A comparative study of iron-vanadium and all-vanadium flow battery for large scale energy storage

The flow battery employing soluble redox couples for instance the all-vanadium ions and iron-vanadium ions, is regarded as a promising technology for large scale energy storage, benefited from its numerous advantages of long cycle life, high energy efficiency and independently tunable power and energy. An open-ended question associated with iron-vanadium and all-vanadium flow battery is which one is more suitable and competitive for large scale energy storage applications. This work attempts to answer this question by means of a comprehensively comparative study with respects to the electrochemical properties, charging-discharging tests, cycling performances and capital cost. The results shown that: i) the overall electrochemical properties of the two batteries are similar because of the limitation of the same negative couple; ii) the iron-vanadium flow battery is of lower energy efficiencies especially at high current densities (9% less at 150 mA cm−2), but superior self-discharge property; iii) the efficiencies of the two batteries are both of outstanding stabilities during long-term running, while the capacity of iron-vanadium flow battery is less stable; iv) The capacity of iron-vanadium flow battery can be recovered by renew the positive electrolyte with acceptable expenses; v) the iron-vanadium flow battery is cost-effective for long duration applications.