Microstructural Analysis of Si-Ti-Fe Alloy Anode Materials for Li-ion Secondary Batteries

For improving anode materials in Li-ion batteries, the Si system has been noted by many researchers because it has higher energy density and capacity than the graphite anode material used currently. However, the life cycle of the Si anode tends to decrease due to the remarkable volume expansion which is caused by insertion of Li ions when the cell is charged. In this study, we controlled the size of active Si particles, which are dispersed in the inactive matrix, down to several tens of nm as active materials by adding heterogeneous elements. To understand the reaction mechanism of active Si dispersed in the inactive matrix, we analyzed the microstructure of the Si-Ti-Fe alloy using high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. The volume expansion behavior was improved by employing the TiFeSi2 matrix and refining the active Si particle size, and life performance of the Li-ion batteries was enhanced. (Received September 28, 2012)