Optimizing sodium ion battery performance with V₂O₅ thin film cathodes

Sodium-ion batteries have gained attention as alternatives to lithium-ion batteries due to their abundance and cost-effectiveness, despite facing challenges in performance optimization. For these batteries to be viable in practical applications, the development of electrode materials with improved electrochemical performance is essential. Vanadium pentoxide (V₂O₅) emerges as a promising cathode candidate, but its integration into sodium-ion batteries is hindered by structural deterioration and sluggish kinetics. Nanoscale material engineering offers solutions with a thin-film V₂O₅ cathode which presents a promising solution by offering binder-free, uniform layers that enhance conductivity and sodium-ion diffusion. In this work, we use radio frequency (RF) magnetron sputtering to fabricate additive-free thin film V₂O₅ cathodes. We investigate their performance by varying the argon (Ar) pressure during sputtering which can affect the oxygen vacancies in the oxide lattice thereby affecting the film density. Our results show that the V₂O₅ thin films prepared at higher pressure (17 mTorr) comes out with lower density (LD_V₂O₅) with superior sodium storage capacity (632.8 mAh cm⁻³/191.7 mAh g⁻¹) compared to the other configuration. Ex-situ SEM (scanning electron microscopy), AFM (atomic force microscopy) and XPS (X-ray photoelectron spectroscopy) analyses confirm that the enhanced performance is attributed to the high surface area with porous structure along with higher oxygen vacancies of the thin film observed in the LD_V₂O₅ configuration. This innovative approach represents a significant step towards enhancing sodium-ion battery technology.