Anhydrous Grotthuss mechanism for fast proton transport in a dense oxide-ion array of α-MoO3

Abstract Developing high-power battery chemistry is an urgent task to buffer fluctuating renewable energies and achieve a sustainable and flexible power supply. Owing to the small size of proton and its ultrahigh mobility in water via the Grotthuss mechanism, aqueous proton batteries are an attractive candidate for high-power energy storage devices. Although Grotthuss proton transfer usually occurs in hydrogen-bonded networks of water molecules, in this work, we discover anhydrous Grotthuss-type proton transport in a dense oxide-ion array of solid α-MoO3 even without structural water. The fast proton transfer and accumulation that occurs during (de)intercalation in α-MoO3 is unveiled using both experiments and first-principles calculations. Coupled with a zinc anode and a superconcentrated dual-ion Zn2+/H+ electrolyte, the solid-state anhydrous Grotthuss proton transport mechanism realizes an aqueous MoO3-Zn battery with both high energy and power densities.