Salt-in-metal-assisted formation of LiF-rich interphase for lithium metal anodes

The uncontrolled growth of dendritic lithium on the lithium surface negatively impacts the lifespan of lithium metal batteries due to the instability of the solid electrolyte interphase (SEI). This paper introduces the concept of incorporating lithium-fluoride (LiF) salt into lithium metal to promote the formation of a LiF-rich interphase through a dissolution and re-deposition process, resulting in longer cycling lithium metal batteries. Solid salt, LiF, is integrated into the entire bulk phase of lithium metal using a simple and cost-effective mechanical rolling method. The surface LiF particles on the lithium metal prevent direct reaction of the electrolyte with the lithium metal underneath. Additionally, they can slowly dissolve into the electrolyte and redeposit onto uncovered areas of the lithium metal during the in-situ SEI formation process. When the in-situ formed SEI ruptures during the cycling process, the lithium metal are exposed to the electrolyte, providing LiF species for SEI healing at the crack region. The symmetrical cell with the designed LiF-rich electrode exhibits stable polarization voltage over 1000 h of cycle time (1 mA cm −2 /1 mAh cm −2 ). Stable charging and discharging cycles over 550 times are also achieved for full cells consisting of the prepared anode and LiFePO 4 cathode at 1C.