Periodic Reporting for period 1 - CYMEIT (Cyanated macrocycles for electron and ion transport)
Reporting period: 2018-09-01 to 2020-08-31
Battery electrodes are a potential application of such materials. Batteries can help to reduce carbon dioxide emissions by storing clean electricity from renewable sources for periods with high demand and by making the electricity available for electric vehicles and other means of transport. However, there are severe environmental and ethical issues associated with the currently used heavy metal-based electrode materials. Organic materials, such as those developed during this project, can provide a more sustainable alternative.
The overall objective of the project was to develop redox-active π-conjugated macrocycles for excellent electron and ion transporting materials and to apply these materials in devices. It can be concluded that such materials can indeed be obtained. The developed macrocycles showed outstanding performance in battery electrodes under fast‐charge/discharge conditions as well as extraordinarily stable cycling performance. The macrocyclic geometry of the molecules and the related properties were found to be highly beneficial for this application.
While the synthesis of cyanated macrocycles was found to be challenging via the proposed synthetic routes, the synthesis of π-conjugated macrocycles with other electron-withdrawing groups was highly successful. In line with the objectives of the project, π-conjugated macrocycles with different aromatic units were synthesised and their properties were investigated. The investigation of the properties has advanced our fundamental understanding of such compounds. The subsequent work on applications has exceeded the expectations by far. The cyclic shape of the molecules was found to be highly beneficial for application as organic battery electrode materials. Even the simplest compound paracyclophanetetraene, a macrocycle without substituents synthesised as a reference compound for the substituted macrocycles, performed surprisingly well when tested as anode material in sodium-ion batteries. These results were recently published (Angew. Chem., Int. Ed. 2020, 59, 12958-12964).
The results of the project will significantly contribute to the further development of organic materials for battery electrodes and related applications. The project has also provided exciting new insights into the fundamental properties of π-conjugated macrocycles related to local and global (anti)aromaticity in such molecules.