• Korean Journal of Materials Research
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• v.12 no.9
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• pp.712-717
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• 2002

New wet chemical method so called precipitation-evaporation method was suggested for preparing spinel structure lithium manganese oxide ($LiMn_2$$O_4$) for Li ion secondary battery. Using precipitation-evaporation method, $LiMn_2$$O_4$ cathode materials suitable for Li ion secondary batteries can be synthesized. Single spinel phase $LiMn_2$$O_4$ powder was synthesized at lower temperature compared to that of prepared by solid-state method. $LiMn_2$$O_4$ powder prepared by precipitation-evaporation method showed uniform, small size and well defined crystallinity particles. Li ion secondary battery using $LiMn_2$$O_4$ as cathode materials prepared by precipitation-evaporation method and calcined at $800^{\circ}C$ showed discharge capacity of 106.03mAh/g and discharge capacity of 95.60mAh/g at 10th cycle. Although Li ion secondary battery showed somewhat smaller initial capacity but good cyclic ability. It is suggested that electro-chemical properties can be improved by controlling particle characteristics by particle morphology modification during calcination and optimizing Li ion secondary battery assembly conditions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.2
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• pp.223-229
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• 2023

Seawater batteries are next-generation secondary batteries that use seawater as a cathode. They utilize marine resources to provide competitive prices, high eco-friendliness, and a structure suitable for marine applications. Based on these advantages, pouch types and prismatic types have been studied and developed assuming natural seawater exposure. However, because of the electrical characteristics of the secondary battery, its capacity and internal resistance vary depending on the use environment. These characteristics are not only utilized for predicting the life of a battery but also have a direct effect on the capacity and power suitable for a specific situation. Therefore, the internal resistance was analyzed in this study by measuring the capacity depending on the seawater battery use environment and the state-of-charge-open-circuit-voltage measurement method.

• Polymer(Korea)
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• v.26 no.1
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• pp.45-52
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• 2002

The separator made from the blends of high density polyethylene (HDPE) and ultrahigh molecular weight polyethylene (UHMWPE) was prepared by wet processing to use as Li-ion secondary battery. We investigated effects of the blending of the polymers and the film extension on the mechanical properties of the separator. The mechanical strength of separator increased with increasing molecular weights and contents of UHMWPE, for instance about $1000 kg/\textrm{cm}^2$ with the five times extended film of 6 wt% UHMWPE. The pores of the separator were very uniform with the size of 0.1~$0.12\mu\textrm{m}$. The shut-down characteristic quickly increased at around $130^{\circ}C$ and the fusion temperature was $160^{\circ}C$, so it could be applied to the lithium ion secondary battery.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.393-398
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• 2021

In order to optimize the performance of a lithium-ion battery, a performance prediction modeling technique that considers various degradation factors is required. In this work, mathematical modeling was carried-out to predict the change in discharging behavior and cycle life, taking into account the cycle aging of lithium-ion batteries. In order to validate the modeling, a cycling test was performed at the charge/discharge rate of 0.25C, and discharging behavior was measured through RPT (Reference Performance Test) performed at 30 cycle intervals. The accuracy of cycle life prediction was improved by considering the break-in mechanism, one of the phenomena occurring in the BOL (beginning of life), in the model for predicting the cycle life of lithium-ion batteries. The predicted change in cycle life based on the model was in good agreement with the experimental results.

• Resources Recycling
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• v.17 no.1
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• pp.66-72
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• 2008

Fundamental studies for the synthesis of Mn-Zn ferrite powder were investigated using a series of leaching and coprecipitation processes from spent alkaline manganese batteries. Zinc and Manganese dissolution rates obtained at the reaction conditions of 100g/L pulp density, 3.0M $H_2SO_4$, $60^{\circ}C$ and 200 rpm with 30 ml $H_2O_2$ as a reducing agent were more than 97.9% and 93.9% and coprecipitation of Mn-Zn ferrite powder was performed according to various reaction conditions such as temperature, time and amount of $O_2$ gas injection using the leaching solution. As a result of coprecipitation, Mn-Zn ferrite could be synthesized directly at low temperature in the reaction condition pH 12, $80^{\circ}C$, $O_2$ 1.3 L/min. and 400 rpm. The synthesized Mn-Zn ferrite powder was spherical powder of $0.143{\mu}m$ particle size and had a saturation magnetization about 80 emu/g.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.5
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• pp.542-549
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• 2016

This paper presents a SoC (System-on-a-Chip) dedicated for a single-chip smart capsule which can be used to continuously monitor human alimentary canal pH and temperature values. The SoC is composed of the pH and temperature sensor interface circuit, a wireless transceiver, the power management circuit and the flow control logic. Fabricated in $0.18{\mu}m$ standard CMOS technology, the SoC occupies a die area of ${\sim}9 mm^2$. The SoC consumes 6.15 mW from a 3 V power supply, guaranteeing the smart capsule battery life is no less than 24 hours when using 50 mAh coin batteries. The experimental results show that measurement accuracy of the smart capsule is ${\pm}0.1$ pH and ${\pm}0.2^{\circ}C$ for pH and temperature sensing, respectively, which meets the requirement of in-body pH and temperature monitoring in clinical practice.

• Journal of the Korean Applied Science and Technology
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• v.22 no.2
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• pp.142-150
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• 2005

The natural graphite particles A and heat-treated graphite particles B at $1800\;^{\circ}C$ after pitch-coating were used as the anode base materials for lithium ion secondary battery. In order to improve the performance of anode materials, the base anode materials were treated with various acids. With the acid treatments of 62% $HNO_3$ and 95% $H_2SO_4$ aqueous solution, the specific surface area and electrical conductivity of base anode materials were increased, and the initial charge-discharge capacity and cycle performance were improved due to the elimination of structural defects.

• Journal of the Korean Ceramic Society
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• v.38 no.8
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• pp.755-760
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• 2001

본 연구에서는 카본전극의 표면개질에 따른 리튬이온 전지의 전지특성 변화에 대해서 연구하였다. 즉, mesocarbon microbeads(MCMB) 카본에 에폭시 수지(resin)를 코팅시킴으로서 카본전극 표면에 개질시켰으며, 이에 따른 전극의 전기화학적 특성을 고찰하였다. 에폭시 수지에 의한 카본의 표면코팅은 30%의 H$_2$SO$_4$용액에서 2시간 동안 refluxing한 MCMB를 에폭시 수지를 용해시킨 THF(tetrahydrofuran) 용액에 넣어 혼합함으로써 MCMB 표면에 에폭시 수지가 코팅되도록 하였다. 이렇게 에폭시 수지가 코팅된 MCMB를 약 1000-130$0^{\circ}C$로 열처리하여 고분해능 투과전자현미경으로 관찰한 결과, 코팅층은 비정질 카본 구조를 갖게됨을 알 수 있었다. 또한, 에폭시 수지에 의하여 코팅된 MCMB는 코팅되지 않은 MCMB보다 더 높은 BET 비표면적을 나타내었다. Li/MCMB 전지 cell을 만들어 충방전시험을 수행한 결과, 에폭시 수지에 의하여 코팅된 MCMB로 만든 전극이 더 우수한 충방전 용량과 싸이클 특성을 나타내었다. 에폭시 수지 코팅으로 전극 표면을 개질시킴으로서 전지특성이 개선된 원인에 관하여 에폭시 코팅의 결정구조와 전극계면에서의 부동태 피막(passivation film) 형성과 연계하여 논의하였다.

• Carbon letters
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• v.8 no.3
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• pp.207-213
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• 2007

The properties and electrochemical characteristics of anode material using pitch-coated graphite residue compounds by heat-treatment at $600^{\circ}C$ for 1 hour were investigated. The distance of layers of pitch-coated graphite residual compounds was 3.3539 ${\AA}$, which was as same as that of graphite. Its electrochemical and charge discharge characteristics were tested according to different four types of carbon material, natural graphite, pitch-coated graphite, amorphous graphite and pitch-coated graphite residual compounds, respectively. So it was shown the best charge-discharge characteristics in all of the samples. For the electrochemical and charge-discharge characteristics, although pitch-coated graphite residual compounds had different carbon contents 70% and 80%, these two samples were shown good electrochemical and charge-discharge characteristics.

• 전자공학회논문지 IE
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• v.46 no.4
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• pp.1-7
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• 2009

The final goal of ITS and ETC will be to improve the traffic efficiency and mobile safety without new road construction. DSRC system is emerging nowadays as a solution of them. China DSRC standard which was released in May 2007 has low bit rate, short message and simple MAC control. The DSRC system users want a long lifetime over 1 year with just one battery. In this paper, we propose the SoC of very low power consumption architecture. Several digital logic concept and analog power control logics were used for very low power consumption. The SoC operation mode and clock speed, operation voltage range, wakeup signal detector, analog comparator and Internal Voltage Regulator & External Power Switch were designed. We confirmed that the SoC power consumption is under 8.5mA@20Mhz, 0.9mA@1Mhz in active mode, and under 5uA in power down mode, by computer simulation. The design of SoC was finished on Aug. 2008, and fabricated on Nov. 2008 with $0.18{\mu}m$ CMOS process.