Boosting Supercapacitor Energy Storage

­Batteries are by far the most popular way of storing energy, but supercapacitors also have a place. The two different devices operate in totally different ways, but they generally complement each other well. The main advantage of supercapacitors is that they use an electrostatic charge to hold energy, meaning that they can be discharged and charged very quickly. Batteries store energy electrochemically and although they cannot supply it as quickly as supercapacitors, they are able to store a much larger amount of energy in the same form factor. This means supercacitors are mainly used to provide short bursts of power in applications that either need a quick boost, for example, to keep equipment functioning until it can be shut down properly in the event of a power cut. While batteries are used to supply energy over a longer period. The two devices are also often used alongside each other to make up for the other’s shortfalls.

If a supercapacitor had the ability to store as much energy as a battery in the same sized package, it would open up new opportunities in areas like the electrification of transport, grid stabilisation and consumer electronics, as well as assisting in miniaturization. That prospect could now be a step closer thanks to a team of scientists at Monash University. The researchers have developed a new type of carbon-based material that provides supercapacitors with the ability to store the same amount of energy as a lead acid battery in a similar form factor. 

Supercapacitors store energy electrostatically between two plates, and the amount of energy that they can hold is dependent on the surface area of the plates, or more correctly, the surface are of the plates that are available to store energy, which is only a fraction of the total area. The Monash University scientists have developed a new material architecture, called multiscale reduced graphene oxide (M-rGO), which is synthesised from widely available natural graphite. M-rGO is a highly curved graphene structure that allows ions to move quickly and efficiently. It was fabricated using a rapid thermal annealing process, and it provides much more usable surface area.  

The team from Monash University included Professor Mainak Majumder, who said, “Our team has unlocked much more of that surface area by changing the way the material is heat-treated. This discovery could allow us to build fast-charging supercapacitors that store enough energy to replace batteries in many applications and deliver it far more quickly.”

The material offers both high energy density and high-power density, which is very rare to find in a single device. Test show that the material has volumetric energy densities of up to 99.5 Wh/L and power densities as high as 69.2 kW/L. The material maintains rapid charging capabilities and has excellent cycle stability. Ionic Industries has been spun-out from the university to commercialize the discovery.