A Truxenone-based Covalent Organic Framework as an All-Solid-State Lithium-Ion Battery Cathode with High Capacity

All-solid-state lithium ion batteries (LIBs) are ideal for energy storage given their safety and long-term stability. However, there is a limited availability of viable electrode active materials. Herein, we report a truxenone-based covalent organic framework (COF-TRO) as cathode materials for all-solid-state LIBs. The high-density carbonyl groups combined with the ordered crystalline COF structure greatly facilitate lithium ion storage via reversible redox reactions. As a result, a high specific capacity of 268 mAh g⁻¹, almost 97.5 % of the calculated theoretical capacity was achieved. To the best of our knowledge, this is the highest capacity among all COF-based cathode materials for all-solid-state LIBs reported so far. Moreover, the excellent cycling stability (99.9 % capacity retention after 100 cycles at 0.1 C rate) shown by COF-TRO suggests such truxenone-based COFs have great potential in energy storage applications.     

The influence of alkyl chain substitution pattern on the two- and three-dimensional self-assembly of truxenone discogens

The synthesis of new discotic liquid crystals and the study of self-assembly behaviours are important for the supramolecular chemistry and organic electronics. Six new truxenone discogens 7a–f with different alkyl chain substitution patterns were synthesised and all exhibited only one three-dimensional ordered hexagonal columnar mesophase with wide temperature ranges including room temperature, which were characterised with polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. The self-assembly behaviours in solutions were studied by using concentration-variation ¹H NMR and scanning electron microscopy. The two-dimensional ordered self-assembly of 7c and 7f on the liquid–solid interface of highly oriented pyrolytical graphite were imaged by scanning tunnelling microscopy, and the results showed that the two-dimensional monolayer self-assembled structures on the atomically flat surfaces can be controlled by the peripheral alkyl chain substitution patterns.