Morphology Control of Ball-Milled Si-Ti Alloy Anode Materials for Li-Ion Batteries

Reduced surface area Si-Ti alloy anode materials for Li-ion batteries were prepared by ball milling. Using a high Ti content of 40 atomic % results in low surface area (23 m 2 /ml) alloy, but also results in a low (∼100 mAh g −1 ) capacity. It was found that by utilizing a two-step ball milling method and controlling the milling time, a high Si content (Si 0.85 Ti 0.15 ) alloy with an amorphous active Si phase and a high capacity (1600 mAh g −1 ) could be synthesized that has a reduced surface area (34 m 2 /ml) compared to the same alloy made by conventional methods (41 m 2 /ml). When utilized as anodes in lithium cells, the low surface area alloy showed an initial improvement in coulombic efficiency, but low and high surface area alloys had similar coulombic efficiency after 50 cycles. This was found to be due to massive increases in surface area that occur during cycling, which overwhelm any initial difference in alloy surface area prior to cycling.