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

Abstract

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.