Simulation of Li ion diffusion near electrolyte-metal interface -- Li$_3$PO$_4$ and Li*

Motivated by recent technological interest in Li$_3$PO$_4$-based electrolytes developed at Oak Ridge National Laboratory\footnote{J. B. Bates, N. J. Dudney, and co-workers, {\em{Solid State Ionics}}, {\bf{53-56}}, 647-654 (1992).} for use in rechargeable solid-state batteries and other technologies, we have used first-principles modeling techniques to study Li ion diffusion near idealized interfaces between Li$_3$PO$_4$ and Li metal. Using the nudged elastic band method, migration energy barriers for Li ion diffusion across interfaces in different crystallographic directions are calculated for both vacancy and interstitialcy mechanisms. Preliminary results find interface migration barriers as low as 0.2 eV and 0.26 eV for the vacancy and interstitialcy mechanisms, respectively. This suggests that interface diffusion barriers are likely to be comparable or lower than the corresponding migration barriers within crystalline Li$_3$PO$_4$.\footnote{Y. A. Du and N. A. W. Holzwarth, {\em{Phys. Rev. B}}, {\bf{76}}, 174302 (2007).}