Adsorption-Assisted Redox Center in Porous Organic Frameworks for Boosting Lithium Storage

Due to the designable structure and capacity, organic materials are promising candidates for lithium-ion batteries. Herein, we report a novel type of porous organic frameworks (POFs) based on the coupling reaction of diazonium salt as the anodes for lithium ion storage. The active center containing an azo group and the adjacent lithium-philic adsorption site is constructed to investigate the electrochemical behaviors and reaction mechanism. As synthesized POF material (named as POF-AN) exhibits high reversible lithium storage capacities of 523 mAh g^-1 at 0.5 A g^-1 and 445 mAh g^-1 at 2.0 A g^-1 after 1500 cycles, showing excellent cycle stability and rate performance. The detailed characterizations reveal that the azo group can act as an electrochemical active site that reversibly bonds with Li-ions, and the adjacent oxygen atoms can electrostatically adsorb with Li-ions to promote the lithium storage reaction. This adsorption-assisted three-atom redox center is beneficial to synergistically enhance the adsorption and intercalation of lithium ions, which can further improve the capacity and cycle stability. By replacing the precursor, it is also facile to synthesize more similar structure types. The reversible redox chemistry of the adsorption-assisted three-atom active center provides new opportunities for the development of long lifespan and high-rate organic anodes.