Properties of Fe-Si Alloy Anode for Lithium-Ion Battery Synthesized Using Mechanical Milling

Silicon (Si)-based anode materials can increase the energy density of lithium (Li)-ion batteries owing to the high weight and volume capacity of Si. However, their electrochemical properties rapidly deteriorate due to large volume changes in the electrode resulting from repeated charging and discharging. In this study, we manufactured structurally stable Fe-Si alloy powders by performing high-energy milling for up to 24 h through the reduction of the Si phase size and the formation of the alpha-FeSi2 phase. The cause behind the deterioration of the electrochemical properties of the Fe-Si alloy powder produced by over-milling (milling for an increased time) was investigated. The 12 h milled Fe-Si alloy powder showed the best electrochemical properties. Through the microstructural analysis of the Fe-Si alloy powders after the evaluation of half/full coin cells, powder resistance tests, and charge/discharge cycles, it was found that this was due to the low electrical conductivity and durability of beta-FeSi2. The findings provide insight into the possible improvements in battery performance through the commercialization of Fe-Si alloy powders produced by over-milling in a mechanical alloying process.

Automated summary

In this study, structurally stable Fe-Si alloy powders were synthesized by high-energy milling, and it was found that the Fe-Si alloy powder after 12 hours of milling showed the best electrochemical properties. The low electrical conductivity and durability of β-FeSi2 were identified as the main factors contributing to the improved battery performance.