A new aqueous Zn-NiCo2O4 rechargeable battery system with a high voltage, consisting of NiCo2O4 as cathode and metal Zn as anode, is proposed for the first time. It is cheap and environmental friendly, and its energy density is about 202.8 Wh kg(-1). The system still maintains excellent capacity retention of about 85% after 100 full cycles at a current rate of 2 A g(-1) between 1.5 and 1.95 V. This work not only provides a new battery system but also shows promise for application in large-scale energy storage for its low cost, good cycling and environmental friendliness.