Supercapacitors are the devices defined by higher power densities than batteries and higher energy densities than conventional dielectric capacitors. Conventional super capacitors consist of two identical activated carbon electrodes placed in symmetrical manner and charges are stored in capacitive fashion at electrochemical double layer. The appropriate way of calculating total capacitive (in F) connected in series is 1/Ctot= 1/C1 + 1/C2. Thus, total capacitance (in F) of symmetric capacitors is Ctot=Celectrode/2 and energy should be calculated as E=1/8 . Celectrode *V2 where V is maximum charging potential of entire cell.
Activated carbons are abundantly used for supercapacitor applications from several decades. This is particularly due to its abundance in earth’s crust, highly conductive nature and being ecofriendly material. Further unique stability of carbons in various electrolyte solutions under wide range of potentials and temperature emboss their candidature for supercapacitors. These carbon matrixes can be fine-tuned for their porosity and surface areas in very much tailor-made fashion. The activation process can provide high surface areas ranging from several hundred to more than 2000 m2/g. These properties are critical for high specific capacity of ion adsoption and also determines high-rate of diffusion in and out of pores of electrodes during charge-discharge processes.
Composite materials which are combinations of carbon core and other components like nanomaterials, oxides/nitrides of metals are being experimented in order to enhance energy density of these capacitors without affecting power density and cycle life. For instance, carbon nanotubes and graphene which are extensively studied also as core active material, gives advantage of large surface area and high conductivity, however, it fails to produce high volumetric capacitance along with agglomeration, tedious fabrications and is very much cost exorbitant. By combination of such unique materials with conventional low-cost materials can serve in best possible way for maximum output in supercapacitors. In recent years our group is heavily involved in studying the systems in which sole materials suffer from a limitation that can be overcome by its hybrid format with other components like nanomaterials, oxides, nitrides, MXene, and organic moieties like quinones. Following Ragone plot is the gist about the scope of our work on supercapacitors.
1. Borenstein, A., Hanna, O., Attias, R., Luski, S., Brousse, T., & Aurbach, D. (2017). Carbon-based composite materials for supercapacitor electrodes: a review. Journal of Materials Chemistry A, 5(25), 12653-12672.
2. Borenstien, A., Noked, M., Okashy, S., & Aurbach, D. (2013). Composite carbon nano-tubes (CNT)/activated carbon electrodes for non-aqueous super capacitors using organic electrolyte solutions. Journal of the Electrochemical Society, 160(8), A1282.
3. Malka, D., Bublil, S., Attias, R., Weitman, M., Cohen, R., Elias, Y., ... & Aurbach, D. (2021). Developing Effective Electrodes for Supercapacitors by Grafting of Trihydroxybenzene onto Activated Carbons. Journal of The Electrochemical Society, 168(5), 050520.
4. Levi, M. D., Lukatskaya, M. R., Sigalov, S., Beidaghi, M., Shpigel, N., Daikhin, L., ... & Gogotsi, Y. (2015). Solving the capacitive paradox of 2D MXene using electrochemical quartz‐crystal admittance and in situ electronic conductance measurements. Advanced Energy Materials, 5(1), 1400815.