Journal Publication


Seungyoung Park, Ziyauddin Khan, Tae Joo Shin, Youngsik Kim and Hyunhyub Ko

Journal of Materials Chemistry A, J. Mater. Chem. A, 2019, 7, 1564–1573 (Website link)

img Rechargeable battery systems that use Na-based anodes as alternatives to Li-ion batteries are highly desirable for grid-scale energy storage systems owing to the high abundance and low cost of Na. Furthermore, aqueous Na batteries are advantageous considering the cost, safety and cycle life. However, the limited energy density is still a critical issue for Na-based batteries. Here, we demonstrate a high performance rechargeable battery using dual electrolytes based on a Na metal anode and a redox couple of hierarchical NiCoAl-layered double hydroxide (NiCoAl-LDH) nanosheets on a carbon microfiber electrode with high energy storage capacity. In this design, the wide potential range of the Na metal anode and the high capacity of hierarchical NiCoAl-LDH nanosheets on a carbon microfiber cathode enable a rechargeable Na/Ni battery with excellent energy storage performance. For stable operation in a hybrid system using non-aqueous and aqueous electrolytes, an alkali-ion solid electrolyte (NASICON,Na3Zr2Si2PO12) is used for the separation of electrolytes. The Na/Ni battery exhibits a stable operating voltage of 3.1 V during discharge which outperforms the low cell voltage (1.23 V) of an aqueous rechargeable battery, a high capacity of ~350 mA h g1, and a resulting high energy density of 1085 W h kg1. With the combination of a solid-state redox couple as the cathode and a metallic sodium anode, our study demonstrates the high potential of Na based batteries for high energy EES systems.

Kang HoShin, Jehee Park, Sul Ki Park, Puritut Nakhaniveja, Soo Min Hwang, Youngsik Kim ,and Ho Seok Park

Journal of Industrial and Engineering Chemistry, Volume 72, 25 April 2019, Pages 250-254 (Website link)

img Herein, we report synthesis of Co3V2O8 nanoparticles for an electrocatalyst of seawater batteries. The cell using Co3V2O8 achieves a higher voltage efficiency of ∼76% than ∼72% of the cell without catalyst. In addition, the Co3V2O8 shows a good rate capability with reduced voltage gaps and an increased power density of ∼5.9 mW cm−2. This cell is stable over 20 cycles for 400 h with reduced voltage gap of ∼0.95 V. These findings are attributed to the facilitated redox kinetics of the clustered Co3V2O8 nanoparticles arising from the optimal metalOH bond strength and large surface area.

S. T. Senthilkumar, Wooseok Go, Jinhyup Han, Linh Pham Thi Thuy, Koshal Kishor, Yongil Kim and Youngsik Kim

Journal of Materials Chemistry A, J. Mater. Chem. A, 2019,7, 22803-22825 (Website link)

img New concepts or chemistry is an urgent requirement for rechargeable batteries to achieve a low-cost, user-friendly nature with adequate energy densities and high levels of safety. Rechargeable seawater batteries (SWBs) are a new electrochemical system for the storage of electrical energy that utilizes seawater, as an infinite resource, as a source of the Na+ ion cathode. Seawater is a naturally available abundant renewable resource that covers nearly 70% of the Earth's surface. This review provides an essential comprehensive introduction to new rechargeable SWBs. First, we present details of seawater and then the history of primary SWBs and rechargeable SWBs, and the structure and chemistry of rechargeable SWBs. Next, we describe the research progress that has so far been made on various components of SWBs, such as cathode current collectors, electrocatalysts, solid electrolyte, anodes, and non-aqueous electrolyte, including the performance metrics reported in the literature. Moreover, some concepts of modified rechargeable SWB design for desalination and CO2 reduction application are discussed. Lastly, we provide our future outlook on the development of rechargeable SWBs and emphasize the main practical issues with the hope of stimulating further research progress.

Jin Hyun Kim, Soo Min Hwang, Inchan Hwang, Jinhyup Han, Jeong Hun Kim, Yim Hyun Jo, Kwanyong Seo, Youngsik Kim, Jae Sung Lee

iScience, Science 19, 232–243 (Website link)

img Conversion of sunlight to chemical energy based on photoelectrochemical (PEC) processes has been considered as a promising strategy for solar energy harvesting. Here, we propose a novel platform that converts solar energy into sodium (Na) as a solid-state solar fuel via the PEC oxidation of natural seawater, for which a Na ion-selective ceramic membrane is employed together with photoelectrode (PE)-photovoltaic (PV) tandem cell. Using an elaborately modified bismuth vanadate-based PE in tandem with crystalline silicon PV, we demonstrate unassisted solar-to-Na conversion (equivalent to solar charge of seawater battery) with an unprecedentedly high efficiency of 8% (expected operating point under 1 sun) and measured operation efficiency of 5.7% (0.2 sun) and long-term stability, suggesting a new benchmark for low-cost, efficient, and scalable solid solar fuel production. The sodium turns easily into electricity on demand making the device a nature-friendly, monolithic solar rechargeable seawater battery.

Nazish Parveena,Ziyauddin Khanb, Sajid Ali Ansaria, Seungyoung Parkb, S.T. Senthilkumarb, Youngsik Kim, Hyunhyub Ko, Moo Hwan Choa

Chemical Engineering Journal, Volume 360, 15 March 2019, Pages 415-422 (Website link)

img Synthesis of the strongly anisotropic materials, such as highly porous hollow double walled cubes are considered excellent approach to maximize the diffusion of electrolytes. Herein, hollow doubled walled (HDW) Mn2O3 nanocubes (NCs) were synthesized by facile hydrothermal method followed by calcination method. The growth of nanocubes were studied by performing hydrothermal reaction at different times ranging from 3 to 9 h. Thereafter, the feasibility of prepared HDW NCs as air cathode in hybrid Na-air battery was systematically investigated. Among all, the sample prepared by 9 h hydrothermal treatment showed superior performance than 3 and 6 h samples. The fabricated hybrid Na-air cell using HDW Mn2O3 NCs displayed 330 mV overpotential gap and 90% electrical energy efficiency at 5 mA g−1 current density, maximum of 0.2Wg−1 power density and good cyclic stability up to 75 cycles which is attributed to the highly porous nature of material that allows efficient diffusion of electrolyte ions and oxygen from air. Thus, present investigation suggests that HDW Mn2O3 NCs can be a potential air cathode and can be utilized in other metal-air battery systems.

Yongil Kim, Guk-Tae Kim, Sangsik Jeong, Xinwei Dou, Chenxi Geng, Youngsik Kim, and Stefano Passerini

Energy Storage Materials, 2019, 16, 56-64 (Website link)

img A new electrolyte (anolyte) for the negative electrode of seawater batteries, based on the combination of two ionic liquids (ILs), a sodium salt, and a SEI-forming additive, is herein reported. The quaternary anolyte is composed of N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (0.6 mol fraction), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl) imide) (0.3 mol fraction), and sodium bis(fluorosulfonyl)imide (0.1 mol fraction). Ethylene carbonate (5 wt% with respect to the ILs and salt mixture) is added to promote SEI formation. The thermal, physicochemical, and electrochemical characterization of the quaternary electrolyte indicate its suitability as an anolyte, as well as the formation of a highly stable interface with the negative (hard carbon) electrode. Lab-scale seawater full cells employing a hard carbon anode and the ionic liquid-based quaternary anolyte show remarkable results in terms of capacity, cyclability, and rate capability at room temperature. Additionally, these cells showed better energy efficiency (voltage efficiency) and cyclability than those based on a conventional organic carbonate-based anolyte.

Soo Min Hwang, Jeong-Sun Park, Yongil Kim, Wooseok Go, Jinhyup Han, Youngjin Kim, and Youngsik Kim

Advanced Materials, 2019, 31, 1804936 (Website link)

img Energy harvesting from natural resources is of significant interest because of their abundance and sustainability. Seawater is the most abundant natural resource on Earth, covering two thirds of the surface. Rechargeable seawater battery is a new energy storage platform that enables interconversion of electrical energy and chemical energy by tapping into seawater as infinite medium. In this report, we provide an overview of the research and development activities of seawater batteries toward practical applications. Seawater batteries consist of anode and cathode compartments that are separated by a Na-ion conducting membrane, which allows only Na+ ion transport between the two electrodes. We cover the roles and drawbacks of the three key components, as well as the development concept and operation principles of the batteries on the basis of previous reports. Moreover, we introduce the prototype manufacturing lines for mass production and automation, and potential applications,particularly in marine environments. Highlighting the importance of engineering the cell components, as well as optimizing the system level for a particular application and thereby successful market entry, we discuss the key issues to be resolved, so that the seawater battery can emerge as a promising alternative to existing rechargeable batteries.

Hyuntae Bae, Jeong-Sun Park, S.T.Senthilkumar, Soo Min Hwang, and Youngsik Kim

Journal of Power Sources, 2019, 410-411, 99-105 (Website link)

img The water and carbon cycles are central to the Earth’s ecosystem, enabling the sustainable development of human societies. To mitigate the global issues of water shortages and climate change, we report a new electrochemical system that fulfills two functions—seawater desalination and carbon dioxide air-capture—during the charge and discharge processes. The seawater desalination-carbon capture system utilizes a seawater battery platform, consisting of three major compartments (desalination, sodium-collection, and carbon-capture), which are separated by sodium superionic conducting ceramic membranes. It is found that the concentrations of sodium ions and chloride ions in fresh seawater (total dissolved solids  34,000 ppm) are significantly decreased by the charging of the seawater desalination-carbon capture system, resulting in brackish water (total dissolved solids  7,000 ppm). The discharge process induces the air-capture of ambient carbon dioxide gases through carbonation reactions, which is demonstrated by the carbon dioxide gas removal in this compartment. The hybrid system suggests a new electrochemical approach for both desalination and carbon capture.