A Comparative Study of Synthetic Graphite and Li Electrodes in Electrolyte Solutions Based on Ethylene Carbonate‐Dimethyl Carbonate Mixtures

Aurbach, Doron; Markovsky, Boris; Shechter, Assaf; Ein‐Eli, Yair; Cohen, Hagai

doi:10.1149/1.1837300

Cited by 693 publications

(572 citation statements)

References 9 publications

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“…Li 2 CO 3 is a product of EC reduction and has characteristic FTIR bands around 863 cm −1 and 1450 cm −1 . 63 Consistent with analysis of the C 1s and O 1s XPS spectra, FTIR also showed Li 2 CO 3 as an important component in the SEI. Features around 1100 cm −1 could be attributed to alkoxides like CH 3 OLi.…”

Section: A1842supporting

confidence: 69%

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Mao

Wood

David

et al. 2018

J. Electrochem. Soc.

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Most lithium-ion batteries still rely on intercalation-type graphite materials for anodes, so it is important to consider their role in full cells for applications in electric vehicles. Here, we systematically evaluate the chemical and physical properties of six commerciallyavailable natural and synthetic graphites to establish which factors have the greatest impact on the cycling stability of full cells with nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Electrochemical data and post-mortem characterization explain the origin of capacity fade. The NMC811 cathode shows large irreversible capacity loss and impedance growth, accounting for much of full cell degradation. However, six graphite anodes demonstrate significant differences with respect to structural change, surface area, impedance growth, and SEI chemistry, which impact overall capacity retention. We found long cycle life correlated most strongly with stable graphite crystallite size. In addition, graphites with lower surface area generally had higher coulombic efficiencies during formation cycles, which led to more stable long-term cycling. The best graphite screened here enables a capacity retention around 90% in full pouch cells over extensive long-term cycling compared to only 82% for cells with the lowest performing graphite. The results show that optimal graphite selection improves cycling stability of high energy lithium-ion cells. With the booming demands for electric vehicles and electronic devices, high energy density lithium-ion batteries with long cycle life are highly desired. Despite the recent progress in Si 1 and Li metal 2 as future anode materials, graphite still remains the active material of choice for the negative electrode. 3,4 Lithium ions can be intercalated into graphite sheets at various stages like Li x C 12 and Li x C 6 , providing a high specific capacity of 372 mAh/g (∼2.5 times higher than LiCoO 2 ) and high volumetric capacity (similar to LiCoO 2 ) corresponding to LiC 6 . 5,6 In addition to its low cost and non-toxicity, graphite has a lowest average voltage (150 mV vs. Li/Li + ) and the flat voltage profile, rendering a high overall cell voltage. 7 Graphite also displays a very low voltage hysteresis, which in turn results in high energy efficiency. 8 For applications in lithium-ion batteries, many properties of the graphite powders must be optimized including crystallinity, particle size, morphology, and surface chemistry. However, most research effort has been placed on the development and characterization of high performance cathodes, while the impact of the graphite anode on full cell performance has been largely unexplored.Compared to widely used battery cathodes such as LiCoO 2 (140 mAh/g), LiFePO 4 (160 mAh/g), LiNi 1/3 Mn 1/3 Co 1/3 O 2 (160 mAh/g), and LiNi 0.5 Mn 0.3 Co 0.2 O 2 (175 mAh/g), 9-11 nickel-rich LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) is delivers a higher specific capacity (180-220 mAh/g), which increases the battery life on a single charge. 12,13 The high capacity arises because Ni is the main red...

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Section: A1842supporting

confidence: 69%

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Mao

Wood

David

et al. 2018

J. Electrochem. Soc.

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“…Electrolyte salts dissolved in either THF or Et 2 6 could not be measured reliably by NMR spectroscopy. However, in all cases low concentrations of residual salt are observed after the reduction reactions and some of the reduction products may precipitate prior to complete reduction, so the number of electrons required for reduction of the different salts should be viewed as approximate.…”

Section: Resultsmentioning

confidence: 99%

Reduction Reactions of Electrolyte Salts for Lithium Ion Batteries: LiPF₆, LiBF₄, LiDFOB, LiBOB, and LiTFSI

Parimalam

Lucht

2018

J. Electrochem. Soc.

236

165

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The reduction products of common lithium salts for lithium ion battery electrolytes, LiPF 6 , LiBF 4 , lithium bisoxalato borate (LiBOB), lithium difluorooxalato borate (LiDFOB), and lithium trifluorosulfonylimide (LiTFSI), have been investigated. The solution phase reduction of different lithium salts via reaction with the one electron reducing agent, lithium naphthalenide, results in near quantitative reactions. Analysis of the solution phase and head space gasses suggests that all of the reduction products are precipitated as insoluble solids. The solids obtained through reduction were analyzed with solution NMR, IR-ATR and XPS. All fluorine containing salts generate LiF upon reduction while all oxalate containing salts generate lithium oxalate. In addition, depending upon the salt other species including, Li x PF y O z , Li x BF y , oligomeric borates, and lithium bis [N-(trifluoromethylsulfonylimino) A typical lithium-ion battery contains a graphite anode, a lithiated transition metal oxide cathode, and an electrolyte solution composed of inorganic lithium salts dissolved in a mixture of organic carbonate solvents which frequently includes electrolyte additives.1 The longterm cyclability of the lithium-ion battery is dependent upon the anode solid electrolyte interphase (SEI), formed due to the electrochemical reduction of the electrolyte solution.2 Understanding the mechanisms of the reduction reactions along with the products of the reactions is essential for the development of better lithium-ion batteries. The SEI has been proposed to contain lithium alkyl carbonates, lithium carbonate, lithium oxalate, lithium alkoxides, and lithium oxide from the carbonate solvents and LiF, lithium fluorophosphates, lithium fluoroborates, and lithium oxalate from the reduction of electrolyte salts, depending upon the salt utilitzed.3-21 Electrolyte additives have also been used to tailor the properties of the SEI through preferential reduction on anode.1 Despite significant effort over the last two decades, the formation mechanism of the SEI is not well understood. One difficulty in understanding the composition of the SEI is that the SEI is a complicated mixture of compounds, which results from multiple simultaneous and competing reduction reactions. In addition, since the SEI is very thin (∼ 50 nm) and unstable in the presence of oxygen or water, characterization is very difficult. We have reported a detailed analysis of binder free graphitic anodes cycled in simplified electrolytes which suggest that the initial reduction reaction of the carbonates generate lithium alkyl carbonates and LiF as the predominant components of the anode SEI.20,21 Synthesis of initial SEI components from carbonate solvents in high yield through reduction of the solvents with lithium naphthalenide has been reported. The unique advantage of this reduction technique is the generation and isolation of SEI constituents from individual electrolyte components in high yield without competing reduction reactions. Reduction of ethylene carbonate re...

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“…13 Actually, significant evolution of gaseous products such as CO 2 , CO, O 2 , H 2 , CH 4 , C 2 H 4 , C 2 H 6 , C 3 H 6 and C 3 H 8 from the decomposition of carbonate solvents and lithium during battery operation has been detected by various characterization techniques. [14][15][16][17][18][19][20][21] In addition, utilizing isotope analysis, Onuk et al have unambiguously identified the origin of gases evolving in LIBs. 22 Furthermore, by adopting in situ transmission electron microscopy (TEM) 23 and neutron radiography (NR), 9,11 the generation of gaseous bubbles channels formed by the gas have recently been visualized.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Visualization of Gas Evolution and Channel Formation inside a Lithium-Ion Battery

Sun

Markötter

Manke

et al. 2016

ACS Appl. Mater. Interfaces

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Gas generation within lithium ion batteries (LIBs) gives rise to safety concerns that question their applicability. By employing synchrotron X-ray imaging, the gas and channel evolution occurring in an operating LIB have been directly visualized in their inherent 3D state as a function of discharge and charge. Using the spatial 3D distribution of gas bubbles and channels, the active particles that dictate the performance of a functional LIB were identified and visualized in 3D. Delithiation and lithiation are interpreted as the process of activating particles continuously in a step-bystep way. The present work not only demonstrates the generation and evolution of gas within LIB in 3D, but also reveals the distribution of active particles for the first time. These fundamentally findings presented here shed light on a range of processes that could not previously be characterized in 3D and can provide practical guidance for the

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A Comparative Study of Synthetic Graphite and Li Electrodes in Electrolyte Solutions Based on Ethylene Carbonate‐Dimethyl Carbonate Mixtures

Cited by 693 publications

References 9 publications

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Reduction Reactions of Electrolyte Salts for Lithium Ion Batteries: LiPF₆, LiBF₄, LiDFOB, LiBOB, and LiTFSI

Three-Dimensional Visualization of Gas Evolution and Channel Formation inside a Lithium-Ion Battery

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A Comparative Study of Synthetic Graphite and Li Electrodes in Electrolyte Solutions Based on Ethylene Carbonate‐Dimethyl Carbonate Mixtures

Cited by 693 publications

References 9 publications

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Reduction Reactions of Electrolyte Salts for Lithium Ion Batteries: LiPF6, LiBF4, LiDFOB, LiBOB, and LiTFSI

Three-Dimensional Visualization of Gas Evolution and Channel Formation inside a Lithium-Ion Battery

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Product

Resources

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Reduction Reactions of Electrolyte Salts for Lithium Ion Batteries: LiPF₆, LiBF₄, LiDFOB, LiBOB, and LiTFSI