Improvement of electrochemical performance of Si thin film anode by rare-earth La PIII technique

Si thin film is considered a good candidate for rechargeable Li-ion thin film battery anode material because it possesses large lithium adsorption capacity, good thermal and chemical stability. However, the fast capacity decay upon charge–discharge cycling has hindered the application of Si thin films. In this investigation, Si thin films were sputtered on Cu foils and characterized. One of the explanations for the bad cycling characteristics is the poor adhesion between the Si film and the Cu substrate. Some Cu foils were treated by Plasma Immersion Ion Implantation (PIII) method using rare-earth La element to improve the adhesion strength between the Si thin films and the Cu substrate in order to enhance the cycling performance. Electrochemical analysis revealed that La PIII surface treatment on the Cu foil substrate was effective in strengthening the interface adhesion between the Si thin films and the Cu substrates. Subsequently, the electrochemical performance of the Si thin film anodes was improved.