Reducing the deposit of discharge products and suppressing the polysulfide shuttle are critical to enhancing reaction kinetics in Li-S batteries. Herein, a Pt@Ni core-shell bimetallic catalyst with a patch-like or complete Ni shell based on a confined catalysis reaction in porous carbon spheres is reported. The Pt nanodots can effectively direct and catalyze in situ reduction of Ni2+ ions to form core-shell catalysts with a seamless interface that facilitates the charge transfer between the two metals. Thus, the bimetallic catalysts offer a synergic effect on catalyzing reactions, which shows dual functions for catalytic oxidation of insoluble polysulfides to soluble polysulfides by effectively reducing the energy barrier with simultaneous strong adsorption, ensuring a high reversible capacity and cycling stability. A novel process based on the Pt@Ni core-shell bimetallic catalyst with a patch-like Ni shell is proposed: electronic migration from Ni to Pt forces Ni to activate Li2 S2 /Li2 S molecules by promoting the transformation of Li-S-Li to Ni-S-Li, consequently releasing Li+ and free electrons, simultaneously enhancing protonic/electronic conductivity. The presence of the intermediate state Ni-S-Li is more active to oxidize Li2 S to polysulfides. The Li2 S bound to adjacent Pt sites reacts with abundant -S-Li species and then releases the Pt sites for the next round of reactions.
Keywords: catalytic oxidation; lithium-sulfur batteries; nanoreactors; polysulfide conversion; synergic effects.
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.