Potencialidades da técnica de SAXS na caracterização de eletrólitos sólidos poliméricos para baterias de íon lítio

Abstract

The climate crisis caused by human industrial activity is increasingly damaging the planet, generating a demand for technologies that can mitigate this impact. In this context, the use of renewable energy sources such as wind and solar power is of great interest, which brings with it the need for safe and efficient energy storage, since these are intermittent energy sources. To this end, lithium-ion batteries are promising candidates, as they have the highest energy densities among the available systems. However, while current devices are relatively suitable for portable electronics, their performance is far from satisfactory for the transportation sector. One of the reasons is the use of liquid electrolytes, which make the battery unsafe for this type of application. Therefore, the use of solid polymer electrolytes is very promising, but some challenges remain, such as reconciling high ionic conductivity, mechanical resistance and electrochemical stability. In this context, there is an urgent need to develop new materials. Among the structural characterization techniques used for this purpose, the small angle X-ray scattering (SAXS) technique has great potential because, although it is an indirect characterization technique, it has numerous advantages such as the possibility of carrying out tests in very diverse conditions, varying temperature conditions and being able to reproduce conditions very close to those that the material is subjected to during application. Therefore, the first objective of this work was to provide an overview of the state of the art in the development of solid polymer electrolytes, the main strategies used and the main challenges faced. Next, a detailed description of the fundamentals of the SAXS technique was presented, which served as a tool for carrying out two case studies based on works in which the technique was used to characterize solid electrolytes based on block copolymers. It was thus concluded that the development of new materials that act as solid electrolytes for lithium-ion batteries is an extremely important field in the context of the energy transition. In addition, the SAXS technique has enormous potential in the characterization and development of these materials, as it allows a better understanding of the correlation between processing, structure, properties and performance in the final application.