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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 1 November 2010, was one of a series of advanced technology reports produced in FY 2010 under the Advanced Aerospace Weapons System Applications (AAWSA) Program. It reviews ultracapacitors as energy and power storage devices. It covers how they work, their materials, their commercial and military uses, and new developments such as carbon nanotubes, thin films and magnetic capacitors. It concludes that the U.S. government must understand and adopt advanced ultracapacitors.
UNCLASSIFIED//FIHl 8FFHil.t.k l!j!ilE 8Hk'/ Initial ultracaps used aqueous electrolytes made with Al2(SO4)3 (aluminum sulfate), H25O4 (sulfuric acid), or KOH (potassium hydroxide) . While these electrolytes have excellent ionic conductivity, the operating voltage is limited to 1.2 volts using carbon electrodes. Organic electrolytes have lower ionic conductivity, but the higher dielectric constant increases the nominal cell voltage up to as high as 3 volts. Carbon has been used as a high-surface-area electrode material since the inception of the electrochemical capacitor. It is still the material of choice for many ultracapacitors; one of the primary reasons is the low cost of carbon materials. However, there are many types of carbon that are available for use as an electrode material. In addition to carbonaceous electrodes, metal oxides and conductive polymers are finding increasing use in ultracap design. Advancements in the understanding of the electric double-layer and ultracapacitor behavior have led to better materials utilization and, consequently, improved devices. Early electrochemical capacitors were rated at a few volts and had capacitance values measured from less than one farad up to several farads. Today cells range in size from small devices with exceptional pulse-power performance in the millifarad range up to devices rated at several kilofarads. There are even some specialized ultracapacitor cells now in production that have ratings of more than 100 kF. The technology is experiencing increasingly broader use, replacing batteries in some cases and in others complementing their performance. Ultracap technology has grown into an industry with sales of several hundred million dollars per year that is poised for rapid growth in the near term due to expansion of power quality needs and the emerging energy management/conservation applications. 11 Advancements in ultracapacitors have led to numerous devices from an array of manufacturers. Table 2 compares the various products on the market, showing voltage, capacity, power density, and additional energy-storage characteristics. Ultracaps have moved away from aqueous electrolytes and are typically organic electrolytes due to the increased voltage performance. Electrodes vary from carbon/carbon systems to hybrid systems using metal oxides or conductive polymers paired with a carbon electrode. Packaging and sizes of ultracapacitors covers a large range as these are now used from cellular communications and small electronics to power delivery and management for seaport cranes. Ultracapacitor technology development is focusing on delivering better energy density, and this is being approached by improved carbon electrodes, better electrolytes, and alternative electrodes that provide pseudocapacitive behavior, including battery-like electrodes. 12 6 UNCLASSIFIED//Flilll. IIFFll!llltt tl!9E OICL I
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 34 pages are in the text index: search them above, or from the library's search.