Metallo‐organic assemblies for dual-function electrochromic supercapacitors

The rapid and global increase in green energy demands has driven the research and development of alternative and efficient energy storage materials and devices.¹ Energy storage systems can be divided to two main categories: batteries and capacitors.² Batteries have a high energy density, whereas capacitors have a high power density. Hybrid supercapacitors combine battery-like and capacitive electrodes. 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 molecular based materials is expected to result in flexible, readily available devices with enhanced functionalities.

We introduced a hybrid device which is composed of carbon nanotubes (CNTs) and PSS:PEDOT, as the counter electrode,³ and metallo-organic assemblies (MA), as the working electrode. Our MA are robust, showed high stability in a non-inert environment at high temperatures. These assemblies can be deposited directly on conductive substrates. During the oxidation of the MA 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 MA are electrochromic⁴ (i.e. change their optical properties with respect to an applied potential) to generate dual-function devices. These devices indicate their charge state by their color.