Browsing by Author "Hou, Dong"

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    Effect of the grain arrangements on the thermal stability of polycrystalline nickel-rich lithium-based battery cathodes
    Hou, Dong; Xu, Zhengrui; Yang, Zhijie; Kuai, Chunguang; Du, Zhijia; Sun, Cheng-Jun; Ren, Yang; Liu, Jue; Xiao, Xianghui; Lin, Feng (Springer, 2022-06-15)
    One of the most challenging aspects of developing high-energy lithium-based batteries is the structural and (electro)chemical stability of Ni-rich active cathode materials at thermally-abused and prolonged cell cycling conditions. Here, we report in situ physicochemical characterizations to improve the fundamental understanding of the degradation mechanism of charged polycrystalline Ni-rich cathodes at elevated temperatures (e.g., ≥ 40 °C). Using multiple microscopy, scattering, thermal, and electrochemical probes, we decouple the major contributors for the thermal instability from intertwined factors. Our research work demonstrates that the grain microstructures play an essential role in the thermal stability of polycrystalline lithium-based positive battery electrodes. We also show that the oxygen release, a crucial process during battery thermal runaway, can be regulated by engineering grain arrangements. Furthermore, the grain arrangements can also modulate the macroscopic crystallographic transformation pattern and oxygen diffusion length in layered oxide cathode materials.
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    Rigid registration algorithm based on the minimization of the total variation of the difference map
    Xiao, Xianghui; Xu, Zhengrui; Hou, Dong; Yang, Zhijie; Lin, Feng (International Union of Crystallography, 2022-07)
    Image registration is broadly used in various scenarios in which similar scenes in different images are to be aligned. However, image registration becomes challenging when the contrasts and backgrounds in the images are vastly different. This work proposes using the total variation of the difference map between two images (TVDM) as a dissimilarity metric in rigid registration. A method based on TVDM minimization is implemented for image rigid registration. The method is tested with both synthesized and real experimental data that have various noise and background conditions. The performance of the proposed method is compared with the results of other rigid registration methods. It is demonstrated that the proposed method is highly accurate and robust and outperforms other methods in all of the tests. The new algorithm provides a robust option for image registrations that are critical to many nanoscale X-ray imaging and microscopy applications.
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    Tailoring Disordered/Ordered Phases to Revisit the Degradation Mechanism of High-Voltage LiNi0.5Mn1.5O4 Spinel Cathode Materials
    Sun, Huabin; Hu, Anyang; Spence, Stephanie; Kuai, Chunguang; Hou, Dong; Mu, Linqin; Liu, Jue; Li, Luxi; Sun, Chengjun; Sainio, Sami; Nordlund, Dennis; Luo, Wei; Huang, Yunhui; Lin, Feng (Wiley-V C H Verlag, 2022-05)
    In the spinel oxide cathode family, LiNi0.5Mn1.5O4 (LNMO) shows a high operating voltage (approximate to 4.7 V vs Li/Li+) and excellent Li-ion mobility with stable 3D conducting channels. Ni/Mn cation disordered and ordered phases usually coexist in LNMO materials, and they have distinct structural and electrochemical properties, resulting in different battery performances for LNMO materials with different phase compositions. Identifying the correlation between phase compositions and electrochemical properties is of significance to the improvement of battery performance and understanding of degradation mechanisms. Herein, the disordered/ordered phase compositions in LNMO materials are tailored by post-annealing strategies and their impacts on electrochemical performance and degradation mechanisms from the surface to the bulk are systematically investigated. The ordered phase increases rapidly as Mn3+ is oxidized to Mn4+ through a post-annealing process. LNMO with an intermediate fraction of disordered and ordered phases gives rise to improved cycling stability. This article further reports that a high ordered phase fraction can preferentially protect Ni from dissolution during cycling. However, these results suggest that the transition metal dissolution and surface structural change of LNMO do not exhibit a direct correlation with cycling stability. These results indicate the capacity fading mainly correlates with the bulk structural distortion, leading to decreased Li-ion kinetics.