Supercapacitors to take 50% of lithium-ion battery market

Currently, supercapacitor electrodes have hierarchical electrode structures with large pores progressing to small pores letting appropriate electrolyte ions into monolithic masses of carbon. Previous research has suggested that better results are obtained from exohedral structures, where the large functional area is created by allotropes of carbon only one atom thick. The structure must, however, be optimally matched to the electrolyte and then the pair assessed for specific capacitance and voltage increase.

Graphene is one such form of carbon. Providing some of the highest energy densities, graphene is particularly effective in exhibiting high specific capacitance with both aqueous and ionic electrolytes. These are low-cost, non-flammable electrolytes which feature a high voltage range, low toxicity and a wide temperature operating range.

There are some setbacks, however. Firstly, when purity and structural integrity are required, graphene is expensive. Secondly, while graphene has the greatest theoretical area and improves gravimetric energy density, it does not do the same for volumetric energy density. Unless supercapacitors prove feasible, this will cut off many applications.

Ultimately, however, the planned replacement of aluminium electrolytic capacitors with graphene supercapacitors can potentially make EV inverters smaller, lighter and more cost-effective.