P-type semiconducting covalent organic frameworks for Li-ion battery cathodes with high-energy density

P-type semiconducting organic cathode materials have received extensive attention in recent years due to their high redox potential, which however suffer from the low capacity and unsatisfactory energy density. Here, two-dimensional covalent organic frameworks (COFs) namely TAPA-Pz-COF and TATTA-Pz-COF were constructed by one p-type semiconductor methylphenazine possessing high capacity with another p-type semiconductor tris-(4-aminophenyl)amine (TAPA) and 4,4′,4′'-(1,3,5-triazine-2,4,6-triayl)trainline (TATTA), respectively. Electron microscopy, powder X-ray diffraction, and N2 adsorption-desorption measurements demonstrate the highly ordered mesoporous structure of both COFs with a Brunauer−Emmett−Teller surface area of 472–855 m2 g–1 and pore size of 3.2–3.9 nm. The cyclic voltammetry curves of these two COFs display a pair of broad redox peaks at ca. 3.15/3.05 V vs. Li+/Li, revealing their p-type semiconductor nature and enabling them to be high energy density cathodes for Li-ion battery. In particular, TATTA-Pz-COF shows a high specific capacity of 324 mA h g–1 at 100 mA g–1 with a record-high energy density of 737 W h kg−1 among all the organic polymer and COF electrodes. This work will help to develop high-performance and low-cost organic cathodes for energy storage.