N-heterocyclic π‑conjugated quinone cathodes with multiple chelation for robust sodium batteries

Abstract

Redox-active organic materials have arisen as promising electrode materials for rechargeable batteries owing to their merit of structural diversity and environmental compatibility. However, their practical application in sodium ions batteries (SIBs) has been hindered by the high dissolution in liquid electrolytes and the sluggish redox kinetics. Herein, a series of π-conjugated N-heterocyclic quinones (TTAQ, DPT, DNQ-PQ, and DNQ-PTO) with chelation groups were systematically developed. Among them, DNQ-PTO exhibited exceptional performance, delivering a reversible capacity of ~275 mA h g-1 at 0.1A g-1, which referred to a six-electron redox process involving a four-electron transfer for C=O/C-O and a two-electron transfer for C=N/C-N group. Moreover, the DNQ-PTO cathodes demonstrated remarkable rate capability, superior cycling stability (~89% capacity retention after 6,000 cycles at 5 A g⁻¹), and excellent low-temperature performance (~91.4% capacity retention over 100 cycles at −40 °C). The outstanding electrochemical performance of DNQ-PTO stemmed from its extended conjugation system and well-dispersed chelation groups, which facilitated efficient charge delocalization and structural stability. This work demonstrated that the critical challenges in capacity, stability, and kinetics of organic electrode materials could be addressed through molecular structure optimization, which established a new paradigm for high-performance organic electrodes.