Van der Waals phase transition investigation toward high-voltage layered cathodes

via visualizing its electron density, elucidating the origin of O3─O1 phase transition. The charge around oxygen is distorted by the increasing Co─O covalency. The charge distortion causes the difference of vdW gap between O3 and O1 phases, verified by a gap corrected vdW equation. In a high charging state, excessive covalency breaks the vdW gap balance, driving the O3 phase toward a stable O1 one. This interpretation of vdWi-dominated phase transition can be applied to other layered materials, as shown by a map regarding degree of covalence. Last, we introduce the cationic potential to provide a solution for designing high-voltage layered cathodes.