a reactor provided with a stirring device, a reflux condenser tube, a thermometer and a constant pressure dropping device, and heating to 60 ℃ and stirring for 60min to swell poly (styrene-butadiene) polymer molecules;
s3: adding 80.0g of the pre-emulsion of the network I into the step S2, and stirring for 30min at 60 ℃; heating to 75 ℃, dropwise adding 3.0g of ammonium persulfate ((NH4)2S2O8) solution initiator solution with the concentration of 5 wt%, continuously heating to 79 ℃, keeping the temperature for 30min, controlling the dropwise adding speed, and dropwise adding the rest network I pre-emulsion and the initiator;
s4: after the dropwise addition, the temperature is kept for 6 hours until the reaction is complete. Cooling to room temperature, and filtering to obtain the poly (acrylic acid-acrylonitrile)/poly (styrene-butadiene) interpenetrating network polymer emulsion.
Example A6 to example A20
Examples a 6-a 20 each provide a polymeric binder and a method of making the same. The polymeric binders of examples a 6-a 20 contained the same ingredients as the polymeric binders of example a1, respectively.
The polymer binder preparation processes of examples a6 through a20 were respectively referenced to the process of example a1, except that the additive components were added in the amounts shown in table 1 below at each step of the preparation processes of examples a6 through a 20.
Table 1 example a6 to example a20 polymer Binder preparation method ingredient addition ratios table
Second, lithium ion Battery embodiment
Example B1 to example B20
Examples B1 through B20 each provide a lithium ion battery. The lithium ion batteries of examples B1-B20 each included the following structures:
negative electrode: respectively preparing negative electrode slurry from the polymer binder and the negative electrode material provided in the embodiments a1 to a20 according to the proportion in table 2, coating the negative electrode slurry on copper foil, and drying to obtain a negative electrode sheet; specific Polymer Binders as provided in example A1 with SiO in Table 2xPreparing negative electrode slurry from an artificial graphite negative electrode, coating the negative electrode slurry on copper foil, drying to obtain the negative electrode sheet of the lithium ion battery in the embodiment B1, and preparing the negative electrode sheets of the lithium ion batteries in the embodiments B1 to B20 respectively by analogy;
and (3) positive electrode: positive electrode sheets of the lithium ion batteries in examples B1 to B20 were prepared with the positive electrode materials described in the respective examples in table 2, respectively;
a diaphragm: the separators described in the respective examples in table 2 were used as separators of lithium ion batteries in examples B1 to B20, respectively;
electrolyte solution: an electrolyte solution in which LiPF6 is a lithium salt and an organic solvent is a solvent was used as the electrolyte solution in each example;
assembling: and respectively winding the positive electrode, the negative electrode and the diaphragm of each lithium ion battery to prepare a battery core, respectively packaging the battery cores through aluminum plastic films, and respectively and sequentially performing the working procedures of baking, injecting electrolyte, formation, final sealing and the like to respectively obtain the lithium ion batteries in the embodiments B1 to B20.
Comparative examples B1 to B5
Comparative examples B1 to B5 each provide a lithium ion battery. The lithium ion batteries of comparative examples B1 to B5 each included the following structures:
negative electrode: respectively preparing negative electrode slurry by using the existing binder and the corresponding negative electrode material in each example in the table 2 according to the proportion in the table 2, coating the negative electrode slurry on copper foil, and drying to prepare negative electrode sheets of the lithium ion batteries in the comparative examples B1 to B5;
and (3) positive electrode: preparing positive electrode sheets of the lithium ion batteries in comparative examples B1 to B5 from the positive electrode materials described in the respective examples in Table 2;
a diaphragm: the separators described in each example in table 2 were used as separators of lithium ion batteries in comparative examples B1 to B5, respectively;
electrolyte solution: an electrolyte solution in which LiPF6 is a lithium salt and an organic solvent is a solvent was used as the electrolyte solution in each example;
correlation characteristic test
The lithium ion batteries assembled from examples B1-B20 and comparative examples B1-B5 were subjected to the first efficiency and cycle performance tests in table 2, respectively, and the test results are shown in table 2.
Wherein, the conditions of the first efficiency and cycle performance test are as follows: under the condition of 25 +/-2 ℃, the batteries of the examples are subjected to constant-current and constant-voltage charging to the upper limit voltage of the battery cell at 1/3C, and discharged to the lower limit voltage of the battery cell at 1C after standing.
TABLE 2 Positive and negative electrodes, separators and electrochemical Properties of lithium ion batteries in examples and comparative examples
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. The polymer binder is characterized by comprising a first polymer binder and a second polymer binder, wherein molecular chains of the first polymer binder and molecular chains of the second polymer binder form a grid structure respectively, and the grid structure of the first polymer binder and the grid structure of the second polymer binder are arranged in a mutually penetrating manner to form an interpenetrating network structure;
the preparation method of the polymer binder comprises the following steps:
preparing a pre-emulsion from a monomer of a first polymer binder, a cross-linking agent, an emulsifier and water;
providing an emulsion of a second polymeric binder and heat treating to swell the second polymeric binder molecules; the molecular chains of the second polymer binder form a grid structure;
and mixing the pre-emulsion and the emulsion of the second polymer binder after the heat treatment to form a mixed emulsion, heating the mixed emulsion to the polymerization reaction temperature range of the monomer, adding an initiator into the mixed emulsion to perform polymerization reaction on the monomer, and generating the first polymer binder in situ in a grid structure contained in the second polymer binder.
2. The polymeric binder of claim 1, whereinCharacterized in that: the first polymeric binder contains-COOH, -OH, -NH2At least one polar functional group; and/or
The second polymeric binder contains at least one hydrophilic group of-COOH, -OH.
3. The polymer binder of claim 2, wherein: the first polymer binder comprises at least one of poly (acrylic acid-acrylonitrile), poly (acrylic acid-acrylonitrile) salt binders and poly (vinyl alcohol); and/or
The second polymeric binder includes at least one of poly (styrene-butadiene), polybutylacrylate.
4. The polymeric binder of any one of claims 1-3, wherein: the mass ratio of the first polymer binder to the second polymer binder is 1: 2-1: 10.
5. a method of preparing a polymeric binder comprising the steps of:
preparing a monomer of a first polymer binder, a cross-linking agent, an emulsifier and water into a pre-emulsion;
providing an emulsion of a second polymeric binder and heat treating to swell the second polymeric binder molecules; molecular chains of the second polymer binder form a grid structure;
and mixing the pre-emulsion and the emulsion of the second polymer binder after the heat treatment to form a mixed emulsion, heating the mixed emulsion to the polymerization reaction temperature range of the monomer, adding an initiator into the mixed emulsion to perform polymerization reaction on the monomer, and generating the first polymer binder in situ in a grid structure contained in the second polymer binder.
6. The method of claim 5, wherein:
the cross-linking agent accounts for 2-10 wt% of the total amount of the monomers; and/or
The proportion of the emulsifier in the total amount of the monomers is 0.5-5 wt%; and/or
In the mixed emulsion, the mass ratio of the emulsion to the pre-emulsion is 1: 2-1: 10; wherein the concentration of the second polymer binder in the emulsion is 10-50 wt%, and the mass ratio of water to the total amount of monomers in the pre-emulsion is 1: 1-5: 1; and/or
A buffering agent is further added into the pre-emulsion, and the buffering agent accounts for 2-10 wt% of the total amount of the monomers;
and the total amount of the initiator added into the mixed emulsion accounts for 1-5 wt% of the total amount of the monomers.
7. The method of claim 6, wherein:
the monomer comprises at least one of mixed monomer of acrylic acid and acrylonitrile and vinyl alcohol monomer;
the cross-linking agent comprises at least one of divinylbenzene, acrylic acid, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, methacrylic acid, N-methylolacrylamide and diacetone acrylamide;
the emulsifier comprises at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium stearate and oleate;
the buffer comprises at least one of ammonium bicarbonate, ammonium acetate and sodium bicarbonate;
the second polymeric binder comprises at least one of poly (styrene-butadiene), polybutylacrylate;
the initiator comprises at least one of ammonium persulfate, sodium persulfate and potassium persulfate.
8. An electrode comprising a current collector and an electrode active layer bonded to a surface of the current collector, characterized in that: the electrode active layer contains a binder which is the polymer binder according to any one of claims 1 to 4.
9. The electrode of claim 8, wherein: the electrode is a negative electrode, and the electrode active material contained in the electrode active layer is a silicon-based negative electrode material.
10. A lithium ion battery, characterized by: including positive pole, negative pole and fold and locate diaphragm between positive pole and the negative pole, its characterized in that: the positive electrode or/and the negative electrode is the electrode according to claim 8.
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