In Situ Construction of Binder-Free Stable Battery-Type Copper Cobaltite and Copper Oxide Composite Electrodes for All-Solid-State Asymmetric Supercapacitors: Cation Concentration and Morphology-Dependent Electrochemical Performance

Binder-free electrode materials offer high active material mass loading and usage rate, excellent connectivity between active materials and current collectors, and efficient electron and ion transport inside the electrodes. Herein, we demonstrate a binder-free in situ synthesis of microstructures of CuCo2O4/CuO composites grown on the Ni foam (CCO/NF) by wet chemical methods. Two different morphologies of microspheres (CCO/NF-IPA) and cross-linked microsheets (CCO/NF-DIW) result from solvents of isopropyl alcohol and deionized water, respectively. Using X-ray techniques, the nonstoichiometry of Cu, Co, and O in composites is measured. In the backdrop of the supercapacitor application, even though both electrodes have consistent electrochemical performance, the Co-excess of the CCO/NF-IPA composite has a higher specific capacity (369.6 C g–1 at 1 A g–1) and an extended cyclic performance (98% retention after 5000 cycles) compared to the other. The all-solid-state CCO/NF-IPA//activated carbon (AC) asymmetric supercapacitor (ASC) device with a full operating potential window of 0–1.5 V has exhibited a high specific capacity of 162.6 C g–1 at 1 A g–1. The ASC device retains its initial capacity of 97% over 5000 cycles and renders a notable energy density of 43.7 Wh kg–1 at 752.4 W kg–1 power density.