Browsing by Subject "lithium ion battery"

Now showing 1 - 9 of 9
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    Blade-Type Reaction Front in Micrometer-Sized Germanium Particles during Lithiation
    (ACS, 2020-09) Zhou, Xinwei; Li, Tianyi; Cui, Yi; Meyerson, Melissa L.; Weeks, Jason A.; Mullins, C. Buddie; Jin, Yang; Shin, Hosop; Liu, Yuzi; Zhu, Likun; Mechanical and Energy Engineering, School of Engineering and Technology
    To investigate the lithium transport mechanism in micrometer-sized germanium (Ge) particles, in situ focused ion beam–scanning electron microscopy was used to monitor the structural evolution of individual Ge particles during lithiation. Our results show that there are two types of reaction fronts during lithiation, representing the differences of reactions on the surface and in bulk. The cross-sectional SEM images and transmission electron microscopy characterizations show that the interface between amorphous LixGe and Ge has a wedge shape because of the higher Li transport rate on the surface of the particle. The blade-type reaction front is formed at the interface of the amorphous LixGe and crystalline Ge and is attributed to the large strain at the interface.
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    Characterization of dynamic morphological changes of tin anode electrode during (de)lithiation processes using in operando synchrotron transmission X-ray microscopy
    (Elsevier, 2019) Li, Tianyi; Zhou, Xinwei; Cui, Yi; Lim, Cheolwoong; Kang, Huixiao; Yan, Bo; Wang, Jiajun; Wang, Jun; Fu, Yongzhu; Zhu, Likun; Mechanical and Energy Engineering, School of Engineering and Technology
    The morphological evolution of tin particles with different sizes during the first lithiation and delithiation processes has been visualized by an in operando synchrotron transmission X-ray microscope (TXM). The in operando lithium ion battery cell was operated at constant current condition during TXM imaging. Two-dimensional projection images with 40 nm resolution showing morphological evolution were obtained and analyzed. The analysis of relative area change shows that the morphology of tin particles with different sizes changed simultaneously. This phenomenon is mainly due to a negative feedback mechanism among tin particles in the battery electrode at a constant current operating condition. For irregular-shaped tin particles, the contour analysis shows that the regions with higher curvature started volume expansion first, and then the entire particle expanded almost homogeneously. This study provides insights for understanding the dynamic morphological change and the particle-particle interactions in high capacity lithium ion battery electrodes.
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    Crack-Free Silicon Monoxide as Anodes for Lithium-Ion Batteries
    (ACS, 2020-12) Lu, Wenquan; Zhou, Xinwei; Liu, Yuzi; Zhu, Likun; Mechanical and Energy Engineering, School of Engineering and Technology
    The volume expansion of Si and SiO particles was investigated using a single-particle battery assembled with a focused ion beam and scanning electron microscopy (FIB-SEM) system. Single Si and SiO particles were galvanostatically charged and discharged as in real batteries. Microstructural changes of the particles were monitored in situ using FIB-SEM from two different angles. The results revealed that the volume expansion of micrometer size particle SiO was not only much smaller than that of Si, but it also kept its original shape with no sign of cracks. This isotropic mechanical property of a SiO particle can be attributed to its microstructure: nanosized Si domains mixed with SiO2 domains. The nanosized Si domains can mitigate the anisotropic swelling caused by the orientation-dependent lithium-ion insertion; the surrounding SiO2 domains can act as a buffer to further constrain the localized anisotropic swelling.
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    In Situ Focused Ion Beam-Scanning Electron Microscope Study of Crack and Nanopore Formation in Germanium Particle During (De)lithiation
    (ACS, 2019-04) Zhou, Xinwei; Li, Tianyi; Cui, Yi; Meyerson, Melissa L.; Mullins, C. Buddie; Liu, Yuzi; Zhu, Likun; Mechanical and Energy Engineering, School of Engineering and Technology
    Germanium has emerged as a promising high-capacity anode material for lithium ion batteries. To understand the microstructure evolution of germanium under different cycling rates, we monitored single germanium particle batteries using an in situ focused ion beam-scanning electron microscope. Our results show that both the lithium concentration and delithiation rate have an impact on nanopore formation. This study reveals that germanium electrodes with low and high cycling rates have better microstructure integrity, which leads to better cycling performance. The nanopores tend to aggregate into large porous structures during cycling which leads to particle pulverization and capacity fading of the electrode.
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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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    Lithium trapping in germanium nanopores during delithiation process
    (Elsevier, 2021-09) Zhou, Xinwei; Li, Tianyi; Cui, Yi; Meyerson, Melissa L.; Weeks, Jason A.; Mullins, C. Buddie; Yang , Shengfeng; Liu, Yuzi; Zhu, Likun; Mechanical and Energy Engineering, School of Engineering and Technology
    Irreversible capacity loss is a critical problem in high capacity anode materials of Li-ion batteries, such as silicon, germanium, and tin. In addition to solid electrolyte interface formation and active material loss, Li trapping in high capacity anode materials during cycling has been considered a new mechanism of capacity loss but received less attention. In this study, we used single particle battery-based in situ focused ion beam-scanning electron microscopy, transmission electron microscopy (TEM), and scanning TEM to investigate the microstructure and composition of germanium nanopores formed at the end of delithiation. Our results show that a significant amount of Li accumulates inside the nanopores.
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    Neutron imaging of lithium concentration in LiNi0.33Mn0.33Co0.33O2 cathode
    (IOS, 2020-04) Wu, Linmin; Zhang, Yi; Yang, Xuehui; Santodonato, Louis; Bilheux, Hassina; Zhang, Jing; Mechanical and Energy Engineering, School of Engineering and Technology
    LiNi0.33Mn0.33Co0.33O2 (NMC) is a promising substitute for LiCoO2 because of its good thermal stability and high energy density. In this work, the lithium concentration distributions in an NMC cathode using neutron computed radiography technique at Oak Ridge National Laboratory’s High Flux Isotope Reactor (HFIR) CG-1D Cold Neutron Imaging Facility. Samples with four different state of charge (SOC) were prepared for neutron imaging: 70% SOC, 100% SOC, 105% SOC, and 110% SOC. The neutron tomographic reconstruction of NMC cathode reveals the information of electrochemical transport and spatial Li distribution inside the cathode. The experimental results were explained by a diffusion numerical model which maps the Li concentration evolution during the electrochemical reactions. The study demonstrates that neutron imaging technique can be a very powerful tool to understand the lithium concentrations and evaluate its state of conditions, thus providing information for design of safe lithium ion batteries and estimating their lives.
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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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    Simulation of Heat Generation in a Reconstructed LiCoO2 Cathode during Galvanostatic Discharge
    (Office of the Vice Chancellor for Research, 2014-04-11) Yan, Bo; Song, Zhibin; Lim, Cheolwoong; Zhu, Likun
    A three dimensional numerical framework with finite volume method was employed to simulate heat generation of a semi lithium ion battery (LIB) cell during isothermal galvanostatic discharge processes. The microstructure of the LIB cathode electrode was experimentally determined using X-ray nano computed tomography technology. Heat generation in the semi LIB cell during galvanostatic discharge processes from different mechanisms, such as electronic resistive heat, ionic resistive heat, contact resistive heat, reaction heat, entropic heat and heat of mixing, was investigated. The spatial distribution of heat generation rates from different mechanisms was also studied. The simulation results demonstrate that the magnitude of heat generation rates spans a wide range in the electrode due to structural inhomogeneity. The simulation results of heat generation from the three dimensional model and the porous-electrode theory model were compared in this study. It is found that the typical Bruggeman coefficient, 1.5, underestimated ionic resistance in the electrolyte and overestimated electronic resistance in the cathode particles. In general, the three dimensional model predicted more heat generation than the porous-electrode theory model at large discharge rates due to the wider distribution of physical and electrochemical properties.