EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Among the various solutions, energy can in particular be stored electrochemically in batteries and supercapacitors. Although supercapacitors are now commercially available, they still require improvements of electrode materials, electrolytes and integration in systems, especially for enhancing their energy density. For reaching these objectives, various strategies have been proposed in the literature, involving the development of new materials, new geometries and new electrolytes. Thus, new positive electrode materials have been developed involving exfoliation and restacking processes of lamellar “building blocks”: AxHyMnO2 for their pseudocapacitive properties and AxHyCoO2 for their high electronic conductivity (10-3 to 1 S.cm-1). These composite materials have been designed by stacking nano-objects of different compositions so as to combine complementary properties to go towards the optimization of performance in terms of power and energy.
In particular, we are interesting to a better understanding of the mechanisms of charge storage on the surface of manganese oxide and cobalt oxide particles of nanocomposite materials for hybrid supercapacitors. Our study is focused on CoO(OH) materials. The surface reactivity (basic and redox character) of the synthesized compounds, which consist in aggregates of particles with 60-100 nm length, has being explored from the adsorption of SO2 molecules followed by X-ray Photoemission Spectroscopy analyses. A kinetic studied of the reactivity allowed us to identify three steps in the adsorption mechanism of our CoO(OH) samples. The coupling of XPS and first-principal calculations allows us to establish a link between the surface reactivity in the identified domains, the formation of sulfate and sulfite species, and the cobalt Co3+ and Co4+ species of the active sites along with the underlying electronic processes. First results obtained on MnO2 materials of different morphologies and size (rigid and veil-like platelets) and will also be discussed.