Preparation And Electrochemical Properties Of TiO 2 - Based Composite Nanowire Arrays For Lithium - Ion Battery Materials

At present, carbon materials have been widely used in commercial lithium ion battery. Among these carbon materials, graphene has low operating voltage and exhibits good electrochemical performance. But using grahene imposes safety issues because of the formation of lithium dendrites. Therefore, over the past decades, a worldwide effort has been made to search for alternative anode materials. Due to its high Li intercalating potential which can avoid the formation of lithium dendrite, titanium dioxide (TiO2) is one of the most promising new anode materials. Thanks to its controllable shape, large space distance, polycrstal structure, abundant resources and environmentally friendly, TiO2 has been widely used in lithium ion battery. However, owe to its low specific capacity and poor electronic conductivity, the electrochemical performance of TiO2 anode is still not satisfactory. In order to improve the specific capacity and conductivity of TiO2, we prepared TiO2-based nanowire arrays and investigated their effects on the electrochemical performances. We hope to provide a new path for the research of lithium ion battery anode to promote its commercial applications.Fristly, we prepared TiO2 nanowire arrays by a simple hydrothermal reaction. X-ray diffraction and Raman results showed that we got different phases of TiO2(Anatase and TiO2(B)). Then we studied its electrochemical performances as the anode for lithium ion battery without polymer binders and conductive agents. Compared with the standard Degussa P25 TiO2 nanoparticles, the T1O2 nanowire arrays exhibited larger reversible capacity, improved cycling stability and rate capability, which attributed to their nanowire array structure.In order to improve the capacity, we successfully prepared TiO2@Fe2O3 composite which was a core-branch hybrid architecture. It could not only provide large surface active sites for lithium ion insertion/extraction, but also enable fast charge transport owing to the reduced diffusion paths for both electrons and lithium ions. The combination of TiO2 (good structural stability) and Fe2O3(large specific capacity) provided the hybrid array electrodes with several desirable electrochemical advantages:large reversible capacity (-800mAh/g) and 88% capacity retention at current density of 100 mA/g. However, the conductivity of TiO2@Fe2O3 composite electrode is still very low and need to be improves. Craftly designed TiO2@C@Fe34 three-layer hybrid structure sufficently combined the advantages of the TiO2@Fe2O3 composites and the high conductivity of carbon layer. It exhibited outstanding rate capability:large reversible capacity (270μAh/cm2) at high current density(1600μA/cm2). So the hierarchical design of compositing different materials with excellent performance solves the big problem that the traditional lithium ion battery anode cannot have high capacity and high conductivity at the same time bacuse of the limitions of the materials, which will greatly promot the development of the lithium ion battery anode.