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Using neutron tomographic imaging, we report for the first time the three-dimensional spatial distribution of lithium products in electrochemically discharged lithium-air cathodes. Neutron imaging finds a nonuniform lithium product distribution across the electrode thickness, with the lithium species concentration being higher near the edges of the Li-air electrode and relatively uniform in the center of the electrode. The experimental neutron images were analyzed in context of results obtained from 3D modeling that maps the spatiotemporal variation of the lithium product distribution using a kinetically coupled diffusion based transport model. The origin of such anomalous behavior is due to the competition between the transport of lithium and oxygen and the accompanying electrochemical kinetics. Quantitative understanding of these effects is a critical step toward rechargeability of Li-air electrochemical systems.

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We demonstrate the lithiation process in graphitic anodes using in situ neutron radiography and diffraction in a single-layer pouch cell. The variation in neutron absorption contrast in graphite shows a direct correlation between the degree of lithiation and the discharge potential. The experimental neutron attenuation line profiles across the graphite electrode at various discharge times (potentials) were compared with lithium concentration profiles computed using a 3D electrochemical transport model. In conjunction with imaging/radiography, in situ neutron diffraction was carried out to obtain information about the local structural changes during various stages of lithiation in carbon. Combined in situ radiography and diffraction supported by 3D multiscale electrochemical modeling opens up a powerful nondestructive tool that can be utilized to understand the multiscale nature of lithium transport as well as observe various inhomogeneities at a cell level.

Lithium-ion batteries are highly complex electrochemical systems whose performance and safety are governed by coupled nonlinear electrochemical-electrical-thermal-mechanical processes over a range of spatiotemporal scales. Gaining an understanding of the role of these processes as well as development of predictive capabilities for design of better performing batteries requires synergy between theory, modeling, and simulation, and fundamental experimental work to support the models. This paper presents the overview of the work performed by the authors aligned with both experimental and computational efforts. In this paper, we describe a new, open source computational environment for battery simulations with an initial focus on lithium-ion systems but designed to support a variety of model types and formulations. This system has been used to create a three-dimensional cell and battery pack models that explicitly simulate all the battery components (current collectors, electrodes, and separator). The models are used to predict battery performance under normal operations and to study thermal and mechanical safety aspects under adverse conditions. This paper also provides an overview of the experimental techniques to obtain crucial validation data to benchmark the simulations at various scales for performance as well as abuse. We detail some initial validation using characterization experiments such as infrared and neutron imaging and micro-Raman mapping. In addition, we identify opportunities for future integration of theory, modeling, and experiments.