UC Santa Cruz

Polysulfide shuttling has been the primary cause of failure in lithium-sulfur (Li-S) battery cycling. Here, we demonstrate an nucleophilic substitution reaction between polysulfides and binder functional groups can unexpectedly immobilizes the polysulfides. The substitution reaction is verified by UV–visible spectra and X-ray photoelectron spectra. The immobilization of polysulfide is in situ monitored by synchrotron based sulfur K-edge X-ray absorption spectra. The resulting electrodes exhibit initial capacity up to 20.4 mAh/cm2, corresponding to 1199.1 mAh/g based on a micron-sulfur mass loading of 17.0 mg/cm2. The micron size sulfur transformed into nano layer coating on the cathode binder during cycling. Directly usage of nano-size sulfur promotes higher capacity of 33.7 mAh/cm2, which is the highest areal capacity reported in Li-S battery. This enhance performance is due to the reduced shuttle effect by covalently binding of the polysulfide with the polymer binder.