Hexaazatriphenylene Based Polyimide with Dense Dual Redox Sites as a High-Performance Organic Cathode for Lithium-Ion Batteries

Organic polymers are promising candidates as cathode materials for lithium storage, however, suffer from low theoretical capacity due to the presence of multiple inactive components in the polymers. Herein, a novel hexaazatriphenylene-based polyimide with high theoretical capacity (436 mAh g-1) is developed via the precise design of monomers and controllable synthesis of corresponding polymers. The as-prepared polymers possess rich edge pyrazine nitrogen (CN) and carbonyl groups (CO), well-defined porosity, and conjugated structure, benefiting for high capacity, rapid ion and charge transport. The resultant polymers electrode achieves a high specific capacity of 303 mAh g-1 at 100 mA g-1, high-rate capability (171 mAh g-1 even at 8 C, 1 C = 400 mA g-1), and stable cycle performance with a high capacity retention of 93.8% at 500 mA g-1 over 200 cycles. Combined experimental and theoretical calculations reveal that both CO and CN sites in the polyimide are served as redox sites for lithium storage, providing high specific capacity. This work offers a novel approach for the development of polymeric cathode materials with dense redox sites for next-generation energy-dense batteries. A novel hexaazatriphenylene (HAT)-based polyimide with high-density dual redox site (pyrazine nitrogen and carboxyl groups) is developed. Benefiting from its insolubility for stable electrode structure, porous structure for rapid ion transport, and conjugated structure/complex with carbon nanotube for quick charge transport, the resultant HAT-based polyimide electrode achieves high-capacity and superior electrochemical performance.image

Automated summary

A novel organic polymer cathode material with high theoretical capacity and superior electrochemical performance is developed through precise monomer design and controllable synthesis. The polymer electrode possesses abundant redox sites, well-defined porosity, and conjugated structure, enabling high capacity and rapid ion/charge transport.