Hierarchical Bimetallic Selenides CoSe2–MoSe2/rGO for Sodium/Potassium-Ion Batteries Anode: Insights into the Intercalation and Conversion Mechanism

As anode materials for high-performance sodium-ion batteries and potassium-ion batteries,bimetallic selenides have attracted great concern due to their relatively high electrical conductivity and electrochemical activity.However,the formidable challenge in the reaction process is the large volume change,leading to the structural collapse of material,and eventually the decline in electrochemical performance.Herein,a composite of hierarchical CoSe2-MoSe2tubes anchored on reduced graphene oxide nanosheets(CoSe2-MoSe2/rGO) is designed by an in situ hydrothermal selenization treatment.Benefiting from the synergistic effects between CoSe2and MoSe2,unique hierarchical structure,and effective reduced graphene oxide coating,the CoSe2-MoSe2/rGO exhibited improved reaction kinetics and structural stability,and thus good electrochemical properties.A combination mechanism of intercalation and conversion of CoSe2-MoSe2/rGO by forming NaxCoSe2and Mo15Se19as intermediate states is put forward on the basis of in situ and ex situ XRD analyses.