Session: 03-03: Micro/Nanoscale Interfacial Transport Phenomena

Paper Number: 132012

132012 - Thermal Transport and Mechanical Properties of Solid Electrolyte Interphases (Sei) of Li-Ion Batteries: Atomistic Insights From Molecular Dynamics Simulations 

Abstract: 

Progress in developing lighter, safer, and longer lasting lithium-ion batteries (LIBs) critically depends not only on the design of mechanically stable and high-capacity electrodes but also on the ability to engineer the interface between electrodes and electrolyte. The formation and growth of solid electrolyte interphase (SEI) on the surfaces of electrodes strongly affect the long-term stability and capacity retention of LIBs. The SEI films are formed as a result of chemical and electrochemical reactions involving the components of electrolyte solutions (such as solvent molecules, salts, and additives) on the electrode surface, appearing as a thin solid film of mixed organic–inorganic nature. Playing the important role of interphase between the electrode bulk and the electrolyte solution, the surface films must be good Li-ion conductors but electronic insulators, in order to prevent further side reactions and continuous growth of surface films. It is therefore important, from the fundamental and practical points of view, to develop a better understanding of dynamics thermal transport and mechanical properties of the forming SEI in battery electrodes, particularly under diverse operational conditions of LIBs.

In this work, a computational exploration focuses on evaluating the mechanical robustness of SEI was performed based on classical molecular dynamics (MD) simulations using large-scale atomic/molecular massively parallel simulator (LAMMPS). One of the inorganic SEI components, namely LiF, serve as the representative component to model SEI film. The tensile calculations of the simulation box are carried out at different temperatures and strain rates, and then the non-equilibrium molecular dynamics simulations (NEMD) are utilized to study the thermal transport performance under different tensile states. The thermal conductivity is simulated under the NVE ensemble with Langevin temperature control. Mechanical and thermal transport properties are analyzed. Elastic moduli, fracture toughness and thermal conductivity of model SEIs are compared over a wide temperature range. The distribution cloud maps of several parameters, namely temperature, stress, as well as density, are compared to better understand the corresponding tensile state. In addition, we focus on the change of local heat flux and thermal conductivity where the defects occur to analyze the effect of SEI fracture and regeneration on thermal transport performance according to the actual operating conditions. Furthermore, the analyzation of structural properties and phonon transport characteristics of the simulation systems are performed to facilitate a comprehensive interpretation of the simulation results. This study highlights the importance of fracture toughness in ensuring the mechanical integrity of SEI and provides suggestions for designing stable SEI for high-performance LIBs.

Presenting Author: Jia Liu Zhejiang University

Presenting Author Biography: Jia Liu is currently pursuing her Ph.D. in the School of Energy Engineering, Zhejiang University. Her research interests mainly focus on microscale heat transfer in Li-ion batteries.

Authors:

Jia Liu Zhejiang University
Liang Wang Zhejiang University
Liwu Fan Zhejiang University