Electrochemical energy storage (EES) devices combining high energy density with high power density are necessary for addressing the growing energy demand and environmental crisis. Nickel oxide (NiO) is a promising electrode material for EES owing to the ultrahigh theoretical specific capacity, but the practical values are far below the theoretical limit to date, with inferior rate and cycling performances. Herein, we report the novel mesostructured NiO/Ni composites, which consist of hetero-NiO/Ni components at nanoscale while displaying 3D porous architectures at mesoscale, with adjustable metallic Ni content in a wide range. The unique mesostructure boosts the EES performance of NiO to its theoretical limit with the ultrahigh specific capacity, high rate capability and stability. The superior performance is well correlated with the synergism of the high accessibility to electrolyte, short solid-state ion diffusion length, and much enhanced conductivity of the mesostructured NiO/Ni composites. This study demonstrates a new strategy likely applicable to other transition metal oxides in maximizing their potential in energy storage, i.e. by constructing the similar mesostructured metal-oxide/metal composites.
