锂离子电池PMMA-VAc聚合物电解质的制备与性质研究

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

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1.85×10-3S?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.

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 copolymer, 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 dispersed 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.