Author: T. Rihayat, I. Mawardi, Usman, A. Safitri, D. Moentamaria, A. R. Hidayana, U. Q. P. Swya, F. Sakinah

DOI: http://doi.org/10.31788/RJC.2026.1919603

This study investigates the modification of lithium-ion battery (LIB) separators using polypropylene (PP), polyurethane (PU), and nano chitosan through a casting method, focusing on the effects of composition ratioandimmersion duration on separator thickness and thermal stability. Nine sample variations with PP: PU: NanoChitosan ratios of 4:2:4, 4:3:3, and 4:4:2 were prepared and immersed for 1–3 days. The separators werecharacterized using thickness measurements, thermal shrinkage analysis, Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). The 4:3:3composition demonstrated the most optimal performance, producing separator thicknesses of 23–25 μmwiththelowest thermal shrinkage (0.5–2.1%), meeting commercial LIB separator standards. TGA results showed that thePCS5 sample (4:3:3, 2-day immersion) exhibited superior thermal resistance, with a degradation onset of 370.10 °C and peak decomposition at 429.73 °C. FTIR confirmed the successful incorporation of urethane andhydroxyl/amine functional groups, indicating chemical modification of the polymer matrix. SEMobservationsrevealed a dense and uniform morphology with well-distributed pores, supporting enhanced ionic transport. Overall, the 4:3:3 formulation with a 2-day immersion significantly improves the physical, thermal, and structural properties of the separator, demonstrating strong potential for high-performance LIB applications and contributingto ongoing advancements in battery safety and efficiency.

Keywords: Lithium-Ion Battery, Separator, Polypropylene, Polyurethane, Nano Chitosan, Thermal Stability, Casting Method.