A comparative study of LiNO₃ and LiTFSI for the cycling performance of δ-MnO₂ cathode in lithium-oxygen batteries

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.