Ultralow Iridium Dopant (2 Oxide for Improved Structure Stability

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Structural instability of lithium nickel oxide (LiNiO2, LNO) cathodes limits high-capacity lithium-ion battery development.
• Phase transitions and cation migration during cycling cause degradation in LNO.

Purpose of the Study:

• To enhance the structural stability of LNO cathodes through trace iridium (Ir) doping.
• To investigate the effects of Ir doping on LNO's electrochemical and structural properties.

Main Methods:

• Iridium (0.5 at. %) doping of LiNiO2 to create LNO-Ir.
• Operando X-ray Diffraction (XRD) to monitor structural changes during cycling.
• Transmission Electron Microscopy (TEM) for microstructural analysis.
• Density Functional Theory (DFT) calculations to understand doping mechanisms.

Main Results:

• Iridium doping completely suppressed the H3 phase formation in LNO-Ir cathodes at high voltages.
• LNO-Ir exhibited minimal lattice contraction (<0.1 Å) and significantly reduced cation migration and surface reconstruction.
• DFT calculations confirmed that Ir doping increases the energy barriers for oxygen vacancy formation and Ni migration.

Conclusions:

• Trace Ir doping effectively enhances the structural stability of LNO cathodes during charge-discharge cycling.
• The stabilization mechanism involves suppressing detrimental phase transitions and inhibiting cation/vacancy mobility.
• This strategy offers a promising route for developing robust, high-nickel-content battery cathodes.