Serial cracking in Van der Waals layered electrodes mediated by electrochemical reaction and mechanical deformation

In battery cycling, mechanical effects introduced by electrochemical reactions are commonly observed. In return, the mechanical deformations also have a large impact on the electrochemical process. However, such a coupling effect of electrochemical reaction and mechanical deformation has a complicated interplay on the atomic scale. Herein, we use in situ transmission electron microscopy to directly visualize the coupling process of two-dimensional Van der Waals MoS2 electrodes. A self-sustained cracking mechanism is identified, and the first crack is initiated by the defects originated from the strain accumulation at the edge of intercalation front. The formed defects, including dislocations and antiphase boundaries, can accelerate the Li-ion diffusion and promote the electrochemical reaction, giving rise to the formation of a second and following cracks that resemble the “avalanche effect.” The present work provides an atomistic insight into a cooperation from the mechanical and electrochemical effects toward the formation of the arrayed cracks.