• 한국자기공명학회논문지
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• 제23권1호
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• pp.1-5
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• 2019

$^{19}F$ NMR experiments were carried out to observe the change of the characteristics of the PVdF binder which is an auxiliary material of the lithium ion battery. PVdF has various crystalline or amorphous phases by thermal treatment. A mixture of cathode and auxiliary materials including PVdF was coated on aluminum foil as an electron collector and then subjected to thermal treatment at various temperatures. The overlapped $^{19}F$ NMR signals obtained from the various phases were separately convoluted into the respective phases, and it was found that there was a relative ratio change of these phases. In addition, the crystal and amorphous phase of PVdF was changed during the vacuum drying, which is the last step of the actual electrode manufacturing. It was observed that the relative amount of amorphous phase, which may affect the flexibility of the electrode or the wettability of the electrolyte, abruptly changes after a certain temperature.

• Journal of Electrochemical Science and Technology
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• 제10권2호
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• pp.131-138
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• 2019

To improve the performance of Si anodes in advanced Li-ion batteries, the design of the electrode plays a critical role, especially due to the large volumetric expansion in the Si anode during Li insertion. In our study, we used a simple fabrication method to prepare Si-based electrodes by grafting polyacrylic acid (PAA) to a carboxymethyl cellulose (CMC) binder (CMC-g-PAA). The procedure consists of first mixing nano-sized Si and the binders (CMC and PAA), and then coating the slurry on a Cu foil. The carbon network was formed via carbonization of the binders i.e., by a simple heat treatment of the electrode. The carbon network in the electrode is mechanically and electrically robust, which leads to higher electrical conductivity and better mechanical property. This explains its long cycle performance without the addition of a conducting agent (for example, carbon). Therefore, the partially carbonized CMC-g-PAA binder presented in this study represents a new feasible approach to produce Si anodes for use in advanced Li-ion batteries.

• 한국표면공학회지
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• 제57권2호
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• pp.92-97
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• 2024

The LiBr aqueous solution, which is the absorption liquid of absorption refrigerator, must be replaced periodically because the concentration of impurities such as Cu²⁺, Fe²⁺, Ca²⁺, etc., increases due to corrosion of the tubes as the period of use increases, and the refrigeration efficiency decreases significantly. In order to reuse the waste absorption liquid, flocculation-precipitation method is mainly applied to precipitate the impurities, which requires hundreds of times the concentration of impurities and generates additional waste. In this study, a process for removing Cu ion impurities from cyclone electrolyzer by electrolytic reduction is presented in a small-scale facility without additional waste. It was confirmed that Cu ion impurities can be removed down to 1 ppm by electrolytic reduction process, and to further improve the removal rate, the mass transfer rate was increased by using a cyclone electrolyzer. The removal rate of Cu ions increased with the increase of flow rate and current density, and it was confirmed that Cu was removed at a rate of 1.48 ppm/h under the condition of 330 mL/sec and 2.5 mA/cm².

• Korean Chemical Engineering Research
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• 제56권4호
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• pp.561-567
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• 2018

본 연구에서는 리튬이온전지 실리콘 음극소재의 사이클 안정성 향상을 위해 실리콘/탄소 음극소재의 전기화학적 특성을 조사하였다. Tetraethyl orthosilicate (TEOS) 로부터 스토버법 및 마그네슘 열 환원법을 통하여 다공성 실리콘을 제조하고, 제조된 다공성 실리콘과 피치의 질량비에 따라 실리콘/탄소 음극소재를 제조하였다. 실리콘/탄소 음극소재의 물리적 특성은 XRD와 TGA를 통해 분석하였다. 1.0 M $LiPF_6$ (EC : DEC = 1 : 1 vol%) 전해액에서 실리콘/탄소 음극소재의 충 방전 사이클, 율속, 순환전압전류, 임피던스 테스트를 통해 전기화학적 특성을 조사하였다. 제조된 실리콘/탄소 음극소재 실리콘 : 탄소 = 5 : 95 일때 453 mAh/g의 향상된 용량을 나타내었으며, 사이클 성능 또한 두 번째 사이클 이후 30 사이클까지 매우 우수한 사이클 안정성을 나타냄을 확인하였다.

• 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.

• The Korean Journal of Physiology
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• 제18권1호
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• pp.1-8
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• 1984

In order to determine the extent of the placental transfer of Lithium ion, pregnant rabbits at $27{\sim}29$ days of gestation, which has hemochorial placenta similar to the human placenta, received 2 mM/Kg of $Li^+$ in the form of LiCl intravenously. Maternal arterial blood, placental sinus blood, fetal blood, amniotic fluid and maternal urine were drawn two hours after the single dose of LiCl. Concentrations of $Li^+$, $Na^+$, $K^+$ and osmolarity were measured in plasma of collected bloods, amniotic fluid and urine. Followings are the results obtained. 1) Evident level of $Li^+$ was detected in fetal blood, although fetal plasma concentration of $Li^+$ found to be almost one third of maternal plasma. 2) Plasma concentration of $Li^+$ in placental sinus blood was higher than that in fetal plasma but lower than that in maternal plasma. It means that downward concentration gradient of $Li^+$ from mother to fetus was still remarkable two hours after the injection. 3) Significant level of $Li^+$ was also detected in amniotic fluid. It seemed likely that $Li^+$, at least in part, excreted by the fetal urinary tract. 4) There were no differences in $Na^+$ and osmolar concentration between fetal and maternal blood. 5) From above results, it was concluded that $Li^+$ may transfer across the placenta but limited passage capacity through placental barrier for $Li^+$ is significant, beacause net transfer assumed to be going on even at two hours, at which time maternal equlibrium has been reached.

• 전력전자학회논문지
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• 제25권4호
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• pp.251-260
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• 2020

A growing interest has emerged in recycling used automobile batteries into energy storage systems (ESSs) to prevent their harmful effects to the environment from improper disposal and to recycle such resources. To transform used batteries into ESSs, composing battery modules with similar performance by grading them is crucial. Imbalance among battery modules degrades the performance of an entire system. Thus, the selection of modules with similar performance and remaining life is the first prerequisite in the reuse of used batteries. In this study, we develop an instrument to measure the impedance spectrum of a battery module to predict the useful remaining life of the used battery. The developed hardware and software are used to apply the AC perturbation to the used battery module and measure its impedance spectrum. The developed instrument can measure the impedance spectrum of the battery module from 0.1 Hz to 1 kHz and calculate the equivalent circuit parameters through curve fitting. The performance of the developed instrument is verified by comparing the measured impedance spectra with those obtained by a commercial equipment.

• 폴리머
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• 제38권4호
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• pp.530-534
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• 2014

다양한 기공도를 갖는 폴리에틸렌 분리막은 리튬이차전지의 격리막과 마이크로필터로 사용되고 있다. 폴리에틸렌 분리막을 대용량 리튬이차전지의 격리막에 응용하기 위해서는 고다공성 분리막의 제조가 요구된다. 본 연구에서는 열유도 상분리 공정으로 고다공성 폴리에틸렌 분리막을 제조하는데 있어, BET가 무독성 희석제로 사용 가능한지 여부를 실험하였다. 폴리에틸렌/BET 혼합물의 UCST-거동을 관찰하여 BET가 폴리에틸렌 다공막 제조용 희석제로 사용 가능함을 확인하였다. 폴리에틸렌/BET 혼합물로부터 제조된 분리막이 같은 조성에서 폴리에틸렌/파라핀 오일로부터 제조된 분리막에 비해 1.8배 높은 기공도를 나타내었다.

• Korean Chemical Engineering Research
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• 제56권3호
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• pp.303-308
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• 2018

본 연구에서는 리튬이차전지 음극활물질인 Silicon/Carbon (Si/C) 복합소재를 제조하여 바인더 및 첨가제가 전지성능에 미치는 영향을 조사하였다. Si/C 합성물은 마그네슘의 열 환원 반응을 통해 SBA-15 (Santa Barbara Amorphous material No. 15)를 제조한 후 페놀 수지의 탄화 과정을 통해 합성하였다. Si/C 음극소재는 충 방전, 순환전압전류, 임피던스 테스트를 통해 전기화학적 성능을 분석하였다. PAA 바인더를 이용한 Si/C 전지의 용량은 1,899 mAh/g으로 다른 바인더를 사용한 합성물보다 우수하였으며, 40 사이클 동안 92%에 달하는 높은 용량 보존율을 나타내었다. 또한, VC 첨가제를 사용한 전지의 경우 3,049 mAh/g의 높은 초기용량을 나타내며, 실리콘 표면에 보호막을 형성해 초기 비가역용량을 감소시켜줌을 알 수 있었다.

• 전기전자학회논문지
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• 제23권4호
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• pp.1328-1336
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• 2019

안전하고 최적의 배터리 성능을 유지하기 위해 정확한 충전상태(SOC) 추정 기술이 필수적이다. 본 논문에서는 기존의 전류적산 방법이 가지고 있는 문제를 해결하기 위해 시간 종속성을 가지는 인공지능 기반의 LSTM을 이용한 SOC 추정 방법을 적용하였다. 훈련과 검증에 필요한 데이터는 전기적 실험을 통해 일정 크기로 방전된 전류, 전압, 온도를 수집하였고 학습을 위한 입력데이터의 질을 향상시키기 위해 데이터 전처리를 수행하였다. 또한, LSTM 모델의 구조 및 하이퍼파라미터 설정에 따른 학습 능력과 SOC 추정 성능을 비교하였다. 학습한 모델은 UDDS 프로파일을 통해 검증하였으며, RMSE 0.82%, MAX 2.54%의 추정 정확도를 달성하였다.