Published Papers - UI Koichi

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   2009.09  [Refereed]

Academic Journal  Multiple authorship

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   2010.01  [Refereed]

Academic Journal  Multiple authorship

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   2010.02  [Refereed]

Academic Journal  Multiple authorship

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   2010.08  [Refereed]

Academic Journal  Multiple authorship

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   2010.09  [Refereed]

Academic Journal  Multiple authorship

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   2011.02  [Refereed]

Bulletin of University, Institute, etc.  Multiple authorship

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   2011.04  [Refereed]

Academic Journal  Multiple authorship

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   2011.04  [Refereed]

Academic Journal  Multiple authorship

DOI

Preparation of Ni-Sn alloy film as negative electrode for lithium secondary batteries by pulse electrolysis

Koichi UI*, Kiwamu KAWARAI, Yoshinobu SATO, Shinei Kikuchi, Naoaki KUMAGAI

Journal of The Surface Finishing Society of Japan ( The Surface Finishing Society of Japan )  63 ( 3 ) 188 - 190   2012.03  [Refereed]

Academic Journal  Multiple authorship

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   2012.04  [Refereed]

Academic Journal  Multiple authorship

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   2012.04  [Refereed]

Academic Journal  Multiple authorship

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   2012.10  [Refereed]

Academic Journal  Multiple authorship

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   2012.08  [Refereed]

Academic Journal  Multiple authorship

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   2012.11  [Refereed]

Academic Journal  Multiple authorship

DOI

Analysis of Electrochemical Reactions of Natural Graphite Electrode in Chloroaluminate Type Room-temperature Ionic Liquid Electrolyte Containing Lithium Ion

Jun TOWADA, Yoshihiro KADOMA, Kazuaki SHIMADA, Naoaki KUMAGAI, and Koichi UI *

Electrochemistry   81 ( 6 ) 432 - 439   2013.06  [Refereed]

Academic Journal  Multiple authorship

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   2014.02  [Refereed]

Academic Journal  Multiple authorship

DOI

Solvothermal Synthesis and Electrochemical Properties of LiMnPO₄ and Its Carbon Composite

Yoshihiro KADOMA,* Koichi HARATA, Hisashi WATANABE, Naoaki KUMAGAI, and Koichi UI

Electrochemistry   82 ( 6 ) 456 - 461   2014.06  [Refereed]

Academic Journal  Multiple authorship

DOI

Influence on charge-discharge characteristics of composition of Ni-Sn alloy film negative electrode for lithium secondary batteries prepared by pulse electrolysis

Koichi UI*, Kiwamu KAWARAI, Yoshihiro KADOMA, Naoaki KUMAGAI

Journal of The Surface Finishing Society of Japan   64 ( 8 ) 460 - 466   2013.08  [Refereed]

Academic Journal  Multiple authorship

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   2015.02  [Refereed]

Academic Journal  Multiple authorship

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   2015.06  [Refereed]

Bulletin of University, Institute, etc.  Multiple authorship

DOI