Improved Compatibility of α-NaMnO₂ Cathodes at the Interface with Ionic Liquid Electrolytes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) are a promising alternative to lithium-ion batteries.
• Developing stable and high-performance cathode materials is crucial for SIB advancement.
• Monoclinic sodium manganite (α-NaMnO₂) is a potential cathode material.

Purpose of the Study:

• To investigate the electrochemical behavior and compatibility of α-NaMnO₂ cathodes with ionic liquid electrolytes.
• To evaluate the long-term cycling performance and stability of these cathode-electrolyte interfaces.
• To understand the surface chemistry and morphology changes influencing cathode performance.

Main Methods:

• Cyclic voltammetry and impedance spectroscopy for analyzing Na⁺ insertion.
• Charge-discharge cycling to assess cell performance.
• X-ray photoelectron spectroscopy (XPS) and Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) for surface analysis.

Main Results:

• α-NaMnO₂ cathodes exhibited high reversibility in N₁₁₁₄FSI-based electrolytes.
• The cathode retained 60% of its initial capacity after 1200 cycles.
• Coulombic efficiency remained consistently above 99% throughout cycling.
• Spectroscopic analysis confirmed the formation of a stable passive layer on the electrode surface.

Conclusions:

• The N₁₁₁₄FSI ionic liquid electrolyte promotes exceptional stability for α-NaMnO₂ cathodes.
• The formation of a protective surface layer is key to the observed high performance and longevity.
• These findings represent a significant advancement for monolithic α-NaMnO₂ cathodes in SIBs.