Defect‐Driven Oxidation Enabled V₂CT_x MXene with Ultralong‐Cycling and High‐Rate Capability in Aqueous K⁺ Storage

Abstract Owing to the adverse influences of irreversible oxidation, the development of MXene‐based materials, especially those with satisfactory performance and longevity for aqueous energy storage, continues to suffer severe challenges. Herein, the strategy of targeted passivation‐supported defect‐lock‐oxygen is conceived, whereby engineered the V₂CT_x material for controllable partial oxidation with enhanced regioselectivity. When the material works, inside the intrinsic defects, the outward diffusion of oxidation is confined by the Lewis bases around the defects, which allows for the controllable progress of oxidation. The defect‐locked oxygen oxidizes the exposed carbon, thus forming sufficient amorphous carbons for enhancing the capacitive‐type adsorption of K‐ions. Then the oxidized defects enabled the fast kinetics via the cross‐layer transport of K‐ions. Benefiting from the strategy, the electrode assembly V₂CT_x‐RTIL (V₂CT_x equipped with room temperature ionic liquid) exhibits high capacity, good rate capability, and ultra‐longevity compared with those of the MXene materials so far reported. This work presents the first strategy of targeted passivation‐supported defect‐lock‐oxygen for high‐rate capability and super long‐cycling aqueous K⁺ storage and hopefully would provide the inspiration for the future design of novel electrodes.