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Graphene-oxide enhances battery performance

Posted: 28 Mar 2016 ?? ?Print Version ?Bookmark and Share

Keywords:graphene? battery electrodes? carbon? battery? polymers?

Researchers from Brown University suggest starting with with graphene-oxidea compound of carbon, oxygen, and hydrogenthen merely wrinkle and crumple to achieve a 400% increase in performance over flat graphene sheets, resulting in vastly higher current densities for more efficient batteries.

"Multigenerational graphene oxide architectures can be programmed by specific sequences of mechanical deformations," said Brown professors Robert Hurt and Ian Wong, along with post-doctoral fellow Po-Yen Chen and five colleagues in an Advanced Materials journal article.

According to the researchers, "each new deformation results in a progressively larger set of features decorated by smaller preexisting patterns, indicating a structural 'memory.' It is shown that these multiscale architectures are superhydrophobic and display excellent functionality as electrochemical electrodes."

graphene

Figure 1: Wrinkles and crumples, introduced by placing graphene on shrinky polymers, can enhance graphene's properties. (Source: Hurt and Wong Labs/Brown University)

"After crumpling and wrinkling, the graphene oxide is highly stretchable and flexible without breaking," Wong told EE Times in an exclusive interview. "And retains good electrical conductivity. Such functionality could be useful for wearable multifunctional devices that can sense and respond to external stimuli, such as chemical detection."

By "programming" and "memory" the Brown researcher mean that the wrinkling and crumpling can be controlled for repeatable results in a manufacturing environment. In fact, the researchers have made a catalogue of repeatable steps showing how to achieve a "memory" of each type of desirable result by "programming" the series of winkling and crumpling steps taken to achieve it.

To accurately control the wrinkling and crumpling, the Brown University researchers deposited the graphene on Shrinky Dinks polymers that shrink in predictable amounts when heated. The polymers were then dissolved away leaving the wrinkled and crumpled graphene. Then the process was repeated until the desirable results were achieved using those programming recipes, the researchers were able to repeatable achieve the same results, opening an avenue to manufacturing superior electrodes to battery makers.

The researchers also experimented with clamping one or the other end of the films prior to crumpling and wrinkling, discovering how to control the process differently in different dimensionslongitudinal and verticalto produce, for instance parallel wrinkles before crumpling. Using what they called this "multi-generational" approach, the researchers creating a catalog of formulas some of which resulted in electrodes 40-times more compact and dense than their original size.

They have published a "taxonomy of structures" cataloged both lingually and graphically. Next, the team plans to try the same techniques of different types of materials.

modes of shrinking

Figure 2: Different modes of shrinking in different orders creates different types of structures. (Source: Hurt and Wong Labs/Brown University)

Other contributors included Jaskiranjeet Sodhi, Yang Qiu, Thomas Valentin, Ruben Spitz Steinberg and Zhongying Wang.

- R. Colin Johnson





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