Lithium−sulfur (Li/S) technology holds great promise for efficient, safe, and economic next-generation batteries. However, commercialization is limited by some issues, which are related to the fast degradation of Li/S cells and poor rate capability. Existing strategies addressing these issues are often unsuitable for commercialization because of their complexity and lack of scalability. This Letter presents a simple, cheap, and scalable synthesis of a sulfur-based cathode material from commercially available poly(methyl methacrylate)/poly-(acrylonitrile) (PMMA/PAN) fibers. Thermal conversion of PMMA/PAN fibers with elemental sulfur yields sulfurized poly(acrylonitrile) (SPAN) with up to 46 wt % covalently bound sulfur. The fibrous morphology with cylindrical macropores helps to form electronic conduction networks in the cathode and provides directed diffusion pathways for ions. Consequently, these Li/SPAN cells show low internal resistances, high initial capacities up to 1672 mAh•g −1 sulfur , high rate capabilities up to 8C, and excellent cycle stabilities over 1200 cycles. In addition, structure and postmortem analysis allow the correlation of electrochemical performance with SPAN's chemical structure.

Solvent-induced phase separation (SIPS) and thermally-induced phase separation (TIPS) derived poly(acrylonitrile) (PAN) based monoliths with different morphology and specific surface area were prepared and thermally converted into monolithic sulfur-poly(acrylonitrile) (SPAN) materials for use as active cathode materials in lithium-sulfur batteries. During thermal processing, the macroscopic monolithic structure fully prevailed while significant changes in porosity were observed. Both the monomer content in the precursor PAN-based monoliths and the tortuosity of the final monolithic SPAN materials correlate with the electrochemical performance of the SPAN-based cathodes. Overall, percolation issues predominate. In percolating SPAN-based cathode materials, the specific capacity of the SPAN-based cells increases with decreasing tortuosity. All monolithic SPAN materials provided highly reversible and cycle stable cathodes reaching reversible discharge capacities up to 1330 mA h g sulfur À1 @ 0.25C, 900 mA h g sulfur À1 @ 2C and 420 mA h g sulfur À1 @ 8C.