Browsing by Author "Shin, Hosop"

Now showing 1 - 7 of 7
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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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    A Comprehensive Study of Black Phosphorus-Graphite Composite Anodes and HEMM Synthesis Conditions for Improved Cycle Stability
    (IOP, 2019) Shin, Hosop; Zhang, Jianyu; Lu, Wei; Mechanical and Energy Engineering, School of Engineering and Technology
    Black phosphorus (BP) is a high capacity anode material and has been synthesized with different carbon materials to mitigate volume changes during lithiation/delithiation. There is a large discrepancy in cycle stability of phosphorus-carbon materials in the literature, and factors affecting cycle performance are not well elucidated. In this study, the electrochemical performance of a black phosphorus-graphite (BP-G) composite anode material with regards to (1) material composition, (2) electrolyte additive, (3) ballmilling synthesis conditions, and (4) electrode loading is thoroughly investigated. In particular, this study reveals how ballmilling synthesis conditions correlate to electrochemical performance. Results show that the main contributors to cycle stability of BP-G composites are material composition and electrode loading, while first cycle efficiency and reversible capacity are strongly dependent on ballmilling synthetic conditions. Composition control is the most effective way to mitigate the volume change-induced mechanical degradation of BP-G composites, while ballmilling processing optimization is the main contributor to BP activation in BP-G composites, improving reversible capacity and first cycle efficiency. We thereby propose an optimized, HEMM-based synthetic route for improved BP-G materials. This study provides a comprehensive understanding of BP-G electrochemical performance and the correlation to HEMM synthesis conditions.
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    Fundamental Investigation of Direct Cathode Regeneration Using Chemically Delithiated Lithium Cobalt Oxides
    (IOP Publishing, 2022-11-03) Bhuyan, Md. Sajibul Alam; Shin, Hosop; Mechanical and Energy Engineering, School of Engineering and Technology
    Reusing valuable cathode materials from end-of-life (EOL) Li-ion batteries can help decrease dependence on mining of raw materials for producing cathodes, while preventing commodity prices from rising. This study employed chemically delithiated cathodes that are analogous to spent cathodes but free of impurities to fundamentally elucidate the effectiveness of cathode regeneration. Two lithium cobalt oxides (LCOs) at different degrees of delithiation were synthesized via chemical delithiation. Their material and electrochemical characteristics were systematically compared before and after hydrothermal-based cathode regeneration. The material and electrochemical characteristics were further evaluated and compared with those of pristine LCO. Both LCOs, at high and low states of health (SOH), recovered their reversible capacity and cycle performance comparable to those of pristine LCO. However, the high-rate performance (2C) of the regenerated LCOs was not comparable to that of pristine LCO. The slight increase in cell resistance of the regenerated LCOs was attributed to their lower high-rate performance, which was identified as a key challenge of cathode regeneration. Our study provides valuable insights into the effectiveness of cathode regeneration by elucidating the process underlying regeneration of disordered Li-deficient LCOs at different levels of SOH.
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    Fundamental Investigation of Direct Recycling Using Chemically Delithiated Cathode
    (2022-12) Bhuyan, Md Sajibul Alam; Shin, Hosop; Zhu, Likun; Wei, Xiaoliang
    Recycling valuable cathode material from end-of-life (EOL) Li-ion batteries (LIBs) is essential to preserve raw material depletion and environmental sustainability. Direct recycling reclaims the cathode material without jeopardizing its original functional structures and maximizing return values from spent LIBs compared to other regeneration processes. This work employed two chemically delithiated lithium cobalt oxide (LCO) cathodes at different states of health (SOH), which are analogous to the spent cathodes but free of any impurities, to investigate the effectiveness of cathode regeneration. The material and electrochemical properties of both delithiated SOHs were systematically examined and compared to pristine LCO cathode. Further, those model materials were regenerated by a hydrothermal-based approach. The direct cathode regeneration of both low and high SOH cathode samples restored their reversible capacity and cycle performance comparable to pristine LCO cathode. However, the inferior performance observed in higher current density (2C) rate was not comparable to pristine LCO. In addition, the higher resistance of regenerated cathodes is attributed to lower high-rate performance, which was pointed out as the key challenge of the cathode recycling process. This study provides valuable knowledge about the effectiveness of cathode regeneration by investigating how the disordered, lithium-deficient cathode at different SOH from spent EOL batteries are rejuvenated without changing any material and electrochemical functional properties.
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    Multi-scale analysis of cathode microstructural effects on electrochemical and stress responses of lithium-ion batteries
    (Elsevier, 2022-11-15) Lee, Yoon Koo; Park , Juhyun; Shin, Hosop; Mechanical and Energy Engineering, School of Engineering and Technology
    The electrochemical and stress responses of lithium-ion batteries (LIBs) are highly dependent on the three-dimensional (3D) microstructure of electrodes, and substantial fundamental research is required to optimize the electrode design for high-energy, high-power LIBs with fast charging capabilities. Herein, we report a multi-scale LIB model that enables the examination of full-cell battery performance while investigating the detailed electrochemical and stress responses of the cathode using the variational multi-scale enrichment method. With the high computational efficiency of the developed model, the cathode microstructural effects were studied systematically by varying the particle size, volume fraction, and particle arrangement of 3D cathode microstructures at different C-rates. The results show that the arrangement of active material particles and their interconnectivity, rather than the particle size itself, are the determining factors for the spatial lithium-ion concentration and stress distribution of the cathode, affecting the overall electrochemical performance of LIBs. Our study provides valuable insights into the design and optimization of the cathode architecture to maximize the electrochemical performance under different operating conditions.
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    Physics-Based Modelling and Simulation Framework for Multi-Objective Optimization of Lithium-Ion Cells in Electric Vehicle Applications
    (2022-05) Gaonkar, Ashwin; El-Mounayri, Hazim; Tovar, Andres; Zhu, Likun; Shin, Hosop
    In the last years, lithium-ion batteries (LIBs) have become the most important energy storage system for consumer electronics, electric vehicles, and smart grids. The development of lithium-ion batteries (LIBs) based on current practice allows an energy density increase estimated at 10% per year. However, the required power for portable electronic devices is predicted to increase at a much faster rate, namely 20% per year. Similarly, the global electric vehicle battery capacity is expected to increase from around 170 GWh per year today to 1.5 TWh per year in 2030--this is an increase of 125% per year. Without a breakthrough in battery design technology, it will be difficult to keep up with the increasing energy demand. To that end, a design methodology to accelerate the LIB development is needed. This can be achieved through the integration of electro-chemical numerical simulations and machine learning algorithms. To help this cause, this study develops a design methodology and framework using Simcenter Battery Design Studio® (BDS) and Bayesian optimization for design and optimization of cylindrical cell type 18650. The materials of the cathode are Nickel-Cobalt-Aluminum (NCA)/Nickel-Manganese-Cobalt-Aluminum (NMCA), anode is graphite, and electrolyte is Lithium hexafluorophosphate (LiPF6). Bayesian optimization has emerged as a powerful gradient-free optimization methodology to solve optimization problems that involve the evaluation of expensive black-box functions. The black-box functions are simulations of the cyclic performance test in Simcenter Battery Design Studio. The physics model used for this study is based on full system model described by Fuller and Newman. It uses Butler-Volmer Equation for ion-transportation across an interface and solvent diffusion model (Ploehn Model) for Aging of Lithium-Ion Battery Cells. The BDS model considers effects of SEI, cell electrode and microstructure dimensions, and charge-discharge rates to simulate battery degradation. Two objectives are optimized: maximization of the specific energy and minimization of the capacity fade. We perform global sensitivity analysis and see that thickness and porosity of the coating of the LIB electrodes that affect the objective functions the most. As such the design variables selected for this study are thickness and porosity of the electrodes. The thickness is restricted to vary from 22microns to 240microns and the porosity varies from 0.22 to 0.54. Two case studies are carried out using the above-mentioned objective functions and parameters. In the first study, cycling tests of 18650 NCA cathode Li-ion cells are simulated. The cells are charged and discharged using a constant 0.2C rate for 500 cycles. In the second case study a cathode active material more relevant to the electric vehicle industry, Nickel-Manganese-Cobalt-Aluminum (NMCA), is used. Here, the cells are cycled for 5 different charge-discharge scenarios to replicate charge-discharge scenario that an EVs battery module experiences. The results show that the design and optimization methodology can identify cells to satisfy the design objective that extend and improve the pareto front outside the original sampling plan for several practical charge-discharge scenarios which maximize energy density and minimize capacity fade.
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    Regeneration of Cathode Materials from Used Li-ion Batteries via a Direct Recycling Process
    (2020-12) Zurange, Hrishikesh; Shin, Hosop; Zhang, Jing; Zhu, Likun
    With the exponential rise in manufacturing and usage of Li-ion batteries (LIBs) in the last decade, a huge quantity of spent LIBs is getting scrapped every year. Along with the efforts to making more capable and safer batteries over the last three decades, there is an immediate need for recycling these scrapped batteries. Most of these batteries typically use lithium manganese oxide (LMO), lithium cobalt oxide (LCO), lithium iron phosphate (LFP), and lithium nickel manganese cobalt oxide (NMC) cathode chemistries, and developing a technique towards regenerating these cathodes can ensure huge economic and environmental benefits for the present and future. This research focuses on a set of direct regeneration techniques with the goal of regenerating used cathode materials to be reused in LIBs. Used Apple iPad2 batteries with LCO chemistry and Nissan LEAF batteries with a combination of LMO-NMC chemistry are selected for this research. The scope of research can be divided into two parts as liberation/separation of cathode material and regeneration of liberated cathode. The liberation/separation process is carried out with the aid of ultrasonication and organic solvents with the objective being keeping the morphology and chemical composition intact for a better quality of the material. The regeneration process uses a hydrothermal technique with variations of parameters. 1:1 and 1:5 molar ratios between cathode material and a lithium lithiation agent are chosen to understand the effects of the molar ratio on cathode regeneration. In addition, the effects of processing solution (water vs. a solvent) are examined by replacing water with TEG. The effects of heat treatment on cathode regeneration are also investigated by observing phase changes of materials at different temperatures.