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

在本项目中，我们将研究以纳米TiN颗粒为活性物质的阳极系统。这些负极体系在锂离子电池中具有很高的应用潜力，因为作为活性材料的锡具有很高的锂存储容量，这导致了较高的比能量。然而，到目前为止，锡基阳极只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，关于锂的储存机制与粒子的性质，如它们的形态和表面的依赖关系，人们知之甚少。此外，锡电极表面SEI层的形成和结构，以及活性物质颗粒与导电碳颗粒和/或集电体失去接触的原因还需要更详细的研究，以获得更深层次的了解。该项目的主要重点在于特定纳米颗粒的尺寸和形状设计，以及其与聚合物(配位体壳层)表面功能化的优化。此外，我们还将研究颗粒的形态特性和表面特性与其电化学行为之间的关系。在本项目中，我们将对颗粒的尺寸和尺寸分布进行优化，以获得高比容量以及高循环稳定性。此外，电极的制备在分散过程、粘结剂材料和成分方面需要进行优化，并根据颗粒的性质进行调整。更重要的是，需要解决迄今尚未得到充分答案的根本问题。特别是，聚合物粘结剂与粒子表面的相互作用及其对电化学性能的影响，如可逆和不可逆容量，SEI的形成和容量保持，是必须研究的。

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.