Totally organic polymer-based, submillimeter-thick, bendable rechargeable devices were fabricated using hydrophilic polymers as electrode-active materials and brine as the electrolyte. The rapid and reversible electrochemical reactions of the polymers enabled quick charging within minutes, long life, and a moderate operation voltage of more than 1V. Quantitative discharge was achieved even when the devices were in a bent state with a radius of curvature of 1 mm.