Preparation of Sulfur-Doped and Pitch-Based Hard Carbon and Its Lithium-Ion Storage Performance

Hard carbon is regarded as one of the most promising anode materials for lithium-ion batteries due to its high specific capacity. However, the commercial application of hard carbon is severely hampered by its poor rate performance and first Coulombic efficiency. Herein, sulfur-doped pitch-based hard carbon materials were prepared through co-carbonization of high-softening-point pitch precursor and sulfur-rich crosslinking agent from the copolymerization of sulfur and dicyclopentadiene. It was found that the crosslinking between the pitch precursor and sulfur-rich polymer, as well as sulfur-doping during the co-carbonization process, could tailor the microscopic crystal structure of the hard carbons. Notably, when the mass ratio of pitch precursor to sulfur polymer was 6∶1, the as-prepared hard carbons with suitable microcrystalline layer spacing and pore structure showed a reversible capacity of 398 mA·h/g with a 73.0% first Coulombic efficiency at 50 mA/g, and a superior rate performance of 176 mA·h/g at 4000 mA/g, which originated from sulfur-doping and rich microcrystal defects.