Synergistically homogeneous and heterogeneous catalytic strategy enables fast sulfur electrochemical conversion kinetics

Abstract

Heterostructures composing of two coupling components are of significance for the kinetic improvements of sulfur electrochemistry. However, they encounter a challenge of being incompetent to simultanesouly catalyze the soluble lithium polysulfides via both homogeneous and heterogeneous ways. In this work, a synergistic homogeneous and heterogeneous catalytic process has been implemented in a delicately designed CoTe/Te heterostructure, which is evenly distributed on a densifying carbon framework. The highly conductive CoTe component can efficiently immobilize lithium polysulfides and heterogeneously catalyze their conversion, while the Te component can homogenously catalyze the lithium polysulfides conversion in a way of forming the electrochemically active soluble polytellurosulfide species with intrinsically accelerated redox kinetics. Besides, the densified carbon framework makes a good balance between macropores and mesopores, guaranteeing the electron conduction and alleviating the electrode volume changes. Benefited from these structural merits, the Li-S batteries based on CoTe/Te heterostructure host exhibit superior rate capability (778.6 mAh/g at 4C, 1.4 times higher than sulfur cathodes without heterostructures) and cycle stability (536.7 mAh/g after 1000 cycles at 2C, 1.6 times than sulfur cathodes without heterostructures).