Flexible Electronics: New Material for High Temperature Energy Storage

Flexible electronics – electric vehicles – aerospace

A team of researchers at Park University in Pennsylvania, in collaboration with engineers from a Penn State University research center, created an ultrafine polymer, reinforced with a two-dimensional material with high performance energy storage properties at room temperature. The material can be used at much higher temperatures than materials on the market, to meet the needs of electric vehicles, aerospace, flexible electronics and others.

This innovation is the creation of a research team led by Qing Wang, Professor of Materials Science and Engineering at Penn State University. The team had already designed a nanomaterial composite sheet made of boron nitride and dielectric polymers. The composite was, however, very difficult to adjust to scale (resize) economically.

Wang’s research group, working on functional polymers and polymer nanocomposites, collaborated with a team from the Center for Two Dimensional and Layered Materials, led by Nasim Alem, Professor of Materials Science and Engineering at Penn State University. This is the first study looking to combine a flexible polymer with a 2D crystalline material to develop a dielectric component. The researchers were able to produce a highly resistant material based on hexagonal boron nitride and polyetherimide (PEI).

Properties of Hexagonal Boron Nitride-Coated PEI

 Hexagonal boron nitride is a broadband material characterized by its high mechanical resistance. It is also a good insulator due to its wide bandgap. In particular, it helps protect the PEI film from dielectric breakdown at high temperatures, which causes failure in other polymer capacitors developed in this type of academic research. A dielectric material starts to lose its efficiency when the ambient temperature reaches 80 degrees Celsius. However, the material produced by both teams remains efficient even in temperatures exceeding 200° C. This feature was demonstrated after tests of more than 55,000 electric charge-discharge cycles.

Wang points out that hexagonal boron nitride can also be used as a coating for other types of electro-active polymers.

Production of the Material

Amin Azizi, UC Berkeley postdoctoral student and Matthew Gadinski, senior engineer at DOW Chemical, developed a manufacturing process using the chemical vapour deposition (CVD) technique to deposit multi-layer hexagonal boron nitride films and nanocrystals on both sides of a polyetherimide (PEI) film. They then bonded the films in a three-layer sandwich structure by applying pressure.

Chemical vapor deposition

While fabricating the material, the researchers found, surprisingly, that adhesion between layers of this dielectric polymer did not require a chemical binder. So the material can be produced using a high-debit roll-to-roll process, which is increasingly accessible in flexible electronics manufacturing.

The roll-to-roll process

Initial calculations of the research group led by Long-Qing Chen, Professor of Materials Science and Engineering, and Donald W. Hamer, Professor of Science, Mechanics and Mathematics at Penn State University, demonstrated that the electric insulation of the interface between the new material and the metal electrodes is much higher than in dielectric polymers currently on the market.

The study, entitled “High-performance Polymers Sandwiched with Chemical Vapor Deposited Hexagonal Boron Nitrides as Scalable High-Temperature Dielectric Material“, was published on July 17, 2017, in the Advanced Materials journal. The research was funded by the US Office of Naval Research and the National Science Foundation.