Electrolytes For Sodium-ion Batteries Research Articles

Spatial-Decomposition Analysis of Electrical Conductivity in Mixtures of Ionic Liquid and Sodium Salt for Sodium-Ion Battery Electrolytes.

Ionic liquid (IL)-based electrolytes are a promising material for the development of sodium-ion batteries, and their performance can be quantified by electrical conductivity. In this highly concentrated ionic system, the correlated motions of ion pairs are influential on the ionic transport properties. Herein, all-atom analyses are conducted through molecular dynamics simulations to bridge the macroscopically observable electrical conductivity with the molecular pictures of correlated motion of ion pairs. The analysis is applied to three mixtures of IL with sodium salt that are relevant to the electrolyte for a sodium-ion battery: [1-ethyl-3-methylimidazolium, Na][bis(fluorosulfonyl)amide] ([C2C1im, Na][FSA]), [N-methyl-N-propylpyrrolidinium, Na][FSA] ([C3C1pyrr, Na][FSA]), and [K, Na][FSA]. The computational results on electrical conductivities are in agreement with the experimental reports, and their dependency on temperature and sodium-ion composition is reproduced well. The overall contributions from cross-correlated motions are found to be negative in all the IL mixtures; thus, the total conductivities are less than their Nernst-Einstein estimates. The spatial view of cross-correlated motions is further obtained by decomposing the time correlation functions of velocities according to the distances between ion pairs. It is observed that ion pairs are moving in the same direction for ∼0.3 ps when they were initially within the first coordination shell, followed by motions toward opposite directions. The cross-correlation terms are also dissected into local and nonlocal components, and it is commonly seen for all the ion pairs that the local component is negative for cation-anion pairs and is positive for cation-cation and anion-anion pairs. The motions of ion pairs are accompanied by a "backflow" that manifests in the form of the nonlocal component whose sign is opposite to the corresponding local component. In fact, the contributions of the correlated motions of ions to the electrical conductivity are not localized to contact pairs and extend spatially beyond the first coordination shell of the cation-anion pairs.

Gel-Polymer Electrolytes for Sodium Batteries - Raman and Electrochemical Impedance Spectroscopic Studies

Sodium-ion batteries (SIBs) as low-cost alternatives to expensive lithium-ion batteries become a hot R&D topic in the recent days due to the natural abundancy of sodium in the Earth’s crust and also in the oceans. As far as solid electrolytes for SIBs are concerned, larger size of Na+ ions compared to that of Li+ ions hinders the ionic mobility resulting to insufficient ionic conductivity for practical applications. Development of quasi-solid state gel-polymer electrolytes (GPEs) would be a feasible solution to overcome this challenge. In this work, we developed Poly (methyl methacrylate) (PMMA) based GPEs with six different compositions dissolved in EC:PC (ethylene carbonate and propylene carbonate, 1:1 wt%) mixture. Among six different GPE samples investigated by Electrochemical Impedance Spectroscopic and Raman Spectroscopic techniques, the best ambient temperature ionic conductivity of 4.2 mS cm-1 was obtained for 9PMMA:9NaPF6:41EC:41PC (wt%). Variation of ionic conductivity with inverse temperature showed Arrhenius behavior with almost constant activation energies. The best conducting GPE showed an activation energy of 0.14 eV. In the Raman spectra, very sharp crystalline peaks (400-850 cm-1 wave number range) of NaPF6 disappear in the gel state of the electrolytes confirming the non-crystalline nature of the GPEs. Boson modes remain almost constant in intensity for all the six different compositions. The best conducting GPE seems to be highly suitable for practical applications in SIBs as it has sufficient ambient temperature ionic conductivity.

Benefits of the Mixtures of Ionic Liquid and Organic Electrolytes for Sodium-ion Batteries

The successful commercialization of sodium-ion batteries is heavily contingent on the development of suitable electrolytes marked with economic feasibility and stable electrochemical performance. To this end, we present a group of hybrid electrolytes made from the [C3C1pyrr][FSA] (C3C1pyrr = N-methyl-N-propylpyrrolidinium) ionic liquid (IL) and propylene carbonate organic liquid (OL) electrolytes with Na[FSA] (FSA = bis(fluorosulfonyl)amide) and Na[ClO4] salts are mixed with exploring the possibilities of cost reduction, high performance and inhibited flammability. The thermal stability tests reveal that the addition of IL can effectively suppress flammability. Herein, the physicochemical and electrochemical properties of the various mixing ratios of the aforementioned hybrid electrolytes (ILOL) are investigated for sodium-ion batteries. Furthermore, full cell tests using hard carbon (HC) negative and NaCrO2 (NCO) positive electrodes using the ILOL systems improve electrochemical performance and enable battery operation at 363 K.

Research progress of organic electrolyte for sodium ion battery

Research progress of organic electrolyte for sodium ion battery

Structure and ionic conductivity of Na3+xSc2SixP3-xO12 (x=0.0, 0.2, 0.4, 0.8) NASICON materials: A combined neutron diffraction, MAS NMR and impedance study

A knowledge of structural parameters that play a role in influencing ionic conduction is the key to the design of improved NASICON materials which have attracted significant attention in recent years as potential solid electrolytes for sodium ion batteries. In this article, we report the results of our study on a series of scandium-based NASICON compounds, namely Na3+xSc2SixP3-xO12 (x= 0.0, 0.2, 0.4, 0.8) that have been prepared by the ceramic route. These materials have been characterized by powder X-ray and neutron diffraction, as well as solid-state 23Na, 45Sc, 31P, and 29Si nuclear magnetic resonance (NMR) spectroscopy at room temperature (RT). The electrical conductivity of the compounds in the temperature range of RT ̶400 °C has been determined by impedance spectroscopy. Rietveld refinement of the diffraction patterns confirms monoclinic C2/c unit cell for the Na3Sc2P3O12 but indicates a rhombohedral R3‾c unit cell for Na3+xSc2SixP3-xO12 compounds. The local environments surrounding sodium, scandium, phosphorus and silicon atoms have been deduced from solid-state NMR. 23Na NMR results gave evidence of Na-ion mobility at RT. AC impedance measurements show that the total conductivity of the sample increases with increasing substitution of P with Si. However, it is much reduced for x = 0.8 composition. Na-ion conductivity of 2.4×10-3 S cm−1 at 30 °C has been measured in Na3.4Sc2Si0·4P2·6O12 compound, which is comparable to the best-performing polycrystalline NASICONs. Parameters such as the area of the bottleneck region, Na–Na hopping distances, and the activation energy for Na-ion conduction have been determined from the structural data. A correlation has been found between the conductivity and the ratio of Na site vacancy to Na site occupancy. Possible reasons for the significant variation of the Na-ion conductivity with x are also discussed in the context of the structure and Na site occupancy.

An interface-reinforced rhombohedral Prussian blue analogue in semi-solid state electrolyte for sodium-ion battery

A semi-solid state (SSS) electrolyte with high ionic conductivity of 2.6 × 10−3 S cm−1 is designed to avoid problems of interfacial side reactions brought by typical liquid carbonate electrolyte in Prussian blue-based sodium-ion batteries, as well as Na dendrite growth. The solidification mechanism is related to FEC polymerization triggered by 5 wt% AlCl3 Lewis acid addition in pristine liquid electrolyte. The SSS electrolyte enables the intrinsic high-reversibility of rhombohedral Prussian blue analogue (r-PBA) cathode, and ultra-long lifetime of 3000 and 4000 cycles at 1 and 2 C, and high rate capacities of 121 mAh g−1 at 1 C and 88 mAh g−1 at 10 C are achieved. The improved cyclability and rate capability are ascribed to interface reinforcement between r-PBA and electrolyte due to the protection of formed poly(vinylene carbonate) on r-PBA. This work provides valuable insights into the growing significance of interface stability for rhombohedral structure in Prussian blue analogue.

Towards Stable Water-in-Salt Electrolytes for Sodium-Ion Batteries

Water-in-salt electrolytes have enabled the development of novel high-voltage aqueous lithium-ion batteries due to their high electrochemical stability compared to traditional aqueous electrolytes.[1, 2] The development of equivalent sodium electrolytes is hindered by two factors: Low solubility of suitable sodium salts. For example, NaTFSI has a solubility at room temperature of only 8 mol/kg compared to 21 mol/kg for LiTFSI.[3]A higher salt concentration is needed to reach the same level of electrochemical stability due to the lower charge density of Na+ compared to Li+.[4] In this study, we screen >100 combinations of up to five sodium salts with water to identify highly concentrated solutions that are thermodynamically in the liquid state at ≤25 °C.[5, 6] An additional criterion for a stable water-in-salt electrolyte is a high content of SEI-forming anions. Furthermore, we find that the electrochemical stability of the electrolyte benefits from anions that are only weakly coordinating. In fact, we discovered a strong correlation between the stability of the electrolyte and the position of the anion in the Hofmeister series.[6]Our findings led to the development of multiple 2 V-class sodium-ion batteries with Coulombic efficiencies of up to 99.8% during cycling at a rate of 1C and record-high energy densities for such devices of up to 77 Wh/kg based on the active masses of both anode and cathode.[6][1] L. Suo, O. Borodin, T. Gao, M. Olguin, J. Ho, X. Fan, C. Luo, C. Wang, K. Xu, Science 350 (2015) 938–943.[2] Y. Yamada, K. Usui, K. Sodeyama, S. Ko, Y. Tateyama, A. Yamada, Nat. Energy 1 (2016) 16129.[3] R.-S. Kühnel, D. Reber, C. Battaglia, ACS Energy Lett. 2 (2017) 2005–2006.[4] D. Reber, R. Figi, R.-S. Kühnel, C. Battaglia, Electrochim. Acta 321 (2019) 134644.[5] D. Reber, R.-S. Kühnel, C. Battaglia, ACS Mater. Lett. 1 (2019) 44–51.[6] D. Reber, M. Becker, R.-S. Kühnel, C. Battaglia, submitted.

Deep Eutectic Solvents As Sodium-Ion Battery Electrolytes with Increased Durability at Higher Temperatures

Sodium-ion batteries (SIBs) are a potential cost-effective alternative for lithium-ion batteries (LIBs) in applications which require large-scale energy storage. In these applications, low cost and sustainability are of prime importance. The extensive use of LIBs for large-scale storage would drive up lithium prices because of the latter’s limited production. As the lightest and smallest alkali metal after lithium, sodium is abundant and widely available, and is therefore more cost-efficient and sustainable. SIBs can use light and inexpensive aluminum current collectors for both the anode and cathode, as opposed to LIBs, which usually require more expensive copper current collectors for the anodes. This further increases the SIB's viability in applications where cost and sustainability are the most crucial factors.Viable battery electrolytes should have sufficient ionic conductivity, be electronically insulating, have a large electrochemical and thermal stability window, and not show reactivity with the other components of the battery. They should be safe, non-toxic, and inexpensive. Ionic liquids, defined as materials which consist entirely out of ions and which remain liquid below 100 °C, were previously studied as electrolytes for SIBs as they have a high intrinsic ionic conductivity, can dissolve high amounts of salt, are non-flammable and have a high thermal and (electro)chemical stability. Ionic liquids are typically expensive due the difficulty of their synthesis. Deep eutectic solvents (DESs) are closely related to ionic liquids and consist of a mixture of Lewis/Brönsted acids and bases, where the melting temperature of the mixture is below that of the individual components. Whereas DESs and ionic liquids can have similar physical properties, DESs can have additional advantages such as ease of preparation and wide availability of reagents, although this depends on the exact composition. Binary and ternary mixtures of different XFSI (FSI = bis(fluorosulfonyl)imide) and XTFSI (TFSI = bis(trifluoromethanesulfonyl)imide) inorganic salts were previously applied as DES electrolyte in sodium-ion half cells, which were constrained to operation at 80 °C or higher because of their relatively high melting points.1,2 These cells showed high reversibility and high Coulombic efficiency.Other DESs may also offer an increase of the stability of battery operation, and may be used at less stringent temperature conditions (with acceptable ionic conductivity even at room temperature). This stability problem is particularly pronounced at 55 °C or higher for conventional electrolytes, where battery performance rapidly degrades when linear carbonates are used as electrolyte solvent.3 Our series of DESs as SIB electrolytes were based on the dissolution of NaTFSI in an amide which is solid at room temperature. For each electrolyte, the effect of the solution structure on its electrochemical properties was studied. The amide was spontaneously reduced when contacted with sodium metal. By increasing the salt concentration, we observe a lower reactivity with sodium metal, a broader electrochemical stability window and a decreased ionic conductivity due to the strong Coulombic interactions among the amide molecules, Na+, and TFSI- ions (Figure). The sample containing 10 mol% of NaTFSI shows an anodic stability limit of ~3.6 V vs Na+/Na and a conductivity of 10.3 mS cm-1 at 55 °C. A DES with 30 mol% NaTFSI is stable up to ~4.6 V vs Na+/Na and has a conductivity of 3.8 mS cm-1 at 55 °C. The variation of conductivity with temperature of both DESs could be fitted with the Vogel-Tamman-Fulcher equation. At 55 °C, (Na3V2(PO4)3/C)/(Na2+x Ti4O9/C) full cells containing DES as electrolyte demonstrate a considerably higher durability and Coulombic efficiency than cells containing a conventional organic solvent-based electrolyte. As such, these DESs form a new class of electrolytes for application in sodium-ion batteries, offering a more durable performance at 55 °C than conventional systems.References(1) Nohira, T.; Ishibashi, T.; Hagiwara, R. Properties of an Intermediate Temperature Ionic Liquid NaTFSA – CsTFSA and Charge – Discharge Properties of NaCrO2 Positive Electrode at 423 K for a Sodium Secondary Battery. J. Power Sources 2012, 205, 506–509.(2) Fukunaga, A.; Nohira, T.; Kozawa, Y.; Hagiwara, R. Intermediate-Temperature Ionic Liquid NaFSA-KFSA and Its Application to Sodium Secondary Batteries. J. Power Sources 2012, 209, 52–56.(3) Yan, G.; Dugas, R.; Tarascon, J. The Na3V2(PO4)2F3/Carbon Na-Ion Battery: Its Performance Understanding as Deduced from Differential Voltage Analysis. J. Electrochem. Soc. 2018, 165 (2), 220–227. Figure 1

Improvement on Electrochemical Performance and Safety Using Mixtures of Ionic Liquid and Conventional Organic Electrolyte for Sodium-Ion Batteries

The success of commercializing sodium-ion batteries is inhibited by the implementation of suitable electrolytes that have economic feasibility and stable electrochemical performance. Organic electrolytes such as Na[ClO4]- or Na[PF6]-including organic solvents, EC, PC, DMC, and DEC, are most widely used to investigate the performance of sodium-ion batteries. These electrolytes are widely accepted because of the analogous studies in LIBs, but their flammability can cause reliability issues. Moreover, the SEI layer composed of sodium cations is known to be inhomogeneous and fragile, giving a higher solubility than that based on lithium cations.(1) In this regard, ionic liquid electrolytes are a drawing huge attention to constructing safe electrochemical devices owing to their unique properties such as low volatility and low flammability. Furthermore, recent studies report ionic liquids show similar electrochemical performance at room temperature to organic electrolytes and better interfacial properties.(2-4) Despite this bright improvement, the cost of ionic liquids drags down the advantage of economical sodium-ion batteries.In this study, ionic liquid and organic liquid electrolytes are mixed to adjust the balance of cost, performance, and safety. The [C3C1pyrr][FSA] (C3C1pyrr+ = N-methyl-N-propylpyrrolidinium) ionic liquid and PC organic solvent are used as mother electrolytes with Na[FSA] (FSA = bis(fluorosulfonyl)amide) and Na[ClO4] salts. The physical and electrochemical properties of the various mixing ratio of those mixture electrolytes are investigated for sodium-ion batteries. These mixture electrolytes improve not only flammability but also show better rate and cycling performance. The detailed electrochemical properties are evaluated by comparing reference electrolytes to clarify the dual salts effect and dual solvents (ionic liquids and organic solvent) effect. This performance will be discussed based on half cell tests using a Na2FeP2O7 positive electrode and full cell tests using a hard carbon negative electrode and a NaCrO2 positive electrode.

Polymer electrolytes for sodium-ion batteries

Sodium-ion batteries are seeing a surge in interest as a potential complementary energy storage technology in light of skyrocketing demand for lithium-ion batteries. One of the frontiers of improving sodium-ion battery competitiveness is replacing liquid electrolytes with polymer electrolytes, which contain no free-flowing solvent, to increase safety and reduce cost. Their development may one day make viable sodium-metal batteries, which would have considerable advantages in energy density. This review provides an overview of the current field of both solid-polymer and gel-polymer electrolytes for sodium-ion batteries, with a focus in the key performance parameters used to assess them. In particular, their targeted manipulation and significance for practical use are discussed. A major theme is also the interdependence of many electrochemical and mechanical properties. In addition, a quantitative comparison of hitherto reported values for these parameters across various polymer classes is undertaken for the first time.

High performance solid-state sodium batteries enabled by boron contained 3D composite polymer electrolyte

Practical application of solid-state batteries has been severely hindered by the relatively low ionic conductivity of electrolyte and high charge-transfer resistance between electrode and solid electrolyte. The development of novel materials and creation of new nanostructures are effective strategies to address the challenges. Here, an innovative 3D composite polymer electrolyte modified with anion-trapping boron (B-CPE) is reported for the first time as a solid electrolyte for sodium-ion batteries (SIBs). The B-CPE is prepared through in situ polymerization of polymer electrolyte inside a mechanically supporting matrix. It shows excellent ionic conductivity of 2.57 × 10−4 S cm−1 at 40 °C, high Na+ transference number of 0.66, and good interfacial compatibility with Na metal anode. Moreover, solid-state SIBs were assembled by one-step in situ solidification method to form “gentle” electrode/electrolyte contact, and it’s found that the charge-transfer efficiency has been significantly improved at the electrode/electrolyte interface as well as in cathode due to the formation of ion-conducting continuous polymer phase. Hence the B-CPE based solid-state SIBs exhibit outstanding electrochemical performances as the synergistic effect of high performance electrolyte and optimized cell structure. It delivers initial discharge capacity of 113.8 mAh g−1 and maintains 80.1% of capacity during 320 cycles under 0.2 C at 40 °C, and even 80.4% of the capacity retention after 700 cycles under 3 C. Notably, the battery achieves a significant improvement in rate capability owing to the introduction of boron moieties. This work opens new possibilities to fabricate high performance other rechargeable solid-state batteries.

Transport Properties of Ionic Liquid and Sodium Salt Mixtures for Sodium-Ion Battery Electrolytes from Molecular Dynamics Simulation with a Self-Consistent Atomic Charge Determination.

Ionic liquid (IL) has been considered as a potential electrolyte for developing next-generation sodium-ion batteries. A highly concentrated ionic system such as IL is characterized by the significant influence of intramolecular polarization and intermolecular charge transfer that vary with the combination of cations and anions in the system. In this work, a self-consistent atomic charge determination using the combination of classical molecular dynamics (MD) simulation and density functional theory (DFT) calculation is employed to investigate the transport properties of three mixtures of ILs with sodium salt relevant to the electrolyte for a sodium-ion battery: [1-ethyl-3-methylimidazolium, Na][bis(fluorosulfonyl)amide] ([C2C1im, Na][FSA]), [N-methyl-N-propylpyrrolidinium, Na][FSA] ([C3C1pyrr, Na][FSA]), and [K, Na][FSA]. The self-consistent method is versatile to address the intramolecular polarization and intermolecular charge transfer in response to the cation-anion combination, as well as the variation in their compositions. The structure and dynamic properties of IL mixtures obtained from the method are in line with those from the experimental works. The comparison to the Nernst-Einstein estimates shows that the electrical conductivity is reduced due to correlated motions among the ions, and the contribution to the conductivity from each ion species is not necessarily ranked in the same order as the diffusion coefficient. It is further seen that the increase of the sodium-ion composition reduces the fluidity of the system. The results highlight the potential of the method and the microscopic description that it can provide to assist the investigation toward a sensible design of IL mixtures as an electrolyte for a high-performance sodium-ion battery.

Greener, Safer, and Sustainable Batteries: An Insight into Aqueous Electrolytes for Sodium-Ion Batteries

Rechargeable Na-ion battery technology has successfully emerged as a replacement to the current Li-ion battery technology, especially in large-scale storage applications. Aqueous electrolytes in re...

A novel approach to ligand-exchange rates applied to lithium-ion battery and sodium-ion battery electrolytes.

A novel approach based on analyzing the forces and velocities of solvents and anions to compute ligand-exchange rates is here presented and applied to lithium-ion battery (LIB) and sodium-ion battery (SIB) electrolytes. By using ab initio molecular dynamics generated data, we find the ligand-exchange rates to increase as functions of electrolyte salt concentration and to be higher in SIB electrolytes as compared to LIB electrolytes. This indicates both that Na+ transport will be more non-vehicular in nature and have improved kinetics vs Li+, and that increasing the salt concentration is beneficial. The systems studied were basically the first cation solvation shells of Li/NaPF6 in propylene carbonate and acetonitrile using three solvent to salt ratios. Overall, the solvation shells are solvent rich at low salt concentrations, and as functions of concentration, the solvents are replaced by anions. As the SIB electrolytes display higher cation coordination and solvation numbers, we also expect an earlier onset of highly concentrated electrolyte behavior for SIB than LIB electrolytes. These observations should all have an impact on the design of electrolytes for optimal bulk properties, but also be useful with respect to interfacial dynamics.

Electrolytes for sodium ion batteries: A short review

Synthesis routes and ion conduction phenomenon in sodium ion conducting solid electrolytes have been reported in the present chapter. The different experimental and theoretical tools have been explained for preparation and ion conduction mechanism of solid electrolytes. The working principle of some polymer electrolyte based conductors has been explained.

Engineering optimization approach of nonaqueous electrolyte for sodium ion battery with long cycle life and safety

Electrolyte design strategies are closely related to the capacities, cycle life and safety of sodium–ion batteries. In this study, we aimed to optimize electrolyte with the focus on engineering aspects. The basic physicochemical properties including ionic conductivity, viscosity, wettability and thermochemical stability of the electrolytes using NaPF6 as the solute and the mixed solvent with different components of EMC, DMC or DEC in PC or EC were systematically measured. Ah pouch cell with NaNi1/3Fe1/3Mn1/3O2/hard carbon electrodes was used to evaluate the performance of the prepared electrolytes. By using the Inductive Coupled Plasma Emission Spectrometer (ICP), X-ray photoelectron spectroscopy (XPS), Thermogravimetric-differential scanning calorimetry (TG-DSC) and Accelerating Rate Calorimeter (ARC), we show that an optimized electrolyte can effectively promote the formation of a protective interfacial layer on two electrodes, which not only retards parasitic reactions between the electrodes and electrolyte but also suppresses dissolution of metal ions from the cathode. With an optimized electrolyte, a NaNi1/3Fe1/3Mn1/3O2/hard carbon cell can attain 56.16% capacity retention under the low temperature of −40 °C, and can be able to retain 80% capacity retention after more than 2500 cycles while presenting excellent thermal safety.

Corrections to “A High-Voltage Aqueous Electrolyte for Sodium-Ion Batteries”

Corrections to “A High-Voltage Aqueous Electrolyte for Sodium-Ion Batteries”

Local structure of a highly concentrated NaClO4 aqueous solution-type electrolyte for sodium ion batteries.

Aqueous Na-ion batteries with highly concentrated NaClO4 aq. electrolytes are drawing attention as candidates for large-scale rechargeable batteries with a high safety level. However, the detailed mechanism by which the potential window in 17 m NaClO4 aq. electrolyte was expanded remains unclear. Therefore, we investigated the local structure around a Na+ ion or a ClO4- ion using X-ray diffraction combined with empirical potential structure refinement (EPSR) modelling and Raman spectroscopy. The results showed that in 17 m NaClO4 aq. electrolyte, most of the water molecules were coordinated to Na+ ions and few free water molecules were present. The 17 m NaClO4 aq. electrolyte could be interpreted as widening the potential window because almost all water molecules participated in hydration of the Na+ ions.

Novel flame retardant rigid spirocyclic biphosphate based copolymer gel electrolytes for sodium ion batteries with excellent high-temperature performance

Spirocyclic biphosphate based GPEs for flame retardant sodium ion batteries with excellent high-temperature performance.

Towards standard electrolytes for sodium-ion batteries: physical properties, ion solvation and ion-pairing in alkyl carbonate solvents.

The currently emerging sodium-ion battery technology is in need of an optimized standard organic solvent electrolyte based on solid and directly comparable data. With this aim we have made a systematic study of "simple" electrolyte systems consisting of two sodium salts (NaTFSI and NaPF6) dissolved in three different alkyl carbonate solvents (EC, PC, DMC) within a wide range of salt concentrations and investigated: (i) their more macroscopic physico-chemical properties such as ionic conductivity, viscosity, thermal stability, and (ii) the molecular level properties such as ion-pairing and solvation. From this all electrolytes were found to have useful thermal operational windows and electrochemical stability windows, allowing for large scale energy storage technologies focused on load levelling or (to a less extent) electric vehicles, and ionic conductivities on par with analogous lithium-ion battery electrolytes, giving promise to also be power performant. Furthermore, at the molecular level the NaPF6-based electrolytes are more dissociated than the NaTFSI-based ones because of the higher ionic association strength of TFSI compared to PF6- while two different conformers of DMC participate in the Na+ first solvation shells - a Na+ affected conformational equilibrium and induced polarity of DMC. The non-negligible presence of DMC in the Na+ first solvation shells increases as a function of salt concentration. Overall, these results should both have a general impact on the design of more performant Na-conducting electrolytes and provide useful insight on the very details of the importance of DMC conformers in any cation solvation studies.