Li₁₅Si₄Formation in Silicon Thin Film Negative Electrodes

The conditions for Li 15 Si 4 formation in Si thin film negative electrodes was studied during charge and discharge cycling in lithium cells. It was found that Li 15 Si 4 formation can be suppressed during cycling of Si thin films by stress induced from the presence of the substrate. Furthermore, Li 15 Si 4 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 Li 15 Si 4 during cycling can be used as a sensitive indicator for weakly bound Si regions.