Interface Stability of Argyrodite Li6PS5Cl toward LiCoO2, LiNi1/3Co1/3Mn1/3O2, and LiMn2O4 in Bulk All-Solid-State Batteries

Abstract

Argyrodite Li 6 PS 5 Cl is a good candidate for being a solid electrolyte for bulk all-solid-state Li-ion batteries because of its high ionic conductivity and its good processability. However, the interface stability of sulfide-based electrolytes toward active materials (negative or positive electrodes) is known to be lower than that of oxide-based electrolytes. In this work, we investigate the interface stability of argyrodite toward several positive electrode materials: LiCoO 2, LiNi 1/3 Co 1/3 Mn 1/3 O 2, and LiMn 2 O 4 . All-solid-state half-cells were cycled, and the interface mechanisms were characterized by Auger electron spectroscopy and X-ray photoelectron spectroscopy. We show that Li 6 PS 5 Cl is oxidized into elemental sulfur, lithium polysulfides, P 2 S x ( x ≥ 5), phosphates, and LiCl at the interface with the positive electrode active materials. In spite of this interface reactivity, good capacity retention was observed over 300 cycles. Li 6 PS 5 Cl shows some reversible electrochemical activity (redox processes) that might contribute to the reversible capacity of the battery.