Insights into mechanics and electrochemistry evolution of SiO/graphite anode by a composite electrode model

Abstract

Silicon-based materials are crucial for high-capacity anodes, but their volume expansion in batteries due to the presence of silicon requires further analysis and research. Silicon monoxide/Graphite (SiO/C) is a composite material that combines the volume expansion of silicon oxide material with the practical application of carbon material. Therefore, understanding its behavior during actual use is important, particularly in full batteries and in pairs with high-capacity LiNi0.8Co0.15Al0.05O2 (NCA) cathode. There are fewer studies on this topic, which highlights the need for research. Thus, in this work, SiO/C composite negative electrodes are prepared with different compaction densities (CDs) of 1.38, 1.52, and 1.62 g cm−3. Pouch cells are assembled with NCA positive electrode to investigate the changes in battery thickness and internal resistance under different CDs and state of charge (SOC), as well as the Coulombic efficiency and cyclic performance of batteries are also examined. Additionally, the capacity-voltage curves, expansion curves under different CDs and SOC, particle stress change, and lithium concentration distribution under different CDs are comprehensively simulated. Thus, the evolution of lithium concentration distribution and electrodes volumetric strain during charge and discharge are directly presented. The established model through matching experimental data provides a research basis for predicting the performance of SiO/C negative electrodes, especially its electrochemical and mechanical performance evolution in high‑nickel full batteries. This study has important implications for the development of high-performance silicon-based anodes in practical applications.