Composition and Structure of the solid electrolyte interphase on Na-Ion Anodes Revealed by Exo- and Endogenous...

Area of Science:

• Materials Science
• Electrochemistry
• Spectroscopy

Background:

• Sodium ion batteries (SIBs) are promising for large-scale energy storage.
• Stable SIB performance relies on the solid electrolyte interphase (SEI) at the anode.
• SEI characterization is challenging due to its heterogeneous and low-quantity nature.

Purpose of the Study:

• To develop and apply a sensitive method for SEI analysis.
• To investigate the SEI composition and spatial distribution on Li4Ti5O12 anodes in SIBs.
• To understand the impact of electrolyte additives on SEI properties and SIB performance.

Main Methods:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
• Dynamic Nuclear Polarization (DNP) enhancement using exogenous and endogenous sources.
• Analysis of the SEI formed on Li4Ti5O12 anodes in sodium ion batteries.

Main Results:

• Detailed compositional mapping and spatial distribution of SEI phases were achieved.
• A compositional gradient was identified within the SEI, from organic to inorganic phases.
• Fluoroethylene carbonate additive resulted in a thicker SEI, rich in NaF and carbonates, correlating with performance degradation.

Conclusions:

• DNP-enhanced solid-state NMR is a powerful tool for SEI investigation.
• Understanding SEI structure and composition is key to optimizing SIBs.
• Methodology can be extended to other anode materials and electrolytes for SIB development.