Multifunctional Electrode Nanoarchitectures for Electrochemical Capacitors
NAVAL RESEARCH LAB WASHINGTON DC
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The term electrochemical capacitor EC describes a diverse class of energy-storage devices that bridges the critical performance gap on the power vs energy density plane between the high power densities offered by conventional capacitors and the high energy densities of batteries. 1 Although from both practical and fundamental perspectives, ECs are closely related to batteries, electrochemical capacitors can be differentiated by charge-discharge response times that are on the order of seconds and by their exceptional cycle life typically many tens to hundreds of thousands of cycles. The most visible technologies that will be impacted by ECs are hybrid-electric power systems, where significant increases in energy efficiency can be achieved through the recovery of energy normally wasted during braking of repetitive motion, thanks to the rapid charge-discharge response of ECs. Hybridelectric power systems will become increasingly beneficial not only for transportation applications but also for large industrial equipment, including cranes and elevators. Improvements in the high-power performance of electrochemical capacitors and batteries for applications ranging from mission-fielded electronics and sensors to hybrid-electric power systems require a fundamental re-design of the underlying electrode architectures on the nanoscale. We recently demonstrated one such example of a multifunctional electrode nano-architecture in which electroactive nanoscale manganese oxide deposits cover the walls of the tortuous aperiodic structure of ultraporous carbon nanofoams and related porous carbons. In such a configuration, the nanostructured carbon substrate serves as a high-surface-area, massively parallel 3D current collector for the poorly conducting MnO2 coatings, and defines the internal pore structure of the electrode, which facilitates the infiltration and rapid transport of electrolyte i.e., solvent and ions to the nanoscopic MnO2 phase.
- Electrical and Electronic Equipment
- Energy Storage
- Electricity and Magnetism