Conductivity and Morphology of Hybrid Electrolytes Based on Blends of Pvdf With PEO-co-PPO Copolymers

Abstract

ABSTRACTHybrid film electrolytes with high room temperature conductivity have been prepared by casting solutions of PVDF-HFP copolymers with PEO-PPO block copolymers and PEO oligomers followed by activation of the polymer blend films in electrolyte solutions. The morphology and conductivity of these solid electrolytes were studied as a function of concentration, molecular weight and sequence order (in the case of PPO-co-PEO-co-PPO or PEO-co-PPO-co-PEO) of the PEO and PEO-PPO copolymers, and also of the casting solvent and evaporation rate of the casting solvent. Structural studies of PVDF-HFP/PEO and PVDF- HFP/PPO-co-PEO blend films (SEM, DSC) before activation with lithium salt electrolyte may indicate the occurrence of spinodal decomposition in the films during slow evaporation of the casting solvent. As a result of spinodal decomposition, an interpenetrating bi-continuous phase may evolve with microphase separation between PVDF-HFP and PPO-PEO phases, in which the PVDF phase provides mechanical support and the PPO-PEO phase pfovides a conductive path.