Commencing an Acidic Battery Based on a Copper Anode with Ultrafast Proton‐Regulated Kinetics and Superior Dendrite‐Free Property

Abstract Building aqueous acidic batteries is in its infancy. There are several sporadic attempts that show desirable electrochemical performance, especially rate stability and high power density. The direct use of a metal anode is regarded as the best protocol for fabricating metal‐based batteries. However, introducing an acid‐tolerant and electrochemically reversible metal anode into an acidic aqueous battery system remains a considerable challenge. In this work, copper (Cu) metal is used as a reversible metal anode to match acidic regimes with a nearly 100% deposition–dissolution efficiency. The reaction kinetics and mechanism of the Cu anode can be regulated by protons with 400% kinetic acceleration compared with a mild electrolyte. In addition, the anode exhibits a dendrite‐free morphology after cycling due to the surface roughening effect, which is different from the morphologies of widely used Zn‐ and Li‐metal anodes. When coupled with the Prussian blue analog as cathodes, the battery delivers ultrafast kinetics of 1830 W kg −1 at 75 C, which is comparable to the power performance of supercapacitors. Long‐term cyclic stability is evaluated, where the capacity retention is 85.6% after 5000 cycles. Finally, flexible fiber‐shaped acidic Cu‐based batteries are demonstrated for potential wearable applications.