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

Abstract

Anhydrous copper(II) fluoride (CuF2) 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 CuF2 cathode, impeding its development. In this work, the reversibility of the anhydrous CuF2 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 CuF2-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 CuF2 as a high-capacity cathode material for Li batteries.