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NEWS
Lightweight Composite Material Developed For Energy Storage
October 20, 2017

As modern society becomes more and more dependent upon electronics, the quest to generate power more efficiently and cost effectively has been the focus of much of the research community. However, many researchers have been focused on the other end of the challenge, how do you most efficiently and cost effectively store the energy once it’s produced? Developing solutions to this problem has taken on a new sense of urgency as electronic devices have become smaller and smaller but simultaneously more powerful.


PEI coated with hexagonal boron nitride (hBN) nanosheets significantly outperforms competitive polymers at operating temperatures needed for electric vehicles and aerospace power applications. Credit: Feihua Liu/ Penn State.

To address this issue, a new, lightweight composite material for energy storage in flexible electronics, electric vehicles and aerospace applications has been experimentally shown to store energy at operating temperatures well above current commercial polymers, according to information provided by Pennsylvania State University (Penn State). The Penn State scientists also note that this polymer-based, ultrathin material can be produced using techniques already used in industry.

“This is part of a series of work we have done in our lab on high-temperature dielectrics for use in capacitors,” said Qing Wang, professor of materials science and engineering at Penn State. “Prior to this work we had developed a composite of boron nitride nanosheets and dielectric polymers, but realized there were significant problems with scaling that material up economically.”

“From a soft materials perspective, 2D materials are fascinating, but how to mass produce them is a question,” Prof. Wang noted. “Plus, being able to combine them with polymeric materials is a key feature for future flexible electronics applications and electronic devices.”

To solve this problem, Prof. Wang’s lab collaborated with a group at Penn State working in two-dimensional crystals.

The research team developed a technique using chemical vapor deposition to make multilayer, hexagonal boron-nitride nanocrystal films and transfer the films to both sides of a polyetherimide (PEI) film. Next, they bonded the films together using pressure into a three-layer sandwich structure. In what turned out to be a surprising result, pressure alone, without any chemical bonding, was enough to make a free-standing film strong enough to potentially be manufactured in a high-throughput roll-to-roll process.

Supported by the U.S. Office of Naval Research and the National Science Foundation, details of the research were reported in a paper, “High-performance Polymers Sandwiched with Chemical Vapor Deposited Hexagonal Boron Nitrides as Scalable High-Temperature Dielectric Materials,” published in the journal Advanced Materials.

Hexagonal boron nitride is a wide band-gap material with high mechanical strength. Its wide band gap makes it a good insulator and protects the PEI film from dielectric breakdown at high temperatures, the reason for failure in other polymer capacitors. At operating temperatures above 176 degrees Fahrenheit, the current best commercial polymers start to lose efficiency, but hexagonal-boron-nitride-coated PEI can operate at high efficiency at over 392 degrees Fahrenheit. Even at high temperatures, the coated PEI remained stable for over 55,000 charge-discharge cycles in testing.

“Theoretically, all these high-performance polymers that are so commercially valuable can be coated with boron nanosheets to block charge injection,” Prof. Wang said. “I think this will make this technology feasible for future commercialization.”


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