Browsing by Author "Sun, Cheng-Jun"

Now showing 1 - 5 of 5
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    Charge distribution guided by grain crystallographic orientations in polycrystalline battery materials
    Xu, Zhengrui; Jiang, Zhisen; Kuai, Chunguang; Xu, Rong; Qin, Changdong; Zhang, Yan; Rahman, Muhammad Mominur; Wei, Chenxi; Nordlund, Dennis; Sun, Cheng-Jun; Xiao, Xianghui; Du, Xi-Wen; Zhao, Kejie; Yan, Pengfei; Liu, Yijin; Lin, Feng (2020-01-08)
    Architecting grain crystallographic orientation can modulate charge distribution and chemomechanical properties for enhancing the performance of polycrystalline battery materials. However, probing the interplay between charge distribution, grain crystallographic orientation, and performance remains a daunting challenge. Herein, we elucidate the spatially resolved charge distribution in lithium layered oxides with different grain crystallographic arrangements and establish a model to quantify their charge distributions. While the holistic "surface-to-bulk" charge distribution prevails in polycrystalline particles, the crystallographic orientation-guided redox reaction governs the charge distribution in the local charged nanodomains. Compared to the randomly oriented grains, the radially aligned grains exhibit a lower cell polarization and higher capacity retention upon battery cycling. The radially aligned grains create less tortuous lithium ion pathways, thus improving the charge homogeneity as statistically quantified from over 20 million nanodomains in polycrystalline particles. This study provides an improved understanding of the charge distribution and chemomechanical properties of polycrystalline battery materials.
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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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    Investigating Particle Size-Dependent Redox Kinetics and Charge Distribution in Disordered Rocksalt Cathodes
    Zhang, Yuxin; Hu, Anyang; Liu, Jue; Xu, Zhengrui; Mu, Linqin; Sainio, Sami; Nordlund, Dennis; Li, Luxi; Sun, Cheng-Jun; Xiao, Xianghui; Liu, Yijin; Lin, Feng (Wiley-V C H Verlag, 2022-04)
    Understanding how various redox activities evolve and distribute in disordered rocksalt oxides (DRX) can advance insights into manipulating materials properties for achieving stable, high-energy batteries. Herein, the authors present how the reaction kinetics and spatial distribution of redox activities are governed by the particle size of DRX materials. The size-dependent electrochemical performance is attributed to the distinct cationic and anionic reaction kinetics at different sizes, which can be tailored to achieve optimal capacity and stability. Overall, the local charged domains in DRX particles display random heterogeneity caused by the isotropic delithiation pathways. Owing to the kinetic limitation, the micron-sized particles exhibit a holistic "core-shell" charge distribution, whereas sub-micron particles show more uniform redox reactions throughout the particles and ensembles. Sub-micron DRX particles exhibit increasing anionic redox activities yet inferior cycling stability. In summary, engineering particle size can effectively modulate how cationic and anionic redox activities evolve and distribute in DRX materials.
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    Regulating the Hidden Solvation-Ion-Exchange in Concentrated Electrolytes for Stable and Safe Lithium Metal Batteries
    Amine, Rachid; Liu, Jianzhao; Acznik, Ilona; Sheng, Tian; Lota, Katarzyna; Sun, Hui; Sun, Cheng-Jun; Fic, Krzysztof; Zuo, Xiaobing; Ren, Yang; Abd El-Hady, Deia; Alshitari, Wael; Al-Bogami, Abdullah S.; Chen, Zonghai; Amine, Khalil; Xu, Gui-Liang (2020-07)
    Lithium-sulfur batteries are attractive for automobile and grid applications due to their high theoretical energy density and the abundance of sulfur. Despite the significant progress in cathode development, lithium metal degradation and the polysulfide shuttle remain two critical challenges in the practical application of Li-S batteries. Development of advanced electrolytes has become a promising strategy to simultaneously suppress lithium dendrite formation and prevent polysulfide dissolution. Here, a new class of concentrated siloxane-based electrolytes, demonstrating significantly improved performance over the widely investigated ether-based electrolytes are reported in terms of stabilizing the sulfur cathode and Li metal anode as well as minimizing flammability. Through a combination of experimental and computational investigation, it is found that siloxane solvents can effectively regulate a hidden solvation-ion-exchange process in the concentrated electrolytes that results from the interactions between cations/anions (e.g., Li+, TFSI-, and S2-) and solvents. As a result, it could invoke a quasi-solid-solid lithiation and enable reversible Li plating/stripping and robust solid-electrolyte interphase chemistries. The solvation-ion-exchange process in the concentrated electrolytes is a key factor in understanding and designing electrolytes for other high-energy lithium metal batteries.
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    Spatial and Temporal Analysis of Sodium-Ion Batteries
    Hou, Dewen; Xia, Dawei; Gabriel, Eric; Russell, Joshua A.; Graff, Kincaid; Ren, Yang; Sun, Cheng-Jun; Lin, Feng; Liu, Yuzi; Xiong, Hui (American Chemical Society, 2021-11-12)
    As a promising alternative to the market-leading lithiumion batteries, low-cost sodium-ion batteries (SIBs) are attractive for applications such as large-scale electrical energy storage systems. The energy density, cycling life, and rate performance of SIBs are fundamentally dependent on dynamic physiochemical reactions, structural change, and morphological evolution. Therefore, it is essential to holistically understand SIBs reaction processes, degradation mechanisms, and thermal/mechanical behaviors in complex working environments. The recent developments of advanced in situ and operando characterization enable the establishment of the structure-processing-property- performance relationship in SIBs under operating conditions. This Review summarizes significant recent progress in SIBs exploiting in situ and operando techniques based on X-ray and electron analyses at different time and length scales. Through the combination of spectroscopy, imaging, and diffraction, local and global changes in SIBs can be elucidated for improving materials design. The fundamental principles and state-of-the-art capabilities of different techniques are presented, followed by elaborative discussions of major challenges and perspectives.