A comparative XPS surface study of Li2FeSiO4/C cycled with LiTFSI- and LiPF6-based electrolytes

Ensling, David; Stjerndahl, Mårten; Nytén, Anton; Gustafsson, Torbjörn; Thomas, John O.

doi:10.1039/b813099j

Cited by 250 publications

(239 citation statements)

References 24 publications

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“…However, when comparing the respective spectra of the washed Blank, unwashed Blank and pristine electrodes (Figure 3), new components at ∼534 eV (O 1s spectrum), ∼170.6 eV and ∼169.4 eV (S 2p spectrum, doublet due to spin-orbit coupling) attributed to the SO 2 groups as well as a peak at ∼293 eV (C 1s spectrum) attributed to the -CF 3 groups of the LiTFSI salt residue are identifiable for all electrodes contacted by the electrolyte. [30][31][32] Therefore, in order to account for the electrolyte salt (as well as insoluble/soluble electrochemical reaction products) on the electrode surface after drying, the electrodes were separated into a washed (in pure diglyme) and an unwashed part prior to analysis. However, the strong contribution of the LiTFSI salt and the diglyme solvent to the global signal attenuated the intensity of several minor species and all analyzed electrodes were washed before XPS characterization.…”

Section: Resultsmentioning

confidence: 99%

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O₂Batteries during the 1st Cycle

Guéguen

Novák

Berg

2016

J. Electrochem. Soc.

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The surface chemistry of the commonly employed positive electrode substrate Super C65 carbon was investigated during the 1 st cycle of a Li-O 2 battery with a typical ether electrolyte (0.2 M LiTFSI in Diglyme) by performing in situ online electrochemical mass spectrometry (OEMS), ex situ scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). During discharge, a nanometer-thin (< 5 nm) layer of Li 2 O 2 forms homogeneously throughout the electrode before it is passivated at a final specific charge of ∼365 mAh/g. Higher discharge charge rates lead to thinner and more densely packed layers of Li 2 O 2 . Electrolyte decomposition also occurs in parallel, as evidenced by the continuous increase of LiF and sulfur containing species of the degraded LiTFSI salt. On charge, O 2 evolves initially according to a 2e − /O 2 rate, but as the cell over-potentials increase, O 2 evolution rate approaches 4e − /O 2 , thus demonstrating a significant extent of parasitic side-reactions. Unlike the discharge, the charge leads to inhomogeneous electrode reactions causing a continuous removal of Li 2 O 2 with no indication of LiO 2 or Li 2 O intermediates. The decomposition side-products formed during discharge are also removed and the spectra of the pristine electrode are nearly retained at a full charge. Our results show that the analysis of Li-O 2 battery chemistry requires broad approach based on the combination of various electrode surface sensitive techniques, such as XPS and OEMS, in order to provide further fundamental understanding of the mechanisms behind the complex electrochemistry involving the Li and O 2 as well as several other predominant degradation products of the electrode and electrolyte. Non-aqueous electrolyte based Li-O 2 batteries have been a subject of intensive research during the past years, mainly because of their high theoretical specific charge (∼1100 mAh/g Li2O2 ), which provide promising prospects for their implementation in future energy storage systems.1 Several challenges do however remain, of which the most notable are the low round-trip efficiency and poor cycling performance, both partly related to the electrode/electrolyte instability.2,3 On discharge of the Li-O 2 cell, gaseous oxygen dissolves in the electrolyte and is reduced at the positive porous electrode where it combines with Li + (from the negative Li metal electrode) to form solid Li 2 O 2 deposits according to forward reaction of 2Li + O 2 Li 2 O 2 . Upon charge, the reaction is reversed to release the initial reactants Li + and O 2 gas. Despite extensive research on several classes of electrodes and electrolytes (including carbons, gold, carbides, oxides substrates combined with carbonate, sulfoxide, [4][5][6] nitrile, 4,5,7 amide, ionic liquid 8,9 or ether 10-13 based electrolytes, to mention a few), no composition has so far displayed sufficient chemical stability toward the reduced oxygen species to sustain a satisfactory number of discharge/charge cycles.1 The cell failure has been...

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Section: Resultsmentioning

confidence: 99%

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O₂Batteries during the 1st Cycle

Guéguen

Novák

Berg

2016

J. Electrochem. Soc.

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“…Li 1s spectrum shows minor compounds like lithium oxide (Li 2 O) 19 at the interface, organic (R-OCO 2 Li) and mineral (Li 2 CO 3 ) carbonates. 20 The most important feature in the Li 1s spectrum is a very high content in LiF 19,20 in the electrode cycled without SA. Nevertheless, when SA is added, the SEI becomes poorer in LiF as indicated by the decrease of Li 1s and F 1s signals and therefore lithium organic (R-OCO 2 Li) and mineral (Li 2 CO 3 ) compounds are present as minor species.…”

Section: Xps Analysis Of Lithiated Graphite Interfaces-symmetricmentioning

confidence: 99%

“…10 O 1s spectrum exhibits two main peaks at 531.7 (C-O) and 533.0 eV (O-C=O and O-C(O)=O) bonds in agreement with that found for the C 1s spectrum. 24 Finally, on the P 2p spectrum, Li x PF y and Li x PO y F z compounds are detected 20 at the Gr SEI surface in low amounts, their atomic percentage being limited to 2% with or without SA.…”

Section: Xps Analysis Of Lithiated Graphite Interfaces-symmetricmentioning

confidence: 99%

Reactivity of Succinic Anhydride at Lithium and Graphite Electrodes

Charton

Santos-Peña

Biller

et al. 2017

J. Electrochem. Soc.

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Succinic anhydride (SA) is an useful electrolyte additive for high voltage cathodes but has also a negative impact on graphite (Gr) or Li anodes. For this reason, the Li/electrolyte and Gr/electrolyte interfaces were investigated at 20 • C and 45 • C using half or symmetrical cells. When SA is added at 1% by weight to the electrolyte (alkylcarbonate mixture + LiPF 6 ), an increase in the Li/Li cell impedance at 20 • C occurs owing to the formation of a resistive solid electrolyte interphase (SEI), composed of an inorganic inner layer and an organic outer layer, whereas at 45 • C or in absence of SA, the interphase is more inorganic in nature. The reversible capacity of graphite, cycled in Gr/Li half-cells in the presence of SA, is very low at 20 • C but almost ten times larger at 45 • C. Cycling symmetrical Gr/Gr cells at 45 • C indicates that Gr capacity is lower in the presence of SA in connection with the presence of an organic and polymer rich SEI. GC-MS analysis of the electrolyte after cycling shows that ethylene glycol bis-(alkylcarbonate) derivatives disappear when SA is present, owing to the ability of SA to react with lithium alkoxides to yield oligopolyester. Lithium ion batteries (LIBs) are a reliable way to store electric energy, with high gravimetric and volumetric energy density, which allows their application in nomad systems including electric and/or hybrid vehicles. However, electric vehicles range is unsuitable for most of the consumers and, therefore, energy density should be improved. In the past twenty years, many researches have been performed on electrode materials and electrolytes with the aim to enhance battery performance. Use of 5V class positive electrodes (cathodes) is a convenient way to increase LIBs energy density. It explains the development of promising "high voltage" materials like Li 3 V 2 (PO 4 ) 3 , 1 Li 2 CoPO 4 F 2 or the LiNi 0.5 Mn 1.5 O 4 (LNMO) 3 spinel. Nevertheless, the use of new cathodes operating at high voltage leads to the degradation of the battery electrolyte, usually based on a mixture of cyclic and linear alkylcarbonates containing LiPF 6 as salt and functional additives. Unfortunately, standard electrolytes are oxidized on 5 V cathodes and this significantly limits the battery cycling life. From the first cycles, electrolyte components degrade forming by-products, which in turn, can interact with electrodes surface. As an example, a passive layer is formed on graphite (Gr)/electrolyte interface at the first charge. This layer, known as the Solid Electrolyte Interphase (SEI), has a strong impact on the LIBs performances. Electrolyte formulation influences the chemical nature and structure of the SEI. With the aim to improve SEI quality and stability, SEI-forming additives like vinylene carbonate (VC) are generally added to the electrolyte in low amount (less than 5% by weight). These additives are designed to generate a protective passive layer on the active material surface preventing continuous electrolyte decomposition reactions.Whereas additives can be ...

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“…Li2FeSiO4, as with other polyanion cathodes, are poor electronic conductors leading to the utilisation of particle size reduction combined with carbon-coating or carbon composite formation to enhance Li-ion performance [501][502][503][504][505][506][507][508][509][510][511]. Reversible intercalation has only been entertained for one of two Li + ions per formula unit in Li2FeSiO4, resulting in cells whose experimental capacities fall in the region of ~130-160 mA h g -1 .…”

Section: Transition Metal Silicates (Li2msio4)mentioning

confidence: 99%

Evaluating the performance of nanostructured materials as lithium-ion battery electrodes

et al. 2013

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Access to the full text of the published version may require a subscription. Rights © Tsinghua University Press and Springer-Verlag Berlin ABSTRACTThe performance of the lithium-ion cell is heavily dependent on the ability of the host electrodes to accommodate and release Li + ions from the local structure. While the choice of electrode materials may define parameters such as cell potential and capacity, the process of intercalation may be physically limited by the rate of solid-state Li + diffusion. Increased diffusion rates in lithium-ion electrodes may be achieved through a reduction in the diffusion path, accomplished by a scaling of the respective electrode dimensions.In addition, some electrodes may undergo large volume changes associated with charging and discharging, the strain of which, may be better accommodated through nanostructuring. Failure of the host to accommodate such volume changes may lead to pulverisation of the local structure and a rapid loss of capacity. In this review article, we seek to highlight a number of significant gains in the development of nanostructured lithium-ion battery architectures (both anode and cathode), as drivers of potential next-generation electrochemical energy storage devices.

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A comparative XPS surface study of Li₂FeSiO₄/C cycled with LiTFSI- and LiPF₆-based electrolytes

Cited by 250 publications

References 24 publications

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O₂Batteries during the 1st Cycle

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O₂Batteries during the 1st Cycle

Reactivity of Succinic Anhydride at Lithium and Graphite Electrodes

Evaluating the performance of nanostructured materials as lithium-ion battery electrodes

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A comparative XPS surface study of Li2FeSiO4/C cycled with LiTFSI- and LiPF6-based electrolytes

Cited by 250 publications

References 24 publications

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O2Batteries during the 1st Cycle

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O2Batteries during the 1st Cycle

Reactivity of Succinic Anhydride at Lithium and Graphite Electrodes

Evaluating the performance of nanostructured materials as lithium-ion battery electrodes

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Product

Resources

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A comparative XPS surface study of Li₂FeSiO₄/C cycled with LiTFSI- and LiPF₆-based electrolytes

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O₂Batteries during the 1st Cycle

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O₂Batteries during the 1st Cycle