Browsing by Author "De Carlo, Francesco"

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    Geometric and Electrochemical Characteristics of LiNi1/3Mn1/3Co1/3O2 Electrode with Different Calendering Conditions
    (Elsevier, 2017-04) Kang, Huixiao; Lim, Cheolwoong; Li, Tianyi; Fu, Yongzhu; Yan, Bo; Houston, Nicole; De Andrade, Vincent; De Carlo, Francesco; Zhu, Likun; Department of Mechanical Engineering, School of Engineering and Technology
    The impact of calendering process on the geometric characteristics and electrochemical performance of LiNi1/3Mn1/3Co1/3O2 (NMC) electrode was investigated in this study. The geometric properties of NMC electrodes with different calendering conditions, such as porosity, pore size distribution, particle size distribution, specific surface area and tortuosity were calculated from the computed tomography data of the electrodes. A synchrotron transmission X-ray microscopy tomography system at the Advanced Photon Source of the Argonne National Laboratory was employed to obtain the tomography data. The geometric and electrochemical analysis show that calendering can increase the electrochemically active area, which improves rate capability. However, more calendering will result in crushing of NMC particles, which can reduce the electrode capacity at relatively high C rates. This study shows that the optimum electrochemical performance of NMC electrode at 94:3:3 weight ratio of NMC:binder:carbon black can be achieved by calendering to 3.0 g/cm3 NMC density.
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    Geometric Characteristics of Lithium Ion Battery Electrodes with Different Packing Densities
    (Office of the Vice Chancellor for Research, 2015-04-17) Lim, Cheolwoong; Lee, Wen Chao; Bo, Yan; Song, Zhibin; De Andrade, Vincent; De Carlo, Francesco; Kim, Youngsik; Zhu, Likun
    The microstructure of electrodes plays a critical role in determining the performance of lithium ion batteries (LIBs), because the microstructure can affect the transport and electrochemical processes within electrodes (1-3). Increasing the volume fraction of active materials in the electrode will increase the energy density. However, the electrodes’ structural properties could also be changed significantly and the critical physical and electrochemical processes in LIBs will be affected. Therefore, the performance of a LIB can be optimized for a specific operating condition by designing electrode microstructures. For instance, Hellweg suggested a spatially varying porous electrode model to improve lithium ion transport in electrolyte phase at high charge/discharge rates (4). He showed that the power density of the graded porosity electrode was higher than a homogeneous porosity electrode without energy loss. In this study, we investigate the realistic geometric characteristics of electrode microstructures under different packing densities and the effect of packing density on the performance of LIBs. Moreover, a spatially varying porous electrode will be studied to increase the electrode energy density without losing rate capability. To investigate geometric characteristics of porous microstructures, cathode electrodes were fabricated from a 94:3:3 (weight %) mixture of LiCoO2 (average particle radius = 5 μm), PVDF, and super-P carbon black. To change the packing density, initial thickness of the electrodes was set in a range of 40 ~ 80 μm. Then all electrodes were pressed down to 40 μm by using a rolling press machine. A synchrotron X-ray nano-computed tomography instrument (nano-CT) at the Advanced Phothon Source of Argonne National Lab was employed to obtain morphological data of the electrodes, with a spatial resolution of 60 nm. The morphology data sets were quantitatively analyzed to characterize their geometric properties. Fig. 1 shows the porosity (ε), specific surface area (As, μm-1), tortuosity (τ), and pore size distribution of 4 different electrode microstructures. The pore size distribution of the un-pressed electrode (ε =0.56, black color) demonstrates nonuniformly dispersed active material. The highest packing density electrode (ε =0.36, red color) shows the highest tortuosity. The charge/discharge experiments were also conducted for these 4 different electrodes. The geometric properties and cell testing results will be analyzed and reported. Acknowledgments: This work was supported by US National Science Foundation under Grant No. 1335850. Fig. 1 Geometric characteristics (porosity ε, specific surface area As, tortuosity τ, pore size distribution) of xray generated porous electrode microstructure with different packing densities.
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    Hard X-ray-induced damage on carbon–binder matrix for in situ synchrotron transmission X-ray microscopy tomography of Li-ion batteries
    (IUCR, 2017) Lim, Cheolwoong; Kang, Huixiao; De Andrade, Vincent; De Carlo, Francesco; Zhu, Likun; Mechanical Engineering, School of Engineering and Technology
    The electrode of Li-ion batteries is required to be chemically and mechanically stable in the electrolyte environment for in situ monitoring by transmission X-ray microscopy (TXM). Evidence has shown that continuous irradiation has an impact on the microstructure and the electrochemical performance of the electrode. To identify the root cause of the radiation damage, a wire-shaped electrode is soaked in an electrolyte in a quartz capillary and monitored using TXM under hard X-ray illumination. The results show that expansion of the carbon–binder matrix by the accumulated X-ray dose is the key factor of radiation damage. For in situ TXM tomography, intermittent X-ray exposure during image capturing can be used to avoid the morphology change caused by radiation damage on the carbon–binder matrix.
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    In Situ and Operando Investigation of the Dynamic Morphological and Phase Changes of Selenium-doped Germanium Electrode during (De)Lithiation Processes
    (RSC, 2020-01) Li, Tianyi; Lim, Cheolwoong; Cui, Yi; Zhou, Xinwei; Kang, Huixiao; Yan, Bo; Meyerson, Melissa L.; Weeks, Jason A.; Liu, Qi; Guo, Fangmin; Kou, Ronghui; Liu, Yuzi; De Andrade, Vincent; De Carlo, Francesco; Ren, Yang; Sun, Cheng-Jun; Mullins, C. Buddie; Chen, Lei; Fu, Yongzhu; Zhu, Likun; Mechanical and Energy Engineering, School of Engineering and Technology
    To understand the effect of selenium doping on the good cycling performance and rate capability of a Ge0.9Se0.1 electrode, the dynamic morphological and phase changes of the Ge0.9Se0.1 electrode were investigated by synchrotron-based operando transmission X-ray microscopy (TXM) imaging, X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). The TXM results show that the Ge0.9Se0.1 particle retains its original shape after a large volume change induced by (de)lithiation and undergoes a more sudden morphological and optical density change than pure Ge. The difference between Ge0.9Se0.1 and Ge is attributed to a super-ionically conductive Li–Se–Ge network formed inside Ge0.9Se0.1 particles, which contributes to fast Li-ion pathways into the particle and nano-structuring of Ge as well as buffering the volume change of Ge. The XRD and XAS results confirm the formation of a Li–Se–Ge network and reveal that the Li–Se–Ge phase forms during the early stages of lithiation and is an inactive phase. The Li–Se–Ge network also can suppress the formation of the crystalline Li15Ge4 phase. These in situ and operando results reveal the effect of the in situ formed, super-ionically conductive, and inactive network on the cycling performance of Li-ion batteries and shed light on the design of high capacity electrode materials.
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    In-Situ Characterization of Dynamic Morphological and Phase Changes of Selenium-doped Germanium Using a Single Particle Cell and Synchrotron Transmission X-ray Microscopy
    (Wiley, 2021-03) Li, Tianyi; Zhou, Xinwei; Cui, Yi; Meyerson, Melissa L.; Weeks, Jason A.; Mullins, Buddie; De Andrade, Vincent; De Carlo, Francesco; Liu, Yuzi; Zhu, Likun; Mechanical and Energy Engineering, School of Engineering and Technology
    The dynamic information of lithium-ion battery active materials obtained from coin cell-based in-situ characterizations might not represent the properties of the active material itself because many other factors in the cell could have impacts on the cell performance. To address this problem, a single particle cell was developed to perform the in-situ characterization without the interference of inactive materials in the battery electrode as well as the X-ray-induced damage. In this study, the dynamic morphological and phase changes of selenium-doped germanium (Ge0.9Se0.1) at the single particle level were investigated via synchrotron-based in-situ transmission X-ray microscopy. The results demonstrate the good reversibility of Ge0.9Se0.1 at high cycling rate that helps understand its good cycling performance and rate capability. This in-situ and operando technique based on a single particle battery cell provides an approach to understanding the dynamic electrochemical processes of battery materials during charging and discharging at the particle level.
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    A Self-Healing Liquid Metal Anode with PEO-Based Polymer Electrolytes for Rechargeable Lithium Batteries
    (Elsevier, 2020-12) Li, Tianyi; Cui, Yi; Fan, Longlong; Zhou, Xinwei; Ren, Yang; De Andrade, Vincent; De Carlo, Francesco; Zhu, Likun; Mechanical and Energy Engineering, School of Engineering and Technology
    Ga-Sn liquid metal material is demonstrated as a self-healing anode system due to its fluidity via operando synchrotron-based transmission X-ray microscopy and X-ray diffraction experiments. Cracks formed due to volume expansions can be recovered by the fluidity of the liquid metals. By incorporating with a poly(ethylene oxide) (PEO)-based electrolyte at 60 °C, the Ga-Sn anode shows a reversible lithium insertion and extraction process with a high initial discharge specific capacity of 682 mAh g − 1, followed by delivering a capacity of 462 mAh g − 1 in the second cycle at C/20 rate. Compared with its solid counterparts, the Ga-Sn liquid metal anode demonstrates a better capability to maintain its mechanical integrity and better contact with PEO solid electrolytes due to its advantageous features of the liquid. This study suggests a potential strategy to use liquid metal alloys with polymer solid electrolyte to solve the challenges in rechargeable lithium batteries.
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    Three-Dimensional Reconstruction and Analysis of All-Solid Li-Ion Battery Electrode Using Synchrotron Transmission X-ray Microscopy Tomography
    (ACS, 2018-05) Li, Tianyi; Kang, Huixiao; Zhou, Xinwei; Lim, Cheolwoong; Yan, Bo; De Andrade, Vincent; De Carlo, Francesco; Zhu, Likun; Mechanical Engineering, School of Engineering and Technology
    A synchrotron transmission X-ray microscopy tomography system with a spatial resolution of 58.2 nm at the Advanced Photon Source was employed to obtain three-dimensional morphological data of all-solid Li-ion battery electrodes. The three-phase electrode was fabricated from a 47:47:6 (wt %) mixture of Li(Ni1/3Mn1/3Co1/3)O2 as active material, Li1.3Ti1.7Al0.3(PO4)3 as Li-ion conductor, and Super-P carbon as electron conductor. The geometric analysis show that particle-based all-solid Li-ion battery has serious contact interface problem which significantly impact the Li-ion transport and intercalation reaction in the electrode, leading to low capacity, poor rate capability and cycle life.