A Simplified Model to Track Si Degradation in Various Systems

Abstract

Silicon (Si) is considered one of the most promising anode materials for next generation lithium-ion batteries (LIBs), due to the extremely high specific capacity (3580mAh/g). However, it is challenging to use Si anodes for LIBs, because of the large volumetric changes and phase evaluation associated with lithiation/delithiation of Si. These intrinsic issues of Si lead to the rapid degradation in capacity during cycling, especially in full cells assembled with commercial lithium-ion battery cathodes. Efforts have been made in order to stabilize the Si anodes including developing new electrolytes to increase the surface stability, inventing new binders to enhance the mechanical integrity, and using nanoarchitecture to reduce mechanical failures. Leveraging the previous research, this work introduces a simple and effective method to fast identify the failure mechanism for Si anodes and decouple the impacts of surface instability and lithium trapping on the electrochemical behavior. Here, we will apply our model for various systems of Si half cells to discuss the effectiveness of adding the fluorinated electrolyte additive and the use of nanoparticles. Moreover, we will study the effects of surface modification via atomic/molecular layer deposition on the electrochemistry of Si anodes by using our developed method and provide the insights in designing the highly reversible Si anodes. In this study, we will investigate how these aforementioned factors may affect the stability of Si particles as well as the cycle performances. Assisted with electrochemical impedance spectroscopy (EIS), we will keep track with the SEI evolution on Si anode and connect with the capacity degradation in order to explain the importance of interface stability.