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Author: Eckert, Jürgen × Author: Giebeler, Lars × DDC: 620 ×

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    SEI-component formation on sub 5 nm sized silicon nanoparticles in Li-ion batteries: The role of electrode preparation, FEC addition and binders
    (Cambridge : Royal Society of Chemistry, 2015) Jaumann, Tony; Balach, Juan; Klose, Markus; Oswald, Steffen; Langklotz, Ulrike; Michaelis, Alexander; Eckert, Jürgen; Giebeler, Lars
    Silicon is a promising negative electrode for secondary lithium-based batteries, but the electrochemical reversibility of particularly nanostructured silicon electrodes drastically depends on their interfacial characteristics, commonly known as the solid electrolyte interface (SEI). The beneficial origin of certain electrolyte additives or different binders is still discussed controversially owing to the challenging peculiarities of interfacial post-mortem investigations of electrodes. In this work, we address the common difficulties of SEI investigations of porous silicon/carbon nanostructures and study the addition of a fluoroethylene carbonate (FEC) as a stabilizing additive as well as the use of two different binders, carboxymethyl cellulose/styrene-butadiene rubber (CMC/SBR) and polyacrylic acid (PAA), for the SEI formation. The electrode is composed of silicon nanocrystallites below 5 nm diameter allowing a detailed investigation of interfacial characteristics of silicon owing to the high surface area. We first performed galvanostatic long-term cycling (400 times) and carried out comprehensive ex situ characterization of the cycled nanocrystalline silicon electrodes with XRD, EDXS, TEM and XPS. We modified the preparation of the electrode for post-mortem characterization to distinguish between electrolyte components and the actual SEI. The impact of the FEC additive and two different binders on the interfacial layer is studied and the occurrence of diverse compounds, in particular LiF, Li2O and phosphates, is discussed. These results help to understand general issues in SEI formation and to pave the way for the development of advanced electrolytes allowing for a long-term performance of nanostructured Si-based electrodes.
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    Role of 1,3-dioxolane and LiNO3 addition on the long term stability of nanostructured silicon/carbon anodes for rechargeable lithium batteries
    (Pennington, NJ : ECS, 2016) Jaumann, Tony; Balach, Juan; Klose, Markus; Oswald, Steffen; Eckert, Jürgen; Giebeler, Lars
    In order to utilize silicon as alternative anode for unfavorable lithium metal in lithium – sulfur (Li–S) batteries, a profound understanding of the interfacial characteristics in ether-based electrolytes is required. Herein, the solid electrolyte interface (SEI) of a nanostructured silicon/carbon anode after long-term cycling in an ether-based electrolyte for Li–S batteries is investigated. The role of LiNO3 and 1,3-dioxolane (DOL) in dimethoxy ethane (DME) solutions as typically used electrolyte components on the electrochemical performance and interfacial characteristics on silicon are evaluated. Because of the high surface area of our nanostructured electrode owing to the silicon particle size of around 5 nm and the porous carbon scaffold, the interfacial characteristics dominate the overall electrochemical reversibility opening a detailed analysis. We show that the use of DME/DOL solutions under ambient temperature causes higher degradation of electrolyte components compared to carbonate-based electrolytes used for Li–ion batteries (LIB). This behavior of DME/DOL mixtures is associated with different SEI component formation and it is demonstrated that LiNO3 addition can significantly stabilize the cycle performance of nanostructured silicon/carbon anodes. A careful post-mortem analysis and a discussion in context to carbonate-based electrolyte solutions helps to understand the degradation mechanism of silicon-based anodes in rechargeable lithium-based batteries.
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    High area capacity lithium-sulfur full-cell battery with prelitiathed silicon nanowire-carbon anodes for long cycling stability
    (London : Nature Publishing Group, 2016) Krause, Andreas; Dörfler, Susanne; Piwko, Markus; Wisser, Florian M.; Jaumann, Tony; Ahrens, Eike; Giebeler, Lars; Althues, Holger; Schädlich, Stefan; Grothe, Julia; Jeffery, Andrea; Grube, Matthias; Brückner, Jan; Martin, Jan; Eckert, Jürgen; Kaskel, Stefan; Mikolajick, Thomas; Weber, Walter M.
    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm2, a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging.
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    Verbundprojekt: Batterie – Stationär in Sachsen (BaSta), Teilvorhaben: Leibniz IFW : Schlussbericht ; Berichtszeitraum: 01.11.2012-30.04.2016
    (Hannover : Technische Informationsbibliothek (TIB), 2016) Eckert, Jürgen; Giebeler, Lars
    Die Entwicklung und Umsetzung umfasst eines völlig neuartigen Batteriekonzeptes, der die Vorteile der bisherigen Na-S-Hochtemperaturbatterien (z.B. niedrige Kosten und hohe Verfügbarkeit der notwendigen Rohstoffe) mit der Performance moderner Lithium-Ionenbatterien, jedoch auf Na-Ionenbasis, im Niedertemperaturbereich verknüpft. Dazu müssen neue Elektroden- bzw. Separatormaterialien mit vorteilhafter Interaktion und Degradationsstabilität in verschiedenen neuartigen Elektrolyten entwickelt werden. Darüber hinaus werden geeignete Verfahren zur Herstellung und Fertigung dieser Komponenten zu Niedertemperatur-Na-S-Batterien generiert. Die Ziele sollen durch die außerordentlich enge Vernetzung mehrerer Professuren der TU Dresden mit verschiedenen Instituten der Fraunhofer Gesellschaft, dem Leibniz IFW Dresden e.V. und der TU Bergakademie Freiberg erreicht werden. Der Arbeitsplan sieht eine 'bottom up' Strategie von der Materialentwicklung und Charakterisierung über die Werkstoffprozessierung hin zur Systementwicklung und -charakterisierung vor. Die universitären Einrichtungen arbeiten dabei vorwiegend grundlagenorientiert auf dem Gebiet der Materialentwicklung für einen völlig neuen Batterietyp. Die dabei gewonnenen Erkenntnisse werden unmittelbar in die anwendungsorientierte Forschung überführt. Entscheidend ist die interaktive Zusammenarbeit zu allen Zeitpunkten und auf allen Ebenen des Gesamtvorhabens.