Plasma grown fluoride-rich artificial SEI for stabilizing Li metal anodes

Abstract

The growth and detachment of lithium (Li) dendrites are regarded as the primary issues hindering the practical application of Li metal anodes, and constructing a stable solid electrolyte interface (SEI) is considered to be the most straightforward solution. Herein, carbon tetrafluoride (CF4) plasma growth instead of adding of additives into electrolyte is proposed to construct an artificial SEI. Highly reactive C- and F-containing species from the ionized CF4 react with the surface Li metal to form a stable fluoride-rich (i.e. LiF and CF) artificial SEI. Profit from the high chemical stability, low diffusion barrier and high mechanical strength of plasma-generated SEI, the distribution of lithium ions (Li+) on the surface of the prepared Li metal (F-Li) anodes is homogenized and the Li dendrites are inhibited. The symmetrical cells composed of F-Li can cycle stably for 1700 (1 mA cm−2, 1 mAh cm−2) and 1400 h (2 mA cm−2, 2 mAh cm−2) with minimum overpotentials of about 13 mV and 80 mV, respectively. The enhanced cyclability in the full cell system paired with NCM811 cathode further demonstrates its practical application. The mechanisms underlying the artificial SEI growth and its component evolution during electrochemical cycling were also discussed.