Multiscale design of organosulfur cathode with superior cycling stability in ether electrolytes under practical conditions by selenium co-doping

The sulfurized polyacrylonitrile (SPAN), featuring the sulfur atoms covalently anchored with the polyacrylonitrile, gives a chance to avoid the dissolutionprecipitation mechanism of the lithium polysulfides (LiPS) in traditional Li-S batteries. However, such a solid-solid conversion in SPAN cathodes is an electrolyte-dependent behavior, and current studies lack a detailed description of the dissolution mechanism of the covalently-bonded sulfur, which is important for understanding the sulfur reduction reaction (SRR) pathway in SPAN cathodes. In this work, interestingly, we discovered that the LiPS still dissolves from the SPAN matrix in the ether-based electrolytes, which may promote the SRR kinetics. It also demonstrates that the sulfur-PAN bonds in the cathode-electrolyte interfaces are vulnerable to be attacked by the ether molecules. A selenization strategy was therefore introduced to further reinforce the bonding between the sulfur atoms and the SPAN matrix. Impressively, the as-designed cathode realizes rapid and stable lithium storage with 77% of capacity retention over 200 cycles under high mass loading of ~7 mg cm⁻², low electrolyte/sulfur ratio of ~2.9 μL mg⁻¹, and limited N/P ratio of 1.5. It is believed that the multiscale design strategy could pave a new avenue for fabricating stable organosulfur cathodes for next-generation energy storage.