Models of Li-ion battery performance and durability often ignore the conductive carbon-binder domains (CBDs), yet recent experimental and modeling work by Wheeler et al and by Garcia et al have indicated that the manner in which CBD is distributed through the electrode plays an important role in ion transport kinetics. Until now, however, the 3-dimensional distribution of CBDs within the electrode has not been measured. While X-ray microscopy (XRM) has been demonstrated by Shearing et al and Eastwood et al to be a powerful technique for imaging graphite electrodes, the active particles and the CBDs exhibit nearly identical CT numbers in the reconstructed volumes due to their similar mass densities. For this work, we doped small amounts of carbon-coated Fe nanoparticles into the CBDs, taking advantage of the resulting increased effective mass density to elevate the CT numbers of the CBDs in the XRM imaging results. The Fe nanoparticles and the conductive carbon have similar sizes (25 nm) and both have carbon surfaces; thus, they were expected to disperse similarly in the binder. The dispersion was confirmed via X-ray radiography, and the specimen was successfully imaged in 3D using nano-scale XRM. This presentation will describe the results of this imaging experiment, focusing on the analysis for how the CBDs are distributed and their effects on ion transport within a Li-ion battery electrode.

3D distribution of the conductive carbon-binder domains in Li-ion batteries

251st National Meeting (2016)

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