The authors reveal the mechanisms of degradation of capacity, charge voltage, and discharge voltage of commercially‐available high‐nickel cathode material when it is cycled without a voltage margin by two different charge protocols: constant‐current charging and constant‐current, constant‐voltage charging. With repeated constant‐current charging, the cathode material changes to a non‐periodic cation‐mixed state, which causes a relatively low voltage degradation, whereas during constant‐current, constant‐voltage charging, the cathode material changes from a layered structure to a periodic cation‐mixed spinel‐like phase, with consequent severe voltage decay. This decay results from a reduction in the equilibrium electrode potential and an increase of overpotential which are aggravated in a periodic cation‐mixed state. The findings provide insights into the use of excess Li without charge‐voltage margin in high‐Ni cathode materials.

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