A family of air-stable chalcogenide solid electrolytes in Li2BMQ4 (B = Ca, Sr and Ba; M = Si, Ge and Sn; Q = O, S and Se) systems
Abstract
Combining high-throughput first-principles calculations and experimental measurements, we have identified a novel family of fast lithium-ion chalcogenide conductors in Li2BMQ4 (2114, B = Ca, Sr and Ba; M = Si, Ge and Sn; Q = O, S and Se) systems. Our calculations demonstrate that most of the thermodynamically and kinetically stable sulfides and selenides in this new system exhibit ultralow Li+ ion migration activation energy (0.16 eV ~ 0.56 eV) and considerable bandgaps varying between ~ 2 eV and 3.5 eV. We have successfully synthesized Li2BaSnS4 and Li2SrSiS4, and they exhibit excellent moisture stability through H2S gas measurements. Electrochemical impedance measurements indicate 2114 systems show the typical features of solid ionic conductors, with a room-temperature Li+ conductivity close to 5×10-4 mS/cm aligning with our molecular dynamics simulations. Furthermore, we have theoretically investigated the substitution of Cl- at S2- site. The doped compounds display significantly higher conductivity, with an increase of about three orders of magnitude (up to a maximum of 0.72 mS/cm) compared to the undoped compounds. These findings offer valuable insights for the further exploration of potential chalcogenide solid electrolyte materials with robust air stability and enhanced ionic conductivity for practical applications in lithium-ion batteries.
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