Elemental and Chemical Mapping of High Capacity Intermetallic Li-ion Anodes with Transmission X-ray Microscopy

X-ray nanotomography has been applied toward the three-dimensional (3D) imaging of a Li-ion battery alloy anode material (Cu 6 Sn 5 ), and subsequent segmentation and analysis has been performed to distinguish the alloy material from its constituent components. Follow-on x-ray absorption near edge structure imaging was performed yielding absorption spectra for Cu, Cu 6 Sn 5 , and Li 2 CuSn. Analyses based on these spectra were performed on two-dimensional (2D) images of samples from cycled electrodes to assess chemical composition in Cu-containing phases. The capability to distinguish the different materials within mixed samples suggests that microstructure and composition changes resulting from lithiation and delithiation in Cu 6 Sn 5 may be observed and better understood with 3D x-ray imaging methods. These methods are expected to be applicable to other intermetallic tin alloy electrodes.