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 theissues 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 propertiesdue to electrostatic interaction. In this work, we report a series of polyarylether sulfone (PSF) binderswith 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 PVDFbinder to capture polysulfide increases in the order of PVDF << PSF-Mo < PSF-Tr< PSF-Im. The delocalizedcharge on the imidazolium cation may promote the interaction between PSF-Im and polysulfide asindicated by an X-ray photoelectron spectroscopic study. The PSF-Im based cathodes showed the highestcapacity retention (77% at 0.2 C after 100 cycles and 84% at 0.5 C after 120 cycles), and the bestrate capability. This work demonstrates the importance of the cation structure in the design of efficientquaternized binders for high performance Li–S batteries.