• Membrane Journal
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• v.30 no.4
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• pp.213-227
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• 2020

As unrenewable energy resources have depleted over the years, the demand for renewable energy has increased promoting research for more effective methods to produce renewable energy. The field of fuel cell development, specifically microbial fuel cells (MFCs), has developed because of the dual performance potential of the technology. MFCs convert power by facilitating electrode-reducing organisms such as bacteria (microbes) as a catalyst to produce electrical energy. MFCs use domestic and industrial wastewater as fuel to initiate the process, purifying the wastewater as a result. Proton exchange membranes (PEM) play a crucial role in MFCs as a separator between the anodes and cathodes chambers allowing only protons to effectively pass through. Nafion is the commercially used PEM for MFCs, but there are many setbacks: such as cost, production time, and less effective proton conductivity properties. In this review there will be largely two parts. Firstly, several newly developed PEM are discussed as possible replacements of Nafion. Secondly, MFC based on PEM, blended PEM and composite PEM are summarized.

• Journal of the Korean Ceramic Society
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• v.56 no.5
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• pp.497-505
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• 2019

Lanthanum-based transition metal cations containing perovskites have emerged as potential catalysts for the intermediate-temperature (600-800℃) oxygen reduction reaction (ORR). Here, we report a facile acetylacetone-assisted combustion route for the synthesis of nanostructured La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF6428) cathodes for intermediate-temperature solid-oxide fuel cells (IT-SOFCs). The as-prepared powder was analyzed by thermogravimetry analysis-differential scanning calorimetry. The powder calcined at 800℃ was characterized by X-ray diffraction, scanning electrode microscopy, energy dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller surface area measurements. It was found that the porosity of the air electrode significantly increased by utilizing the nanostructured LSCF6428 instead of commercial powder. The performance of a single cell fabricated with the nanostructured LSCF6428 cathode increased by 112%, from 0.4 to 0.85 W cm^-2, at 700℃. Electrochemical impedance spectroscopy showed a considerable reduction in the area-specific resistance and activation energy from 133.5 to 61.5 kJ/mol, resulting in enhanced electrocatalytic activity toward ORR and overall cell performance.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.06a
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• pp.435-438
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• 2009

A navigation aid buoy is a kind of safety facility for maritime navigation with a purpose of leading the vessels for navigating, docking and sail off. An advanced rechargeable battery is required for stable power supply for navigation aid buoy as the high magnitude LED lamps, real time location/control for navigation aids and e-Navigation support systems with maritime climate observation equipments have recently been deployed. This study is focused on the lithium battery, especially lithium polymer battery which is believed to be safer than the other types of batteries. The lithium polymer battery reviewed in this study is designed with $LiFePO_4$-based cathode, which has superior safety features to the oxide-based cathodes. Besides, a 3.6kWh battery pack has been built with the above-mentioned unit cells for the purpose of comparative research with lead acid battery system.

• Journal of Electrochemical Science and Technology
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• v.14 no.3
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• pp.293-300
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• 2023

The global energy storage markets have gravitated to high-energy-density and low cost of lithium-ion batteries (LIBs) as the predominant system for energy storage such as electric vehicles (EVs). High-Ni layered oxides are considered promising next-generation cathode materials for LIBs owing to their significant advantages in terms of high energy density. However, the practical application of high-Ni cathodes remains challenging, because of their structural and surface instability. Although extensive studies have been conducted to mitigate these inherent instabilities, a two-step process involving the synthesis of the cathode and a dry/wet coating is essential. This study evaluates a one-step β-Li₂SnO₃ layer coating on the surface of LiNi_0.8Co_0.2O₂ (NC82) via the thermal segregation of Sn owing to the solubility limit with respect to the synthesis temperature. The doping, segregation, and phase transition of Sn were systematically revealed by structural analyses. Moreover, surface-engineered 5 mol% Sn-coated LiNi_0.8Co_0.2O₂ (NC82_Sn5%) exhibited superior capacity retention compared to bare NC82 owing to the stable surface coating layer. Thus, the developed one-step coating method is suitable for improving the properties of high-Ni layered oxide cathode materials for application in LIBs.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.1-7
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• 1998

For the purpose of finding new cathode materials for medium-temperature $(700\~800^{\circ}C)$ solid oxide fuel cells, $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3,\;(x=0.0\~0.5)$ are prepared, and their thermal stability and conductivity characteristics are investigated. Also, the cathodic activities are measured after the cathode layer being attached on CGO (cerium-gadolinium oxide) electrolyte disk. The X-ray analyses indicate that the materials prepared by calcining the citrate-gels at $800^{\circ}C$ have the orthorhombic perovskite structure without discernible impurities. The thermal stability of the undoped Co perovskite is so poor that it is decomposed to the individual binary oxide even at $1300^{\circ}C$. But the partially Fe-doped cobaltates exhibit a better thermal stability to retain their structural integrity up to $1400^{\circ}C$. The observation whereby both the undoped and Fe-doped cobaltates melt at ca. $1300^{\circ}C$ leads us to perform the electrode adhesion at <$1300^{\circ}C$. The cathodic activity of $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3,\;(x=0.0\~0.5)$, electrodes is superior to $La_{0.9}Sr_{0.1}MnO_3$, among the samples of $x=0.0\~0.5$, the x=0.2 cathode shows the best activity for the oxygen reduction reaction. It is likely that the Fe-doping provides a better thermal stability to the materials but in turn imparts an inferior cathodic activity, such that the optimum trade-off is made at x=0.2 between the two factors. The total electrical conductivity and ion conductivity of $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3$, are measured to be 51 S/cm and $6.0\times10^{-4}S/cm\;at\;800^{\circ}C$, respectively. The conductivity values illustrate that the materials are a mixed conductor and the reaction sites can be expanded to the overall electrode surface, thereby providing a better cathodic activity than $La_{0.9}Sr_{0.1}MnO_3$.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.574-581
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• 2022

Nanofibers comprising reduced graphene oxide (rGO) and Mo₂C/Mo₂N nanoparticles (Mo₂C/Mo₂N rGO NFs) were prepared for a functional interlayer of Li-S batteries (LSBs). The well-dispersed Mo₂C and Mo₂N nanoparticles in the nanofiber structure served as active polar sites for efficient immobilization of dissolved lithium polysulfide. The rGO nanosheets in the structure also provide conductive channels for fast ion/electron transport during charging-discharging and ensured reuse of lithium polysulfide during redox reactions through a fast charge transfer process. As a result, the cell assembled with Mo₂C/Mo₂N rGO NFs-coated separator and pure sulfur electrode (70 wt% of sulfur content and 2.1 mg cm^-2 of sulfur loading) showed a stable discharge capacity of 476 mA h g^-1 after 400 charge-discharge cycles at 0.1 C. Furthermore, it exhibited a discharge capacity of 574 mA h g^-1 even at a high current density of 1.0 C. Therefore, we believe that the proposed unique nanostructure synthesis strategy could provide new insights into the development of sustainable and highly conductive polar materials as functional interlayers for high performance LSBs.

• Journal of the Korean Electrochemical Society
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• v.15 no.3
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• pp.172-180
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• 2012

The $LiMn_2O_4$ cathodes for lithium ion battery were synthesized from various precursors of manganese oxides and manganese hydroxides. As the first step, nanosized precursors such as ${\alpha}-MnO_2$ (nano-sticks), ${\beta}-MnO_2$ (nano-rods), $Mn_3O_4$ (nano-octahedra), amorphous $MnO_2$(nano-spheres), and $Mn(OH)_2$ (nano-plates) were prepared by a hydrothermal or a precipitation method. Spinel $LiMn_2O_4$ with various sizes and shapes were finally synthesized by a solid-state reaction method from the manganese precursors and LiOH. Nano-sized (500 nm) octahedron $LiMn_2O_4$ showed high capacities of 107 mAh $g^{-1}$ and 99 mAh $g^{-1}$ at 1 C- and 50 C-rate, respectively. Three dimensional octahedral crystallites exhibit superior electrochemical characteristics to the other one-dimensional and two-dimensional shaped $LiMn_2O_4$ nanoparticles. After 500 consecutive charge discharge battery cycles at 10 C-rate with the nano-octahedron $LiMn_2O_4$ cathode, the capacity retention of 95% was observed, which is far better than any other morphologies studied in this work.

• Journal of the Korean Electrochemical Society
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• v.4 no.2
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• pp.58-64
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• 2001

YSZ ($8mol\%$ yttria-stabilized zirconia)-modified LSM $(La_{0.85}Sr_{0.15}MnO_3)$ composite cathodes were fabricated by formation of YSZ film on triple phase boundary (TPB) of LSM/YSZ/gas. The YSZ coating film greatly enlarged electrochemical reaction sites from the increase of additional TPB. The composite cathode was formed on thin YSZ electrolyte (about 30 Um thickness) supported on an anode and then I-V characterization and AC impedance analyses were performed at temperature between $700^{\circ}C\;and\;800^{\circ}C$. As results of the impedance analysis on the cell at $800^{\circ}C$ with humidified hydrogen as the fuel and air as the oxidant, R1 around the frequency of 1000 Hz represents the anode Polarization. R2 around the frequency of 100Hz indicates the cathode polarization, and R3 below the frequency of 10 Hz is the resistance of gas phase diffusion through the anode. The cell with the composite cathode produced power density of $0.55\;W/cm^2\;and\;1W/cm^2$ at air and oxygen atmosphere, respectively. The I-V curve could be divided into two parts showing distinctive behavior. At low current density region (part I) the performance decreased steeply and at high current density region (part II) the performance decreased gradually. At the part I the performance decrease was especially resulted from the large cathode polarization, while at the part H the performance decrease related to the electrolyte polarization.