Electrolyte Solvents For Batteries Research Articles

Co-Intercalation-Free Fluorinated Ether Electrolytes for Lithium-Ion Batteries

Lithium-ion batteries are widely used to power portable electronics because of their high energy densities and have shown great promise in enabling the electrification of transport. However, the commercially used carbonate-based electrolytes are limited by a narrow operating temperature window and suffer against next generation lithium-ion battery chemistries such as silicon-containing anodes. The lack of non-carbonate electrolyte alternatives such as ether-based electrolytes is due to undesired solvent co-intercalation that occurs with graphitic anodes. Recently, fluorinated ether solvents have become promising electrolyte solvent candidates for lithium metal batteries but their applications in other battery chemistries have not been studied. In this work, we synthesize a group of novel fluorinated ether solvents and study them as electrolyte solvents for lithium-ion batteries. Using X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (ssNMR), we show that fluorinated ether electrolytes support reversible lithium-ion intercalation into graphite without solvent co-intercalation at conventional salt concentrations. To the best of our knowledge, they are the first class of ether solvents that intrinsically suppress solvent co-intercalation without the need for high or locally high salt concentration. In full cells using graphite anode, fluorinated ether electrolytes enable much higher energy densities compared to conventional glyme ethers, and better thermal stability over carbonate electrolytes (operation up to 60°C). As single-solvent-single-salt electrolytes, they remarkably outperform carbonate electrolytes with fluoroethylene carbonate (FEC) and vinylene carbonate (VC) additives when cycled with graphite-silicon composite anodes. Using X-ray photoelectron spectroscopy (XPS), NMR and density functional theory (DFT) calculations, we show that fluorinated ethers produce a solvent-derived solid electrolyte interphase, which is likely the key to suppressing solvent co-intercalation. Rational molecular design of fluorinated ether solvents will produce novel electrolytes that enable next generation lithium-ion batteries with higher energy density and wider working temperature window.

Hydrodynamic voltammetry of Fe2+/3+ in aqueous deep eutectic solvents towards redox flow batteries

Deep eutectic solvents (DESs) have recently attracted much attention as potential green electrolyte solvents for redox flow batteries. DESs are considered not only as environmentally sustainable but also economically attractive electrolytes because they can be resourced from biological feedstock (alcohols, urea, choline) and are earth-abundant and of low toxicity. Despite these advantages, DESs still have limitations in important aspects such as reactant and ion transport, which is inhibited due to hydrogen-bonding-induced viscosity. Thus, improving the transport properties of redox species in DESs is essential. In addition, we explore the quantitative addition of water to ethaline (a 1:2 choline chloride: ethylene glycol mixture) in order to understand its influence on the kinetics and mass transport properties of DESs. In this work, we show that DESs can be made more fluid and less dense, while avoiding most of the electrochemical instabilities of water. Herein, we investigate the effects of gradually increasing amounts of water to the redox system of Fe2+/3+in ethaline. Our study shows that systematic addition of water leads to a three-fold increase in ionic conductivity and decrease in viscosity that enhances the mass transport and kinetics of DES-based electrolytes while still maintaining an electrochemical window of approximately 1.90 V. The use of environmentally benign electrolyte components together with the observed increase in conductivity will result in a more efficient redox flow battery (RFB) that operates at higher power density without relying on harmful solvents and fossil fuel-based processes.

Extension of the TraPPE Force Field for Battery Electrolyte Solvents.

Optimizing electrolyte formulations is key to improving performance of Li-/Na-ion batteries, where transport properties (diffusion coefficient, viscosity) and permittivity need to be predicted as functions of temperature, salt concentration and solvent composition. More efficient and reliable simulation models are urgently needed, owing to the high cost of experimental methods and the lack of united-atom molecular dynamics force fields validated for electrolyte solvents. Here the computationally efficient TraPPE united-atom force field is extended to be compatible with carbonate solvents, optimizing the charges and dihedral potential. Computing the properties of electrolyte solvents, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and dimethoxyethane (DME), we observe that the average absolute errors in the density, self-diffusion coefficient, permittivity, viscosity, and surface tension are approximately 15% of the corresponding experimental values. Results compare favorably to all-atom CHARMM and OPLS-AA force fields, offering computational performance improvement of at least 80%. We further use TraPPE to predict the structure and properties of LiPF6 salt in these solvents and their mixtures. EC and PC form complete solvation shells around Li+ ions, while the salt in DMC forms chain-like structures. In the poorest solvent, DME, LiPF6 forms globular clusters despite DME's higher permittivity than DMC.

Durable semi-crystalline interphase engineering to stabilize high voltage Ni-rich cathode in dilute ether electrolyte

Ethers are promising electrolyte solvents for secondary Li metal batteries because of their excellent reduction stability. However, their oxidation stability has been mostly relying on the high concentration approach, and limited progress has been made on building effective interphase to protect the cathode from the corrosion of the electrolyte. In this work, we construct a semi-crystalline interfacial layer on the surface of Li(Ni0.8Co0.1Mn0.1)O2 cathode that can achieve improved electrochemical stability in the highly corrosive chemical environment formed by the decomposition of ether molecules. Different from traditional brittle crystalline interphases, the optimized semi-crystalline layer with low modulus and high ionic conductivity can effectively relieve electrode strain and maintain the integrity of the interface layer. Due to this design, the continuous oxidation decomposition of ether-based electrolytes could be significantly suppressed and the battery shows outstanding cycling stability (84% capacity retention after 300 cycles). This article provides a solution to address the oxidation instability issue of ether-based electrolytes.

A Thermodynamic Cycle‐Based Electrochemical Windows Database of 308 Electrolyte Solvents for Rechargeable Batteries

AbstractRational design of wide electrochemical window (ECW) electrolytes to pair with high‐voltage cathodes is an emerging trend to push the energy density limits of current rechargeable batteries. Traditional single‐electronic/gas‐phase approximation‐based methods (e.g., highest occupied molecular orbital/lowest unoccupied molecular orbital) are increasingly recognized to have large deviations from experiments when predicting ECWs of electrolytes involving complex solvent interactions. Specifically, by examining available experimental ECWs of 68 electrolyte solvents extracted from ≈140 000 literature sources, which are conventionally divided into five functional‐group categories (covering commonly used carbonate‐based ethylene carbonate (EC)/propylene carbonate (PC) and ether‐based tetrahydrofuran), it is found that mean‐absolute‐errors (MAE) of traditional methods reach up to 3.25 V. Herein, a thermodynamic cycle‐based ECW prediction approach is proposed including two long‐term overlooked reorganization‐energy and solvation‐energy corrections, each of which can be quantified by two geometric descriptors (λ and ΔGsol), reducing MAE below 0.68 V. Following this, a database containing ECWs for 308 electrolyte solvents, obtained by traversing single functional‐group substitutions, is established. Furthermore, two omitted solvents with ECWs over 6.00 V and excellent structural stabilities (bond‐length change < 0.10 Å during redox process) are retrieved by stepwise screening of structural/electronic parallel properties. This study demonstrates the benefits of improving ECW prediction accuracy and accumulating descriptors to accelerate rapid screening of superior battery electrolytes.

Emerging electrolytes with fluorinated solvents for rechargeable lithium-based batteries.

Electrolytes that can ensure the movement of ions and regulate interfacial chemistries for fast mass and charge transfer are essential in many types of electrochemical energy storage devices. However, in the emerging energy-dense lithium-based batteries, the uncontrollable side-reactions and consumption of the electrolyte result in poor electrochemical performances and severe safety concerns. In this case, fluorination has been demonstrated to be one of the most effective strategies to overcome the above-mentioned issues without significantly contributing to engineering and technical difficulties. Herein, we present a comprehensive overview of the fluorinated solvents that can be employed in lithium-based batteries. Firstly, the basic parameters that dictate the properties of solvents/electrolytes are elaborated, including physical properties, solvation structure, interface chemistry, and safety. Specifically, we focus on the advances and scientific challenges associated with different solvents and the enhancement in their performance after fluorination. Secondly, we discuss the synthetic methods for new fluorinated solvents and their reaction mechanisms in depth. Thirdly, the progress, structure-performance relationship, and applications of fluorinated solvents are reviewed. Subsequently, we provide suggestions on the solvent selection for different battery chemistries. Finally, the existing challenges and further efforts on fluorinated solvents are summarized. The combination of advanced synthesis and characterization approaches with the assistance of machine learning will enable the design of new fluorinated solvents for advanced lithium-based batteries.

Unlocking the Low-Temperature Potential of Propylene Carbonate to -30 °C via N-Methylpyrrolidone.

As the one of the core electrolyte solvents for Li-ion batteries, ethylene carbonate (EC) is still irreplaceable for its balance of ionic conductivity and interfacial stability. However, it also defines the boundary for the low-temperature performance of the battery because of its high melting point (36.4 °C). Its immediate sibling, propylene carbonate (PC), has been proposed as its convenient substitute for its much lower melting point (-48.8 °C). Unfortunately, the propylene carbonate-graphite anode interfacial problem has been a puzzle since the days before the advent of the Li-ion battery. Among various strategies to mitigate this issue, blending in selected strong solvents for Li+ to bring down propylene carbonate's presence in the solvation shell has been proven often effective but the mechanism from the interfacial chemistry perspective remains unexplored. Herein, we study a new cosolvent, N-methylpyrrolidone (NMP), for PC-based electrolyte and observe excellent reversibility that approaches the commercial standard, far beyond the similar systems in the past. To understand the mechanism, solvation chemistry analysis and in situ characterizations are undertaken to probe the interfacial chemistry from various standpoints. Based on these results and further theoretical calculation, it is proposed that N-methylpyrrolidone has mediated the reduction process of propylene carbonate to facilitate the growth of a solid electrolyte interphase (SEI) layer akin to ethylene carbonate. Finally, an electrolyte has also been successfully developed based on the NMP/PC couple to outperform the commercial electrolyte by a clear margin when tested in a LiNi0.8Co0.1Mn0.1O2-graphite cell at -30 °C.

Low-viscosity quaternary ammonium-based ionic liquid electrolytes for lithium air batteries

• Ionic liquids are investigated as an electrolyte for Li-air batteries. • Low-viscosity ionic liquids with reduced molecular weight are synthesized. • High stability with a lithium metal electrode is demonstrated. Ionic liquids (ILs) have attracted significant attention as candidates for Li-air battery electrolyte solvents owing to their novel properties, such as non-volatility and low reactivity with lithium metal anodes. However, the main drawback of IL-based electrolytes is their high viscosity, which results in poor battery capacity and conductivity. In this study, we synthesized low-viscosity ILs with reduced molecular weights using the side-chain shortening method. In particular, the IL: trimethyl ethoxymethyl ammonium bis(fluoromethylsulfonyl)imide (N111(1O2) FSI), has a lower viscosity (111.4 cP) than that of the electrochemically stable reference material, diethylmethyl (2-methoxyethyl) ammonium bis(fluoromethylsulfonyl)imide (DEME FSI; viscosity of 131.1cP). The use of the optimal IL, N111(1O2) FSI, resulted in an initial capacity 3.75 times higher than that obtained using DEME FSI in the cell test. The chemical stability of N111(1O2) FSI with lithium metal was confirmed by microstructure analysis of the lithium surface. The physicochemical properties, such as viscosity, ionic conductivity, melting point, and electrochemical properties, were thoroughly characterized.

Lotte and Solvent study plant for battery electrolyte solvents

Lotte and Solvent study plant for battery electrolyte solvents

Eutectic Electrolytes Composed of LiN(SO2F)2 and Sulfones for Li-Ion Batteries

Sulfones are polar molecules that can be used as thermally stable electrolyte solvents for Li-ion batteries (LIBs). Li salts form stoichiometric solvates with sulfones in the electrolytes. The melting points of the solvates tend to be higher than room temperature, thereby limiting the operating temperature range of the batteries. In this study, the applicability of ternary eutectic mixtures of LiN(SO2F)2 (LiFSA), sulfolane (SL), and dimethyl sulfone (DMS) as LIB electrolytes was assessed. Relative to the binary LiFSA–sulfone electrolytes, the ternary eutectic electrolytes remained liquid over a wide temperature range due to the increased entropy of mixing. Sulfone-bridged Li+–sulfone–Li+ and anion-bridged Li+–FSA––Li+ network structures were formed in the eutectic electrolyte with a composition of [LiFSA]/[SL]/[DMS] = 1/1.5/1.5. Pulsed-field gradient NMR measurements revealed that the Li+ ion dynamically exchanges sulfones and anions and diffuses more rapidly than these ligands, resulting in the relatively high Li+ transference number of the electrolyte. Highly reversible charge–discharge processes of the LiCoO2 and graphite electrodes were attained using the ternary eutectic electrolyte. The rate capability of the Li/LiCoO2 cell in the eutectic electrolyte was comparable to that of the cell in the conventional 1 M LiPF6 in an ethylene carbonate/dimethyl carbonate solution despite its lower ionic conductivity.

Solvent Degradation and Polymerization in the Li-Metal Battery: Organic-Phase Formation in Solid-Electrolyte Interphases.

The products of solvent polymerization and degradation are crucial components of the Li-metal battery solid-electrolyte interphase. However, in-depth mechanistic studies of these reactions are still scarce. Here, we model the polymerization of common lithium battery electrolyte solvents─ethylene carbonate (EC) and vinylene carbonate (VC)─near the anode surface. Being consistent with the molecular calculation, ab initio molecular dynamic (AIMD) simulations reveal fast solvent decompositions upon contact with the Li anode. Additionally, we assessed the thermochemical impacts of decarboxylation reactions as well as the lithium bonding with reaction intermediates. In both EC and VC polymerization pathways, lithium bonding demonstrated profound catalytic effects while different degrees of decarboxylation were observed. The VC polymerization pathways with and without ring-opening events were evaluated systematically, and the latter one which leads to poly(VC) formation was proven to dominate the oligomerization process. Both the decomposition and polymerization reactivities of VC are found to be higher than EC, while the cross-coupling between EC and VC has an even lower-energy barrier. These findings are in good agreement with experimental evidence and explanatory toward the enhanced performance of VC-added lithium-metal batteries.

Steric Effect Tuned Ion Solvation Enabling Stable Cycling of High-Voltage Lithium Metal Battery.

1,2-Dimethoxyethane (DME) is a common electrolyte solvent for lithium metal batteries. Various DME-based electrolyte designs have improved long-term cyclability of high-voltage full cells. However, insufficient Coulombic efficiency at the Li anode and poor high-voltage stability remain a challenge for DME electrolytes. Here, we report a molecular design principle that utilizes a steric hindrance effect to tune the solvation structures of Li+ ions. We hypothesized that by substituting the methoxy groups on DME with larger-sized ethoxy groups, the resulting 1,2-diethoxyethane (DEE) should have a weaker solvation ability and consequently more anion-rich inner solvation shells, both of which enhance interfacial stability at the cathode and anode. Experimental and computational evidence indicates such steric-effect-based design leads to an appreciable improvement in electrochemical stability of lithium bis(fluorosulfonyl)imide (LiFSI)/DEE electrolytes. Under stringent full-cell conditions of 4.8 mAh cm-2 NMC811, 50 μm thin Li, and high cutoff voltage at 4.4 V, 4 M LiFSI/DEE enabled 182 cycles until 80% capacity retention while 4 M LiFSI/DME only achieved 94 cycles. This work points out a promising path toward the molecular design of non-fluorinated ether-based electrolyte solvents for practical high-voltage Li metal batteries.

Investigation of the effect of dimethyl methylphosphonate (DMMP) on flame extinction limit of lithium-ion battery electrolyte solvents

An experimental and numerical study was conducted to quantify the flame retardant effects of different DMMP addition loadings on the flame extinction limits of four lithium-ion battery electrolyte solvents. The minimum extinguishing concentration (MEC) of CO2, which was measured using the cup-burner method, was applied to characterize the flame retardant effects of different DMMP loadings. Then, a model based on the perfectly stirred reactor concept was constructed to calculate the MEC and interpret the measurements established in the cup-burner test. A comparison was conducted between the measured and calculated MECs of N2 and a satisfactory agreement was obtained. Further investigation found that DMMP could significantly improve the extinction temperature by clearing the H radical, suppressing the reaction temperature and increasing the sensitivity of temperature to reaction rate constants, which caused the decrease in the flame extinction limit of solvents. The experimental results showed that DMMP has a certain saturation effect on reducing the flame extinction limits of solvents. For the four solvents, the sensibilities of the flame extinction limits to the DMMP additions were different, which were ranked in the order of diethyl carbonate > ethyl methyl carbonate > dimethyl carbonate > ethyl acetate.

Comparative calculation on Li+ solvation in common organic electrolyte solvents for lithium ion batteries**Project supported by International Science & Technology Cooperation of China (Grant No. 2019YFE0100200), the National Natural Science Foundation of China (Grant No. 51902024), the National Postdoctoral Program for Innovative Talents of China (Grant No. BX20180038), China Postdoctoral Science Foundation (Grant No. 2019M650014), NASF, China (Grant No. U1930113),

It is important for the electrolytes to maintain and enhance the lithium ion battery electrochemical performance, and solvation of Li+ is a key parameter for the property of the electrolytes. The comparative study on Li+ solvation structures, energy, enthalpy, Gibbs free energy, infrared and Raman spectra in common organic electrolyte solvents is completed by density functional theory (DFT) method. The solvation reaction energy results suggest that the Li+ solvation priority order is propylene carbonate (PC) > ethylene carbonate (EC) > ethyl methyl carbonate (EMC) > diethyl carbonate (DEC) > tetrahydrofuran (THF) > dimethyl carbonate (DMC) > 1,3-dioxolane (DOL) > dimethoxyethane (DME) to form 5sol-Li+. It is also indicated that the most innermost solvation shell compounds formations by stepwise spontaneous solvation reaction are four cyclic solvent molecules and three linear solvent molecules combining one Li+ forming 4sol-Li+ and 3sol-Li+, respectively, at room temperature. Besides, the vibration peaks for C=O and C–O bonds in carbonate ester solvents-Li+ compounds shift to lower frequency and higher frequency, respectively, when the Li+ concentration increases in the solvation compounds. All Li–O stretching vibration peaks shift to higher frequency until forming 2solvent-Li+ complexes, and C–H stretching also shifts to higher frequency except for nDME-Li+ solvation compounds. The Raman spectrum is more agile to characterize C–H vibrations and IR is agile to C=O, C–O, and Li–O vibrations for Li+ solvation compounds.

Piperidinium-Based Ionic Liquids as an Electrolyte Solvent for Li-Ion Batteries: Effect of Number and Position of Oxygen Atom in Cation Side Chain on Electrolyte Property

In the pursuit of developing reliable Li-ion batteries with high performance and safety, the use of ionic liquids is one of the most promising approaches due to its high thermal stability. There is, however, the critical issue concerning the significantly low Li-ion diffusion in an electrolyte solution, which is directly linked to the degradation of their rapid charge−discharge properties. Ionic liquids with ether-substituted cation have generated much interest as electrolyte solvents for Li-ion batteries because the ether group functions to reduce the coordination number and increase ionic conductivity. In the present study, we synthesized six types of ionic liquids consisting of bis(trifluoromethanesulfonyl)amide (TFSA) anions and piperidinium-based cations in which the attached side chains are 1-((2-methoxyethoxy)methyl)-1-methylpiperidinium (PP1MEM), 1-butoxymethyl-1-methylpiperidinium (PP1BM), 1-methyl-(2-propoxyethyl)piperidinium (PP1PE), 1-(3-ethoxypropyl)-1-methylpiperidinium (PP1EP), 1-(4-methoxybutyl)-1-methylpiperidinium (PP1MB), and 1-hexyl-1-methylpiperidinium (PP16). It was found that the ionic liquid with PP1MEM cations with two oxygen atoms in the side chain exhibited the lowest solvation number of TFSA anions (1.56), whereas PP1BM (1.78), PP1PE (1.86), PP1EP (2.08), and PP1MB-TFSA (2.07) resulted in a larger number, as the oxygen atoms in the alkyl side chain are located far from the positively charged nitrogen atoms. PP1MEM-TFSA with small solvation numbers enhanced the ionic conductivity and thereby achieved high electrode performance.

Experimental study on flame stability limits of lithium ion battery electrolyte solvents with organophosphorus compounds addition using a candle-like wick combustion system

To evaluate the fire-retardant effectiveness of organophosphorus compounds (OPC) added to Li-ion battery electrolyte solvents, the limiting oxygen concentration (LOC) method is used in conjunction with a wick combustion system, called as wick-LOC method. With the wick-LOC method, two modes of stabilized flame are found, namely, wake flame and full flame. When OPC is added to the electrolyte, two distinct branches of extinction processes occur according to the different flame modes near extinction with no transition from the full flame to the wake flame in the case of higher OPC addition. The flame stability limits are measured as a function of OPC addition for both flame modes. The wake flame is shown to be consistently more stable at low levels of OPC addition. However, once the OPC addition exceeds a critical amount, the full flame shows higher stability with a lower LOC than the wake flame. These phenomena in the two regimes are also found in other cases of high OPC addition (different type of OPC and electrolyte solvent). In the most stable flame mode, the regime switches from the wake flame to the full flame with increasing OPC addition, and they are defined correspondingly as “blow-off regime” and “quenching regime”. To explain the presence of these two regimes, the thermal balance effect is considered in the discussion of flame extinction mechanisms. The difference in flame volume near the extinction limit shows that the quenching mechanism dominates flame extinction under higher OPC addition. The thermal balance effect on flame stabilization or extinction can be the additional impact on the fire retardation abilities of OPC itself.

Machine learning prediction of coordination energies for alkali group elements in battery electrolyte solvents.

We combined a data science-driven method with quantum chemistry calculations, and applied it to the battery electrolyte problem. We performed quantum chemistry calculations on the coordination energy (Ecoord) of five alkali metal ions (Li, Na, K, Rb, and Cs) to electrolyte solvent, which is intimately related to ion transfer at the electrolyte/electrode interface. Three regression methods, namely, multiple linear regression (MLR), least absolute shrinkage and selection operator (LASSO), and exhaustive search with linear regression (ES-LiR), were employed to find the relationship between Ecoord and descriptors. Descriptors include both ion and solvent properties, such as the radius of metal ions or the atomic charge of solvent molecules. Our results clearly indicate that the ionic radius and atomic charge of the oxygen atom that is connected to the metal ion are the most important descriptors. Good prediction accuracy for Ecoord of 0.127 eV was obtained using ES-LiR, meaning that we can predict Ecoord for any alkali ion without performing quantum chemistry calculations for ion-solvent pairs. Further improvement in the prediction accuracy was made by applying the exhaustive search with Gaussian process, which yields 0.016 eV for the prediction accuracy of Ecoord.

Solvating power series of electrolyte solvents for lithium batteries

From dictating the redox potential of electrolyte solvents to shaping the stability of solid-electrolyte interfaces, solvation plays a critical role in the electrochemistry of electrolytes.

Polarizable Molecular Dynamics and Experiments of 1,2-Dimethoxyethane Electrolytes with Lithium and Sodium Salts: Structure and Transport Properties

The structure and transport properties of electrolyte solutions of 1,2-dimethoxyethane (DME) having salts of Li+ with bis(trifluoromethanesulfonyl)imide ([TFSI]-) or Na+ with [TFSI]- are investigated with polarizable molecular dynamics and experiments. Polarizable force fields for Li+ and Na+ with DME and [TFSI]- were developed based on quantum chemistry calculations, ab initio molecular dynamics simulations, and thermodynamic liquid-state properties. Simulation results for density, viscosity, self-diffusion coefficient, and conductivity of the electrolytes all agree well with the trends and magnitudes of available experimental data for a wide range of salt concentrations. As the concentration of salt increases, the electrolytes become more viscous and molecular species become less mobile. Ionic conductivity does not change monotonically with salt concentration and exhibits a maximum between 0.5 and 1.0 M for both Li[TFSI] and Na[TFSI] electrolytes. Comparatively, both cations are solvated by 5-6 DME or [TFSI]- oxygen atoms and exhibit similar diffusivities and conductivities. The solvation shell of Na+ is found to be more weakly bound and to have a lower binding residence time than that of Li+. The transport of Li+ therefore is more vehicular, through the motion of the solvation shell, while the transport of Na+ is based more on exchange, through the replacement of solvating species. The atomistic insight provided by this work can be used as the basis for future rational design of improved electrolyte solvents for lithium-oxygen, sodium-oxygen, and lithium-sulfur batteries.

(Invited) Recent Progress in Understanding Battery Electrolyte Electrochemical Stability and Its Relationship with Electrolyte Structural Properties

Designing compatible electrochemical interfaces is paramount for enabling energy storage devices from batteries to electric double layer capacitors as electrolytes should be either electrochemically stable at the electrode and current collectors surfaces or form a stable electronically insulating but ionically conducting solid electrolyte interphase (SEI). Electrical double layer capacitors with narrow pores cannot rely on the SEI to extend their operating window placing more stringent requirements on electrolyte intrinsic electrochemical stability compared to batteries. In this presentation I will discuss a molecular scale insight into the initial mechanisms of battery electrolyte electrochemical degradation on the active and non-active electrodes obtained from a coordinated density functional theory (DFT) study and non-reactive molecular dynamics (MD) simulations of bulk and interfacial properties of electrolytes and the relationship between them. In the first part of the presentation, I will focus on understanding of electrolyte oxidation reactions on active and non-active electrodes. While HOMO screening for redox shuttle molecules was previously successful for quantitatively predicting trends, such screening is often not sufficient for traditional battery electrolyte solvents including cycling and linear carbonates, phosphates and sulfones.(1) Instead, quantum chemistry calculations have shown that the majority of battery solvents with the exception of the solvents with unsaturated functionalities such C=C double bonds do not undergo direct oxidation within typical operating range, instead their oxidation is coupled with the H-transfer to another solvent or oxygen of the electrode surface. Analogously, on the anode the F-transfer and LiF formation during anion and semi-fluorinated solvent reduction occurs at higher potentials compared to direct reduction of isolated anions and solvents.(2) Local ion and solvent environment influences both oxidation and reduction stability and initial decomposition reactions of electrolytes making electrolyte electrochemical stability dependent on the salt concentration and ion and solvent partitioning with the double layer that is in turn is dependent on the applied potential. Highly concentrated aqueous and non-aqueous electrolytes were found in MD simulations to exclude the solvent molecules from directly interacting with the positive electrode surface providing an additional mechanism for extending the electrolyte oxidation stability in addition to the widely discussed elimination of the “free” solvent from the electrolytes by increasing salt concentration.(3) In this presentation, I will give multiple examples on how changes in the double layer partitioning could be beneficial or detrimental to improving the electrode – electrolyte compatibility with aqueous and non-aqueous electrolytes. (4) References Borodin, O.; Olguin, M.; Spear, C. E.; Leiter, K.; Knap, J., Towards High Throughput Screening of Electrochemical Stability of Battery Electrolytes. Nanotechnology 2015, 26, 354003.Borodin, O.; Olguin, M.; Spear, C.; Leiter, K.; Knap, J.; Yushin, G.; Childs, A.; Xu, K., Challenges with Quantum Chemistry-Based Screening of Electrochemical Stability of Lithium Battery Electrolytes. ECS Transactions 2015, 69, 113-123.Vatamanu, J.; Borodin, O., Ramifications of Water-in-Salt Interfacial Structure at Charged Electrodes for Electrolyte Electrochemical Stability. J. Phys. Chem. Lett. 2017, 8, 4362-4367.Borodin, O. ; Ren, X.; Vatamanu, J.; Cresce, A. von Wald; Knap, J.; Xu, K. "A Modeling Insight into Battery Electrolyte Electrochemical Stability and Interfacial Structure" Acc. Chem. Res. 2017 (ASAP)