High rate, solid-state electrochemical capacitors

The electrodes presently described are based upon RuO₂, prepared by thermal decomposition of RuCl₃-xH₂ 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 RuO₂ or IrO₂, without appreciably sacrificing rate capability. The feasibility of constructing ultrathin bipolar devices utilizing Ti/RuO 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, H₂SO₄ or Nafion. This indicates that the author was able to achieve the same penetration of the electrode with Nafion as with H₂SO₄