Thin Solid Polymer Electrolyte with High‐Strength and Thermal‐Resistant via Incorporating Nanofibrous Polyimide Framework for Stable Lithium Batteries

Abstract Polyethylene oxide (PEO) based polymer electrolytes show promise in expanding the practical applications of lithium (Li) batteries. However, their applications in Li batteries are usually restricted owing to the lack of mechanical strength, poor oxidative stability, and relatively large thickness. Herein, a nanofibrous polyimide (PI) framework enhanced plasticized‐PEO solid electrolyte is prepared to realize good mechanical and electrochemical performances. Following the configuration with the PI matrix, this “ polymer in polymer ” composite electrolyte with a thickness of 17.5 µm exhibits enhanced mechanical strength (13.9 MPa) and outstanding thermal stability. Additionally, it preserves the high ionic conductivity (2.25 × 10 −4 S cm −1 , 25 °C). The Li||Li symmetrical battery with the modified electrolyte could achieve a steady Li plating/stripping of more than 500 h, and the critical current density reaches up to 0.6 mA cm −2 at ambient temperature. The LiFePO 4 batteries delivery favorable capacity of 132.2 mAh g −1 with capacity retentions of 96.4% and 85.9% after 500 and 1000 cycles at 1 C, respectively. Acceptable cycling performance also could be achieved in LiNi 0.5 Co 0. 2 Mn 0. 3 O 2 solid batteries via an inorganic‐rich artificial cathode electrolyte interphase.