Modeling of lithium segregation induced delamination of a-Si thin film anode in Li-ion batteries

Amorphous silicon thin film deposited on copper current collector is a promising candidate for the high capacity lithium-ion battery (LIB) anode. However these systems exhibit a rapid capacity fade, and as a result, poor cyclic performance. Interfacial delamination due to lithium intercalation induced stress is the primary reason behind this capacity fade. For the case of a clean interface, crack blunting resulting from the plastic flow of the metallic substrate will eventually arrest the delamination. However, experimental observations suggest a complete delamination of the thin film from the substrate indicating the existence of interface embrittling mechanisms. Further experiments have revealed the evidence of segregation of lithium into the interfacial region that can potentially embrittle the interface. The focus of the current study is to investigate the role of such irreversible mechanisms at the interface on its delamination response during electrochemical cycling. Towards this end, we have developed a computational framework that accounts for coupled diffusion induced large deformation in silicon thin film, elasto-plastic deformation of the copper current collector, as well as the nucleation and propagation of interfacial delamination. A detailed parametric study has been presented to investigate the effect of segregation induced embrittlement on the delamination growth. Present analysis provides a mechanistic understanding of the delamination behavior of the interface between the silicon thin film and copper current collector that may help in the design of future thin film based LIB anodes with improved cyclic performance.