Nickel–cobalt double hydroxides microspheres with hollow interior and hedgehog-like exterior structures for supercapacitors

Abstract

Nickel–cobalt double hydroxide microspheres (Ni–Co-DHM) have been synthesized by a facile and cost-effective in situ method. The obtained Ni–Co-DHM displays a three-dimensional architecture with hollow interior and hedgehog-like exterior structures. The unique architecture greatly improves the faradaic redox reaction and mass transfer. The Ni–Co-DHM electrode offers an excellent pseudocapacitance performance, including high specific capacitance and rate capability, good charge–discharge stability and long-term cycling life. Its maximum specific capacitance was found to be 2275.5 F g⁻¹ at current density of 1 A g⁻¹, which is more than 3-fold that of common nickel–cobalt double hydroxides and 2-fold that of the mechanical mixture of Co(OH)₂ and Ni(OH)₂ microspheres. The specific capacitance can remain at 1007.8 F g⁻¹ when the current density increases to 25 A g⁻¹. The capacitance can keep at least 92.9% at current density of 10 A g⁻¹ after 5000 cycles. Therefore, this work provides a promising approach for the design and synthesis of structure tunable materials with largely enhanced supercapacitor behavior, which can be potentially applied in energy storage/conversion devices.