Crystal Modulation of Mn-Based Layered Oxide toward Long-Enduring Anionic Redox with Fast Kinetics for Sodium-Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) are promising for energy storage due to cost-effectiveness.
• Mn-based layered oxides with anionic redox offer high capacity but face challenges like oxygen-redox failure and structural degradation.
• Developing stable and high-performance cathodes is crucial for SIB advancement.

Purpose of the Study:

• To investigate the effect of crystal modulation on Mn-based layered oxide cathodes for SIBs.
• To enhance rate capability and long-term stability by addressing oxygen-redox failure and structural degradation.
• To demonstrate a universal strategy for developing advanced SIB cathodes.

Main Methods:

• Crystal modulation strategy using Mn-based Na$_{0.72}$Li$_{0.24}$Mn$_{0.76}$O$_{2}$ with exposed {010} facets.
• Electrochemical performance testing including rate capability and cycling stability.
• Time-resolved operando two-dimensional X-ray diffraction for structural analysis.
• Fabrication and testing of a full cell with hard carbon anode.

Main Results:

• The modulated cathode exhibited enhanced rate capability (119.6 mAh g$^{-1}$ at 10 C) and fast kinetics.
• Reinforced Mn-O bonds suppressed oxygen oxidation and O-O cohesion loss, leading to stable anionic redox activity (100% retention after 100 cycles at 0.5 C).
• Operando XRD confirmed robust structural stability with ultra-low volume variation during cycling.
• The full cell achieved a high energy density of ~211 Wh kg$^{-1}$.

Conclusions:

• Crystal modulation is a significant strategy for developing high-performance Mn-based oxide cathodes for SIBs.
• The exposed {010} facets and reinforced Mn-O bonds effectively stabilize anionic redox reactions and structural integrity.
• This approach offers a universal pathway for creating stable, high-capacity cathodes for next-generation sodium-ion batteries.