We have developed the new energy storage system utilizing a radical redox reaction of poly (2,2,6-tetramethylpiperidinoxy methacrylate). PTMA. The coin-type cell with PTMA cathode demonstrates the charge capacity of is 72 Ah/kg, which corresponds to 65% of the theoretical capacity and the coulombic efficiency was 90% in first charge-discharge Cycle, The results indicate that the stable polyradical cathodes are promising materials due to their high charge utilization and the possibilities for the wide diversity of molecular design.