• 한국재료학회지
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• 제28권6호
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• pp.337-342
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• 2018

Using a high pressure homonizer, we report on the electrochemical performance of $Li_4Ti_5O_{12}(LTO)$ particles manufactured as anode active material for lithium ion battery. High-pressure synthesis processing is performed under conditions in which the mole fraction of Li/Ti is 0.9, the synthesis pressure is 2,000 bar and the numbers of passings-through are 5, 7 and 10. The observed X-ray diffraction patterns show that pure LTO is manufactured when the number of passings-through is 10. It is found from scanning electron microscopy analysis that the average size of synthesized particles decreases as the number of passings-through increases. $LiCoO_2-based$ active cathode materials are used to fabricate several coin half/full cells and their battery characteristics such as lifetime, rate capability and charge transfer resistance are then estimated, revealing quite good electrochemical performance of the LTO particles as an effective anode active material for lithium secondary batteries.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.631-636
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• 2018

This paper proposed an optimal operation strategy for a hybrid energy storage system (HESS) with a lithium-ion battery and lead-acid battery for mild hybrid electric vehicles (mild HEVs). The proposed mild HEV system is targeted to mount the electric motor and the battery to a conventional internal combustion engine vehicle. Because the proposed mild HEV includes the motor and energy storage device of small capacity, the system focuses on low system cost and small size. To overcome these limitations, it is necessary to use a lead acid battery which is used for a vehicle. Thus, it is possible to use more energy using HESS with a lithium battery and a lead storage battery. The HESS, which combines the lithium-ion battery and the secondary battery in parallel, can achieve better performance by using the two types of energy storage systems with different characteristics. However, the system requires an operation strategy because accurate and selective control of the batteries for each situation is necessary. In this paper, an optimal operation strategy is proposed considering characteristics of each energy storage system, state-of-charge (SOC), bidirectional converters, the desired output power, and driving conditions in the mild HEV system. The performance of the proposed system is evaluated through several case studies with respect to energy capacity, SOC, battery characteristic, and system efficiency.

• 한국세라믹학회지
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• 제43권2호
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• pp.121-125
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• 2006

[ $LiFePO_4$ ] is one of the promising materials for cathode material of secondary lithium batteries due to its high energy density, low cost, environmental friendliness and safety. $LiFePO_4$ was synthesized by the solid-state reaction method at 500 - 800°C. The crystal structure of $LiFePO_4$ was analyzed by X-ray powder diffraction. The samples synthesized at 600 and $700^{\circ}C$ showed a single phase of a olivine structure. The particle sizes were increased and the specific surface areas were decreased with heating temperatures. The electrochemical performance was investigated by coin cell test. The discharge capacities at 0.1 C-rate were 118 mAh/g and 112 mAh/g at $600^{\circ}C,\;700^{\circ}C$, respectively. In an attempt to improve the electrical conductivity of cathode materials, $LiFePO_4/graphite$ composite was prepared with various graphite contents. The electrical conductivity and discharge capacity were increased with increasing the graphite contents in composite samples. The rate capabilities at high current densities were also improved.

• 공업화학
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• 제26권3호
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• pp.294-305
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• 2015

본 특허정성분석은 "층상구조 기반의 리튬이차전지용 양극 활물질"의 우리나라, 미국, 일본, 유럽, PCT (WO)의 유효특허 1,294건을 분석한 것으로, 특허가 갖는 기술 중요도 부분과 특허 중요도 부분으로 나누어 Table 1과 같은 기준으로 평가하였고, 이를 토대로 104건의 주요특허와 20건의 핵심특허를 선정하였다. 그리고 선정된 주요특허와 핵심특허를 시계열적 기술 흐름도로 작성하여 각 기술 분류별로 특허 출원 시점과 발전 과정, 핵심특허의 위치를 확인하였다. 마지막으로 특허 분석 내용을 토대로 향후 기술개발을 위하여 현재 출원 등록된 기술들과의 차별화 방안 및 회피전략을 제시하였다.

• 한국재료학회지
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• 제25권6호
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• pp.279-287
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• 2015

In order to prepare anode materials for high power lithium ion secondary batteries, carbon composites were fabricated with a mixture of petroleum pitch and coke (PC) and a mixture of petroleum pitch, coke, and natural graphite (PC-NG). Although natural graphite has a good reversible capacity, it has disadvaantages of a sharp decrease in capacity during high rate charging and potential plateaus. This may cause difficulties in perceiving the capacity variations as a function of electrical potential. The coke anodes have advantages without potential plateaus and a high rate capability, but they have a low reversible capacity. With PC anode composites, the petroleum pitch/cokes mixture at 1:4 with heat treatment at $1000^{\circ}C$ (PC14-1000C) showed relatively high electrochemical properties. With PC-NG anode composites, the proper graphite contents were determined at 10~30 wt.%. The composites with a given content of natural graphite and remaining content of various petroleum pitch/cokes mixtures at 1:4~4:1 mass ratios were heated at $800{\sim}1200^{\circ}C$. By increasing the content of petroleum pitch, reversible capacity increased, but a high rate capability decreased. For a given composition of carbonaceous composite, the discharge rate capability improved but the reversible capacity decreased with an increase in heat treatment temperature. The carbonaceous composites fabricated with a mixture of 30 wt.% natural graphite and 70 wt.% petroleum pitch/cokes mixture at 1:4 mass ratio and heat treated at $1000^{\circ}C$ showed relatively high electrochemical properties, of which the reversible capacity, initial efficiency, discharge rate capability (retention of discharge capacity in 10 C/0.2 C), and charge capacity at 5 C were 330 mAh/g, 79 %, 80 %, and 60 mAh/g, respectively.

• 한국전기전자재료학회논문지
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• 제32권4호
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• pp.341-348
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• 2019

This paper reports the microstructure and electrochemical properties of Si-Al-Fe ternary amorphous alloys prepared by rapid solidification as an anode for lithium secondary batteries. The microstructure was analyzed using XRD and HR-TEM with EDS mapping. In accordance with DSC analysis, annealing was performed to crystallize the active nano-Si in the amorphous alloy. Thus, nano-Si forms (~80 nm) embedded in the matrix alloy, such as $Fe_2Al_3Si_3$, $FeSi_2$, and $Fe_{0.42}Si_{2.67}$, were successfully synthesized. The electrode based on the Si-Al-Fe ternary alloy delivered an initial discharge capacity of approximately $700mAh^{g-1}$, and exhibited a high Coulombic efficiency of 99.0~99.6% from the $2^{nd}$ to $70^{th}$ cycles.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.11-25
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• 2024

Lithium-ion batteries (LIBs) have attracted great attention as the common power source in energy storage fields of large-scale applications such as electrical vehicles (EVs), industries, power plants, and grid-scale energy storage systems (ESSs). Insertion, alloying, and conversion reactions are the main electrochemical energy storage mechanisms in LIBs, which determine their electrochemical properties and performances. The electrochemical reaction mechanisms are determined by several factors including crystal structure, components, and composition of electrode materials. This article reviews a new strategy to compensate for the intrinsic shortcomings of each reaction mechanism by introducing the material systems to form a single compound with different types of reaction mechanisms and to allow the simultaneous hybrid electrochemical reaction of two different mechanisms in a single solid solution phase.

• 전기화학회지
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• 제18권2호
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• pp.51-57
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• 2015

상온 이온성 액체인 propylmethylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PMPyr-TFSI)를 리튬이차전지 전해질 용매로 사용 시 PMPyr-TFSI 내 수분 및 브롬 불순물이 전지의 성능에 미치는 영향을 연구하였다. 고전압 양극 물질인 $LiNi_{0.5}Mn_{1.5}O_4$ 스피넬 구조 양극을 이용한 반쪽 전지의 전해질로 PMPyr-TFSI를 사용 하는데 있어, PMPyr-TFSI의 수분 함유량을 각각 12, 77, 1060 ppm으로 제어하고 전압 곡선 개형 및 쿨롱 효율 거동 추적을 통해 PMPyr-TFSI 수분량이 전지 성능에 부정적인 영향을 미치는 것을 구체적으로 확인하였다. 또한, PMPyr-TFSI 전해질 내의 브롬 이온 불순물 양 제어를 통하여, 전지 내에서 브롬 이온 불순물과 관련한 전기화학 부반응을 찾아 내었다. 이들 할로겐 불순물에 의한 초기 전지 쿨롱 효율저하는 눈에 띠었으나, 수명 저하에는 큰 변화가 없음을 확인하였다.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2022년도 제66차 하계학술대회논문집 30권2호
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• pp.149-152
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• 2022

최근 전기차의 기술 발전이 급속도로 증가함에 따라 이차전지의 수요가 증가하게 되었다. 그로인해 다량의 고품질 전지를 생산하기 위해 제조 공장이 가동되고 있지만 생산된 전지의 품질의 핵심이 되는 화성공정의 에이징 과정 진행 중 온도 관리에 실패할 경우, 전지의 폭발 및 화재의 위험이 있다. 본 논문은 이차전지를 생산하는 에이징 공정의 효율적인 온도 관리를 위해 목업 모형을 만들어 온도 센서를 통한 온도 수집 및 모니터링 시스템을 개발하고, 공조기 바람을 통해 전지의 온도가 변화하는 속도를 계산하고, 이상온도에 도달해 고온의 상태가 되었을 경우 주변 전지로 전달되는 열을 시뮬레이션 통한 효율적인 공조 대책을 제시하여 이차전지 생산의 품질 향상과 화재 예방을 통해 전기차 생산에 따른 리튬이온 전지의 수요 해결에 기여한다.

• Journal of Information Technology Applications and Management
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• 제29권6호
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• pp.135-144
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• 2022

In this study, we transformed 4680 type lithium-ion batteries to 3-dimensional CAD models and present a methodology to detect defects using Radon inverse transformation. Transparency was applied to the model to make it look like a CT image when viewed from the front. One normal and three defect models were created and analyzed. The models were saved as image files while rotating at a certain angle. Then, we used the Radon inverse transformation to reconstruct the original 3D geometry from the image files. Finally, we successfully found defects in the defect models for three cases.