Liquid K/Na Alloyon Metal Oxide-Coated Cu: A PromisingAnode for Organic Potassium Batteries

Liquid K/Na alloys represent one of the most promising anodes for potassium batteries; however, their practical application is challenged by the poor wettability of the most commonly used current collectors with liquid metals. Herein, we address this problem by modification of porous copper with uniform and ultrathin oxide coatings (ZnO, Al₂O₃, SnO₂, and TiO₂) grown using an atomic layer deposition process. The highly positive effect of the ZnO coating on the electrode stability was observed in symmetrical cells with a K/Na alloy on both sides. All studied oxide coatings improved the specific capacity and operational stability of potassium batteries with organic polyimide-type cathodes compared to the reference cells fabricated using nonmodified porous copper. The best capacity retention characteristics of 90–94% after 100 charge–discharge cycles were obtained using TiO₂ and SnO₂ coatings, which are believed to undergo redox reactions with K/Na to form M_<i>x</i>TiO₂ and M_<i>x</i>SnO₂ interlayers, improving the alloy adhesion to copper. The revealed benefits of oxide coatings open new opportunities for the rational engineering of K/Na alloy anodes for the emerging types of potassium-based electrochemical energy storage devices.