Copper metal electrode reversibly hosts fluoride in a 16 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 CuF 2 , 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. A copper electrode in an electrolyte of 16 m KF was reversibly converted to copper fluoride via a two-electron transfer. The electrode exhibits a reversible capacity of up to 222 mA h g −1 with stable cycling for 300 cycles.