Abstract
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.
Highlights
Sodium-ion batteries (SIBs) have attracted much attention as generation energy storage devices due to the abundance and lower cost of sodium resources compared to those of lithium [1,2,3,4]
We introduced well-designed porous structured bimetallic ZnSe/CoSe2/carbon composite nanofibers (PZCN), with uniformly distributed pores, prepared by electrospinning and subsequent simple heat-treatment processes
The 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 selected PS nanobeads were removed during heat-treatment
Summary
Sodium-ion batteries (SIBs) have attracted much attention as generation energy storage devices due to the abundance and lower cost of sodium resources compared to those of lithium [1,2,3,4]. As with other metal compounds, bimetallic compounds show insufficient electrical conductivity, and suffer from structural expansion, pulverization, and aggregation during repeated charge–discharge processes, which causes mechanical fracture, electrical contact loss, and an unstable solid electrolyte interphase (SEI) Their practical application in SIBs has not fulfilled expectations, mainly due to poor cycle and rate properties, which greatly hinder use of these active materials in SIBs. their practical application in SIBs has not fulfilled expectations, mainly due to poor cycle and rate properties, which greatly hinder use of these active materials in SIBs To solve these issues, nanostructuring has proved to be an effective way forward, as nanostructured anode materials share a large contact area with the electrolyte, possess short Na ion and electron pathways, and can accommodate the strain associated with repeated cycles [13,14,15,16]. The PZCN synthesis mechanism was examined in detail, and the electrochemical performance of the composite nanofibers, as anodes for SIBs, was compared with that of bare ZnSe/CoSe2 powders
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