Desenvolvimento de matrizes carbonáceas derivadas de casca de arroz e CMK-3 para baterias de lítio-enxofre: caracterização e aplicação em coin cells

Abstract

Lithium-sulfur batteries (LSBs) emerge as a promising alternative for energy storage, gaining renewed international interest due to their high theoretical energy density and the low cost of sulfur. However, they still face challenges, such as sulfur’s low electrical conductivity, the shuttle effect caused by soluble polysulfides, and volumetric expansion during cycling, which can compromise performance and lifespan. In this thesis, first- and second-generation carbonaceous materials derived from rice husk (RHC) and mesoporous carbon (CMK-3), respectively, were developed and characterized, focusing on their application as cathode materials in LSBs. For the development of CMK-3, SBA-15 was used as a mesoporous template, followed by an optimized washing protocol that ensured efficient removal of residual silica, resulting in a carbonaceous matrix with high surface area and suitable porosity for sulfur infiltration. Sulfur infiltration studies showed that silica content influences the optimal infiltration temperature, which is 155 °C for CMK-3 with low silica content and 165 °C for both CMK-3 with high silica content (CMK-3_SiO2) and RHC. Electrochemical characterization demonstrated that CMK-3 with low silica content achieved a specific capacity of up to 771 mAh/g, with a capacity retention of around 75% after 150 cycles at C/10. In contrast, RHC, even without additional treatments for silica removal, exhibited significant cycle stability, maintaining a capacity close to 500 mAh/g over prolonged cycling. The addition of Nb2O5 nanofibers as a coating on RHC/S electrodes promoted faster stabilization of specific capacity and sustained stability over 150 cycles. Optimizing cell assembly parameters, including the selection of a Whatman glass fiber separator and proper electrolyte distribution, was essential for enhancing electrochemical performance. The results obtained demonstrate the potential of the developed materials for applications in lithium-sulfur batteries and provide new insights into the underlying mechanisms, paving the way for future research and technological innovations in the field.