Vanadate ion promoting the transformation of a-phase molybdenum trioxide (a-MoO3) to h-phase MoO3 (h-MoO3) for boosted Zn-ion storage

Molybdenum trioxide (MoO3) has been widely studied in the energy storage field due to its various phase states and unique structural advantages. Among them, lamellar a-phase MoO3 (alpha-MoO3) and tunnel-like h-phase MoO3 (h-MoO3) have attracted much attention. In this study, we demonstrate that vanadate ion (VO3-) can transform a-MoO3 (a thermodynamically stable phase) to h-MoO3 (a metastable phase) by altering the connection of [MoO6] octahedra configurations. h-MoO3 with VO3- inserted (referred to as h-MoO3-V) as the cathode material for aqueous zinc ion batteries (AZIBs) exhibits excellent Zn2+ storage performances. The improvement in electrochemical properties is attributed to the open tunneling structure of the h-MoO3-V, which offers more active sites for Zn2+ (de)intercalation and diffusion. As expected, the Zn//h-MoO3-V battery delivers specific capacity of 250 mAh.g (-1) at 0.1 A.g(- 1) and rate capability (73% retention from 0.1 to 1 A.g (-1), 80 cycles), well exceeding those of Zn//h-MoO3 and Zn//alpha-MoO3 batteries. This study demonstrates that the tunneling structure of h-MoO3