The oxyhalide-based solid electrolyte
Li2OHCl usually
forms the thermodynamically stable orthorhombic phase at room temperature
and shows poor lithium ionic conductivity. Above 35 °C, a structural
phase transition into the cubic phase occurs and ionic conductivity
is enhanced. In this work, mechanochemical synthesis of Li2OHCl is reported. The as-prepared Li2OHCl formed a cubic Pm3̅m structure and showed an ionic
conductivity of 2.6 × 10–6 S cm–1 at 25 °C. Once the cubic phase was treated at 200 °C,
the orthorhombic Pmc21 structure appeared
at 25 °C and the ionic conductivity decreased down to 1.4 ×
10–7 S cm–1. Formation of the
metastable cubic phase could be explained in terms of low crystallinity
of Li2OHCl derived from mechanochemical synthesis.