Improved Na⁺/K⁺ Storage Properties of ReSe₂-Carbon Nanofibers Based on Graphene Modifications

Rhenium diselenide (ReSe₂) has caused considerable concerns in the field of energy storage because the compound and its composites still suffer from low specific capacity and inferior cyclic stability. In this study, ReSe₂ nanoparticles encapsulated in carbon nanofibers were synthesized successfully with simple electrospinning and heat treatment. It was found that graphene modifications could affect considerably the microstructure and electrochemical properties of ReSe₂-carbon nanofibers. Accordingly, the modified compound maintained a capacity of 227 mAh g^-1 after 500 cycles at 200 mA g^-1 for Na⁺ storage, 230 mAh g^-1 after 200 cycles at 200 mA g^-1, 212 mAh g^-1 after 150 cycles at 500 mA g^-1 for K⁺ storage, which corresponded to the capacity retention ratios of 89%, 97%, and 86%, respectively. Even in Na⁺ full cells, its capacity was maintained to 82% after 200 cycles at 1C (117 mA g^-1). The superior stability of ReSe₂-carbon nanofibers benefitted from the extremely weak van der Waals interactions and large interlayer spacing of ReSe₂, in association with the role of graphene-modified carbon nanofibers, in terms of the shortening of electron/ion transport paths and the improvement of structural support. This study may provide a new route for a broadened range of applications of other rhenium-based compounds.