Interest in graphene for energy storage applications has hugely increased over the last ten years. Almost 500 papers were published on the subject in the first half of this year alone, with many more certain to happen. In 2008, one of the first graphene-based ultracapacitors (also known as supercapacitors) was announced and interest has been increasing ever since.
Published in NanoLetters by Meryl D. Stoller and colleagues, the 2008 work illustrated the performance of chemically modified graphene in an ultracapacitor cell. The author stated, the strong performance and high electrical conductivity over a wide span of voltage scan rates showed the “exciting potential for high performance, electrical energy storage devices based on this new class of carbon material.”
One of the numerous sought after properties of graphene is its high surface area (up to 2630 m2 g-1). This is of notable interest for supercapacitors. Researchers from Tsinghua University, Beijing, and Arizona State University recently detailed the intrinsic capacitance of single layer graphene to be 21 µF cm-2.
This sets the upper limit for electric double layer (EDL) capacitance for all carbon-based substances. These valuable characteristics of graphene mean, if the whole surface area can be fully utilized, a supercapacitor based on graphene could in theory attain an EDL capacity as high as 550 F g-1. This combination of capacitance and surface area assures an exceptional future for energy storage.
The performance of graphene supercapacitors has been outstanding since the initial early studies. Recently, a researcher at Australia’s Swinburne University has created a battery that can be used repeatedly and charges up in seconds. A supercapacitor that not only overcomes the barriers of long charging times and costs less than a traditional lithium ion battery over its lifetime has been developed by Dr. Han Lin, of the Centre for Micro-Photonics.
Researchers from UC Santa Cruz and Lawrence Livermore National University recently doubled the performance of 3D printed graphene-based supercapacitors. Their method entails sandwiching perchlorate ion and lithium ion between layers of graphene in aerogel electrodes.
This allowed the researchers to strengthen the 3D printed graphene aerogel. Yat Li, UCSC professor and corresponding author said that they, “exfoliated the stacked graphene layers and functionalizing their surface, without damaging structural integrity.”
Graphene is also useful for a wide scope of batteries as well as supercapacitors:
- Lithium-ion batteries
- Redox flow
First principles calculations reveal that lithium ions can be stored on both sides of graphene to form C3Li. Graphene can accordingly deliver a theoretical capacity of 744 mAh g-1, which is about double the capacity of conventional graphite electrodes. This was shown in a recent example featured in the Journal of Materials Chemistry.
This information has been sourced, reviewed and adapted from materials provided by Graphitene.
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