Solvent - free processed polymer electrolyte for Li -metal batteries

Several polymer electrolyte compositions have been proposed in the literature as candidates for next generation Li solid state batteries. Among them, PEO-based ones are the current state-of-the-art. Indeed, solvent free processing, which is beneficial in terms of performance and cost, has been reported for PEO1. PVdF and its copolymers are also interesting as polymer matrices owing to their high polarity, oxidative stability, and mechanical strength2. However, the studies based on the solvent free processing of alternative polymers are less abundant. In this work, we processed PVDF-HFP based gel polymer electrolytes using LiTFSI as the lithium salt and an ionic liquid as a plasticizer. In addition to this, PEO was also added to some of the compositions with the aim to improve ionic conductivity. The effect of processing conditions using an internal mixer was evaluated in the characteristics of the obtained mixtures. Moreover, after defining the optimum processing conditions, self-standing membranes with several compositions were prepared by hot calendering. Produced membranes were chemical, mechanical and electrochemically characterized and full cells with solid state NMC-811 based cathodes were tested using the best performing gel polymer electrolyte composition.