An in situ growth strategy of NiCo-MOF nanosheets with more activity sites for asymmetric supercapacitors

Abstract

NiCo layered double hydroxides (LDHs) for supercapacitors have been studied by virtue of the high specific capacitance theoretical values. However, less active sites limit the further increase of their specific capacitances. Metal-organic framework (MOF), as a promising material, has attracted intense attention with enormous specific area and adjustable structure. Herein, a practical strategy was designed to improve the active sites of the binder-free electrode by potentiostatic deposition and soaking NiCo-LDHs in 2-methylimidazole for in situ growth of MOF. This layered NiCo-MOF was obtained at room temperature which can retain more active sites to enhance capacitive properties. In particular, the prepared layered NiCo-MOF obtained a superior capacitance (1289 F g−1 at 0.5 A g−1), along with a remarkable rate capability (767 F g−1 at 20 A g−1). In addition, the as-prepared asymmetric supercapacitor exhibited a maximum specific energy of 57.8 Wh kg−1 at 748.7 W kg−1 (at a working potential of 1.5 V), and it retained 71.40% capacitance after 6000 cycles. All of these findings suggest that this work gives a practical way to synthesize NiCo-MOF nanosheets, and it exhibits excellent prospect in further energy field.