Facile Nitrogen Doping of Electrospun Mesoporous Carbon Nanofibers via Urea Addition for Polysulfide-Confining Li-S Cathodes and Interlayers

Lithium-sulfur (Li-S) batteries offer high theoretical capacity, but polysulfide dissolution and shuttling cause rapid capacity fade. Nitrogen functional groups can anchor polysulfides, yet in our previous work, introducing them through a post-carbonization cyclized-PAN treatment sacrificed much of the carbon nanofiber (CNF) mesoporosity, and Nfunctionalizing both cathode and interlayer performed worst. Here, nitrogen is introduced during fiber formation by adding urea to a PAN/PMMA precursor before gas-assisted electrospinning, followed by stabilization, carbonization, and CO2 activation. This gives N-doped mesoporous CNFs with better control over the balance between nitrogen content and pore structure. Across four cathode/interlayer combinations ,every cell with at least one N-doped component outperformed the undoped cell. The N-doped cathode with N-doped interlayer performed best, delivering 1271 mAh g-1 at 2C with the lowest charge-transfer resistance (8 Ω vs. 11 Ω undoped). Post-mortem XPS revealed Li-N interactions and polysulfide retention, strongest in the interlayers. Precursor-level nitrogen doping is therefore an effective route to Li-S cathodes and interlayers that balance nitrogen and mesoporosity.