Study On The Amorphous Silicon Based Thin Film As Anode For Lithium Ion Battery

Energy crisis and environmental pollution speed up the pace of finding renewable resources and clean energy. With the increasing production of renewable resources, energy storage has become a serious problem. Li-ion battery has the advantage of high operating voltage, high capacity and long capacity retention. People pay great attention to the Li-ion battery and investigate it extensively. Silicon is the excellent element as anode material for Li-ion battery. It has the highest theoretical capacity and plays an important role in improving the capacity of full Li-ion battery.In this theses, the a-Si thin films and MWNTs/a-Si composite films were prepared by inductively coupled Plasma enhanced CVD onto the copper substrate. The electrochemical performances of the two films as anode materials for Li-ion batteries have been investigated. The results are shown as follows:1. The a-Si film electrode was prepared directly by ICP-PECVD on the Copper foil.The thickness of Si film is about 300 nm. For a-Si films electrode, the first discharge capacity can reach a capacity of about 4000 mAh/g at current density of 0.02 mA/cm2.the discharge plateau is at about 0.3 V. However, after 17th cycles, the capacity dropped suddenly and after 100 cycles, the electrode almost lost its reversible capacity entirely.2. The first discharge capacity of MWNTs/a-Si composite films can reach 2200 mAh/g. The discharge plateau is at about 0.3 V. The capacity in the following cycles dropped slowly. After 100th cycles, the reversible capacity is still kept at 900 mAh/g. 3. By comparing the structure of the two different films and analyzing the cycle performances of a-Si film deposited on Ni foam, we draw the conclusions that stress in the silicon films during Li ion intercalation into the matrix is the main reason leading to the capacity fading. By using the composites, the cycle performances of silicon film as anode material could be improved.