Substitution-triggered broken symmetry of cobalt tungstate boosts redox kinetics in pseudocapacitive storage

Achieving delicate broken symmetry enables significant modifica-tion of crystals, from which a variety of property or performance modulation can be expected. Here, we report that the electrochem-ical performance of wolframite-type CoWO4 is significantly boosted using a Mo-substituted-W strategy. Experimental and theoretical analyses reveal that molybdenum substitution achieves WO6 coo-rdination broken symmetry effectively, and it renders electroactive cobalt centers more polar, thus promoting the charge diffusion ki-netics. Additionally, the enhancement of OH- adsorption energy can also alter the pseudocapacitive charge storage property, which significantly reinforces ion diffusion kinetics. As a result, the opti-mized molybdenum substitution (20 mol%) in CoWO4 exhibits a spe-cific capacitance of 840 F g-1 at 1 A g-1, as well as a maximal energy density of 33.68 Wh kg -1 at power density of 800 W kg -1. Inspired by manipulating symmetry of crystals, our findings may provide in-sights into the origin of the substitution-promoted enhanced reac-tion kinetics.