FeSe 2 nanocrystalline aggregated microspheres with ultrahigh pseudocapacitive contribution for enhanced sodium-ion storage

FeSe 2 has attracted considerable attention as one of the alternative anodes for sodium-ion batteries (SIBs) owing to its high theoretical capacities. However, the severe volume variation during the charge and discharge processes should be mitigated and rate performance at large current density should be further improved for the application of FeSe 2 . In this study, pomegranate-like FeSe 2 @NC microspheres assembled from FeSe 2 nanoblocks coated with N-doped carbon layers were successfully fabricated through a hydrothermal method and subsequent annealing treatment. When used as anode materials for SIBs, the FeSe 2 @NC microspheres exhibited superior electrochemical performance with high specific capacity, superior rate performance, and long cycling stability. The excellent rate performance is attributed to the pseudocapacitive behavior during the charge and discharge processes. The excellent electrochemical performance revealed that FeSe 2 @NC microspheres can be considered as a promising high-rate anode for SIBs.