Insight into pore structures evolution and applications in lithium-sulfur battery of pitch fractions-based activated carbons

Highlights: • Illustrating the relationship between molecular/chemical structure and pyrolysis reactivity by introduced an index D. • Elaborating the pore structure evolution of porous carbons derived from pitch fractions which have different reactivity. • Establishing the relationship between structure and electrochemical performance of fraction-based porous carbons. -- Abstract: Difference in composition of pitch determines the porosity of pitch-based activated carbons on a large scale. Toluene-soluble (TS), toluene-insoluble and pyridine-soluble (PS), pyridine insoluble (PI) fractions were separated by extracting pitch with different solvents followed by the activation using alkali KOH to obtain porous carbons which were used as sulfur host materials. It is found that different fractions possess different reactivity which mainly relies on the molecular weight and structures. The light component TS, equipped with more active sites, tends to be activated to porous carbon with well-developed pores and it promotes the optimal distribution of sulfur compared to heavy fractions PS and PI. When used as sulfur host, TS-based carbon displays better electrochemical performance compared to PS/PI-based carbon. The relationship between the structure and electrochemical performance of fraction-based porous carbon has been established. The findings provide a method for judging and regulating the structure and electrochemical performance of porous carbons derived from pitch-based precursors.