Three-dimensional nanotube-array anode enables a flexible Ni/Zn fibrous battery to ultrafast charge and discharge in seconds

Ni/Zn batteries show the high theoretical capacity (370-619 mAh g(-1)) and output voltage (similar to 1.8 V) in aqueous solution, while they are limited by the poor rate capability and cycling stability due to the shape change, dendrite formation and corrosion of anodic zinc electrode. Besides, the continued miniaturization of portable electronics requires the construction of fiber-shaped energy storage devices due to its exceptional flexibility, machinability, lightweight and large volumetric energy (power) density. Herein, we propose a three-dimensional nanotube-array supported fiber-shaped anode (Li-RTiO2) of Ni/Zn battery with the ability to accommodate zinc deposition as nanoparticles instead of bulk dendritic crystals, greatly facilitating the anodic reaction rate of the Zn/ZnO22- couple. Thus the flexible fibrous battery reveals the impressive maximum volumetric energy density of 0.034 Wh cm(-3), power density of 17.5 W cm(-3), high electric energy efficiency of 91% and about 5% capacity loss after 20,000 cycles.