Solvent molecule mobilities in propylene carbonate-based electrolyte solutions coexisting with fumed oxide nanoparticles

Abstract

Non-aqueous LiClO4 solutions kneaded with various fumed oxides (fumed silica, fumed alumina, and fumed titania) were employed as model systems of lithium ion batteries. The properties of the solid phase and Li + ions, which affect solvent molecules, were evaluated using 1 H NMR spectroscopy and 1 H NMR relaxation time (T1, T2) measurements. The 1 H NMR signals of propylene carbonate (PC) molecules were influenced by the coexisting solid phase in the LiClO4-PC solution/fumed oxide nanoparticle dispersion. The mobilities of the PC molecules drastically decreased in the presence of only 1-2 vol% of the solid phase (liquid phase thickness is 15-20 nm or less), regardless of the fumed oxide employed. In the IR spectra of the PC/fumed alumina systems, the vibrations at higher wavenumbers were predominantly observed because of indirect electron-donation

Conductivity of LiClO₄/PC-DME Solution Impregnated in LiCoO₂ Powder

“…A previous study has reported that the liquid phase near the solid phase is influenced by the solid surface in the solid-liquid mixture. [5][6][7][8] In this study, we measured the electrical conductivity of a sample mixed with LiCoO 2 powder and LiClO 4 solution using propylene carbonate (PC) and 1,2-dimethoxyethane (DME) as solvents (LiClO 4 -PC 1¹x DME x ). Although a system including EC as conventional solvent might be focused, they indicate the simple decreasing of conductivity by adding low viscose solvent, therefore each effect of solvent for conductivity is not distinguish clearly.…”

Why Does ¹H NMR Signal Intensity of Concentrated Aqueous Acids and Bases Decrease Anomalously?

“…3 However, since the resolution of the signal intensity is not very clear when using 14 N qNMR, 1 H qNMR is presently becoming a more popular quantitative technique. [4][5][6][7][8] In qNMR, solutes are generally the analysis targets; using solvents as analysis targets for 1 H qNMR is rare, 9 and only trace amounts of residual solvent in solution can be thus quantified. 10,11 Therefore, the cause of this "anomaly of decreasing 1 H NMR signal intensity" is mostly unknown, although one likely explanation is that the motility of water molecules in the primary hydration shell of metal ions is significantly reduced.…”

“…The gain of the RF amplifier in the NMR spectrometer (i.e., receiver gain) was set to a constant of -10 dB. To avoid inaccuracies in the integrated intensities of the 1 H NMR signals, all 1 H NMR spectral data after the Fourier transform were carefully corrected for the phase and baseline5,6,9,13 using the NMR analysis software Mnova ver.14.2 (Mestrelab…”

Quantitative NMR in Analytical Chemistry

“…For example, chemical species that exist inside or near polymer compounds, such as solid-liquid interfaces and proteins, and molecules which strongly solvated to central ions, are often not detected by general solution NMR because their motility is extremely limited. 11,12 Therefore, attempts have started to directly convert the NMR signal intensity into a concentration using a theoretical analysis of the nuclear spin state, or to determine the concentration of an observed chemical species by a calibration curve method using a standard substance. 13 In a broad sense, the current situation is that these attempts are quantitative NMR (qNMR) methods.…”