Microstructure Study on Initial Lithiation/Delithiation Cycle of Crystalline Silicon Wafer

In this work, we found that Si wafer has a preferential expansion along <110> directions during the initial lithiation/delithiation cycle, as the evidence of wider <110> cracks. These cracks also propagate much deep, at least 5 um. The morphology of the amorphous Si layer appearing after the initial cycle shows a dependence on the plane orientation, i.e., multi and deep layers on the {110} plane, where as a single layer with ~200nm on the {100} plane.A PAA coating layer on the Si wafer mitigates the cracks and reduces the thickness of the amorphous Si layer.