Synthesis And Electrochemical Performance Of SnO₂@TiO₂ Composite Film Materials

With the growing energy demand and increasing environmental pollution, the development and utilization of energy have drawn more and more attention. In this context, it has become an important topic to look for efficient, safe, environment friendly energy storage devices. Lithium ion batteries have become a hotspot in the field of electrochemical energy storage devices due to their high specific energy and environmentally benign nature. At present, graphite is widely applied as anode material for commercial lithium ion batteries. However, due to its low theoretical capacity, graphite cannot meet the demand for lithium ion batteries. So searching for new lithium ion battery materials and improving the battery performance have attracted much attention. Among many new materials, TiO2 become one promising replacement of graphite owing to its good stability and negligible volume effect. But the application of TiO2 is limited due to its low theoretical capacity and poor electrical conductivity. In contrast, SnO2, as another promising replacement of graphite, has high theoretical capacity and good electrical conductivity. However, the rapid capacity fading induced by huge volume effect limits its practical application. SnO2/TiO2 composite materials show good electrochemical performance because of the combination of large capacity of SnO2 and high cycle stability of TiO2. In this paper, SnO2@TiO2 composite film materials are fabricated by photodepositing SnO2 nanoparticles on TiO2 nanotubes, and their lithium storage properties are investigated.In the third chapter, SnO2@TiO2 composite film materials are formed by photodepositing SnO2 on hydrogenated TiO2 nanotubes at open circuit, followed by thermal treatment at 400?. The electrochemical properties are investigated by applying SnO2@TiO2 composite materials as anode materials for lithium ion batteries. Physical characterizations show that SnO2 nanoparticles are uniformly deposited on the TiO2 nanotubes. Electrochemical results show that the specific capacity of the SnO2@TiO2 composite film electrode is 75.1?Ah cm-2 after 100 cycles at a current density of 100?A cm-2, demonstrating the improved lithium storage performance compared to bare TiO2 nanotube array film (18.7?Ah cm-4). In another section of this chapter, we investigate the effect of the electric bias on the photodeposition of SnO2 on TiO2 nanotubes.In the fourth chapter, SnO2@TiD2 composite film materials are fabricated via the photodeposition at the positive bias, followed by thermal treatment. SEM, TEM and XRD characterizations confirm that SnO2 nanoparticles are distributed evenly on the internal and external walls of TiO2 nanotubes. The specific capacity of the SnO2@TiO2 composite film electrode fabricated by the photodeposition at the positive bias is 130?Ah cm-2 after 100 cycles at a current density of 100?A cm-2, demonstrating its prominent lithium storage performance and good cycling stability. The improved electrochemical properties of the composite film electrode are attributed to its unique structure characteristics.