Argyrodite Li6 PS5 Cl with high Li+ conductivity is a promising material for solid-state electrolytes (SSEs) in all-solid-state lithium batteries (ASSLBs). However, the narrow electrochemical window of Li6 PS5 Cl limits its applications in ASSLBs with high energy densities, and those that consist of high-voltage cathode materials and metallic lithium anodes. Unstable lithium deposition and stripping at interfaces is also a factor that restricts its industrialization. Herein, the authors investigated the electrochemical stability of Li6 PS5 Cl using it as both the cathode and electrolyte. The Li6 PS5 Cl-C/Li6 PS5 Cl/Li cell and symmetric Li/Li6 PS5 Cl/Li cells failed after a certain number of cycles, and subsequently healed electrochemically. This failure/healing phenomenon recurred during the cycling process. The self-healing behavior is closely related to the electrochemical window, which suggests that it can be controlled by the charge-discharge voltage range. In-depth X-ray photoelectron spectroscopy, in situ Raman spectroscopy, and in situ electrochemical impedance spectroscopy revealed the reversible Li6 PS5 Cl decomposition and metallic lithium growth inside the electrolyte during the cycling process. This self-healing behavior is mainly attributed to the reciprocating lithium growth and reversible redox reaction of the Li6 PS5 Cl decomposition. The proposed self-healing mechanism is a key aspect for sulfide-based SSEs, guiding the interface modification, and material design of ASSLBs.
Keywords: all-solid-state lithium batteries; argyrodite Li 6PS 5Cl; in situ characterization; lithium growth; self-healing.
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