《A Stable Covalent Organic Framework Cathode Enables Ultra-Long Cycle Life for Alkali and Multivalent Metal Rechargeable Batteries》

Organic electrode materials are considered to have great potential for sustainable and large-scale energy storage in the future. However, its low redox activity and high solubility in organic electrolytes seriously restrict its application. In this work, a highly stable organic framework material HATN-HHTP was synthesized by bonding high-capacity organic molecules HATN (hexaazatetraazonaphthalene) and HHTP (hexahydroxybenzophenanthrene) in ether-oxygen bonding form by using organic synthesis to improve the structural stability of HATN and inhibit its dissolution. By further compounding the CNTs, the resulting HATN-HHTP@CNT cathode achieves high capacity utilization (> 210 mAh g-1) due to the more fully exposed active sites and stronger conductivity of the composite. More stable chemical bonds and pseudocapacitance characteristics have enabled HATN-HHTP@CNT to achieve the longest cycle life of a cathode material in its class today, approximately 4100 hours (6900 turns, 100% capacity retention) in lithium battery testing. The cathode also shows good activity and stability in Mg and Al batteries, which further proves that it has the potential of universal cathode. Spectroscopic characterization and DFT theoretical calculations show that the pyrazine group in the material provides the redox active site and the ether-oxygen bond provides the structural stability. This work provides design ideas for the synthesis of long-life organic electrodes.

https://doi.org/10.1016/j.ensm.2022.03.033