Insight into the Structural Disorder in Honeycomb-Ordered Sodium-Layered Oxide Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Crystallography

Background:

• Honeycomb-layered Na3M2XO6 (M = Ni, Cu, Co; X = Sb, Bi) are promising cathode materials for sodium-ion batteries (NIBs).
• Their high voltage and rate capabilities are hindered by poorly understood crystal structures.

Purpose of the Study:

• To elucidate the crystallographic features of pristine Na3Ni2SbO6.
• To investigate the intrinsic structural disorder in this cathode material.

Main Methods:

• Electron microscopy
• Associated spectroscopies
• Analysis along multiple zone axes

Main Results:

• Structural disorder is inherent in Na3Ni2SbO6.
• The material exhibits randomly stacked layers with three monoclinic structure variants.
• Stacking disorder was evidenced by Ni2SbO6 layer relationships, Ni/Sb atomic arrangements, and Ni/Sb overlap along specific zone axes.

Conclusions:

• The intrinsic structural disorder in Na3Ni2SbO6 is a key crystallographic feature.
• Understanding this disorder is crucial for studying phase transformations during battery cycling.
• Insights into structural disorder may help address voltage and capacity decay in these NIB cathode materials.