Nonafluorobutyl ether enhancing the stability of fluorobenzene-based diluted high-concentration electrolytes in high-voltage lithium metal batteries

The development of stable electrolytes for high-voltage lithium metal batteries (LMBs) is crucial for advancing battery technology. Diluted high-concentration electrolytes (DHCEs) have shown promise in enhancing interfacial stability, yet challenges persist due to the thermodynamic instability associated with conventional hydrofluoroether diluents and the interphase issues of monofluoroaromatic hydrocarbon diluents under high voltage conditions. In this study, we propose the incorporation of methyl 1,1,2,2,3,3,4,4,4-nonafluorobutyl ether (CNFE) as an additive to fluorobenzene (FB)-based DHCEs for high-voltage LMBs. CNFE with a molecular structure devoid of β-hydrogen guarantees the thermodynamic stability of FB-based DHCEs compared to conventional hydrofluoroether-based DHCEs. Moreover, CNFE promotes the formation of a LiF-rich and stable solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI). Consequently, a Li‖LiNi0.8Co0.1Mn0.1O2 (NCM811) cell demonstrates a remarkable capacity retention of 84.8% in the 700th cycle at a high cutoff voltage of 4.4 V.