Study On Lithiation Mechanism And Electron Beam Irradiation Effects Of Tin Disulfide Anode Material

With the rapid development of industries such as consumer electronics and new energy vehicles,lithium ion batteries have become the most widely used energy storage devices due to their high energy density,high power density,green environmental protection,and no memory effect.At present,graphite is the mainly utilized anode material of commercial lithium-ion batteries.Due to its low lithium storage capacity,it limits the energy storage performance of lithium-ion batteries,resulting in that lithium-ion batteries are gradually unable to meet people’s increasing demand.Therefore,there is an urgent need to find high-capacity anode materials to replace graphite to promote the development of next-generation lithium-ion batteries.Among them,tin disulfide（SnS₂）has the advantages of abundant reserves,environmental safety,and high theoretical capacity,which is a promising anode material for lithium ion batteries.However,in actual tests,SnS₂ has several problems such as low reversible specific capacity and poor cycle performance,which hinders its further application in lithium-ion batteries.Therefore,in order to improve the battery design and improve the performance of the battery,it is necessary to have a clear understanding of the lithiation mechanism of the SnS₂ anode material,especially the evolution of the microstructure and phase composition during lithium intercalation and deintercalation.In response to this problem,SnS₂ anode materials of different sizes were prepared by hydrothermal method and chemical vapor deposition method,and the mechanism of lithiation at the atomic scale was studied using in-situ transmission electron microscopy.The electron beam irradiation effects were also investigated.The main research contents and results of this article are as follows:（1）SnS₂ samples with different grain sizes were prepared by hydrothermal method and chemical vapor deposition method,respectively.The SnS₂ samples prepared by the two methods both have hexagonal morphology and good crystallization.（2）The lithiation mechanism of SnS₂ was studied: SnS₂ transforms into Li₂ S and Li_4.4Sn after complete lithiation,and Li_4.4Sn alloy evenly distributed in Li₂S crystal;Li₂S and Li_4.4Sn can transform into SnS₂ after delithiation,which indicates that the lithiation reaction of SnS₂ can be completely reversible.（3）The effects of electron beam irradiation on the structural stability of SnS₂ was studied:under the action of high-energy electron beam（300 ke V）irradiation,small randomly-oriented crystal particles rapidly appeared in the local area of SnS₂,with the interplanar spacing mainly at 0.34 nm,corresponding to the（120）crystal plane of SnS;the area where new particles generated increases with continuous irradiation,and lattice fringes of SnS other crystal plane spacing appear,which indicates that SnS₂ is transformed into SnS under the action of electron beam irradiation.（4）The effect of electron beam irradiation on incomplete lithiation reaction products was studied: incomplete lithiation products of SnS₂ were amorphous,and after electron beam irradiation,non-continuous small-area lattice fringes appeared in the amorphous region;subsequent non-continuous the lattice fringes grow and merge,and finally form a large lattice spacing of 0.60 nm and cover the entire amorphous region.The analysis concluded that this structure corresponds to the（001）crystal plane of a large vertical array structure SnS₂.（5）The effect of electron beam irradiation on completely lithiation reaction products was studied: completely lithiation reaction products of SnS₂ randomly generated Sn nanoparticles with the effect of electron beam irradiation.The emergence of Sn nanoparticles has gone through two processes:（1）Electron beam irradiation drives the decomposition of Li_4.4Sn alloy to form Sn clusters;（2）Continued irradiation,the size of Sn clusters continues to increase and appears randomly throughout the sample.