Unveiling Na-ion storage mechanism and interface property of layered perovskite Bi2TiO4F2@rGO anode in ether-based electrolyte

Abstract

To unveil the charge storage mechanisms and interface properties of electrode materials is very challenging for Na-ion storage. In this work, we report that the novel layered perovskite Bi₂TiO₄F₂@reduced graphene oxides (BTOF@rGO) serves as a promising anode for Na-ion storage in an ether-based electrolyte, which exhibits much better electrochemical performance than in an ester-based electrolyte. Interestingly, BTOF@rGO possesses a prominent specific capacity of 458.3–102 mAh g⁻¹/0.02–1 A g⁻¹ and a high initial coulombic efficiency (ICE) of 70.3%. Cross-sectional morphology and depth profile surface chemistry indicate not only a denser reactive interfacial layer but also a superior solid electrolyte interface film containing a higher proportion of inorganic components, which accelerates Na⁺ migration and is an essential factor for the improvement of ICE and other electrochemical properties. Electrochemical tests and ex situ measurements demonstrate the triple hybridization Na-ion storage mechanism of conversion, alloying, and intercalation for BTOF@rGO in the ether-based electrolyte. Furthermore, the Na-ion batteries assembled with the BTOF@rGO anode and the commercial Na₃V₂(PO₄)₂F₃@C cathode exhibit remarkable energy densities and power densities. Overall, the work shows deep insights on developing advanced electrode materials for efficient Na-ion storage.