Selective Adsorption and Electrocatalysis of Polysulfides through Hexatomic Nickel Clusters Embedded in N-Doped Graphene toward High-Performance Li-S Batteries

摘要

The shuttle effect hinders the practical application of lithium-sulfur(Li-S)batteries due to the poor affinity between a substrate and Li polysulfides(LiPSs)and the sluggish transition of soluble LiPSs to insoluble Li2S or elemental S.Here,we report that Ni hexatomic clusters embedded in a nitrogen-doped three-dimensional(3D)graphene framework(Ni-N/G)possess stronger interaction with soluble polysulfides than that with insoluble polysulfides.The synthetic electrocatalyst deployed in the sulfur cathode plays a multifunctional role:(i)selectively adsorbing the polysulfides dissolved in the electrolyte,(ii)expediting the sluggish liquid-solid phase transformations at the active sites as electrocatalysts,and(iii)accelerating the kinetics of the electrochemical reaction of multielectron sulfur,thereby inhibiting the dissolution of LiPSs.The constructed S@Ni-N/G cathode delivers an areal capacity of 9.43 mAh cm-2 at 0.1 C at S loading of 6.8 mg cm-2,and it exhibits a gravimetric capacity of 1104 mAh g-1 with a capacity fading rate of 0.045％per cycle over 50 cycles at 0.2 C at S loading of 2.0 mg cm-2.This work opens a rational approach to achieve the selective adsorption and expediting of polysulfide transition for the performance enhancement of Li-S batteries.