In this work for the first time we identify a new layered oxysulfide LiAlSO in orthorhombic structure as a novel lithium superionic conductor through first-principles calculations and crystal structure prediction techniques. Two kinds of stacking sequences of AlS2O2 layer are found in different temperature ranges. Phonon and molecular dynamics simulations verify their dynamic stabilities, and wide band gaps up to 5.6 eV are found by electronic structure calculations. The lithium migration energy barrier simulations reveal the collective interstitial-host ion “kick-off” hopping mode with barriers lower than 50 meV as the dominating conduction mechanism for LiAlSO, making it a promising solid state electrolyte in lithium secondary batteries with fast ionic conductivity and wide electrochemical window. This is a first attempt that the lithium superionic conductors are designed by crystal structure prediction method and may help explore other mixed-anion battery materials.
We acknowledge the National Natural Science Foundation of China (Grant No. 11234013), ‘‘863’’ Project (Grant No. 2015AA034201), and the Beijing S&T Project (Grant No. D161100002416003) for financial support and the Shanghai Supercomputer Center for providing computing resources. We would like to express our thanks to Prof. Jiawang Hong (Beijing Institute of Technology) for his fruitful discussion.