Negative electrode binder, negative electrode plate and electrochemical energy storage device

Abstract

The invention belongs to the technical field of electrochemistry, and particularly relates to a negative electrode binder which is composed of a core layer and a shell layer, and the core layer is coated with the shell layer. In one of the negative electrode binders, a core layer monomer used for synthesizing a core layer comprises o-phenyl phenoxy ethyl acrylate. Furthermore, the diameter of the core layer is 50 to 500 nm, and the thickness of the shell layer is 1 to 10 nm; the glass transition temperature of the core layer is-20 DEG C to 20 DEG C, and the glass transition temperature of the shell layer is 80 DEG C to 160 DEG C; the swelling degree of the core layer in the electrolyte is 20%-200%, and the swelling degree of the shell layer in the electrolyte is 1%-10%. The negative electrode binders have good flexibility, dispersibility, mechanical modulus and bonding strength, are beneficial to inhibition of volume expansion generated by a negative electrode active material in the charging and discharging process, and are beneficial to maintenance of structural stability in the long cycle process, so that the cycle performance of the battery is improved.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical technology, and specifically relates to a negative electrode binder, a negative electrode plate and an electrochemical energy storage device, and in particular to a negative electrode binder for a lithium ion secondary battery. Background Art

[0002] Lithium-ion batteries are widely used due to their advantages such as high mass energy density, high volume energy density and long cycle life. Their application scope includes electronic products such as laptops, mobile phones or digital products, as well as power batteries such as electric vehicles or energy storage power stations.

[0003] Electrode binders adhere to the surface of the current collector, providing strong adhesion to maintain the integrity of the electrode structure, thereby ensuring that lithium-ion batteries can cycle properly. The performance of the electrode binder directly affects the electrochemical performance of the battery. Currently, the main commercial negative electrode binder is styrene-butadiene rubber (SBR). Existing SBR binders have good elasticity and adhesion, providing good electrode bonding and flexibility. However, they have a low elastic modulus and weak expansion resistance. They have poor expansion inhibition effect on graphite active materials and silicon-carbon negative electrode materials, and are not conducive to the uniform dispersion of negative electrode active materials and conductive agents. Summary of the Invention

[0004] To solve the above problems, the present invention aims to provide a negative electrode binder for preparing negative electrode sheets of electrochemical energy storage devices such as lithium-ion secondary batteries.

[0005] The technical solution adopted in the present invention is as follows: In a first aspect, the present invention provides a negative electrode binder having a core-shell structure, wherein the core-shell structure is composed of a core layer and a shell layer, wherein the shell layer covers the core layer; Wherein, the core layer monomer used to synthesize the core layer includes: o-phenylphenoxyethyl acrylate.

[0006] In some embodiments, the diameter of the core layer is 50-500 nm, the thickness of the shell layer is 1-10 nm, and / or The glass transition temperature of the core layer is -20°C to 20°C, the glass transition temperature of the shell layer is 80°C to 160°C, and / or The swelling degree of the core layer in the electrolyte is 20%-200%, and the swelling degree of the shell layer in the electrolyte is 1%-10%.

[0007] In some embodiments, the core layer monomers used to synthesize the core layer include: o-phenylphenoxyethyl acrylate, and at least two or at least three of acrylonitrile, unsaturated carboxylic acid, acrylate, unsaturated amide, and styrene; The shell monomers used to synthesize the shell layer include at least two or at least three of unsaturated sulfonates, unsaturated hydroxyesters, unsaturated carboxylic acids, unsaturated sulfonates, unsaturated amides, unsaturated phosphates, and other monomers; In some embodiments, the unsaturated carboxylic acid is selected from at least one of acrylic acid, methacrylic acid, ethyl acrylic acid, propyl acrylic acid, isopropyl acrylic acid, n-butyl acrylic acid, isobutyl acrylic acid, tert-butyl acrylic acid, cyclopropyl acrylic acid, n-pentyl acrylic acid, isopentyl acrylic acid, cyclopentyl acrylic acid, n-hexyl acrylic acid, isohexyl acrylic acid, and cyclohexyl acrylic acid; and / or The acrylic acid esters are selected from at least one of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, cyclopropyl acrylate, isooctyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, isooctyl methacrylate, hydroxypropyl methacrylate, 2-hydroxyethyl methacrylate, lauryl methacrylate, glycidyl methacrylate, tert-butylaminoethyl methacrylate, dimethylaminoethyl methacrylate, tert-butylaminoethyl acrylate, vinyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, phenyl methacrylate, dodecyl methacrylate, and hexadecyl methacrylate; and / or The unsaturated amide is selected from at least one of acrylamide, methacrylamide, N-hydroxymethyl acrylamide, N,N-dimethyl acrylamide, N-methyl acrylamide, and N-hydroxymethyl methacrylamide; and / or The unsaturated sulfonate is selected from at least one of styrene sulfonate, 2-acrylamido-2-methylpropane sulfonate, vinyl sulfonate, methyl allyl sulfonate, allyl sulfonate, and methacrylamide isopropyl sulfonate; and / or The unsaturated sulfonic acid ester is at least one selected from methyl styrenesulfonate, ethyl styrenesulfonate, propyl styrenesulfonate, 2-acrylamido-2-methylpropanesulfonate, vinylsulfonate, allylsulfonate, methylallylsulfonate, and methacrylamide isopropylsulfonate; and / or The unsaturated hydroxy ester is selected from at least one of β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, bis(2-hydroxyethyl)maleate, and 2-hydroxyethyl methyl fumarate; and / or The unsaturated phosphate is selected from at least one of di(2-methacryloyloxyethyl)phosphate, 2-hydroxyethyl methacrylate phosphate, 2-hydroxyethyl acrylate phosphate, and allyl polyether phosphate; and / or The other monomers are selected from at least one of polyethylene glycol acrylate, vinyl pyridine, vinyl pyrrolidone, polyethylene glycol methacrylate, ethylene glycol dimethacrylate, β-carboxyethyl acrylate, sodium 1-allyloxy-2-hydroxypropyl sulfonate, and diallyl maleate.

[0008] In some embodiments, the raw materials for preparing the negative electrode binder include: a core layer monomer for synthesizing the core layer, a shell layer monomer for synthesizing the shell layer, an initiator, an emulsifier, and water; Wherein, the weight ratio of the shell monomer to the core monomer is (0.13-0.52):1, or Based on the total weight of the shell layer monomer and the core layer monomer being 180-220 parts, the weight of the emulsifier is 8-15 parts, or Based on the total weight of the shell layer monomer and the core layer monomer being 180-220 parts, the weight of the initiator is 8-12 parts, or Based on the total weight of the shell layer monomers and the core layer monomers being 180-220 parts, the weight of the water is 500-1000 parts.

[0009] In some embodiments, the negative electrode binder is used to prepare a secondary battery, which includes a lithium ion battery or a sodium ion battery.

[0010] In a second aspect, the present invention further provides a negative electrode plate, on which the above-mentioned negative electrode binder is loaded.

[0011] In a third aspect, the present invention provides an electrochemical energy storage device, comprising: the aforementioned negative electrode binder, or the aforementioned negative electrode plate; In some embodiments, the electrochemical energy storage device comprises a secondary battery comprising a lithium ion battery or a sodium ion battery.

[0012] Compared with the prior art, the present invention has the following effects: The negative electrode binder has good flexibility, dispersibility, mechanical modulus and bonding strength, which is beneficial to inhibiting the volume expansion of the negative electrode active material during the charge and discharge process, and is also beneficial to maintaining structural stability during long cycles, thereby improving the cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of the core-shell structure of the negative electrode binder provided in an embodiment of the present invention; Figure 2 The chemical structure of one of the polymer monomers used to synthesize the core layer in an embodiment of the present invention. DETAILED DESCRIPTION

[0014] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0015] In a first aspect, an embodiment of the present invention provides a negative electrode binder having a core-shell structure, wherein the core-shell structure is composed of a core layer and a shell layer, wherein the shell layer covers the core layer; Wherein, the core layer monomer used to synthesize the core layer includes: o-phenylphenoxyethyl acrylate.

[0016] In some embodiments, the core layer monomers used to synthesize the core layer include: o-phenylphenoxyethyl acrylate, and at least two or at least three of acrylonitrile, unsaturated carboxylic acid, acrylate, unsaturated amide, and styrene. The shell monomers used to synthesize the shell layer include at least two or at least three of unsaturated sulfonates, unsaturated hydroxyesters, unsaturated carboxylic acids, unsaturated sulfonates, unsaturated amides, unsaturated phosphates, and other monomers.

[0017] In the embodiments of the present invention, a monomer refers to a small molecule organic compound that forms a polymer through chemical polymerization. For convenience, "polymer monomer" is sometimes referred to simply as "monomer." That is, "core layer monomers for synthesizing the core layer," "core layer polymer monomers," "core layer polymer monomers," and "core layer monomers" are the same type of substance. Similarly, "shell layer monomers for synthesizing the shell layer," "shell layer polymer monomers," "shell layer polymer monomers," and "shell monomers" are the same type of substance.

[0018] In some embodiments, the above unsaturated carboxylic acids are selected from at least one of acrylic acid, methacrylic acid, ethyl acrylic acid, propyl acrylic acid, isopropyl acrylic acid, n-butyl acrylic acid, isobutyl acrylic acid, tert-butyl acrylic acid, cyclopropyl acrylic acid, n-pentyl acrylic acid, isopentyl acrylic acid, cyclopentyl acrylic acid, n-hexyl acrylic acid, isohexyl acrylic acid, and cyclohexyl acrylic acid.

[0019] In some embodiments, the above acrylates are selected from at least one of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, cyclopropyl acrylate, isooctyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, isooctyl methacrylate, hydroxypropyl methacrylate, 2-hydroxyethyl methacrylate, lauryl methacrylate, glycidyl methacrylate, tert-butylaminoethyl methacrylate, dimethylaminoethyl methacrylate, tert-butylaminoethyl acrylate, vinyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, phenyl methacrylate, dodecyl methacrylate, and hexadecyl methacrylate.

[0020] In some embodiments, the above unsaturated amides are selected from at least one of acrylamide, methacrylamide, N-hydroxymethyl acrylamide, N,N-dimethyl acrylamide, N-methyl acrylamide, and N-hydroxymethyl methacrylamide.

[0021] In some embodiments, the unsaturated sulfonates are selected from at least one of styrene sulfonate, 2-acrylamido-2-methylpropane sulfonate, vinyl sulfonate, allyl sulfonate, methallyl sulfonate, and methacrylamide isopropyl sulfonate.

[0022] In some embodiments, the above unsaturated sulfonates are selected from at least one of methyl styrenesulfonate, ethyl styrenesulfonate, propyl styrenesulfonate, 2-acrylamido-2-methylpropanesulfonate, vinylsulfonate, allylsulfonate, methallylsulfonate, and methacrylamide isopropylsulfonate.

[0023] In some embodiments, the above unsaturated hydroxy ester is selected from at least one of β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, bis(2-hydroxyethyl)maleate, and 2-hydroxyethyl methyl fumarate.

[0024] In some embodiments, the unsaturated phosphates are selected from at least one of bis(2-methacryloyloxyethyl)phosphate, 2-hydroxyethyl methacrylate phosphate, 2-hydroxyethyl acrylate phosphate, and allyl polyether phosphate.

[0025] In some embodiments, the above other monomers are selected from at least one of polyethylene glycol acrylate, vinyl pyridine, vinyl pyrrolidone, polyethylene glycol methacrylate, ethylene glycol dimethacrylate, β-carboxyethyl acrylate, sodium 1-allyloxy-2-hydroxypropyl sulfonate, and diallyl maleate.

[0026] In some embodiments, the core layer monomers for synthesizing the core layer include: 10-15 parts of o-phenylphenoxyethyl acrylate, 45-55 parts of acrylonitrile, 10-15 parts of methacrylic acid, and 160-185 parts of ethyl acrylate, and the shell layer monomers for synthesizing the shell layer include: 18-25 parts of sodium styrene sulfonate, 0.8-1.2 parts of hydroxybutyl methacrylate, 0.8-1.2 parts of hydroxypropyl acrylate, and 22-28 parts of acrylic acid; or In some embodiments, the core layer monomers for synthesizing the core layer include: 8-12 parts of o-phenylphenoxyethyl acrylate, 35-45 parts of acrylonitrile, 8-12 parts of methacrylic acid and 125-150 parts of ethyl acrylate, and the shell layer monomers for synthesizing the shell layer include: 45-50 parts of sodium styrene sulfonate, 0.8-2.2 parts of hydroxybutyl methacrylate, 0.8-3.2 parts of hydroxypropyl acrylate and 48-57 parts of acrylic acid.

[0027] In some embodiments, the raw materials for preparing the negative electrode binder include: a core layer monomer for synthesizing the core layer, a shell layer monomer for synthesizing the shell layer, an initiator, an emulsifier, and water. Wherein, the weight ratio of the shell monomer to the core monomer is (0.13-0.52):1, or Based on the total weight of the shell layer monomer and the core layer monomer being 180-220 parts, the weight of the emulsifier is 8-15 parts, or Based on the total weight of the shell layer monomer and the core layer monomer being 180-220 parts, the weight of the initiator is 10 parts, or Based on the total weight of the shell layer monomers and the core layer monomers being 180-220 parts, the weight of the water is 500-1000 parts.

[0028] By controlling the relative amounts of raw materials such as the core monomer used to synthesize the core layer, the shell monomer used to synthesize the shell layer, the initiator, the emulsifier and water, the physicochemical properties of the negative electrode binder can be adjusted to a certain extent.

[0029] In some embodiments, the diameter of the core layer is 50-500 nm, the thickness of the shell layer is 1-10 nm, or The glass transition temperature of the core layer is -20°C to 20°C, the glass transition temperature of the shell layer is 80°C to 160°C, and / or The swelling degree of the core layer in the electrolyte is 20%-200%, and the swelling degree of the shell layer in the electrolyte is 1%-10%.

[0030] In some specific embodiments, the diameter of the core layer is 50 nm, 75 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 330 nm, 350 nm, 380 nm, 400 nm, 430 nm, 450 nm, 470 nm, or 500 nm.

[0031] In some specific embodiments, the shell layer has a thickness of 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm.

[0032] In some embodiments, the glass transition temperature of the shell layer is greater than the glass transition temperature of the core layer. In some specific embodiments, the glass transition temperature of the core layer is -20°C to 20°C, and the glass transition temperature of the shell layer is 80°C to 160°C. In some specific embodiments, the glass transition temperature of the core layer is -20°C, -19°C, -18°C, -17°C, -16°C, -15°C, -14°C, -13°C, -12°C, -11°C, -10°C, -9°C, -8°C, -7°C, -6°C, -5°C, -4°C, -3°C, -2°C, -1°C, 0°C, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, 18°C, 19°C or 20°C. In some specific embodiments, the glass transition temperature of the shell layer is 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C or 160°C.

[0033] In some specific embodiments, the degree of swelling of the core layer in the electrolyte is 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190% or 200%.

[0034] In some specific embodiments, the degree of swelling of the shell in the electrolyte is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0035] In some embodiments, the negative electrode binder is used to prepare a secondary battery, which includes a lithium ion battery or a sodium ion battery.

[0036] In some embodiments, the negative electrode binder forms a negative electrode with the negative electrode collector, the negative electrode material, and the conductive agent, or the negative electrode binder forms a negative electrode sheet with the negative electrode collector, the negative electrode material, the conductive agent, and the thickener.

[0037] In some embodiments, the negative electrode material is graphite, the conductive agent is Super-P, and the thickener is carboxymethyl cellulose.

[0038] The preparation method of the above-mentioned inorganic binder comprises the following steps: (1) Adding core layer monomers to an aqueous solution containing an emulsifier, mixing and heating the solution once, and adding an initiator to react the solution once; (2) Pre-emulsify the shell monomer, emulsifier and water. After the pre-emulsification is completed, add the pre-emulsified liquid and the aqueous solution of the initiator to the reaction product of (1) for a secondary reaction. After cooling, the following is obtained: Figure 1 The negative electrode binder shown has a core-shell structure.

[0039] In some embodiments, the negative electrode binder is used to prepare a secondary battery, and the secondary battery includes a lithium ion battery or a sodium ion battery; Optionally, the negative electrode binder, the negative electrode current collector, the negative electrode material, and the conductive agent form a negative electrode, or the negative electrode binder, the negative electrode current collector, the negative electrode material, the conductive agent, and the thickener form a negative electrode sheet; Optionally, the negative electrode material is graphite, the conductive agent is Super-P, and the thickener is carboxymethyl cellulose.

[0040] In a third aspect, based on the above technical solution, an embodiment of the present invention further provides a negative electrode plate, on which the above negative electrode binder is loaded.

[0041] In a fourth aspect, an embodiment of the present invention further provides an electrochemical energy storage device based on the above technical solution, the electrochemical energy storage device comprising: the aforementioned negative electrode binder, or the aforementioned negative electrode plate; Optionally, the electrochemical energy storage device includes a secondary battery, and the secondary battery includes a lithium-ion battery or a sodium-ion battery.

[0042] In order to enable those skilled in the art to clearly understand the above implementation details and operations of the present invention, the embodiments of the present invention are illustrated below through specific examples.

[0043] The following examples and comparative examples illustrate the present invention in more detail, but the present invention is not limited thereto. Furthermore, "parts" and "%" in the examples and comparative examples represent parts by mass and % by mass, respectively, unless otherwise specified. Physical properties and performance evaluation tests of the lithium-ion secondary battery electrode binders obtained in the examples and comparative examples, and batteries obtained using these electrode binders, were conducted using the following methods. Example 1

[0044] This embodiment prepares a negative electrode binder, wherein the core layer monomer is o-phenylphenoxyethyl acrylate (its chemical structure is as follows Figure 2 As shown), acrylonitrile, methacrylic acid and ethyl acrylate, the shell monomers are sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell monomers to the core monomers is 0.2:1.

[0045] Prepare the negative electrode binder as follows: (1) Deionized water (300 parts), an emulsifier (4 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of sodium persulfate) were added to a reactor according to parts by weight, and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 50 parts of acrylonitrile, 12 parts of methacrylic acid and 176 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 22 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate and 25 parts of acrylic acid are mixed with an emulsifier (6 parts of sodium dodecylbenzene sulfonate) and 200 parts of water, stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B, and then the shell emulsion B is added dropwise to the core emulsion A, and an initiator (5 parts of sodium persulfate) is added. After the initiator is added, the temperature is raised to 77°C for reaction for 1.2 hours, and then the temperature is raised to 85°C for reaction for 5 hours to obtain the core-shell structured negative electrode binder. Example 2

[0046] In this embodiment, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, and ethyl acrylate; the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate, and acrylic acid; and the weight ratio of the shell layer monomers to the core layer monomers was 0.52:1.

[0047] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (5 parts of nonylphenol polyether sulfate, 4 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of sodium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 10 parts of o-phenylphenoxyethyl acrylate, 39 parts of acrylonitrile, 10 parts of methacrylic acid and 139 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 47 parts of sodium styrene sulfonate, 2 parts of hydroxybutyl methacrylate, 3 parts of hydroxypropyl acrylate and 52 parts of acrylic acid were mixed with an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium dodecylbenzene sulfonate) and 200 parts of water, and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain shell emulsion B. The mixture of emulsion B was then uniformly added dropwise to core emulsion A, an initiator (5 parts of sodium persulfate) was added, and the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Example 3

[0048] In this embodiment, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, and ethyl acrylate; the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate, and acrylic acid; and the weight ratio of the shell layer monomers to the core layer monomers was 0.16:1.

[0049] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of sodium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 51 parts of acrylonitrile, 13 parts of methacrylic acid and 180 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 19 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate and 21 parts of acrylic acid, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium dodecylbenzene sulfonate) and 200 parts of water were mixed, stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain shell emulsion B, and then the mixture of emulsion B was uniformly added dropwise to the core emulsion A, an initiator (5 parts of sodium persulfate) was added, and then the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Example 4

[0050] In this embodiment, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, and ethyl acrylate; the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate, and acrylic acid; and the weight ratio of the shell layer monomers to the core layer monomers was 0.13:1.

[0051] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of sodium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 53 parts of acrylonitrile, 13 parts of methacrylic acid and 185 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 16 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate and 17 parts of acrylic acid, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium dodecylbenzene sulfonate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then evenly added dropwise to the core emulsion A. An initiator (5 parts of sodium persulfate) was added, and the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Example 5

[0052] In this embodiment, a negative electrode binder is prepared, wherein the core layer monomers are o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid and ethyl acrylate, the shell layer monomers are sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers is 0.25:1.

[0053] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of sodium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 12 parts of o-phenylphenoxyethyl acrylate, 48 parts of acrylonitrile, 12 parts of methacrylic acid and 168 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 26 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 2 parts of hydroxypropyl acrylate, 30 parts of acrylic acid, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium dodecylbenzene sulfonate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then uniformly added dropwise to the core emulsion A. An initiator (5 parts of sodium persulfate) was added. The temperature was then raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Example 6

[0054] In this embodiment, a negative electrode binder is prepared, wherein the core layer monomers are o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid and butyl acrylate, the shell layer monomers are sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers is 0.20:1.

[0055] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium lauryl sulfate) and an initiator (5 parts of potassium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 76 parts of acrylonitrile, 13 parts of methacrylic acid and 152 parts of butyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 21 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate, 24 parts of acrylic acid, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then evenly added dropwise to the core emulsion A. An initiator (5 parts of potassium persulfate) was added. The temperature was then raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the core-shell structured negative electrode binder. Example 7

[0056] In this embodiment, a negative electrode binder is prepared, wherein the core layer monomers are o-phenylphenoxyethyl acrylate, acrylonitrile, styrene and methyl acrylate, and the weight ratio of the shell layer monomers to the core layer monomers is 0.18:1.

[0057] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium lauryl sulfate) and an initiator (5 parts of potassium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 5 parts of o-phenylphenoxyethyl acrylate, 13 parts of acrylonitrile, 5 parts of styrene and 231 parts of methyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 21 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate, 23 parts of acrylic acid, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed and stirred at 45°C to make them uniformly mixed and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then evenly added dropwise to the core emulsion A. An initiator (5 parts of potassium persulfate) was added. The temperature was then raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the core-shell structured negative electrode binder. Example 8

[0058] In this embodiment, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, and ethyl acrylate; the shell layer monomers were sodium styrene sulfonate, hydroxypropyl acrylate, and acrylic acid; the weight ratio of the shell layer monomers to the core layer monomers was 0.18:1; and the emulsifier was 10 parts.

[0059] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium lauryl sulfate) and an initiator (5 parts of potassium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of core layer monomers of o-phenylphenoxyethyl acrylate, 51 parts of acrylonitrile, 13 parts of methacrylic acid and 177 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 2 parts of sodium styrene sulfonate, 7 parts of hydroxypropyl acrylate, 38 parts of acrylic acid, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then evenly added dropwise to the core emulsion A. An initiator (5 parts of potassium persulfate) was added. The temperature was then raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the core-shell structured negative electrode binder. Embodiment 9

[0060] In this embodiment, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, and ethyl acrylate; the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, methacrylic acid amide, and ethyl styrene sulfonate; and the weight ratio of the shell layer monomers to the core layer monomers was 0.19:1.

[0061] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium lauryl sulfate) and an initiator (5 parts of potassium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 50 parts of acrylonitrile, 13 parts of methacrylic acid and 177 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 22 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 24 parts of methacrylic acid amide, 1 part of ethyl styrene sulfonate, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed, stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain shell emulsion B, and then the mixture of emulsion B was uniformly added dropwise to the core emulsion A, an initiator (5 parts of potassium persulfate) was added, and then the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Example 10

[0062] In this embodiment, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, and isooctyl acrylate; the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate, and acrylic acid; the weight ratio of the shell layer monomers to the core layer monomers was 0.20:1, and 10 parts of the emulsifier was used.

[0063] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of sodium dodecylbenzenesulfonate, 2 parts of sodium dodecyl sulfate) and an initiator (5 parts of ammonium persulfate) were added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 13 parts of acrylonitrile, 100 parts of methacrylic acid and 125 parts of isooctyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 22 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate and 25 parts of acrylic acid, an emulsifier (3 parts of sodium dodecylbenzenesulfonate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then evenly added dropwise to the core emulsion A, an initiator (5 parts of ammonium persulfate) was added, and the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Example 11

[0064] In this embodiment, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, methyl acrylate and butyl acrylate, the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, the weight ratio of the shell layer monomers to the core layer monomers was 0.20:1, and the emulsifier was 10 parts.

[0065] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of sodium dodecylbenzenesulfonate, 2 parts of sodium dodecyl sulfate) and an initiator (5 parts of ammonium persulfate) were added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 75 parts of acrylonitrile, 13 parts of methacrylic acid, 175 parts of methyl acrylate and 88 parts of butyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 22 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate, 25 parts of acrylic acid, an emulsifier (3 parts of sodium dodecylbenzenesulfonate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then evenly added dropwise to the core emulsion A. An initiator (5 parts of ammonium persulfate) was added. The temperature was then raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the core-shell structured negative electrode binder. Example 12

[0066] In this embodiment, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, and ethyl acrylate; the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, acrylamide, and acrylic acid; and the weight ratio of the shell layer monomers to the core layer monomers was 0.17:1.

[0067] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of sodium dodecylbenzenesulfonate, 2 parts of sodium dodecyl sulfate) and an initiator (5 parts of ammonium persulfate) were added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 12 parts of o-phenylphenoxyethyl acrylate, 50 parts of acrylonitrile, 12 parts of methacrylic acid and 175 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 1 part of sodium styrene sulfonate, 3 parts of hydroxybutyl methacrylate, 5 parts of acrylamide, 33 parts of acrylic acid, an emulsifier (3 parts of sodium dodecylbenzenesulfonate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed, stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B, and then the mixture of emulsion B was uniformly added dropwise to the core emulsion A, an initiator (5 parts of ammonium persulfate) was added, and then the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the core-shell structured negative electrode binder. Example 13

[0068] In this embodiment, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, and ethyl acrylate; the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, di(2-methacryloyloxyethyl) phosphate, and N-hydroxymethyl acrylamide; the weight ratio of the shell layer monomers to the core layer monomers was 0.19:1, and the emulsifier was 10 parts.

[0069] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of sodium dodecylbenzenesulfonate, 2 parts of sodium dodecyl sulfate) and an initiator (5 parts of ammonium persulfate) were added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 50 parts of acrylonitrile, 13 parts of methacrylic acid and 176 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 7 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 39 parts of di(2-methacryloyloxyethyl) phosphate and 1 part of N-hydroxymethyl acrylamide, an emulsifier (3 parts of sodium dodecylbenzenesulfonate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then evenly added dropwise to the core emulsion A, an initiator (5 parts of ammonium persulfate) was added, and the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Comparative Example 1

[0070] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid and ethyl acrylate, the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers was 1.22:1.

[0071] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, emulsifier (8 parts of nonylphenol polyether sulfate, 7 parts of sodium dodecylbenzenesulfonate) and initiator (5 parts of sodium persulfate) were added to a reactor, and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 7 parts of o-phenylphenoxyethyl acrylate, 27 parts of acrylonitrile, 7 parts of methacrylic acid and 94 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 74 parts of sodium styrene sulfonate, 3 parts of hydroxybutyl methacrylate, 5 parts of hydroxypropyl acrylate and 83 parts of acrylic acid, an emulsifier (5 parts of nonylphenol polyether sulfate, 5 parts of sodium dodecylbenzene sulfonate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then uniformly added dropwise to the core emulsion A, an initiator (5 parts of sodium persulfate) was added, and the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Comparative Example 2

[0072] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid and ethyl acrylate, the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers was 0.08:1.

[0073] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (1.5 parts of nonylphenol polyether sulfate, 1.5 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of sodium persulfate) were added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 14 parts of o-phenylphenoxyethyl acrylate, 56 parts of acrylonitrile, 14 parts of methacrylic acid and 195 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 10 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate and 11 parts of acrylic acid, an emulsifier (1 part of nonylphenol polyether sulfate, 1 part of sodium dodecylbenzene sulfonate) and 200 parts of water were mixed, stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain shell emulsion B. The mixture of emulsion B was then uniformly added dropwise to the core emulsion A, an initiator (5 parts of sodium persulfate) was added, and the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Comparative Example 3

[0074] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid and ethyl acrylate, the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, the weight ratio of the shell layer monomers to the core layer monomers was 0.70:1, and 10 parts of the emulsifier was used.

[0075] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of sodium persulfate) were added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 9 parts of o-phenylphenoxyethyl acrylate, 35 parts of acrylonitrile, 9 parts of methacrylic acid and 123 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 56 parts of sodium styrene sulfonate, 2 parts of hydroxybutyl methacrylate, 4 parts of hydroxypropyl acrylate and 62 parts of acrylic acid, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium dodecylbenzene sulfonate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then uniformly added dropwise to the core emulsion A, an initiator (5 parts of sodium persulfate) was added, and the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Comparative Example 4

[0076] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid and ethyl acrylate, the emulsifier was 10 parts, and no shell layer polymer was added.

[0077] Prepare the negative electrode binder as follows: According to parts by weight, 500 parts of deionized water, an emulsifier (5 parts of nonylphenol polyether sulfate, 5 parts of sodium dodecylbenzenesulfonate) and an initiator (10 parts of sodium persulfate) are added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature rises to 80°C, 15 parts of o-phenylphenoxyethyl acrylate, 60 parts of acrylonitrile, 15 parts of methacrylic acid and 210 parts of ethyl acrylate are dropwise added to the reactor over 15 to 25 minutes. After the addition is complete, the mixture is kept warm for 30 minutes and reacted for 6 hours to obtain the core-shell structured negative electrode binder. Comparative Example 5

[0078] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, acrylamide and ethyl acrylate, the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers was 0.19:1.

[0079] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of potassium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 50 parts of acrylonitrile, 38 parts of acrylamide and 151 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 22 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate, 24 parts of acrylic acid, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium dodecylbenzenesulfonate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then evenly added dropwise to the core emulsion A. An initiator (5 parts of potassium persulfate) was added. The temperature was then raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the core-shell structured negative electrode binder. Comparative Example 6

[0080] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, ethyl acrylate and butyl acrylate, the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers was 0.19:1.

[0081] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of potassium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 50 parts of acrylonitrile, 38 parts of ethyl acrylate and 151 parts of butyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 22 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate, 24 parts of acrylic acid, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium dodecylbenzenesulfonate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then evenly added dropwise to the core emulsion A. An initiator (5 parts of potassium persulfate) was added. The temperature was then raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the core-shell structured negative electrode binder. Comparative Example 7

[0082] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid and butyl acrylate, the shell layer monomers were hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers was 0.18:1.

[0083] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of potassium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 102 parts of acrylonitrile, 13 parts of methacrylic acid and 127 parts of butyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 18 parts of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate, 26 parts of acrylic acid, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium dodecylbenzene sulfonate) and 200 parts of water were mixed, stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B, and then the mixture of emulsion B was uniformly added dropwise to the core emulsion A, an initiator (5 parts of potassium persulfate) was added, and then the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Comparative Example 8

[0084] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid and ethyl acrylate, the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, methacrylamide and methacrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers was 0.19:1.

[0085] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of nonylphenol polyether sulfate, 2 parts of sodium dodecylbenzenesulfonate) and an initiator (5 parts of potassium persulfate) were added to a reactor, and the mixture was stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 50 parts of acrylonitrile, 13 parts of methacrylic acid and 176 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was completed, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 10 parts of sodium styrene sulfonate, 2 parts of hydroxybutyl methacrylate, 2 parts of methacrylamide, 34 parts of methacrylic acid, an emulsifier (3 parts of nonylphenol polyether sulfate, 3 parts of sodium dodecylbenzenesulfonate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then uniformly added dropwise to the core emulsion A. An initiator (5 parts of potassium persulfate) was added, and the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Comparative Example 9

[0086] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, butyl acrylate, methacrylic acid and acrylic acid, the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers was 0.22:1.

[0087] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of sodium dodecylbenzenesulfonate, 2 parts of sodium dodecyl sulfate) and an initiator (5 parts of ammonium persulfate) were added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 12 parts of o-phenylphenoxyethyl acrylate, 112 parts of butyl acrylate, 12 parts of methacrylic acid and 100 parts of acrylic acid were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 23 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 2 parts of hydroxypropyl acrylate and 26 parts of acrylic acid, an emulsifier (3 parts of sodium dodecylbenzenesulfonate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed, stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain shell emulsion B, and then the mixture of emulsion B was uniformly added dropwise to the core emulsion A, an initiator (5 parts of ammonium persulfate) was added, and then the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the core-shell structured negative electrode binder. Comparative Example 10

[0088] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, acrylic acid, methyl acrylate and butyl acrylate, and the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers was 0.20:1.

[0089] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of sodium dodecylbenzenesulfonate, 2 parts of sodium dodecyl sulfate) and an initiator (5 parts of ammonium persulfate) were added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 12 parts of o-phenylphenoxyethyl acrylate, 124 parts of acrylonitrile, 12 parts of acrylic acid, 2 parts of methyl acrylate and 109 parts of butyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 24 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 2 parts of hydroxypropyl acrylate and 26 parts of acrylic acid, an emulsifier (3 parts of sodium dodecylbenzenesulfonate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed and stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B. The mixture of emulsion B was then evenly added dropwise to the core emulsion A. An initiator (5 parts of ammonium persulfate) was added, and the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Comparative Example 11

[0090] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid and ethyl acrylate, the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, butyl acrylate and vinyl pyrrolidone, and the weight ratio of the shell layer monomers to the core layer monomers was 0.19:1.

[0091] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of sodium dodecylbenzenesulfonate, 2 parts of sodium dodecyl sulfate) and an initiator (5 parts of ammonium persulfate) were added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 13 parts of o-phenylphenoxyethyl acrylate, 50 parts of acrylonitrile, 13 parts of methacrylic acid and 176 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 10 parts of sodium styrene sulfonate, 2 parts of hydroxybutyl methacrylate, 5 parts of butyl acrylate, 32 parts of vinyl pyrrolidone, an emulsifier (3 parts of sodium dodecylbenzenesulfonate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed, stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B, and then the mixture of emulsion B was uniformly added dropwise to the core emulsion A, an initiator (5 parts of ammonium persulfate) was added, and then the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the core-shell structured negative electrode binder. Comparative Example 12

[0092] In this comparative example, a negative electrode binder was prepared, wherein the core layer monomers were acrylonitrile, methacrylic acid and ethyl acrylate, the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate and acrylic acid, and the weight ratio of the shell layer monomers to the core layer monomers was 0.20:1.

[0093] Prepare the negative electrode binder as follows: (1) 300 parts by weight of deionized water, an emulsifier (2 parts of sodium dodecylbenzenesulfonate, 2 parts of sodium dodecyl sulfate) and an initiator (5 parts of ammonium persulfate) were added to a reactor and stirred and dispersed in a nitrogen atmosphere for 10 to 20 minutes. When the temperature was raised to 80°C, 63 parts of acrylonitrile, 13 parts of methacrylic acid and 175 parts of ethyl acrylate were added dropwise to the reactor over a period of 15 to 25 minutes. After the addition was complete, the mixture was kept warm for 30 minutes and reacted for 4.5 hours to obtain a core layer A emulsion. (2) 22 parts of sodium styrene sulfonate, 1 part of hydroxybutyl methacrylate, 1 part of hydroxypropyl acrylate and 25 parts of acrylic acid, an emulsifier (3 parts of sodium dodecylbenzenesulfonate, 3 parts of sodium lauryl sulfate) and 200 parts of water were mixed, stirred at 45°C to make the mixture uniform and pre-emulsified for 1.5 hours to obtain a shell emulsion B liquid, and then the mixture of emulsion B was uniformly added dropwise to the core emulsion A, an initiator (5 parts of ammonium persulfate) was added, and then the temperature was raised to 77°C for reaction for 1.2 hours, and then the temperature was raised to 85°C for reaction for 5 hours to obtain the negative electrode binder of the core-shell structure. Performance Testing

[0094] (1) Take the negative electrode binders prepared in Examples 1-13 and Comparative Examples 1-12 and prepare negative electrode sheets respectively: A negative electrode slurry is prepared by mixing 96.5% graphite, 1% Super-P as a conductive agent, 1.5% anode binder, and 1% CMC solution (a thickener made by dissolving carboxymethyl cellulose in water) in a certain mass ratio. Water is then added and mixed again to create a negative electrode slurry. This slurry, after roller pressing, is applied to both sides of a 10μm thick Cu foil serving as a current collector, to a thickness of 120μm. The foil is dried at 100°C for 5 minutes and then pressed to form a coating of the negative electrode active material. A non-coated area is created on one of the two end surfaces, where a negative electrode conductive sheet is attached to complete the negative electrode.

[0095] (2) Assemble the negative electrode prepared in step (1) into a lithium-ion battery and perform performance testing.

[0096] ① Cycling performance: The test was mainly conducted with reference to the IEC61960-3:2017 standard: a. Charge at a constant current of 0.5C to a voltage of 4.2V, then charge at a constant voltage of 4.2V until the current drops to 0.05C; b. Wait for 10 minutes; c. Discharge at a constant current of 0.5C to 3V; d. Wait for 10 minutes; e. Repeat the above charge and discharge cycles 500 times.

[0097] ② Swelling: Dry the core layer material into a film, weigh W1, and immerse it in an electrolyte (EC: PC: DEC = 1:1:1, LFP6 1M) at 60°C for 48 hours. Wipe off the electrolyte and dry it to obtain a film weight W2. The core swelling Y1 = (W2-W1) / W1 * 100%; The negative electrode binder composed of core and shell is dried to form a film, and the original weight is weighed as W3. After immersion for 48 hours under the same conditions, the swelling weight W4 is obtained, and the shell swelling Y2=(W4-W2) / (W3-W1)*100%.

[0098] ③ Adhesion: Refer to the standard GB / T 2790-1995 to test the peel strength.

[0099] ④ Elastic modulus: Prepare samples according to ASTM D2094 and test tensile strength and elastic modulus. GB / T 6329-1996 Adhesive Butt Joints - Determination of Tensile Strength.

[0100] ⑤ Pole flexibility: Due to the continuous cyclic alternating stress, the pole piece will become fatigued and even damaged.

[0101] The pole piece is rolled to a compaction density of 1.6g / cm 3 Then fold the electrode in half, roll the crease with a 2kg roller, fold it in half in the opposite direction, roll it, and point the crease toward the light source to observe whether it is light-transmitting.

[0102] ⑥ Pole expansion: A pole piece was prepared using the negative electrode binder of the present invention, with an original thickness of T1. When fully charged to 4.2V, the thickness was T2. The pole piece expansion F = (T2-T1) / T1.

[0103] ⑦ Diameter / thickness test: During the preparation of the negative electrode binder, the core layer emulsion and the negative electrode binder emulsion were tested for particle size using a Malvern particle size analyzer to obtain the radius of the core layer and the thickness of the shell layer.

[0104] Table 1 shows the test results.

[0105]

[0106] Note: Tg represents the glass transition temperature, core swelling represents the swelling degree of the core layer in the electrolyte solution, and shell swelling represents the swelling degree of the shell layer in the electrolyte solution.

[0107] As shown in Table 1, the shell thicknesses and core diameters of Examples 1-5 and Comparative Examples 1-4 vary, resulting in different battery performance. The shell thickness and core diameter can be adjusted by adjusting the weight ratio of the shell to core monomers.

[0108] The core diameter and shell thickness of Example 1 are 255.3 nm and 7.8 nm, respectively. The bonding force is normal and the battery cycle performance is high.

[0109] The core diameter and shell thickness of Example 2 are 105.6 nm and 8.0 nm, respectively. Compared with Example 1, the weight ratio of the shell monomer and the core monomer of Example 2 is increased, making the core smaller and the shell thickness normal, resulting in lower adhesion, higher modulus, and slightly reduced number of cycles.

[0110] Compared with Example 1, the core thickness of Example 3 is larger and the shell thickness is normal, which leads to increased bonding force, decreased modulus, and reduced cycle life.

[0111] Compared with Example 1, the shell thickness of Example 4 is smaller, which results in a lower elastic modulus, more significant expansion of the pole piece, and a shorter cycle life.

[0112] Compared with Example 1, the shell thickness of Example 5 is thicker and the core layer diameter is normal, which leads to a larger modulus and a shorter lifespan.

[0113] Compared with Example 1, the shell thickness of Comparative Example 1 is normal, the core thickness is very small, the bonding force is low, the modulus is large, the pole piece is tough, the pole piece expansion is slightly low, and the life is very short.

[0114] Compared with Example 1, the shell thickness of Comparative Example 2 is normal, the core thickness is very large, the bonding force is relatively large, the modulus is large, the pole piece has no toughness, the pole piece expands greatly, and the life is very short.

[0115] Compared with Example 1, the core thickness of Comparative Example 3 is normal, the shell thickness is very large, the bonding force is relatively large, the modulus is very large, the pole piece is tough, the pole piece expands greatly, and the life is very short.

[0116] Compared with Example 1, Comparative Example 4 does not add shell monomers, the core layer diameter is normal, there is no shell layer, the bonding force is very small, the modulus is relatively small, the pole piece has no toughness, the pole piece expands greatly, and the life is very short.

[0117] Based on the experimental results of Examples 1-5 and Comparative Examples 1-4, it can be concluded that when the diameter of the core layer is 50-500nm and the thickness of the shell layer is 1-10nm, the negative electrode binder has both good flexibility and a high elastic modulus, which can reduce the brittleness of the negative electrode sheet while effectively ensuring cycle stability. When the core layer diameter is less than 50nm, the negative electrode binder will be insufficiently flexible, which can easily lead to the prepared negative electrode sheet being brittle and prone to cracking, and the cycle life will be affected. When the core layer diameter is greater than 500nm, the binder modulus is insufficient, the ability to inhibit expansion is insufficient, and the cycle life is reduced. When the shell layer thickness is greater than 10nm, the negative electrode sheet will be brittle and prone to cracking, and the cycle life will be affected. When the shell layer thickness is less than 1nm, the modulus is low, the ability to inhibit expansion is reduced, and the cycle life is reduced.

[0118] As shown in Table 1, the core and shell glass transition temperatures of Examples 1, 6-9, and Comparative Examples 5-8 differ. Different core and shell glass transition temperatures correspond to different battery performance. The difference in core and shell glass transition temperatures can be adjusted by adjusting the types of shell and core monomers.

[0119] The core and shell glass transition temperatures of Example 1 were 4.2 and 125.1, respectively, indicating normal adhesion and high battery cycle performance. The core monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, and ethyl acrylate, while the shell monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate, and acrylic acid.

[0120] The core and shell glass transition temperatures of Example 6 were -9.5 and 124.3, respectively. Compared to Example 1, Example 6 had a lower core glass transition temperature, a slightly stronger negative electrode binder, a low elastic modulus, and excessive electrode expansion, resulting in a shorter battery life. In the core layer monomer, the ethyl acrylate in Example 1 was replaced with butyl acrylate.

[0121] The core and shell glass transition temperatures of Example 7 are 8.9 and 125.2, respectively. Compared to Example 1, the core glass transition temperature of Example 7 is higher, resulting in a slightly decreased viscosity of the negative electrode binder, a larger elastic modulus, slightly reduced electrode expansion, and a lower cycle life. Specifically, the core layer monomers of Example 1 are replaced by styrene, and ethyl acrylate is replaced by methyl acrylate.

[0122] The core and shell glass transition temperatures of Example 8 were 4.2 and 102.2, respectively. Compared to Example 1, the shell glass transition temperature of Example 8 was lower, which had little effect on the viscosity of the negative electrode binder. The elastic modulus was slightly lower, the electrode expansion was normal, and the cycle life was lower. Hydroxybutyl methacrylate was omitted from the shell monomer compared to Example 1.

[0123] The core and shell glass transition temperatures of Example 9 are 4.2 and 138.1, respectively. Compared to Example 1, the shell glass transition temperature of Example 9 is slightly higher, which has little effect on the viscosity of the negative electrode binder. However, the elastic modulus is slightly higher, the electrode expansion is slightly higher, and the cycle life is lower. In the shell monomers, hydroxypropyl acrylate and acrylic acid are replaced with methacrylic acid amide and ethyl styrenesulfonate.

[0124] The core and shell glass transition temperatures of Comparative Example 5 are 29.5 and 125.1, respectively. Compared to Example 1, Comparative Example 5 has a higher core glass transition temperature, lower viscosity, and a higher elastic modulus. The electrode is tough, but the battery cycle life is shorter. In the core layer monomer, the methacrylic acid in Example 1 is replaced with acrylamide.

[0125] The core and shell glass transition temperatures of Comparative Example 6 were -25.1°C and 125.1°C, respectively. Compared to Example 1, Comparative Example 6 exhibited a significantly lower core glass transition temperature, normal viscosity, and an extremely low elastic modulus. The electrode plate exhibited a lack of toughness, exhibited significant expansion, and exhibited a short battery cycle life. In the core layer monomer, the methacrylic acid of Example 1 was replaced with butyl acrylate.

[0126] The core and shell glass transition temperatures of Comparative Example 7 were 4.2 and 65.3, respectively. Compared to Example 1, the shell glass transition temperature of Comparative Example 7 was significantly lower, resulting in lower viscosity and an extremely low elastic modulus. The electrode was not tough, exhibited significant expansion, and had a very short battery cycle life. In the core layer monomer, the ethyl acrylate in Example 1 was replaced with butyl acrylate, and in the shell polymer monomer, the sodium styrene sulfonate in Example 1 was deleted.

[0127] The core and shell glass transition temperatures of Comparative Example 8 were 4.2 and 178.8, respectively. Compared to Example 1, Comparative Example 8 exhibited a higher shell glass transition temperature, lower viscosity, and a higher elastic modulus. The electrode was tough and exhibited low electrode expansion, resulting in a very short battery cycle life. In the core layer monomers, the hydroxypropyl acrylate and acrylic acid of Example 1 were replaced with methacrylamide and methacrylic acid.

[0128] Based on the experimental results of Examples 1, 6-9 and Comparative Examples 5-8, it can be concluded that the shell layer has a higher glass transition temperature than the core layer, which can better maintain the morphology of the negative electrode binder during the operation of the lithium-ion battery, thereby better suppressing the expansion of the negative electrode plate and effectively extending the cycle life of the lithium-ion battery. When the glass transition temperature of the polymer of the core layer is -20°C to 20°C, and the glass transition temperature of the polymer of the shell layer is 80°C to 160°C, the negative electrode binder has both good flexibility and high elastic modulus, which can reduce the brittleness of the negative electrode plate and effectively ensure cycle stability. When the glass transition temperature of the polymer of the core layer is less than -20°C, the modulus of the negative electrode binder will be insufficient, and the ability to suppress expansion will decrease; when the glass transition temperature of the polymer of the core layer is greater than 20°C, the flexibility is insufficient and the plate is prone to cracking. When the glass transition temperature of the shell is greater than 160°C, the electrode will become brittle and easy to crack, and the cycle life will be affected; when the glass transition temperature of the shell is less than 80°C, the expansion of the negative electrode will be inhibited, reducing the cycle life of the lithium-ion battery.

[0129] As shown in Table 1, the core layer and shell layer swelling degrees in the electrolyte differed in Examples 1, 10-13, and Comparative Examples 9-11. Different swelling degrees of the core and shell layers in the electrolyte corresponded to different battery performance. The swelling degrees of the core and shell layers in the electrolyte can be adjusted by adjusting the types of polymer monomers used in the shell and core layers.

[0130] In Example 1, the swelling levels in the core layer electrolyte and the shell layer electrolyte were 50.5% and 5.5%, respectively. The bonding strength was normal and the battery cycle performance was high. The core layer monomers were o-phenylphenoxyethyl acrylate, acrylonitrile, methacrylic acid, and ethyl acrylate, while the shell layer monomers were sodium styrene sulfonate, hydroxybutyl methacrylate, hydroxypropyl acrylate, and acrylic acid.

[0131] In Example 10, the core layer electrolyte swelling was 35.5% and the shell layer electrolyte swelling was 5.5%, respectively. Compared to Example 1, the core swelling was lower, the negative electrode binder adhesion was minimal, the elastic modulus was higher, the electrode expansion was lower, and the battery life was relatively normal. Specifically, the core layer monomer was replaced with isooctyl acrylate in Example 1 instead of ethyl acrylate.

[0132] In Example 11, the core layer electrolyte swelling was 95.5% and the shell layer electrolyte swelling was 5.5%, respectively. Compared to Example 1, the core swelling was higher, the negative electrode binder adhesion was not significantly affected, the elastic modulus was not significantly affected, the electrode expansion was low, and the battery life was relatively normal. Specifically, the core layer monomers were replaced with methyl acrylate and butyl acrylate in place of the ethyl acrylate in Example 1.

[0133] The swelling levels in the core and shell electrolytes of Example 12 were 50.5% and 1.9%, respectively. Compared to Example 1, the shell swelling was lower, the negative electrode binder strength was slightly reduced, and the battery life was relatively normal. In the shell monomer, the hydroxypropyl acrylate of Example 1 was replaced with acrylamide.

[0134] In Example 13, the core layer and shell layer swelling levels were 50.5% and 7.5%, respectively. Compared to Example 1, the shell swelling was higher, the negative electrode binder strength was slightly increased, the electrode sheet expansion was slightly increased, and the battery life was relatively normal. In the shell layer monomers, the hydroxypropyl acrylate and acrylic acid in Example 1 were replaced with bis(2-methacryloyloxyethyl) phosphate and N-hydroxymethyl acrylamide.

[0135] The swelling levels in the core layer electrolyte and shell layer electrolyte of Comparative Example 9 were 13.2% and 5.5%, respectively. Compared to Example 1, the core swelling was lower, resulting in a shorter lifespan, but other effects were minor. In the core layer monomers, the ethyl acrylate and acrylonitrile of Example 1 were replaced with butyl acrylate and acrylic acid.

[0136] The swelling levels in the core and shell electrolytes of Comparative Example 10 were 250.3% and 5.5%, respectively. Compared to Example 1, the core swelled significantly, the adhesion was relatively normal, the modulus was low, the electrode expanded significantly, and the lifespan was extremely short. In the core monomers, the ethyl acrylate and methacrylic acid of Example 1 were replaced with acrylic acid, methyl acrylate, and butyl acrylate.

[0137] The swelling levels in the core and shell electrolytes of Comparative Example 11 were 50.5% and 20%, respectively. Compared to Example 1, the shell swelled significantly, exhibited relatively normal adhesion and modulus, but exhibited excessive electrode expansion and a very short lifespan. The shell polymer monomers replaced the hydroxypropyl acrylate and acrylic acid of Example 1 with vinyl pyrrolidone and butyl acrylate.

[0138] Based on the experimental results of Examples 1, 10-13, and Comparative Examples 9-11, it can be concluded that when the swelling degree of the core layer in the electrolyte is 20%-200% and the swelling degree of the shell layer in the electrolyte is 1%-10%, the negative electrode binder has both good flexibility and high elastic modulus, which can reduce the brittleness of the negative electrode sheet while effectively ensuring cycle stability. When the swelling degree of the core-shell electrolyte is less than 20%, ion transmission becomes difficult, the internal resistance is too high, and the cycle life is ultimately affected. When the swelling degree of the core layer electrolyte is greater than 200%, the ability to suppress expansion decreases, and the cycle life is reduced. When the swelling degree of the shell layer electrolyte is less than 1%, ion transmission becomes difficult and the internal resistance is too high. When the swelling degree of the shell layer electrolyte is greater than 10%, the ability to suppress expansion decreases, and the cycle life is reduced.

[0139] Compared to Example 1, Comparative Example 12, which did not contain o-phenylphenoxyethyl acrylate in its core layer monomers, exhibited poor adhesion and a poor battery cycle life. Therefore, the inclusion of o-phenylphenoxyethyl acrylate as a core layer monomer significantly contributes to improved adhesion, effectively enhancing the adhesive's bonding and cycle life.

[0140] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A negative electrode binder, characterized in that The negative electrode binder has a core-shell structure, which consists of a core layer and a shell layer, and the shell layer covers the core layer; Wherein, the core layer monomer used to synthesize the core layer includes: o-phenylphenoxyethyl acrylate.

2. The negative electrode binder according to claim 1, characterized in that The diameter of the core layer is 50-500 nm, the thickness of the shell layer is 1-10 nm, and / or The glass transition temperature of the core layer is -20°C to 20°C, the glass transition temperature of the shell layer is 80°C to 160°C, and / or The swelling degree of the core layer in the electrolyte is 20%-200%, and the swelling degree of the shell layer in the electrolyte is 1%-10%.

3. The negative electrode binder according to claim 1, characterized in that The core layer monomers used to synthesize the core layer include: o-phenylphenoxyethyl acrylate, and at least two or at least three of acrylonitrile, unsaturated carboxylic acid, acrylate, unsaturated amide, and styrene. The shell monomers used to synthesize the shell layer include at least two or at least three of unsaturated sulfonates, unsaturated hydroxyesters, unsaturated carboxylic acids, unsaturated sulfonates, unsaturated amides, unsaturated phosphates, and other monomers.

4. The negative electrode binder according to claim 3, characterized in that The unsaturated carboxylic acid is at least one selected from acrylic acid, methacrylic acid, ethacrylic acid, propyl acrylic acid, isopropyl acrylic acid, n-butyl acrylic acid, isobutyl acrylic acid, tert-butyl acrylic acid, cyclopropyl acrylic acid, n-pentyl acrylic acid, isopentyl acrylic acid, cyclopentyl acrylic acid, n-hexyl acrylic acid, isohexyl acrylic acid, and cyclohexyl acrylic acid; and / or The acrylic acid esters are selected from at least one of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, cyclopropyl acrylate, isooctyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, isooctyl methacrylate, hydroxypropyl methacrylate, 2-hydroxyethyl methacrylate, lauryl methacrylate, glycidyl methacrylate, tert-butylaminoethyl methacrylate, dimethylaminoethyl methacrylate, tert-butylaminoethyl acrylate, vinyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, phenyl methacrylate, dodecyl methacrylate, and hexadecyl methacrylate; and / or The unsaturated amide is selected from at least one of acrylamide, methacrylamide, N-hydroxymethyl acrylamide, N,N-dimethyl acrylamide, N-methyl acrylamide, and N-hydroxymethyl methacrylamide; and / or The unsaturated sulfonate is selected from at least one of styrene sulfonate, 2-acrylamido-2-methylpropane sulfonate, vinyl sulfonate, methyl allyl sulfonate, allyl sulfonate, and methacrylamide isopropyl sulfonate; and / or The unsaturated sulfonic acid ester is at least one selected from methyl styrenesulfonate, ethyl styrenesulfonate, propyl styrenesulfonate, 2-acrylamido-2-methylpropanesulfonate, vinylsulfonate, allylsulfonate, methylallylsulfonate, and methacrylamide isopropylsulfonate; and / or The unsaturated hydroxy ester is selected from at least one of β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, bis(2-hydroxyethyl)maleate, and 2-hydroxyethyl methyl fumarate; and / or The unsaturated phosphate is selected from at least one of di(2-methacryloyloxyethyl)phosphate, 2-hydroxyethyl methacrylate phosphate, 2-hydroxyethyl acrylate phosphate, and allyl polyether phosphate; and / or The other monomers are selected from at least one of polyethylene glycol acrylate, vinyl pyridine, vinyl pyrrolidone, polyethylene glycol methacrylate, ethylene glycol dimethacrylate, β-carboxyethyl acrylate, sodium 1-allyloxy-2-hydroxypropyl sulfonate, and diallyl maleate.

5. The negative electrode binder according to any one of claims 1 to 5, characterized in that The raw materials for preparing the negative electrode binder include: a core layer monomer for synthesizing the core layer, a shell layer monomer for synthesizing the shell layer, an initiator, an emulsifier and water; Wherein, the weight ratio of the shell monomer to the core monomer is (0.13-0.52):1, or Based on the total weight of the shell layer monomer and the core layer monomer being 180-220 parts, the weight of the emulsifier is 8-15 parts, or Based on the total weight of the shell layer monomer and the core layer monomer being 180-220 parts, the weight of the initiator is 8-12 parts, or Based on the total weight of the shell layer monomers and the core layer monomers being 180-220 parts, the weight of the water is 500-1000 parts.

6. The negative electrode binder according to any one of claims 1 to 5, characterized in that The negative electrode binder is used to prepare a secondary battery, which includes a lithium ion battery or a sodium ion battery.

7. A negative electrode plate, characterized in that: The negative electrode sheet is loaded with the negative electrode binder according to any one of claims 1 to 6.

8. An electrochemical energy storage device, characterized in that: The electrochemical energy storage device comprises: the negative electrode binder according to any one of claims 1 to 6, or the negative electrode plate according to claim 7.

9. The electrochemical energy storage device according to claim 8, characterized in that: The electrochemical energy storage device includes a secondary battery, and the secondary battery includes a lithium ion battery or a sodium ion battery.

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