Journal Publication


Joseph M. Valle, Claire Huang, Dhruv Tatke, Jeffrey Wolfenstine, Wooseok Go, Youngsik Kim, Jeff Sakamoto

Solid State Ionics, 369 (2021) 115712 (Website link)

img The Na-ion conducting solid electrolyte NASICON is a promising solid state electrolyte (SSE) for use in Na based electrochemical systems. The effects of particle morphology and synthesis of von Alpen type NASICON via hot-pressing were investigated. Spray dried particles were shown to improve mechanical and electrochemical properties. X-ray diffraction, scanning electron microscopy, impulse excitation measurements, Vickers hardness, and impedance spectroscopy were used to correlate relationships between phase purity, microstructure, mechanical properties, and electrochemical properties. Scanning electron microscopy showed the presence of a glass phase as between 19.08% and 28.23% area percentage and a ZrO2 phase between 0.46% and 3.51% area percentage in the hot-pressed samples. Impulse excitation showed elastic modulus varying from 83.65 to 97.65 GPa. The first values of Poisson's ratio and shear modulus of NASICON are reported as between 0.23 and 0.26 and 33.87 to 38.79 GPa, respectively. Vickers hardness and fracture toughness measurements showed Vickers hardness ranging from 4.30 to 4.68 GPa and fracture toughness ranging from 1.05 to 1.09 MPa m½. Impedance spectroscopy showed grain conductivities ranging from 1.023 to 1.287 mS/cm, with grain boundary resistance percentages between 73.22 and 47.5%. Total conductivities ranged from 0.292 to 0.596 mS/cm, with 0.596 mS/cm being achieved at room temperature for the spray dried powders with lower grain boundary resistance percentages.

Wooseok Go, Jongwoo Kim, Jinho Pyo, Jeffery B. Wolfenstine, Youngsik Kim

ACS Appl. Mater. Interfaces, 2021, 13, 44, 52727–52735 (Website link)

img The ionic conductivity, bend strength, and electrochemical performance in a seawater battery (SWB) of an Na3.1Zr1.55Si2.3P0.7O11 (vA-NASICON) solid electrolyte were compared to those of Na3Zr2Si2PO12 (H-NASICON). vA-NASICON exhibited three times higher total ionic conductivity (8.6 × 10–4 S/cm) than H-NASICON (2.9 × 10–4 S/cm). This is due to the higher bulk ionic conductivity and lower grain boundary resistance of vA-NASICON. The higher bulk conductivity of vA-NASICON is a result of its higher Na content, leading to a larger concentration of charge carriers and/or the formation of a higher conductive rhombohedral phase. The lower grain boundary resistance of vA-NASICON is a result of its larger grain size and reduced ZrO2 content. The bend strength of vA-NASICON (95 MPa) was 30% higher than that of the H-NASICON ceramic. The higher bend strength of vA-NASICON was attributed to its reduced ZrO2 secondary phase (1.1 vol %) compared to that of H-NASICON (2.6 vol %). When the vA-NASICON ceramic was tested in the SWB as a solid electrolyte, an 8.27% improved voltage efficiency and 81% higher power output were demonstrated, compared to those of H-NASICON, as a result of its higher total ionic conductivity and mechanical strength. At the same time, the vA-NASICON membrane revealed comparable cycle life (1000 h) to that of H-NASICON. These results suggest that vA-NASICON can be a better alternative than H-NASICON for use in the SWB.

Pankaj Sharma, Jinhyup Han, Jaehyun Park, Dong Yeon Kim, Jinho Lee, Dongrak Oh, Namsu Kim, Dong-Hwa Seo, Youngsik Kim, Seok Ju Kang, Soo Min Hwang, and Ji-Wook Jang

JACS Au, 2021, 1, 12, 2339–2348 (Website link)

img The economic viability and systemic sustainability of a green hydrogen economy are primarily dependent on its storage. However, none of the current hydrogen storage methods meet all the targets set by the US Department of Energy (DoE) for mobile hydrogen storage. One of the most promising routes is through the chemical reaction of alkali metals with water; however, this method has not received much attention owing to its irreversible nature. Herein, we present a reconditioned seawater battery-assisted hydrogen storage system that can provide a solution to the irreversible nature of alkali-metal-based hydrogen storage. We show that this system can also be applied to relatively lighter alkali metals such as lithium as well as sodium, which increases the possibility of fulfilling the DoE target. Furthermore, we found that small (1.75 cm2) and scaled-up (70 cm2) systems showed high Faradaic efficiencies of over 94%, even in the presence of oxygen, which enhances their viability.

Yongil Kim, Alberto Varzi, Alessandro Mariani, Gun-Tae Kim, Youngsik Kim, Stefano Passerini

Adv. Energy Mater., 2021, 2102061 (Website link)

img Sodium-seawater batteries (Na-SWB) are considered among the most promising electrochemical devices for large-scale energy storage and the marine sector. In fact, by employing an open-structured cathode, they benefit from the unlimited supply of sodium from seawater. This means, that the energy of such systems is intrinsically limited by the capacity of the anode. In order to increase the energy of Na-SWB, it is therefore necessary to introduce a high-capacity anode such as, e.g., red phosphorus. However, due to its large volume changes upon charge/discharge processes, obtaining thick electrodes and large areal capacity is extremely challenging. Herein, the areal/absolute capacity of the red phosphorus anode is increased by employing a semi-liquid electrode, which includes two redox mediators, i.e., sodium-biphenyl and sodium-pyrene, as reducing and oxidizing species for the exploitation of the full red phosphorus capacity. As a result, the red phosphorus semi-liquid anode in Na-SWB provides a high-capacity of 15 mAh cm–2 in a static anode, showing great energy storage potential for operation in flow-mode when storing the semi-liquid negative electrode in a storage tank.

Jeong-Sun Park, Seohae Kim, Yunseok Choi, Ahmad M. Harzandi, and Youngsik Kim

ACS ES&T Water, 2021, 1, 2146-2154 (Website link)

img With increasing population growth, it is necessary to meet safe water demands. Water disinfection through chlorination is the most commonly used method for safe water production. The electrolysis of salted water is a promising technology for the on-site generation of disinfecting agents, however, its low efficiency and inability to neutralize the remaining free chlorine makes electrolysis inefficient. The introduction of a cation permeable membrane between anode and cathode can help to improve the disinfection efficiency and also dechlorinate the remained free chlorine by switching the anode and cathode. However, the scale formation on the membrane will reduce the performance of the system. In this study, with using a Na-selective membrane for separating anode and cathode, we propose a disinfection-dechlorination battery (DD-battery) consisting of an anode for energy storage through Na+ reduction to metal Na and a cathode for disinfection via Cl– oxidation to free chlorine species. The stored energy in the anode is released during discharge, and the system can dechlorinate the remaining free chlorine to prevent disinfectant toxicity. This self-disinfection-dechlorination during battery cycling can be combined with renewable energy sources for efficient water disinfection in remote regions.

Jeonghoon Cho. Myeongwoo Kim, Youngjin Kim, Jeongsun Park, Dohee Lee, Youngsik Kim, Jaejoon Kim

IEEE, 2021, 9, 104104-104114 (Website link)

img This paper presents a wireless marine buoy system based on the seawater battery (SWB), providing self-powered operation, power-efficient management, and degradation prediction and fault detection. Since conventional open circuit voltage (OCV) methods cannot be applied due to inherent cell characteristics of SWB, the coulomb counting (CC) method is adopted for the state of charge (SOC) monitoring. For the state of health (SOH), a variance-based detection scheme is proposed to provide degradation prediction and fault detection of the SWB. The self-powered operation is augmented by two proposed power optimization schemes such as multiple power management and three-step LED light control. A wireless buoy system prototype is manufactured, and its functional feasibility is experimentally verified, where its location and SOC are periodically monitored in a smartphone-based wireless platform.

Moon Son, Sanghun Park, Namhyeok Kim, Anne Therese Angles, Youngsik kim, Kyung Hwa Cho

Advanced Science, 2021, 2101289 (Website link)

img Rechargeable seawater battery (SWB) is a unique energy storage system that can directly transform seawater into renewable energy. Placing a desalination compartment between SWB anode and cathode (denoted as seawater battery desalination; SWB-D) enables seawater desalination while charging SWB. Since seawater desalination is a mature technology, primarily occupied by membrane-based processes such as reverse osmosis (RO), the energy cost has to be considered for alternative desalination technologies. So far, the feasibility of the SWB-D system based on the unit cost per desalinated water ($ m−3) has been insufficiently discussed. Therefore, this perspective aims to provide this information and offer future research directions based on the detailed cost analysis. Based on the calculations, the current SWB-D system is expected to have an equipment cost of ≈1.02 $ m−3 (lower than 0.60–1.20 $ m−3 of RO), when 96% of the energy is recovered and stable performance for 1000 cycles is achieved. The anion exchange membrane (AEM) and separator contributes greatly to the material cost occupying 50% and 41% of the total cost, respectively. Therefore, future studies focusing on creating low cost AEMs and separators will pave the way for the large-scale application of SWB-D.

D.-H.Lim, C.Dong, H.W.Kim, G.-H Bae, K.Choo, G.-B.Cho, Y.Kim, B.Jin, J.-K.Kim

Materials Today Energy, 2021, 21, 100805 (Website link)

img Although rechargeable seawater batteries are promising energy storage systems, their electrochemical performance is inferior to that of lithium batteries; moreover, opportunities for improving their performance are restricted by the limited range of available anode materials to complement seawater cathodes. Organic redox materials can help overcome the drawbacks associated with seawater batteries because of their inherent fast charge transfer capability. Therefore, in this study, we design a unique hybrid seawater battery in which poly (4-styrenesulfonate) as a sodium-ion storage polymer is functionalized with hard carbon (HC) to form a functional anode with high capacity by in situ polymerization. Sodium-ion storage mechanisms of the poly (4-styrenesulfonate) (PSS) and HC-PSS functional material are investigated through electron spin resonance, solid nuclear magnetic resonance, X-ray photoelectron spectroscopy, and molecular orbital studies. Each HC and PSS in the HC-PSS electrode clearly contribute to reversible electrochemical reactions. This polymer is observed to prevent the growth of a solid electrolyte interface on the surface of the functionalized HC-PSS anode, and the seawater battery exhibits excellent electrochemical properties, making it suitable for high-performance eco-friendly energy storage systems.

Hyuntae Bae and Youngsik Kim

Materials Advances, 2021,2, 3234-3250 (Website link)

img The consumption of lithium-based materials has more than doubled in eight years due to the recent surge in demand for lithium applications as lithium ion batteries. The lithium-ion battery market has grown steadily every year and currently reaches a market size of $40 billion. Lithium, which is the core material for the lithium-ion battery industry, is now being extracted from natural minerals and brines, but the processes are complex and consume a large amount of energy. In addition, lithium consumption has increased by 18% from 2018 to 2019, and it can be predicted that the depletion of lithium is imminent with limited lithium reserves. This has led to the development of technologies to recycle lithium from lithium-ion batteries. This article focuses on the technologies that can recycle lithium compounds from waste lithium-ion batteries according to their individual stages and methods. The stages are divided into the pre-treatment stage and lithium extraction stage, while the latter is divided into three main methods: pyrometallurgy, hydrometallurgy, and electrochemical extraction. Processes, advantages, disadvantages, lithium extraction efficiency, price, environmental pollution and the degree of commercialization of each method are compared and analyzed quantitatively. Despite the growing attention and the development of various lithium recycling technologies, less than 1 percent of lithium is recycled currently. We propose future needs to improve the recycling technologies from waste lithium materials and hope that this article can stimulate further interest and development in lithium recycling.

Sanghun Park, Mayzonee Ligaray, Youngsik Kim, Kangmin Chon, Moon Son, and Kyung Hwa Cho

Desalination, Desalination 506 (2021) 115018 (Website link)

img The seawater battery (SWB) is a promising desalination technology that utilizes abundant sodium ions as an energy storage medium. Recently, the alternative desalination system, seawater battery desalination (SWBD), was developed by placing an SWB next to the desalination compartment. This SWB-D system can desalt water while charging the SWB next to it. However, only a fixed catholyte solution has been investigated, although the catholytes impact the overall SWB-D performance. Therefore, we evaluated the effect of different catholytes on the desalination performance. High-saline reverse osmosis (RO) concentrate or brackish water exhibited excellent salt removal capability (>85.3% of sodium and >76.6% of chloride ions) with relatively short operation times (36.4 h for RO concentrate and 39.5 h for brackish water) upon charging, whereas the relatively low-saline river water showed the longest operation time (81.0 h), implying that river water should be excluded as a potential catholyte. The amount of desalinated water was marginally reduced due to osmosis through the anion exchange membrane; however, the amount of treated salt was >82.9% even after the reduction in water volum e. These findings suggest that the catholyte with a resistance of >0.041 kΩ·cm can be ideal for the SWB-D.

Tae-Ung Wi, Chanhee Lee, M. Fahmi Rahman, Wooseok Go, Su Hwan Kim, Dae Yeon Hwang, Sang Kyu Kwak, Youngsik Kim, and Hyun-Wook Lee

Chemistry of Materials, Chem. Mater. 2021, 33, 1, 126–135 (Website link)

img Research on the interface between solid electrolytes and electrode materials or catholyte is important to effectively and safely use their high energy densities. However, compared to interfaces with electrode materials, the interface between solid electrolytes and liquid media lacks research. Herein, the stability of NA superionic conductor (NASICON) pellets is studied in various aqueous solutions, including deionized (DI) water and a marine environment, associated with different degradation mechanisms. A representative detrimental hydronium exchange reaction between solid electrolytes and aqueous media is suppressed with increasing concentration and ion types dissolved in the solutions. Results of density functional theory calculation and electron energy loss spectroscopy reveal the different activation energies and chemical bonding states of solid electrolytes based on the aqueous solutions’ conditions. NASICON’s ionic conductivity decreases to ∼10–6 S/cm because of severe changes in aqueous solutions with insufficient dissolved ions resulting in inferior chemical stability. Furthermore, chemical stability variations at a steady state can severely affect battery performance. Seawater batteries fabricated with NASICON in immersed DI water for 1 year exhibit a large resistance region from the first cycle; this system breaks down before 200 h, unlike a cell fabricated using NASICON immersed for 1 year in a marine environment.

S.T.Senthilkumar, Jeong-Sun Park, Rebeca Marcilla, Jesus Palma, and Youngsik Kim

Chemical Engineering Journal, Chemical Engineering Journal 411 (2021) 128416 (Website link)

img Aqueous hybrid Zn2+/Na+ ion batteries (AHZSIBs) have gained considerable attention for stationary energy storage applications because of their outstanding safety, sustainability, abundance, and low raw material costs. However, the low capacity values (<100 mAh/g) of the Na+ ion deinsertion/insertion cathodes limit the overall capacity storage of AHZSIBs. Herein, we propose a novel concept to extend the charge storage performance of AHZSIBs using electrolyte with redox characteristics. The benefits of using redox aqueous electrolytes such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) and sodium ferrocyanide (Na4[Fe(CN)6]) were investigated in an AHZSB, which consists of Zn metal as an anode and sodium nickel hexacyanoferrate (Na-NiHCF) as the Na+ deinsertion/insertion cathode. The proposed AHZSB using Na4[Fe(CN)6] redox electrolyte provided a capacity (144 mAh/g) that was ~2.94 times higher than AHZSIB using a conventional Na2SO4 electrolyte (49 mAh/g). This capacity enhancement emanated from the faradaic contribution of the Fe2+(CN)64−/Fe3+(CN)63− redox pair present in the electrolyte and Fe2+/Fe3+ redox pair in the lattice of Na-NiHCF. In addition, the TEMPOL-based redox electrolyte also improved the capacity (from 49 to 120 mAh/g) through the combined faradaic contribution of the TEMPOL/TEMPOL+ redox pair dissolved in the electrolyte and the Fe2+/Fe3+ redox pair in the Na-NiHCF lattice. These results confirm the competence of the redox electrolyte in AHZSIB in enhancing the charge storage capacity. We anticipate that this proof-of-concept study will provide a new direction for developing high-capacity storage AHZSIBs. More importantly, this approach can be used in any aqueous/non-aqueous batteries.

Ahmad M. Harzandi, Sahar Shadman, Arun S. Nissimagoudar, Dong Yeon Kim, Hee‐Dae Lim, Jong Hoon Lee, Min Gyu Kim, Hu Young Jeong, Youngsik Kim, and Kwang S. Kim

Advanced Energy Materials, Adv. Energy Mater. 2021, 2003448 (Website link)

img To develop effective electrocatalytic splitting of acidic water, which is a key reaction for renewable energy conversion, the fundamental understanding of sluggish/destructive mechanism of the oxygen evolution reaction (OER) is essential. Through investigating atom/proton/electron transfers in the OER, the distinctive acid–base (AB) and direct‐coupling (DC) lattice oxygen mechanisms (LOMs) and adsorbates evolution mechanism (AEM) are elucidated, depending on the surface‐defect engineering condition. The designed catalysts are composed of a compressed metallic Ru‐core and oxidized Ru‐shell with Ni single atoms (SAs). The catalyst synthesized with hot acid treatment selectively follows AB‐LOM, exhibiting simultaneously enhanced activity and stability. It produces a current density of 10/100 mA cm−2 at a low overpotential of 184/229 mV and sustains water oxidation at a high current density of up to 20 mA cm−2 over ≈200 h in strongly acidic media.