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.

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>

Alternative electrochemical energy storage: potassium-based dual-graphite batteries

2017 ◽  
Vol 10 (10) ◽  
pp. 2090-2094 ◽  
Author(s):  
K. Beltrop ◽  
S. Beuker ◽  
A. Heckmann ◽  
M. Winter ◽  
T. Placke
Keyword(s):  
Ionic Liquid ◽  
Energy Storage ◽  
Electrode Material ◽  
Liquid Electrolyte ◽  
Potassium Ion ◽  
Electrochemical Energy Storage ◽  
Ionic Liquid Electrolyte ◽  
First Time ◽  
Electrochemical Energy

In this contribution, we report for the first time a novel potassium ion-based dual-graphite battery concept (K-DGB), applying graphite as the electrode material for both the anode and cathode, in combination with an ionic liquid electrolyte.

scholarly journals Ordered LiNi0.5Mn1.5O4 Cathode in Bis(fluorosulfonyl)imide-Based Ionic Liquid Electrolyte: Importance of the Cathode-Electrolyte Interphase

2020 ◽  
Author(s):  
Hyeon Jeong Lee ◽  
Zachary Brown ◽  
Ying Zhao ◽  
Jack Fawdon ◽  
Weixin Song ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
High Voltage ◽  
Rate Capability ◽  
Lithium Ion ◽  
Cycling Performance ◽  
High Energy ◽  
Liquid Electrolyte ◽  
High Energy Density ◽  
X Ray ◽  
Ionic Liquid Electrolyte

<div><div><div><p>The high voltage (4.7 V vs. Li+ /Li) spinel lithium nickel manganese oxide (LiNi0.5 Mn1.5 O4 , LNMO) is a promising candidate for the next-generation of lithium ion batteries due to its high energy density, low cost and environmental impact. However, poor cycling performance at high cutoff potentials limits its commercialization. Herein, hollow structured LNMO is synergistically paired with an ionic liquid electrolyte, 1M lithium bis(fluorosulfonyl)imide (LiFSI) in N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr1,3 FSI) to achieve stable cycling performance and improved rate capability. The optimized cathode-electrolyte system exhibits extended cycling performance (>85% capacity retention after 300 cycles) and high rate performance (106.2mAhg–1 at 5C) even at an elevated temperature of 65 ◦C. X-ray photoelectron spectroscopy and spatially resolved x-ray fluorescence analyses confirm the formation of a robust, LiF-rich cathode electrolyte interphase. This study presents a comprehensive design strategy to improve the electrochemical performance of high-voltage cathode materials.</p></div></div></div>

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>

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