Sodium storage performance of ultrasmall SnSb nanoparticles

Abstract

Sodium-ion batteries have been emerging as a potential alternative to lithium-ion batteries, especially for large-scale applications. In this work, a hybrid of ultrasmall SnSb nanoparticles (the diameter <2 nm) encapsulated in three-dimensional N-doped nanoporous carbon frameworks (SnSb/3D-NPC) was synthesized by a facile chemical reduction method. To the best of our knowledge, this is the smallest SnSb nanoparticle ever reported. As a sodium-ion battery anode, SnSb/3D-NPC delivers a high reversible capacity (693.6 mAh g−1 at 0.2 A g−1 after 100 cycles), superior rate performance (359.1 mAh g−1 at 20 A g−1) and cycling stability (266.6 mAh g−1 at 5 A g−1 after 15,000 cycles), which outperform other SnSb-based materials. These remarkable performances originate from: (i) ultrasmall SnSb nanoparticles and their uniform distribution, which increase the specific surface of electrodes and thus guarantee the full utilization of active materials, enhance pseudocapacitive contributions for Na storage, shorten Na+ diffusion distance, and reduce the strain during the sodiation/desodiation process; and (ii) the unique 3D integrated structure of SnSb/3D-NPC, which supplies a conductive network, efficient electrolyte diffusion paths and more active sites for Na+ insertion/extraction, suppresses the aggregation of SnSb nanoparticles, and buffers large volume change of SnSb through carbon nanocages during the cycling process.