Hierarchical sea-urchin-like bimetallic zinc-cobalt selenide for enhanced battery-supercapacitor hybrid device

Battery-supercapacitor hybrid (BSH) devices have become a bridge to unit high specific energy and power, but they are usually limited in applications by low specific energy of the electroactive materials. Hierarchical bi-metallic selenides are regarded as promising materials to break the restriction because of their superior conductivities, synergistic effect and more electroactive sites. Here, we first apply a bimetallic zinc-cobalt selenide (ZCS) to a BSH device as a battery-type electrode material. Its 3D structure consists of hierarchical sea-urchin-like microspheres, whose surfaces are covered by very rough and porous needle-like nanorods. Benefiting from the unique hierarchical structure, the ZCS delivers a satisfied specific capacity of 1419 C g(-1) at 2 A g(-1), higher than those of ZnSe, CoSe2 and bimetallic zinc-cobalt oxide synthesized under the similar conditions. A ZCS//AC BSH device achieves a broad potential window of 1.6 V, high specific energy of 77.78 Wh kg(-1) at the specific power of 222 W kg(-1) and outstanding cycling performance (80% retention after 10,000 cycles). Two cells in series successfully power a LED for 50 min, suggesting their future application in green energy-storage devices.