Supercapacitors or coconuts

The key ingredient in powerful devices for storing energy has been charred coconut. Now a company in icy Estonia has figured out how to make a supercapacitor without tropical fruit

“ The problem with coconut shells, naturally, is that the distribution and size of their pores has great variability,” says ­Taavi Madiberk, chief executive of Skeleton Technologies, a company established in Estonia where, one might expect, the main problem with coconuts would be the small likelihood of finding them, rather than the qualities of their shells. What’s truly surprising is that a company in this northern country is solving a truly important coconut problem.

“Ultracapacitors are the backbone, the skeleton of an energy system.”

This coconut issue is, in fact, a multi-billion euro problem, when you consider the size of the market for supercapacitors, which are devices for storing energy. By 2024 it’s expected to rise to EUR 6 billion. They have thus far been made of activated carbon generated by charring discarded coconut shells. Until an inorganic – and much more efficient – alternative was developed by Skeleton Technologies. In 2017, the company received a EUR 15 million loan from the EIB to continue its R&D, backed by the EU budget guarantee of the Investment Plan for Europe.

Why not just keep using cocon

When a coconut is charred, it produces carbon that, if thinly spread on a sheet of foil and exposed to electrically charged ions, can store the ions in its pores. The more densely the carbon is covered by correctly sized pores, the more energy it can store for a given gram of material. Trouble is, depending on the weather and the time of its harvest, a charred coconut will have a varying density of pores.

With its proprietary technology for deriving carbon from inorganic carbides, Skeleton Technologies can tune the pores. The result: curved sheets that are one atom thick, one gram of which contains close to 2,000 square metres of uniformly porous area for ions to fit into. The way Skeleton then attaches the carbon to the aluminium foil and stacks or rolls these sheets tightly into cells creates supercapacitors with four times the power density of coconut-based competitors. The name Skeleton, by the way, comes from the fact that under a microscope, the company’s material resembles a human skeleton. Madiberk adds, “Ultracapacitors are the backbone, the skeleton of an energy system.”