Part of Electrode lithiation stages and Lattice Gas Model.

When intra-layer attraction (and inter-layer repulsion) forces are weaker in the electrode material, entropy distributes Lithium atoms among adjacent layers, short of reaching pronounced patterns such as stage II ($\mathrm{LiC_{12}}$). Therefore, the open-circuit function doesn't have plateaus:

Picture from [2]

In [1], Derosa and Balbuena say there are second-order phase transitions are happening in this model. I'm not sure whether we could say there are stages (and hence phase transitions) on this picture at all.

NMC electrodes exhibit such an open-circuit voltage function without plateaus:

Picture from here. This is open-circuit voltage of a full cell, not a half-cell with NMC cathode and Lithium metal, so the open-

References

[1] A Lattice-Gas Model Study of Lithium Intercalation in Graphite (1999)