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

Abstract

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.