Copper metal electrode reversibly hosts fluoride in a 16 m KF aqueous electrolyte

Fluoride is a promising charge carrier for batteries due to its high charge/mass ratio and small radius. Here, we report commercial copper powder exhibits a reversible capacity of up to 222 mA h g(-1) in a saturated electrolyte of 16 m KF. This electrolyte suppresses dissolution of CuF2, the charged product. Furthermore, the KF solid comprised in the Cu electrode facilitates a high initial capacity. Our results showcase the potential of aqueous fluoride batteries using copper as an electrode.