Morphology-dependent binder-free CuNiO₂electrode 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 (~153.02 mA h g⁻¹ at 2 A g⁻¹), excellent rate capability (~87.4% retains even at 10 A g⁻¹), and outstanding cycling stability (~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.