Eric Winter


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Winter

First Name

Eric

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0000-0003-4700-0983

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2022 - 20245
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Publications 1 - 5 of 5
  • Potentiostatic lithium plating as a fast method for electrolyte evaluation in lithium metal batteries
    Item type: Journal Article
    Winter, Eric; Schmidt, Thomas; Trabesinger, Sigita (2023)
    Electrochimica Acta
    One of the most crucial factors to enable metallic lithium anodes is having an electrolyte that allows stable and safe battery cycling, however, the commonly used carbonate electrolytes typically perform poorly, highlighting the need for the development of new electrolyte compositions. Evaluating potential electrolyte candidates is typically a lengthy procedure that does need time-consuming long-term cycling experiments. To speed this process up, we have investigated potentiostatic lithium plating, inspired from hydrogen-pumping performed for fuel cell performance evaluation, as a potential method for fast electrolyte suitability investigation. First, scanning electron microscopy was used to establish a link between lithium surface coverage and measured current response in a model carbonate electrolyte. Afterwards, a selection of carbonate and ether electrolytes was used for validation of our testing procedure, showing that individual, characteristic patterns can be distinguished. Apart from giving an insight into Li transport in each electrolyte, a correlation to physical electrolyte properties can be found. Consequently, our findings may be a first step towards using potentiostatic plating as a fast, easy and high-throughput method to investigate suitability of new electrolyte formulations for lithium metal batteries and beyond.
  • Enabling LiNO3 in carbonate electrolytes by flame-retardant electrolyte additive as a cosolvent for enhanced performance of lithium metal batteries
    Item type: Journal Article
    Winter, Eric; Briccola, Mariano; Schmidt, Thomas; et al. (2024)
    Applied Research
    Most contemporary liquid Li-ion battery chemistries are based on carbonate electrolytes, however, these typically perform poorly with metallic lithium. Especially, when only a small reservoir of metal is present, cells fail quickly due to the complete consumption of electrochemically active Li. Electrolyte modification is, therefore, a commonly chosen strategy to increase cycling stability and prolong lifetime of the cell. At the same time, complete redevelopment of an electrolyte usually creates a new set of problems, as conductivity, suitable electrochemical stability window and compatibility to all components of the cell needs to be ensured. It is, therefore, a reasonable strategy to alter existing electrolytes slightly, as has been done for the aforementioned carbonate electrolytes by incorporating lithium nitrate salt with triethyl phosphate as cosolvent into the mixture. As the role of the organophosphate is not fully clarified, our study aims to investigate its effect onto cycling stability, morphology, and reversibility of Li metal cycling both with and without LiNO3 salt. Using close-to-industrial conditions with limited excess of metallic Li at high current density, we are comparing cycling performance of the different electrolyte combinations. Contribution of the additive components to irreversible thickness growth due to the formation of inactive (“dead”) lithium and deposited lithium morphology is investigated by operando dilatometry and postmortem scanning electron microscopy. Finally, we are looking at modified solvent-salt ratios to see whether further improvements of cell lifetime and morphology can be achieved.
  • Identifying Pitfalls in Lithium Metal Battery Characterization
    Item type: Journal Article
    Winter, Eric; Schmidt, Thomas; Trabesinger, Sigita (2022)
    Batteries & Supercaps
    Over the past decade, there has been a revival of research activity on lithium metal batteries (LMBs) as these could be a solution for key challenges of electromobility and the energy revolution. While there is growing consensus in the scientific community that common reporting standards and testing conditions for LMBs have to be established, a vast majority of research activities on lithium metal use lab-dependant testing protocols. For that reason, this publication aims to shed light on various, potentially neglected aspects in battery assembly and testing. Firstly, the long-term cycling, regarding a range of experimental parameters, such as current density, capacity, electrolyte type and its quantity, as well as contribution of the electrode edges, is shown in both symmetric (Li||Li) and asymmetric (Cu||Li) configurations. The second part focuses on the reversibility of lithium thickness during cycling with and without protected electrode edges, investigated by operando dilatometry. By bringing the insights from this parameter study together, we aim to contribute to better experiment design for future LMB studies, as well as a better understanding for the failure mechanism of Li metal anodes.
  • Spectroscopic neutron imaging for resolving hydrogen dynamics changes in battery electrolytes
    Item type: Journal Article
    Carreón Ruiz, E. Riccardo; Lee, Jongmin; Márquez Damián, J. Ignacio; et al. (2023)
    Materials Today Advances
    We present the use of spectroscopic neutron imaging (SNI), a bridge between imaging and scattering techniques, for analyzing battery electrolytes. The scattering information of CHn–based organic solvents and electrolytes was mapped in a two-dimensional space through time-of-flight neutron imaging, which exploits the wavelength-dependent properties of hydrogen atoms. The results show partial solidification and concertation change of electrolyte as a function of temperature. Our investigation demonstrates a novel approach to tracking real-time physical and chemical changes in H-containing compounds, by which limitations of new electrolyte mixtures and additives can be evaluated. The sensitivity of SNI to hydrogen in CHn functional groups extends the use of spectral methods to inspect electrolytes in Li-ion batteries and organic solvents for relevant applications beyond electrochemical systems.
  • Fundamental Understanding of Critical Parameters Enabling Lithium Metal Batteries
    Item type: Doctoral Thesis
    Winter, Eric (2023)
    Over the past decade, there has been a revival of research activity on lithium metal batteries (LMBs) because these could be a solution for key challenges in electromobility and mobile device autonomy. Compared to conventional cell chemistries, an energy density increase by a factor of 1.5-2 would be possible, which makes enabling LMBs in commercial applications highly attractive. However, the poor reversibility of Li deposition and stripping is still impeding a breakthrough: especially when only a small reservoir of metal is present, cells fail quickly due to the complete consumption of electrochemically active Li. At the same time, processes leading to cell failure are poorly understood, as most studies focus on the suppression of symptoms instead of looking for the root causes. Therefore, three core questions are being clarified in this thesis: what are the critical parameters for reversible cycling of lithium metal, how electrolyte compatibility to metallic lithium can be enhanced, and which tools can help to better understand the kinetics and dynamics of lithium deposition and stripping. A baseline study is first addressing factors that are often neglected during battery characterisation, such as current density, type and quantity of electrolyte and the contribution of more-reactive electrode edges. It is found that the latter play a significant role in the formation of dendrites and thus eventually leads to premature cell failure. On another hand, the excess of lithium metal and electrolyte in a cell conceals important detrimental effects, even when cycling takes place at elevated current density. Having identified key factors that influence the outcome of experiments, the modification of carbonate electrolyte with an organophosphate–lithium nitrate mixture has been investigated. Using close-to-industrial conditions with limited excess of metallic lithium and electrolyte at high current density, a positive contribution of the additive is observed, leading to larger particle size, less surface decomposition products and prolongation of cell lifetimes. The contribution of electrolyte chemistry remains an important topic throughout the thesis and is investigated from a methodological point of view. Potentiostatic lithium plating, inspired by hydrogen pumping as a widespread method in fuel cell characterisation, is explored as a method for fast electrolyte suitability investigation. Scanning electron microscopy helps to establish a link between measured current response and lithium surface coverage before a selection of different electrolytes is used to validate the testing procedure. Electrolyte-specific patterns highlight the potential of the method for electrolyte screening, especially due to an observed direct correlation between measured activation overpotentials and lithium kinetics. Finally, a methodology for neutron imaging as a powerful method for operando tracking of lithium deposition and stripping has been developed. Using a neutron microscope, conventional coin cells are cycled normally, in a slightly modified configuration, while the deposition and removal of Li are recorded at high resolution. In addition to providing temporal information on lithium nucleation, a simple processing step also allows for determining the quantitative lateral distribution of lithium metal on the current collector. By using three carbonate electrolytes with varying content of fluoroethylene carbonate additive, the contribution of an electrolyte additive to cycling is further clarified. Combining neutron imaging and operando dilatometry, the density of lithium deposition can also be identified. In summary, this work contributes to the identification of critical cycling parameters, a better understanding of the role of electrolyte additives as well as new methodologies. The gained knowledge will help to accelerate progress in the field of Li metal batteries and systematic experimental design. With a better understanding of metal plating and stripping, it will be possible to address safety concerns and use lithium metal as a safe and long-lived electrode for high-capacity cells.
Publications 1 - 5 of 5