A dendrite-and oxygen-proof protective layer for lithium metal in lithium-oxygen batteries

The problem of Li metal degradation, which leads to drastic side reactions, must be solved for improving the long-term cycle performance of lithium–oxygen (Li–O₂) batteries. Recently, a number of methodologies have been proposed for Li metal surface protection, but evaluation of the stability of the protective materials is insufficient. Therefore, in this study, we fabricated an NCL (Nafion-based composite layer) as a mechanically and chemically stable protective layer for Li metal in Li–O₂ batteries. In addition, comparative experiments were conducted to investigate the mechanical and chemical stability of protective layers. Li–O₂ batteries using NCL-coated Li metal exhibited reversible oxygen reduction and evolution without any side reactions caused by reactive oxygen species that decompose chemically unstable protective materials. The NCL also exhibited effective mechanical strength which was verified with not only a Li stripping and plating test but also using a large scale Li–O₂ pouch cell which had has severe operating conditions with high current and capacity values.