Stabilizing the Halide Solid Electrolyte to Lithium by a β-LiN Interfacial Layer.

As a new class of solid electrolytes, halide solid electrolytes have the advantages of high ionic conductivity at room temperature, stability to high-voltage cathodes, and good deformability, but they generally show a problem of being unstable to a lithium anode. Here, we report the use of LiN as an interface modification layer to improve the interfacial stability of LiZrCl to the Li anode. We found that commercial LiN can be easily transformed into an α-phase and a β-phase by ball-milling and annealing, respectively, in which β-phase LiN simultaneously has high room-temperature ionic conductivity and good stability to both Li and LiZrCl, making it a good choice for an artificial interface layer material. After the modification of the β-LiN interfacial layer, the interfacial impedance between LiZrCl and the Li anode decreased from 1929 to ∼400 Ω. At a current density of 0.1 mA cm, the overpotential of the Li symmetric cell decreased from 250 to ∼50 mV, which did not show an obvious increase for at least 300 h, indicating that the β-LiN interface layer effectively improves the interfacial stability between LiZrCl and Li.