Effect of anion identity on ion association and dynamics of sodium ions in non-aqueous glyme based electrolytes—OTf vs TFSI

Li, Ke; Don, Visal Subasinghege; Gupta, Chris S.; David, Rolf; Kumar, Revati

doi:10.1063/5.0046073

Cited by 14 publications

(20 citation statements)

References 71 publications

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“…The decrease in diffusion coefficients for ions and diglyme at higher concentration of NaPF 6 /diglyme can be attributed to the strong interaction of diglyme and sodium ions and higher viscosity in the concentrated electrolyte, which restricts the diffusive motion of ions. These results are consistent with the previous findings of Kumar and coworkers ,, where the authors showed that an increase in the concentration of the salt and the length of the glyme chain leads to reduced diffusion coefficients.…”

Section: Results and Discussionsupporting

confidence: 93%

Effect of Concentration and Temperature on the Structure and Ion Transport in Diglyme-Based Sodium-Ion Electrolyte

et al. 2022

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Glyme-based sodium electrolytes show excellent electrochemical properties and good chemical and thermal stability compared with existing carbonate-based battery electrolytes. In this investigation, we perform classical molecular dynamics (MD) simulations to examine the effect of concentration and temperature on ion−ion interactions and ion− solvent interactions via radial distribution functions (RDFs), mean residence time, ion cluster analysis, diffusion coefficients, and ionic conductivity in sodium hexafluorophosphate (NaPF 6 ) salt in diglyme mixtures. The results from MD simulations show the following trends with concentration and temperature: The Na + ---O(diglyme) interactions increase with concentration and decrease with temperature, while the Na + ---F(PF 6 − ) interactions increase with concentration and temperature. The mean residence time suggests that Na + ---O(diglyme) are significantly longer lived compared with that of Na + ---F(PF 6 − ) and H (diglyme)---F(PF 6 − ), which shows the affinity of diglyme to the Na + ions. The ion cluster analysis suggests that the Na + ions largely exist as solvated ions (coordinated to diglyme molecules), whereas some fractions exist as contact-ion pairs, and negligible fractions as aggregated ion pairs, with the latter two increasing slightly with temperature and more with ion concentration. The magnitude of the diffusion coefficients of Na + and PF 6 − ions decreases with concentration and increases with temperature, where the Na + ion has slightly lower mobility compared with the PF 6 − anion. The simulated total ionic conductivities show qualitative trends comparable to experimental data and highlight the need for the inclusion of ion−ion correlations in the Nernst−Einstein equation, especially at higher concentrations and lower temperatures.

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Section: Results and Discussionsupporting

confidence: 93%

Effect of Concentration and Temperature on the Structure and Ion Transport in Diglyme-Based Sodium-Ion Electrolyte

et al. 2022

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“…The ionic transport and corresponding mechanisms are intensively dependent on the electrolyte structures because the cation− solvent, cation−anion, and plausible anion−solvent interactions determine the exchanging behaviors of Li + -coordinated species. 397,398 Weak and strong cation−solvent interactions are beneficial to vehicular and structural diffusions, respectively. Considering the high correlation between solvation structures and ionic transport, factors relevant to solvation structures also influence ionic transport.…”

Section: Ionic Transportmentioning

confidence: 99%

Applying Classical, Ab Initio, and Machine-Learning Molecular Dynamics Simulations to the Liquid Electrolyte for Rechargeable Batteries

et al. 2022

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Rechargeable batteries have become indispensable implements in our daily life and are considered a promising technology to construct sustainable energy systems in the future. The liquid electrolyte is one of the most important parts of a battery and is extremely critical in stabilizing the electrode–electrolyte interfaces and constructing safe and long-life-span batteries. Tremendous efforts have been devoted to developing new electrolyte solvents, salts, additives, and recipes, where molecular dynamics (MD) simulations play an increasingly important role in exploring electrolyte structures, physicochemical properties such as ionic conductivity, and interfacial reaction mechanisms. This review affords an overview of applying MD simulations in the study of liquid electrolytes for rechargeable batteries. First, the fundamentals and recent theoretical progress in three-class MD simulations are summarized, including classical, ab initio, and machine-learning MD simulations (section 2). Next, the application of MD simulations to the exploration of liquid electrolytes, including probing bulk and interfacial structures (section 3), deriving macroscopic properties such as ionic conductivity and dielectric constant of electrolytes (section 4), and revealing the electrode–electrolyte interfacial reaction mechanisms (section 5), are sequentially presented. Finally, a general conclusion and an insightful perspective on current challenges and future directions in applying MD simulations to liquid electrolytes are provided. Machine-learning technologies are highlighted to figure out these challenging issues facing MD simulations and electrolyte research and promote the rational design of advanced electrolytes for next-generation rechargeable batteries.

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“…However, the larger ionic size and greater atomic mass of Na vis-a-vis Li severely restrict the energy density of Na-based systems. 3 An important research area for enhancing the performance of NIBs involves electrolyte design, which governs the overall performance of the device with its properties such as ionic conductivity, electronic resistance, chemical/electrochemical stability, thickness, etc. 4 A large variety of liquid/solid/ polymeric electrolytes has been employed in NIBs, which have different merits and demerits.…”

Section: Introductionmentioning

confidence: 99%

“…5−7 In recent years, etherbased solvents such as glymes have gained much focus. 3 Glymes are basically polar aprotic saturated polyethers with a chemical formula of CH 3 (CH 2 CH 2 O) n OCH 3 [n = 1, 2, 3, etc. ], e.g., monoglyme (G1), diglyme (G2), triglyme (G3), etc.…”

Section: Introductionmentioning

confidence: 99%

“…Glymes can chelate metal ions via donation of electron density from oxygen lone-pair electrons. 3 The electron transfer is indicated by increased oxidative stability of glyme−metal complexes. The glyme-based electrolytes are reported to retain much larger capacity during cycling than the carbonate-based electrolytes and have better discharge characteristics.…”

Section: Introductionmentioning

confidence: 99%

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Diglyme-Incorporated Gelled Polymer: An Efficient Quasi-Solid-State Electrolyte for Sodium-Ion Batteries

Parveen

Sehrawat

Hashmi

2021

ACS Appl. Energy Mater.

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Glyme-based electrolytes have been gaining increasing attention in sodium-ion batteries (NIBs) for their attractive electrochemistry involving good complexation ability with Na-ions, high electrochemical stability, good transport characteristics, low volatility, and high safety. Here, we report a flexible and freestanding sodium-ion conducting gel polymer electrolyte containing an equimolar ratio of Na-salt NaTFSI and diglyme (G2), referred to as a solvate ionic liquid (SIL), immobilized inside host polymer poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP). Fourier-transform infrared (FTIR) and Raman analyses are employed to investigate the conformational evolutions in PVdF-HFP on incorporating G2 and NaTFSI, whereas structural changes are observed using X-ray diffraction. The electrochemical investigations on the electrolyte revealing a wide electrochemical stability window (∼5.2 V) versus Na/Na + , high room-temperature ionic conductivity (∼1.12 × 10 −3 S cm −1 ), and a large Na + transference number (t Na + ∼ 0.58) along with thermal stability up to ∼100 °C render the electrolyte suitable for Na-storage applications. The Na deposition/extraction tests over a long period indicate excellent cyclic stability of the cells, revealing low and stable polarization with values limited to ±19 mV at a current density of 0.01 mA cm −2 . Further, the prepared solvate ionic liquid-incorporated gel polymer electrolyte (SIL-GPE) is tested in Naion battery cells comprising Na 0.7 CoO 2 cathode using galvanostatic charge−discharge cycling, with a first discharge capacity of ∼91.76 mA h g −1 at a 0.05C rate. Studies indicate a class of gel polymer electrolytes based on solvate ionic liquids, suitable for Nastorage applications.

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Effect of anion identity on ion association and dynamics of sodium ions in non-aqueous glyme based electrolytes—OTf vs TFSI

Cited by 14 publications

References 71 publications

Effect of Concentration and Temperature on the Structure and Ion Transport in Diglyme-Based Sodium-Ion Electrolyte

Effect of Concentration and Temperature on the Structure and Ion Transport in Diglyme-Based Sodium-Ion Electrolyte

Applying Classical, Ab Initio, and Machine-Learning Molecular Dynamics Simulations to the Liquid Electrolyte for Rechargeable Batteries

Diglyme-Incorporated Gelled Polymer: An Efficient Quasi-Solid-State Electrolyte for Sodium-Ion Batteries

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