Browsing by Author "Li, Xintong"

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    Effect of Cationic (Na+) and Anionic (F-) Co-Doping on the Structural and Electrochemical Properties of LiNi1/3Mn1/3Co1/3O2 Cathode Material for Lithium-Ion Batteries
    (MDPI, 2022-06-17) Wang, Hua; Hashem, Ahmed M.; Abdel-Ghany, Ashraf E.; Abbas, Somia M.; El-Tawil, Rasha S.; Li, Tianyi; Li, Xintong; El-Mounayri, Hazim; Tovar, Andres; Zhu, Likun; Mauger, Alain; Julien, Christian M.; Mechanical and Energy Engineering, School of Engineering and Technology
    Elemental doping for substituting lithium or oxygen sites has become a simple and effective technique to improve the electrochemical performance of layered cathode materials. Compared with single-element doping, this work presents an unprecedented contribution to the study of the effect of Na+/F- co-doping on the structure and electrochemical performance of LiNi1/3Mn1/3Co1/3O2. The co-doped Li1-zNazNi1/3Mn1/3Co1/3O2-zFz (z = 0.025) and pristine LiNi1/3Co1/3Mn1/3O2 materials were synthesized via the sol-gel method using EDTA as a chelating agent. Structural analyses, carried out by X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy, revealed that the Na+ and F- dopants were successfully incorporated into the Li and O sites, respectively. The co-doping resulted in larger Li-slab spacing, a lower degree of cation mixing, and the stabilization of the surface structure, which substantially enhanced the cycling stability and rate capability of the cathode material. The Na/F co-doped LiNi1/3Mn1/3Co1/3O2 electrode delivered an initial specific capacity of 142 mAh g-1 at a 1C rate (178 mAh g-1 at 0.1C), and it maintained 50% of its initial capacity after 1000 charge-discharge cycles at a 1C rate.
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    Lithium Storage Mechanisms and Electrochemical Behavior of Molybdenum Disulfide
    (2024-05) Li, Xintong; Zhu, Likun; Hosop, Shin; Wei, Xiaoliang
    This study investigates the electrochemical behavior of molybdenum disulfide (MoS2) when utilized as an anode material in Li-ion batteries, particularly focusing on the intriguing phenomenon of extra capacity observed beyond theoretical expectations and the unique discharge curve of the first cycle. Employing a robust suite of advanced characterization methods such as in situ and ex situ X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM), the research unravels the complex structural and chemical evolution of MoS2 throughout its cycling process. A pivotal discovery of the research is the identification of a distinct lithium intercalation mechanism in MoS2, which leads to the formation of reversible LixMoS2. These phases play a crucial role in contributing to the extra capacity observed in the MoS2 electrode. Additionally, density functional theory (DFT) calculations have been utilized to explore the potential for overlithiation within MoS2, suggesting that Li5MoS2 could be the most energetically favorable phase during the lithiation-delithiation process. This study also explores the energetics of a Li-rich phase forming on the surface of Li4MoS2, indicating that this configuration is energetically advantageous and could contribute further to the extra capacity. The incorporation of reduced graphene oxide (RGO) as a conductive additive in MoS2 electrodes, demonstrating that RGO notably improves the electrochemical performance, rate capability, and durability of the electrodes. These findings are supported by experimental observations and are crucial for advancing the understanding of MoS2 as a high-capacity anode material. The implications of this research are significant, offering a pathway to optimize the design and composition of electrode materials to exceed traditional performance and longevity limits in Li-ion batteries.
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    Silver Nanocoating of LiNi0.8Co0.1Mn0.1O2 Cathode Material for Lithium-Ion Batteries
    (MDPI, 2023-04-23) Li, Xintong; Chang, Kai; Abbas, Somia M.; El-Tawil, Rasha S.; Abdel-Ghany, Ashraf E.; Hashem, Ahmed M.; Wang, Hua; Coughlin, Amanda L.; Zhang, Shixiong; Mauger, Alain; Zhu, Likun; Julien, Christian M.; Mechanical and Energy Engineering, School of Engineering and Technology
    Surface coating has become an effective approach to improve the electrochemical performance of Ni-rich cathode materials. In this study, we investigated the nature of an Ag coating layer and its effect on electrochemical properties of the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material, which was synthesized using 3 mol.% of silver nanoparticles by a facile, cost-effective, scalable and convenient method. We conducted structural analyses using X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy, which revealed that the Ag nanoparticle coating did not affect the layered structure of NCM811. The Ag-coated sample had less cation mixing compared to the pristine NMC811, which could be attributed to the surface protection of Ag coating from air contamination. The Ag-coated NCM811 exhibited better kinetics than the pristine one, which is attributed to the higher electronic conductivity and better layered structure provided by the Ag nanoparticle coating. The Ag-coated NCM811 delivered a discharge capacity of 185 mAh·g-1 at the first cycle and 120 mAh·g-1 at the 100th cycle, respectively, which is better than the pristine NMC811.