Localized Mechanical Stress Induced Ionic Redistribution in a Layered LiCoO2 Cathode

Controlling the transport of ions within electrodes is highly desirable for the operation of rechargeable ion batteries. Here, for the first time, we report the role of mechanical stress in controlling the redistribution of lithium ions in a layered LiCoO2 electrode at a resolution of ∼100 nm. Under a higher stress field, more active redistribution of lithium ions was observed along the grain boundaries than the interiors of the layered LiCoO2. The dynamic force ramping test proved the external stress field (<100 nN) is capable of inducing the resistive-switching effect of the layered LiCoO2. The comparison test on the highly ordered pyrolytic graphite (HOPG) substrate further demonstrated the improved current responses from the layered LiCoO2 resulted from the deficiency of lithium ions, rather than the increase of tip–sample contact area. Our findings will pave the road for a full understanding of how mechanical stimulus can affect the distribution of ions in the layered electrodes of rechargeable ion batteries.