锂离子电池PMMA-VAc聚合物电解质的制备与性质研究

以甲基丙烯酸甲酯(MMA)和醋酸乙烯酯(VAc)为单体, 用乳液聚合法合成聚甲基丙烯酸甲酯-醋酸乙烯酯聚合物(PMMA-VAc), 并以此聚合物制备了新型聚烯烃膜支撑的聚合物膜及聚合物电解质. 用红外光谱(FTIR)、凝胶色谱(GPC)、差热和热重分析(DSC/TG)、扫描电镜(SEM)及电池充放电实验等方法研究了聚合物、聚合物膜和聚合物电解质的性质. 红外光谱结果表明, MMA与VAc通过各自的C＝C双键打开聚合成PMMA-VAc. PMMA-VAc易于分散在混合碳酸酯溶剂中并形成凝胶, 凝胶粘度随PMMA-VAc浓度的增加而增加, 当浓度为4%时成膜效果最佳. PMMA-VAc膜具有大量的微孔结构, 具有极强的吸液性能. PMMA-VAc膜具有良好的热稳定性: 在380 ℃范围内保持稳定. 聚烯烃膜支撑的PMMA-VAc膜室温下的离子电导率为1.85×10^－3 S•cm^－1, 用作为锂离子电池的聚合物电解质时, 电池具有良好的循环稳定性和倍率性能.

Study on the Preparation and Performances of PMMA-Vac Polymer Electrolyte for Lithium Ion Battery Use

A copolymer, poly-methyl methacrylate-vinyl acetate (PMMA-VAc), was synthesized by emulsion polymerization with methyl methacrylate (MMA) and vinyl acetate (VAc) as monomers. With this co-polymer, polymer membrane and polymer electrolyte were prepared on the basis of polyethylene membrane. Performances of the synthesized copolymer and prepared polymer membrane and electrolyte were studied with FTIR, GPC, DSC/TG, SEM and battery charging and discharging experiments. It was found from FTIR that PMMA-VAc was formed by breaking the double bonds of monomers. PMMA-VAc can be easily dis-persed in mixed carbonates to form a gel. The viscosity of the gel increases with the content of PMMA-VAc in carbonates, and the best content of PMMA-VAc for polymer membrane is 4%. PMMA-VAc copolymer has a porous structure, which has a good electrolyte absorptivity. It is stable up to 380 ℃. The conductivity of the polymer electrolyte at room temperature is 1.85×10^－3 S•cm^－1. With the polymer electrolyte as the gel polymer electrolyte (GPE) of battery Li/GPE/LiCoO₂, the battery shows its good cyclic stability and high rate discharge performance.