The influence of calendering process on the mechanical performance and sodium storage mechanism of hard carbon electrodes

Calendering is an important step to densify the battery electrodes, enhance energy density, and improve mechanical properties. This study explores the effects of incremental calendering on the mechanical performance and sodium storage mechanism of hard carbon electrodes for sodium-ion batteries. In order to analyze the fracture and adhesion failure behavior of the electrode, tensile and peeling tests are performed to examine the relationship between the compression rate and the mechanical strength of the electrode as well as the adherence within the coating. Through expansion experiments, the sodium storage mechanism of the hard carbon electrode is revealed. The results indicate that increasing the compression rate enhances the electrode's mechanical properties and the adhesion strength at the coating-substrate interface, but reduces the cohesion between hard carbon particles. Under conditions of high compacted density (2.74 g/cm³), the sodium ion absorption rate of the hard carbon electrode in the high voltage plateau region is diminished. This research clarifies the fracture and sodium ion transport mechanisms of hard carbon electrodes under the action of structure densification during calendaring, providing a reference for optimizing the preparation process parameters of hard carbon electrodes in sodium-ion batteries and for coordinated control.