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Electrolytes for Lithium-Sulfur Batteries
Published in Władysław Wieczorek, Janusz Płocharski, Designing Electrolytes for Lithium-Ion and Post-Lithium Batteries, 2021
Li-S batteries are based on the principle of reduction of sulfur (the cathode material) to polysulfide species (PS), which by interacting with lithium cations form lithium sulfide (Li2S). During discharge of the battery on the anode (built with metallic lithium) the process of lithium oxidation takes place: Li = Li+ + e−. At the same time, on the cathode, sulfur reduction takes place: S + 2e− = S2−. The overall reaction is as follows: 2Li + S = Li2S. Because sulfur in nature exists in the form of octasulfur+(S8),=it is necessary to modify the overall reaction equation to the following form: 16Li + S8 = 8Li2S. A mechanism of sulfur compound propagation in the electrolyte is described very well by Barghamadi et al. in a review paper [7]. In Li-S cells, various lithium polysulfides with a general formula Li2Sx (2 < x < 8) are formed during the cell discharge process. It is assumed that the elemental sulfur in the solid phase S8(s) is first dissolved in the electrolyte as S8 (solvated) and gradually reduce. During cell discharge, lithium polysulfides soluble in common organic solvents (Li2Sx, 4 < x < 8), insoluble in common organic solvents (Li2Sx, 1 < x < 2), and finally lithium sulfide (Li2S) appear one after another [8–13].
Applications and challenges of elemental sulfur, nanosulfur, polymeric sulfur, sulfur composites, and plasmonic nanostructures
Published in Critical Reviews in Environmental Science and Technology, 2019
Yong Teng, Qixing Zhou, Peng Gao
Metal sulfides have strong sulfidic properties to sulfur-containing species and low lithiation voltages vs Li/Li+ to avoid overlap in the working voltage window of Li-S batteries. The application of nanostructured metal oxides and sulfides for high sulfur utilization are also reviewed by Liu, Huang, et al. (2017). In addition, the using of lithium sulfide as a cathode material has been demonstrated to be an effective choice to overcome the safety problem of Li-S batteries. Especially, the traditional lithium anode can be replaced by lithium-free anodes when Li2S was used as a cathode material. After the replacement, the theoretical capacity can be 1166 mAh/g which is several times higher than that of traditional cathode materials (Zeng et al., 2017).