Re-evaluating the nano-sized inorganic protective layer on Cu current collector for anode free lithium metal batteries

Anode free lithium metal batteries (AF-LMBs) have conspicuous advantages both in energy density and the compatibility of battery manufacturing process. However, the limited cycle life of AF-LMBs is a crucial factor hindering its practical application. Fluorinated or nitride artificial inorganic solid electrolyte interphase (SEI) has been found as an effective method to prolong the lifespan of AF-LMBs. Herein, by investigating the impact of nano-sized inorganic gradient layers (LiF or Li₃N) on initial Li deposition behavior, we notice that the Li⁺ diffusion barrier and the deposition morphology are highly depended on the thickness of inorganic layers. Thicker protective layers cause larger overpotential as well as more aggregated Li⁺ distribution. This study reveals that the ideal SEI should be synthesized thin and uniformly enough and uncontrollable artificial SEI can cause damage to the lifespan of AF-LMBs.