Magnetic resonance imaging: an innovative approach to observe rare metal extraction using ionic liquid.

In the present work, a novel approach has been made to evaluate the extraction mechanism of neodymium (Nd) using trihexyl-tetradecyl-phosphonium benzoate (TTPB) ionic liquid through nuclear magnetic resonance (NMR) techniques. A detailed study on the interactions between the extractant (Nd) and the ionic liquid (IL) is presented. The 1H NMR spectral analysis confirmed that Nd extraction took place through the benzoate anion. Furthermore, the NMR relaxation time of the anion is greatly affected affirming that Nd extraction indeed took place through the benzoate anion. This change in the relaxation time caused by the Nd ion on the protons in the anion and cation in TTPB has been used to visualize the extraction mechanism using 1H MRI. A strong change in the image intensity with respect to the time observed in the IL phase validates the extraction of Nd from the aqueous phase into the IL phase. Also, combining the 1H NMR, diffusion coefficient, Karl-Fischer and ultraviolet-visible absorption spectroscopic (UV-Vis) results, we have elucidated the co-ordination structure around Nd during the extraction process.

Understanding Ion Dynamics in Closoborate-Type Lithium-Ion Conductors on Different Time-Scales.

The lithium-ion transport mechanism in 0.7Li(CB9H10)-0.3Li(CB11H12) complex hydride solid electrolyte was studied over a wide time-scale (ns-ms) by choosing appropriate techniques for assessing ionic motion on the desired time-scale using nuclear magnetic resonance (NMR) relaxation, AC impedance, and pulsed field gradient-NMR (PFG-NMR) measurements. The 7Li NMR line width decreased with increasing temperature, and the spin-lattice relaxation time T1 for the cation and anions showed a minimum near 303 K, indicating that the lithium ions and the anions were highly mobile. The activation energy estimated from the analysis of the NMR relaxation time matched well with the values estimated from the AC impedance and PFG-NMR. This confirms that the lithium-ion motion in 0.7Li(CB9H10)-0.3Li(CB11H12) is the same over a wide time-scale, suggesting steady Li-ion motion over a wide transport range. This understanding offers insights into strategies for designing complex hydride lithium superionic conductors.

Effect of vinylene carbonate on SEI formation on LiMn2O4 in carbonate-based electrolytes.

Spinel LiMn2O4 (LMO) is a well-known cathode material for lithium-ion batteries. In order to elucidate the molecular mechanism of the solid electrolyte interface (SEI) formation and the effect of an additive, vinylene carbonate (VC), we systematically studied the spontaneous and electrochemical reactions of solvents and a salt (LiPF6) in electrolytes with LMO in the absence and presence of VC. X-ray photoelectron spectroscopy (XPS) results of the LMO surfaces after soaking in the electrolyte solutions showed that the carbonate solvents as well as VC spontaneously decomposed on the LMO surfaces to form new compounds, such as alcohols, ethers, and carboxylates. The ratio of the produced LiF to MnF2 was similar for both with and without VC. Considering these spontaneously formed initial SEI components, we then investigated the variation of the SEI compositions during the initial electrochemical process until 3.8 V vs. Li+/Li. The role of the additive was studied and found that the electrochemical reaction of VC produced more organic compounds and led to an increase in the LiF/MnF2 ratio of the SEI layer. Based on the hard and soft acid and base theory, we proposed the mechanisms of the SEI formation via spontaneous and electrochemical reactions on the LMO thin film cathode with and without VC.

Measurement of the diffusion of multiple nuclei in restricted spaces by pulsed field gradient NMR.

In this study, the restricted diffusion of a solvent, anion, and cation in an electrolyte solution was measured by pulsed field gradient (PFG) NMR for 1H, 19F, and 7Li nuclei. Further, the time dependences of the diffusion coefficients were measured for a 1 M LiPF6 electrolyte solution in porous polyethylene, which has pores with sizes of tens of micrometers. The decreasing ratio of the diffusion coefficients of the solvent, cation, and anion based on the diffusion time can be scaled similarly for each diffusion distance. The experimentally obtained time dependences of the diffusion coefficients of the solvent, anion, and cation agreed with the results of the analytical equation with the same structural parameters. Furthermore, the abovementioned experimental results were produced via Monte Carlo simulation in the same model-restricted structure for the solvent, anion, and cation. Based on PFG-NMR, it can be concluded that the solvent, anion, and cation exhibit the same restricted diffusion behavior in polyethylene pores measuring tens of micrometers. It was confirmed that measuring the time dependences of the diffusion coefficients via PFG-NMR with multiple nuclei is effective for studying the diffusion mechanisms of electrolyte solutions in restricted spaces.

Tracer diffusion coefficients of Li+ ions in c-axis oriented LixCoO2 thin films measured by secondary ion mass spectrometry.

Lithium diffusion is a key factor in determining the charge/discharge rate of Li-ion batteries. Herein, we study the tracer diffusion coefficient (D*) of lithium ions in the c-axis oriented LiCoO2 thin film using secondary ion mass spectrometry (SIMS). We applied a step-isotope-exchange method to determine D* in the Li-extracted LixCoO2. The observed values of D* ranged from 2 × 10-12 to 3 × 10-17 cm2 s-1 depending on the compositions in the range of 0.4 < x < 1.0. Approaching the stoichiometric composition (x = 1.0), D* decreases steeply to the minimum, which can be explained by the vacancy diffusion mechanism. Electrochemically determined diffusion coefficients corrected by thermodynamic factors are found to be in good agreement with D* determined by our method, over a wide range of compositions. The c-axis diffusion was explained by the migration of Li+ ions from one layer to another through additional diffusion channels, such as antiphase boundaries and a pair of Li antisite and oxygen vacancies in cobalt oxide layers.

A complex hydride lithium superionic conductor for high-energy-density all-solid-state lithium metal batteries.

All-solid-state batteries incorporating lithium metal anode have the potential to address the energy density issues of conventional lithium-ion batteries that use flammable organic liquid electrolytes and low-capacity carbonaceous anodes. However, they suffer from high lithium ion transfer resistance, mainly due to the instability of the solid electrolytes against lithium metal, limiting their use in practical cells. Here, we report a complex hydride lithium superionic conductor, 0.7Li(CB9H10)-0.3Li(CB11H12), with excellent stability against lithium metal and a high conductivity of 6.7 × 10-3 S cm-1 at 25 °C. This complex hydride exhibits stable lithium plating/stripping reaction with negligible interfacial resistance (<1 Ω cm2) at 0.2 mA cm-2, enabling all-solid-state lithium-sulfur batteries with high energy density (>2500 Wh kg-1) at a high current density of 5016 mA g-1. The present study opens up an unexplored research area in the field of solid electrolyte materials, contributing to the development of high-energy-density batteries.

Electrochemically Synthesized Tin/Lithium Alloy To Convert Laser Light to Extreme Ultraviolet Light.

This paper describes lithium-tin alloys as a novel target material to enhance the efficiency of 13.5 nm extreme ultraviolet (EUV) light from generated laser-produced plasmas. Both lithium and tin exhibit EUV emission with the same peak at 13.5 nm. We show that lithium-tin (LiSn) alloys exhibit emission also at 13.5 nm and a mixture of tin and lithium emission by illuminating Nd:YAG laser (1 ns, 2.5 × 1010, 7.1 × 1010 W/cm2). The emission spectra and emission angular distribution by using phosphor imaging plates were analyzed to obtain the conversion efficiency from laser light to 13.5 nm light. The Li-Sn alloys were slightly higher than planar tin and between tin and lithium. It would be due to the suppression of self-absorption of 13.5 nm light by the tin plasma.

Structural change of NaO1/2-WO3-NbO5/2-LaO3/2-PO5/2 glass induced by electrochemical substitution of sodium ions with protons.

Structural changes of 35NaO1/2-1WO3-8NbO5/2-5LaO3/2-51PO5/2 glass (1W-glass) before and after the electrochemical substitution of sodium ions with protons by alkali-proton substitution (APS) are studied by Raman and (31)P magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopies. The glass before APS consists of (PO3(-))8.6(P2O7(4-)) chains on average and the terminal Q(1) units (-O-PO3(3-)) are bound to MO6 octahedra (M denotes niobium or tungsten) through P-O-M bonds. Some non-bridging oxygens (NBOs) in the MO6 octahedra are present in addition to the bridging oxygens (BOs) in P-O-M bonds. APS induces fragmentation of the phosphate chains because the average chain length decreases to (PO3(-))3.7(P2O7(4-)) after APS, despite the total number of modifier cations of sodium and lanthanum ions and protons being unaffected by APS. This fragmentation is induced by some of the NBOs in the MO6 octahedra before APS, changing to BOs of the newly formed M-O-P bonds after APS, because of the preferential formation of P-OH bonds over M-OH ones in the present glass. We show that APS under the conditions used here is not a simple substitution of sodium ions with protons, but it is accompanied by the structural relaxation of the glass to stabilize the injected protons.

Lithium ion diffusion in Li ß-alumina single crystals measured by pulsed field gradient NMR spectroscopy.

The lithium ion diffusion coefficient of a 93% Li ß-alumina single crystal was measured for the first time using pulsed field gradient (PFG) NMR spectroscopy with two different crystal orientations. The diffusion coefficient was found to be 1.2 × 10(-11) m(2)/s in the direction perpendicular to the c axis at room temperature. The Li ion diffusion coefficient along the c axis direction was found to be very small (6.4 × 10(-13) m(2)/s at 333 K), which suggests that the macroscopic diffusion of the Li ion in the ß-alumina crystal is mainly two-dimensional. The diffusion coefficient for the same sample was also estimated using NMR line narrowing data and impedance measurements. The impedance data show reasonable agreement with PFG-NMR data, while the line narrowing measurements provided a lower value for the diffusion coefficient. Line narrowing measurements also provided a relatively low value for the activation energy and pre-exponential factor. The temperature dependent diffusion coefficient was obtained in the temperature range 297-333 K by PFG-NMR, from which the activation energy for diffusion of the Li ion was estimated. The activation energy obtained by PFG-NMR was smaller than that obtained by impedance measurements, which suggests that thermally activated defect formation energy exists for 93% Li ß-alumina single crystals. The diffusion time dependence of the diffusion coefficient was observed for the Li ion in the 93% Li ß-alumina single crystal by means of PFG-NMR experiments. Motion of Li ion in fractal dimension might be a possible explanation for the observed diffusion time dependence of the diffusion coefficient in the 93% Li ß-alumina system.