Tortuosity characterization of 3D microstructure at nano-scale for energy storage and conversion materials

A distance propagation method is presented for calculating tortuosity with relatively low computation time from three-dimensional (3D) tomographic data. Moreover, a novel concept of tortuosity distribution is developed to provide a more comprehensive picture of inhomogeneous microstructures where tortuosity depends on the actual 3D paths. Instead of using one single tortuosity value, the tortuosity distribution both as spatial distribution map and also statistic histogram can provide a more complete description. The method, which can be applied to any porous medium, is tested against a diffusion-based tortuosity calculation on two 3D microstructures: a LiCoO2 cathode electrode of lithium ion battery measured by x-ray nano-tomography and a lanthanum strontium manganite-yttria-stabilized zirconia, solid oxide fuel cells cathode measured using focused ion beam-scanning electron microscopy serial sectioning. The present method is shown to provide good-agreement with the effective diffusion-based tortuosity values.