Confinement and Self‐Supply of Carbon Sources by Micro‐Containers Enable Efficient In Situ Growth of Carbon Nanotubes for Li‐Ion Storage

ABSTRACT Confinement effects generated by micro/nanoscale physical spaces for chemical reactions may enable to effectively modulate nanostructures or create novel nanostructures by remarkably changing reaction kinetics and behaviors, which needs to be explored. Herein, a productive and up‐scalable approach is proposed for in situ growth of nitrogen‐doped carbon nanotubes (N/CNTs) by introducing commercial expanded graphites (EGs) as micro‐containers for enhancement of reaction rates and reduction of energy costs. With the solid carbonaceous (polyvinylpyrrolidone, PVP) and catalytic (Fe‐based or Co‐based) precursors incubated in the micro‐containers, the local sufficient self‐supply of C/N sources ensures the in situ growth of high‐quality N/CNTs with a high yield over 14% and a faster formation rate compared to a conventional open configuration. Growth behavior, morphology, and structure of products are conditioned by the dimension and structure of micro‐containers, the ratio of source/catalyst precursors, and pyrolyzation temperature. The N/CNTs‐based hierarchical architectures are demonstrated to have superior Li‐ion storage performance as anode materials, say, a capacity of 1129.5 mAh g ⁻¹ at 0.05 A g ⁻¹ and a retention of 99.5% (95.0%) for 0.1 A g ⁻¹ (10 A g ⁻¹ ) after 100 (10 000) cycles. This strategy can be generalized for the preparation of other nanostructures.