Characteristics of PVdF-HFP/TiO2 composite electrolytes prepared by a phase inversion technique using dimethyl acetamide solvent and water non-solvent

Highly porous poly[(vinylidene fluoride)co-hexafluoropropylene] (PVdF-HFP)/TiO2 membranes were prepared by a phase inversion technique, using dimethyl acetamide (DMAc) as a solvent and water as a non-solvent. Their physical and electrochemical properties were then characterized in terms of thermal and crystalline behavior, as well as ionic conductivity after absorbing an electrolyte solution of 1 M LiPF6 dissolved in an equal weight mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). For comparison, cast films and their electrolytes were also made by a conventional casting method without using the water non-solvent. In contrast to the case of using N-methyl-2-pyrrolidone (NMP) as a solvent, the PVdF-BFP/TiO2 composite electrolytes, obtained using DMAc, exhibited superior properties of electrochemical stability and interfacial resistance with a lithium electrode but had lower ionic conductivities. It was also demonstrated that the phase inversion. membrane was more effective than the cast film as the polymer electrolyte of a lithium rechargeable battery. As a result, a phase inversion membrane with 50 wt.-% TiO2 was demonstrated to be the optimal choice for application in a lithium rechargable battery.