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This Defense Intelligence Reference Document was prepared by the Defense Intelligence Agency's Defense Warning Office and dated 1 November 2010. It is one of a series of advanced technology reports produced under the Advanced Aerospace Weapons System Applications Program. The report reviews how ultracapacitors work, how they compare with batteries, their history and materials, and their commercial, military and aerospace uses. It concludes that new materials and cell designs will raise energy density and that the U.S. government must understand the devices' spectral signatures.
From the source:Release of 2026-09-18 Incident: 11/1/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys ultracapacitors as high-power energy-storage devices and argues that their main value lies in extremely rapid charge and discharge, very long cycle life, and usefulness in systems that need short bursts of power rather than sustained energy delivery. The report explains how ultracapacitors differ from batteries, reviews the materials and cell designs that determine their performance, and emphasizes that they are especially useful for power stabilization, backup power, load leveling, regenerative braking, and other applications where fast energy transfer matters more than total stored energy. It also notes their drawbacks, including lower energy density, self-discharge, and voltage-management requirements that limit their usefulness as stand-alone replacements for batteries in many applications. The document presents ultracapacitors as a maturing and increasingly important technology whose most credible aerospace and military uses lie in pulsed-power, missile and munitions systems, electric propulsion support, and other hybrid power architectures rather than in long-duration primary energy storage.
UNCLASSIFIED1/FOR 8ffl@IAL tt91! e"t I Chapter 4: Recent Developments There have been several recent advances in ultracapacitors focused on increasing energy density by using different active materials24 and designs, 25 activated carbons, 26 polymers, 27 and metal oxides. 28 Conducting polymers have good performance, 29 but lack microfabrication protocols. Oxide-based t hin-film ultracaps have shown high performance, approaching t he theoretical limit for capacitance ( ~1,000 F/g for MnO2). 30 However, the poor electrical conductivity and high impedances associated with surface intercalation redox reactions of these oxides have limited practical film thicknesses to a few microns. Carbon nanotubes have been added to the films to increase the electrical conductivity, but the complexity of manufacturing limits practical applications of such composite electrodes. In th is section we will discuss advances in appl ication of CNT and advanced carbons to ultracapacitor materials, the application of thin-film manufacturing processes, and a revolutionary new super capacitor using a giant magneto capacitive effect. CNTS AND ADVANCED CARBONS Carbon electrodes constitute both electrodes in a symmetric ultracapacitor and one of the electrodes in an asymmetric, or pseudocapacitive, design. Improvements to the carbon electrode rely upon increasing the specific capacitance (in Farads per gram). These improvements come by tailoring the surface area and porosity to achieve the best balance t hat maximizes the interaction with the electrolyte. There is a linear relationship to the surface area and the capacitance up to a point where capacitance plateaus with activated carbons. By controlling the porosity and surface area, it is possible to increase the capacitance beyond this plateau. Carbon nanotubes could provide performance increases with aligned CNT forests of tailored sizes. The characteristics of an ultracapacitor are highly dependent on the nanostructure of the carbon used for the thin-film electrodes. Advanced carbons will provide better control over the pore size and distribution, leading to an expected 50- to 100-percent improvement over the carbons in use today . Carbon nanotubes can be produced with a wide variety of properties. Depending on synthesis parameters, nanotubes can be single walled or multiwalled, with varying numbers of tubes. CNT diameters can be tailored from a few nanometers to tens of nanometers, with lengths up to hundreds of microns. CNTs can be grown in random orientations or as aligned forests. CNTs have a fully accessible surface area and very high electrical conductivity. Methods for incorporating CNTs into electrodes for ultracaps include using CNTs as an additive for conductivity enhancement, creating dense mats of ra ndomly oriented tubes, and creating electrodes from vertically aligned forests of tubes . Initial results of CNT-enabled ultracaps tended to show much lower capacitance than expected, which has been attributed to the hydrophobic nature of the CNT walls. Surface functionalization is a common approach to mitigating the hydrophobicity issues and t hus enabling higher capacitance. Another benefit of the functionalization is the ability to introduce and control pseudocapacitance. Most efforts in CNT ultracaps are directed toward vertica lly aligned forests. It is possible to controllably grow a dense, aligned forest that is perpendicular to the current collector. The size and density of the tubes and the number of walls can be controlled with catalyst design and reaction parameters. Manipulation of t he CNT forest leads to increased capacitance by fine -tuning the distance between tubes. Additionally, fine- UNCLASSIFIEO/fFOA OFFI&I:.l.b YS& ONLY 17
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Official release, from the pursue 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.