Novel Na+ Ion Diffusion Mechanism in Mixed Organic–Inorganic Ionic Liquid Electrolyte Leading to High Na+ Transference Number and Stable, High Rate Electrochemical Cycling of Sodium Cells.

2016 ◽  
Vol 120 (8) ◽  
pp. 4276-4286 ◽  
Author(s):  
Maria Forsyth ◽  
Hyungook Yoon ◽  
Fangfang Chen ◽  
Haijin Zhu ◽  
Douglas R. MacFarlane ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Diffusion Mechanism ◽  
Transference Number ◽  
Liquid Electrolyte ◽  
High Rate ◽  
Ion Diffusion ◽  
Ionic Liquid Electrolyte ◽  
Electrochemical Cycling

Transport Anomalies Emerging from Strong Correlation in Ionic Liquid Electrolytes

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Nathan Craig ◽  
Jake Christensen ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Species Interactions ◽  
Clustering Algorithm ◽  
Experimental Studies ◽  
Transference Number ◽  
Liquid Electrolyte ◽  
Total Conductivity ◽  
Single Linkage ◽  
Ionic Liquid Electrolyte ◽  
Dynamics Simulations

<div>Recent works on ionic liquid electrolyte systems motivate the present study of transport regimes where strong species interactions result in significant correlations and deviations from ideal solution behaviour. In order to obtain a complete description of transport in these systems we use rigorous concentrated solution theory coupled with molecular dynamics simulations, beyond the commonly used uncorrelated Nernst-Einstein equation. As a case study, we investigate the NaFSI - Pyr<sub>13</sub>\FSI room temperature ionic liquid electrolyte. When fully accounting for intra- and inter-species correlation, an anomalously low and even negative transference number emerges for NaFSI molar fractions lower than 0.2, emphasising that strong ion-ion coupling in the electrolyte can significantly impact the rate performance of the cell. With increasing concentration the transference number monotonically increases, approaching unity, while the total conductivity decreases as the system transitions to a state resembling a single-ion solid-state electrolyte. The degree of spatial ionic association is explored further by employing a variant of unsupervised single-linkage clustering algorithm. Using this combination of numerical techniques we examine the microscopic mechanisms responsible for the trade-off between key electrolyte transport properties, previously overlooked in both computational and experimental studies.</div>

scholarly journals Insights into Ionic Liquid Electrolyte Transport and Structure via Operando Raman Microspectroscopy

2021 ◽  
Author(s):  
Jack Fawdon ◽  
Gregory Rees ◽  
Fabio La Mantia ◽  
Mauro Pasta
Keyword(s):  
Ionic Liquid ◽  
Rate Capability ◽  
Transference Number ◽  
High Viscosity ◽  
Liquid Electrolyte ◽  
Raman Microspectroscopy ◽  
Concentration Gradients ◽  
Ionic Liquid Electrolyte ◽  
Apparent Diffusion ◽  
First Time

Ionic liquid electrolytes (ILEs) have become popular in various advanced Li-ion battery chemistries because of their high electrochemical and thermal stability, and low volatility. However, due to their relatively high viscosity and poor Li+ diffusion, it is thought large concentration gradients form, reducing their rate capability. Here, we utilised operando Raman microspectroscopy to visualise ILE concentration gradients for the first time. Specifically, using lithium bis(fluorosulfonyl)imide (LiFSI) in N-propyl- N-methylpyrrolidinium FSI, its "apparent" diffusion coefficient, lithium transference number, thermodynamic factor, ionic conductivity and resistance of charge-transfer against lithium metal, were isolated. Furthermore, the analysis of these concentration gradients led to insights into the bulk structure of ILEs, which we propose is composed of large, ordered aggregates.

scholarly journals Modeling Lithium Transport and Electrodeposition in Ionic-Liquid Based Electrolytes

2021 ◽  
Vol 9 ◽  
Author(s):  
Guanchen Li ◽  
Charles W. Monroe
Keyword(s):  
Ionic Liquid ◽  
Electrical Response ◽  
Lithium Ion ◽  
Transference Number ◽  
Liquid Electrolyte ◽  
Double Layers ◽  
Exchange Reactions ◽  
Ionic Liquid Electrolyte ◽  
Mechanical Coupling ◽  
Chemomechanical Coupling

Purely ionic electrolytes—wherein ionic liquids replace neutral solvents—have been proposed to improve lithium-ion-battery performance, on the basis that the unique microscopic characteristics of polarized ionic-liquid/electrode interfaces may improve the selectivity and kinetics of interfacial lithium-exchange reactions. Here we model a “three-ion” ionic-liquid electrolyte, composed of a traditional ionic liquid and a lithium salt with a common anion. Newman's concentrated-solution theory is extended to account for space charging and chemomechanical coupling. We simulate electrolytes in equilibrium and under steady currents. We find that the local conductivity and lithium transference number in the diffuse double layers near interfaces differ considerably from their bulk values. The mechanical coupling causes ion size to play a crucial role in the interface's electrical response. Interfacial kinetics and surface charge on the electrodes both affect the apparent transport properties of purely ionic electrolytes near interfaces. Larger ionic-liquid cations and anions may facilitate interfacial lithium-exchange kinetics.

Transport Anomalies Emerging from Strong Correlation in Ionic Liquid Electrolytes

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Nathan Craig ◽  
Jake Christensen ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Species Interactions ◽  
Clustering Algorithm ◽  
Experimental Studies ◽  
Transference Number ◽  
Liquid Electrolyte ◽  
Total Conductivity ◽  
Single Linkage ◽  
Ionic Liquid Electrolyte ◽  
Dynamics Simulations

<div>Recent works on ionic liquid electrolyte systems motivate the present study of transport regimes where strong species interactions result in significant correlations and deviations from ideal solution behaviour. In order to obtain a complete description of transport in these systems we use rigorous concentrated solution theory coupled with molecular dynamics simulations, beyond the commonly used uncorrelated Nernst-Einstein equation. As a case study, we investigate the NaFSI - Pyr<sub>13</sub>\FSI room temperature ionic liquid electrolyte. When fully accounting for intra- and inter-species correlation, an anomalously low and even negative transference number emerges for NaFSI molar fractions lower than 0.2, emphasising that strong ion-ion coupling in the electrolyte can significantly impact the rate performance of the cell. With increasing concentration the transference number monotonically increases, approaching unity, while the total conductivity decreases as the system transitions to a state resembling a single-ion solid-state electrolyte. The degree of spatial ionic association is explored further by employing a variant of unsupervised single-linkage clustering algorithm. Using this combination of numerical techniques we examine the microscopic mechanisms responsible for the trade-off between key electrolyte transport properties, previously overlooked in both computational and experimental studies.</div>

Capacitive Performance of Ordered Mesoporous Carbons in Ionic Liquids

2011 ◽  
Vol 284-286 ◽  
pp. 2086-2089 ◽  
Author(s):  
Jin Zhou ◽  
Shu Ping Zhuo
Keyword(s):  
Ionic Liquid ◽  
Liquid Electrolyte ◽  
Mesoporous Carbons ◽  
Ion Diffusion ◽  
Ordered Mesoporous Carbons ◽  
Templating Method ◽  
Capacitive Performance ◽  
Ionic Liquid Electrolyte ◽  
Ordered Mesoporous ◽  
Surface Chemical Property

Ordered mesoporous carbons (BOMC) were prepared by doping boric acid using a hard-templating method, while a CMK-3 carbon (OMC) was also prepared for comparison. The capacitive performance of these two carbons was investigated in ionic liquid of EMImBF4 and EMImTSFI. As demonstrated by the structure analysis, BOMC possesses almost same surface area and pore size as OMC, while the former carbon possesses higher content of oxygen-containing groups. In ionic liquid electrolyte, the carbons mainly show typical electric double layer capacitance, and the capacitance retention ratio and ion diffusion of electrolyte is determined to the surface chemical property. BOMC present visible pseudo-capacitance due to the oxygenated groups in hydrophilic EMImBF4, while no visible pseudo-capacitive behavior was observed in hydrophobic EMImTSFI.

Enhanced Ion Transport in an Ether Aided Super Concentrated Ionic Liquid Electrolyte for Long-Life Practical Lithium Metal Battery Applications

2020 ◽  
Author(s):  
Urbi Pal ◽  
Fangfang Chen ◽  
Derick Gyabang ◽  
Thushan Pathirana ◽  
Binayak Roy ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Ion Transport ◽  
Current Density ◽  
Coulombic Efficiency ◽  
High Energy ◽  
Liquid Electrolyte ◽  
High Mass ◽  
Lithium Metal ◽  
Ionic Liquid Electrolyte ◽  
Lithium Metal Battery

We explore a novel ether aided superconcentrated ionic liquid electrolyte; a combination of ionic liquid, <i>N</i>-propyl-<i>N</i>-methylpyrrolidinium bis(fluorosulfonyl)imide (C<sub>3</sub>mpyrFSI) and ether solvent, <i>1,2</i> dimethoxy ethane (DME) with 3.2 mol/kg LiFSI salt, which offers an alternative ion-transport mechanism and improves the overall fluidity of the electrolyte. The molecular dynamics (MD) study reveals that the coordination environment of lithium in the ether aided ionic liquid system offers a coexistence of both the ether DME and FSI anion simultaneously and the absence of ‘free’, uncoordinated DME solvent. These structures lead to very fast kinetics and improved current density for lithium deposition-dissolution processes. Hence the electrolyte is used in a lithium metal battery against a high mass loading (~12 mg/cm<sup>2</sup>) LFP cathode which was cycled at a relatively high current rate of 1mA/cm<sup>2</sup> for 350 cycles without capacity fading and offered an overall coulombic efficiency of >99.8 %. Additionally, the rate performance demonstrated that this electrolyte is capable of passing current density as high as 7mA/cm<sup>2</sup> without any electrolytic decomposition and offers a superior capacity retention. We have also demonstrated an ‘anode free’ LFP-Cu cell which was cycled over 50 cycles and achieved an average coulombic efficiency of 98.74%. The coordination chemistry and (electro)chemical understanding as well as the excellent cycling stability collectively leads toward a breakthrough in realizing the practical applicability of this ether aided ionic liquid electrolytes in lithium metal battery applications, while delivering high energy density in a prototype cell.

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