Electrocatalytic tungsten boride quantum dots anchored reduced graphene oxide as the desolvation promotor for efficient sulfur redox kinetics

Abstract

Lithium-sulfur (Li-S) batteries boast a multitude of compelling attributes, chief among them being their exceptional energy density and relatively low raw material costs. However, the sluggish redox kenitics of sulfur stemming from the considerable desolvation energy barrier and the notorious shuttle effect of lithium polysulfides, pose significant challenges in the commercialization of Li-S batteries. In this work, ultra-fine WB quantum dots were in-situ and uniformly dispersed on reduced graphene oxide nanosheets (WB-rGO) by mild melting-salt method, in which the abundant oxygen-containing functional groups in graphene oxide effectively prevent the agglomeration of WB. Such ultra-fine WB quantum dot as well as dual-active sites stemming from W and electronics-deficient B, confer the WB-rGO composite with improved electrochemical active surface area for dissociating Li+-solvents molecules and catalyzing polysulfides transformations, thus improving cycling and rate performance of Li-S battery. Hence, the cells with WB-rGO@PP maintained a stable long-term cycling (650 mAh g-1 after 900 cycles at 1C with an average decay rate of 0.038% per cycle) and an impressive rate capability (740 mAh g-1 at 4C). Even at a sulfur loading of 4.7mgcm-2, the cell performed a high areal capacity of 3.6 mAh cm-2 after 200 cycles.