Nanostructured 2D Calcium Cobalt Oxides for Enhanced Electrochemical Energy Storage in Supercapacitors

Supercapacitors are gaining more attention for their capacity to fill the gap between conventional capacitors and batteries, offering high power density, rapid charge–discharge capabilities, and improved energy storage. Exfoliated calcium cobalt oxide nanosheets (CCONSs), featuring a few-layer CaCoO2–CoO2 superstructure, were explored as advanced electrode materials. The exfoliation of bulk Ca3Co4O9 (CCO) into 2D nanosheets significantly increased the surface area and active site accessibility, leading to improved electrochemical performance. Electrochemical testing in 1 M LiOH and 3 M KOH electrolytes revealed impressive specific capacitances of 242 F g−1 and 247 F g−1, respectively, representing substantial improvements over bulk phase of CCO. A symmetric supercapacitor using CCONS electrodes in 1 M LiOH demonstrated an excellent energy density of 28.5 Wh kg−1 and a power density of 2.4 kW kg−1, while maintaining 93% capacitance retention over 5000 cycles, confirming its strong long-term stability. These findings highlight the potential of CCONSs as high-performance supercapacitor materials, offering enhanced energy and power densities suitable for practical energy storage applications.