Flame-retardant concentrated electrolyte enabling a LiF-rich solid electrolyte interface to improve cycle performance of wide-temperature lithium-sulfur batteries

Lithium-sulfur batteries have been regarded as the most promising high-energy electrochemical energy storage device owing to the high energy density, low cost and environmental friendliness. However, traditional lithium-sulfur batteries using ether-based electrolytes often suffer from severe safety risks (i.e. combustion). Herein, we demonstrated a novel kind of flame-retardant concentrated electrolyte (6.5 M lithium bis(trifluoromethylsulphonyl)imide/fluoroethylene carbonate) for highly-safe and wide temperature lithium-sulfur batteries. It was found that such concentrated electrolyte showed superior flame retardancy, high lithium-ion transference number (0.69) and steady lithium plating/stripping behavior (2.5 mAh cm(-2) over 3000 h). Moreover, lithium-sulfur batteries using this flame-retardant concentrated electrolyte delivered outstanding cycle performance in a wide range of temperatures (-10 degrees C, 25 degrees C and 90 degrees C). This superior battery performance is mainly attributed to the LiF-rich solid electrolyte inter phase formed on lithium metal anode, which can effectively suppress the continuous growth of lithium dendrites. Above-mentioned fascinating characteristics would endow this flame-retardant concentrated electrolyte a very promising candidate for highly-safe and wide-temperature lithium-sulfur batteries. (c) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.