Dr. Won-Jin Kwak, PhD - Pacific Northwest National Laboratory

Dr. Won-Jin Kwak

PhD

Pacific Northwest National Laboratory

Richland, WA | United States

Main Specialties: Chemistry

ORCID logohttps://orcid.org/0000-0002-9807-1434

Dr. Won-Jin Kwak, PhD - Pacific Northwest National Laboratory

Dr. Won-Jin Kwak

PhD

Introduction

Primary Affiliation: Pacific Northwest National Laboratory - Richland, WA , United States

Specialties:

Research Interests:

Education

Feb 2018
Hanyang University
Ph.D.
Energy Engineering
Mar 2008 - Feb 2012
Hanyang University
B.S.
Chemical Engineering

Experience

Mar 2018 - Feb 2019
Hanyang University
Postdoc
Energy Engineering
Pacific Northwest National Laboratory
Postdoc
Energy

Publications

31Publications

117Reads

8Profile Views

A dendrite- and oxygen-proof protective layer for lithium metal in lithium–oxygen batteries

Journal of Materials Chemistry A

NCL is rationally designed as the stable protective layer on Li metal for dendrite- and oxygen-proof in Li–O2 batteries.

http://dx.doi.org/10.1039/c8ta11941d

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2019
1 Read

Deactivation of redox mediators in lithium-oxygen batteries by singlet oxygen.

Nat Commun 2019 03 26;10(1):1380. Epub 2019 Mar 26.

Department of Energy Engineering, Hanyang University, Seoul, 04763, Republic of Korea.

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http://dx.doi.org/10.1038/s41467-019-09399-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435713PMC
March 2019
109 Reads
10.742 Impact Factor

Shedding Light on the Oxygen Reduction Reaction Mechanism in Ether-Based Electrolyte Solutions: A Study Using Operando UV-Vis Spectroscopy.

ACS Appl Mater Interfaces 2018 Apr 20;10(13):10860-10869. Epub 2018 Mar 20.

Department of Chemistry and BINA (BIU Institute of Nanotechnology and Advanced Materials) , Bar Ilan University , Ramat-Gan 5290002 , Israel.

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http://dx.doi.org/10.1021/acsami.7b18376DOI Listing
April 2018
8 Reads
6.723 Impact Factor

Clarification of Solvent Effects on Discharge Products in Li-O2 Batteries through a Titration Method

ACS Appl. Mater. Interfaces, Just Accepted Manuscript

ACS Applied Materials & Interfaces

As a substitute for current lithium-ion batteries (LIBs), rechargeable Li-O2 batteries have attracted much attention due to their theoretically high energy density, but many challenges continue to exist. For the development of this still problematic battery, understanding and controlling the main discharge product (Li2O2, lithium peroxide) are of paramount importance. Here, we comparatively analyzed the amount of Li2O2 in the cathodes discharged at various discharge capacities and current densities.in DMSO and TEGDME solvents. The precise assessment entailed revisiting and revising the UV-Vis titration analysis. The amount of Li2O2 electrochemically formed in DMSO was less than that formed in TEGDME at the same capacity and even at a much higher full discharge capacity in DMSO than in TEGDME. Based on our analytical experimental results, this unexpected result was ascribed to the presence of soluble LiO2-like intermediates that remained in the DMSO solvent and the chemical transformation of Li2O2 to LiOH, both of which originated from the inherent properties of the DMSO solvent.

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December 2017
2 Reads

Optimized Concentration of Redox Mediator and Surface Protection of Li Metal for Maintenance of High Energy Efficiency in Li–O2 Batteries

Adv. Energy Mater. 2018, 8, 1702258.

Advanced Energy Materials

Recently, various approaches for adding redox mediators to electrolytes and introducing protective layers onto Li metal have been suggested to overcome the low energy efficiency and poor cycle life of Li–O2 batteries. However, the catalytic effect of the redox mediator for oxygen evolution gradually deteriorates during repeated cycling owing to its decomposition at the surfaces of both the oxygen electrode (cathode) and the Li metal electrode (anode). Here, optimized Li–O2 batteries are designed with a continuously effective redox mediator and a stable protective layer for the Li metal electrode by optimizing the LiBr concentration and introducing a graphene–polydopamine composite layer, respectively. These synergistic modifications lead to a reduction of the charge potential to below 3.4 V and significantly improve the stability and cycle life of Li–O2 batteries. Consequently, a high energy efficiency of above 80% is maintained over 150 cycles. Herein, it is confirmed that the relationships between all the battery materials should be understood in order to improve the performance of Li–O2 batteries.

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December 2017
2 Reads

Optimized Bicompartment Two Solution Cells for Effective and Stable Operation of Li–O2 Batteries

Adv. Energy Mater. 2017, 7, 1701232.

Advanced Energy Materials

Lithium–oxygen batteries are in fact the only rechargeable batteries that can rival internal combustion engines, in terms of high energy density. However, they are still under development due to low-efficiency and short lifetime issues. There are problems of side reactions on the cathode side, high reactivity of the Li anode with solution species, and consumption of redox mediators via reactions with metallic lithium. Therefore, efforts are made to protect/block the lithium metal anode in these cells, in order to mitigate side reactions. However, new approach is required in order to solve the problems mentioned above, especially the irreversible reactions of the redox mediators which are mandatory to these systems with the Li anode. Here, optimized bicompartment two solution cells are proposed, in which detrimental crossover between the cathode and anode is completely avoided. The Li metal anode is cycled in electrolyte solution containing fluorinated ethylene carbonate, in which its cycling efficiency is excellent. The cathode compartment contains ethereal solution with redox mediator that enables oxidation of Li2O2 at low potentials. The electrodes are separated by a solid electrolyte membrane, allowing free transport of Li ions. This approach increases cycle life of lithium oxygen cells and their energy efficiency.

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August 2017
2 Reads

Large-Scale Li−O2 Pouch Type Cells for Practical Evaluation and Applications

Adv. Funct. Mater. 2017, 27, 1605500.

Advanced Functional Materials

Due to their high theoretical specific capacity and energy density, Li-O2 batteries are considered as candidates for next-generation battery systems in place of conventional Li-ion batteries for advanced applications such as electric vehicles. However, low energy efficiency, poor cycle life, and Li-metal safety issues make the use of Li-O2 batteries yet impractical. In addition, actual cell capacities are very low, and since only small-scale electrodes are currently tested, it is hard to predict the properties of large-size electrodes and cells, thus evaluating and judging real practical challenges related to this battery technology. In this work, the behavior of pouch-type Li-O2 cells using 3 × 5 cm2 sized electrodes is investigated and it is confirmed that Li-metal is a key issue for the upscale of Li-O2 cells. This study can help to determine which parameters are the most important for developing practical Li-O2 batteries.

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January 2017
2 Reads

Li–O2 cells with LiBr as an electrolyte and a redox mediator

Energy Environ. Sci. 2016, 9, 2334-2345.

Energy & Environmental Science

After many years of successful and disappointing results, the field of Li–O2 research seems to have reached an equilibrium state. The extensive knowledge that has accrued through advanced analytical studies enables us to delineate the weaknesses of the Li–O2 battery. It is now clear that the instability of the cell components toward extreme conditions existing during cell operation leads to early cell failure as well. One serious challenge is the high oxidation potential applied during the charge process. Redox-mediators may reduce the over-potential and, therefore, improve the efficiency and cyclability of Li–O2 cells. Their use in Li–O2 cells is mandatory. We have previously shown that LiI can indeed behave in such a manner; however, it also promotes the formation of side products during cell operation. We have, therefore, embarked on a comprehensive study of lithium halide salts as electrolytes for use in Li–O2 cells. We examine herein the effect of other components in the cell, such as solvents and contaminants, on the lithium halide salt activity. Based on the electrochemical behavior and the identity of the final cell products under various conditions, we can glean substantial information regarding the detailed operation mechanisms for each specific case. We have concluded that low concentration of LiBr in diglyme solution can improve the cell performance with fewer side effects than LiI. With LiBr, only the desired Li2O2 is formed during discharge. During charge, the bromine redox couple (Br−/Br3−) can reduce the oxidation potential to only 3.5 V. Higher efficiency and better cyclability of cells containing LiBr demonstrate that the electrolyte solution is the key to a successful Li–O2 battery.

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May 2016
39 Reads

Iron–cobalt bimetal decorated carbon nanotubes as cost-effective cathode catalysts for Li–O2 batteries

J. Mater. Chem. A, 2016, 4, 7020–7026

Journal of Materials Chemistry A

Despite the extremely high theoretical specific capacity of lithium oxygen (Li–O2) electrochemistry, low energy efficiency resulting from the large potential gap between the discharge and charge makes this system impractical. In this report, an iron cobalt bimetal decorated carbon nanotube (FeCo–CNT) composite was synthesized as a catalytic air cathode material for Li–O2 batteries. An Li–O2 battery using FeCo–CNT air electrodes exhibited higher efficiency (72.15%) than that of pristine CNTs (62.57%) as well as higher capacity (3600 mA h g−1vs. 1276 mA h g−1). Spectroscopic and electron microscopy analyses showed that the improved cell performances can be attributed to the catalytic effect of FeCo. As cost-effective non-noble metal catalysts, FeCo–CNTs demonstrated performance comparable to noble metal catalysts in Li–O2 systems.

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March 2016
2 Reads

Green Strategy to Single Crystalline Anatase TiO2 Nanosheets with Dominant (001) Facets and Its Lithiation Study toward Sustainable Cobalt-Free Lithium Ion Full Battery

ACS Sustainable Chem. Eng. 2015, 3, 3086−3095

ACS Sustainable Chemistry & Engineering

A green hydrothermal strategy starting from the Ti powders was developed to synthesis a new kind of well dispersed anatase TiO2 nanosheets (TNSTs) with dominant (001) facets, successfully avoiding using the HF by choosing the safe substitutes of LiF powder. In contrast to traditional approaches targeting TiO2 with dominant crystal facets, the strategy presented herein is more convenient, environment friendly and available for industrial production. As a unique structured anode applied in lithium ion battery, the TNSTs could exhibit an extremely high capacity around 215 mAh g−1 at the current density of 100 mA g−1 and preserved capacity over 140 mAh g−1 enduring 200 cycles at 400 mA g−1. As a further step toward commercialization, a model of lithiating TiO2 was built for the first time and analyzed by the electrochemical characterizations, and full batteries employing lithiated TNSTs as carbon-free anode versus spinel LiNixMn2−xO4 (x = 0, 0.5) cathode were configured. The full batteries of TNSTs/LiMn2O4 and TNSTs/LiNi0.5Mn1.5O4 have the sustainable advantage of cost-effective and cobalt-free characteristics, and particularly they demonstrated high energy densities of 497 and 580 Wh kganode −1 (i.e., 276 and 341 Wh kgcathode −1) with stable capacity retentions of 95% and 99% respectively over 100 cycles. Besides the intriguing performance in batteries, the versatile synthetic strategy and unique characteristics of TNSTs may promise other attracting applications in the fields of photoreaction, electro-catalyst, electrochemistry, interfacial adsorption photovoltaic devices etc.

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November 2015
2 Reads

An Advanced Lithium−Air Battery Exploiting an Ionic Liquid-Based

Nano Lett. 2014 Oct 14; 6572−6577

Nano Letters

A novel lithium–oxygen battery exploiting PYR14TFSI–LiTFSI as ionic liquid-based electrolyte medium is reported. The Li/PYR14TFSI–LiTFSI/O2 battery was fully characterized by electrochemical impedance spectroscopy, capacity-limited cycling, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The results of this extensive study demonstrate that this new Li/O2 cell is characterized by a stable electrode–electrolyte interface and a highly reversible charge–discharge cycling behavior. Most remarkably, the charge process (oxygen oxidation reaction) is characterized by a very low overvoltage, enhancing the energy efficiency to 82%, thus, addressing one of the most critical issues preventing the practical application of lithium–oxygen batteries.

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October 2014
6 Reads

Lithiation of an Iron Oxide-Based Anode for Stable, High-Capacity Lithium-Ion Batteries of Porous Carbon–Fe3O4/Li[Ni0.59Co0.16Mn0.25]O2

Energy Technol. 2014 October 9-10;778-785

Energy Technology

The lithium storage capacity of an iron oxide-based anode of porous carbon–Fe3O4 (i.e., PC–Fe3O4) was investigated by varying the initial current and mass density of the electrode to achieve a good utilization coefficient of the oxide. It was confirmed that these factors largely affected the capacity of PC–Fe3O4 and a certain mass density of the electrode was key to achieve a high area capacity (μAh cm−2). Moreover, the chemical and electrochemical lithiation of PC–Fe3O4 were related to the lithiation time and pressure and both were both systemically studied. After optimization, a new battery of PC–Fe3O4/Li[Ni0.59Co0.16Mn0.25]O2 with a high area capacity of 748 μAh cm−2 (≈150 mAh g−1) and superior energy density of 483 Wh kg−1 (work voltage≈3.2 V) was developed. The battery showed reversible work ability in the rate window of 50–800 mA g−1, and also it could be charged/discharged for well over 1000 cycles with a capacity retention of 63.8 % under the high current value of 0.505 mA (current density, 50 mA g−1).

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August 2014
3 Reads

Top co-authors

Yang-Kook Sun
Yang-Kook Sun

Hanyang University

2
Michal Afri
Michal Afri

Bar-Ilan University

1
Daniel Sharon
Daniel Sharon

Bar Ilan University

1
Daniel Hirshberg
Daniel Hirshberg

Bar Ilan University

1
Ronit Lavi
Ronit Lavi

Bar-Ilan University

1
Doron Aurbach
Doron Aurbach

Bar-Ilan University

1
Noam Eliaz
Noam Eliaz

Tel-Aviv University

1
Noa Metoki
Noa Metoki

Tel Aviv University

1
Stefan A Freunberger
Stefan A Freunberger

School of Chemistry

1