Wrapping CuCo2S4 arrays on nickel foam with Ni2(CO3)(OH)2 nanosheets as a high-performance faradaic electrode†
Ternary metal sulfides represent a new class of faradaic electrode material outperforming their oxide counterparts. In this work, a hierarchically structured electrode is fabricated via a two-step hydrothermal reaction. By in situ growth of CuCo2S4 arrays on a nickel foam substrate (NF) and subsequent cladding with Ni2(CO3)(OH)2, the optimized electrode, NF/CuCo2S4-200@Ni2(CO3)(OH)2, exhibits a specific capacity of 343.9 C g−1 (5159 mF cm−2 at the current density of 2 mA cm−2) along with an excellent cycling stability (96.7% capacity retention after 10 000 cycles) in aqueous KOH electrolyte. Assembled by using NF/CuCo2S4-200@Ni2(CO3)(OH)2 nanosheets as the positive electrode and commercial activated carbon (AC) as the negative electrode, the hybrid supercapacitor delivers an energy density of 44.0 W h kg−1 at a power density of 139.3 W kg−1 and 17.7 W h kg−1 at 2733 W kg−1. Moreover, a satisfactory cycling stability (capacity retention of 93.0% after 10 000 cycles) is attained. The series circuit made up of a yellow LED and a pair of hybrid electrodes can power the LED bulb at 3 V for 30 minutes. These outstanding performances of the NF/CuCo2S4@Ni2(CO3)(OH)2 electrode are attributed to the binder-free design and oriented growth of CuCo2S4 arrays by wrapping with Ni2(CO3)(OH)2 nanosheets, which enhances the conductivity of the electrode material and successfully prevents CuCo2S4 from undergoing structure collapse in the alkaline electrolyte solution during the charging/discharging process. With large specific capacity and excellent cycling stability, the hierarchical NF/CuCo2S4@Ni2(CO3)(OH)2 electrode may hold great potential for practical application in hybrid supercapacitors.