A self-buffering structure for application in high-performance sodium-ion batteries

Abstract

Electrode materials with high specific capacities such as metal sulfides always experience conversion and/or alloying reactions, which cause large volume changes during cycling. These repetitive volume changes eventually pulverize the active material and electrically isolate it from the current collector, consequently diminishing cycle stability. Here, we develop a self-buffering electrode constructed by ultra-large Fe7S8 nanoplates (S-Fe7S8) for sodium-ion batteries (SIBs). This hierarchical structure has a self-buffering effect on the large volume changes during cycling, which greatly enhances the cycling stability. In addition, the nano-micro hybrid structure as a whole does not show any apparent volume changes during cycling. Therefore, it is safe to conclude that the self-buffering structure is expected to be effective in accommodating volume changes in real batteries. Moreover, the combination of pseudocapacitance and redox reactions in the sodiation and desodiation processes provides the S-Fe7S8 electrode an exceptional rate capability.