In situ triggered rich-LiF/Mg multifunctional passivation layer for modifying the anode interface of all-solid-state lithium metal batteries

Lithium (Li) is a promising anode material for all-solid-state Li metal batteries (ASSLMBs) due to its high energy density. However, the interface incompatibility of Li/solid electrolyte and uneven Li deposition induces the penetration of Li dendrites. Herein, a multifunctional rich-LiF/Mg artificial solid electrolyte interphase (SEI) layer is constructed from a MgF${}_2$-PVDF-HFP film to passivate the Li anode and achieve effective inhibition of Li dendrites. Notably, the triggered Li${}_x$Mg alloys rivet the Li${}_6$PS${}_5$Cl (LPSCl) electrolyte and Li anode together well, producing satisfactory interface contact and reducing overpotential. The mechanism of LiF and Li${}_x$Mg alloys to enhance the stability of the Li/LPSCl interface is further elucidated by density functional theory (DFT). Moreover, the synergistic interaction of LiF with high interfacial energy and Li${}_x$Mg alloys with low diffusion barrier promotes uniform deposition of Li during plating/stripping and structural stability. Therefore, the modified Li-symmetric cell exhibits ultra-high critical current density (2.0 mA cm${}^{-2}$) and considerable cyclic stability (more than 1000 h at 0.5 mA cm${}^{-2}$). Remarkably, NCM//LPSCl//3% MgF${}_2$-PVDF-HFP@Li ASSLMBs exhibit considerable long-term cycle stability (86.9% capacity retention after 100 cycles at 0.2 C). This work highlights the critical role of the intermediate passivating layer in mitigating side reactions and preventing Li penetration. (© 2024 Wiley‐VCH GmbH)