Probing the effect of surface parameters and particle size in the diffusion-induced stress of electrodes during lithium insertion

This article reviews polarizability properties of particles and clusters. Especially the effect of surface geometry is given attention. The important parameter of normalized dipolarizability is studied as function of the permittivity and the shape of the surface of the particle. For nonsymmetric particles, the quantity under interest is the average of the three polarizability dyadic eigenvalues. The normalized polarizability, although different for different shapes, has certain universal characteristics independent of the inclusion form. The canonical shapes (sphere, spheroids, ellipsoids, regular polyhedra, circular cylinder, semisphere, double sphere) are studied as well as the correlation of surface parameters with salient polarizability properties. These geometrical and surface parameters are essential in the material modeling problems in the nanoscale.

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A Diffusion Model in a Two-Phase Interfacial Zone for Nanoscale Lithium-Ion Battery Materials

Volume 6: Energy, Parts A and B ◽

10.1115/imece2012-89235 ◽

2012 ◽

Author(s):

Cheng-Kai ChiuHuang ◽

Hsiao-Ying Shadow Huang

Keyword(s):

Lithium Ion Batteries ◽

Lithium Ion Battery ◽

Electric Vehicle ◽

Cathode Materials ◽

Electrode Materials ◽

Lithium Ion ◽

Capacity Loss ◽

Induced Stress ◽

Stress Formation ◽

Diffusion Induced Stress

The development of lithium-ion batteries plays an important role to stimulate electric vehicle (EV) and plug-in electric vehicle (PHEV) industries and it is one of many solutions to reduce US oil import dependence. To develop advanced vehicle technologies that use energy more efficiently, retaining the lithium-ion battery capacity is one of major challenges facing by the electrochemical community today. During electrochemical processes, lithium ions diffuse from and insert into nanoscaled cathode materials in which stresses are formed. It is considered that diffusion-induced stress is one of the factors causing electrode material capacity loss and failure. In this study, we present a model which is capable for describing diffusion mechanisms and stress formation in nano-platelike cathode materials, LiFePO4 (Lithium-iron-phosphate). We consider particle size >100 nm in this study since it has been suggested that very small nanoparticles (<100 nm) may not undergo phase separation during fast diffusion. To evaluate diffusion-induced stress accurately, factors such as the diffusivity and phase boundary movements are considered. Our result provides quantitative lithium concentrations inside LiFePO4 nanoparticles. The result could be used for evaluating stress formation and provides potential cues for precursors of capacity loss in lithium-ion batteries. This study contributes to the fundamental understanding of lithium ion diffusion in electrode materials, and results from this model help better electrode materials design in lithium-ion batteries.

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