Confinement and Encapsulation of Nano-Sn in a Multimodal Porous Carbon Matrix for High-Performance Sodium-Ion Batteries.

Metallic tin (Sn) is a promising anode material for sodium-ion batteries (SIBs) due to the high theoretical capacity and suitable operating voltage. Nevertheless, its widespread application is hindered by significant volume fluctuations during sodiation/desodiation, leading to mechanical degradation, unstable solid-electrolyte interphase (SEI), and rapid capacity fading. Herein, a rational composite design is developed by confining nano-Sn within a bamboo-derived porous carbon matrix through a facile melt-impregnation strategy, followed by coating with a pitch-derived carbon layer. This hierarchical architecture not only accommodates the large volume variation of Sn but also mitigates unnecessary side reactions by limiting direct electrolyte contact. Moreover, the multimodal pore system provides spatially separated domains: open meso/macropores for Sn encapsulation and closed micropores for efficient Na+ storage, enabling both mechanisms to operate synergistically without interference. As a result, the optimized Sn@PC/C electrode delivers a high reversible capacity of 447.5 mAh g- 1 at 0.03 A g-1 with a remarkable initial Coulombic efficiency of 90.4%, and demonstrates outstanding long-term cyclability, retaining 77.5% of its capacity after 1000 cycles at 0.9 A g-1. When paired with a NFPP cathode, the full cell maintains over 80% capacity after 500 cycles at 0.3 A g-1, substantially outperforming the control cell. The scalable synthesis combined with the multimodal-pore domain concept offers a compelling pathway toward high-performance alloy-based anodes for next-generation SIBs.