cm303611z_si_001.pdf (3.35 MB)
Intercalation of Sodium Ions into Hollow Iron Oxide Nanoparticles
journal contribution
posted on 2016-02-20, 00:53 authored by Bonil Koo, Soma Chattopadhyay, Tomohiro Shibata, Vitali B. Prakapenka, Christopher S. Johnson, Tijana Rajh, Elena V. ShevchenkoCation vacancies in hollow γ-Fe2O3 nanoparticles
are utilized for efficient sodium ion transport. As a result, fast
rechargeable cathodes can be assembled from Earth-abundant elements
such as iron oxide and sodium. We monitored in situ structural and
electronic transformations of hollow iron oxide nanoparticles by synchrotron
X-ray adsorption and diffraction techniques. Our results revealed
that the cation vacancies in hollow γ-Fe2O3 nanoparticles can serve as hosts for sodium ions in high voltage
range (4.0–1.1 V), allowing utilization of γ-Fe2O3 nanoparticles as a cathode material with high capacity
(up to 189 mAh/g), excellent Coulombic efficiency (99.0%), good capacity
retention, and superior rate performance (up to 99 mAh/g at 3000 mA/g
(50 C)). The appearance of the capacity at high voltage in iron oxide
that is a typical anode and the fact that this capacity is comparable
with the capacities observed in typical cathodes emphasize the importance
of the proper understanding of the structure–properties correlation.
In addition to that, encapsulation of hollow γ-Fe2O3 nanoparticles between two layers of carbon nanotubes
allows fabrication of lightweight, binder-free, flexible, and stable
electrodes. We also discuss the effect of electrolyte salts such as
NaClO4 and NaPF6 on the Coulombic efficiency
at different cycling rates.