Mesoporous nanoreactor with accelerated ion transport for high-performance SnO2-based anodes in sodium-ion batteries.

Tin dioxide (SnO2) is a promising anode material for sodium-ion batteries owing to its high theoretical capacity, yet its practical application is severely hindered by drastic volume expansion and intrinsically sluggish Na+ diffusion kinetics. Herein, we report a mesoporous yolk-shell SnO2-based nanoreactor (SnO2mCNR) constructed via a facile interfacial polymerization assembly and selective etching strategy. The architecture features a SnO2 nanocube core, an internal void space, and a mesoporous carbon shell permeated with interconnected channels (∼7 nm). This unique design simultaneously accommodates the large volume changes during sodiation/desodiation and provides low-resistance pathways for rapid Na+ transport. Compared with its non-porous counterpart (SnO2 CNR), SnO2mCNR exhibits a ∼ 3.5-fold higher Na+ diffusion coefficient and a transition toward pseudocapacitive-dominated charge storage (b-value of 0.90). Consequently, SnO2mCNR delivers a high reversible capacity of 650.3 mAh g-1 at 0.05 A g-1, excellent rate capability (218.7 mAh g-1 at 5 A g-1), and outstanding cycling stability with 95.1% capacity retention over 1800 cycles at 1 A g-1. A full pouch cell assembled with a Na3V2(PO4)3-based cathode achieves a high energy density of 292.2 Wh kg-1, indicating promising application potential at the electrode-material level. This work establishes shell porosity engineering as a generalizable design principle for high-performance conversion/alloying-type anodes in sodium-ion batteries.