Li-argyrodite solid-state electrolytes with lithium compatibility and air stability for all-solid-state batteries

Abstract

Li-argyrodite solid-state electrolytes (SSEs) have attracted much attention owing to their high ionic conductivity and low-cost raw materials. However, achieving high lithium-metal compatibility and air stability along with high ionic conductivity remains a challenge. Herein, novel Li_6+xP_1−xZr_xS_5−2xO_2xCl (0 ≤ x ≤ 0.15) Li-argyrodite SSEs were synthesized via ZrO₂ doping. X-ray and neutron diffraction results from Rietveld refinement confirmed the successful substitution of P and S sites in the Li₆PS₅Cl structure by the ZrO₂ dual dopant. The optimized best composition of Li_6.05P_0.95Zr_0.05S_4.9O_0.1Cl had a high ionic conductivity of 3.97 mS cm⁻¹ and a high ionic mobility number (0.986). Notably, the modified electrolyte exhibited more compatibility with lithium metal compared to the pristine Li₆PS₅Cl. It also exhibited an ultra-high critical current density (1.7 mA cm⁻²) and ultra-long cycling performance (800 h, 0.1 mA cm⁻²) relative to pristine Li₆PS₅Cl (0.6 mA cm⁻²) and excellent direct current cycling performance at 0.5 and 0.85 mA cm⁻². In addition, the good structural stability after exposure to humid air for a certain period of time, low H₂S release, and decrease in ionic conductivity indicated its excellent air stability. Finally, the assembled all-solid-state battery exhibited an initial discharge capacity of 115.9 mA h g⁻¹ at 0.05C magnification and a high capacity retention (79.3%) after 100 cycles. Therefore, Li-argyrodite SSEs with ZrO₂ substitution may be a prospective candidate in the future exploration of electrolytes with excellent overall performance.