Graphene-based supercapacitors have already proven the equal of conventional supercapacitors – in the lab. But now researchers at Melbourne’s Monash University claim to have developed of a new scalable and cost-effective technique to engineer graphene-based supercapacitors that brings them a step closer to commercial development.
With their almost indefinite lifespan and ability to recharge in seconds, supercapacitors have tremendous energy-storage potential for everything from portable electronics, to electric vehicles and even large-scale renewable energy plants. But the drawback of existing supercapacitors has been their low energy density of around 5 to 8 Wh/liter, which means they either have to be exceedingly large or recharged frequently.
Professor Dan Li and his team at Monash University’s Department of Materials Engineering has created a graphene-based supercapacitor with an energy density of 60 Wh/liter, which is around 12 times higher than that of commercially available supercapacitors and in the same league as lead-acid batteries. The device also lasts as long as a conventional battery.
To maximize the energy density, the team created a compact electrode from an adaptive graphene gel film they had previously developed. To control the spacing between graphene sheets on the sub-nanometer scale, the team used liquid electrolytes, which are generally used as the conductor in conventional supercapacitors.
Unlike conventional supercapacitors that are generally made of highly porous carbon with unnecessarily large pores and rely on a liquid electrolyte to transport the electrical charge, the liquid electrolyte in Li’s team’s supercapacitor plays a dual role of conducting electricity and also maintaining the minute space between the graphene sheets. This maximizes the density without compromising the supercapcitor’s porosity, they claim.
To create their compact electrode, the researchers used a technique similar to one used in traditional paper making, which they say makes the process cost-effective and easily scalable for industrial applications.
"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.