Modelling the structure-property relationships in redox active π-conjugated materials

Electrochemical energy storage (EES) devices, including batteries and supercapacitors, rely heavily on electrode materials that govern their efficiency and durability. Organic functional materials have emerged as promising electrode candidates owing to their low cost, sustainability, and superior mechanical/thermal properties. This study systematically investigates three classes of such organic conjugated redox materials: para-graphdiyne (p-CNGDY), conjugated redox polymers (OCRPs), and hexaazatriphenylene-hexacarboxylic acid (HATCOOH) and its alkali metal derivatives (HATCOOM, M=Na/K). The first project focuses on graphdiyne derivatives. By modulating the number and positions of cyano groups, we used density functional theory (DFT) to analyze their bulk structures, packing modes, and layer arrangements. Results demonstrate that cyano group arrangement profoundly affects interlayer distances, electronic band structures, and lithium adsorption capacities, clarifying the redox mechanism connecting functional groups to material properties. The second project examines OCRPs (polyquinoxalines/PQL and SBBL). Combining DFT and broken-symmetry DFT (BS-DFT), we identified multi-radicaloid characteristics in their electronic structures across multiple redox states. Standard DFT fails to accurately estimate reorganization energies, while BS-DFT yields physically meaningful trends. DFT and force-field analysis further determined the interaction sites and optimal adsorption locations between polymer segments and cations, revealing the interaction mechanism. The third project explores HATCOOH and HATCOOM. Based on experimental X-ray structures, we adopted ωB97X-D DFT to investigate their electrochemical properties and alkali metal adsorption sites, simulating metal ion intercalation. Future work will extend to larger clusters to probe Na/K diffusion pathways and the electrochemical performance of HATCOOM anodes for Na/K-ion batteries. Overall, this study provides a bottom-up understanding of structure–property relationships in organic conjugated redox materials, correlating electrochemical states, metal-organic substrate interactions, and the physicochemical mechanisms of EES devices.