Graphene oxide-mediated decoupling of structural and surface-chemical modification in sonochemical vanadate synthesis

The effect of oxygen-functionalized graphene oxide (GO) introduced during sonochemical synthesis on the nanostructural growth, crystal structure, and surface chemistry of layered potassium vanadate was investigated. Two distinct modification regimes were identified depending on GO loading. Lower GO loadings primarily altered the crystal structure, which enhanced capacity mainly at low current densities without sustaining this advantage at high current densities. Higher GO loadings additionally modified the surface chemistry, which, combined with expanded interlayer spacing, increased capacity across all current densities and preserved high-rate capability. The vanadate synthesized with 10 wt% GO (denoted as GP10), in which both structural and surface-chemical modifications were observed, exhibited the best rate performance among the samples studied and maintained a high capacity of 251.9 mAh g^-1 after 1000 cycles at 10 A g^-1, which was 1.6 times that of the GO-free potassium vanadate nanofibers (PVNF). At 20 A g^-1, GP10 achieved an energy density of 152.8 Wh kg^-1 (twice that of PVNF) at a power density of 11,317 W kg^-1. This study demonstrates that incorporating GO during synthesis enables the comprehensive engineering of layered vanadate through simultaneous modification of the crystal structure and surface chemistry toward high-performance cathodes for aqueous zinc-ion batteries (AZIBs).