Unlocking Grotthuss Proton Energy Storage in Pyrochlore‐Type Tungsten Oxide

Abstract

Abstract It is of momentous significance to identify suitable proton‐storage electrode materials inherent with Grotthuss topochemistry toward high‐power aqueous proton batteries. However, currently reported oxide electrode materials have seldom conformed to the Grotthuss mechanism. Here Grotthuss mechanism‐dominated proton storage is showcased in a novel 3D‐tunnel‐structured pyrochlore‐type WO 3 ·0.5H 2 O (WOH), together with a reliable and effective approach to amplifying its Grotthuss conduction effect. Different from other phases of tungsten oxide (e.g., orthorhombic, monoclinic, and hexagonal), the zeolitic‐water‐enriched cubic pyrochlore WOH favors proton‐hopping akin to “Newton's cradle” instead of traditional “vehicle‐like” transport. Interestingly, introducing trace Ni(II) ions into the WOH (NWOH) is find to notably increase the content of structural water in lattice, thereby reframing the hydrogen‐bonding network along with enhanced proton transfer capability as a consequence of its largely reduced activation energy as low as 0.08 eV. Hence, NWOH shows boosted reversible capacity of 71 mAh g −1 at 100C, ultrafast charging capability up to 500C, and ultralong cycling life over 30,000 cycles. Once coupled with Prussian blue analogue cathodes with identical Grotthuss conduction mechanism, the resultant high‐output‐voltage full‐cells (≈1.1 V) sustain high‐rate cycling with high energy/power density and operate at a wide working temperature from −20 to 50 °C.