RESUMO
Synchrotron high-energy X-ray diffraction computed tomography has been employed to investigate, for the first time, commercial cylindrical Li-ion batteries electrochemically cycled over the two cycling rates of C/2 and C/20. This technique yields maps of the crystalline components and chemical species as a cross-section of the cell with high spatiotemporal resolution (550 × 550 images with 20 × 20 × 3 µm3 voxel size in ca. 1 h). The recently developed Direct Least-Squares Reconstruction algorithm is used to overcome the well-known parallax problem and led to accurate lattice parameter maps for the device cathode. Chemical heterogeneities are revealed at both electrodes and are attributed to uneven Li and current distributions in the cells. It is shown that this technique has the potential to become an invaluable diagnostic tool for real-world commercial batteries and for their characterization under operating conditions, leading to unique insights into "real" battery degradation mechanisms as they occur.
RESUMO
Large protein structures at atomic resolution can be solved in minutes using charge-flipping techniques operating on hundreds of virtual machines (computers) on the Amazon Web Services cloud-computing platform driven by the computer programs TOPAS or TOPAS-Academic at a small financial cost. The speed of operation has allowed charge-flipping techniques to be investigated and modified, leading to two strategies that can solve a large range of difficult protein structures at atomic resolution. Techniques include the use of space-group symmetry restraints on the electron density as well as increasing the intensity of a randomly chosen high-intensity electron-density peak. It is also shown that the use of symmetry restraints increases the chance of finding a solution for low-resolution data. Finally, a flipping strategy that negates `uranium atom solutions' has been developed for structures that exhibit such solutions during charge flipping.
