Enhancing Stability and Safety of Commercial Solid‐State Lithium Batteries Through Ternary Eutectic Solvents for Solid‐State Electrolyte Interface Modification

Solid‐state polymerized electrolytes exhibit advantageous properties, making them optimal candidates for next‐gen commercial solid‐state batteries. However, these electrolytes present significant challenges in terms of long‐term cycling stability, energy density, and safety. In this study, a ternary eutectic solid electrolyte (TESE) is prepared by combining deep eutectic solvents (DESs), polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP), and fluorinated ethylene carbonate (FEC). TESE also facilitates uniform lithium deposition, interfacial stability, and long‐cycle stability. N‐Methylacetamide in DESs preferentially occupies the lithium dissolution sheath, which in turn initiates a concentration gradient‐driven decomposition of FEC and stimulates the generation of inorganic solid electrolyte interphase (SEI) layers. The lithium metal and graphite soft pack full batteries are successfully assembled, demonstrating that Li/P‐0.8‐FEC/LFP exhibits excellent long‐cycle performance, with a capacity of 139.9 mAh g −1 after 500 cycles at 1 C 25 °C, accompanied by 97.8 % capacity retention. Furthermore, the Gr/P‐0.8‐FEC/LFP commercial solid‐state flexible pack full cell exhibits stable cycling performance at a high rate of 1 C. Moreover, the device exhibits remarkable safety in a series of rigorous safety tests, including 100 repeated bendings, pinning, 7100 N force extrusion, and cutting. The study results demonstrate that the electrolyte exhibits excellent cycling performance and safety characteristics, indicating significant potential for commercialization.