Pd quantum dots supported on rhombic dodecahedral porous carbons connected by CNTs as multifunctional electrocatalysts for Li–S batteries

Abstract

Lithium sulfide (Li2S) is considered as one of the promising cathode materials for secondary batteries owing to its high lithium storage capacity and low–cost advantage of sulfur. However, the commercial application of Li2S is hindered by the sluggish reaction kinetics of electrochemical conversion from Li2S to S and the shuttle effect of their soluble lithium polysulfides (LiPSs). Herein, we report a multifunctional electrocatalyst composed of 5.9 wt% Pd quantum dots supported on rhombic dodecahedral porous carbons connected by CNTs (Pd@RDPC–CNT) to improve the electrochemical reaction kinetics of Li2S and to alleviate the shuttle effect of LiPSs. The Pd@RDPC–CNT/Li2S nanocomposite exhibits a low first activation barrier of 2.56 V and fast reaction kinetics with a high reversible capacity of 1119 mAh g−1 at 0.2 A g−1, very close to the theoretical capacity of 1166 mAh g−1. The superior electrochemical performance including high reversible capacity, good rate capability and long–term cycling stability over 1000 cycles can be attributed to the multifunctional electrocatalyst of Pd@RDPC–CNT with high catalytic activation, strong LiPSs adsorption and high electronic/ionic conductivity, which is demonstrated by our experimental results and DFT calculation results. This study provides a way to apply Li2S to secondary batteries by using multifunctional electrocatalysts.