Electrolyte-dominated reversible Na ion storage in Na0.4V2O5 using the DME-based electrolyte for high-performance Na-ion batteries

Abstract

Layered Na0.4V2O5 (NVO) is a promising high-capacity cathode material for Na-ion batteries (NIBs), yet its practical application is severely hampered by rapid capacity degradation in conventional carbonate-based electrolytes. Herein, we uncover a stark performance dichotomy where an 1,2-dimethoxyethane (DME)-based electrolyte enables exceptional cycling stability, retaining 84.1% capacity over 250 cycles at 2 C, and superior rate capability. This stands in stark contrast to the catastrophic failure observed in a standard ethylene carbonate/diethyl carbonate (EC/DEC) electrolyte. The EC/DEC-based electrolyte leads to an unstable, organic-rich cathode electrolyte interphase (CEI) layer due to the continuous interfacial decomposition with insertion of solvent into crystal structure, leading to the rapid capacity failure. In contrast, the DME-based electrolyte forms a [Na-DME]* dominated solvation structure that suppresses continuous solvent and anion decomposition, enabling the formation of a thin, inorganic-rich, and stable CEI layer. This unique interfacial environment subsequently facilitates reversible [Na-DME]* co-intercalation into the NVO crystal structure. In situ X-ray diffraction reveals a highly reversible solvent co-intercalation mechanism involving solvated [Na-DME]* complexes, which density functional theory calculations show to be kinetically favored due to their high desolvation energy barrier. This advantageous co-intercalation mechanism, operating synergistically with the formation of a remarkably stable cathode-electrolyte interface, unlocks exceptional cycling stability and rate capability, suggesting an effective methodology for enhancing charge storage in NIBs.