Component-tunable hierarchical flower-shaped bimetallic zinc-cobalt selenides for high-performance hybrid supercapacitor

Bimetallic selenides have been considered as promising energy storage materials because of synergistic effect between different metal cations and low electronegativity of large selenide anion. However, their investigations are still scare and mainly focus on nickel-cobalt bimetallic selenides. Here, bimetallic zinc-cobalt (Zn-Co) selenides with three-dimensional flower-shaped morphology are obtained, and the surfaces of flowers are covered by interlaced nanosheets. Zn-Co selenides with different Zn/Co ratios are further investigated to optimize the electrochemical properties. With the increase of Zn/Co ratio, the electrochemical activity first increases and then decreases. Benefiting from the morphological and compositional merits, the optimal bimetallic selenide exhibits a satisfied specific capacity (1107 C g−1 at 1 A g−1). The optimal Zn-Co selenide anode and activated carbon cathode are also used to construct a hybrid supercapacitor device, which achieves high specific energy (66.25 Wh kg−1) and power (208 W kg−1), and outstanding cycling stability (97 % retention of its original capacitance after 10000 cycles).