Journal Publication


Dongyeop Kim, Jeong-Sun Park, Wang-Geun Lee, Yunseok Choi and Youngsik Kim

Journal of The Electrochemical Society, 2022, 169 040508 (Website link)

img Rechargeable seawater batteries (SWBs) use Na+ ions dissolved in water (seawater or salt-water) as the cathode material. They are attracting attention for marine applications such as light buoys, marine drones, auxiliary power for sailing boats and so on. So far, SWB design has been developed from the coin-type to prismatic-shape cell for research purposes to investigate cell components and electrochemical behaviors. However, for commercial applications, that generally require >12 V and >15 W, the development of an SWB module is required, including cell assembly and packing design. The purpose of this work was to conduct research on the SWB cell assembly method while considering the SWB's properties and minimizing current imbalance. Additionally, a 5 Series (S) 4 Parallel (P) SWB module is constructed and validated using commercially available light buoys (12 V, 15 W).

Junho Bae, Hyuntae Bae, Jihun Cho, Jaebeom Jung, Yunseok Choi and Youngsik Kim

Journal of Materials Chemistry A, 2022, 10, 6481 (Website link)

img The energy storage system (ESS) safety issue caused by battery thermal runaway is becoming severe, and its solution for perfect fire suppression method has not yet been optimized. Herein, we propose the concept of a Water-in-Battery (WiB) system, which utilizes water for functional elements in an existing battery to manage the generated heat and remove the fire-causing elements in the battery. Under general conditions (at high C-rates and high temperatures), the system acts as a coolant and extends the battery life. Under abuse conditions such as overcharging or overheating, the water in the WiB delays the thermal runaway of the battery. In addition, the system blocks fire by eliminating oxygen and decreasing the temperature of the battery. Moreover, this system can be simply implemented in an existing ESS by a low-cost and eco-friendly method.

Myung-Jin Baek, Jieun Choi, Tae-Ung Wi, Hyoeng Yong Lim, Min Hoon Myung, Chanoong Lim, Jinsu Sung, Jeong-Sun Park, Ju Hyun Park, Yul Hui Shim, Jaehyun Park, Seok Ju Kang, Youngsik Kim, So Youn Kim, Sang Kyu Kwak, Hyun-Wook Lee, and Dong Woog Lee

Journal of Materials Chemistry A, 2022, 10, 4601 (Website link)

img Conventional binders, such as polyvinylidene fluoride, are not ideal candidates for aqueous sodium–air batteries (SABs) because of their relatively low adhesiveness, weak mechanical strength, and inherent hydrophobicity. The low adhesion strength often leads to electrocatalysts and carbon current collector detachments, followed by degradation of electrochemical performance over time. For SABs to possess excellent performance, development of advanced polymeric binders with high wettability and underwater adhesion is required. In this study, the adhesion stability of the electrocatalyst/current collector interface is significantly enhanced by using synthesized catechol-derivative hydrophilic binders, whereas catalyst desorption and carbon corrosion are effectively prevented. Using high-resolution transmission electron microscopy, we demonstrated the role of synthesized binders on the morphological stability of the composite electrode. Furthermore, surface forces apparatus and density functional theory calculations reveal insights into how polymeric binders impact the adhesion mechanism and battery performance of SAB based on their functional groups.

Youngjin Kim, Kwangho Shin, Youngjae Jung, Wang-Geun Lee, Youngsik Kim

Advanced Sustainable System, 2022, 2100484 (Website link)

img Rechargeable seawater batteries (SWBs) using seawater as a catholyte have attracted extensive attention owing to the ocean's high theoretical energy density (3051 Wh L-1, 3145 Wh kg-1) and excellent thermal management. However, despite many improvements in materials and cell designs used in SWBs so far, there is a limit on the energy density in practical use, because of the lack of optimization of the cell structure. Herein, this work introduces a novel design by applying a rigid frame with an extended space called “prismatic-type.” Consequently, an energy density of 23 Wh (242 Wh L-1) is obtained by increasing the specific area of the unit cell and the capability of the anode active materials in the internal space. In addition, it enables the design of a discrete type that can improve the power density by increasing the surface area of the cathode current collectors. With the increased surface area, a peak power of 1162 mW is achieved for the discrete type compared to 727 mW for the integral type. These results suggest that these newly designed prismatic SWBs could contribute to practical applications in the near future.

Jehee Park, Kyojin Ku, Seoung-Bum Son, Jihyeon Gim, Youngsik Kim, Eungje Lee and Christopher Johnson

Journal of The Electrochemical Society, 2022 169 030536 (Website link)

img Iron (Fe)-based layered oxide cathodes that employ Fe3+/Fe4+ redox reaction present a family of attractive cathode materials for sodium-ion batteries as iron is abundant, low-cost, and environmentally benign. However, their electrochemical performance is not yet satisfactory and requires further improvement. In this study, we investigate the effect of electrolytes on the electrochemical performance of α-NaFeO2, a prototypical model of Fe-based layered cathodes. First, we established the critical impact of the poor cathode-electrolyte interfacial stability on cell performances. Systematic electrochemical tests and material characterizations further revealed the degradation mechanism in which the highly reactive Fe4+ state in the charged Na1−xFeO2 electrodes promotes severe electrolyte decomposition and subsequent growth of a thick interface layer that leads to impedance rise and performance degradation. In addition, the superior performance of NaPF6 over NaClO4 and the beneficial effect of the FEC additive are reported.

Namhyeok Kim, Seongwoo Jeong, Wooseok Go, Youngsik Kim

Water Research, 215 (2022) 118250 (Website link)

img Seawater is a virtually unlimited source of minerals and water. Hence, electrodialysis (ED) is an attractive route for selective seawater desalination due to the selectivity of its ion exchange membrane (IEM) toward the target ion. However, a solution-like IEM, which is permeable to water and ions other than the target ion, results in the leakage of water as well as extraction of unwanted ions. This degrades the productivity and purity of the system. In this study, A novel desalination system was developed by replacing the cation exchange membrane (CEM) with a Na super ionic conductor (NASICON) in ED. NASICON exceptionally permits Na+ ion migration, and this enhanced the productivity of desalted water by removing 98% of Na+ while retaining water and other cationic minerals. Therefore, the final volume of desalted water in N-ED was 1.36 times larger compared to that of ED. In addition, the specific energy consumption for salt (NaCl) extraction was reduced by ∼13%. Furthermore, the NASICON in N-ED was replaced into a two-sided NASICON-structured rechargeable seawater battery, thereby further conserving ∼20% energy by simultaneously coupling selective desalination with energy storage. Our findings have positive implications and further optimizations of the NASICON will enable practical and energy-effective applications for seawater utilization.

Sanghyun Park, Namhyeok Kim, Youngsik Kim, Moon Son, Kyunghwa Cho

Journal of Cleaner Production, 233 (2022) 130188 (Website link)

img As it is typically disposed of to the ocean, naturally produced brine water has been an avoidable issue in seawater desalination technology, particularly in the reverse osmosis (RO) process. To address this issue, a seawater battery-desalination (SWB-D) system was used to reduce the concentration of RO brine while also storing electrical energy by harvesting sodium ions from the brine. The SWB equipped with an anion exchange membrane (AEM) can lower the RO brine concentration to seawater levels, but the use of AEM for brine treatment is costly and the slow kinetics of salt transport require long operation times. In this study, we present a proof of concept for using RO membrane as an alternative to AEM in the SWB desalination system. Owing to its low cost and unexpected support for salt removal via diffusion across the RO membrane, using RO membrane is a viable application. The effect of diffusion enables SWB-D with RO membrane to reduce the charging time by 36.8% (up to ∼40.5% salt removal) compared with SWB-D with AEM. In addition, ∼52.5 kWh m−3 of energy (assuming 80% energy recovery) was saved while lowering the concentration of brine to seawater levels (from 1.2 to ∼0.6 M).

Jong Hun Ryu, Jaehyun Park, Jeongwoo Park, Jinhong Mun, Eunmi Im, Hojeong Lee, Sung You Hong, Kwangjin An, Geunsik Lee, Youngsik Kim, Pil Sung Ho, Seok Ju Kang

Energy Storage Materials, 45 (2022) 281-290 (Website link)

img Seawater batteries consisting of Na anode, Na super-ionic conductor separators, and seawater catholytes have received wide attention because of their theoretical specific capacity of 1160 mAh g−1 and cost-effective Na anode in comparison to rare-earth Li. However, large overpotential during charge and discharge caused by parasitic reactions limits their practical applications. In this work, we employ the bifunctional Pt-Co alloy electrocatalysts produced by carbothermal shock (CTS) method to improve the oxygen evolution and reduction reaction activities of seawater batteries. The CTS induced Pt-Co alloy nanoparticles are well synthesized and dispersed on a carbon current collector within a few s, resulting in improved overpotential and cycle endurance of seawater batteries compared to pristine carbon cathode. In particular, the cell can operate for over 500 h in a seawater catholyte at a fixed capacity of 0.25 mA cm−2 without significant performance degradation. Furthermore, CTS can be readily applied to large-area prismatic seawater battery cells. We observe excellent cyclability in a large-scale seawater battery, suggesting that bifunctional Pt-Co alloy electrocatalysts produced by CTS are viable for use in seawater batteries.