State Key Laboratory of Material Processing and Die and Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

Supplementary Information

In situ protection of a sulfur cathode and a lithium anode via

adopting a fluorinated electrolyte for stable lithiumsulfur batteries

Xue Chen, Haijin Ji, Weilun Chen, Jingyi Wu, Fei Hu, Lixia Yuan, Zhen Li*, Yunhui Huang*

State Key Laboratory of Material Processing and Die and Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

*Corresponding authors.

E-mail addresses: li_zhen@hust.edu.cn (Z. Li), huangyh@hust.edu.cn (Y.H. Huang).

Figure. S1 The morphological and structural characterizations of the CMK-3 before and after sulfur impregnation. (a) SEM image of CMK-3; (b) SEM image of CMK-3/S; (c) N2 adsorption-desorption curves; (d) Pore distribution; (e) XRD patterns; (f) TGA curves.

Figure. S2 The Raman spectrum of (a) 1.0 mol L⁻¹ ether-based electrolyte and (b) 1.0 mol L⁻¹ carbonate- based electrolyte. (c−e) The Raman spectrum (axis start from origin of coordinates) of different solvents and electrolytes.

Figure. S3 (a) Electrolyte viscosities as functions of shear-rate and (b) the corresponding viscosities value.

Figure. S4 (a) Cycling performance and (b) charge-discharge curves of the CMK-3/S cathodes in the HFE-based eletrolyte (0.8−3.0 V).

Figure. S6 (a) XPS spectra of the CMK-3/S cathode at fresh state and after formation in ether-based and

HFE-based electrolyte, respectively. (b) TEM image and (c) the corresponding EELS elemental mappings of the CMK-3/S composite material.

Figure. S7 The electrochemical performances of CMK-3/S cathode (after formation in carbonate-based electrolyte and starting from the 4^th). (a) Cycle performance and CE (0.2 C) and (b) corresponding charge- discharge curves.

Figure. S8 Voltage vs specific capacity at various rates of the CMK-3/S (after formation) in (a) HFE- based electrolyte and (b) ether-based electrolyte.

Figure. S9 (a) Cycling performance of the Li||Cu cells (current density = 1 mA cm⁻², areal capacity = 1 mA h cm⁻²) with different electrolytes. (b) Cycling performance of the symmetric Li||Li cells (current density = 2 mA cm⁻², areal capacity = 4 mA h cm⁻²) with different electrolytes and (c) the corresponding galvanostatic discharge/charge voltage profiles at the 7^th, 30^th and 50^th.

Figure. S10 (a−c) Top view and (d−f) cross-sectional SEM images of the Li plating on the Cu substrate at 5^th cycle in the Li||Cu cells (current density = 1 mA cm⁻², areal capacity = 4 mA h cm⁻²) with different electrolytes (a,d) ether-based; (b,e) carbonate-based; (c,f) HFE-based.