Activated carbon-MnO2 hybrid electrochemical supercapacitor cells have been assembled and characterized in K2SO4 aqueous media. A laboratory cell achieved 195,000 cycles with stable performance. The maximal cell voltage was 2 V associated with 21 +/- 2 Fg(-1) of total composite electrode materials (including activated carbon and MnO2, binder and conductive additive) and an equivalent serie resistance (ESR) below 1.3 Omega cm(2). Long-life cycling was achieved by removing dissolved oxygen from the electrolyte, which limits the corrosion of current collectors. Scaling up has been realized by assembling several electrodes in parallel to build a prismatic cell. A stable capacity of 380 F and a cell voltage of 2 V were maintained over 600 cycles. These encouraging results show the interest of developing such devices, including non-toxic and safer components as compared to the current organic-based devices. (C) 2007 Elsevier B.V. All rights reserved.