In Situ Measurements of the Mechanical Properties of Electrochemically Deposited Li₂CO₃ and Li₂O 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 Li${}_2$CO${}_3$ and Li${}_2$O are identified as the major components of SEI, their mechanical properties are not well understood. Herein, SEI-related materials such as Li${}_2$CO${}_3$ and Li${}_2$O 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 Li${}_2$CO${}_3$ and Li${}_2$O exhibit nanocrystalline structures and good plasticity. The ultimate strength of Li${}_2$CO${}_3$ ranges from 192 to 330 MPa, while that of Li${}_2$O is less than 100 MPa. These results provide a new understanding of the SEI and its related dendritic problems in lithium batteries.