Polyoxometalate-based flexible conductive materials with superionic conductivity

Abstract

Flexible ion-conductive materials exhibit intriguing advantages for applications in flexible electronic devices. Currently, the further enhancement of their conductivity within environmental limitations is an urgent demand for the development of flexible electronic devices, yet remains as a great challenge. Herein, we report a “dual-acid” strategy, via the encapsulation of two acids, H₃PW₁₂O₄₀ (HPW) and NH₂SO₃H (SA), with synergistic interaction into poly(vinyl alcohol)-glycerol (PVA-Gly) hydrogel, to achieve polyoxometalate(POM)-based flexible materials with superionic conductivity under various environmental conditions. As a representative example, the prepared PVA-Gly/HPW-SA-20% hydrogel presents an ultrahigh proton conductivity ranging from −30 °C (3.33×10⁻² S cm⁻¹) to room temperature (2.78×10⁻¹ S cm⁻¹) under ambient humidity. Moreover, the PVA-Gly/HPW-SA-20% hydrogel exhibits remarkable advantages in anti-freezing, mechanical flexibility and self-adhesiveness, making it a promising multifunctional electrolyte for flexible electronic devices. Both experimental results and molecular dynamics (MD) simulations jointly demonstrate that SA bridges HPW clusters to form a dense proton transport pathway induced by multiple electrostatic and hydrogen bonding interactions between SA and HPW counterparts, which contributes to the high-level proton conductivity of the PVA-Gly/HPW-SA-20% hydrogel. This work provides new insights into the design of POM-based flexible materials with superionic conductivity.