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

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 Li6+xP1-xZrxS5-2xO2xCl (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 Li6.05P0.95Zr0.05S4.9O0.1Cl 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. The novel Li-argyrodite solid-state electrolyte Li6.05P0.95Zr0.05S4.9O0.1Cl prepared via ZrO2 doping further obtains excellent lithium-metal compatibility and air stability while maintaining high ionic conductivity.