A carbonyl-rich conjugated organic compound for aqueous rechargeable Na⁺ storage with wide voltage window workability

Organic compounds have become an important electrode material for aqueous electrochemical energy storage. However, organic electrodes still face poor performance in aqueous batteries due to insufficient electrochemical activity. In this work, a novel conjugated quinone compound containing a rich carbonyl group was designed. The quinone compound was synthesized by a simple dehydration reaction of pyrene-4,5,9,10-tetrone (PTO) and 1,2-diaminoanthraquinone (1,2-AQ); it contains 4 pyrazines (CN) from AQ and 4 carbonyl groups (CO), as well as a large number of active sites and the excellent conductivity brought by its conjugated structure ensures the high theoretical capacity of PTO-AQ. In the context of aqueous sodium ion batteries (ASIBs), the electrode material known as PTO-AQ exhibits a notable reversible discharge capacity of 117.9 mAh/g when subjected to a current density of 1 A/g; impressively, it maintained a capacity retention rate of 74.3 % even after undergoing 500 charge and discharge cycles, a performance significantly surpassing that of pristine PTO and AQ. Notably, PTO-AQ exhibits a wide operating voltage range (-1.0-0.5 V) and a cycle life of up to 10,000 cycles. In situ Raman and ex situ measurements were used to analyze the structural changes of PTO-AQ during charge and discharge and the energy storage mechanism in NaAC. The effective promotion of Na⁺ storage brought by a rich carbonyl group was obtained. The structural energy level and electrostatic potential of PTO-AQ were calculated, and the active center distribution of PTO-AQ was obtained. This work serves as a guide for designing high-performance aqueous organic electrode materials that operate across a wide voltage range while also explaining their energy storage mechanism.