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Effects of surface tension and electrochemical reactions in Li-ion battery electrode nanoparticles

Stein, Peter and Zhao, Ying and Xu, Bai-Xiang (2016):
Effects of surface tension and electrochemical reactions in Li-ion battery electrode nanoparticles.
In: Journal of Power Sources, pp. 154-169, 332, ISSN 03787753,
[Article]

Abstract

The size- and shape-dependency of the chemo-mechanical behavior of spherical and ellipsoidal nanoparticles in Li-ion battery electrodes are investigated by a stress-assisted diffusion model and 3D finite element simulations. The model features surface tension, a direct coupling between diffusion and elasticity, concentration-dependent diffusivity, and a modified Butler-Volmer relation for the description of electrochemical reactions. Simulation results on spherical particles reveal that surface tension causes additional pressure fields in the particles, shifting the stress state towards the compressive regime. This provides mechanical stabilization, allowing, in principle, for higher charge/discharge rates. However, due to this pressure the attainable lithiation for a given potential difference is reduced during insertion, whereas a higher amount of ions is given off during extraction. Ellipsoidal particles with an aspect ratio deviating from that of a sphere with the same volume expose a larger surface area to the intercalation reactions. Consequently, they exhibit accelerated (dis)charge rates. However, due to the enhanced pressure in regions with high curvature, the accessible capacity of ellipsoidal particles is less than that of spherical particles.

Item Type: Article
Erschienen: 2016
Creators: Stein, Peter and Zhao, Ying and Xu, Bai-Xiang
Title: Effects of surface tension and electrochemical reactions in Li-ion battery electrode nanoparticles
Language: English
Abstract:

The size- and shape-dependency of the chemo-mechanical behavior of spherical and ellipsoidal nanoparticles in Li-ion battery electrodes are investigated by a stress-assisted diffusion model and 3D finite element simulations. The model features surface tension, a direct coupling between diffusion and elasticity, concentration-dependent diffusivity, and a modified Butler-Volmer relation for the description of electrochemical reactions. Simulation results on spherical particles reveal that surface tension causes additional pressure fields in the particles, shifting the stress state towards the compressive regime. This provides mechanical stabilization, allowing, in principle, for higher charge/discharge rates. However, due to this pressure the attainable lithiation for a given potential difference is reduced during insertion, whereas a higher amount of ions is given off during extraction. Ellipsoidal particles with an aspect ratio deviating from that of a sphere with the same volume expose a larger surface area to the intercalation reactions. Consequently, they exhibit accelerated (dis)charge rates. However, due to the enhanced pressure in regions with high curvature, the accessible capacity of ellipsoidal particles is less than that of spherical particles.

Journal or Publication Title: Journal of Power Sources
Volume: 332
Uncontrolled Keywords: Lithium-ion batteries, Butler-Volmer equation, Reaction kinetics, Stress-enhanced diffusion, Surface tension, Nanoparticles
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Mechanics of functional Materials
Exzellenzinitiative
Exzellenzinitiative > Graduate Schools > Graduate School of Computational Engineering (CE)
Exzellenzinitiative > Graduate Schools
Date Deposited: 15 Sep 2016 09:58
Identification Number: doi:10.1016/j.jpowsour.2016.09.085
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