Co_0.85Se–Fe₇Se₈ nanocuboids embedded in reduced graphene oxides as cycle-stable anodes for sodium-ion batteries

The enhancement of the reaction kinetics and structural stability of transition metal selenides during the discharge-charge process remains a big challenge in realizing the further application of sodium-ion batteries (SIBs). Herein, we report a novel anode by strategically constructing the heterointerfaces in hollow Co_0.85Se–Fe₇Se₈ nanocuboids uniformly dispersed on reduced graphene oxide (Co_0.85Se–Fe₇Se₈@rGO). The graphene decorated advanced hollow nanostructures could effectively buffer the volumetric stress and improve electrical conductivity. More importantly, by intelligently constructing heterostructures, a built-in electric field boosted on the heterointerface affords rapid ionic diffusion kinetics and improves electron transfer. With these merits, the Co_0.85Se–Fe₇Se₈@rGO anode exhibits a distinguished reversible capacity of 332.3 mAh g⁻¹ at 0.1 A g⁻¹ after 200 cycles, even retaining 300.8 mAh g⁻¹ at 1.0 A g⁻¹ after 1000 cycles. This work casts a new light on the smart design of metal selenide anode materials for SIBs.