Preparation and performance study of flexible all-solid-state Co9S8@P–C @ NiCo-LDH / / AC asymmetric supercapacitors

Abstract

Supercapacitors, emerging as energy storage devices, face challenges in practical applications due to their relatively low energy density. In this study, we fabricate a novelty supercapacitor cathode composed of Co₉S₈, conductive phosphorus-doped carbon (P–C), and layered double hydroxides (LDH). The incorporation of a conductive layer significantly enhances charge transfer, capacity, and electrochemical stability, ultimately elevating the electrochemical performance of the cathode. The fabricated Co₉S₈@P–C@NiCo-LDH demonstrates an exceptional area-specific capacitance of 3.9 F cm⁻² at a current density of 2 mA cm⁻², along with remarkable cyclic stability, maintaining 98.9% of their capacity after 2000 cycles. The flexible asymmetric all-solid-state supercapacitor (AAS) assembled with Co₉S₈@P–C@NiCo-LDH and activated carbon (AC) exhibits a remarkable energy density of 0.065 mWh cm⁻², corresponding to 325.0 W h kg⁻¹. Moreover, it maintains excellent cycling stability even at elevated current densities of 10 mA cm⁻². Following 5000 consecutive charge/discharge cycles, the AAS device maintains approximately 91.1% of its initial specific capacity. The AAS device successfully powered a 3V white LED for 5 min, further emphasizing its practicality.