Water-based negative electrode binder as well as preparation method and application thereof

Abstract

The invention relates to the technical field of binders, in particular to a water-based negative electrode binder as well as a preparation method and application thereof. The water-based adhesive is prepared from the following raw materials in parts by weight: 60 to 120 parts of unsaturated carboxylic acid, 75 to 140 parts of acrylonitrile, 35 to 55 parts of amide monomer, 10 to 12 parts of acrylate monomer, 300 to 400 parts of deionized water, 25 to 50 parts of water-based dispersant, 15 to 25 parts of initiator aqueous solution and 3000 to 4000 parts of alkaline aqueous solution. The content of an initiator in the initiator aqueous solution is 0.8-2.5 parts. The water-based negative electrode binder prepared by specific raw material components and a specific precipitation method can remove oligomers and retain effective components, so that the water-based negative electrode binder has excellent peel strength (greater than or equal to 17N / m) and cycle performance.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to an aqueous negative electrode adhesive, its preparation method, and its application. Background Technology

[0002] In the field of lithium-ion batteries, the performance of the negative electrode binder directly affects the battery's cycle stability, bonding strength, and process adaptability. Currently, aqueous negative electrode binders are gradually replacing oil-based binders due to their advantages in environmental protection and safety, but existing technologies still have many shortcomings. Binders prepared by traditional emulsion polymerization often have residual emulsifiers, which can easily lead to increased interfacial impedance and affect cycle performance. Although some precipitation polymerization methods can reduce oligomer residues, they often use a single dispersant, resulting in limited dispersion effects and unreasonable monomer ratios, making it difficult to balance adhesion and flexibility. In addition, existing binders are prone to producing high-viscosity products during high-temperature polymerization due to uncontrolled reaction conditions, affecting subsequent coating processes. At the same time, some formulations lack polar monomers such as acrylamide, making it difficult to improve electrolyte wettability and further restricting the battery's cycle performance.

[0003] Chinese invention patent CN111500228B discloses a solution-type polyacrylic acid adhesive prepared by precipitation polymerization. It improves the adhesion by controlling the oligomer content. However, it uses a single phosphate dispersant, which has low dispersion efficiency. It does not introduce monomers with strong polar groups such as acrylonitrile, and lacks anchoring effect on new negative electrode materials such as silicon-based materials. The molecular weight distribution is wide, resulting in insufficient electrode flexibility, easy cracking after rolling, and limited cycle life. Summary of the Invention

[0004] The first aspect of this invention provides an aqueous negative electrode binder, which, by weight, comprises the following raw materials: 60-120 parts of unsaturated carboxylic acid, 75-140 parts of acrylonitrile, 35-55 parts of amide monomer, 10-12 parts of acrylate monomer, 300-400 parts of deionized water, 25-50 parts of aqueous dispersant, 15-25 parts of initiator aqueous solution, and 3000-4000 parts of alkaline aqueous solution; wherein the initiator content in the initiator aqueous solution is 0.8-2.5 parts.

[0005] The aqueous dispersant comprises disodium hydrogen phosphate and sodium dihydrogen phosphate, wherein the weight ratio of disodium hydrogen phosphate to sodium dihydrogen phosphate is 1:(0.8-1.2).

[0006] This study found that when disodium hydrogen phosphate (Na2HPO4) and sodium dihydrogen phosphate (NaH2PO4) are combined in a ratio of 1:(0.8-1.2), a stable phosphate buffer system is first formed by the weakly alkaline Na2HPO4 and the weakly acidic NaH2PO4. This system can precisely control the pH of the reaction system in the near-neutral range, avoiding local pH fluctuations caused by the dissociation of unsaturated carboxylic acid monomers or the decomposition of initiators during polymerization. This ensures the uniform dissolution and dispersion of monomers in deionized water, laying the foundation for the uniformity of subsequent precipitation polymerization. Secondly, both are ionic dispersants. The anions released after dissolution will preferentially adsorb on the surface of oligomers or polymer particles formed in the early stage of polymerization. Through the double-layer effect, the surface charge density of the particles is increased, enhancing the electrostatic repulsion between particles. At the same time, the synergistic adsorption of the two anions can form a denser adsorption layer with a more uniform charge distribution. Combined with the steric hindrance effect, this effectively inhibits particle agglomeration, significantly improves the dispersion stability of the system, and solves the problems of limited adsorption capacity and uneven dispersion effect of single dispersants. Furthermore, the compound system at this specific ratio can achieve a dynamic balance between dispersant adsorption and desorption, ensuring the amount of adsorption required for particle dispersion during polymerization while avoiding residues caused by excessive adsorption of dispersant. In subsequent filtration and washing steps, the free dispersant that is not strongly adsorbed is easily removed, while the small amount of residual phosphate is in a buffer equilibrium state and will not form a high impedance layer at the interface between the binder and the electrode material or damage the interfacial bonding force between the binder and the graphite and copper foil, as a single dispersant would. Ultimately, while improving dispersion performance, it minimizes the negative impact of dispersant residue on binder peel strength and battery cycle performance.

[0007] The amide monomer includes at least one of methacrylamide, N-methacrylamide, N,N-dimethylacrylamide, and acrylamide.

[0008] The acrylate monomers include at least one of ethyl acrylate, isobutyl acrylate, ethyl methacrylate, isobutyl methacrylate, butyl acrylate, and butyl methacrylate.

[0009] The initiator includes at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0010] The solute in the alkaline aqueous solution includes at least one of sodium hydroxide and potassium hydroxide.

[0011] The unsaturated carboxylic acid includes at least one of acrylic acid and methacrylic acid.

[0012] A second aspect of this invention provides a method for preparing an aqueous negative electrode binder, comprising the following steps: S1, the dispersant and deionized water are mixed evenly, and unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer are added to obtain a mixture; the initiator aqueous solution is added dropwise to the mixture to carry out the reaction, and the solid particles are obtained by filtration and washing; S2, add an alkaline aqueous solution to the solid particles and adjust the pH to neutral to obtain an aqueous negative electrode binder.

[0013] The temperature of the mixture during the dropwise addition is 50-70℃.

[0014] Optionally, the temperature of the mixture during the dropwise addition is 50-60°C.

[0015] The reaction time is 8-15 hours.

[0016] Optionally, the reaction time is 10-14 hours.

[0017] The dripping time is 30-70 minutes.

[0018] Optionally, the dripping time is 40-50 minutes.

[0019] Optionally, the solid content of the aqueous negative electrode binder is 4-8 wt%.

[0020] The third aspect of this invention provides an application of an aqueous negative electrode binder in the preparation of battery negative electrode materials.

[0021] The raw materials for preparing the battery negative electrode material include: graphite material, conductive agent and aqueous negative electrode binder; the amount of aqueous negative electrode binder added in the battery negative electrode material is 1-3 wt%.

[0022] Beneficial effects 1. By limiting the aqueous dispersant to include disodium hydrogen phosphate and sodium dihydrogen phosphate, and the weight ratio of disodium hydrogen phosphate to sodium dihydrogen phosphate is 1:(0.8-1.2), the present invention can improve the dispersion performance of the system while reducing the negative impact of dispersant residue on the binder.

[0023] 2. This invention uses specific precipitation polymerization to remove oligomers while retaining effective components, resulting in an aqueous negative electrode binder with a narrow molecular weight distribution.

[0024] 3. The binder prepared by this invention has a number average molecular weight ≥ 30w and a weight average molecular weight ≥ 100w.

[0025] 4. By limiting the temperature of the mixture during dripping to 50-70℃, the dripping time to 30-70 min, and the reaction time to 8-15 h, this invention can effectively reduce the generation of high-viscosity products and maintain the toughness of the binder.

[0026] 5. The adhesive prepared by this invention has a peel strength of ≥17N / m, which can meet the requirements for the use of battery negative electrode materials. Attached Figure Description

[0027] Figure 1 The image shows the cycle test results of the battery prepared with the binder in Example 1.

[0028] Figure 2 Cyclic test diagram of the battery prepared with binder for Comparative Example 2.

[0029] Figure 3 Cyclic test results for the battery prepared using binder in Comparative Example 6.

[0030] Figure 4 Cyclic test diagram of the battery prepared with binder for Comparative Example 8.

[0031] Figure 5 The graph shows the molecular weight of the GPC binder in Example 1, where the blue curve corresponds to the molecular weight distribution curve and the red curve corresponds to the integral curve of the molecular weight. Detailed Implementation

[0032] Example 1 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 23 parts of water-based dispersant (11.5 parts of disodium hydrogen phosphate and 11.5 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate); and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0033] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0034] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0035] Example 2 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 25 parts of water-based dispersant (disodium hydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate), and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0036] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0037] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0038] Example 3 A water-based negative electrode binder, prepared by weight, comprises: 120 parts of unsaturated carboxylic acid (acrylic acid), 75 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 23 parts of water-based dispersant (11.5 parts of disodium hydrogen phosphate and 11.5 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate), and the alkaline aqueous solution contains 55 parts of alkaline monomer (sodium hydroxide).

[0039] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0040] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0041] Example 4 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 55 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 23 parts of water-based dispersant (11.5 parts of disodium hydrogen phosphate and 11.5 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate), and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0042] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0043] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0044] Example 5 A water-based negative electrode binder, prepared by weight, comprises: 82 parts of unsaturated carboxylic acid (70 parts acrylic acid, 12 parts methacrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 23 parts of water-based dispersant (11.5 parts disodium hydrogen phosphate, 11.5 parts sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate); and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0045] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0046] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0047] Example 6 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 11 parts of acrylate monomer (butyl methacrylate), 345 parts of deionized water, 23 parts of water-based dispersant (11.5 parts of disodium hydrogen phosphate and 11.5 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate), and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0048] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0049] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0050] Example 7 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 46 parts of water-based dispersant (23 parts of disodium hydrogen phosphate and 23 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate), and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0051] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0052] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0053] Comparative Example 1 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 23 parts of water-based dispersant (11.5 parts of disodium hydrogen phosphate and 11.5 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate); and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0054] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 45°C; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0055] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0056] Comparative Example 2 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 23 parts of water-based dispersant (11.5 parts of disodium hydrogen phosphate and 11.5 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate); and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0057] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 min, keep warm for 18 h, filter and wash under a 60 mesh sieve to obtain solid particles.

[0058] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0059] Comparative Example 3 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 12 parts of water-based dispersant (6 parts disodium hydrogen phosphate, 6 parts sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate); and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0060] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0061] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0062] Comparative Example 4 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 23 parts of water-based dispersant (11.5 parts of disodium hydrogen phosphate and 11.5 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 0.46 parts of initiator (ammonium persulfate); and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0063] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0064] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0065] Comparative Example 5 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 140 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 23 parts of water-based dispersant (11.5 parts of disodium hydrogen phosphate and 11.5 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate), and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0066] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, which is completed in 45 min, keep warm for 12 h, filter and wash under a 60 mesh sieve to obtain solid particles.

[0067] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0068] Comparative Example 6 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 23 parts of water-based dispersant (11.5 parts of disodium hydrogen phosphate and 11.5 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate), and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0069] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer and acrylonitrile in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, which is completed in 45 min, keep warm for 12 h, filter and wash under a 60 mesh sieve to obtain solid particles.

[0070] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0071] Comparative Example 7 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 650 parts of deionized water, 23 parts of water-based dispersant (11.5 parts of disodium hydrogen phosphate and 11.5 parts of sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate); and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0072] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0073] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0074] Comparative Example 8 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 11.5 parts of water-based dispersant (disodium hydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate), and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0075] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0076] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0077] Comparative Example 9 A water-based negative electrode binder, prepared by weight, comprises: 80 parts of unsaturated carboxylic acid (acrylic acid), 105 parts of acrylonitrile, 35 parts of amide monomer (acrylamide), 10 parts of acrylate monomer (butyl acrylate), 345 parts of deionized water, 11.5 parts of water-based dispersant (sodium dihydrogen phosphate), 21.8 parts of initiator aqueous solution, and 3515 parts of alkaline aqueous solution; wherein the initiator aqueous solution contains 1.8 parts of initiator (ammonium persulfate), and the alkaline aqueous solution contains 35 parts of alkaline monomer (sodium hydroxide).

[0078] A method for preparing an aqueous negative electrode binder comprises the following steps: 1. Preparation of solid particles: Add aqueous dispersant and deionized water to the reaction vessel and stir until completely dissolved; then add unsaturated carboxylic acid, acrylate monomer, acrylonitrile and amide monomer in sequence; adjust the stirring speed until no layering is observed, remove oxygen from the reaction vessel under vacuum, protect with nitrogen, and heat to 55℃; add initiator aqueous solution dropwise using a peristaltic pump, completing the dropwise addition in 45 minutes, keep warm for 12 hours, filter and wash under a 60-mesh sieve to obtain solid particles.

[0079] 2. Preparation of water-based negative electrode binder: Add alkaline aqueous solution to solid particles, stir evenly, and adjust pH to 7.0 to obtain water-based negative electrode binder.

[0080] Performance testing methods The water-based negative electrode binders prepared in the examples and comparative examples were subjected to performance tests, and the test data are listed in Table 1.

[0081] The solid content test refers to GB / T 2793-1995 Determination of nonvolatile matter content in adhesives; the viscosity test refers to GB / T 2794-2022 Determination of viscosity of adhesives, 40℃. Peel strength test: The obtained binder was mixed evenly at a mass ratio of graphite material (Shanghai Shanshan Technology Co., Ltd. FSN-1): conductive agent (Shanghai Huiping New Energy Co., Ltd.): binder = 97:1:2, and sieved through a 150-mesh sieve. The resulting negative electrode slurry was coated onto the surface of the conductive copper foil current collector, heated and dried, and rolled to a density of 1.5 g / dm³. 3 Cut the substrate into slices to obtain the finished electrode sheet; test the peel strength according to GB / T 2790-1995 Adhesives 180° Peel Strength Test Method, where "-" indicates that it cannot pass through the sieve at 150 mesh and was not tested.

[0082] Battery Testing: The above-mentioned negative electrode and oil-based lithium iron phosphate positive electrode (lithium iron phosphate material (Taiwan Likai Electric Power Technology Co., Ltd. M12): conductive agent (Shanghai Huiping New Energy Co., Ltd.): PVDF = 93:4:3) were stacked to prepare a 1Ah pouch battery. Cyclic testing was then performed using the battery testing system. Figure 1 As shown, in Example 1, the battery prepared with the binder had 87% capacity remaining after 2000 charge-discharge cycles; in Comparative Example 2, the battery prepared with the binder had 77% capacity remaining after 1000 charge-discharge cycles; in Comparative Example 6, the battery prepared with the binder had 76% capacity remaining after 1000 charge-discharge cycles; and in Comparative Example 8, the battery prepared with the binder had 81% capacity remaining after 2000 charge-discharge cycles.

[0083] Performance test data Table 1

[0084] According to Table 1 and Figures 1-4 As can be seen, the water-based negative electrode binder prepared by the present invention using specific raw material components and a specific precipitation method possesses both excellent peel strength (≥17 N / m) and cycling performance, such as... Figure 5 As shown, the water-based negative electrode binder prepared by the precipitation method in this invention has a number-average molecular weight of approximately 374,100 and a weight-average molecular weight of approximately 1,127,300.

Claims

1. An aqueous negative electrode binder, characterized by, Preparation raw materials include: 60-120 parts by weight of unsaturated carboxylic acid, 75-140 parts of acrylonitrile, 35-55 parts of amide monomer, 10-12 parts of acrylate monomer, 300-400 parts of deionized water, 25-50 parts of aqueous dispersant, 15-25 parts of initiator aqueous solution, 3000-4000 parts of alkaline aqueous solution; the content of initiator in the initiator aqueous solution is 0.8-2.5 parts.

2. The aqueous negative electrode binder of claim 1, wherein, The aqueous dispersant includes disodium hydrogen phosphate and sodium dihydrogen phosphate, and the weight ratio of the disodium hydrogen phosphate to the sodium dihydrogen phosphate is 1: (0.8-1.2).

3. The aqueous negative electrode binder of claim 1, wherein, The amide monomer includes at least one of methacrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide, and acrylamide.

4. The aqueous negative electrode binder of claim 1, wherein, The acrylate monomer includes at least one of ethyl acrylate, isobutyl acrylate, ethyl methacrylate, isobutyl methacrylate, butyl acrylate, and butyl methacrylate; The initiator includes at least one of ammonium persulfate, potassium persulfate, and sodium persulfate; The solute in the alkaline aqueous solution includes at least one of sodium hydroxide and potassium hydroxide; The unsaturated carboxylic acid includes at least one of acrylic acid and methacrylic acid.

5. A method of preparing the aqueous negative electrode binder according to any one of claims 1 to 4, characterized by, The method includes the following steps: S1, uniformly mix the dispersant and deionized water, add the unsaturated carboxylic acid, acrylate monomer, acrylonitrile, and amide monomer to obtain a mixture; drop the initiator aqueous solution into the mixture, perform a reaction, and obtain solid particles through filtration and washing; S2, add the alkaline aqueous solution to the solid particles, adjust the pH to neutral, and obtain the aqueous negative electrode binder.

6. The method of claim 5, wherein the aqueous negative electrode binder is prepared by mixing the polyepoxide, the polyamine, and the water. The temperature of the mixture during the dropping is 50-70℃.

7. The method of claim 6, wherein the aqueous negative electrode binder is prepared by mixing the polyepoxide, the polyamine, and the water. The reaction time is 8-15h.

8. The method of claim 7, wherein the aqueous negative electrode binder is prepared by adding the water to the mixture of the binder resin, the thickener, and the surfactant, and then adding the dispersant thereto. The dropping time is 30-70min.

9. Use of the aqueous negative electrode binder according to any one of claims 1 to 4, characterized in that, Applied to the preparation of a battery negative electrode material.

10. The use of the aqueous negative electrode binder according to claim 9, characterized in that, The preparation raw materials of the battery negative electrode material include: a graphite material, a conductive agent, and the aqueous negative electrode binder; the addition amount of the aqueous negative electrode binder in the battery negative electrode material is 1-3wt%.

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