The first known application of stable radicals for energy storage systems is presented. A stable nitroxyl polyradical, poly (2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA) has been synthesized and applied to the cathode active materials in rechargeable batteries. These fabricated batteries have demonstrated an average discharge voltage of 3.5 V and a discharge capacity of 77 Ah/kg, which corresponds to 70% of the theoretical capacity. It should be noted that the capacity remains unchanged for over 500 cycles of charging and discharging at a high current density of 1.0 mA/cm(2). Stable radicals promise to open new fields of use for plastic batteries. (C) 2002 Elsevier Science B.V. All rights reserved.