Evidence for near-superionic conductivity in the Li3BS3 electrolyte and insights on the lithium orthothioborate transport mechanisms

In developing battery technology toward Li anode systems rather than Li ion, it has become necessary to discover superior ionic conductors for solid-state electrolyte batteries. Li₃BS₃ is among these candidate superior ionic conductors. We report here molecular dynamics (MD) simulations to predict the diffusivity, conductivity, and activation energy for Li⁺ transport in lithium orthothioborate (Li₃BS₃) as a function of temperature using the universal force field (UFF) retrained with quantum mechanics (QM). This leads to an ionic conductivity of ∼2.1 mS cm⁻¹ with an activation energy of ∼+0.19 eV (+18.2 kJ) at 300 K and 1 atm, based on 20 ns of MD. These results are in good agreement with those of experiments (0.1 to 10 mS cm⁻¹) on −PS₄ based argyrodite electrolytes with similar activation energies (0.15 to 0.5 eV). Our calculations indicate that Li₃BS₃ is a superior ionic conductor, with potential as a future electrolyte for solid-state Li anode batteries.