Justin G. Connell

Sulfide-based solid-state electrolytes (SSEs) are a promising class of materials for next-generation all-solid-state Li-ion batteries due to their high ionic conductivity and favorable mechanical properties that make them amenable to processing at scale. Despite their significant promise, widespread adoption of sulfide SSEs is hindered by processability in manufacturing environments, as well as by lower performance and lifetime due to (electro)chemical instability against reactive electrodes. We have developed a computationally guided, atomic layer deposition (ALD)-based approach for realizing ultrathin coatings on sulfide SSE powders to address both of these key issues. Computational evaluation of coating stability against multiple relevant interfaces indicates specific design rules for selecting candidate coatings. Utilizing this approach, we have demonstrated several oxide-based ALD coatings on argyrodite Li₆PS₅Cl (LPSCl) powders that stabilize them to oxidizing atmospheres while significantly improving their (electro)chemical properties. Specifically, we achieve up to a factor of 2 increase in the ionic conductivity of pellets fabricated from coated LPSCl powders relative to those made from uncoated material, with a simultaneous decrease in their electronic conductivity. Furthermore, coated materials exhibit improved stability against Li metal, along with the formation of favorable reaction products for maintaining Li⁺ conductive interphases. These benefits result in significantly improved room temperature cycle life of Li||Li symmetric cells at high capacity and current density (≥150 cycles at 1 mAh/cm² per cycle and 0.5 mA/cm²). This strategy enables a new framework for designing sulfide SSEs for next-generation solid-state batteries.