Bridging multiscale interfaces for developing ionically conductive high-voltage iron sulfate-containing sodium-based...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Non-aqueous sodium-ion batteries (SiBs) show promise for grid storage.
• Challenges include sluggish kinetics and interfacial instability of positive electrodes at high voltages.

Purpose of the Study:

• To improve Na-ion storage performance by multiscale interface engineering of Na2.26Fe1.87(SO4)3.
• To address limitations of polyanion-type iron-based sulfates in SiBs.

Main Methods:

• Multiscale interface engineering involving bulk heterostructure and exposed crystal plane tuning.
• Physicochemical characterizations and theoretical calculations.
• Testing in a laboratory-scale single-layer pouch cell with a FeS/carbon negative electrode.

Main Results:

• A Na6Fe(SO4)4 heterostructure phase facilitated ionic kinetics by optimizing Na-ion migration channels.
• The (11-2) plane of Na2.26Fe1.87(SO4)3 promoted electrolyte adsorption, forming a stable, inorganic-rich interphase.
• The engineered electrode achieved an initial discharge capacity of 83.9 mAh g-1 at 2.35 V, with 97% capacity retention after 40 cycles.

Conclusions:

• Multiscale interface engineering is effective for enhancing the performance of Na2.26Fe1.87(SO4)3 positive electrodes.
• The developed material demonstrates potential for practical SiBs in grid storage applications.