Published on August 3rd, 2013 | by James Ayre1
Graphene-Based Supercapacitors — Next-Generation Energy Storage?
An entirely new strategy for engineering graphene-based supercapacitors has been developed by researchers at Monash University — potentially leading the way to powerful next-generation renewable energy storage systems. The new strategy also opens up the possibility of using graphene-based supercapacitors in electric vehicles and consumer electronics.
Supercapacitors — which are typically composed of highly porous carbon that is impregnated with a liquid electrolyte — are known for possessing an almost indefinite lifespan and the impressive ability to recharge extremely rapidly, in seconds even. But existing versions also possess a very low energy-storage-to-volume ratio — in other words, a low energy density. Because of this low energy density — 5-8 Watt-hours per liter in most supercapacitors — they’re not practical for most purposes. They would either need to be extremely large or be recharged very, very often for most uses.
But, now, new research has resulted in the creation of a supercapacitor free from the above-mentioned limitations. Through the use of graphene, the researchers created a supercapacitor that possesses an energy density of 60 Watt-hours per liter, which is comparable to lead-acid batteries and about twelve 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,” stated lead researcher Professor Dan Li of the Department of Materials Engineering.
Monash University continues:
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 supercapacitors (SCs) — 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 conventional, “hard” porous carbon, where space is wasted with unnecessarily large “pores,” density is maximized without compromising porosity in Professor Li’s electrode. To create its 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,” explained Professor Li.