In situ formed FeS_(2)@CoS cathode for long cycling life lithium-ion battery

Pyrite FeS_(2)exhibits an ultrahigh energy density(1671 W·h·kg^(-1),for the reaction of FeS_(2)+4Li=Fe+2Li_(2)S)in secondary lithium-ion batteries,but its poor cycling stability,huge volume expansion,the shuttle effect of polysulfides,and slow kinetic properties limit its practical application.In this work,we synthesize a composite structure material CoS on FeS_(2)surface(FeSx@CoS,1<x≤2)by using a cobalt-containing MOF to improve its cycle stability.It is found that CoS inhibits the side reactions and adsorbs polysulfides.As a result,the modified FeS_(2)shows a higher discharge capacity of 577 mA·h·g^(-1)(919 W·h·kg^(-1))after 60 cycles than 484 mA·h·g^(-1)(778 W·h·kg^(-1))of bare pyrite FeS_(2).This efficient strategy provides a valuable step toward the realization of high cycling stability FeS_(2)cathode materials for secondary lithium-ion batteries and enriches the basic understanding of the influence of FeS_(2)interfacial stability on its electrochemical performances.