Effect of the surface treatment of the TiO2 fillers on the properties of hexanoyl chitosan/polystyrene blend-based composite polymer electrolytes

Abstract

Surface treatment of TiO2 was done by immersing filler particles in 2 and 4 % sulphuric acid (H2SO4) aqueous solutions. Untreated, 2 and 4 % H2SO4-treated TiO2 were referred as neutral, weakly acidic, and acidic TiO2, respectively. Composite polymer electrolytes (CPEs) based on hexanoyl chitosan–polystyrene blend were prepared by using lithium trifluromethanesulfonate (LiCF3SO3) as the doping salt and three different types of the TiO2 fillers. X-ray diffraction (XRD) results showed that the addition of TiO2 reduced the crystalline fraction of the electrolytes. The conductivity performance of the CPEs varied in the order: acidic < weakly acidic < TiO2 free < neutral TiO2. A model based on the interaction between Lewis acid–base sites of TiO2 with ionic species of LiCF3SO3 has been proposed to understand the conductivity mechanism brought about by the different types of fillers. The conductivity enhancement by neutral TiO2 is attributed to the increase in the mobility of Li+ cations. Acidic TiO2 decreased the conductivity by decreasing the anionic contribution. The conductivity variation with filler content was discussed on the basis of the number of free ions.