Bismuth and Fluorine Dual‐Doping of Lithium Argyrodite toward High‐Performance All‐Solid‐State Lithium Metal Batteries

Abstract Chlorine‐rich lithium argyrodite is considered as a promising superionic conductor electrolyte, but its practical application is limited due to poor air stability and instability toward lithium metal. In this work, BiF 3 is proposed as a multi‐functional dopant for electrolyte modification, and the effects on the ionic conductivity, air stability, critical current density, and electrolyte/Li metal interfacial stability are studied. The results show that the doped electrolyte Li 5.54 P 0.98 Bi 0.02 S 4.5 Cl 1.44 F 0.06 (LPBiSClF 0.06 ) still maintains a relatively high ionic conductivity of 5.37 mS cm −1 . Additionally, the formation of BiS 4 5− unit and LiBiS 2 phase provides high air/moisture resistibility. Meanwhile, the critical current density of the Li/LPBiSClF 0.06 /Li cell is increased two‐fold (2.1 mA cm −2 ). The in‐situ formation of LiF and Li−Bi alloy at the lithium metal/electrolyte interface plays a key role in achieving high performance. As a result, the assembled LCO@LNO/LPBiSClF 0.06 /Li battery retains 78.4 % of its capacity after 100 cycles at 0.2C.