Li/Ni Intermixing: The Real Origin of Lattice Oxygen Stability in Co-Free Ni-Rich Cathode Materials

The Co-free Ni-rich layered cathode materials with excellent structural stability and low-cost in Ni-rich family are emerging as the promising candidates for the next generation of high-energy density cathodes. Previously, Mn is generally regarded as the structural stabilizer in Co-free Ni-rich cathodes, while the role of inevitable Li/Ni intermixing is underestimated. Herein, the study reveals that the real origin of the lattice oxygen/structure stability of Co-free Ni-rich cathodes is dominated more by Li/Ni intermixing than the widely accepted Mn. In the Li/Ni intermixing configuration, the intermixed Ni ions can suppress the oxidation of lattice oxygen by increasing the formation energy of oxygen vacancy and reducing charge compensation. Besides, the Li vacancy formed via the delithiation of intermixed Li in transition metal layer can serve as O2 capture sites. This dual stabilization mechanism is proposed and proved to be effectively in enhancing the reversibility of lattice oxygen and the stability of material structural. This work sheds light on the mechanism of stabilizing lattice oxygen through Li/Ni intermixing, which provides new insights for designing better batteries. The dual oxygen stabilization mechanisms of Ni and Li ions in Li/Ni intermixing configurations for inhibiting oxygen vacancy formation and storing O2 are proposed, which reveal that the real origin of the lattice oxygen and structure stability in Co-free Ni-rich cathode materials is Li/Ni intermixing rather than the traditional Mn stabilization mechanism.image