Electrochemically Induced Fractures in Crystalline Silicon Anodes

This communication presents our recent discovery on electrochemically induced fracture behavior of a single-crystal silicon (Si) anode, with particular focus on the initialization and propagation of cracks. Intensive efforts have investigated mechanical properties and cracking behavior of Si electrodes overextended electrochemical cycles. However, it is still elusive how cracks nucleate and propagate in the crystalline Si anodes at the very early stage. Here, we examined the morphology evolution of the Si (100) wafer electrodes during the first electrochemical cycle, and we found that the formation of <110>-oriented buckles—induced by the anisotropic lithiation in crystalline Si during 1st lithiation—results in cracks propagated along the <110> direction in the buckled region during 1st delithiation. Surprisingly, as the delithiation proceeds, new cracks oriented along the <100> direction appear in the intact area where no macroscopic deformation occurred during the previous lithiation. The <100>-oriented cracks have not been studied previously. Herein, we introduce a linear elastic fracture mechanics model to help understand underlying mechanisms for such crack propagation. The findings in this work provide significant insights into the fracture behavior and formation mechanism, as well as possible strategies to inhibit crack propagations of Si electrodes at the beginning stage of cycling.