The supercapacitor electrode material reported herein is a type of NiIIIO(OH)/Ni coaxial nanocomposite with NiIIIO(OH) wrapping around a Ni scaffold, featuring vertically oriented nanochannels with periodically-corrugated channel walls. A Ni scaffold was constructed through the electrodeposition of a Ni–Cu alloy film by using a square-wave voltage followed by a dealloying treatment to selectively remove Cu. By further coating the fabricated Ni framework with NiIIIO(OH) through anodic electrodeposition, we obtained wavy-channel NiIIIO(OH)/Ni coaxial nanostructures, which readily served as a supercapacitor electrode. The as-fabricated supercapacitor electrode exhibited superior performance with a remarkable specific capacitance (SC) of 2372 F g−1 (after the contribution from the bare Ni scaffold was subtracted), measured at the charge and discharge rate of 1 A g−1. This is 48 % higher than the straight-channel counterpart and is almost a three-fold increase compared to the compact NiIIIO(OH) thin film. Moreover, superior cycling stability was achieved at high charge and discharge current densities, for example, only 10 % of the SC was lost over the first 200 cycles with no further change in the subsequent 800 cycles at 50 A g−1.