論文 - 宇井　幸一

Electrodeposition of Nb₃Sn Alloy Film from Lewis Basic NbCl₅-SnCl₂-EMIC Melt

Koichi Ui*, Hirokazu SAKAI, Ken TAKEUCHI, Guo-ping LING, and Nobuyuki KOURA

Electrochemistry   77 ( 9 ) 798 - 800   2009年09月  [査読有り]

学術誌  共著・分担

Optimization of electrochemical properties of LiFePO₄/C prepared by an aqueous solution method using sucrose

Yoshihiro Kadoma, Jung-Min Kim, Katsutoshi Abiko, Keitaro Ohtsuki, Koichi Ui, and Naoaki Kumagai*

Electrochim. Acta.   55 ( 3 ) 1034 - 1041   2010年01月  [査読有り]

学術誌  共著・分担

Spray-drying Synthesized Lithium-excess Li_4+xTi_5−xO_12−δ and its Electrochemical Property as Negative Electrode Material for Li-ion Batteries

Yoshihiro Kadoma, Jung-Min Kim, Koichi Ui, Naoaki Kumagai*, Naoto Kitamura, and Yasushi Idemoto

Electrochim. Acta.   55 ( 6 ) 1872 - 1879   2010年02月  [査読有り]

学術誌  共著・分担

Synthesis and Electrochemical Properties of LiNi_0.5-xMn_1.5-xM_2xO₄ (M ＝Al, Cr) Cathode Materials Prepared by PVA Method

Yoshihiro KADOMA, Seiyu SATO, Koichi UI, and Naoaki KUMAGAI*

Electrochemistry   78 ( 8 ) 658 - 661   2010年08月  [査読有り]

学術誌  共著・分担

Spray-Drying Synthesized Lithium-excess Li_4+xTi_4.95-xNb_0.05O_12-δ and its Electrochemical Property as Negative Electrode Material for Li-ion Batteries

Naoaki KUMAGAI*, Daisuke YOSHIKAWA, Yoshihiro KADOMA, and Koichi UI

Electrochemistry   78 ( 9 ) 754 - 756   2010年09月  [査読有り]

学術誌  共著・分担

Li4+xTi4.95−xNb0.05O12−δ (x=0.11∼0.13) materials were synthesized by using a spray-drying method followed by heat treating at 600∼900°C in air. Chemical and structural studies of the final products were done by X-ray diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS) etc. The optimum synthesis condition of the materials was examined in relation to the electrochemical characteristics including charge-discharge cycling tests. The charge-discharge cycling results of several the Nb-substituted samples indicated that the samples prepared at heat treatment temperature of 700°C for 12 h showed best cycling performance with the discharge capacity of 175∼140 mAh g−1 at the discharge rate of 0.5∼3C.

DOI

Preparation and cycle performance of Sn-SnO_x/C composite electrode for lithium-ion battery

Ren, H.-J., Liu, W., Liu, G.-C., Ui, K., and Kumagai, N.

Journal of Functional Materials   42 ( 1 ) 19 - 22   2011年02月  [査読有り]

国際的学術誌  共著・分担

Influence of the binder types on the electrochemical characteristics of natural graphite electrode in room-temperature ionic liquid

Koichi Ui*, Jun Towada, Sho Agatsuma, Naoaki Kumagai, Keigo Yamamoto, Hiroshi Haruyama, Ken Takeuchi, and Nobuyuki Koura

J. Power Sources   196 ( 8 ) 3900 - 3905   2011年04月  [査読有り]

学術誌  共著・分担

DOI

Preparation of Co-Sn alloy film as negative electrode for lithium secondary batteries by pulse electrodeposition method

Koichi Ui*, Shinei Kikuchi, Yasuhiro Jimba, and Naoaki Kumagai

J. Power Sources   196 ( 8 ) 3916 - 3920   2011年04月  [査読有り]

学術誌  共著・分担

DOI

パルス電解法を用いるリチウムイオン二次電池用Ni-Sn合金めっき膜負極の作製

宇井幸一*, 瓦井　究, 佐藤吉信, 菊地信栄, 熊谷直昭

表面技術 ( 一般社団法人 表面技術協会 )  63 ( 3 ) 188 - 190   2012年03月  [査読有り]

学術誌  共著・分担

DOI

Synthesis and electrochemical properties of nano fiber hollandite-type manganese oxides using a hydrothermal method

Yoshihiro Kadoma, Tatsuya Akahira, Tsubasa Fukuda, Koichi Ui, and Naoaki Kumagai

Functional Materials Letters   5 ( 1 ) 1250004X   2012年04月  [査読有り]

学術誌  共著・分担

Hollandite-type MnO2 and its Co-substituted samples have been synthesized by hydrothermal method from MnSO4, CoSO4 and K2S2O8 solutions. The hydrothermal products from MnSO4 and K2S2O8 solutions consisted of the hollandite-type [2 × 2] tunnel structure at 100°C–150°C for 12 h, which was transformed to pyrolusite-type [1 × 1] tunnel structure by hydrothermal treatment at 150°C for longer times of 24–48 h or at a higher temperature of 180°C. On the other hand, the hydrothermal products from MnSO4, CoSO4 and K2S2O8 solutions at 150°C–180°C for 12–48 h consisted of the hollandite-type MnO2 phase. The Co-substituted samples showed higher initial discharge capacity (180–200 mAh (g-oxide)-1) than that of non-substituted hollandite-type MnO2 (130–160 mAh (g-oxide)-1) at 50 mA g-1.

DOI

Li excess Li_4+xTi_5-xO1_2-λ/C composite using spray-drying method and its electrode properties

Daisuke Yoshikawa, Norio Suzuki, Yoshihiro Kadoma, Koichi Ui, and Naoaki Kumagai

Functional Materials Letters   5 ( 1 ) 12500014   2012年04月  [査読有り]

学術誌  共著・分担

We have prepared a lithium excess carbon composite material, Li4+xTi5-xO12-δ/C (LTO/C), using various amounts of sucrose as a carbon source by the spray-drying method. The prepared materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and elemental analysis. The prepared material had the Li4Ti5O12 phase including 3.9–18.4 wt.% carbon. Transmission electron microscopy images and the selected area diffraction (SAD) pattern showed that the prepared materials consisted of a carbon nanonetwork in the LTO/C composite. The charge–discharge cycling tests were carried out using the R2032 coin-type cell under the following conditions; 1.2–3.0 V, 0.1 C–10 C (1 C = 175 mA g-1), 25°C. Based on the electrochemical results, the electrode performance of the prepared material was improved with increasing amounts of residual carbon, in particular, LTO/C including 6.2 wt.% residual carbon exhibited the best electrode performance of 156 mAh g-1 at 1 C during 50 cyclings when compared to the other materials.

DOI

Influence of the Carbon Source on the Surface and Electrochemical Characteristics of Lithium Excess Li_4.3Ti₅O₁₂ Carbon Composite

Yoshihiro KADOMA, Yusuke CHIBA, Daisuke YOSHIKAWA, Yuko MITOBE, Naoaki KUMAGAI, and Koichi UI*

Electrochemistry ( 公益社団法人　電気化学会 )  80 ( 10 ) 759 - 761   2012年10月  [査読有り]

学術誌  共著・分担

We have investigated the preparation and electrochemical characteristics of a lithium excess Li4.3Ti5O12 carbon composite (Li4.3Ti5O12/C) with different carbon sources (polyacryl acid, polyvinyl alcohol, and carboxy methyl cellulose sodium). We have prepared the lithium excess Li4.3Ti5O12/C by a spray-drying method followed by calcining at 800oC in a nitrogen atmosphere. The TEM observations indicated that the surface of the Li4.3Ti5O12/C particle was clearly covered with an amorphous carbon layer. The Li4.3Ti5O12/C materials employing polyvinyl alcohol as the carbon source showed the best rate performance with the highest discharge capacity of 117 mAh (g-Li4.3Ti5O12/C)-1 at the 10C rate.

DOI

Fabrication of binder-free SnO₂ nanoparticle electrode for lithium secondary batteries by electrophoretic deposition method

Koichi Ui*, Soshi Kawamura, and Naoaki Kumagai

Electrochim. Acta.   76   383 - 388   2012年08月  [査読有り]

学術誌  共著・分担

DOI

Influence of the binder types on the electrochemical characteristics of tin nanoparticle negative electrode for lithium secondary batteries

Guichang Liu*, Xiaoxiao Shen, Koichi Ui, Lida Wang, and Naoaki Kumagai

J. Power Sources   217   108 - 113   2012年11月  [査読有り]

学術誌  共著・分担

DOI

リチウムイオンを含む塩化アルミニウム系室温イオン液体中における天然黒鉛電極の電気化学反応の解析

十和田 潤, 門磨義浩, 嶋田和明, 熊谷直昭, 宇井幸一 *

Electrochemistry   81 ( 6 ) 432 - 439   2013年06月  [査読有り]

学術誌  共著・分担

DOI

Analysis of SEI formation reaction and surface deposit of natural graphite negative electrode employing polyacrylic acid as a binder

Koichi Ui*, Daisuke Fujii, Yuki Niwata, Tomohiro Karouji, Yu Shibata, Yoshihiro Kadoma, Kazuaki Shimada, and Naoaki Kumagai

J. Power Sources   247   981 - 990   2014年02月  [査読有り]

学術誌  共著・分担

DOI

ソルボサーマル法によるLiMnPO₄の合成とその炭素複合体の電気化学的特性

門磨義浩,* 原田晃一, 渡辺　久, 熊谷直昭, 宇井幸一

Electrochemistry   82 ( 6 ) 456 - 461   2014年06月  [査読有り]

学術誌  共著・分担

DOI

パルス電解法で作製したリチウム二次電池用Ni-Sn合金めっき膜負極の組成が充放電特性に及ぼす影響

宇井幸一*, 瓦井　究, 門磨義浩, 熊谷直昭

表面技術 ( 一般社団法人 表面技術協会 )  64 ( 8 ) 460 - 466   2013年08月  [査読有り]

学術誌  共著・分担

Using pulse electrolysis, Ni-Sn alloy films of three compositions (NiSn9, Ni2Sn8, and Ni3Sn7) were prepared for a negative electrode. FESEM observations indicated that the crystal grain size of the film decreased, and that the film was densified with increased Ni contents. Tape tests indicated that adhesion between the film and a current collector increased concomitantly with increased Ni content. The galvanostatic charge-discharge tests indicated that the capacity retention rate at the 30th cycle rose with increased Ni content. Ex-situ FE-SEM observations indicated that cracks in the film were generated in the Ni2Sn8 and Ni3Sn7 alloy films after the first discharge. Ex-situ XRD measurements showed that the charge-discharge reaction of the Ni3Sn7 alloy film was attributable to alloying/dealloying a Ni3Sn4 phase with lithium. No β-Sn phase was extricated after the first discharging. In addition to the decrease in the crystal grain size and the increase in the adhesion between the film and the current collector along with increase in the Ni content, results showed that cycle performance can be improved if extrication of the β-Sn phase can be repressed, even if a crack is generated in the film during charging and discharging.

DOI

Charge-discharge Characteristics of Natural Graphite Electrode in N, N-Diethyl- N-Methyl-N-(2-methoxyethyl)ammonium Bis(trifluoromethylsulfonyl)amide Containing Lithium Ion for Lithium-ion Secondary Batteries

Jun Towada, Tomohiro Karouji, Hiroki Sato, Yoshihiro Kadoma, Kazuaki Shimada, Koichi Ui*

J. Power Sources   275   50 - 54   2015年02月  [査読有り]

学術誌  共著・分担

DOI

In situ SEM observation of the Si negative electrode reaction in an ionic-liquid-based lithium-ion secondary battery

Tetsuya Tsuda*, Tsukasa Kanetsuku, Teruki Sano, Yoshifumi Oshima, Koichi Ui, Masaki Yamagata, Masashi Ishikawa, Susumu Kuwabata

Microscopy   64 ( 3 ) 1 - 10   2015年06月  [査読有り]

国際的学術誌  共著・分担

DOI