Lithium metal protection through in-situ formed solid electrolyte interphase in lithium-sulfur batteries: The role of polysulfides on lithium anode

• Published in: Journal of power sources 2016-09, Vol.327, p.212-220
• Main Authors: Yan, Chong, Cheng, Xin-Bing, Zhao, Chen-Zi, Huang, Jia-Qi, Yang, Shu-Ting, Zhang, Qiang
• Format: Article
• Language: English
• Subjects: Li metal anode; Li-S battery; LiNO3; Polysulfides; Solid electrolyte interphase
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2016.07.056

The dissolution and diffusion of Li polysulfide (LiPS) intermediates are regarded as one of the most serious problems for capacity decay and cell failure of lithium-sulfur (Li-S) batteries. Herein we proposed a failure mechanism of Li metal anode in Li-S cells based on the mechanistic investigation into the complex interactions between LiPSs and Li metal. The LiPSs participate the formation of inorganic layers in the solid electrolyte interphase (SEI) in a LiPS-LiNO3 containing ether-based electrolyte. Li metal anode is well protected by the stable inorganic layer in-situ formed in an electrolyte containing 0.020 M Li2S5 (0.10 M sulfur) and 5.0 wt % LiNO3. The metal anode with LiF-Li2Sx riched SEI rendered a stable Coulombic efficiency of 95% after 233 cycles for Li-Cu half cells. A dendrite-free morphology of Li metal anode is observed under the harsh condition. When the LiPS is with a very high concentration of higher than 0.50 M sulfur in the organic electrolyte, the in-situ formed SEI cannot well maintain and the Li metal is gradually etched. Therefore, the polysulfide dissolution and diffusion should be delicately regulated to render a practical Li-S cell when the areal sulfur loading is high. [Display omitted] •The failure mechanism of Li metal etching at a high sulfur loading in a Li-S cell.•Excellent electrolyte additives for Li metal anode.•New understanding towards electrolyte additive design used in Li-S batteries.