High performance composite polymer electrolytes for lithium-ion polymer cells composed of a graphite negative electrode and LiFePO4 positive electrode

Abstract

Core-shell structured SiO2 particles with different core diameters were synthesized by radical polymerization of 4-styrenesulfonic acid sodium salt with vinyl-functionalized SiO2 core particles and were used as Li+ ion-conducting fillers in composite polymer electrolytes. Composite polymer electrolytes prepared with core-shell SiO2 particles exhibited high ionic conductivity exceeding 10(-3) S cm(-1) at room temperature and good mechanical properties, allowing the preparation of a free-standing film with a thickness of 30 mu m. Lithium-ion polymer cells composed of graphite negative electrode, composite polymer electrolyte and LiFePO4 positive electrode were assembled, and their cycling performance was evaluated. Cells assembled with a composite polymer electrolyte containing core-shell SiO2 particles with a core diameter of 250 nm exhibited good cycling performance in terms of discharge capacity, capacity retention and rate capability.