V2O5 nanopaper as a cathode material with high capacity and long cycle life for rechargeable aqueous zinc-ion battery

Aqueous batteries are suitable for large scale energy storage due to cost and safety concerns. Among all aqueous batteries, rechargeable aqueous zinc-ion battery is a promising choice because zinc electrode has low equilibrium potential, high exchange current density, and high hydrogen evolution overpotential. However, since zinc ion is a divalent cation, it is difficult to find a cathode material in which zinc ion can reversibly insert and extract. In this work, we introduce a novel V2O5 nanopaper consisting of V2O5 nanofibers and carbon nanotubes as reversible Zn-ion cathode. V2O5 has a layered crystalline structure. The spaces between the oxide layers may serve as 2-dimensional diffusion pathways for Zn ions. Meanwhile, the nanofiber morphology endows the material with short ionic diffusion distance and may tolerate high volume change. As a result, the V2O5 nanopaper cathode delivers a high capacity of 375 mAh g−1 and long cycle life up to 500 cycles.