  Molecular dynamics simulations are a powerful tool to study diffusion
processes in battery electrolyte and electrode materials. From a single
molecular dynamics simulation many properties relevant to diffusion can be
obtained, including the diffusion path, attempt frequency, activation energies,
and collective diffusion processes. These detailed diffusion properties provide
a thorough understanding of diffusion in solid electrolytes, and provides
direction for the design of improved solid electrolyte materials. Here a
thorough analysis methodology is developed, and applied to DFT MD simulations
of Li-ion diffusion in \beta-Li3PS4. The methodology presented is generally
applicable to crystalline materials and facilitates the analysis of molecular
dynamics simulations. The code used for the analysis is freely available at:
https://bitbucket.org/niekdeklerk/md-analysis-with-matlab. The results on
\beta-Li3PS4 demonstrate that jumps between bc-planes limit the conductivity of
this important class of solid electrolyte materials. The simulations indicate
that by adding Li-interstitials or Li-vacancies the rate limiting jump process
can be accelerated significantly, which induces three dimensional diffusion,
resulting in an increased Li-ion diffusivity. Li-vacancies can be introduced
through Br-doping, which is predicted to result in an order of magnitude larger
Li-ion conductivity in \beta-Li3PS4. Furthermore, the present simulations
rationalise the improved Li-ion diffusivity upon O-doping through the creation
of local Li-interstitials.
