Graphene-like VO₂ vertically growing on carbon cloth enables fast and high-capacity ammonium ion storage

Among these aqueous (non-)metal ion battery systems, ammonium ions are drawing increasing attention due to its unique advantages including small molar mass, abundant reserves and nontoxicity. However, suitable NH₄⁺ hosting materials with rational structure design are still in high demand to build high performance ammonium ion batteries (AIB). Herein, a graphene-like vanadium dioxide (VO₂) vertically growing on carbon cloth (CC) is reported as self-supporting electrode for AIB. The three-dimensional conductive carbon fiber substrate and the warped graphene-like VO₂ lead to enhanced NH₄⁺ transport and shortened diffusion length. As a result, the as-prepared VO₂@CC displays an initial specific capacity up to 250.1 mAh g⁻¹ at the current density of 1 A g⁻¹. After 1000 cycles, it still maintains a capacity of 60.4 m Ah g⁻¹. A series of ex-situ characterizations provides firm evidence that the insertion and extraction of NH₄⁺ in VO₂ are realized through the formation and breakage of hydrogen bonds. When combined with activated carbon (AC) to form a hybrid battery VO₂@CC//AC, an initial discharge capacity of 74.98 mAh g⁻¹ with the capacity retention of 43.64 % after 200 cycles is achieved, while the efficiency is maintained at about 92 %, surpassing other reported vanadium-based materials.