Despite their promising potential, the real performance of lithium-sulfur batteries is still heavily impeded by the notorious shuttle behavior and sluggish conversion of polysulfides. Complex structures with multiple components have been widely employed to address these issues by virtue of their strong polarity and abundant surface catalytic sites. Nevertheless, the tedious constructing procedures and high cost of these materials make the exploration of alternative high-performance sulfur hosts increasingly important. Herein, we report an intrinsic defect-rich hierarchically porous carbon architecture with strong affinity and high conversion activity toward polysulfides even at high sulfur loading. Such an architecture can be prepared using a widely available nitrogen-containing precursor through a simple yet effective in situ templating strategy and subsequent nitrogen removal procedure. The hierarchical structure secures a high sulfur loading, while the intrinsic defects strongly anchor the active species and boost their chemical conversion because of the strong polarity and accelerated electron transfer at the defective sites. As a result, the lithium-sulfur batteries with this carbon material as the sulfur host deliver a high specific capacity of 1182 mAh g–1 at 0.5 C, excellent cycling stability with a capacity retention of 70% after 500 cycles, and outstanding rate capability, one of the best results among pure carbon hosts. The strategy suggested here may rekindle interest in exploring the potential of pure carbon materials for lithium-sulfur batteries as well as other energy storage devices.

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Thermal reaction experiments of vacuum residuum were conducted in a micro-batch reactor at 410–480 °C. The product yield variation with time indicated that the secondary cracking reaction mainly occurs in the heavy fraction of the liquid product. A narrow fraction model for low-severity thermal cracking of heavy oil, with the secondary reaction taken into account, was developed. To simplify the reaction network, a pseudo-lump was introduced, which was defined as the fraction generated from the secondary cracking reaction of the heavy fraction (420–540 °C). Furthermore, a sequential method to estimate rate constants in complex models was employed, and the kinetic parameters were estimated by Arrhenius’ law. The model-predicted lump yields agreed well with the experimental values. The ratio of secondary cracking/primary cracking was calculated. The result indicated that, even at the initial stage of the reaction, the ratio in the heavy distillate reaches up to 15–36%; therefore, the secondary cracking reaction cannot be ignored even in low-severity thermal cracking.

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