Tortuosity‐Limited Ion Transport in Coal Waste‐Derived Carbons Dictates the Performance of Lithium–Sulfur Batteries

Hierarchical porous carbons (HPCs) are attractive sulfur host materials for lithium–sulfur (Li–S) batteries because they can accommodate high sulfur loadings, suppress polysulfide migration, and enhance ion transport. However, quantifying the intrinsic transport limitations of porous hosts remains challenging, as most methods rely on electrolyte infiltration, thereby obscuring the specific effect of microstructure. In this work, HPCs derived from coal waste are synthesized and systematically investigated to reveal how pore architecture governs transport and electrochemical behavior. Using computational methods, we calculated the tortuosity of the porous hosts without interference from liquid‐phase properties. The materials exhibit porosity/tortuosity ( ε / τ ) ratios of 1.59, 1.47, and 1.20, which correlate strongly with rate capability, polarization, and sulfur utilization. The sample with the lowest tortuosity delivers the highest capacity and most stable performance at elevated current densities, whereas increased tortuosity leads to pronounced transport limitations. These results demonstrate that tortuosity‐limited, intrinsic microstructural transport plays a dominant role in determining Li‐S cathode performance and highlight electrolyte‐independent tortuosity measurements as a powerful design tool for optimizing carbon hosts.