Prussian blue analogs (PBA) derived heterostructure Zn-Fe bimetallic selenide nanospheres with high capacity sodium-ion storage

Abstract

Metal selenides have excellent theoretical capacity when used to store sodium. Compared with single metal selenides, bimetallic selenides stand out with excellent theoretical capacity, sufficient electrochemical reaction sites and good conductivity. In this work, Zn3[Fe(CN)6]2 prussian blue analogue nanospheres are prepared by a static method with PVP as dispersant, and then heterostructure ZnSe/FeSe nanospheres (ZnSe/FeSe NS) composite are prepared by gas-phase selenation. PVP is conducive to the formation of loose and porous structures and alleviate the volume expansion during sodium storage. In this structure, heterostructures can create abundant active sites and increase the electrochemical capacity. Therefore, the ZnSe/FeSe NS show high sodium storage capacity with a reversible capacity of 549.0 mAh g−1 at 100 mA g−1 and 436.8 mAh g−1 even after 100 cycles at 1 A g−1. It also shows excellent rate performance with high stable capacities of 524.6, 486.1, 447.3, 431.1, 417.9 mAh g−1 in a series of current densities of 100, 200, 500, 1000, 2000 mA g−1 separately. The excellent capacity of the ZnSe/FeSe NS composite comes from the active sites provided by the heterostructure and the high conductivity provided by the built-in electric field.