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Ion interactions strongly determine the solvation environments of multivalent electrolytes even at concentrations below that required for practical battery-based energy storage. This statement is particularly true of electrolytes utilizing ethereal solvents due to their low dielectric constants. These solvents are among the most commonly used for multivalent batteries based on reactive metals (Mg, Ca) due to their reductive stability. Recent developments in multivalent electrolyte design have produced a variety of new salts for Mg

Multivalent batteries represent an important beyond Li-ion energy storage concept. The prospect of calcium batteries, in particular, has emerged recently due to novel electrolyte demonstrations, especially that of a ground-breaking combination of the borohydride salt Ca(BH4)2 dissolved in tetrahydrofuran. Recent analysis of magnesium and calcium versions of this electrolyte led to the identification of divergent speciation pathways for Mg2+ and Ca2+ despite identical anions and solvents, owing to differences in cation size and attendant flexibility of coordination. To test these proposed speciation equilibria and develop a more quantitative understanding thereof, we have applied pulsed-field-gradient nuclear magnetic resonance and dielectric relaxation spectroscopy to study these electrolytes. Concentration-dependent variation in anion diffusivities and solution dipole relaxations, interpreted with the aid of molecular dynamics simulations, confirms these divergent Mg2+ and Ca2+ speciation pathways. These results provide a more quantitative description of the electroactive species populations. We find that these species are present in relatively small quantities, even in the highly active Ca(BH4)2/tetrahydrofuran electrolyte. This finding helps interpret previous characterizations of metal deposition efficiency and morphology control and thus provides important fundamental insight into the dynamic properties of multivalent electrolytes for next-generation batteries.

Author(s): Fong, KD; Self, J; McCloskey, BD; Persson, KA | Abstract: The development of next-generation polymer-based electrolytes for energy storage applications would greatly benefit from a deeper understanding of transport phenomena in these systems. In this Perspective, we argue that the Onsager transport equations provide an intuitive but underutilized framework for analyzing transport in polymer-based electrolytes. Unlike the ubiquitous Stefan-Maxwell equations, the Onsager framework generates transport coefficients with clear physical interpretation at the atomistic level and can be computed easily from molecular simulations using Green-Kubo relations. Herein we present an overview of the Onsager transport theory as it applies to polymer-based electrolytes and discuss its relation to experimentally measurable transport properties and the Stefan-Maxwell equations. Using case studies from recent computational work, we demonstrate how this framework can clarify nonintuitive phenomena such as negative cation transference number, anticorrelated cation-anion motion, and the dramatic failure of the Nernst-Einstein approximation. We discuss how insights from such analysis can inform design rules for improved systems.

Electrolytes featuring negatively charged polymers, such as nonaqueous polyelectrolyte solutions and polymerized ionic liquids, are currently under investigation as potential high cation transferen...

Summary As a legacy left behind by classical analytical electrochemistry in pursuit of ideal electrodics, and classical physical electrochemistry in pursuit of the most conductive ionics, the study of non-aqueous electrolytes has been historically confined within a narrow concentration regime around 1 molarity (M). This confinement was breached in recent years when unusual properties were found to arise from the excessive salt presence, which often bring benefits to electrochemical, thermal, transport, interfacial, and interphasial properties that are of significant interest to the electrochemical energy storage community. This article provides an overview on this newly discovered and under-explored realm, with emphasis placed on their applications in rechargeable batteries.

Superconcentrated electrolytes for lithium-ion batteries have shown promise in circumventing certain limitations of conventional carbonate electrolytes at lower concentrations while introducing new...

Reliable prediction of freezing point depression in liquid electrolytes will accelerate the development of improved Li-ion batteries which can operate in low temperature environments. In this work we establish a computational methodology to calculate activity coefficients and liquidus lines for battery-relevant liquid electrolytes. Electronic structure methods are used in conjuction with classical molecular dynamics simulations and theoretical expressions for Born solvation energy, ion-atmosphere effects from Debye-Hückel theory and solvent entropic effects. The framework uses no a priori knowledge beyond neat solvent properties and the concentration of salt. LiPF6 in propylene carbonate (PC), LiPF6 in dimethyl carbonate (DMC) and LiClO4 in DMC are investigated up to 1 molal with accuracy better than 3 °C when compared to experimental freezing point measurements. We find that the difference in freezing point depression between the propylene carbonate-based electrolyte and the dimethyl carbonate electrolytes originates from the difference in the solvent dielectric constant.

Understanding and predicting the freezing point depression of liquid electrolytes is of interest particularly for low-temperature battery applications. We will present a computational methodology to calculate activity coefficients and the freezing point depression of liquid electrolytes relevant to Li-ion batteries. Theoretical expressions for Born solvation, Debye-Huckel ion atmosphere effects and solvent entropy are used with results from classical molecular dynamics simulations and electronic structure methods to calculate the activity coefficients of liquid electrolytes. Using the calculated activity coefficients as well as neat solvent properties, liquidus lines of the studied electrolytes are obtained up to 1 molal. The liquid electrolytes studied include LiPF6 in dimethyl carbonate and LiPF6 in propylene carbonate. It is found that the more significant freezing point depression of the propylene carbonate-based electrolyte versus dimethyl carbonate-based electrolyte originates in large part from the much higher dielectric constant of propylene carbonate versus dimethyl carbonate.

Magnesium is attractive as an anode owing to its high capacity and abundance in the Earth's crust. It remains a challenge to realize efficient plating and stripping in electrochemical cells with a Mg anode, due to its reactivity with conventional liquid electrolytes comprising fluorinated salts. We hypothesized that the reactivity of species in the electrolyte may be controlled through solvation structure in concentrated electrolytes as well as those featuring a fluorinated diluent, which aids in reducing the viscosity and maintaining high ionic conductivity. Here, I will describe our efforts to understand solvation structure and reactivity at Mg–electrolyte interfaces. In turn, I will highlight how specific compositions are impactful in sustaining the electroreversibility of Mg anodes for hundreds of hours of continuous operation with low overpotential. I will tie this behavior to the structure of the interphase, whose composition is divergent from what is typically observed for dilute and concentrated electrolytes. There are emerging implications stemming from our work that motivates the future design of artificial interphases for Mg anodes obviating the use of chlorides, which would otherwise corrode other components of the cell.

The solid electrolyte interphase (SEI), a nanoscale passivation film formed by reductive electrolyte decomposition during initial battery charging, is a key component of lithium-ion batteries (LIBs). When properly formed, an SEI layer allows ion mobility and prevents further degradation of the battery anode and electrolyte. Despite the essential protective role of the SEI and its importance in promoting reversible cycling in LIBs, the mechanisms underlying SEI formation remain poorly understood. In this work, we use first-principles quantum chemical calculations and stochastic methods to directly model mechanistic reactive competition during SEI formation for the first time. Our simulations, which are general to any LIB with an ethylene carbonate (EC)-based electrolyte, suggest that the separation of the SEI into primarily inorganic and primarily organic layers arises due to reductive decomposition of major organic products near the electrode interface. By varying the initial quantities of water and carbon dioxide, we also explore the role of impurity species in SEI formation. We validate that water is critical to the formation of lithium ethylene monocarbonate (LEMC) and could promote the formation of the postulated dilithium ethylene monocarbonate (DLEMC). Further, we observe that carbon dioxide reduction can compete with EC reduction, leading to downstream competition between organic carbonates, inorganic carbonates, and lithium oxalate. In addition to furnishing fundamental insights into the complex chemistry of the SEI, these findings provide a roadmap for future mechanistic studies of SEI formation in LIBs as well as next-generation batteries.

Electrolytes featuring negatively-charged polymers such as nonaqueous polyelectrolyte solutions and polymerized ionic liquids are currently under investigation as potential high cation transference number (t+) electrolytes for lithium ion batteries. Herein, we use coarse-grained molecular dynamics simulations to characterize the Onsager transport coefficients of polyelectrolyte solutions as a function of chain length and concentration. For all systems studied, we find that the rigorously computed transference number is substantially lower than that approximated by the ideal solution (Nernst-Einstein) equations typically used to characterize these systems due to the presence of strong anion-anion and cation-anion correlations. None of the polyelectrolyte solutions achieve t+ greater than that of the conventional binary salt electrolyte, with some solutions having negative t+. This work demonstrates that the Nernst-Einstein assumption does not provide a physically meaningful estimate of the transference number in these solutions and calls into question the expectation of polyelectrolytes to exhibit high cation transference number.

Electrolytes featuring negatively-charged polymers such as nonaqueous polyelectrolyte solutions and polymerized ionic liquids are currently under investigation as potential high cation transference number (t+) electrolytes for lithium ion batteries. Herein, we use coarse-grained molecular dynamics simulations to characterize the Onsager transport coefficients of polyelectrolyte solutions as a function of chain length and concentration. For all systems studied, we find that the rigorously computed transference number is substantially lower than that approximated by the ideal solution (Nernst-Einstein) equations typically used to characterize these systems due to the presence of strong anion-anion and cation-anion correlations. None of the polyelectrolyte solutions achieve t+ greater than that of the conventional binary salt electrolyte, with some solutions having negative t+. This work demonstrates that the Nernst-Einstein assumption does not provide a physically meaningful estimate of the transference number in these solutions and calls into question the expectation of polyelectrolytes to exhibit high cation transference number.

Detailed speciation of electrolytes as a function of chemical system and concentration provides the foundation for understanding bulk transport as well as possible decomposition mechanisms. In particular, multivalent electrolytes have shown a strong coupling between anodic stability and solvation structure. Furthermore, solvents that are found to exhibit reasonable stability against alkaline-earth metals generally exhibit low permittivity, which typically increases the complexity of the electrolyte species. To improve our understanding of ionic population and associated transport in these important classes of electrolytes, the speciation of Mg(TFSI)2 in monoglyme and diglyme systems is studied via a multiscale thermodynamic model using first-principles calculations for ion association and molecular dynamics simulations for dielectric properties. The results are then compared to Raman and dielectric relaxation spectroscopies, which independently confirm the modeling insights. We find that the significant presence of free ions in the low-permittivity glymes in the concentration range from 0.02 to 0.6 M is well-explained by the low-permittivity redissociation hypothesis. Here, salt speciation is largely dictated by long-range electrostatics, which includes permittivity increases due to polar contact ion pairs. The present results suggest that other low-permittivity multivalent electrolytes may also reach high conductivities as a result of redissociation.

In this article, we present evidence that the dielectric constant of an electrolyte solution can be effectively used to infer the association regime of the salt species from computational methods. As case studies, we consider the low dielectric constant solvent dimethyl carbonate with LiAsF6 and LiPF6 salts at low concentrations. Using both quantum “ab initio” methods as well classical molecular dynamics simulations, we elucidate the salt’s contribution to the dielectric constant as well as the dipolar relaxation times, which act as quantitative signatures. By comparing to previously published measurements, we provide strong evidence for the presence of contact-ion pairs at these low concentrations. Interestingly, these ion pairs increase the dielectric constant of the solution, allowing for significantly improved ionic conductivity as a function of salt concentrations. We also discuss the role of multimeric equilibrium species as contributors to the functional properties of designer electrolytes, such as...

Lithium-ion batteries face low temperature performance issues, limiting the adoption of technologies ranging from electric vehicles to stationary grid storage. This problem is thought to be exacerbated by slow transport within the electrolyte, which in turn may be influenced by ion association, solvent viscosity, and cation transference number. How these factors collectively impact low temperature transport phenomena, however, remains poorly understood. Here we show using all-atom classical molecular dynamics (MD) simulations that the dominant factor influencing low temperature transport in LP57 (1 M LiPF6 in 3:7 ethylene carbonate (EC)/ethyl methyl carbonate (EMC)) is solvent viscosity, rather than ion aggregation or cation transference number. We find that ion association decreases with decreasing temperature, while the cation transference number is positive and roughly independent of temperature. In an effort to improve low temperature performance, we introduce γ-butyrolactone (GBL) as a low viscosity co-solvent to explore two alternative formulations: 1 M LiPF6 in 15:15:70 EC/GBL/EMC and 3:7 GBL/EMC. While GBL reduces solution viscosity, its low dielectric constant results in increased ion pairing, yielding neither improved bulk ionic conductivity nor appreciably altered ion transport mechanisms. We expect that these results will enhance understanding of low temperature transport and inform the development of superior electrolytes.

Here we describe the use of organo ionic phosphonium salts to access a broad range of useful binary and ternary (super)-concentrated liquid electrolytes for rechargeable magnesium batteries.

Nonaqueous polyelectrolyte solutions have been recently proposed as high Li+ transference number electrolytes for lithium ion batteries. However, the atomistic phenomena governing ion diffusion and migration in polyelectrolytes are poorly understood, particularly in nonaqueous solvents. Here, the structural and transport properties of a model polyelectrolyte solution, poly(allyl glycidyl ether-lithium sulfonate) in dimethyl sulfoxide, are studied using all-atom molecular dynamics simulations. We find that the static structural analysis of Li+ ion pairing is insufficient to fully explain the overall conductivity trend, necessitating a dynamic analysis of the diffusion mechanism, in which we observe a shift from largely vehicular transport to more structural diffusion as the Li+ concentration increases. Furthermore, we demonstrate that despite the significantly higher diffusion coefficient of the lithium ion, the negatively charged polyion is responsible for the majority of the solution conductivity at all concentrations, corresponding to Li+ transference numbers much lower than previously estimated experimentally. We quantify the ion–ion correlations unique to polyelectrolyte systems that are responsible for this surprising behavior. These results highlight the need to reconsider the approximations typically made for transport in polyelectrolyte solutions., Molecular dynamics simulations reveal the mechanisms governing charge transport in nonaqueous polyelectrolyte solutions for application in Li ion batteries.

We provide a quantum chemical computational framework to calculate ion association constants relevant to lithium ion battery electrolytes. We compare our method to reported experimental values as the solvent, cation, and anion are varied. For solvent, anion, and cation variations, the standard errors are respectively 0.2 eV, 0.12 eV, and 0.11 eV for the chosen data set, where Pearson correlation values are all above 0.92.

Density functional theory (DFT) is used in conjunction with experimental results to propose decomposition pathways that describe the role and ultimate fate of the PES additive in Li-ion batteries. Oxidation of PES produces carbonyl sulfide gas and ethene at the positive electrode, both experimentally observed byproducts. However, the calculated standard potential for simple PES oxidation, E 0 o x ∼ 6.7 V vs. Li/Li+, is quite high, suggesting this pathway is unlikely. A “reactive electrode model” is presented, in which the positive electrode material is a reagent in the pseudo-combustion of PES (and other solvents). This spontaneous process produces carbonyl sulfide, carbon dioxide, and a rock salt surface layer, all of which are experimentally observed. At the negative electrode, the reduction of PES occurs via two one-electron steps, where E 0 r e d , 1 = 0.9 V and E 0 r e d , 2 = 4.3 V. The reduced species, Li2PES, can react with hydrogen and methyl radicals to produce propene, methylpropene, propane and lithium sulfite. Nucleophilic Li2PES can also react with electrophilic PES, ethylene carbonate, or ethyl methyl carbonate. Eighteen possible organic sulphate ‘building blocks’ for the solid-electrolyte interphase (SEI) are presented. X-ray photoelectron spectroscopy (XPS) measurements demonstrate that PES reduction indeed results in both lithium sulfite and organic sulphate SEI components.

Li[Ni 1/3 Mn 1/3 Co 1/3 ]O 2 /graphite, Li[Ni 0.5 Mn 0.3 Co 0.2 ]O 2 /graphite and Li[Ni 0.6 Mn 0.2 Co 0.2 O 2 ]/graphite pouch cells were examined with and without electrolyte additives using the ultra high precision charger at Dalhousie University, electrochemical impedance spectroscopy, gas evolution measurements and “cycle-store” tests. The electrolyte additives tested were vinylene carbonate (VC), prop-1-ene-1,3-sultone (PES), pyridine-boron trifluoride (PBF), 2% PES + 1% methylene methanedisulfonate (MMDS) + 1% tris(trimethylsilyl) phosphite (TTSPi) and 0.5% pyrazine di-boron trifluoride (PRZ) + 1% MMDS. The charge end-point capacity slippage, capacity fade, coulombic efficiency, impedance change during cycling, gas evolution and voltage drop during “cycle-store” testing were compared to gain an understanding of the effects of these promising electrolyte additives or additive combinations on the different types of pouch cells. It is hoped that this report can be used as a guide or reference for the wise choice of electrolyte additives in Li[Ni 1/3 Mn 1/3 Co 1/3 ]O 2 /graphite, Li[Ni 0.5 Mn 0.3 Co 0.2 ]O 2 /graphite and Li[Ni 0.6 Mn 0.2 Co 0.2 O 2 ]/graphite pouch cells and also to show the shortcomings of particular positive electrode compositions.

Many of the liquid electrolyte candidates for multivalent batteries exhibit increasing molar conductivity with concentration. In other words, the concentration-normalized conductivity increases as a function of salt concentration. This is in contrast to conventional electrolytes, e.g. aqueous or cyclic carbonate-based electrolyte solutions, where the molar conductivity decreases with concentration due to increased viscosity and ion aggregation. Low permittivity electrolytes with increasing molar conductivity include Ca(BH4)2 in tetrahydrofuran, Mg(TFSI)2 in monoglyme and Mg(TFSI)2 in diglyme. In order to investigate the origin of this anomalous molar conductivity trend, we study the physicochemical properties of the electrolytes using a combined computational/experimental approach. Ab initio calculations and classical molecular dynamics simulations are undertaken to study ion speciation, ion activity and changes to solution permittivity. Furthermore, we undertake conductivity, microwave and raman spectroscopy measurements.

This work reports measurements of the dielectric constants of ethylene carbonate (EC)/ethyl methyl carbonate (EMC) blends between 25 and 60 °C. Dielectric constants were measured using a cylindrical capacitance cell and a frequency response analyzer. EC and EMC form nonideal mixtures that cannot be described by a simple linear mixing model. A quadratic mixing rule was instead adopted, and the mixing parameter is reported for 25–60 °C. The results of this research may be used to calculate the dielectric constant of any EC/EMC mixture over this temperature range with ≤4% estimated error. By modeling the ionic dissociation of lithium hexafluorophosphate (LiPF6) in various solvents, the significance of the dielectric constant on quantum chemistry simulations of chemical processes is explored. The effect of the dielectric constant accuracy on electrochemical processes was similarly evaluated by calculating the solvation energy of neutral and singly oxidized vinylene carbonate in various solvents. It is demonst...

Fluoroethylene carbonate (FEC) has been proposed as an effective electrolyte additive that enhances the stability and elasticity of the solid electrolyte interphase (SEI) of emerging Si and Li metal anodes. However, uncertainties still remain on the exact mechanism through which FEC alters the electrolyte decomposition and SEI formation process. Herein, the influence of FEC on LiPF6/ethylene carbonate (EC) electrolytes for Si anodes is investigated through classical molecular dynamics, Fourier-transform infrared spectroscopy, and quantum chemical calculations. Albeit a minority species, FEC is found to significantly modify the solvation structure and reduction behavior of the electrolyte while being innocuous to transport properties. Even with limited 10% of FEC, the Li+ solvation structure exhibits a notably higher contact-ion pair ratio (14%) than the parent EC electrolyte (6%). Moreover, FEC itself, as a new fluorine-containing species, appears in 1/5 of the Li+ solvation shells. The Li+-coordinated FEC is found to reduce prior to EC and uncoordinated FEC which will passivate the anode surface at an early onset (ca. 0.3 V higher than EC) by forming LiF. The critical role of FEC in tailoring the Li+ solvation structure and as-formed protective SEI composition provides mechanistic insight that will aid in the rational design of novel electrolytes.

Beyond Li-ion electrochemical energy storage systems based on divalent metal cations occupy a new frontier of research and development efforts related to materials chemistry and design. High energy density batteries based on the promise of high capacity Mg or Ca metal anodes are yet to be realized due to problems associated with the stability and ion transport properties of organic electrolytes and insertion cathodes. Controlling the stability of Ca2+ electrolytes at calcium metal anodes has been a particularly challenging task, although a recent demonstration suggests a possible path forward for reversible calcium electrodeposition in ethereal electrolytes.1 The calcium system, then, represents an intriguing exemplar for understanding divalent metal electrodeposition under conditions that push the boundaries of organic electrolyte stability. In this presentation we will discuss how interactions among species within Ca2+ electrolytes such as Ca(BH4)2/THF and other recently developed systems facilitate transport and delivery of the working cation to the interface for deposition and how surface interactions influence the stability of supporting electrolyte species and direct the system toward inefficiency and byproduct formation as a function of species susceptibility. These studies utilize a combination of experimental spectroscopy, microscopy and electrochemistry along with computational simulation of Ca2+ coordination cluster structures and stabilities. We will discuss the impact of these factors on calcium metal morphology and composition providing new insight into the rules connecting Ca2+ electrolyte properties to interfaces for Ca metal deposition. These design principles will serve as a guide to the development of advanced electrolyte concepts capable of pushing the boundaries of reductive stability in divalent metal electrolytes toward higher voltage beyond Li-ion batteries. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. References Wang, D.; Gao, X.; Chen, Y.; Jin, L.; Kuss, C.; Bruce, P. G., Plating and stripping calcium in an organic electrolyte. Nature Materials 2017, 17, 16.

Delay differential equations (DDE) can have "chaotic" solutions that can be used to mimic Brownian motion. Since a Brownian motion is random in its velocity, it is reasonable to think that a random number generator (RNG) might be constructed from such a model. In this preliminary study, we consider one specific example of this and show that it satisfies criteria commonly employed in the testing of random number generators (from TestU01's very stringent "Big Crush" battery of tests). A technique termed digit discarding, commonly used in both this generator and physical RNG's using laser feedback systems, is discussed with regard to the maximal Lyapunov exponent. Also, we benchmark the generator to a contemporary common method: the multiple recursive generator, MRG32k3a. Although our method is about 7 times slower than MRG32k3a, there is in principle no apparent limit on the number of possible values that can be generated from the scheme we present here., Comment: 9 pages, 5 figures, 1 table

INTRODUCTION For over a decade, the most common electrolyte solution in commercially available lithium-ion cells has remained LiPF6 dissolved in some blend of organic carbonate solvents.1 Rather than change the salt or the solvent, many industrial production lines have adopted the use of electrolyte additives to improve cycling performance, extend calendar lifetime, decrease detrimental gas formation and improve lithium-ion cell safety. The practical advantage of this move to electrolyte additives is that performance improvements can be achieved with minimal changes to existing supply chains for electrolyte salts and solvents. However, the optimization of lithium-ion cells for various applications (automotive, grid storage, etc.) would be greatly enhanced by a more detailed understanding of the cell chemistry. In particular, it is desirable to characterize the chemical and electrochemical reactions that occur during solid-electrolyte interphase (SEI) formation for the various additives in use. This presentation will demonstrate how our group has used computational and experimental methods, together, to study SEI formation for two additives, prop-1-ene-1,3-sultone (PES)2 and pyridine boron trifluoride (PBF).3 EXPERIMENTAL Density functional theory (DFT) calculations were performed with the Gaussian 09 (G09.D01) software package using the B3LYP and M06-2X hybrid functionals. The IEFPCM-UFF solvation model and its parameterization will be discussed.4 Several experimental methods will be discussed, including coulometry, in situ volumetric measurements using the Measuring Archimedes’ Gas Evolution (MAGE) instrument, gas-chromatography coupled with mass spectrometry (GC-MS) and thermal conductivity detection (GC-TCD), X-ray photoelectron spectroscopy (XPS), and isothermal microcalorimetry. Experimental details have been described previously.5–9 RESULTS AND DISCUSSION During the initial formation cycle (i.e., the first charge step), PES forms a passive SEI at the negative electrode surface via a two-electron electrochemical reduction, which produces Li2PES (Figure 1). The decomposition of this compound and its various reactions with the solvent (EC and EMC) and with other PES molecules will be discussed. These reactions are spontaneous and result in the formation of Li2SO3 and organic sulfate species (RSO3Li) at the anode. This is a good match to the S2ppeaks observed in the XPS spectrum of the anode after formation. The predicted gas-phase products, including several hydrocarbons at the anode, are also consistent with those observed by GC-MS. PBF similarly forms a passive SEI at the graphite surface by electrochemical reduction. The reduced species, LiPBF, forms a bipyridine boron trifluoride adduct, which is accompanied by the reduction of the solvent component, ethylene carbonate (EC). This reaction produces lithium ethyl carbonate, a soluble lithium semicarbonate. This reaction pathway does not produce an appreciable amount of any gas-phase species, as demonstrated by MAGE, GC-MS, and GC-TCD results. The predicted PBF-derived dimer is consistent with the C1s and N1s peaks observed in the XPS spectrum of the anode surface after formation. In summary, carefully developed theoretical methods coupled with experimental data reveal several spontaneous pathways for the reductive decomposition of two additives, PES and PBF. It is hoped that these results will prove useful for developing new and improved electrolyte additives. Moreover, these results provide new insight into the role of the solvent molecules during SEI formation that may have significance for research into new solvents and solvent blends. REFERENCES 1. K. Xu, Chem. Rev., 114, 11503–11618 (2014). 2. B. Li, M. Xu, T. Li, W. Li, and S. Hu, Electrochem. Commun., 17, 92–95 (2012). 3. M. Nie, J. Xia, and J. R. Dahn, J. Electrochem. Soc., 162, A1186–A1195 (2015). 4. D. S. Hall, J. Self, and J. R. Dahn, J. Phys. Chem. C, 119, 22322–22330 (2015). 5. C. P. Aiken et al., J. Electrochem. Soc., 161, A1548–A1554 (2014). 6. V. L. Chevrier et al., J. Electrochem. Soc., 161, A783–A791 (2014). 7. L. Madec et al., J. Phys. Chem. C, 118, 29608–29622 (2014). 8. R. Petibon, L. M. Rotermund, and J. R. Dahn, J. Power Sources, 287, 184–195 (2015). 9. J. Self, D. S. Hall, L. Madec, and J. R. Dahn, J. Power Sources, 298, 369–378 (2015). Figure 1

Background: Cyclic neutropenia is characterized by oscillatory fluctuations in blood neutrophil counts, usually with nadirs Methods: We have implemented a website application for easy and direct data entry of serial blood counts to detect statistically significant periodicities using the Lomb periodogram. Physicians, nurses, other healthcare providers or patients can directly enter the blood count data for analysis on a website to allow immediate visualization of the serial counts and calculation of the probability of statistically significant cycling and the period, i.e., length of the cycle. Results: We have analyzed the counts from 42 patients (21 ELANE positive, 8 ELANE negative, 13 ELANE unknown) enrolled in the Severe Chronic Neutropenia International Registry with a clinical diagnosis of cyclic neutropenia to determine the accuracy of clinical diagnoses based on this form of statistical analysis. Our preliminary results showed that it is easy to learn how to use this program. We estimate that at least 20 counts obtained at 2-3 day intervals for 6 weeks are the minimum needed to detect cyclic neutropenia on a statistically sound basis, while 20-40 counts obtained at 2-3 day intervals over an 8-10 week period was more likely to yield statistical and clinical certainty about the diagnosis. The figure below shows readouts for the periodogram analysis for one patient. It shows the influence of 17 counts versus 31 counts for a patient with the clinical diagnosis of cyclic neutropenia and a mutation in ELANE. The confidence intervals (95%) and (99%) are exceeded for the series of 31 counts but not for the shorter series. The peak, approximate cycle length is 22 days for this series of counts. As of yet, we do not have the sufficient daily count data to determine if more frequent testing (e.g. daily testing) is better than testing every 2-3 days. We are currently testing the patterns of neutrophil fluctuations in patients on G-CSF to see if cyclic neutropenia can be diagnosed in patients that are on (or during) treatment. We have learned that many patients with the clinical diagnosis of CyN do not have sufficient serial blood cell count data to confirm this diagnosis on a statistical basis. Conclusion: We have developed a simple method for making periodogram analysis much more widely available to clinicians and patients on a world-wide basis. Statistical analysis of carefully collected serial data will help to secure the diagnosis of cyclic neutropenia and provide patients with important prognostic information. Figure 1. Figure 1. Disclosures Dale: Amgen: Consultancy, Honoraria, Research Funding.

INTRODUCTION One way to improve the cycling performance and stability of Li-ion cells is the use of electrolyte additives. In recent years, prop-1-ene-1,3-sultone (PES) has shown great promise for improving cell lifetime and decreasing gas formation.1–5Voltage cycling experiments and surface analysis studies have provided important clues for understanding the fate of PES in cells. However, the details of this additive’s mechanism of action remains unknown. This presentation will discuss computational chemistry methods, including the accurate representation of solvation for ethylene carbonate (EC)/ethylmethyl carbonate (EMC) mixtures, and the application of these methods to gain insight into the role and ultimate fate of PES in Li-ion cells. EXPERIMENTAL Calculations were performed with the Gaussian 09 (G09.D01) software package using the B3LYP/6-311++G(d,p) method. The IEFPCM-UFF solvation model and its parameterization will be discussed. A cylindrical, stainless steel capacitance cell, based on the design of Greer and Jacobs, was used for dielectric constant measurements.6 Machine-made 220 mAh graphite/Li[Ni1/3Mn1/3Co1/3]O2 (NMC) pouch cells were filled with 3:7 EC/EMC, 1 M LiPF6, and 0 – 2 % PES, and galvanostatically cycled.4 Select cells were disassembled in an argon-filled glove box for XPS surface analysis as described by Madec et al.7 Volumetric and GC-MS analysis of gas formation was performed as described by Self et al.5 RESULTS AND DISCUSSION Computational chemistry can be used to determine standard electrode potentials, free energies of reactions and transition state energies. It is, however, imperative that solvation is properly modeled to obtain meaningful results. The polarizable continuum model (PCM) is a simple yet robust approach that requires only the dielectric constant (static permittivity) of the reaction medium. Therefore, dielectric constants of EC/EMC solvent blends were measured at various compositions and temperatures. It was found that measured values do not exactly match those predicted by a simple linear combination of EC and EMC. The reactions of PES at the electrodes were then investigated. PES reduction has a calculated reduction potential of 1.0 V vs. Li/Li+, which closely matches experimental dQ/dV plots.4 The subsequent reduction is predicted to occur very rapidly and results in the reactive Li2PES compound shown in Figure 1. The decomposition of this compound and its various reactions with the solvent (EC and EMC) and with other PES molecules will be discussed. These reactions are spontaneous and result in the formation of Li2SO3 and organic sulfate species (RSO3Li) at the anode. This is a good match to the S 2p peaks observed in the XPS spectrum of the anode after formation. The predicted gas-phase products, including several hydrocarbons at the anode and the formation of O=C=S at the cathode, are also consistent with those observed by GC-MS. In summary, carefully developed theoretical methods coupled with experimental data reveal several spontaneous pathways for the reductive decomposition of PES. It is hoped that these results will also prove useful for developing new and improved electrolyte additives. REFERENCES 1. B. Li et al., J. Mater. Chem. A, 1, 12954–12961 (2013). 2. B. Li et al., Electrochimica Acta, 105, 1–6 (2013). 3. B. Li, M. Xu, T. Li, W. Li, and S. Hu, Electrochem. Commun., 17, 92–95 (2012). 4. J. Xia et al., J. Electrochem. Soc., 161, A1634–A1641 (2014). 5. J. Self, C. P. Aiken, R. Petibon, and J. R. Dahn, J. Electrochem. Soc., 162, A796–A802 (2015). 6. D. T. Jacobs and S. C. Greer, Rev. Sci. Instrum., 51, 994–995 (1980). 7. L. Madec et al., J. Phys. Chem. C, 118, 29608–29622 (2014). 8. K. Xu, Chem. Rev., 114, 11503–11618 (2014). Figure 1 – The reduced Li2PES compound predicted to form at the anode during cell formation. Figure 1