Morphology-dependent binder-free CuNiO2 electrode material with excellent electrochemical performances for supercapacitors

Rational design for structure and morphology of multi-component metal oxides is an efficient and promising way to enhance energy storage performance of electrode materials. In this present work, nanosheet-like CuNiO2 heterostructures are fabricated using facile one-step hydrothermal route by introducing various amounts of ammonium fluoride (NH4F) as structure-directing agent. The NH4F assisted synthesis of CuNiO2 materials on Ni foam current collector can be effectively utilized as binder-free battery-type electrode materials for supercapacitors. With an assistance of NH4F, the structural, morphological and composition evolutions of CuNiO2 electrodes are discussed effectively using X-ray diffraction, scanning electron microscopy and transmission electron microscopy and X-ray photoelectron spectroscopy characterizations. The CuNiO2 electrode material prepared with 0.4 M NH4F provides large number of active sites, superior conductivity and rapid charge transfer, which are promote fast Faradaic redox reactions. As a battery-type material, the optimized 0.4-CuNiO2 electrode material (NH4F is 0.4 M) exhibits a high specific capacity (similar to 153.02 mA h g at 2 A g(-1)), excellent rate capability (similar to 87.4% retains even at 10 A g(-1)), and outstanding cycling stability (similar to 94.14% at 6 A g(-1) over 3000 cycles), respectively. Thereby, this study paves the path into rational design for structure and morphology of multi-component metal oxides for improving energy storage performance.