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.