Iron-Driven Internal Percolation Enables Topological Construction of 3D Interconnected Porous Si@C Anodes

Constructing internal voids is an effective strategy to mitigate the severe lithiation-induced volume expansion of Si anodes for lithium-ion batteries. Nevertheless, porous Si prepared via conventional reduction methods commonly undergoes structural shrinkage and uncontrollable pore configuration. Herein, a novel iron-driven internal percolation mechanism is proposed to fabricate porous Si@C composites (p-Si@C) through the ion exchange between Fe-based Prussian blue templates and silicate anions, followed by low-temperature molten-salt aluminothermic reduction. The in-situ formed Fe network acts as an electronic highway to accelerate the reduction of SiO₂, while functioning as a sacrificial template to maintain a non-shrinking topological framework with interconnected pores. Moreover, iron species catalyze the growth of graphitized carbon shells, inducing the formation of a LiF-rich solid electrolyte interphase. Benefiting from the optimized structure, the p-Si@C anode delivers a high reversible capacity of 605 mAh g^-1 at 8 A g^-1, and the full cell paired with LiFePO₄ retains 95% of its capacity after 550 cycles. This work develops an innovative fabrication strategy for controllable porous Si based on the metal-driven internal percolation mechanism, which can be extended to the rational design of other porous electrode materials.