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Graphene boosts energy storage potential

Electric car

In electric cars, supercapacitors will be used to capture and store the energy generated by braking(Source: wakila/iStockphoto)


Professor Dan Li and colleagues from Monash University have developed a graphene-based supercapacitor.

The new device, reported in the journal Science, is more compact and holds 10 times as much energy as existing supercapacitors.

"This is a new way to store renewable energy," says Li.

"The graphene material has allowed us to increase energy density, the amount of energy stored in a given volume. That means we can make supercapacitors which are smaller and last longer, without compromising their ability to recharge quickly."

Existing supercapacitors use highly porous carbon impregnated with a liquid electrolyte, giving them a low energy density, typically five to eight Watt-hours per litre, so they need to be frequently recharged.

This has prevented their use as a replacement for batteries.

New approach

The new graphene based supercapacitor developed by Li and colleagues, has an energy density of around 60 Watt-hours per litre, which is similar to lead-acid car batteries.

This will allow them to be smaller and lighter than existing supercapacitors.

According to Li, they'll also last longer than batteries because they store charge, rather than generating current through chemical reactions.

But he says they'll supplement rather than replace the battery.

"I think supercapacitor technology is more complementary to traditional batteries, working together to improve the performance of energy storage," says Li.

"In electric cars, supercapacitors will [be used to] capture and store the energy generated by braking."

Simple build

Li and colleagues used a method similar to that used in traditional paper making to produce their graphene sheets.

The sheets were then placed in a liquid electrolyte solution which both kept the layers separated and acted as an electric conductor.

"The next step will be to commercialise the technology," says Li.

"We still need a way to manufacture the graphene material in large quantities. It's not hard to produce, but it hasn't been done on large scales yet."
