Synthesis and characterization of paper-like, nanostructured electrodes for advanced secondary batteries

本项目的主要任务是开发具有改进性能的纸状电极，用于锂离子电池。这些纳米复合材料的分层结构被设想同时利用石墨烯非凡的机械/化学稳定性和导电性以及无机纳米结构的高效锂离子存储能力，以提高电极的充放电动力学和寿命。在第一期项目中，改进了V2O5纳米纤维的自组装，获得了坚韧柔韧的类纸薄膜，并成功合成和表征了所需的其他无机组分SnO2纳米片/纤维和LiMnPO4纳米片。重要的是，可以证明，特别是对于由V2O5纳米纤维和氧化石墨烯（GO）组成的复合材料，石墨烯片的实施确实可以改善机械稳定性，导电性和驱动性能。此外，这些复合材料的结构质量与力学性能之间存在相关性。在此基础上，第二个项目阶段的目标是完成三种不同类型复合材料的合成和表征，包括交替层结构薄膜的研究。一个主要的焦点将是确定薄膜的机械和电化学性能，这取决于所加入的氧化石墨烯的含量、分布和还原程度。另一个中心任务是详细评估电化学循环对电极的微纳米结构和机械性能的影响。通过这种方式，将获得对此类锂离子电极电化学性能下降的主要机制的有价值的见解。在这方面特别相关的将是诸如石墨烯和无机纳米结构的体积分数等参数的影响，以及两种成分之间的界面耦合。

The major task of the present project is the development of paper-like electrodes with improved performance for use in Li-ion batteries. The layered architecture of these nanocomposites is envisioned to simultaneously exploit the extraordinary mechanical/chemical stability and electrical conductivity of graphene and the efficient lithium ion storage capability of inorganic nanostructures, in order to enhance the charge-discharge kinetics and lifetime of the electrodes. In the first project period, the self-assembly of V2O5 nanofibers was improved to yield tough and flexible paper-like films, and the other required inorganic components SnO2 nanosheets/-fibers and LiMnPO4 nanoplatelets were successfully synthesized and characterized. Importantly, it could be proven in particular for composites comprising V2O5 nanofibers and graphene oxide (GO) that the implementation of graphene sheets indeed leads to improved mechanical stability, electrical conductivity and actuation properties. Moreover, a correlation was observed between the structural quality of these composites and their mechanical performance. On this basis, the second project stage aims at completing the synthesis and characterization of the three different types of composites, including the investigation of films with alternating layer structure. A major focus will be on determining the films' mechanical and electrochemical properties in dependence of the content, distribution and reduction extent of the incorporated GO. Another central task is the detailed evaluation of the impact of electrochemical cycling on the micro- and nanostructure as well as mechanical performance for the electrodes. In this manner, valuable insights shall be gained into the major mechanisms responsible for electrochemical performance degradation of such type of Li-ion electrodes. Of particular relevance in this respect will be the influence of parameters such as the volume fraction of graphene and the inorganic nanostructures, as well as the interfacial coupling between the two components.