Activating Sodium Intercalation in Cation-Deficient Fe₃O₄ Through Mo Substitution

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Magnetite (Fe3O4) is a promising, cost-effective anode material for energy storage.
• Sodium-ion batteries face challenges with Na+ intercalation in conversion-type oxides.
• Developing efficient anode materials is crucial for large-scale energy storage.

Purpose of the Study:

• To enhance the electrochemical performance of magnetite anodes in sodium-ion batteries.
• To investigate the role of iron vacancies in Fe3O4 for improved sodium intercalation.
• To establish a method for modulating defective structures in transition metal oxides.

Main Methods:

• Gradient molybdenum (Mo) doping to create controllable Fe vacancies in Fe3O4.
• Pair distribution function (PDF) analysis for local structure elucidation.
• Physical-electrochemical characterizations and theoretical calculations.

Main Results:

• Achieved a vacancy-rich Fe3O4 structure with 7.3% Fe vacancies.
• Enhanced capacity of 127 mAh g-1 after 150 cycles, compared to 37 mAh g-1 for defect-free Fe3O4.
• Mo doping improved electronic conductivity and facilitated Na+ migration.

Conclusions:

• Tailoring Fe vacancies through Mo doping is an effective strategy to enhance sodium-ion battery performance.
• Defective structures in transition metal oxides can activate fast and reversible sodium intercalation.
• This work offers a pathway for designing high-performance sodium-ion batteries.