Solvation structure in dilute to highly concentrated electrolytes for lithium-ion and sodium-ion batteries

Flores, Eibar; Åvall, Gustav; Jeschke, Steffen; Johansson, Patrik

doi:10.1016/j.electacta.2017.03.031

Cited by 66 publications

(61 citation statements)

References 51 publications

(87 reference statements)

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“…For electrolytes containing NaPF 6 (Figure a), 1 m NaPF 6 has the highest ionic conductivity within the whole temperature range (e.g., 7.0 mS cm −1 at 20 °C). This result can be explained by the combination of the high number of free conductive charge carriers and the low viscosity . However, although the viscosity of 0.1 m NaPF 6 is the lowest at 20 °C, the number of charge carriers is also the lowest, which leads to the lowest ionic conductivity above 5 °C.…”

Section: Resultsmentioning

confidence: 97%

Influence of Salt Concentration on the Properties of Sodium‐Based Electrolytes

et al. 2018

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Electrolytes based on organic carbonates are widely used for sodium‐ion batteries (SIBs) due to several advantages such as high ionic conductivity, wide liquidus range, and high electrochemical stability. In this work, this class of electrolyte is investigated focusing on two conductive salts, namely NaPF6 (sodium hexafluorophosphate) and NaTFSI (sodium bis(trifluoromethanesulfonyl)imide), using PC (propylene carbonate) as solvent. The investigation of different salt concentrations, from rather diluted to highly concentrated (i.e., 0.1, 1, and 3 m), extends from their glass transition temperature to viscosity, ionic conductivity, electrochemical stability window, and electrochemical stability toward Al. Raman spectroscopy discloses the salt–solvent coordination and its possible modification due to changes in temperature, proving that the viscosity played a major role in influencing ionic conductivity rather than ions and molecules' coordination. Finally, the electrochemical performance of half‐cells employing Na x Ni0.22Co0.11Mn0.66O2 as the cathode material with the various electrolytes is also reported, and cells containing electrolyte with 1 m salt concentration outperform the other in terms of delivered capacity and rate performance.

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Section: Resultsmentioning

confidence: 97%

Influence of Salt Concentration on the Properties of Sodium‐Based Electrolytes

et al. 2018

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“…One last parameter of electrolytes that also needs to be considered is the concentration of the salt species. Of all the papers surveyed in the literature, an overwhelming majority used a concentration of 1.0 m . Whether this is done for practical purposes, or is a holdover from the LIB literature is not really known, as no studies have been found comparing the effects of different salt concentrations paired with the same material.…”

Section: Electrolytes For Nibsmentioning

confidence: 99%

Electrolytes, SEI Formation, and Binders: A Review of Nonelectrode Factors for Sodium‐Ion Battery Anodes

Bommier

2018

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Through intense effort in recent years, knowledge of Na-ion batteries has been advanced significantly, pertaining to electrodes. Often, such progress has been accompanied by using a convenient choice of electrolyte or binder. Nevertheless, it has been witnessed that "external" factors to electrodes, such as electrolytes, solid electrolyte interphase, and binders, affect the functions of electrodes profoundly. And generally, certain types of electrodes favor some electrolytes or binders. With a rapidly increasing number of publications in the area, trends in terms of electrolytes and binders are possibly exploitable. Unfortunately, the field has yet to see a review article that devotes itself to these nonelectrode aspects of Na-ion batteries. Here, the gap is filled by conducting a comprehensive review of these nonelectrode external factors, especially by looking into their correlation with electrochemical properties, such as cycle life, and first cycle coulombic efficiency. Not only are the representative reports reviewed, but also quantitative analyses on the database that are constructed are provided. With such analyses, some new data-driven perspectives are postulated, which are of great value to the community.

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“…If the coordination sites of the cation are to be constant, bidentate coordination can be expected by either TFSI or the solvent. For cyclic carbonates, bidentate coordination to Li + and Na + has been proposed for highly concentrated electrolytes, 45 and as the band for the coordinated solvent is actually composed of two contributions shifted by ca. 5 cm −1 (Figure S10), bidentate coordination could also be the case for Ca 2+ .…”

Section: Articlementioning

confidence: 99%

Cation Solvation and Physicochemical Properties of Ca Battery Electrolytes

et al. 2019

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Divalent-cation-based batteries are being considered as potential high energy density storage devices. The optimization of electrolytes for these technologies is, however, still largely lacking. Recent demonstration of the feasibility of Ca and Mg plating and stripping in the presence of a passivation layer or an artificial interphase has paved the way for more diverse electrolyte formulations. Here, we exhaustively evaluate several Ca-based electrolytes with different salts, solvents, and concentrations, via measuring physicochemical properties and using vibrational spectroscopy. Some comparisons with Mg-and Li-based electrolytes are made to highlight the unique properties of the Ca 2+ cation. The Ca-salt solubility is found to be a major issue, calling for development of new highly dissociative salts. Nonetheless, reasonable salt solubility and dissociation are achieved using bis(trifluoromethanesulfonyl)imide (TFSI), BF 4 , and triflate anion based electrolytes and high-permittivity solvents, such as ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (gBL), and N,N-dimethylformamide (DMF). The local Ca 2+ coordination is concentrationdependent and rather complex, possibly involving bidentate coordination and participation of the nitrogen atom of DMF. The ionicity and the degree of ion-pair formation are both investigated and found to be strongly dependent on the nature of the cation, solvent donicity, and salt concentration. The large ion−ion interaction energies of the contact ion pairs, confirmed by density functional theory (DFT) calculations, are expected to play a major role in the interfacial processes, and thus, we here provide electrolyte design strategies to engineer the cation solvation and possibly improve the power performance of divalent battery systems.

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Solvation structure in dilute to highly concentrated electrolytes for lithium-ion and sodium-ion batteries

Cited by 66 publications

References 51 publications

Influence of Salt Concentration on the Properties of Sodium‐Based Electrolytes

Influence of Salt Concentration on the Properties of Sodium‐Based Electrolytes

Electrolytes, SEI Formation, and Binders: A Review of Nonelectrode Factors for Sodium‐Ion Battery Anodes

Cation Solvation and Physicochemical Properties of Ca Battery Electrolytes

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