Unprecedented Self-Healing Effect of Li6 PS5 Cl-Based All-Solid-State Lithium Battery

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.