A state-of-the-art review of electrolyte systems for vanadium redox flow battery – status of the technology, and future research directions

Increasing use of renewable energy (RE) has raised awareness of energy storage technologies, with research focusing on developing vanadium redox flow batteries (VRFB) for large-scale storage due to their affordability, flexibility, and efficiency. This bibliometric study provides a general overview of research trends for electrolytes in VRFBs during the period from 2000 to 2024. The research field observed huge development with an expanding number of publications, heterogeneity of research themes, and increased international cooperation. Research was initially driven by fundamental electrochemical processes and efficiency in energy, whereas recent research was intended for performance optimization through the use of advanced materials and system design. Key advancements include membrane design to reduce ion crossover, the use of deep eutectic solvents, architected electrodes, and additive-improved electrolytes for improved thermal stability and robustness. Electrochemical diagnostics and imaging techniques have pushed redox kinetics and mass transport phenomena insight, and modeling approaches offer predictive insight into system function and failure mechanisms. Despite these breakthroughs, there remain long-standing challenges to overcome capacity fade, electrolyte degradation, and long-term stability in normal operating conditions. Future studies of VRFBs should be guided by the maximization of electrolyte composition and additive interactions for the minimization of side reactions like ion crossover and gas evolution. Integration of electrolyte design into system-level components will deliver improved stability and performance. Scalability and thermal stability can be realized through advanced modeling, low-cost materials, and multifunctional additives.