Novel hyperbranched PEU polymer electrolytes for lithium-ion batteries

A novel type of hyperbranched PEU (PHEU) was prepared from the reaction of the hyperbranched poly ether (PHEMO) with hexaethylene diisocyanate (HDI) in electrolytes containing lithium salts. The thermal stabilities and ionic conductivities of the as-prepared electrolytes were investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and alternating current (AC) impedance. When the concentration of the electrolyte is 3 mol/L, and the mass of the electrolyte is three folds as high as that of the polymer matrix, the polymer electrolyte can achieve an ionic conductivity of 6.12 × 10^-4 S/cm at room temperature. Cyclic voltammogram indicates that the electrochemical stability window is from 2.2 to 4.0 V. In addition, the small molecules of electrolyte were perfectly enclosed by the polymer chains, which can avoid liquid leaking. Therefore, it is benefit for the safety of lithium-ion batteries.