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Fracture, interfacial delamination and fatigue in patterned silicon thin film electrodes subject to lithium cycling

Hamed Haftbaradaran (Brown University), Huajian Gao (Brown University), Xingcheng Xiao (General Motors)

Lithium ion batteries: When Chemistry meets Mechanics

Mon 2:40 - 4:00

Salomon 003

It is a common observation that emergence of a variety of mechanical failure modes is responsible for capacity loss in thin film electrodes after only a few cycles. Recently, it has been proposed that mechanical stability of thin film electrodes could be improved via patterning. Here, we present a theoretical study of fracture, interfacial delamination and fatigue in patterned thin film electrodes, with reference to the available experimental observations. It is shown that sliding at the interface between the Si thin film and underlying metallic substrate could explain why fracture spacing in continuous thin films is orders of magnitude larger than the film thickness. Based on the idea of interfacial sliding, it is also explained why interfacial delamination of Si island electrodes exhibits a size effect around the size of the fracture spacing in a continuous film. It is also shown that variations in yield stress and/or interfacial shear resistance during Li insertion and extraction could potentially induce ratcheting in Si islands, leading to incremental accumulation of plastic deformation.