Ab initiocalculation 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 $x<\mathrm{}2.5\mathrm{}$ in ${\mathrm{Li}}_x\mathrm{Sn}.$ For $x>\mathrm{}2.5,$ 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.