Ionic Liquid Electrolyte for Lithium Oxygen and Lithium Ion Oxygen Cell
Authors: Elia Giuseppe Antonio , Hassoun Jusef , Kwak Won Jin , Sun Yang-Kook , Scrosati Bruno , Müller Franziska , Bresser Dominic , Passerini Stefano , Oberhumer Philipp , Reiter Jakub , Tsiouvaras Nikolaos 
Published: February 2020

The replacement of the combustion-engine by sustainable electric or hybrid vehicles, may effectively limit environmental issues such as the global warming greenhouse-gas emission and pollution [1-2]. Lithium-ion battery represents the most promising candidate due to its high energy density, conventionally of about 180 Wh kg-1 that may assure a driving range of 150 km by single charge, i.e. acceptable value, however far from that granted by the conventional combustion engine vehicles. The lithium oxygen system, can theoretically allow to obtain an energy density of 1000 Wh kg-1, i.e. a value that may increase the driving range by single charge [3]. The applicability of the lithium air batteries is limited by several drawbacks, such as the poor electrolyte stability, the short cycle life and the low energy efficiency due to high charge-discharge polarization [4]. A deep knowledge of the lithium-oxygen reaction mechanism [5] and the identification of a stable electrolyte [6] play important role fundamental in allowing the practical application of the system. Furthermore, the safety concerns associated to the reactivity of the lithium metal anode are still hindering the application of the lithium-oxygen battery [7]. We report a Li/O2 cell exploiting an ionic liquid(IL)-based, N-Methyl-N-Butyl-Pyrrolidinium Bis-(trifluoromethanesulfonyl)-Imide Lithium bis-(trifluormethanesulfonyl)-imide, Pyr14TFSI-LiTFSI electrolyte. The use of non-flammable IL-based electrolyte stable up to a 300-400 °C resulted in an improved safety level of the battery [8].  In addition, the ionic-liquid electrolyte allows a fast kinetics of the lithium oxygen electrochemical process, thus lead to an high energy efficiency. The results here obtained, and reported in summary in the figure evidence low cell polarization, most likely due to the reduced particle size of the discharged products [9]. The replacement of the reactive lithium metal by an alternative, safe anode material may be required to further enhance the lithium oxygen cell characteristics [10]. Herein, we employed an alternative, nanostructured tin-carbon composite instead of lithium metal, in lithium ion-oxygen cell characterized in terms of electrochemical properties, focusing particular attention to the study of the oxygen cross-over process.

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Figure 1