Lifetime Optimization of Amorphous Silicon Thin-Film Anodes for Lithium-Ion Batteries

Abstract

Silicon has emerged as a highly promising anode material for lithium-ion batteries (LIBs) owing to its high specific capacity and low voltage. However, previous research on silicon-based anodes has not adequately addressed inherent issues, leading to limited commercial applications on a large scale. Therefore, further scientific investigation is necessary to uncover the lithiation/delithiation process in silicon materials and understand the influence of electrode potential and charge state on the kinetic process during charge and discharge. This understanding will be instrumental in gradually enhancing the performance of silicon materials. Herein, amorphous silicon films were prepared for LIB anodes using the magnetron sputtering method. Molecular dynamics simulations were conducted to investigate the microstructure and volumetric changes of the sputtered amorphous silicon anode during the lithiation and delithiation processes. Additionally, electrochemical characterization techniques such as a galvanostatic intermittent titration technique, electrochemical impedance spectroscopy, and galvanostatic charge–discharge test were employed to explore the electrochemical properties of silicon electrodes. Electrochemical analysis techniques, such as the differential capacity method and distribution of relaxation times, were also used to investigate the deterioration mechanisms of the electrochemical and conversion properties of amorphous silicon anodes. Results revealed that the lithium-ion content in LixSi, determined through the set cutoff voltage during charge/discharge cycling, considerably affected the volume change of the silicon anode and the composition and integrity of the solid electrolyte interface after cycling. The optimum discharge cutoff voltage was found to be 0.08 V for the amorphous silicon electrode, leading to an optimum cycle life with a capacity retention of 87.17% after 100 cycles.