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 preparation raw materials comprise unsaturated carboxylic acid, acrylonitrile, an amide monomer, an acrylate monomer, an inorganic alkali aqueous solution, an initiator aqueous solution and deionized water. The weight ratio of the unsaturated carboxylic acid to the acrylonitrile to the amide monomer to the acrylate monomer is 1: (1.5-2): (0.3-1): (0.03-0.2). According to the present invention, the high solid content and high viscosity aqueous negative electrode binder is prepared by using the one-pot method, and by optimizing the monomer ratio and the low temperature polymerization process, the problems of easy gelation and reaction interruption of the traditional high solid content system are solved, the peeling strength of the pole piece is improved (greater than or equal to 3.5 N / cm), and the cycle life of the battery is prolonged (the capacity retention rate after 1000 cycles is greater than or equal to 85%).

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of binders, in particular to a water-based negative electrode binder and a preparation method and application thereof. BACKGROUND

[0002] The negative electrode binder of a lithium ion battery is a core material for maintaining the stability of the electrode structure and ensuring the cycle performance of the battery. With the increasing requirements of the lithium battery industry for environmental protection and production efficiency, water-based binders that replace oil-based polyvinylidene fluoride (PVDF) have become a research focus. Among them, water-based binders with high initial solid content can reduce the energy consumption of subsequent drying processes, and products with high viscosity can ensure the uniformity of negative electrode slurry dispersion. Binders with both properties are of great significance to industrial production. Currently, there are key technical bottlenecks in the preparation of such high-solid-content and high-viscosity water-based binders using one-pot method. Under high solid content system, monomer polymerization is prone to cause high viscosity due to rapid crosslinking of molecular chains, thereby causing the reaction to stop and the system to gel.

[0003] To solve this problem, complex process routes are currently used. For example, Chinese patent application CN119432267A proposes a two-step polymerization process, which prepares a water-based binder by introducing a protective glue and implementing double-stage monomer dropping. Although this method can control the reaction stability to some extent, it has complicated process steps and requires additional auxiliary reagents, which is not conducive to industrial production and does not solve the problem of reaction continuity under high solid content conditions. Therefore, it is urgent to develop a water-based negative electrode binder that is simple in process, can stably prepare high-solid-content and high-viscosity products, and has excellent peel strength and cycle performance. SUMMARY

[0004] The first aspect of the present application provides a water-based negative electrode binder, and the preparation raw materials include unsaturated carboxylic acid, acrylonitrile, amide monomer, acrylic ester monomer, inorganic alkali aqueous solution, initiator aqueous solution and deionized water.

[0005] The weight ratio of the unsaturated carboxylic acid, acrylonitrile, amide monomer, and acrylic ester monomer is 1: (1.5-2): (0.3-1): (0.03-0.2).

[0006] Optionally, the weight ratio of the unsaturated carboxylic acid, acrylonitrile, amide monomer, and acrylic ester monomer is 1: (1.5-1.75): (0.375-0.75): (0.05-0.1).

[0007] The unsaturated carboxylic acid, acrylonitrile, amide monomer, and acrylic ester monomer in the present application are collocated in a weight ratio of 1:(1.5-2):(0.3-1):(0.03-0.2) to achieve a peeling strength of 10 N / m. The unsaturated carboxylic acid serves as a basic bonding unit, and its carboxyl group can form polar adsorption with the hydroxyl group and oxygen-containing group on the surface of graphite and the copper foil current collector through hydrogen bonds, thereby providing initial interface anchoring points for the bonding agent and being the core source of interface bonding force. The acrylonitrile further enhances the interfacial adhesion of the polymer to graphite and copper foil with its strong polar cyano group, and its linear molecular structure can adjust the glass transition temperature of the polymer to balance the interface bonding and structural stability. The amide monomer forms intramolecular and intermolecular hydrogen bonds between the amide group and the carboxyl group of the unsaturated carboxylic acid, thereby constructing a tight interpolymer chain network and significantly improving the cohesive force of the bonding agent. Meanwhile, the amide group itself can produce additional adsorption with the surface of graphite, thereby further strengthening the interface bonding and balancing the cohesive force and interfacial adhesion to avoid insufficient cohesive force caused by too low content or hard and brittle polymer caused by too high content. A small amount of acrylic ester monomer is used to supplement the flexibility of the system with flexible long-chain alkyl groups, thereby relieving the interfacial stress caused by the volume expansion of graphite caused by lithium intercalation and deintercalation during battery charging and discharging, reducing the interfacial peeling caused by stress concentration, and avoiding excessive flexibility from damaging the bonding force of the overall polar system.

[0008] The solid content of the aqueous negative electrode binder is 5-8 wt%, and the viscosity at 40℃ is 6000-16000 mPa·s.

[0009] Optionally, the solid content of the aqueous negative electrode binder is 6-7 wt%, and the viscosity at 40℃ is 9000-16000 mPa·s.

[0010] The amide monomer includes at least one of methyl acrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide, and acrylamide.

[0011] The acrylic ester monomer includes at least one of ethyl acrylate, isobutyl acrylate, ethyl methacrylate, isobutyl methacrylate, butyl acrylate, and butyl methacrylate.

[0012] The initiator includes at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0013] The solute in the alkaline aqueous solution includes at least one of sodium hydroxide, lithium hydroxide monohydrate, and potassium hydroxide.

[0014] The unsaturated carboxylic acid includes at least one of acrylic acid and methacrylic acid.

[0015] The second aspect of the present application provides a preparation method of the aqueous negative electrode binder, comprising the following steps: uniformly mixing unsaturated carboxylic acid, acrylonitrile, amide monomer and acrylic ester monomer, and then uniformly mixing with inorganic alkali aqueous solution to obtain a mixture; adding an initiator aqueous solution into the mixture to perform a reaction, and then adding deionized water to dilute the mixture after post-treatment to obtain the aqueous negative electrode binder.

[0016] The solid content in the mixture is 20-30 wt%.

[0017] Optionally, the solid content in the mixture is 24-28 wt%.

[0018] The temperature of the reaction is 40-50 DEG C, and the time is 15-22 h.

[0019] Optionally, the temperature of the reaction is 40-45 DEG C, and the time is 15-20 h.

[0020] The dropping time is 30-70 min.

[0021] Optionally, the dropping time is 40-50 min.

[0022] The post-treatment comprises vacuum single-removal at 70-90 DEG C for 1-3 h.

[0023] Optionally, the initiator aqueous solution accounts for 1-2 wt% of the mixture, and the content of the initiator in the initiator aqueous solution is 1-5 wt%.

[0024] The third aspect of the present application provides an application of the aqueous negative electrode binder, which is applied to the preparation of the battery negative electrode material.

[0025] Optionally, the preparation raw material of the battery negative electrode material comprises, in terms of weight percentage: 0.5-1.5% of conductive agent, 1-3% of the aqueous negative electrode binder, and the balance of graphite material.

[0026] Advantages 1. The present application can reach 10 N / m in peel strength by limiting the weight ratio of unsaturated carboxylic acid, acrylonitrile, amide monomer and acrylic ester monomer to be 1: (1.5-2): (0.3-1): (0.03-0.2).

[0027] 2. The present application can conveniently and simply prepare the aqueous negative electrode binder with high viscosity (40 DEG C, ≥6000 mPa s) through one-pot process, and effectively improves the production efficiency.

[0028] 3. The present application can prepare the aqueous negative electrode binder with high solid content (≥6 wt%) and high viscosity (40 DEG C, ≥9000 mPa s) through one-pot process by limiting the solid content in the mixture to be 20-30 wt%.

[0029] 4. The aqueous negative electrode binder with viscosity ≥ 10000 mPa-s (40℃) can be further prepared by limiting the solid content of the mixture to 24-28 wt% and the reaction temperature to 40-50℃ and the reaction time to 15-22h in the one-pot process of the present application.

[0030] 5. The binder obtained by the one-pot process of the present application is applied to the battery negative electrode material, and the capacity remaining after 2000 times of charge and discharge can still be > 85%. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The cycle test graph of the battery prepared by the binder of Example 1.

[0032] Figure 2 The cycle test graph of the battery prepared by the binder of Comparative Example 1.

[0033] Figure 3 The cycle test graph of the battery prepared by the binder of Comparative Example 6.

[0034] Figure 4 The cycle test graph of the battery prepared by the binder of Comparative Example 8.

[0035] Figure 5 The GPC molecular weight graph of the binder of Example 1, wherein the blue curve corresponds to the molecular weight distribution curve and the red curve corresponds to the integral curve of the molecular weight. DETAILED DESCRIPTION

[0036] Example 1 An aqueous negative electrode binder, the preparation raw materials consist of: unsaturated carboxylic acid (acrylic acid), acrylonitrile, amide monomer (acrylamide), acrylic ester monomer (butyl acrylate), inorganic alkali aqueous solution (inorganic alkali is sodium hydroxide), initiator aqueous solution (initiator is ammonium persulfate) and deionized water.

[0037] A preparation method of an aqueous negative electrode binder, the following steps, wherein the parts are weight parts: 44 parts of sodium hydroxide and 876 parts of deionized water are added to a reaction vessel, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, then 80 parts of acrylic acid, 4 parts of butyl acrylate, 120 parts of acrylonitrile and 60 parts of acrylamide are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted to no stratification, the oxygen in the reaction kettle is removed under vacuum, then protected by nitrogen, heated to 45℃ to obtain a mixture with a solid content of 26 wt%; a solution of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture by using a peristaltic pump, the dropping is controlled to be completed in 45 min, the reaction is carried out at 45℃ for 18h, then the monomers (reactants) are removed under vacuum at 85℃ for 2h, then diluted with deionized water to obtain the aqueous negative electrode binder.

[0038] Example 2 An aqueous negative electrode binder, the raw materials for preparation consisting of: unsaturated carboxylic acid (acrylic acid), acrylonitrile, amide monomer (acrylamide), acrylic ester monomer (butyl acrylate), aqueous inorganic base (inorganic base is sodium hydroxide), initiator aqueous solution (initiator is ammonium persulfate) and deionized water.

[0039] A preparation method of an aqueous negative electrode binder, the steps being as follows, wherein the parts are weight parts: 44 parts of sodium hydroxide and 876 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an aqueous inorganic base, then 80 parts of acrylic acid, 4 parts of butyl acrylate, 120 parts of acrylonitrile and 30 parts of acrylamide are sequentially added to the aqueous inorganic base, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, then nitrogen protection is used, the temperature is raised to 45℃ to obtain a mixture with a solid content of 26wt%; an initiator aqueous solution consisting of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture using a peristaltic pump, the dropwise addition is controlled to be completed in 45min, 45℃ reaction is carried out for 18h, then monomers (reactants) are removed under vacuum at 85℃ for 2h, then deionized water is added for dilution to obtain the aqueous negative electrode binder.

[0040] Example 3 An aqueous negative electrode binder, the raw materials for preparation consisting of: unsaturated carboxylic acid (acrylic acid), acrylonitrile, amide monomer (acrylamide), acrylic ester monomer (butyl acrylate), aqueous inorganic base (inorganic base is sodium hydroxide), initiator aqueous solution (initiator is ammonium persulfate) and deionized water.

[0041] A preparation method of an aqueous negative electrode binder, the steps being as follows, wherein the parts are weight parts: 44 parts of sodium hydroxide and 876 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an aqueous inorganic base, then 80 parts of acrylic acid, 4 parts of butyl acrylate, 120 parts of acrylonitrile and 30 parts of acrylamide are sequentially added to the aqueous inorganic base, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, then nitrogen protection is used, the temperature is raised to 45℃ to obtain a mixture with a solid content of 26wt%; an initiator aqueous solution consisting of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture using a peristaltic pump, the dropwise addition is controlled to be completed in 45min, 45℃ reaction is carried out for 18h, then monomers (reactants) are removed under vacuum at 85℃ for 2h, then deionized water is added for dilution to obtain the aqueous negative electrode binder.

[0042] Example 4 An aqueous negative electrode binder, the raw materials for preparation consisting of: unsaturated carboxylic acid (acrylic acid), acrylonitrile, amide monomer (acrylamide), acrylic ester monomer (butyl acrylate), aqueous inorganic base (inorganic base is sodium hydroxide), initiator aqueous solution (initiator is ammonium persulfate) and deionized water.

[0043] A preparation method of a water-based negative electrode binder is as follows: 45 parts of lithium hydroxide monohydrate and 876 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, 80 parts of acrylic acid, 4 parts of butyl acrylate, 120 parts of acrylonitrile and 60 parts of acrylamide are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, nitrogen protection is performed, the temperature is raised to 45°C to obtain a mixture with a solid content of 26wt%, an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture by using a peristaltic pump, the dropping is controlled to be completed in 45 minutes, 45°C reaction is performed for 18 hours, monomers (reactants) are removed under vacuum at 85°C for 2 hours, deionized water is added for dilution to obtain the water-based negative electrode binder.

[0044] Example 5 A water-based negative electrode binder is prepared from the following raw materials: an unsaturated carboxylic acid (acrylic acid), an acrylonitrile, an amide monomer (acrylamide), an acrylate monomer (butyl acrylate), an inorganic alkali aqueous solution (the inorganic alkali is sodium hydroxide), an initiator aqueous solution (the initiator is ammonium persulfate) and deionized water.

[0045] A preparation method of a water-based negative electrode binder is as follows: 44 parts of sodium hydroxide and 876 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, 80 parts of acrylic acid, 8 parts of butyl acrylate, 120 parts of acrylonitrile and 60 parts of acrylamide are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, nitrogen protection is performed, the temperature is raised to 45°C to obtain a mixture with a solid content of 26wt%, an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture by using a peristaltic pump, the dropping is controlled to be completed in 45 minutes, 45°C reaction is performed for 18 hours, monomers (reactants) are removed under vacuum at 85°C for 2 hours, deionized water is added for dilution to obtain the water-based negative electrode binder.

[0046] Example 6 A water-based negative electrode binder is prepared from the following raw materials: an unsaturated carboxylic acid (acrylic acid), an acrylonitrile, an amide monomer (acrylamide), an acrylate monomer (butyl acrylate), an inorganic alkali aqueous solution (the inorganic alkali is sodium hydroxide), an initiator aqueous solution (the initiator is ammonium persulfate) and deionized water.

[0047] A preparation method of a water-based negative electrode binder is as follows: 44 parts of sodium hydroxide and 876 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, 80 parts of acrylic acid, 4 parts of butyl acrylate, 140 parts of acrylonitrile, and 60 parts of acrylamide are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, nitrogen protection is performed, and the temperature is raised to 45°C to obtain a mixture with a solid content of 26wt%; an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture using a peristaltic pump, the dropping is controlled to be completed in 45 min, 45°C reaction is performed for 18 h, monomers (reactants) are removed under vacuum at 85°C for 2 h, deionized water is added for dilution, and a water-based negative electrode binder is obtained.

[0048] Example 7 A water-based negative electrode binder is prepared from the following raw materials: an unsaturated carboxylic acid (acrylic acid), an acrylonitrile, an amide monomer (acrylamide), an acrylate monomer (butyl acrylate), an inorganic alkali aqueous solution (the inorganic alkali is sodium hydroxide), an initiator aqueous solution (the initiator is ammonium persulfate), and deionized water.

[0049] A preparation method of a water-based negative electrode binder is as follows: 80 parts of acrylic acid, 4 parts of butyl acrylate, 120 parts of acrylonitrile, and 60 parts of acrylamide are sequentially added to a reaction container, mixed uniformly, 44 parts of sodium hydroxide and 876 parts of deionized water are added, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, nitrogen protection is performed, and the temperature is raised to 45°C to obtain a mixture with a solid content of 26wt%; an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture using a peristaltic pump, the dropping is controlled to be completed in 45 min, 45°C reaction is performed for 18 h, monomers (reactants) are removed under vacuum at 85°C for 2 h, deionized water is added for dilution, and a water-based negative electrode binder is obtained.

[0050] Example 8 A water-based negative electrode binder is prepared from the following raw materials: an unsaturated carboxylic acid (acrylic acid), an acrylonitrile, an amide monomer (acrylamide), an acrylate monomer (butyl acrylate), an inorganic alkali aqueous solution (the inorganic alkali is sodium hydroxide), an initiator aqueous solution (the initiator is ammonium persulfate), and deionized water.

[0051] A preparation method of a water-based negative electrode binder is as follows: 44 parts of sodium hydroxide and 876 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, then 120 parts of acrylonitrile, 60 parts of acrylamide, 80 parts of acrylic acid, and 4 parts of butyl acrylate are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, then nitrogen protection is performed, the temperature is raised to 45°C to obtain a mixture with a solid content of 26wt%, an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture using a peristaltic pump, the dropping is controlled to be completed in 45 min, 45°C reaction is performed for 18 h, then monomers (reactants) are removed under vacuum at 85°C for 2 h, deionized water is added for dilution to obtain the water-based negative electrode binder.

[0052] Comparative Example 1 A water-based negative electrode binder is prepared from the following raw materials: an unsaturated carboxylic acid (acrylic acid), an acrylonitrile, an amide monomer (acrylamide), an acrylate monomer (butyl acrylate), an inorganic alkali aqueous solution (the inorganic alkali is sodium hydroxide), an initiator aqueous solution (the initiator is ammonium persulfate), and deionized water.

[0053] A preparation method of a water-based negative electrode binder is as follows: 44 parts of sodium hydroxide and 876 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, then 80 parts of acrylic acid, 4 parts of butyl acrylate, 120 parts of acrylonitrile, and 60 parts of acrylamide are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, then nitrogen protection is performed, the temperature is raised to 60°C to obtain a mixture with a solid content of 26wt%, an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture using a peristaltic pump, the dropping is controlled to be completed in 45 min, 60°C reaction is performed for 18 h, then monomers (reactants) are removed under vacuum at 85°C for 2 h, deionized water is added for dilution to obtain the water-based negative electrode binder.

[0054] Comparative Example 2 A water-based negative electrode binder is prepared from the following raw materials: an unsaturated carboxylic acid (acrylic acid), an acrylonitrile, an amide monomer (acrylamide), an acrylate monomer (butyl acrylate), an inorganic alkali aqueous solution (the inorganic alkali is sodium hydroxide), an initiator aqueous solution (the initiator is ammonium persulfate), and deionized water.

[0055] A preparation method of a water-based negative electrode binder is as follows: 44 parts of sodium hydroxide and 876 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, 80 parts of acrylic acid, 4 parts of butyl acrylate, 120 parts of acrylonitrile, and 60 parts of acrylamide are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, nitrogen protection is performed, the temperature is raised to 45°C to obtain a mixture with a solid content of 26wt%, an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise in the mixture by using a peristaltic pump, the dropping is controlled to be completed in 45 minutes, 45°C reaction is performed for 12 hours, monomers (reactants) are removed under vacuum at 85°C for 2 hours, deionized water is added for dilution to obtain the water-based negative electrode binder.

[0056] Comparative Example 3 A water-based negative electrode binder is prepared from the following raw materials: an unsaturated carboxylic acid (acrylic acid), an acrylonitrile, an amide monomer (acrylamide), an acrylate monomer (butyl acrylate), an inorganic alkali aqueous solution (the inorganic alkali is sodium hydroxide), an initiator aqueous solution (the initiator is ammonium persulfate), and deionized water.

[0057] A preparation method of a water-based negative electrode binder is as follows: 44 parts of sodium hydroxide and 876 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, 80 parts of acrylic acid, 4 parts of butyl acrylate, 120 parts of acrylonitrile, and 60 parts of acrylamide are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, nitrogen protection is performed, the temperature is raised to 45°C to obtain a mixture with a solid content of 26wt%, an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise in the mixture by using a peristaltic pump, the dropping is controlled to be completed in 45 minutes, 45°C reaction is performed for 12 hours, monomers (reactants) are removed under vacuum at 85°C for 2 hours, deionized water is added for dilution to obtain the water-based negative electrode binder.

[0058] Comparative Example 4 A water-based negative electrode binder is prepared from the following raw materials: an unsaturated carboxylic acid (acrylic acid), an acrylonitrile, an amide monomer (acrylamide), an acrylate monomer (butyl acrylate), an inorganic alkali aqueous solution (the inorganic alkali is sodium hydroxide), an initiator aqueous solution (the initiator is ammonium persulfate), and deionized water.

[0059] A preparation method of a water-based negative electrode binder is as follows: 44 parts of sodium hydroxide and 502 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, 80 parts of acrylic acid, 3 parts of butyl acrylate, 120 parts of acrylonitrile, and 60 parts of acrylamide are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, nitrogen protection is performed, the temperature is raised to 45°C to obtain a mixture with a solid content of 38wt%, an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture using a peristaltic pump, the dropping is controlled to be completed in 45 min, 45°C reaction is performed for 18 h, monomers (reactants) are removed under vacuum at 85°C for 2 h, deionized water is added for dilution to obtain the water-based negative electrode binder.

[0060] Comparative Example 5 A water-based negative electrode binder is prepared from the following raw materials: an unsaturated carboxylic acid (acrylic acid), acrylonitrile, an amide monomer (acrylamide), an acrylate monomer (butyl acrylate), an inorganic alkali aqueous solution (the inorganic alkali is sodium hydroxide), an initiator aqueous solution (the initiator is ammonium persulfate), and deionized water.

[0061] A preparation method of a water-based negative electrode binder is as follows: 44 parts of sodium hydroxide and 876 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, 80 parts of acrylic acid, 30 parts of butyl acrylate, 120 parts of acrylonitrile, and 60 parts of acrylamide are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, nitrogen protection is performed, the temperature is raised to 45°C, deionized water is added to obtain a mixture with a solid content of 26wt%, an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture using a peristaltic pump, the dropping is controlled to be completed in 45 min, 45°C reaction is performed for 18 h, monomers (reactants) are removed under vacuum at 85°C for 2 h, deionized water is added for dilution to obtain the water-based negative electrode binder.

[0062] Comparative Example 6 A water-based negative electrode binder is prepared from the following raw materials: an unsaturated carboxylic acid (acrylic acid), acrylonitrile, an acrylate monomer (butyl acrylate), an inorganic alkali aqueous solution (the inorganic alkali is sodium hydroxide), an initiator aqueous solution (the initiator is ammonium persulfate), and deionized water.

[0063] A preparation method of a water-based negative electrode binder is as follows: 44 parts of sodium hydroxide and 700 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, 80 parts of acrylic acid, 4 parts of butyl acrylate, and 120 parts of acrylonitrile are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, nitrogen protection is performed, the temperature is raised to 45℃, deionized water is added to obtain a mixture with a solid content of 26wt%, an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture using a peristaltic pump, the dropping is controlled to be completed in 45 min, 45℃ reaction is performed for 18 h, monomers (reactants) are removed under vacuum at 85℃ for 2 h, deionized water is added for dilution to obtain a water-based negative electrode binder.

[0064] Comparative Example 7 A water-based negative electrode binder is prepared from the following raw materials: unsaturated carboxylic acid (acrylic acid), acrylonitrile, amide monomer (acrylamide), acrylate monomer (butyl acrylate), inorganic alkali aqueous solution (inorganic alkali is sodium hydroxide), initiator aqueous solution (initiator is ammonium persulfate), and deionized water.

[0065] A preparation method of a water-based negative electrode binder is as follows: 44 parts of sodium hydroxide and 1092 parts of deionized water are added to a reaction container, stirred until completely dissolved to obtain an inorganic alkali aqueous solution, 80 parts of acrylic acid, 4 parts of butyl acrylate, 120 parts of acrylonitrile, and 60 parts of acrylamide are sequentially added to the inorganic alkali aqueous solution, the stirring speed is adjusted until no stratification is observed, oxygen in the reaction kettle is removed under vacuum, nitrogen protection is performed, the temperature is raised to 45℃ to obtain a mixture with a solid content of 22wt%, an initiator aqueous solution composed of 0.62 parts of ammonium persulfate and 20 parts of water is added dropwise to the mixture using a peristaltic pump, the dropping is controlled to be completed in 45 min, 45℃ reaction is performed for 18 h, monomers (reactants) are removed under vacuum at 85℃ for 2 h, deionized water is added for dilution to obtain a water-based negative electrode binder.

[0066] Performance test method and data The water-based negative electrode binders prepared in the examples and comparative examples are tested for performance, and the test data are shown in Table 1.

[0067] The solid content test refers to GB / T 2793-1995 Adhesion agent Determination of non-volatile content; the viscosity test refers to GB / T 2794-2022 Adhesion agent Determination of viscosity, 40℃; Peeling strength test: the obtained binder was stirred uniformly according to the mass ratio of graphite material (Shanghai Sunshun Technology Co., Ltd. FSN-1): conductive agent (Shanghai Hui Ping New Energy Co., Ltd.): binder = 97:1:2, and sieved through 150 meshes. The obtained negative electrode slurry was coated on the surface of a conductive copper foil current collector, and was heated, dried, and rolled to a density of 1.5 g / dm 3 The lower slice was obtained to obtain a finished electrode sheet; the peeling strength was tested according to the adhesive 180° peeling strength test method of GB / T 2790-1995, wherein "-" indicates that it cannot be sieved through 150 meshes and is not tested.

[0068] Battery test: the above negative electrode sheet and oily lithium iron positive electrode sheet (lithium iron phosphate material (LTK Energy Technology Co., Ltd. M12): conductive agent (Shanghai Hui Ping New Energy Co., Ltd.): PVDF = 93:4:3) were prepared into a soft package battery with a capacity of 1 Ah through a lamination process. Under a battery test system, a cycle test was performed, as shown in Figure 1 As shown in the table, the battery prepared by the binder of Example 1 remained 86% of the capacity after 2000 times of charge and discharge; the battery prepared by the binder of Comparative Example 1 remained 80% of the capacity after 1400 times of charge and discharge; the battery prepared by the binder of Comparative Example 6 remained 72% of the capacity after 250 times of charge and discharge; and the battery prepared by the binder of Comparative Example 8 remained 81% of the capacity after 2000 times of charge and discharge.

[0069] Table 1

[0070] As shown in Table 1 and Figures 1-4 It can be seen that the water-based negative electrode binder prepared by the specific raw material components and the simple one-pot method has excellent peeling strength (≥9.75 N / m) and cycle performance on the basis of high solid content (6-7 wt%) and high viscosity (≥7300 mPa·s), as shown in Figure 5 As shown in the table, the battery prepared by the binder of Example 1 remained 86% of the capacity after 2000 times of charge and discharge; the battery prepared by the binder of Comparative Example 1 remained 80% of the capacity after 1400 times of charge and discharge; the battery prepared by the binder of Comparative Example 6 remained 72% of the capacity after 250 times of charge and discharge; and the battery prepared by the binder of Comparative Example 8 remained 81% of the capacity after 2000 times of charge and discharge.

Claims

1. An aqueous negative electrode binder, characterized by, The preparation raw materials include unsaturated carboxylic acid, acrylonitrile, amide monomer, acrylate monomer, aqueous inorganic base solution, aqueous initiator solution and deionized water; the weight ratio of the unsaturated carboxylic acid, acrylonitrile, amide monomer and acrylate monomer is 1: (1.5-2): (0.3-1): (0.03-0.2), the solid content of the aqueous negative electrode binder is 5-8wt%, and the viscosity at 40℃ is 6000-16000mPa·s.

2. The aqueous negative electrode binder of claim 1, wherein, The solid content of the aqueous negative electrode binder is 6-7wt%, and the viscosity at 40℃ is 9000-16000mPa·s.

3. The aqueous negative electrode binder of claim 2, wherein, The weight ratio of the unsaturated carboxylic acid, acrylonitrile, amide monomer and acrylate monomer is 1: (1.5-1.75): (0.375-0.75): (0.05-0.1). The amide monomer includes at least one of methacrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide and acrylamide. The acrylate monomer includes at least one of ethyl acrylate, isobutyl acrylate, ethyl methacrylate, isobutyl methacrylate, butyl acrylate and butyl methacrylate. The unsaturated carboxylic acid includes at least one of acrylic acid and methacrylic acid.

4. A method of preparing the aqueous negative electrode binder according to any one of claims 1 to 3, characterized by, The method comprises the following steps: The unsaturated carboxylic acid, acrylonitrile, amide monomer and acrylate monomer are uniformly mixed, and then uniformly mixed with the aqueous inorganic base solution to obtain a mixture; The aqueous initiator solution is added dropwise into the mixture to perform a reaction, deionized water is added for dilution after post-treatment to obtain the aqueous negative electrode binder.

5. The method of claim 4, 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 solid content in the mixture is 20-30wt%.

6. The method of claim 5, wherein the aqueous negative electrode binder is prepared by mixing the polyepoxide, the polyamine, and the water. The solid content in the mixture is 24-28wt%.

7. The method of claim 6, wherein the aqueous negative electrode binder is prepared by mixing the polyepoxide, the polyamine, and the water. The temperature of the reaction is 40-50℃, and the time is 15-22h.

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 aqueous initiator solution accounts for 1-2wt% of the mixture, and the content of the initiator in the aqueous initiator solution is 1-5wt%.

9. Use of the aqueous negative electrode binder according to any one of claims 1 to 3, characterized in that, The aqueous negative electrode binder is 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, in terms of weight percentage, 0.5-1.5% of conductive agent, 1-3% of the aqueous negative electrode binder, and the balance of graphite material.

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