Negative electrode binder composition, negative electrode binder and preparation method therefor, negative electrode sheet, battery cell and battery

Abstract

Disclosed are a negative electrode binder composition, a negative electrode binder and a preparation method therefor, a negative electrode sheet, a battery cell, and a battery. The negative electrode binder composition comprises the following components: an acrylic monomer, a hydroxydopamine monomer, a long-chain alkyl (meth) acrylate monomer, and a vinyl siloxane monomer.

Description

Negative electrode binder composition, negative electrode binder and preparation method thereof, negative electrode sheet, electric cell and battery

[0001] The present application claims priority from the Chinese patent application No. 202410866953.X filed on June 28, 2024, and entitled "Negative electrode binder composition, negative electrode binder and preparation method thereof, negative electrode sheet, electric cell and battery", the content of which is incorporated herein in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of batteries, in particular, the present application relates to a negative electrode binder composition, a negative electrode binder and a preparation method thereof, a negative electrode sheet, an electric cell and a battery. BACKGROUND

[0003] With the rapid development of electronic technology, lithium ion batteries are widely used in fields such as electric vehicles, smart phones, etc. due to their high energy density, long life and environmental protection advantages.

[0004] However, when the battery operates in a high temperature environment, the traditional SBR (styrene butadiene rubber emulsion), PAA (polyacrylic acid) negative electrode binder has insufficient adhesion in the electrolyte and is prone to aging and brittleness, which can cause the negative electrode material to crack and powderize, and then fall off from the current collector (such as copper sheet), thereby seriously reducing the cycle life of the battery. Therefore, it is of great significance to develop a negative electrode binder with strong adhesion and stability in the electrolyte to improve the cycle life of the lithium ion battery. SUMMARY

[0005] The purpose of the present application is to provide a new technical solution of a negative electrode binder composition, a negative electrode binder and a preparation method thereof, a negative electrode sheet, an electric cell and a battery.

[0006] According to a first aspect of the present application, the embodiments of the present application provide a negative electrode binder composition, which comprises the following components:

[0007] The acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer and the vinyl siloxane monomer.

[0008] Optionally, the mass fraction of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer and the vinyl siloxane monomer is as follows:

[0009] The acrylic monomer is 50-100 parts;

[0010] The hydroxydopamine monomer is 90-180 parts;

[0011] The long-chain alkyl (meth) acrylate monomer is 20-40 parts;

[0012] The vinyl siloxane monomer is 30 parts to 60 parts.

[0013] Optionally, the negative electrode binder composition further comprises an initiator and a surfactant.

[0014] The amount of the initiator is 0.1 wt% to 1 wt% of the total mass of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer, and the vinyl siloxane monomer; and / or,

[0015] The amount of the surfactant is 0.5 wt% to 1 wt% of the total mass of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer, and the vinyl siloxane monomer.

[0016] Optionally, the acrylic monomer comprises at least one of acrylic acid and methacrylic acid.

[0017] The long-chain alkyl (meth) acrylate monomer comprises at least one of lauryl methacrylate, myristyl methacrylate, stearyl methacrylate, and 2-ethylhexyl acrylate.

[0018] Optionally, the vinyl siloxane monomer comprises at least one of vinyl trimethoxysilane, vinyl triethoxysilane, vinyl triisopropoxysilane, and γ-methacryloyloxypropyl trimethoxysilane.

[0019] Optionally, the initiator comprises at least one of potassium persulfate, ammonium persulfate, and sodium persulfate.

[0020] Optionally, the surfactant comprises at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate, dioctyl phthalate sodium sulfonate, polyoxyethylene-p-nonylphenol ether, and polyoxyethylene-p-octylphenol ether.

[0021] According to a second aspect of the present application, the embodiments of the present application provide a negative electrode binder, and a chemical structural formula of the negative electrode binder is as follows:

[0022] In the formula, x, y, and z represent quantities, x, y, and z are positive integers, and the ratio of x, y, and z is 5-10:1-2:2-4.

[0023] According to a third aspect of the present application, the embodiments of the present application provide a preparation method of a negative electrode binder, and the preparation method comprises:

[0024] The acrylic monomer and the hydroxydopamine monomer are mixed and then reacted to obtain a reaction product.

[0025] The long-chain alkyl (meth) acrylate monomer and the vinyl siloxane monomer are added to the reaction product, and then polymerization is carried out in the presence of a surfactant and an initiator to obtain the negative electrode binder.

[0026] Optionally, the mass ratio of the hydroxydopamine monomer to the vinyl siloxane monomer is 1.5-6:1.

[0027] Optionally, the reaction of the acrylic monomer and the hydroxydopamine monomer to obtain the reaction product comprises:

[0028] The acrylic monomer and the hydroxydopamine monomer are mixed and reacted at 50-70°C for 1-2 hours.

[0029] Optionally, the long-chain alkyl (meth) acrylate monomer and the vinyl siloxane monomer are added to the reaction product, and then polymerization is carried out in the presence of a surfactant and an initiator to obtain the negative electrode binder, which comprises:

[0030] The long-chain alkyl (meth) acrylate monomer and the surfactant are added to the reaction product obtained by mixing and reacting the acrylic monomer and the hydroxydopamine monomer, and deionized water is added to form a pre-emulsion.

[0031] The initiator is added to the pre-emulsion, nitrogen gas is introduced as a protective gas, the temperature is raised to 75-85°C and then held, and then the vinyl siloxane monomer is added and held at 75-85°C to obtain an emulsion; the total time of the second holding is 1-3 hours.

[0032] The emulsion is subjected to suction filtration and drying to obtain the negative electrode binder.

[0033] According to a fourth aspect of the present application, the embodiments of the present application provide a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material and a conductive agent; the negative electrode active material layer is bonded to the negative electrode current collector by a binder.

[0034] The binder is the negative electrode binder composition according to the first aspect or the negative electrode binder according to the second aspect.

[0035] According to a fifth aspect of the present application, the embodiments of the present application provide an electric core, which comprises a positive electrode sheet, a negative electrode sheet, and a separator.

[0036] The negative electrode sheet is the negative electrode sheet according to the fourth aspect.

[0037] According to a sixth aspect of the present application, the embodiments of the present application provide a battery, comprising a shell, an electrode core and an electrolyte; wherein the electrode core is the electrode core according to the fifth aspect.

[0038] An advantageous effect of the embodiments of the present application is that:

[0039] According to the negative electrode binder composition provided by the embodiments of the present application, the components at least include four monomers. Specifically, the copolymer synthesized by modifying the acrylic acid and long-chain alkyl (methyl) acrylate monomers by using hydroxydopamine and vinyl siloxane monomers can finally prepare the negative electrode binder with excellent adhesion, chemical stability and high and low temperature resistance. The ortho-diphenol hydroxyl in the hydroxydopamine can form a strong hydrogen bond, and this characteristic can greatly enhance the adhesion of the prepared negative electrode binder to the current collector. By introducing the vinyl siloxane monomer for modification, the chemical stability of the negative electrode binder is significantly improved. The strength of the Si-O bond is obviously higher than that of the C-C bond and the C-O bond, which makes the modified binder show higher stability when facing the chemical environment such as the electrolyte. In addition, since the silicon atom connected with the carbon atom is connected with three alkoxy groups, this structure makes the molecular chain more stable and less prone to rotation, thereby further enhancing the chemical stability and structural strength of the formed negative electrode binder.

[0040] Other characteristics and advantages of the present application will become clear from the following detailed description of exemplary embodiments of the present application. DETAILED DESCRIPTION

[0041] Various exemplary embodiments of the present application will now be described in detail. It should be noted that the relative arrangement of components and steps, numerical expressions, and numerical values set forth in these embodiments are not limitations on the scope of the present application unless otherwise specifically stated.

[0042] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way limiting of the application or its applications or uses.

[0043] Techniques and equipment known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as part of the specification where appropriate.

[0044] In all examples shown and discussed herein, any specific value should be interpreted as merely illustrative, not as a limitation. Thus, other examples of the exemplary embodiments can have different values.

[0045] The negative electrode binder composition, the negative electrode binder and the preparation method thereof, the negative electrode sheet, the electrode core and the battery provided by the embodiments of the present application are described in detail below.

[0046] According to one embodiment of the present application, a negative electrode binder composition is provided, which includes the following components:

[0047] an acrylic monomer, a hydroxydopamine monomer, a long-chain alkyl (meth) acrylate monomer, and a vinyl siloxane monomer.

[0048] The negative electrode binder composition provided by the embodiment of the present application mainly involves four different monomers, i.e., the above-mentioned four monomers: an acrylic monomer, a hydroxydopamine monomer, a long-chain alkyl (meth) acrylate monomer, and a vinyl siloxane monomer. The above-mentioned four monomers are prepared through specific chemical reaction steps to obtain a negative electrode binder with specific properties.

[0049] Specifically, the process of obtaining the negative electrode binder includes the following key steps:

[0050] In the first step, the acrylic monomer is mixed and reacted with the hydroxydopamine monomer. The acrylic monomer (such as acrylic acid, methacrylic acid, etc.) is mixed and reacted with the hydroxydopamine monomer. The purpose of this step is to replace the carboxyl group in the binder with the ortho-diphenol hydroxyl group in the hydroxydopamine, thereby helping to enhance the adhesion of the binder to the current collector.

[0051] In the second step, the long-chain alkyl (meth) acrylate monomer and the vinyl siloxane monomer are added. Based on the first step reaction described above, the long-chain alkyl (meth) acrylate monomer and the vinyl siloxane monomer are added to further improve the chemical stability, aging resistance, high and low temperature resistance, and solvent resistance of the formed negative electrode binder.

[0052] In the third step, a polymerization reaction is performed. For example, the product obtained in the second step can be subjected to a polymerization reaction in the presence of a surfactant and an initiator. The purpose of this step is to allow the various monomers to fully react, thereby forming a negative electrode binder with specific structure and properties.

[0053] The negative electrode binder provided by the embodiment of the present application, in which the hydroxydopamine used exhibits excellent adhesion due to its unique ortho-diphenol hydroxyl structure, which is derived from its ability to form strong hydrogen bonds. In the preparation process of the negative electrode binder, the ortho-diphenol hydroxyl group of the hydroxydopamine is used to replace the original carboxyl group, which not only significantly enhances the adhesion of the negative electrode binder to the current collector, but also further improves the stability and reliability of the battery. In other words, due to the introduction of hydroxydopamine, the adhesion of the finally formed negative electrode binder to the negative electrode current collector, for example, is significantly enhanced, which helps to prevent the shedding of the negative electrode material during charging and discharging.

[0054] Further, the chemical stability of the negative electrode binder is improved by introducing the vinyl siloxane monomer for silicone modification. This is because the strength of the Si-O bond is significantly higher than that of the traditional C-C bond and C-O bond, which makes the obtained negative electrode binder exhibit higher stability when facing complex chemical environments such as electrolyte. It is worth mentioning that the silicon atom connected to the carbon atom is connected to three alkoxy groups, and this structure makes the molecular chain more stable and less prone to rotation, thereby further enhancing the tensile strength and structural strength of the negative electrode binder. At the same time, this silicone modification also endows the negative electrode binder with excellent aging resistance, high and low temperature resistance, and solvent resistance. In extreme working environments, it can still maintain stable performance, especially the durability to electrolyte under high temperature conditions.

[0055] Therefore, the negative electrode sheet prepared by using the negative electrode binder provided in the application can exhibit higher cycle life, lower internal resistance and better rate performance in, for example, a lithium ion battery, thereby improving the overall performance of the battery.

[0056] The negative electrode binder scheme provided in the application is quite different from the traditional polyacrylic acid PAA which is simply synthesized by using acrylic acid and its ester. The technical scheme provided in the application uses hydroxydopamine monomers and vinyl siloxane monomers to modify the acrylic acid and its long-chain ester, thereby endowing the finally formed negative electrode binder with new performance and characteristics. This method not only breaks the traditional constraints, but also significantly improves the adhesion, chemical stability, and aging resistance, high and low temperature resistance, and solvent resistance of the negative electrode binder, thereby opening up a new way for the optimization of negative electrode materials and the improvement of battery performance.

[0057] The negative electrode binder composition provided in the application includes at least four monomers. Specifically, by using hydroxydopamine and vinyl siloxane monomers to modify the copolymer synthesized by using acrylic monomers and long-chain alkyl (methyl) acrylate monomers, a negative electrode binder with excellent adhesion, chemical stability and high and low temperature resistance can be finally prepared. The ortho-diphenol hydroxyl group in the hydroxydopamine can form a strong hydrogen bond, which greatly enhances the adhesion of the obtained negative electrode binder to the current collector. By introducing the vinyl siloxane monomer for modification, the chemical stability of the negative electrode binder is significantly improved. The strength of the Si-O bond is significantly higher than that of the C-C bond and C-O bond, which makes the modified binder exhibit higher stability when facing chemical environments such as electrolyte. In addition, since the silicon atom connected to the carbon atom is connected to three alkoxy groups, this structure makes the molecular chain more stable and less prone to rotation, thereby further enhancing the chemical stability and structural strength of the formed negative electrode binder.

[0058] In some examples of the present application, the mass fraction of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer, and the vinyl siloxane monomer is as follows: the acrylic monomer is 50-100 parts, the hydroxydopamine monomer is 90-180 parts, the long-chain alkyl (meth) acrylate monomer is 20-40 parts, and the vinyl siloxane monomer is 30-60 parts.

[0059] According to examples of the present application, the mass fraction range of each of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer, and the vinyl siloxane monomer in the raw materials of the negative electrode binder composition is described.

[0060] The mass fraction of the acrylic monomer is 50-100 parts. The acrylic monomer is a basic raw material for preparing the negative electrode binder, which provides the basic structure and performance of the negative electrode binder. Within this dosage range, the dosage of the acrylic monomer is sufficient to ensure the basic performance of the binder, and there is also a certain adjustment space to meet different application requirements.

[0061] The mass fraction of the hydroxydopamine monomer is 90-180 parts. The hydroxydopamine monomer is one of the modifiers, and its high content (relative to the acrylic monomer) is introduced to significantly enhance the adhesion of the finally prepared negative electrode binder. Within this range of 90-180 parts, the adhesion of the hydroxydopamine can be fully exhibited in combination with the acrylic monomer, ensuring the firm connection between the negative active material and the negative current collector, while not causing other performance problems due to too high content.

[0062] The mass fraction of the long-chain alkyl (meth) acrylate monomer is 20-40 parts. The addition of the long-chain alkyl (meth) acrylate monomer can improve the flexibility and processing performance of the finally prepared negative electrode binder, and also helps to improve the compatibility of the negative electrode binder with the negative active material and the negative current collector. The content in this range can ensure the improvement of the above-mentioned properties, and will not have a negative impact on the overall performance.

[0063] The mass fraction of the vinyl siloxane monomer is 30-60 parts. The addition of the vinyl siloxane monomer can significantly improve the chemical stability, aging resistance, high and low temperature resistance, and solvent resistance of the finally prepared negative electrode binder. The content in this range, in combination with the content of other monomers, ensures the improvement of the above-mentioned properties, and will not increase the cost or reduce other properties due to too high content.

[0064] The mass parts of the above components are combined to prepare the negative electrode binder with excellent adhesion, chemical stability, aging resistance, high and low temperature resistance, and solvent resistance. The binder can not only ensure the firm connection between the negative active material and the negative current collector, but also improve the stability and reliability of the battery using the negative electrode sheet, and prolong the service life of the battery.

[0065] Further preferably, the mass parts of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer, and the vinyl siloxane monomer are as follows:

[0066] The mass parts of the acrylic monomer are 50-100 parts, the mass parts of the hydroxydopamine monomer are 90-120 parts, the mass parts of the long-chain alkyl (meth) acrylate monomer are 20-40 parts, and the mass parts of the vinyl siloxane monomer are 30-50 parts.

[0067] The mass parts of the above-mentioned preferred scheme provide a more accurate and efficient formula for the preparation of the negative electrode binder. Compared with the previous examples, the amount of hydroxydopamine monomer and vinyl siloxane monomer is further optimized. Specifically:

[0068] The mass parts of the hydroxydopamine monomer are preferably 90-120 parts. The addition of the hydroxydopamine monomer can enhance the adhesion of the finally prepared negative electrode binder. Within this range, the content is sufficient to play the strong adhesion of the ortho-diphenol hydroxyl group, and will not cause other performance degradation due to excessive amount, and can also reduce the production cost.

[0069] The mass parts of the vinyl siloxane monomer are 30-50 parts. The addition of the vinyl siloxane monomer can improve the chemical stability, aging resistance, high and low temperature resistance, and solvent resistance of the negative electrode binder. In particular, the mass parts of the vinyl siloxane monomer are controlled to be 30-50 parts, so that the mass ratio of the vinyl siloxane monomer to the hydroxydopamine monomer is maintained in the preferred range of 1.8-4:1. This more preferred ratio enables the binder to maintain high adhesion while also having excellent stability and durability.

[0070] It should be noted that increasing the mass parts of the vinyl siloxane monomer, such as more than 60 parts, or decreasing the mass parts of the vinyl siloxane monomer, such as less than 30 parts, will result in a decrease in the viscosity or peel force of the formed negative electrode binder.

[0071] The mass part range of each monomer provided in the examples of the present application is optimized, which can bring the following technical effects:

[0072] (1) Excellent adhesion: The optimized control of the amount of hydroxydopamine monomer ensures the firm connection between the negative electrode binder and the negative active material and the negative current collector.

[0073] (2) Enhanced chemical stability: The addition of vinyl siloxane-based monomers significantly improves the chemical stability of the negative electrode binder, enabling it to remain stable in complex chemical environments.

[0074] (3) Good aging resistance, high and low temperature resistance, and solvent resistance: By optimizing the formulation, the final negative electrode binder exhibits excellent aging resistance, high and low temperature resistance, and solvent resistance, which helps to prolong the service life of the battery.

[0075] (4) Balance of comprehensive performance: This optimization scheme not only maintains high adhesion, but also focuses on the balance of other performance such as chemical stability, aging resistance, etc., providing strong support for the preparation of high-performance negative electrode binders.

[0076] In some examples of the present application, the negative electrode binder composition further comprises an initiator, and the amount of the initiator is 0.1wt% to 1wt% of the total mass of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer, and the vinyl siloxane-based monomer.

[0077] The initiator plays a key role in starting or initiating the polymerization process in the polymerization reaction, and its main function is to convert monomers into polymers. In the technical scheme provided in the embodiments of the present application, the initiator plays a crucial role in the polymerization reaction of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer, and the vinyl siloxane-based monomer.

[0078] (1) Initiating the polymerization process: The initiator can be thermally decomposed into active intermediates such as free radicals, cations or anions, which can attack monomer molecules, thereby starting the polymerization process. In the present application, an appropriate amount of initiator can ensure the smooth progress of the polymerization reaction and form high molecular chains.

[0079] (2) Control the rate of polymerization reaction: The concentration and activity of the initiator directly affect the rate of the polymerization reaction. In the embodiments of the present application, by precisely controlling the amount of initiator, i.e. 0.1wt% to 1wt%, the control of the polymerization reaction rate can be realized to meet the needs of different application scenarios.

[0080] (3) The selection and use of the initiator not only affects the progress of the polymerization reaction, but also affects the performance of the final product. In the present application, by optimizing the amount of initiator, the adhesion, chemical stability and other properties of the negative electrode binder can be improved.

[0081] In some examples of the present application, the composition of the negative electrode binder further comprises a surfactant, the amount of the surfactant is 0.5wt% to 1wt% of the total mass of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer and the vinyl siloxane monomer.

[0082] In examples of the present application, the surfactant has the following effects:

[0083] The surfactant can interact with the negative electrode binder molecules to form stronger chemical bonds, which helps to improve the adhesion and adhesion of the negative electrode binder. This is particularly important in the preparation of the negative electrode binder, as it ensures a firm connection between the negative electrode material and the current collector.

[0084] The surfactant can improve the emulsion stability. The binder often contains impurities such as fillers and additives, which can easily cause delamination and precipitation. The role of the surfactant is to disperse these impurities in the water phase to form a stable emulsion state, thereby ensuring the stability and service life of the binder.

[0085] The type and amount of surfactant can affect the flowability, viscosity, drying time and other properties of the negative electrode binder finally prepared. By adjusting the amount of surfactant, the properties and functions of the negative electrode binder can be customized to meet different application requirements.

[0086] In some examples of the present application, the acrylic monomer includes at least one of acrylic acid and methacrylic acid.

[0087] In some examples of the present application, the long-chain alkyl (meth) acrylate monomer includes at least one of lauryl methacrylate, myristyl methacrylate, stearyl methacrylate and 2-ethylhexyl acrylate.

[0088] According to the above examples provided by the present application, the specific types of acrylic monomers and long-chain alkyl (meth) acrylate monomers used are further described.

[0089] The acrylic monomer includes, for example, at least one of acrylic acid and methacrylic acid. These two monomers are the basic raw materials for preparing polymers, and they have good polymerization activity.

[0090] Among them, acrylic acid is an unsaturated carboxylic acid with double bond and carboxyl functional groups, which can copolymerize with various monomers. Acrylic acid polymers have good adhesion, film forming property and water resistance.

[0091] Among them, methacrylic acid is a methyl derivative of acrylic acid, and its polymer has higher hardness and weather resistance than acrylic acid polymer.

[0092] It should be noted that the acrylic monomer can be other acrylates besides the above-mentioned acrylic acid or methacrylic acid, which is not limited in the present application.

[0093] The long-chain alkyl (meth) acrylate monomer includes at least one of lauryl methacrylate, myristyl methacrylate, stearyl methacrylate, and 2-ethylhexyl acrylate. These monomers contain long-chain alkyl groups, which can provide the polymer with excellent hydrophobicity, softness, lubricity, etc.

[0094] Lauryl methacrylate: lauryl is a C12 long-chain alkyl group, and the polymer of lauryl methacrylate has good softness and hydrophobicity.

[0095] Myristyl methacrylate: a C14 long-chain alkyl group, and the polymer thereof has a longer alkyl chain than the polymer of lauryl methacrylate, thus having better hydrophobicity and softness.

[0096] Stearyl methacrylate: stearyl is a C18 long-chain alkyl group, and the polymer of stearyl methacrylate has excellent hydrophobicity, softness, and lubricity.

[0097] 2-Ethylhexyl acrylate: this monomer combines the unsaturation of acrylic acid and the long-chain alkyl group of 2-ethylhexyl, and the polymer thereof has excellent flexibility and weather resistance.

[0098] The acrylic monomer provided in the examples of the present application is at least one of acrylic acid and methacrylic acid, which can enable the prepared negative electrode binder to have excellent adhesion and film-forming property.

[0099] The long-chain alkyl (meth) acrylate monomer provided in the examples of the present application includes at least one of lauryl methacrylate, myristyl methacrylate, stearyl methacrylate, and 2-ethylhexyl acrylate. The introduction of the long-chain alkyl (meth) acrylate monomer provides the polymer with good softness and hydrophobicity, so that the polymer material has excellent water resistance and flexibility while maintaining certain mechanical strength.

[0100] In some examples of the present application, the vinyl siloxane monomer includes at least one of vinyl trimethoxysilane, vinyl triethoxysilane, vinyl triisopropoxysilane, and γ-methacryloyloxypropyl trimethoxysilane.

[0101] Monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltriisopropoxysilane have excellent reactivity and cross-linking ability, and they can effectively copolymerize with the acrylic monomers, the hydroxydopamine monomers, and the long-chain alkyl (meth) acrylate monomers to form polymers with excellent properties. Such polymers not only have good adhesion and mechanical strength, but also have excellent weather resistance, chemical corrosion resistance, and heat resistance.

[0102] Gamma-methacryloxypropyltrimethoxysilane is a silane monomer with acryloxy reactivity. It can improve the mechanical properties of the composite material and improve the compatibility between the inorganic filler and the polymer.

[0103] The various vinyl siloxane monomers described above can copolymerize with other monomers to form polymers with excellent adhesion and mechanical strength, ensuring that the product can maintain stable performance during use.

[0104] The various vinyl siloxane monomers described above impart good weather resistance and chemical corrosion resistance to the polymer, allowing the product to be used for a long time in harsh environments without being damaged.

[0105] The various vinyl siloxane monomers described above can significantly improve the heat resistance and aging resistance of the final negative electrode binder.

[0106] Silane monomers with acryloxy reactivity such as gamma-methacryloxypropyltrimethoxysilane can improve the compatibility between the inorganic filler and the polymer and improve the performance of the composite material.

[0107] In some examples of the present application, the initiator is at least one of potassium persulfate, ammonium persulfate, and sodium persulfate.

[0108] An initiator is a compound that can generate free radicals or ions in a polymerization reaction, thereby initiating the polymerization of monomers. The initiators involved in the examples of the present application include one or more of potassium persulfate, ammonium persulfate, and sodium persulfate. These initiators described above are all persulfate compounds, which can decompose to generate sulfate radicals under heat or light conditions, thereby initiating the polymerization of monomers. These initiators described above have high initiation efficiency and stability, and can be used in a wide range of temperatures and pH. By selecting the appropriate initiator and adjusting its amount, the rate of polymerization and the molecular weight distribution of the polymer can be controlled, thereby obtaining a polymer with specific properties.

[0109] In a polymerization reaction, the amount of initiator used is usually small, but it has an important influence on the polymerization process and the properties of the final product.

[0110] In some examples of the present application, the surfactant includes at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate, dioctyl sodium sulfosuccinate, polyoxyethylene-p-nonylphenyl ether, and polyoxyethylene-p-octylphenyl ether.

[0111] A surfactant is a substance that can significantly reduce the surface tension of a solvent. The surfactants involved in the examples of the present application include one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecyl benzene sulfonate.

[0112] Sodium dodecyl sulfate (SDS): A common anionic surfactant with good detergency and emulsification ability.

[0113] Sodium dodecyl sulfonate (also known as sodium lauryl sulfonate): Different from SDS, but also an anionic surfactant.

[0114] Sodium dodecyl benzene sulfonate (SDBS): Another anionic surfactant with good stability and biodegradability.

[0115] Dioctyl sodium sulfosuccinate: Can be used as a cosolvent.

[0116] Polyoxyethylene-p-nonylphenyl ether and polyoxyethylene-p-octylphenyl ether: Both are polyoxyethylene ether derivatives, used as nonionic surfactants, with good emulsification, dispersion, and solubilization ability.

[0117] These surfactants mentioned above can be used as emulsifiers, dispersants, solubilizers, etc. in polymerization reactions, which help to improve the stability and uniformity of the polymerization system. In the final prepared negative electrode binder, they can endow the material with specific surface properties such as wettability, emulsification, dispersion, etc., thus meeting different application requirements.

[0118] According to a second embodiment of the present application, a negative electrode binder is provided, the chemical structural formula of which is as follows:

[0119] In the formula, x, y, z represent quantities, x, y, z are positive integers, and the ratio of x, y, z is 5-10:1-2:2-4.

[0120] According to the chemical structural formula of the above negative electrode binder, it contains methyl (CH3), methylene (CH2-), carbonyl (CO, C=O), amino (NH), hydroxyl (OH), and siloxane group (Si—O—CH3). The negative electrode binder can be considered as a hydroxydopamine modified acrylic acid and ester polymer.

[0121] In the chemical structure of the negative electrode binder, the siloxane group (Si—O—CH3) indicates that this is a siloxane-modified molecule. Siloxane modification can be used to improve the surface properties, stability, or compatibility with other materials of the material. Acrylic and ester polymers are polymers with carbon-carbon double bond (C=C) and carbonyl (C=O) structures.

[0122] Hydroxydopamine is a hydroxylated derivative of dopamine. From the chemical structure of the negative electrode binder, there are multiple hydroxyl groups (OH), which is one of the significant features of hydroxydopamine.

[0123] In the negative electrode binder, hydroxydopamine interacts with the siloxane-modified acrylic and ester polymer through its specific functional groups, enhancing the adhesion and stability of the binder. Hydroxydopamine also has certain electrochemical activity and can participate in electrode reactions during charging and discharging, improving the electrochemical performance of the negative electrode material.

[0124] The negative electrode binder provided by the embodiments of the present application is prepared by using the above-mentioned negative electrode binder composition, has excellent adhesion and stability, and can effectively bond the negative electrode active material and components such as current collectors together, preventing the active material from falling off and pulverizing during charging and discharging. This material design helps to improve the overall performance of the battery, such as cycle life, energy density, and safety. At the same time, its excellent adhesion and stability also help to improve the reliability and durability of the battery.

[0125] According to a third embodiment of the present application, a preparation method of a negative electrode binder is provided, and the negative electrode binder is the above-mentioned negative electrode binder.

[0126] The preparation method of the negative electrode binder provided by the embodiments of the present application includes the following steps 1 and step 2:

[0127] Step 1, mixing an acrylic monomer and a hydroxydopamine monomer and then reacting to obtain a reactant;

[0128] Step 2, adding a long-chain alkyl (methyl) acrylate monomer and a vinyl siloxane monomer to the reactant, and then performing a polymerization reaction in the presence of a surfactant and an initiator to obtain a negative electrode binder.

[0129] The prepared negative electrode binder is a hydroxydopamine and a siloxane-modified acrylic and ester polymer, and the chemical structure of the negative electrode binder is as follows:

[0130] In the formula, x, y, and z represent quantities, x, y, and z are positive integers, and the ratio of x, y, and z is 5-10:1-2:2-4.

[0131] According to the preparation method of the negative electrode binder provided in the embodiments of the present application, the copolymer synthesized by using hydroxydopamine and vinyl siloxane monomer to modify acrylic acid and long-chain alkyl (methyl) acrylate monomer is modified, and a negative electrode binder with excellent adhesion, chemical stability and high and low temperature resistance is prepared; wherein the ortho-diphenol hydroxyl group in hydroxydopamine can form strong hydrogen bonds, and this property greatly enhances the adhesion of the formed negative electrode binder to the current collector; by introducing the vinyl siloxane monomer for modification, the chemical stability of the negative electrode binder is significantly improved, and the strength of the Si-O bond is obviously higher than that of the C-C bond and the C-O bond, which makes the modified binder exhibit higher stability in the chemical environment such as electrolyte. In addition, since the silicon atom connected to the carbon atom is connected to three alkoxy groups, this structure makes the molecular chain more stable and less prone to rotation, thereby further enhancing the chemical stability and structural strength of the formed negative electrode binder.

[0132] In some examples of the present application, the mass fraction ratio of the hydroxydopamine monomer to the vinyl siloxane monomer is 1.5-6:1.

[0133] In the raw materials for synthesizing the negative electrode binder, two modifiers, i.e., the hydroxydopamine monomer and the vinyl siloxane monomer, are used, and the mass fraction ratio of the hydroxydopamine monomer to the vinyl siloxane monomer is controlled at, for example, 1.5-6:1.

[0134] The hydroxydopamine monomer provides strong adhesion with its unique ortho-diphenol hydroxyl group structure. When the mass fraction ratio of the hydroxydopamine monomer to the vinyl siloxane monomer is controlled in the range of 1.5-6:1, the adhesion performance of the hydroxydopamine can be fully utilized, and the content is not too high to cause the decline of other performances.

[0135] The introduction of the vinyl siloxane monomer enhances the chemical stability of the negative electrode binder through the Si-O bond. Within the above ratio range (i.e., 1.5-6:1), the content of the vinyl siloxane monomer is sufficient to provide a stable Si-O bond structure, but it is not too much to avoid possible negative effects, such as the increase of material cost or the decrease of processing performance.

[0136] The structure in which the silicon atom connected to the carbon atom is connected to three alkoxy groups plays a key role in the vinyl siloxane monomer provided in the embodiments of the present application, increases the stability of the molecular chain, makes it less prone to rotation, and thus can enhance the tensile strength and structural strength of the material. The appropriate content of the vinyl siloxane monomer helps to fully exhibit this structure and improve the overall performance of the negative electrode binder.

[0137] According to the examples provided in the present application, the mass fraction ratio of the hydroxydopamine monomer to the vinyl siloxane monomer is 1.5-6:1. Within this ratio range, the content of the vinyl siloxane monomer is sufficient to endow the negative electrode binder with excellent aging resistance, high and low temperature resistance, and solvent resistance. The improvement of these properties helps the battery to maintain stable performance in complex environments and prolong the service life of the battery.

[0138] More preferably, the mass fraction ratio of the hydroxydopamine monomer to the vinyl siloxane monomer is 1.8-4:1. This can further improve the adhesion and chemical stability of the formed negative electrode binder. Specifically:

[0139] Within the optimized ratio range of 1.8-4:1, the ortho-diphenol hydroxyl structure of hydroxydopamine can more effectively exert its adhesion, ensuring the firm connection between the negative active material and the negative current collector.

[0140] Within the optimized ratio range of 1.8-4:1, the amount of the introduced vinyl siloxane monomer is more finely controlled, making the number and distribution of Si-O bonds more uniform, thereby further improving the chemical stability of the formed negative electrode binder. This precise control helps to ensure that the negative electrode binder can maintain stable performance in various chemical environments. Moreover, the appropriate content of the vinyl siloxane monomer not only ensures that the structure of three alkoxy groups connected to a silicon atom connected to a carbon atom is fully exhibited, but also makes this structure more uniformly distributed in the negative electrode binder. This uniform distribution helps to improve the tensile strength and structural strength, so that the negative electrode binder can withstand greater external force without being easily broken.

[0141] Moreover, within the optimized ratio range of 1.8-4:1, the content of the vinyl siloxane monomer is more precisely controlled, thereby ensuring that the formed negative electrode binder has more excellent aging resistance, high and low temperature resistance, and solvent resistance. The significant improvement of these properties helps to improve the adaptability and reliability of the battery in various complex environments.

[0142] By further precisely controlling the mass fraction ratio of the hydroxydopamine and the vinyl siloxane monomer, the preferred scheme provided in the examples of the present application not only improves various performance indicators, but also balances the comprehensive performance. This balance enables the negative electrode binder to maintain high performance while also having good stability and reliability, which provides strong support for preparing high-performance negative electrode sheets.

[0143] In some examples of the present application, the acrylic monomer is mixed with the hydroxydopamine monomer to obtain a reactant, which includes:

[0144] The acrylic monomer and the hydroxydopamine monomer are mixed and reacted at 50-70°C for 1-2h.

[0145] According to this example of the present application, the acrylic monomer (such as acrylic acid and / or methacrylic acid, etc.) is mixed and reacted with the hydroxydopamine monomer. Specifically, the whole reaction temperature condition is 50-70°C. This temperature range is selected to ensure that the reaction can be carried out at a faster rate, while avoiding unnecessary side reactions or decomposition of monomers caused by excessively high temperature. Moreover, the reaction time condition is 1-2h. The reaction time is selected to ensure that the reaction is sufficiently carried out to achieve the desired degree of polymerization. Too short a time can result in incomplete reaction, while too long a time can increase energy consumption and can trigger unnecessary side reactions.

[0146] Under the selected reaction temperature and time conditions, the mixed reaction of the acrylic monomer and the hydroxydopamine monomer can be carried out efficiently, ensuring the completeness of the reaction and the uniformity of the product.

[0147] Further, by precisely controlling the reaction conditions, a polymer with specific properties can be obtained. For example, the combination of the acrylic monomer and the hydroxydopamine monomer can impart unique adhesion, biocompatibility to the polymer. In addition, selecting appropriate reaction conditions can reduce energy consumption and production costs. At the same time, avoiding excessively high temperature can reduce unnecessary side reactions, which is beneficial to environmental protection.

[0148] In some examples of the present application, the long-chain alkyl (meth) acrylate monomer and the vinyl siloxane monomer are added to the reactant, and then a polymerization reaction is carried out in the presence of a surfactant and an initiator to obtain a negative electrode binder, including the following steps S1-S3:

[0149] Step S1, the long-chain alkyl (meth) acrylate monomer and the surfactant are added to the reactant obtained by mixing the acrylic monomer and the hydroxydopamine monomer, and deionized water is added to prepare a pre-emulsion;

[0150] Step S2, the initiator is added to the pre-emulsion, nitrogen gas is introduced as a protective gas, the temperature is raised to 75-85°C and then held, and then the vinyl siloxane monomer is added and the temperature is continued to be held at 75-85°C to obtain an emulsion; wherein the total time of the second holding is 1-3h;

[0151] Step S3, the emulsion is filtered and dried to obtain the negative electrode binder.

[0152] According to the above steps S1 to S3, the preparation of the negative electrode binder is described, including the mixing of long-chain alkyl (meth) acrylate monomers and vinyl siloxane monomers, the preparation of the pre-emulsion, the addition of the initiator, the polymerization reaction under nitrogen protection, and the subsequent emulsion treatment and drying steps.

[0153] Regarding step S1, the preparation of the pre-emulsion. Specifically, long-chain alkyl (meth) acrylate monomers are added to the reactants of the already mixed and reacted acrylic monomers and hydroxydopamine monomers together with a surfactant, and then deionized water is added to prepare the pre-emulsion.

[0154] By adding long-chain alkyl (meth) acrylate monomers, the polymer material can be given better softness, hydrophobicity and lubricity, which is crucial for the application of the negative electrode binder in the battery.

[0155] The addition of surfactants can improve the dispersibility of monomers in water, helping to form a stable pre-emulsion and providing a good basis for subsequent polymerization.

[0156] Regarding step S2: the polymerization reaction. Specifically, an initiator is added to the pre-emulsion and heated to 75-85°C under nitrogen protection for a period of time (e.g. 1h). During the incubation, vinyl siloxane monomers are added and incubated for a period of time (e.g. temperature 75-85°C, i.e. initiation temperature) (e.g. 0.5h).

[0157] The addition of the initiator can initiate the polymerization reaction, allowing chemical bonding between the monomers to form polymer chains. Nitrogen as a protective gas can prevent the adverse effects of oxygen in the air on the polymerization reaction, such as inhibiting the formation of free radicals or causing oxidation of the polymer. Incubation at a specific temperature range can ensure that the polymerization reaction proceeds at a faster rate, while avoiding side reactions caused by excessive temperature. The addition of vinyl siloxane monomers can introduce siloxane groups, enhancing the adhesion and weather resistance of the polymer, which has a positive impact on the application of the negative electrode binder in the battery.

[0158] Regarding step S3: emulsion post-treatment. Specifically, the emulsion obtained by polymerization is subjected to suction filtration and drying to obtain the negative electrode binder.

[0159] Suction filtration can remove water and unreacted monomers from the emulsion to obtain a pure polymer emulsion. The drying step can remove water from the emulsion to obtain a solid negative electrode binder. Through this step, a negative electrode binder with specific properties and morphology can be obtained to meet the requirements of battery production.

[0160] In summary, the preparation process can produce negative electrode adhesives with excellent performance and stability through precise step control and condition optimization, which is of great significance to improve the performance and stability of the battery.

[0161] By adopting the preparation method of the negative electrode adhesive provided in the embodiments of the present application, the negative electrode adhesive prepared can have stable composition and excellent performance. The preparation method ensures uniform mixing and efficient reaction of the components in the polymerization reaction through precise step control and condition optimization, thereby obtaining a negative electrode adhesive with excellent performance.

[0162] The negative electrode adhesive provided in the embodiments of the present application has the following performance:

[0163] Adhesion: The negative electrode adhesive prepared finally has excellent adhesion due to the introduction of acrylic monomers and hydroxydopamine monomers in the polymerization reaction.

[0164] Flexibility: The addition of long-chain alkyl (methyl) acrylate monomers gives the negative electrode adhesive good flexibility, enabling it to adapt to the volume change of the battery during charging and discharging, reducing the risk of battery failure caused by material expansion or contraction.

[0165] Weather resistance: The introduction of vinyl siloxane monomers enhances the weather resistance of the negative electrode adhesive, enabling it to maintain stable performance under different environmental conditions and prolong the service life of the battery.

[0166] According to a fourth embodiment of the present application, a negative electrode sheet is provided, which comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material and a conductive agent; the negative electrode active material layer is bonded to the negative electrode current collector by an adhesive; wherein the adhesive is the negative electrode adhesive composition or the negative electrode adhesive as described above.

[0167] The negative electrode sheet provided in the embodiments of the present application mainly consists of a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material and a conductive agent, and is firmly bonded to the negative electrode current collector by a specific adhesive, which is the negative electrode adhesive provided in the embodiments of the present application.

[0168] The negative electrode current collector is an important component of the battery negative electrode, which is responsible for collecting and conducting current. The negative electrode current collector material includes, for example, metals or alloys such as copper, nickel, etc.

[0169] Negative electrode active material: This is the main material for storing and releasing electric charge in the battery negative electrode, and the negative electrode active material includes, for example, graphite, silicon-based materials, etc.

[0170] Conductive agent: The role of the conductive agent is to improve the conductivity of the negative active material layer, ensure that the current can flow smoothly, and reduce the polarization phenomenon. The conductive agent includes, for example, carbon black, carbon nanotubes, and the like.

[0171] Negative electrode binder: The adhesion between the negative active material layer and the negative current collector is achieved by the negative electrode binder provided by the embodiments of the present application. Such a negative electrode binder not only has excellent adhesion performance, which can ensure the firm connection between the negative active material layer and the negative current collector, but also has good electrochemical stability and mechanical strength, which can maintain stable structure and performance during the charging and discharging process of the battery.

[0172] The embodiments of the present application provide a negative electrode sheet based on a specific negative electrode binder. By optimizing the adhesion mode and material selection between the negative active material layer and the negative current collector, the performance and stability of the battery can be significantly improved.

[0173] According to a fifth embodiment of the present application, an electric core is provided, which comprises: a positive electrode sheet, a negative electrode sheet and a separator; wherein the negative electrode sheet is the negative electrode sheet as described above.

[0174] According to the embodiments of the present application, a structure of an electric core is described, which mainly consists of a positive electrode sheet, a negative electrode sheet and a separator. The negative electrode sheet here specifically refers to the negative electrode sheet described before, which uses a specific negative electrode binder. This electric core design makes full use of the optimized negative electrode sheet to improve the overall performance of the electric core.

[0175] Since the negative electrode sheet uses the negative electrode binder provided by the embodiments of the present application, the optimization of the negative electrode binder ensures the firm connection between the negative active material layer and the negative current collector, reduces the interface resistance, and thus improves the charging and discharging efficiency and energy utilization rate of the electric core. In addition, the optimized negative electrode sheet also has improved mechanical strength and chemical stability, which helps to reduce the failure risk of the electric core during the charging and discharging process and improve the safety of the battery.

[0176] The electric core provided by the embodiments of the present application can adapt to different working environments and charging and discharging conditions, such as high temperature, low temperature, etc., and shows strong stability and reliability.

[0177] According to a sixth embodiment of the present application, a battery is provided, which comprises: a shell, an electric core and an electrolyte; wherein the electric core is the electric core as described above.

[0178] According to the embodiments of the present application, a structure of a battery is described, which consists of a shell, an electric core and an electrolyte. The electric core is the electric core described before, which contains a specific negative electrode sheet. This battery design aims to provide a safer and higher performance energy storage solution.

[0179] The application will be described in detail below with reference to specific embodiments.

[0180] Example 1

[0181] (1) The preparation method of the negative electrode binder is as follows:

[0182] In a 500 mL flask equipped with a glass conduit, a reflux condenser, a stirrer, and a thermometer, 50 parts by mass of acrylic acid and 90 parts by mass of hydroxydopamine monomer were mixed and reacted at 60°C for 1 h;

[0183] 30 parts by mass of acrylic acid-2-ethylhexyl ester (a long-chain alkyl (meth) acrylate monomer) was added as a monomer together with a surfactant to the above reaction vessel (500 mL flask), and deionized water was added to prepare a pre-emulsion;

[0184] Then, an initiator was added, and nitrogen gas was introduced as a protective gas. The temperature was heated to 80°C and maintained for 1 h. Then, 40 parts by mass of vinyl trimethoxysilane (a vinyl siloxane monomer) was added and maintained at 80°C (initiation temperature) for 0.5 h to obtain a white emulsion with a blue light;

[0185] Finally, the white powder product was obtained by filtration and vacuum drying at 60°C. The white powder product was the negative electrode binder.

[0186] (2) The preparation process of the negative electrode sheet is as follows:

[0187] First, the white powder product, i.e., the negative electrode binder, prepared above was dissolved in 50 wt% deionized water to form an aqueous dispersion with a slurry solid content of 0.8 wt%;

[0188] Then, 0.5 wt% of conductive carbon black Super P was added and stirred and dispersed for 1 h at a speed of 1200 rpm;

[0189] Ammonia water was added to adjust the pH to 7-7.5, and the stirring and dispersion was continued;

[0190] 0.7 wt% of hydroxymethyl cellulose CMC was added, and the stirring and dispersion was continued;

[0191] 48 wt% of graphite was added, and the stirring was continued for 3 h at a speed of 1000 rpm-1500 rpm;

[0192] A clean copper foil (current collector) was placed on an automatic coating machine, a work-shaped doctor blade was placed on it, a vacuum pump was turned on, and the copper foil was flattened using a dust-free paper. The speed of the coating machine was adjusted to 15 mm / s, and the stirred slurry was uniformly placed in front of the doctor blade. The coating operation was started to obtain a coated electrode sheet.

[0193] The obtained pole piece is transferred to the surface of a paperboard (or other flat plate), and then dried in a 60°C air drying oven for 15-30 minutes after the oven door is closed;

[0194] The baked pole piece is sequentially subjected to rolling and cutting to obtain a negative pole piece.

[0195] A part of the negative pole piece is soaked in an electrolyte, and then dried in a 60°C oven for 24 hours.

[0196] Cell winding: the pole pieces are stacked together in the order of positive pole piece-separator-negative pole piece, and then wound into a cell by an automatic winding device. After the finished pole piece is subjected to packaging, liquid injection, formation, aging and other steps, the following electrochemical performance test can be performed.

[0197] Example 2

[0198] This example 2 is basically the same as example 1, and the difference between the two is that in the preparation of the negative electrode binder, the mass fraction of hydroxydopamine monomer is adjusted from 90 parts to 160 parts, and the others remain unchanged. That is, compared with example 1, the amount of hydroxydopamine monomer is only increased in example 2.

[0199] Example 3

[0200] This example 3 is basically the same as example 1, and the difference between the two is that in the preparation of the negative electrode binder, the mass fraction of hydroxydopamine monomer is adjusted from 90 parts to 30 parts, and the others remain unchanged. That is, compared with example 1, the amount of hydroxydopamine monomer is greatly reduced in example 3, and the mass fraction of hydroxydopamine monomer is lower than the lower limit value 90 parts, which will reduce the viscosity, peel force and other properties of the negative electrode binder to some extent, which can be seen in Table 1 below.

[0201] Example 4

[0202] This example 4 is basically the same as example 1, and the difference between the two is that in the preparation of the negative electrode binder, the mass fraction of hydroxydopamine monomer is adjusted from 90 parts to 120 parts, and the others remain unchanged. That is, compared with example 1, the amount of hydroxydopamine monomer is increased in example 4. It should be noted that the amount of hydroxydopamine monomer in this example 4 is more preferred, so it has a good effect on the viscosity and peel force of the negative electrode binder, which can be seen in Table 1 below.

[0203] Example 5

[0204] This example 5 is basically the same as example 1, the difference between the two is that, in the preparation of the negative electrode binder, the mass fraction of vinyl trimethoxysilane is adjusted from 40 parts to 80 parts, and the rest is unchanged. That is, compared with example 1, the amount of vinyl trimethoxysilane is increased in example 5, and the mass fraction of vinyl trimethoxysilane is higher than the upper limit value of 60 parts, which will reduce the viscosity, peel strength and other properties of the final negative electrode binder to some extent, see table 1 below.

[0205] Example 6

[0206] This example 6 is basically the same as example 1, the difference between the two is that, in the preparation of the negative electrode binder, the mass fraction of vinyl trimethoxysilane is adjusted from 40 parts to 10 parts, and the rest is unchanged. That is, compared with example 1, the amount of vinyl trimethoxysilane is reduced in example 6, and the mass fraction of vinyl trimethoxysilane is lower than the lower limit value of 30 parts, which will reduce the viscosity, peel strength and other properties of the final negative electrode binder to some extent, see table 1 below.

[0207] Example 7

[0208] This example 7 is basically the same as example 1, the difference between the two is that, in the preparation of the negative electrode binder, the mass fraction of vinyl trimethoxysilane is adjusted from 40 parts to 60 parts, and the rest is unchanged. That is, compared with example 1, the amount of vinyl trimethoxysilane is increased in example 7, and the mass fraction of vinyl trimethoxysilane is reasonable (in the range of 30 parts to 60 parts), compared with example 5 and example 6, which will improve the viscosity, peel strength and other properties of the negative electrode binder to some extent, see table 1 below.

[0209] Example 8

[0210] This example 8 is basically the same as example 1, the difference between the two is that, in the preparation of the negative electrode binder, the mass fraction of vinyl trimethoxysilane is adjusted from 40 parts to 30 parts, and the rest is unchanged. That is, compared with example 1, the amount of vinyl trimethoxysilane is reduced in example 8, but since the mass fraction of vinyl trimethoxysilane is reasonable (in the range of 30 parts to 60 parts), compared with example 5 and example 6, it will also improve the viscosity, peel strength and other properties of the negative electrode binder to some extent, see table 1 below.

[0211] Example 9

[0212] This Example 9 is substantially the same as Example 1, except that in the preparation of the negative electrode binder, 2-ethylhexyl acrylate is replaced by lauryl methacrylate. That is, the long-chain alkyl (meth)acrylate monomer in Example 9 is different from that in Example 1.

[0213] Example 10

[0214] This Example 10 is substantially the same as Example 1, except that in the preparation of the negative electrode binder, acrylic acid is replaced by methacrylic acid. That is, the acrylic monomer in Example 10 is different from the acrylic monomer in Example 1.

[0215] Comparative Example 1

[0216] Comparative Example 1 is substantially the same as Example 1, except that no hydroxydopamine monomer is added in the reaction.

[0217] Comparative Example 2

[0218] Comparative Example 2 is substantially the same as Example 1, except that no vinyl siloxane monomer is added in the reaction.

[0219] It should be noted that the performance of the negative electrode binder obtained in Examples 1 to 10, and Comparative Examples 1 and 2 described above can be seen from Table 1 below.

[0220] The test methods and results of Examples 1 to 10, and Comparative Examples 1 and 2 described above are as follows:

[0221] (1) Peel strength test, GB / T2791-1995 was used to test the peel strength of the negative electrode sheet.

[0222] (2) Viscosity test, GB / T2794-2013 was used to test the viscosity.

[0223] (3) Capacity retention rate test, the charge and discharge rates were both 1C, the average of the first three discharge capacities after activating the battery with a small current was taken as the initial capacity, and the discharge capacity after 200 cycles was taken as the post-cycle capacity. Capacity retention rate = post-cycle capacity / initial capacity * 100%.

[0224] From the viscosity and peel strength tests of Examples 1 to 4 and Comparative Example 1, it can be seen that the addition of hydroxydopamine monomer has a great influence on the viscosity of the polymer and the peel strength of the negative electrode slurry, and the more the amount of hydroxydopamine monomer, the greater the peel strength.

[0225] From the cycle capacity retention rates of Example 1 to Example 4, Comparative Example 1, it can be seen that when the amount of hydroxydopamine monomer is 90 to 120 parts by mass, the adhesion to the negative active material and the influence on the internal resistance are in the best state. The possible reason is that although the hydroxydopamine monomer can improve the adhesion between the negative current collector and the negative active material and between the negative active materials, the hydroxydopamine monomer can increase the internal resistance, which is not conducive to the transmission of lithium ions and electrons, so that too much hydroxydopamine monomer can increase the internal resistance, and too little hydroxydopamine monomer can reduce the adhesion of the negative electrode binder, and the adhesion to the negative active material is insufficient. Therefore, the optimal amount of hydroxydopamine monomer is 90 to 150 parts by mass, and the best amount is 90 to 120 parts by mass.

[0226] From Example 1, Example 5, Example 6, Example 7, Example 8 and Comparative Example 2, it can be seen that, compared with Comparative Example 2 without adding vinyl siloxane, the peel strength of the electrode plate after electrolyte immersion is significantly increased, and the adhesion of the negative active material to the negative current collector is significantly enhanced. The peel strength of the electrode plate after electrolyte immersion is: Example 1 and Example 8 have the same peel strength, which is greater than Example 7, the peel strength of Example 7 is greater than Example 5, the peel strength of Example 5 is greater than Example 6, and the peel strength of Example 6 is greater than Comparative Example 2. It can also be seen that too much vinyl siloxane does not significantly improve the peel strength of the negative electrode after electrolyte immersion, but rather reduces the peel strength. The possible reason is that too much vinyl siloxane can increase the structural strength of the negative electrode binder, reduce the flexibility, and make the texture brittle, which ultimately reduces the peel strength of the negative electrode binder.

[0227] From Example 1, Example 5, Example 6, Example 7, Example 8 and Comparative Example 2, it can be seen that, compared with Comparative Example 2 without adding vinyl siloxane, the peel strength of the electrode plate after electrolyte immersion is significantly increased, and the adhesion of the negative active material to the negative current collector is significantly enhanced. The peel strength of the electrode plate after electrolyte immersion is: Example 1 and Example 8 have the same peel strength, which is greater than Example 7, the peel strength of Example 7 is greater than Example 5, the peel strength of Example 5 is greater than Example 6, and the peel strength of Example 6 is greater than Comparative Example 2. It can also be seen that too much vinyl siloxane does not significantly improve the peel strength of the negative electrode after electrolyte immersion, but rather reduces the peel strength. The possible reason is that too much vinyl siloxane can increase the structural strength of the negative electrode binder, reduce the flexibility, and make the texture brittle, which ultimately reduces the peel strength of the negative electrode binder.

[0228] Table 1 below shows the slurry viscosity and peel strength test results of each example and each comparative example.

[0229] Table 1

[0230] The following Table 2 shows the capacity retention test results of each example and each control example.

[0231] Table 2

[0232] In general, according to the components and amounts of the negative electrode binder provided in the embodiments of the present application, the prepared negative electrode binder has better performance in viscosity, peel strength, etc.

[0233] In the above embodiments, the focus is on the differences between the various embodiments, and the different optimization features between the various embodiments can be combined to form a better embodiment as long as they are not contradictory. In view of the brevity of the writing, it will not be repeated here.

[0234] Although some specific embodiments of the present application have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A negative electrode binder composition, characterized in that, The negative electrode binder composition comprises the following components: Acrylic monomers, hydroxydopamine monomers, long-chain alkyl (meth)acrylate monomers, and vinylsiloxane monomers.

2. The negative electrode binder composition according to claim 1, characterized in that, The mass fractions of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth)acrylate monomer, and the vinylsiloxane monomer are as follows: The acrylic monomer is in the range of 50 to 100 parts; The hydroxydopamine monomer is in the range of 90 to 180 parts; The long-chain alkyl (meth)acrylate monomer is 20 to 40 parts; The vinylsiloxane monomer is in the range of 30 to 60 parts.

3. The negative electrode binder composition according to claim 1 or 2, characterized in that, The negative electrode binder composition also includes an initiator and a surfactant; The initiator is used in an amount of 0.1 wt% to 1 wt% of the total mass of the acrylic monomers, the hydroxydopamine monomers, the long-chain alkyl (meth)acrylate monomers, and the vinylsiloxane monomers; and / or, The amount of the surfactant used is 0.5 wt% to 1 wt% of the total mass of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth) acrylate monomer and the vinyl siloxane monomer.

4. The negative electrode binder composition according to any one of claims 1-3, characterized in that, The acrylic monomers include at least one of acrylic acid and methacrylic acid; The long-chain alkyl (meth)acrylate monomers include at least one of lauryl methacrylate, tetradecyl methacrylate, stearate methacrylate, and 2-ethylhexyl acrylate.

5. The negative electrode binder composition according to any one of claims 1-4, characterized in that, The vinylsiloxane monomers include at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

6. The negative electrode binder composition according to claim 3, characterized in that, The initiator is at least one of potassium persulfate, ammonium persulfate, and sodium persulfate.

7. The negative electrode binder composition according to claim 3, characterized in that, The surfactant includes at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium dioctyl succinate sulfonate, p-nonylphenol polyoxyethylene ether, and p-octylphenol polyoxyethylene ether.

8. A negative electrode binder, characterized in that, The chemical structural formula of the negative electrode binder is as follows: In the formula: x, y, z represent quantities, x, y, z are positive integers, and the ratio of x, y, z is 5~10:1~2:2~4.

9. A method for preparing a negative electrode binder, characterized in that, include: Acrylic monomers and hydroxydopamine monomers are mixed and reacted to obtain the reactants; Long-chain alkyl (meth)acrylate monomers and vinyl siloxane monomers are added to the reactants, and then a polymerization reaction is carried out in the presence of surfactants and initiators to obtain a negative electrode binder.

10. The method for preparing the negative electrode binder according to claim 9, characterized in that, The mass ratio of the hydroxydopamine monomer to the vinylsiloxane monomer is 1.5 to 6:

1.

11. The method for preparing the negative electrode binder according to claim 9 or 10, characterized in that, The reaction of the acrylic monomer and the hydroxydopamine monomer yields reactants including: The acrylic monomer and the hydroxydopamine monomer are mixed and reacted at 50°C to 70°C for 1 to 2 hours.

12. The method for preparing the negative electrode binder according to any one of claims 9-11, characterized in that, The addition of long-chain alkyl (meth)acrylate monomers and vinyl siloxane monomers to the reactants, followed by polymerization in the presence of surfactants and initiators, yields a negative electrode binder, comprising: The long-chain alkyl (meth) acrylate monomer and the surfactant are added to the reactant obtained by mixing and reacting the acrylic monomer and the hydroxydopamine monomer, and deionized water is added to prepare a pre-emulsion. The initiator is added to the pre-emulsion, nitrogen gas is introduced as a protective gas, the temperature is raised to 75℃~85℃ and then kept at this temperature, then the vinylsiloxane monomer is added and kept at 75℃~85℃ to obtain the emulsion; wherein the total time of the two holding times is 1h~3h. The emulsion is filtered and dried to obtain the negative electrode binder.

13. A negative electrode sheet, characterized in that, The device includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material and a conductive agent. The negative electrode active material layer is bonded to the negative electrode current collector by an adhesive. The adhesive used is the negative electrode adhesive composition as described in any one of claims 1-7 or the negative electrode adhesive as described in claim 8.

14. A battery cell, characterized in that, include: A positive electrode, a negative electrode, and a separator; wherein the negative electrode is the negative electrode as described in claim 13.

15. A battery, characterized in that, Includes the casing, battery cell, and electrolyte; The battery cell is the battery cell as described in claim 14.

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