A Novel Vanadium–Titanium Redox Flow Battery with Enhanced Electrochemical Performance & Greener Alternative

Abstract In the pursuit of efficient and cost-effective grid-scale energy storage solutions, redox flow batteries (RFBs) have emerged as champions by offering a promising solution owing to their design scalability. However, conventional vanadium RFBs are limited by high material costs. Here, we present a novel vanadium–titanium redox flow battery (VTRFB) that combines the redox potential of vanadium (V⁵⁺/V⁴⁺) with the low cost and abundance of titanium (Ti³⁺/Ti⁴⁺). The system demonstrates a cell voltage of 1.3 V, high ionic conductivities (0.319 and 0.353 Sꞏcm⁻¹), and low dynamic viscosities (2.7 and 1.3 mPa·s) for catholyte and anolyte, respectively, at 298 K. Charge–discharge testing over 500 hours yielded ~100% CE, ~80% VE, and ~80% EE. Further, an ionic-liquid-based catholyte was employed to enhance sustainability, with performance evaluated and compared using Nafion and SPEEK membranes. This VTRFB design integrates low-cost materials and high electrochemical performance, representing a significant step toward next-generation sustainable RFBs.