Cross-linked trimethylolpropane trimethylacrylate-based gel polymer electrolytes (GPE) were prepared by in situ thermal polymerization. The ionic conductivity of the GPEs are >10−3 Scm−1 at 25°C, and continuously increased with the increase of liquid electrolyte content. The GPEs have excellent electrochemical stability up to 5.0V versus Li/Li+. The LiCoO2|TMPTMA-based GPE|graphite cells exhibit an initial discharge capacity of 129mAhg−1 at the 0.2C, and good cycling stability with around 83% capacity retention after 100 cycles. Both the simple fabricating process of polymer cell and outstanding electrochemical performance of such new GPE make it potentially one of the most promising electrolyte materials for next generation lithium ion batteries.