CN117801297A - BAB type block copolymer, preparation method, binder, positive electrode slurry, positive electrode plate, secondary battery and power utilization device - Google Patents

BAB type block copolymer, preparation method, binder, positive electrode slurry, positive electrode plate, secondary battery and power utilization device Download PDF

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Publication number
CN117801297A
CN117801297A CN202310735467.XA CN202310735467A CN117801297A CN 117801297 A CN117801297 A CN 117801297A CN 202310735467 A CN202310735467 A CN 202310735467A CN 117801297 A CN117801297 A CN 117801297A
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positive electrode
acrylic acid
bab
poly
block copolymer
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曾子鹏
李�诚
刘会会
孙成栋
王景明
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to CN202310735467.XA priority Critical patent/CN117801297A/en
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G81/00—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
    • C08G81/02—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers at least one of the polymers being obtained by reactions involving only carbon-to-carbon unsaturated bonds
    • C08G81/021—Block or graft polymers containing only sequences of polymers of C08C or C08F
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Graft Or Block Polymers (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The application relates to a BAB block copolymer, a preparation method, a binder, positive electrode slurry, a positive electrode sheet, a secondary battery and an electric device. In particular, the present application provides a BAB-type block copolymer comprising an A-block containing structural units derived from a monomer of formula I and a B-block containing structural units derived from a monomer of formula II. The adhesive prepared from the BAB type block copolymer can effectively slow down the gelation phenomenon of the slurry, improve the stability of the slurry, improve the flexibility of the pole piece, improve the adhesive force, reduce the sheet resistance, reduce the direct current impedance growth rate of the battery and/or improve the circulation capacity retention rate of the battery.

Description

BAB type block copolymer, preparation method, binder, positive electrode slurry, positive electrode plate, secondary battery and power utilization device
The present application is a divisional application based on the invention application with application number 202211206844.2, application date 2022, 09 and 30, and the invention name "BAB block copolymer, preparation method, binder, positive electrode sheet, secondary battery, and electric device".
Technical Field
The application relates to the technical field of secondary batteries, in particular to a BAB type block copolymer, a preparation method, a binder, positive electrode slurry, a positive electrode plate, a secondary battery and an electric device.
Background
In recent years, secondary batteries are widely used in energy storage power supply systems such as hydraulic power, thermal power, wind power and solar power stations, and in various fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace, and the like.
The binder is a common material in secondary batteries and is widely applied to battery pole pieces, isolating films, packaging parts and the like. However, the traditional binder has high production cost, insufficient productivity, large damage to the environment, and gel is easy to appear in the preparation process, so that the slurry has poor stability and high processing cost, the pole piece prepared by the binder has poor flexibility, low binding power, high resistance and low yield, and the battery has high direct current impedance growth rate, low cycle capacity retention rate and unstable performance, and is difficult to meet the requirements of the market on the cost and performance of the battery. Thus, the existing adhesives remain to be improved.
Disclosure of Invention
The present invention has been made in view of the above problems, and an object of the present invention is to provide a BAB-type block copolymer, in which a binder prepared from the BAB-type block copolymer can effectively slow down the gelation of a slurry, improve the stability of the slurry, improve the flexibility of a pole piece, improve the adhesion, reduce the sheet resistance, reduce the rate of increase in the direct current resistance of a battery, and/or improve the cycle capacity retention rate of the battery.
In a first aspect the present application provides a BAB-type block copolymer comprising an A-block comprising structural units derived from a monomer of formula I and a B-block comprising structural units derived from a monomer of formula II,
wherein R is 1 、R 2 、R 3 Each independently selected from hydrogen, fluorine, C containing at least one fluorine atom 1-3 One or more of alkyl groups, R 4 、R 5 、R 6 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 An alkyl group.
The adhesive prepared by the BAB type block copolymer can maximize the weight average molecular weight of the fluorine-containing block and the non-fluorine block, fully exert the respective advantages of the fluorine-containing adhesive and the non-fluorine adhesive, and realize the effect of complementary advantages. The adhesive can effectively slow down the gelation phenomenon of the slurry, improve the stability of the slurry, improve the flexibility of the pole piece, improve the adhesive force, reduce the resistance of the diaphragm, reduce the DC resistance growth rate of the battery and/or improve the circulation capacity retention rate of the battery.
In any embodiment, the B-block further comprises structural units derived from a monomer of formula III,
wherein R is 7 、R 8 、R 9 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 Alkyl, R 10 Selected from the group consisting ofOne of ester group, cyano group and amide group.
In any embodiment, the molar content of structural units derived from the monomer of formula I is 30% to 70% based on the total moles of all structural units in the block copolymer.
The molar content of the structural unit derived from the monomer shown in the formula I is controlled within a proper range, so that the gelation phenomenon of the slurry can be effectively slowed down, the stability of the slurry is improved, the flexibility of the pole piece is improved, the membrane resistance is reduced, and the cycle capacity retention rate of the battery is improved.
In any embodiment, the weight average molecular weight of the block copolymer is from 40 to 200 tens of thousands, the weight average molecular weight of the block copolymer is optionally from 120 to 200 tens of thousands, and the weight average molecular weight of the block copolymer is optionally from 120 to 150 tens of thousands.
The weight average molecular weight of the segmented copolymer is controlled within a proper range, so that the gelation of the slurry can be effectively slowed down, the stability of the slurry is improved, the flexibility of the pole piece is improved, the binding force is improved, the membrane resistance is reduced, the direct current impedance growth rate of the battery is reduced, and the circulation capacity retention rate of the battery is improved.
In any embodiment, the weight average molecular weight of the a-block in the block copolymer is from 20 ten thousand to 105 ten thousand.
The weight average molecular weight of the A-block in the block copolymer is controlled within a proper range, so that the gelation phenomenon of the slurry can be effectively slowed down, the stability of the slurry is improved, the flexibility of the pole piece is improved, the membrane resistance is reduced, and the cycle capacity retention rate of the battery is improved.
In any embodiment, the weight average molecular weight of each B-block in the block copolymer is from 10 to 50 tens of thousands.
Controlling the weight average molecular weight of each B-block in the block copolymer within a proper range can improve the adhesion and improve the cycle capacity retention of the battery.
In any embodiment, the monomer shown in the formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene and vinyl fluoride. In this case, the adhesion can be improved, and the cycle capacity retention rate of the battery can be improved.
In any embodiment, the monomer shown in the formula II is selected from one or more of acrylic acid, methacrylic acid and ethacrylic acid.
In any embodiment, the monomer shown in the formula III is selected from one or more of acrylamide, acrylic acid ester and acrylonitrile.
At this time, the gel phenomenon of the slurry can be effectively slowed down, the stability of the slurry is improved, the flexibility of the pole piece is improved, the membrane resistance is reduced, and the circulation capacity retention rate of the battery is improved.
The raw materials are simple and easy to obtain, and compared with the traditional adhesive, the adhesive can greatly reduce the production cost and improve the yield.
In any embodiment, the block copolymer is a polyacrylic acid-polyvinylidene fluoride-polyacrylic acid triblock copolymer, a polyacrylic acid-polyvinyl fluoride-polyacrylic acid triblock copolymer, a polyacrylic acid-polytetrafluoroethylene-polyacrylic acid triblock copolymer, a poly (acrylic acid-acrylic acid ester) -polyvinylidene fluoride-poly (acrylic acid-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylic acid ester) -polyvinyl fluoride-poly (acrylic acid-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylic acid ester) -polytetrafluoroethylene-poly (acrylic acid-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylonitrile-acrylic acid ester) -polyvinylidene fluoride-poly (acrylic acid-acrylic acid nitrile-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylic acid ester) -polyvinyl fluoride-poly (acrylic acid-acrylonitrile-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylic acid ester) -polytetrafluoroethylene-poly (acrylic acid-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylic acid amide-acrylic acid ester) -polyvinylidene fluoride-poly (acrylic acid-acrylic acid ester) triblock copolymer, one or more of poly (acrylic acid-acrylamide-acrylate) -polyvinyl fluoride-poly (acrylic acid-acrylamide-acrylate) triblock copolymers, poly (acrylic acid-acrylamide-acrylate) -polytetrafluoroethylene-poly (acrylic acid-acrylamide-acrylate) triblock copolymers. In this case, the cycle capacity retention rate of the battery can be improved.
The second aspect of the present application also provides a method for producing a BAB type block copolymer, comprising the steps of:
preparation of the A-block: polymerizing at least one monomer shown in formula I to prepare an A-block,
wherein R is 1 、R 2 、R 3 Each independently selected from hydrogen, fluorine, C containing at least one fluorine atom 1-3 One or more of alkyl groups;
preparation of the B-block: polymerizing monomer units comprising at least one monomer of formula II to produce a B-block,
wherein R is 4 、R 5 、R 6 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 An alkyl group;
preparation of a BAB type block copolymer: joining the a-block and the B-block to produce a BAB-type block copolymer.
Compared with the traditional copolymerization method, the preparation method can maximize the weight average molecular weight of the fluorine-containing block and the non-fluorine-containing block, fully exert the respective advantages of the fluorine-containing binder and the non-fluorine binder, and realize the effect of complementary advantages. The adhesive of the BAB triblock copolymer prepared by the method can effectively slow down the gelation phenomenon of the slurry, improve the stability of the slurry, improve the flexibility of a pole piece, improve the adhesive force, reduce the membrane resistance, reduce the direct current impedance growth rate of a battery and/or improve the circulation capacity retention rate of the battery.
In any embodiment, the monomer unit further comprises at least one monomer of formula III,
wherein R is 7 、R 8 、R 9 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 Alkyl, R 10 One selected from ester group, cyano group and amide group.
In any embodiment, the method of preparing a B-block comprises:
and (3) carrying out reversible addition-fragmentation chain transfer polymerization on the monomer units, the chain transfer agent and the first initiator at a reaction temperature of 60-80 ℃ for 4.5-7 hours to obtain the B-block with the terminal alkynyl or azido group as a terminal group.
By adopting the preparation method, controllable polymerization can be realized, and the molecular weight distribution of the product is narrower.
In any embodiment, the method of making an a-block comprises:
at least one monomer shown in the formula I and a second initiator are polymerized for 2.5-5 hours at the reaction temperature of 80-95 ℃, and substitution reaction is carried out on the end group of the product to prepare the A-block with the azide group or the alkynyl group at both ends as the end group.
By adopting the preparation method, the end azide or end alkynyl A-block is successfully prepared.
In any embodiment, the method of preparing a BAB-type block copolymer comprises:
Mixing the A-block with azide groups or alkynyl groups at two ends as end groups with the B-block with alkynyl groups or azide groups at the ends as end groups, and performing click reaction to prepare the BAB type block copolymer, wherein the end groups of the A-block and the B-block are different.
The preparation method has the advantages of high efficiency, stability and high specificity, and improves the yield of products.
In any embodiment, the chain transfer agent is a RAFT chain transfer agent containing terminal alkynyl or azido groups.
In any embodiment, the first initiator is an azo initiator selected from one or two of azobisisobutyronitrile and azobisisoheptonitrile.
In any embodiment, the second initiator is a symmetrical difunctional initiator selected from the group consisting of 4- (chloromethyl) benzoyl peroxide.
A third aspect of the present application provides the use of the BAB-type block copolymer of any embodiment or the BAB-type block copolymer prepared by the preparation method of any embodiment in a secondary battery.
The fourth aspect of the present application provides a positive electrode sheet, including a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, where the positive electrode film layer includes a positive electrode active material, a conductive agent, and a binder, and the binder is a BAB-type block copolymer in any embodiment or a BAB-type block copolymer prepared by a preparation method in any embodiment.
The positive pole piece has excellent flexibility and binding force, and simultaneously has lower diaphragm resistance.
In any embodiment, the mass fraction of the binder is 0.1% -3%, and the mass fraction of the binder may be selected to be 1% -3% based on the total mass of the positive electrode active material.
The mass fraction of the binder is controlled within a reasonable range, so that the gelation phenomenon of the slurry can be obviously slowed down, the stability of the slurry is improved, the flexibility of the pole piece is improved, and the cycle capacity retention rate of the battery is improved.
In any embodiment, the binding force per unit length between the positive electrode film layer and the positive electrode current collector is not less than 8N/m, optionally the binding force per unit length between the positive electrode film layer and the positive electrode current collector is not less than 10N/m.
The positive electrode film layer of the pole piece and the positive electrode current collector have high bonding strength, and the positive electrode film layer is not easy to fall off from the positive electrode current collector in the use process, so that the cycle performance and the safety of the battery are improved.
In any embodiment, after the positive electrode plate is subjected to bending test for at least 3 times, the positive electrode plate has a light transmission phenomenon.
The pole piece has excellent flexibility, is not easy to crack in the production process, and is beneficial to improving the yield.
In any embodiment, the sheet resistance of the positive electrode sheet is less than or equal to 0.52 Ω, alternatively the sheet resistance of the positive electrode sheet is less than or equal to 0.46 Ω.
In a fifth aspect of the present application, there is provided a secondary battery comprising an electrode assembly comprising a separator, a negative electrode tab, and a positive electrode tab of the fourth aspect of the present application, and an electrolyte, optionally, the secondary battery comprises at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.
In a sixth aspect of the present application, there is provided a battery module including the secondary battery of the fifth aspect of the present application.
In a seventh aspect of the present application, there is provided a battery pack comprising the battery module of the sixth aspect of the present application.
In an eighth aspect of the present application, there is provided an electric device including at least one of the secondary battery of the fifth aspect, the battery module of the sixth aspect, or the battery pack of the seventh aspect of the present application.
Drawings
FIG. 1 is a schematic illustration of the preparation of a BAB type block copolymer according to an embodiment of the present application;
fig. 2 is a schematic view of a secondary battery according to an embodiment of the present application;
fig. 3 is an exploded view of the secondary battery of the embodiment of the present application shown in fig. 2;
Fig. 4 is a schematic view of a battery module according to an embodiment of the present application;
FIG. 5 is a schematic view of a battery pack according to an embodiment of the present application;
FIG. 6 is an exploded view of the battery pack of one embodiment of the present application shown in FIG. 5;
fig. 7 is a schematic view of an electric device in which the secondary battery according to an embodiment of the present application is used as a power source.
Reference numerals illustrate:
1, a battery pack; 2, upper box body; 3, lower box body; 4, a battery module; 5 a secondary battery; 51 a housing; 52 electrode assembly; 53 cover plates; a block copolymer of type 6 BAB; 61A-blocks; 611A-block; 612 a monomer of formula I; 62B-block; end groups of 621B-blocks; 622 monomers of formula II.
Detailed Description
Hereinafter, embodiments of the positive electrode active material and the method of manufacturing the same, the positive electrode tab, the secondary battery, the battery module, the battery pack, and the electrical device of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.
The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.
All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.
All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.
All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.
Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.
The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).
The traditional adhesive has the advantages of high production cost, insufficient productivity, large environmental hazard, and easy occurrence of gel in the preparation process, so that the slurry has poor stability and high processing cost, the pole piece prepared by the adhesive has the advantages of poor flexibility, low adhesive force, high resistance, low yield, high direct current impedance growth rate, low cycle capacity retention rate and unstable performance, and the requirements of the market on the battery cost and performance are difficult to meet. Thus, the existing adhesives remain to be improved.
[ adhesive ]
Based on this, the present application proposes a BAB-type block copolymer comprising an A-block containing structural units derived from a monomer of formula I and a B-block containing structural units derived from a monomer of formula II,
wherein R is 1 、R 2 、R 3 Each independently selected from hydrogen, fluorine, C containing at least one fluorine atom 1-3 One or more of alkyl groups, R 4 、R 5 、R 6 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 An alkyl group.
In some embodiments, the B-block further comprises structural units derived from monomers of formula III,
wherein R is 7 、R 8 、R 9 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 Alkyl, R 10 One selected from ester group, cyano group and amide group.
In this context, the term "binder" refers to a chemical compound, polymer or mixture that forms a colloidal solution or colloidal dispersion in a dispersing medium.
As used herein, the term "block copolymer" is a particular polymer prepared by joining together two or more polymer segments that differ in nature. Block polymers with a specific structure will exhibit properties that differ from simple linear polymers, as well as mixtures of many random copolymers and even homopolymers. There are commonly known AB and BAB types, of which A, B is a long segment; there are Also (AB) n-type multistage copolymers in which the A, B segments are relatively short.
As used herein, the term "BAB-type block copolymer" refers to a triblock copolymer having an A-block in the middle and B-blocks on both sides. Wherein the A-block and the B-block are each a polymer segment having a predetermined weight average molecular weight formed by polymerizing different monomers. In some embodiments, the a-block is a long sequence segment formed by polymerization of a fluoromonomer and the B-block is a long sequence segment formed by polymerization of one or more non-fluoromonomers. The A-blocks and B-blocks are covalently bonded in an ordered manner to form a BAB type block copolymer. Taking example 1 of the present application as an example, wherein the A-block is polyvinylidene fluoride having a weight average molecular weight of 45 ten thousand g/mol, formed by polymerization of vinylidene fluoride monomers; the B-block is poly (acrylic acid-acrylamide-ethyl methacrylate), the weight average molecular weight is 40 ten thousand g/mol, and the polymer is formed by polymerizing acrylic acid, ethyl methacrylate and acrylamide monomers; the BAB block copolymer finally synthesized is poly (acrylic acid-acrylamide-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer, and the weight average molecular weight is 120 ten thousand g/mol.
In this context, the term "polymer" includes on the one hand the collection of chemically homogeneous macromolecules prepared by polymerization, but differing in terms of degree of polymerization, molar mass and chain length. The term on the other hand also includes derivatives of such macromolecular assemblies formed by polymerization, i.e. compounds which can be obtained by reaction of functional groups in the macromolecules described above, for example addition or substitution, and which can be chemically homogeneous or chemically inhomogeneous.
In this context, the term "ester group" refers to-COOR 11 A group R 11 Selected from alkyl groups substituted or unsubstituted with substituents.
Herein, the term "amide group" refers toR 12 、R 13 Each independently selected from hydrogen, alkyl of substituted or unsubstituted groups.
In this context, the term "cyano" refers to a-CN group.
In some embodiments, the dispersion medium of the binder is an aqueous solvent, such as water. I.e. the binder is dissolved in an aqueous solvent.
In some embodiments, the dispersion medium of the binder is an oily solvent, examples of which include, but are not limited to, dimethylacetamide, N-dimethylformamide, N-methylpyrrolidone, acetone, dimethyl carbonate, ethylcellulose, polycarbonate. That is, the binder is dissolved in an oily solvent.
In some embodiments, a binder is used to secure the electrode materials and/or conductive agents in place and adhere them to the conductive metal components to form the electrode.
In some embodiments, the binder serves as a positive electrode binder for binding the positive electrode active material and/or the conductive agent to form an electrode.
In some embodiments, the binder serves as a negative electrode binder for binding a negative electrode active material and/or a conductive agent to form an electrode.
Herein, the term "C 1-3 Alkyl "refers to a straight or branched hydrocarbon chain group consisting of only carbon and hydrogen atoms, no unsaturation present in the group, having from one to three carbon atoms, and attached to the remainder of the molecule by a single bond. C (C) 1-3 Examples of alkyl groups include, but are not limited to: methyl, ethyl, n-propyl, n-butyl, 1-methylethyl (isopropyl).
Herein, the term "C 1-5 Alkyl "refers to a straight or branched hydrocarbon chain group consisting of only carbon and hydrogen atoms, no unsaturation present in the group, having from one to five carbon atoms, and attached to the remainder of the molecule by a single bond. C (C) 1-5 Examples of alkyl groups include, but are not limited to: methyl, ethyl, n-propyl, 1-methylethyl (isopropyl), n-butyl, t-butyl, isopentyl.
In this context, the term "substituted" means that at least one hydrogen atom of the compound or chemical moiety is substituted with another chemical moiety with a substituent, wherein each substituent is independently selected from the group consisting of: hydroxy, mercapto, amino, cyano, nitro, aldehyde, halogen, alkenyl, alkynyl, aryl, heteroaryl, C 1-6 Alkyl, C 1-6 An alkoxy group.
In some embodiments, the molar content of structural units derived from the monomer of formula I is 30% to 70% based on the total moles of all structural units in the block copolymer. In some embodiments, the molar content of structural units derived from the monomer of formula I may be selected to be any one of 30% -35%, 35% -40%, 40% -45%, 45% -50%, 50% -55%, 55% -60%, 60% -65%, 65% -70%, 30% -40%, 40% -50%, 50% -60%, 60% -70%, 35% -45%, 45% -55%, 55% -65%, 30% -45%, 45% -60%, 35% -50%, 50% -65%, 40% -55%, 55% -70%, 30% -50%, 50% -70%, 35% -55%, 40% -60%, 45% -65%, 30% -55%, 35% -60%, 40% -65%, 45% -70%, 30% -60%, 35% -65%, 40% -70%, 30% -65%, 35% -70% based on the total moles of all structural units in the block copolymer.
If the molar content of structural units derived from the monomer of formula I is too low, the adhesion of the pole piece is reduced; if the molar content of the structural unit derived from the monomer shown in the formula I is too high, the gelation phenomenon of the slurry is accelerated, the stability of the slurry is reduced, and the sheet resistance becomes large.
The molar content of the structural unit derived from the monomer shown in the formula I is controlled within a proper range, so that the gelation phenomenon of the slurry can be effectively slowed down, the stability of the slurry is improved, the flexibility of the pole piece is improved, the membrane resistance is reduced, and the cycle capacity retention rate of the battery is improved.
In some embodiments, the block copolymer has a weight average molecular weight of 40 ten thousand to 200 ten thousand. In some embodiments, the weight average molecular weight of the block copolymer may be selected from any one of 40 to 60, 60 to 80, 80 to 100, 100 to 120, 120 to 140, 140 to 160, 160 to 180, 180 to 200, 60 to 90, 90 to 120, 120 to 150, 150 to 180, 180 to 200, 120 to 200.
In this context, the term "weight average molecular weight" refers to the sum of the weight fractions of the polymer occupied by molecules of different molecular weights multiplied by their corresponding molecular weights.
If the weight average molecular weight of the block copolymer is too large, the binder is difficult to dissolve and is easy to agglomerate with the conductive agent, the internal resistance of the membrane is increased, in addition, the viscosity of the slurry is larger, the dispersibility of the binder is reduced, and the flexibility of the pole piece is affected; if the weight average molecular weight of the block copolymer is too small, a three-dimensional network bonding structure is difficult to form, an effective bonding effect cannot be achieved, and in addition, the internal resistance of the membrane becomes large.
The weight average molecular weight of the segmented copolymer is controlled within a proper range, so that the gelation of the slurry can be effectively slowed down, the stability of the slurry is improved, the flexibility of the pole piece is improved, the binding force is improved, the membrane resistance is reduced, the direct current impedance growth rate of the battery is reduced, and the circulation capacity retention rate of the battery is improved.
In some embodiments, the weight average molecular weight of the a-block in the block copolymer is 20 tens of thousands to 105 tens of thousands. In some embodiments, the weight average molecular weight of the A-block can be selected from any of 20-30, 30-40, 40-50, 50-60, 60-70, 70-80, 80-90, 90-105, 40-60, 40-80, 40-105.
If the weight average molecular weight of the A-block in the block copolymer is too large, structural units derived from the monomer shown in the formula I have too many strong polar groups, so that the stability of the slurry is affected; if the weight average molecular weight of the A-block in the block copolymer is too small, the adhesion of the pole piece is lowered.
The weight average molecular weight of the A-block in the block copolymer is controlled within a proper range, so that the gelation phenomenon of the slurry can be effectively slowed down, the stability of the slurry is improved, the flexibility of the pole piece is improved, the membrane resistance is reduced, and the cycle capacity retention rate of the battery is improved.
In some embodiments, the weight average molecular weight of each B-block in the block copolymer is from 10 ten thousand to 50 ten thousand. In some embodiments, the weight average molecular weight of each B-block can be selected from any of 10-20, 20-30, 30-40, 40-50, 20-40, 20-50.
Controlling the weight average molecular weight of each B-block in the block copolymer within a proper range can improve the adhesion and improve the cycle capacity retention of the battery.
In some embodiments, the monomer of formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, and vinyl fluoride.
In some embodiments, the monomer of formula II is selected from one or more of acrylic acid, methacrylic acid, ethacrylic acid.
In some embodiments, the monomer of formula III is selected from one or more of acrylamide, acrylate, acrylonitrile. In some embodiments, the monomer of formula III is selected from one or more of acrylamide, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, methyl ethacrylate, ethyl ethacrylate, acrylonitrile. In some embodiments, the monomer of formula III is selected from one or more of acrylamide, ethyl methacrylate, acrylonitrile.
In some embodiments of the present invention, in some embodiments, the BAB-block copolymer is a polyacrylic acid-polyvinylidene fluoride-polyacrylic acid triblock copolymer, a polyacrylic acid-polyvinyl fluoride-polyacrylic acid triblock copolymer, a polyacrylic acid-polytetrafluoroethylene-polyacrylic acid triblock copolymer, a poly (acrylic acid-acrylic acid ester) -polyvinylidene fluoride-poly (acrylic acid-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylic acid ester) -polyvinyl fluoride-poly (acrylic acid-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylic acid ester) -polytetrafluoroethylene-poly (acrylic acid-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylonitrile-acrylic acid ester) -polyvinylidene fluoride-poly (acrylic acid-acrylonitrile-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylonitrile-acrylic acid ester) -polyvinyl fluoride-poly (acrylic acid-acrylonitrile-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylonitrile-acrylic acid ester) -polytetrafluoroethylene-poly (acrylic acid-acrylic acid ester) triblock copolymer, a poly (acrylic acid-acrylic acid amide-acrylic acid ester) -polyvinylidene fluoride-poly (acrylic acid-acrylic acid ester) triblock copolymer, one or more of poly (acrylic acid-acrylamide-acrylate) -polyvinyl fluoride-poly (acrylic acid-acrylamide-acrylate) triblock copolymers, poly (acrylic acid-acrylamide-acrylate) -polytetrafluoroethylene-poly (acrylic acid-acrylamide-acrylate) triblock copolymers. In some embodiments, the BAB-block copolymer is one or more of a polyacrylic acid-polyvinylidene fluoride-polyacrylic acid triblock copolymer, a poly (acrylic acid-acrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylate) triblock copolymer, a poly (acrylic acid-acrylonitrile-acrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylonitrile-acrylate) triblock copolymer, a poly (acrylic acid-acrylamide-acrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylamide-acrylate) triblock copolymer, a poly (acrylic acid-acrylamide-acrylate) -polyvinyl fluoride-poly (acrylic acid-acrylamide-acrylate) triblock copolymer, a poly (acrylic acid-acrylamide-acrylate) -polytetrafluoroethylene-poly (acrylic acid-acrylamide-acrylate) triblock copolymer. In some embodiments, the BAB-block copolymer is one or more of a polyacrylic acid-polyvinylidene fluoride-polyacrylic acid triblock copolymer, a poly (acrylic acid-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-ethyl methacrylate) triblock copolymer, a poly (acrylic acid-acrylonitrile-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylonitrile-ethyl methacrylate) triblock copolymer, a poly (acrylic acid-acrylamide-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer, a poly (acrylic acid-acrylamide-ethyl methacrylate) -polyvinyl fluoride-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer, a poly (acrylic acid-acrylamide-ethyl methacrylate) -polytetrafluoroethylene-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer.
In this context, the term "acrylate" refers to the generic term for esters of acrylic acid and its homologs. Examples include, but are not limited to, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and the like.
The fluorine element contained in the A-block forms hydrogen bond action with hydroxyl or/and carboxyl on the surface of the positive electrode active material and the surface of the current collector, so that the pole piece has excellent adhesive force. The carboxyl group of the strong polar group in the B-block can form strong hydrogen bond and dipole-dipole interaction with the hydroxyl group on the surface of the positive electrode active material, so that the binding force of the pole piece is improved, the dispersibility of the binder for substances in slurry is improved, the resistance of the membrane is reduced, and compared with the traditional polyvinylidene fluoride, the addition amount of the binder in the slurry can be reduced. In addition, the carboxyl group with strong polar groups can enhance the stability of a molecular structure, can improve the glass transition temperature of the copolymer, improve the rigidity and the thermal stability of the copolymer, is beneficial to improving the oxidation stability of the positive electrode material, and can greatly improve the cycle performance of the battery.
The adhesive prepared by the BAB type block copolymer can maximize the weight average molecular weight of the fluorine-containing block and the non-fluorine block, fully exert the respective advantages of the fluorine-containing adhesive and the non-fluorine adhesive, and realize the effect of complementary advantages.
In summary, the adhesive prepared from the BAB type block copolymer can effectively slow down the gelation of the slurry, improve the stability of the slurry, improve the flexibility of the pole piece, improve the adhesive force, reduce the sheet resistance, reduce the direct current impedance growth rate of the battery, and/or improve the cycle capacity retention rate of the battery.
In one embodiment of the present application, there is provided a method for preparing a BAB-type block copolymer, comprising the steps of:
preparation of the A-block: polymerizing at least one monomer shown in formula I to prepare an A-block,
wherein R is 1 、R 2 、R 3 Each independently selected from hydrogen, fluorine, C containing at least one fluorine atom 1-3 One or more of alkyl groups;
preparation of the B-block: polymerizing monomer units comprising at least one monomer of formula II to produce a B-block,
wherein R is 4 、R 5 、R 6 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 An alkyl group;
preparation of a BAB type block copolymer: joining the a-block and the B-block to produce a BAB-type block copolymer.
In some embodiments, the monomer units further comprise at least one monomer of formula III,
wherein R is 7 、R 8 、R 9 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 Alkyl, R 10 One selected from ester group, cyano group and amide group.
In some embodiments, the preparation method of the BAB type block copolymer 6 is schematically shown in FIG. 1, wherein two end groups 611 of an A-block 61 prepared by polymerization of a monomer represented by formula I are active groups, a terminal group 621 of a B-block 62 prepared by polymerization of a monomer represented by formula II is active groups, and the two end groups 611 of the A-block react with the terminal group 621 of the B-block to achieve bonding of polymer segments, thereby preparing the BAB type block copolymer 6.
The preparation method has the advantages of cheap raw materials, reduced cost, reduced environmental pollution and contribution to the improvement of the yield of the binder. Meanwhile, the adhesive prepared by the method can effectively slow down the gelation phenomenon of the slurry, improve the stability of the slurry, improve the flexibility of the pole piece, improve the adhesive force, reduce the membrane resistance, reduce the direct current impedance growth rate of the battery and/or improve the cycle capacity retention rate of the battery.
In some embodiments, a method of preparing an a-block comprises:
at least one monomer shown in the formula I and a second initiator are polymerized for 2.5-5 hours at the reaction temperature of 80-95 ℃, and substitution reaction is carried out on the end group of the product to prepare the A-block with the azide group or the alkynyl group at both ends as the end group.
As used herein, the term "azido" refers to-N 3 A group.
In this context, the term "alkynyl" refers to a-C.ident.C group.
In some embodiments, the A-block is synthesized by polymerizing the monomer of formula I with a second initiator to form the A-block as follows. Because the end groups at two sides of the second initiator are halogen substituted alkyl or trimethylsilyl ethynyl groups, the halogen or trimethylsilyl groups at two sides of the A-block are easy to be substituted, so that the two ends of the A-block are provided with azide groups or alkynyl groups.
The azide end-capped A-block prepared by the preparation method is convenient for the A-block to be connected with the B-block in an efficient and mild way to generate the BAB type block copolymer.
In some embodiments, a method of preparing a B-block comprises:
and (3) carrying out reversible addition-fragmentation chain transfer polymerization on the monomer units, the chain transfer agent and the first initiator at a reaction temperature of 60-80 ℃ for 4.5-7 hours to obtain the B-block with the terminal alkynyl or azido group as a terminal group.
Herein, the term "reversible addition-fragmentation chain transfer polymerization" (RAFT polymerization) is a reversible deactivation radical polymerization, also referred to as "living"/controlled radical polymerization process. The main principle of RAFT polymerization is that a RAFT reagent serving as a chain transfer reagent is added in free radical polymerization, so that free radicals which are easy to terminate are protected in a chain transfer mode, most of the free radicals in the polymerization reaction are converted into dormant species of free radicals, and a dormant chain segment and a reactive chain segment exist simultaneously in the reaction process and are continuously and rapidly switched with each other through dynamic reversible reaction, so that only a few polymer chains exist in the form of the reactive chain at any moment and are grown, and finally the growth probability of each polymer chain segment is approximately equal, and the characteristic of living polymerization is shown.
In some embodiments, the synthetic route to the B-block is shown below, wherein the chain transfer agent is a trithiocarbonate, Z' is a reactive group terminated with an alkynyl or azido group, and R is an alkyl group. A B-block having an alkynyl or azido group at the end is prepared by the following reaction, where m is the degree of polymerization of structural units derived from the monomer of formula II, n is the degree of polymerization of structural units derived from the monomer of formula III, m is a positive integer greater than zero, and n may be zero or a positive integer greater than zero. When the B-block contains structural units derived from the monomer of formula II and structural units derived from the monomer of formula III, the B-block may be a random copolymer, a block copolymer or an alternating copolymer.
As used herein, the term "random copolymer" refers to a disordered copolymer produced by copolymerizing two or more monomers to form an ordered product.
The term "alternating copolymer" as used herein refers to a copolymer in which two or more structural units are alternately arranged with each other in a polymer chain.
Controllable polymerization can be realized by adopting reversible addition-fragmentation chain transfer polymerization, and the molecular weight distribution of the product is narrower. Moreover, through the above reaction, the B-block only has alkynyl or azido groups at the terminal, which facilitates the bonding with the A-block in a highly efficient and gentle manner, resulting in a BAB type triblock copolymer.
In some embodiments, a method of preparing a BAB-type block copolymer comprises:
mixing the A-block with azide groups or alkynyl groups at two ends as end groups with the B-block with alkynyl groups or azide groups at the ends as end groups, and performing click reaction to prepare the BAB type block copolymer, wherein the end groups of the A-block and the B-block are different.
As used herein, the term "click reaction" refers to a reaction in which an alkynyl group undergoes a cycloaddition reaction with an azide group, such that the A-block is attached to the B-block. In some embodiments, the click reaction is performed in the presence of a Cu (I) catalyst at ambient temperature and pressure.
In some embodiments, the end groups of the A-block are azide groups and the end groups of the B-block are alkyne groups.
In some embodiments, the end groups of the A-block are alkynyl groups and the end groups of the B-block are azide groups.
The preparation method has the advantages of high yield, harmless byproducts, simple and mild reaction conditions and easily available reaction raw materials, can realize the controllable polymerization of the block polymer, and is beneficial to improving the yield of products.
In some embodiments, the chain transfer agent is a RAFT chain transfer agent containing terminal alkynyl or azido groups. In some embodiments, the chain transfer agent is a trithiocarbonate containing terminal alkynyl or azido groups. In some embodiments, the chain transfer agent has a structural formula selected from the group consisting of,
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The RAFT chain transfer agent containing the terminal alkynyl or azido group enables the terminal of the B-block to be provided with the alkynyl or azido group during the synthesis of the B-block, thereby providing a basis for the click reaction of the B-block and the A-block, avoiding complex post-treatment steps and improving the reaction efficiency.
In some embodiments, the first initiator is an azo initiator selected from one or more of azobisisobutyronitrile, azobisisoheptonitrile. Azo initiator is a common free radical polymerization initiator, is easy to decompose to form free radicals, and is convenient to initiate free radical polymerization.
In some embodiments, the second initiator is a symmetrical difunctional initiator selected from the group consisting of 4- (chloromethyl) benzoyl peroxide. The symmetrical bi-functionality initiator enables both sides of the A-block to carry the same active functional groups symmetrically, which is helpful for the simultaneous realization of the azide or alkyne of both side end groups of the A-block.
In some embodiments, the BAB-type block copolymer may be applied in a secondary battery, optionally including at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, a potassium ion battery.
[ Positive electrode sheet ]
The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active substance, a conductive agent and a binder, and the binder is a BAB type block copolymer in some embodiments or a BAB type block copolymer prepared by a preparation method in some embodiments.
The positive electrode plate has excellent flexibility, binding force and/or lower diaphragm resistance.
In some embodiments, the mass fraction of the binder is 0.1% -3% based on the total mass of the positive electrode active material. In some embodiments, the mass fraction of the binder may be selected to be any one of 0.1% -0.2%, 0.1% -1%, 0.1% -1.2%, 0.2% -1%, 0.2% -1.2%, 0.2% -3%, 1% -1.2%, 1% -3%, 1.2% -3% based on the total mass of the positive electrode active material.
When the content of the binder is too low, the binder cannot exert a sufficient binding effect. On one hand, the adhesive can not fully disperse the conductive agent and the active substance, so that the resistance of the membrane of the pole piece is increased; on the other hand, the positive electrode active material and the conductive agent in the slurry cannot be tightly combined with the binder, the positive electrode active material and the conductive agent particles are settled and agglomerated, and the stability of the slurry is reduced.
In contrast, when the binder content is too high, the viscosity of the slurry is too high, which results in too thick binder coating layer coating the surface of the positive electrode active material, which affects the transmission of electrons and ions during the battery cycle, and increases the internal resistance of the membrane.
The mass fraction of the binder is controlled within a reasonable range, so that the gelation phenomenon of the slurry can be obviously slowed down, the stability of the slurry is improved, the flexibility of the pole piece is improved, and the cycle capacity retention rate of the battery is improved.
In some embodiments, the adhesion force per unit length between the positive electrode film layer and the positive electrode current collector is not less than 8N/m. In some embodiments, the adhesion force per unit length between the positive electrode film layer and the positive electrode current collector is not less than 10N/m.
The adhesion between the positive electrode film layer and the positive electrode current collector in unit length can be tested by any means known in the art, for example, by referring to GB-T2790-1995 national standard "180 DEG peel Strength test method of adhesive". As an example, the positive electrode sheet was cut into test specimens of 20mm×100mm size for use; the pole piece is adhered to one surface of the positive electrode film layer by double-sided adhesive tape, and is compacted by a pressing roller, so that the double-sided adhesive tape is completely adhered to the pole piece; the other surface of the double-sided adhesive tape is adhered to the surface of stainless steel, one end of the sample is reversely bent, and the bending angle is 180 degrees; and (3) testing by adopting a high-speed rail tensile machine, fixing one end of the stainless steel on a clamp below the tensile machine, fixing the bent tail end of the sample on the clamp above, adjusting the angle of the sample, ensuring that the upper end and the lower end are positioned at vertical positions, and then stretching the sample at the speed of 50mm/min until the positive electrode current collector is completely stripped from the positive electrode membrane, and recording the displacement and acting force in the process. The force in the stress balance is divided by the width of the pole piece attached to the double faced adhesive tape (the width direction of the pole piece is perpendicular to the stripping direction) to be used as the adhesive force of the pole piece in unit length, and the width of the pole piece in the test is 20mm.
The positive electrode film layer of the pole piece and the positive electrode current collector have high bonding strength, and the positive electrode film layer is not easy to fall off from the positive electrode current collector in the use process, so that the cycle performance and the safety of the battery are improved.
In some embodiments, the positive electrode sheet is subjected to bending test for at least 3 times, and the positive electrode sheet has a light transmission phenomenon.
Bending tests, also known as flexibility tests, may be used to test the flexibility of the pole piece, which may be performed by any means known in the art. As an example, the cold-pressed positive electrode sheet was cut into test specimens of 20mm×100mm size; after the light-transmitting slit is folded forward, flattening by using 2kg of pressing rollers, unfolding the light-transmitting slit to check whether light transmission occurs, and if not, folding the slit reversely, flattening by using 2kg of pressing rollers, checking the light again, repeating the steps until the light transmission phenomenon occurs in the slit, and recording folding times; at least three patterns are taken for testing, and an average value is taken as a test result of the bending test.
The pole piece can be subjected to bending tests for at least 3 times, so that the pole piece has good flexibility, the pole piece is not easy to crack in the production process, the pole piece is not easy to brittle fracture in the use process, the yield of the battery is improved, and the safety performance of the battery is improved.
In some embodiments, the sheet resistance of the positive electrode sheet is less than or equal to 0.52 Ω. In some embodiments, the sheet resistance of the positive electrode sheet is less than or equal to 0.46 Ω.
The sheet resistance test may be used to test the resistance of the pole piece, which may be performed by any means known in the art. As an example, a small disc with the diameter of 20mm is cut at the left, middle and right parts of the pole piece; turning on a meta-energy science and technology pole piece resistance meter indicator lamp, placing the meta-energy science and technology pole piece resistance meter indicator lamp at a proper position of a probe of a diaphragm resistance meter, clicking a start button, and reading when the indication is stable; and testing two positions of each small wafer, and finally calculating the average value of six measurements, namely the diaphragm resistance of the pole piece.
As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.
In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, the positive electrode active material may employ a positive electrode active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials can beOnly one kind may be used alone, or two or more kinds may be used in combination. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) 2 ) Lithium nickel oxide (e.g. LiNiO) 2 ) Lithium manganese oxide (e.g. LiMnO 2 、LiMn 2 O 4 ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM) 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also referred to as NCM) 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM) 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM) 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM) 811 ) Lithium nickel cobalt aluminum oxide (e.g. LiNi 0.85 Co 0.15 Al 0.05 O 2 ) And at least one of its modified compounds and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO 4 (also abbreviated as LFP)), composite material of lithium iron phosphate and carbon, and manganese lithium phosphate (such as LiMnPO) 4 ) At least one of a composite material of lithium manganese phosphate and carbon, and a composite material of lithium manganese phosphate and carbon.
In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.
[ negative electrode sheet ]
The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material.
As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode current collector.
In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.
In some embodiments, the negative electrode film layer further optionally includes a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).
In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
In some embodiments, the negative electrode film layer may optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.
In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.
[ electrolyte ]
The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The type of electrolyte is not particularly limited in this application, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.
In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.
In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.
In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.
In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.
[ isolation Membrane ]
In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability may be used.
In some embodiments, the material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.
In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.
In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.
In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The exterior package of the secondary battery may also be a pouch type pouch, for example. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
Secondary battery
The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 2 is a secondary battery 5 of a square structure as one example. The secondary battery may be a sodium ion battery, a magnesium ion battery, or a potassium ion battery.
In some embodiments, referring to fig. 3, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to specific practical requirements.
[ Battery Module ]
In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.
Fig. 4 is a battery module 4 as an example. Referring to fig. 4, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.
Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.
[ Battery pack ]
In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
Fig. 5 and 6 are battery packs 1 as an example. Referring to fig. 5 and 6, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.
[ electric device ]
In one embodiment of the present application, an electrical device is provided that includes at least one of any of the secondary battery of any embodiment, the battery module of any embodiment, or the battery pack of any embodiment.
The electricity utilization device comprises at least one of a secondary battery, a battery module or a battery pack. The secondary battery, the battery module, or the battery pack may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.
As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.
Fig. 7 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.
As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.
Examples
Hereinafter, embodiments of the present application are described. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
1. Preparation method
Example 1
1) Preparation of the adhesive
Preparation of the B-block: using an alkynyl compound as a chain transfer agent, and performing polymerization reaction to prepare alkynyl-terminated poly (acrylic acid-acrylamide-ethyl methacrylate);
acrylic acid, ethyl methacrylate and acrylamide are respectively weighed according to the molar ratio of 8:1:1, 500ml of tetrahydrofuran is measured, a four-neck flask is added, a large amount of nitrogen is introduced, the stirring speed is gradually increased to 1200 revolutions per minute, a RAFT chain transfer agent (CTA-alkyne) accounting for 1% of the mass of the monomer and azodiisobutyronitrile accounting for 0.1% of the mass of the monomer are added, and the temperature is increased to 75 ℃. After 6 hours of reaction, the reaction was stopped by cooling in liquid nitrogen and the solution was precipitated in excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform with methanol. The resulting product was dried overnight at room temperature in vacuo to remove all traces of residual solvent to give an alkynyl-capped poly (acrylic acid-acrylamide-ethyl methacrylate) with a weight average molecular weight of 40 ten thousand, i.e., a B-block polymer.
Preparation of the A-block: using azide as initiator, polymerization to prepare azide terminated polyvinylidene fluoride;
1% by mass of the monomer of 4- (chloromethyl) benzoyl peroxide was dissolved in 300ml of anhydrous acetonitrile, and the solution was introduced into a high-pressure reactor and was treated with nitrogen (N) 2 ) Purging for 30 minutes. Subsequently 4g of vinylidene fluoride monomer was transferred to the reactor at room temperature. The temperature inside the reactor was raised to 90℃and the reaction mixture was stirred for an additional 3 hours at a speed of 500 revolutions per minute. The reactor was cooled to room temperature with water and depressurized to remove unreacted monomers. The solvent was removed in vacuo and the resulting solid was washed with chloroform multiple times to remove the initiator residue. Finally, the polymer was dried in vacuo at 45℃to give a white product. 3mmol of chlorine-terminated polyvinylidene fluoride and 60mmol of sodium azide (NaN 3 ) Dissolved in 600ml of N, N-Dimethylformamide (DMF) and stirred at 60℃overnight. Concentrating the polymer solution and mixing the polymer solution with a mixed solvent (volume ratio of methanol to water is1:1) was precipitated three times. The pale yellow product was then dried under vacuum at 45℃to give an azide-capped polyvinylidene fluoride, a-block polymer, having a weight average molecular weight of 45 ten thousand.
Preparation of a BAB type block copolymer:
the azide-capped polyvinylidene fluoride, the alkyne-capped single-ended poly (acrylic acid-acrylamide-ethyl methacrylate) and cuprous bromide were added in a molar ratio of 1:2.5:4 to a dry Schlenk tube, and after degassing, 4ml of anhydrous N, N-Dimethylformamide (DMF) and 0.14 mmole of N, N ', N,' N "-Pentamethyldiethylenetriamine (PMDETA) were added. The reaction was stirred at 60 ℃ for 3 days and terminated by exposure to air. The reaction mixture was filtered through a neutral alumina column to remove the copper catalyst, the solution was concentrated under reduced pressure and precipitated with a 20-fold excess of mixed solvent (volume ratio of methanol to water 1:1), the product was collected by filtration and dried under vacuum to give a poly (acrylic acid-acrylamide-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer having a weight average molecular weight of 120 tens of thousands, which was used as a battery binder.
2) Preparation of positive electrode plate
The weight ratio of the lithium Nickel Cobalt Manganese (NCM) material, the conductive agent carbon black, the binder prepared in example 1 and N-methyl pyrrolidone (NMP) is 96.9:2.1:1:21, stirring and mixing uniformly to obtain positive electrode slurry, wherein the solid content of the slurry is 73%; and uniformly coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and cutting to obtain the positive electrode plate.
3) Preparation of negative electrode plate
The active material artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR) and thickener sodium hydroxymethyl cellulose (CMC) are mixed according to the weight ratio of 96.2:0.8:0.8:1.2, dissolving in deionized water serving as a solvent, and uniformly mixing to prepare negative electrode slurry; and uniformly coating the negative electrode slurry on a negative electrode current collector copper foil once or a plurality of times, and drying, cold pressing and cutting to obtain a negative electrode plate.
4) Isolation film
A polypropylene film was used as a separator.
5) Preparation of electrolyte
In an argon atmosphere glove box (H 2 O<0.1ppm，O 2 <0.1 ppm), mixing organic solvent Ethylene Carbonate (EC)/methyl ethyl carbonate (EMC) according to volume ratio of 3/7, adding 12.5% LiPF 6 The lithium salt was dissolved in an organic solvent and stirred uniformly to obtain an electrolyte of example 1.
6) Preparation of a Battery
The positive electrode plate, the isolating film and the negative electrode plate of the embodiment 1 are sequentially stacked, the isolating film is positioned between the positive electrode plate and the negative electrode plate to play a role of isolation, then the bare cell is obtained by winding, the tab is welded on the bare cell, the bare cell is arranged in an aluminum shell, baking and dewatering are carried out at 80 ℃, and then electrolyte is injected and sealed, so that the uncharged battery is obtained. The uncharged battery was subjected to the processes of standing, hot and cold pressing, formation, shaping, capacity test and the like in sequence to obtain the lithium ion battery product of example 1.
Examples 2 to 11
The batteries of examples 2 to 11 were similar to the battery preparation method of example 1, but the weight average molecular weights of the poly (acrylic acid-acrylamide-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer were adjusted by adjusting the polymerization reaction temperature and reaction temperature of the a-block and the B-block, respectively, adjusting the polymerization degree of the a-block and the B-block, adjusting the weight average molecular weights of the a-block and the B-block, and specific parameters are shown in tables 1 and 2.
TABLE 1 polymerization temperature and time parameters for examples 2-11
Examples 12 to 15
The batteries of examples 12 to 15 were similar to the battery preparation method of example 1, but the mass fractions of the binders were adjusted to 0.1% (example 12), 0.2% (example 13), 1.2% (example 14), 3% (example 15), respectively, based on the mass of the positive electrode active material, and the remaining parameters were the same as in example 1, and the specific parameters are shown in tables 1 and 2.
Example 16
The cell of example 16 was prepared similarly to the cell of example 5, except that the a-block was replaced with a polyvinyl fluoride block, the specific parameters are shown in tables 1 and 2, and the preparation method is as follows:
a-block: 1% by mass of the monomers of 4- (chloromethyl) benzoyl peroxide was dissolved in 300ml of anhydrous acetonitrile and introduced into a high-pressure reactor and used with N 2 Purging for 30 minutes. 3.8g of vinyl fluoride were transferred to the reactor at room temperature. The temperature inside the reactor was raised to 90℃and the reaction mixture was stirred at a speed of 500 rpm for 3 hours. After the reaction was completed, the solvent was removed, and the resulting solid was washed with chloroform several times to remove the initiator residue, and dried in vacuo at 45℃to give a white product, i.e., chlorine-terminated polyvinyl fluoride. 3mmol of chlorine-terminated polyvinyl fluoride and 60mmolNaN 3 Dissolved in 600ml DMF and stirred overnight at 60℃the polymer solution was concentrated and precipitated three times in a mixed solvent (volume ratio of methanol to water 1:1). The azide blocked end polyvinyl fluoride, the A-block polymer, is then obtained by vacuum drying at 45 ℃.
Example 17
The cell of example 17 was prepared similarly to the cell of example 5, except that the a-block was replaced with a polytetrafluoroethylene block, the specific parameters are shown in tables 1 and 2, and the preparation method is as follows:
a-block: 1% by mass of the monomers of 4- (chloromethyl) benzoyl peroxide was dissolved in 300ml of anhydrous acetonitrile, introduced into a high-pressure reactor and treated with N 2 Purging for 30 minutes. 4.2g of tetrafluoroethylene was transferred to the reactor at room temperature, the temperature inside the reactor was increased to 90℃and the reaction mixture was stirred at 500 rpm for 3 hours. After the reaction was completed, the solvent was removed, and the resulting solid was washed with chloroform several times to remove the initiator residue, and dried in vacuo at 45℃to give a white product, i.e., chloro-terminated polytetrafluoroethylene. 3mmol of chlorine-terminated polytetrafluoroethylene and 60mmolNaN 3 Dissolved in 600ml DMF and stirred at 60℃overnight. The polymer solution was concentrated and dissolved in a mixed solvent (volume ratio of methanol to water 1:1)And precipitating for three times, and vacuum drying at 45 ℃ to obtain the azide-sealed end polytetrafluoroethylene, namely the A-block polymer.
Example 18
The cell of example 18 was prepared similarly to the cell of example 5, except that the B-block was replaced with poly (acrylic acid-acrylonitrile-ethyl methacrylate), the specific parameters are shown in tables 1 and 2, and the preparation method is as follows:
b-block: acrylic acid, ethyl methacrylate and acrylonitrile are respectively weighed according to the molar ratio of 8:1:1, 500ml of tetrahydrofuran is measured, a four-necked flask is added, a large amount of nitrogen is introduced, the stirring speed is gradually increased to 1200 revolutions per minute, a RAFT chain transfer agent (CTA-alkyne) accounting for 1% of the mass of the monomer and azodiisobutyronitrile accounting for 0.1% of the mass of the monomer are added, and the temperature is increased to 75 ℃. After 5 hours of reaction, the reaction was stopped by cooling in liquid nitrogen and the solution was precipitated in excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform with methanol. The resulting product was dried overnight at room temperature in vacuo to remove all traces of residual solvent to give an alkynyl-capped poly (acrylic acid-acrylonitrile-ethyl methacrylate) with a weight average molecular weight of 25 ten thousand, i.e., a B-block polymer.
Example 19
The cell of example 19 was prepared similarly to the cell of example 5, except that the B-block was replaced with poly (acrylic acid-ethyl methacrylate), the specific parameters are shown in tables 1 and 2, and the preparation method is as follows:
b-block: acrylic acid and ethyl methacrylate are respectively weighed according to the molar ratio of 8:1, 500ml of tetrahydrofuran is measured, a four-neck flask is added, a large amount of nitrogen is introduced, the stirring speed is gradually increased to 1200 revolutions per minute, RAFT chain transfer agent (CTA-alkyne) accounting for 1% of the mass of the monomer and azodiisobutyronitrile accounting for 0.1% of the mass of the monomer are added, and the temperature is increased to 60 ℃. After 7 hours of reaction, the reaction was stopped by cooling in liquid nitrogen and the solution was precipitated in excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform with methanol. The resulting product was dried overnight at room temperature in vacuo to remove all traces of residual solvent to give an alkynyl-capped poly (ethyl acrylate-methacrylate) with a weight average molecular weight of 25 ten thousand, i.e., a B-block polymer.
Example 20
The cell of example 20 was prepared similarly to the cell of example 5, except that the B-block was replaced with polyacrylic acid, the specific parameters are shown in tables 1 and 2, and the preparation method was as follows:
B-block: acrylic acid is weighed, 500ml of tetrahydrofuran is measured, a four-necked flask is added, a large amount of nitrogen is introduced, the stirring speed is gradually increased to 1200 revolutions per minute, RAFT chain transfer agent (CTA-alkyne) accounting for 1% of the mass of the monomer and azodiisobutyronitrile accounting for 0.1% of the mass of the monomer are added, and the temperature is raised to 60 ℃. After 7 hours of reaction, the reaction was stopped by cooling in liquid nitrogen and the solution was precipitated in excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform with methanol. The resulting product was dried overnight at room temperature in vacuo to remove all traces of residual solvent to give an alkynyl-capped single-ended polyacrylic acid, B-block polymer, having a weight average molecular weight of 25 ten thousand.
Comparative example 1
The cell of comparative example 1 was similar to the cell preparation method of example 1, but the binder was polyvinylidene fluoride, the specific parameters are shown in tables 1 and 2, purchased from 5130 of the sor group.
Comparative example 2
The cell of comparative example 2 was similar to the cell of example 1, except that the binder was polyacrylic acid, and the specific parameters are shown in tables 1 and 2, and the preparation method was as follows:
acrylic acid is weighed, 500ml of tetrahydrofuran is measured, a four-necked flask is added, a large amount of nitrogen is introduced, the stirring speed is gradually increased to 1200 revolutions per minute, RAFT chain transfer agent (CTA-alkyne) accounting for 1% of the mass of the monomer and azodiisobutyronitrile accounting for 0.1% of the mass of the monomer are added, and the temperature is raised to 60 ℃. After 7 hours of reaction, the reaction was stopped by cooling in liquid nitrogen and the solution was precipitated in excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform with methanol. The resulting polymer was dried at room temperature under vacuum overnight to remove all traces of residual solvent to give the target binder.
Comparative example 3
The cell of comparative example 3 was similar to the cell preparation method of example 1, except that the binder was poly (acrylic acid-ethyl methacrylate), and specific parameters are shown in tables 1 and 2, and the preparation method was as follows:
acrylic acid and ethyl methacrylate are respectively weighed according to the molar ratio of 8:1, 500ml of tetrahydrofuran is measured, a four-neck flask is added, a large amount of nitrogen is introduced, the stirring speed is gradually increased to 1200 revolutions per minute, RAFT chain transfer agent (CTA-alkyne) accounting for 1% of the mass of the monomer and azodiisobutyronitrile accounting for 0.1% of the mass of the monomer are added, and the temperature is increased to 60 ℃. After 7 hours of reaction, the reaction was stopped by cooling in liquid nitrogen and the solution was precipitated in excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform with methanol. The resulting polymer was dried at room temperature under vacuum overnight to remove all traces of residual solvent to give the target binder.
Comparative example 4
The cell of comparative example 4 was prepared similarly to the cell of example 1, except that the binder was poly (acrylic acid-acrylonitrile-ethyl methacrylate), and specific parameters are shown in tables 1 and 2, and the preparation method was as follows:
acrylic acid, ethyl methacrylate and acrylonitrile are respectively weighed according to the molar ratio of 8:1:1, 500ml of tetrahydrofuran is measured, a four-necked flask is added, a large amount of nitrogen is introduced, the stirring speed is gradually increased to 1200 revolutions per minute, a RAFT chain transfer agent (CTA-alkyne) accounting for 1% of the mass of the monomer and azodiisobutyronitrile accounting for 0.1% of the mass of the monomer are added, and the temperature is increased to 60 ℃. After 7 hours of reaction, the reaction was stopped by cooling in liquid nitrogen and the solution was precipitated in excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform with methanol. The resulting polymer was dried at room temperature under vacuum overnight to remove all traces of residual solvent to give the target binder.
Comparative example 5
The cell of comparative example 5 was prepared similarly to the cell of example 1, except that the binder was poly (acrylic acid-acrylamide-ethyl methacrylate), and the specific parameters are shown in tables 1 and 2, and the preparation method was as follows:
acrylic acid, ethyl methacrylate and acrylamide are respectively weighed according to the molar ratio of 8:1:1, 500ml of tetrahydrofuran is measured, a four-neck flask is added, a large amount of nitrogen is introduced, the stirring speed is gradually increased to 1200 revolutions per minute, a RAFT chain transfer agent (CTA-alkyne) accounting for 1% of the mass of the monomer and azodiisobutyronitrile accounting for 0.1% of the mass of the monomer are added, and the temperature is increased to 60 ℃. After 7 hours of reaction, the reaction was stopped by cooling in liquid nitrogen and the solution was precipitated in excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform with methanol. The resulting polymer was dried at room temperature under vacuum overnight to remove all traces of residual solvent to give the target binder.
Comparative example 6
The cell of comparative example 6 was prepared similarly to the cell of example 1, except that the binder was a blend of polyvinylidene fluoride and poly (acrylic acid-acrylamide-ethyl methacrylate), the specific parameters are shown in tables 1 and 2, and the preparation method is as follows:
Blending: the poly (acrylic acid-acrylamide-ethyl methacrylate) blend of comparative example 5 was blended with the polyvinylidene fluoride blend of comparative example 1 in a molar ratio of 6:4 to give a blend binder of polyvinylidene fluoride and poly (acrylic acid-acrylamide-ethyl methacrylate).
2. Performance testing
1. Slurry performance test
1) Slurry viscosity test
After the slurry was shipped, 500ml of the slurry was placed in a beaker, a rotor was selected using a rotary viscometer, the rotation speed was set at 12 rpm, the rotation time was set at 5 minutes, and after the values were stabilized, the viscosity values were read and recorded.
2) Slurry stability test
And (3) after the slurry is stirred for 30 minutes again, pouring a certain amount of slurry into a sample bottle of the stability instrument, closing a test tower cover after the slurry is put into the sample bottle, opening the test tower cover, starting to generate a scanning curve on a test interface, starting to test the stability of the sample, and continuously testing for more than 48 hours to finish the test.
2. Pole piece performance test
1) Diaphragm resistance test
Cutting small discs with the diameter of 20mm at the left, middle and right parts of the pole piece. And (3) turning on the meta-energy science and technology pole piece resistance instrument indicator lamp, placing the meta-energy science and technology pole piece resistance instrument indicator lamp at a proper position of a probe of a diaphragm resistance instrument, clicking a start button, and reading after the indication is stable. And testing two positions of each small wafer, and finally calculating the average value of six measurements, namely the diaphragm resistance of the pole piece.
2) Adhesion test
Cutting the positive pole piece into a test sample with the size of 20mm multiplied by 100mm for later use; the pole piece is adhered to one surface of the positive electrode film layer by double-sided adhesive tape, and is compacted by a pressing roller, so that the double-sided adhesive tape is completely adhered to the pole piece; the other surface of the double-sided adhesive tape is adhered to the surface of stainless steel, one end of the sample is reversely bent, and the bending angle is 180 degrees; and (3) testing by adopting a high-speed rail tensile machine, fixing one end of the stainless steel on a clamp below the tensile machine, fixing the bent tail end of the sample on the clamp above the tensile machine, adjusting the angle of the sample, ensuring that the upper end and the lower end are positioned at vertical positions, and then stretching the sample at the speed of 50mm/min until the current collector is completely stripped from the positive membrane, and recording the displacement and acting force in the process. The force at the time of stress balance is divided by the width of the pole piece attached to the double-sided tape (the width direction of the pole piece is perpendicular to the stripping direction) to be used as the adhesive force of the pole piece in unit length, and the width of the pole piece attached to the double-sided tape in the test is 20mm.
3) Flexibility test (bending test)
Cutting the cold-pressed positive pole piece into a test sample with the size of 20mm multiplied by 100 mm; after the light-transmitting slit is folded forward, flattening by using 2kg of pressing rollers, unfolding the light-transmitting slit to check whether light transmission occurs, and if not, folding the slit reversely, flattening by using 2kg of pressing rollers, checking the light again, repeating the steps until the light transmission phenomenon occurs in the slit, and recording folding times; the test was repeated three times and averaged as reference data for pole piece flexibility.
3. Battery performance test
1) Battery cycle capacity retention (500 ds) test
The battery capacity retention test procedure was as follows: the prepared battery was charged to 4.3V at a constant current of 1/3C, charged to 0.05C at a constant voltage of 4.3V, left for 5min, and discharged to 2.8V at 1/3C, and the resulting capacity was designated as initial capacity C0. Repeating the above steps for the same battery, and recording the discharge capacity Cn of the battery after the nth cycle, wherein the battery capacity retention ratio Pn=Cn/C0×100% after each cycle takes 500 point values of P1, P2 … … P500 as ordinate and the corresponding cycle times as abscissa, so as to obtain a graph of the battery capacity retention ratio and the cycle times. In this test procedure, the first cycle corresponds to n=1, the second cycle corresponds to n=2, and the 500 th cycle of … … corresponds to n=500. The battery capacity retention rate data corresponding to the examples or comparative examples in table 3 are data measured after 500 cycles under the above-described test conditions, i.e., the value of P500. The test procedure for the comparative example and the other examples is the same as above.
2) Battery DC impedance growth rate (100 cls) test
The DC impedance test process of the battery is as follows: the battery was charged to 4.3V at a constant current of 1/3C at 25C, and then charged to 0.05C at a constant voltage of 4.3V, and after resting for 5min, the voltage V1 was recorded. Then discharging for 30s at 1/3C, and recording the voltage V2, and obtaining the internal resistance DCR1 of the battery after the first circulation by (V2-V1)/(1/3C). The above steps are repeated for the same battery, and the internal resistance DCRn (n=1, 2, 3 … … 100) of the battery after the nth cycle is recorded, and the graph of the battery discharge DCR and the cycle number is obtained by taking the 100 point values of the DCR1, DCR2, DCR3 … … DCR100 as the ordinate and the corresponding cycle number as the abscissa.
In this test procedure, the first cycle corresponds to n=1, the second cycle corresponds to n=2, and … … the 100 th cycle corresponds to n=100. The battery internal resistance increase ratio= (DCRn-DCR 1)/dcr1×100% of example 1 in table 2, the test procedure of comparative example and other examples were the same. The data in table 3 are measured after 100 cycles under the above test conditions.
4. Polymer detection
1) Weight average molecular weight (W g/mol) test method
A Waters 2695 Isocric HPLC gel chromatograph (differential refractive detector 2141) was used. A sample of 3.0% by mass polystyrene solution was used as a reference and a matched column was selected (oiliness: styragel HT5 DMF 7.8. Times. 300mm+Styragel HT4). Preparing a 3.0% polymer glue solution by using a purified N-methyl pyrrolidone (NMP) solvent, and standing the prepared solution for one day for later use. During the test, tetrahydrofuran is firstly sucked by a syringe, and then the syringe is washed, and the test is repeated for several times. Then, 5ml of the test solution was aspirated, the air in the syringe was removed, and the needle tip was wiped dry. And finally, slowly injecting the sample solution into the sample inlet. And obtaining data after the indication is stable. 3. Analysis of test results for examples and comparative examples
Table 2 examples and comparative examples preparation parameters and weight average molecular weight test results
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Table 3 results of performance tests of examples and comparative examples
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From the above results, it is understood that the binders in examples 1 to 20 each contain a polymer containing an A-block containing a structural unit derived from a monomer represented by formula I and a B-block containing a structural unit derived from a monomer represented by formula II or containing a structural unit derived from a monomer represented by formula II and a structural unit derived from a monomer represented by formula III. As can be seen from a comparison of examples 1-7, 16-20 and comparative examples 1-6, the binder is effective in slowing down the gelation of the slurry, improving the stability of the slurry, improving the flexibility of the pole pieces, improving the adhesion, reducing the sheet resistance, reducing the rate of increase in the dc resistance of the battery, and/or improving the cycle capacity retention of the battery.
As can be seen from the comparison of examples 1-7 and 18-20 with comparative example 1, when the molar content of the structural units derived from the monomer represented by formula I is 30% -70%, the gelation of the slurry can be effectively slowed down, the stability of the slurry can be improved, the flexibility of the pole piece can be improved, the resistance of the membrane can be reduced, and the retention rate of the cycling capacity of the battery can be improved based on the total number of moles of all the structural units in the block copolymer.
As can be seen from the comparison of examples 1-11 and comparative example 6, the binder has a weight average molecular weight of 40-200 ten thousand, which can effectively slow down the gelation of the slurry, improve the stability of the slurry, improve the flexibility of the pole pieces, improve the binding force, reduce the membrane resistance, reduce the DC resistance increase rate of the battery, and improve the cycle capacity retention rate of the battery. As can be seen from the comparison of examples 1 to 7 and 10 to 11 with comparative examples 1, 5 and 6, the binder has a weight average molecular weight of 120 to 200 ten thousand, and can improve the flexibility of the pole piece and improve the adhesion. As can be seen from the comparison of examples 1 to 7 and 10 with comparative examples 1, 5 and 6, the binder has a weight average molecular weight of 120 to 150 ten thousand, and can improve the flexibility of the pole piece, improve the adhesion, and improve the cycle capacity retention rate of the battery.
As can be seen from the comparison of examples 1-7 and 18-20 with comparative example 1, the A-block has a weight average molecular weight of 20-105 ten thousand, which can effectively slow down the gelation of the slurry, improve the stability of the slurry, improve the flexibility of the pole piece, reduce the sheet resistance, and improve the cycle capacity retention rate of the battery.
As can be seen from the comparison of examples 1 to 7 and 16 to 17 with comparative example 5, the weight average molecular weight of the B-block was 10 to 50 ten thousand hours, which can improve the adhesion and improve the cycle capacity retention rate of the battery.
As can be seen from the comparison of examples 1 to 7 and 16 to 17 with comparative example 5, when the monomer represented by formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, and vinyl fluoride, in particular, when the a-block is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, and polyvinyl fluoride, it is possible to improve the adhesion and improve the cycle capacity retention rate of the battery.
As can be seen from the comparison of examples 1 to 7 and 18 to 20 with comparative example 1, the monomer of formula II is selected from one or more of acrylic acid, methacrylic acid and ethacrylic acid, the monomer of formula III is selected from one or more of acrylamide, acrylic acid ester and acrylonitrile, and particularly, when the monomer of formula III is selected from one or more of acrylamide, ethyl methacrylate and acrylonitrile, particularly, the B-block is selected from one or more of poly (acrylic acid-acrylamide-ethyl methacrylate), poly (acrylic acid-acrylonitrile-ethyl methacrylate), polyacrylic acid and poly (acrylic acid-ethyl methacrylate), the gel phenomenon of the slurry can be effectively slowed down, the stability of the slurry can be improved, the flexibility of the pole piece can be improved, the resistance of the membrane can be reduced, and the cycle capacity retention rate of the battery can be improved. As can be seen from a comparison of examples 5, 18 and 20 with comparative example 1, the B-block is selected from one or more of poly (acrylic acid-acrylamide-ethyl methacrylate), poly (acrylic acid-acrylonitrile-ethyl methacrylate), and polyacrylic acid, and is effective in slowing down the gelation of the slurry, improving the stability of the slurry, improving the flexibility of the pole piece, improving the adhesion, reducing the sheet resistance, and improving the cycle capacity retention of the battery. Examples 5 and 18, when compared with comparative example 1, show that the B-block is selected from one or more of poly (acrylic acid-acrylamide-ethyl methacrylate), poly (acrylic acid-acrylonitrile-ethyl methacrylate), can effectively slow down the gelation of the slurry, improve the stability of the slurry, improve the flexibility of the pole piece, improve the adhesion, reduce the sheet resistance, reduce the dc resistance increase rate of the battery, and improve the cycle capacity retention rate of the battery.
As can be seen from the comparison of examples 1 to 7 and 16 to 20 with comparative examples 1 to 6, the block copolymer was one or more of a polyacrylic acid-polyvinylidene fluoride-polyacrylic acid triblock copolymer, a poly (acrylic acid-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-ethyl methacrylate) triblock copolymer, a poly (acrylic acid-acrylonitrile-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylonitrile-ethyl methacrylate) triblock copolymer, a poly (acrylic acid-acrylamide-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer, a poly (acrylic acid-acrylamide-ethyl methacrylate) -polyvinyl fluoride-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer, a poly (acrylic acid-acrylamide-ethyl methacrylate) -polytetrafluoroethylene-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer, and was capable of improving the cycle capacity retention rate of the battery. As can be seen from the comparison of examples 1 to 7 with comparative examples 1, 5 and 6, when the block copolymer is a poly (acrylic acid-acrylamide-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer, it is possible to improve the flexibility of the electrode sheet, improve the adhesive force, and improve the cycle capacity retention rate of the battery. As can be seen from comparison of examples 16 to 17 with comparative example 5, when the block copolymer is one or more of poly (acrylic acid-acrylamide-ethyl methacrylate) -polyvinyl fluoride-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer, poly (acrylic acid-acrylamide-ethyl methacrylate) -polytetrafluoroethylene-poly (acrylic acid-acrylamide-ethyl methacrylate) triblock copolymer, it is possible to improve the adhesive force and to improve the cycle capacity retention rate of the battery. As can be seen from the comparison of example 18 with comparative examples 1 and 4, when the block copolymer is a poly (acrylic acid-acrylonitrile-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylonitrile-ethyl methacrylate) triblock copolymer, it is possible to improve the adhesion, reduce the rate of increase in the direct current resistance of the battery, and improve the cycle capacity retention rate of the battery. As can be seen from a comparison of example 19 with comparative examples 1 and 3, when the block copolymer is a poly (acrylic acid-ethyl methacrylate) -polyvinylidene fluoride-poly (acrylic acid-ethyl methacrylate) triblock copolymer, it is possible to improve the flexibility of the pole piece, reduce the direct current resistance increase rate of the battery, and improve the cycle capacity retention rate of the battery. As can be seen from the comparison of example 20 with comparative examples 1-2, when the block copolymer is a polyacrylic acid-polyvinylidene fluoride-polyacrylic acid triblock copolymer, it is possible to improve the adhesion and improve the cycle capacity retention rate of the battery.
As can be seen from the comparison of examples 1 to 7 and 12 to 15 with comparative example 6, when the mass fraction of the binder is 0.1% to 3%, the gelation of the slurry can be significantly slowed down, the slurry stability can be improved, the flexibility of the electrode sheet can be improved, and the cycle capacity retention rate of the battery can be improved based on the total mass of the positive electrode active material. As can be seen from the comparison of examples 1 to 7 and 14 to 15 with comparative example 6, the mass fraction of the binder is 1% to 3%, based on the total mass of the positive electrode active material, it is possible to remarkably slow down the gelation phenomenon of the slurry, improve the stability of the slurry, improve the flexibility of the pole piece, improve the adhesion, reduce the sheet resistance, reduce the direct current resistance increase rate of the battery, and improve the cycle capacity retention rate of the battery.
The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims (29)

1. A BAB-type block copolymer comprising an A-block containing structural units derived from a monomer of formula I and a B-block containing structural units derived from a monomer of formula II,
wherein R is 1 、R 2 、R 3 Each independently selected from hydrogen, fluorine, C containing at least one fluorine atom 1-3 One or more of alkyl groups, R 4 、R 5 、R 6 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 An alkyl group.
2. The BAB-type block copolymer according to claim 1, wherein said B-block further comprises structural units derived from a monomer represented by formula III,
wherein R is 7 、R 8 、R 9 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 Alkyl, R 10 One selected from ester group, cyano group and amide group.
3. The BAB-type block copolymer according to claim 1 or 2, characterized in that the molar content of the structural units derived from the monomer of formula I is 30-70% based on the total number of moles of all structural units in the BAB-type block copolymer.
4. A BAB-type block copolymer according to any of claims 1 to 3, characterized in that the BAB-type block copolymer has a weight average molecular weight of 40-200 ten thousand, optionally 120-200 ten thousand, more optionally 120-150 ten thousand.
5. The BAB-type block copolymer as claimed in any of claims 1 to 4, characterized in that, in said BAB-type block copolymer, the weight average molecular weight of the a-block is 20 ten thousand to 105 ten thousand.
6. The BAB-type block copolymer as claimed in any one of claims 1 to 5, characterized in that the weight average molecular weight of each B-block in the BAB-type block copolymer is 10 to 50 tens of thousands.
7. The BAB-type block copolymer as claimed in any one of claims 1 to 6, characterized in that the monomer of formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, vinyl fluoride.
8. The BAB-type block copolymer as claimed in any one of claims 1 to 7, characterized in that said monomer represented by formula II is selected from one or more of acrylic acid, methacrylic acid, ethacrylic acid.
9. The BAB-type block copolymer as claimed in any of claims 2 to 8, characterized in that said monomer of formula III is selected from one or more of acrylamide, acrylate, acrylonitrile.
10. The BAB-type block copolymer according to any one of claim 1 to 9, the BAB type block copolymer is polyacrylic acid-polyvinylidene fluoride-polyacrylic acid triblock copolymer, polyacrylic acid-polyfluorene-polyacrylic acid triblock copolymer, polyacrylic acid-polytetrafluoroethylene-polyacrylic acid triblock copolymer, poly (acrylic acid-acrylic ester) -polyvinylidene fluoride-poly (acrylic acid-acrylic ester) triblock copolymer, poly (acrylic acid-acrylic ester) -polyfluorene-poly (acrylic acid-acrylic ester) triblock copolymer, poly (acrylic acid-acrylic ester) -polytetrafluoroethylene-poly (acrylic acid-acrylic ester) triblock copolymer poly (acrylic acid-acrylonitrile-acrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylonitrile-acrylate) triblock copolymer, poly (acrylic acid-acrylonitrile-acrylate) -polyvinyl fluoride-poly (acrylic acid-acrylonitrile-acrylate) triblock copolymer, poly (acrylic acid-acrylonitrile-acrylate) -polytetrafluoroethylene-poly (acrylic acid-acrylonitrile-acrylate) triblock copolymer, poly (acrylic acid-acrylamide-acrylate) -polyvinylidene fluoride-poly (acrylic acid-acrylamide-acrylate) triblock copolymer, one or more of poly (acrylic acid-acrylamide-acrylate) -polyvinyl fluoride-poly (acrylic acid-acrylamide-acrylate) triblock copolymers, poly (acrylic acid-acrylamide-acrylate) -polytetrafluoroethylene-poly (acrylic acid-acrylamide-acrylate) triblock copolymers.
11. A process for the preparation of a BAB-type block copolymer comprising the steps of:
preparation of the A-block: polymerizing at least one monomer shown in formula I to prepare an A-block,
wherein R is 1 、R 2 、R 3 Each independently selected from hydrogen, fluorine, C containing at least one fluorine atom 1-3 One or more of alkyl groups;
preparation of the B-block: polymerizing monomer units comprising at least one monomer of formula II to produce a B-block,
wherein R is 4 、R 5 、R 6 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 An alkyl group;
preparation of a BAB type block copolymer: joining the a-block and the B-block to produce a BAB-type block copolymer.
12. The process of claim 11, wherein the monomer unit further comprises at least one monomer of formula III,
wherein R is 7 、R 8 、R 9 Each independently selected from hydrogen, substituted or unsubstituted C 1-5 Alkyl, R 10 One selected from ester group, cyano group and amide group.
13. The process of claim 11 or 12, wherein the process for preparing a B-block comprises:
and (3) carrying out reversible addition-fragmentation chain transfer polymerization on the monomer units, the chain transfer agent and the first initiator at a reaction temperature of 60-80 ℃ for 4.5-7 hours to obtain the B-block with the terminal alkynyl or azido group as a terminal group.
14. The method of any one of claims 11 to 13, wherein the method of preparing an a-block comprises:
at least one monomer shown in the formula I and a second initiator are polymerized for 2.5-5 hours at the reaction temperature of 80-95 ℃, and substitution reaction is carried out on the end group of the product to prepare the A-block with the azide group or the alkynyl group at both ends as the end group.
15. The production method according to any one of claims 11 to 14, characterized in that the method for producing a BAB-type block copolymer comprises:
mixing the A-block with azide groups or alkynyl groups at two ends as end groups with the B-block with alkynyl groups or azide groups at the ends as end groups, and performing click reaction to prepare the BAB type block copolymer, wherein the end groups of the A-block and the B-block are different.
16. The method of claim 13, wherein the chain transfer agent is a RAFT chain transfer agent containing terminal alkynyl or azido groups.
17. The method of claim 13, wherein the first initiator is an azo initiator, optionally one or both of azobisisobutyronitrile and azobisisoheptonitrile.
18. The method of claim 14, wherein the second initiator is a symmetrical difunctional initiator, optionally 4- (chloromethyl) benzoyl peroxide.
19. A binder comprising the BAB-type block copolymer of any one of claims 1 to 10 or the BAB-type block copolymer prepared by the preparation method of any one of claims 11 to 18.
20. Use of the BAB-type block copolymer as defined in any one of claims 1 to 10 in a secondary battery.
21. A positive electrode slurry, characterized in that the positive electrode active material, a conductive agent, and a binder, the binder being the BAB-type block copolymer according to any one of claims 1 to 12 or the BAB-type block copolymer produced by the production method according to any one of claims 12 to 22.
22. The positive electrode slurry according to claim 21, wherein the mass fraction of the binder is 0.1-3%, optionally 1-3%, based on the total mass of the positive electrode active material.
23. A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer being prepared from the positive electrode slurry according to claim 21 or 22.
24. The positive electrode tab of claim 23, wherein the adhesion per unit length between the positive electrode film layer and the positive electrode current collector is not less than 8N/m, optionally not less than 10N/m.
25. The positive electrode sheet according to claim 23 or 24, wherein the positive electrode sheet exhibits a light transmission phenomenon after being subjected to a bending test no less than 3 times.
26. The positive electrode sheet according to any one of claims 23 to 25, wherein the sheet resistance of the positive electrode sheet is 0.52 Ω or less, optionally 0.46 Ω or less.
27. A secondary battery comprising an electrode assembly and an electrolyte, the electrode assembly comprising a separator, a negative electrode tab, and the positive electrode tab of any one of claims 23 to 36.
28. The secondary battery of claim 27, wherein the secondary battery comprises at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.
29. An electric device comprising the secondary battery according to claim 27 or 28.
CN202310735467.XA 2022-09-30 2022-09-30 BAB type block copolymer, preparation method, binder, positive electrode slurry, positive electrode plate, secondary battery and power utilization device Pending CN117801297A (en)

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