Electronic band structure engineering of π-d conjugated metal-organic framework for sodium organic batteries

Cu-mediated bipolar-type extended π-conjugated microporous polymers for lithium-ion battery cathodes with high energy density and fast-charging capability

Engineering lithium-ion battery (LIB) cathode materials with high energy density and fast-charging capability plays a significant role in the development of next-generation lightweight and high-performance storage devices for near space vehicles and electric aircraft. Herein, we propose a post-coordination strategy using Cu2+ to mediate a redox-active bipolar-type conjugated microporous polymer (CMP) incorporating porphyrin and pyrrole active groups (PPCMP). The as-synthesized Cu2+ mediated PPCMP (PPCMP-Cu) not only retains the high surface area (618 m2 g-1) of PPCMP, but also features an extended π-conjugated structure, a narrowed band gap, increased bipolar active sites, and optimized micro/mesopores, maximizing the utilization of active sites and enhancing ion diffusion kinetics. As the LIB cathode, PPCMP-Cu demonstrates an improved ion diffusion rate of 10-9 cm2 s-1 and a higher capacity of 285.1 mA h g-1 at 300 mA g-1, compared to the 10-10 cm2 s-1 and 135.5 mA h g-1 achieved by PPCMP. Moreover, PPCMP-Cu delivers an exceptional energy density of 702 W h kg-1 (based on the cathode) at 300 mA g-1 and an ultra-fast charging capability of 12 464 W kg-1 with an ultra-short charging time of just 76 s at 5 A g-1. Besides, PPCMP-Cu shows a stable cycling life, with a 0.010% capacity fading rate per cycle at 2 A g-1 over 5000 cycles. This work paves an avenue for designing high-performance CMP cathode materials for LIBs with high energy density and fast-charging capability.