Stabilizing the Halide Solid Electrolyte to Lithium by a β-Li3N 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 Li₃N as an interface modification layer to improve the interfacial stability of Li₂ZrCl₆ to the Li anode. We found that commercial Li₃N can be easily transformed into an α-phase and a β-phase by ball-milling and annealing, respectively, in which β-phase Li₃N simultaneously has high room-temperature ionic conductivity and good stability to both Li and Li₂ZrCl₆, making it a good choice for an artificial interface layer material. After the modification of the β-Li₃N interfacial layer, the interfacial impedance between Li₂ZrCl₆ and the Li anode decreased from 1929 to ∼400 Ω. At a current density of 0.1 mA cm^-2, 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-Li₃N interface layer effectively improves the interfacial stability between Li₂ZrCl₆ and Li.