Robust Transport:An Artificial SEI Design for Anode Free Lithium Metal Battery.

One of the most challenging issue in the practical implementation of high-energy-density anode-free lithium metal batteries (AFLMBs) is the sharp capacity attenuation caused by the mechanical degradation of the solid electrolyte interphase (SEI). However, developing an artificial SEI to address this issue remains challenge due to the trade-off between ionic conductivity and mechanical robustness for general ionic conducting films. In this study, a tenacious composite artificial SEI with integrated heterostructure of lithium fluoride (LiF) and lithium phosphorus oxynitride (LiPON) is prepared using a co-sputtering approach to achieve both high ionic conductivity and fracture toughness. The embedded LiF domain has an extremely high Young's modulus and surface energy compared with those of bulk LiPON film, enabling a significant increase in fracture toughness by an order of magnitude. Most importantly, the interface between LiPON and LiF in the integrated structure generates additional fast Li + transport pathways, providing the artificial SEI with a conductivity higher than 10 -6 S cm -1 . Consequently, the artificial SEI implementation significantly increases the cycling lifetime of the corresponding AFLMBs by more than 250%. This study highlights the importance of fracture toughness for the structural integrity of batteries and provides suggestions for designing viable SEI materials for high-performance AFLMBs. This article is protected by copyright. All rights reserved.