High capacity semi-liquid lithium sulfur cells with enhanced reversibility for application in new-generation energy storage systems

• Published in: Journal of power sources Vol. 412; pp. 575 - 585
• Main Authors: Di Lecce, Daniele, Marangon, Vittorio, Benítez, Almudena, Caballero, Álvaro, Morales, Julián, Rodríguez-Castellón, Enrique, Hassoun, Jusef
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2019
• Subjects: Catholyte polysulfide; DEGDME; LiCF3SO3; LiTFSI; Lithium-sulfur battery; X-ray photoelectron spectroscopy; DEGDME; Catholyte polysulfide; LiTFSI; Lithium-sulfur battery; LiCF3SO3; X-ray photoelectron spectroscopy
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2018.11.068

Semi-liquid configuration of sulfur cell is proposed as simple strategy to develop high-energy lithium battery. Two solutions of Li2S8 in diethylene glycol dimethyl ether (DEGDME), containing either lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium trifluoromethansulfonate (LiCF3SO3) and lithium nitrate (LiNO3), are studied as catholytes for Li/S cells exploiting the polysulfides electrochemical reaction at about 2.2 V vs. Li+/Li. X-ray photoelectron spectroscopy (XPS) and thermal analyses, respectively, reveal composition and high-temperature stability of the catholyte solutions. Ad hoc study conducted by impedance spectroscopy, voltammetry, and galvanostatic techniques suggests well suitable characteristics in terms of Li+-transport ability, electrochemical stability window, and electrode/electrolyte interphase features. Cells with sulfur loading ranging from about 3 to 6 mg cm−2 into the solution are successfully studied with remarkable performances in terms of current rates, efficiency and cycle life. Hence, the lithium cells based on the catholyte deliver maximum capacity of the order of 1100 mAh gS−1 at C/10 rate and stable capacity of about 800 mAh gS−1 at C/3 rate with Coulombic efficiency exceeding 99%. Therefore, the catholyte solutions studied herein are considered as a very promising candidates for high-energy storage in next generation systems, such as the intriguing hybrid and electric vehicles. [Display omitted] •Semi-liquid Li/S cells are investigated as suitable alternative for energy storage.•Li2S8 in DEGDME exploits the polysulfides electrochemical reaction at about 2.2 V.•The use of LiTFSI and LiCF3SO3 salts leads to different cell behavior.•The cells show capacity from 800 to 1100 mAh gS−1 with Coulombic efficiency >99%.