The Salt Matters: Enhanced Reversibility of Li–O2 Batteries with a Li[(CF3SO2)(n-C4F9SO2)N]-Based Electrolyte

Abstract

The safety hazards and cycle instability of lithium metal anodes (LMA) constitute significant barriers to progress in lithium metal batteries. This situation is worse in Li–O₂ batteries because the LMA is prone to be chemically attacked by O₂ shuttled from the cathode. Notwithstanding, efforts on LMA are much sparse than those on the cathode in the realm of Li–O₂ batteries. Here, a novel lithium salt of Li[(CF₃SO₂)(n-C₄F₉SO₂)N] (LiTNFSI) is reported, which can effectively suppress the parasitic side reactions and dendrite growth of LMA during cycling and thereby significantly enhance the overall reversibility of Li–O₂ batteries. A variety of advanced research tools are employed to scrutinize the working principles of the LiTNFSI salt. It is revealed that a stable, uniform, and O₂-resistive solid electrolyte interphase is formed on LMA, and hence the "cross-talk" between the LMA and O₂ shuttled from the cathode is remarkably inhibited in LiTNFSI-based Li–O₂ batteries.

A lithium salt comprising Li[(CF₃SO₂)(n-C₄F₉SO₂)N] (LiTNFSI) is introduced to stabilize the lithium metal anode (LMA) in aprotic Li–O₂ batteries. When combined with tetraglyme, the benchmark solvent of current Li–O₂ batteries, the LiTNFSI enables the formation of a stable, uniform, and O₂-resistive solid electrolyte interphase on LMA, and drastically enhances the reversibility of Li–O₂ batteries.

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