A Comparative Study of LiNO3 and LiTFSI for the Cycling Performance of δ-MnO2 Cathode in Lithium−Oxygen Batteries

Abstract

Lithium nitrate (LiNO3) is a potential option for the lithium salt in lithium−oxygen (Li−O2) batteries because it reduces the charging overpotential on carbon-based cathodes and protects the lithium metal anode from side reactions. However, the cycling stability of an electrolyte containing LiNO3 in the presence of cathode catalysts has not yet been studied. In this paper, we report an improvement in the cycling performance of δ-MnO2 cathodes in Li−O2 batteries using LiNO3 in comparison with that of batteries using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in DMSO-based electrolytes. A >50% improvement in cycling performance is obtained from the electrolyte with LiNO3 versus that with LiTFSI. While the charge−discharge voltage profiles of the two electrolytes are identical to each other, the electrolyte containing LiNO3 produces less side products such as C−F group compounds, Li2SO3, and Li2SO4 on the cathode surface. This may be due to the electrochemically stable behavior of LiNO3 and the preventive effect of NO3− on solvent decomposition, which stabilizes reactive species of superoxide radicals in the electrolyte.