With nanotechnology, new electrode materials have softened the boundaries between electrochemical double-layer capacitors (EDLCs) and batteries based on Na+ or Li+ ion intercalation. Thus, a pseudocapacitive device and a battery can share the same type of negative electrode in different asymmetric configurations, i.e., the same negative electrode combined with a positive high surface area porous electrode (i.e., activated carbon) or a battery-type positive electrode, such as mixed layered oxides derived from abundant elements (i.e., Na, Fe, Mg, and Mn). When compared to lithium-ion batteries (LIBs), electrochemical capacitors present very high cyclability and low energy density. In contrast, sodium-ion batteries (SIBs) present lower energy densities, although of the same order of magnitude, and lower aging aspects, coulomb efficiency, and average working voltage. In this regard, we will explore the boundaries between sodium-ions electrochemical capacitors and batteries. We will produce buckypaper electrodes with good physical and electrochemical properties based on MXene (Ti3C2), carbon materials (e.g., hard carbons and carbon nanotubes) and mixed metal oxides. The electrodes' performance will be studied using electrochemical and physicochemical characterization techniques. Specifically, regarding SIBs, the studies will also be performed via operando Raman spectroscopy, focusing on these devices' energy efficiency and cyclability. We expect the consolidation of new composite materials as negative electrodes of pseudocapacitor devices and SIBs, and positive electrodes of SIBs with higher average working voltages and better aging and cyclability aspects, resulting in safer and more sustainable batteries.
News published in Agência FAPESP Newsletter about the scholarship: