Hybrid Composite Electrodes for Asymmetric Full Cell Supercapacitors

Tuesday, 3 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
T. Mokkelbost, J. R. Tolchard, K. Jayasayee, A. O. Barnett, S. M. Hanetho (SINTEF Materials and Chemistry), A. M. Svensson (Norwegian University of Science and Technology), and M. F. Montemor (Instituto Superior Tecnico)
Supercapacitors, which can store energy by a combination of electrostatic (double layer capacitance) and electrochemical (pseudocapacitance) storage of electrical energy, are an important energy storage device applicable for a variety of uses and technologies, especially in applications which requires rapid charge/discharge cycles and several thousands of cycles, e.g. short term energy storage and high powder delivery. The asymmetric electrode configuration which allows for the use of aqueous electrolytes are a promising route to low-cost and environmentally friendly supercapacitors without compromising power and energy density.

Here we present a novel approach based on easy synthesis methods to prepare hybrid electrode materials consisting of mixed transition metal oxides for the redox contribution together with carbonaceous materials contributing to the double layer response. The synthesis methods used are possible to scale up and results in nanosized, high surface area hybrid electrode materials. Different methods have been selected which results in significant different morphologies and characteristics. The electrode materials have been characterized by standard physical techniques, e.g. SEM, TEM, EDX and XRD. To prepare final electrode materials, inks using PTFE, ketjen black and H2O/isopropanol, was spray coated on carbon paper with different loading to be able to balance a asymmetric cell. The electrodes were tested for electrochemical performance as capacitors, such as cyclic voltammetry and charge and discharge curves, as a function of electrode composition, time and type of water based electrolyte, and compared with e.g. electrodeposition. Some of the composite electrode demonstrated specific capacitances of 300 Fg-1. Asymmetric cells were prepared using electrodes of metal oxide/carbon and pure "capacitor grade" carbon with tailored loading for balancing the cell and mounted in a El-cell using aqueous electrolytes.

The project is funded through the m-ERA.net program and financial support from Research Council of Norway and Fundação para a Ciência e a Tecnologia is appreciated.