Precise construction optimal pores and amorphous layer for micron-sized silicon with high Coulombic efficiency and mechanical stability

Al-Si dealloying has been widely adopted for fabricating porous Si-based anodes to address mechanical stress induced by substantial volume variations during cycling. However, the method often suffers from localized structural collapse due to the inadequate control over the α-phase (Al-based solid solution containing solid-soluted Si atoms) separation. Herein, the micron-sized porous Si anode featuring both optimal pores and amorphous SiO_x layer was constructed through phase-field and membrane diffusion modeling, enabling precise separation of the dendritic α-phase. The results show that an optimal separation time of 10,000 s yields well-developed pores with a volumetric separation ratio of 63.2%, offering sufficient buffering capacity for the volume expansion of the Si. The resulting electrode exhibits ultralow volumetric strain (0.005%) and Von Mises stress (0.12 MPa) under full lithiation. Furthermore, a novel dissociation-diffusion-nucleation-growth mechanism was revealed by in-situ argon ion etching, explaining how solid-soluted Si atoms reorganize into an amorphous SiO_x layer (∼5 nm), contributing to a high initial Coulombic efficiency (ICE) of 84.9%, which facilitate the formation of a stable ion-conducting buffer shell. This work offers fundamental mechanistic insights into the controlled α-phase separation and amorphous SiO_x formation in micron-sized porous Si-based structures.