In Situ Transmission Electron Microscopy Study Of The Lithiation Mechanism Of Lithium-ion Battery Electrode Material

Lithium-ion batteries have been widely used due to their low electrode potential,high theoretical capacity and high energy density.The morphology change and phase transition process of electrode materials in the process of storing lithium ions greatly affect the electrochemical performance of the battery.The changes in morphology and structure can deepen the understanding of the lithium storage mechanism of materials,which has become a research hotspot.In situ TEM technology has ultra-high spatial and temporal resolution,and can observe the morphology and structure changes of electrode materials during the charging and discharging process of lithium-ion batteries in real time,which has become an effective means to study the lithium storage mechanism of lithium-ion batteries.In this paper,the lithiation mechanism of chalcogen Te and alloy material Ag was studied by means of in-situ transmission electron microscopy,and the ion migration paths and morphology changes of lithium ions in Te and Ag nanowires were studied.The lithiation mechanism and failure mechanism can guide the optimization of device performance and promote the development of the energy field.The main research results of this paper are as follows:Te nanowires were prepared by hydrothermal method,and the morphology change and phase evolution mechanism of Te nanowires in Li-ion batteries were investigated.The results show that there is an anisotropic expansion of Te nanowires during the lithiation process,the diffusivity of lithium ions in Te is 0.9-3.5×10^-13 cm²/s,and the phase transition process between Li Te₃ and Li₂Te during lithium storage is reversible.It is found from the topography that the nanowires still maintain the original structure after two cycles,indicating that the Te electrode material has good flexibility when applied to rechargeable lithium-ion batteries.This provides experimental evidence for the morphology change of Te nanowires during lithiation.The morphology changes and reaction mechanism of Ag nanowires during lithium storage under different working voltages were studied.When the applied voltage is-1V,Ag nanowires will alloy with Li ions to form Li Ag alloys without obvious volume deformation.With the subsequent lithiation,when the ratio x in the Li_xAg alloy exceeds1,the nanowires will be broken and the phase composition are Li₃Ag and Li₉Ag₄;when the applied voltage is-2 V,Li ions will be quickly transported on the surface of the nanowires,and the react with Ag to form alloys,resulting in material fragmentation.It is indicated that Ag is suitable for the reaction with lithium at low operating voltage,and improves the electrochemical performance of the battery.