Hierarchical mesoporous binary nickel cobalt selenides nanospheres for enhanced sodium-ion storage

Abstract

Owing to high theoretical specific capacity, transition metal selenides as prospective anode materials for sodium-ion batteries (SIBs) have caused extraordinary concern. However, the poor electrochemical property caused by the large volume changes and relatively low electrical conductivity limits their practical application. Herein, uniform Ni0.33Co0.67Se2 nanosphere with hierarchical mesoporous structure was synthesized successfully through a feasible solvothermal selenization strategy. The unique hierarchical mesoporous nanostructure and enhanced electrical conductivity from binary metal selenide combination result in excellent Na+ storage performance. The as-prepared Ni0.33Co0.67Se2 anode material delivers ultra-long cycling life (301.9 mAh g−1 after 1300 cycles at 1.0 A g−1 with low per-cycle capacity decay ∼ 0.062 mAh g−1) and excellent rate capability (314.5 mAh g−1 at 8.0 A g−1) for SIBs. Besides, the quantitative kinetic analysis results indicate the superior Na+ storage performance of the Ni0.33Co0.67Se2 electrode might be imputed to the dominant pseudocapacitive behavior. These results prove the binary nickel cobalt selenides have great potential as anode materials for SIBs.