• Title/Summary/Keyword: LiPO

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Synthesis and Investigation of LiVPO4O1-xFxvia Control of the Fluorine Content for Cathode of Lithium-ion Batteries (플루오린 함량 제어를 통한 LiVPO4O1-xFx 합성 및 리튬 이차전지 양극소재 전기화학 특성 분석)

  • Minkyung Kim;Dong-hee Lee;Changyu Yeo;Sooyeon Choi;Chiwon Choi;Hyunmin Yoon
    • Journal of Powder Materials
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    • v.30 no.6
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    • pp.516-520
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    • 2023
  • Highly safe lithium-ion batteries (LIBs) are required for large-scale applications such as electrical vehicles and energy storage systems. A highly stable cathode is essential for the development of safe LIBs. LiFePO4 is one of the most stable cathodes because of its stable structure and strong bonding between P and O. However, it has a lower energy density than lithium transition metal oxides. To investigate the high energy density of phosphate materials, vanadium phosphates were investigated. Vanadium enables multiple redox reactions as well as high redox potentials. LiVPO4O has two redox reactions (V5+/V4+/V3+) but low electrochemical activity. In this study, LiVPO4O is doped with fluorine to improve its electrochemical activity and increase its operational redox potential. With increasing fluorine content in LiVPO4O1-xFx, the local vanadium structure changed as the vanadium oxidation state changed. In addition, the operating potential increased with increasing fluorine content. Thus, it was confirmed that fluorine doping leads to a strong inductive effect and high operating voltage, which helps improve the energy density of the cathode materials.

CHROMATIC SUMS OF SINGULAR MAPS ON SOME SURFACES

  • Li, Zhao-Xiang;Liu, Yan-Pei
    • Journal of applied mathematics & informatics
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    • v.15 no.1_2
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    • pp.159-172
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    • 2004
  • A map is singular if each edge is on the same face on a surface (i.e., those have only one face on a surface). Because any map with loop is not colorable, all maps here are assumed to be loopless. In this paper po-vides the explicit expression of chromatic sum functions for rooted singular maps on the projective plane, the torus and the Klein bottle. From the explicit expression of chromatic sum functions of such maps, the explicit expression of enumerating functions of such maps are also derived.

LiFePO4의 spin reorientation 특성 연구

  • Bang, So-Yeon;Choe, Hyeon-Gyeong;Kim, Yeon-Jun;Kim, Ju-Hyeon;Kim, Hyo-Jin;Yu, Gyu-Hang;Lee, Seong-Ryong;Han, Jong-Dae;Kim, Mun-Hwan;Kim, Cheol-Seong
    • Proceedings of the Korean Magnestics Society Conference
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    • 2014.11a
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    • pp.173-173
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    • 2014
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Temperature-Dependent Electrochemical Characteristic Analysis for 10kW Li-Polymer Energy Storage System (ESS) (10kW급 에너지 저장장치(ESS)의 전기화학적 온도특성 분석)

  • Kim, J.H.;Choi, H.J.;Song, J.W.;Kim, S.J.;Park, J.P.
    • Proceedings of the KIPE Conference
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    • 2012.11a
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    • pp.61-62
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    • 2012
  • 본 논문에서는 10kW급 리튬계열 에너지 저장장치 (ESS;Energy storage system)의 전기화학적 온도특성을 분석하였다. 70개 $LiFePO_4$ 단위 셀의 직렬결합(70S1P)으로 이루어진 ESS의 온도특성 분석을 위해 여름(7월)과 겨울(1월)일때의 ESS Tray/Rack/Cell 전압(표준편차) 및 온도데이터(최대값/최소값)의 통계처리를 실시하였다. 실험결과를 통해, 주변 외기온도에 영향을 최소화한 안정적인 ESS의 최적구축을 위한 가이드 라인을 제시할 수 있다.

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X-Ray Absorption Spectroscopy: A Complementary Tool for Structural and Electronic Characterization of Solids

  • Jean Etourneau
    • Bulletin of the Korean Chemical Society
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    • v.19 no.1
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    • pp.5-21
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    • 1998
  • The purpose of this paper is to show that X-ray absorption spectroscopy (XANES and EXAFS) is a powerful technique for characterizing both crystalline and amorphous solids from structural (local order) and electronic point of view. The principle of this technique is briefly described by showing the main factors which must be considered for recording and fitting the experimental results. Some non-trivial examples have been selected for demonstrating that XAS spectroscopy is the only technique for bringing a definitive answer as for example: the determination of the local distortion of the $NiO_6$ octahedra in the $Li_{1-z}Ni_{1+z}O_2$ layered oxides and the evidence of the presence of copper pairs in the NASICON-type phosphate $CuZr_2 (PO_4)_3$. Are also reported some significant examples for which XAS spectroscopy is decisive with other characterization methods as (i) Raman spectroscopy for glasses (ii) Mossbauer spectroscopy for $LiNi_{1+z-t}Fe_To_2$ oxides (iii) magnetic measurements for Ce-based intermetallic compounds.

Characterization of RF Sputter-deposited Sodium Phosphorous Oxynitride Thin Films as a Solid-state Sodium-ion Conductor

  • Chun, Sang-Eun
    • Journal of the Korean institute of surface engineering
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    • v.50 no.4
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    • pp.237-243
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    • 2017
  • We demonstrated the thin film deposition of sodium phosphorous oxynitride (NaPON) via RF magnetron sputtering of $Na_3PO_4$, as a solid-state Na-ion conductor similar to lithium phosphorous oxynitride (LiPON), which is a commonly used solid electrolyte. The deposited NaPON thin film was characterized by scanning electron microscopy, X-ray diffractometry, and electrochemical impedance spectroscopy, to investigate the feasibility of the solid-state electrolyte in several different cell configurations. The key properties of a solidstate electrolyte, i.e., ionic conductivity and activation energy, were estimated from the complex non-linear least square fitting of the measured impedance spectra at various temperatures in the range of $27-90^{\circ}C$. The ionic conductivity of the NaPON film was measured to be $8.73{\times}10^{-6}S\;cm^{-1}$ at $27^{\circ}C$, which was comparable to that of the LiPON film. The activation energy was estimated to be 0.164 eV, which was lower than that of the LiPON film (0.672 eV). The obtained values encourage the use of a NaPON thin film in the future as a reasonable solid-state electrolyte.

Effects of Nitrogen and Phosphorus Fertilization on Ectomycorrhiza Development, N-Fixation and Growth of Red Alder Seedlings (질소(窒素)와 인산(燐酸) 시비(施肥)가 루브라 오리나무(Alnus rubra Bong.) 묘목(苗木)의 외생균근발달(外生菌根發達)과 질소고정(窒素固定) 및 생장(生長)에 미치는 영향(影響))

  • Koo, Chang-Duck;Molina, Randolph J.;Miller, Steven L.;Li, Ching Y.
    • Journal of Korean Society of Forest Science
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    • v.85 no.1
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    • pp.96-106
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    • 1996
  • Red alder(Alnus rubra Bong.) seedlings inoculated with Frankia only or both Frankia and spores of Alpova diplophloeus(Zeller & Dodge) Trappe & Smith were grown in a greenhouse for ten weeks. The ten-week-old seedlings were fertilized with six nitrogen(N) and phosphorus(P) fertility regimes (no fertilization, 10mM $NH_4NO_3$, 50mM $NH_4NO_3$, 5mM $KH_2PO_4$, 10mM $NH_4NO_3+5mM$ $KH_2PO_4$, and 50mM $NH_4NO_3+5mM$ $KH_2PO_4$) three times a week for ten weeks. The higher N-fertilization significantly increased mycorrhiza formation by greenhouse contaminant mycorrhizal fungi, but decreased N-fixation and P concentration in nodule tissues. P-fertilization significantly increased nodule and shoot dry weight, and P concentration in plant tissues. When N was highly fertilized, however, the P-fertilization effect disappeared in nodule P concentration but doubled in leaf P concentration. A. diplophloeus inoculation significantly increased diameter growth and $CO_2$ exchange rate, but decreased leaf dry weight. Our results suggest that the higher N- or P-fertilization affect nitrogenase activity and mycorrhizal development but the effects are changed by their interactions.

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3.7-V Single Battery-Cell High-Efficiency Power Management Circuit and System for UAV-Drones (무인항공기를 위한 3.7V 단일 배터리 셀 고효율 전력관리 회로시스템)

  • Kang, Woonsung;Hwang, Sunnam;Chang, Ho Jung;Kim, Hyun-Sik
    • Journal of the Microelectronics and Packaging Society
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    • v.24 no.3
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    • pp.63-69
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    • 2017
  • This paper presents a highly efficient power management system for UAV-drones. For free from the battery cell-balancing issue, the proposed system allows the drone to utilize a single-cell Li-Po battery. To realize low-voltage input of 3.7V, the switch-mode step-up DC-DC converter is optimally designed with high power efficiency. The prototype DC-DC converter was implemented with an output voltage of 5V, which will be provided to digital parts of the drone. The power efficiency was measured to be max. 91.3% with low surface temperature. The measured line and load regulations were 0.02V/V and 0.15V/A, respectively. Thanks to the proposed power management system, the available time-to-fly of the drone is expected to be significantly extended in virtue of the enhanced power efficiency.

Configuration and Ground Tests of Solar Cell and Fuel Cell Powered System for Long Endurance UAV (장기체공 무인기용 태양전지-연료전지를 활용한 동력원 구성 및 지상시험)

  • Park, Byeongseob;Kim, Hyuntak;Baek, Seungkwan;Kwon, Sejin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.19 no.4
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    • pp.94-101
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    • 2015
  • Each of power systems of solar cell and fuel cell were configured and validated for long endurance UAV, as the preliminary research for the integration of power systems. Solar power system consisted of solar modules fabricated by solar cells of Sunpower's C60, commercial solar MPPT controller and Li-po battery, and then was validated. The re-start characteristics of hydrogen production from $NaBH_4$ hydrolysis was validated for operating the commercial fuel cell. The average voltage drop of Li-po battery in solar power system was -2.9 V/hour. The performance of re-start characteristics of $NaBH_4$ hydrolysis was stable in sequence mode of mission profile. Each of single systems were satisfied for the proposed mission profile.

Isolation of New Strain of Cordyceps militaris HB8 and Optimal Condition for Production of Adenosine and Cordycepin in Fruit Body

  • Li, Jin Feng;Hoang, Van An;Ahn, Jong Chan;Yang, Dong Uk;Lee, Dong Wook;Yang, Deok Chun
    • Korean Journal of Plant Resources
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    • v.33 no.6
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    • pp.696-706
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    • 2020
  • Cordyceps has been used in traditional Chinese medicine more than 2000 year ago. In this study, the new Cordyceps militaris was founded and isolated from O-dae mountain in Korea, and was identified its genetic characteristics. The newly isolation strain HB8 was most closet to Cordyceps militaris W141449 (99.82%), Cordyceps militaris JLCY-LI819 (99.82%) and Cordyceps militaris 4642 (99.81%), respectively. the genotypic result was show that train HB8 was belonging to the Cordyceps militaris genus, therefore, Cordycep militaris HB8 proposed with accession number MT835161. This study we find the optimal condition for production of cordycepin from Cordyceps militaris HB8 was 8 mg/g (200 g of pupa, 1 g of KH2PO4, 0.5 g of K2HPO4, 20 g of glucose, 1 g of MgSO4, 0.05 g of vitamin B1, and 1 mg of NAA per liter; light condition 300-700 Lux and day/night was 14 h/10 h) and the optimum condition for the production of adenosine was 2.6 mg/g (15 g of skim milk powder, 1 g of KH2PO4, 0.5 g of K2HPO4, 20 g of glucose, 1 g of MgSO4, 0.05 g of vitamin B1, and 1 mg of NAA per liter; light condition 300-700 Lux and day/night was 14 h/10 h).