Anomalous Discharge Product Distribution in Lithium-Air Cathodes

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.