Lithium-ion batteries presents safety hazards due to their electrolyte. The
electrolyte is typically an organic flammable liquid, and their proximity to
an oxidizing agent can lead to thermal runaway and explosion in extreme
cases.
To overcome those inconveniences, the use of solid state electrolyte has been
suggested. They are inflammable and exhibit a higher stability. However,
their low ionic conductivity (less than 10^{^-4} S cm-1) hindered so far their
use in commercial batteries.
LiZr2(PO4)3 in the NASICON structure is a promising solid state electrolyte
with attractive Li-ion conductivity of 10^{^-5} S cm-1 and stability. This
compound undergoes a reversible phase transition from a triclinic structure
(called alpha') to a rhomboedral one (alpha phase) at 330K. It is
experimentally known that the conductivity of the alpha' phase is three
orders of magnitude lower than the estimated conductivity of the rhomboedral
phase at room temperature.
It is however not clear yet to what atomistic mechanism could explain this
large difference between two very close structures: the alpha and alpha’
phases. In this work, we have performed an ab initio study of Li diffusion in
both alpha and alpha’ phases using ab initio molecular dynamics and nudge
elastic band. Based on this computational insight, we identify the
differences and similarity between the two phases and shine light on the
reason for the higher performance of the alpha phase.