Anion Donicity of Liquid Electrolytes for Lithium Carbon Fluoride Batteries

Abstract The increasing demand for high‐energy powers have greatly incentivized the development of lithium carbon fluoride (Li||CF x ) cells. Five kinds of non‐aqueous liquid electrolytes with various kinds of lithium salts (LiX, X=PF 6 − , TFSI − , BF 4 − , ClO 4 − , and CF 3 SO 3 − ) were comparatively studied. Intriguingly, the LiBF 4 ‐based electrolyte show relatively moderate ionic conductivities; yet, the corresponding Li||CF x cells deliver the highest discharge capacities among them. A combination of morphological and compositional analyses of the discharge CF x cathode suggest that the moderate donicity of BF 4 − anion is accountable for favoring the breakdown of C−F bonds, and subsequently forming crystalline lithium fluoride as the main discharge products. This work brings not only fresh understanding on the role of salt anions for Li||CF x cells, but also inspire the electrolyte design for other conversion‐type (sulfur and/or organosulfur) cathode materials desired for high‐energy applications.