A pretreatment method to form high-quality LiF-enriched solid-electrolyte interfaces for Li anode protection in Li–O2 batteries

Abstract

The development of high-energy-density lithium-oxygen batteries (LOBs) is hindered by the poor stability of lithium metal anodes. Lithium fluoride (LiF) was reported as an effective solid-electrolyte interface (SEI) component to enhance the stability of lithium anodes. It is desirable to improve the quality of LiF based SEIs to bear the volume expansion during the cycling process. In this work, a uniform and highly dense LiF-rich artificial SEI consisting of LiF nanoparticles close to Li with organic sulfonates wrapped on the outside is fabricated on a Li surface via the reaction of a fluorinated agent perfluorooctanesulfonyl fluoride (PFOSF) with lithium hydroxide. The reaction conditions are mild and the formed dense and insulating LiF-rich layer can prevent the thickening of the SEI film during cycling. With such a PFOSF treatment, the interface stability of lithium anodes is largely improved. The lithium dendrite growth is significantly suppressed and the corrosion in O₂-rich electrolytes is alleviated. The PFOSF treated Li‖Li cells show stable polarization voltage and long cycle life up to 1700 h in an Ar and 900 h in an O₂ atmosphere. Moreover, the Li–O₂ battery with the PFOSF treated lithium anode shows excellent cyclability up to 185 cycles at a fixed capacity of 1000 mA h g⁻¹, which is more than 4 times longer than that of pristine Li anodes.