Pendant radical polymers were used as electroactive charge-storage materials for secondary batteries. The radical polymers were designed to be slightly swelled but not to be dissolved in electrolyte solutions. Stable organic radicals such as nitroxides and galvinoxyl were employed as the redox centers, which were characterized by a rapid electron transfer process with current collectors and an efficient charge propagation (i.e. site-hopping) process within the polymer layer. The organic-based approach leads to the fabrication of transparent, light and flexible thin-film rechargeable devices, with rapid charging and high power rate characteristics.