Monday, 14 August 2017

Energy Storage Solution Combines Polymers and Nanosheets

Energy Storage

Fresh Lightweight Composite Material – Energy Storage 

 

According to a team of Penn State scientists a fresh lightweight composite material for the purpose of energy storage in flexible electronics, electric vehicles and aerospace application has experimentally revealed energy storage at operating temperatures beyond present commercial polymers.

The said polymer-based ultrathin energy storage material can be produced utilising techniques which are already being used in industry. Professor of materials science and engineering, Penn State, Qing Wang had stated that this is part of a series of work which had been done in the lab on high temperature dielectrics for use in capacitors.

 Prior to this work they had developed a composite of boron nitride nanosheets and dielectric polymers, though had realized that there had been significant issues with scaling that energy storage material up economically’. The defining challenge for several of the new, two-dimensional energy storage materials that are being established in academic labs is scalability or making advanced materials in commercially significant quantities for devices.

Wang has mentioned that `from a soft material perspective, 2D materials are fascinating though how to mass produce them is a question. Moreover, being able to combine them with polymeric materials is a key feature for future flexible electronics applications and electronic devices’.

Functional Dielectric Device-

 

In order to resolve this issue, his lab collaborated with a group at Penn State operating in two-dimensional crystals. Nasim Alem, assistant professor of materials science and engineering as well as a faculty member in Penn State’s Centre for 2-Dimensional and Layered Materials had stated that the work had been conceived in conversations between his graduate students, Amin Azizi together with graduate student of Dr Wang, Matthew Gadinski. He further informed that this was the first strong experiment wherein a soft polymeric material together with a hard 2D crystalline material had come together in order to develop a functional dielectric device.

Azizi who presently is a post-doctoral fellow at University of California, Berkeley and Gadinski, a senior engineer at DOW Chemical had generated a technique utilising chemical vapour deposition in order to make multilayer, hexagonal boron-nitride nanocrystal films to transfer the films to both areas of a polyetherimide (PEI) film.

Thereafter they bonded the films together by utilising force on the three-layer sandwich structure. In the outcome which was surprising to the researchers, pressure itself without the need of any chemical bonding had been adequate in making a free-standing film essentially strong to potentially be manufactured in a high-throughput roll-to-roll process.

 

Hexagonal Boron Nitride – Wide Band Gap Material

 

In a recent issue of the journal Advanced Materials in a paper titled `High-performance Polymers Sandwiched with Chemical Vapour Deposited Hexagonal Boron Nitrides as Scalable High-Temperature Dielectric Materials’, the results had been reported. Hexagonal boron nitride is said to be a wide band gap material having high mechanical strength.

 Its wide band gap tends to make it a worthy insulator, protecting the PEI film from dielectric breakdown at high temperatures, the cause for failure in the other polymer capacitors. Above 176 degrees Fahrenheit, at operating temperatures, the prevailing best commercial polymers begins to lose its efficiency though hexagonal-boron-nitride-coated PEI tends to function at high efficiency at above 392 degrees Fahrenheit.

The coated PEI seems to be stable for over 55,000 charge-discharge cycles in testing even at high temperature. Wang has mentioned that `theoretically all these high performance polymers which seem to be so commercially valuable could be coated with boron nanosheets in order to block charge injection. He further added that he is of the opinion that this would make this technology feasible for forth-coming commercialization.

 

Supported – U.S. Office/National Science Foundation 


Alem has also commented that there are several devices that are made with 2D crystals at the laboratory scale; however the defects tend to make them an issue for manufacturing. With the help of huge band-gap material such as boron nitride, it tends to do a good work in spite of the fact that small microstructural features could not be perfect.

 The first-principles calculations resolute that the electron barrier recognized at the interface of the PEI/hexagonal boron-nitride structure as well as the metal electrodes practical to the structure for the purpose of delivering current was said to be significantly higher than typical metal electrode-dielectric polymers contacts, thus making energy storage materials more complex for charges from the electrode to get injected into the film.

This task had been done by the theoretical research group of Long-Qing Chen, Professor of Materials, Science and Engineering, professor of engineering science and mechanics as well as mathematics – Penn State, Donald W. Hamer. Several others contributing to this work comprise of post-doctoral scholar Qi Li as well as graduate student Feihua Liu in the lab of Wang, undergraduate Mohammed Abu AlSaud in the lab of Alem, senior scientist Jianjun, Wang, post-doctoral scholar Yi Wang together with graduate student Bo Wang who were all from the Chen group at that point of time. This work had also been supported by the U.S. Office of Naval Research as well as the National Science Foundation.

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