Superior electrochemical performance of CuS/FeSe₂ for advanced asymmetric supercapacitor applications

Supercapacitor devices face significant challenges, including limited energy density, high self-discharge rates, and poor performance over extended cycling. The present study developed a high-performance asymmetric supercapacitor using novel CuS/FeSe₂ nanocomposites fabricated using a scalable wet chemical method. The CuS/FeSe₂ nanocomposites exhibited exceptional electrochemical performance, including significant capacitance and redox behavior improvements. Integrating two pseudocapacitive materials in a three-electrode configuration exhibited a synergistic effect, substantially reducing resistance and surpassing individual CuS and FeSe₂ electrodes. The CuS/FeSe₂ nanocomposite demonstrated the highest Cs among the electrodes, achieving 821.3 Fg⁻¹ at 1 Ag⁻¹, surpassing the performance of the individual CuS (248.3 Fg⁻¹) and FeSe₂ (508 Fg⁻¹) electrodes along with 80.4 % retention. The asymmetric supercapacitor (CuS/FeSe₂||AC) demonstrated excellent cycling stability, retaining 90.1 % of its initial capacity after 7000 continuous charge/discharge cycles at the highest current rate. Operating at a voltage cutoff of 1.6 V in an aqueous electrolyte, it achieved a high energy density of 51.1 Wh/kg, delivering power at 2426.3 W/kg, and exhibiting a specific capacitance of 143.6 F/g. The CuS/FeSe₂ nanocomposite shows significant potential for high-performance energy storage devices, particularly for developing next-generation asymmetric supercapacitors.