Insight on the LiS electrochemical process in a composite configuration electrode

• Published in: New journal of chemistry 2016-03, Vol.4 (3), p.2935-2943
• Main Authors: Carbone, Lorenzo, Verrelli, Roberta, Gobet, Mallory, Peng, Jing, Devany, Matthew, Scrosati, Bruno, Greenbaum, Steve, Hassoun, Jusef
• Format: Article
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c5nj03402g

A novel, low cost and environmentally sustainable lithium sulfide-carbon composite cathode, suitably prepared by combining polyethylene oxide (PEO), LiCF 3 SO 3 and Li 2 S-C powders is presented herein. The cathode is characterized in a lithium-metal cell employing a solution of LiCF 3 SO 3 salt in dioxolane-dimethylether (DOL:DME) as the electrolyte. The detailed NMR investigation of the diffusion properties of the electrolyte is reported in order to determine its suitability for the proposed cell. The addition of LiNO 3 to the electrolyte solution allows its practical application in a lithium sulfur cell using an Li 2 S-C-based cathode characterized by a specific capacity of about 500 mA h g −1 (with respect to the Li 2 S mass). The cell holds its optimal performances for over 70 cycles at a C/5 rate, with a steady state efficiency approaching 99%. The X-ray diffraction patterns of the cell upon operation suggest the reversibility of the Li 2 S electrochemical process, while the repeated electrochemical impedance spectroscopy (EIS) measurements indicate the suitability of the electrode-electrolyte interface in terms of low and stable cell impedance. Furthermore, the EIS study clarifies the activation process occurring at the Li 2 S cathode during the first charge process, leading to a decrease of cell polarization during the following cycles. The data reported here shed light on important aspects which should be considered for the efficient application of a Li 2 S cathode in lithium batteries. A novel, low cost, environmentally sustainable cathode combining PEO, LiCF 3 SO 3 and Li 2 S-C is reported for application in high-energy lithium batteries.