Construction of high-performance lithium–sulfur batteries with NiCu bimetallic phthalocyanine-functionalized separators

Lithium–sulfur batteries are considered to be an ideal alternative to the next generation of lithium-ion batteries due to their high energy density and low cost. However, the shuttle effect of lithium polysulfides (LiPSs) seriously affects their electrochemical performance. In this paper, we designed and synthesized two-dimensional NiCu bimetallic polyphthalocyanine (NiCuTnPc), monometallic polyphthalocyanine nickel (NiTnPPc), and monometallic polyphthalocyanine copper (CuTnPPc) with strong electron-withdrawing groups. These materials were used to modify the separator on the cathode side of lithium–sulfur batteries to explore the effect of the phthalocyanine metal center on promoting the catalytic conversion of LiPSs. It was found that NiCuTnPc could accelerate the redox reaction of LiPSs due to its synergistic catalytic effect. The results showed that the interaction between Ni and Cu can regulate the electronic structure and improve the catalytic ability of the material, thus effectively promoting the reversible conversion of Li₂S and further improving the rate performance and cycle life of the battery.