Metal Oxide Nanostructures Generated from In Situ Sacrifice of Zinc in Bimetallic Textures as Flexible Ni/Fe Fast Battery Electrodes

An “in situ sacrifice” process was devised in this work as a room-temperature, all-solution processed electrochemical method to synthesize nanostructured NiOx and FeOx directly on current collectors. After electrodepositing NiZn/FeZn bimetallic textures on a copper net, the zinc component is etched and the remnant nickel/iron are evolved into NiOx and FeOx by the “in situ sacrifice” activation we propose. As-prepared electrodes exhibit high areal capacities of 0.47 mA h cm−2 and 0.32 mA h cm−2, respectively. By integrating NiOx as the cathode, FeOx as the anode, and poly(vinyl alcohol) (PVA)-KOH gel as the separator/solid-state electrolyte, the assembled quasi-solid-state flexible battery delivers a volumetric capacity of 6.91 mA h cm−3 at 5 mA cm−2, along with a maximum energy density of 7.40 mWh cm−3 under a power density of 0.27 W cm−3 and a maximum tested power density of 3.13 W cm−3 with a 2.17 mW h cm−3 energy density retention. Our room-temperature synthesis, which only consumes minute electricity, makes it a promising approach for large-scale production. We also emphasize the in situ sacrifice zinc etching process used in this work as a general strategy for metal-based nanostructure growth for high-performance battery materials.