-
Masahiko HAYASHI, Hironobu MINOWA, Masaya TAKAHASHI, Takahisa SHODAI
2010 年 78 巻 5 号 p.
325-328
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The electrochemical properties of air electrodes for lithium-air batteries using various kinds of carbon materials were investigated in an organic electrolyte of 1 mol l
−1 LiPF
6/PC. High-surface-area carbons such as Ketjen Black EC600JD exhibited large discharge capacities of more than 700 mAh g
−1, which were roughly proportional to the surface areas. The high-performance carbons had very similar pore distributions. Moreover, pore distribution measurements revealed that carbons with larger numbers of mesopores delivered larger discharge capacities.
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Hiroyuki USUI, Hiroyuki NISHINAMI, Takahisa IIDA, Hiroki SAKAGUCHI
2010 年 78 巻 5 号 p.
329-331
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Thick film electrodes of Cu-coated Si particles were fabricated by an electroless deposition and a successive gas-deposition, and were evaluated their electrochemical properties as an anode of Li-ion battery. The discharge capacity and its retention at the 1000th cycle were 570 mAh g
−1 and 61%. The excellent cycle life performance is attributed to an enhanced electrical conductivity due to the Cu-coating and a reversible conversion reaction between Li and Cu
2O which was formed on the Cu surface. The high capacity retention is caused by a high fracture toughness of the coated Cu which can effectively relax a stress induced by volume expansion of Si as a buffer matrix.
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Boor Singh LALIA, Nobuko YOSHIMOTO, Minato EGASHIRA, Masayuki MORITA
2010 年 78 巻 5 号 p.
332-335
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The electrochemical and thermal properties of non-flammable polymer gel electrolyte (NPGE) have been studied to examine its potential application as an electrolyte in lithium ion batteries. Diphenyl phosphite (DPP) was used as a fire retardant component of NPGE. The electrochemical studies showed that NPGE has high ionic conductivity of 0.9 mS cm
−1 at 30°C and a wide electrochemical window of
ca. 4 V
vs. Li/Li
+, which are suitable for a practical battery system. Good thermal properties are confirmed by thermal safety calorimetry (TSC) measurements.
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Yoshihiro NONO, Masayuki KOUZU, Kouichi TAKEI, Kazumi CHIBA, Yuichi SA ...
2010 年 78 巻 5 号 p.
336-338
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
In this study, we investigated the electrochemical behavior of various types of activated carbons with different properties, such as the specific surface area and pore size distribution in an electrolyte containing TEA-BF
4 and in that containing a spiro-type quaternary ammonium salt (SBP-BF
4). EDLC cells using 1 M SBP-BF
4/DMC+PC showed higher capacitances for the various activated carbons and good rate capabilities even for an activated carbon with a small pore size distribution compared to EDLC cells using 1 M TEA-BF
4/PC. These results may be attributed to the higher mobility of SBP with a smaller cation size and the lower viscosity of 1 M SBP-BF
4/DMC+PC due to the addition of DMC.
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Hideyuki MORIMOTO, Hiroki WATANABE, Shin-ichi TOBISHIMA
2010 年 78 巻 5 号 p.
339-341
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
α-Fe
2O
3 fine powder that the particle size is
ca. 0.3 µm were estimated as negative electrode materials for lithium cells using lithium-ion conductive organic electrolytes. The sheet-type electrodes were fabricated by using the two differential binder solutions of conventional polyvinylidene fluoride (PVDF) and polyamic acid solutions dissolved in N-methyl pyrrolidinone (NMP). The electrodes exhibited high capacities of over 1000 mAh g
−1 corresponding to 6 Li per Fe
2O
3 at potentials ranging from the open circuit potential to 0.005 V (vs. Li/Li
+) in the first charging (lithium insertion) process. First discharge capacities during lithium extraction process exhibited high capacities of over 700 mAh g
−1. However, cycle life of α-Fe
2O
3 electrodes made using the conventional binder (PVDF) solution was poor. On the other hand, Fe
2O
3 electrodes made using polyamic acid solution showed better cycling performance than electrodes made from the PVDF binder solution during charge-discharge cycles and high charge-discharge efficiencies (coulombic efficiencies) over 85%. We suggest that new binders will be needed to improve cycle performance and first charge-discharge efficiencies of high-capacity iron oxide negative electrodes.
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Masaya TAKAHASHI, Takahisa SHODAI
2010 年 78 巻 5 号 p.
342-344
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
We performed a long-term test to determine the float charging durability of prismatic cells with Mn containing LiFePO
4-based cathode material at various temperatures. The cell maintained more than 70% of its initial discharge capacity after float charging at 4.0 V and 25°C for 24 months. In contrast, the capacity decreased rapidly in a few months for a cell float charged at 55°C. To investigate the capacity fading mechanisms, we analyzed the cathode and the anode sheets removed from the prismatic cell used for the float charging test at 55°C with electrochemical, XRD and EPMA techniques.
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Takeshi KITAGAWA, Kazuki AZUMA, Meiten KOH, Akiyoshi YAMAUCHI, Michiru ...
2010 年 78 巻 5 号 p.
345-348
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
We applied fluorine-containing solvents (FCSs) to an electrolyte for lithium (Li)-ion batteries with a cobalt oxide (LiCoO
2) cathode to enhance the upper voltage limit and investigated its electrochemical properties in a proposed FCS-based electrolyte. FCSs were expected to have high oxidation resistance by introducing electron withdrawing fluorine atoms. A test cell containing a FCS-based electrolyte exhibited high and stable discharge capacity in 30 cycles even with a high upper cutoff voltage of 4.5 V when compared with a cell containing a conventional electrolyte. This improvement in the cycle performance was confirmed by an electrochemical impedance measurement. We found that the FCS-based electrolyte provides a favorable solid electrolyte interface (SEI) at the LiCoO
2 cathode, leading to reversible charge-discharge behavior of the cathode.
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Naoki TACHIKAWA, Jun-Woo PARK, Kazuki YOSHIDA, Takashi TAMURA, Kaoru D ...
2010 年 78 巻 5 号 p.
349-352
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The relationship between Li(I) transport property and the limiting current density was investigated in
N-methyl-
N-propylpyrrolidinium bis(trifluoromethylsulfonyl)amide (P13TFSA) at 30°C. The limiting current density in a LiTFSA/P13TFSA binary ionic liquid electrolyte was evaluated by chronoamperometry for a symmetric cell of Li|ionic liquid|Li, where the ionic liquid was incorporated in a porous polyethylene separator that was sandwiched between two Li electrodes. The diffusion process of Li(I) in the ionic liquid dominates the limiting current density in the cell. In addition to the Li(I) transport property of the electrolyte, the porosity and tortuosity of the separator has a significant effect on the limiting current density.
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Hironobu MINOWA, Masahiko HAYASHI, Masaya TAKAHASHI, Takahisa SHODAI
2010 年 78 巻 5 号 p.
353-356
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Lithium-air batteries using Ketjen Black-EC600JD for their air electrodes exhibited a rather large discharge capacity of about 3000 mAh g
−1 at a current density of 0.05 mA cm
−2. However, the cycle performance of the batteries was very poor due to the high overpotential for charging. The cycle properties were greatly improved by adding the Fe–Mn-based perovskite-type oxide, La
0.6Sr
0.4Fe
0.6Mn
0.4O
3, to the air electrodes as an electrocatalyst.
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Masaharu IBARAGI, Hiroshi KAJIRO, Yuji KUBO, Kazuto YAMAMURA, Koki INA ...
2010 年 78 巻 5 号 p.
357-359
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The development of “LAMINELIGHT
®” laminated stainless steel foil for the packaging of lithium-ion batteries is now complete. As a result of simulation, the degree of the deformation of battery packaging made from laminated stainless steel foil caused by rising inner pressure is less than that made from laminated aluminum foil. The simulation also shows that stainless steel foil packaging has a high level of stability and can withstand stress as the laminated resin film is smaller than that of laminated aluminum foil. In addition, the result of laminated stainless steel foil’s critical piercing load is about four times higher than that of laminated aluminum foil. These results show that laminated stainless steel foil can make packaging tougher and more durable than laminated aluminum foil.
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Tao ZHANG, Sisi LIU, Nobuyuki IMANISHI, Atsushi HIRANO, Yasuo TAKEDA, ...
2010 年 78 巻 5 号 p.
360-362
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
A water-stable lithium electrode (WSLE) consisting of a lithium sheet as active layer, a nanocomposite polymer membrane as buffer layer, and lithium-ion conducting glass ceramics as water-stable protective layer, was fabricated as the anode for aqueous lithium-air secondary batteries. The WSLE with the polymer electrolyte containing BaTiO
3 nano-filler (average particle size 40 nm) showed a total electrode resistance of 118 Ω cm
2 in the WSLE/1 M LiCl/Pt black, air cell at 60°C, and exhibited a good cyclic performance for the dissolution and deposition of the lithium ions.
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Naoaki YABUUCHI, Yuto YAMAKAWA, Kazuhiro YOSHII, Shinichi KOMABA
2010 年 78 巻 5 号 p.
363-366
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Li
2FeSiO
4 was prepared by the hydrothermal method, and the influences of synthesis conditions (temperature, time, and lithium-ion concentration) were systematically examined. Low-temperature phase of Li
2FeSiO
4 (space group;
Pmn2
1,
a=6.23,
b=5.36, and
c=4.98 Å) was hydrothermally prepared from LiOH, FeCl
2, and amorphous SiO
2 at 150°C for 3 day. As-prepared Li
2FeSiO
4 (
ca. 1 µm size) shows poor electrochemical reactivity with 20 mAh g
−1 of discharge capacity at room temperature in aprotic Li cell. Electrochemical reactivity of the as-prepared Li
2FeSiO
4 has been considerably improved by the ballmilling process with acetylene black because particle size of Li
2FeSiO
4 is reduced to 50–200 nm size, and the individual particles are uniformly covered by acetylene black. The ballmilled Li
2FeSiO
4 can deliver 130 mAh g
−1 of the rechargeable capacity at room temperature or 150 mAh g
−1 at 60°C.
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Oki SEKIZAWA, Naoto KITAMURA, Yasushi IDEMOTO
2010 年 78 巻 5 号 p.
367-369
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
We investigated the crystal and electronic structures of Li
1+xNi
0.5Mn
0.5O
2 by Rietveld analysis and first-principle calculations. The crystal structure was well refined by Rietveld analysis using
R-3
m as the space group, and it was found with MEM using synchrotron X-ray diffraction that the sample showing better cycle performance had higher electron density at a saddle point of 3b–6c. The first-principle calculation clarified that the covalent bond of Ni–O and Mn–O in near a cation mixing position was stronger than that of normal position.
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Minato EGASHIRA, Akinori KANETOMO, Nobuko YOSHIMOTO, Masayuki MORITA
2010 年 78 巻 5 号 p.
370-374
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The compatibility of the mixed electrolyte of two ionic liquids based on 1,3-substituted imidazolium cations with lithium manganese oxide LiMn
2O
4, lithium iron phouphate LiFePO
4, graphite, and a hard carbon has been confirmed. For LiMn
2O
4 and LiFePO
4, the mixed imidazolium ionic liquid electrolyte provides slightly higher plateau in discharge curves, while the initial capacity is slightly lower, when compared with piperidinium ionic liquid. In case of LiMn
2O
4, the capacity in the mixed ionic liquid is recovered by subsequent cycling. The thermal stabilities of charged positive electrodes with the mixed ionic liquid, as well as with the piperidinium one, from accelerating rate calorimetry are far over those in conventional carbonate electrolyte. A hard carbon electrode is compatible with the mixed ionic liquid electrolyte.
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Noboru OYAMA, Shuichiro YAMAGUCHI, Yasumasa MOCHIZUKI, Tomoo SARUKAWA, ...
2010 年 78 巻 5 号 p.
375-379
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Instead of W. R. McKinnon
1) theory based on interaction energy in lattice-gas model, which has been used widely to analyze the charge-discharge curve for electrode materials of lithium ion battery, Laviron’s
7) and Matsuda’s
8) theoretical treatments about the cyclic voltammetry (CV) for the electro-active molecular confined on an electrode are applied for clarifying the experimentally accessible physical quantities, i.e. the parameters of electrostatic interaction between redox sites and of electrode kinetics for the Li
4Ti
5O
12 (LTO) solid-state layers. From the width at half height (
ΔEp 1/2) of the reversible CV at slowest potential scan-rate, the corresponding attractive force in their active-materials was evaluated as
W/RT=1.64 (4.07 kJ mol
−1), being an identical factor for the interaction energy evaluated by the lattice-gas model. From the shift of peak potential and the changes of
ΔEp 1/2 and peak current for the irreversible CVs against the moderate potential scan-rates, the values of the rate constant (
k°’ s
−1) and the transfer coefficients (α) regarding a redox-electrode reaction process were evaluated as 6.7×10
−3 and 0.47–0.48, respectively. The interaction parameter
ΔW‡/
RT being related to the kinetics of the electrode process was evaluated as −4.28∼−4.68.
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Atsushi ITO, Yuichi SATO, Takashi SANADA, Tsukuru OHWAKI, Masaharu HAT ...
2010 年 78 巻 5 号 p.
380-383
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The local structure of Li[Ni
0.17Li
0.2Co
0.07Mn
0.56]O
2 was analyzed by high resolution scanning transmission electron microscopy (HR-STEM) and X-ray absorption spectroscopy (XAS). The HR-STEM images clearly showed a new type of stacking fault, as well as visual patterns of Li-ordering in the transition-metal (TM) layers. The XAS data showed that the valence states of the component TMs are Ni(II), Co(III) and Mn(IV), suggesting that some of the Li(I) in the TM layers of Li
2MnO
3 structure is replaced by Ni(II). Based on the results obtained, a detailed structural model for Li-rich solid-solution cathode materials was proposed.
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Yuichi MITA, Shiro SEKI, Nobuyuki TERADA, Nobuo KIHIRA, Katsuhito TAKE ...
2010 年 78 巻 5 号 p.
384-386
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
We proposed accelerated life estimation test methods for high-power lithium-ion batteries used in electrical vehicle. The effects of temperature and state of charge on the degradation of full-scale prototype cells (>5 Ah) were investigated from the viewpoints of capacity performance and output performance by carrying out storage tests over more than 100 days. The most appropriate charging method during storage was also investigated.
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Yusuke SHINTANI, Hiromori TSUTSUMI
2010 年 78 巻 5 号 p.
387-389
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Solid polymer electrolytes, the electrolytes without a flammable solvent, can solve a safety problem of rechargeable lithium (Li) batteries. We prepared poly(oxetane) with nitrile groups, P(CYAMEO), by ring-opening polymerization of the oxetane derivative and used it for a matrix of solid polymer electrolytes. Charge-discharge performance of the Li|P(CYAMEO)-based electrolyte|LiCoO
2 cells was tested under constant current charge-discharge cycling condition. The test cells with the P(CYAMEO)-based electrolyte that contained LiN(CF
3SO
2)
2, showed better discharge performance than those with the electrolytes that contained other Li salts. The polarization behaviors of the Li electrode in the electrolyte suggest that performance of the test cells partially depend on the structure of the solid electrolyte interphase on the Li electrode surface in the P(CYAMEO)-based electrolyte.
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Tomohiro ITO, Masakatsu KOBAYASHI, Mayumi YOSHIDA, Tomohito SEKINE, Ka ...
2010 年 78 巻 5 号 p.
390-392
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
In this study, the behavior of carbon radicals has been observed in a model cell of an electric double layer capacitor (EDLC) by using an
in situ electron spin resonance (ESR) method and ac cyclic voltammetry (CV). The maximum ESR signal intensity of the carbon radical was observed during the anodic sweep of the applied voltage using the simultaneous measurement of the ESR, the impedance and the CV. It was found that the degradation progress of the EDLC was mainly due to the change in the concentration of the carbon radical, and that its phenomenon was not observed by CV.
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Izumi YAMADA, Shin R. MUKAI
2010 年 78 巻 5 号 p.
393-396
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Silicon powder was encased within carbon gel microspheres with different porosities by simply adding silicon powder to the water phase during the inverse emulsion polymerization of resorcinol with formaldehyde, followed by drying and carbonization. From the results of charge-discharge experiments, it was confirmed that the reversible capacity of silicon and its cycle ability could be improved through such encasement and that the degree of improvement depended on the porosity of the carbon gel matrix.
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Yasutaka TANAKA, Junya KANEKO, Masanori MINOSHIMA, Yasutoshi IRIYAMA, ...
2010 年 78 巻 5 号 p.
397-399
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
A blend of several boric esters was adopted as a novel electrolyte solvent exhibiting the high oxidation potential and favorable lithium ion conductivity. Spontaneous transesterification between boric esters takes place resulting in a mixed boric ester. The electrochemical properties that the mixed ester acquired seem to be descended from the properties of parent boric esters: thus B(OCH
3)
3 (
1) or B(OCH
2CH
3)
3 (
2), and B(OCH
2CH
2CN)
3 (
3) were low viscous, and a good solvent for lithium salts respectively.
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Shizukuni YATA, Hisashi SATAKE, Mayumi KURIYAMA, Tomoki ENDO, Hajime K ...
2010 年 78 巻 5 号 p.
400-402
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
In this study, we investigated the results based on the “C.R.M. resistance” of positive electrodes (Co-, Ni- and Mn-based materials), which was directly related to the input-output power characteristics, using the “four-electrode cell”.
1,2) By comparing the resistance of these positive electrodes, we found that the Ni-based electrode had the lowest C.R.M. resistance in the range of 4.0 V–3.5 V and the Mn-based electrode had a stationary C.R.M. resistance over a wide range of both the charge and discharge states.
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Fuminori MIZUNO, Shinji NAKANISHI, Yukinari KOTANI, Shoji YOKOISHI, Hi ...
2010 年 78 巻 5 号 p.
403-405
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Rechargeable Li-air battery is a candidate for post Li-ion battery with high energy density. In this paper, the rechargeability of Li-air battery over 100 cycles was confirmed and its capacity retention over 60% was achieved. Nevertheless, a large voltage gap between the discharge-charge profiles was observed. Here, a discharged product formed on a cathode was investigated by TEM observation and FT-IR spectroscopy. It was found that the main product formed in discharge was not an ideal compound, Li
2O
2, but was carbonate species issued from the decomposition of carbonate-based electrolyte solvent.
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Hiroe NAKAGAWA, Yohei SHIBATA, Yukiko FUJINO, Toru TABUCHI, Tokuo INAM ...
2010 年 78 巻 5 号 p.
406-408
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The use of nonflammable electrolytes containing a solvent that includes alkyl fluoride groups to improve the safety of lithium-ion cells has been investigated. The positive electrodes of the cells comprise a mixture of a multi-component transition metal oxide and a polyanionic compound. The nonflammability of the electrolyte is shown by adding 30 vol% of a phosphate solution to the base electrolyte. It is observed that the cycle-life performances of the cells with the nonflammable electrolyte at 45°C are higher than that of the cell containing the base electrolyte.
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Muneo KODAIRA, Masahiro SEIDO, Gen SASAKI
2010 年 78 巻 5 号 p.
409-412
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The deformation behavior of copper foil collectors electrodeposited with Ni
3Sn
4 during the charge-discharge cycle was observed in situ using an optical cantilever method. It was found that in the high yield strength copper foil, cyclical deformation due to charge-discharge were observed, while in low yield strength copper foil, the deformation which occurred during the first charge period remained. The former is elastic deformation and the latter is plastic deformation. As plastic deformation promotes determination through peeling and shedding of the active material during sequential cycles, the high yield strength copper should be adopted. For example, 3 µm Ni
3Sn
4 film requires a 31 µm pure copper foil collector with a yield strength of 350 MPa or a 18 µm Corson copper alloy foil collector with the yield strength of 700 MPa.
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Masaaki HIRAYAMA, Masao YONEMURA, Kouta SUZUKI, Naoya TORIKAI, Hillary ...
2010 年 78 巻 5 号 p.
413-415
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The electrode surface of a lithium battery was characterized using
in situ reflectivity techniques and epitaxial thin films. Epitaxial LiFePO
4 thin films were fabricated by pulsed laser deposition. Changes in interfacial structures on the surface are determined by X-ray and neutron reflectivity (NR) measurements using an X-ray-transmission electrochemical cell. The LiFePO
4 surface is stable during the first charge/discharge process. NR analysis indicates a reversible change in the concentration gradient of lithium ions at the LiFePO
4/electrolyte interface on lithium deintercalation.
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Takeshi KOBAYASHI, Shiro SEKI, Yuichi MITA, Hajime MIYASHIRO, Nobuyuki ...
2010 年 78 巻 5 号 p.
416-419
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
We measured impedance spectra for lithium-ion batteries with a large capacity over 10 Ah and a small capacity under 1 Ah. We assigned the impedance spectra to the electrochemical parameters for the positive and negative electrode interfaces without disassembling. We proposed an advanced impedance analysis technique with constant phase element normalized by battery capacity for lithium-ion batteries of 10 Ah-class.
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Eiji HIGUCHI, Touta MIZUTA, Hiroshi INOUE
2010 年 78 巻 5 号 p.
420-422
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Effect of discharging before initial activation (pretreatment) of Co(OH)
2-coated Ni(OH)
2 positive electrodes for use in Ni-metalhydride (Ni-MH) batteries on their electrochemical properties was investigated. The high-rate dischargeability (HRD) of the positive electrode was improved by the pretreatment. The effect of the pretreatment was more conspicuous as the amount of the Co(OH)
2-coated Ni(OH)
2 as an active material increased. The charge transfer resistance (
Rct) of the positive electrode evaluated by AC impedance measurements significantly increased at the depths of charge (DOCs) less than 20%, while the increase in
Rct was effectively suppressed by the pretreatment. Moreover, the cyclic voltammogram of the pretreated positive electrode showed that metallic Co was produced during the pretreatment and oxidized to CoOOH. The formation of the conductive oxidation products from not only the pristine Co(OH)
2 but also metallic Co can lead to the formation of more dense conductive network which may be responsible for the improvement of HRD and
Rct.
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Minato EGASHIRA, Nobuko YOSHIMOTO, Masayuki MORITA
2010 年 78 巻 5 号 p.
423-426
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The influence of the component of the gel polymer electrolyte containing imidazolium ionic liquid on its cathodic stability and mobility of lithium ion has been investigated. The selection of the mixed ionic liquid based on 1-ethyl-3-methyl (EMI) imidazolium and 1-cyanomethyl-3-methyl imidazolium (CmMI) cations exhibits higher cathodic stability for the gel electrolyte than the one containing EMI ionic liquid alone. The addition of alumina filler increases the mobility of lithium ion in the gel, and promotes the reversible lithium deposition-dissolution.
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Yuya SHIMADA, Kengo OKITA, Yuki OKUNO, Yasutoshi IRIYAMA
2010 年 78 巻 5 号 p.
427-430
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Multi-layered solid electrolyte sheets (OHARA sheet (Ohara Inc., Kanagawa, Japan)/lithium phosphorus oxynitride (LiPON)) with a copper current collector film on the LiPON side were prepared, and the effects of Ti modification at the OHARA sheet/LiPON interface on the electrochemical lithium deposition-dissolution reaction were investigated. Lithium plating-stripping current in cyclic voltammograms increased with an appropriate amount of Ti modification, indicating that Li
+ transfer resistance at the OHARA sheet/LiPON interface decreased due to the modification. In addition, the Ti modification stabilized the electrochemical lithium deposition-dissolution reaction. This suggested that Ti modification increase the number of Li
+ transfer sites at the interface, resulting in a good distribution of nucleation reaction sites on the copper film as well as the stabilization of the current collector film.
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Yosuke MUROTA, Yasuyuki OBA, Mikihiro TAKAGI, Takayuki ASAO, Morihiro ...
2010 年 78 巻 5 号 p.
431-434
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Li
+ ion insertion/extraction properties of TiO
2(B) powder, which was prepared from a K
2Ti
4O
9 precursor by ion-exchange and dehydration, was investigated as a high-potential negative electrode. The irreversible capacity greatly decreased from 124 mAh g
−1 to
ca. 40 mAh g
−1 when the lower potential limit was raised from 1.0 V to
E≥1.2 V, which indicated that the irreversible capacity mainly originated from surface reactions, such as solvent decomposition, at
E≤1.2 V in the first cycle. In galvanostatic intermittent titration tests, large polarization was observed at the beginning and the end of charging. This clearly indicated that a slow process is involved in the insertion reaction at the beginning and the end of charging, which causes solvent decomposition at potentials lower than 1.4 V. The reversible capacity was greatly improved to 246 and 276 mAh g
−1 at an elevated temperature of 60°C and at a lower rate of C/60, respectively. The TiO
2(B) sample contained
ca. 14 wt% of the anatase phase as an impurity, and a reduction of the anatase phase was found to be effective for an increase in reversible capacity at moderate charge/discharge rates.
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Tomomi HARADA, Jun-ichi TANAKA, Akira NAKAZAWA, Minoru UMEDA, Yoshitsu ...
2010 年 78 巻 5 号 p.
435-437
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
An investigation of the thermal deterioration characteristics of a lithium-ion secondary cell is inevitable for in utilization for electric vehicles. An accelerating rate calorimeter study revealed that the thermal runaway of the cell occurs over 130°C. In the present study, the thermal deterioration characteristics of a lithium-ion secondary cell during a 100°C storage have been investigated by varying the state of charge (SOC). The measured impedance spectra have been analyzed based on an equivalent circuit, which consists of resistances of the anode and cathode (R1 and R2). Based on the analyses, the increasing rates of R1 and R2 can be defined. The rate of R1 is lower than that of R2 for an SOC of 87%; conversely, that of R1 is greater than that of R2 for SOCs of 66 and 44%. Moreover, the increasing rates of both R1 and R2 are found to become significant when the magnitude of the SOC increases. The increasing rate of R2 more strongly depends on the SOC than that of R1. These results mean that the cathode material is thermally unstable when the extent of lithium deterioration is high.
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Kenta NAKAI, Ikuro TSUCHIOKA, Morihiro SAITO, Akimasa TASAKA, Toshio T ...
2010 年 78 巻 5 号 p.
438-441
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Pure Si platelets (Si-LP, thickness: 100 nm) and Ni layer-laminated Si platelets with different thicknesses (Si/Ni/Si-LP50 (50/50/50 nm) and Si/Ni/Si-LP30 (30/30/30 nm)) were prepared by a vapor deposition method, and their charge/discharge properties were investigated as alternative negative electrode materials to graphite for lithiumion batteries. The shape of thin platelet effectively relieved the stress during the alloying and de-alloying processes, and improved the charge/discharge cycleability as compared with a commercially available Si powder. In particular, the laminated platelet samples showed very good cycleability, probably because of a shorter diffusion length of Li
+ ions in the Si layers and an improved mechanical strength by the presence of the Ni layer.
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Noritoshi NANBU, Kohei YAMAGUCHI, Junya YAMAMOTO, Yukio SASAKI
2010 年 78 巻 5 号 p.
442-445
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Sydnones are known as typical mesoionic compounds, which can be represented by the resonance hybrid of different polarized ionic structures. We have newly synthesized 3-ethyl-4-propylsydnone (EPSD) and investigated its physical, chemical, and electrochemical properties. The electron-pair donability for EPSD was higher than that for propylene carbonate (PC), though the electron-pair acceptability for EPSD was lower. The addition of EPSD to an ethylene carbonate (EC)-diethyl carbonate (DEC) equimolar binary mixture at the molar ratio of 1:1:0.05 was effective for an increase in cycling efficiency of a lithium anode.
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Noritoshi NANBU, Yuta SUZUKI, Kiyoshi OHTSUKI, Takeshi MEGURO, Masahir ...
2010 年 78 巻 5 号 p.
446-449
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Ethyl acetate (EA) shows low viscosity for its relative permittivity. Monofluorinated solvents exert the polar effect on the physical and electrochemical properties. Relative permittivity of 2-fluoroethyl acetate (2FEA) was lower than that of ethyl fluoroacetate (EFA), though viscosity of 2FEA was higher. Ionic conductivity of 2FEA was lower than that of EFA, but higher than that of EA at high temperatures. The anodic stability of 2FEA and EFA was higher than that of EA. The use of 2FEA as a co-solvent improved cycling efficiency of a lithium anode.
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Noritoshi NANBU, Kosuke HAGIYAMA, Masahiro TAKEHARA, Makoto UE, Yukio ...
2010 年 78 巻 5 号 p.
450-453
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Difluorination of 3-methyl-2-oxazolidinone (3Me2Ox or NMO (
N-methyloxazolidinone)) decreased the relative permittivity and the ionic conductivity and increased the dynamic viscosity and the anodic stability. The difluorinated NMOs (DFNMO
mix) consisted of a mixture of 4,4′-difluoro-3-methyl-2-oxazolidinone (4,4′-DFNMO) and 4,5-difluoro-3-methyl-2-oxazolidinone (4,5-DFNMO), and its molar ratio was 3:7. The addition of DFNMO
mix to an ethylene carbonate (EC)-diethyl carbonate (DEC) equimolar binary mixture suppressed discharge capacity fading in a Li/LiCoO
2 coin cell.
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Shinjiro HAYAKAWA, Yuta KUBOUCHI, Tetsutaro HAYASHI, Toshiaki ONAKADO, ...
2010 年 78 巻 5 号 p.
454-456
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
X-ray absorption near edge (XANES) measurements at K-edges of Ni and Co were carried out on the Li deintercalated Li
1−xNi
0.82Co
0.15M
0.03O
2 (M=Nb, Ti) cathode materials for Li secondary batteries. Samples were prepared by two different ways of Li deintercalation. One was cathode materials removed from the coin cell charged in the different degree of Li deintercalation and the other was chemically processed with hydrochloric acid in the aqueous solution. Comparisons of XANES spectra between LNCO and Ti or Nb doped LNCO were made, and it was found that the formation of Ni
4+ was greatly reduced in the charged cathode materials with the dope of Ti or Nb. The similar results were obtained within samples prepared by the real charge and the chemical charge. Valence of Co was invariable during the charge, and was supposed to be trivalent.
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Toyoki OKUMURA, Tomokazu FUKUTSUKA, Yoshiharu UCHIMOTO, Morihiro SAITO ...
2010 年 78 巻 5 号 p.
457-459
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
The extended X-ray absorption fine structure (EXAFS) was measured to study the effects of the local structures on the Li-ion transfer in the La
2/3−xLi
3xTiO
3 perovskite model compound with different lanthanum ion concentrations. The results indicate that the local structure is more distorted and the interatomic distances of Ti–La and Ti–O–Ti become shorter with the decrease of lanthanum ion concentration. The change in Li-ion conductivity with different lanthanum ion concentration is well explained by the relation between the estimation of activation energy with which Li ions hop through the bottleneck and the results of local distortion by EXAFS analysis.
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Tetsu ICHITSUBO, Kousuke HIRAI, Shunsuke YUKITANI, Eiichiro MATSUBARA
2010 年 78 巻 5 号 p.
460-462
発行日: 2010/05/05
公開日: 2012/03/26
ジャーナル
フリー
Sn and Sn-based compounds have attracted great interest as a candidate for anode materials of Li-ion batteries. In the present work, in a Sn–Li battery system we have investigated effects of the volume change associated with the formation of Li–Sn compounds on the electrode potential from the viewpoint of the Gibbs free energy and associated elastic-strain energy. Our experimental results show that the experimental electrode potential is much lower than the value expected thermodynamically, when a Sn plate-shape electrode is lithiated. These experimental results can be consistently explained by considering the contribution of the elastic-strain energy to the chemical free energy of formation.
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