Cobalt And Tin As Nanoarray Structures: Synthesis And Application For Anodes Of Lithium-ion Batteries

Energy has become more and more important with the rapid development of human society. Large-scale development and use of traditional fossil fuels has brought serious environmental pollution and ecological damage, therefore, the energy crisis and environmental deterioration have become a huge challenge. The development of new and renewable energy to achieve energy efficient storage became the focus of global scientific research. Among them, lithium-ion batteries attract great attention due to the high efficiency and environment friendly. Anode materials are the important part of the lithium-ion batteries. Now, the commercial anode materials is graphite, while its low theoretic capacity limits its further application. Therefore, people want to search alternative new anode materials. Co3O4 and Tin have been extensively studied as the lithium-ion battery anode materials due to a good electrochemical behavior and high specific capacity values. However, they still face the problems such as poor cycling performance. This thesis use the nanoarray and composite core-shell nanostructures to enhance the performance of Co3O4 and Tin anodes.Co3O4-Sn core-shell nanowire arrays were prepared by hydrothermal synthesis of Co3O4 nanowire arrays and subsequent deposition of Sn layer via an rf-sputtering method. Sn layer introduced to Co3O4 nanowires can improve the conductivity and structural stability, thus leading to the improved performance. Co3O4-Sn core-shell nanowire arrays deliver an initial discharge capacity of 1078.5 mAhg-1 which can maintain at 773.1 mAh g-1 after 50 cycles at a current density of 300mA g-1. The performance is better than bare Co3O4 nanowire array anode. Both Co3O4 and Sn are electrochemically active materials, and the hybridization of Co3O4 and Sn into an integrated core-shell nanowire structure makes them an elegantly designed electrode when participating in the lithium-ion charge-discharge process. The improved performance can be attributed to the introduction of a Sn layer, which improves the electrical conductivity and structure stability of the Co3O4 nanowire arrays.Co-Sn core-shell nanowire arrays were prepared by the deposition of Sn nanoparticles onto the hydrothermal-synthesized Co nanowire arrays. The as-synthesized Co-Sn core-shell nanowire arrays have been applied as the anode materials of lithium-ion batteries, which delivered a reversible capacity of 710.8mAh g-1 at a current density of 495 mA g-1 (0.5C) after 50 cycles. The electrochemical performance of Co-Sn core-shell nanowire array anode is better than corresponding planar anode, which can be ascribed to the efficient buffering of the volume change, fast transport of electrons, and good contact to the current collector. The effect of the thickness of Sn layer on the cycling performance has also been investigated.