Protonated chitosan nanostructures for enhancing ionic conductivity of solid-state electrolytes

Solid polymer electrolytes (SPEs) have aroused widespread attention for their high flexibility and good interface contact with electrode. However, the low ionic conductivity severely hinders their application in energy storage devices. Herein, a novel protonated nanostructure was synthesized through the reaction between PEO and Chitosan (Chi) and applied as fillers to form PEO/Chi composite solid-state electrolytes (PCCSEs). The fillers, which achieve nanization by the reaction with PEO, plays an important role in promoting the property of transporting Li+, due to the protonated amino (–NH3+) improving the dissociation of LiTFSI and the nanoscale size with high dispersity. Various characterizations and density functional theory (DFT) calculations were applied to reveal the enhanced Li+ transport mechanism in PCCSE. Owing to the unique design, PCCSE exhibits excellent ionic conductivity at room temperature (1.02 × 10−4 S cm−1) and the Li||SSEs||Li symmetric cells and LFP||SSEs||Li batteries with PCCSE show great cycling stability. This strategy of taking full use of the cations in protonated Chi provides effective design guidance for promoting the Li+ transport in polymer-based electrolytes.