Study On The Preparation Of Tin Selenide-based Anode Material And Its Lithium Storage Behavior

Tin-selenide-based material is one of the candidates for the new generation of lithium ion batteries anode materials due to its high theoretical specific capacity and abundant reserves.However,during the process of repeated lithium insertion/extraction,the anode material of tin-selenide-based material has a huge volume variation.At present,there are still some problems in the research progress of tin selenide materials:one-dimensional SnSe materials are difficult to synthesize;SnSe/C composite materials are only simple physical effects;the lithium storage mechanism of SnSe2 is controversial.In order to solve the above problems,this paper has carried out the following three works:(1)We prepared one-dimensional SnSe nanobelts by using Sn nanorods as precursor through liquid-phase selenization.And the one-dimensional belt-like structure can increase the rate of charge transfer.As the anode electrode of lithium ion batteries,the material exhibits higher initial Coulombic efficiency and better rate performance.The initial discharge and charging specific capacities were 1087.9/954.9 mA h g-1,and the initial coulomb efficiency was 87.8%,at the current density of 0.1 A g-1.The average capacity retention at 1 A g-1 vs.0.1 A g-1 is as high as 46.4%.(2)We prepared a graphene-coated SnSe nanobelts(SnSe NB@rGO)framework material by liquid-phase selenization and thermal treatment by using a graphene-coated Sn nanorod aerogel as a precursor.SnSe nanobelts are uniformly dispersed in the rGO framework through physical and chemical interaction.Based on the SnSe nanobelt itself capable of buffering volume expansion and improving charge transfer capability,the three-dimensional interconnected rGO framework can provide space for the volume change of SnSe,but also give full play to its excellent electrical conductivity.As the negative electrode of lithium ion batteries,the composite material has long cycle span and good rate performance.The reversible specific capacity was 412 mA h g-1,after 800 cycles at the current density of 1 A g-1.The average specific capacities at current densities of 0.1 and 1 A g-1 were respectively 700 and 551 mA h g-1,and the average capacity retention at 1 A g-1 vs 0.1 A g-1 is as high as 78.7%(3)We prepared a carbon-coated tin-iron composite selenide(denoted as SnSe2-FeSe2@C)framework material by heat treatment and selenization process by using citric acid composite Sn-Fe cyanide as precursor.The uniform distribution of FeSe2 and SnSe2 in the three-dimensional carbon network buffers the volume expansion of the composite and improves the electrical conductivity of the composite.More importantly,Fe nanoparticles generated by FeSe2 during the cycle process can effectively catalyze the reversible decomposition of Li2Se.Therefore,as the negative electrode of lithium-ion batteries,it exhibits a high specific capacity and a good rate performance.The reversible specific capacity was 572 mA h g-1,and the capacity retention rate was 80.4%,after 400 cycles at a current density of 0.5 A g-1.The average specific capacity at current densities of 0.1 and 2 A g-1 were respectively 742.9 and 563.9 mA h g-1,and the average capacity retention at 2 A g-1 vs 0.1 A g-1 is 75.9%.