Construction of Three-Dimensional Hierarchical CoSe2 Microflowers Assembled by Thin Nanosheets for High-Performance Sodium-Ion Batteries

Abstract

Transition metal selenides are considered as promising anode materials for sodium-ion batteries (SIBs) due to their high capacity and low cost. However, they suffer from large volume change, serious polyselenide dissolution and sluggish reaction kinetics during charge/discharge process, resulting in poor cycling stability and low rate performance for SIBs, which further restrict their widespread application. Here, we developed carbon-free three-dimensional (3D) hierarchical microflower-shaped CoSe2 with a diameter size of approximately 2[Formula: see text][Formula: see text]m, composed of nanosheets through a one-step solvothermal method. The thin nanosheets are conducive to shortening the Na[Formula: see text] diffusion channels and relieving the volume expansion, and the 3D hierarchical microflower architecture could effectively prevent the agglomeration of nanosheets; accordingly, the resulting CoSe2 microflowers deliver a high specific capacity of 451.94[Formula: see text]mA[Formula: see text]h[Formula: see text]g[Formula: see text] even at 0.5[Formula: see text]A[Formula: see text]g[Formula: see text] after 100 cycles, compared with CoSe2 nanoparticles. This work offers an approach for designing metal selenides with high capacities and rate capability for SIBs.