Lattice Reordering from High-Valence Mo Segregation for High-Nickel Cobalt-Free Cathodes.

Abstract

High-nickel cobalt-free cathodes are deemed promising candidates for next-generation lithium-ion batteries owing to their superior energy density, cost-effectiveness, and environmental benignity. However, their practical implementation is hindered by inherent structural instability and rapid capacity degradation. Herein, we develop a Mo/F cation-anion modified single-crystalline LiNi_0.8Mn_0.2O₂ cathode material (SC-MFNM) via a designed facile high-temperature solid-state synthesis route. During high-temperature calcination, the lattice strain induced by structural transition promotes the outward migration of Mo⁶⁺ ions from the Ni-rich core to the surface region, leading to lattice reorganization and expansion of surface interplanar spacing. The resultant lattice gradient facilitates rapid ion transport from the electrolyte through the expanded surface lattice, while the compact inner lattice enables ordered ion insertion. Consequently, this structure effectively mitigates irreversible phase transitions and stabilizes the layered framework by suppressing cation mixing, while simultaneously preserving the high specific capacity to the Ni-rich layer core, offering an approach to improve the structural and electrochemical stability of the Ni-rich cathode. Benefiting from the structural merits, the SC-MFNM cathode exhibits exceptional cycling stability, delivering a reversible capacity of 164.9 mAh g^-1 after 300 cycles at 1.0 C compared with the lower capacity of 51.5 mAh g^-1 from the polycrystalline cathode. This work demonstrates the importance of lattice regulation and structural evolution in improving the structural and electrochemical stability of high-nickel cobalt-free cathodes, contributing significantly to the development of high-energy-density lithium-ion batteries with long-term cycling durability.