Porous Polyamide Skeleton-Reinforced Solid-State Electrolyte: Enhanced Flexibility, Safety, and Electrochemical Performance

The growing demand for safer lithium-ion batteries draws researchers' attention to solid-state electrolytes. In general, a desired electrolyte should be flexible, mechanically strong, and with high ionic conductivity. A solid-state electrolyte with a polymer as a matrix seems to be able to meet these demands. However, a pure polymer electrolyte lacks sufficient strength to suppress Li dendrites, and hybrids with ceramic components often lead to poor flexibility, both far from satisfactory. Herein, a solid-state electrolyte is designed by employing a mass-produced porous polyamide (PA) film infiltrated with polyethylene oxide (PEO)/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The PA/PEO/LiTFSI electrolyte is flexible but robust with a Young's modulus of up to 1030 MPa, ensuring steady Li//Li cycling without short circuit for more than 400 h. Also, the porous structure of the PA film decreases the crystalline regions and effectively enhances the ionic conductivity (2.05 × 10-4 S cm-1 at 30 °C). When cycled at 1C, solid-state LiFePO4//Li batteries assembled with the PA/PEO/LiTFSI electrolyte retain 82% capacity after 300 cycles (60 °C). In addition, a flexible LiFePO4//PA/PEO/LiTFSI//Li pouch cell can also work well in harsh operating environments, such as being folded, crimped, and pierced.