Effect of Grain Boundaries on Li Superionic Conductivity in the Solid Electrolyte LGPS: Understanding and Property Data from Atomistic Simulations

摘要

The conductivity of lithium ions in the solid material Li[10]GeP[2]S[12] (LGPS) at room temperature is about one order of magnitude higher than in other known solid electrolytes and it does exceed even those of liquid organic electrolytes. Recent experiments suggest a retarding effect caused by grain boundaries, which is noticeable especially below room temperature. In order to understand and quantify this effect, we have performed large scale molecular dynamics (MD) simulations using a newly developed forcefield, which is exclusively based on ab initio data. The present simulations confirm the proposed anisotropic Li ionic conductivity: Li diffuses about twice as fast along channels formed by LiS tetrahedra as perpendicular to these channels. At room temperature grain boundaries cause a significant reduction of the Li diffusion and, hence, ionic conductivity, whereas above 500 K this effect disappears. All calculations have been performed using a single computational environment, MedeA , which includes tools for creating atomistic models, VASP for performing solid state quantum mechanical computations, automated forcefield optimization tools, LAMMPS for molecular dynamics simulations, and a suite of analysis tools for materials property calculations. The highly efficient exploration and optimization of structural, dynamic, and electrochemical properties of materials and interfaces in batteries are now possible on the atomic level thus turning the power of large-scale computing into a competitive advantage for materials engineering.