Impact of Silicon Content on the Behavior of Graphite/Silicon Composite Anodes for High-Performance Lithium-Ion Batteries: Insights from Multi-Scale Simulations
Authors: Permatasari Agnesia , So Magnus , Nguyen Van Lap , Yano Takeru , Inoue Gen 
Published: December 2024

Lithium-ion batteries (LIBs) are critical components in various electronic devices and electric vehicles, driving the need for enhanced performance and efficiency. Graphite has been a popular choice as an anode material due to its stability and conductivity. However, to meet the increasing demand for higher energy densities, silicon has emerged as a promising candidate owing to its high theoretical specific capacity [1]. In this study, we explore the behavior of graphite/silicon (Gr/Si) composite anodes for LIBs.

Our investigation focuses on varying the silicon content within the composite anode (ranging from 0% to 20%) to understand its impact on the electrochemical performance. We employ micro-scale simulations by discrete element method (DEM) to provide insights into the evolution of the electrode morphology, including intercalation, particle size distribution, porosity, and tortuosity [1]. Moreover, to analyze the lithiation and delithiation processes, voltage, and energy density considering the morphological of anode, we utilize LIB simulation with Gr/Si, 1.0 M LiPF6 solution in EC-EMC solvent, and lithium metal were used for the anode, electrolyte, and cathode, respectively. The evaluation used three different constant charging rate (C-rate) conditions (0.5 C, 1 C and 2 C).

This approach allows us to elucidate the structural evolution and mechanical stability of the composite anode during charge-discharge cycles. Additionally, Gr/Si electrodes display voltage hysteresis, attributed to the influence of the charge-discharge history on the equilibrium potential of the lithium-silicon intercalation reaction [2]. Through simulations, we can explore how the silicon content affects this voltage hysteresis. It becomes more pronounced with a higher content of silicon and at lower states of charge (SOCs). Furthermore, increasing the charging rate will amplify the hysteresis.

Our comprehensive analysis aims to provide valuable insights into the intricate interplay between material composition, electrode morphology, and electrochemical performance, facilitating the development of high-performance LIBs with improved energy density and cycling stability. This detailed abstract highlights the computational framework, specific simulation methods, and key variables involved in the investigation of Gr/Si composite anodes, providing a more in-depth overview of the research approach and objectives.

Acknowledgement: This research was carried out under the project (Grant Number JPMJMI24G1) supported by the JST-Mirai Program, Japan.

References:

M. So, S. Yano, A. Permatasari, T.D. Pham, K. Park, G. Inoue, Mechanism of silicon fragmentation in all-solid-state battery evaluated by discrete element method, J. Power Sources. 546 (2022) 231956.

D.R. Baker, M.W. Verbrugge, X. Xiao, An approach to characterize and clarify hysteresis phenomena of lithium-silicon electrodes, J. Appl. Phys. 122 (2017) 165102.