Sulfur-doped biocarbon as a sulfur host and a polysulfide trapping agent in lithium-sulfur batteries
摘要
Lithium-sulfur batteries (LSBs) offer an impressive energy density of 2600 Wh kg−1. However, the insulating nature of sulfur renders significant kinetic challenges, leads to volume expansion during cycling, and contributes to polysulfide shuttle effects, which reduces the coulombic efficiency and cyclic stability. This work uses an in situ sulfur-bioderived carbon (S-doped Bio-C) from the waste cauliflower stems to recycle waste into a sulfur host in LSBs. These Bio-C benefits are due to their sustainability, low cost, and scalability. The S-doped Bio-C and S composite fabricated on a 3D carbon fiber (S-doped Bio-C-S@CF) cathode exhibits an initial discharge capacity of 500 mAh g−1 with a stable capacity of 425 mAh g−1 at 500 mA g−1 with 85% capacity retention and a coulombic efficiency of 99% after 350 cycles. The decrease in Rct after cycling (⁓4 Ω.cm2) compared to the 1st (⁓7 Ω.cm2) and an increase of diffusion coefficient indicates an improved reaction kinetics upon cycling. Therefore, the Bio-C-S@CF benefits the LSBs by assisting the polysulfide shuttle phenomena, providing good electrolyte wettability for the Li-ion diffusion, resulting in improved sulfur utilization and minimized polarization. Bio-C-S@CF also strongly interacts with the polysulfides, considerably enhancing cycling stability over long-term cycling, and is believed to be a cathode in LSBs.