Insights on the Properties of the O-Doped Argyrodite Sulfide Solid Electrolytes (Li₆PS_5–xClO_x, x=0–1)

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–x ClO x, 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–x ClO x 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.

A Low-Cost Liquid-Phase Method of Synthesizing High-Performance Li6PS5Cl Solid-Electrolyte

“…The battery performances of LPSCl _30 and LPSCl _BM were then systematically compared by measuring their electrochemical performance in Li–In/LPSCl/LPSCl-LNO-NCM811 batteries. In order to determine the electrochemical windows of both LPSCl _30 and LPSCl _BM , CV was performed on the Li|LPSCl|LPSCl-C|Steel half-cell configurations according to literature methods. , Figure a illustrates three cycles of negative scanning in the voltage range of 0–0.65 V vs Li + /Li (−0.62–0.03 V vs Li–In) for testing the reduction characteristics of LPSCl _30 . A very weak reduction hump appears at 0.33 V in the first cycle, but disappears afterward.…”

Li metal anode interface in sulfide‐based all‐solid‐state Li batteries

“…In addition to the operation of electrolytes in the inert atmosphere, several approaches are adopted to enhance the ambient stability of SSEs. For example, the substitution of few S atoms with O atoms in SSEs can markedly enhance their resistance to humid air 20,33–35 . The addition of metal sulfide (e.g., FeS 2 ) can inhibit the generation of H 2 S gas 36 .…”

“…For example, the substitution of few S atoms with O atoms in SSEs can markedly enhance their resistance to humid air. 20,[33][34][35] The addition of metal sulfide (e.g., FeS 2 ) can inhibit the generation of H 2 S gas. 36 Furthermore, coating with a protective layer is another method, e.g., oxysulfide-coated LPSC exhibited considerable chemical stability in moist air.…”

Dual Protection of a Li–Ag Alloy Anode for All-Solid-State Lithium Metal Batteries with the Argyrodite Li6PS5Cl Solid Electrolyte

“…Various inorganic SSEs have been developed so far, such as sulfides and oxides. − Among them, sulfide SSEs demonstrate a more promising application potential than their counterparts due to the advantages of high ionic conductivity (12 mS cm –1 of Li 10 GeP 2 S 12 (LGPS) and 1–6 mS cm –1 of Li 6 PS 5 Cl (LPSC) − ), simple preparation process, and abundant reserves of elements (P, S, and Cl). Nevertheless, most of the sulfide SSEs are unstable with Li metal, causing severe interface side reactions and uneven Li-deposit morphology, consequently accelerating Li dendrite growth and causing failure of the batteries. − Therefore, lots of efforts have been endeavored to improve the stability of various sulfide SSEs and Li anodes, such as interface protection, − electrolyte optimization, − and Li-alloy anode implementation. − Among these proposed approaches, Li-alloy anodes, which exhibit high capacities and promote the even deposition of Li, , are promising solutions for the aforementioned problems in ASSLMBs.…”