Li15Si4Formation in Silicon Thin Film Negative Electrodes

The conditions for Li15Si4 formation in Si thin film negative electrodes was studied during charge and discharge cycling in lithium cells. It was found that Li15Si4 formation can be suppressed during cycling of Si thin films by stress induced from the presence of the substrate. Furthermore, Li15Si4 formation was found to be coincidental with capacity fade and delamination of the Si film from the current collector. These results deepen the understanding of the cycling of Si thin films. Moreover, they have profound implications for Si alloy negative electrodes for Li-ion batteries, as the presence of Li15Si4 during cycling can be used as a sensitive indicator for weakly bound Si regions.