(Image Credit: Mizter_X94/pixabay)
Capacitors are extremely useful components found in everyday applications. They store a battery's electrical charge and provide rapid charge/discharge capabilities. Although those are some nice-to-have features, their energy storage efficiency could be better. Washington University researchers recently devised a new heterostructure capacitor design that stores up to 19x more energy than ferroelectric capacitors. It also charges rapidly and remains durable throughout its use.
Ferroelectric materials in a capacitor can deliver high maximum polarization, which is practical for rapid charging/discharging. However, this may also reduce a conductor's relaxation time. "This precise control over relaxation time holds promise for a wide array of applications and has the potential to accelerate the development of highly efficient energy storage systems," the team wrote in the paper.
The team discovered an effective way to address that limitation. They sandwiched 2D and 3D materials in atomically thin layers with chemical and nonchemical bonds between each layer. They then placed an extremely thin 3D core between two outer 2D layers, forming a 30-nanometer-thick stack. "Initially, we weren't focused on energy storage, but during our exploration of material properties, we found a new physical phenomenon that we realized could be applied to energy storage, and that was both very interesting and potentially much more useful," assistant professor of mechanical engineering and materials science Sang-Hoon Bae said.
So this 2D/3D/2D structure has electric properties that sit between conductivity and nonconductivity --- ideal for energy storage. The new design's energy density is 19 times higher than ferroelectric capacitors. It also has a higher efficiency --- over 90%.
A tiny gap in the material structure allows the capacitor to store energy. "We found that dielectric relaxation time can be modulated or induced by a very small gap in the material structure," Bae explained. "That new physical phenomenon is something we hadn't seen before. It enables us to manipulate dielectric material in such a way that it doesn't polarize and lose charge capability."
The team plans to optimize the structure further so that it can rapidly charge/discharge with a high-energy density. "Fundamentally, this structure we've developed is a novel electronic material," Bae said. "We’re not yet 100% optimal, but already we’re outperforming what other labs are doing. Our next steps will be to make this material structure even better, so we can meet the need for ultrafast charging and discharging and very high energy densities in capacitors. We must be able to do that without losing storage capacity over repeated charges to see this material used broadly in large electronics, like electric vehicles, and other developing green technologies.”
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