Electrochromic charge storage devices based on metallo-organic assemblies

The rapid and global increase in energy demands has driven the research and development of new energy storage materials and devices. Energy storage systems are divided into two main categories: batteries and capacitors.¹ Batteries have a high energy density, whereas capacitors have a high power density. Hybrid supercapacitors combine battery-like and capacitive electrodes in a single device. This combination allows the best of both worlds: high power and high energy density. The replacement of conventional inorganic materials (eg. lithium, lead, antimony, cadmium) by metallo-organic materials enables low-cost, flexible, and functional storage devices.

In our research, we developed a hybrid device which is composed of carbon nanotubes (CNTs), as the counter electrode,² and metallo-organic assemblies, as a working electrode. During oxidation process of the metallo-organic films at the working electrode, the charge will be stored by the CNTs deposited on the counter electrode. We take advantage of the fact that our metallo-organic assemblies are electrochromic³ (i.e. change their optical properties with respect to an applied potential), in order to indicate the charge state of our devices by their color.

References:

1. Dubal, D. P.; Ayyad, O.; Ruiz, V.; Gómez-Romero, P. Hybrid Energy Storage: The Merging of Battery and Supercapacitor Chemistries. Soc. Rev. 2015, 44, 1777– 1790.
2. Zhai, Y.; Dou, Y.; Zhao, D.; Fulvio, P. F.; Mayes, R. T.; Dai, S. Carbon Materials for Chemical Capacitive Energy Storage. Mater. 2011, 23, 4828–4850.
3. Elool Dov, N.; Shankar, S.; Cohen, D.; Bendikov, T.; Rechav, K.; Shimon, L. J. W.; Lahav, M.; van der Boom, M. E. Electrochromic Metallo-Organic Nanoscale Films: Fabrication, Color Range, and Devices. Am. Chem. Soc. 2017, 139, 11471–11481.