Homologous design of fluorinated amide-based deep eutectic gel electrolyte for dual-protected interfaces in high-voltage lithium metal batteries.

The development of high-voltage lithium metal batteries (LMBs) is significantly hindered by interfacial instability at both the lithium metal anode and high-voltage cathode. To address this challenge, we present a molecularly homologous design of a novel fluorinated amide-based deep eutectic gel electrolyte (FA-DGE). This gel electrolyte is formulated from confining a liquid deep eutectic electrolyte, consisting of N-methyltrifluoroacetamide and lithium bis(fluorosulfonyl)imide, within a poly(N,N'-methylenebisacrylamide) networks, featuring structurally congruent amide groups. This homologous design ensures outstanding interfacial compatibility and stability, exhibiting high oxidation stability and facilitating the formation of a LiF/Li3N-rich solid electrolyte interphase. The Li||Li symmetric cell incorporating the FA-DGE demonstrates remarkable cycling stability for over 3000 h without short-circuiting. Moreover, the Li||NCM811 cell cycled at a high voltage of 4.3 V achieves an impressive capacity retention ratio of 76.5% after 300 cycles. This work highlights the significant potential of synergistic bulk and interfacial engineering through homologous design for stabilizing next-generation high-energy-density batteries.