A systematic investigation of cycle number, temperature and electric field strength effects on Si anode

Abstract

Cycling number, crystal orientation, temperature and electric field strength play key roles in affecting the capacity and cycling ability of Li-ion battery. However, the detailed dynamic and continuous process of capacity decline mechanism from above factors need to be further understood at nanoscale. Herein, we report deformation behavior and microstructure evolution of Si anode under electric field using molecular dynamics simulations. The results show larger cycling number and electric field strength cause larger volume expansion of Si electrode, leading to the capacity loss and the reducing cycling ability as well as the decreasing structural stability. The phase transformation from diamond cubic structure to body-centred tetragonal structure and the amorphous formation depend on lithiated and delithiated depths. The crystal orientation [100] Si anode produces the volume expansion owing to a large number of nanoscale void. The various temperatures strongly affect the number and radius of nanovoid. The associated transition in the nanovoid nucleation due to the involuntary diffusion process is driven by larger cycling number or electric field strength, resulting in the irreversible capacity loss of Li-ion battery. An established analytical model suggests that diffusion-induced stress not only relies on the position of Si anode but depends upon the cycling time.