Synergistic Effects of Bisalt Additives in High‐Voltage Rechargeable Lithium Batteries

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Abstract
The stability of high‐energy‐density lithium metal batteries (LMBs) heavily relies on the composition of the solid electrolyte interphase (SEI) formed on lithium metal anodes. In this study, the inorganic‐rich SEI layer was achieved by incorporating bisalts additives into carbonate‐based electrolytes. Within this SEI layer, the presence of LiF, polythionate, and Li3N was observed, generated by combining 1.0 м lithium bis(trifluoromethanesulfonyl)imide in ethylene carbonate: ethyl methyl carbonate:dimethyl carbonate in a 1 : 1 : 1 volume ratio, with the addition of 2 wt% lithium difluorophosphate and 2 wt% lithium difluoro(oxalato)borate additives (EL‐DO). Furthermore, this formulation effectively mitigated corrosion of aluminum current collectors. EL‐DO exhibited outstanding performance, including an average coulombic efficiency of 98.2 % in Li||Cu cells and a stable discharge capacity of approximately 162 mAh g−1 after 200 cycles in a Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) configuration. Moreover, EL‐DO displayed the potential to enhance the performance not only of LMBs but also of lithium‐ion batteries. In the case of Gr||NCM811 cell using EL‐DO, it consistently maintained high discharge capacities, even achieving around 135 mAh g−1 after the 100th cycle, surpassing the performance of other electrolytes. This study underscores the synergistic impact of bisalts additives in elevating the performance of lithium batteries.

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