Emulsion polymerization adhesive for lithium battery negative electrode substituted SBR (Styrene Butadiene Rubber) and preparation method thereof

Abstract

The invention discloses an emulsion polymerization adhesive for a lithium battery negative electrode substituted SBR (Styrene Butadiene Rubber), the emulsion polymerization is performed in an emulsion prepared from an unsaturated monomer and water under the action of an emulsifier, and the system is mainly composed of the unsaturated monomer, the water, the emulsifier (compounding a plurality of emulsifiers) and a water-soluble initiator. The monomer comprises but is not limited to one or more of acrylic acid, methacrylic acid, methyl methacrylate, styrene, vinyl acetate, butyl acrylate, 2-ethylhexyl acrylate, acrylamide and N-methacrylamide. According to the invention, a simple and environment-friendly method is adopted to obtain a high-molecular adhesive which is more excellent than an SBR (styrene butadiene rubber) emulsion, is more suitable for lithium batteries and can improve the performance of the existing lithium batteries to replace an imported SRB adhesive which is widely used nowadays, and the selected monomer is very stable and reliable after polymerization and has good aging resistance, high temperature resistance and low temperature resistance; and the crosslinking and electrolyte absorption are moderate, so that the stability of a lithium ion storage and release frame of the negative electrode layer is kept.

Description

technical field [0001] The invention relates to the technical field of polymer materials, in particular to an emulsion-polymerized binder for lithium battery negative electrodes replacing SBR and a preparation method thereof. Background technique [0002] Nowadays, the negative electrode binder used by most lithium battery manufacturers is still SBR, and the Chinese explanation is mostly modified carboxylated styrene-butadiene rubber emulsion. Our analysis of why the modification is: first, the ordinary SBR itself is not resistant to the electrolyte solvent, and second, the SBR emulsion is mainly composed of butadiene-styrene-acrylic acid through low-temperature emulsion polymerization, and there is still a butadiene in the polymer main chain. After olefin free polymerization -C=C-unsaturated double bond, it is not resistant to aging and oxidation. To sum up the above two reasons, it is necessary to carry out vulcanization and cross-linking to remove double bonds and improv...

AI Technical Summary

Problems solved by technology

The low-temperature emulsion polymerization method requires the use of a special disproportionated rosin emulsifier, peroxide, ferrous sulfate, and white block oxidation-reduction initiation system to initiate polymerization, and there is separation of unreacted butadiene and styrene in the later stage. The process is complicated. Add There are too many kinds of materials, so the SBR film is usually opaque, dark in color, high in impurity content, poor in conductivity and low temperature (too dense cross-linking), and there are not many comonomers that can be improved by low temperature reaction, and it is difficult to improve performance. The following disadvantages: a. In order to eliminate unsaturated double bonds and improve aging resistance, the degree of crosslinking is very large, the flexibility is lost, and the low temperature resistance is relatively poor, thus affecting the low temperature performance of lithium batteries

b. The production process of SBR is complicated, and the continuous production and modification are not easy

c. The emulsifier used is an inert emulsifier and does not participate in the polymer chain. It is easy to float out of the polymer in the future and affect the performance

d. Too many additives during low-temperature synthesis of SBR may affect the performance of the battery

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