The study of novel gel polymer electrolytes plasticized with non-volatile tris(methoxypolyethyleneglycol) aluminate esters

A series of novel gel polymer electrolytes (GPEs) based on a co-polymer matrix of methoxy-poly(ethylene glycol) methacrylate (MPEGM) and hexadecal-poly(ethylene glycol) methacrylate (HPEGM) are synthesized in this study using non-volatile tris(methoxypolyethyleneglycol) aluminate ester ((MPEG_n)₃-Al) as the plasticizer. Their thermal stability and ionic conductivity are studied by differential scanning calorimeter, thermogravimetric analysis and alternating current impedance techniques. The results show that all the synthesized GPEs possess excellent thermal stability and exhibit relatively high ionic conductivity. Among all the synthesized GPEs, one with the composition of 40 wt% MPEGM, 10 wt% HPEGM and 50 wt% (MPEG ₇)₃-Al exhibits the highest ionic conductivity, up to 0.59 × 10^-3 S cm^-1 at 30 °C when the salt concentration is [Li]:[EO] = 1:20. In addition, a coin cell based on this GPE, with LiFePO₄ as cathode and metallic lithium as anode shows discharge capacities as high as 146 mAh g^-1 and 151 mAh g^-1 when cycled at 30 °C and 50 °C, respectively, under a current rate of 0.1 C.