Solid solution of semiconducting contorted small molecules for high-performance Li/Na-ion host electrodes
Multicomponent solid solutions have attracted wide attention because they have great potential to improve the physical and chemical properties of pure materials. However, there are stringent prerequisite conditions, such as shape similarity and isomorphism of the crystal phase, for forming a solid solution. These conditions have not been studied extensively in organic solid solution materials, although they have great advantages in terms of the energy storage properties of materials. Herein, we investigate the solid solution of semiconducting contorted hexabenzocoronene (cHBC) and its tetra-fluorinated derivative (FcHBC) as small molecules for a high-performance Li/Na-ion host electrode. Our systematic study, combined with a grazing incidence wide-angle X-ray scattering (GIWAXS) characterization and a computational study thereof, reveals that the molecular interrelationship between cHBC and FcHBC molecules forms P21/n crystal phase of cHBC/FcHBC solid solution owing to their similar molecular and crystal structures. The continuous solid solution of cHBC/FcHBC electrodes, in particular, not only effectively enhances the electron charge transfer without adding the conducting agent but also delivers a better rate capability as both Li- and Na-ion hosting electrodes. Furthermore, the solid solution electrodes maintain a reliable cycling performance in the conventional aprotic electrolyte, which suggests that organic solid solution electrodes are promising organic electroactive materials for alkali ion-based energy storage cells.