Li+ ion conductivity and diffusion mechanism in α-Li3N and β-Li3N

β-Li3N of hexagonal D46h (P63/mmc) structure was synthesized by high-energy ball milling commercial Li3N (composed of both α and β phases). Ionic conductivities of α-Li3N and β-Li3N were tested by direct current (D.C.) and alternating current (A.C.) impedance methods. β-Li3N exhibited the same order of magnitude of Li+ ion conductivity (2.085 × 10−4 S cm−1) as that of α-Li3N (5.767 × 10−4 S cm−1) at room temperature. First-principles calculations were employed to simulate the diffusion mechanism of Li+ ion in α-Li3N and β-Li3N. Our results indicate that the diffusion of Li+ ion in β-Li3N likely occurs between pure Liβ(1) planes, which is different from that in α-Li3N, where the diffusion of Li+ ion occurs within Li2N plane. The Li+ ion migration energy barriers (Em) for α-Li3N and β-Li3N are 0.007 eV and 0.038 eV, respectively.