Abstract:
Lithium zinc silicate, Li2ZnSiO4, is a promising ceramic solid electrolyte material for
Li-ion batteries. In this study, atomistic simulation techniques were employed to examine intrinsic
defect processes; long range Li-ion migration paths, together with activation energies; and candidate
substitutional dopants at the Zn and the Si sites in both monoclinic and orthorhombic Li2ZnSiO4 phases.
The Li-Zn anti-site defect is the most energetically favourable defect in both phases, suggesting that
a small amount of cation mixing would be observed. The Li Frenkel is the second lowest energy
process. Long range Li-ion migration is observed in the ac plane in the monoclinic phase and the
bc plane in the orthorhombic phase with activation energies of 0.88 eV and 0.90 eV, respectively,
suggesting that Li-ion diffusivities in both phases are moderate. Furthermore, we show that Fe3+ is a
promising dopant to increase Li vacancies required for vacancy-mediated Li-ion migration, and that
Al3+ is the best dopant to introduce additional Li in the lattice required for increasing the capacity of
this material. The favourable isovalent dopants are Fe2+ at the Zn site and Ge4+ at the Si site.
