Synthesis of carbon-coated FeSe2 nano microsphere with stable SEI film as anode materials for high-performance sodium-ion batteries

Abstract

Sodium-ion batteries (SIBs) have recently gained significant interest for grid-scale energy storage due to sodium's abundance, low cost, environmental friendliness, and similarities to lithium-ion batteries (LIBs). Nevertheless, the widespread application of SIBs remains severely constrained by their inadequate rate capability and suboptimal cycling durability a fundamental challenge stemming from the larger ionic radius of Na⁺. This inherent characteristic not only compromises the structural integrity of electrode materials but also leads to significantly sluggish reaction kinetics, thereby hindering efficient energy conversion processes. Herein, N-doped carbon-coated FeSe2 (FeSe2@NC) nano microspheres have been synthesized via solvothermal and selenizing technique. The engineered anode demonstrates exceptional cycling durability (376.6 mAh g⁻¹ retention at 5 A g⁻¹ over 2000 cycles) coupled with practical viability in full-cell configuration (322.0 mAh g⁻¹ at 2 A g⁻¹ when paired with Na₃V₂(PO₄)₃ cathode), collectively demonstrating considerable promise for large-scale energy storage solutions. In-depth investigation employing ex situ X-ray photoelectron spectroscopy combined with electrochemical measurements demonstrates that the enhanced sodium storage capability of FeSe₂ is attributed to a stable solid electrolyte interphase formation, improved Na⁺ diffusion kinetics, and increased electronic conductivity.