Integrating the multiple functionalities in metalloporphyrin porous organic polymers enabling strong polysulfide anchoring and rapid electrochemical kinetics in Li–S batteries

Abstract

Ready lithium polysulfide (LiPS) diffusion and sluggish redox kinetics hamper lithium–sulfur (Li–S) batteries from achieving high cyclability and rate capability. Herein, metalloporphyrin-based porous organic polymers [Por(M)-POPs] integrated with electrolyte accessible, Li-ion conductive, LiPS-trapping, and LiPS-catalytic functions were elaborately engineered by constructing a conformal Por(M) and imidazolium connector to form a 2D polymeric ionic liquid (PIL) framework through a click reaction. The synthesized POPs are incorporated with a single-atomic catalyst and fully exposed lithiophilic sites to afford effective catalysis and a robust chemical/physical barrier for LiPSs as well as improve electrolyte affinity and Li-ion transport. Consequently, the coordinated Mg or Co atom Por(M)-POP hybridized with graphene nanosheets (GNs) as separator coatings. Our Por(M)-POP/GN-modified separators showed a high initial capacity of >1500 mA h g⁻¹ at 0.1C, stable cycling life (only <0.05% capacity decay rate per cycle at 1C) with 1000 cycles, excellent rate performance (>830 mA h g⁻¹ at 2C), anti-self-discharge ability, and high areal capacity up to 2.8–3.1 mA h cm⁻² with a sulfur loading of ≈4 mg cm⁻² after 100 cycles. This work opens up a new insight into POP integrating single-atomic catalysts and PIL framework to effectively alleviate LiPS shuttling and accelerate the electrochemical kinetics.