A free-standing ZnO@NiCo2O4 nanofilm for supercapacitors and zinc-ion batteries with high-rate performance and high energy density

Abstract

Transition metal oxides are promising candidates for high-performance electrode materials due to their high conductivity and abundant active sites. Nevertheless, its low energy density and poor rate performance limit its application in energy storage devices. Herein, a free-standing ZnO@NiCo2O4-4 nanofilm was sythesised through simple hydrothermal method. This novel material exhibited excellent electrochemical properties as a result of the synergistic effect of ZnO and NiCo2O4. Specially, the ZnO@NiCo2O4-4 electrode a high specific capacitance of 812.5 F g−1 at 1 A g−1 with remarkable rate performance delivers (615.8 F g−1 even at 10 A g−1). The as-prepared ZnO@NiCo2O4-4//AC supercapacitor exhibits a large energy density of 48.8 W h kg−1 at a power density of 375 W kg−1, and the specific capacitance retention rate of the device maintains 82% after 5000 cycles at 3 A g−1. Furthermore, the assembled ZnO@NiCo2O4-4//Zn zinc ion battery can deliver a high specific capacity of 71 mA h g−1. This work offers important guidance for preparing transition metal oxide nanofilms with excellent performance for supercapacitors and zinc-ion batteries.