Effect Of Crystal-Structure Type Evolution on Sodium Storage of CoSe ₂

CoSe2 is attracting extensive attention as anode material of sodium-ions batteries (SIBs) owing to its high theoretical specific capacity and abundant investigations have been carried out on it. Nevertheless, the effect of crystal-structure type evolution of CoSe2 on sodium storage capability still need to be further revealed. In this work, orthorhombic CoSe2 with a tree-branch-like shape (o-CoSe2) and cubic CoSe2 cluster assembled from irregular short rods (c-CoSe2) are successfully synthesized, respectively. Although o-CoSe2 exhibits great advantages in architecture over c-CoSe2, c-CoSe2 delivers more remarkable electrochemical performance than o-CoSe2 when served as anode of SIBs. c-CoSe2 can maintain a high specific capacity of 404.7 mAh g-1 with an oustanding retention of 99.9 % after 200 cycles under 0.1 A g-1. c-CoSe2 also presents preeminent rate property and long-cycling performance (378.5 mAh g-1 after 1100 cycles under 1.0 A g-1). This work reveals the significant effect of the crystal-structure type on the sodium storage of CoSe2 and the cubic CoSe2 is more suitable as an anode material for SIBs.