A mechanism of ionic conduction of poly (vinylidene fluoride)-lithium perchlorate hybrid films

Abstract

Polymeric solid electrolytes were prepared by the hybridisation of poly(vinylidene fluoride) and lithium perchlorate. These were obtained as films of about 0.1 mm thickness, and showed high lithium ionic conductivity of about 10 −5 (S cm −1). The conductivity depended on the contents of lithium perchlorate and polar additives having high boiling temperature. The amount of lithium perchlorate and the logarithm of the conductivity showed linear relation up to a certain (critical) amount of lithium perchlorate. Beyond the critical value, crystals of lithium perchlorate grew in polymer matrix, and the conductivity was not increased so much. Viscosity and dielectric constant of the additives were potent factors to increase the conductivity of the hybrid film. Organic polar materials with lower viscosity such as N, N-dimethyl formamide or γ-butyrolactone strongly contributed to the improvement of lithium ionic conductivity. The activation energy of conduction decreased dramatically by increasing mole ratio of additive and lithium perchlorate. The lithium ions were considered to migrate in the conduction path which was formed by polymer matrix with organic additive molecules.