An aqueous rechargeable zinc ion battery is provided, the battery comprising a cathode comprising a V3O7.H2O-graphene composite, the composite comprising a plurality of V3O7.H2O nanostructures in contact with graphene, an anode in electrical communication with the cathode, the anode comprising zinc, and an aqueous electrolyte between the cathode and the anode, the aqueous electrolyte comprising zinc ions and an ether of a type and at an amount selected to maximize a capacity retention value of the battery.