Porous PVDF with LiClO₄ complex as 'solid' and 'wet' polymer electrolyte

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.