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 bimetallic 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.