Autoxidation in amide-based electrolyte and its suppression for enhanced oxygen efficiency and cycle performance in non-aqueous lithium oxygen battery

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>In spite of several desirable properties such as high stability against superoxide anion and low vapor pressure, <I>N</I>-methyl-2-pyrrolidone (NMP) electrolyte is reported not suitable for use in lithium-oxygen (Li-O<SUB>2</SUB>) batteries because of severe degradation upon cycling and low oxygen efficiency. In this work, we find that NMP electrolyte is reactive with O<SUB>2</SUB> gas in the presence of lithium metal and such O<SUB>2</SUB>-consuming reaction (<I>i.e.,</I> autoxidation) is a possible cause for the poor performance in Li-O<SUB>2</SUB> batteries with NMP electrolyte. The autoxidation of NMP is verified by direct measurement of the depletion of O<SUB>2</SUB> gas in the hermetically sealed symmetric Li/Li cells via in-situ gas pressure analysis. In-situ differential electrochemical mass spectroscopy (DEMS) experiment reveals that the autoxidation resulted in significant O<SUB>2</SUB> consumption upon discharge, very low O<SUB>2</SUB> efficiency upon charge, and eventually fast capacity fading. Lithium nitrate (LiNO<SUB>3</SUB>), which provides a protective layer on the surface of lithium metal, is employed to suppress the autoxidation, leading to significantly enhanced oxygen efficiency and cycle life.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NMP electrolyte is reactive with O<SUB>2</SUB> gas in the presence of lithium metal. </LI> <LI> Autoxidation is verified by in-situ gas pressure analysis and DEMS. </LI> <LI> Autoxidation results in low O<SUB>2</SUB> efficiency and fast capacity fading. </LI> <LI> LiNO<SUB>3</SUB> is employed to suppress the autoxidation. </LI> <LI> LiNO<SUB>3</SUB> is efficient in enhancing oxygen efficiency and cycle life. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>