• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.133-134
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• 2018

배터리의 효율적인 사용을 위해 배터리 관리 시스템(BMS)는 중요하다. 그 중 배터리의 잔존 수명을 나타내는 지표인 SOH(State of Health)를 예측하기 위해 본 논문에서는 18650 리튬이온 셀에 전기적 노화 실험(Cycle Life Test)을 적용하였다. 방전 용량 및 저항 변화에 의한 SOH 변화를 인공 신경망(Artificial Neural Network)을 사용하여 예측하도록 설계하고 이에 대한 검증을 수행하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.99-105
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• 2014

$LiCoO_2$ thin film have received attention as cathodes of thin-film microbatteries. In this study, $LiCoO_2$ thin films were synthesized on Au substrates by sol-gel spin coating method and electrochemical properties were investigated under annealing temperature and time. The phycochemical properties of $LiCoO_2$ thin film were investigated by X-ray diffraction, scaning electron microscopy and atomic force microscopy. The electrochemical properties were characterized using galvanostatic charging/discharging cycling tests. From X-ray diffraction, as-grown films annealed at $550^{\circ}C$ and $750^{\circ}C$ are presumed to be spinel structure and a single phase of the layered-rock-salt, respectively. The RMS roughness and grain size of the films which annealed at $750^{\circ}C$ has similar values for annealing time 10 and 30 min, while for annealing time 120 min surface roughness, grain size increase and pore appearance were observed. The first discharge capacity of $LiCoO_2$ thin films annealed at $750^{\circ}C$ for 10, 30 and 120 min is about 54.5, 56.8 and $51.87{\mu}Ah/cm^2{\mu}m$, respectively. Corresponding capacity retention at 50th cycle is 97.25, 76.69, 77.19%.

• Analytical Science and Technology
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• v.11 no.5
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• pp.360-365
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• 1998

We have studied structural characterization, electrical charge and discharge, and impedence properties for the $LiMn_2O_4$ synthesized by solid state reaction. From the X-ray diffraction results, diffraction patterns for compounds of the four kinds of $LiMn_2O_4$ compounds were observed to peaks of (111), (311), (004) and (400). Also, Small similar peaks (110), (222) and (313) were observed for sample C1 and C2. Concerning to new peaks of (113) and (331) for the sample C4, we can found that structural transitions were accompanied from C1 and C2 to C4 via C3 structure. A electrical charge and discharge data showed that efficiency of C1 was very poor state and efficiencies of C2 and C3 were about 60-70% of theoretical capacity. But, the C4 showed good charge and discharge properties of more than 70% of theoretical capacity. From the impedence properties for finding the effect of ions and electrons transfer of battery, C2 and C3 of high frequency of real number showed good electrical impedence properties.

• Membrane Journal
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• v.24 no.1
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• pp.10-19
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• 2014

Porous flat sheet membranes for separators in Zn air batteries were prepared with polyethersulfone (PES) solutions by immersion precipitation phase inversion method. PES/polyvinylpyrrolidone(PVP)/N-methylpyrrolidone(NMP) mixtures were used for casting solutions and water was used for coagulant. With the separators, Zn air batteries were fabricated. The separators were characterized by means of stress-strain test, impedance test and SEM. The Zn air batteries were tested by current interrupt method (CIM) and galvanostatic discharge method. The tensile strength increased with increasing PES content in the casting solution while the ionic conductivity decreased. On the other hand, the ionic conductivity increased while the tensile strength decreased with increasing PVP content. The effect of ionic conductivity trend of the separator in the Zn air battery was confirmed through current interrupt method and galvanostatic discharge method experiments. The battery with the separator from casting solution with higher PES content showed higher IR drop and lower discharge capacity. And the battery with the separator from casting solution with higher PVP content showed lower IR drop and higher discharge capacity.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.161-166
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• 2014

In this study, effects of pyrite ($FeS_2$) particle sizes on the electrochemical characteristics of thermal batteries are investigated using unit cells made of pulverized pyrite by ball-milling. At $450^{\circ}C$ unit cell discharge test, the electrochemical capacity of $1.46{\mu}m$ pyrite-cell largely increases compared to $98.4{\mu}m$ pyrite-cell, and their internal resistances also decrease. These results are attributed to the increase in the active reaction area of pyrite by ball milling. However, at $500^{\circ}C$ unit cell discharge test, a $1.46{\mu}m$ pyrite cell shows lower internal resistance than that of $98.4{\mu}m$ pyrite cell only at Z-phase region ($FeS_2{\rightarrow}Li_3Fe_2S_4$). After that, a $1.46{\mu}m$ pyrite cell shows a decrease in the cell voltage and an rapid increase of the internal resistance in J-phase region ($Li_3Fe_2S_4{\rightarrow}LiFe_2S_4$) is observed compared to those of $98.4{\mu}m$ pyrite cell. It can be concluded that at the higher temperature, the thermally unstable pulverized pyrite is decomposed thermally as well as self discharged, simultaneously, which causes the higher resistance and lower capacity at $500^{\circ}C$ in J-phase than that of $98.4{\mu}m$ pyrite cell.

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.205-210
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• 2011

Structural and electrochemical properties of spinel oxide $LiMn_2O_4$ thin films prepared by using a sol-gel method on Pt/Ti/$SiO_2$/Si substrates were investigated. When Li/Mn molar ratio of the film was smaller than 0.5, $Mn_2O_3$hase was found to coexist with $LiMn_2O_4$. Half-cell batteries fabricated using the $LiMn_2O_4$ films as the cathode were put into chargedischarge (C-D) cycles and the change in structural properties of the cathode after the cycles was examined by X-ray diffraction and Raman spectroscopy. As the C-D cycle number increases, the discharge capacity of pure $LiMn_2O_4$ battery gradually decreases, being reduced to 72% of the initial capacity at 300 cycles. Such capacity fading is attributable to the decrease in the number of $Li^+$ ions that return to the tetrahedral sites of the spinel structure during the discharge step and the resultant increase in $Mn^{4+}$ density in the film. Also, $Mn_2O_3$ phase gradually appeared in the film as the cycle number increases.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.574-581
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• 2022

Nanofibers comprising reduced graphene oxide (rGO) and Mo₂C/Mo₂N nanoparticles (Mo₂C/Mo₂N rGO NFs) were prepared for a functional interlayer of Li-S batteries (LSBs). The well-dispersed Mo₂C and Mo₂N nanoparticles in the nanofiber structure served as active polar sites for efficient immobilization of dissolved lithium polysulfide. The rGO nanosheets in the structure also provide conductive channels for fast ion/electron transport during charging-discharging and ensured reuse of lithium polysulfide during redox reactions through a fast charge transfer process. As a result, the cell assembled with Mo₂C/Mo₂N rGO NFs-coated separator and pure sulfur electrode (70 wt% of sulfur content and 2.1 mg cm^-2 of sulfur loading) showed a stable discharge capacity of 476 mA h g^-1 after 400 charge-discharge cycles at 0.1 C. Furthermore, it exhibited a discharge capacity of 574 mA h g^-1 even at a high current density of 1.0 C. Therefore, we believe that the proposed unique nanostructure synthesis strategy could provide new insights into the development of sustainable and highly conductive polar materials as functional interlayers for high performance LSBs.

• Journal of the Korean Electrochemical Society
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• v.16 no.2
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• pp.65-69
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• 2013

In order to improve capacitance of activated carbon for electric double layer capacitors, peptide bond was induced on the surface of the activated carbon by urea. Urea induced activated carbon has been stabilized through carbonization. Electrochemical characteristics was observed by cyclic voltammetry for specific capacitance, electrochemical impedance spectroscope for measuring resistance and charge-discharge for testing the cyclic ability. In the result, specific capacitance is increased about 22.9% than the activated carbon. And it shows excellent cycle performance and decreasing resistance with the introduction of nitrogen functional groups.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.69-75
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• 2008

Discharge capacity of $LiCoO_2$ in preparation by mechanochemical process decreased remarkably over 4.3V. However, Zr coating of $LiCoO_2$ showed very stable electrochemical properties up to 4.5V. Zr coating of $LiCoO_2$ in this experiment showed the discharge capacity of 197 mAh/g at 3.0-4.5V, and it maintained 96% of the initial discharge capacity after 50 cycle of charge/discharge.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.188.1-188.1
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• 2012

인공위성에 사용되는 배터리 기술은 1960년대 최초로 사용된 니켈 카드뮴(NiCd)을 시작으로 발전하기 시작해서 현재는 리튬-이온(Li-Ion)에 이르렀다. 리튬-이온 배터리는 높은 Energy Density(작은 크기와 무게), 낮은 자가 방전율을 가짐과 동시에 메모리 효과가 거의 없다는 장점이 있다. 하지만 리튬-이온 배터리 팩의 성능(Voltage, Capacity, Lifetime)은 사용된 Cell간 특성차이(State of Charge, Total Capacity Difference, Internal Impedance)에 의해 제한된다. 일반적으로 배터리는 원하는 전압과 용량을 확보하기 위해 직렬-병렬 혹은 병렬-직렬 구조를 가지는 팩 형태로 제작 된다. Cell간 특성차이가 존재하는 상태에서 배터리 팩을 사용할 경우 특정 Cell의 과충전 및 과방전이 발생하며 이로 인해 수명이 단축될 수 있고 심한 경우 폭발이 발생할 수 도 있다. 또한 Cell간 특성차이는 배터리팩의 사용가능 용량을 제한하는 효과를 가져 온다. 본 논문에서는 Battery 팩을 구성하는 Cell들에 특성 차이가 존재할 경우 발생할 수 있는 Battery 팩의 수명 단축 및 용량 감소 Mechanism에 대해서 고찰한다. 또한 Cell간 특성차이를 극복하기 위해 실제 위성 운용에 적용될 수 있는 배터리팩의 Balancing 방안과 함께 위성에 장착을 위해 보관중인 4p12s Battery의 Balancing 방안에 대해 고찰하고 Balancing 전후의 Cell간 특성(Voltage Dispersion) 차이 측정결과를 보인다. 이렇게 본 논문에서 소개한 리튬-이온 배터리의 전반적인 Balancing 방안은 추후 인공위성에 적용되는 리튬-이온 배터리의 운용 및 보관에 Guide Line을 제시할 것이라고 판단한다.