Additive effect of ionic liquids on the electrochemical property of a sulfur composite electrode for all-solid-state lithium-sulfur battery

We investigated additive effect of five kinds of ionic liquids, such as 1-ethyl-3-methyl-imidazolium bis(trifluoromethane-sulfonyl)imide [EMI][TFSI], 1-ethyl-3-methyl-imidazolium tetrafluoroborate [EMI] [BF4], 1-buthyl-3-methyl-imidazolium bis(trifluoromethane- sulfonyl) imide [BMI][TFSI], 1-buthy1-3-methyl-imidazolium tetrafluoroborate [BMI][BF4], and/or 1-buthyl-3-methyl-imidazolium iodide [BMI] [I], on electrochemical properties of the sulfur composite electrode for all-solid-state lithium sulfur batteries. The sulfur composite electrode that was composed of sulfur (29.9 wt%), vapor-grown carbon fiber (VGCF, 9.9 wt%), solid electrolyte (amorphous Li3PS4, 60.0 wt%), and [EMI][TFSI] (0.2 wt%) showed high initial specific capacity of 1270 mAh g(-1) at 25 degrees C, which was calculated on the base of the weight of sulfur. To construct a laboratory-scale all-solid-state battery, amorphous Li3PS4 and meta-stable Li4.4Si alloy were used as solid electrolyte and as negative electrode materials, respectively. The laboratory-scale all-solid-state battery showed good discharge charge cycle performance under a constant current density of 0.1 mA cm(-2) (24 mA g(-1)) at room temperature and retained the large specific capacity more than 1230 mAh g(-1) even after 50 cycles at 25 degrees C. The capacity after 50 cycles was about 97% of the initial capacity of the test cell. (C) 2014 Elsevier B.V. All rights reserved.