One-step synthesis of copper-cobalt carbonate hydroxide microsphere for electrochemical capacitors with superior stability

Abstract

Copper cobalt carbonate hydroxide (Cu-Co CH) microspheres were synthesized as a pseudocapacitive electrode material via a simple one-step hydrothermal method. Morphological characterization of the Cu-Co CH microspheres was carried out by scanning electron microscopy and transmission electron microscopy, showing their dandelion-like structure with the size approximately 4–7μm. The crystalline structure, morphology and electrochemical performances of Cu-Co CH materials could be readily dominated by the molar ratio of Cu to Co. Among various stoichiometries of Cu-Co CHs, sample Cu0.48Co1.52 CH delivered the highest specific capacitance of 397.3Fg−1 at 1Ag−1 with a good rate capability. Cu0.48Co1.52 CH electrode material also exhibited a remarkably excellent cycling stability, ~99% of initial capacitance retention even after 10,000 charge/discharge cycles at 2Ag−1. An asymmetric energy storage device was assembled by using Cu0.48Co1.52 CH as positive electrode and activated carbon as negative electrode in 2M KOH electrolyte. The hybrid capacitor device could deliver an energy density of 26.3Whkg−1 at a power density of 400.2Wkg−1, and remain 16.7Whkg−1 at 8374.2Wkg−1. Meanwhile, it also showed amazing stability with ~99% capacity retention after 10,000cycles. Based on the above results, Cu-Co CH microspheres possessed practical application as electrode materials for electrochemical capacitors due to their good structural stability in KOH electrolyte.