Researchers at Australia’s Monash University have developed a compact graphene-based supercapacitor device that lasts as long as a conventional battery, an advance with the potential to bring next-generation energy storage a step closer. Professor Dan Li of the Department of Materials Engineering and his team published their work this week in Science.
Supercapacitors (SCs) are valued for their almost indefinite lifespan and their ability to recharge in seconds, but existing SCs have a low energy density – typically five to eight Watt-hours per liter – which means that they are unfeasibly large, or must be recharged frequently. Professor Li’s team has created a SC with an energy density of 60 Watt-hours per liter, 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.
SCs are generally made of highly porous carbon impregnated with a liquid electrolyte to transport the electrical charge. To make their compact electrode, Professor Li’s team used a graphene gel film. Graphene, which is formed when graphite is broken down into layers one atom thick, is very strong, chemically stable and an excellent conductor. The team used liquid electrolytes to control the spacing between graphene sheets on the sub-nanometer scale. The liquid electrolyte played a dual role: maintaining the minute space between the graphene sheets and conducting electricity.
To create their material, the team used a method similar to that used in traditional paper making, so 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.