Insights on the Properties of the O-Doped Argyrodite Sulfide Solid Electrolytes (Li<sub>6</sub>PS<sub>5–<i>x</i></sub>ClO<sub><i>x</i>,</sub> <i>x</i>=0–1)
Zhen Sun, Yanqing Lai, Na Lv, Yaqi Hu, Bingqin Li, Liangxing Jiang, Jiong Wang, Shuo Yin, Kui Li, Fangyang Liu
Abstract
Argyrodite sulfide solid electrolytes, such as Li6PS5Cl (LPSC), have received much attention due to their high ionic conductivity (>1 mS cm–1) and success in all-solid-state batteries (long cycle performance, high energy density, etc.). Numerous efforts are spent on modifying the properties of the electrolyte itself. Here, we combine first-principles calculations with experiments to investigate O-doped argyrodite sulfide solid electrolytes (Li6PS5–xClOx, x = 0–1). It is found that Li6PS4.75ClO0.25 (LPSCO0.25) with x = 0.25 and cubic phase (F4̅3 m) shows the highest ion conductivity of 4.7 mS cm–1 (cold-pressed), higher than that of undoped Li6PS5Cl (4.2 mS cm–1). The bare LiCoO2/LPSCO0.25/Li–In all-solid-state battery exhibits an initial capacity of 131 mA h g–1 at 0.1 C and satisfactory cycling stability with 86% capacity retention after 250 cycles to the 4th cycle at 0.3 C under 25 °C. In addition, the NCM811/LPSCO0.25/Li–In cell is assembled using bare LiNi0.83Co0.06Mn0.11O2 cathode and shows an initial discharge capacity of 181 mA h g–1 at 0.1 C and 160 mA h g–1 at 0.3 C. The doping of oxygen-forming Li6PS5–xClOx also improves the stability to Li metal, proven by cyclic voltammetry and powder X-ray diffraction tests. The calculation results for the band structure reveals that LPSC has the lowest unoccupied molecular orbital than LPSCO0.25, further confirming the above conclusion.