IU Indianapolis ScholarWorks :: Browsing by Author "Li, Tianyi"

Browsing by Author "Li, Tianyi"

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Bayesian Optimization of Active Materials for Lithium-Ion Batteries
(SAE, 2021-04) Valladares, Homero; Li, Tianyi; Zhu, Likun; El-Mounayri, Hazim; Tovar, Andres; Hashem, Ahmed; Abdel-Ghany, Ashraf E.; Mechanical Engineering, School of Engineering and Technology
The design of better active materials for lithium-ion batteries (LIBs) is crucial to satisfy the increasing demand of high performance batteries for portable electronics and electric vehicles. Currently, the development of new active materials is driven by physical experimentation and the designer’s intuition and expertise. During the development process, the designer interprets the experimental data to decide the next composition of the active material to be tested. After several trial-and-error iterations of data analysis and testing, promising active materials are discovered but after long development times (months or even years) and the evaluation of a large number of experiments. Bayesian global optimization (BGO) is an appealing alternative for the design of active materials for LIBs. BGO is a gradient-free optimization methodology to solve design problems that involve expensive black-box functions. An example of a black-box function is the prediction of the cycle life of LIBs. The cycle life cannot be predicted using a simple closed-form expression but only through the cycling performance test or a numerical simulation. BGO has two main components: a surrogate probabilistic model of the black-box function and an acquisition function that guides the optimization. This research employs BGO in the design of cathode active materials for LIB cells. The training data corresponds to the initial capacity and cycle life of five coin cells with different compositions of LiNixMn2 − xO4 in their cathode, where x is the content of Ni. BGO utilizes the experimental data to identify five new compositions that can produce cells with high initial capacity and\or large cycle life. The surrogate models of the initial capacity and cycle life are Gaussian Processes. The acquisition function is the constrained multi-objective expected improvement. The results show that BGO can identify high-performance active materials for LIBs. Designers can use the data generated during the optimization to decide the composition of the next batch of active materials to be tested, i.e., guide the physical experimentation.
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.
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.
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.
Electrochemical behavior of tin foil anode in half cell and full cell with sulfur cathode
(Elsevier, 2019-01) Cui, Yi; Li, Tianyi; Zhou, Xinwei; Mosey, Aaron; Guo, Wei; Cheng, Ruihua; Fu, Yongzhu; Zhu, Likun; Mechanical Engineering, School of Engineering and Technology
Tin-based (Sn) metal anode has been considered an attractive candidate for rechargeable lithium batteries due to its high specific capacity, safety and low cost. However, the large volume change of Sn during cycling leads to rapid capacity decay. To address this issue, Sn foil was used as a high capacity anode by controlling the degree of lithium uptake. We studied the electrochemical behavior of Sn foil anode in half cell and full cell with sulfur cathode, including phase transform, morphological change, discharge/charge profiles and cycling performance. Enhanced cycling performance has been achieved by limiting the lithiation capacity of the Sn foil electrode. A full cell consisting of a pre-lithiated Sn foil anode and a sulfur cathode was constructed and tested. The full cell exhibits an initial capacity of 1142 mAh g−1 (based on the sulfur mass in the cathode), followed by stable cycling performance with a capacity retention of 550 mAh g−1 after 100 cycles at C/2 rate. This study reports a potential prospect to utilize Sn and S as a combination in rechargeable lithium batteries.
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.
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.
In Situ Focused Ion Beam Scanning Electron Microscope Study of Microstructural Evolution of Single Tin Particle Anode for Li-Ion Batteries
(ACS, 2019-01) Zhou, Xinwei; Li, Tianyi; Cui, Yi; Fu, Yongzhu; Liu, Yuzi; Zhu, Likun; Mechanical and Energy Engineering, School of Engineering and Technology
Tin (Sn) is a potential anode material for highenergy density Li-ion batteries because of its high capacity, safety, abundance and low cost. However, Sn suffers from large volume change during cycling, leading to fast degradation of the electrode. For the first time, the microstructural evolution of micrometer-sized single Sn particle was monitored by focused-ion beam (FIB) polishing and scanning electron microscopy (SEM) imaging during electrochemical cycling by in situ FIB-SEM. Our results show the formation and evolution of cracks during lithiation, evolution of porous structure during delithiation and volume expansion/contraction during cycling. The electrochemical performance and the microstructural evolution of the Sn microparticle during cycling are directly correlated, which provides insights for understanding Sn-based electrode materials.
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.
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.

Browsing by Author "Li, Tianyi"

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