High-Stability Composite Solid Polymer Electrolyte Composed of PAEPU/PP Nonwoven Fabric for Lithium-Ion Batteries

Solid polymer electrolytes have attracted considerable attention, owing to their flexibility and safety. At present, poly(ethylene oxide) is the most widely studied polymer electrolyte matrix. It exhibits higher safety than the polyolefin diaphragm used in traditional lithium-ion batteries. However, it readily crystallizes at room temperature, resulting in low ionic conductivity, and the preparation process involves organic solvents. In this study, from the perspective of molecular design, solvent-free polyaspartate polyurea (PAEPU) and the cheap and easily available polypropylene (PP) nonwoven fabric were used as support materials for the PAEPU/PP composite solid polymer electrolyte (PAEPU/PP -CPE). This CPE has good thermal stability, dimensional stability, flexibility, and mechanical properties. Among the different CPEs that were analyzed, PAEPU/PP₁₀-CPE@20 had the highest ionic conductivity, which was reinforced with 10 g/m² PP nonwoven fabric and the content of lithium salt was 20 wt %. Furthermore, PAEPU/PP₁₀-CPE@20 exhibited the highest electrochemical stability with an electrochemical window value of 5.53 V. Moreover, the capacity retention rate of the Li//PAEPU/PP₁₀-CPE@20//LiFePO₄ half-cell was 96.82% after 150 cycles at 0.05 C and 60 °C, and the capacity recovery rate in the rate test reached 98.81%.