Ultralow Iridium Dopant (<0.5 at. %) in LiNiO₂ Oxide for Improved Structure Stability

The structural instability of LiNiO₂ (LNO) during charge-discharge cycles is a significant challenge in developing high-capacity cathodes for lithium-ion batteries. In this work, we doped a trace amount of Ir (0.5 at. %) into the LNO structure (LNO-Ir) to enhance its stability. Operando XRD reveals that the formation of the H3 phase, which typically occurs at high voltages upon delithiation in LNO, was completely suppressed in the LNO-Ir cathode, resulting in a minimal lattice contraction (<0.1 Å). TEM images reveal that cation migration and surface structural reconstruction can also be significantly reduced in LNO-Ir. DFT calculations confirm that Ir doping not only increases the formation energy of oxygen vacancies but also the energy barrier for Ni migration. Collectively, these effects endow the LNO-Ir cathode with promising structural stability over extended cycling, highlighting a potential strategy for stabilizing high-nickel-content cathodes.