Thermochemical Core–Shell Architecturing of Si‐SWCNT Composites for High‐Performance Li‐Ion Battery Anodes

Silicon (Si) is a promising anode for next‐generation lithium‐ion batteries (LIBs) because of its ultrahigh theoretical capacity, yet its practical application is hindered by severe volume expansion, unstable interfaces, and sluggish reaction kinetics. Here, we report a thermochemically engineered core–shell Si architecture integrating alloy stabilization, nanoporous strain buffering, and chemically anchored conductive networks. Starting from a SWCNT‐coated Mg 2 Si precursor, a CH 4 ‐assisted thermochemical treatment induces localized exothermic Mg oxidation, followed by selective MgO etching to construct a SiC‐anchored SWCNT conductive network and a nanoporous Si shell surrounding a robust Mg‐containing Si core. Reactive molecular dynamics simulations reveal that localized hot‐atom generation during Mg oxidation activates CH 4 molecules, providing atomistic insight into the low‐temperature formation of the SiC interfacial layer. The resulting architecture decouples mechanical strain from charge transport, enabling an initial reversible capacity of 1890 mAh g −1 with 74% capacity retention after 100 cycles. Graphite composite electrodes containing 20 wt.% Si deliver 640 mAh g −1 and retain 78% capacity after 200 cycles, substantially exceeding the Si content used in commercial electrodes. Pouch‐type full cells paired with Li[Ni 0.6 Co 0.2 Mn 0.2 ]O 2 cathodes achieve an energy density of 275 Wh kg −1 with 75% capacity retention after 1000 cycles, demonstrating a scalable strategy for high‐energy‐density LIBs.