Ion Mobilities, Transference Numbers, and Inverse Haven Ratios of Polymeric Ionic Liquids

Zhang, Zidan; Wheatle, Bill K.; Krajniak, Jakub; Keith, Jordan R.; Ganesan, Venkat

doi:10.1021/acsmacrolett.9b00908

Cited by 52 publications

(88 citation statements)

References 41 publications

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“…As explained above, the b D values neglect ion cross-correlation effects and b D equals b EF only in case there are no interactions between the ions, e.g., in very dilute solutions 14 . Ion cross-correlation effects can be quantified by evaluating diffusion coefficients D ij from the slope of the long time correlated displacements of the species i and j. Zhang et al 24 uses D ij to calculate σ −− , σ ++ , and σ +− , which represent the conductivity contributions arising from the anion-anion, cation-cation, and cation-anion correlated motions, with the total conductivity defined as σ =…”

Section: What Causes a High Conductivity?mentioning

confidence: 99%

“…Using state-of-the-art equilibrium and non-equilibrium computer simulations of molten salts of the general formula LiF α Cl β I γ with α + β + γ = 1 (Table 1), we show that the highest conductivity not necessarily coincides with the highest Li + electrical mobility. Furthermore, the ionic electrical mobilities are investigated by means of non-equilibrium simulations where an external electric field was applied [22][23][24] . Partial conductivities were determined from the partial mobility values; it is challenging to determine these properties experimentally 14,15 and they often are approximated based on diffusion coefficients, which, as shown below, is quantitatively and qualitatively incorrect.…”

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confidence: 99%

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Microscopic origins of conductivity in molten salts unraveled by computer simulations

Walz

Spoel

2021

Commun Chem

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Molten salts are crucial materials in energy applications, such as batteries, thermal energy storage systems or concentrated solar power plants. Still, the determination and interpretation of basic physico-chemical properties like ionic conductivity, mobilities and transference numbers cause debate. Here, we explore a method for determination of ionic electrical mobilities based on non-equilibrium computer simulations. Partial conductivities are then determined as a function of system composition and temperature from simulations of molten LiFαClβIγ (with α + β + γ = 1). High conductivity does not necessarily coincide with high Li+ mobility for molten LiFαClβIγ systems at a given temperature. In salt mixtures, the lighter anions on average drift along with Li+ towards the negative electrode when applying an electric field and only the heavier anions move towards the positive electrode. In conclusion, the microscopic origin of conductivity in molten salts is unraveled here based on accurate ionic electrical mobilities and an analysis of the local structure and kinetics of the materials.

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Section: What Causes a High Conductivity?mentioning

confidence: 99%

mentioning

confidence: 99%

Microscopic origins of conductivity in molten salts unraveled by computer simulations

Walz

Spoel

2021

Commun Chem

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“…Therefore, it is important to stress that even if the suggested chemical structure of the electrolyte assumes this kind of features, one cannot neglect the counter effect of side reactions occurring in the synthetic step, as well as, the exploitation phase structure deterioration processes causing the existence of the mobile anionic charge carriers. Whereas one can easily find publications neglecting the importance of this factor for the battery performance [ 38 ] the majority of authors correlate these two phenomena upon both theoretical analysis performed in a system [ 39 , 40 ] and molecular scale [ 41 , 42 , 43 , 44 , 45 ] as well as, the results of the experimental investigations [ 46 , 47 ].…”

Section: Introductionmentioning

confidence: 99%

Transference Number Determination in Poor-Dissociated Low Dielectric Constant Lithium and Protonic Electrolytes

et al. 2021

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Whereas the major potential of the development of lithium-based cells is commonly attributed to the use of solid polymer electrolytes (SPE) to replace liquid ones, the possibilities of the improvement of the applicability of the fuel cell is often attributed to the novel electrolytic materials belonging to various structural families. In both cases, the transport properties of the electrolytes significantly affect the operational parameters of the galvanic and fuel cells incorporating them. Amongst them, the transference number (TN) of the electrochemically active species (usually cations) is, on the one hand, one of the most significant descriptors of the resulting cell operational efficiency while on the other, despite many years of investigation, it remains the worst definable and determinable material parameter. The paper delivers not only an extensive review of the development of the TN determination methodology but as well tries to show the physicochemical nature of the discrepancies observed between the values determined using various approaches for the same systems of interest. The provided critical review is supported by some original experimental data gathered for composite polymeric systems incorporating both inorganic and organic dispersed phases. It as well explains the physical sense of the negative transference number values resulting from some more elaborated approaches for highly associated systems.

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“…Positive correlations on the other hand can occur in electrolyte solutions and binary salt mixtures where momentum can also be exchanged with solvent molecules or a third ion species. These separate effects have been confirmed in molecular dynamics simulations of salts, electrolyte solutions and polymeric ionic liquids …”

Section: Transport Propertiesmentioning

confidence: 66%

Electrolytes for Lithium (Sodium) Batteries Based on Ionic Liquids: Highlighting the Key Role Played by the Anion

Rüther

Bhatt

Best

et al. 2020

Batteries & Supercaps

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Research since 2000 has clearly shown that ionic liquids (ILs) and their metal salt containing mixtures have good potential to be considered as electrolytes (ILELs) in lithium and other electropositive metal (ion) batteries. This outcome is particularly relevant for the operation of such devices in elevated temperature regimes where ILELs would have a significant advantage over the conventional organic carbonate solvent/LiPF6 electrolytes that, due to their limited thermal stability and flammability, cause concerns about the safety of current LIB technology. There is evidence from a number of review articles that physicochemical properties can be tailored such that ILELs could meet requirements for operating in batteries at lower temperature regimes. By drawing on a broad range of cation/anion combinations, there is further evidence from these papers that within a particular family of cations, the physicochemical properties of ILs and ILELs are largely defined by the anion component. Despite the key role of the anion there are few reviews that have sections dedicated to this aspect. This review surveys the physicochemical, transport and structural properties of ILs (mainly pyrrolidinium salts) and ILELs employing prominent and representative anion classes.

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Ion Mobilities, Transference Numbers, and Inverse Haven Ratios of Polymeric Ionic Liquids

Cited by 52 publications

References 41 publications

Microscopic origins of conductivity in molten salts unraveled by computer simulations

Microscopic origins of conductivity in molten salts unraveled by computer simulations

Transference Number Determination in Poor-Dissociated Low Dielectric Constant Lithium and Protonic Electrolytes

Electrolytes for Lithium (Sodium) Batteries Based on Ionic Liquids: Highlighting the Key Role Played by the Anion

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