High Volume, High Power Graphene Supercapacitors

By: Siân Fogden (Graphene Flagship)

Supercapacitors are storage devices capable of charging and discharging with high speed. Unlike conventional batteries, which use chemical reactions to store energy, supercapacitors use electrostatics. This means that they can be charged and discharged much faster with a much longer lifetime than batteries, being able to cycle hundreds of thousands of times. However, most supercapacitors currently used can only store small amounts of energy compared to batteries. This depends on their porous layer electrodes, which dictates the amount of electrostatic charge stored at the interface with the electrolyte. The higher the surface area and conductivity, the higher the charge the supercapacitor can store and thus its energy and power. Being a two-dimensional material, graphene has the highest surface area and it also an electrical conductor. Therefore it has the potential to greatly increase the storage capacity of supercapacitors.

Thales have been working on incorporating graphene into supercapacitors since the start of the Graphene Flagship and have been able to significantly increase the storage potential of supercapacitor devices.

"Using graphene, we have been able to increase the power of supercapacitors by five times. We deposited our supercapacitors using spray coating, enabling us to use a variety of substrates, thus allowing us to develop flexible, high power supercapacitors," said Paolo Bondavalli, Thales Research and Technology.

For these novel supercapacitors to be used to their full potential in the automotive or space industries they need to be produced in a reliable and repeatable manner. Thales collaborated with M-SOLV to scale up their spray coating technique.

"At M-SOLV we are leaders in developing tools for deposition. Thus, working closely with Thales, we were excited to develop a larger scale, high throughput spray deposition tool with inline, equipped with real-time characterisations ranging from the temperature of the chuck to the density and thickness of the graphene layer," said Maria Cann, Development Engineer for M-SOLV, "this enabled us to produce an innovative user interface for the tool with enabling high reproducibility."

"The spray coating machine developed by M-SOLV can be used to spray films that have a thickness from nanometres to dozens of microns," said Saied Jafaar, Thales Research and Development, "this machine is a preparation for the industrial scale because it can spray 30cm by 30cm at 200um of thickness in less than 10 minutes."

"Thales wants to achieve an operational prototype in two years to be used in space or air-crafts. In aeronautics alone we need to produce 300 thousand supercapacitors per year and this machine is a first step towards this goal," said Bondavalli.

Both Thales and M-SOLV are members of the Graphene Flagship. "Within the Graphene Flagship structure people are willing the talk about their research in a manner that can aid everyone's understanding of the field and in our case led to this fruitful collaboration where we took a lab scale result, and through process engineering developed a large scale production tool," said Cann.

"This project is an example on how the Graphene Flagship operates to fulfil its mission to bring graphene technologies into the market. The work of Thales and M-SOLV offers one of the first possibilities of creating a patent-protected value chain encompassing material production and device manufacturing able to address a specific need of a market" said Vittorio Pellegrini, director of the Graphene Labs of the Italian Institute of Technology and leader of the energy storage Work Package of the Flagship.

Andrea C. Ferrari, Science and Technology Officer of the Graphene Flagship, added: "We are just past halfway of the first 10 years of the Graphene Flagship. This work demonstrates how our innovation and technology roadmap is steadily progressing. It also shows that our framework partnership agreement allows companies to work together for mutual benefit. This work is a milestone towards large scale commercialization of yet another technology developed by the Graphene Flagship."