Study Of Properties And Mechanism Of Sb-based Anode Materials For Sodium/Lithium Ion Batteries

Combustion of fossil fuel and resource depletion led to severe environmental problems and energy crisis. Electricity is the most promising substitute to fossil fuels. Lithium-ion battery is now the leading technology of mobile power supplies. However, lithium resource in the earth mantle is quite limited, which can not meet the long-term demand of lithium-ion batteries for electric vehicles.With the advantages of high abundance and low cost, sodium-ion batteries have been considered as potential alternatives to lithium-ion batteries. The main purpose of this study is to develop Sbbased anode materials for Na/Li ion batteries and to understand the working mechanism of Sb based anodes in sodium-ion batteries. Solid state nuclear magnetic resonance(NMR) has been adopted as the major characterization method of tracking the structural change of Sb and Sn Sb anodes upon Na insertion/extraction in Sb and Sn Sb anodes.In this study, Sb metal has been selected as the model anode material of both sodium-ion batteries and lithium-ion batteries. We have successfully identified the optimal formula: ball-milled micron-size antimony powder as the active material, 3.5%(mass fraction) CMC solution as the binder, VGCF and Super P Li(mass ratio of 2:1) as the conductive agent. The charge and discharge specific capacity of the assembled lithium-ion battery and sodium-ion battery is 660 m Ah/g and 625 m Ah/g respectively, close to the theoretical capacity.A solvothermal(ethanol) route has been adopted to synthesize Sn Sb alloy. The determined optimal technological formula for Sn Sb is active material: conductive agent(Super P Li): binder(CMC) with a mass ratio of 7.0:1.5:1.5. The assembled sodium-ion batteries and lithium-ion batteries both show relatively stable cycle performance: the charge and discharge specific capacity of the assembled lithium-ion battery and sodium-ion battery is 752 m Ah/g and 430 m Ah/g respectively.The structural changes of Sb and Sn Sb anode materials at different stages during the charge and discharge processes have been tracked by ex-situ 23 Na MAS NMR. The NMR results analyzed the change of each signal and the mechanism of insertion and extraction. It indicates that the sodiation process of Sb and Sn Sb invole formation of amorphors species during a fairly long stage. The key structure that controls the formation of crystalline Na-Sb alloy is a Na-Sb sheet structure breaking all the Sb-Sb linkage. The difference between the first and the following discharge process is due to a "memory effect" of atomic position formed during the first cycle, which changes the nucleation mechanism.In this study, we also used high-temperature hydrothermal method to synthesize Ag PbmSb Tem+2 anode material, determined the influence of hydrothermal conditions on the morphology of the product; by observing the SEM and TEM images of product at different hydrothermal time, explored the Ag PbmSb Tem+2 microspheres morphology evolution mechanism; through the electrochemical tests, Ag Pb10 Sb Te12 is not suitable as sodium-ion batteries anode materials, while lithium-ion batteries show the better cycle stability, except irreversible capacity loss is large in the first cycle, the charge and discharge capacity close to the theoretical capacity(531m Ah/g) in the post-cycle.