LiFePO₄와 Li₄P₂O₇의 ⁷Li MAS NMR 특성 연구

한덕영,박남신,이상혁,이학만,김창삼,Han, Doug-Young,Park, Nam-Sin,Lee, Sang-Hyuk,Lee, Hak-Man,Kim, Chang-Sam 한국결정성장학회 2011 한국결정성장학회지 Vol.21 No.1

[ $^7Li$ ]Magic Angle Spinning(MAS) NMR Spectroscopy를 활용하여 $Li_4P_2O_7$와 $LiFePO_4$ 물질에서 $^7Li$ 핵의 NMR 특성 및 화합물 분자내의 국부적 구조 연구를 수행하였다. $Li_4P_2O_7$와 $LiFePO_4$ 물질 연구는 리튬이온전지에서 고체-전해질 경계상(SEI, solid-electrolyte interphase) 물질 연구를 위한 것이다. $Li_4P_2O_7$와 $LiFePO_4$ 분말은 고상합성법으로 제조하였다.$^7Li$MAS NMR 실험은 $27^{\circ}C$에서 $97^{\circ}C$의 영역에서 변온 실험을 수행하였으며 이는 주변 온도 변화 환경에서 $Li_4P_2O_7$ 물질 내의 Li 핵의 구조 변화를 관찰하기 위한 것이다. $^7Li$ MAS NMR 측정 결과 시료 온도가 $27^{\circ}C$에서 $97^{\circ}C$의 온도 분포 영역에서는 $Li_4P_2O_7$ 물질 내부의 Li 핵은 구조적으로 변화하지 않는 것이 확인되었다. 금번 실험을 통하여 $LiFePO_4$ 분말에 5.0 wt%이내로 포함되어있는 $Li_4P_2O_7$ 물질의 $^7Li$ MAS NMR 신호를 측정할 수 있는 측정 조건을 알았다. [ $^7Li$ ]Magic Angle Spinning (MAS) NMR spectroscopy has been used to study the lithium local environments in $Li_4P_2O_7$ and$LiFePO_4$ materials. The purpose of this study was to know the structure of the solid electrolyte interphase (SEI) in lithium ion cells composed of $LiFePO_4$ as cathode material. $Li_4P_2O_7$ and $LiFePO_4$ were prepared by a solid-state reaction. The $^7Li$ MAS NMR experiments were carried out at variable temperatures in order to observe the local structure changes at the temperatures in $Li_4P_2O_7$ system. The $^7Li$ MAS NMR spectra of in $Li_4P_2O_7$ indicate that the lithium local environments in $Li_4P_2O_7$ were not changed in the temperature range between $27^{\circ}C$ and $97^{\circ}C$ Through this work, we confirmed that the small amount of $Li_4P_2O_7$ less than 5.0 wt% in $LiFePO_4$ could be clearly measured by the $^7Li$ MAS NMR spectroscopy at high spinning rate over than 11 kHz.

Synthesis and electrochemical performance of (100-x)Li7P3S11-xLi3SI composite solid electrolyte for all-solid-state lithium batteries

정수연,Rajesh Rajagopal,류광선 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.95 No.-

Li7P3S11 (LPS) solid electrolytes have great advantages, such as high lithium-ion conductivity, and caneasily fabricate to make bulk-type all-solid-state lithium batteries. However, LPS has a disadvantagebecause of large interfacial resistance with lithium, which give a limitation for all-solid-state battery. Inthis study, (100-x)Li7P3S11-x Li3SI (x = 0. 2 and 5) solid electrolyte composites are prepared by mechanicalball milling process. Various physiochemical analysis was carried out to confirm the proper mixing ofLi7P3S1 and Li3SI solid electrolytes. The addition of Li3SI solid electrolyte, effectively influence the ionicconductivity and electrochemical properties of the Li7P3S1 solid electrolyte. The prepared Li7P3S11/Li3SIsolid electrolyte composites are stable against the lithium metal anode even after 100 h chargedischargingprocess and has stable potential window up to 10 V. In particular, 98Li7P3S11-2Li3SI solidelectrolyte based ASSLBs shows the highest capacity, of 110 mA/g at the current density of 7.5 mA g 1(0.05 C). The charge – discharge cycle stability test also proved the Li3SI mixing to Li7P3S11 helped tomaintain the capacity retention value of100 % after 10 cycles. Therefore, the Li3SI into the Li7P3S11electrolyte helps improve the electrochemical performance.

124Te 핵의 다중 입자 준위

문창범 한국물리학회 2009 새물리 Vol.59 No.5

The excited states of the nucleus 124Te have been studied by using in-beam gamma-ray spectroscopy with the 122Sn (7Li, p4n) 124Te reaction at Elab = 54 MeV. Several states above Iπ = 10+ at 3154 keV have been newly identified. The resulting level scheme was interpreted in the frame work of energy systematics and Total Routhian surface(TRS) calculations. The Iπ = 10+ level is consistent with the systematic trend in 118-122Te and thus interpreted as being based on the two-quasineutron h11/2 orbital, namely ν(h11/2)2 configuration. The Iπ= 16+ level at 5480 keV was found not to be energetically favored but to be a little higher in energy than those in light isotopes of 118-122Te. This state was suggested as being a noncollective oblate state based on the four-quasiparticle [π(g7/2)2]6+×ν[(h11/2)2]]10+ configuration. 124Te의 들뜬 상태들이 감마선 분광학에 의해 조사되었다. 사용된 핵반응은122Sn (7Li, p4n) 124Te이고 사용된 빔 에너지는 54 MeV 이었다. 본 연구를 통하여 Iπ = 10+ 이상의 고스핀 상태들이 처음으로 발견되었다. 총회전틀에너지분포(TRS) 계산에 의하면, Iπ= 10+ 준위는 h11/2 궤도의 두-준중성자의 들뜸 즉 ν(h11/2)2으로 생성된 것임을 알 수 있었다. 스핀-반전성이 Iπ= 16+ 준위는 그 들뜸 에너지가 5480 keV로 비집단적 성질을 보였으나 보다 낮은 동위원소들인 118-122Te 에서 보이는 들뜸 에너지 경향보다는 다소 높은 수준을 보였다. 이러한 성질은 g7/2궤도의 두개의 양성자와 h11/2 궤도에 있는 두개의 중성자가 결합을 한 네-준입자 [π(g7/2)2]6+×ν[(h11/2)2]]10+ 배열에 의한 들뜸 상태로 해석되었다.

Reactivity of Li14P6S22 as a Potential Solid Electrolyte for All-Solid-State Lithium-Ion Batteries

도칠훈,하윤철,이유진,유지현 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.10

The electrochemical reactivity of Li14P6S22 (Li7P3S11) as a sulfur-based solid electrolyte for Li+ conduction was evaluated by electrochemical cell tests and ab initio calculations to determine its utility for all-solid-state lithium secondary batteries. Reversible removal and incorporation of lithium into Li14P6S22 with a gradient of lithium concentration was confirmed as thermodynamically unfavorable. Otherwise, reductive/oxidative decomposition of Li14P6S22 by the addition/removal of lithium was thermodynamically favorable. The electrochemical stability window (ESW) of Li14P6S22 was 0.429?V between 1.860 and 2.289?V (Li/Li+). The lowest potential of Li elimination was 2.289?V and occurred as oxidative decomposition. The highest potential of lithium addition was 1.860?V as reductive decomposition. Formation of Li14+xP6S22 and Li14?xP6S22 could be simultaneously achieved with reductive and oxidative decomposition by applying negative and positive over-potentials. The exposure of Li14P6S22 electrodes to positive and negative electric fields generated a large amount of irreversible specific capacity, which confirmed the oxidative and reductive decomposition. Considering the results of ab initio calculations on ESW and electrochemical cell tests, Li14P6S22 material should be protected from direct contact to the potential of cathode and anode so that it can appropriately serve as a solid electrolyte. The high Li+ conductivity of Li14P6S22 might originate from temporal (kinetic) and endurable formation of Frenkel defects resulting in a Li-deficient/excess composition of Li14P6S22.

Mono-energetic Neutron Source Using the 7Li(p,n)7Be Reaction

G. D. Kim,H. J. Woo,W. Hong,Y. K. Kim 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.4

The facilities for the production and the measurement of neutrons with energies below 1000 keV were completed in 2008. The facilities are based on the 7Li(p,n)7Be reaction and a neutron timeof- flight (TOF) system. Neutrons with an energy width of 300 keV were obtained by controlling the thickness of Li. The energy spectrum, which was measured by using TOF, was established by the resonance states of Al below energies of about 1000 keV. This width is in good agreement, within about 2%, with the attenuation energy of incident protons, which was calculated by using the Stopping and Range of Ions in Matter (SRIM) code. Neutron total cross-sections on Al and W were measured by using these neutrons and were compared with the data in the Evaluated Nuclear Data File-6 (ENDF-6). The facilities for the production and the measurement of neutrons with energies below 1000 keV were completed in 2008. The facilities are based on the 7Li(p,n)7Be reaction and a neutron timeof- flight (TOF) system. Neutrons with an energy width of 300 keV were obtained by controlling the thickness of Li. The energy spectrum, which was measured by using TOF, was established by the resonance states of Al below energies of about 1000 keV. This width is in good agreement, within about 2%, with the attenuation energy of incident protons, which was calculated by using the Stopping and Range of Ions in Matter (SRIM) code. Neutron total cross-sections on Al and W were measured by using these neutrons and were compared with the data in the Evaluated Nuclear Data File-6 (ENDF-6).

126Te 핵의 감마선 분광학 연구

문창범 한국물리학회 2010 새물리 Vol.60 No.12

The excited states of the nucleus 126Te have been studied by using in-beam gamma-ray spectroscopy with the 124Sn (7Li, p4n)) 126Te reaction at Elab = 50 MeV. Several states above Jπ = 10+ have been newly identified. The 10+ state at 2974 keV has been found to be an isomer, and its half-life has been shown to be 13.6(4) ns. The resulting level scheme was interpreted in the framework of energy systematics in comparison with those for neighboring Te isotopes and Tin cores. The Jπ =10+ level is consistent with the systematic trend in 118-124Te and is, thus, interpreted as being based on the two-quasineutron alignment in the h11/2 orbital, namely, the υ(h11/2)2 configuration, while the Jπ = 8+ state can be interpreted as the two-proton π(g7/2)2 orbital coupled to the 2+ phonon state. The Jπ = 15+ level at 5095 keV was newly identified and is interpreted as being a four-quasiparticle configuration strongly coupled to the υ(h11/2)2 orbital. 핵융합-증발 124Sn (7Li, p4n) 126Te 반응을 통하여126Te의 들뜸 상태들이 감마선 분광학에 의해 조사되었다. 사용된빔 에너지는 50 MeV 이었다. 들뜸 에너지가 2974 keV이며 스핀-반전성이Jπ = 10+ 준위는 아이소머임이 확인되었고 측정된 반감기는T1/2 = 13.6(4)ns이었다. 그리고 본 연구를 통하여 Jπ =10+ 이상의 고스핀 상태들이 처음으로 발견되었다. Te 동위원소들과Sn 핵들의 준위들에 대한 체계성 분석결과 Jπ = 10+는 중성자침입궤도인 h11/2에 의한 두중성자 결합, 즉 υ(h11/2)2배위에 따른 들뜸상태로 설명되었다. 이와 반면에 Jπ = 8+는두개의 양성자 π(g7/2)2 들뜸이 1-진동자 즉 Jπ = 2+에결합된 상태로 해석되었다. Jπ = 15+ 준위는 그 들뜸에너지가5095 keV로 에너지 체계성이 Jπ = 10+ 비슷한 경향을 보였다. 이는 이 준위가 h11/2 궤도에 있는 두중성자의 들뜸과 강하게연관되어 있는 4-준입자 배열 상태임을 말해준다고 하겠다.

Measurement of Energy-angular Neutron Distribution for ^7Li, ^9Be(p,xn) Reaction at EP = 70 MeV and 11 MeV

So Kamada,Toshiro Itoga,Yasuhiro Unno,Wataru Takahashi,Takuji Oishi,MAMORU BABA 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

We have measured energy angular distribution of secondary neutrons for 1) ^7Li(p,xn) and ^9Be(p,xn) reactions with thin targets at 70 MeV, 2)^9Be(p,xn) reactions with a thick target at 11 MeV, using the time-of-flight technique at Tohoku University Cyclotron facility. Data were obtained at several laboratory angles from 0° to 110° using a beam swinger system and an NE213 scintillation detector placed at a well collimated neutron flight path. The energy range was from maximum to ~4 MeV (at 70 MeV). The spectrum results at 70 MeV showed very strong angular dependence which should be considered in detail in the applied purposes, while the data at 11 MeV showed much milder dependence and in fair agreement with the prediction of MCNPX.

상대습도가 황금배( (Pyrus pyrifolia Nakai cv.) 동녹발생에 미치는 영향

조일환,한점화,우영희,최장전,서흥수 (사) 한국생물환경조절학회 2002 시설원예‧식물공장 Vol.11 No.1

The occurrence rate of russet in hangkeumbaepear showed significant difference by yearsbecause the russet occurrence is greatly affected by the amount of rainfall. This study was conductedto analyse the relationship between rainfall and russet occurrence by artificial treatment of highhumidity. Under high relative humidity condition, stomatal resistance decreased and average fruitweight was higher since the increased net photosynthesis rate accumulation accelerated fruit growth.The russet occurrence began on July 25, when the growth speed of fruit weight and fruit surface is themost fast. Russet occurrence rate was higher in high relative humidity condition because the fruitgrowth was accelerated. Since the fruit calcium concentration change is extreme in late July, it isassumed that the deceased calcium content is related to the occurrence of russet in 'Whangkeumbae'pear. When the high relative humidity condition is maintained after rainfall, the amount of net photo-synthesis rate increase and fruit growth is accelerated. Therefore, the unbalance in the amounts oftransferred photosynthesis assimilation product, water and mineral elements would be one of the rea-sons for the russet occurrence in hangkeumbaepear.

Reference Neutron Fields of the KIGAM for the Neutron Energy Range between 144 keV and 2.5 MeV

김기동,H. J. Woo,H. W. Choi,J. W. Park,T. A. Trinh 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.4

The Korea Institute of Geoscience and Mineral Resources (KIGAM) is under the construction of the neutron standard facility as a national project. Neutron standards based on 1.7-MV tandem accelerator consist of the neutrons with the neutron energies of 144 keV, 250 keV, 565 keV, 2.5 MeV and with the fluence range from 10<SUP>2</SUP> neutrons/cm<SUP>2</SUP>/sec to 10<SUP>3</SUP> neutrons/cm<SUP>2</SUP>/sec. The systems for the neutron standards such as a duo-plasmatron ion source, a 4 MHz beam bunching system, a neutron chamber, an irradiation room, an n-TOF system, a long-counter, and a sample moving system, were designed and fabricated. Neutron energies of neutron standards and their spreads were observed by the n-TOF system. Their neutron fluencies were estimated by the long-counter at the neutron standard energies below 1 MeV and the proton-recoil counter at the neutron standard energy of 2.5 MeV. Long-counter efficiency was calibrated by JAEA FRS system, which was well known for maintaing the international neutron standards. The efficiency of the proton-recoil counter was obtained by the calculation with its detail construction information.

Characterization of ANITA and QMN Neutron Beams at TSL Using Proton Recoil Techniques

Y. Naitou,Y. Watanabe,S. Hirayama,M. Hayashi,A. Prokofiev,A. Hjalmarsson,S. Pomp,P. Andersson,R. Bevilacqua,C. Gustavsson,M. Osterlund,V. Simutkin,H. Sjostrand,M. Tesinsky,U. Tippawan 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

Neutron beam characterization measurements have been carried out in both the ANITA and QMN modes using the incident proton beam of 180 MeV at the The Svedverg Laboratory (TSL) in Uppsala. The spectral neutron flux data have been obtained by measuring elastic np-scattering with the Medley setup. The experimental results in the ANITA and QMN modes are compared with an MCNPX simulation and with the systematics of QMN spectra, respectively.