Predicting Li-Rich Layered Oxide Compounds as High-Conductivity and Stable Solid Electrolytes

The search for new solid-state electrolytes (SSEs) with fast ionic conductivity and high electrochemical stability is one of most challenging issues for developing all-solid-state batteries. Most SSEs have specific ionic transport channels with the crystal structures of perovskite, NASICON, LISICON, and garnet. In this work, we predicted Li-rich layered Li3NbO4-type compounds as high-rate and stable SSEs. First-principles calculations show that the predicted Li3NbO4 compound has peculiar stacked structures of edge-shared [LiO5] and [NbO5] hexahedrons and exhibits higher thermodynamic stability than the experimentally synthesized compound with an octahedral stacked structure at <495 K. Its intralayer Li+ conductivity along the hexahedron–octahedron–hexahedron (h-o-h) path has a low energy barrier and low ionic conductivity. We further predicted Li2Mg0.5NbO4 as an SSE with a low ionic migration barrier of 0.33 eV, which is comparable with those of most other oxide SSEs. Therefore, the present study opens a new avenue to design high-performance SSEs in crystal space of layered rocksalt.