Electrochemically Induced Phase Transition in V3O7 • H2O Nanobelts/Reduced Graphene Oxide Composites for Aqueous Zinc-Ion Batteries

V3O7 center dot H2O nanobelts/reduced graphene oxide (rGO) composites (weight ratio: 86%/14%) are synthesized by a microwave approach with a high yield (85%) through controlling pH with acids. The growth mechanisms of the highly crystalline nanobelts (average diameter: 25 nm; length: approximate to 20 mu m; oriented along the [101] direction) have been thoroughly investigated, with the governing role of the acid upon the morphology and oxidation state of vanadium disclosed. When used as the ZIB cathode, the composite can deliver a high specific capacity of 410.7 and 385.7 mAh g(-1) at the current density of 0.5 and 4 A g(-1), respectively, with a high retention of the capacity of 93%. The capacity of the composite is greater than those of V3O7 center dot H2O, V2O5 nanobelts, and V5O12 center dot 6H(2)O film. Zinc ion storage in V3O7 center dot H2O/rGO is mainly a pseudocapacitive behavior rather than ion diffusion. The presence of rGO enables outstanding cycling stability of up to 1000 cycles with a capacity retention of 99.6%. Extended cycling shows a gradual phase transition, that is, from the original orthorhombic V3O7 center dot H2O to a stable hexagonal Zn-3(VO4)(2)(H2O)(2.93) phase, which is a new electrochemical route found in V3O7 materials. This phase transition process provides new insight into the reactions of aqueous ZIBs.

Automated summary

V3O7·H2O nanobelts/reduced graphene oxide composites were synthesized with high yield and exhibited high specific capacity and excellent cycling stability. The results provide new insight into the reactions of aqueous zinc-ion batteries.