CN116554815A - Composite binder, secondary battery and electric equipment - Google Patents

Composite binder, secondary battery and electric equipment Download PDF

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Publication number
CN116554815A
CN116554815A CN202310774910.4A CN202310774910A CN116554815A CN 116554815 A CN116554815 A CN 116554815A CN 202310774910 A CN202310774910 A CN 202310774910A CN 116554815 A CN116554815 A CN 116554815A
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China
Prior art keywords
binder
composite
positive electrode
average particle
particle size
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Pending
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CN202310774910.4A
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Chinese (zh)
Inventor
陈洋
张旭辉
陈涛
王宝玉
陈辉
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Xinwangda Power Technology Co ltd
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Xinwangda Power Technology Co ltd
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Priority to CN202310774910.4A priority Critical patent/CN116554815A/en
Publication of CN116554815A publication Critical patent/CN116554815A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/08—Macromolecular additives
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J129/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Adhesives based on hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Adhesives based on derivatives of such polymers
    • C09J129/14—Homopolymers or copolymers of acetals or ketals obtained by polymerisation of unsaturated acetals or ketals or by after-treatment of polymers of unsaturated alcohols
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/18—Homopolymers or copolymers of nitriles
    • C09J133/20—Homopolymers or copolymers of acrylonitrile
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J179/00—Adhesives based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen, with or without oxygen, or carbon only, not provided for in groups C09J161/00 - C09J177/00
    • C09J179/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • C09J179/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/623—Binders being polymers fluorinated 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The embodiment of the invention provides a composite binder, a secondary battery and electric equipment, wherein the particle sizes of a first binder, a second binder and a third binder in the composite binder are regulated, so that the composite binder can form a cross-linked network structure, the bonding strength of the binder is improved, and simultaneously, halogen in the first binder, cyano, imide and other groups in the second binder, aldehyde and hydroxyl and other groups in the third binder can be cross-linked with each other in a hydrogen bond form on the surface of an anode active material to form a denser coating layer to form a three-dimensional cross-linked network, and can also generate a hydrogen bond with a strong interaction with the surface groups of the anode active material, thereby forming effective coating on the anode active material, reducing the dissolution of transition metal ions and improving the cycle stability under high cut-off voltage.

Description

Composite binder, secondary battery and electric equipment
Technical Field
The invention relates to the technical field of battery manufacturing, in particular to a composite binder, a secondary battery and electric equipment.
Background
Currently, secondary batteries, particularly lithium ion batteries, are widely used in various fields due to their high specific energy, cycle life, and other advantages.
The energy density of the lithium battery mainly depends on the anode material, and the energy density of the anode material is obviously improved by improving the charging voltage, but the anode material with higher theoretical specific capacity is easy to generate irreversible phase change under high voltage, so that the battery structure is damaged, transition metal ions are dissolved out and gas is separated out, the electrochemical performance of the battery is greatly reduced, the cycle life is shortened, and larger potential safety hazards are brought.
Disclosure of Invention
The invention aims to solve the technical problems of poor structural stability and poor cycle performance of the traditional lithium ion battery under high voltage by providing a composite binder, a secondary battery and electric equipment.
In order to solve the problems, the invention is realized by the following technical scheme:
the invention provides a composite adhesive, wherein the composite adhesive comprises a first adhesive, a second adhesive and a third adhesive, and the first adhesive comprises halogen; the second binder comprises at least one group of cyano and imide, and the third binder comprises at least one group of aldehyde and hydroxyl;
the first binder has an average particle size smaller than the second binder, and the second binder has an average particle size smaller than the third binder.
Further, in the composite adhesive, the first adhesive comprises at least one of polyvinylidene fluoride and polyvinyl chloride;
the second binder comprises at least one of polyacrylonitrile and polyimide;
the third binder includes at least one of polyvinyl butyral and polyvinyl alcohol.
Further, in the composite adhesive, the average particle size of the first adhesive is 0.2-5 um, the average particle size of the second adhesive is 5-100 um, and the average particle size of the third adhesive is 10-110 um.
Further, in the composite binder, the average particle diameter X of the first binder, the average particle diameter Y of the second binder, and the average particle diameter Z of the third binder satisfy: (4X+Y)/Z is not more than 1.5.
Further, in the composite binder, the content of the first binder is 1wt% to 20wt%, the content of the second binder is 1wt% to 80wt%, and the content of the third binder is 1wt% to 80wt%, based on the mass content of the composite binder.
Further, in the composite adhesive, the composite adhesive further comprises a functional additive, and the functional additive comprises at least one of dextran sulfate, beta-dextran and gamma-polyglutamic acid.
Further, in the composite adhesive, the content of the functional additive in the composite adhesive is 0.01-5 wt%.
Further, in the composite binder, the number average molecular weight of the first binder is 40-120 ten thousand; the number average molecular weight of the second binder is 15-100 ten thousand; the number average molecular weight of the third binder is 9-25 ten thousand.
The invention also provides a secondary battery, which comprises a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer arranged on the positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material and the composite binder, and the composite binder is used for adhering the positive electrode active material to the current collector.
The invention also provides electric equipment, which comprises the secondary battery, wherein the secondary battery is used as a power supply of the electric equipment.
Compared with the prior art, the embodiment of the invention has the following advantages:
in an embodiment of the present invention, a composite binder is provided that includes a first binder, a second binder, and a third binder, the first binder including a halogen; the second binder comprises at least one group of cyano and imide, and the third binder comprises at least one group of aldehyde and hydroxyl; the first binder has an average particle size smaller than that of the second binder, and the second binder has an average particle size smaller than that of the third binder. The particle sizes of the first binder, the second binder and the third binder in the composite binder are regulated, so that the composite binder can form a crosslinked network structure, the bonding strength of the binder is improved, groups such as cyano groups, imide groups and the like in the halogen second binder in the first binder, groups such as aldehyde groups and hydroxyl groups in the third binder can be crosslinked with each other in a hydrogen bond form on the surface of the positive electrode active material to form a more compact coating layer to form a three-dimensional crosslinked network, and hydrogen bonds with the surface groups of the positive electrode active material can be formed to form a hydrogen bond with strong interaction, thereby forming an effective coating layer on the positive electrode active material, reducing the dissolution of transition metal ions and improving the circulation stability under high cut-off voltage.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
FIG. 1 is an SEM test chart of polyacrylonitrile of example 1 of the present invention;
FIG. 2 is an SEM test chart of the positive electrode sheet of example 1 of the present invention;
FIG. 3 is a TEM test chart of the positive electrode sheet in example 1 of the present invention;
FIG. 4 is an SEM test chart of polyvinylidene fluoride of comparative example 1 of the present invention;
fig. 5 is an SEM test chart of the positive electrode sheet in comparative example 1 of the present invention.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
The applicant of the invention discovers that although the lithium ion battery is used as a new generation green energy storage system and has the advantages of long cycle life, good low-temperature discharge performance, high specific capacity, wide working temperature range, short charging time and the like, the positive electrode active material with higher theoretical specific capacity in the lithium ion battery is easy to generate irreversible phase change under high voltage, so that the battery structure is damaged, transition metal ions are dissolved out and gas is separated out, and the electrochemical performance of the battery is greatly reduced and the cycle life is shortened.
In order to solve the problems described above, an embodiment of the present invention provides a composite adhesive, wherein the composite adhesive includes a first adhesive, a second adhesive, and a third adhesive, and the first adhesive includes halogen; the second binder includes at least one of cyano group and imide group, and the third binder includes at least one of aldehyde group and hydroxyl group; the first binder has an average particle size smaller than that of the second binder, and the second binder has an average particle size smaller than that of the third binder.
The composite binder provided by the embodiment of the invention is used for adhering the positive electrode active material in the secondary battery to the positive electrode current collector, wherein the particle sizes of the first binder, the second binder and the third binder in the composite binder have the above relation, so that the first binder, the second binder and the third binder are subjected to size particle grading, a cross-linked network structure can be formed, the bonding strength of the binder is increased, and simultaneously, halogen in the first binder, cyano, imide groups and the like in the second binder, aldehyde groups, hydroxyl groups and the like in the third binder and the like can be mutually crosslinked on the surface of the positive electrode active material in a hydrogen bond mode, so that a denser coating layer is formed, a three-dimensional cross-linked network is formed, and hydrogen bonds with the surface groups of the positive electrode active material can be generated, so that the positive electrode active material is effectively coated, the dissolution of transition metal ions is effectively reduced, the cycle stability under high-cut-off voltage is improved, and the cycle stability under high-off voltage of 4.6V can be maintained.
Optionally, in one embodiment, the first binder includes at least one of polyvinylidene fluoride and polyvinyl chloride; the second binder comprises at least one of polyacrylonitrile and polyimide; the third binder includes at least one of polyvinyl butyral and polyvinyl alcohol. Among them, polyvinylidene fluoride and polyvinyl chloride can provide halogen, polyacrylonitrile can provide cyano, polyimide can provide imide, polyvinyl butyral can provide aldehyde and hydroxyl, polyvinyl alcohol can provide hydroxyl, and these substances can be three-dimensionally crosslinked with each other in the form of hydrogen bond, so that when the composite binder is prepared according to the above components, a dense coating layer can be formed on the surface of the positive electrode active material.
Alternatively, in one embodiment, the first binder has an average particle size of 0.2 to 5um, the second binder has an average particle size of 5 to 100um, and the third binder has an average particle size of 10 to 110um. In some embodiments, the first binder has an average particle size of 0.5 to 4um, the second binder has an average particle size of 10 to 50um, and the third binder has an average particle size of 20 to 100um. In some embodiments, the first binder has an average particle size of 1 to 3um, the second binder has an average particle size of 20 to 40um, and the third binder has an average particle size of 60 to 80um.
Optionally, in a specific embodiment, the average particle size X of the first binder, the average particle size Y of the second binder, and the average particle size Z of the third binder satisfy: (4X+Y)/Z is not more than 1.5.
In the specific embodiment, the combination characteristics of the size and the particle diameter of each component of the composite adhesive are regulated to meet the grading conditions, so that the adhesive strength of the composite adhesive can be greatly improved.
Alternatively, in another embodiment, the average particle size X of the first binder and the average particle size Z of the third binder satisfy: Z/X is more than or equal to 4.
In the specific embodiment, the particle size relation of each component in the composite binder is regulated to meet the grading condition, so that the composite binder can form a crosslinked network structure, the bonding strength of the binder is increased, and the active material surface can be crosslinked in a hydrogen bond mode to form a compact coating layer.
Alternatively, in another embodiment, the average particle size X of the first binder, the average particle size Y of the second binder, and the average particle size Z of the third binder satisfy: (4X+Y)/Z is less than or equal to 1.5 and Z/X is more than or equal to 4. In other embodiments 0.6.ltoreq.4X+Y)/Z. In other embodiments, 0.8.ltoreq.4X+Y)/Z.ltoreq.1.2.
In the specific embodiment, the particle size relation of each component in the composite binder is regulated to meet the grading condition, so that the composite binder can form a crosslinked network structure, the bonding strength of the binder is increased, and simultaneously, the active material surface can be crosslinked in a hydrogen bond mode to form a more compact coating layer.
Optionally, in an embodiment, in the composite adhesive provided by the embodiment of the invention, the content of the first adhesive is 1wt% to 20wt%, the content of the second adhesive is 1wt% to 80wt%, and the content of the third adhesive is 1wt% to 80wt%, based on the mass content of the composite adhesive. Under the content ratio, the groups in each component can be effectively subjected to three-dimensional crosslinking, so that a compact coating layer is formed on the surface of the positive electrode active material.
Alternatively, in some embodiments, the first binder is present in an amount of 5wt% to 15wt%, the second binder is present in an amount of 10wt% to 70wt%, and the third binder is present in an amount of 10wt% to 70wt%, based on the mass content of the composite binder.
Alternatively, in some embodiments, the first binder is present in an amount of 8wt% to 12wt%, the second binder is present in an amount of 30wt% to 60wt%, and the third binder is present in an amount of 30wt% to 60wt%, based on the mass content of the composite binder.
Optionally, in the composite binder provided by the embodiment of the invention, the number average molecular weight of the first binder is 40-120 ten thousand; the number average molecular weight of the second binder is 15-100 ten thousand; the number average molecular weight of the third binder is 9-25 ten thousand, so that the third binder can be crosslinked on the surface of the active material in a hydrogen bond mode to form a denser coating layer, and the energy density of the battery can be effectively considered.
Alternatively, in some embodiments, the first binder has a number average molecular weight of 50 to 100 tens of thousands; the number average molecular weight of the second binder is 30-80 ten thousand; the number average molecular weight of the third binder is 10-20 ten thousand; in some embodiments, the first binder has a number average molecular weight of 60 to 80 ten thousand; the number average molecular weight of the second binder is 50-60 ten thousand; the number average molecular weight of the third binder is 12-15 ten thousand.
Optionally, in some embodiments, the composite binders provided by the examples of this invention further include a functional additive comprising at least one of dextran sulfate, beta-dextran, gamma-polyglutamic acid. The functional additive is rich in a large amount of hydroxyl or carboxyl, can enhance a dynamic hydrogen bond network formed by imide groups and cyano groups in the second binder and aldehyde groups in the third binder, and endows the binder with self-repairing capability and improves cycle performance.
Optionally, in some specific embodiments, the content of the functional additive in the composite adhesive is 0.01wt% to 5wt%, so that the self-repairing performance of the composite adhesive can be effectively improved without affecting the adhesive performance of the composite adhesive.
Optionally, in some embodiments, the content of the above functional additive in the composite adhesive is 0.5wt% to 4wt%.
Optionally, in some embodiments, the content of the above functional additive in the composite adhesive is 1wt% to 3wt%.
The invention also provides a secondary battery, which comprises a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer arranged on the positive electrode current collector, the positive electrode active material layer comprises the positive electrode active material and the composite binder, and the composite binder is used for adhering the positive electrode active material to the current collector. Wherein the secondary battery comprises a lithium ion secondary battery.
Alternatively, in one embodiment, the cutoff voltage of the secondary battery is 4.6V or more.
Alternatively, in one embodiment, the positive electrode active material includes a layered lithium salt, a lithium transition metal phosphate.
Optionally, the layered lithium salt comprises at least one of lithium cobaltate and nickel cobalt manganese oxide, and the lithium transition metal phosphate comprises LiMPO 4 Wherein M comprises at least one element of Fe, mn, co, ni, ti, cu.
Optionally, in an embodiment, the positive electrode sheet further includes a conductive agent, and the conductive agent may include at least one of conductive carbon black, acetylene black, ketjen black, carbon nanotubes, graphene, hard carbon, carbon fibers, and carbon microspheres.
Optionally, in one embodiment, the mass ratio of the positive electrode active material, the composite binder and the conductive agent in the positive electrode sheet is (80-96): 3-10): 1-10, so that the high-voltage cycling stability of the secondary battery can be obviously improved, and the safety risk caused by dissolution of transition metal ions such as cobalt ions in the cycling process can be avoided.
In some embodiments, the positive electrode sheet is prepared as follows: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material comprising the positive electrode material, an adhesive and a conductive agent, in solvents such as N-methyl pyrrolidone and the like to form positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector such as aluminum foil; and drying, rolling, die cutting and the like to obtain the positive electrode plate.
The sodium ion battery provided by the embodiment of the invention further comprises a negative electrode plate, an isolating film and an electrolyte.
The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer may be a negative electrode active material for a battery, such as artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, or the like, which is known in the art.
Wherein the electrolyte plays a role of conducting ions between the positive electrode plate and the negative electrode plate, and the electrolyte can be liquid, gel state or all solid state. In some embodiments, the electrolyte is an electrolyte solution, the electrolyte solution includes an electrolyte salt and a solvent, and the electrolyte salt is a lithium salt.
Optionally, the secondary battery includes any one of a liquid lithium ion battery, a quasi-solid metal lithium battery, an all-solid lithium ion battery, and a solid metal lithium battery.
The embodiment of the invention also provides electric equipment, which comprises the secondary battery, wherein the secondary battery is used for providing power.
For the secondary battery embodiment and the consumer embodiment, the positive electrode sheet includes a positive electrode active material layer, where the positive electrode active material layer includes the positive electrode material and the composite binder, and the composite binder is used to adhere the positive electrode active material to the current collector and achieve the same technical effects, so that the repetition is avoided, and details of the description of the composite binder embodiment are omitted herein.
In order to make the objects, technical solutions and advantageous effects of the present invention clearer, the present invention is further described below with reference to examples. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention.
The present invention will be described in detail with reference to examples.
Example 1
(1) Preparation of the composite binder:
uniformly mixing polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and beta-glucan according to the mass ratio of 9.5:60:30:0.5 to obtain a composite binder; wherein, the average grain diameter of the polyvinylidene fluoride is 3um, the number average molecular weight is 70 ten thousand, the average grain diameter of the polyacrylonitrile is 30um, the number average molecular weight is 50 ten thousand, the average grain diameter of the polyvinyl butyral is 70um, and the number average molecular weight is 15 ten thousand.
(2) Preparation of positive electrode plate
Dry-mixing 90 parts of lithium cobaltate and 5 parts of conductive carbon black for 2 hours to obtain a dry mixed material, adding 5 parts of a composite binder into the dry mixed material, supplementing a certain amount of a dispersing solvent N-methylpyrrolidone, and uniformly stirring to obtain positive electrode slurry;
coating the positive electrode slurry on two sides of an aluminum foil in an extrusion coating mode, baking at 105-130 ℃, and then rolling and die cutting to obtain the positive electrode plate.
(3) Preparation of negative electrode plate
The negative electrode material of hard carbon, styrene Butadiene Rubber (SBR), conductive carbon black and sodium carboxymethylcellulose (CMC) are mixed according to the proportion of 85:5.5:5.5:4, homogenizing in a mass ratio, uniformly coating on two sides of a negative electrode current collector, and drying at high temperature, rolling, cutting and stripping to prepare the negative electrode plate.
(4) Preparation of lithium ion batteries
And taking polypropylene (PP) with the thickness of 20um as a diaphragm, winding the positive pole piece, the negative pole piece and the diaphragm, packaging, and injecting lithium salt electrolyte to prepare the lithium ion battery.
Example 2
Example 2 differs from example 1 in that in step (1), polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and β -glucan were uniformly mixed at a mass ratio of 19.9:20:60:0.1 to obtain a composite binder.
Example 3
Example 3 differs from example 1 in that in step (1), polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and dextran sulfate were uniformly mixed at a mass ratio of 1:79:19.99:0.01 to obtain a composite binder.
Example 4
Example 4 differs from example 1 in that in step (1), polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and dextran sulfate were uniformly mixed at a mass ratio of 1:79.9:19:0.1 to obtain a composite binder.
Example 5
Example 5 differs from example 1 in that in step (1), polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and dextran sulfate were uniformly mixed at a mass ratio of 1:19:79.9:0.1 to obtain a composite binder.
Example 6
Example 6 differs from example 1 in that in step (1), polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and β -glucan were uniformly mixed at a mass ratio of 9.9:30:60:0.1 to obtain a composite binder.
Example 7
Example 7 differs from example 1 in that in step (1), polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol and beta-glucan are uniformly mixed according to the mass ratio of 9.9:30:60:0.1, so as to obtain a composite binder; wherein, the average grain diameter of the polyvinylidene fluoride is 3um, the number average molecular weight is 70 ten thousand, the average grain diameter of the polyacrylonitrile is 30um, the number average molecular weight is 50 ten thousand, the average grain diameter of the polyvinyl alcohol is 70um, the number average molecular weight is 15 ten thousand.
Example 8
Example 8 differs from example 1 in that in step (1), polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and gamma-polyglutamic acid are uniformly mixed according to a mass ratio of 9.99:30:60:0.01 to obtain a composite binder; wherein, the average grain diameter of the polyvinylidene fluoride is 3um, the number average molecular weight is 70 ten thousand, the average grain diameter of the polyacrylonitrile is 30um, the number average molecular weight is 50 ten thousand, the average grain diameter of the polyvinyl butyral is 70um, and the number average molecular weight is 15 ten thousand.
Example 9
Example 9 is different from example 8 in that in step (1), polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and gamma-polyglutamic acid were uniformly mixed in a mass ratio of 9.9:50:40:0.1 to obtain a composite binder.
Example 10
Example 10 differs from example 8 in that in step (1), polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and gamma-polyglutamic acid were uniformly mixed at a mass ratio of 8:30:60:2 to obtain a composite binder.
Example 11
Example 11 differs from example 8 in that in step (1), polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and gamma-polyglutamic acid were uniformly mixed at a mass ratio of 5:30:60:5 to obtain a composite binder.
Example 12
Example 12 differs from example 1 in that in step (1), the average particle diameter of polyvinylidene fluoride was adjusted to 2um, the average particle diameter of polyacrylonitrile was adjusted to 50um, and the average particle diameter of polyvinyl butyral was adjusted to 60um.
Example 13
Example 13 differs from example 1 in that in step (1), the average particle diameter of polyvinylidene fluoride was adjusted to 0.2um, the average particle diameter of polyacrylonitrile was 100um, and the average particle diameter of polyvinyl butyral was 110um.
Example 14
Example 14 differs from example 1 in that in step (1), the average particle diameter of polyvinylidene fluoride was adjusted to 5um, the average particle diameter of polyacrylonitrile was adjusted to 6um, and the average particle diameter of polyvinyl butyral was adjusted to 20um.
Example 15
Example 15 differs from example 1 in that in step (1), the average particle diameter of polyvinylidene fluoride was adjusted to 2.5um, the average particle diameter of polyacrylonitrile was 6um, and the average particle diameter of polyvinyl butyral was 10um.
Example 16
Example 16 differs from example 1 in that in step (1), the number average molecular weight of polyvinylidene fluoride was adjusted to 60 ten thousand, the number average molecular weight of polyacrylonitrile was 55 ten thousand, and the number average molecular weight of polyvinyl butyral was 12 ten thousand.
Example 17
Example 17 differs from example 1 in that in step (1), the number average molecular weight of polyvinylidene fluoride was adjusted to 40 ten thousand, the number average molecular weight of polyacrylonitrile was 100 ten thousand, and the number average molecular weight of polyvinyl butyral was 9 ten thousand.
Example 18
Example 18 differs from example 1 in that in step (1), polyvinylidene fluoride was replaced with polyvinyl chloride, the number average molecular weight of polyvinyl chloride was adjusted to 120 ten thousand, polyacrylonitrile was replaced with polyimide, the number average molecular weight of polyimide was 15 ten thousand, polyvinyl butyral was replaced with polyvinyl alcohol, and the number average molecular weight of polyvinyl alcohol was 25 ten thousand.
Comparative example 1
Comparative example 1 differs from example 1 in that in step (2), the composite binder was adjusted to polyvinylidene fluoride, i.e., step (1) was not provided.
Comparative example 2
Comparative example 2 is different from example 1 in that the average particle diameters of polyvinylidene fluoride, polyacrylonitrile and polyvinyl butyral in the composite binder were 70 μm, 30 μm, and 3 μm, respectively.
The binder components and parameters of each of the examples and comparative examples are shown in table 1.
The batteries prepared in each example were subjected to discharge rate performance test and volumetric energy density test, and the test data are shown in table 2.
TABLE 1
In table 1, w= (4x+y)/Z, where X is the average particle size of the first binder, Y is the average particle size of the second binder, and Z is the average particle size of the third binder.
SEM test of polyacrylonitrile of example 1 was carried out, and the results are shown in FIG. 1.
The results of SEM test and TEM test on the positive electrode sheet in example 1 are shown in fig. 2 (a), 2 (b) and 3, respectively.
SEM test was performed on polyvinylidene fluoride in comparative example 1, and the results are shown in fig. 4.
The results of SEM testing of the positive electrode sheet of comparative example 1 are shown in fig. 5 (a) and 5 (b).
Comparing fig. 2 (a), 2 (b) with fig. 5 (a), 5 (b), it can be seen that when a composite binder of uniformly mixed polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and beta-glucan is used, the active material lithium cobaltate can be completely encapsulated by the binder and the conductive agent.
As can be seen from fig. 1 and fig. 4, the particles of different components have obvious differences, and as can be seen from fig. 4, when a composite binder prepared by uniformly mixing polyvinylidene fluoride, polyacrylonitrile, polyvinyl butyral and beta-glucan is adopted, a compact coating layer is formed on the surface of lithium cobaltate by the binder.
In addition, electrochemical performance tests were performed on the secondary batteries prepared in each of examples and comparative examples to determine the capacity at 0.1C magnification, the capacity retention rate at 1C magnification at 300 cycles, and the first coulombic efficiency at 0.05C magnification for the first cycle; wherein, the charge-discharge cut-off voltage of the cycle is 3.0-4.6V, and the charge-discharge current is 1C; the rate test range was 0.1 to 10C, and the charge-discharge cutoff voltage was 3.0 to 4.6V, and the results are shown in table 2.
The cycle performance of the secondary batteries prepared in example 1 and comparative example 1 at 1C rate is shown in fig. 1.
The rate properties of the secondary batteries prepared in example 1 and comparative example 1 are shown in fig. 2.
TABLE 2
Battery numbering 0.1C Capacity (mAh/g) 300 cycles capacity retention (1C) First coulombic efficiency
Example 1 222.2 95.54％ 95.81％
Example 2 223.1 93.73％ 96.24％
Example 3 222.3 91.76％ 95.82％
Example 4 221.3 94.61％ 95.26％
Example 5 225.1 93.11％ 97.11％
Example 6 221.3 93.45％ 95.38％
Example 7 220.8 93.92％ 95.17％
Example 8 219.7 90.21％ 94.69％
Example 9 221.4 93.51％ 95.43％
Example 10 222.7 94.14％ 96.00％
Example 11 223.5 95.1％ 96.2％
Example 12 222.9 95.84％ 95.98％
Example 13 219.8 94.93％ 96.45％
Example 14 221.5 95.22％ 95.92％
Example 15 221.3 95.61％ 95.63％
Example 16 222.1 95.62％ 95.75％
Example 17 221.5 94.8％ 96.23％
Example 18 219.6 91.8％ 94.56％
Comparative example 1 218.7 83.76％ 94.22％
Comparative example 2 221.3 89.35％ 94.56％
In summary, in this embodiment, by adjusting the particle sizes of the first binder, the second binder and the third binder in the composite binder to increase sequentially, the composite binder can form a crosslinked network structure, so as to increase the bonding strength of the binder, and at the same time, the halogen and carbon-carbon double bond groups in the first binder, the cyano and imide groups in the second binder, and the aldehyde and hydroxyl groups in the third binder can crosslink with each other in the form of hydrogen bonds on the surface of the positive electrode active material to form a more compact coating layer to form a three-dimensional crosslinked network, and can also generate a hydrogen bond with the surface groups of the positive electrode active material to form a hydrogen bond with strong interaction, so that an effective coating layer is formed on the positive electrode active material, the dissolution of transition metal ions is effectively reduced, and the cycle stability under high cut-off voltage is improved.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all such alterations and modifications as fall within the scope of the embodiments of the invention.
The above description of the composite binder, secondary battery and electric equipment provided by the invention applies specific examples to illustrate the principle and implementation of the invention, and the above examples are only used for helping to understand the method and core idea of the invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.

Claims (10)

1. A composite binder, wherein the composite binder comprises a first binder, a second binder, and a third binder, the first binder comprising a halogen; the second binder comprises at least one group of cyano and imide, and the third binder comprises at least one group of aldehyde and hydroxyl;
the first binder has an average particle size smaller than the second binder, and the second binder has an average particle size smaller than the third binder.
2. The composite binder of claim 1 wherein the first binder comprises at least one of polyvinylidene fluoride, polyvinyl chloride;
the second binder comprises at least one of polyacrylonitrile and polyimide;
the third binder includes at least one of polyvinyl butyral and polyvinyl alcohol.
3. The composite binder of claim 1 wherein the first binder has an average particle size of 0.2 to 5um, the second binder has an average particle size of 5 to 100um, and the third binder has an average particle size of 10 to 110um.
4. The composite binder of claim 3 wherein the average particle size X of the first binder, the average particle size Y of the second binder, and the average particle size Z of the third binder satisfy: (4X+Y)/Z is not more than 1.5.
5. The composite binder of claim 1 wherein the first binder is present in an amount of 1wt% to 20wt%, the second binder is present in an amount of 1wt% to 80wt%, and the third binder is present in an amount of 1wt% to 80wt%, based on the mass content of the composite binder.
6. The composite binder of claim 1 further comprising a functional additive comprising at least one of dextran sulfate, beta-dextran, gamma-polyglutamic acid.
7. The composite adhesive according to claim 6, wherein the functional additive is present in the composite adhesive in an amount of 0.01wt% to 5wt%.
8. The composite binder of any one of claims 1-7 wherein the first binder has a number average molecular weight of 40-120 ten thousand; the number average molecular weight of the second binder is 15-100 ten thousand; the number average molecular weight of the third binder is 9-25 ten thousand.
9. A secondary battery comprising a positive electrode sheet including a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, and the composite binder according to any one of claims 1 to 8, the composite binder being for adhering the positive electrode active material to the current collector.
10. An electric device comprising the secondary battery according to claim 9 as a power supply source of the electric device.
CN202310774910.4A 2023-06-27 2023-06-27 Composite binder, secondary battery and electric equipment Pending CN116554815A (en)

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