Localized acoustic streaming-mediated efficiency enhancement for vanadium redox flow battery

The effective functioning of a vanadium redox flow battery (VRFB) is heavily dependent on the consistency of its electrolyte distribution. Ultrasound technology has been recognized as a promising method for enhancing the mixing and reaction rates of electrolytes by leveraging acoustic thermal, acoustic cavitation, and acoustic streaming effects. However, previous research on ultrasonic impact on batteries often combined multiple acoustic effects, making it unclear how specifically acoustic streaming affects battery performance. In this study, we introduce localized acoustic streaming to improve electrolyte uniformity in VRFB. By isolating the thermal effect from other ultrasonic effects, we demonstrate that acoustic streaming alone can boost cell energy efficiency by 2.9 %. Additionally, electrolyte uniformity in the negative electrode significantly increases from 0.22 to 0.53, marking a 141.0 % enhancement ratio. This effectively reduces concentration polarization within the battery, thereby enhancing its voltage efficiency. In addition, the energy consumption of an intermittent ultrasonic application strategy is reduced by 90 % when compared to continuous ultrasonic application. The study provides a new paradigm to promote the localized uniformity of electrolytes, leading to potential impacts in enhancing battery performance.