Highly reversible alloying/dealloying behavior of SnSb nanoparticles incorporated into N-rich porous carbon nanowires for ultra-stable Na storage

Alloying-type anode materials for sodium ion batteries have high theoretical capacity and efficient utilization without any insulating products. However, sluggish ion diffusion kinetics and severe volume changes induce irreparable particle pulverization and re-agglomeration, and accordingly electrode degradation. More seriously, irreversible phase transition during electrochemical reactions is harmful for fast and long-cycle Na⁺ storage. In this work, ultra-small SnSb nanocrystallites incorporated into N-rich porous carbon nanowires (SnSb/N- PCNWs) are prepared via electrospinning and sequential calcination. N-rich porous carbon nanowires not only disperse SnSb particles homogeneously in nanoscale, but also optimize the electronic properties and provide numerous edges/defects for Na⁺ adsorption, which would promote surface or near-surface reactions of ultrafast pseudocapacitance behaviors. SnSb/N-PCNWs sustain a ultralong cycle life of ~180 mA h g^-1 at 2 A g^-1 up to 10,000 robust cycles with superb capacity retention ratio of almost 100%. The distinctive nanostructure enables highly reversible alloying/dealloying behavior and conspicuous crystalline-phase reservation of SnSb even after 10,000 cycles, which guarantees the ultralong cycle life for Na⁺ storage. These results shed new insight to achieve alloying-type anode materials for practical sodium ion batteries.