Rational Design of Nickel Hydroxide-Based Nanocrystals on Graphene for Ultrafast Energy Storage

Compact, light, and powerful energy storage devices are urgently needed for many emerging applications; however, the development of advanced power sources relies heavily on advances in materials innovation. Here, the findings in rational design, one-pot synthesis, and characterization of a series of Ni hydroxide-based electrode materials in alkaline media for fast energy storage are reported. Under the guidance of density functional theory calculations and experimental investigations, a composite electrode composed of Co-/Mn-substituted Ni hydroxides grown on reduced graphene oxide (rGO) is designed and prepared, demonstrating capacities of 665 and 427 C g(-1) at current densities of 2 and 20 A g(-1), respectively. The superior performance is attributed mainly to the low deprotonation energy and the facile electron transport, as elaborated by theoretical calculations. When coupled with an electrode based on organic molecular-modified rGO, the resulting hybrid device demonstrates an energy density of 74.7 W h kg(-1) at a power density of 1.68 kW kg(-1) while maintaining capacity retention of 91% after 10,000 cycles (20 A g(-1)). The findings not only provide a promising electrode material for high-performance hybrid capacitors but also open a new avenue toward knowledge-based design of efficient electrode materials for other energy storage applications.