Tin Dioxide Based Nanomaterials As Anode Materials For Lithium Ion Batteries

Lithium ion batteries (LIBs) have attracted much attention as important power sources for many portable electronic devices due to their superior specific energy, excellent rate capability, environmental friendliness and low cost. However, the currently commercial used graphite anode materials have limited theoretical specific capacity of372mAhg-1and poor rate capability, restricting the development of high energy-and high power-LIBs. In recent years, SnO2-based anode materials have been intensively explored as future anode materials for LIBs, owing to good processibility, widespread availability and low toxity and high theoretical capacity (which is two to three times as much as that of a commercial graphite anode). In this paper, we designed nanocomposites with carbonaceous materials and hollow nanostructured SnO2materials to accommodate volume change that occurs during lithiation and delithiation cycling. Meanwhile, the design of SnO2-based composites with conducting materials such as carbonaceous materials and metal cationic doping have been considered to be effective strategies to improve electrical conductivity of metal oxide anode materials. The main contents are summarized as follows:1. We developed a facile infiltration chemical route to fabricate SnO2@OMC nanocomposites with SnO2nanoparticles embedded in ordered mesoporous carbon. The content of SnO2in the composites can be optimized by changing the mass ratio of SnCl2-2H2O to OMC. Electrochemical performance results reveal that the SnO2@OMC composite containing20at%SnO2displays an extraordinarily reversible capacity up to769mAhg-1even after60cycles at a current density of100mAg-1. Even at a current rate as high as1600mAg-1, it still maintains a stable charge/discharge capacity of440mAhg-1, which is3times and30times as much as that of OMC(135mAg-1) and pure SnO2samples(14mAg-1). The outstanding electrochemical performance of the synthesized SnO2@OMC composites could be ascribed to its unique structural characteristics, taking advantage of both the OMC and the oxide nanoparticles, and meanwhile avoiding the disadvantages, and then greatly improving the properties of the OMC based composites.2. We synthesized SnO2@CA nanocomposites via a facile infiltration chemical route using SnCl2-2H2O as tin precursor and CA as carbon source. Electrochemical performance results reveal that the10SnO2@CA and20SnO2@CA composites exhibit remarkably reversible capacity up to689and580mAhg-1even after30cycles at a current density of100mAg-1. The significantly enhanced electrochemical performance could be ascribed to the synergistic effect of CA and SnO2. CA matrix provides a physical buffering layer for the large volume change (cushion effect) and increases the electrical conductivity. SnO2nanoparticles embedded within the CA matrix may offer a higher specific capacity than pure CA, decrasing the active sites of CA matrix to increase the initial coulombic efficiency and reversible specific capacity of the composites.3. We designed a facile infiltration route to prepare hollow structured molybdenum doped tin dioxide (MTO) materials with controlled morphology using silica spheres as a template, SnCl2·2H2O as tin precursor and ammonium heptamolybdate (AHM) as molybdenum source. The diameter of MTO products is about300nm, which is coincident with the size of SiO2spheres. Mo dopant is uniformly distributed among the MTO materials, and incorporated into Sn4+sites in the SnO2lattice. Electrochemical results reveal that SnO2hollow spheres doped with14at%Mo (MTO-1) depict a high specific capacity up to798mAhg-1after60cycles at a high current density of100mAg-1(about1.66times higher than that of non-doped sample). In addition, even at the current density as high as1600mAg-1after60cycles, it could still retain a stable specific capacity of530mAhg-1, exhibiting an extraordinary rate capability. The greatly improved electrochemical performance of MTO-1sample could be attributed to two design rationales, namely, advantangeous hollow interior space and cationic doping.