Flexible and ultralong-life cuprous oxide microsphere-nanosheets with superior pseudocapacitive properties

Abstract

Nanostructured transition metal oxides have been investigated extensively for supercapacitor electrodes due to their high theoretical specific capacitance, low-cost, environment benignity and abundance. However, pristine transition metal oxides suffer from difficulty of synthesis, poor electronic conductivity and mechanical flexibility. In this work, we report a facile, low-cost and high-throughput synthesis of hierarchical structure which consists of cuprous oxide (Cu₂O) microsphere-nanosheets on the surface of flexible Cu foil (namely Cu₂O@Cu) via a two-step electrochemical method (anodization and electro-oxidation). The influence of the anodization parameters on surface roughness of Cu foil has been investigated, and the optimum anodization procedure was determined to be 50 V for 4 cycles. This Cu₂O@Cu electrode exhibits excellent capacitance properties, such as up to 390.9 mF cm⁻² at 2 mA cm⁻² in areal capacitance, and high flexibility, as observed by cyclic voltammetry measurement under various deformation (bending and folding) situations. Furthermore, the Cu₂O@Cu electrode presents superior long-term cycling stability over 100 000 cycles, with the capacitance retention of over 80%. The present binder-free Cu₂O@Cu microsphere-nanosheets electrode is highly promising for future applications in flexible supercapacitors.