Rational design of hierarchical FeSe2 encapsulated with bifunctional carbon cuboids as an advanced anode for sodium-ion batteries

Abstract

Earth-abundant transition-metal selenides (TMSs) have aroused great interest towards their application in sodium-ion batteries (SIBs). Herein, we present Fe-based Prussian blue analogs (PBA) modified by graphene oxide as precursors to synthesize FeSe₂ nanoparticles within a nitrogen-doped carbon (NC) matrix and graphene layer (FeSe₂/NC@G). The bifunctional carbon wrapped FeSe₂/NC@G shows excellent sodium-storage performance with a large reversible capacity of 331 mA h g⁻¹ at 5.0 A g⁻¹ and a high cyclability of 323 mA h g⁻¹ at the current density of 2.0 A g⁻¹ after 1000 cycles (82% capacity retention). Furthermore, full SIBs are also fabricated and exhibit superior capacities and stabilities. The remarkable electrochemical properties result from the formation of an Fe–O–C chemical bond in the composite with enhanced electronic/ionic diffusion kinetics and structural integrity. This study paves the way for the successful synthesis of novel nanostructural TMSs which can be utilized in energy storage system application.