NiSe₂ Nanooctahedra as an Anode Material for High-Rate and Long-Life Sodium-Ion Battery

In this article, we report NiSe₂ nanooctahedra as a promising anode material for sodium-ion batteries (SIBs). They exhibit outstanding long-term cyclic stability (313 mAh/g after 4000 cycles at 5 A/g) and excellent high-rate capability (175 mAh/g at 20 A/g). Besides, the initial Coulombic efficiency of NiSe₂ is also very impressive (over 90%). Such remarkable performances are attributed to good conductivity, structural stability, and the pseudocapacitive behavior of the NiSe₂. Furthermore, the sodium ion storage mechanism of NiSe₂ is first investigated by in situ XRD and ex situ XRD. These highlights give NiSe₂ a competitive strength for rechargeable SIBs.