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 NiO x and FeO x 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 NiO x and FeO x 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 NiO x as the cathode, FeO x 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.