ORALS

SESSION: PhysicalFriPM1-R10	Vayenas International Symposium on Physical Chemistry and its applications for sustainable development
Fri Oct, 25 2019 / Room: Aphrodite B (100/Gr. F)
Session Chairs: Katerina Aifantis; Eftychia Martino; Session Monitor: TBA

14:50: [PhysicalFriPM107] Invited
Next Generation Electrodes for Na-Ion Batteries
Katerina Aifantis¹ ; Pu Hu² ; ¹University of Florida, Gainesville, United States; ²Univ of Florida, Gainesville, Greece;
Paper Id: 324 [Abstract]

Na-ion batteries are the most promising energy sources for stationary applications. Numerous electrode materials that are used in Li-ion cells seem promising for use in Na-ion cells as well. A stable long term capacity, however, is yet to be achieved by these electrode materials. The present talk will compare the differences between the sodiation and lithiation mechanisms of TiS₂ which can serve as a cathode material. X-ray diffraction and electron microscopy illustrate that cycling with respect to lithium results in long term electrochemical stability, whereas with respect to sodium, irreversible phases and cracks form, giving rise to a capacity decay. The experimental results are supported with continuum mechanics studies on stress evolution during cycling.

SESSION: BatteryFriPM2-R11	6th Intl. Symp. on Sustainable Secondary Battery Manufacturing and Recycling
Fri Oct, 25 2019 / Room: Coralino
Session Chairs: Katsuya Teshima; Deise Menezes Santos; Session Monitor: TBA

16:45: [BatteryFriPM211] Invited
Size Effects in Nanostructured Li-Ion Batteries
Sundararajan Natarajan¹ ; Katerina Aifantis² ; ¹Indian Institute of Technology Madras, Chennai, India; ²University of Florida, Gainesville, United States;
Paper Id: 355 [Abstract]

Materials such as Si, Al and Sn are considered as active sites during the formation of Li-alloys. During the Li insertion, the volume of the active sites expands over 100\% at maximum capacity. As a result, large internal stresses are produced. The effect of stresses is widely acknowledged. As the size of these particles is small, however, the gradient effects cannot be ignored. In this paper, we present, for the first time, the size effects within a purely gradient elasticity framework. A coupled mechanical equilibrium and Li diffusion accounting for the effect of stress on diffusion and the effect of diffusion on stress are considered. We also consider the effect of concentration on the Young's modulus. As the constitutive equation involves higher order gradient terms, the conventional finite element method is not suitable. Moreover, the two-way coupling necessitates the need for higher order shape functions. In this study, we employ B-spline functions with the framework of the iso-geometric analysis for spatial discretization. The effect of internal characteristic length on the concentration evolution and the hydrostatic stresses are studied. It is observed that the internal length has significant impact on the stress amplitudes.

SESSION: BatterySatAM-R11	6th Intl. Symp. on Sustainable Secondary Battery Manufacturing and Recycling
Sat Oct, 26 2019 / Room: Coralino
Session Chairs: Vasant Kumar; Ali Reza Kamali; Session Monitor: TBA

12:10: [BatterySatAM03]
Si-Polymer Nanocomposite Anodes for Li-Ion Batteries
Pu Hu¹ ; Utkarsh Ahuja² ; Bo Wang³ ; Katerina Aifantis⁴ ; ¹Univ of Florida, Gainesville, Greece; ²Uni. of Florida, Gainesville, United States; ³Univ. of Florid, Gainesville, United States; ⁴University of Florida, Gainesville, United States;
Paper Id: 325 [Abstract]

Si has recently been commerialized as an active material in anodes for Li-ion batteries. Due to large volume expansion, however, it experiences low amounts of graphite anodes during Li-insertion, resulting in a small capacity of increase over purely graphitic ones. The present talk illustrates new Si based anodes comprised of Si nanoparticles that are coated with polymers. These configurations allow for improved mechanical properties over those of pure Si nanoparticle anodes. A mechanics model is formulated that can predict and design criteria that can prolong the mechanical and electrochemical stability of high content Si based anodes. The model predictions are in agreement with the experimental observations and can also capture the size effect for which fractures can be avoided by tuning the particle diameter and polymer coating. Different polymers have been considered, including conductive and non-conductive ones, while in some cases, the binder was not added in producing the porous electrode.