Morphology and ion-conductivity of gelatin-LiClO4 films: fractional diffusion analysis

Biopolymers are expected to replace synthetic polymers in the quest for cost-effective, environment friendly, and pollution free technology. We report here a study on gelatin films with different concentrations of lithium perchlorate, which may be a candidate for electrolyte material in solid polymer batteries. Morphology studies and impedance spectroscopy both are done on the same set of samples. We study the microstructure of the film by SEM and try to see if a correlation between impedance spectroscopy results and features of gel morphology can be identified. A network structure is revealed in the SEM images where details of the network parameters appear to depend on the salt fraction. Analysis of the impedance measurements is done using a physically meaningful model based on material properties instead of the usual equivalent circuit formalism, where circuit elements are difficult to interpret. We find that anomalous diffusion of charge carriers plays an important role; this is incorporated through a fractional calculus approach.