Ab initio calculation of the lithium-tin voltage profile

Abstract

An ab initio pseudopotential plane-wave method was used to calculate the total energies for several structures (Sn, ${\mathrm{Li}}_{2}{\mathrm{Sn}}_{5},$ LiSn, ${\mathrm{Li}}_{7}{\mathrm{Sn}}_{3},$ ${\mathrm{Li}}_{5}{\mathrm{Sn}}_{2},$ ${\mathrm{Li}}_{13}{\mathrm{Sn}}_{5},$ ${\mathrm{Li}}_{7}{\mathrm{Sn}}_{2},$ and Li) of the lithium-tin phase diagram. This information was used to determine a theoretical electrochemical voltage profile, which compares well with experiment for $x<2.5$ in ${\mathrm{Li}}_{x}\mathrm{Sn}.$ For $x>2.5,$ it was found that the equilibrium structures predicted by the phase diagram were not formed in the room-temperature electrochemical cell, which explains why the calculated results are less good there. Calculations of this type are useful for materials research in lithium-ion batteries.