Inorganic-Enriched Solid Electrolyte Interphases: A Key to Enhance Sodium-Ion Battery Cycle Stability?

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• The performance of sodium-ion batteries (SIBs) is critically dependent on the solid electrolyte interphase (SEI) formed at electrode interfaces.
• Existing research often focuses on inorganic-rich SEI layers, potentially limiting interfacial stability and battery longevity.

Purpose of the Study:

• To investigate the impact of a balanced organic-inorganic hybrid SEI on SIB performance.
• To optimize the SEI composition for enhanced interfacial stability and reduced impedance.

Main Methods:

• Development of a customized electrolyte containing organic sodium alkyl sulfonate (ROSO2Na) and sodium fluoride (NaF).
• Characterization of the resulting SEI layer on Na0.9Ni0.4Fe0.2Mn0.4O2 cathodes and hard carbon anodes.
• Electrochemical testing of battery performance, including cycling stability and capacity retention.

Main Results:

• Formation of a thin, uniform NaF/ROSO2Na-rich SEI layer that effectively protects against interface deterioration and transition metal dissolution.
• Significant reduction in interfacial impedance.
• The Na0.9Ni0.4Fe0.2Mn0.4O2 cathode achieved >99.9% average Coulombic efficiency and 81% capacity retention after 500 cycles.
• An Ah-level pouch cell demonstrated 87% capacity retention after 400 cycles.

Conclusions:

• A customized organic-inorganic hybrid SEI formulation offers a superior alternative to purely inorganic SEI layers for SIBs.
• This approach significantly enhances interfacial stability, leading to improved battery performance and cycle life.
• The findings present an adaptable strategy for advancing sodium-ion battery technology.