In-situ TEM experiment of quantitative tensile strength measurements of lithiated nanowires
Akihiro Kushima (MIT), Jianyu Huang (), Ju Li (MIT)
Lithium ion batteries: When Chemistry meets Mechanics
Mon 10:45 - 12:15
Salomon 003
Utilization of nano-structured materials for Li-ion battery electrodes has attracted attention for their ability to accommodate large volume changes of the high capacity electrode materials during the lithiation/delithiation process. To design the nano-structure to stabilize the electrode during battery operations, it is important we understand the mechanical property at the lithiated states. We developed an in-situ transmission electron microscopy (TEM) technique for tensile strength measurement of lithiated nanowires (NWs). Using a specially designed dual-probe equipped with an atomic force microscopy cantilever and a scanning tunneling microscopy electrode, we lithiated NWs and performed in-situ tensile experiments of the lithiated NWs. The method allows seamless transition between the lithiation and the tension inside TEM. The measurement was conducted for Si and ZnO NWs and the effect of the lithiation on the mechanical strength was quantified. The tensile strength decreased from the initial value of 3.6 GPa for the pristine Si NWs to 0.72 GPa for the lithiated ones. We also observed large fracture strain ranging from 8-16% for the lithiated Si NWs, 70% of which remained permanent after fracture. This indicates certain degree of tensile plasticity in the lithiated Si before fracture, important for constitutive modeling of battery cyclability. The reduction in the tensile strength of the ZnO NWs after the lithiation was much larger than that of the Si NWs due to the segmentation of the NWs during the lithiation. The lithiated ZnO NW was fractured at the interface between two adjacent segments. The technique developed in this work can provide useful information for designing nano-structured electrode for high-performance Li-ion batteries.