One-Step Integration of Sulfonated Polymer Films with Separators for Shuttle Mitigation in Lithium-Sulfur Batteries

Interfacial polymerization (IP) offers a rapid and inexpensive method to fabricate thin polymer films. In this work, a one-step, scalable IP reaction between a tri-acyl chloride monomer and sulfonated diamine monomer is employed to add a dense, charge-selective sulfonated thin-film coating onto a commercial separator to improve selective transport in lithium-sulfur batteries. The coating effectively suppresses polysulfide shuttling, enhancing capacity retention, though at the expense of compromised rate performance due to hindered lithium conduction through the dense film. Fractional substitution of the tri- functionalized acyl chloride monomer for a di-functionalized analog reduces the film crosslink density, which improves rate performance but decreases uniformity in film coverage. Uniform film coverage is achieved upon addition of a small fraction (0.25 wt%) of higher reactivity, non-sulfonated diamine in the IP reaction. This optimized thin film coating breaks the rate-capacity retention tradeoff, enabling a capacity of 885.5 mAh g-1 after 100 cycles at 0.2 C while still reaching over 800 mAh g-1 during rate testing at 2 C.