Hierarchically Porous Fe₂CoSe₄ Binary‐Metal Selenide for Extraordinary Rate Performance and Durable Anode of Sodium‐Ion Batteries

Owing to high energy capacities, transition metal chalcogenides have drawn significant research attention as the promising electrode materials for sodium-ion batteries (SIBs). However, limited cycle life and inferior rate capabilities still hinder their practical application. Improvement of the intrinsic conductivity by smart choice of elemental combination along with carbon coupling of the nanostructures may result in excellence of rate capability and prolonged cycling stability. Herein, a hierarchically porous binary transition metal selenide (Fe₂ CoSe₄ , termed as FCSe) nanomaterial with improved intrinsic conductivity was prepared through an exclusive methodology. The hierarchically porous structure, intimate nanoparticle-carbon matrix contact, and better intrinsic conductivity result in extraordinary electrochemical performance through their synergistic effect. The synthesized FCSe exhibits excellent rate capability (816.3 mA h g^-1 at 0.5 A g^-1 and 400.2 mA h g^-1 at 32 A g^-1 ), extended cycle life (350 mA h g^-1 even after 5000 cycles at 4 A g^-1 ), and adequately high energy capacity (614.5 mA h g^-1 at 1 A g^-1 after 100 cycles) as anode material for SIBs. When further combined with lab-made Na₃ V₂ (PO₄ )₃ /C cathode in Na-ion full cells, FCSe presents reasonably high and stable specific capacity.