First-principles study of Li-ion distribution at γ−Li3PO4/metal interfaces

We investigated Li-ion distribution profiles at the interfaces between $\ensuremath{\gamma}\text{\ensuremath{-}}{\mathrm{Li}}_{3}{\mathrm{PO}}_{4}$ and metal electrodes using first-principles and one-dimensional continuum-model calculations. Within the allowed range of the chemical potential of Li in $\ensuremath{\gamma}\text{\ensuremath{-}}{\mathrm{Li}}_{3}{\mathrm{PO}}_{4}$, $\ensuremath{-}6.11\phantom{\rule{0.16em}{0ex}}\mathrm{eV}\phantom{\rule{4pt}{0ex}}\ensuremath{\le}{\ensuremath{\mu}}_{\mathrm{Li}}\ensuremath{\le}\phantom{\rule{4pt}{0ex}}\ensuremath{-}2.59\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$, which is estimated from the chemical potential diagram of Li, P, O-related chemical compounds, we predict upward band bending near Au(111) and Ni(111) interfaces. We found interstitial Li-ion accumulation for the larger ${\ensuremath{\mu}}_{\mathrm{Li}}$ values and its depth is ca. 3 \AA{} for ${\ensuremath{\mu}}_{\mathrm{Li}}=\ensuremath{-}2.59\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$. For the Li(100) interface with ${\ensuremath{\mu}}_{\mathrm{Li}}=\ensuremath{-}2.59\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$, we predict slight upward band bending and the formation of interstitial Li-ions. However, the downward band bending occurs for ${\ensuremath{\mu}}_{\mathrm{Li}}=\ensuremath{-}6.11\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$, where the accumulated charge carrier corresponds to the Li-ion vacancies. Finally, we suggest that the interstitial Li-ions accumulated within a few \AA{} from the Au(111) interface and the Li-Au alloying play a central role in the switching of the novel memory device.