A Low-Volatile and Durable Deep Eutectic Electrolyte for High-Performance Lithium-Oxygen Battery

The lithium-oxygen battery (LOB) with a high theoretical energydensity (similar to 3500 Wh kg-1) has been regarded as a strong competitor for next-generation energy storage systems. However, its performance is still far from satisfactory due to the lack of stable electrolyte that can simultaneously withstand the strong oxidizingenvironment during battery operation, evaporation by the semiopen feature, and high reactivity of lithium metal anode. Here, we have developed a deep eutectic electrolyte(DEE) that can fulfill all the requirements to enable the long-term operation of LOBs byjust simply mixing solidN-methylacetamide (NMA) and lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI) at a certain ratio. The unique interactionof the polar groups in the NMA with the cations and anions in the LiTFSI enables DEEformation, and this NMA-based DEE possesses high ionic conductivity, good thermal, chemical, and electrochemical stability, and good compatibility with the lithium metalanode. As a result, the LOBs with the NMA-based DEE present a high discharge capacity (8647 mAh g-1), excellent rate performance, and superb cycling lifetime (280cycles). The introduction of DEE into LOBs will inject new vitality into the design of electrolytes and promote the development of high-performance LOBs.