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

Abstract

This application discloses a negative electrode binder composition, a negative electrode binder and its preparation method, a negative electrode sheet, a battery cell and a battery; wherein, the negative electrode binder composition includes the following components: acrylic monomers, hydroxydopamine monomers, long-chain alkyl (meth)acrylate monomers and vinylsiloxane monomers.

Description

Technical Field

[0001] This application belongs to the field of battery technology. Specifically, this application relates to a negative electrode binder composition, a negative electrode binder and its preparation method, a negative electrode sheet, a battery cell, and a battery. Background Technology

[0002] With the rapid development of electronic technology, lithium-ion batteries have been widely used in fields such as electric vehicles and smartphones due to their advantages such as high energy density, long life and environmental friendliness.

[0003] However, when batteries operate at high temperatures, traditional SBR (styrene-butadiene rubber latex) and PAA (polyacrylic acid) negative electrode binders exhibit insufficient adhesion in the electrolyte and are prone to aging and embrittlement. This can lead to the cracking and powdering of the negative electrode material, causing it to detach from the current collector (such as the copper sheet), severely reducing the battery's cycle life. Therefore, developing negative electrode binders with strong adhesion and stability in the electrolyte is of great significance for improving the cycle life of lithium-ion batteries. Summary of the Invention

[0004] The purpose of this application is to provide a new technical solution for a negative electrode binder composition, a negative electrode binder and its preparation method, a negative electrode sheet, a battery cell and a battery.

[0005] According to a first aspect of this application, embodiments of this application provide a negative electrode binder composition, the negative electrode binder composition comprising the following components:

[0006] Acrylic monomers, hydroxydopamine monomers, long-chain alkyl (meth)acrylate monomers, and vinylsiloxane monomers.

[0007] Optionally, the mass fractions of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth)acrylate monomer, and the vinylsiloxane monomer are as follows:

[0008] The acrylic monomer is in the amount of 50 to 100 parts;

[0009] The hydroxydopamine monomer is present in quantities of 90–180 parts;

[0010] The long-chain alkyl (meth)acrylate monomer is 20-40 parts;

[0011] The vinylsiloxane monomer is 30 to 60 parts.

[0012] Optionally, the negative electrode binder composition further includes an initiator and a surfactant;

[0013] 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,

[0014] 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.

[0015] Optionally, the acrylic monomer includes at least one of acrylic acid and methacrylic acid;

[0016] The long-chain alkyl (meth)acrylate monomers include at least one of lauryl methacrylate, tetradecyl methacrylate, stearate methacrylate, and 2-ethylhexyl acrylate.

[0017] Optionally, the vinylsiloxane monomers include at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0018] Optionally, the initiator is at least one selected from potassium persulfate, ammonium persulfate, and sodium persulfate.

[0019] Optionally, 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.

[0020] According to a second aspect of this application, embodiments of this application provide a negative electrode binder, the chemical structural formula of which is as follows:

[0021]

[0022] 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.

[0023] According to a third aspect of this application, embodiments of this application provide a method for preparing a negative electrode binder, comprising:

[0024] Acrylic monomers and hydroxydopamine monomers are mixed and reacted to obtain the reactants;

[0025] 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.

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

[0027] Optionally, the reaction of the acrylic monomer and the hydroxydopamine monomer to obtain the reactants includes:

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

[0029] Optionally, the addition of long-chain alkyl (meth)acrylate monomers and vinyl siloxane monomers to the reactants, followed by polymerization in the presence of a surfactant and an initiator, yields a negative electrode binder, comprising:

[0030] 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.

[0031] 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, the vinyl siloxane monomer is added and the temperature is kept at 75℃~85℃ to obtain the emulsion; wherein the total time of the two holding times is 1~3h.

[0032] The emulsion is filtered and dried to obtain the negative electrode binder.

[0033] According to a fourth aspect of this application, an embodiment of this application provides a negative electrode sheet, the negative electrode sheet comprising 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;

[0034] The adhesive used is the negative electrode adhesive composition as described in the first aspect or the negative electrode adhesive as described in the second aspect.

[0035] According to a fifth aspect of this application, an embodiment of this application provides a battery cell, the battery cell comprising: a positive electrode, a negative electrode, and a separator;

[0036] The negative electrode sheet is the negative electrode sheet as described in the fourth aspect.

[0037] According to a sixth aspect of this application, an embodiment of this application provides a battery, the battery including a casing, a cell, and an electrolyte; wherein the cell is the cell described in the fifth aspect.

[0038] One beneficial effect of the embodiments of this application is that:

[0039] The negative electrode binder composition proposed in the embodiments of this application comprises at least four monomers. Specifically, by modifying a copolymer synthesized from acrylic acid and long-chain alkyl (meth)acrylate monomers with hydroxydopamine and vinylsiloxane monomers, a negative electrode binder with excellent adhesion, chemical stability, and high and low temperature resistance can be prepared. The ortho-dihydroxyl groups in hydroxydopamine can form strong hydrogen bonds, which greatly enhances the adhesion of the prepared negative electrode binder to the current collector. By introducing vinylsiloxane monomers 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 and CO bonds, resulting in higher stability of the modified binder when facing chemical environments such as electrolytes. Furthermore, the presence of three alkoxy groups attached to the silicon atoms bonded to carbon atoms makes the molecular chain more stable and less prone to rotation, further enhancing the chemical stability and structural strength of the formed negative electrode binder.

[0040] Other features and advantages of this application will become clear from the following detailed description of exemplary embodiments. Detailed Implementation

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

[0042] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0043] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0044] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0045] The following describes in detail the negative electrode binder composition, negative electrode binder and its preparation method, negative electrode sheet, battery cell and battery provided in the embodiments of this application.

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

[0047] Acrylic monomers, hydroxydopamine monomers, long-chain alkyl (meth)acrylate monomers, and vinylsiloxane monomers.

[0048] The negative electrode binder composition provided in the embodiments of this application mainly involves the preparation of a negative electrode binder with specific properties by using different monomers, namely the four monomers mentioned above: acrylic monomers, hydroxydopamine monomers, long-chain alkyl (meth)acrylate monomers, and vinylsiloxane monomers, through specific chemical reaction steps.

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

[0050] The first step involves mixing and reacting acrylic monomers with hydroxydopamine monomers. Acrylic monomers (such as acrylic acid and methacrylic acid) are mixed with hydroxydopamine monomers and then reacted. The purpose of this step is to replace the carboxyl hydroxyl groups in the adhesive with the ortho-dihydroxyl groups in the hydroxydopamine, thereby helping to enhance the adhesion of the adhesive to the current collector.

[0051] The second step involves adding long-chain alkyl (meth)acrylate monomers and vinyl siloxane monomers. Building upon the first step reaction described above, the addition of long-chain alkyl (meth)acrylate monomers and vinyl siloxane monomers aims to further improve the chemical stability, aging resistance, high and low temperature resistance, and solvent resistance of the formed negative electrode binder.

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

[0053] According to the negative electrode binder provided in this application, the hydroxydopamine used exhibits excellent adhesion due to its unique ortho- and tho-dihydroxyl structure, which stems from its ability to form strong hydrogen bonds. In the preparation process of the negative electrode binder, the ortho- and tho-dihydroxyl groups of hydroxydopamine are used to replace the original carboxyl hydroxyl groups, significantly enhancing the adhesion of the negative electrode binder to the current collector and further improving the stability and reliability of the battery. In other words, the introduction of hydroxydopamine significantly enhances the adhesion of the final negative electrode binder to, for example, the negative electrode current collector, helping to prevent the detachment of the negative electrode material during charging and discharging.

[0054] Furthermore, organosilicon modification using vinylsiloxane monomers enhances the chemical stability of the negative electrode binder. This is because the strength of the Si-O bond is significantly higher than that of traditional C-C and CO bonds, resulting in a negative electrode binder exhibiting greater stability in complex chemical environments such as electrolytes. Notably, the silicon atom bonded to the carbon atom is attached to three alkoxy groups. This structure makes the molecular chain more stable and less prone to rotation, further enhancing the tensile and structural strength of the negative electrode binder. Simultaneously, this organosilicon modification also endows the negative electrode binder with excellent aging resistance, high and low temperature resistance, and solvent resistance. It maintains stable performance even under extreme operating environments, particularly demonstrating remarkable durability against electrolytes at high temperatures.

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

[0056] The negative electrode binder solution provided in this application differs significantly from traditional polyacrylic acid (PAA) synthesized solely from acrylic acid and its esters. The technical solution provided in this application utilizes hydroxydopamine monomers and vinylsiloxane monomers to modify acrylic acid and its long-chain esters, thereby endowing the final negative electrode binder with new properties and characteristics. This method not only breaks through traditional constraints but also achieves significant improvements in the adhesion, chemical stability, aging resistance, high and low temperature resistance, and solvent resistance of the negative electrode binder, paving new avenues for the optimization of negative electrode materials and the improvement of battery performance.

[0057] According to the negative electrode binder composition provided in the embodiments of this application, its components include at least four monomers. Specifically, by modifying copolymers synthesized from acrylic monomers and long-chain alkyl (meth)acrylate monomers with hydroxydopamine and vinylsiloxane monomers, a negative electrode binder with excellent adhesion, chemical stability, and high and low temperature resistance can be prepared. The ortho-dihydroxyl groups in hydroxydopamine can form strong hydrogen bonds, which greatly enhances the adhesion of the prepared negative electrode binder to the current collector. By introducing vinylsiloxane monomers 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 and CO bonds, resulting in higher stability of the modified binder when facing chemical environments such as electrolytes. Furthermore, because three alkoxy groups are attached to the silicon atoms bonded to carbon atoms, 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 this application, the mass parts of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth)acrylate monomer, and the vinylsiloxane monomer are as follows: 50-100 parts of the acrylic monomer, 90-180 parts of the hydroxydopamine monomer, 20-40 parts of the long-chain alkyl (meth)acrylate monomer, and 30-60 parts of the vinylsiloxane monomer.

[0059] According to an example of this application, the mass fraction ranges of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth)acrylate monomer, and the vinylsiloxane monomer in the raw materials of the negative electrode binder composition are described.

[0060] The mass fraction of acrylic monomers is 50–100 parts. Acrylic monomers are the basic raw materials for preparing negative electrode binders, providing the basic structure and properties of the negative electrode binder. Within this range, the amount of acrylic monomers is sufficient to ensure the basic properties of the binder, while also allowing for some adjustment to meet different application requirements.

[0061] The mass fraction of hydroxydopamine monomer is 90–180 parts. As a modifier, the high content of hydroxydopamine monomer (relative to acrylic monomers) is intended to significantly enhance the adhesion of the final negative electrode binder. In this range of 90–180 parts, when combined with acrylic monomers, the adhesive properties of hydroxydopamine are fully demonstrated, ensuring a strong bond between the negative electrode active material and the negative electrode current collector, without causing other performance problems due to excessive content.

[0062] The long-chain alkyl (meth)acrylate monomer is present in a mass fraction of 20–40 parts. The addition of the long-chain alkyl (meth)acrylate monomer improves the flexibility and processability of the final negative electrode binder, and also helps to improve the compatibility of the negative electrode binder with the negative electrode active material and the negative electrode current collector. The content within this range ensures the improvement of these properties without negatively impacting the overall performance.

[0063] The vinylsiloxane monomers are present in a mass fraction of 30–60 parts. The addition of vinylsiloxane monomers significantly improves the chemical stability, aging resistance, high and low temperature resistance, and solvent resistance of the final negative electrode binder. This range of content, combined with the content of other monomers, ensures the improvement of these properties without increasing costs or reducing other properties due to excessively high content.

[0064] Based on the combined mass proportions of the above components, this formulation can produce a negative electrode binder with excellent adhesion, chemical stability, aging resistance, high and low temperature resistance, and solvent resistance. This binder not only ensures a strong connection between the negative electrode active material and the negative electrode current collector, but also improves the stability and reliability of batteries using this negative electrode sheet, extending the battery's lifespan.

[0065] More preferably, the mass proportions of the acrylic monomer, the hydroxydopamine monomer, the long-chain alkyl (meth)acrylate monomer, and the vinylsiloxane monomer are as follows:

[0066] The acrylic monomer is 50-100 parts, the hydroxydopamine monomer is 90-120 parts, the long-chain alkyl (meth)acrylate monomer is 20-40 parts, and the vinylsiloxane monomer is 40-50 parts.

[0067] The aforementioned preferred formulation provides a more precise and efficient formulation for the preparation of the negative electrode binder. Compared to the examples described above, the amounts of hydroxydopamine monomer and vinylsiloxane monomers have been further optimized. Specifically:

[0068] The preferred mass fraction of hydroxydopamine monomer is 90–120 parts. Optimizing the addition of hydroxydopamine monomer can enhance the adhesion properties of the final negative electrode binder. Within this range, its content is sufficient to exert the strong adhesion effect of the ortho-dihydroxyl group without causing a decline in other properties due to excessive amount, and it can also reduce production costs.

[0069] The vinyl siloxane monomer is present in a mass fraction of 40–50 parts. Optimizing the addition of vinyl siloxane monomers improves the chemical stability, aging resistance, high and low temperature resistance, and solvent resistance of the negative electrode binder. In particular, controlling the mass fraction of vinyl siloxane monomers to 40–50 parts maintains a preferred mass ratio of 1.8–3:1 to hydroxydopamine monomers. This preferred ratio allows the binder to maintain high adhesion while also possessing excellent stability and durability.

[0070] It should be noted that increasing the mass fraction of vinylsiloxane monomers, such as to more than 60 parts, or decreasing the mass fraction of vinylsiloxane monomers, such as to less than 30 parts, will lead to a decrease in the viscosity or peel strength of the formed negative electrode binder.

[0071] The optimized mass fraction range of each monomer provided in this application example can bring the following technical effects:

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

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

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

[0075] (4) Balance of comprehensive performance: While maintaining high adhesion, this optimization scheme also focuses on the balance of other properties, such as chemical stability and aging resistance, providing strong support for the preparation of high-performance negative electrode binders.

[0076] In some examples of this application, the negative electrode binder composition further includes an initiator, the amount of which 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 vinylsiloxane monomer.

[0077] Initiators play a crucial role in initiating or launching polymerization processes, primarily converting monomers into polymers. In the technical solutions provided in this application, the initiator plays a vital role in the polymerization reactions of the acrylic monomers, the hydroxydopamine monomers, the long-chain alkyl (meth)acrylate monomers, and the vinylsiloxane monomers.

[0078] (1) Initiating the polymerization process: The initiator can decompose into active intermediates such as free radicals, cations, or anions when heated. These active intermediates can attack monomer molecules, thereby initiating the polymerization process. In this application, an appropriate amount of initiator can ensure the smooth progress of the polymerization reaction and the formation of polymer chains.

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

[0080] (3) The selection and use of initiators not only affect the polymerization reaction but also the performance of the final product. In this application, optimizing the amount of initiator helps to improve the adhesion, chemical stability, and other properties of the negative electrode binder.

[0081] In some examples of this application, the composition of the negative electrode binder further includes a surfactant, the amount of which 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 vinylsiloxane monomer.

[0082] In the examples of this application, the surfactant functions as follows:

[0083] Surfactants can interact with negative electrode binder molecules to form stronger chemical bonds, which helps improve the adhesion and bonding strength of the negative electrode binder. This is especially important in the preparation of negative electrode binders because it ensures a strong bond between the negative electrode material and the current collector.

[0084] Surfactants can improve emulsion stability. Binders often contain impurities such as fillers and additives, which can easily lead to stratification and precipitation. The role of surfactants is to disperse these impurities in the aqueous phase, forming 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 final negative electrode binder. By adjusting the amount of surfactant, the binding properties and functions of the negative electrode can be customized to meet different application requirements.

[0086] In some examples of this application, the acrylic monomers include at least one of acrylic acid and methacrylic acid.

[0087] In some examples of this application, the long-chain alkyl (meth)acrylate monomers include at least one of lauryl methacrylate, tetradecyl methacrylate, stearate methacrylate, and 2-ethylhexyl acrylate.

[0088] Based on the examples provided in this application, the specific types of acrylic monomers and long-chain alkyl (meth)acrylate monomers used are further described.

[0089] The acrylic monomers include, 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] Acrylic acid is an unsaturated carboxylic acid with two functional groups: a double bond and a carboxyl group. It can copolymerize with a variety of monomers. Acrylic polymers exhibit good adhesion, film-forming properties, and water resistance.

[0091] Methacrylic acid is a methyl derivative of acrylic acid, and its polymers have higher hardness and weather resistance than acrylic acid polymers.

[0092] It should be noted that, in addition to acrylic acid or methacrylic acid as described above, other types of acrylic acid may also be used, and this application does not impose any restrictions on this.

[0093] The long-chain alkyl (meth)acrylate monomers include at least one selected from lauryl methacrylate, tetradecyl methacrylate, stearate methacrylate, and 2-ethylhexyl acrylate. These monomers contain long-chain alkyl groups, which can provide the polymer with excellent hydrophobicity, softness, and lubricity.

[0094] Lauryl methacrylate: Lauryl is a C12 long-chain alkyl group. Polymers of lauryl methacrylate have good flexibility and hydrophobicity.

[0095] Tetradecyl methacrylate: It is a C14 long-chain alkyl group. Its polymers have longer alkyl chains than lauryl methacrylate polymers, and therefore have better hydrophobicity and flexibility.

[0096] Stearate methacrylate: The stearyl group is a C18 long-chain alkyl group. Polymers of stearate methacrylate have excellent hydrophobicity, softness and lubricity.

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

[0098] According to the example provided in this application, the acrylic monomer is at least one of acrylic acid and methacrylic acid, which enables the prepared negative electrode binder to have excellent adhesion and film-forming properties.

[0099] The long-chain alkyl (meth)acrylate monomers provided according to the examples in this application include at least one selected from lauryl methacrylate, tetradecyl methacrylate, stearate methacrylate, and 2-ethylhexyl acrylate. The introduction of long-chain alkyl (meth)acrylate monomers provides the polymer with good flexibility and hydrophobicity, enabling the polymer material to maintain a certain mechanical strength while exhibiting excellent water resistance and flexibility.

[0100] In some examples of this application, the vinylsiloxane monomers include at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0101] Monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltriisopropoxysilane possess excellent reactivity and crosslinking ability. They can undergo effective copolymerization reactions with acrylic monomers, hydroxydopamine monomers, and long-chain alkyl (meth)acrylate monomers to form polymers with superior properties. These polymers not only exhibit good adhesion and mechanical strength but also possess excellent weather resistance, chemical corrosion resistance, and heat resistance.

[0102] γ-Methacryloxypropyltrimethoxysilane is a silane monomer with acryloyloxy reactivity. It can improve the mechanical properties of composite materials and enhance the compatibility between inorganic fillers and polymers.

[0103] The aforementioned vinylsiloxane monomers can copolymerize with other monomers to form polymers with excellent adhesion and mechanical strength, ensuring that the product maintains stable performance during use.

[0104] The various vinyl siloxane monomers mentioned above endow polymers with good weather resistance and chemical corrosion resistance, enabling products to be used for a long time in harsh environments without damage.

[0105] The aforementioned vinylsiloxane monomers can significantly improve the heat resistance and aging resistance of the final negative electrode binder.

[0106] Silane monomers with acryloyloxypropyltrimethoxysilane and other silanes with acryloyloxy reactivity can improve the compatibility between inorganic fillers and polymers and enhance the performance of composite materials.

[0107] In some examples of this 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 during a polymerization reaction, thereby initiating monomer polymerization. In the examples described in this application, initiators include one or more of potassium persulfate, ammonium persulfate, and sodium persulfate. These initiators are all persulfate compounds that decompose under heat or light to generate sulfate free radicals, thereby initiating monomer polymerization. These initiators exhibit high initiation efficiency and stability and can be used over a wide temperature and pH range. By selecting a suitable initiator and adjusting its dosage, the polymerization rate and molecular weight distribution of the polymer can be controlled, thereby obtaining polymers with specific properties.

[0109] In polymerization reactions, initiators are typically used in small quantities, but they have a significant impact on the polymerization process and the performance of the final product.

[0110] In some examples of this application, 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.

[0111] Surfactants are substances that can significantly reduce the surface tension of solvents. The surfactants mentioned in the examples of this application include one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate.

[0112] Sodium dodecyl sulfate (SDS): a common anionic surfactant with good detergency and emulsifying abilities.

[0113] Sodium dodecyl sulfonate (also known as sodium lauryl sulfonate): Unlike SDS, it is also an anionic surfactant.

[0114] Sodium dodecylbenzenesulfonate (SDBS): This is another anionic surfactant with good stability and biodegradability.

[0115] Sodium dioctyl succinate sulfonate: can be used as a cosolvent.

[0116] p-Nonylphenol polyoxyethylene ether and p-octylphenol polyoxyethylene ether: These two are polyoxyethylene ether derivatives used as nonionic surfactants, and have good emulsifying, dispersing and solubilizing abilities.

[0117] The surfactants mentioned above can act as emulsifiers, dispersants, and solubilizers in polymerization reactions, helping to improve the stability and uniformity of the polymerization system. In the final negative electrode binder, they can impart specific surface properties to the material, such as wettability, emulsification, and dispersibility, thereby meeting different application requirements.

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

[0119]

[0120] 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.

[0121] According to the chemical structural formula of the above-mentioned negative electrode binder, it contains methyl (CH3), methylene (CH2-), carbonyl (CO, C=O), amino (NH), hydroxyl (OH), and siloxane groups (Si—O—CH3). The negative electrode binder can be considered as an acrylic acid and ester polymer modified with hydroxydopamine and siloxane.

[0122] In the chemical structural formula 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 of materials with other materials. Acrylic acid and ester polymers are polymers with carbon-carbon double bonds (C=C) and carbonyl groups (C=O).

[0123] Hydroxydopamine is a hydroxylated derivative of dopamine. The chemical structure of the negative electrode binder shows the presence of multiple hydroxyl groups (OH), which is one of the notable characteristics of hydroxydopamine.

[0124] In negative electrode binders, hydroxydopamine interacts with siloxane-modified acrylic acid and ester polymers through its specific functional groups, enhancing the binder's adhesion and stability. Hydroxydopamine also possesses certain electrochemical activity, enabling it to participate in electrode reactions during charge and discharge processes, thereby improving the electrochemical performance of the negative electrode material.

[0125] The negative electrode binder provided in this application embodiment is prepared using the aforementioned negative electrode binder composition. It exhibits excellent adhesion and stability, effectively bonding the negative electrode active material to components such as the current collector, preventing the active material from detaching and pulverizing during charging and discharging. This material design helps improve the overall performance of the battery, such as cycle life, energy density, and safety. Simultaneously, its excellent adhesion and stability also contribute to improving the battery's reliability and durability.

[0126] According to a third embodiment of this application, a method for preparing a negative electrode binder is provided, wherein the negative electrode binder is the negative electrode binder described above.

[0127] The method for preparing the negative electrode binder provided in this application includes the following steps 1 and 2:

[0128] Step 1: Mix acrylic monomers and hydroxydopamine monomers and react them to obtain the reactants;

[0129] Step 2: Add long-chain alkyl (meth)acrylate monomers and vinyl siloxane monomers to the reactants, and then carry out a polymerization reaction in the presence of surfactants and initiators to obtain a negative electrode binder.

[0130] The prepared negative electrode binder is an acrylic acid and ester polymer modified with hydroxydopamine and siloxane, and the chemical structural formula of the negative electrode binder is as follows:

[0131]

[0132] 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.

[0133] According to the preparation method of the negative electrode binder proposed in the embodiments of this application, a negative electrode binder with excellent adhesion, chemical stability, and high and low temperature resistance is prepared by modifying a copolymer synthesized from acrylic acid and long-chain alkyl (meth)acrylate monomers with hydroxydopamine and vinylsiloxane monomers. The ortho-dihydroxyl groups in hydroxydopamine can form strong hydrogen bonds, which greatly enhances the adhesion of the formed negative electrode binder to the current collector. By introducing vinylsiloxane monomers 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 and CO bonds, resulting in higher stability of the modified binder when facing chemical environments such as electrolytes. Furthermore, the presence of three alkoxy groups attached to the silicon atoms bonded to carbon atoms makes the molecular chain more stable and less prone to rotation, further enhancing the chemical stability and structural strength of the formed negative electrode binder.

[0134] In some examples of this application, the mass ratio of the hydroxydopamine monomer to the vinylsiloxane monomer is 1.5 to 6:1.

[0135] In the raw materials for synthesizing the negative electrode binder, two modifiers are used: hydroxydopamine monomer and vinylsiloxane monomer, and the mass ratio of the hydroxydopamine monomer to the vinylsiloxane monomer is controlled at, for example, 1.5 to 6:1.

[0136] Hydroxydopamine monomers, with their unique ortho- and tho-dihydroxyl structures, provide strong adhesive properties. When the mass ratio of hydroxydopamine monomers to vinylsiloxane monomers is controlled within the range of 1.5 to 6:1, the adhesive properties of hydroxydopamine can be fully utilized without causing a decline in other properties due to excessive content.

[0137] The introduction of vinylsiloxane monomers enhances the chemical stability of the negative electrode binder through Si-O bonds. Within the aforementioned ratio range (i.e., 1.5 to 6:1), the content of vinylsiloxane monomers is sufficient to provide a stable Si-O bond structure without being excessive, thus avoiding potential negative impacts such as increased material costs or reduced processing performance.

[0138] The technical solution provided in this application utilizes a structure in which three alkoxy groups are attached to a silicon atom bonded to a carbon atom. This structure plays a crucial role in vinylsiloxane monomers, increasing the stability of the molecular chain and making it less prone to rotation, thereby enhancing the tensile and structural strength of the material. An appropriate content of vinylsiloxane monomers helps to fully realize this structure, improving the overall performance of the negative electrode binder.

[0139] According to the example provided in this application, the mass ratio of the hydroxydopamine monomer to the vinylsiloxane monomer is 1.5 to 6:1. Within this range, the content of the vinylsiloxane monomer is sufficient to impart excellent aging resistance, high and low temperature resistance, and solvent resistance to the negative electrode binder. These improved properties help the battery maintain stable performance under complex environments and extend its lifespan.

[0140] More preferably, the mass ratio of the hydroxydopamine monomer to the vinylsiloxane monomer is 1.8 to 3:1. This can further improve the adhesion and chemical stability of the formed negative electrode binder. Specifically:

[0141] Within the optimized ratio range of 1.8 to 3:1, the ortho-dihydroxyl structure of hydroxydopamine can more effectively exert its adhesive force, ensuring a strong connection between the negative electrode active material and the negative electrode current collector.

[0142] Within the optimized ratio range of 1.8 to 3:1, the amount of vinylsiloxane monomers introduced is more precisely controlled, resulting in a more uniform number and distribution of Si-O bonds, thereby further improving the chemical stability of the formed negative electrode binder. This precise control helps ensure that the negative electrode binder maintains stable performance under various chemical environments. Furthermore, the appropriate content of vinylsiloxane monomers not only ensures the full expression of the structure with three alkoxy groups attached to the silicon atom bonded to the carbon atom, but also makes this structure more uniformly distributed in the negative electrode binder. This uniform distribution helps improve tensile strength and structural strength, enabling the negative electrode binder to withstand greater external forces without easily breaking.

[0143] Furthermore, within the optimized ratio range of 1.8 to 3:1, the content of vinylsiloxane monomers was more precisely controlled, thereby ensuring that the formed negative electrode binder exhibits superior aging resistance, high and low temperature resistance, and solvent resistance. These significant improvements in performance contribute to enhancing the battery's adaptability and reliability in various complex environments.

[0144] By further precisely controlling the mass ratio of the hydroxydopamine and the vinylsiloxane monomers, the preferred solution provided in this application improves various performance indicators while achieving a balance in overall performance. This balance allows the negative electrode binder to maintain high performance while also possessing good stability and reliability, providing strong support for the preparation of high-performance negative electrode sheets.

[0145] In some examples of this application, the reaction of acrylic monomers with hydroxydopamine monomers to obtain reactants includes:

[0146] The acrylic monomer and the hydroxydopamine monomer are mixed and reacted at 50°C to 70°C for 1 to 2 hours.

[0147] According to this example, acrylic monomers (such as acrylic acid and / or methacrylic acid) are mixed with hydroxydopamine monomers and reacted. Specifically, the entire reaction temperature is 50°C to 70°C. This temperature range was chosen to ensure the reaction proceeds at a relatively fast rate while avoiding unnecessary side reactions or monomer decomposition caused by excessively high temperatures. Furthermore, the reaction time is 1 hour to 2 hours. The reaction time is chosen to ensure the reaction proceeds fully to achieve the desired degree of polymerization. Too short a time may lead to incomplete reaction, while too long a time may increase energy consumption and potentially trigger unnecessary side reactions.

[0148] Under selected reaction temperature and time conditions, the mixed reaction of acrylic monomers and hydroxydopamine monomers can proceed efficiently, ensuring the sufficiency of the reaction and the homogeneity of the products.

[0149] Furthermore, by precisely controlling reaction conditions, polymers with specific properties can be obtained. For example, the combination of acrylic monomers and hydroxydopamine monomers may endow polymers with unique adhesiveness and biocompatibility. In addition, selecting appropriate reaction conditions can reduce energy consumption and lower production costs. At the same time, avoiding excessively high temperatures can reduce unnecessary side reactions, which is beneficial to environmental protection.

[0150] In some examples of this application, the addition of long-chain alkyl (meth)acrylate monomers and vinyl siloxane monomers to the reactants, followed by polymerization in the presence of a surfactant and an initiator to obtain a negative electrode binder, includes the following steps S1 to S3:

[0151] Step S1: Add the long-chain alkyl (meth) acrylate monomer and the surfactant to the reactant obtained after mixing and reacting the acrylic monomer and the hydroxydopamine monomer, add deionized water, and prepare a pre-emulsion;

[0152] Step S2: Add the initiator to the pre-emulsion, introduce nitrogen as a protective gas, raise the temperature to 75℃~85℃ and keep it at that temperature, then add the vinylsiloxane monomer and continue to keep it at 75℃~85℃ to obtain the emulsion; wherein, the total time for the two heat treatments is 1~3h.

[0153] Step S3: Filter and dry the emulsion to obtain the negative electrode binder.

[0154] Based on steps S1 to S3 above, the polymerization reaction process for preparing the negative electrode binder is described, including mixing with long-chain alkyl (meth)acrylate monomers and vinyl siloxane monomers, preparation of pre-emulsion, addition of initiator, polymerization reaction under nitrogen protection, and subsequent emulsion treatment and drying steps.

[0155] Regarding step S1, namely the preparation of the pre-emulsion, specifically, long-chain alkyl (meth)acrylate monomers and surfactants are added to the reactants of the previously mixed and reacted acrylic monomers and hydroxydopamine monomers, followed by the addition of deionized water to prepare the pre-emulsion.

[0156] Adding long-chain alkyl (meth)acrylate monomers can impart better flexibility, hydrophobicity, and lubricity to polymer materials, which is crucial for the application of negative electrode binders in batteries.

[0157] The addition of surfactants can improve the dispersibility of monomers in water, help form a stable pre-emulsion, and provide a good foundation for subsequent polymerization reactions.

[0158] Regarding step S2: the polymerization reaction. Specifically, an initiator is added to the pre-emulsion, and the temperature is raised to 75℃~85℃ under nitrogen protection and held for a period of time (e.g., 1 hour). During the holding period, vinylsiloxane monomers are added and the temperature is continued to be maintained (e.g., 75℃~85℃, i.e., the initiation temperature) for a period of time (e.g., 0.5 hours).

[0159] The addition of an initiator can initiate the polymerization reaction, causing chemical bonding between monomers to form polymer chains. Nitrogen, as a protective gas, can prevent oxygen in the air from adversely affecting the polymerization reaction, such as inhibiting free radical formation or causing polymer oxidation. Maintaining a specific temperature range ensures that the polymerization reaction proceeds at a relatively fast rate while avoiding side reactions caused by excessively high temperatures. The addition of vinylsiloxane monomers can introduce siloxane groups, enhancing the polymer's adhesion and weather resistance, which has a positive impact on the application of negative electrode binders in batteries.

[0160] Regarding step S3: i.e., emulsion post-treatment. Specifically, the emulsion obtained from the polymerization reaction is filtered and dried to obtain the negative electrode binder.

[0161] Filtration removes water and unreacted monomers from the emulsion, yielding a pure polymer emulsion. The drying step removes water from the emulsion, resulting in a solid negative electrode binder. This process allows for the production of negative electrode binders with specific properties and morphologies, meeting the requirements of battery manufacturing.

[0162] In summary, this preparation process, through precise step control and condition optimization, can produce anode binders with excellent performance and stability, which is of great significance for improving battery performance and stability.

[0163] By employing the preparation method of the negative electrode binder provided in this application, it is possible to ensure that the prepared negative electrode binder has a stable composition and excellent performance. This preparation method, through precise step control and condition optimization, ensures uniform mixing and efficient reaction of each component in the polymerization reaction, thereby obtaining a negative electrode binder with superior performance.

[0164] The negative electrode binder provided in this application embodiment has the following properties:

[0165] Adhesion: Due to the introduction of acrylic monomers and hydroxydopamine monomers in the polymerization reaction, the final negative electrode binder has excellent adhesion.

[0166] Flexibility: The addition of long-chain alkyl (meth)acrylate monomers gives the negative electrode binder good flexibility, enabling it to adapt to volume changes during battery charging and discharging, reducing the risk of battery failure caused by material expansion or contraction.

[0167] Weather resistance: The introduction of vinylsiloxane monomers enhances the weather resistance of the negative electrode binder, enabling it to maintain stable performance under different environmental conditions and extend the battery's lifespan.

[0168] According to a fourth embodiment of this application, a negative electrode sheet is provided, the negative electrode sheet including 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 including 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 a negative electrode adhesive composition or a negative electrode adhesive as described above.

[0169] The negative electrode sheet provided in this 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 this application embodiment.

[0170] The negative electrode current collector is an important component of the battery's negative electrode, responsible for collecting and conducting current. Materials for the negative electrode current collector include metals or alloys such as copper and nickel.

[0171] Negative electrode active material: This is the main material used in the negative electrode of the battery to store and release charge. Negative electrode active materials include graphite, silicon-based materials, etc.

[0172] Conductive agents: The function of conductive agents is to improve the conductivity of the negative electrode active material layer, ensuring smooth current flow and reducing polarization. Examples of conductive agents include carbon black and carbon nanotubes.

[0173] Negative electrode binder: The bonding between the negative electrode active material layer and the negative electrode current collector is achieved by the negative electrode binder provided in the embodiments of this application. This negative electrode binder not only has excellent adhesion properties, ensuring a firm connection between the negative electrode active material layer and the negative electrode current collector, but also has good electrochemical stability and mechanical strength, enabling it to maintain stable structure and performance during battery charging and discharging.

[0174] This application provides a negative electrode sheet based on a specific negative electrode binder. By optimizing the bonding method and material selection between the negative electrode active material layer and the negative electrode current collector, the performance and stability of the battery can be significantly improved.

[0175] According to a fifth embodiment of this application, a battery cell is provided, the battery cell comprising: a positive electrode, a negative electrode, and a separator; wherein the negative electrode is the negative electrode as described above.

[0176] According to embodiments of this application, a battery cell structure is described, which mainly consists of a positive electrode, a negative electrode, and a separator. The negative electrode here specifically refers to the negative electrode described previously in this application that employs a specific negative electrode binder. This battery cell design fully utilizes the optimized negative electrode to improve the overall performance of the battery cell.

[0177] Because the negative electrode sheet uses the negative electrode binder provided in the embodiments of this application, the optimization of the negative electrode binder ensures a strong connection between the negative electrode active material layer and the negative electrode current collector, reducing interfacial resistance and thus improving the charge-discharge efficiency and energy utilization of the cell. Furthermore, the optimized negative electrode sheet also exhibits improved mechanical strength and chemical stability, which helps reduce the risk of cell failure during charge-discharge processes and improves battery safety.

[0178] The battery cell provided in this application embodiment can adapt to different working environments and charging / discharging conditions, such as high temperature and low temperature, and exhibits strong stability and reliability.

[0179] According to a sixth embodiment of this application, a battery is provided, the battery including a casing, a cell and an electrolyte; wherein the cell is a cell as described above.

[0180] According to embodiments of this application, a battery structure is described, comprising a casing, a cell, and an electrolyte. The cell is a cell previously described in this application that includes a specific negative electrode. This battery design aims to provide a safer and higher-performance energy storage solution.

[0181] The embodiments according to this application will be described in detail below with reference to specific examples.

[0182] Example 1

[0183] (1) The specific preparation method of the negative electrode binder is as follows:

[0184] In a 500 mL flask equipped with a glass tube, a reflux condenser, a stirrer, and a thermometer, 50 parts by weight of acrylic acid and 90 parts by weight of hydroxydopamine monomer were mixed and reacted at 60 °C for 1 h.

[0185] 30 parts by mass of 2-ethylhexyl acrylate (a long-chain alkyl (meth) acrylate monomer) were added together with a surfactant into the above reaction vessel (500 mL flask), and then deionized water was added to prepare a pre-emulsion.

[0186] Then an initiator was added, and nitrogen was introduced as a protective gas. The temperature was heated to 80°C and held for 1 hour. Then 40 parts by mass of vinyltrimethoxysilane (vinylsiloxane monomer) were added and held at 80°C (initiation temperature) for 0.5 hours to obtain a bluish white emulsion.

[0187] Finally, after being filtered and dried under vacuum at 60°C, a white powdery product is obtained, which is the negative electrode binder.

[0188] (2) The specific preparation process of the negative electrode is as follows:

[0189] First, take the white powder product obtained above, i.e., the negative electrode binder, and dissolve it in 50wt% deionized water at a slurry solid content of 0.8wt% to form an aqueous dispersion.

[0190] Next, add 0.5 wt% conductive carbon black Super P and stir and disperse for 1 hour at 1200 rpm;

[0191] Add ammonia to adjust the pH to 7-7.5, and continue stirring to disperse.

[0192] Add 0.7 wt% carboxymethyl cellulose (CMC) and continue stirring to disperse;

[0193] Add 48wt% graphite and continue stirring for 3 hours at a speed of 1000-1500 rpm;

[0194] Place the clean copper foil (current collector) on the automatic coating machine, place the I-shaped doctor blade, turn on the vacuum pump, use lint-free paper to flatten the copper foil, adjust the speed of the coating machine to 15mm / s, evenly place the mixed slurry in front of the doctor blade, and start the coating operation to obtain the electrode sheet coated with slurry.

[0195] The obtained electrode sheets are transferred to a cardboard (or other flat surface) and then placed together in a 60°C forced-air drying oven. After closing the oven door, the sheets are dried for 15 to 30 minutes.

[0196] The baked electrode sheets are rolled and cut sequentially to prepare the negative electrode sheet;

[0197] A portion of the negative electrode sheet was immersed in the electrolyte and then dried in a 60°C oven for 24 hours.

[0198] Cell winding: The electrode sheets are stacked together in the order of positive electrode-separator-negative electrode, and then wound into a cell using an automatic winding machine. After the finished electrode sheets undergo encapsulation, electrolyte injection, formation, and aging, they can be subjected to subsequent electrochemical performance testing.

[0199] Example 2

[0200] Example 2 is basically the same as Example 1, except that in the preparation of the negative electrode binder, the mass fraction of hydroxydopamine monomer is adjusted from 90 parts to 160 parts, while other aspects remain unchanged. In other words, compared with Example 1, Example 2 only increases the amount of hydroxydopamine monomer.

[0201] Example 3

[0202] Example 3 is essentially the same as Example 1, except that the mass fraction of hydroxydopamine monomer in the preparation of the negative electrode binder is adjusted from 90 parts to 30 parts, while other aspects remain unchanged. In other words, compared to Example 1, Example 3 significantly reduces the amount of hydroxydopamine monomer used, and the mass fraction of hydroxydopamine monomer is lower than the standard lower limit of 90 parts. This will, to some extent, reduce the viscosity, peel strength, and other properties of the negative electrode binder, as shown in Table 1 below.

[0203] Example 4

[0204] Example 4 is essentially the same as Example 1, except that the mass fraction of hydroxydopamine monomer in the preparation of the negative electrode binder is increased from 90 parts to 120 parts, while other parameters remain unchanged. In other words, compared to Example 1, Example 4 increases the amount of hydroxydopamine monomer. It should be noted that the amount of hydroxydopamine monomer used in Example 4 is optimal, thus having a positive impact on the viscosity and peel strength of the negative electrode binder, as shown in Table 1 below.

[0205] Example 5

[0206] Example 5 is essentially the same as Example 1, except that the mass fraction of vinyltrimethoxysilane in the preparation of the negative electrode binder is increased from 40 parts to 80 parts, while other aspects remain unchanged. In other words, compared to Example 1, Example 5 increases the amount of vinyltrimethoxysilane, and the mass fraction of vinyltrimethoxysilane exceeds the standard upper limit of 60 parts. This will, to some extent, reduce the viscosity, peel strength, and other properties of the final negative electrode binder, as shown in Table 1 below.

[0207] Example 6

[0208] Example 6 is essentially the same as Example 1, except that the mass fraction of vinyltrimethoxysilane in the preparation of the negative electrode binder is adjusted from 40 parts to 10 parts, while other aspects remain unchanged. In other words, compared to Example 1, Example 6 reduces the amount of vinyltrimethoxysilane used, and the mass fraction of vinyltrimethoxysilane is lower than the standard lower limit of 30 parts. This will, to some extent, reduce the viscosity, peel strength, and other properties of the final negative electrode binder, as shown in Table 1 below.

[0209] Example 7

[0210] Example 7 is essentially the same as Example 1, except that the mass fraction of vinyltrimethoxysilane in the preparation of the negative electrode binder is adjusted from 40 parts to 60 parts, while other aspects remain unchanged. In other words, compared to Example 1, Example 7 increases the amount of vinyltrimethoxysilane, and the mass fraction of vinyltrimethoxysilane is more reasonable (within the specified range of 30-60 parts). Compared to Examples 5 and 6, it will improve the viscosity, peel strength, and other properties of the negative electrode binder to a certain extent, as shown in Table 1 below.

[0211] Example 8

[0212] Example 8 is essentially the same as Example 1, except that the mass fraction of vinyltrimethoxysilane in the preparation of the negative electrode binder is adjusted from 40 parts to 30 parts, while other aspects remain unchanged. In other words, compared to Example 1, Example 8 reduces the amount of vinyltrimethoxysilane. However, because the mass fraction of vinyltrimethoxysilane is relatively reasonable (within the specified range of 30-60 parts), it will also improve the viscosity, peel strength, and other properties of the negative electrode binder to a certain extent compared to Examples 5 and 6, as shown in Table 1 below.

[0213] Example 9

[0214] Example 9 is essentially the same as Example 1, except that in the preparation of the negative electrode binder, 2-ethylhexyl acrylate is replaced with lauryl methacrylate. In other words, the long-chain alkyl (meth)acrylate monomer in Example 9 is different from that in Example 1.

[0215] Example 10

[0216] Example 10 is basically the same as Example 1, except that in the preparation of the negative electrode binder, acrylic acid is replaced with methacrylic acid. That is to say, the acrylic monomers in Example 10 are different types from the acrylic monomers in Example 1.

[0217] Compare with Example 1

[0218] Comparative Example 1 is basically the same as Example 1, except that no hydroxydopamine monomer was added in the reaction.

[0219] Compare with Example 2

[0220] Comparative Example 2 is basically the same as Example 1, except that no vinylsiloxane monomer was added during the reaction.

[0221] It should be noted that the performance of the negative electrode binders obtained in Examples 1 to 10, as well as Comparative Examples 1 and 2, can be found in Table 1 below.

[0222] The test methods and results of Examples 1 to 10 and Comparative Examples 1 and 2 are as follows:

[0223] (1) Peel strength test, using GB / T2791-1995, to test the peel strength of the negative electrode sheet.

[0224] (2) Viscosity test, using GB / T2794-2013, to test viscosity.

[0225] (3) Capacity retention test: The charge / discharge rate was 1C. After activating the battery with a small current, the average capacity of the first three discharge cycles 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%

[0226] Viscosity and peel strength tests conducted in Examples 1 to 4 and Comparative Example 1 show that the addition of hydroxydopamine monomer has a significant impact on both the viscosity of the polymer and the peel strength of the negative electrode slurry. The more hydroxydopamine monomer used, the greater the peel strength.

[0227] The capacity retention rates after cycling in Examples 1-4 and Comparative Example 1 show that when the amount of hydroxydopamine monomer is 90-120 parts by mass, its effect on the adhesion and internal resistance of the negative electrode active material is optimal. This may be because, while hydroxydopamine monomer can improve the adhesion between the negative electrode current collector, the negative electrode active material, and the negative electrode material itself, it may also increase internal resistance, hindering the transport of lithium ions and electrons. Therefore, excessive hydroxydopamine monomer leads to increased internal resistance, while insufficient hydroxydopamine monomer reduces the viscosity of the negative electrode binder, resulting in insufficient adhesion to the negative electrode active material. Considering both factors, a dosage of 90-150 parts by mass of hydroxydopamine monomer is preferable, with 90-120 parts by mass being optimal.

[0228] Through comparison of Examples 1, 5, 6, 7, 8, and Control Example 2, it can be seen that, compared to Control Example 2 without added vinylsiloxane, the peel strength of the electrode sheet after immersion in the electrolyte significantly increases with the increase of vinylsiloxane content, and the adhesion of the negative electrode active material to the negative electrode current collector is significantly enhanced. The peel strength is as follows: Example 1 ≈ Example 7 > Example 5 > Example 6 > Control Example 2. It is also evident that excessive vinylsiloxane does not significantly improve the peel strength of the negative electrode sheet after immersion in the electrolyte; on the contrary, it reduces the peel strength. This may be because the addition of excessive vinylsiloxane increases the structural strength of the negative electrode binder, correspondingly reducing its flexibility and making it more brittle, ultimately reducing the peel strength of the negative electrode binder.

[0229] By comparing the capacity retention rates after cycling using Examples 1, 5, 6, 7, 8, and Comparative Example 2, it is evident that the addition of vinylsiloxane significantly improves the capacity retention rate after battery cycling compared to Comparative Example 2 without vinylsiloxane. However, excessive addition of vinylsiloxane may lead to excessive binder strength and reduced flexibility, causing the negative electrode active material to become brittle. Therefore, the increase and decrease in the volume of the negative electrode active material during charge and discharge may lead to cracking and collapse of the negative electrode, thereby reducing the capacity retention rate. Therefore, the preferred amount of vinylsiloxane added is 30–60 parts by mass, and the optimal amount is 40–50 parts by mass.

[0230] Table 1 below shows the slurry viscosity and peel strength test results for each embodiment and control example.

[0231] Table 1

[0232]

[0233]

[0234] Table 2 below shows the capacity retention test results for each embodiment and each control example.

[0235] Table 2

[0236] Serial Number Capacity retention after 200 cycles Example 1 95.5 Example 2 93.5 Example 3 93.9 Example 4 95.4 Example 5 94.8 Example 6 95.0 Example 7 94.3 Example 8 95.5 Example 9 95.5 Example 10 95.6 Compare with Example 1 93.1 Compare with Example 2 92.8

[0237] In summary, based on the components and dosage of the negative electrode binder provided in the embodiments of this application, the prepared negative electrode binder exhibits superior performance in terms of viscosity and peel strength.

[0238] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0239] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this 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; 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 amount of 50 to 100 parts; The hydroxydopamine monomer is present in quantities of 90–180 parts; The long-chain alkyl (meth) acrylate monomer is 20-40 parts; The vinylsiloxane monomer is 30 to 60 parts.

2. The negative electrode binder composition according to claim 1, characterized in that, The negative electrode binder composition also includes an initiator and a surfactant; The amount of the initiator is 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.

3. The negative electrode binder composition according to claim 1, 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.

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

5. The negative electrode binder composition according to claim 2, characterized in that, The initiator is at least one of potassium persulfate, ammonium persulfate, and sodium persulfate.

6. The negative electrode binder composition according to claim 2, 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.

7. 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.

8. 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. 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 amount of 50 to 100 parts; The hydroxydopamine monomer is present in quantities of 90–180 parts; The long-chain alkyl (meth) acrylate monomer is 20-40 parts; The vinylsiloxane monomer is 30 to 60 parts.

9. The method for preparing the negative electrode binder according to claim 8, characterized in that, The mass ratio of the hydroxydopamine monomer to the vinylsiloxane monomer is 1.5~6:

1.

10. The method for preparing the negative electrode binder according to claim 8, 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.

11. The method for preparing the negative electrode binder according to claim 8, 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, the vinyl siloxane monomer is added and the temperature is kept at 75℃~85℃ to obtain the emulsion; wherein the total time of the two holding times is 1~3h. The emulsion is filtered and dried to obtain the negative electrode binder.

12. 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 1-6 or the negative electrode adhesive as described in claim 7.

13. 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 12.

14. A battery, characterized in that, Includes the casing, battery cell, and electrolyte; The battery cell is the battery cell as described in claim 13.

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