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The electrode of Li-ion batteries is required to be chemically and mechanically stable in the electrolyte environment for in situ monitoring by transmission X-ray microscopy (TXM). Evidence has shown that continuous irradiation has an impact on the microstructure and the electrochemical performance of the electrode. To identify the root cause of the radiation damage, a wire-shaped electrode is soaked in an electrolyte in a quartz capillary and monitored using TXM under hard X-ray illumination. The results show that expansion of the carbon-binder matrix by the accumulated X-ray dose is the key factor of radiation damage. For in situ TXM tomography, intermittent X-ray exposure during image capturing can be used to avoid the morphology change caused by radiation damage on the carbon-binder matrix. [ABSTRACT FROM AUTHOR]

The impact of calendering process on the geometric characteristics and electrochemical performance of LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC) electrode was investigated in this study. The geometric properties of NMC electrodes with different calendering conditions, such as porosity, pore size distribution, particle size distribution, specific surface area and tortuosity were calculated from the computed tomography data of the electrodes. A synchrotron transmission X-ray microscopy tomography system at the Advanced Photon Source of the Argonne National Laboratory was employed to obtain the tomography data. The geometric and electrochemical analysis show that calendering can increase the electrochemically active area, which improves rate capability. However, more calendering will result in crushing of NMC particles, which can reduce the electrode capacity at relatively high C rates. This study shows that the optimum electrochemical performance of NMC electrode at 94:3:3 weight ratio of NMC:binder:carbon black can be achieved by calendering to 3.0 g/cm 3 NMC density. [ABSTRACT FROM AUTHOR]

A multiscale platform has been developed to model lithium ion battery (LIB) electrodes based on the real microstructure morphology. This multiscale framework consists of a microscale level where the electrode microstructure architecture is modeled and a macroscale level where discharge/charge is simulated. The coupling between two scales are performed in real time unlike using common surrogate based models for microscale. For microscale geometry 3D microstructure is reconstructed based on the nano-scale X-ray computed tomography data replacing typical computer generated microstructure. It is shown that this model can predict the experimental performance of LiFePO 4 (LFP) cathode at different discharge rates more accurate than the conventional homogenous models. The approach employed in this study provides valuable insight into the spatial distribution of lithium -ion inside the real microstructure of LIB electrodes. The inhomogenous microstructure of LFP causes a wider range of physical and electrochemical properties in microscale compared to homogenous models. [ABSTRACT FROM AUTHOR]

Abstract: A three dimensional numerical framework with finite volume method was employed to simulate heat generation of a semi lithium ion battery (LIB) cell during isothermal galvanostatic discharge processes. The microstructure of the LIB cathode electrode was experimentally determined using X-ray nano computed tomography technology. Heat generation in the semi LIB cell during galvanostatic discharge processes from different mechanisms, such as electronic resistive heat, ionic resistive heat, contact resistive heat, reaction heat, entropic heat and heat of mixing, was investigated. The spatial distribution of heat generation rates from different mechanisms was also studied. The simulation results demonstrate that the magnitude of heat generation rates spans a wide range in the electrode due to structural inhomogeneity. The simulation results of heat generation from the three dimensional model and the porous-electrode theory model were compared in this study. It is found that the typical Bruggeman coefficient, 1.5, underestimated ionic resistance in the electrolyte and overestimated electronic resistance in the cathode particles. In general, the three dimensional model predicted more heat generation than the porous-electrode theory model at large discharge rates due to the wider distribution of physical and electrochemical properties. [Copyright &y& Elsevier]