Oxidative Stability and Initial Decomposition Reactions of Carbonate, Sulfone, and Alkyl Phosphate-Based Electrolytes

Borodin, Oleg; Behl, Wishvender K.; Jow, T. Richard

doi:10.1021/jp400527c

Cited by 311 publications

(388 citation statements)

References 64 publications

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“…In two cases, HF did not form (DMC and HF-DEC), but the reaction products involved transferring a hydrogen to a fluorine and resulted in lower energy structures. A similar decomposition reaction upon oxidation resulting in HF was also noted by Borodin et al 18 In all cases, the interaction of the solvent with PF 6 − lowers the oxidation potential of the solvent, and due to the different interaction between the solvent and PF 6 − , the oxidation stability of the cyclic carbonates are in the order of FEC > TFPC ∼ EC > TFP-PC-E, and the linear carbonates are in the order of HF-DEC > F-EMC > DMC ∼ TF-DEC. The oxidation potentials of solvent/TFSI − complexes were also calculated.…”

Section: Resultssupporting

confidence: 80%

Fluorinated Electrolytes for 5-V Li-Ion Chemistry: Probing Voltage Stability of Electrolytes with Electrochemical Floating Test

Xue

et al. 2015

J. Electrochem. Soc.

123

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A series of electrolyte formulations containing fluorinated cyclic carbonates and fluorinated linear carbonates with LiPF 6 has been evaluated as electrolyte solvents for high-voltage Li-ion batteries. The anodic stability of the new electrolytes on fully charged spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) cathode was examined by electrochemical floating tests. The effects of fluorine substitution on the cyclic and linear carbonate, ratio of cyclic vs. linear carbonate, and LiPF 6 concentration on the electrolyte oxidation stability were investigated. Based on this study, the floating test proved to be an effective tool for identification of stable electrolyte materials. have been proposed. Because of the large number of candidates for high-voltage electrolyte solvents, screening the voltage stability of each solvent would be very labor-intensive. Traditional methods of measuring the oxidation potential of organic solvents usually involves linear/cyclic voltammetry using an inert electrode such as platinum and glassy carbon. However, such measurements are in many cases misleading, because interactions of these organic solvents with actual electrode materials are usually more complicated and may happen at a much lower potential due to the catalytic effect of the cathode material lowering the kinetic barrier of oxidation. Unfortunately, using active cathode material to run voltammetry measurement has a drawback in that the material itself is redox active and can interfere with the observation of electrolyte oxidation. Thus, developing a fast and effective method to screen the voltage stability of electrolyte solvents on actual cathode materials is of vital importance. Herein, we report a method using constant potential electrolysis with a slightly overcharged LNMO cathode as the working electrode, abbreviated as an "electrochemical floating test", where the cell potential is allowed to "float" at different values to evaluate the voltage stability of the electrolyte. For an ideal electrolyte with no impurities and no oxidation at the working electrode, the only current observed when a potential is applied is the capacitance current, which should decline to zero when the equilibrium is reached. However, in reality, the electrolytes are oxidized, and the current intensity measured corresponds to the severity of oxidation. As a result, the leakage currents of each electrolyte at different potentials can be compared to produce a voltage stability profile of a given solvent. The effect of different ratios of mixed solvents and lithium salt concentrations can also be probed. * Electrochemical Society Active Member.z E-mail: zzhang@anl.gov Materials and MethodsTheoretical calculations.-The Gaussian 09 code was used for all calculations.14 Oxidation and reduction potentials were calculated by optimizing the geometries of the neutral and ionic species at the B3LYP/6-31G * level, followed by frequency calculations to determine gas-phase free energies. Solvation effects were taken into account by using a single-point B3LYP/6-31+G * PCM...

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Section: Resultssupporting

confidence: 80%

Fluorinated Electrolytes for 5-V Li-Ion Chemistry: Probing Voltage Stability of Electrolytes with Electrochemical Floating Test

Xue

et al. 2015

J. Electrochem. Soc.

123

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“…In particular, it explains why EC, despite having among the lowest calculated HOMO energy of all alkyl carbonate solvents, leads to electrolytes with lower practical anodic stabilities as compared to it intrinsic stability. In fact, Borodin et al noted the detrimental effects of BF4, PF6 and B(CN)4 on alkyl carbonate solvents, while, on the other hand, they have less influence of sulfone-based solvents such as sulfolane (SL) (Figure 1a), which explains their better performance at high voltage [18,19]. According to these studies, however, DMC anodic stability was found to be also significantly lowered by the presence of Li salts, whereas mixtures of SL and other solvents, such as EMC [20] or ethyl acetate [21] are reported having similar anodic stability as SL alone.…”

Section: Introductionmentioning

confidence: 99%

Towards practical sulfolane based electrolytes: Choice of Li salt for graphite electrode operation

Zhang

Porcher

Paillard

2018

Journal of Power Sources

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Abstract:Sulfolane (tetramethylene sulfone, SL) is known for leading to Li-ion electrolytes with high anodic stability. However, the operation of graphite electrodes in alternative electrolytes is usually challenging, especially when ethylene carbonate (EC) is not used as co-solvent. Thus, we study here the influence of the lithium salt on the physico-chemical and electrochemical properties of EC-free SL-based electrolytes and on the performance of graphite electrodes based on carboxymethyl cellulose (CMC). SL mixed with dimethyl carbonate (DMC) leads to electrolytes as conductive as state-of-theart alkyl carbonate-based electrolytes with wide electrochemical stability windows. The compatibility with graphite electrodes depends on the Li salt used and, even though cycling is possible with most salts, lithium difluoro-oxalato borate (LiDFOB) is especially interesting for graphite operation.LiDFOB electrolytes are conductive at room temperature (ca. 6 mS cm -1 ) with an anodic stability slightly below 5 V vs. Li/Li + on particulate carbon black electrodes. In addition, it allows cycling graphite electrodes with steady capacity and high coulombic efficiency without any additive. The testing of graphite electrodes in half-cells is, however, problematic with SL:DMC mixtures and, by switching the Li metal counter electrode for LiFePO4, the graphite electrode achieves better practical performance in terms of rate capability.

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“…This may be due to the increased oxidative stability of the electrolyte when LiPF 6 is present. 36 There was concern about the size of the error bars in Figure 5 for the pouch bags with control + 2% PES electrolyte. These error bars originate from measurements on at least three different pouch bags.…”

Section: Resultsmentioning

confidence: 99%

Rapid Impedance Growth and Gas Production at the Li-Ion Cell Positive Electrode in the Absence of a Negative Electrode

Xiong

Ellis

Nelson

et al. 2016

J. Electrochem. Soc.

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The effects of electrolyte additives on gas evolution, gas consumption and impedance growth at elevated temperature have been studied using Li [Ni 0.42 Mn 0.42 Co 0.16 ]O 2 (NMC442)/graphite pouch cells and pouch bags containing delithiated NMC442 or lithiated graphite electrodes plus electrolyte. It was found that there was much more gas, mostly CO 2 , generated in pouch bags containing charged positive electrodes than pouch cells. It was found that the impedance of the charged positive electrodes stored in pouch bags increased dramatically, while those stored in pouch cells did not. The two observations show that there are interactions between positive and negative electrodes that limit gas evolution and reduce impedance growth in Li-ion cells. To verify this, CO 2 intentionally added to pouch bags containing lithiated graphite and electrolyte was consumed. The use of several electrolyte additives, known to affect gassing and high voltage cycling did not substantially alter these conclusions. XPS studies were used to eliminate some possible mechanisms responsible for these phenomena. Lithium-ion battery packs for electrified vehicles and grid energy storage need longer lived cells, operating over a wide range of temperatures. A pouch-type lithium-ion cell, cycled at elevated temperature, may experience volume expansion due to gas production, leading to rapid capacity fade.1-6 When Li-ion cells are charged above 4.2 V, reactions between the electrolyte and the positive electrode can cause charge-transfer impedance (R ct , electron transfer and diffusion of lithium ions through the SEI) growth at the positive electrodeelectrolyte interface, depletion of liquid electrolyte, capacity loss and eventual cell failure.7-12 The use of electrolyte additives is an effective way to suppress gas evolution and impedance growth for cells cycled at high voltage and high temperature. [13][14][15][16][17][18][19] Xia et al. and Li et al. found that prop-1-ene-1,3-sultone (PES) suppressed gas evolution when cells were cycled to an upper cutoff voltage of 4.2 V at elevated temperature.13,14 Nie et al. found that pyridine boron trifluoride (PBF) also suppressed gassing at high temperature, when cells were cycled to 4.4. [16][17][18] Vinylene carbonate (VC) is a popular additive which is widely used in industry and has been extensively studied. [20][21][22][23][24] This additive can cause severe gas evolution at high temperature and high voltage if residual VC remains in the electrolyte after the formation cycle. 26-28 However, impedance growth for NMC442/graphite cells containing these additives or additive blends cannot yet be controlled as the cutoff voltage increases above 4.4 V.27 Figure 1 shows that the impedance of NMC442/graphite cells increases dramatically as the cycle number increases. Symmetric cells made from electrodes harvested from pouch cells tested above 4.4 V showed that the impedance growth originates from the positive electrode ( Figure 1b) rather than from the negative electrode (Figure 1c). Detailed informa...

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Oxidative Stability and Initial Decomposition Reactions of Carbonate, Sulfone, and Alkyl Phosphate-Based Electrolytes

Cited by 311 publications

References 64 publications

Fluorinated Electrolytes for 5-V Li-Ion Chemistry: Probing Voltage Stability of Electrolytes with Electrochemical Floating Test

Fluorinated Electrolytes for 5-V Li-Ion Chemistry: Probing Voltage Stability of Electrolytes with Electrochemical Floating Test

Towards practical sulfolane based electrolytes: Choice of Li salt for graphite electrode operation

Rapid Impedance Growth and Gas Production at the Li-Ion Cell Positive Electrode in the Absence of a Negative Electrode

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