| 1. |
H. Sato, R. Sakamoto, H. Minami, H. Izumi, K. Ideta, A. Inoishi, S. Okada, The in situ formation of an electrolyte via the lithiation of Mg(BH4)(2) in an all-solid-state lithium battery, CHEMICAL COMMUNICATIONS, 10.1039/d0cc08366f, 57, 21, 2605-2608, 2021.03, 本研究では、Mg(BH4)2電極に電解質をその場で形成することにより、全固体電池の容量を増加させる新しいアプローチを提案した。(BH4)2とアセチレンブラックで構成された電極の充放電評価では、初期の可逆容量は563 mA h g-1-Mg(BH4)2に達した。. |
| 2. |
Baowei Xie, Ryo Sakamoto, Ayuko Kitajou, Kosuke Nakamoto, Liwei Zhao, Shigeto Okada, Yuki Fujita, Nobuto Oka, Tetsuaki Nishida, Wataru Kobayashi, Masaki Okada, Toshiya Takahara, Cathode Properties of Na3FePO4CO3 Prepared by the Mechanical Ball Milling Method for Na-ion Batteries, Scientific Reports, 10.1038/s41598-020-60183-3, 10, 1, 3278-3285, 2020.12, The carbonophosphate Na3FePO4CO3 was synthesized by the mechanical ball milling method for the first time. The composition of the obtained sample with a higher amount of Fe2+ was Na2.66Fe2+ 0.66Fe3+ 0.34PO4CO3 as confirmed by Mössbauer analysis, owing to the good airtight properties of this method. The obtained samples in an organic electrolyte delivered an initial discharge capacity of 124 mAh/g at room temperature, and a larger discharge capacity of 159 mAh/g (1.66 Na+/mole) at 60 °C. With 17 m NaClO4 aqueous electrolyte, a discharge capacity of 161 mAh/g (1.69 Na+/mole) was delivered because of the high ionic conductivity of the concentrated aqueous electrolyte. During the charge-discharge process, the formation of Fe4+ after charging up to 4.5 V and the return of Fe2+ after discharging down to 1.5 V were detected by ex-situ X-ray absorption near edge structure (XANES) analysis.. |
| 3. |
Yuji Ishado, Atsushi Inoishi, Shigeto Okada, Exploring Factors Limiting Three-Na+ Extraction from Na3V2(PO4)3, Electrochemistry, https://doi.org/10.5796/electrochemistry.20-00080, 88, 5, 457-462, 2020.07, ナシコン型Na3V2(PO4)3はNaイオン電池の有望な正極材料である。Na3V2(PO4)3を充電すると2つのNa+が抽出されることがよく知られているが、電気化学的に3つのNa+を抽出した例はまだない。本研究では、Na3V2(PO4)3からの3Na+抽出を制限する要因を調べた。DFT計算では、3Na+抽出の電圧は4.5V vs. Na+/Na0以上と予測され、これは従来の有機電解質のポテンシャルウィンドウを超えていた。今回のNa3V1.5Al0.5(PO4)3の研究では、ナシコン構造のNa1サイトからNaイオンを抽出する際に、このような高い電圧が必要になることを明らかにした。NEB計算により、NaV2(PO4)3のNa1サイトからのNa+抽出の活性化エネルギーは753meVと予測された。また、Ab-initio法による分子動力学シミュレーションでは、NaV2(PO4)3に残ったNaイオンは、Na1サイトに運動的にロックアップされていることが示唆された。この結果は、高電圧と大きな活性化エネルギーのために、3つのNa+の抽出が制限されることを示している。また、Na3V2(PO4)3とは対照的にLi3V2(PO4)3では3Li+抽出が可能であることも比較議論した。. |
| 4. |
Kosuke Nakamoto, Ryo Sakamoto, Yuki Sawada, Masato Ito, Shigeto Okada, Over 2 V Aqueous Sodium-Ion Battery with Prussian Blue-Type Electrodes, Small Methods, 10.1002/smtd.201800220, 3, 4, 1800220-1800224, 2019.04, High discharge voltage of more than 2 V is achieved in a novel aqueous sodium-ion battery with the combination of a Prussian blue-type sodium manganese hexacyanoferrate cathode, and a similar potassium manganese hexacyanochromate anode. Here, a highly concentrated sodium perchlorate aqueous electrolyte with a 2.8 V electrochemical window is used. By element analysis, the novel anode containing little potassium element possibly serves as a suitable host–guest anode, similarly as the cathode extracting/inserting sodium ion in a highly concentrated sodium-ion aqueous electrolyte. Open-framework electrodes and a highly concentrated but mobile aqueous electrolyte contribute to high voltage and high rate performance of the aqueous sodium-ion battery.. |
| 5. |
Atsushi Inoishi, ＃Yuto Yoshioka, L.iwei Zhao, Ayuko Kitajou, Shigeto. Okada, Improvement in the Energy Density of Na3V2(PO4)(3) by Mg Substitution, ChemElectroChem, 10.1002/celc.201700540, 4, 11, 2755-2759, 2017.11. |
| 6. |
Kosuke Nakamoto, Ryo Sakamoto, Masato Ito, Ayuko Kitajou, Shigeto Okada, Effect of Concentrated Electrolyte on Aqueous Sodium-ion Battery with Sodium Manganese Hexacyanoferrate Cathod, Electrochemistry, 85, 4, 179-185, 2017.04, コストや安全性の観点から、水系のナトリウムイオン電池は大規模なエネルギー貯蔵のための魅力的な候補である。水系電池の動作電圧範囲は、水の電気分解により理論的には1.23Vに制限されるが、実際の水系電池システムでは、充放電時の過電圧により電圧制限が若干緩和される。放電電圧の向上を目的として、Na2MnFe(CN)6ヘキサシアノ鉄系正極とNaTi2(PO4)3ナシコン系負極を用いた水系Naイオン電池において、濃縮電解液が動作電圧に及ぼす影響を調べた。サイクリックボルタンメトリーによると、1mol kg-1 NaClO4水系電解液を希釈した場合の電気化学窓は1.9Vしかなく、Na2MnFe(CN)6正極のフレームワークは、希釈された1mol kg-1水系電解液中で発生した水酸化物アニオンによって破壊された。対照的に、17mol kg-1 NaClO4水系電解液を濃縮した場合の電気化学窓は2.8Vに拡大することに成功した。. |
| 7. |
＃Ying-Ching Lu, ＠Chuze Ma, ＠Judith Alvarado, Dimov Nikolay Kirilov, Ying Shirley Meng, Shigeto Okada, Improved electrochemical Performance of Tin-sulfide Anodes fer Sodium-ion Batteries, J. Mater. Chem. A, ３, 16971-16977, 2015.06, スズ硫化物は、その大きな可逆容量のため、LiのみならずNaイオン電池用負極として注目される。Naイオン電池用スズ硫化物負極の電気化学的性能を改善するため、三種の異なるSnS／炭素複合負極をメカニカルミリング法で作製した。充放電過程でのコンバージョンおよび合金化反応機構は、TEMにより明らかにされた。 さらにSnS負極の実現可能性を実証するため、Na3V2（PO4）2F3正極を用いたNaイオンフルセル構成で良好な電池特性が確認された。. |
| 8. |
1．ナトリウムイオン電池における低コスト大容量化の元素戦略. |
| 9. |
Ayuko Kitajyou, Junpei Yamaguchi, Satoshi Hara, Shigeto Okada, Discharge/charge reaction mechanism of a pyrite-type FeS2 cathode for sodium secondary batteries, JOURNAL OF POWER SOURCES, 10.1016/j.jpowsour.2013.08.123, 247, 391-395, 2014.02. |
| 10. |
＃Jie Zhao, ZHAO LI WEI, Kuniko Chihara, Shigeto Okada, Jun-ichi Yamaki, ＠Shingo Matsumoto, ＠Satoru Kuze, ＠Kenji Nakane, Electrochemical and thermal properties of hard carbon-type anodes for Na-ion batteries, J. Power Sources, 10.1016/j.jpowsour.2013.06.109, 244, 752-757, 2013.12. |
| 11. |
＃Jie Zhao, Lewei Zhao, Nikolay Dimov, Shigeto Okada, Tetsuaki Nishida, Electrochemical and Thermal Properties of α-NaFeO2 Cathode for Na-Ion Batteries, J. Electrochem. Soc., 160, A3077-A3081, 2013.04. |
| 12. |
＃Kuniko Chihara, Ayuko Kitajou, Irina D. Gocheva, Shigeto Okada, Jun-ichi Yamaki, Cathode Properties of Na3M2(PO4)2F3 [M = Ti, Fe, V] for Sodium-Ion Batteries, J. Power Sources, 227, 80-85, 2013.02. |
| 13. |
S.-I. Park, I. Gocheva, S. Okada, J. Yamaki, Electrochemical Properties of NaTi2(PO4)3 Anode for Rechargeable Aqueous Sodium-Ion Batteries, J. Electrochem. Soc., 156, 10, A1067-A1070, 2011.09. |
| 14. |
L.S. Plashnitsa, E. Kobayashi, S. Okada, and J. Yamaki, Symmetric lithium-ion cell based on lithium vanadium fluorophosphate with ionic liquid electrolyte, Electrochimica Acta, 56, 1344-1351, 2011.02. |
| 15. |
L.S. Plashnitsa, E. Kobayashi, ＃Y. Noguchi, S. Okada, J. Yamaki, Performance of NASICON Symmetric Cell with Ionic Liquid Electrolyte, J. of the Electrochem. Soc., 10.1149/1.3298903, 157, 4, A536-A543, 2010.01. |
| 16. |
Masatoshi Nagahama, Norifumi Hasegawa, Shigeto Okada, High Voltage Performances of Li2NiPO4F Cathode with Dinitrile-Based Electrolytes, Journal of the Electrochemical Society, 10.1149/1.3417068, 157, 6, A748-A752, 2010.01, A sebaconitrile-based electrolyte, 1 M LiBF4 /ethylene carbonate-dimethyl carbonate -sebaconitrile (25:25:50 by vol %) exhibits excellent electrochemical stability above 6 V against Li/ Li+. To confirm that the electrolyte can work at high voltages, LiFePO4 was intentionally charged at 6 V vs Li/ Li+. After the 6 V charging, the discharge capacity was 137 mAh/g and the coulomb efficiency was 91%. In addition, this oxidation resistant electrolyte was able to prove that Li 2 NiPO4 F has actually ca. 5.3 V redox potential against Li anode through cyclic voltammetry and charge/discharge cycle test.. |
| 17. |
＃M.Nishijima, ＃I.D.Gocheva, T.Doi, S.Okada, J.Yamaki, ＠T.Nishida, Cathode properties of metal trifluorides in Li and Na secondary batteries, J. Power Sources, 10.1016/j.jpowsour.2009.01.051, 190, 2, 558-562, Vol.190, Issue 2, 558-562, 2009.05. |
| 18. |
X.Liu, ＃T.Saito, T.Doi, S.Okada, J.Yamaki, Electrochemical properties of rechargeable aqueous lithium ion batteries with an olivine-type cathode and a Nasicon-type anode, J. Power Sources, 10.1016/j.jpowsour.2008.08.050, 189, 1, 706-710, 2009.04. |
| 19. |
＃I.D.Gocheva, ＃M.Nishijima, T.Doi, S.Okada, J.Yamaki, ＠T.Nishida, Mechanochemical synthesis of NaMF3 (M = Fe, Mn, Ni) and their electrochemical properties as positive electrode materials for sodium batteries, J. Power Sources, 187, 1, 247-252, 187(1), 247-252, 2009.02. |
| 20. |
T. Shiratsuchi, S. Okada, T. Doi, J. Yamaki, Cathodic Performance of LiMn1-xMxPO4(M = Ti, Mg and Zr) Annealed in an Inert Atmosphere, Electrochim. Acta,, 54, 11, 3145-3151, 2009.01. |
| 21. |
T. Kawamura, S. Okada, J. Yamaki, Decomposition reaction of LiPF6-based electrolytes for lithium ion cells, J. Power Sources, 10.1016/j.jpowsour.2005.05.084, 156, 2, 547-554, 156(2), 547-554, 2006.06.  |
| 22. |
S. Okada, ＃T. Yamamoto, ＃Y. Okazaki, J. Yamaki, ＠M. Tokunaga, T. Nishida, Cathode Properties of Amorphous and Crystalline FePO4, J. Power Sources, 10.1016/j.jpowsour.2005.03.200, 146, 1-2, 570-574, 146, 570-574, 2005.12. |
| 23. |
S. Okada, ＃M. Ueno, ＃Y. Uebou and J. Yamaki, Fluoride phosphate Li2COPO4F as a high-voltage cathode in Li-ion batteries, J. Power Sources, 10.1016/j.jpowsour.2005.03.149, 146, 1-2, 565-569, 146, 565-569, 2005.08. |
| 24. |
M. Egashira, S. Okada, J. Yamaki, D. A. Dri, F. Bonadies, B. Scrosati, The preparation of quaternary ammonium-based ionic liquid containing a cyano group and its properties in a lithium battery electrolyte, J. Power Sources, 10.1016/j.jpowsour.2004.06.022, 138, 1-2, 240-244, 138, 240-244, 2004.11. |
| 25. |
Yasunori Baba, Shigeto Okada, and Jun-ichi Yamaki, Thermal Stability of LiCoO2 Cathode for Lithium Batteries, Solid State Ionics, 10.1016/S0167-2738(02)00067-X, 148, 3-4, 311-316, 148, 311-316, 2002.06. |
| 26. |
Tetsuya Kawamura, Arihisa Kimura, Minato Egashira, Shigeto Okada, Jun-ichi Yamaki, Thermal stability of alkyl carbonate mixed-solvent electrolytes for lithium ion cells, J. Power Sources, 104, 2, 260-264, 104, 260 - 264, 2002.02. |
| 27. |
S. Okada, ＃S. Sawa, M. Egashira, J. Yamaki, ＠M. Tabuchi, ＠H. Kageyama, ＠T. Konishi, ＠A. Yoshino, Cathode properties of phospho-olivine LiMPO4 for lithium secondary batteries, J. Power Sources, 97-8, 430-432, 97-98 430-432, 2001.07. |
| 28. |
H. Arai, S. Okada, Y. Sakurai, J. Yamaki, Thermal behavior of Li1-yNiO2 and the decomposition mechanism, Solid State Ionics, 109, 3-4, 295-302, 109, 295, 1998.01. |
| 29. |
Hajime Arai, Shigeto Okada, Yoji Sakurai, Jun Ichi Yamaki, Cathode performance and voltage estimation of metal trihalides, Journal of Power Sources, 68, 2, 716-719, 1997.10, Compounds with highly ionic metal-ligand bonds are attractive for use as high voltage cathodes. Therefore, we investigated metal trihalide cathodes, in particular trifluorides (MF3). FeF3 shows a mean discharge voltage and quasi open-circuit voltage (QOCV) of 3.0 and 3.4 V, respectively. X-ray analysis shows that the lithiation reaction proceeds in a topotactic manner. TiF3 and VF3 have mean discharge voltages of 2.5 and 2.2 V, respectively. These three compounds have the same layer structures and almost the same rechargeable capacity of 80 mAh g-1. MnF3, which has a monoclinic lattice, exhibits an initial voltage of 4.2 V, however, lithiation does not proceed due to a high overvoltage. These high voltages indicate the highly ionic nature of MF3 cathodes, and they correspond to values estimated using the standard electrode potentials of the 'naked' ions.. |
| 30. |
Hajime Arai, Shigeto Okada, Yoji Sakurai, Jun Ichi Yamaki, Electrochemical and thermal behavior of LiNi1-zMzO2 (M = Co, Mn, Ti), Journal of the Electrochemical Society, 10.1149/1.1837968, 144, 9, 3117-3125, 1997.09, We report the synthesis and electrochemical properties of highly stoichiometric LiNi1-zMzO2 (M = Co, Mn, Ti, z ≤ 0.3) samples. With the excess lithium method, samples with a well-defined layered structure can be prepared in air. A large rechargeable capacity of about 200 mAh g-1 is obtained for 10% substitutives. Structural changes during charging and lithium ordering phenomena are discussed. We describe the thermal behavior of the substitutives and report the enhanced thermal stability and large rechargeable capacity of the manganese substitutives.. |
| 31. |
A. K. Padhi, K. S. Nanjundaswamy, C. Masquelier, S. Okada, J. B. Goodenough, Effect of structure on the Fe3+/Fe2+ redox couple in iron phosphates, Journal of the Electrochemical Society, 10.1149/1.1837649, 144, 5, 1609-1613, 1997.05, To understand the role of structure on the position of the octahedral Fe3+/Fe2+ redox couple in compounds having the same polyanions, four iron phosphates: Li3Fe2(PO4)3, LiFeP2O7, Fe4(P2O7)3, and LiFePO4 were investigated. They vary in structure as well as in the manner in which the octahedral iron atoms are linked to each other. The Fe3+/Fe2+ redox couple in the above compounds lies at 2.8, 2.9, 3.1, and 3.5 eV, respectively, below the Fermi level of lithium. The reason for the difference in the position of the redox couples is related to changes in the P-O bond lengths as well as to changes in the crystalline electric field at the iron sites.. |
| 32. |
＠Hajime Arai, Shigeto Okada, ＠Yoji Sakurai, Jun Ichi Yamaki, Reversibility of LiNiO2 cathode, Solid State Ionics, 10.1016/s0167-2738(96)00598-x, 95, 3-4, 275-282, 1997.03, LiNiO2 is a promising cathode material for secondary lithium batteries with a reversible capacity of over 200 mAh g-1. However, a low cycle efficiency of about 80% is observed in the first charge-discharge cycle. To explain this irreversibility, we have assumed a model in which part of the cathode domain becomes electrochemically inactive before the first discharging starts, while the rest remains electrochemically active throughout the cycle. By this model, the active domain is shown to have excellent reversibility. The reversibility in the first cycle can be improved by limiting the charge capacity. An application of this model to a LiCoO2 cathode is also described.. |
| 33. |
S. Okada, H. Arai, K. Asakura, Y. Sakurai, J. Yamaki, K. S. Nanjundaswamy, A. K. Padhi, C. Masquelier, J. B. Goodenough, Characteristics of 3D Framework Cathodes with (XO4)n- Polyanions, Progress in Batteries and Battery Materials, １６, ３０２-３０８, 1997.01. |
| 34. |
K. S. Nanjundaswamy, A. K. Padhi, J. B. Goodenough, S. Okada, H. Ohtsuka, H. Arai, J. Yamaki, Synthesis, redox potential evaluation and electrochemical characteristics of NASICON-related-3D framework compounds, Solid State Ionics, 92, 1-2, 1-10, 1996.11, The framework compounds M2(SO4)3 with M = (Ti Fe), (V Fe), Fe and LixM2(PO4)3 with M = Ti, (V Fe), Fe, were synthesized and electrochemically characterized by the coin-cell method. Use of larger (XO4)n- polyanions not only allows fast Li+-ion conduction in an open three-dimensional framework that is selective for the working alkali ion on discharge; it also stabilizes operative redox potentials Fe3+/Fe2+, Ti4+/Ti3+ and V3+/V2+ that give open-circuit voltages Voc > 2.5 Vas well as access to V4+/V3+, Ti3+/Ti2+ and Fe2+/Fe+ couples. Separation of the V4+/V3+ and V3+/V2+ couples were found to be 2.0 V. Fe2(SO4)3 has both monoclinic and rhombohedral modifications that give a flat open-circuit voltage Voc = 3.6 V versus Li and a reversible capacity for ∼ 1.8 lithium atoms per formula unit. LixFe2(SO4)3 shows an abrupt voltage drop occurring for x > 2 that can be held in check by the addition of buffers such as Li3Fe2(PO4)3, FeV(SO4)3 and LiTi2(PO4)3. Changing the polyanion group from (SO4)2- to (PO4)3- in these framework compounds decreases the redox potentials from 3.2 to 2.5 V for the Ti4+/Ti3+ couple, 2.5 to 1.7 V for the V3+/V2+ couple and 3.6 to 2.8 V for the Fe3+/Fe2+ couple. Comparative advantages and disadvantages of framework cathodes for Li rechargeable battery applications are discussed.. |
| 35. |
Takahisa Shodai, Shigeto Okada, Shin-Ichi Tobishima, Jun-Ichi Yamaki, Study of Li3-xMxN (M
Co, Ni or Cu) system for use as anode material in lithium rechargeable cells, Solid State Ionics, 10.1016/0167-2738(96)00174-9, 86-88, PART 2, 785-789, 1996.07, We have investigated the Li3-xMxN (M: Co, Ni, or Cu, x = 0.1-0.6) system as an anode material for lithium rechargeable cells. Li metal/Li3-xMxN cells were prepared and the anode properties evaluated galvanostatically. Li2.6Co0.4N exhibits a high specific capacity of 760 mA h/g in the 0.0-1.4 V range. This value is more than twice the theoretical capacity of C6Li (372 mA h/g). The capacity of the Li3-xCoxN system depends on the amount of lithium ions removed during the first extraction. These systems are expected to increase substantially the energy density of lithium rechargeable cells.. |
| 36. |
H. Arai, S. Okada, H. Ohtsuka, M. Ichimura, J. Yamaki, Characterization and cathode performance of Li1 - xNi1 + xO2 prepared with the excess lithium method, Solid State Ionics, 10.1016/0167-2738(95)00144-U, 80, 3-4, 261-269, 1995.09, Samples of Li1 - zNi1 + xO2 with various x values were synthesized and their electrochemical properties, phase transitions, and ordering phenomena were investigated comparatively. In order to synthesize samples with a small x value, an excess lithium was used as a starting material to compensate for lithium loss during the calcination process. A stoichiometric sample with a large reversible capacity of more than 200 mAh g-1 is also described.. |
