Oxidation Controlled Anode Materials for Li Ion Battery

Silicon is considered one of the best candidates as an anode material for the next generation of Lithium ion batteries due to its enormous capacity of 3579 mAh/g (Li₁₅Si₄) compared to that of graphite (372 mAh/g). However, Lithium ion insertion and extraction results in a volumetric expansion of 300 ~ 400%, which can lead to fracture that cause the capacity fading and poor cycle efficiency of the silicon anode during electrochemical cycling.

In this study, we introduce a Si-based alloy covered with oxide layer on the surface of particles. Inactive oxide layer component plays a structural buffering role to minimize the mechanical stress induced by huge volume change of active silicon. Si-Fe powders from ferrosilicon and Fe2O3 were synthesized by a high-energy mechanical milling process. The electrochemical properties were measured using coin cell with LCO as the counter electrode. From the electrochemical cell test, we observed the smaller degradation of the initial capacity and better efficiency compared to that of Si-Fe, and the capacity retention rate is also improved compared to that of Si-Fe alloy. A high-resolution transmission electron microscope and X-ray diffraction were used for detailed phase analysis of Si-Fe-O compounds.