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||CFx) cells. Five kinds of non‐aqueous liquid electrolytes with various kinds of lithium salts (LiX, X=PF6−, TFSI−, BF4−, ClO4−, and CF3SO3−) were comparatively studied. Intriguingly, the LiBF4‐based electrolyte show relatively moderate ionic conductivities; yet, the corresponding Li||CFx cells deliver the highest discharge capacities among them. A combination of morphological and compositional analyses of the discharge CFx cathode suggest that the moderate donicity of BF4− 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||CFx cells, but also inspire the electrolyte design for other conversion‐type (sulfur and/or organosulfur) cathode materials desired for high‐energy applications.

Fundamentals of Li/CFxbattery design and application

“…À anion is favourable for C-F bond breakdown and that the capacity of the Li/CF x battery with the LiBF 4 -based electrolyte (674 mA h g À1 , 0.1 C) was higher than that of the LiPF 6 -based electrolyte (579 mA h g À1 , 0.1 C) at 25 1C. 219 Typically, electrolytes with 1 M salts exhibit the best ionic conductivity (Fig. 13m).…”

“…Wang et al tested five salts in PC/DME (1 : 1 w/w) and concluded that the ionic conductivities increase in the order of: 6.08 (LiSO 3 CF 3 ) < 8.73 (LiBF 4 ) < 13.22 (LiTFSI) < 13.32 (LiClO 4 ) < 15.38 mS cm −1 (LiPF 6 ). 219 The LiPF 6 -based electrolyte exhibited the highest ionic conductivity owing to its high degree of dissociation and moderate anion size. However, the LiBF 4 -based electrolyte exhibited favourable charge transfer resistance.…”

“…In addition, a recent study suggested that the BF 4 − anion is favourable for C–F bond breakdown and that the capacity of the Li/CF x battery with the LiBF 4 -based electrolyte (674 mA h g −1 , 0.1 C) was higher than that of the LiPF 6 -based electrolyte (579 mA h g −1 , 0.1 C) at 25 °C. 219…”

Improving the Electrochemical Performance of Fluorinated Carbons by Solvent Co–Intercalation for Rechargeable Na–Ion Battery Cathodes

“…The theoretical specific energy of CF x is the highest, which compared to other SOCl 2 , MnO 2, and SO 2 in lithium primary battery systems [3,4]. Besides, CF x cathodes have the advantages of a steady discharge plateau, excellent security, and wide working temperature [5,6].…”

Porifera-like nickel nanodendrite for the efficient electrosynthesis of C–N compounds from carbon dioxide and nitrate anions

“…Meanwhile, NtRR is a green process to produce ammonia (NH 3 ) in comparison with the traditional Haber-Bosch process, which consumes high energy and emits lots of greenhouse CO 2 gas. 12,13 Therefore, developing active catalysts to simultaneously reduce CO 2 and NO 3 − could potentially promote the formation of C-N bonds and C 2+ chemicals under ambient conditions. Recently, a C-N bond compound, urea (NH 2 CONH 2 ), was synthesized via the electrochemical coupling method (CO 2 and N 2 ).…”