Room-temperature reversible F-ion batteries based on sulfone electrolytes with a mild anion acceptor additive

Abstract

A non-boron anion acceptor with moderate Lewis acidity is proposed to prepare a F-ion electrolyte with high conductivity at the mS cm−1 level at room temperature. A fluoride ion battery is successfully operated with high conversion reaction reversibility.

A Water-in-Salt Electrolyte for Room-Temperature Fluoride-Ion Batteries Based on a Hydrophobic–Hydrophilic Salt

“…Therefore, the F − transference number would be higher than 0.5. 6,23 This is consistent with the higher partial conductivity of F − anions than that of TMA + cations, as predicted by theoretic calculations (Table S1). In concentrated electrolytes, the movement of both TMA + cations and F − anions will be constricted, thus leading to a lower conductivity (Figure 1d).…”

“…Here, the cutoff charge capacity is set to prevent potentially undesired side reactions occurring at the electrode/ electrolyte interface. 23 As shown in Figure 3e,f, the CuF 2 //Pb@ PbF 2 full cell exhibits an initial discharge capacity of 109.9 mAh g −1 , which slowly increases to 134.8 mAh g −1 and finally delivers a capacity of 128.5 mAh g −1 after 160 cycles. These results indicate the excellent stability of WIS and its good suppressing capability toward CuF 2 dissolution.…”

“…Based on the detailed peak deviation of different element spectra, the reaction mechanism of CuF 2 can also be deduced. For example, in the pristine CuF 2 electrode, Cu 0 and Cu–C peaks in the Cu LMM spectrum can be deconvoluted (Figure h), which are due to the reduction of CuF 2 by carbon (forming Cu 0 ) and further the alloying between Cu 0 and carbon (forming CuC x ) during the ball milling process . Comparatively, the relative Cu 0 peak intensity increases in discharged CuF 2 , indicating the defluorination of CuF 2 .…”

“…A galvanostatic cycling test was conducted at a current density of 50 mA g –1 under a discharge cutoff voltage of −0.15 V and a charge cutoff capacity of 150 mAh g –1 . Here, the cutoff charge capacity is set to prevent potentially undesired side reactions occurring at the electrode/electrolyte interface . As shown in Figure e,f, the CuF 2 //Pb@PbF 2 full cell exhibits an initial discharge capacity of 109.9 mAh g –1 , which slowly increases to 134.8 mAh g –1 and finally delivers a capacity of 128.5 mAh g –1 after 160 cycles.…”

Insights into the first multi-transition-metal containing Ruddlesden–Popper-type cathode for all-solid-state fluoride ion batteries

“…The research on FIBs focused strongly on conversion-type cathode chemistries, i.e. metal/metal uorides (Me/MeF x ) [9][10][11][12][13][14][15] which offer the highest theoretical capacities due to the possibility of taking part in a multi-electron conversion process. For example, Fichtner et al 16 reported the use of CuF 2 as the conversion-type electrode material in FIBs.…”