Tin-nanoparticle as anode material in lithium-ion batteries - Influence of morphological and surface properties on the electrochemical performance

本课题将研究以纳米锡粒子为活性材料的阳极体系。这些阳极系统在锂离子电池中具有很高的应用潜力，因为锡作为活性材料提供了高锂存储容量，从而产生高比能。然而，到目前为止，锡基阳极仅显示出有限的循环稳定性。为了提高锡基材料的电化学性能，需要从根本上了解锡基材料的行为。到目前为止，人们对锂的储存机制与颗粒性质的依赖关系知之甚少，例如它们的形态和表面。此外，锡电极表面SEI层的形成和结构，以及活性材料颗粒与导电碳颗粒和/或集流器之间失去接触的原因也需要进行更详细的研究，以获得更深入的理解。该项目的主要重点在于特定纳米颗粒的尺寸和形状设计，以及聚合物（配体壳）表面功能化的优化。此外，我们将研究颗粒的形态性质和表面性质及其电化学行为之间的关系。在这个项目中，我们将优化颗粒的尺寸及其尺寸分布，以获得高比容量和高循环稳定性。此外，电极的制备，在分散程序，粘合剂材料和组成方面，需要优化和调整，以适应颗粒的性质。更重要的是，迄今尚未得到充分回答的基本问题需要得到解决。特别是，必须研究聚合物粘合剂与颗粒表面的相互作用，以及它对电化学性能的影响，如可逆和不可逆容量，SEI形成和容量保持。

In this project, anode systems based on nanoscale tin particles as active material will be studied. These anode systems have a high potential for application in lithium-ion batteries, because tin as active material offers a high lithium storage capacity, which results in a high specific energy. However, tin-based anodes display only a limited cycling stability, so far. In order to improve their electrochemical characteristics, the behavior of the tin-based materials needs to be understood fundamentally. So far, little is known about the dependence of the lithium storage mechanism on the properties of the particles, such as their morphology and surface. Also the formation and structure of the SEI layer on the surface of the tin electrodes, and the reasons for the loss of the contact between the active material particles and conductive carbon particles and/or the current collector need to be studied in more detail to gain a deeper understanding.The main focus of the project lies on the specific nanoparticle design in terms of their size and shape, as well as on the optimization of their surface functionalization with polymers (ligand shells). Furthermore, we will study the correlation between the morphological properties and the surface properties of the particles and their electrochemical behavior. In this project, we will optimize the size of the particles and their size distribution in order to obtain a high specific capacity as well as a high cycling stability. Furthermore, the electrode preparation, in terms of the dispersion procedure, binder material and composition, needs to be optimized and adjusted to the properties of the particles. What is more, fundamental questions that have not been sufficiently answered so far need to be addressed. In particular, the interaction of the polymer binder with the surface of the particles has to be studied, as well as its impact on the electrochemical properties, such as, the reversible and irreversible capacity, SEI formation and capacity retention.