Supramolecularly Confined Catalysis in Polyphthalocyanine-Crown-Ether Frameworks Boosts Sulfur Redox Kinetics

Metal phthalocyanines are considered as potent catalysts in lithium-sulfur (Li-S) chemistry. However, their adsorption capability is deficient to inhibit polysulfides from shuttling, which in turn retards the S-redox reaction in the cathode. Here we report flexible, two-dimensional (2D) polyphthalocyanine-crown-ether (PPc-CE) frameworks that provide a supramolecularly confined space created with the single-atom catalytic nickel phthalocyanine nodes and crown-ether linkers as Li host. Electrochemical and theoretical analyses reveal that a cooperative redox catalysis with the enhanced lithiophilicity of PPc-CE-coated carbon nanotubes (PPc-CE/CNTs) boosts Li-S redox kinetics and, meanwhile, suppresses the growth of Li dendrites for the long term. A Li||S cell employing PPc-CE/CNT catalysts delivers a high discharge capacity of 1,363 mAh g^-1 at 0.1C and still retains a specific capacity of ∼700 mAh g^-1 over 500 cycles at 1C. Our work provides insights into the molecular design of redox catalysts for Li-S batteries based on 2D polymers.