Carbon-Based Conductive Frameworks and Metal Catalytic Sites Derived from Cross-Linked Porous Porphyrin-Based Polyimides for Enhanced Conversion of Lithium Polysulfides in Li-S Batteries

Shuttling behavior of lithium polysulfides (LiPSs) resulting from insufficient adsorption capacity, delayed diffusion, and sluggish catalytic kinetics severely hampers further exploitation of lithium-sulfur (Li-S) batteries. A reasonable and optimized composition of the cathodic host in Li-S batteries is an efficient approach to utilize polysulfides and impede their loss. The combination of the factors preferable porosity parameters, efficient electrical framework, and intrinsic catalytic sites achieves the kinetic equilibrium of adsorption-dispersion-conversion to significantly restrain the shuttling behavior of LiPSs. In this article, carbon-based metal-doping materials (CR-Por-PPIs@800) derived from cross-linked porous porphyrin-based polyimides are constructed by a few simple reaction steps, which are used as the cathode host in Li-S batteries. These well-fabricated materials exhibit excellent porosity parameters to adsorb LiPSs and limit their diffusion shuttle and afford a high-temperature-treated conductive carbon skeleton to accelerate charge/ion transfer and expedite LiPS diffusion. Besides, metal-based substances serve as catalytic sites to elevate the conversion reaction kinetics of LiPSs. By virtue of the superior kinetic equilibrium, including adsorption from the well-constructed carbon-based framework, diffusion in the conductive network, and conversion via efficient metal catalytic sites, these CR-Por-PPIs@800 sulfur cathodes exhibit excellent cycle stability (0.051-0.081% attenuation rate under a current of 1C) and superior rate behavior. Remarkably, CR-Por-Cu-PPI@800 maintains up to 520 mAh g(-1) after 500 cycles at 1C.