Free Electrolyte Research Articles

Truly quasi-solid-state lithium cells utilizing carbonate free polymer electrolytes on engineered LiFePO4

Stable and safe functioning of a Li-ion battery is the demand of modern generation. Herein, we are demonstrating the application of an in-situ free radical polymerisation process (thermal curing) to fabricate a polymer electrolyte that possesses mechanical robustness, high thermal stability, improved interfacial and ion transport characteristics along with stable cycling at ambient conditions. The polymer electrolyte is obtained by direct polymerization over the electrode surface in one pot starting from a reactive mixture comprising an ethylene oxide-based dimethacrylic oligomer (BDM), dimethyl polyethylene glycol (DPG) and lithium salt. Furthermore, an engineered cathode is used, comprising a LiFePO4/PEDOT:PSS interface at the current collector that improves the material utilization at high rates and mitigates the corrosive effects of LiTFSI on aluminium current collector. The lithium cell resulting from the newly elaborated multiphase assembly of the composite cathode with the DPG-based carbonate-free polymer electrolyte film exhibits excellent reversibility upon prolonged cycling at ambient as well as elevated temperatures, which is found to be superior compared to previous reports on uncoated electrodes with polymer electrolytes.

Fluorination of free lithium residues on the surface of lithium nickel cobalt aluminum oxide cathode materials for lithium ion batteries

Lithium nickel cobalt aluminum oxide (LNCA) cathode materials for lithium ion batteries (LIBs) were treated with NH4FHF to convert free Li2CO3 and LiOH, which are natively present on the LNCA surface, into a stable LiF layer. Gas evolution caused by a side-reaction between the reactive free lithium compounds and electrolyte was greatly reduced using this method. The pH of the water dispersion of LNCA was also lower; this indicates that LiOH, which causes rapid polymerization of the polyvinylidene fluoride binder in the slurry for electrode casting, was effectively eliminated. No significant decrease of the electrochemical performance of LNCA was observed with the treatment. Designed as a one-step simple wet process, the developed method is expected to be practically applicable for mass production with suppressed swelling of LIBs and stabilization of the electrode fabrication process.

Tris(pentafluorophenyl) borane as an electrolyte additive for Li-O2 batteries

TPFPB was used as an additive in a rechargeable Li-O2 cell utilizing an electrolyte composed of a solution 1 M LiPF6 in tetraethylene glycol dimethyl ether (TEGDME) to investigate the effects on capacity and cycling performances. Capacity limitation was also applied to the cells and results were compared with full charging and discharging condition. Galvanostatic charge/discharge (GC) measurements were performed in the assembled Li-O2 cells using assembled cells, designed with different electrolytes. Cell discharge capacities were cyclically tested by a battery tester at a constant current in voltage range between 2.15 V–4.25 V. Discharge products of the electrolytes characterized by SEM and XRD techniques. The electrochemical results showed increasing discharge capacity and cycleability of the assembled cells produced with TPFPB as compared to TPFPB free electrolytes.

Theory of Phase Separation and Polarization for Pure Ionic Liquids.

Room temperature ionic liquids are attractive to numerous applications and particularly, to renewable energy devices. As solvent free electrolytes, they demonstrate a paramount connection between the material morphology and Coulombic interactions: the electrode/RTIL interface is believed to be a product of both polarization and spatiotemporal bulk properties. Yet, theoretical studies have dealt almost exclusively with independent models of morphology and electrokinetics. Introduction of a distinct Cahn-Hilliard-Poisson type mean-field framework for pure molten salts (i.e., in the absence of any neutral component), allows a systematic coupling between morphological evolution and the electrokinetic phenomena, such as transient currents. Specifically, linear analysis shows that spatially periodic patterns form via a finite wavenumber instability and numerical simulations demonstrate that while labyrinthine type patterns develop in the bulk, lamellar structures are favored near charged surfaces. The results demonstrate a qualitative phenomenology that is observed empirically and thus, provide a physically consistent methodology to incorporate phase separation properties into an electrochemical framework.

Factors Controlling the Ionic Mobility of Lithium Electrolyte Solutions in Separator Membranes

The interactions between the mobile ions and membrane substrate were investigated for lithium electrolyte solutions confined within the separator membrane in lithium batteries through NMR and electrochemical measurements as well as theoretical analyses. Fundamental dynamic properties such as ionic mobility, dissociation degree of the salt, and microviscosities of the ion, which are responsible for ionic mobility, were different for the electrolyte confined within the membranes compared with the corresponding values for the free electrolyte. We also found that the interactions between the ion and membrane substrate depend on the type of membrane. The results of this study suggest that the ionic mobility of the electrolyte in a lithium battery can be controlled by selecting separator membranes with suitable chemical or physical properties, which would be significant for improving the performance of the battery system.

Potentiodynamic anodizing of aluminum alloys in Cr(VI)‐free electrolytes

The aerospace industry progressively develops alternatives for chromic acid anodizing, because Cr(VI) is known to be toxic and carcinogenic. In this work, potentiodynamic anodizing of AA1050 and AA2024‐T3 clad was performed in phosphoric‐sulfuric acid (PSA) and sulfuric acid (SAA). All anodizing cycles started with a linear voltage sweep, followed by a constant voltage, or a dynamic voltage. Current density responses were recorded during each anodizing cycle and comprised different stages, which could be related to growth phases of the anodic oxide film. Interesting differences were found between cycles with an intermediate increase in anodizing voltage versus cycles with an intermediate decrease in voltage. Cycles including an increase in voltage resulted in higher anodic oxide formation efficiencies because of a temporary exceedance of the steady state current (recovery period) directly after the voltage step. Also, a sudden decrease in voltage led to distinct border between a fine and coarse region in the film morphology, while a sudden increase in voltage did not. For prolonged anodizing in PSA, coarsening of the upper film part was observed because of the high solubility of Al2O3 in phosphoric acid. Pore walls close to the outer surface did not only get thinner, but completely dissolved in the electrolyte. Consequently, anodic oxide formation efficiencies were higher for SAA than for PSA. Copyright © 2016 John Wiley & Sons, Ltd.

Gas Evolution during Unwanted Lithium Plating in Li-Ion Cells with EC-Based or EC-Free Electrolytes

Lithium plating can be induced in any Li-ion cell that has a graphite negative electrode by increasing the charge rate sufficiently at fixed temperature or by lowering the temperature at a fixed charge rate. Recently, ethylene carbonate (EC)-free electrolytes, such as 1 M LiPF6 in 98% ethyl methyl carbonate (EMC): 2% vinylene carbonate (VC), have been shown to passivate lithiated graphite effectively and allow Li[Ni0.42Mn0.42Co0.16]O2/graphite (NMC442/graphite) Li-ion cells to operate effectively for hundreds of charge discharge cycles. High charge rates and low temperatures were applied to Li[Ni1/3Mn1/3Co1/3]O2/graphite (NMC111/graphite) pouch cells containing EC-free EMC-based electrolytes with additives to study unwanted lithium plating. In such electrolytes, the plated lithium metal is not well passivated and reacts to create gas while in the same cells with 1 M LiPF6 EC:EMC (3:7) electrolyte no gas is observed when Li plating occurs because EC passivates metallic Li well. The volume of the pouch cells with EC-free electrolytes increased sharply when Li plating occurred as measured using in-situ methods. In cells having both EC-based and EC-free electrolytes, lithium plating was the cause of rapid capacity loss at high charge rates at both 10°C and 22°C.

Metabolic monitoring on small and medium sized dairy farms in Emsland, Germany

The aim of this study was to evaluate metabolic analyses on small dairy farms regarding indications, realization, and results over 5years. In 793 serum samples (122 submissions from 53 farms) originating from cows of different lactation stages and from heifers, the parameters free fatty acids (FFA), β-hydroxybutyrate (BHB), cholesterol, urea, creatinine, glucose, total protein, albumin, bilirubin, liver enzymes, creatine kinase (CK), β-carotene, electrolytes and trace elements were analyzed. In 20% of cases, investigations were initiated to control for the metabolic status. Further reasons for laboratory diagnostics were consistent with the culling causes. FFA with 56.7% displayed the most frequent deviations from the normal range during the lactation ante partum. At 8weeks post partum (p.p.) it fell to 36-38% and later to <11%. The BHB deviations from the normal range exceeded 68% throughout the whole lactation. During the middle and late lactation, 40-50% of the measured urea concentrations were above the upper reference limit. Hypocalcemia occurred during the first week p.p. to 13.2% and hypophosphatemia to 6.6%. For CK, deviations from the reference value of 60.4-90.0% were determined. Selenium and copper deficiencies were present in approximately 15% of cases. Heifers more frequently displayed a copper deficiency (21.3%) than cows. β-carotene deficiency was measured ante partum at 50% and p.p. at 47.1-77.8%. Adverse deviations increased between 2006 and 2011 for FFS, urea, β-carotene, and selenium in correlation with a reduction in the milk price between 2009 and 2010. Deviations from the normal range for BHB, CK, cholesterol, calcium, and inorganic phosphate remained constant. On 80% of the farms, the metabolic status improved during the investigation period. Even on smaller farms, peripartal metabolic screenings enable early discovery of causes of the most common culling reasons and provide options for corrective action.

Efficient electrochemical water oxidation in neutral and near-neutral systems with a nanoscale silver-oxide catalyst.

In electrocatalytic water splitting systems pursuing for renewable energy using sunlight, developing robust, stable and easily accessible materials operating under mild chemical conditions is pivotal. We present here a unique nanoparticulate type silver-oxide (AgOx-NP) based robust and highly stable electrocatalyst for efficient water oxidation. The AgOx-NP is generated in situ in a HCO3(-)/CO2 system under benign conditions. Micrographs show that they exhibit a nanoscale box type squared nano-bipyramidal configuration. The oxygen generation is initiated at low overpotential, and a sustained O2 evolution current density of >1.1 mA cm(-2) is achieved during prolonged-period water electrolysis. The AgOx-NP electrocatalyst performs exceptionally well in metal-ion free neutral or near-neutral carbonate, phosphate and borate buffers relative to recently reported Co-oxide and Ni-oxide based heterogeneous electrocatalysts, which are unstable in metal-ion free electrolytes and tend to deactivate with time and lose catalytic performance during long-term experimental tests.

Rational Integration of Polypropylene/Graphene Oxide/Nafion as Ternary‐Layered Separator to Retard the Shuttle of Polysulfides for Lithium–Sulfur Batteries

The reversible electrochemical transformation from lithium (Li) and sulfur (S) into Li2 S through multielectron reactions can be utilized in secondary Li-S batteries with very high energy density. However, both the low Coulombic efficiency and severe capacity degradation limits the full utilization of active sulfur, which hinders the practical applications of Li-S battery system. The present study reports a ternary-layered separator with a macroporous polypropylene (PP) matrix layer, graphene oxide (GO) barrier layer, and Nafion retarding layer as the separator for Li-S batteries with high Coulombic efficiency and superior cyclic stability. In the ternary-layered separator, ultrathin layer of GO (0.0032 mg cm(-2) , estimated to be around 40 layers) blocks the macropores of PP matrix, and a dense ion selective Nafion layer with a very low loading amount of 0.05 mg cm(-2) is attached as a retarding layer to suppress the crossover of sulfur-containing species. The ternary-layered separators are effective in improving the initial capacity and the Coulombic efficiency of Li-S cells from 969 to 1057 mAh g(-1) , and from 80% to over 95% with an LiNO3 -free electrolyte, respectively. The capacity degradation is reduced from 0.34% to 0.18% per cycle within 200 cycles when the PP separator is replaced by the ternary-layered separators. This work provides the rational design strategy for multifunctional separators at cell scale to effective utilizing of active sulfur and retarding of polysulfides, which offers the possibility of high energy density Li-S cells with long cycling life.

Production and Performance of Copper-based Anode-supported SOFCs

The production of tubular SOFCs supported by a cermet anode formulated with copper was successfully achieved. The optimization and the experience developed in the process of extrusion allowed to produce the composite anodes quickly and with good reliability. The low melting temperature of copper and its two oxides imposed a limit on the maximum temperature reachable during co-sintering of the cell. The study of the effect of different sintering aids on the densification of the GDC10 permitted to select Li2O as the most effective, being able to enhance the sinterability of the material and to decrease of more than 600°C its sintering temperature. Although its effect was remarkable, the densification of the thin electrolytic layer when bonded to the supporting anode could not be accomplished without analyzing and solving the issues related to its constrained sintering. A complete cell with a 10 um perfectly dense and crack free Li2O-GDC10 electrolyte, Li2O-GDC10:Cu2O 75:25 vol% anode and GDC10:LSF20 50:50 vol% cathode was obtained after one step sintering for 3h at 1020°C in argon atmosphere. The co-sintering permitted perfect adhesion of the three layers and no sign of debonding. One of the main fabrication problems related to the employment of Cu2O in the cermet anode was its low coefficient of thermal expansion that caused the onset of tensile stress in the electrolyte during cooling and the opening of brittle fractures on its surface. When the Cu2O was increased to 35vol% to insure the electrical conductivity of the anode, the sintering temperature had to be decreased to 995°C to minimize the cracks formation, although this affected the densification of the electrolyte layer. Cells formulated with Cu2O suffered from incomplete densification, cracks and oxidation of the cuprite during reduction. These issues made impossible to perform electrochemical tests. Employment of CuO was less problematic, thanks to its resistance to oxidation and its higher CET. SOFCs were fabricated with Li2O-GDC10 electrolyte, Li2O-GDC10:CuO 60:40 vol% anode and GDC10:LSF20 50:50 vol% cathode. Sintering at 1020°C resulted in a fully dense electrolyte with a fine grain structure, although some cracks due to differential shrinkage could not be completely avoided. Despite this, the cell had a maximum OCV of 0.54 V and the highest measured power density was 8.98 mW cm-2 with a peak power density projected to be 27.5 mW cm-2 when tested at 600°C in dry H2. More test at lower temperatures are currently in progress. These results do show that SOFCs can be produced with a copper cermet anode using similar methods used with NiO-based anodes by a one-step firing procedure at relatively low temperatures, thus having cost and high energy savings. The use of copper can allow for the use of light hydrocarbons in the cell without external reforming equipment or need of high steam to carbon ratio, and without the risk of carbon deposition in the cell

Intensity Modulated Photocurrent Spectroscopy (IMPS) Used to Detect Photoactive Intermediates during Ni-W Electrodeposition

Intensity modulated photocurrent spectroscopy (IMPS) is a technique conventionally used to characterize the semiconductor/electrolyte interface. It is used here in a new way, to track the presence of adsorbed, photoactive intermediates during the electrodeposition process, using Ni-W alloy electrodeposition as an example. Interest in Ni-W alloys are related to their high corrosion resistance, ability to catalyze the hydrogen evolution reaction from water, and superior wear resistance. The Ni-W deposition behavior from aqueous solutions is described as a coupled reaction mechanism and better understanding of the mechanism can help to control the deposit composition, which in turn is related to the resulting properties. To this end, IMPS was used to examine codeposition using an ammonia free citrate-boric acid electrolyte. The IMPS spectra was generated for different applied potentials. A significant current response to the incident modulated UV light was detected where steady state Ni-W codeposition takes place. The results confirm the presence of photoactive intermediates during codeposition, and demonstrates the first use of this technique in the electrodeposition process of a metallic alloy. The attached figure shows a typical response during cathodic deposition of a Ni-W alloy at -1 V vs AglAgCl (42 wt % W) during IMPS compared to a potential where open circuit conditions are achieved and when clearly the alloy is treated anodically. A three electrode, single compartment cell with a flat quartz window was used with the following electrolyte: 0.375 M sodium citrate, 1.0 M boric acid, 0.075 M sodium tungstate, and 0.1 M nickel sulfate at a pH of 7. The response during deposition is significantly larger than that which occurs when a surface oxide is purposely generated; helping to valid that the deposition intermediate contributes to the observed impedance results. A simple model that includes the generated photocurrent contributing to an electrochemical reaction at the electrode/electrolyte interface or being lost to recombination was used to interpret the IMPS results. The dominate process occurring during IMPS is electron-hole pair recombination and thus, the modulated light does not significantly change the deposit composition, which was experimentally confirmed. Acknowledgments This material is based upon work supported by the U.S. National Science Foundation under Grant No.0957448. Figure 1

Multiscale Lithium and Counterion Transport in an Electrospun Polymer-Gel Electrolyte

We explore fundamental lithium ion (Li+) and triflate counterion (CF3SO3–) transport properties within an electrospun UV-cross-linked poly(ethylene oxide) polymer-gel electrolyte. With modulation of cross-linker (10–30 wt %), the fully swollen fibrous framework swells and retains between 1700 and 1200 wt % liquid electrolyte and exhibits room temperature ionic conductivity up to 6 mS cm–1. 7Li and 19F spin–spin relaxation (T2) measurements reveal the presence of inter- and intrafiber lithium ions, where the long- and short-T2 lithium ion and counterion components enable quantification of the fractions of free liquid electrolyte between fibers and liquid electrolyte within fibers. Pulsed-field-gradient NMR diffusometry shows increases in lithium and triflate diffusion coefficients with cross-linker content, suggestive of enhanced ion transport within the free liquid electrolyte phase due to a reduction in morphological restrictions. Arrhenius fits to temperature-dependent diffusion experiments show that lithium and triflate values for the activation energy of diffusion (15 and 12 kJ mol–1, respectively) are identical for ions in pure liquid solutions and for ions within the electrospun gel, showing that the framework does not influence the local energetics of ion transport. The present study thus offers new insights into understanding ion transport properties within lithium-ion battery materials on length scales ranging from sub-nanometer to micrometer scales.

Electrochromic Properties of Non-Stoichiometric Ni1-Xo Thin Films

NiO is a well known anodic electrochromic (EC) material showing optical modulation under electrochemical oxidation and reduction [1]. Despite the simplicity of this oxide, electrochromism in NiO thin films is rather complicated although it is generally accepted that the optical modulation is related to a charge-transfer process between Ni(II) and Ni(III). The NiO is commonly associated to WO3 in inorganic EC devices, a combination leading to a neutral color due to the simultaneous brownish and blue color of NiO in oxidized state and WO3 reduced state, respectively. Nevertheless, their association is complicated owing to their different stabilities in acidic/basic media, a factor which also impinges on the device stability. In our group, an unusual reactivity for non-stoichiometric Ni1-xO thin films cycled in various electrolytes was recently reported opening the choice of materials for complete devices working in both lithium and lithium free electrolyte [2]. Ni1-xO thin films were grown at room temperature by sputtering deposition on ITO-glass substrate. The influence of various partial pressures of O2 (a 4 Pa total pressure was maintained during deposition) on the stoichiometry, morphology and cristallinity of Ni1-xO thin films was studied and correlated to their EC behavior. Unsurprisingly, an increase in oxygen partial pressure is related to a stronger brownish appearance associated with to an increase in the Ni3+ amount as well as a decrease in film porosity and roughness. Moreover, the comparison of the electrochemical properties of Ni1-xO films cycled in aqueous (KOH), lithium based and lithium free ionic liquid electrolytes, shows an evolution from a faradic to a pseudo-capacitive behavior, while optical contrast from colorless to brownish remains in all cases. This suggests that electrochromism is not only the result of of small cations (de)insertion but also depends on surface phenomena including possible participation of anions. Herein, the relationship between the physical-chemical properties and EC performances of non-stoichiometry Ni1-xO thin films will be investigated. Finally, the combination of Ni1-xO with WO3 and PEDOT in full devices will be discussed. [1] C.G. Granqvist, Handbook of inorganic electrochromic materials, Elsevier, Amsterdam, Netherlands, 1995 [2] Moulki, H., Faure, C., Mihelčič, M., Vuk, A.S., Švegl, F., Orel, B., Campet, G., Rougier, A. Electrochromic performances of non-stoichiometric NiO thin films, Thin Solid Films, 2014, 553, 63-66.

A novel laminated separator with multi functions for high-rate dischargeable lithium–sulfur batteries

A novel high-rate dischargeable semi-solid Li–S battery without free liquid electrolyte is assembled using a multi-functional separator with a polysulfide shield. The polysulfide shield is composed of Li+-Nafion, polyethylene oxide, and super P carbon. Hierarchical porous carbon is used as a sulfur holder to anchor polysulfide and improve cathode conductivity. Unlike all-solid Li–S batteries, the resultant Li–S battery shows excellent performance in both rate capacity and cycleability. The sulfur lithiation capacity reaches 1330 mAh g−1 at 0.2C (0.335 A g−1 of S) and 690 mAh g−1 (338 mAh g−1 of electrode materials) at 10C (16.75 A g−1 of S). The cell with the fabricated separator (SNP/Celgard) showed very low capacity degradation rate of less than 0.1% per cycle at 1C (a discharge current density of 1.675 A g−1).

Dissolution of Platinum in Presence of Chloride Traces

One of the main issues on the way to a commercial use of fuel cells is the durability of the cell compartments, in particular electrocatalysts. Chloride impurities, originating from airborne salts or synthesis residues, can have severe effects on degradation in general. The quantitative impact on dissolution of Pt, which is the most common electrocatalyst material in polymer electrolyte membrane fuel cells, and the mechanism are still not fully understood. In the current work, potentiodynamic and potentiostatic measurements of platinum in acidic electrolytes containing chlorides in the range of 1 to 1000μM were carried out utilizing a scanning flow cell (SFC) coupled to an inductively coupled plasma mass spectrometer (ICP-MS). We show that during potentiodynamic measurements dissolution accelerates with increase in amount of chlorides, as expected. Similarly as in Cl−-free electrolytes, dissolution is a predominantly transient process taking place during oxide formation and reduction. While thus in general the mechanism remains the same as reported before in the absence of chlorides, evidence for additional dissolution processes during oxide formation and reduction are observed. This leads to a variation in the ratio between anodic and cathodic dissolution when chlorides are present. Based on the experimental results a tentative dissolution mechanism is proposed.

Ion Transport in Separator Membranes of Lithium Secondary Batteries

The migration properties of cations and anions in lithium electrolyte solutions through separator membranes were evaluated on the basis of diffusion coefficients. The observed diffusion coefficients for the cationic (DLi), anionic (DF), and solvent species (DH) of the electrolyte solution in the membrane are lower than those of the free electrolyte solution. Two main effects are responsible for the reduction in D. One is the physical barrier effect of the membrane substrate. The magnitude of this effect depends on the size, configuration, and the total volume of the pore spaces which hold the solution. The other is a chemical interaction effect, which is associated with polar groups or sites in the membrane substrate. For example, DF values are anomalously lower than DLi values for solutions in polyvinylidene difluoride- (PVDF-) based membranes, leading to an increase in the apparent cation transport number. This would indicate that the anions selectively interact with the membrane substrate through a Cou...

Determination of ζ-potential, charge, and number of organic ligands on the surface of water soluble quantum dots by capillary electrophoresis.

The number of charges and/or organic ligands covalently attached to the surface of CdTe quantum dot nanoparticles has been determined from their electrophoretic mobilities measured in capillaries filled with free electrolyte buffers. Three sizes of water soluble CdTe quantum dots with 3-mercaptopropionic and thioglycolic acids as surface ligands were prepared. Their electrophoretic mobilities in different pH and ionic strength values of separation buffers were measured by capillary electrophoresis with laser induced fluorescence detection. The ζ-potentials determined from electrophoretic mobilities using analytical solution of Henry function proposed by Ohshima were in the range from -30 to -100 mV. Charges of QDs were calculated from ζ-potentials. As a result, numbers of organic ligands bonded to QDs surface were determined to be 13, 14, and 15 for the sizes of 3.1, 3.5, and 3.9 nm, respectively. The dissociation constants of organic ligands bonded on QDs surfaces estimated from the dependence of QDs charge on pH of the separation buffer were 7.8 and 7.9 for 3-mercaptopropionic acid and 6.9 for thioglycolic acid.

Carbonate Free Electrolyte for Lithium Ion Batteries Containing γ-Butyrolactone and Methyl Butyrate

A novel carbonate free electrolyte, 1 M lithium difluoro(oxalato) borate (LiDFOB) in 1:1 gamma-butyrolactone (GBL)/methyl butyrate (MB), has been compared to a standard electrolyte, 1 M LiPF6 in 1:1:1 EC/DMC/DEC, and a 1 M LiDFOB in 1:1:1 EC/DMC/DEC electrolyte. The conductivity of 1 M LiDFOB in GBL/MB is higher at low temperature, but slightly lower at higher temperature compared to the standard electrolyte. The 1 M LiDFOB in GBL/MB electrolyte has comparable cycling performance to the standard electrolyte, and better cycling performance than the 1 M LiDFOB in EC/DMC/DEC electrolyte. The reversible cycling performance suggests that the LiDFOB in GBL/MB electrolyte forms a stable anode solid electrolyte interface (SEI) in the presence of GBL. Ex-situ surface analysis of the extracted electrodes has been conducted via a combination of XPS, FTIR-ATR and SEM which suggests that the stable anode SEI results is primarily composed of reduction products of LiDFOB.

Sulfolane-Based Electrolyte for High Voltage Li(Ni0.42Mn0.42Co0.16)O2 (NMC442)/Graphite Pouch Cells

Ethylene carbonate (EC)-free electrolyte composed of sulfolane (SL), ethylmethyl carbonate (EMC) and vinylene carbonate (VC) was studied in Li(Ni0.42Mn0.42Co0.16)O2 (NMC442)/graphite pouch cells using in situ measurements of gas evolution, ultra high precision coulometry (UHPC), automated storage experiments, long-term cycling and electrochemical impedance spectroscopy (EIS). Although cells using 1 M LiPF6 in SL:EMC 3:7 (w:w) do not function at all, the addition of only 1% VC allows the cells to operate normally. In situ gas measurements show that NMC442/Graphite pouch cells containing SL:EMC:VC electrolyte produce less gas during formation than cells containing control (1 M LiPF6 EC:EMC 3:7 (w:w)) electrolyte or 2% VC in control electrolyte. Cycling and storage experiments show that cells containing SL:EMC:VC electrolytes can provide better performance than control electrolyte without additives and similar performance to state-of-the-art electrolyte with the ternary additive blend 2% prop-1-ene-1,3-sultone (PES) +1% methylene methanedisulfonate (MMDS) +1% tris(trimethylsilyl) phosphite (TTSPi) (“PES-211”) in EC:EMC 3:7 (w:w). The SL:EMC:VC system needs to be further explored with additional additives and from a safety perspective.