Fabricating Co9S8@NiWO4 Electrode toward Record Area Capacitance of 18.8 F cm–2 for High Performance Supercapacitor

Realizing ultrahigh area capacitance based on suitable electrodes is a challenge for supercapacitors. In this work, an electrode is designed consisting of Co₉S₈ nanotubes and NiWO₄ nanoparticles (named Co₉S₈@NiWO₄) and fabricated by a hydrothermal process. The Co₉S₈@NiWO₄ electrode realizes a record area capacitance of 18.8 F cm^–2 at a current density of 5 mA cm^–2 among the reports in the literature. The corresponding asymmetric supercapacitor shows high energy density of 0.48 mW h cm^–2 at 2.42 mW cm^–2 and superior cyclic stability of 79.2% retention over 7000 cycles at 10 mA cm^–2. The great promotion in performance of Co₉S₈@NiWO₄ electrode is synergistically attributed to high intrinsic theoretical capacitances of compounds, abundance polyvalent states, improved conductivity, and increases in reaction sites and rate of the electrode. This work provides a new route for designing highly efficient electrode for developing supercapacitors with high performance in practical applications.