Curtailing Carbon Usage with Addition of Functionalized NiFe2O4 Quantum Dots:Toward More Practical S Cathodes for Li-S Cells

摘要

Smartcombination of manifold carbonaceous materials with admirable functionalities(like full of pores/functional groups,high specific surface area) is still a mainstream/preferential way to address knotty issues of polysulfides dissolution/shuttling and poor electrical conductivity for S-based cathodes.However,extensive use of conductive carbon fillers in cell designs/technology would induce electrolytic overconsumption and thereby shelve high-energy-density promise of Li-S cells.To cut down carbon usage,we propose the incorporation of multi-functionalized NiFe2O4 quantum dots(QDs) as affordable additive substitutes.The total carbon content can be greatly curtailed from 26%(in traditional S/C cathodes) to a low/commercial mass ratio(~5%).Particularly,note that NiFe2O4 QDs additives own superb chemisorption interactions with soluble Li2Sn molecules and proper catalytic features facilitating polysulfide phase conversions and can also strengthen charge-transfer capability/redox kinetics of overall cathode systems.Benefiting from these intrinsic properties,such hybrid cathodes demonstrate prominent rate behaviors(decent capacity retention with ~526 mAh g^-1 even at 5 A g^-1) and stable cyclic performance in LiNO3-free electrolytes(only ~0.08% capacity decay per cycle in 500 cycles at 0.2 A g^-1).This work may arouse tremendous research interest in seeking other alternative QDs and offer an economical/more applicable methodology to construct low-carbon-content electrodes for practical usage.