Effects of calendering state on coupled electrochemical-mechanical performance of silicon based composite electrodes

The super volume changes and severe mechanical degradation have been a hindrance in the wide application of silicon based composite electrodes in commercial lithium-ion batteries (LIBs). Calendering, one procedure in producing LIBs' electrodes, is indispensable to ensure low porosity and energy density. However, the repercussions of the calendering process on the physical characteristics related to the behavior of silicon (Si) based electrodes during the electrochemical reaction have not been well understood. Thus, on account of the deformation characteristic of cantilever electrodes, an in-situ technique is employed to analyze the repercussions of calendering status on the coupled electro-chemo-mechanical performances. During the electrochemical cycling, Young's modulus and diffusion-induced stress in composite electrodes are quantified. The results show that the swelling strain, the stress and the modulus of the Si-based electrode and the calendering degree are positively correlated. Meanwhile, the stress induced by diffusion in the active layer tends to increase in the stage of lithiation and reverses during the delithiation process. Accompany with the SEM analysis, we conclude that the calendering process can induce larger stress, driving the formation of cracks in electrodes. These findings can help understand how the calendering process could affect the capacity dissipating and lifetime of Si based electrodes.