Sandwich-like polyimide nanofiber membrane of PEO-based solid-state electrolytes to promote mechanical properties and security for lithium metal batteries

The safety and high mechanical strength of all-solid state lithium battery are the main challenges that limit their development and application. Although polypropylene (PP) separators have excellent mechanical properties, their poor thermal stability remains a problem that requires immediate attention. Herein, a sandwich-structured composite solid electrolyte consisting of polyimide-Celgard-polyimide/PEO-LiTFSI (PI-PP-PI/PEO-LiTFSI) is reported for use in lithium metal batteries. The presence of a carbonyl group in the PI enhances its overall electrochemical performance and thermal stability. The composite solid electrolyte exhibited an ionic conductivity of 1.32 mS/cm at 60 °C and a tensile strength of up to 21.1 Mpa. Particularly, we discovered that the film maintained its shape without deformation at 180 °C, thereby facilitating steady cycling of the lithium battery for 1600 h at 0.1 mA/cm 2 and demonstrating excellent resistance to lithium dendrite formation. After 120 and 150 cycles at 0.2 C and 1 C, respectively, the capacity was 104.8 and 79.60 mAhg −1 and the coulombic efficiency was close to 100%. This study provides a potential strategy for the development of solid-state lithium-metal batteries with excellent mechanical properties and high-temperature resistance.