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

本项目将通过静电纺丝和热处理相结合的方法合成氧化钒/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/性能关联。这些知识对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是设计某种法拉第电极材料，掺入碳导电剂(以确保导电性)，并通过使用粘结剂(通常是基于聚合物的)将这两种组分固定在电流收集器上。这种复合材料限制了对控制(和限制)电极活性成分的电化学性能的内在参数的理解。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的杂化而不是机械混合来实现。我们的工作将使用静电纺丝来设计杂化纤维，这样我们就可以立即获得无粘结剂的电极。我们可以用“一锅法”合成氧化钒/碳杂化材料，这种杂化材料可以在硫化氢处理后转化为硫化钒/碳纤维。这种方法实现了离子储存完成电荷储存的相和导电碳之间的高水平纳米级相互作用，这比这两个组分的机械混合要好。为了获得导电和电化学稳定的锂离子和钠离子电池电极，我们的目标是(1)研究导电碳含量以及碳性质(即孔隙率和孔径)的影响；(2)钒氧化物/硫化物的晶体结构；(3)纤维结构对杂化形态和电化学性能的影响。这项工作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来量化离子扩散和化学状态，并通过X射线光电子能谱来补充化学分析。电化学测试将包括有机电解液中的基本电化学、速率处理和寿命基准。为了进一步确定限制因素，我们将使用原位测量来量化结构变化，通过原位X射线衍射、原位电化学膨胀测量和电化学石英晶体微天平测量，并使用阻抗谱和恒流间歇滴定技术。结构性尸检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.