Lithium thiophosphates (LPSs) with the composition (Li
2
S)
x
(P
2
S
5
)
1–
x
are among the most promising
prospective electrolyte
materials for solid-state batteries (SSBs), owing to their superionic
conductivity at room temperature (>10
–3
S cm
–1
), soft mechanical properties, and low grain boundary
resistance. Several glass–ceramic (
gc
) LPSs
with different compositions and good Li conductivity have been previously
reported, but the relationship among composition, atomic structure,
stability, and Li conductivity remains unclear due to the challenges
in characterizing noncrystalline phases in experiments or simulations.
Here, we mapped the LPS phase diagram by combining first-principles
and artificial intelligence (AI) methods, integrating density functional
theory, artificial neural network potentials, genetic-algorithm sampling,
and
ab initio
molecular dynamics simulations. By
means of an unsupervised structure-similarity analysis, the glassy/ceramic
phases were correlated with the local structural motifs in the known
LPS crystal structures, showing that the energetically most favorable
Li environment varies with the composition. Based on the discovered
trends in the LPS phase diagram, we propose a candidate solid-state
electrolyte composition, (Li
2
S)
x
(P
2
S
5
)
1–
x
(
x
∼ 0.725), that exhibits high ionic conductivity
(>10
–2
S cm
–1
) in our simulations,
thereby demonstrating a general design strategy for amorphous or glassy/ceramic
solid electrolytes with enhanced conductivity and stability.