Directional Lithium Embedding and Swelling of 2D Silicon Micro-Nano Sheet Promotes Anode Surface Stability

The volume expansion behavior of silicon anodes during lithium embedding usually exhibits anisotropy. However, the reason for the anisotropy has not been explored in detail. One speculation is that the spontaneous evolution of the crystal microstructure after lithium ion embedding expands the most in the ⟨1 1 0⟩ direction, and the other speculation is that the energy barrier is lowest on the Si (1 1 0) crystal plane and highest on the (1 1 1) crystal plane, resulting in the gap between the "lithium fluxes" of the two crystal phases. In this work, an ultraflat two-dimensional silicon wafer was processed and prepared to control the embedding direction of lithium ions by its geometry, and its expansion behavior was observed. We summarized the behavioral model of "competition for lithium embedding and expansion of each crystal phase" when lithium is embedded in a silicon anode, and based on this model, we developed a silicon anode for lithium-ion batteries with high interfacial stability and achieved a specific capacity of 892 mAh g^-1 after 1000 cycles, with a well-maintained active material structure.