Micrometer-Sized Nanoporous Sb/C Anode with High Volumetric Capacity and Fast Charging Performance for Sodium-Ion Batteries

Designing metal/C nanocomposites has been a prevalent strategy to address the volume expansion issue of alloying metal Na-ion battery (NIB) anodes but typically suffers from poor volumetric capacity. Here, micrometer-sized nanoporous Sb/C anode with high volumetric capacity and outstanding electrochemical performance is successfully synthesized using facile synthesis of a new class of solid-state reduction chemistry. The resulting Sb/C composite, containing 10 wt % C, possesses the combination of unique structural characteristics, including (1) micrometer-sized secondary particle, enabling high particle density; (2) nanoscale Sb crystallites, permitting reversible phase transformation during cycling; and (3) uniformly distributed nanoporosity, providing accommodation for Sb expansion and facile Na-ion diffusion. The Sb/C composite anode, showing outstanding cycling stability, exhibits a gravimetric capacity of 436 mAh g–1-(Sb+C), a volumetric capacity of 427 mAh cm–3 and over 80% capacity retention at nearly 5 C rate, all of which substantially excel those of the conventional C-based anodes. In situ transmission X-ray microscopy analysis reveals fracture-free reversible and considerably reduced deformation of the composite particles during the sodiation/desodiation cycle. The synthesis method demonstrates general applicability to developing other alloying metal anodes for NIBs, as well as Li-ion batteries.