Atomic Structural Features of Stacking Faults and Domain Connections in the Li- and Mn-Rich Cathode

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Li- and Mn-rich layered oxides (LMRs) are promising earth-abundant cathode materials for Li-ion batteries.
• LMRs crystallize in two distinct symmetries: C2/m (Li2MnO3-like) and R3̅m (LiNixMnyO2-like).
• Understanding the spatial correlation and stacking fault behavior of these domains within single grains is crucial for optimizing battery performance.

Purpose of the Study:

• To investigate the atomic-scale structural and compositional details of domain connections and stacking faults in LMRs.
• To elucidate the relationship between C2/m and R3̅m domains within a prototypical cobalt-free LMR material.
• To demonstrate the utility of STEM-iDPC for analyzing complex oxide structures.

Main Methods:

• Utilized integrated differential phase contrast imaging in scanning transmission electron microscopy (STEM-iDPC).
• Probed structural and compositional details at the atomic level.
• Analyzed a prototypical cobalt-free LMR material: 0.3Li2MnO3·0.7LiMn0.5Ni0.5O2 (Li1.13Mn0.57Ni0.3O2).

Main Results:

• Identified abrupt connections between C2/m and R3̅m domains, attributed to minimal lattice mismatch.
• Observed atomic plane shifting in C2/m stacking faults, explaining their random arrangement.
• Discovered a local disordering mechanism correlated with C2/m stacking faults.
• Confirmed coexistence of Ni and Mn at transition metal sites within the Li2MnO3 domain.

Conclusions:

• STEM-iDPC is highly effective for capturing elemental distribution and revealing atomic-level structural features in LMRs.
• The findings provide fundamental insights into the structural complexity and domain interactions within LMR cathode materials.
• This work advances the understanding of LMR structure-property relationships for improved battery design.