Highly Conductive Plastic Crystals Based on Fluorohydrogenate Anions

Taniki, Ryosuke; Matsumoto, Kazuhiko; Hagiwara, Rika; Hachiya, Kan; Morinaga, Takashi; Sato, Takaya

doi:10.1021/jp311558h

Cited by 25 publications

(25 citation statements)

References 37 publications

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“…OIPCs demonstrate unique combinations of proper-ties, such as nonflammability, low volatility, plasticity, high electrochemical and thermal stability, and most importantly high ionic conductivity (up to 10 −2 S cm −1 at 25 °C). 1 These features make OIPCs extremely attractive candidates for electrolytes in electrochemical devices including lithium-ion batteries and solar and fuel cells. 2−7 However, the ion transport properties of different OIPCs, and in different phases of a particular OIPC, can vary dramatically.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic MRI Contrast Reveals Enhanced Ionic Transport in Plastic Crystals

et al. 2014

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Organic ionic plastic crystals (OIPCs) are attractive as solid-state electrolytes for electrochemical devices such as lithium-ion batteries and solar and fuel cells. OIPCs offer high ionic conductivity, nonflammability, and versatility of molecular design. Nevertheless, intrinsic ion transport behavior of OIPCs is not fully understood, and their measured properties depend heavily on thermal history. Solid-state magnetic resonance imaging experiments reveal a striking image contrast anisotropy sensitive to the orientation of grain boundaries in polycrystalline OIPCs. Probing triethyl(methyl)phosphonium bis(fluorosulfonyl)imide (P1222FSI) samples with different thermal history demonstrates vast variations in microcrystallite alignment. Upon slow cooling from the melt, microcrystallites exhibit a preferred orientation throughout the entire sample, leading to an order of magnitude increase in conductivity as probed using impedance spectroscopy. This investigation describes both a new conceptual window and a new characterization method for understanding polycrystalline domain structure and transport in plastic crystals and other solid-state conductors.

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Section: Introductionmentioning

confidence: 99%

Anisotropic MRI Contrast Reveals Enhanced Ionic Transport in Plastic Crystals

et al. 2014

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“…In this region, more DMPyr + cations are present on the surface of the activated carbon electrode than (FH) n Fanions are. As shown in the previous study for DMPyr(FH) 2.0 F IPC, only (FH) n Fworks as a charge carrier in the IPC phase and the long-range migration of DMPyr + cations does not occur[30]. A conceivable explanation about the double-layer formation in this potential region is that (FH) Ag QRE).…”

mentioning

confidence: 59%

All solid-state electrochemical capacitors using N,N-dimethylpyrrolidinium fluorohydrogenate as ionic plastic crystal electrolyte

Taniki

Matsumoto

Hagiwara

2014

Journal of Power Sources

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An electrochemical capacitor using an ionic plastic crystal of N,N-dimethypyrrolidinium fluorohydrogenate (DMPyr(FH) 2 F) as a solid electrolyte has been successfully operated with activated carbon electrodes at 298 K. Typical square-shapes for electric double-layer capacitors are observed in the cyclic voltammogram within the narrow potential regions. In the wide potential regions, the redox reactions involving fluorohydrogenate anions occur on both the positive and negative electrodes. The galvanostatic charge-discharge test confirms stable operation of the electrochemical capacitor using the present ionic plastic crystal. The capacitances of the positive and negative electrodes are 263 and 221 F g-1 (capacitance per gram of electrode weight), respectively, at the 300 th cycle when the cell is charged up to the voltage of 2.5 V with a current density of 238 mA g-1. The ac impedance test shows that ions in the ionic plastic crystal form double-layer between electrolyte and internal surface of the pore of activated carbon. The open-circuit voltage decreases proportionally to the square root of time within the first 10 s after galvanostatic charging, which confirms that the ions in the ionic plastic crystal inhomogeneously distributed in the pore of activated carbon migrate to be homogeneous under a diffusion-limited process.

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“…Although the ionic conductivity of this ionic plastic crystal is 10 −4 mS cm −1 at 333 K in the neat form, it increases up to 2 × 10 −1 mS cm −1 at 333 K by the addition of a lithium salt (5 mol% Li[TFSA]) [97,98] Fluorohydrogenate salts based on some alkylammonium and phosphonium cations form ionic plastic crystals. N,N-dimethylpyrrolidinium and N-ethyl-N-methylpyrrolidinium fluorohydrogenate salts ([C 1 C 1 pyrr][(FH) 2 F] and [C 2 C 1 pyrr][(FH) 2 F]) have ionic plastic crystal phases in the temperature ranges of 258-325 and 236−303 K, respectively [99]. The differential scanning calorimetric curve for [C 1 C 1 pyrr][(FH) 2 F] is shown in Figure 5.11.…”

Section: Fluorohydrogenate Ionic Plastic Crystalsmentioning

confidence: 99%

“…Thus, their crystal structures can be analyzed by X-ray diffraction. X-ray diffraction patterns of the crystal and plastic crystal phases for [C 1 C 1 pyrr][(FH) 2 F] are shown in Figure 5.12 [99]. The ionic plastic crystal phases of [C 1 C 1 pyrr][(FH) 2 lattice of an inverse NiAs-type structure with a = 8.02 Å and c = 11.84 Å, where the larger P 2222 + are hexagonally close packed and the smaller (FH) 2 F − occupies the octahedral interstitial site [34].…”

Section: Fluorohydrogenate Ionic Plastic Crystalsmentioning

confidence: 99%