Aug 01, 2013 |
'Soft' approach leads to high-performance graphene-based supercapacitor
|
(Nanowerk News) Monash University researchers have brought next generation energy storage closer with an engineering first - a graphene-based device that is compact, yet lasts as long as a conventional battery.
|
Published today in Science ("Liquid-Mediated Dense Integration of Graphene Materials for Compact Capacitive Energy Storage"), a research team led by Professor Dan Li of the Department of Materials Engineering has developed a completely new strategy to engineer graphene-based supercapacitors (SC), making them viable for widespread use in renewable energy storage, portable electronics and electric vehicles.
|
SCs are generally made of highly porous carbon impregnated with a liquid electrolyte to transport the electrical charge. Known for their almost indefinite lifespan and the ability to re-charge in seconds, the drawback of existing SCs is their low energy-storage-to-volume ratio - known as energy density. Low energy density of five to eight Watt-hours per litre, means SCs are unfeasibly large or must be re-charged frequently.
|
Professor Li's team has created an SC with energy density of 60 Watt-hours per litre - comparable to lead-acid batteries and around 12 times higher than commercially available SCs.
|
"It has long been a challenge to make SCs smaller, lighter and compact to meet the increasingly demanding needs of many commercial uses," Professor Li said.
|
Graphene, which is formed when graphite is broken down into layers one atom thick, is very strong, chemically stable and an excellent conductor of electricity.
|
To make their uniquely compact electrode, Professor Li's team exploited an adaptive graphene gel film they had developed previously. They used liquid electrolytes - generally the conductor in traditional SCs - to control the spacing between graphene sheets on the sub-nanometre scale. In this way the liquid electrolyte played a dual role: maintaining the minute space between the graphene sheets and conducting electricity.
|
Unlike in traditional 'hard' porous carbon, where space is wasted with unnecessarily large 'pores', density is maximised without compromising porosity in Professor Li's electrode.
|
To create their material, the research team used a method similar to that used in traditional paper making, meaning the process could be easily and cost-effectively scaled up for industrial use.
|
"We have created a macroscopic graphene material that is a step beyond what has been achieved previously. It is almost at the stage of moving from the lab to commercial development," Professor Li said.
|