CN116845177A - Negative electrode material composition, negative electrode sheet, electrochemical device, and electronic device - Google Patents

Negative electrode material composition, negative electrode sheet, electrochemical device, and electronic device Download PDF

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Publication number
CN116845177A
CN116845177A CN202310615724.6A CN202310615724A CN116845177A CN 116845177 A CN116845177 A CN 116845177A CN 202310615724 A CN202310615724 A CN 202310615724A CN 116845177 A CN116845177 A CN 116845177A
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negative electrode
material composition
electrode material
monomer
shell
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闫永思
孙化雨
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Yuanjing Power Technology Ordos Co ltd
Vision Power Technology Hubei Co ltd
Envision Power Technology Jiangsu Co Ltd
Envision Ruitai Power Technology Shanghai Co Ltd
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Yuanjing Power Technology Ordos Co ltd
Vision Power Technology Hubei Co ltd
Envision Power Technology Jiangsu Co Ltd
Envision Ruitai Power Technology Shanghai Co Ltd
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Priority to CN202310615724.6A priority Critical patent/CN116845177A/en
Publication of CN116845177A publication Critical patent/CN116845177A/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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F265/00—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00
    • C08F265/02—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00 on to polymers of acids, salts or anhydrides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M4/624—Electric conductive fillers
    • 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
    • H01M2004/027—Negative electrodes

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

Abstract

The application discloses a negative electrode material composition, a negative electrode sheet, an electrochemical device and an electronic device. The negative electrode material composition comprises a negative electrode active material, a conductive agent and a preservative; the liquid retention agent is in a core-shell structure, the core of the liquid retention agent is a polymer of a core monomer, and the shell of the liquid retention agent is a polymer of a shell monomer; the mass ratio of the preservative agent to the conductive agent is 9:2-1:3. According to the application, through the specially designed liquid retention agent and the control of the specific surface areas of the conductive agent and the negative electrode active material, the liquid retention capacity of the negative electrode plate is improved, so that the cycle capacity retention rate of the battery is improved, and the cycle life of the lithium ion battery is prolonged.

Description

Negative electrode material composition, negative electrode sheet, electrochemical device, and electronic device
Technical Field
The application relates to a negative electrode material composition, a negative electrode plate, an electrochemical device and an electronic device.
Background
With the continuous development of the lithium ion battery industry, the requirements on the lithium ion battery are more and more strict, and the requirements on the cycle life of the lithium ion battery are more and more improved. In a lithium ion battery, as the number of battery cycles increases, a solid electrolyte interface film (SEI film) on the surface of the negative electrode is damaged, an electrolyte is continuously decomposed, and a graphite negative electrode is continuously damaged, resulting in continuous degradation of battery cycle performance.
In order to improve the cycle life of the lithium ion battery, a special film forming additive is generally considered to be added into the electrolyte to improve the stability of the SEI film on the surface of the negative electrode so as to improve the cycle life of the lithium ion battery; however, the effect of a single film-forming additive is limited, the film-forming resistance of the surface of the negative electrode can be greatly increased, and the cycle life of the lithium battery is limited.
Disclosure of Invention
The application provides a negative electrode material composition, a negative electrode plate, an electrochemical device and an electronic device, which are used for overcoming the defects that the improvement degree is limited and the film forming resistance of the surface of a negative electrode can be increased when the cycle life of a lithium battery is prolonged in the prior art. According to the application, through the specially designed liquid retention agent and the control of the specific surface areas of the conductive agent and the negative electrode active material, the liquid retention capacity of the negative electrode plate is improved, so that the cycle capacity retention rate of the battery is improved, and the cycle life of the lithium ion battery is prolonged.
The application mainly solves the technical problems through the following technical scheme.
In a first aspect, the present application provides a negative electrode material composition comprising a negative electrode active material, a conductive agent, and a preservative,
the liquid retention agent is in a core-shell structure, the core of the liquid retention agent is a polymer of a core monomer, and the shell of the liquid retention agent is a polymer of a shell monomer, wherein the core monomer comprises an acrylic monomer, and the acrylic monomer comprises one or more of acrylic acid, methacrylic acid and methacrylic acid ester; the shell monomers comprise a first shell monomer and a second shell monomer, wherein the first shell monomer is styrene, and the second shell monomer is one or two of acrylonitrile and methyl methacrylate; the mass ratio of the preservative to the conductive agent is 9:2-1:3.
In a second aspect, the present application provides a negative electrode tab comprising a negative electrode current collector and a negative electrode material layer comprising a negative electrode material composition as described above.
In a third aspect, the present application provides an electrochemical device comprising a negative electrode tab as described above.
In a fourth aspect, the present application provides an electronic device comprising an electrochemical device as described above.
The application has the positive progress effects that:
according to the application, the high specific surface area of the conductive agent is controlled in the negative electrode plate, and meanwhile, the relation between the specific surface areas of the conductive agent and the negative electrode active material is controlled, so that the film forming impedance of the surface of the negative electrode plate is not increased by matching with the specially designed electrolyte retaining agent, the stability of the SEI film on the surface of the negative electrode plate is improved, the electrolyte retaining capacity of the negative electrode plate is increased, the cycle performance of the battery is improved, the cycle capacity retention rate of the battery is improved, and the cycle life of the battery is prolonged.
Drawings
Fig. 1 is a TEM electron microscope image of the preservative solution according to example 1 of the present application.
Detailed Description
Negative electrode material composition
The first aspect of the present application provides a negative electrode material composition comprising a negative electrode active material, a conductive agent, and a preservative,
the liquid retention agent is in a core-shell structure, the core of the liquid retention agent is a polymer of a core monomer, and the shell of the liquid retention agent is a polymer of a shell monomer, wherein the core monomer comprises an acrylic monomer, and the acrylic monomer comprises one or more of acrylic acid, methacrylic acid and methacrylic acid ester; the shell monomers comprise a first shell monomer and a second shell monomer, wherein the first shell monomer is styrene, and the second shell monomer is one or two of acrylonitrile and methyl methacrylate; the specific surface areas of the conductive agent and the anode active material satisfy: bcon is more than or equal to 180m 2 And/g, wherein Bam is greater than 90, bcon is the specific surface area of the conductive agent, bam is the specific surface area of the anode active material, and the mass ratio of the preservative to the conductive agent is 9:2-1:3.
In the present application, in the core of the preservative, the acrylic monomer may homopolymerize to nucleate; in the shell of the preservative, the first shell monomer and the second shell monomer may be copolymerized into the shell.
In a preferred embodiment, the core monomer further comprises styrene. In the core of the preservative, the acrylic monomer may also copolymerize with styrene to form a core. Styrene is preferably introduced into the core of the preservative so that the styrene can be compatible with the shell of the preservative similarly, and the performance of the material is further improved.
In some embodiments, the core monomers are styrene, methacrylic acid, and methyl methacrylate; wherein the mass ratio of the styrene to the methacrylic acid to the methyl methacrylate is 1:2:1.
In a preferred embodiment, in the preservative agent, the mass ratio of the core monomer to the shell monomer is 1:1.
In a specific embodiment, in the shell of the liquid retention agent, the first shell monomer is styrene, the second shell monomer is acrylonitrile and methyl methacrylate, and the mass ratio of the styrene, the acrylonitrile and the methyl methacrylate is 2:2:1.
In a preferred embodiment, in the core of the preservative solution, the core monomer comprises a methacrylate ester comprising one or more of methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate.
The preparation method of the preservative agent comprises the step of carrying out polymerization reaction on the core monomer and the shell monomer. In a preferred embodiment, the polymerization is carried out in an aqueous solution of sodium persulfate and sodium dodecyl sulfate; preferably, the mass ratio of the sodium persulfate to the sodium dodecyl sulfate is 1:10.
In a preferred embodiment, the temperature of the polymerization reaction is 50-95 ℃.
In a preferred embodiment, the polymerization time is 12 to 24 hours.
In some embodiments, the preservative is used in an amount of 0.1% -1.0% by mass of the preservative to the negative electrode material composition.
In some embodiments, the conductive agent is used in an amount of 0.1% to 1.0% by mass of the conductive agent to the negative electrode material composition.
In some embodiments, the mass ratio of the preservative to the conductive agent is 1:2-2:1.
Negative pole piece
The second aspect of the present application provides a negative electrode tab comprising a negative electrode current collector and a negative electrode material layer comprising a negative electrode material composition as described above.
In the above-described anode material composition, the anode material composition may generally include a thickener and a binder in addition to the anode active material, the conductive agent, and the retention agent described above. The application does not limit the types of the thickener and the binder, and can be selected according to actual requirements.
As an example, the thickener may be sodium carboxymethyl cellulose solution (CMC).
The binder may be Styrene Butadiene Rubber (SBR).
In a preferred embodiment, in the anode material composition, the mass ratio of the anode active material, the conductive agent, the thickener, the binder and the retention agent is (97.4-x): y:1.2:1.4:x, x is 0.1% to 1.0%, y is 0.1% to 1.0%.
Electrochemical device
A third aspect of the present application provides an electrochemical device comprising a negative electrode tab as described above; such as lithium ion batteries.
In the present application, those skilled in the art know that the electrochemical device generally further includes a positive electrode tab, a negative electrode tab, a separator, and an electrolyte.
In the present application, the negative electrode sheet is the same as that described previously, so a detailed description thereof will be omitted, and only the remaining components will be described in detail.
Positive electrode plate
In the present application, the electrochemical device may be a lithium ion battery in which the positive electrode sheet generally comprises a positive electrode current collector and a positive electrode active material layer formed on one or both sides of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material and optionally a conductive agent and a binder, and the addition amount may be adjusted in 1 to 50% of the total amount of the positive electrode active material according to various requirements.
Wherein the positive electrode active material may be a material conventionally used in the art, including, but not limited to, one or more of a lithium iron phosphate material, a lithium manganese iron phosphate material, a nickel cobalt manganese ternary material, and a lithium-rich manganese-based material.
Wherein the conductive agent is an agent for ensuring good charge and discharge performance of the electrode. Optionally, the metal powder may be selected from graphite materials such as natural graphite and artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, conductive fibers such as carbon fibers and metal fibers, conductive whiskers such as metal powder such as carbon fluoride powder, aluminum powder and nickel powder, conductive metal oxides such as zinc oxide and potassium titanate, and polyphenylene derivatives.
Wherein the binder is a component that facilitates bonding between the active material and the conductive agent and facilitates bonding of the active material to the current collector. And may be generally selected from polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.
Wherein the positive electrode current collector is used as a substrate for supporting electrode active materials and is usually a metal foil with a thickness of 3-500 micrometers. The material is not particularly limited as long as it has high conductivity and does not cause chemical reaction in the system of the secondary battery. For example, a foil formed by surface treatment of nickel, titanium, aluminum, nickel, silver, stainless steel, carbon, or the like may be used. The positive electrode current collector is generally smooth in surface, but fine lines or the like may be formed on the surface thereof to improve adhesion between the positive electrode active material and the current collector. The positive electrode current collector may be used in combination of any one or more of a plurality of forms such as a film, a mesh, a porous form, a foam, and a nonwoven fabric, in addition to the foil.
Diaphragm
An insulating film having high ion permeability and high mechanical strength is used as a separator provided between the positive electrode sheet and the negative electrode sheet. The separator typically has a thickness of 9-18 μm; the aperture is 5-300 mu m; the air permeability is 180-380s/100mL; the porosity is 30% to 50%. As the separator, a sheet or nonwoven fabric made of: olefin polymers such as polypropylene; glass fibers or polyethylene, which have chemical resistance and hydrophobicity.
Electrolyte solution
The electrolyte used in the lithium ion battery prepared as above generally includes a nonaqueous solvent, a lithium salt, and an additive.
Wherein the non-aqueous solvent may be a conventional non-aqueous solvent in the art, preferably an ester solvent, more preferably a carbonate solvent. Among them, the carbonate-based solvent is preferably one or more of ethylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), methylethyl carbonate (EMC), ethylene Carbonate (EC), propylene Carbonate (PC) and Butylene Carbonate (BC).
Among them, as the lithium salt, liPF can be exemplified 6 、LiBF 4 、LiN(SO 2 F) 2 (abbreviated as LiFSI), liClO 4 、LiAsF 6 、LiB(C 2 O 4 ) 2 (abbreviated as LiBOB), liBF 2 (C 2 O 4 ) (abbreviated as LiDFOB), liN (SO) 2 RF) 2 、LiN(SO 2 F)(SO 2 RF). Preferably, the content thereof in the electrolyte is 5 to 20%.
Among them, the additive is preferably one or more of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), ethylene carbonate (VEC), ethylene sulfate (DTD), vinylene sulfate, 1, 3-Propane Sultone (PS), propenyl sultone, and 1, 4-butane sultone. The additives are conventionally used in the electrolyte in amounts of 1-4%, for example 2%, of the electrolyte.
In the present application, the battery is generally any one of a square battery, a pouch battery, and a cylindrical battery, and a square battery is exemplified here.
The battery may be manufactured using methods conventional in the art. Generally, the method of manufacturing the battery includes the steps of: the positive plate, the negative plate and the diaphragm are orderly manufactured into bare cells according to the slitting process, the cut piece lamination process or the winding process, the bare cells are put into a shell, the water content is kept below 450ppm through sufficient baking, and the square shell battery is manufactured through the working procedures of liquid injection, formation, sealing, inspection and the like.
Electronic device
A fourth aspect of the present application provides an electronic device comprising an electrochemical device as described above.
Illustratively, the electronic device of the present application may be, but is not limited to, a mobile device (e.g., a cell phone, tablet computer, notebook computer, video recorder, portable printer/copier, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a watercraft and satellite, an energy storage system, a backup power source, etc.
The application is further illustrated by means of the following examples, which are not intended to limit the scope of the application. The experimental methods, in which specific conditions are not noted in the following examples, were selected according to conventional methods and conditions, or according to the commercial specifications.
Example 1
The present embodiment is a lithium ion secondary battery.
1. Liquid retention agent
The components of the preservative agent are as follows: the core monomer comprises 20 parts of styrene, 40 parts of methacrylic acid and 20 parts of methyl methacrylate by mass; the shell monomer comprises 40 parts of styrene, 40 parts of acrylonitrile and 20 parts of methyl methacrylate; the mass ratio of the core monomer to the shell monomer is 1:1.
Preparation of a preservative: adding 0.18 part of sodium persulfate and 1.8 parts of sodium dodecyl sulfate into deionized water; and (3) adding the components of the liquid retention agent, and performing polymerization reaction at the reaction temperature of 70 ℃ for 18 hours to obtain the liquid retention agent with a core-shell structure, wherein the core of the liquid retention agent is a copolymer of styrene, methacrylic acid and methyl methacrylate, and the shell of the liquid retention agent is a copolymer of styrene, acrylonitrile and methyl methacrylate. A TEM image of the preservative is shown in fig. 1.
2. Negative pole piece
The negative electrode material composition is prepared by mixing a negative electrode active substance, a conductive agent, a thickening agent, a binder and a preservative agent according to the mass ratio of (97.4-x-y) to (y) of 1.2:1.4:x; in this embodiment, the mass of the conductive agent is 0.2% of the total mass of the negative electrode material composition (i.e., y=0.2), the mass of the retention agent is 0.1% of the total mass of the negative electrode material composition (i.e., x=0.1), and the mass ratio of the retention agent to the conductive agent is 1:2. Wherein the specific surface area of the conductive agent is 180, and the specific surface area of the negative electrode active material is 1.5.
Adding deionized water as a solvent into the negative electrode material, and fully stirring and mixing to obtain negative electrode slurry; and uniformly coating the negative electrode slurry on a negative electrode current collector copper foil, and performing procedures such as drying, cold pressing, slitting and the like to prepare the negative electrode plate.
3. Positive electrode plate
Mixing a lithium iron phosphate anode material, conductive carbon black (Super P) as a conductive agent, polyvinylidene fluoride as a binder and a polystyrene acrylate dispersing agent according to a weight ratio of 92:5:2.5:0.5, adding N-methylpyrrolidone (NMP) as a solvent, and fully stirring and mixing to obtain anode slurry; and coating the positive electrode slurry on a positive electrode current collector aluminum foil, and performing procedures such as drying, cold pressing, cutting and the like to prepare the positive electrode plate.
4. Electrolyte solution
Mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) according to a volume ratio of 1:1:1 to obtain an organic solvent, and then fully drying lithium salt LiPF 6 Dissolving in the mixed organic solvent to prepare the electrolyte with the concentration of 1 mol/L.
5. Diaphragm
A PE porous film having a thickness of 11um was used as a separator.
6. Lithium ion secondary battery
And laminating the prepared positive pole piece, the diaphragm and the negative pole piece in sequence, so that the diaphragm is positioned between the positive pole piece and the negative pole piece to play a role in isolation. And then coating an aluminum plastic film, drying, injecting the prepared electrolyte, and finally preparing the soft-packaged battery (namely the lithium ion secondary battery) with the capacity of 1Ah through the procedures of packaging, standing, forming and the like.
Example 2
In the negative electrode material composition, the mass of the conductive agent accounts for 0.2 percent (namely y=0.2) of the total mass of the negative electrode material composition, the mass of the liquid retention agent accounts for 0.2 percent (namely x=0.2) of the total mass of the negative electrode material composition, and the mass ratio of the liquid retention agent to the conductive agent is 1:1. Other conditions were the same as in example 1.
Example 3
In the negative electrode material composition, the mass of the conductive agent accounts for 0.2 percent (namely y=0.2) of the total mass of the negative electrode material composition, the mass of the liquid retention agent accounts for 0.3 percent (namely x=0.3) of the total mass of the negative electrode material composition, and the mass ratio of the liquid retention agent to the conductive agent is 3:2. Other conditions were the same as in example 1.
Example 4
In the negative electrode material composition, the mass of the conductive agent accounts for 0.2 percent (namely y=0.2) of the total mass of the negative electrode material composition, the mass of the liquid retention agent accounts for 0.4 percent (namely x=0.4) of the total mass of the negative electrode material composition, and the mass ratio of the liquid retention agent to the conductive agent is 2:1. Other conditions were the same as in example 1.
Example 5
In the negative electrode material composition, the mass of the conductive agent accounts for 0.2 percent (namely y=0.2) of the total mass of the negative electrode material composition, the mass of the liquid retention agent accounts for 0.5 percent (namely x=0.5) of the total mass of the negative electrode material composition, and the mass ratio of the liquid retention agent to the conductive agent is 5:2. Other conditions were the same as in example 1.
Example 6
In the negative electrode material composition, the mass of the conductive agent accounts for 0.2 percent (namely y=0.2) of the total mass of the negative electrode material composition, the mass of the liquid retention agent accounts for 0.6 percent (namely x=0.6) of the total mass of the negative electrode material composition, and the mass ratio of the liquid retention agent to the conductive agent is 3:1. Other conditions were the same as in example 1.
Example 7
In the negative electrode material composition, the mass of the conductive agent accounts for 0.2 percent (namely y=0.2) of the total mass of the negative electrode material composition, the mass of the liquid retention agent accounts for 0.7 percent (namely x=0.7) of the total mass of the negative electrode material composition, and the mass ratio of the liquid retention agent to the conductive agent is 7:2. Other conditions were the same as in example 1.
Example 8
In the negative electrode material composition, the mass of the conductive agent accounts for 0.2 percent (namely y=0.2) of the total mass of the negative electrode material composition, the mass of the liquid retention agent accounts for 0.8 percent (namely x=0.8) of the total mass of the negative electrode material composition, and the mass ratio of the liquid retention agent to the conductive agent is 4:1. Other conditions were the same as in example 1.
Example 9
In the negative electrode material composition, the mass of the conductive agent accounts for 0.2 percent (namely y=0.2) of the total mass of the negative electrode material composition, the mass of the liquid retention agent accounts for 0.9 percent (namely x=0.9) of the total mass of the negative electrode material composition, and the mass ratio of the liquid retention agent to the conductive agent is 9:2. Other conditions were the same as in example 1.
Example 10
In the negative electrode material composition, the mass of the conductive agent accounts for 0.1% of the total mass of the negative electrode material composition (i.e., y=0.1), and the mass of the retention agent accounts for 0.3% of the total mass of the negative electrode material composition (i.e., x=0.3). Other conditions were the same as in example 1.
Example 11
In the negative electrode material composition, the mass of the conductive agent accounts for 0.3% of the total mass of the negative electrode material composition (i.e., y=0.3), and the mass of the retention agent accounts for 0.3% of the total mass of the negative electrode material composition (i.e., x=0.3). Other conditions were the same as in example 1.
Example 12
In the negative electrode material composition, the mass of the conductive agent accounts for 0.4% of the total mass of the negative electrode material composition (i.e., y=0.4), and the mass of the retention agent accounts for 0.3% of the total mass of the negative electrode material composition (i.e., x=0.3). Other conditions were the same as in example 1.
Example 13
In the negative electrode material composition, the mass of the conductive agent accounts for 0.5% of the total mass of the negative electrode material composition (i.e., y=0.5), and the mass of the retention agent accounts for 0.3% of the total mass of the negative electrode material composition (i.e., x=0.3). Other conditions were the same as in example 1.
Example 14
In the negative electrode material composition, the mass of the conductive agent accounts for 0.6% of the total mass of the negative electrode material composition (i.e., y=0.6), and the mass of the retention agent accounts for 0.3% of the total mass of the negative electrode material composition (i.e., x=0.3). Other conditions were the same as in example 1.
Example 15
In the negative electrode material composition, the mass of the conductive agent accounts for 0.7% of the total mass of the negative electrode material composition (i.e., y=0.7), and the mass of the retention agent accounts for 0.3% of the total mass of the negative electrode material composition (i.e., x=0.3). Other conditions were the same as in example 1.
Example 16
In the negative electrode material composition, the mass of the conductive agent accounts for 0.8% of the total mass of the negative electrode material composition (i.e., y=0.8), and the mass of the retention agent accounts for 0.3% of the total mass of the negative electrode material composition (i.e., x=0.3). Other conditions were the same as in example 1.
Example 17
In the negative electrode material composition, the mass of the conductive agent accounts for 0.9% of the total mass of the negative electrode material composition (i.e., y=0.9), and the mass of the retention agent accounts for 0.3% of the total mass of the negative electrode material composition (i.e., x=0.3). Other conditions were the same as in example 1.
Comparative example 1
The preservative was not polymerized, but a mixed solution of 20 parts of styrene, 40 parts of methacrylic acid, 20 parts of methyl methacrylate, 40 parts of styrene, 40 parts of acrylonitrile and 20 parts of methyl methacrylate was used as the preservative, and the preservative of the comparative example had a non-core-shell structure. Other conditions were the same as in example 3.
Comparative example 2
In the negative electrode material composition, the mass of the conductive agent accounts for 2% of the total mass of the negative electrode material composition (i.e., y=2), and the mass of the retention agent accounts for 0.3% of the total mass of the negative electrode material composition (i.e., x=0.3). Other conditions were the same as in example 1.
Comparative example 3
The preservative is a homopolymer of acrylic ester and does not have a core-shell structure. Other conditions were the same as in example 3.
Comparative example 4
The preservative is a homopolymer of methyl methacrylate and does not have a core-shell structure. Other conditions were the same as in example 3.
Comparative example 5
In this negative electrode material composition, no conductive agent is added, (i.e., y=0). Other conditions were the same as in example 1.
Effect example 1
(1) Circulation capacity retention test method
At 25 ℃, the cycle is carried out in a charge-discharge system of 0.21A/g (calculated by the mass of the anode material) and 2.5-3.65V. After cycling to 800 weeks, dividing the discharge capacity of the battery at the moment by the discharge capacity after cycling for the 1 st circle, namely the 800-circle cycling capacity retention rate of the battery.
(2) Pole piece resistance test
The resistance of the pole piece was tested using a Hitachi diaphragm resistance meter RM 9003.
The effect data of examples 1-17 and comparative examples 1-5 are shown in Table 1.
TABLE 1
As can be seen from table 1, the lithium ion secondary battery prepared by using the negative electrode sheet containing the negative electrode material composition of the present application has a higher cycle capacity retention rate and a lower sheet resistance, and the capacity retention rate data and the sheet resistance data of examples 1 to 17 are specifically shown.
According to examples 1 to 17, when the retention agent has a core-shell structure and the anode active material and the conductive agent have specific surface areas, the product has a higher capacity retention rate and a lower pole piece resistance; further, when the ratio of the amount of the preservative to the amount of the conductive agent is (1-7): 2, the prepared product has lower pole piece resistance and higher capacity retention rate. In the case of the comparative example 2 in which the amount of the conductive agent used was too large, the sheet resistance was very low (as low as 0.101 Ω×cm), but the cycle capacity retention rate of the product was reduced.
Comparative example 1 compared with example 3, the retention agent of comparative example 1 did not undergo polymerization reaction and had a capacity retention rate of 82%, whereas the retention agent of example 3 formed a core-shell structure and had a capacity retention rate as high as 89.3% and improved by 9%.
Compared with example 3, since the homopolymers of acrylic ester and methyl methacrylate are used as the retention agents in comparative examples 3 and 4, respectively, the capacity retention rates of the products in comparative examples 3 and 4 are only 81% and 78%, and the sheet resistance is also increased to 0.361 Ω×cm and 0.321 Ω×cm.
In comparative example 5, the cycle capacity retention rate of the product was lowered without adding a conductive agent, and the capacity retention rate of the product of comparative example 5 was only 81.2%.

Claims (10)

1. A negative electrode material composition comprising a negative electrode active material, a conductive agent and a preservative agent, characterized in that,
the liquid retention agent is in a core-shell structure, the core of the liquid retention agent is a polymer of a core monomer, the shell of the liquid retention agent is a polymer of a shell monomer, wherein,
the core monomer comprises an acrylic monomer comprising one or more of acrylic acid, methacrylic acid, and methacrylate esters;
the shell monomers comprise a first shell monomer and a second shell monomer, wherein the first shell monomer is styrene, and the second shell monomer is one or two of acrylonitrile and methyl methacrylate;
the mass ratio of the preservative to the conductive agent is 9:2-1:3.
2. The negative electrode material composition of claim 1, wherein the core monomer further comprises styrene.
3. The anode material composition according to claim 1, wherein a mass ratio of the core monomer and the shell monomer in the liquid retention agent is 1:1.
4. The negative electrode material composition of claim 1, wherein the shell of the chaotropic agent satisfies one of the following conditions:
(a) The first shell monomer is styrene, the second shell monomer is acrylonitrile, and the mass ratio of the styrene to the acrylonitrile is 1:1;
(b) The first shell monomer is styrene, the second shell monomer is methyl methacrylate, and the mass ratio of the styrene to the methyl methacrylate is 2:1;
(c) The first shell monomer is styrene, the second shell monomer is acrylonitrile and methyl methacrylate, and the mass ratio of the styrene to the acrylonitrile to the methyl methacrylate is 2:2:1.
5. The negative electrode material composition of claim 1, wherein the core monomer comprises a methacrylate ester comprising one or more of methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate.
6. The negative electrode material composition according to claim 1, wherein the amount of the preservative is 0.1-1.0%, the percentage being the mass percentage of the preservative in the negative electrode material composition;
the consumption of the conductive agent is 0.1% -1.0%, and the conductive agent accounts for the mass percent of the cathode material composition.
7. The negative electrode material composition according to claim 1, wherein the mass ratio of the liquid retention agent and the conductive agent is 1:2 to 2:1.
8. A negative electrode tab comprising a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer comprises the negative electrode material composition of any one of claims 1-7.
9. An electrochemical device comprising the negative electrode tab of claim 8.
10. An electronic device comprising the electrochemical device according to claim 9.
CN202310615724.6A 2023-05-24 2023-05-24 Negative electrode material composition, negative electrode sheet, electrochemical device, and electronic device Pending CN116845177A (en)

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