Effect of a One-Dimensional Columnar Structure on the Cathode Active Material Performance of Single-Component Hexaazatriphenylene Derivatives

Organic cathode active materials for lithium-ion batteries (LIBs) have attracted considerable attention as viable alternatives to conventional cathode active materials based on rare-element-containing transition metal oxides. Structural pores that efficiently intercalate Li+ ions play an important role in a typical organic cathode active material in terms of battery performance. In this study, we investigated the correlation between packing structure and the charge/discharge properties of redox-active hexaazatriphenylene (HAT) derivatives composed of one-dimensional (1D) columnar structures. We synthesized 3,7,11-triethoxy-2,6,10-tricyano-1,4,5,8,9,12-hexaazatriphenylene (HATCNOC2), a single-component HAT derivative containing alternating electron-accepting nitrile (−CN) and electron-donating ethoxy (−OC2H5) groups. Furthermore, HATCNOC-poly, which was synthesized by the olefin metathesis of 3,7,11-tri(5-hexenyloxy)-2,6,10-tricyano-1,4,5,8,9,12-hexaazatriphenylene (HATCNO-hex) bearing 5-hexenyloxy side chains, exhibited improved structural stability. The testing of battery performance revealed that HATCNOC2 exhibits a fast charge/discharge performance (353.5 mA h g–1 at a current density of 500 mA g–1 in the first cycle) that originates from the rapid diffusion of Li+ ions via the intercolumnar voids between its 1D columnar structures, whereas HATCNOC-poly exhibits a slow charge/discharge performance (188.5 mA h g–1 at a current density of 500 mA g–1 in the first cycle) due to the absence of a 1D columnar structure and intercolumnar voids, thereby limiting any such diffusion process. This study provides clear structural insights into the design of organic-molecule-based cathode active material packing structures for LIBs.