Porous Hybrid Nanofibers Comprising ZnSe/CoSe2/Carbon with Uniformly Distributed Pores as Anodes for High-Performance Sodium-Ion Batteries

Well-designed porous structured bimetallic ZnSe/CoSe2/carbon composite nanofibers with uniformly distributed pores were prepared as anodes for sodium-ion batteries by electrospinning and subsequent simple heat-treatment processes. Size-controlled polystyrene (PS) nanobeads in the electrospinning solution played a key role in the formation and uniform distribution of pores in the nanofiber structure, after the removal of selected PS nanobeads during the heat-treatment process. The porous ZnSe/CoSe2/C composite nanofibers were able to release severe mechanical stress/strain during discharge-charge cycles, introduce larger contact area between the active materials and the electrolyte, and provide more active sites during cycling. The discharge capacity of porous ZnSe/CoSe2/C composite nanofibers at the 10,000th cycle was 297 mA h g(-1), and the capacity retention measured from the second cycle was 81%. The final rate capacities of porous ZnSe/CoSe2/C composite nanofibers were 438, 377, 367, 348, 335, 323, and 303 mA h g(-1) at current densities of 0.1, 0.5, 1, 3, 5, 7, and 10 A g(-1), respectively. At the higher current densities of 10, 20, and 30 A g(-1), the final rate capacities were 310, 222, and 141 mA h g(-1), respectively.