Sb@Ni₆ superstructure units stabilize Li-rich layered cathode in the wide voltage window

In the practical operations of Li-ion batteries, inevitable deep charge/discharge happens locally due to the intrinsic (de)lithiation inhomogeneity at the electrode and particle level, which would damage the health of batteries and even cause the safety concern. It is essential to develop the stable cathodes operating in a wide voltage window to ensure the health and safety of Li-ion batteries. Herein, we comprehensively investigate the charge/discharge behaviors of a representative Li-rich cathode Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ in a wide voltage window of 1.0–4.8 V, and reveal that, deep-lithiation would drive violent TM migration and severe Li/TM mixing, thereby leading to the irreversible structural transformation from layered to spinel then to rock salt, eventually causing the fast decay in electrochemical performance. Based on these understandings, a novel Li-rich cathode Li[Li_1/4Mn_1/2Ni_1/6Sb_1/12]O₂ is successfully synthesized through introducing aromatic Sb@Ni₆ superstructure units in the TM layers. The introduced Sb@Ni₆ superstructure units can effectively tune the local oxygen environment, suppress TM migration, and stabilize the layered framework under deep lithiation. Finally, a stable charge/discharge is achieved in 1.0–4.8 V. This work deepens the understanding into the structural stability of Li-rich cathodes in a wide voltage window, and benefits the development of high-energy-density and safe cathodes.