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1.
ChemSusChem ; 2020 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-32216087

RESUMO

The performance of structurally and chemically well-defined Ni-free and Ni-modified single-crystalline Co3 O4 (1 1 1) thin-film electrodes in the oxygen reduction and evolution reactions (ORR and OER) was investigated in a combined surface science and electrochemistry approach. Pure and Ni-modified Co3 O4 (1 1 1) film electrodes were prepared and characterized under ultrahigh-vacuum conditions by scanning tunneling microscopy and X-ray photoelectron spectroscopy. Both Ni decoration (by post-deposition of Ni) and Ni doping (by simultaneous vapor deposition of Ni, Co, and O2 ) induced distinct differences in the base cyclic voltammograms in 0.5 m KOH at potentials higher than 0.7 V compared with Co3 O4 (1 1 1) electrodes. Also, all oxide film electrodes showed a higher overpotential for the ORR but a lower one for the OER than polycrystalline Pt. Ni modification significantly improved the ORR current densities by increasing the electrical conductivity, whereas the OER onset of approximately 1.47 VRHE (RHE: reversible hydrogen electrode) at 0.1 mA cm-2 was almost unchanged.

2.
ChemSusChem ; 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32196973

RESUMO

The process of solid-electrolyte interphase (SEI) formation is systematically investigated along with its chemical composition on carbon electrodes in an ionic liquid-based, Li-containing electrolyte in a combined surface science and electrochemical model study using highly oriented pyrolytic graphite (HOPG) and binder-free graphite powder electrodes (Mage) as model systems. The chemical decomposition process is explored by deposition of Li on a pre-deposited multilayer film of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][TFSI]) under ultrahigh vacuum conditions. Electrochemical SEI formation is induced by and monitored during potential cycling in [BMP][TFSI]+0.1 m LiTFSI. The chemical composition of the resulting layers is characterized by X-ray photoelectron spectroscopy (XPS), both at the surface and in deeper layers, closer to the electrode|SEI interface, after partial removal of the film by Ar+ ion sputtering. Clear differences between chemical and electrochemical SEI formation, and also between SEI formation on HOPG and Mage electrodes, are observed and discussed.

3.
J Am Chem Soc ; 142(3): 1278-1286, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31875391

RESUMO

Employing Pt(111) supported 2D Pt-core Au-shell model catalysts, we demonstrate that 2D core-shell surfaces prepared under ultrahigh vacuum (UHV) conditions constitute excellent model systems to determine the activity of step sites in electrocatalysis, especially because UHV-scanning tunneling microscopy (STM) enables control of the quality of narrow step modifications with high accuracy on such systems. As verified with STM, cyclic voltammetry (CV), and temperature-programmed desorption (TPD) measurements, this approach allows us (i) to increase the step density by homoepitaxial growth of monolayer high islands on the respective single crystal and (ii) to modify the step sites for adsorption of reactants by selective deposition of a guest metal. Herein, STM imaging in combination with electrochemical characterization provides a direct control to ascertain a selective modification of the entire steps. Comparing the electrocatalytic activity of 2D core-shell systems with and without the shell enables us to identify the activity of step sites for electrocatalytic reactions, as demonstrated for the bulk CO electro-oxidation.

4.
ACS Appl Mater Interfaces ; 12(3): 3697-3708, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31886648

RESUMO

Utilization of high-capacity alloying anodes is a promising yet extremely challenging strategy in building high energy density alkali-ion batteries (AIBs). Excitingly, it was very recently found that the (de-)sodiation of tin (Sn) can be a highly reversible process in specific glyme electrolytes, enabling high specific capacities close to the theoretical value of 847 mA h g-1. The unique solid electrolyte interphase (SEI) formed on Sn electrodes, which allows highly reversible sodiation regardless of the huge volume expansion, is herein demonstrated according to a series of in situ and ex situ characterization techniques. The SEI formation process mainly involves NaPF6 decomposition and the polymerization/oligomerization of the glyme solvent, which is induced by the catalytic effect of tin, specifically. This work provides a paradigm showing how solvent, salt, and electrode materials synergistically mediate the SEI formation process and obtains new insights into the unique interfacial chemistry between Na-alloying electrodes and glyme electrolytes, which is highly enlightening in building high energy density AIBs.

5.
Chemphyschem ; 20(24): 3276-3288, 2019 12 16.
Artigo em Inglês | MEDLINE | ID: mdl-31705610

RESUMO

Aiming at a better understanding of correlations between the activity and selectivity of Au electrodes in the oxygen reduction reaction (ORR) under controlled transport conditions, we have investigated this reaction by combined electrochemical and in situ FTIR measurements, performed in a flow cell set-up in an attenuated total reflection (ATR) configuration in acid and alkaline electrolytes. The formation of incomplete reduction products (hydrogen peroxyde/peroxyls) was detected by a collector electrode, the onset of OHad formation was probed by bulk CO oxidation. Using an electroless-deposited, annealed Au film on a Si prism as working electrode and three different electrolytes for comparison (sulfuric acid, perchloric acid, sodium hydroxide solution), we could derive detailed information on the anion adsorption behavior, and could correlate this with the ORR characteristics. The data reveal pronounced effects of the anions and the pH on the ORR characteristics, indicated e. g., by a grossly different activity and selectivity for the 4-electron pathway to water/hydroxyls, with the onset ranging from ca. 1.0 V in alkaline electrolyte to 0.6 V in sulfuric acid electrolyte, and the selectivity for the 4-electron pathway ranging from 100 % (alkaline electrolyte, low overpotentials) to 40 % (acidic electrolytes, alkaline electrolyte at high overpotentials). In contrast, the effect of the ORR on the anion adsorption characteristics is small. Anion effects as well as correlations between anion adsorption and ORR are discussed.

6.
J Chem Phys ; 151(13): 134704, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31594361

RESUMO

Aiming at a detailed molecular understanding of the initial stage of the solid|electrolyte interphase (SEI) formation in Li-ion batteries, we have investigated the interaction of the battery-relevant ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][TFSI]) (solvent/electrolyte) and Li (Li+ ion shuttle) on well-defined Li-poor Li4Ti5O12(111) and Li-rich Li4.3Ti5O12(111) surfaces/electrodes in a combined surface science and electrochemical model study. X-ray photoelectron spectroscopy (XPS) measurements reveal that postdeposition of Li0 under ultrahigh vacuum (UHV) conditions on a Li-poor Li4Ti5O12(111) surface precovered with a molecularly adsorbed [BMP][TFSI] adlayer leads to little IL decomposition at 80 and 300 K. We assume that most of the Li diffuses through the IL adlayer and rapidly inserts into the Li4Ti5O12(111) bulk. More pronounced IL decomposition was obtained upon IL deposition on a Li-rich Li4.3Ti5O12 phase at 80 K and subsequent heating to 300 K. Cyclic voltammograms (CVs) recorded on the Li4Ti5O12(111) electrodes in Li-TFSI/[BMP][TFSI] indicate an almost reversible Li (de-)insertion, with a slight decay of the amount of (de-)inserted Li with increasing cycle number. XPS measurements performed on the electrode after potential cycling show low intensity signals of IL decomposition products, in addition to dominant signals from residual IL electrolyte, which are related to reaction of the adsorbed IL with Li inserted into/extracted from Li4Ti5O12 during the CV. The results indicate a close similarity between IL decomposition products formed under UHV and under electrochemical conditions, underlining the validity of this experimental approach and the potential of such kind of model studies for obtaining detailed understanding of the SEI formation.

7.
J Phys Chem Lett ; 10(13): 3645-3653, 2019 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-31192610

RESUMO

The impact of CO on the activation and reaction characteristics of Au/ZnO catalysts in methanol synthesis from a CO2/H2 mixture was studied by kinetic, near ambient pressure X-ray photoelectron spectroscopy and X-ray absorption spectroscopy at the O K-edge, together with in situ Foureir transform infrared measurements. Transient measurements under up to industrial reaction conditions (50 bar, 240 °C) show a pronounced transient increase of the activity for methanol formation from CO2/H2 after exposure to a CO/H2 reaction gas mixture, while the steady-state activity is similar to that observed directly after oxidative pretreatment. For the reaction in CO/H2, the much longer activation phase is accompanied by formation of CO2 due to reaction of CO with the ZnO catalyst support. This leads to O-vacancy formation on the support at an extent significantly higher than in CO2/H2. The consequences of these findings on the mechanistic understanding of methanol formation from CO2/H2 on Au/ZnO and for ZnO-supported catalysts in general are discussed.

8.
Angew Chem Int Ed Engl ; 58(31): 10732-10736, 2019 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-31095821

RESUMO

Ru/TiO2 catalysts exhibit an exceptionally high activity in the selective methanation of CO in CO2 - and H2 -rich reformates, but suffer from continuous deactivation during reaction. This limitation can be overcome through the fabrication of highly active and non-deactivating Ru/TiO2 catalysts by engineering the morphology of the TiO2 support. Using anatase TiO2 nanocrystals with mainly {001}, {100}, or {101} facets exposed, we show that after an initial activation period Ru/TiO2 -{100} and Ru/TiO2 -{101} are very stable, while Ru/TiO2 -{001} deactivates continuously. Employing different operando/in situ spectroscopies and ex situ characterizations, we show that differences in the catalytic stability are related to differences in the metal-support interactions (MSIs). The stronger MSIs on the defect-rich TiO2 -{100} and TiO2 -{101} supports stabilize flat Ru nanoparticles, while on TiO2 -{001} hemispherical particles develop. The former MSIs also lead to electronic modifications of Ru surface atoms, reflected by the stronger bonding of adsorbed CO on those catalysts than on Ru/TiO2 -{001}.

9.
Angew Chem Int Ed Engl ; 58(30): 10325-10329, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-30980453

RESUMO

The electronic and structural properties of Au/ZnO under industrial and idealized methanol synthesis conditions have been investigated. This was achieved by kinetic measurements in combination with time-resolved operando infrared (DRIFTS) as well as in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and X-ray absorption near-edge spectroscopy (XANES) measurements at the O K-edge together with high-resolution electron microscopy. The adsorption of CO during the reaction revealed the presence of negatively charged Au nanoparticles/Au sites during the initial phase of the reaction. Near-ambient-pressure XPS and XANES demonstrate the build-up of O vacancies during the reaction, which goes along with a substantial increase in the rate of methanol formation. The results are discussed in comparison with previous findings for Cu/ZnO and Au/ZnO catalysts.

10.
ChemSusChem ; 12(12): 2609-2619, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-30896892

RESUMO

Aluminum is an appealing anode material for high-energy-density lithium-ion batteries (LIBs), owing to its low cost, environmental benignity, high specific capacity, and lower relative volume expansion compared with other alloying materials. However, both, the working and capacity fading processes are not yet consistently and comprehensively understood, which has largely hindered its development. In this study, the electrochemical alloying process of aluminum anodes with lithium is systematically studied by the combination of several in situ and ex situ techniques, providing new insights into phase transitions, electrode dynamics, and surface chemistry. Particular attention is paid to the role of the Li-rich alloys (Li1+x Al). Its existence on the surface of the Al electrode is unexpectedly observed, and its growth in the electrode bulk is found to be strictly correlated with cell failure. Interestingly, cell failure can be delayed by choosing an appropriate electrolyte. This work contributes to a solid and comprehensive understanding of the puzzling Al (de-)lithiation processes, which is fundamental and highly enlightening for future research work on Al and other alloyed anodes.

11.
J Am Chem Soc ; 141(13): 5201-5210, 2019 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-30852893

RESUMO

Single-atom catalysts are often considered as the ultimate design principle for supported catalysts, due to their unique geometric and electronic properties and their highly efficient use of precious materials. Here, we report a single-atom catalyst, Cu/UiO-66, prepared by a covalent attachment of Cu atoms to the defect sites at the zirconium oxide clusters of the metal-organic framework (MOF) UiO-66. Kinetic measurements show this catalyst to be highly active and stable under realistic reaction conditions for two important test reactions, the oxidation of CO at temperatures up to 350 °C, which makes this interesting for application in catalytic converters for cars, and for CO removal via selective oxidation of CO in H2-rich feed gases, where it shows an excellent selectivity of about 100% for CO oxidation. Time-resolved operando spectroscopy measurements indicate that the activity of the catalyst is associated with atomically dispersed, positively charged ionic Cu species. Density functional theory (DFT) calculations in combination with experimental data show that Cu binds to the MOF by -OH/-OH2 ligands capping the defect sites at the Zr oxide clusters.

12.
J Chem Phys ; 150(4): 041724, 2019 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-30709319

RESUMO

Aiming at a detailed understanding of the interaction between an ionic liquid, O2, and electrodes in Mg-air batteries, we performed a combined differential electrochemical mass spectrometry and in situ infrared spectroscopy model study on the interaction between the ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (BMP-TFSI) and a gold film electrode in the presence and absence of O2 and Mg2+ ions in the potential range relevant for the oxygen reduction reaction (ORR) and evolution reaction. Detailed information on the dynamic exchange of adsorbed ions, on the stability/decomposition of the ionic liquid, and on the activity/selectivity/reversibility of the ORR is derived from measurements performed under potentiodynamic and potentiostatic conditions. In neat BMP-TFSI, we find the dynamics of the potential induced exchange of adsorbed ions to depend significantly on the exchange direction. In the presence of O2, the anions formed in the ORR distinctly affect the adsorption characteristics of the IL ions and the exchange dynamics. Furthermore, the ORR changes from reduction to superoxide anions at moderate potentials to reduction to peroxide anion at more negative potentials. In the additional presence of Mg2+ ions, dominant magnesium peroxide and oxide formation result in an irreversible ORR, in contrast to the requirements of an efficient re-chargeable Mg-air battery. In addition, these ions result in the increasing formation of a blocking adlayer, reducing the coverage of adsorbed IL species.

13.
Nat Commun ; 9(1): 5115, 2018 11 30.
Artigo em Inglês | MEDLINE | ID: mdl-30504910

RESUMO

Rechargeable magnesium batteries are one of the most promising candidates for next-generation battery technologies. Despite recent significant progress in the development of efficient electrolytes, an on-going challenge for realization of rechargeable magnesium batteries remains to overcome the sluggish kinetics caused by the strong interaction between double charged magnesium-ions and the intercalation host. Herein, we report that a magnesium battery chemistry with fast intercalation kinetics in the layered molybdenum disulfide structures can be enabled by using solvated magnesium-ions ([Mg(DME)x]2+). Our study demonstrates that the high charge density of magnesium-ion may be mitigated through dimethoxyethane solvation, which avoids the sluggish desolvation process at the cathode-electrolyte interfaces and reduces the trapping force of the cathode lattice to the cations, facilitating magnesium-ion diffusion. The concept of using solvation effect could be a general and effective route to tackle the sluggish intercalation kinetics of magnesium-ions, which can potentially be extended to other host structures.

14.
J Chem Phys ; 148(19): 193821, 2018 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-30307189

RESUMO

Ionic liquids (ILs) are considered as attractive electrolyte solvents in modern battery concepts such as Li-ion batteries. Here we present a comprehensive review of the results of previous model studies on the interaction of the battery relevant IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]+[TFSI]-) with a series of structurally and chemically well-defined model electrode surfaces, which are increasingly complex and relevant for battery applications [Ag(111), Au(111), Cu(111), pristine and lithiated highly oriented pyrolytic graphite (HOPG), and rutile TiO2(110)]. Combining surface science techniques such as high resolution scanning tunneling microscopy and X-ray photoelectron spectroscopy for characterizing surface structure and chemical composition in deposited (sub-)monolayer adlayers with dispersion corrected density functional theory based calculations, this work aims at a molecular scale understanding of the fundamental processes at the electrode | electrolyte interface, which are crucial for the development of the so-called solid electrolyte interphase (SEI) layer in batteries. Performed under idealized conditions, in an ultrahigh vacuum environment, these model studies provide detailed insights on the structure formation in the adlayer, the substrate-adsorbate and adsorbate-adsorbate interactions responsible for this, and the tendency for chemically induced decomposition of the IL. To mimic the situation in an electrolyte, we also investigated the interaction of adsorbed IL (sub-)monolayers with coadsorbed lithium. Even at 80 K, postdeposited Li is found to react with the IL, leading to decomposition products such as LiF, Li3N, Li2S, LixSOy, and Li2O. In the absence of a [BMP]+[TFSI]- adlayer, it tends to adsorb, dissolve, or intercalate into the substrate (metals, HOPG) or to react with the substrate (TiO2) above a critical temperature, forming LiOx and Ti3+ species in the latter case. Finally, the formation of stable decomposition products was found to sensitively change the equilibrium between surface Li and Li+ intercalated in the bulk, leading to a deintercalation from lithiated HOPG in the presence of an adsorbed IL adlayer at >230 K. Overall, these results provide detailed insights into the surface chemistry at the solid | electrolyte interface and the initial stages of SEI formation at electrode surfaces in the absence of an applied potential, which is essential for the further improvement of future Li-ion batteries.

15.
Phys Chem Chem Phys ; 20(27): 18319-18327, 2018 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-29938292

RESUMO

Aiming at a detailed understanding of the Li adsorption and insertion behavior on/into lithium titanate (Li4Ti5O12, LTO), which is a promising anode material in Li-ion batteries, we have investigated the interaction of vapor deposited Li with LTO in the temperature range between 80 K and room temperature by angle-resolved X-ray photoelectron spectroscopy (ARXPS). The experiments were performed under ultrahigh vacuum (UHV) conditions, and the presence of additional Li species was detected by the formation of Ti3+ in the Ti 2p core level signal due to charge transfer from adsorbed/inserted Li to Ti. Even at 80 K most of the deposited Li diffuses into the bulk of LTO, reflecting the facile insertion and diffusion of Li into and in LTO. Deposition of up to 3 monolayers equivalent (MLE) of Li at 80 K results in an increase in Li concentration in the surface region (topmost 6 nm), up to a stoichiometry of Li4+xTi5O12 with x > 0.3, and slightly lower values in the near-surface region (topmost 1 nm). For higher Li doses, the amount of Li in the near-surface region, including adsorbed Li, increases more than the concentration in the underlying surface region. This is attributed to the blocking of diffusion channels by inserted Li at a stoichiometry of Li4.3Ti5O12 and above. Upon increasing the temperature, Li+ starts to diffuse into the LTO bulk at temperatures between 120 K and 175 K, depending on the concentration in the surface region. It has completely disappeared at 260 K. The consequences of these results for the understanding of physical Li insertion will be discussed.

16.
Langmuir ; 34(29): 8451-8463, 2018 07 24.
Artigo em Inglês | MEDLINE | ID: mdl-29943996

RESUMO

Aiming at a better understanding of the solid-electrolyte interphase formation in Li-ion batteries, we have investigated the interaction of ultrathin films of ethylene carbonate (EC), which is a key solvent of battery electrolytes, with pristine and lithiated highly oriented pyrolytic graphite (HOPG) and with postdeposited Li. Employing X-ray and ultraviolet photoelectron spectroscopy as well as Fourier transform infrared spectroscopy under ultrahigh-vacuum conditions, in combination with density functional theory (DFT)-based calculations, we find that EC adsorbs molecularly intact on pristine HOPG in the entire temperature range between 80 K and desorption at 200 K. Features in the ultraviolet photoelectron spectra could be related to the molecular orbitals of EC obtained from DFT calculations, and a similar adsorption/desorption behavior is obtained also on lithiated HOPG. In contrast, stepwise postdeposition of ∼0.5 and one monolayer of Li0 on a preadsorbed EC adlayer leads not only to stabilization of Li+/Liδ+ at the surface, possibly as adsorbed Li+(EC) n species, but also to EC decomposition, forming products such as Li2CO3, ROCO2Li (CH2OCO2Li)2, and Li2O. Consequences on the electronic surface properties and on the stabilization of the resulting adlayer are discussed. Upon annealing up to room temperature, some residual Li-containing decomposition products remain on the surface, which is considered as the initial stage of the solid|electrolyte interphase formation at the electrode|electrolyte interface.

17.
ACS Omega ; 3(9): 11290-11299, 2018 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31459238

RESUMO

Here, we provide a deeper insight into the state of sulfur confined in ultramicroporous carbon (UMC) and clarify its electrochemical reaction mechanism with lithium by corroborating the results obtained using various experimental techniques, such as X-ray photoelectron spectroscopy, electron energy loss spectroscopy, in situ Raman spectroscopy, and in situ electrochemical impedance spectroscopy. In combination, these results indicate that sulfur in UMC exists as linear polymeric sulfur rather than smaller allotropes. The electrochemical reactivity of lithium with sulfur confined in UMC (pore size ≤0.7 nm) is different from that of sulfur confined in microporous carbon (≤2 nm, or ultramicroporous carbon containing significant amount of micropores) and mesoporous carbon (>2 nm). The observed quasi-solid-state reaction of lithium with sulfur in UMC with a single voltage plateau during the discharge/charge process is due to the effective separation of solvent molecules from the active material. The size of carbon pores plays a vital role in determining the reaction path of lithium with sulfur confined in UMC.

18.
ACS Appl Mater Interfaces ; 10(2): 1662-1671, 2018 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-29256594

RESUMO

Two approaches of engineering surface structures of V-Ti-based solid solution hydrogen storage alloys are presented, which enable improved tolerance toward gaseous oxygen (O2) impurities in hydrogen (H2) gas. Surface modification is achieved through engineering lanthanum (La)- or nickel (Ni)-rich surface layers with enhanced cyclic stability in an H2/O2 mixture. The formation of a Ni-rich surface layer does not improve the cycling stability in H2/O2 mixtures. Mischmetal (Mm, a mixture of La and Ce) agglomerates are observed within the bulk and surface of the alloy when small amounts of this material are added during arc melting synthesis. These agglomerates provide hydrogen-transparent diffusion pathways into the bulk of the V-Ti-Cr-Fe hydrogen storage alloy when the remaining oxidized surface is already nontransparent for hydrogen. Thus, the cycling stability of the alloy is improved in an O2-containing hydrogen environment as compared to the same alloy without addition of Mm. The obtained surface-engineered storage material still absorbs hydrogen after 20 cycles in a hydrogen-oxygen mixture, while the original material is already deactivated after 4 cycles.

19.
ChemSusChem ; 11(3): 562-573, 2018 02 09.
Artigo em Inglês | MEDLINE | ID: mdl-29171938

RESUMO

Increasing the environmental benignity of lithium-ion batteries is one of the greatest challenges for their large-scale deployment. Toward this end, we present herein a strategy to enable the aqueous processing of high-voltage LiNi0.5 Mn1.5 O4 (LNMO) cathodes, which are considered highly, if not the most, promising for the realization of cobalt-free next-generation lithium-ion cathodes. Combining the addition of phosphoric acid with the cross-linking of sodium carboxymethyl cellulose by means of citric acid, aqueously processed electrodes with excellent performance are produced. The combined approach offers synergistic benefits, resulting in stable cycling performance and excellent coulombic efficiency (98.96 %) in lithium-metal cells. Remarkably, this approach can be easily incorporated into standard electrode preparation processes with no additional processing step.


Assuntos
Fontes de Energia Elétrica , Eletrodos , Química Verde , Compostos de Lítio/química , Manganês/química , Níquel/química , Carboximetilcelulose Sódica/química , Ácido Cítrico/química , Microscopia Eletrônica de Varredura , Ácidos Fosfóricos/química , Difração de Pó , Água/química
20.
J Phys Chem Lett ; 8(23): 5804-5809, 2017 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-29131962

RESUMO

The intercalation and deintercalation of lithium (Li) into / out of graphite(0001), which is a highly important process in Li-ion batteries, was investigated under ultrahigh vacuum conditions as a function of temperature, employing X-ray and ultraviolet photoelectron spectroscopy. Both the up-shifts of the core-level binding energy and the lowering of the work function ΔΦ reveal that heating of a monolayer of the battery-relevant ionic liquid (IL) 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]+[TFSI]-) adsorbed on lithiated graphite at 80 K to >230 K facilitates an accumulation of partially charged Liδ+ atoms at the IL-graphite(0001) interface. This is accompanied by a partial IL decomposition, which is associated with the initial stages of the chemical formation of the solid-electrolyte interphase.

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