First Principles Investigations of the Li10GeP2S12 Superionic Conductor and Related Materials

Li10GeP2S12 (LGPS) is a recently discovered lithium super ionic conductor.[1] This new material has the highest conductivity ever achieved among solid lithium electrolytes of 12 mS/cm at room temperature and outstanding electrochemical performance in Li batteries. In this talk, we present a first-principles analysis of the stability, and electrochemical window and Li diffusivity of LGPS. We find that LGPS is a metastable phase in the calculated phase diagram and that LGPS is not stable against reduction by lithium at low voltage or extraction of Li with decomposition at high voltage. A hypothesis is provided for the observed wide electrochemical window of LGPS. We also identified the diffusion pathways and calculated the corresponding activation energies and diffusion coefficient. Our simulations show that LGPS is in fact a three-dimensional ion conductor rather than a one dimensional ion conductor, and our calculated overall activation barrier and conductivity are in remarkable agreement with the experimental results.[2