Defect Electrochemistry in Stabilizing Corrugated Layered NaMnO₂.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Lattice defects in layered metal oxides significantly affect structural stability and electrode reversibility in rechargeable batteries.
• The precise role of these defects, particularly stacking faults (SFs) in corrugated-layered materials like β-NaMnO₂, is not well understood.
• Understanding and controlling SFs in β-NaMnO₂ is crucial for improving its thermodynamic stability and electrochemical performance.

Purpose of the Study:

• To investigate how partial substitution of manganese (Mn) with copper (Cu) or zinc (Zn) in β-NaMnO₂ influences stacking fault (SF) formation.
• To elucidate the relationship between the distribution of SFs and the electrochemical performance of β-NaMnO₂-based electrodes.
• To demonstrate defect engineering as a viable strategy for enhancing the durability of battery materials.

Main Methods:

• Synchrotron X-ray diffraction (XRD) was employed to analyze the crystal structure and defect arrangements.
• Scanning transmission electron microscopy (STEM) provided high-resolution imaging of the material's microstructure and defect morphology.
• Raman spectroscopy was used to probe vibrational modes and identify distinct defect structures.

Main Results:

• Pristine β-NaMnO₂ exhibited ordered stacking fault domains.
• Cu-substitution led to defect-free zigzag stacking, while Zn-substitution introduced randomly distributed SFs.
• Both Cu- and Zn-substituted materials showed improved capacity retention during electrochemical cycling, with suppressed evolution of α-phase defects.

Conclusions:

• A direct correlation between stacking fault distribution and electrochemical reversibility was established.
• Partial substitution of Mn with Cu or Zn effectively modulates SF formation in β-NaMnO₂, leading to enhanced cycling stability.
• Defect engineering, specifically controlling SF distribution, is a promising approach for designing advanced, durable rechargeable battery materials.