Zinc-nickel-cobalt oxide@NiMoO4 core-shell nanowire/nanosheet arrays for solid state asymmetric supercapacitors

Abstract

In the search for advanced positive pseudocapacitive electrode material for potential application to practical energy storage and conversion devices, innovative design and alteration of the assemblage of the complex transition metal oxide based core-shell heterostructures are technically highly essential undertakings. Herein, uniquely assembled three-dimensional porous Zn-Ni-Co oxide (ZNCO)@NiMoO4 core-shell nanowire/nanosheet arrays (NWNSAs) supported on Ni foam as integrated pseudocapacitive electrode are fabricated for the first time by a facile and scalable two-step hydrothermal process combined with post-annealing methods. Taking advantage of the synergistic interaction in core-shell architecture, the hierarchical porous ZNCO@NiMoO4 NWNSAs offers excellent conductivity, durability, effective nanoporous network, and proper channels for the rapid transfer of ions/electron for reversible Faradaic reaction. In a three-electrode assembly, the hierarchical as-synthesized ZNCO@NiMoO4 electrode exhibits higher specific capacity (CS; 338.5 mA h g−1 at 3 mA cm−2), rate performance (71% up to 25 mA cm−2), and good cyclic stability (86% capacity retention after 10,000 cycles) than the ZNCO electrode (CS; 266.1 mA h g−1 and 57% up to 25 mA cm−2). The all-solid-state asymmetric supercapacitor (ASC) device consisting of ZNCO@NiMoO4 NWNSAs as cathode and Fe2O3/graphene hydrogel as anode electrodes shows superior specific capacity (87.5 mA h g−1 at 4 mA cm−2), high rate capability (50.5% up to 50 mA cm−2), excellent life-span (91% after 10,000 GCD cycles), and very high energy and power densities (~70 W h kg−1 and 5115.1 W kg−1), suggesting its potential applicability to advanced hybrid supercapacitors.