Probing plastic and adhesive self-healing interface using in situ electrochemical atomic force microscopy for high-rate Si/C anode

There are many recent strategies using self-healing functionality to effectively address the chemo-mechanical interface evolution and extend battery performance. Revealing how the mechanical properties affect interface stability is important but challenging. Here, taking a self-healing Ga-interface-encapsulated Si/C as a model, we perform electrochemical atomic force microscopy to probe the mechanical properties of the shallow interface (<30 nm) upon cycling. Instead of bearing a high Young's modulus, the Ga-Si/C interface exhibits distinctive plastic deformation and adhesion features related to the liquid-to-solid transition. In quantitative analysis using a plastic index, the Ga layer sustains a pronounced degree of plastic deformation, in sharp contrast to the neat Si/C. We also identify the maximum adhesion for liquid and semi-solid Ga, which forms a heterogeneous but continuous network. COMSOL modeling corroborates the plastic deformation and adhesion, effectively alleviating the local stress at the interface and accommodating the dynamic solid-electrolyte interface evolution.