title: Intensive Study on the Catalytical Behavior of N-Methylphenothiazine as a Soluble Mediator to Oxidize the Li2O2Cathode of the Li-O2Battery.
abstract: Aprotic Li-O2batteries have attracted worldwide interest owing to their ultrahigh theoretical energy density. However, the practical Li-O2batteries still suffer from high charge overpotential and low energy efficiency resulting from the sluggish kinetics in electrochemically oxidizing the insulating lithium peroxide (Li2O2). Recently, dissolved redox mediators in the electrolyte have enabled the effective catalytic oxidation of Li2O2at the liquid-solid interface. Here, we report that the incorporation of N-methylphenothiazine (MPT), as a redox shuttle in Li-O2batteries, provides a dramatic reduction in charge overpotential to 0.67 V and an improved round-trip efficiency close to 76%. Moreover, the efficacy of MPT in Li-O2cells was further investigated by various characterizations. On charging, MPT+cations are first generated electrochemically at the cathode surface and subsequently oxidize the solid discharge products Li2O2through a chemical reaction. Furthermore, the presence of MPT has been demonstrated to improve the cycling stability of the cells and suppress side reactions arising from carbon and electrolytes at high potentials.
authors.affiliation: Center of Energy Storage Materials & Technology, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, P. R. China.
authors.forename: Ningning
authors.identifier: http://orcid.org/0000-0003-0358-1659
authors.initials: N
authors.lastname: Feng
authors.affiliation: Center of Energy Storage Materials & Technology, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, P. R. China.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Mu
authors.affiliation: Center of Energy Storage Materials & Technology, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, P. R. China.
authors.forename: Xueping
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Center of Energy Storage Materials & Technology, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, P. R. China.
authors.forename: Ping
authors.initials: P
authors.lastname: He
authors.affiliation: Center of Energy Storage Materials & Technology, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, P. R. China.|Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) , Umezono 1-1-1, Tsukuba 3058568, Japan.
authors.forename: Haoshen
authors.initials: H
authors.lastname: Zhou
keywords: N-methylphenothiazine; charge overpotential; chemical oxidation of Li2O2; dissolved redox mediators; liquid−solid interface; lithium−oxygen batteries