Oxygen Vacancies Boosted Hydronium Intercalation: A Paradigm Shift in Aluminum‐based Batteries

In aqueous aluminum‐ion batteries (AAIBs), the insertion/extraction chemistry of Al 3+ often leads to poor kinetics, whereas the rapid diffusion kinetics of hydronium ions (H 3 O + ) may offer the solution. However, the presence of considerable Al 3+ in the electrolyte hinders the insertion reaction of H 3 O + . Herein, we report how oxygen‐deficient α‐MoO 3 nanosheets unlock selective H 3 O + insertion in a mild aluminum‐ion electrolyte. The abundant oxygen defects impede the insertion of Al 3+ due to excessively strong adsorption, while allowing H 3 O + to be inserted/diffused through the Grotthuss proton conduction mechanism. This research advances our understanding of the mechanism behind selective H 3 O + insertion in mild electrolytes.