Enhanced stability of lithium metal batteries by using synergistic effects of LiTFA salt and LiDFBP additive

Abstract

Lithium metal batteries (LMBs) are widely studied for their potential to offer superior energy storage capabilities. However, their practical use is hindered by issues such as lithium dendrite formation and the instability of the solid electrolyte interphase (SEI). In this study, we present a new electrolyte formulation that replaces conventional LiPF₆ salt with lithium trifluoroacetate (LiTFA) and incorporates lithium difluorobis(oxalato)phosphate (LiDFBP) as an additive. The electrolyte composed of 1.0 M LiTFA in EC:DMC (1:1:1 by volume) with 2 wt% LiDFBP minimizes unwanted reactions between lithium anode and organic components of electrolyte, promoting the formation of a durable SEI layer. The Li||Cu cells demonstrated an outstanding Coulombic efficiency of 99.1 %, highlighting the effectiveness of this system. Additionally, cells paired with LFP and NMC622 cathodes demonstrated outstanding performance, with average efficiencies of approximately 99 % and stable discharge capacities of around 135 mAh g⁻¹ and 150 mAh g⁻¹, respectively, over 200 cycles. These results highlight the combined effectiveness of LiTFA and LiDFBP in enhancing the stability of the electrolyte-electrode interface. Considering the scarcity of lithium salts that satisfy the strict demands of battery electrolytes, this study presents a viable alternative for advancing future LMBs and broadens the possibilities for electrolyte system development.