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'Ideal' energy storage material for electric vehicles developed
http://news.psu.edu/story/421927/2016/08/22/research/ideal-energy-storage-material-electric-vehicles-developed[font face=Serif][font size=5]'Ideal' energy storage material for electric vehicles developed[/font]
By Walt Mills
August 22, 2016
[font size=3]UNIVERSITY PARK, Pa. -- The energy-storage goal of a polymer dielectric material with high energy density, high power density and excellent charge-discharge efficiency for electric and hybrid vehicle use has been achieved by a team of Penn State materials scientists. The key is a unique three-dimensional sandwich-like structure that protects the dense electric field in the polymer/ceramic composite from dielectric breakdown. Their results are published today (Aug. 22) in the Proceedings of the National Academy of Sciences (PNAS).
“Polymers are ideal for energy storage for transportation due to their light weight, scalability and high dielectric strength,” says Qing Wang, professor of materials science and engineering and the team leader. “However, the existing commercial polymer used in hybrid and electric vehicles, called BOPP, cannot stand up to the high operating temperatures without considerable additional cooling equipment. This adds to the weight and expense of the vehicles.”
The researchers had to overcome two problems to achieve their goal. In normal two-dimensional polymer films such as BOPP, increasing the dielectric constant, the strength of the electric field, is in conflict with stability and charge-discharge efficiency. The stronger the field, the more likely a material is to leak energy in the form of heat. The Penn State researchers originally attacked this problem by mixing different materials while trying to balance competing properties in a two-dimensional form. While this increased the energy capacity, they found that the film broke down at high temperatures when electrons escaped the electrodes and were injected into the polymer, which caused an electric current to form.
“That’s why we developed this sandwich structure,” Wang says. “We have the top and bottom layers that block charge injection from the electrodes. Then in the central layer we can put all of the high dielectric constant ceramic/polymer filler material that improves the energy and power density.”
…[/font][/font]
By Walt Mills
August 22, 2016
[font size=3]UNIVERSITY PARK, Pa. -- The energy-storage goal of a polymer dielectric material with high energy density, high power density and excellent charge-discharge efficiency for electric and hybrid vehicle use has been achieved by a team of Penn State materials scientists. The key is a unique three-dimensional sandwich-like structure that protects the dense electric field in the polymer/ceramic composite from dielectric breakdown. Their results are published today (Aug. 22) in the Proceedings of the National Academy of Sciences (PNAS).
“Polymers are ideal for energy storage for transportation due to their light weight, scalability and high dielectric strength,” says Qing Wang, professor of materials science and engineering and the team leader. “However, the existing commercial polymer used in hybrid and electric vehicles, called BOPP, cannot stand up to the high operating temperatures without considerable additional cooling equipment. This adds to the weight and expense of the vehicles.”
The researchers had to overcome two problems to achieve their goal. In normal two-dimensional polymer films such as BOPP, increasing the dielectric constant, the strength of the electric field, is in conflict with stability and charge-discharge efficiency. The stronger the field, the more likely a material is to leak energy in the form of heat. The Penn State researchers originally attacked this problem by mixing different materials while trying to balance competing properties in a two-dimensional form. While this increased the energy capacity, they found that the film broke down at high temperatures when electrons escaped the electrodes and were injected into the polymer, which caused an electric current to form.
“That’s why we developed this sandwich structure,” Wang says. “We have the top and bottom layers that block charge injection from the electrodes. Then in the central layer we can put all of the high dielectric constant ceramic/polymer filler material that improves the energy and power density.”
…[/font][/font]
