Atomic-Scale Mechanisms of Sliding along an Interdiffused Li–Si–Cu Interface

We perform ab initio calculations on the shear deformation response of the interdiffused Li–Si–Cu phase structure existing between a lithiated Si electrode and a Cu current collector. We show that the formation of well-delineated and weakly bonded Si–Cu and Li–Cu crystalline atomic layers within this phase structure facilitates interface sliding. However, sliding can be terminated by the formation of LiSi3 compounds across these atomic layers, which causes the abrupt capacity fade of the electrode after repeated cycling.