  Understanding the atomistic mechanism of ion conduction in solid electrolytes
is critical for the advancement of all-solid-state batteries. Glass-ceramics,
which undergo crystallization from a glass state, frequently exhibit unique
properties including enhanced ionic conductivities compared to both the
original crystalline and glass forms. Despite these distinctive features,
specific details regarding the behavior of ion conduction in glass-ceramics,
particularly concerning conduction pathways, remain elusive. In this study, we
demonstrate the crystallization process of glass-Li$_3$PS$_4$ through molecular
dynamics simulations employing machine learning interatomic potentials
constructed from first principles calculation data. Our analyses of Li
conduction using the obtained partially crystallized structures reveal that the
diffusion barriers of Li decrease as the crystallinity in Li$_3$PS$_4$
glass-ceramics increases. Furthermore, Li displacements predominantly occur in
the precipitated crystalline portion, suggesting that percolation conduction
plays a significant role in enhanced Li conduction. These findings provide
valuable insights for the future utilization of glass-ceramic materials.
