Summary: 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‐HFP/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 rechargeable battery.
Time evolutions of interfacial resistance between polymer electrolyte and lithium electrodes.
