Synergistic Effect\nof Sn-Substituted Argyrodite Solid\nElectrolyte with Enhanced Air Stability and Li Metal Compatibility\nfor All-Solid-State Li Metal Batteries

Sulfide solid-state electrolytes (SSEs) are promising\nfor all-solid-state\nLi metal batteries (ASSLMBs) due to their high ionic conductivity\nand mechanical strength. Despite these advantages, challenges, such\nas poor air stability and compatibility issues with Li metal, have\nhindered their widespread application. To solve these issues, we developed\nLi<sub>6+<i>x</i></sub>P<sub>1–<i>x</i></sub>Sn<sub><i>x</i></sub>S<sub>5</sub>Cl electrolytes\nwith doping of Sn<sup>4+</sup>, replacing P<sup>5+</sup> in Li<sub>6</sub>PS<sub>5</sub>Cl electrolyte. The Li<sub>6.1</sub>P<sub>0.9</sub>Sn<sub>0.1</sub>S<sub>5</sub>Cl electrolyte with optimized dopant\nconcentrations shows improved ionic conductivity (2.14 × 10<sup>–3</sup> S cm<sup>–1</sup>), enhanced moisture resistance,\nand superior compatibility with Li metal. The Li symmetric cell with\nLi<sub>6.1</sub>P<sub>0.9</sub>Sn<sub>0.1</sub>S<sub>5</sub>Cl electrolyte\nshows a good critical current density (CCD) of 0.68 mA cm<sup>–2</sup> and long-term cycling performance (over 600 h at 0.1 mA cm<sup>–2</sup>) due to the Li–Sn alloy. Moreover, the assembled LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub>/Li cell with\nthe Li<sub>6.1</sub>P<sub>0.9</sub>Sn<sub>0.1</sub>S<sub>5</sub>Cl\nelectrolyte exhibits a high initial discharge capacity of 163.1 mAh\ng<sup>–1</sup> at 0.05 C. It shows a discharge capacity of\n108.9 mAh g<sup>–1</sup> with a capacity retention rate of\n75.4% after 60 cycles at 0.1 C. These results demonstrate the potential\nof Sn substitution in enhancing the electrochemical stability and\noverall performance of SSEs for next-generation battery technologies.