Good cyclability is essential for the potential application of cathode materials. Here, we investigate the structural stability of two-dimensional (2D) Li-layered and three-dimensional (3D) structured polymorphs of Li2FeSiO4 and Li2MnSiO4 using the density functional theory calculation. We find that all 2D Li-layered polymorphs of both materials are unstable upon full-delithiation owing to layer exfolilation, which can lead to an amorphous structure.