The
lithium–oxygen battery (LOB) with a high theoretical
energy density (∼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
oxidizing environment 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 by
just simply mixing solid N-methylacetamide (NMA)
and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) at a
certain ratio. The unique interaction of the polar groups in the NMA
with the cations and anions in the LiTFSI enables DEE formation, and
this NMA-based DEE possesses high ionic conductivity, good thermal,
chemical, and electrochemical stability, and good compatibility with
the lithium metal anode. 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 (280 cycles).
The introduction of DEE into LOBs will inject new vitality into the
design of electrolytes and promote the development of high-performance
LOBs.
The severe performance degradation of high‐capacity Li−O2 batteries induced by Li dendrite growth and concentration polarization from the low Li+ transfer number of conventional electrolytes hinder their practical applications. Herein, lithiated Nafion (LN) with the sulfonic group immobilized on the perfluorinated backbone has been designed as a soluble lithium salt for preparing a less flammable polyelectrolyte solution, which not only simultaneously achieves a high Li+ transfer number (0.84) and conductivity (2.5 mS cm−1), but also the perfluorinated anion of LN produces a LiF‐rich SEI for protecting the Li anode from dendrite growth. Thus, the Li−O2 battery with a LN‐based electrolyte achieves an all‐round performance improvement, like low charge overpotential (0.18 V), large discharge capacity (9508 mAh g−1), and excellent cycling performance (225 cycles). Besides, the fabricated pouch‐type Li–air cells exhibit promising applications to power electronic equipment with satisfactory safety.
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