Preparation And Electrochemical Properties Of Tin Selenide-Based Anode Materials For Lithium Ion Batteries

Lithium-ion batteries（LIBs）are extensively utilized among the field of portable electronic devices and electric vehicles because of their low self-discharge while relatively high energy density.But the commercial graphite anode for LIBs holds a theoretical capacity of merely372 m Ah g^-1,which cannot satisfy the large-scale application.It is known that tin-based anode materials have the advantages of high theoretical capacity,environmental friendliness,and economy,and is regarded as an engaging electrode candidate for the next generation anode of LIBs.It includes metallic tin,tin oxide（Sn O₂,Sn₃O₄）,tin sulfide（Sn S,Sn S₂）and tin selenide（SnSe,SnSe₂）.Among them,SnSe has a theoretical capacity of up to 847 m Ah g^-1,but its inherent weak conductivity leads to sluggish kinetics,and experience the serious volume variation during the charge and discharge operation can leads to structural instability,resulting in the poor rate capability and cycle performance.We attempt to address these issues by constructing ideal nanostructures and synthesizing heteroatom-doped graphene composites,and investigating their lithium storage properties.The main research contents are as follows:Oriented growth of SnSe crystals assisted by amino-organic complexes of tin.The effects of different reaction times,ligand species and material concentrations on the crystal morphology of SnSe were investigated.A possible mechanism for the directional growth of SnSe crystals assisted by metal complexes is proposed from the point of view of reaction.SnSe nanorods with a length of about 1-2μm and a width of about100 nm were synthesized by using thioacetamide as the organic ligand to form metal complexes with Sn²⁺.The phase transition of SnSe undergoing redox reaction was characterized by XRD diffraction to study the lithium ion storage mechanism of SnSe material.The SnSe nanorods exhibited good electrochemical performance,delivering an initial specific capacity of 683.6 m Ah g^-1 at 100 m A g^-1 and maintaining 302 m Ah g^-1 specific capacity after 100 cycles.The composite of SnSe nanoparticles in situ grown on the surface of nitrogen/sulfur dual-doped reduced graphene oxide（SnSe@N/S-r GO）was prepared by a two-step hydrothermal reaction.The effects of nitrogen/sulfur doping on the lithium storage properties of the composites were investigated by material characterization means and electrochemical testing methods.The effects of different SnSe loadings and nitrogen/sulfur doping contents on the lithium storage properties of the composites were studied.The electrochemical reaction kinetics and charge storage behavior of SnSe@N/S-r GO were investigated by cyclic voltammetry,revealing the reason for its excellent capacity.SnSe@N/S-r GO exhibits a specific capacity of 785 m Ah g^-1 after 100 cycles at 200 m A g^-1 and 568 m Ah g^-1after 200 cycles at 500 m A g^-1,the average decay of capacity per cycle is merely 0.24%.