Modified Tetrathiafulvalene as an Organic Conductor for Improving Performances of Li−O2 Batteries

• Published in: Angewandte Chemie International Edition 2017-07, Vol.56 (29), p.8505-8509
• Main Authors: Zhang, Jinqiang, Sun, Bing, Zhao, Yufei, Kretschmer, Katja, Wang, Guoxiu
• Format: Article
• Language: English
• Subjects: Batteries; Conductors; Energy charge; Energy efficiency; Energy management; Kinetics; Lithium; Lithium chloride; lithium-oxygen batteries; Metal air batteries; organic conductors; Power efficiency; Reaction kinetics; redox mediators; TTF
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201703784

Large over‐potentials owing to the sluggish kinetics of battery reactions have always been the drawbacks of Li−O2 batteries, which lead to short cycle life. Although redox mediators have been intensively investigated to overcome this issue, side‐reactions are generally induced by the solvated nature of redox mediators. Herein, we report an alternative method to achieve more efficient utilization of tetrathiafulvalene (TTF) in Li−O2 batteries. By coordinating TTF+ with LiCl during charging, an organic conductor TTF+Clx− precipitate covers Li2O2 to provide an additional electron‐transfer pathway on the surface, which can significantly reduce the charge over‐potential, improve the energy efficiency of Li−O2 batteries, and eliminate side‐reactions between the lithium metal anode and TTF+. When a porous graphene electrode is used, the Li−O2 battery combined with TTF and LiCl shows an outstanding performance and prolonged cycle life. A pinch of salt: TTF+Clx− precipitates on the surface of the Li2O2 discharge product upon the addition of LiCl to tetrathiafulvalene‐containing electrolytes during charging. This efficiently reduces the risk of side‐reactions and enhances the cycling performances of Li−O2 batteries.