Co2(OH)3Cl/Nb2CT x : Advanced Composite Electrodes for High-Performance Aqueous Asymmetric Supercapacitors

Abstract Cobalt hydroxy chloride-based mixed anionic frameworks are attracting attention as supercapacitor electrode materials because of their high theoretical capacity and enhanced redox-active cobalt centers with increased interlayer spacing. on the other hand, Nb2CTx MXene provides conductive, hydrophilic, multivalent Nb that improves electronic transport and maintains good structural stability during electrochemical reactions. In this work, Co2(OH)3Cl/Nb2CTx composites containing 1, 3, and 5 wt % Nb2CTx relative to the mass of Co2(OH)3Cl were synthesized. Further, the specific electrochemical characteristics of the as-prepared composite and bare sample were evaluated using a three-electrode configuration. We fabricated asymmetric supercapacitors using the as-prepared materials as the positive electrode and activated carbon as the negative electrode, with PVA–KOH gel as the electrolyte. The asymmetric supercapacitor fabricated using CN-1 delivered a specific capacity of 158.81 C g–1 at 1 A g–1 and showed a maximum specific energy of 35.29 Wh kg–1 at a specific power of 1.6 kW kg–1. The composite electrode-based device showed an enhanced cycle life of up to 20,000 cycles, with 76.7% capacitance retention and a Coulombic efficiency of around 99%. In contrast, the bare Co2(OH)3Cl-based device retained about 50.6% capacitance after 20,000 cycles. Thus, the optimistic Co2(OH)3Cl/Nb2CTx composites are a potential positive electrode for high-performance supercapacitor applications.