Quaternized polymer binder for lithium–sulfur batteries: The effect of cation structure on battery performance

Lithium–sulfur (Li–S) batteries are great candidates for energy storage systems, but need to overcome the issues of low sulfur utilization and polysulfide shuttling for use in large-scale commercial applications. Recently, quaternized polymers have received much attention for their polysulfide trapping properties due to electrostatic interaction. In this work, we report a series of polyarylether sulfone (PSF) binders with different cation structures including imidazolium (Im), triethylammonium (Tr), and morpholinium (Mo). The ability of the these quaternized binders and the conventional poly(vinylidene fluoride) or PVDF binder to capture polysulfide increases in the order of PVDF << PSF-Mo < PSF-Tr< PSF-Im. The delocalized charge on the imidazolium cation may promote the interaction between PSF-Im and polysulfide as indicated by an X-ray photoelectron spectroscopic study. The PSF-Im based cathodes showed the highest capacity retention (77% at 0.2 C after 100 cycles and 84% at 0.5 C after 120 cycles), and the best rate capability. This work demonstrates the importance of the cation structure in the design of efficient quaternized binders for high performance Li–S batteries.