Hierarchical Nitrogen‐Doped Carbon Hosts for Low‐Polarization Sulfur Cathodes in Molten‐Salt Aluminum–Sulfur Batteries

Rechargeable aluminum–sulfur (Al–S) batteries are promising candidates for low‐cost and high‐capacity energy storage, but their practical performance is restricted by the insulating nature of sulfur/discharge products, sluggish conversion kinetics, and structural instability of sulfur cathodes. Herein, a corn‐cob‐derived nitrogen‐doped activated carbon host (NAC) was prepared through a one‐step activation–carbonization process and used as a sulfur host for molten‐salt Al–S batteries. Compared with undoped AC, NAC exhibits a wrinkled hierarchical porous structure, which promotes sulfur dispersion, facilitates ion/electron transport, and helps accommodate volume variation during cycling. Benefiting from this host structure, the S@NAC cathode delivers an initial discharge capacity of 1557 mAh g ⁻¹ at 1 A g ⁻¹ and retains 501 mAh g ⁻¹ after 500 cycles, clearly outperforming S@AC. S@NAC also shows reduced electrochemical polarization, with a peak potential separation of 0.289 V at 1 mV s ⁻¹ , compared with 0.698 0.658 V for S@AC. Electrochemical impedance spectroscopy further reveals a much lower charge–transfer resistance for S@NAC. X‐ray diffraction and X‐ray photoelectron spectroscopy analyses support the reversible conversion between S and Al ₂ S ₃ during discharge/charge. This work provides a feasible host‐design strategy for improving sulfur conversion kinetics in molten‐salt Al–S batteries.