Temperature-Dependent Properties for Recycling Solid Electrolytes of All-Solid-State Lithium-Ion Batteries Using Deep Eutectic Solvents

The efficiency of metal leaching in the solid electrolyte of all-solid-state lithium-ion batteries is strongly influenced by the temperature when deep eutectic solvents (DESs) are utilized. The properties of DESs play a crucial role in this process. However, the temperature-dependent physical properties of DESs have not been thoroughly investigated. Here, we systematically investigate the temperature-dependent property changes of the DESs (e.g., arginine/lactic acid = 1:6) during their application in recycling the solid electrolyte, aluminum-doped lithium lanthanum zirconium oxide. As the temperature increases, the viscosity, pH, density, surface tension, and optical rotation of DESs decrease, whereas their conductivity increases. Furthermore, thermal gravimetric analysis demonstrates that DESs exhibit good thermal stability before and after dissolution of the solid electrolyte.