Hollow NiCoSe2 microspheres@N-doped carbon as high-performance pseudocapacitive anode materials for sodium ion batteries

Transition metal selenides (TMSs) have been considering as a kind of promising alternative anode materials for the application of sodium ion batteries due to their high electrical conductivity and high capacity. Here, hollow NiCoSe2 microspheres was prepared via an easy hydrothermal method, followed by the dopamine derived N-doped carbon coated which formed the hollow NiCoSe2@C composite. As-prepared hollow NiCoSe2@C composite has been first used as a new anode material for sodium ion batteries (SIBs). Our selenides displays a quite good electrochemical sodium storage performance. For example, the reversible capacity of as-prepared hollow NiCoSe2@C composite electrode can be maintained at 464.7 mAh g−1 at a current density of 100 mA g−1 after 200 cycles. Moreover, the rate performance of the hollow NiCoSe2@C composite is outstanding. The reversible capacities of 425.3, 420.8, 403.2, 394.7, 378.7, 367.8 and 337.5 mAh g−1 can be achieved at the current densities of 100, 200, 500, 1000, 2000, 3000 and 5000 mA g−1, respectively. Meanwhile, hollow NiCoSe2@C composite electrode exhibits a high discharge capacity of 338 mAh g−1 at a relatively high current density of 0.5 A g−1 after 250 cycles. In addition, the kinetic analysis of electrochemical Na + storage properties of the hollow NiCoSe2@C composite demonstrates that the extrinsic pseudo capacitive behaviour contributes significantly to excellent rate performance and good long-term cycling life. This method can be used to modify the morphologies and structures of the other TMSs for the development of new anode materials as anode materials in the application of sodium ion batteries.