Multifunctional Polymeric Phthalocyanine‐Coated Carbon Nanotubes for Efficient Redox Mediators of Lithium–Sulfur Batteries

Abstract

AbstractMetal phthalocyanine (Pc) complexes are considered to be promising functional organic materials owing to their tunable properties and unique π‐electron structure. Despite these advantages, the application of polymeric metal Pc into lithium–sulfur (LiS) batteries has yet to be explored. Herein, this work demonstrates a molecular design of multifunctional polymeric cobalt Pc with triethylene glycol linkers (TCP) that provide a redox mediating capability for the Co ion in the center of the Pc, a strong polar interaction of N atoms with Li, and the lithiophilic sites of crown ether mimicking linkers for highly efficient LiS batteries. As verified by electrochemical and theoretical analyses, the cooperative redox mediating and lithiophilic effects of TCP coated onto multiwalled carbon nanotube (TCP/MC) are attributed to the facilitated conversion reaction kinetics of S cathodes for the high utilization efficiency of S and the inhibition of polysulfide shuttling. Consequently, the S@TCP/MC delivers high discharge capacity of 1392.8 mA h g−1 and high‐rate capacity of 667.9 mA h g−1 at 5.0 C. Moreover, this cathode achieves a high capacity retention of 81.5% over 200 cycles, along with a high areal capacity of 6.83 mA h cm−2 at 0.2 C with a high S loading of 6.6 mg cm−2.