Sulfonic Acid Based Complex Framework Materials (CFM): Nanostructured Polysulfide Immobilization Systems for Rechargeable Lithium–Sulfur Battery

Lithium-sulfur (Li-S) secondary batteries with sulfur cathodes and theoretical energy density of ∼2600 Wh/kg, are promising high energy-density system for next-generation electric-vehicles (EVs) potentially mitigating the gravimetric and volumetric energy density limitations of existing lithium-ion (Li-ion) batteries. Herein, a chemically synthesized sulfonic acid-based complex framework material (CFM) termed as (SCFM), was used as sulfur host (S-SCFM) to prevent polysulfide dissolution in Li-S batteries. The S-SCFM based CFM cathodes show an initial capacity of 1190 mAh/g and a capacity of 1044 mAh/g after 100 cycles. In addition, the S-SCFM based CFM cathodes exhibited good cycling stability with a minimal fade rate of ∼0.0012% per cycle. XPS analysis of the cycled separators with the S-SCFM electrodes shows complete absence of polysulfide species after 100 charge-discharge cycles. It was also identified that the SCFM based CFM chemically binds sulfur via -C-S- linkages thereby exhibiting an affinity for the polysulfide species formed during the charge-discharge cycles. As a result, the SCFM based CFM prevent polysulfide species from dissolving and diffusing into the electrolyte. A thorough understanding of these engineered SCFM based CFM sulfur host in Li-S battery outlined herein will be vital in designing promising sulfur hosts for next generation sulfur cathodes in Li-S batteries.