Polyoxometalate-Poly(Ethylene Oxide) Nanocomposites for Flexible Anhydrous Solid-State Proton Conductors

Abstract

Films that can maintain their flexibilities and conductivities under low humidity and broad temperature range represent the next generation of solid-state proton conductors, which would extend the applications of energy storage and conversion devices in extreme environments. Owing to their strong interactions with poly(ethylene oxide) (PEO), polyoxometalates (POMs), a group of nanoscale metal oxide clusters, can form stable nanocomposites with PEO and fully inhibit its crystallization, facilitating the fast dynamics of PEO chains/segments, as evidenced from dielectric spectroscopy studies. It thus enables the fast proton transportation in the PEO matrix and the improvement of the composites’ proton conductivities. With POMs’ loading ratio approaching to 70% wt, the nanocomposite’s proton conductivity reaches as high as 6.86 × 10–3 S cm–1 at 100 °C in anhydrous environment. The composites’ mechanical properties can be further optimized upon the tuning of PEOs’ molecular weight and finally, a flexible, self-supported anhydrous proton conductor can be obtained, which also demonstrates high compatibility to electrodes. The nanocomposite can maintain promising proton conductivities ranging from −20 to 100 °C in an anhydrous environment, enabling the fabrication of long-term robust performance of supercapacitor devices under extreme conditions, which has never been achieved before.