120 of 729: how few lithium solid electrolytes clear 1 mS/cm at room temperature

Solid-state batteries are usually held to a simple bar: an electrolyte should conduct lithium ions at 1 mS/cm (10⁻³ S/cm) or better at room temperature. We counted how many measured materials actually clear it.

We merged two curated, openly licensed datasets into 1,127 measured room-temperature conductivities for 729 distinct lithium solid electrolytes. The median composition conducts at 2.6×10⁻⁵ S/cm. Only 120 compositions reach 1 mS/cm, and 13 reach 10 mS/cm, on par with liquid electrolytes.

Anion chemistry splits the field

42% of sulfides and selenides exceed 1 mS/cm, against 6% of oxides and 14% of halides. The two leading structural families are sulfides: LGPS-type compositions have a median of 4.5×10⁻³ S/cm, with 81% clearing 1 mS/cm, and argyrodites a median of 1.6×10⁻³ S/cm, with 59% clearing it.

The workhorse oxides sit about a decade lower. Garnets (LLZO-type) have a median of 1.4×10⁻⁴ S/cm and NASICONs (LATP-type) 1.0×10⁻⁴ S/cm. Only 4% of garnets and 6% of NASICONs clear 1 mS/cm.

A range of more than ten orders of magnitude

The best value in the merged data is 2.8×10⁻² S/cm, for Li9.54Si1.74P1.44S11.4Cl0.3O0.3. The lowest values, below about 10⁻¹² S/cm, are extrapolated to room temperature from high-temperature measurements, so they say more about the method than the material.

Why the count matters

A screen that proposes a new solid electrolyte is competing with a short, mostly sulfide list. The useful question for any candidate is which family it belongs to and where that family's measured median sits, not only whether a calculation says it is stable.

The study page has the full family and chemistry tables, a leaderboard of the 30 most conductive compositions with a reference for each value, and a searchable list of all 729 compositions. The merged data is downloadable as a CSV.