Browsing by Subject "LiCoO2"

Now showing 1 - 6 of 6
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    Finite element study of Li diffusion and stress in LiNi0.33Mn0.33Co0.33O2 cathode using microstructures reconstructed by synchrotron X-ray tomography
    (Office of the Vice Chancellor for Research, 2016-04-08) Wu, Linmin; Zhang, Yi; Zhang, Jing
    LiNi0.33Mn0.33Co0.33O2 is a good substitute for LiCoO2 because of its good thermal stability and high energy density. In this study, the diffusion and stress in LiNi0.33Mn0.33Co0.33O2 cathode with realistic three-dimensional (3D) microstructures have been studied systematically. Synchrotron Xray tomography was used to obtain the 3D reconstructions of porous LiNi0.33Mn0.33Co0.33O2 microstructures. Li concentration distributions under various C-rates were investigated. The obtained charge/discharge curves under various C-rates were compared with the results from Newman’s model. The stress generation in the cathode was computed coupled with the diffusion. The hydrostatic stress, shear stress and von Mises stress in the particles were analyzed. The results show that the von Mises stress in particle boundaries is higher than the stress inside the particle due to the Li concentration gradient during discharge, which is consistent with the literature. Additionally, the von Mises stress near the particle contact region is much higher than other areas.
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    First principles study on the electrochemical, thermal and mechanical properties of LiCoO2 for thin film rechargeable battery
    (2014) Wu, Linmin; Hoh Lee, Weng; Zhang, Jing
    Thin film rechargeable battery has become a research hotspot because of its small size and high energy density. Lithium cobalt oxide as a typical cathode material in classical lithium ion batteries is also widely used in thin film rechargeable batteries. In this work, the electrochemical, mechanical and thermal properties of LiCoO2 were systematically investigated using the first principles method. Elastic constants under hydrostatic pressures between 0 to 40 GPa were computed. Specific heat and Debye temperature at low temperature were discussed. Thermal conductivity was obtained using the imposed-flux method. The results show good agreements with experimental data and computational results in literature.
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    Numerical Simulation of Li Diffusion in 3D Polycrystalline LiCoO2
    (Office of the Vice Chancellor for Research, 2015-04-17) Wu, Linmin; Zhang, Jing
    LiCoO2 is a commonly used cathode material of Li-ion rechargeable batteries. In battery applications, crystal anisotropy and grain boundaries have large influence on ion diffusion properties. To improve the battery performance, a thorough understanding of the diffusion process of Li ions is significant. In this study, 3D microstructures of various grain sizes were generated using phase field models. The apparent Li diffusion coefficient was obtained using finite element method. The relationship between the apparent Li diffusion coefficient, the grain boundary diffusivity, spatial distribution of grain orientations, and the grain size was discussed.
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    Three-Dimensional Finite Element Study on Li Diffusion Induced Stress in FIB-SEM Reconstructed LiCoO2 Half Cell
    (Elsevier, 2016-12) Wu, Linmin; Wen, Youhai; Zhang, Jing; Department of Mechanical Engineering, School of Engineering and Technology
    In this study, the diffusion induced stress of LiCoO2 half cell with a realistic 3D microstructure has been studied using finite element method. The electrochemical properties under various C rates were studied. The discharged curves under various C rates were simulated. Results show that the potential drops significantly with the increase of C rates. The lithium ion concentration distribution under high discharging rates shows strong inhomogeneity. At high C rates, the small LiCoO2 particles near the separator have higher lithium ion concentration because of the shorter lithium migration and diffusion paths. The diffusion induced stress inside LiCoO2 particles was calculated coupled with lithium diffusion. The results show that the stress near the concave and convex regions is the highest. The neck regions of the connected particles will break first and form several isolated particles. For isolated particles, cracks are more likely to form on the surface rather than inside the particle. Failure may occur in large grains ahead of small grains.
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    Three-Dimensional Finite Element Study on Lithium Diffusion and Intercalation-Induced Stress in Polycrystalline LiCoO2 Using Anisotropic Material Properties
    (ASME, 2019-05) Wu, Linmin; Zhang, Jing; Mechanical Engineering and Energy, School of Engineering and Technology
    In this study, lithium (Li) intercalation-induced stress of LiCoO2 with anisotropic properties using three-dimensional (3D) microstructures has been studied systematically. Phase field method was employed to generate LiCoO2 polycrystals with varying grain sizes. Li diffusion and stresses inside the polycrystalline microstructure with different grain size, grain orientation, and grain boundary diffusivity were investigated using finite element method. The results show that the anisotropic mechanical properties and Li concentration-dependent volume expansion coefficient have a very small influence on the Li chemical diffusion coefficients. The low partial molar volume of LiCoO2 leads to this phenomenon. The anisotropic mechanical properties have a large influence on the magnitude of stress generation. Since the Young's modulus of LiCoO2 along the diffusion pathway (a–b axis) is higher than that along c–axis, the Li concentration gradient is larger along the diffusion pathway. Thus, for the same intercalation-induced strain, the stress generation will be higher (∼40%) than that with isotropic mechanical properties as discussed in our previous study (Wu, L., Zhang, Y., Jung, Y.-G., and Zhang, J., 2015, “Three-Dimensional Phase Field Based Finite Element Study on Li Intercalation-Induced Stress in Polycrystalline LiCoO2,” J. Power Sources, 299, pp. 57–65). This work demonstrates the importance to include anisotropic property in the model.
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    Three-Dimensional Phase Field Based Finite Element Study on Li Intercalation-Induced Stress in Polycrystalline LiCoO2
    (Elsevier, 2015-12) Wu, Linmin; Zhang, Yi; Jung, Yeon-Gil; Zhang, Jing; Department of Mechanical Engineering, School of Engineering
    In this study, the stress generation of LiCoO2 with realistic 3D microstructures has been studied systematically. Phase field method was employed to generate the 3D microstructures with different grain sizes. The effects of grain size, grain crystallographic orientation, and grain boundary diffusivity on chemical diffusion coefficient and stress generation were studied using finite element method. The calculated chemical diffusion coefficient is about in the range of 8.5 × 10−10 cm2/s–3.6 × 10−9 cm2/s. Stresses increase with the increase of grain size, due to more accumulation of Li ion near the grain boundary regions in larger grain size systems, which causes a larger concentration gradient. Failure is more likely to occur in large grain systems. The chemical diffusion coefficients increase with increasing grain orientation angle irrespective of grain boundary diffusivity, due to alignment of global Li ion diffusion path with high grain orientations. Grain boundary diffusivity has opposite effect on the hydrostatic stress. As small grain boundary diffusivity, the stress increases with increasing grain orientation angle, due to grain boundary blockage of Li ion diffusion. In contrast, with large grain boundary diffusivity, the stress decreases with increasing grain orientation angle due to reduced concentration gradients in grain boundary regions.