  Management of heat during charging and discharging of Li-ion batteries is
critical for their safety, reliability, and performance. Understanding the
thermal conductivity of the materials comprising batteries is crucial for
controlling the temperature and temperature distribution in batteries. This
work provides systemic quantitative measurements of the thermal conductivity of
three important classes of solid electrolytes (oxides, sulfides, and halides)
over the temperature range 150-350 K. Studies include the oxides
Li1.5Al0.5Ge1.5(PO4)3 and Li6.4La3Zr1.4Ta0.6O12, sulfides Li2S-P2S5, Li6PS5Cl,
and Na3PS4, and halides Li3InCl6 and Li3YCl6. Thermal conductivities of sulfide
and halide solid electrolytes are in the range 0.45-0.70 W m-1 K-1; thermal
conductivities of Li6.4La3Zr1.4Ta0.6O12 and Li1.5Al0.5Ge1.5(PO4)3 are 1.4 W m-1
K-1 and 2.2 W m-1 K-1, respectively. For most of the solid electrolytes studied
in this work, the thermal conductivity increases with increasing temperature;
i.e., the thermal conductivity has a glass-like temperature dependence. The
measured room-temperature thermal conductivities agree well with the calculated
minimum thermal conductivities indicating the phonon mean-free-paths in these
solid electrolytes are close to an atomic spacing. We attribute the low,
glass-like thermal conductivity of the solid electrolytes investigated to the
combination of their complex crystal structures and the atomic-scale disorder
induced by the materials processing methods that are typically needed to
produce high ionic conductivities.
