Publications by authors named "Isidora Cekic-Laskovic"

11 Publications

  • Page 1 of 1

Conventional Electrolyte and Inactive Electrode Materials in Lithium-Ion Batteries: Determining Cumulative Impact of Oxidative Decomposition at High Voltage.

ChemSusChem 2020 Oct 17;13(19):5301-5307. Epub 2020 Aug 17.

Helmholtz-Institute Münster (HI MS) IEK-12, Forschungszentrum Jülich GmbH, Corrensstrasse 46, 48149, Münster, Germany.

High-voltage electrodes based on, for example, LiNi Mn 0 (LNMO) active material require oxidative stability of inactive materials up to 4.95 V vs. Li|Li . Referring to literature, they are frequently supposed to be unstable, though conclusions are still controversial and clearly depend on the used investigation method. For example, the galvanostatic method, as a common method in battery research, points to the opposite, thus to a stability of the inactive materials, which can be derived from, for example, the high decomposition plateau at 5.56 V vs. Li|Li and stable performance of the LNMO charge/discharge cycling. This work aims to unravel this apparent contradiction of the galvanostatic method with the literature by a thorough investigation of possible trace oxidation reactions in cumulative manner, that is, over many charge/discharge cycles. Indeed, the cumulated irreversible specific capacity amounts to ≈10 mAh g during the initial 50 charge/discharge cycles, which is determined by imitating extreme LNMO high-voltage conditions using electrodes solely consisting of inactive materials. This can explain the ambiguities in stability interpretations of the galvanostatic method and the literature, as the respective irreversible specific capacity is obviously too low for distinct detection in conventional galvanostatic approaches and can be only detected at extreme high-voltage conditions. In this regard, the technique of chronoamperometry is shown to be an effective and proper complementary tool for electrochemical stability research in a qualitative and quantitative manner.
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http://dx.doi.org/10.1002/cssc.202001530DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589409PMC
October 2020

Poly(Ethylene Oxide)-based Electrolyte for Solid-State-Lithium-Batteries with High Voltage Positive Electrodes: Evaluating the Role of Electrolyte Oxidation in Rapid Cell Failure.

Sci Rep 2020 Mar 9;10(1):4390. Epub 2020 Mar 9.

Helmholtz-Institute Münster, IEK-12, Forschungszentrum Jülich GmbH, Corrensstraße 46, 48149, Münster, Germany.

Polyethylene oxide (PEO)-based solid polymer electrolytes (SPEs) typically reveal a sudden failure in Li metal cells particularly with high energy density/voltage positive electrodes, e.g. LiNiMnCoO (NMC622), which is visible in an arbitrary, time - and voltage independent, "voltage noise" during charge. A relation with SPE oxidation was evaluated, for validity reasons on different active materials in potentiodynamic and galvanostatic experiments. The results indicate an exponential current increase and a potential plateau at 4.6 V vs. Li|Li, respectively, demonstrating that the main oxidation onset of the SPE is above the used working potential of NMC622 being < 4.3 V vs. Li|Li. Obviously, the SPE│NMC622 interface is unlikely to be the primary source of the observed sudden failure indicated by the "voltage noise". Instead, our experiments indicate that the Li | SPE interface, and in particular, Li dendrite formation and penetration through the SPE membrane is the main source. This could be simply proven by increasing the SPE membrane thickness or by exchanging the Li metal negative electrode by graphite, which both revealed "voltage noise"-free operation. The effect of membrane thickness is also valid with LiFePO electrodes. In summary, it is the cell set-up (PEO thickness, negative electrode), which is crucial for the voltage-noise associated failure, and counterintuitively not a high potential of the positive electrode.
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http://dx.doi.org/10.1038/s41598-020-61373-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7062893PMC
March 2020

Fluorinated Cyclic Phosphorus(III)-Based Electrolyte Additives for High Voltage Application in Lithium-Ion Batteries: Impact of Structure-Reactivity Relationships on CEI Formation and Cell Performance.

ACS Appl Mater Interfaces 2019 May 26;11(18):16605-16618. Epub 2019 Apr 26.

Forschungszentrum Jülich GmbH Helmholtz-Institute Münster , Corrensstrasse 46 , 48149 Münster , Germany.

Two selected and designed fluorinated cyclic phosphorus(III)-based compounds, namely 2-(2,2,3,3,3-pentafluoropropoxy)-1,3,2-dioxaphospholane (PFPOEPi) and 2-(2,2,3,3,3-pentafluoro-propoxy)-4-(trifluormethyl)-1,3,2-dioxaphospholane (PFPOEPi-1CF), were synthesized and comprehensively characterized for high voltage application in lithium-ion batteries (LIBs). Cyclic voltammetry (CV) and constant current cycling were conducted, followed by post mortem analysis of the NMC111 electrode surface via scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). To support and complement obtained experimental results, density functional theory (DFT) calculations and molecular dynamics (MD) simulations were performed. Theoretical and experimental findings show that the considered phospholane molecule class enables high voltage LIB application by sacrificial decomposition on the cathode surface and involvement in the formation of a cathode electrode interphase (CEI) via polymerization reaction. In addition, obtained results point out that the introduction of the CF group has a significant influence on the formation and dynamics of the CEI as well as on the overall cell performance, as the cell impedance as well as the thickness of the CEI is increased compared to the cells containing PFPOEPi, which results in a decreased cycling performance. This systematic approach allows researchers to understand the structure-reactivity relationship of the newly synthesized compounds and helps to further tailor the vital physicochemical properties of functional electrolyte additives relevant for high voltage LIB application.
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http://dx.doi.org/10.1021/acsami.9b03359DOI Listing
May 2019

Intrinsically Safe Gel Polymer Electrolyte Comprising Flame-Retarding Polymer Matrix for Lithium Ion Battery Application.

ACS Appl Mater Interfaces 2018 Dec 27;10(49):42348-42355. Epub 2018 Nov 27.

Forschungszentrum Jülich GmbH Helmholtz-Institute Münster , Corrensstrasse 46 , 48149 Münster , Germany.

State-of-the-art (SOTA) liquid electrolyte/polyolefin separator setups used in lithium ion batteries (LIBs) suffer from the hazard of leakage and high flammability. To address these issues, phosphonate, a flame-retarding moiety, is chemically bonded to a polymer matrix to fabricate a nonflammable gel polymer electrolyte (GPE). The obtained phosphonate-based polymer matrix as well as its corresponding GPE (gelled with flammable SOTA nonaqueous liquid electrolyte) shows remarkable flame resistivity. Unlike poly(vinylidene fluoride- co-hexafluoropropylene)-based GPEs, the phosphonate-based GPE does not react with lithiated graphite at high temperatures. Both features indicate that the phosphonate-based GPE is superior to SOTA GPEs in the aspect of safety performance. As the flame-retarding moiety is chemically bonding to the polymer, the parasitic reactions between the flame-retarding moiety and the electrodes are avoided. Consequently, LIB cells comprising phosphonate-based GPE show good capacity retention comparable to cells comprising SOTA GPEs. Compared with SOTA GPEs, phosphonate-based polymer-based GPEs show improved intrinsic safety performance and comparable cycle life. Therefore, phosphonate-based polymers exhibit high potential to be used as a new class of polymer matrix for GPE used in LIBs.
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http://dx.doi.org/10.1021/acsami.8b15505DOI Listing
December 2018

Electrolyte solvents for high voltage lithium ion batteries: ion correlation and specific anion effects in adiponitrile.

Phys Chem Chem Phys 2018 Oct;20(40):25701-25715

Institute for Computational Physics, University of Stuttgart, Allmandring 3, 70569 Stuttgart, Germany.

We studied dynamic and structural properties of two lithium conducting salts in the aprotic organic solvent adiponitrile by a combination of atomistic molecular dynamics (MD) simulations, quantum chemical calculations, and experimental findings. The outcomes of our simulations reveal significant differences between both lithium salts, namely lithium tetrafluoroborate (LiBF4) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) at various concentrations, which can be mainly attributed to the solvation behavior of the individual anions. The increased tendency of ion complex formation for LiBF4 is reflected by lower values regarding the measured and computed effective ionic conductivities when compared to LiTFSI. All findings highlight the crucial importance of specific anion effects in combination with molecular details of solvation, and advocate the use of adiponitrile as a beneficial solvent in modern lithium ion battery technology with high voltage electrodes.
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http://dx.doi.org/10.1039/c8cp04102dDOI Listing
October 2018

Interfaces and Materials in Lithium Ion Batteries: Challenges for Theoretical Electrochemistry.

Top Curr Chem (Cham) 2018 Apr 18;376(3):16. Epub 2018 Apr 18.

Helmholtz-Institute Münster, IEK-12, Forschungszentrum Jülich GmbH, Corrensstrasse 46, 48149, Münster, Germany.

Energy storage is considered a key technology for successful realization of renewable energies and electrification of the powertrain. This review discusses the lithium ion battery as the leading electrochemical storage technology, focusing on its main components, namely electrode(s) as active and electrolyte as inactive materials. State-of-the-art (SOTA) cathode and anode materials are reviewed, emphasizing viable approaches towards advancement of the overall performance and reliability of lithium ion batteries; however, existing challenges are not neglected. Liquid aprotic electrolytes for lithium ion batteries comprise a lithium ion conducting salt, a mixture of solvents and various additives. Due to its complexity and its role in a given cell chemistry, electrolyte, besides the cathode materials, is identified as most susceptible, as well as the most promising, component for further improvement of lithium ion batteries. The working principle of the most important commercial electrolyte additives is also discussed. With regard to new applications and new cell chemistries, e.g., operation at high temperature and high voltage, further improvements of both active and inactive materials are inevitable. In this regard, theoretical support by means of modeling, calculation and simulation approaches can be very helpful to ex ante pre-select and identify the aforementioned components suitable for a given cell chemistry as well as to understand degradation phenomena at the electrolyte/electrode interface. This overview highlights the advantages and limitations of SOTA lithium battery systems, aiming to encourage researchers to carry forward and strengthen the research towards advanced lithium ion batteries, tailored for specific applications.
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http://dx.doi.org/10.1007/s41061-018-0196-1DOI Listing
April 2018

Synergistic Effect of Blended Components in Nonaqueous Electrolytes for Lithium Ion Batteries.

Top Curr Chem (Cham) 2017 Apr 15;375(2):37. Epub 2017 Mar 15.

Helmholtz Institute Münster, IEK-12, Forschungszentrum Jülich GmbH, 48149, Münster, Germany.

Application of different electrolyte components as blends in nonaqueous electrolyte formulations represents a viable approach towards improving the overall performance and reliability of a lithium ion battery cell. By combining the advantages of different electrolyte constituents, cell chemistry can be optimized and tailored for a specific purpose. In this paper, the current progress on possibilities, advantages, as well as limitations of blended nonaqueous electrolyte formulations, including solvent, salt and additive blends is reviewed and discussed. Emphasis is set on the physicochemical, electrochemical, and safety aspects. In addition, the aim of this review is to provide perspective and possible strategy for further and future development of blended nonaqueous electrolytes with long life, high energy density, high power, and adequate safety at competitive manufacturing costs. The provided overview and perspective on blended nonaqueous electrolyte formulations should encourage researchers to proceed with further and deeper investigations in this promising field of advanced batteries.
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http://dx.doi.org/10.1007/s41061-017-0125-8DOI Listing
April 2017

Impact of Selected LiPF Hydrolysis Products on the High Voltage Stability of Lithium-Ion Battery Cells.

ACS Appl Mater Interfaces 2016 Nov 4;8(45):30871-30878. Epub 2016 Nov 4.

MEET Battery Research Center/Institute of Physical Chemistry, University of Münster , Corrensstrasse 46, 48149 Münster, Germany.

Diverse LiPF hydrolysis products evolve during lithium-ion battery cell operation at elevated operation temperatures and high operation voltages. However, their impact on the formation and stability of the electrode/electrolyte interfaces is not yet investigated and understood. In this work, literature-known hydrolysis products of LiPF dimethyl fluorophosphate (DMFP) and diethyl fluorophosphate (DEFP) were synthesized and characterized. The use of DMFP and DEFP as electrolyte additive in 1 M LiPF in EC:EMC (1:1, by wt) was investigated in LiNiMnCoO/Li half cells. When charged to a cutoff potential of 4.6 V vs Li/Li, the additive containing cells showed improved cycling stability, increased Coulombic efficiencies, and prolonged shelf life. Furthermore, low amounts (1 wt % in this study) of the aforementioned additives did not show any negative effect on the cycling stability of graphite/Li half cells. DMFP and DEFP are susceptible to oxidation and contribute to the formation of an effective cathode/electrolyte interphase as confirmed by means of electrochemical stability window determination, and X-ray photoelectron spectroscopy characterization of pristine and cycled electrodes, and they are supported by computational calculations.
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http://dx.doi.org/10.1021/acsami.6b09164DOI Listing
November 2016

High Voltage LiNiMnO/LiTiO Lithium Ion Cells at Elevated Temperatures: Carbonate- versus Ionic Liquid-Based Electrolytes.

ACS Appl Mater Interfaces 2016 Oct 23;8(39):25971-25978. Epub 2016 Sep 23.

MEET Battery Research Center, Institute for Physical Chemistry, University of Münster , Corrensstraße 46, 48149 Münster, Germany.

Thanks to its high operating voltage, the LiNiMnO (LNMO) spinel represents a promising next-generation cathode material candidate for Lithium ion batteries. However, LNMO-based full-cells with organic carbonate solvent electrolytes suffer from severe capacity fading issues, associated with electrolyte decomposition and concurrent degradative reactions at the electrode/electrolyte interface, especially at elevated temperatures. As promising alternatives, two selected LiTFSI/pyrrolidinium bis(trifluoromethane-sulfonyl)imide room temperature ionic liquid (RTIL) based electrolytes with inherent thermal stability were investigated in this work. Linear sweep voltammetry (LSV) profiles of the investigated LiTFSI/RTIL electrolytes display much higher oxidative stability compared to the state-of-the-art LiPF/organic carbonate based electrolyte at elevated temperatures. Cycling performance of the LNMO/LiTiO (LTO) full-cells with LiTFSI/RTIL electrolytes reveals remarkable improvements with respect to capacity retention and Coulombic efficiency. Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns indicate maintained pristine morphology and structure of LNMO particles after 50 cycles at 0.5C. The investigated LiTFSI/RTIL based electrolytes outperform the LiPF/organic carbonate-based electrolyte in terms of cycling performance in LNMO/LTO full-cells at elevated temperatures.
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http://dx.doi.org/10.1021/acsami.6b07687DOI Listing
October 2016

Alternative Single-Solvent Electrolytes Based on Cyanoesters for Safer Lithium-Ion Batteries.

ChemSusChem 2016 07 30;9(13):1704-11. Epub 2016 May 30.

MEET Battery Research Center, University of Münster, Corrensstraße 46, 48149, Münster, Germany.

To identify alternative single-solvent-based electrolytes for application in lithium-ion batteries (LIBs), adequate computational methods were applied to screen specified physicochemical and electrochemical properties of new cyanoester-based compounds. Out of 2747 possible target compounds, two promising candidates and two structurally equivalent components were chosen. A constructive selection process including evaluation of basic physicochemical properties as well assessing the compatibility towards graphitic anodes was initiated to identify the most promising candidates. With addition of a film-forming additive in a low concentration, the most promising candidate showed an adequate long-term cycling stability with LiNi1/3 Mn1/3 Co1/3 O2 [NMC(111)] in a full-cell setup using graphite as anode material. The main advantages of the new electrolyte formulation are related to its good thermal behavior, especially with regard to safety in combination with satisfying electrochemical performance.
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http://dx.doi.org/10.1002/cssc.201600369DOI Listing
July 2016

Lithium-cyclo-difluoromethane-1,1-bis(sulfonyl)imide as a stabilizing electrolyte additive for improved high voltage applications in lithium-ion batteries.

Phys Chem Chem Phys 2015 Apr 11;17(14):9352-8. Epub 2015 Mar 11.

Westfälische Wilhelms-Universität Münster, Institute of Physical Chemistry, MEET Battery Research Center, Corrensstr. 46, 48149 Muenster, Germany.

Lithium-cyclo-difluoromethane-1,1-bis(sulfonyl)imide (LiDMSI) was evaluated as an electrolyte additive in lithium-ion batteries for improved high voltage applications. Cycling the cathode at high potentials leads to the electrochemical oxidation of the salt to form a cathode electrolyte interphase (CEI) layer on the cathode surface. With the addition of 2 wt% of LiDMSI to the 1 M LiPF6 in 1 : 1 (by wt) EC : DEC electrolyte, the capacity retention and the Coulombic efficiency in LiNi1/3Co1/3Mn1/3O2/Li-half-cells as well as in LiNi1/3Co1/3Mn1/3O2/graphite-full-cells were improved. The cycling results point out the less over-potential and resistance at the cathode/electrolyte interface. These improvements are studied by SEM, EIS and XPS techniques.
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http://dx.doi.org/10.1039/c5cp00483gDOI Listing
April 2015
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