Interface Regulation in Sodium-Ion Batteries Using a Magnesium Fluoride-Modified Polyimide Composite Separator

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• The separator is crucial for sodium-ion battery (SIB) performance, impacting interfacial stability and ion transport.
• Developing advanced separators is key to unlocking the potential of SIBs.

Purpose of the Study:

• To engineer a high-performance polyimide-based separator for SIBs.
• To enhance interfacial properties and sodium-ion flux using a nano-MgF2 coating.

Main Methods:

• A facile alkaline activation and in situ precipitation method was used to coat polyimide separators with nano-MgF2.
• The modified separators were characterized for their properties and performance in SIB half-cells.

Main Results:

• The MgF2 layer exhibited strong polarity and a negative surface charge, improving electrolyte affinity and regulating ion flux.
• Modified separators facilitated rapid Na+ migration and promoted a stable solid electrolyte interphase (SEI) formation.
• Na||hard carbon cells with modified separators showed a discharge capacity of 160 mAh g-1 (vs. 82.1 mAh g-1 without modification).
• Na||NFPP cells demonstrated excellent cycling stability, retaining 90.9 mAh g-1 after 500 cycles.

Conclusions:

• Interface engineering of separators with nano-MgF2 is a promising strategy for high-performance SIBs.
• The modified separators significantly improve interfacial kinetics, ion transport, and cycling stability in SIBs.