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 of lithium-ion batteries for its high specific capacity. However, the commercial application of hard carbon is severely hampered by its poor rate performance and first Coulomb 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 copolymerization of sulfur and dicyclopentadiene (DCPD). It is found that the crosslinking between pitch precursor and sulfur-rich polymer and the 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 is 6∶1, the as-prepared hard carbons with suitable microcrystalline layer spacing and pore structure show a reversible capacity of 398 mA·h/g with 73.0% first coulomb efficiency at 50 mA/g and superior rate performance of 176 mA·h/g at 4000 mA/g originated from the sulfur-doping and rich microcrystal defects.