Encapsulated SnSe in carbon nanofibers as anode of sodium ion batteries with improved properties

Abstract

SnSe is commonly used as anode material for sodium ion batteries (SIBs) because of its high theoretical sodium storage capacity (780 mAh/g). However, low electrical conductivity and serious volume expansion during the processes of sodiation/desodiation lead to poor cyclic stability. In this paper, a new synthesis strategy based on electrospinning was developed for encapsulated SnSe nanoparticles in carbon nanofibers (CNFs) to improve the structural and cyclic stability. The significant feature of this method is that selenium (Se) powder is directly added into electrospinning solution during annealing treatment to form SnSe nanoparticles encapsulated in CNFs instead of using Se powder during the thermal treatment process. SnSe carbon nanofibers-1 (SnSe@CNFs-1) anode material exhibits the discharge capacities of 326 mAh/g at 0.1 A/g after 100 cycles and 249.4 mAh/g at 1 A/g after 900 cycles at room temperature (25 °C). It still exhibits stable electrochemical performance at low temperature (0 °C) after 100 cycles of 267 mAh/g at 0.1 A/g. This design not only improves the rate of electron transmission but also prevents SnSe nanoparticles from agglomerating and buffering the large volume changes of electrode material during sodiation/desodiation processes. This strategy also helps to alleviate pulverization of anode material during the recycling process and improve the cycle stability.