Protecting Li-metal in O ₂ atmosphere by a sacrificial polymer additive in Li–O ₂ batteries

Li-O₂ batteries (LOBs) with Li-metal as the anode are characterized by their high theoretical energy density of 3500 W h kg^-1 and are thus considered next-generation batteries with an unlimited potential. However, upon cycling in a harsh O₂ atmosphere, the poor-quality solid electrolyte interphase (SEI) film formed on the surface of the Li-metal anode cannot effectively suppress the shuttle effect from O₂, superoxide species, protons, and soluble side products. These issues lead to aggravated Li-metal corrosion and hinder the practical development of LOBs. In this work, a polyacrylamide-co-polymethyl acrylate (PAMMA) copolymer was innovatively introduced in an ether-based electrolyte as a sacrificial additive. PAMMA was found to preferentially decompose and promote the formation of a dense and Li₃N-rich SEI film on the Li-metal surface, which could effectively prohibit the shuttle effect from a series of detrimental species in the Li-O₂ cell during the discharge/charge process. Using PAMMA, well-protected Li-metal in a harsh O₂ atmosphere and significantly enhanced cycling performance of the Li-O₂ cell could be achieved. Thus, the use of a sacrificial polymer additive provides a promising strategy for the effective protection of Li-metal in Li-O₂ cells in a severe O₂ atmosphere during practical applications.