Developing multifunctional amide additive by rational molecular design for high-performance Li metal batteries

Rechargeable lithium batteries based on lithium metal anodes and high-nickel cathodes have unparalleled advantages in energy density. However, the massive growth of lithium dendrites and the rapid degradation of high-nickel ternary oxides in commercial electrolyte have greatly hindered their application. To circumvent this issue, we design a series of analogs as electrolyte additives by adopting acetyls as connecting units to splice multiple functional groups. Among these additives, N-methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA) stands out due to the rational molecular configuration and the synergistic complementarity of amide, trifluoromethyl and trimethylsilyl groups. The cycling reversibility of the lithium metal anode (1050 h at 1 mA cm−1 to 1 mAh cm−1) and the capacity retention of the LiNi0.9Co0.05Mn0.05O2 cathode (85.9 % at 3–4.3 V after 300 cycles) in MSTFA modified carbonate electrolyte are tremendously enhanced. In addition, the safety of the battery and the tolerance to harsh working conditions (high & low temperature, high-voltage) are also ameliorated. This work sheds light on the relationship between structure and activity of molecules as well as provides a novel idea for modular design of additives. [Display omitted] •A series of new additives such as MSTFA, DTA, MSA and TATE were developed based on molecular design.•MSTFA not only greatly extend the reversibility of LM anodes but also improve the cycle stability of Ni90 cathodes.•MSTFA effectively enhances the adaptability of the LMBs with Ni90 cathodes under harsh conditions.•The safety of the battery (gas generation, heat release, thermal stability of electrolyte) has also been optimized.