[SY-G2] Symposium G-2

[SY-G2] Multiscale mechanical analysis of silicon and silicon dioxide as high capacity anode materials for lithium ion batteries.

^○Janghyuk Moon¹, Kyeongjae Cho², Maenghyo Cho³ (1.School of Energy System Engineering, Chung-Ang Univ., Korea, 2.Department of Materials Science and Engineering, University of Texas at Dallas, United States of America, 3.School of Mechanical & Aerospace Engineering, Seoul National University, Korea)

The mechanical issues on high capacity electrode materials, such as silicon, tin, and silicon oxide, prevents their usage for lithium ion batteries. So, the oxides (i.e. silicon dioxide) are the prevalent materials used for a high-expected capacity and strong mechanical stability during cycles. Although tremendous efforts have devoted to the study of the electro-chemo-mechanical behaviors of high-capacity electrode materials, the mechanical behavior of amorphous SiO₂ during electro-chemical reaction remains largely unknown. Here we systematically investigate the inelastic stress evolution, the electronic structure and the mechanical deformation of lithiated silicon dioxide through first-principles computation and finite element method. The structural and thermodynamics analysis was performed to predict electrochemistry characteristics Si and Si-O system. The mechanical strength and brittle behavior of SiO2 due to strong Si-O bonds are also compared with Si. Although both Si and SiO2 experience mechanical softening during lithiation, the clearly distinguishable relaxation kinetic of SiO₂ inducing deviatoric inelastic strains due to mechanical constraints is found by density functional theory calculation. These results would provide fundamental perspectives on the chemo-mechanical behavior of silicon and silicon oxide electrode for the practical use.


ACKNOWLEDGMENT
This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2017R1C1B5017837).