There has been significant research over the years regarding electrical storage devices of high energy and power density. The efficient packaging of the active materials, with minimum wasted volume, is important in reaching these goals. The space separating two electrodes in a capacitor or a battery is necessary to electronically insulate the two electrodes. However, for efficient packaging, this space or gap should be a minimum. It would therefore by highly desirable to have a method to create a space separator or gap that is substantially uniform and of small dimension (less than 5 mil).
A common way to maintain separation between electrodes in an electrical storage device with an electrolyte present (such as a battery or capacitor) is by use of an ion permeable electrically insulating porous membrane. This membrane is commonly placed between the electrodes and maintains the required space separation between the two electrodes. Porous separator material, such as paper, glass, is useful for this application and is used in aluminum electrolytic and double layer capacitors. However, for dimensions below 1 or 2 mil in separation, material handling is difficult and material strength of the capacitor is usually very low. In addition, the open crosssectional areas typical of these porous membrane separators are on the order of 50-70%.
Polymeric ion permeable porous separators have been used in carbon double layer capacitors as discussed by Sanada et al. in IEEE, pp. 224-230, 1982 and Suzuki et al. in NEC Research and Development, No. 82, pp. 118-123, July 1986. These type of separators suffer from the problem of a small open area which leads to increased electrical resistance.
U.S. patents of general interest include U.S. Pat. Nos. 3,718,551; 4,052,271; and 5,055,169.
None of these references individually or collectively teach or suggest the present invention.
All of the applications, patents, articles, references, and standards cited in this application are incorporated herein by reference in their entirety.
It would be very useful to have a method to produce a reliable small space separation between electrodes in electrical storage devices with a large open crosssectional area. It is, therefore, an object of the present invention to provide efficient packaging of an electrical storage device by reducing the gap between the anode and cathode and to reduce the electrical resistance of the ionically conducting electrolyte by providing large open cross-sectional areas of about 95-98%.