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233 results on '"Yoshizawa‐Fujita, Masahiro"'

3. Phase transition and ionic conductivity of pyrrolidinium-based ionic plastic crystals with magnesium salts.

Author

Hirotsu, Yoshifumi, Sekiguchi, Ryotaro, Takeoka, Yuko, Rikukawa, Masahiro, and Yoshizawa-Fujita, Masahiro

Subjects
IONIC conductivity, PLASTIC crystals, MAGNESIUM salts, SOLID electrolytes, ELECTROCHEMISTRY
Abstract

Despite being safe for use in secondary Mg batteries, solid electrolytes exhibit lower ionic conductivities than those of traditional liquid electrolytes. Organic ionic plastic crystals—soft crystals with excellent thermal and electrochemical stabilities and ionic conductivities—are promising solid electrolytes. Herein, we investigated the effects of various anion species and Mg salt concentrations on the properties of pyrrolidinium-based organic ionic plastic crystals (N , N -diethylpyrrolidinium bis(fluorosulfonyl)amide [[C2epyr][FSA]] and N , N -diethylpyrrolidinium bis(trifluoromethylsulfonyl)amide [[C2epyr][TFSA]]) upon Mg(TFSA)2 addition. The Mg-ion transference number (t Mg2 + ) was measured using the Vincent–Bruce method; ionic conductivity via impedance measurements; and phase transition via differential scanning calorimetry. The phase transition behavior, dissociation state of the Mg salt, and electrochemical properties varied with the organic ionic plastic crystal anionic structure. The FSA system became liquid when the Mg salt concentration exceeded 15 mol%. The ionic conductivity of the pyrrolidinium-based organic ionic plastic crystals increased substantially with the Mg salt concentration. In the solid state, [C2epyr][FSA]/Mg(TFSA)2 (5 mol%) (FT5) showed the highest ionic conductivity (2.9 × 10−4 S cm−1 at 25 °C). The t Mg2 + of FT5 at 60 °C was 0.29. Mg exhibited redox behavior in FT5 but not in [C2epyr][TFSA]/Mg(TFSA)2 (5 mol%). The FSA− structure is suitable for Mg electrochemistry and will aid in developing high-performance secondary Mg batteries. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Extraction and Isolation of Natural Organic Compounds from Plant Leaves Using Ionic Liquids

Author

Usuki, Toyonobu, Yoshizawa-Fujita, Masahiro, Scheper, Thomas, Series Editor, Belkin, Shimshon, Editorial Board Member, Bley, Thomas, Editorial Board Member, Bohlmann, Jörg, Editorial Board Member, Gu, Man Bock, Editorial Board Member, Hu, Wei-Shou, Editorial Board Member, Mattiasson, Bo, Editorial Board Member, Nielsen, Jens, Editorial Board Member, Seitz, Harald, Editorial Board Member, Ulber, Roland, Editorial Board Member, Zeng, An-Ping, Editorial Board Member, Zhong, Jian-Jiang, Editorial Board Member, Zhou, Weichang, Editorial Board Member, Itoh, Toshiyuki, editor, and Koo, Yoon-Mo, editor

Published
2019
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23. Improving the Electrochemical Stability of a Polyester-Polycarbonate Solid Polymer Electrolyte by Zwitterionic Additives

Author

Johansson, Isabell, Sångeland, Christofer, Uemiya, Tamao, Iwasaki, Fumito, Yoshizawa-Fujita, Masahiro, Brandell, Daniel, Mindemark, Jonas, Johansson, Isabell, Sångeland, Christofer, Uemiya, Tamao, Iwasaki, Fumito, Yoshizawa-Fujita, Masahiro, Brandell, Daniel, and Mindemark, Jonas

Abstract

Rechargeable batteries with solid polymer electrolytes (SPEs), Li-metal anodes, and high-voltage cathodes like LiNixMnyCozO2 (NMC) are promising next-generation high-energy-density storage solutions. However, these types of cells typically experience rapid failure during galvanostatic cycling, visible as an incoherent voltage noise during charging. Herein, two imidazolium-based zwitterions, with varied sulfonate-bearing chain length, are added to a poly(epsilon-caprolactone-co-trimethylene carbonate):LiTFSI electrolyte as cycling-enhancing additives to study their effect on the electrochemical stability of the electrolyte and the cycling performance of half-cells with NMC cathodes. The oxidative stability is studied with two different voltammetric methods using cells with inert working electrodes: the commonly used cyclic voltammetry and staircase voltammetry. The specific effects of the NMC cathode on the electrolyte stability is moreover investigated with cutoff increase cell cycling (CICC) to study the chemical and electrochemical compatibility between the active material and the SPE. Zwitterionic additives proved to enhance the electrochemical stability of the SPE and to facilitate improved galvanostatic cycling stability in half-cells with NMC by preventing the decomposition of LiTFSI at the polymer-cathode interface, as indicated by X-ray photoelectron spectroscopy (XPS).

Published
2022
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32. Heterogeneous dynamics of diffusive motion in organic ionic plastic crystal studied using spin–spin relaxation time: N,N-diethylpyrrolidinium bis(fluorosulfonyl)amide

Author

Nishikawa, Keiko, Fujii, Kozo, Matsumoto, Kazuhiko, Abe, Hiroshi, and Yoshizawa-Fujita, Masahiro

Abstract

The temperature dependences of the spin–spin relaxation times (T2) of 1H and 19F nuclei were measured for N,N-diethylpyrrolidinium bis(fluorosulfonyl)amide with a plastic crystal phase. In the plastic crystal phase, 2 types of T2were observed in both 1H and 19F experiments, which were considered to be the appearance of heterogeneous dynamics of diffusive motion. By examining temperature dependences of the T2values and the existence ratios, the following conclusions were reached. (i) The prepared plastic crystal sample was in a polycrystalline state, and each crystallite comprised 2 phases: the core phase (plastic crystal phase) and the surface phase formed to relieve surface stress. (ii) The 1H-T2(19F-T2) values of the 2 phases differed, and ions in the surface phase were more mobile. The 1H-T2(19F-T2) values for the 2 phases increased with temperature rise. In particular, the 1H-T2(19F-T2) values of the surface phase were smoothly connected to the liquid T2values. (iii) The cations and anions exhibited a cooperative diffusive motion. (iv) When the temperature was considerably lower than the melting point, the ratio of the surface phase did not significantly differ from when it first formed. However, it rapidly increased near the melting point and became liquid.Graphical AbstractFree induction decay signal of 1H-NMR for N,N-diethylpyrrolidinium bis(fluorosulfonyl)amide, [C2epyr][FSA], at 390 K. The chart shows that there are 2 types of diffusive motion of the [C2epyr]+cations, namely, a hard component (green curve, ratio 0.844) and a soft component (orange curve, ratio 0.156).

Published
2024
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33. Polyketones as Host Materials for Solid Polymer Electrolytes

Author

Eriksson, Therese, Mace, Amber, Manabe, Yumehiro, Yoshizawa-Fujita, Masahiro, Inokuma, Yasuhide, Brandell, Daniel, Mindemark, Jonas, Eriksson, Therese, Mace, Amber, Manabe, Yumehiro, Yoshizawa-Fujita, Masahiro, Inokuma, Yasuhide, Brandell, Daniel, and Mindemark, Jonas

Abstract

While solid polymer electrolytes (SPEs) have great potential for use in future lithium-based batteries, they do, however, not display conductivity at a sufficient level as compared to liquid electrolytes. To reach the needed requirements of lithium batteries it is therefore necessary to explore new materials classes to serve as novel polymer hosts. In this work, SPEs based on the polyketone poly(3,3-dimethylpentane-2,4-dione) were investigated. Polyketones are structurally similar to several polycarbonate and polyester SPE hosts investigated before but have, due to the lack of additional oxygen atoms in the coordinating motif, even more electronwithdrawing carbonyl groups and could therefore display better properties for coordination to the salt cation. In electrolyte compositions comprising 25-40 wt% LiTFSI salt, it was observed that this polyketone indeed conducts lithium ions with a high cation transference number, but that the ionic conductivity is limited by the semi-crystallinity of the polymer matrix. The crystallinity decreases with increasing salt content, and a fully amorphous SPE can be produced at 40 wt% salt, accompanied by an ionic conductivity of 3 x 10(-7) S cm(-1) at 32 degrees C. This opens up for further exploration of polyketone systems for SPE-based batteries.

Published
2020
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43. Ion Conductive Behavior of Oligoether/Zwitterion Diblock Copolymers Containing Magnesium Salt.

Author

Yoshizawa‐Fujita, Masahiro, Ota, Ryoma, Ishii, Jun, Takeoka, Yuko, and Rikukawa, Masahiro

Subjects
*ZWITTERIONS, *DIBLOCK copolymers, *MAGNESIUM salts, *POLYELECTROLYTES, *GLASS transition temperature, *ATOMIC force microscopes, *SOLID electrolytes, *IONIC conductivity
Abstract

Rechargeable magnesium (Mg) batteries are envisioned as next generation batteries. The development of solid polymer electrolytes with high ionic conductivity will contribute to realize not only high performance Mg batteries but also reliable and safe devices. In this study, diblock copolymers (PPEGMAm‐b‐SPBn) with oligoether (PEGMA) and zwitterionic (SPB) side‐chains are synthesized in order to develop novel Mg‐ion electrolytes. PPEGMAm‐b‐SPBn copolymers with various unit ratios are synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization. PPEGMAm‐b‐SPBn exhibited two distinct glass transition temperatures. Phase‐separated structures are observed by atomic force microscope (AFM) measurements. PPEGMAm‐b‐SPBn/Mg‐salt composites exhibited a glass transition temperature due to the mixture formation of PEGMA and SPB blocks. When the unit numbers of m and n are 44 and 75, respectively, PPEGMAm‐b‐SPBn/Mg‐salt ([EO]: [Mg] = 6: 1) exhibits the highest ionic conductivity of over 10−4 S cm−1 at 60 °C among 11 composites prepared in this study. [ABSTRACT FROM AUTHOR]

Published
2022
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