Porous PVDF with LiClO4 complex as ‘solid’ and ‘wet’ polymer electrolyte
Abstract The structure and ion dynamics of the PVDF/LiClO4 solid polymer electrolyte prepared by a new approach is discussed. The DSC, XRD and SEM results evidenced the decrease in crystallinity of PVDF in the presence of the lithium ionic salt. Strong growth in the CF2 stretching in FTIR with increasing lithium salt implies the acid–base complexation of PVDF with lithium. However, the ClO4− absorption indicated presence of both free and ion-paired structure in PVDF/LiClO4 film. Nevertheless, the ionic conductivity of the ‘dry’ PVDF/LiClO4 film continues to increase with increasing lithium salt. This is contrasted with the PEO solid polymer electrolyte systems, where development of ion pairing retards the ion conduction. In comparison, PVDF/LiClO4 SPE ‘wetted’ with PC and mixture of EC/PC showed less salt concentration. The charge migration in the “wet” polymer electrolyte originated from ion transport through swollen polymer via diffusion of organic small molecules, and a second path via amorphous PVDF matrix. The room-temperature ion conductivity approaching 10−3 S/cm is an impressive value for most applications as solid polymer electrolyte.