Relationship between Mechanical and Electrochemical Property in Silicon Alloy Designed by Grain Size as Anode for Lithium-Ion Batteries

Abstract

While silicon has a very high theoretical capacity but has relatively the stresses produced by volume changes during charge/discharge cycling lead to structural modifications (around 300%). To overcome this problem, many studies are being conducted to commercialize silicon. Herein, we produced amorphous silicon alloy using a melt-spinning method. Then, through annealing under various temperatures, we gradually recrystallized the silicon phase. Average silicon grain sizes were 70 and 130 nm for silicon alloys annealed at 800 and 873 K, respectively. The initial reversible capacities of silicon alloy-based anodes were 844.3 (800 K) and 865.1 mAh g−1 (873 K), and, after 100 cycles, capacity retention rates were found to be 68.5 (800 K) and 40.5% (873 K). At this stage, to elucidate the effect of grain sizes on cycle life retention rate, we determined mechanical hardness through nanoindentation. And, by measuring volume expansion values between cycles through in situ dilation, we could identify the relationship between electrochemical property and mechanical hardness of silicon alloy samples depending on recrystallized grain sizes. Thus, by analyzing the mechanical and electrochemical properties of silicon alloys depending on silicon grain sizes, we want to highlight the importance of controlling silicon grain size.