• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.97-102
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• 2020

Recently, various degradation mechanisms of lithium secondary battery cathode materials have been revealed. As a result, many studies on overcoming the limitation of cathode materials and realizing new electrochemical properties by controlling the degradation mechanism have been reported. Li-rich layered oxide is one of the most promising cathode materials due to its high reversible capacity. However, the utilization of Li-rich layered oxide has been restricted, because it undergoes a unique atomic structure change during the cycle, in turn resulting in unwanted electrochemical degradations. To understand an atomic structure deterioration mechanism and suggest a research direction of Li-rich layered oxide, we deeply evaluated the atomic structure of 0.4Li₂MnO₃_0.6LiNi_1/3Co_1/3Mn_1/3O₂ Li-rich layered oxide during electrochemical cycles, by using an atomic-resolution analysis tool. During a charge process, Li-rich materials undergo a cation migration of transition metal ions from transition metal slab to lithium slab due to the structural instability from lithium vacancies. As a result, the partial structural degradation leads to discharge voltage drop, which is the biggest drawback of Li-rich materials.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.58-63
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• 2022

Graphite has been used as an anode material for lithium-ion batteries for the past 30 years due to its low de-/lithiation voltage, high theoretical capacity of 372 mAh/g, low price, and long life properties. Recently, all-solid-state lithium-ion batteries (ASSLB), which are composed of inorganic solid materials with high stability, have received great attention as electric vehicles and next-generation energy storage devices, but research works on graphite that works well for ASSLB systems are insufficient. Therefore, we induced the performance improvement of ASSLB anode electrode graphite material by removing the amorphous carbon present in the carbon material surface, acting as a resistive layer from the graphite. As a result of X-ray diffraction (XRD) analysis using heat treated graphite in air at 400, 500, and 600 ℃, the full width at half maximum (FWHM) at (002) peak was reduced compared to that of bare graphite, indicating that the crystallinity of graphite was improved after heat treatment. In addition, the discharge capacity, initial coulombic efficiency (ICE) and cycle stability increased as the crystallinity of graphite increased after heat treatment. In the case of graphite annealed in air at 500 ℃, the high capacity retention rate of 331.1 mAh/g and ICE of 86.2% and capacity retention of 92.7% after 10-cycle measurement were shown.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.164.2-164
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• 2002

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.36-42
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• 2007

In general, the battery and the(electric) condenser are pictured as electrical energy storage devices. Although there were lots of inventions and utilizations of morden conveniences according to enormous growth of the science and technologies after the Industrial Revolution, a speed of technology development on these devices being closely used in civilized human lives and many electric or electronic systems as a core component are relatively slower to the other fields of technologies. Nevertheless, based on a remarkable progress of the material science and technologies for the last ten years, a new type of electrical energy storage device so called as 'electrochemical capacitors' are being developed and used practically. The electrochemical capacitors exhibit their own characteristics of much enhanced capacitance over the conventional condensers and also distinctively exhibit a longer lift time and higher power capability that the nickel hydrogen batteries and secondary batteries such as lithium ion and polymer batteries does not show up so for. Hence, in this paper, it is intended to introduce a fundamental understanding and updated technology trends on the electrochemical capacitors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.144-148
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• 1997

We synthesized polyaniline films electrochemically under constant current conditions, which exhibited electric conductivity as high as 100 S/cm. By charge and discharge cycling of polyaniline films, we obtained specific discharge capacity as high as 195 mAH/g using HSO$_4$- doped polyaniline. For the polyaniline synthesized using H$_2$SO$_4$ and HClO$_4$ composite electrolyte. we also obtained specific discharge capacity as high as 134 mAHg which rivals inorganic electro- active materials.

• Journal of Environmental Impact Assessment
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• v.32 no.2
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• pp.123-133
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• 2023

Wastewater generated in the secondary battery production process contains lithium and high-concentration sulfate. Recently, as demand as demand for high-Ni precursors with high-energy density has surged, nickel emission is also a concern. Lithium and sulfate are not included in the current water pollutant discharge standard, so if they are not properly processed and discharged, the negative effect on future environment may be great. Therefore, in this study, the ecotoxicity of lithium, nickel, and sulfate, which are potential contaminants that can be discharged from the secondary battery production process, was evaluated using water flea (Daphnia magna) and luminescent bacteria (Aliivibrio fischeri). As a result of the ecotoxicity test, 24-hour and 48-hour D. magna EC₅₀ values of lithium were 18.2mg/L and 14.5mg/L, nickel EC50 values were 7.2mg/L and 5.4mg/L, and sulfate EC₅₀ values were 4,605.5mg/L and 4,345.0mg/L, respectively. In the case of D. magna, it was found that there was a difference in ecotoxicity according to the contaminants and exposure time (24 hours, 48 hours). Comparing the EC₅₀ of D. magna for lithium, nickel, and sulfate, the EC₅₀ of nickel at 24h and 48h was 39.6-37.2% compared to lithium and 0.1-0.2% compared to sulfate, which was the most toxic among the three substances. The difference appeared to be at a similarlevelregardless of the exposure time. The EC₅₀ of sulfate was 253.0-299.7% and 639.5-804.6%, respectively, compared to lithium and nickel, showing the least toxicity among the three substances. The 30-minute EC₅₀ values of luminescent bacteria forlithium, nickel, and sulfate were 2,755.8mg/L, 7.4mg/L, and 66,047.3mg/L,respectively. Unlike nickel, it was confirmed that there was a difference in sensitivity between D. magna and A. fischeri bacteria to lithium and sulfate. Studies on the mixture toxicity of these substances are needed.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.131-136
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• 2008

Silica- or titania-filled poly (vinylidene fluoride-co-hexafluoropropylene)-based polymer electrolytes were prepared by phase inversion technique using N-methyl-2-pyrrolidone and dimethyl acetamide as solvent and water as non-solvent. The polymer electrolytes were adopted to the lithium metal polymer battery using high-capacity cathode $Li[Ni_{0.15}Co_{0.10}Li_{0.20}Mn_{0.55}]O_2$ and lithium metal anode. After the repeated charge-discharge test for the cell, it was proved that the cell adopting the polymer electrolyte based on the phase-inversion membrane containing 40~50 wt% silica showed the highest discharge capacity (180 mAh/g) until 80th cycle and then abrupt capacity fade was just followed. The capacity fade might be due to the deposition of lithium dendrite on the polymer electrolyte, in which the capacity retention was no longer sustainable.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.212.1-212
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• 2003

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.544-547
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• 2011

This paper describes on hardware simulation of passive power control of propulsion system for electric propulsion aircraft of KARI. The propulsion system uses hybrid power system that is composed of solar cell, fuel cell and battery. The fuel cell is replaces by simulator due to its difficulty in handling while the other components are the same as that will be used on board. As the result, reliable power supply for propulsion is confirmed and each power source is well operated showing its characteristics.

• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.76-86
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• 2021

Technologies for lithium secondary batteries are now increasingly expanding to simultaneously improve the safety and higher energy and power densities of large-scale battery systems, such as electric vehicles and smart-grid energy storage systems. Next-generation lithium batteries, such as lithium-sulfur (Li-S) and lithium-air (Li-O₂) batteries by adopting solid electrolytes and lithium metal anode, can be a solution for the requirements. In this analysis of battery technology trends, solid electrolytes, including polymer (organic), inorganic (oxides and sulfides), and their hybrid (composite) are focused to describe the electrochemical performance achievable by adopting optimal components and discussing the interfacial behaviors that occurred by the contact of different ingredients for safe and high-energy lithium secondary battery systems. As next-generation rechargeable lithium batteries, Li-S and Li-O₂ battery systems are briefly discussed coupling with the possible use of solid electrolytes. In addition, Electronics and Telecommunications Research Institutes achievements in the field of solid electrolytes for lithium rechargeable batteries are finally introduced.