Molecular Dynamics Simulations of the Traction-Separation Response at the Interface between PVDF Binder and Graphite in the Electrode of Li-Ion Batteries

Abstract

Fracture in Li-ion battery electrodes is one of the main degradation mechanisms that limit the battery performance and lifetime. Debonding between the active and binder materials damages mechanical integrity, which leads to the loss of active materials and increased resistance. In this work, molecular dynamics (MD) simulation is used to evaluate the strength of the connectivity between polyvinylindene fluoride (PVDF) binder and graphite in the opening and sliding modes. The simulations revealed detailed failure behaviors at the atomistic scale. We have found that the separation occurs at the interface rather than inside the bulk materials, suggesting that the mechanical strength at the interface between PVDF binder and graphite is weaker than that of PVDF or graphite. Therefore, debonding at the interface is critical to themechanical integrity of the electrode.Our calculations have provided quantitative traction-separation curves, and identified the maximum stresses of 300 MPa and 30 MPa for the normal and shear traction curves, respectively. The traction-separation curves obtained from the MD simulations will provide the critical input for the continuum level cohesive zone model to further study the inter-particle crack propagation in the electrode.

Department(s)

Mechanical and Aerospace Engineering

Keywords and Phrases

Binders; Computer simulation; Debonding; Degradation; Electric batteries; Electrodes; Graphite; Lithium; Lithium batteries; Molecular dynamics; Separation; Strength of materials, Battery performance; Cohesive zone model; Degradation mechanism; Failure behaviors; Li-ion battery electrodes; Mechanical integrity; Molecular dynamics simulations; Traction-separation, Interfaces (materials)

International Standard Serial Number (ISSN)

0013-4651; 1945-7111

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2014 Electrochemical Society Inc., All rights reserved.

Publication Date

01 May 2014

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