Self-supported nickel iron selenide@nickel cobalt boride core-shell nanosheets electrode for asymmetric supercapacitors

Optimizing the electrode structure and interface is a promising approach to achieve high energy density asymmetric supercapacitors. In this study, a core–shell heterostructure based on crystalline nickel iron selenide (NiSe2-Fe3Se4) and amorphous nickel cobalt boride (NiCoB) is for the first time in-situ fabricated on carbon cloth substrate though a hydrothermal approach, a selenization process, followed by a chemical precipitation method. In this well-defined hybrid material (denoted as NiSe2-Fe3Se4@NiCoB), the close combination of NiSe2-Fe3Se4 nanosheets core and NiCoB nanosheets shell results in a large specific surface area with rich open channels, and numerous crystalline/amorphous interfaces with regulated electronic structure. Owing to its unique hierarchical pore architecture and synergistic effect of dual battery-type materials, the resultant NiSe2-Fe3Se4@NiCoB electrode displays a specific capacity of 887.0C g−1 at 1 A g−1, wonderful rate retention (71.3% at 20 A g−1), and good cycling stability (86.4% after 5000cycles). Additionally, the assembled NiSe2-Fe3Se4@NiCoB//porous carbon asymmetric supercapacitor illustrates a remarkable energy density of 72.7 Wh kg−1 at 710.7 W kg−1, and exceptional cycling life with capacity retention of 91.1% over 20,000cycles.