High-viscosity SBR-based battery adhesive for lithium-ion battery anode and its preparation method

Abstract

This invention belongs to the field of battery adhesive technology, specifically relating to a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes and its preparation method. The preparation method of the high-viscosity SBR-based battery adhesive for lithium-ion battery anodes includes the following steps: mixing SBR emulsion, DVB, emulsifier, coupling agent, and deionized water; emulsifying under the action of an initiator to obtain a core layer pre-emulsion; then heating and adding a functional layer mixture for reaction; subsequently adding a shell layer mixture and maintaining the temperature for reaction; finally cooling, adjusting the pH, and filtering to obtain the SBR-based battery adhesive. This invention provides a method for preparing a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes, employing a segmented emulsion polymerization method. The core layer forms a stable framework through cross-linking of DVB and SBR, and a modifier is introduced into the shell layer, which synergistically enhances the viscosity of the adhesive with nano-silica, further optimizing the compatibility of the adhesive. The prepared SBR-based battery adhesive exhibits high adhesion and high stability.

Description

Technical Field

[0001] This invention belongs to the field of battery adhesive technology, specifically relating to a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes and its preparation method. Background Technology

[0002] Lithium-ion batteries, as the core carrier of the new energy industry, are widely used in new energy vehicles, energy storage systems, consumer electronics, and other fields. Their performance directly determines the core competitiveness of downstream products. The negative electrode, as the key electrode for lithium-ion batteries to achieve charge-discharge cycles, undertakes the core functions of lithium-ion insertion and extraction, and electron conduction. The negative electrode adhesive (also known as the negative electrode binder) is an indispensable key auxiliary material in the preparation of the negative electrode.

[0003] Early lithium-ion battery anodes primarily used oil-based binders, polyvinylidene fluoride (PVDF), which possessed good electrochemical stability. However, it suffered from drawbacks such as high cost, the use of organic solvents (NMP) which was environmentally unfriendly, and difficulty in adapting to the volume expansion of silicon-based anodes. Therefore, it was gradually replaced by water-based binders. Currently, water-based binders have become the industry mainstream, mainly including styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), and polyacrylic acid (PAA). Among these, the CMC and SBR composite system is widely used in graphite anodes, dominating the market due to its advantages of being environmentally friendly, low-cost, and having good dispersibility.

[0004] CN109638286A discloses a carboxymethyl cellulose-based binder suitable for lithium batteries and its application. Its main components are sodium carboxymethyl cellulose, modified SBR-SiO2 paste, tea saponin, thickener, and diluent. The preparation involves permeating the diluent into sodium carboxymethyl cellulose to form a premix, then sequentially adding modified SBR and tea saponin while stirring at high speed, and finally adding the thickener and stirring again. This binder solves the problems of large particles, insufficient electrode flexibility, and surface defects that occur when sodium carboxymethyl cellulose is mixed with multiple components in traditional methods. The problem of numerous defects is that it has the characteristics of fine particle size and good miscibility, which can reduce surface defects of the electrode, improve the flexibility of the electrode and avoid electrode cracking. However, this binder mainly relies on CMC as a thickener to adjust the rheological properties of the adhesive solution, and the thickening mechanism is simple, which is difficult to meet the coating requirements of high-load negative electrodes. At the same time, although SiO2 is introduced for modification, it mainly exists in the form of physical blending or simple grafting, lacking strong chemical bond bridging. During the high-temperature cycling of the battery, the inorganic phase and the organic phase are prone to phase separation, resulting in the collapse of the colloidal network.

[0005] CN115850591A discloses a method for preparing an emulsion-type binder and its application in the negative electrode of a lithium-ion battery. The binder adopts a core-shell structure design. The core layer is made of vinyl aromatic monomers, alkyl acrylate monomers, etc., through pre-emulsification and polymerization, with a high glass transition temperature to ensure structural stability under high temperature and electrolyte immersion. The shell layer contains alkyl acrylate monomers, cyano monomers, etc., with a low glass transition temperature, imparting good adhesion, slurry dispersibility, and film-forming properties. The preparation process involves stepwise pre-emulsification, seed polymerization, simultaneous dropwise addition of core-shell pre-emulsion and initiator solution, followed by neutralization and filtration to obtain the finished product. The binder shell layer is rich in carboxyl groups, and the emulsifier... It can participate in polymerization to reduce small molecule residues, and the differentiated design of core-shell crosslinking density takes into account both mechanical strength and flexibility. It is suitable for anode active materials such as artificial graphite and silicon-carbon, and can improve the high-temperature performance, cycle life and low-temperature conductivity of lithium batteries. However, the emulsion-type binder prepared by this method mainly relies on the difference in monomer composition to form, and there is a lack of efficient interfacial chemical bridging between the core and shell layers. During long-term battery cycling, due to electrolyte wetting and repeated lithium ion insertion and extraction, the core-shell interface is prone to peeling, resulting in rapid decay of the bonding strength. At the same time, although the shell design introduces carboxyl-containing monomers, the anti-expansion ability of the pure organic polymer system is limited when facing anode materials with high volume expansion.

[0006] In summary, although existing technologies have optimized the dispersibility and electrochemical stability of SBR-based battery adhesives, they still suffer from insufficient colloidal stability, severe volume expansion at high temperatures, and rapid decay of bond strength. Summary of the Invention

[0007] To overcome the aforementioned deficiencies in the existing technology, this invention provides a method for preparing a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes. The adhesive is prepared using a segmented emulsion polymerization method. The core layer forms a stable framework through crosslinking of DVB and SBR, while the shell layer incorporates a methacryloyloxypropyl heptaisobutyl cage-like polysilsesquioxane modifier. This modifier works synergistically with nano-silica to significantly increase the adhesive viscosity. Simultaneously, coupling agent A-171 bridges the interface between the organic and inorganic phases, and the modifier further optimizes the compatibility of the adhesive. The prepared SBR-based battery adhesive exhibits high adhesion and high stability.

[0008] A method for preparing a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes includes the following steps:

[0009] (1) Mix styrene-butadiene rubber (SBR) emulsion, divinylbenzene (DVB), emulsifier, coupling agent and deionized water, add initiator, stir and emulsify at 50-70℃ to obtain core layer pre-emulsion;

[0010] (2) Heat the core layer pre-emulsion from step (1) to 65-75°C, add the functional layer mixture containing hydroxyethyl methacrylate (HEMA), methacrylic acid (MAA) and initiator, and keep the mixture warm for 0.5-1h after the addition is complete.

[0011] (3) After the reaction in step (2) is completed, the reaction solution is heated to 75-85℃, and a shell mixture containing acrylate compounds, nano silica dispersion, crosslinking agent and modifier is added. After the addition is completed, the reaction is kept at the temperature for 0.5-1h.

[0012] (4) Post-processing: After the reaction is completed, the temperature is lowered, and the pH of the system is adjusted to neutral using an ammonia solution with a concentration of 25-28 wt.%. The mixture is filtered to obtain a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes.

[0013] In the core layer pre-emulsion, the emulsifier is sodium dodecyl sulfate and the coupling agent is vinyltrimethoxysilane A-171.

[0014] The core layer pre-emulsion comprises, by mass parts, the following raw materials: 30-50 parts of styrene-butadiene rubber (SBR) emulsion, 5-15 parts of divinylbenzene (DVB), 1-5 parts of emulsifier, 0.5-3 parts of coupling agent, and 40-60 parts of deionized water.

[0015] The styrene-butadiene rubber latex is obtained by emulsion polymerization of styrene and butadiene. The preparation process is as follows: by mass, 30-40 parts of styrene, 60-70 parts of butadiene, 2-5 parts of sodium dodecyl sulfate, 0.3-0.8 parts of ammonium persulfate and 100-150 parts of deionized water are added to a reaction vessel, stirred and emulsified at 60-70℃, and the polymerization reaction is carried out for 6-8 hours. After cooling and filtration, a styrene-butadiene rubber latex with a solid content of 45-50 wt.% is obtained. Further, the mass fraction of the styrene-butadiene rubber latex in step (1) is based on the total mass of the latex.

[0016] The functional layer mixture in step (2) includes the following raw materials by mass: 10-20 parts of hydroxyethyl methacrylate (HEMA), 5-15 parts of methacrylic acid (MAA), and 0.2-1 parts of initiator.

[0017] In steps (1) and (2), the initiator is ammonium persulfate. In step (1), the amount of initiator is 0.3-0.5% of the total mass of styrene-butadiene rubber (SBR) emulsion and divinylbenzene (DVB).

[0018] In step (3), the shell mixture also contains one or more of the following: polyurethane dispersion, phosphate plasticizer, and antioxidant. The amounts added, by weight, are: 1-5 parts polyurethane dispersion, 0.5-3 parts phosphate plasticizer, and 0.1-1 parts antioxidant. Preferably, the polyurethane dispersion is Bayhydrol from Covestro Polymers (China) Co., Ltd. ® UH 2558, the phosphate ester plasticizer is Disflamoll from Lanxess Chemicals (China) Co., Ltd. ® TP, the nano silica dispersion, is Evonik Industries' AERODISP. ® WF 7620.

[0019] The acrylate compound is a mixture of butyl acrylate and 2,2,2-trifluoroethyl acrylate (TFEA), with a mass ratio of butyl acrylate to 2,2,2-trifluoroethyl acrylate of (5-10):1, preferably 8:1.

[0020] The modifier is methacryloyloxypropylheptaisobutyl cage-like polysilsesquioxane, and the crosslinking agent is N-hydroxymethylacrylamide.

[0021] In step (3), the amount of each raw material used by weight is as follows: 20-40 parts of acrylate compound, 5-15 parts of nano silica dispersion, 1-5 parts of crosslinking agent, and 0.5-3 parts of modifier.

[0022] The high-viscosity SBR-based battery adhesive for lithium-ion battery anodes of the present invention is prepared by the above-described preparation method.

[0023] The SBR-based battery adhesive prepared in this invention is used as an aqueous binder in the preparation process of lithium-ion battery anodes. The specific application process is as follows: the battery adhesive is mixed with anode active materials, conductive agents and deionized water in a certain proportion, and a uniformly dispersed anode slurry is prepared by high-speed dispersion. Then, the slurry is filtered and uniformly coated onto a copper foil current collector. After drying, rolling and other processes, a negative electrode sheet is formed. The SBR-based battery adhesive of this invention can be directly mixed with other anode components. Its high viscosity can effectively suspend solid particles, prevent slurry sedimentation, and ensure coating uniformity. Thickeners (sodium carboxymethyl cellulose aqueous solution) can also be added appropriately according to the actual slurry formulation or coating requirements for rheological control. The amount added is 10-15% of the total mass of the SBR-based battery adhesive.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The present invention discloses a method for preparing high-viscosity SBR-based battery adhesive for lithium-ion battery anodes. The method employs a core-shell layered polymerization process, combined with DVB crosslinking, A-171 modification, and the synergistic effect of the modifier and nano-silica, which significantly improves the viscosity of the adhesive solution, meets the coating and bonding requirements of lithium-ion battery anodes, and enhances the uniformity and storage stability of the adhesive solution, avoids delamination and demulsification, and maintains good performance even after long-term storage.

[0026] The high-viscosity SBR-based battery adhesive for lithium-ion battery anodes of this invention, through the construction of interface connections, layered crosslinking design and modification agent optimization, has high interfacial bonding force and adhesion strength, reducing the phenomenon of anode shedding and pulverization during battery cycling; at the same time, it has excellent heat resistance, water resistance and chemical stability, ensuring battery cycle stability and safety. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the embodiments and comparative examples. Unless otherwise specified, the raw materials used in the embodiments and comparative examples are all conventional commercial raw materials, and the process methods used are all conventional methods in the art unless otherwise specified. All parts involved are parts by mass.

[0028] Both the examples and comparative examples were implemented using the following raw materials, the specific raw material descriptions of which are as follows:

[0029] Divinylbenzene: Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0030] Emulsifier: Sodium dodecyl sulfate: Sinopharm Chemical Reagent Co., Ltd.;

[0031] Coupling agent: Vinyltrimethoxysilane A-171, Momentive Advanced Materials Group, Silquest A-171™;

[0032] Hydroxyethyl methacrylate: Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0033] 2,2,2-Trifluoroethyl acrylate (TFEA): Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0034] Nano-silica dispersion: Evonik Industries, AEROSIL ® AERODISP (Fused Phase Silicon Dioxide) ® WF7620;

[0035] Crosslinking agent N-hydroxymethylacrylamide: Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0036] Modifier: Methacryloxypropylheptaisobutyl cage-like polysilsesquioxane, Guangzhou Yixin Technology Co., Ltd.;

[0037] Polyurethane dispersion: Bayhydrol from Covestro Polymers (China) Co., Ltd. ® UH 2558;

[0038] Phosphate ester plasticizers: Disflamoll from Lanxess Chemicals (China) Co., Ltd. ® TP;

[0039] Antioxidant: Irganox from BASF AG ® 1010.

[0040] The specific preparation process of the SBR emulsion used in the examples and comparative examples is as follows: 35 parts by mass of styrene, 65 parts by mass of butadiene, 3.5 parts by mass of sodium dodecyl sulfate, 0.5 parts by mass of ammonium persulfate and 125 parts by mass of deionized water are added to the reactor, stirred and emulsified at 65°C, and polymerized for 7 hours. After cooling and filtration, an SBR emulsion with a solid content of 45.4 wt.% is obtained.

[0041] The preparation method of the high-viscosity SBR-based battery adhesive for the lithium-ion battery negative electrode includes the following steps:

[0042] (1) By mass, mix 30-50 parts of SBR emulsion, 5-15 parts of DVB, 1-5 parts of sodium dodecyl sulfate, 0.5-3 parts of vinyltrimethoxysilane A-171 and 40-60 parts of deionized water, add ammonium persulfate, and stir emulsify at 50-70°C to obtain a core layer pre-emulsion, wherein the amount of ammonium persulfate is 0.3-0.5% of the total mass of SBR emulsion and DVB;

[0043] (2) Heat the core layer pre-emulsion from step (1) to 65-75℃, add 10-20 parts HEMA, 5-15 parts MAA and 0.2-1 parts ammonium persulfate, and keep the reaction at the temperature for 0.5-1h after the addition is complete;

[0044] (3) After the reaction in step (2) is completed, the reaction solution is heated to 75-85℃, and 20-40 parts of acrylate compound, 5-15 parts of nano silica dispersion, 1-5 parts of N-hydroxymethylacrylamide, and 0.5-3 parts of methacryloyloxypropylheptaisobutyl cage polysilsesquioxane are added. After the addition is completed, the reaction is kept at the temperature for 0.5-1h. In addition, one or more of polyurethane dispersion, phosphate plasticizer, and antioxidant can be added to the mixture. The amount added by mass is as follows: 1-5 parts of polyurethane dispersion, 0.5-3 parts of phosphate plasticizer, and 0.1-1 parts of antioxidant.

[0045] (4) Post-processing: After the reaction is completed, the temperature is lowered to 40°C, and the pH of the system is adjusted to neutral using an ammonia solution with a concentration of 25-28wt.%. The system is then filtered through a 200-mesh sieve to obtain a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes.

[0046] Example 1

[0047] The preparation method of the high-viscosity SBR-based battery adhesive for the lithium-ion battery negative electrode includes the following steps:

[0048] (1) By mass, 30 parts of SBR emulsion, 5 parts of DVB, 1 part of sodium dodecyl sulfate, 0.5 parts of vinyltrimethoxysilane A-171 and 40 parts of deionized water are mixed, and ammonium persulfate is added. The mixture is stirred and emulsified at 50°C to obtain a core layer pre-emulsion. The amount of ammonium persulfate is 0.3% of the total mass of SBR emulsion and DVB.

[0049] (2) Heat the core layer pre-emulsion from step (1) to 65°C, add 10 parts HEMA, 5 parts MAA and 0.2 parts ammonium persulfate, and keep the reaction at the temperature for 0.5 h after the addition is complete;

[0050] (3) After the reaction in step (2) is completed, the reaction solution is heated to 75°C, and 20 parts of acrylate compound (the mass ratio of butyl acrylate to TFEA is 8:1), 5 parts of nano silica dispersion, 1 part of N-hydroxymethylacrylamide, 0.5 parts of methacryloyloxypropyl heptaisobutyl cage polysilsesquioxane, and 5 parts of polyurethane dispersion are added. After the addition is completed, the reaction is kept at the temperature for 0.5 h.

[0051] (4) Post-processing: After the reaction is completed, the temperature is lowered to 40°C, and the pH of the system is adjusted to neutral using an ammonia solution with a concentration of 25wt.%. The mixture is then filtered through a 200-mesh sieve to obtain a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes.

[0052] Example 2

[0053] The preparation method of the high-viscosity SBR-based battery adhesive for the lithium-ion battery negative electrode includes the following steps:

[0054] (1) By mass, 40 parts of SBR emulsion, 10 parts of DVB, 3 parts of sodium dodecyl sulfate, 1.5 parts of vinyltrimethoxysilane A-171 and 50 parts of deionized water are mixed, ammonium persulfate is added, and the mixture is stirred and emulsified at 60°C to obtain a core layer pre-emulsion. The amount of ammonium persulfate is 0.5% of the total mass of SBR emulsion and DVB.

[0055] (2) Heat the core layer pre-emulsion from step (1) to 70°C, add 15 parts HEMA, 10 parts MAA and 1 part ammonium persulfate, and keep the reaction at the temperature for 1 hour after the addition is complete.

[0056] (3) After the reaction in step (2) is completed, the reaction solution is heated to 80°C, and 30 parts of acrylate compound (the mass ratio of butyl acrylate to TFEA is 8:1), 10 parts of nano silica dispersion, 3 parts of N-hydroxymethylacrylamide, 2 parts of methacryloyloxypropyl heptaisobutyl cage polysilsesquioxane, 1 part of polyurethane dispersion, 0.5 parts of phosphate plasticizer, and 1 part of antioxidant are added. After the addition is completed, the reaction is kept at the temperature for 0.5 h.

[0057] (4) Post-processing: After the reaction is completed, the temperature is lowered to 40°C, and the pH of the system is adjusted to neutral using an ammonia solution with a concentration of 26wt.%. The system is then filtered through a 200-mesh sieve to obtain a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes.

[0058] Example 3

[0059] The preparation method of the high-viscosity SBR-based battery adhesive for the lithium-ion battery negative electrode includes the following steps:

[0060] (1) By mass, 50 parts of SBR emulsion, 15 parts of DVB, 5 parts of sodium dodecyl sulfate, 3 parts of vinyltrimethoxysilane A-171 and 60 parts of deionized water are mixed, ammonium persulfate is added, and the mixture is stirred and emulsified at 70°C to obtain a core layer pre-emulsion. The amount of ammonium persulfate is 0.4% of the total mass of SBR emulsion and DVB.

[0061] (2) Heat the core layer pre-emulsion from step (1) to 75°C, add 20 parts HEMA, 15 parts MAA and 0.5 parts ammonium persulfate, and keep the reaction at the temperature for 1 hour after the addition is complete.

[0062] (3) After the reaction in step (2) is completed, the reaction solution is heated to 85°C, and 40 parts of acrylate compound (the mass ratio of butyl acrylate to TFEA is 8:1), 15 parts of nano silica dispersion, 5 parts of N-hydroxymethylacrylamide, 3 parts of methacryloyloxypropyl heptaisobutyl cage polysilsesquioxane, 3 parts of polyurethane dispersion, 2 parts of phosphate plasticizer, and 0.1 parts of antioxidant are added. After the addition is completed, the reaction is kept at the temperature for 1 hour.

[0063] (4) Post-processing: After the reaction is completed, the temperature is lowered to 40°C, and the pH of the system is adjusted to neutral using an ammonia solution with a concentration of 27wt.%. The system is then filtered through a 200-mesh sieve to obtain a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes.

[0064] Example 4

[0065] The preparation method of the high-viscosity SBR-based battery adhesive for the lithium-ion battery negative electrode includes the following steps:

[0066] (1) By mass, 35 parts of SBR emulsion, 7 parts of DVB, 2 parts of sodium dodecyl sulfate, 1 part of vinyltrimethoxysilane A-171 and 45 parts of deionized water are mixed, ammonium persulfate is added, and the mixture is stirred and emulsified at 55°C to obtain a core layer pre-emulsion. The amount of ammonium persulfate is 0.3% of the total mass of SBR emulsion and DVB.

[0067] (2) Heat the core layer pre-emulsion from step (1) to 65°C, add 12 parts HEMA, 8 parts MAA and 1 part ammonium persulfate, and keep the reaction at the temperature for 1 hour after the addition is complete.

[0068] (3) After the reaction in step (2) is completed, the reaction solution is heated to 80°C, and 25 parts of acrylate compound (the mass ratio of butyl acrylate to TFEA is 8:1), 10 parts of nano silica dispersion, 2 parts of N-hydroxymethylacrylamide, 1 part of methacryloyloxypropyl heptaisobutyl cage polysilsesquioxane, 3 parts of phosphate plasticizer, and 0.5 parts of antioxidant are added. After the addition is completed, the reaction is kept at the temperature for 0.5 h.

[0069] (4) Post-processing: After the reaction is completed, the temperature is lowered to 40°C, and the pH of the system is adjusted to neutral using an ammonia solution with a concentration of 28wt.%. The system is then filtered through a 200-mesh sieve to obtain a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes.

[0070] Example 5

[0071] The preparation method of the high-viscosity SBR-based battery adhesive for the lithium-ion battery negative electrode includes the following steps:

[0072] (1) By mass, 45 parts of SBR emulsion, 12 parts of DVB, 4 parts of sodium dodecyl sulfate, 2.5 parts of vinyltrimethoxysilane A-171 and 55 parts of deionized water are mixed, ammonium persulfate is added, and the mixture is stirred and emulsified at 55°C to obtain a core layer pre-emulsion. The amount of ammonium persulfate is 0.5% of the total mass of SBR emulsion and DVB.

[0073] (2) Heat the core layer pre-emulsion from step (1) to 75°C, add 17 parts HEMA, 13 parts MAA and 1 part ammonium persulfate, and keep the reaction at the temperature for 1 hour after the addition is complete.

[0074] (3) After the reaction in step (2) is completed, the reaction solution is heated to 85°C, and 35 parts of acrylate compound (the mass ratio of butyl acrylate to TFEA is 8:1), 13 parts of nano silica dispersion, 4 parts of N-hydroxymethylacrylamide, 2.5 parts of methacryloyloxypropyl heptaisobutyl cage polysilsesquioxane, 2 parts of polyurethane dispersion, and 1 part of antioxidant are added. After the addition is completed, the reaction is kept at the temperature for 1 hour.

[0075] (4) Post-processing: After the reaction is completed, the temperature is lowered to 40°C, and the pH of the system is adjusted to neutral using an ammonia solution with a concentration of 28wt.%. The system is then filtered through a 200-mesh sieve to obtain a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes.

[0076] Comparative Example 1

[0077] The SBR emulsion used in this comparative example is the same as that in Example 1. The preparation method of the battery adhesive is as follows: 150g of SBR emulsion and 50g of sodium carboxymethyl cellulose (CMC) aqueous solution with a solid content of 2wt.% are placed in a reaction vessel and stirred for 30min to obtain the battery adhesive for later use.

[0078] Comparative Example 2

[0079] The raw materials and amounts used in this comparative example are exactly the same as those in Example 1. The difference is that the raw materials are added to the reactor all at once and reacted at 80°C for 2 hours. After the reaction is completed, post-processing is performed, and the post-processing process is exactly the same as that in Example 1.

[0080] Comparative Example 3

[0081] This comparative example is the same as Example 1, except that no nano silica dispersion is added in step (3). The remaining steps are the same as in Example 1. The nano silica dispersion is mixed with the SBR battery adhesive before use and used after being mixed evenly.

[0082] Comparative Example 4

[0083] This comparative example is the same as Example 1, except that the modifier methacryloyloxypropyl heptaisobutyl cage polysilsesquioxane is not added in step (3), and the remaining steps are the same as in Example 1.

[0084] The battery adhesives prepared in the above examples and comparative examples were subjected to performance testing. The specific testing process was as follows: At room temperature, 2 parts of the battery adhesive prepared in the examples and comparative examples, 96 parts of graphite (negative electrode active material), and 1 part of carbon black conductive agent were added to 50 parts of deionized water and stirred at high speed for 30 minutes. After mixing evenly, the mixture was filtered through a 200-mesh sieve to obtain a negative electrode slurry. The prepared negative electrode slurry was uniformly coated on a copper foil current collector with a coating thickness of 100 μm. After coating, the mixture was placed in a 110℃ oven and dried for 5-10 minutes until constant weight. The negative electrode sheet was obtained by rolling at room temperature using a roller press.

[0085] Electrolyte swelling test was performed on the prepared product, and the bonding strength, thermal stability and cycle performance of the prepared negative electrode sheet were tested. Peel strength was tested at 180° according to GB / T 2792-2014 standard. Thermal stability was the 5% weight loss temperature determined by TGA. Cyclic performance was tested as an assembled half cell, and the capacity retention rate was tested after 100 cycles. The test results are shown in Table 1.

[0086] Table 1. Performance test results of the examples and comparative examples.

[0087]

[0088] As shown in Table 1, Comparative Example 1 uses a traditional mixing process that relies on CMC physical adhesion. The colloidal network has poor stability, is easily decomposed at high temperatures, and easily swells in the electrolyte. During cycling, the bonding strength decays rapidly, leading to the pulverization and detachment of the negative electrode sheet and a rapid decrease in battery capacity.

[0089] Compared with Example 1, Comparative Example 2 used the same raw materials and amounts, but all raw materials were added at once. The monomers and fillers could not achieve orderly chemical bonding. The colloid was a random polymer with poor interfacial compatibility. The organic and inorganic phases were easily separated, which led to a significant reduction in adhesion and stability.

[0090] Compared with Example 1, Comparative Example 3 shows that the nano-SiO2 and the organic phase are only physically blended. Under battery cycling and high temperature conditions, the inorganic phase is easily precipitated from the organic colloid, which leads to the failure of the colloid network reinforcement effect, increased swelling degree and decreased adhesion.

[0091] Compared with Example 1, Comparative Example 4 did not include a modifier. The modifier is the key to achieving the synergistic effect between nano-SiO2 and organic colloid. Its cage-like structure can form a spatial network with nano-SiO2, while optimizing the interfacial compatibility of the colloid and improving the binding force between the core and shell layers. Without the modifier, the role of nano-SiO2 is limited, and the anti-swelling and high-temperature resistance of the colloid decreases.

Claims

1. A process for the preparation of high viscosity SBR based battery gum for lithium ion battery negative electrode, characterized by, Includes the following steps: (1) Mix styrene-butadiene rubber latex, divinylbenzene, emulsifier, coupling agent and deionized water, add initiator, stir and emulsify at 50-70℃ to obtain core layer pre-emulsion; (2) Heat the core layer pre-emulsion from step (1) to 65-75°C, add the functional layer mixture containing hydroxyethyl methacrylate, methacrylic acid and initiator, and keep the mixture warm for 0.5-1h after the addition is complete. (3) After the reaction in step (2) is completed, the reaction solution is heated to 75-85℃, and a shell mixture containing acrylate compounds, nano silica dispersion, crosslinking agent and modifier is added. After the addition is completed, the reaction is kept at the temperature for 0.5-1h. (4) Post-processing: After the reaction is completed, the temperature is lowered, and the pH of the system is adjusted to neutral using an ammonia solution with a concentration of 25-28 wt.%. The mixture is filtered to obtain a high-viscosity SBR-based battery adhesive for lithium-ion battery anodes. The emulsifier is sodium dodecyl sulfate, the coupling agent is vinyltrimethoxysilane A-171, the initiator is ammonium persulfate, the modifier is methacryloyloxypropyl heptaisobutyl cage polysilsesquioxane, and the crosslinking agent is N-hydroxymethylacrylamide.

2. The process for the preparation of high viscosity SBR based battery gum for lithium ion battery negative electrode as claimed in claim 1 wherein, In step (1), the amount of initiator used is 0.3-0.5% of the total mass of styrene-butadiene rubber latex and divinylbenzene.

3. The process for the preparation of high viscosity SBR based battery gum for lithium ion battery negative electrode as claimed in claim 1 wherein, The core layer pre-emulsion comprises, by mass parts, the following raw materials: 30-50 parts styrene-butadiene rubber latex, 5-15 parts divinylbenzene, 1-5 parts emulsifier, and 0.5-3 parts coupling agent; 40-60 parts deionized water.

4. The process for the preparation of high viscosity SBR based battery gum for lithium ion battery negative electrode as claimed in claim 3 wherein, The styrene-butadiene rubber latex is obtained by emulsion polymerization of styrene and butadiene. The preparation process is as follows: by mass, 30-40 parts of styrene, 60-70 parts of butadiene, 2-5 parts of sodium dodecyl sulfate, 0.3-0.8 parts of ammonium persulfate and 100-150 parts of deionized water are added to a reactor, stirred and emulsified at 60-70℃, and the polymerization reaction is carried out for 6-8 hours. After cooling and filtration, a styrene-butadiene rubber latex with a solid content of 45-50 wt.% is obtained.

5. The process for the preparation of high viscosity SBR based battery gum for lithium ion battery negative electrode as claimed in claim 1 wherein, The functional layer mixture in step (2) includes the following raw materials by mass: 10-20 parts of hydroxyethyl methacrylate, 5-15 parts of methacrylic acid, and 0.2-1 parts of initiator.

6. The method for preparing high-viscosity SBR-based battery adhesive for lithium-ion battery anodes according to claim 1, characterized in that, In step (3), one or more of the following are added to the shell mixture: polyurethane dispersion, phosphate plasticizer, and antioxidant. The amount added by mass is: 1-5 parts of polyurethane dispersion, 0.5-3 parts of phosphate plasticizer, and 0.1-1 parts of antioxidant.

7. The method for preparing high-viscosity SBR-based battery adhesive for lithium-ion battery anodes according to claim 1, characterized in that, The acrylate compound is a mixture of butyl acrylate and 2,2,2-trifluoroethyl acrylate, with a mass ratio of butyl acrylate to 2,2,2-trifluoroethyl acrylate of (5-10):

1.

8. The method for preparing high-viscosity SBR-based battery adhesive for lithium-ion battery anodes according to claim 1, characterized in that, In step (3), the amount of each raw material used by mass is as follows: 20-40 parts of acrylate compound, 5-15 parts of nano silica dispersion, 1-5 parts of crosslinking agent, and 0.5-3 parts of modifier.

9. A high-viscosity SBR-based battery adhesive for lithium-ion battery anodes, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

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