Three-dimensionally mesostructured Fe₂O₃ electrodes with good rate performance and reduced voltage hysteresis

Ni scaffolded mesostructured 3D Fe₂O₃ electrodes were fabricated by colloidal templating and pulsed electrodeposition. The scaffold provided short pathways for both lithium ions and electrons in the active phase, enabling fast kinetics and thus a high power density. The scaffold also resulted in a reduced voltage hysteresis. The electrode showed a reversible capacity of ∼1000 mAh g^-1 at 0.2 A g^-1 (∼0.2 C) for about 20 cycles, and at a current density of 20 A g^-1 (∼20 C), the deliverable capacity was about 450 mAh g^-1. The room-temperature voltage hysteresis at 0.1 A g^-1 (∼0.1 C) was 0.62 V, which is significantly smaller than that normally reported in the literature. The hysteresis further reduced to 0.42 V at 45 °C. Potentiostatic electrochemical impedance spectroscopy (PEIS) studies indicated that the small voltage hysteresis may be due to a reduction in the Li₂O/Fe interfacial area in the electrode during cycling relative to conventional conversion systems.