Cathode-Electrolyte Interphase in a LiTFSI/Tetraglyme Electrolyte Promoting the Cyclability of V₂O₅

V₂O₅, one of the earliest intercalation-type cathode materials investigated as a Li⁺ host, is characterized by an extremely high theoretical capacity (441 mAh g^-1). However, the fast capacity fading upon cycling in conventional carbonate-based electrolytes is an unresolved issue. Herein, we show that using a LiTFSI/tetraglyme (1:1 in mole ratio) electrolyte yields a highly enhanced cycling ability of V₂O₅ (from 20% capacity retention to 80% after 100 cycles at 50 mA g^-1 within 1.5-4.0 V vs Li⁺/Li). The improved performance mostly originates from the V₂O₅ electrode itself, since refreshing the electrolyte and the lithium electrode of the cycled cells does not help in restoring the V₂O₅ electrode capacity. Electrochemical impedance spectroscopy (EIS), post-mortem scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the origin of the improved electrochemical behavior. The results demonstrate that the enhanced cyclability is a consequence of a thinner but more stable cathode-electrolyte interphase (CEI) layer formed in LiTFSI/tetraglyme with respect to the one occurring in 1 M LiPF₆ in EC/DMC (1:1 in weight ratio, LP30). These results show that the cyclability of V₂O₅ can be effectively improved by simple electrolyte engineering. At the same time, the uncovered mechanism further reveals the vital role of the CEI on the cyclability of V₂O₅, which can be helpful for the performance optimization of vanadium-oxide-based batteries.