Dual-carbon Modified SnS-based Composite For Lithium/sodium-ion Storage

Tin sulfide?SnS?can store lithium/sodium ions through conversion and alloying reactions with high theoretical specific capacity.However,SnS is easily agglomerate and grow into mi-croplates during the thermal reduction in the conventional preparation procedure.Moreover,due to the drastic volume change of SnS and Sn growth during discharge/charge process,the SnS anode faces fast capacity fading in the lithium/sodium storage process.To improve the cycling stability of SnS during lithium/sodium ion storage process,we constructed a series of dual-carbon modified SnS-based composite,which is prepared from thermal reduction of SnS₂/r GO precursor with carbon coated on the surface and reduced graphene oxide?r GO?as anchored framework.First,ethanol vapour is decomposed and coated on the surface of SnS during the thermal reduction of SnS₂,with the growth of SnS being effectively confined.In the discharge/charge process,the volume change of SnS is relieved due to the confined grain size.r GO combined with carbon coating provide fast channel for electron transport,as well as buffer the volume expansion,and thus the SnS composite owns enhanced structural stability and greatly im-proved lithium storage cyclic performance.The structural optimized SnS@C/r GO composite exhibits a high initial reversible capacity of 934 m Ah g^-1 and maintains 918 m Ah g^-1 after 330cycles at the current density of 1 A g^-1.In our second work,the polydopamine?PDA?was pre-coated on the surface of SnS₂,and then SnS₂ was reduced to SnS in the high temperature calcination process,with the sur-face-coated PDA in-situ decomposed into N-doped carbon layer.The pre-coated PDA layer isolated SnS₂ nanoparticles and effectively played a limiting role during high temperature re-duction.Thus,the N-doped carbon coated SnS nanoplate is smaller in size and more uniform when compared with ethanol vapor derived carbon coated SnS,and its cyclic stability during reversible lithium storage is furtherly enhanced.The further structural optimized SnS@N-C/r GO composite shows an initial reversible capacity of 885.3 m Ah g^-1 and remains824 m Ah g^-1 after 550 cycles.In our third work,we use polypyrrole as carbon source to prepare dual-carbon modified SnS-SnS₂@N-C/r GO composite by reducing the calcination temperature and realize the par-tial reduction of SnS₂.The SnS₂ and SnS mutually confined each other during the calcination process,thus realizing small grain size.Moreover,the stepwise electrochemical reaction be-tween SnS₂ and SnS confined each other and thus alleviate the volume effect.As anode mate-rial for lithium-ion batteries,the SnS-SnS₂@N-C/r GO maintains a high reversible capacity of1233.3 m Ah g^-1 after 450 cycles at 1 A g^-1.When evaluated as anode for sodium-ion batteries,the SnS-SnS₂@N-C/r GO maintains a reversible capacity of 479.3 m Ah g^-1 after 120 cycles at1 A g^-1.