A general strategy for the in situ construction of CoSe2–MSex@GA (M = Zn, Ni, and Fe) heterostructures for effective sodium storage†

Effective strategies for constructing micro-/nanostructures with fast electrochemical reaction kinetics and excellent structural integrity can promote the practical application of metal selenide-based anode materials in sodium-ion batteries (SIBs). However, the precise control of their synthesis is still elusive. Herein, a facile and general precursor template strategy was developed for constructing three types of graphene aerogels (GAs) with in situ encapsulated bimetallic selenide (CoSe₂–MSe_x@GA, M = Zn, Ni, and Fe) heterostructure materials. Rich heterogeneous interfaces, large graphene aerogel layer conductive networks and abundant porous structures engender more active sites, rapid reaction kinetics, enhanced electric/ionic conductivity and good structural stability in the prepared CoSe₂–MSe_x@GA anodes, which thereby exhibit enhanced rate capabilities and cycling performances in SIBs. In particular, CoSe₂–FeSe₂@GA spherical heterostructure materials derived from Co–Fe PBA precursors exhibit a high capacity of 722.8 mA h g⁻¹ at 1 A g⁻¹ with 96.4% capacity retention after 1000 cycles. The kinetic analysis of the redox reaction showed that the CoSe₂–MSe_x@GA electrodes were mainly dominated by pseudo-capacitive behaviors during the charging and discharging process. Besides, galvanostatic intermittent titration technique confirmed the rapid Na⁺ diffusion rate using the CoSe₂–MSe_x@GA electrodes. This current scalable and simple preparation method for bimetallic selenide@GA heterostructures may be a promising strategy to provide more possibilities for the development of advanced electrode materials for sodium-ion batteries.