Research On Structure Control And Lithium Storage Performance Of Hollow MnS Core-shell Composite Electrode Material

MnS possesses considerable research potential owing to its high theoretical capacity(616 m Ah g^-1),eco-friendliness and crustal abundance.However,MnS exposes tardy ion migration kinetics during lithiation process,and the agglomeration of nanoparticles(NPs)constituted in the delithiation/lithiation process,which distressingly impedes its cycle performance and rate performance.Contrary to the above weak points,this dissertation devised and synthesisd MnS@N-C composites with a hollow core-shell structure,The test results show that when the mass ratio of the current drive body S@MnO₂ to dopamine hydrochloride(DA)is 5:1and the heat treatment temperature is 500°C,the MnS@N-C composite possess the best structure and electrochemical performance.At the current density of 0.1 A g^-1,MnS@N-C indicate a high specific capacity of 1157 m Ah g^-1.This hollow core-shell structure can effectively alleviate volume changes.Furthermore,in accordance with the finite element analysis,we can conclude that as the thickness of carbon layer increases,the volume expansion method of MnS will alternate.When the thickness of the carbon layer is 5 nm,the stress in the process of lithium insertion is tensile stress,and the volume of MnS expands outward,reaching a certain limit,causing the hollow structure to collapse.When the thickness of the carbon layer is 12.5 nm,the tensile stress and the compressive stress almost offset each other,ensuring the structural stability of the MnS curd during the lithiation process.When the thickness of the carbon layer is 22.5 nm,the inward distribution of the interfacial stress points to the expansion of the space reserved for the volume,which is not enough to break the carbon coating layer.Based of the above,firstly,S@MnO₂@PDA@GO precursor is obtained by electrostatic self-assembly technology,and the hollow core-shell MnS@N-C@r GO composite material with 3D conductive network is obtained at different calcination temperatures.When the calcination temperatures is 700°C,As the MnS@N-C@r GO runs a long cycle of 1000 cycles at the current density of 5 A g^-1,the specific capacity could be preserved at 294.6 m Ah g^-1.The hollow core-shell structure reserves space for the volume change of the material.The carbon layer on the surface of the nano-curd MnS not only improves the electronic conductivity of the overall structure,but also limits the volume expansion of the MnS sphere.The ultra-thin graphene sheet is cross-linked and bonded with the nano-curd MnS@N-C to play the role of secondary restriction.Two-dimensional honeycomb graphene and nano-curd MnS@N-C form a 3D three-dimensional conductive network structure,giving fully forthputting to the structural advantages of the both.