Morphology-based analysis of li-ion storage behavior of single crystal hematite (α-FE2O3) nanostructures

Hematite iron oxide (α-Fe2O3) is a promising anode material for Li, Na, and Kion batteries. Its theoretical capacity is greater than that of commercially available graphite. In addition, it is cheap. It can also be easily synthesized. The complex ion storage mechanisms, which involve the insertion of Li-ion followed by a conversion reaction, impede its utilization. The insertion process has received less attention in the literature and is thought to have little effect on the Li-ion storage process. The behavior of Li-ion insertion into single-crystal α-Fe2O3 nanostructures with specific facets and its role in the storage process were studied in this work. In Li-ion insertion voltage window, three morphologies are electrochemically investigated, namely rhombohedral, cubic, and bipyramidal morphologies, with primarily {104}, {012}, and {113} facets, respectively. The contribution of the Li-ion insertion charge transfer process was investigated from distinct facets. For each morphology, formation and development of a solid electrolyte interface (SEI) was observed. Galvanostatic cycling and impedance measurements were used to investigate the reversibility of the insertion process. The observed results indicate improved Li-ion insertion through the {113} facet. As the cells cycled, capacity degradation and continuous SEI growth were observed, indicating that the Li-ion insertion process should be optimized further