New lithium-conducting gel electrolytes containing superbranched polymers

Abstract

New polymer gel electrolytes containing superbranched polymers were developed. The gel electrolyte containing 20 wt % superbranched polymer, 6 wt % methylmethacrylate, 4 wt % triethyleneglycol dimethacrylate, and 70 wt % 1 M propylene carbonate solution of LiClO₄ was found to have a maximum conductivity of ∼9 × 10⁻⁴ S/cm at room temperature and an effective activation energy of conductivity of 18 kJ/mol. The physicochemical properties of the gel electrolyte were correlated with its composition using electrochemical impedance spectroscopy, thermomechanics, and differential scanning calorimetry. The glass-transition temperature of these electrolytes depended only on the liquid electrolyte content and decreased from −80 to −93°C when the concentration of 1 M LiClO₄/PC increased from 60 to 80 wt %. As the content of the superbranched polymer increased from 0 to 20 wt % at positive temperatures, the modulus of elasticity decreased, while the conductivity increased. When the content of the superbranched polymer increased at the expense of the liquid electrolyte, the conductivity of the system decreased.