Development and Fundamental Understanding of Self-healing Flexible Li-S Batteries with High Cycle Stability (FlexBatt)

具有高能量密度的成功未来锂硫电池的设计具有显著改善现有电池技术和促进环保汽车发展的前景。Li-S电池相对于现有的锂离子电池可以将能量密度提高三倍，同时具有快速充放电循环的高可逆性和数千次循环的寿命。锂硫电池的最新进展表明了一种复杂的工作机制，因此需要对所有电池组件进行进一步深入的机制研究和材料开发。主要的性能和稳定性限制因素与导电性、多硫化物溶解和氧化还原穿梭现象、体积膨胀和（多）硫化物的电极钝化有关。柔性电池允许采用任何所需的形状。使用进行自主自我修复以修复由体积膨胀产生的裂缝的自我修复材料可以在大量循环中保持导电通路。本文提出的概念“FlexBatt”涵盖了整个Li-S电池的柔性组件的开发。阳极、阴极、隔膜和固体聚合物电解质将以凭借自修复材料实现柔性的方式设计。此外，弯曲行为和电池性能之间的相关性将通过流变学（电阻抗）和操作中的电化学和光谱方法进行研究。一种灵活的，独立的，低粘结剂含量的阴极将开发基于柔性硫共聚物碳纳米管网络。这些将与新型弹性固体电解质和锂沉积纺织品为基础的阳极相结合。结合流变学和恒电位仪的定制设置将用于通过蠕变和松弛现象来理解电极的自愈行为。通过阻抗分析监测施加变形前、变形后和自愈合后的阻抗数据。在电化学循环过程中，离子跨膜传输和形态变化将通过在operando技术来研究，以了解循环性能和弯曲行为之间的关系。将通过小角度X射线散射、显微镜和光谱方法对电极进行间歇分析，以确保自修复性能。将对多次充放电循环后和不同放电深度下的电池部件进行事后分析，以了解在不同弯曲角度下操作的电池的功能性和耐久性。完整的研究旨在了解整个柔性电池的机械化学稳定性的重要性，并最终将深入了解限制电池性能和寿命的硫/有机硫物质的不可逆反应的机制和命运。

The design of successful future Li-S batteries with high energy density has the prospect to significantly improve existing battery technology and boost environmentally friendly automotive development. Li-S batteries could triple the energy density relative to existing Li-ion batteries combined with high reversibility of fast charging-discharging cycles and lifetime of thousands of cycles. Recent progress on Li-S batteries indicates a complex mechanism of operation, and hence calls for further in-depth mechanistic studies and material development of all battery components alike. Major performance- and stability-limiting factors are related to conductivity, polysulfide dissolution and redox shuttle phenomena, volume expansion and electrode passivation by (poly)sulfides. Flexible batteries allow to adopt any desired shape. The use of self-healing materials that undergo autonomous self-repairing to heal cracks created by volume expansion could retain conductive pathways for a high number of cycles. The herein proposed concept "FlexBatt" encompasses the development of flexible components for an entire Li-S battery. Anode, cathode, separator and solid polymer electroyte will be designed in a way that flexibility is realized by virtue of self-healing materials. Moreover, the correlation between flex behavior and cell performance will be studied by rheology (rheo-impedance) and in-operando electrochemical and spectroscopic approaches. A flexible, free-standing, low binder content cathode will be developed based on flexible sulfur-copolymer-CNT networks. These will be combined with novel elastomeric solid electrolytes and a lithium-deposited textile based anode. A custom-build setup combining rheology and potentiostat will be used to understand the self-healing behavior of the electrodes by creep and relaxation phenomena. Impedance data before appying deformation, after deformation and after self-healing will be monitored by impedance analyses. During electrochemical cycling, ion transport across the membrane and morphological changes will be investigated by in-operando techniques to understand the correation between cycle performance and flex behavior. Intermittent analyses of the electrodes to ensure the self-healing properties will be conducted by small anagle X-ray scattering, microscopy and spectroscopic approaches. The post-mortem analysis of the cell parts after multiple charging-discharging cycles and at different depth of discharge will be carrried out to understand the functionality and durability of the cell operated at different bending angles. The complete study aims at understanding the importance of mechano-chemical stability of the entire flexible battery and finally will provide insight into the mechanism and fate of irreversible reactions of sulfur/organosulfur species limiting battery performance and life time.