The Research of Different Strategies to Enhance Coulombic Efficiency of Sn/SnOx Modified TiO2 As Anode Material in Lithium-Ion Battery By in Operando Analytical Techniques

Abstract

In recent years, electrochemical energy storage technologies had become global concerns due to the emergent need for electric vehicles and portable electronics. Recently, Lithium ion batteries cannot meet the requirements of gravimetric/volumetric energy density, rate capability, cycling stability, and safety in various applications. As one of the most promising anode materials for LIBs, titanium dioxide(TiO2) has received considerable attention due to its superior cycling stability, rate performance, low cost, environmental friendliness, and safety compared to traditional graphite anode. However, the major challenges of this material are poor electronic/ionic conductivity and poor theoretical capacity. In order to overcome this issue, our research has been modifying high-capacity material (e.g., Sn/SnOx) into TiO2 with an eye to promoting its capacity. Modifying Sn/SnOx into TiO2 reduces the impedance and increases the Li-ion diffusion rate. The Sn@TiO2 is synthesized by the chemical bath with Sn(BF4)2, HBF4, Na2S2O3 and TiO2 (rutile and anatase mixed phase) followed by annealing at different temperature. From the TEM and XRD results, we had successfully synthesized Sn@TiO2 core-shell structure. The table below shows that the serious fading problem of Sn@TiO2 during the first and second cycle. Active lithium loss(ALL) in the initial charge process causes irreversible capacity of LIBs due to the formation of unstable solid electrolyte interface (SEI) layer on the electrode surface. To solve the problem, pre-lithiation has been widely accepted as one of the most promising strategies to compensate for active lithium loss. Our group is about to trying various pre-lithiation techniques, such as electrochemical and chemical pre-lithiation and using in operando XRD/Raman to point out the mechanism of SEI layers. The ultimate goal would be giving out advantages and challenges of each one then finding out the optimal approach to improve cycling performance of tin-based anodes in lithium-ion batteries. Figure 1