Poly(quinone-thiourea) with Improved Auxiliary Coordination Zn²⁺ Insertion/Extraction Positive Performance for Aqueous Zinc Ion Battery Cathodes

Abstract

Sustainable organic quinone-based polymers exhibit numerous promising advantages in cathode application, and suitable structure design is important to improve their electrochemical performances. In this work, a designed organic material structure of redox units linked by auxiliary coordination chains poly(quinone-thiourea) is achieved and used as a cathode for aqueous zinc ion batteries. The cell displays improved electrochemical performances with a maximum discharge specific capacity of 211 mA h g–1 at 0.02 A g–1 and long cycle performance of 83% capacity retention after 1000 cycles under 0.1 A g–1 (118 mA h g–1 initial discharge capacity). The Zn2+ storage mechanism through the ex situ XPS investigations proves that the oxygen atoms of phenol and the sulfur and nitrogen atoms of the thiourea group all contribute to the Zn2+ intercalation, which stabilizes the Zn2+ coordination and improve the specific capacity. The ex situ FT-IR also supports the redox of quinone carbonyl and the coordination of the thiourea group with Zn2+. Furtherly, the thiourea groups acting as auxiliary coordination sites can alleviate the zinc deposition on the cathode surface and improve the redox reversibility and long cycle performance. Such a structural design is expected to be a promising strategy for developing high-performance organic cathode materials for multivalent ion batteries.