Stabilizing the Halide Solid Electrolyte to Lithium by a β-Li 3 N 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 Li 3 N as an interface modification layer to improve the interfacial stability of Li 2 ZrCl 6 to the Li anode. We found that commercial Li 3 N can be easily transformed into an α-phase and a β-phase by ball-milling and annealing, respectively, in which β-phase Li 3 N simultaneously has high room-temperature ionic conductivity and good stability to both Li and Li 2 ZrCl 6 , making it a good choice for an artificial interface layer material. After the modification of the β-Li 3 N interfacial layer, the interfacial impedance between Li 2 ZrCl 6 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-Li 3 N interface layer effectively improves the interfacial stability between Li 2 ZrCl 6 and Li.