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Compact graphene device could shrink supercapacitors

MONASH U. (AUS) — A new strategy to engineer graphene-based supercapacitors could make them viable for widespread use in renewable energy storage, portable electronics, and electric vehicles.

Supercapacitors 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 supercapacitors is their low energy-storage-to-volume ratio—known as energy density. Low energy density of five to eight watt-hours per liter, means supercapacitors are unfeasibly large or must be re-charged frequently.

Dan Li, a materials engineering professor at Monash University, and his team created a supercapacitor with energy density of 60 watt-hours per liter—comparable to lead-acid batteries and around 12 times higher than commercially available supercapacitors.

“It has long been a challenge to make supercapacitors smaller, lighter, and compact to meet the increasingly demanding needs of many commercial uses,” says Li.

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, Li’s team exploited an adaptive graphene gel film they had developed previously. They used liquid electrolytes—generally the conductor in traditional supercapacitors—to control the spacing between graphene sheets on the sub-nanometer 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 maximized without compromising porosity in 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,” Li says.

The Australian Research Council supported the work, which was reported in the journal Science.

Source: Monash University

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