MXene‐Derived LiV 3 O 8 Nanorods for High‐Performance Aqueous Ammonium‐Ion Batteries

ABSTRACT Aqueous ammonium‐ion batteries offer safe and low‐cost energy storage but are limited by the lack of electrode materials combining high capacity, fast kinetics, and long‐term stability. Herein, MXene‐derived LiV 3 O 8 nanorods are synthesized via an in situ thermal conversion strategy as high‐performance anodes. The open 1D architecture enables efficient ion transport, delivering a high capacity of 185 mAh g −1 at 1 A g −1 , excellent rate capability of 93 mAh g −1 at 10 A g −1 , and outstanding cycling durability. A dynamic storage mechanism involving reversible H + /NH 4 + co‐intercalation and ion‐exchange‐driven phase transition to NH 4 V 3 O 8 ·H 2 O is revealed, inducing a self‐adaptive nanorod‐to‐nanowire structural evolution that continuously enhances ion transport and active surface area. Density functional theory calculations further reveal ultralow ammonium‐ion diffusion barriers along the V–O chain direction and strong adsorption stabilized by hydrogen‐bond interactions, providing atomic‐level insight into the fast kinetics. Full cells with δ‐MnO 2 cathodes exhibit high voltage output and long‐term stability, demonstrating practical feasibility.