Effects of Oxygen Vacancy on the Electronic Properties of LiNiO2 Cathodes: Consequences for Lithium-ion Batteries

Abstract

Lithium-rich LiNiO₂ cathodes hold immense promise for next-generation lithium-ion batteries due to their exceptional energy density, yet their structural stability and commercial viability are severely bottlenecked by oxygen vacancy formation, which alters electronic properties and triggers catastrophic capacity loss and thermal failure. In this study, we investigate the structural, electronic, thermodynamic, and degradation properties of cobalt-free layered LiNiO₂, which crystallizes in a hexagonal structure with space group R3̄m, using first-principles density functional theory (DFT+U) calculations with U_eff value of 3.32 eV implemented in Quantum ESPRESSO. The structural results indicate a stable bulk formation energy of -0.337 eV/atom for the pristine phase. Electronic structure analysis reveals a narrow-gap profile governed by strong Ni-3d/O-2p hybridization. Crucially, the introduction of oxygen vacancies triggers a semiconductor-to-metal transition, introducing flat bands along the A-L high-symmetry path and localized electronic states at the Fermi level. Thermodynamically, oxygen vacancy generation drives a comprehensive degradation pathway, prompting localized NiO₆ octahedral distortion and providing the energetic drivers for subsequent nickel migration and layered-to-spinel phase reconstruction. Overall, these results confirm that while oxygen defects transiently elevate carrier density, they fundamentally destabilize the host lattice. This offers a fresh perspective on vacancy-induced phase reconstruction, providing practical design rules to prevent battery breakdown and build longer-lasting, safer nickel-rich lithium-ion batteries..