  To achieve the further development of supercapacitors (SCs), which have
intensively received attention as a next-generation energy storage system, the
rational design of active electrode materials with electrochemically more
favorable structure is one of the most important factors to improve the SC
performance with high specific energy and power density. We propose and
successfully grow copper sulfide (CuS) nanowires (NWs) as a chalcogenide-based
electrode material directly on a Cu mesh current collector using the
combination of a facile liquid-solid chemical oxidation process and an anion
exchange reaction. We found that the as-prepared CuS NWs have well-arrayed
structures with nanosized crystal grains, a high aspect ratio and density, as
well as a good mechanical and electrical contact to the Cu mesh. The obtained
CuS NW based electrodes, with additional binder- and conductive material-free,
exhibit a much higher areal capacitance of 378.0 mF/cm2 and excellent
cyclability of an approximately 90.2 percentage retention during 2000
charge/discharge cycles due to their unique structural, electrical, and
electrochemical properties. Furthermore, for practical SC applications, an
asymmetric supercapacitor is fabricated using active carbon as an anode and CuS
NWs as a cathode, and exhibits the good capacitance retention of 91% during
2000 charge/discharge processes and the excellent volumetric energy density of
1.11 mW h/cm3 compared to other reported pseudo-capacitive SCs.
