In Situ Measurements of the Mechanical Properties of Electrochemically Deposited LiCO and LiO Nanorods.

Solid-electrolyte interface (SEI) is "the most important but least understood (component) in rechargeable Li-ion batteries". The ideal SEI requires high elastic strength and can resist the penetration of a Li dendrite mechanically, which is vital for inhibiting the dendrite growth in lithium batteries. Even though LiCO and LiO are identified as the major components of SEI, their mechanical properties are not well understood. Herein, SEI-related materials such as LiCO and LiO were electrochemically deposited using an environmental transmission electron microscopy (ETEM), and their mechanical properties were assessed by in situ atomic force microscopy (AFM) and inverse finite element simulations. Both LiCO and LiO exhibit nanocrystalline structures and good plasticity. The ultimate strength of LiCO ranges from 192 to 330 MPa, while that of LiO is less than 100 MPa. These results provide a new understanding of the SEI and its related dendritic problems in lithium batteries.