Investigation of ionic conductivity and mechanical characteristics of synthesized sulfonated PEEK separators for power composites

Official URL: https://dx.doi.org/10.1016/j.jallcom.2026.186757

Controlled sulfonation of polyetheretherketone (PEEK) is performed to produce electrospun nanofibers. The produced electrospun nanofibers are used as a separator to fabricate the polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) solid electrolyte for utilization in the power composite. Successful sulfonation is confirmed by the presence of the -SO3H functional group after a protocol under eight hours at 60°C. Electrospinning controls the amount and shape of the porosity and diameter of fibers, enabling the fabrication of a thin layer of separator with enhanced mechanical performance, thermal stability, and ion conductivity. The optimal conditions for electrospinning have been identified as an applied voltage of 16 kV, a feed rate of 3 µl/min, a collector distance of 10 cm, and a solution concentration of 35 wt%. These parameters result in the production of bead-free fibers and electrospun nanofibers, which have better wettability and mechanical properties. The diameter of nanofibers is measured to range from 50 to 71 nm under optimal conditions. Woven carbon fiber fabrics are employed as electrodes, and the ionic conductivity of the electrolyte is enhanced by utilizing a Sulfonated PEEK (SPEEK) membrane, leading to a high ionic conductivity of 1.27 × 10−3 S·cm−1 at room temperature. The results of dynamic mechanical analysis indicate that the sulfonated PEEK separator exhibits better storage and loss moduli and offers a wide range of service temperatures due to its higher glass transition temperature.