Lithium-sulfur batteries hold great promise due to sulfur’s high abundance and theoretical capacity; however, Li-S batteries undergo the formation of soluble polysulfide intermediates which can lead to sulfur depletion and ultimately cell death. Sulfurized polymers like sulfurized polyacrylonitrile, SPAN, can be used to mitigate this problem, but SPAN cathodes experience a drop in capacity from the first cycle to subsequent cycles. The functional groups of SPAN were examined to see where the capacity loss comes from in the work by Wang et al. (J. Am. Chem. Soc. 2023). This work demonstrates the non-aromatic functional groups lead to capacity loss and show a modified synthesis to reduce this irreversible capacity.