High-performance all-solid-state sulfurized polyacrylonitrile batteries enabled by iodine coupling

초록

Sulfurized polyacrylonitrile (SPAN) is an attractive cathode material for next-generation lithium (Li)-ion batteries owing to its low cost, facile synthesis, and high theoretical capacity. However, its practical use in all-solid-state batteries is hindered by poor intrinsic ionic and electrical transport properties. This study reports a high-areal-capacity LiI-incorporated all-solid-state Li–SPAN battery with high sulfur utilization, achieved through an unexpected chemical interaction between SPAN and iodine. Structural and spectroscopic analyses reveal that iodine is not merely dispersed as an additive, but forms a reversible chemical interaction with the SPAN/Carbon nanotube (SPAN/CNT) matrix. This interaction alters the local electronic environment of SPAN, enhancing electrical transport during iodine association and lowering the interfacial charge-transfer resistance of the composite cathode during iodine dissociation. As a result, the iodine-coupled composite cathode enables more efficient sulfur conversion and delivers improved specific capacity. X-ray photoelectron spectroscopy and differential capacity analyses further show that iodine promotes more complete conversion to Li2S during discharge and facilitates the reconversion of Li2S to sulfur upon charge through reversible coupling/decoupling behavior. Consequently, the iodine-coupled SPAN cathode delivered a high areal capacity of 8.41 mAh cm−2 at 0.05 C and sustained stable cycling over 200 cycles at 0.15 C, with a capacity decay of only 0.23% per cycle. This straightforward iodine-coupling strategy provides an effective route to constructing high-areal-capacity, high-utilization SPAN cathodes for advanced all-solid-state Li–sulfur batteries.

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