A Pretreatment Method to Form High-quality LiF-enriched Solid-electrolyte-interface for Li Anode Protection in Li-O2 Battery

The development of high-energy-density lithium-oxygen battery (LOB) is hindered by the poor stability of lithium metal anode. Lithium fluoride (LiF) was reported as an effective solid-electrolyte interface (SEI) component to enhance the stability of lithium anode. It is desirable to improve the quality of LiF based SEI to bear the volume expansion during the cycling process. In this work, uniform and high-dense LiF-rich artificial SEI consist of LiF nanoparticles close to Li with organic sulfonate wrapped outside is fabricated on Li surface via reaction of a fluorinated agent perfluorooctanesulfonylfluoride (PFOSF) with lithium hydroxide. The reaction conditions are mild and the formed dense and insulating LiF-rich layer can prevent the thicken of the SEI film during cycling. With such PFOSF treatment, the interface stability of lithium anode is largely improved. The lithium dendrites growth is significantly suppressed and the corrosion of O2 rich electrolyte is alleviated. The PFOSF treated Li||Li cells show stable polarization voltage and long cycle up to 1700 h in Ar or 900 h in O2 atmosphere. Moreover, the Li-O2 battery with PFOSF treated lithium anode shows excellent cyclability up to 180 cycles at a fixed capacity of 1000 mAh g-1, which is more than 4 times longer than that of pristine Li anode.