Improving organic cathode cycling stability through molecular modification of a dianhydride structure for aqueous rechargeable zinc-ion batteries

Rechargeable zinc-ion batteries (ZIBs) are an attractive energy storage system for the growing renewable energy sector but still face technological bottlenecks such as a lack of high-capacity cathode materials with long cycling stability. Organic redox-active molecules, a class of cathode material, offer potential for high discharge capacities. However, they suffer from undesired degradation reactions over repeated charge and discharge cycling causing limited capacity retention, emphasizing there is still a need for structural modifications to enhance material stability. In this work, [ N , N ′-bis(2-anthraquinone)]-perylene-3,4,9,10-tetracarboxydiimide (PTCDI-DAQ) was synthesized from 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and 2-aminoanthraquinone for use as cathode material in ZIBs. The discharge capacity of PTCDI-DAQ cathodes was found to be 186 mAh/g. At 100 mA/g, PTCDI-DAQ showed a capacity retention of 76.0% by cycle 20, outperforming PTCDA that retained only 33.3%. X-ray diffraction revealed crystal structure alterations of both PTCDA and PTCDI-DAQ starting at the first discharge, which could contribute to the observed capacity degradation. This work proposes an approach towards enhancing the capacity retention of organic cathodes that will accelerate the development and commercialization of ZIBs.