Inverse vulcanization of all-cis-fluorinated cyclohexylacrylate: Tailored polymers for Li-S battery cathode materials

The use of elemental sulfur as an alternative feedstock for polymer synthesis by inverse vulcanization has shown to be an elegant, yet simple way towards materials with high sulfur contents. Besides, their use as fertilizers, optical lenses, and heavy metal sorbents, those materials are considered as next generation cathode materials for lithium-sulfur batteries with exceptionally high specific capacities. However, Li-S battery cathodes typically exhibit a rapid capacity fading caused by a phenomenon called ‘polysulfide shuttle-effect’. Herein, we report the synthesis of a terpolymer comprised of all-cis-fluorinated cyclohexyl acrylate and triethoxyvinylsilane via inverse vulcanization in N-methyl-2-pyrrolidone at 150$^◦$C with subsequent silane polycondensation to obtain stable Li-S battery cathodes with sulfur contents of 61 wt%. Electrochemical analysis of Li-S cells showed higher lithium-ion diffusion, superior cycling capacity retention (98 % after 200 cycles at 1C), and suppressed self-discharge (0.02 V after 21 days) compared to the non-fluorinated reference material (38 % capacity retention after 200 cycles at 1C and 0.07 V self-discharge after 21 days). ... mehrThe highly polar nature of fluorinated cyclohexane moieties is believed to significantly inhibit the ‘polysulfide shuttle-effect’, by coordination of polysulfides.