N-heterocyclic compound with conjugated systems and multiple pyrazine and quinone redox active sites for high-performance aqueous zinc ion batteries

Abstract

Organic electrodes featuring low cost, abundant sources, and designable structure hold a bright future in aqueous zinc ion batteries (AZIBs). Nevertheless, most organic electrodes still encounter drawbacks such as sluggish kinetics, low capacity, and poor cycling stability. Herein, an anthraquinone derivative (PAQD) is reported for AZIBs. The five-membered ring structure and multiple redox center of PAQD achieve a high active site density, offering a brilliant capacity of 308 mAh g⁻¹ under 0.05 A g⁻¹. Additionally, the establishment of anthraquinone units and N atoms not only expand π conjugated plane, but also improve conductivity, thus obtaining a superior rate capacity (100 mAh g⁻¹ under 10 A g⁻¹). Besides, the flexible molecular framework enables PAQD to obtain a superior cycling lifespan with 30,000 cycles under 10 A g⁻¹ (with a 73 % capacity retention). The comprehensive in-situ and ex-situ characterizations and theoretical calculations prove that CO and CN groups are the redox active sites of PAQD cathode and reveal the mechanism of Zn²⁺/H⁺ co-storage. Impressively, PAQD electrodes exhibit decent specific capacity in high load mass, low-temperature environments, and flexible devices. This work demonstrates a method for designing small molecule organic electrodes with high redox density and expands the applications in the field of flexible AZIBs.