• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1315-1323
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• 2018

We studied the carbonization due to the annealing condition of waste coffee powder for application as an active anode material for lithium-ion batteries (LIBs). The coffee powder used as an active anode material for LIBs was obtained from coffee beans, not from a coffee shells. The waste coffee powder was dried in air and heat-treated in an $Ar/H_2$ atmosphere to obtain a pore-forming activated carbon powder. The specific capacity of the sample annealed at $700^{\circ}C$ was still 303 mAh/g after 1000 cycles at a current density of 1000 mA/g and with a coulombic efficiency of over 99.5%. The number of pores and the pore size of the waste coffee powder were increased due to chemical treatment with KOH, which had the some effect as an increased specific surface area. The waste coffee powder is considered to be a very promising active anode material because of both its excellent electrochemical properties due to enhanced carrier conduction and its being a cost effective resource for use in LIBs.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.290-298
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• 2021

A purification process was performed for the application of natural graphite as an anode material. The influence of the structural change and impurity content of graphite according to the process on the anode electrochemical characteristics was investigated. Natural graphite was chemically/physically purified by acid-treatment which used different amounts of solution of ammonium fluoride/sulfuric acid in the same ratio and thermal treatment used different temperatures (800~2500 ℃). Acid-treatment had limitation to remove impurities, and identified that all impurity contents was removed except some traces of atom such as Si by after progressed thermal-treatment until 2500 ℃. The anode materials characteristic of graphite treated by purification process was improved, and changes in the structure and impurity contents affected dominantly the capacity, rate property and initial Coulombic efficiency. Consequently, the complex purification process improved the graphite structure and also the performance of lithium ion battery by controlling the excessive formation of solid electrolyte interphase and expanding Li⁺ insertion space originated from the effective removal of impurities.

• Journal of the Korean Electrochemical Society
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• v.24 no.2
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• pp.28-33
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• 2021

Many researchers have increased the loading level of electrodes to improve the energy density of secondary batteries. In this study, high-loading NCM523 (LiNi_0.5Co_0.2Mn_0.3O₂) positive electrode is manufactured using a polytetrafluoroethylene (PTFE) binder, not the conventional polyvinylidene fluoride (PVdF) binder, which has been commonly used in lithium-ion batteries. Through the kneading process using PTFE suspension, not the conventional slurry process using PVdF solution in N-methyl-2-pyrrolidinone (NMP), thick electrodes with high loading are easily manufactured. When the PTFE and PVdF-based electrodes are prepared at a loading level of 5.0 mAh/cm², respectively, the PTFE-based electrode shows better cycle performance and rate capability than those of PVdF-based electrodes. The electrode manufactured by the kneading process using a PTFE binder has high electrode porosity due to insufficient roll-press, but the porosity can be lowered by high temperature roll-press over 120℃. However, there is no significant difference in cycle performance according to the roll press temperature. In addition, the cycle performance of the high loading electrode is slightly improved by increasing the content of the conductive material. Overall, the PTFE binder can improve the performance of the high loading electrode, but additional solutions will be needed.

• Resources Recycling
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• v.31 no.5
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• pp.34-41
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• 2022

Smelting reduction of spent lithium-ion batteries results in metallic alloys, slag, and dust containing Li(I). Precipitation of Li₂CO₃ was performed using the synthetic leachate of the dust. Herein, the effects of the precipitant and addition of non-aqueous solvents on the precipitation of Li(I) were investigated. Na₂CO₃ was a more effective precipitating agent than (NH₄)₂CO₃ owing to the hydrolysis reaction of dissolved ammonium and carbonate. The addition of acetone or ethanol improved the Li(I) precipitation percentage for both the precipitants. When using (NH₄)₂CO₃, the Li(I) precipitation percentage increased at a solution pH of 12. Under the same conditions, the Li(I) precipitation percentage using Na₂CO₃ was much higher than that using (NH₄)₂CO₃.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.631-638
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• 2022

Microgrid, which enables the production and consumption of electricity to be done independently on a small scale, has been studied on one of the solutions of reinforcement for flexibility of electronic system. This study examined the application effect of new microgrid by applying hybrid battery in electric power storage device. We designed the system to highlight the advantage of each battery and complement the disadvantage by using hybrid system with Lithium-ion battery and interval Redox flow battery. It runs with lithium-ion battery during the initial startup while the Redox flow battery operates for a long time at the end of excessive period, and it enables a discharge of Lithium-ion and Redox flow battery at the same time when the load has a large output. We chose Maldives as a subject of this study for organizing and optimizing independent microgrid. Maldives is the country to accomplish 100% domestic electricity in South Asia, but the whole electric power is supplied through diesel generation imported fossil fuel. We organized and optimized microgrid for energy independence on Malahini island to solve Maldives energy cost problem and global energy environment matters. We analyzed the daily power supply and accumulated the power supply from September 18, 2018~February 11, 2019. The accumulated power supply was about 120.4 MWh and the daily power supply was about 800~1000 kWh. Based on the collected information, we divided the cases into three models which are only diesel generator, solar generator as well as diesel generator, and solar+ESS+diesel generator. We analyzed the amount of oil consumption compared to the cost of construction and power output. The result showed that solar+ESS+diesel generator was most economically feasible. As well, we obtained that our considering hybrid battery system reduced the fuel consumption for diesel power generation about 10~15%.

• Journal of the Korean Electrochemical Society
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• v.26 no.3
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• pp.35-41
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• 2023

The carbon-coated silicon monoxide (c-SiO_x), which is a negative electrode active material for lithium-ion batteries (LIBs), has a limited cycle performance due to severe volume changes during cycles, despite its high specific capacity. In particular, the significant volume change of the active material can deform the electrode structure and easily damage the electron transfer pathway. To improve performance and mitigate electrode damage caused by volume changes, we replaced parts of the carbon black conducting agent with carbon nanotubes (CNTs) having a linear shape. The content of the entire conductive material in the electrode was fixed at 10% by mass, and the relative content of CNTs ranged from 0% to 25% by mass to prepare electrodes and evaluate electrochemical performance. As the CNT content in the electrode increased, both cycle life and rate capability improved. Even a small amount of CNT can significantly improve the electrochemical performance of a c-SiO_x negative electrode with large volume changes. Furthermore, dispersing CNTs effectively can lead to achieving the equivalent performance with a reduced quantity of CNTs.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.3
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• pp.27-34
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• 2023

In this study, various plant-based biomass are recycled into carbon materials to employ as anode materials for lithium-ion batteries. Firstly, various biomass of rice husk, chestnut, tea bag, and coffee ground are collected, washed, and ground. The carbonization process is followed under a nitrogen atmosphere at 850℃. The morphological and chemical properties of materials are investigated using FE-SEM, EDS, and FT-IR to compare the characteristic differences between various biomass. It is noticeable that biomass-derived carbon materials vary in shape and degree of carbonization depending on their precursor materials. These materials are applied as anode materials to measure the electrochemical performance. The specific capacities of rice husk-, chetnut-, tea bag-, and coffee ground-derived carbon materials are evaluated as 65.8, 80.2, 90.6, and 104.7 mAh g^-1 at 0.2C. Notably, coffee ground-based carbon exhibited the highest specific capacity owing to the difference in elemental composition and the degree of carbonization. Conclusively, this study suggests the possibility of utilizing as energy storage devices by employing various plant-based biomass into active materials for anodes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.6
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• pp.638-646
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• 2023

Recently, active research has been conducted to enhance the power characteristics and thermal stability of lithium-ion batteries (LiBs) by modifying separators using a ceramic coating method. However, since the thermal properties and surface features of the separator vary depending on the characteristics of the ceramic powders applied to the separator, it is crucial to manufacture ceramic powders optimized for the separator's performance. In this study, we evaluated the characteristics of three types of α-alumina (A-1, A-2, and A-3) produced with varying dispersant contents and milling times, in addition to commercial α-alumina (AES-11). Subsequently, the optimized powders (A-3) were coated onto the separator using an aqueous binder for comparison with the characteristics of an AES-11 coated separator and an uncoated PE separator. The A-3 coated separator improved electrolyte wettability with a low contact angle (44.69°) and increased puncture strength (538 gf). Furthermore, it exhibited excellent thermal stability, with a shrinkage value of 5.64% when exposed to 140℃ for 1 hour, compared to the AES11 coated separator (6.09%) and the bare PE separator (69.64%).

• Journal of the Korean Electrochemical Society
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• v.27 no.1
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• pp.40-46
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• 2024

Among the electrode manufacturing processes for lithium-ion batteries, the drying process is crucial for production speed and process cost. Particularly, as the loading level of the electrode increases to enhance the energy density of the battery, optimizing process conditions for electrode drying becomes more critical. In this study, we compared the drying time and electrochemical performance of the positive electrode prepared at different drying temperatures. LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) was used as the active material and manufactured under various drying temperature conditions ranging from 120 ℃ to 210 ℃ at loading levels of 2.5 and 4.5 mAh cm^-2. The physical and electrochemical properties of the electrodes were compared. As the loading level of the electrode increases, the drying time of the electrode also increases, but this time can be reduced by increasing the drying temperature. The drying temperature used in manufacturing the NCM622 positive electrode does not significantly affect the electrochemical performance but drying above 210 ℃ resulted in an increase in the volume resistivity of the electrode and a decrease in electrochemical performance. Accordingly, in the manufacture of high-loading electrodes, the drying temperature was increased to 190 ℃ to shorten the electrode manufacturing time without a loss of performance.

• Journal of Surface Science and Engineering
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• v.57 no.4
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• pp.317-324
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• 2024

We demonstrate a direct growth of carbon nanotubes (CNTs) on the surface of LiFePO₄ (LFP) powders for use in lithium-ion batteries (LIB). LFP has been widely used as a cathode material due to its low cost and high stability. However, there is a still enough room for development to overcome its low energy density and electrical conductivity. In this study, we fabricated novel structured composites of LFP and CNTs (LFP-CNTs) and characterized the electrochemical properties of LIB. The composites were prepared by direct growth of CNTs on the surface of LFP using a rotary chemical vapor deposition. The growth temperature and rotation speed of the chamber were optimized at 600 ℃ and 5 rpm, respectively. For the LIB cell fabrication, a half-cell was fabricated using polytetrafluoroethylene (PTFE) and carbon black as binder and conductive additives, respectively. The electrochemical properties of LIBs using commercial carbon-coated LFP (LFP/C), LFP with CNTs grown for 10 (LFP/CNTs-10m) and 30 min(LFP/CNTs-30m) are comparatively investigated. For example, after the formation cycle, we obtained 149.3, 160.1, and 175.0 mAh/g for LFP/C, LFP/CNTs-10m, and LFP/CNTs-30m, respectively. In addition, the improved rate performance and 111.9 mAh/g capacity at 2C rate were achieved from the LFP/CNTs-30m sample compared to the LFP/CNTs-10m and LFP/C samples. We believe that the approach using direct growth of CNTs on LFP particles provides straightforward solution to improve the conductivity in the LFP-based electrode by constructing conduction pathways.