In-situ growth of Co3O4 nanowire-assembled clusters on nickel foam for aqueous rechargeable Zn-Co3O4 and Zn-air batteries

With the urgent requirements for advanced energy storage systems, rechargeable Zn-based batteries attract research interest due to the remarkable theoretical capacity, low cost, and environmental benignity. Hence, developing effective battery materials are in great need. In this work, an electrode composed of Co3O4 nanowire-assembled clusters is developed. The porous Co3O4 nanowires are directly coupled to the underlying nickel foam to form clusters, avoiding the use of additional binders and conductive carbons. This hierarchical structure not only provides large active surfaces and facilitates species transport, but also favors the structural stability. In an alkaline solution, this electrode exhibits high activity toward both oxygen reduction and evolution reactions and large specific capacitance, indicating the excellent electrochemical performance. A Zn-Co3O4 battery using this electrode delivers an energy density up to 239 Wh kg−1 on the basis of the Co3O4 loading and the theoretical capacity of zinc, and the capacity retention reaches 84.1% after 1000 cycles. Moreover, a hybrid Zn-Co3O4/air battery fitted with the present electrode exhibits a high capacity of 771 mAh gZn−1 and excellent cycling stability for over 1000 cycles (over 333 h) at 10 mA cm−2 with a fixed capacity of 1.67 mA cm−2 while maintaining the energy efficiency of ∼70%. The results show that the nickel foam coated with Co3O4 nanowire-assembled clusters is a promising electrode for high-performance rechargeable Zn-based batteries with high energy density, energy efficiency, and cycling stability.