Engineering Molecular Polymerization for Template-Free SiO_x/C Hollow Spheres as Ultrastable Anodes in Lithium-Ion Batteries

SiO_x/C composites with a void-reserving structure are promising anodes for lithium-ion batteries. However, the facile and controllable synthesis of uniformly dispersed SiO_x and carbon components, simultaneously incorporating ample voids, still remains a great challenge. Herein, a molecular polymerization strategy is devised to construct SiO_x/C hollow particles for lithium-ion batteries. 3-aminopropyltriethoxysilane and dialdehyde molecules are judiciously engineered as silicon and carbon precursors to produce the polymer hollow spheres (PHSs) through a one-step aldimine condensation without any template and additive. A range of PHSs is obtained using terephthalaldehyde, glutaraldehyde, and glyoxal as the crosslinkers, demonstrating the high tunability of the strategy. Importantly, in situ pyrolysis of the PHSs warrants the homogeneous incorporation of SiO_x (<5 nm) in carbon hollow capsids at a nanocluster scale. The obtained SiO_x/C hollow spheres exhibit excellent Li⁺-ion storage behaviors, including cycling lifespan, coulombic efficiency, and rate performance. The superior performance is attributed to the well-dispersed SiO_x nanoclusters in carbon substrate and the hollow structure. This molecular polymerization approach not only enables Si-based hollow composites effective and scalable anode materials but also opens up a new avenue for the controllable synthesis of template-free hollow architectures.