High rate, solid-state electrochemical capacitors

The electrodes presently described are based upon RuO/sub 2/, prepared by thermal decomposition of RuCl/sub 3/-xH/sub 2/O onto titanium or tantalum foil substrates. A high area, thin, bipolar cell design is needed to derive full advantage from the high capacitance densities intrinsic to electrochemical capacitors. Capacitance loading (Farads/gram) can be maximized by the use of pseudocapacitive electrode materials such as RuO/sub 2/ or IrO/sub 2/, without appreciably sacrificing rate capability. The feasibility of constructing ultrathin bipolar devices utilizing Ti/RuO/sub 2/ electrodes, and the solid polymer electrolyte Nafion, cast from solution phase, was demonstrated. A significant finding was that the same capacitance value per unit area was achieved, independent of the electrolyte used, H/sub 2/SO/sub 4/ or Nafion. This indicates that the author was able to achieve the same penetration of the electrode with Nafion as with H/sub 2/SO/sub 4/.<>