A Nanocomposite Polymer Electrolyte with High-Temperature Stability for Rechargeable Lithium Batteries

A kind of nanocomposite polymer electrolyte (NCPE) based on poly(vinylidene fluoride-co-hexafluoropropylene) was prepared by a solution casting technology, in which a room temperature ionic liquid, 1-ethyl-3-methyl-imidazolium tetrafluoroborate was used as plasticizer to improve the thermal stability. The obtained NCPE displayed a porous structure composed of many spherical polymer grains and its crystallinity decreased with the amount of SiO2 nanoparticles. Effect of SiO2 nanoparticles on its electrochemical properties was studied by impedance spectroscopy, linear sweep voltammetry and cyclic voltammetry. When the NCPE is filled with 2 % of SiO2 nanoparticles, it has a room temperature ionic conductivity of 4.7 × 10−4 S cm−1, and exhibits a high decomposition temperature up to 289 °C. The Li/LiFePO4 cells using this NCPE as separator show a good rate capability and a satisfied cycling performance. The results confirmed the feasibility of the as-prepared NCPE in rechargeable lithium batteries.