Oxygen Vacancies Boosted Hydronium Intercalation: A Paradigm Shift in Aluminum-Based Batteries.

In aqueous aluminum-ion batteries (AAIBs), the insertion/extraction chemistry of Al often leads to poor kinetics, whereas the rapid diffusion kinetics of hydronium ions (HO) may offer the solution. However, the presence of considerable Al in the electrolyte hinders the insertion reaction of HO. Herein, we report how oxygen-deficient α-MoO nanosheets unlock selective HO insertion in a mild aluminum-ion electrolyte. The abundant oxygen defects impede the insertion of Al due to excessively strong adsorption, while allowing HO to be inserted/diffused through the Grotthuss proton conduction mechanism. This research advances our understanding of the mechanism behind selective HO insertion in mild electrolytes.