Supercapacitors are energy storage systems characterized by long cycle life and high power density. They store energy in electric double layers formed in the immediate vicinity to highly porous electrodes. In their electrical performance they align between conventional capacitors and batteries: Their power densities are typically 10-fold compared with Li-ion batteries, their charge times can be of the order of few seconds, and their cycle life can exceed 1 000 000 cycles. However, their energy density is considerably low, only about 10 % of the energy density of a typical Li-ion battery. The performance of a supercapacitor depends on several factors, such as active surface area, pore size and distribution, conductivity of the electrode materials, and mechanical and chemical stability of the materials.
In our group we study conducting polymer-graphene composite materials as active components in flexible supercapacitors. Composite materials can offer higher capacitances and improved mechanical stability compared with bare conducting polymer and graphene supercapacitors. New materials are first thoroughly characterized with electrochemistry, spectroscopic techniques, and spectroelectrochemical methods before they are applied on flexible supercapacitor substrates and device performance is studied. Supercapacitor research is made in collaboration with electronics group in Tampere University of Technology.