Scalable Synthesis of Robust Polyimide Covalent Organic Framework Cathodes for High-Capacity and Durable Aqueous Zn-Ion Batteries.

Aqueous Zn-ion batteries are promising due to their high safety, low cost, and environmental friendliness, but developing cathode materials with high capacity, excellent rate capability, and long cycle life remains challenging. Herein, we design and construct a series of highly crystalline, stable, and porous polyimide covalent organic frameworks (COFs) featuring large conjugated aromatic structures and dense multiple active groups, making them ideal cathodes for Zn-ion batteries. The resulting COF cathodes deliver a high reversible capacity of 320 mAh/g at 0.1 A/g (energy density 240 Wh/kg), excellent rate capability (55% retention at 100 A/g), and exceptional durability (98% capacity retention after 50,000 cycles at 10 A/g), placing them among the best reported COF-based cathodes. A combination of in situ/ex-situ characterizations and DFT calculations reveals the behavior and mechanism of charge storage in detail. Benefiting from gram-scale flux synthesis, we assemble large-sized functional COF-based pouch batteries that achieve a reversible capacity of 300 mAh/g at 0.1 A/g (total capacity 0.6 Ah, approaching theoretical design), along with outstanding rate capability and long-term stability. This work paves a new avenue for designing multifunctional COFs toward high-performance, long-life aqueous Zn-ion batteries.