Enabling the reversibility of anhydrous copper(II) fluoride cathodes for rechargeable lithium batteries via fluorinated high-concentration electrolytes

Anhydrous copper(II) fluoride (CuF 2 ) has a high specific capacity of 528 mA h g −1 with an operating voltage of 3.55 V vs. Li/Li+, achieving a high gravimetric energy density of 1874 W h kg −1 , which makes it a promising cathode candidate for next-generation rechargeable lithium (Li) batteries. However, the notorious dissolution of Cu during charging triggers the rapid failure of the CuF 2 cathode, impeding its development. In this work, the reversibility of the anhydrous CuF 2 electrode was enabled via the use of a fluorinated high-concentration (FHC) electrolyte to effectively suppress the dissolution of Cu. With the FHC electrolyte, the CuF 2 -Ketjen Black nanocomposite cathode delivered a reversible capacity of 228 mA h g −1 after 30 cycles, which nearly tripled that of the baseline electrolyte. Thus, the strategy of electrolyte engineering is proposed to harness CuF 2 as a high-capacity cathode material for Li batteries.