An Air‐Stable and Electrode‐Compatible Lithium Superionic Conductor

The development of high-performance sulfide solid electrolytes necessitates materials that simultaneously exhibit superior ionic conductivity, excellent electrochemical stability, and enhanced environmental tolerance. This work reports a novel lithium solid electrolyte, Li5.3P0.98Nb0.02S4.25O0.05Cl1.7 (LPNbSOCl), which demonstrates remarkable improvements in these critical properties. The optimized composition achieves an ionic conductivity of 10.6 mS cm⁻¹ at room temperature with an activation energy of 0.249 eV. Electrochemical characterization reveals exceptional stability against lithium metal, with a critical current density （CCD) reaching 3.82 mA cm⁻² and stable cycling performance for 1000 h in symmetric cell configurations. The material exhibits significantly improved air stability, maintaining 78.4% of its initial conductivity after air exposure while substantially reducing H₂S evolution compared to conventional sulfide electrolytes. Interfacial analysis indicates the formation of a stable solid electrolyte interphase containing Li─Nb alloy and Li₂O at the anode. In all-solid-state battery configurations with LiCoO₂ (LCO) cathodes, this electrolyte enables outstanding cycling stability over 90% capacity retention after 1000 cycles at a 1C rate and delivers 115.4 mAh g⁻¹ at high current densities of 5C. These results demonstrate the potential of compositionally optimized lithium argyrodite materials to address the key challenges in solid-state battery technology.