FeSe2 micro-nanorods confined in N-doped carbon as an advanced anode for fast sodium ion storage

Abstract

Metal selenides have aroused significant attention in the realm of efficient ion storage attributed to their exceptional chemical and physical properties, whereas their utilization in sodium-ion batteries (SIBs) is hindered by poor rate performance and cycle stability that originated from their substantial volume expansion throughout Na⁺ insertion/extraction procedures. This work proposes a productive approach to preserve the structure of the FeSe₂ anode via in situ coating nitrogen-doped carbon (NC). The powerful interfacial interaction between FeSe₂ micro-nanorods and NC facilitates fast Na⁺/e⁻ transport kinetics and ensures excellent structural stability of FeSe₂@NC. Consequently, FeSe₂@NC exhibits a capacity of 379.2 mA h g⁻¹ at a high current density of 10 A g⁻¹ and up to 100% reversible capacity over 1000 cycles at 5 A g⁻¹. Furthermore, the invertible Na⁺ storage mechanism of FeSe₂@NC is investigated by ex situ methods. When FeSe₂@NC is used as the anode and Na₃V₂(PO₄)₂F₃@reduced graphene oxide is used as the cathode to assemble a full battery, it also exhibits a capacity of 167.2 mA h g⁻¹ even after 1000 cycles at 1 A g⁻¹. These exemplary results underscore the potential application value of FeSe₂@NC in fast-charging SIBs.