A multifunctional separator based on dilithium tetraaminophthalocyanine self-assembled on rGO with improved cathode and anode performance in Li–S batteries

Li–S batteries are strong candidates for next-generation energy-storage applications. However, practical cells face critical challenges including the dissolution and shuttling of polysulfides on the cathode as well as the uncontrolled dendrite growth and degradation of the anode. Herein, we demonstrate a multifunctional separator based on dilithium tetraaminophthalocyanine (Li2TaPc) self-assembled on rGO that exhibits a comprehensive regulation effect on important ion transport properties to address the above issues in one configuration. Li2TaPc presents strong sulfiphilic/lithiophilic binding sites for the confinement of polysulfides within the cathode region to improve sulfur utilization. Charge transfers from the central cavity of the TaPc ligand to the rGO promotes the dissociation of Li+ cations to produce additional charge carriers. The negatively-charged TaPc ligand exhibits strong electrostatic repulsions to the salt anions and hinders their migration across the separator. The apparently increased Li+ transference number (0.41–0.89) suppresses dendrite formation and improves the reversibility of the Li anode. Meanwhile, the strong coordination effects of Li+ with Li2TaPc enable a high retention of Li + conductivity. The comprehensive functionalities of the separator result in significantly improved electrochemical performance of Li–S full cells. Pouch cells with a high areal sulfur loading and limited electrolyte addition are also demonstrated.