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Instruments / Technical Area	Publication Details	Published	Actions
I11-High Resolution Powder Diffraction	Spatially resolved operando synchrotron-based x-ray diffraction measurements of Ni-rich cathodes for Li-ion batteries Andrew Stephen Leach , Alice Llewellyn , Chao Xu , Chun Tan , Thomas M. M. Heenan , Alex Dimitrijevic , Karin Kleiner , Clare P. Grey , Dan J. L. Brett , Chiu C. Tang , Paul R. Shearing , Rhodri Jervis Frontiers In Chemical Engineering 3 DOI: 10.3389/fceng.2021.794194 Diamond Proposal Number(s): [22498, 24122] Open Access Show Abstract ▼ Abstract: Understanding the performance of commercially relevant cathode materials for lithium-ion (Li-ion) batteries is vital to realize the potential of high-capacity materials for automotive applications. Of particular interest is the spatial variation of crystallographic behavior across (what can be) highly inhomogeneous electrodes. In this work, a high-resolution X-ray diffraction technique was used to obtain operando transmission measurements of Li-ion pouch cells to measure the spatial variances in the cell during electrochemical cycling. Through spatially resolved investigations of the crystallographic structures, the distribution of states of charge has been elucidated. A larger portion of the charging is accounted for by the central parts, with the edges and corners delithiating to a lesser extent for a given average electrode voltage. The cells were cycled to different upper cutoff voltages (4.2 and 4.3 V vs. graphite) and C-rates (0.5, 1, and 3C) to study the effect on the structure of the NMC811 cathode. By combining this rapid data collection method with a detailed Rietveld refinement of degraded NMC811, the spatial dependence of the degradation caused by long-term cycling (900 cycles) has also been shown. The variance shown in the pristine measurements is exaggerated in the aged cells with the edges and corners offering an even lower percentage of the charge. Measurements collected at the very edge of the cell have also highlighted the importance of electrode alignment, with a misalignment of less than 0.5 mm leading to significantly reduced electrochemical activity in that area.	Jan 2022
I14-Hard X-ray Nanoprobe	Identifying the origins of microstructural defects such as cracking within Ni‐rich NMC811 cathode particles for lithium‐ion batteries Thomas M. M. Heenan , Aaron Wade , Chun Tan , Julia E. Parker , Dorota Matras , Andrew S. Leach , James B. Robinson , Alice Llewellyn , Alexander Dimitrijevic , Rhodri Jervis , Paul D. Quinn , Dan J. L. Brett , Paul R. Shearing Advanced Energy Materials 1 DOI: 10.1002/aenm.202002655 Diamond Proposal Number(s): [20841, 23858] Open Access Show Abstract ▼ Abstract: The next generation of automotive lithium‐ion batteries may employ NMC811 materials; however, defective particles are of significant interest due to their links to performance loss. Here, it is demonstrated that even before operation, on average, one‐third of NMC811 particles experience some form of defect, increasing in severity near the separator interface. It is determined that defective particles can be detected and quantified using low resolution imaging, presenting a significant improvement for material statistics. Fluorescence and diffraction data reveal that the variation of Mn content within the NMC particles may correlate to crystallographic disordering, indicating that the mobility and dissolution of Mn may be a key aspect of degradation during initial cycling. This, however, does not appear to correlate with the severity of particle cracking, which when analyzed at high spatial resolutions, reveals cracking structures similar to lower Ni content NMC, suggesting that the disconnection and separation of neighboring primary particles may be due to electrochemical expansion/contraction, exacerbated by other factors such as grain orientation that are inherent in such polycrystalline materials. These findings can guide research directions toward mitigating degradation at each respective length‐scale: electrode sheets, secondary and primary particles, and individual crystals, ultimately leading to improved automotive ranges and lifetimes.	Nov 2020

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