Optimization of dimensional stability and capacity of amorphous silicon anode by amorphous aluminum oxide coating: molecular dynamics simulation

Silicon is considered one of the most appealing materials for lithium-ion battery anodes owing to its high capacity. However, during the lithiation process silicon suffers from considerable volume expansion which results in the massive cracking and subsequent loss of capacity. Amorphous aluminum oxide is a protective layer that can improve the battery performance. In the present research, molecular dynamic simulation is performed to improve the optimal thickness and porosity (density) of the coating layer of amorphous nanowires to maintain dimensional stability as well as a reasonable capacity. The results of the simulations clearly show that coatings with thickness of 4 and 6 Å have a very subtle effect on Structural stability of the amorphous nanowires and will be cracked. Nanowires with 8 Å coating can resistant to detrimental deformation so that volume change reaches about 50 % but capacity reduce to 1000 mAh g-1 during lithiation. Reducing the density as well as increasing the porosity of the coating up to 10 %, maintains the stability of the coating and results in 82 % volume change which increases the capacity to 1500 mAh g-1. The radial distribution of residual stresses is also calculated to examine the impact of coating and porosity on structural integrity.