Preparation of efficient and eco-friendly solid polymer electrolyte based on anionic polyurethane dispersion, polyethylene oxide, and halloysite nanotube

With the ever-increasing need for energy storage devices with high energy density, lithium (Li) metal anodes have been revisited. Due to the high reactivity of Li metal and the safety issues associated with liquid electrolytes, solid polymer electrolytes (SPEs) have gain attention. Polyethylene oxide (PEO) with the highest ionic conductivity (sigma) among the polymers faces serious problems. The inability to meet the practical limit of sigma due to its high crystallinity, and its low thermomechanical stability above its melting temperature, have limited its large-scale application. In this research, anionic polyurethane dispersion (PUD) based on poly (epsilon-caprolactone) (PCL) was synthesized and different PUD:PEO compositions was prepared using water as a solvent. Halloysite nanotube (HNT) was also used to improve the ionic conductivity by providing a new pathway for conducting lithium ions in the composition. The results corroborated that the presence of PUD stabilized the storage modulus of the host polymer above T-m of PEO. The ionic nature of the selected PUDs resulted in a transference number of 0.59 and the presence of HNT increased this value to 0.72. The presence of HNTs also led to a significant increase in sigma by about three times compared to the control sample.