Vanadium oxide and vanadium sulfide/carbon hybrid electrodes by electrospinning for lithium and sodium ion batteries (HEROES-4-Li-Na-batteries)

我们的项目将通过静电纺丝和热处理相结合来合成氧化钒/碳和硫化钒/碳杂化纤维，并研究它们作为锂离子电池和钠离子电池电极的性能。通过修改杂化材料的关键参数，我们将建立详细的结构/性能相关性。这些知识对于建立下一代锂离子和钠离子电池电极的设计指南和合成策略非常重要。大多数锂离子和钠离子电池的工作都是设计一种法拉第电极材料，混合碳导电添加剂（以确保导电性），并通过使用粘合剂（通常是聚合物基）将两种成分结合到集流体上。这样的复合材料限制了对支配（和限制）电极的活性组分的电化学性能的固有参数的理解。此外，锂离子或钠离子主体材料与导电相之间更紧密的纳米级界面只能通过纳米级杂化而不是机械混合来实现。我们的工作将采用静电纺丝来设计杂化纤维，我们可以立即获得无粘合剂的电极。我们可以使用“一锅法”合成方法来获得氧化钒/碳混合物，其可以在H2S处理时转化为硫化钒/碳纤维。该方法使得在其中离子存储完成电荷存储的相和导电碳之间能够实现高水平的纳米级相互作用，这上级于两种组分的机械混合。为了实现导电和电化学稳定的Li-和Na-离子电池电极，我们的目标是（1）研究导电碳含量以及碳特性（即，孔隙率、孔径）;（2）钒的氧化物/硫化物晶体结构;（3）纤维结构对杂化形貌和电化学性能的影响。这将通过将广泛的材料表征与标准和现场电化学测试相结合来完成。工作包括用X射线衍射、电子显微镜、能量色散X射线光谱、拉曼和红外光谱以及热分析对电极材料进行系统分析。在合作中，我们还将通过核磁共振光谱法量化离子扩散和化学状态，并通过X射线光电子能谱法进行补充化学分析。电化学测试将包括有机电解质中的基本电化学、速率处理和寿命基准测试。为了进一步确定限制方面，我们将采用原位测量，以量化结构的变化，通过原位X射线衍射，原位电化学衍射，电化学石英晶体微天平测量，并通过使用阻抗谱和恒电流间歇滴定技术。结构事后分析将进一步有助于确定退化机制。

Our project will synthesize vanadium oxide/carbon and vanadium sulfide/carbon hybrid fibers through the combination of electrospinning and thermal treatments, and investigate their properties as electrodes for Li- and Na-ion batteries. By modifying key parameters of the hybrid material, we will establish detailed structure/property correlations. This knowledge is of high importance to establish design guidelines and synthesis strategies for future generation Li- and Na-ion battery electrodes.Most work on Li- and Na-ion batteries designs a certain Faradaic electrode material, admix a carbon conductive additive (to ensure electrical conductivity), and consolidate both components onto a current collector by use of a binder (often polymer-based). Such composites limit the understanding of the intrinsic parameters governing (and limiting) the electrochemical performance of the active components of the electrodes. Also, a more intimate, nanoscale interface between Li- or Na-ion host materials and the conductive phase can only be realized by nanoscale hybridization instead of mechanical mixing.Our work will employ electrospinning to design hybrid fibers where we obtain right away binder-free electrodes. We can use a “one-pot” synthesis approach to obtain vanadium oxide / carbon hybrids that can be converted in vanadium sulfide / carbon fibers upon H2S treatment. This approach enables a high level of nanoscale interaction between the phase where ion storage accomplishes charge storage and conductive carbon, which is superior to mechanical mixing of the two components. To achieve conductive and electrochemically stable Li- and Na-ion battery electrodes, we aim to (1) study the effect of conductive carbon content, as well as carbon character (i.e., porosity, pore size); (2) vanadium oxide/sulfide crystal structure, and (3) fiber architecture on the hybrid morphology and electrochemical properties. This will be done by combining extensive materials characterization with standard and in situ electrochemical testing.The work includes systematic analysis of the electrode materials with X-ray diffraction, electron microscopy, energy-dispersive X-ray spectroscopy, Raman and IR spectroscopy, and thermal analysis. In collaboration, we will also quantify ion diffusion und chemical states via nuclear magnetic resonance spectroscopy and complement chemical analysis via X-ray photoelectron spectroscopy. Electrochemical tests will include basic electrochemistry in organic electrolyte, rate handling, and longevity benchmarking. To further identify limiting aspects, we will employ in situ measurements to quantify structural changes by in situ X-ray diffraction, in situ electrochemical dilatometry, and electrochemical quartz crystal microbalance measurements and by use of impedance spectroscopy and galvanostatic intermittent titration technique. Structural post mortem analyses will further contribute to identify degradation mechanisms.