Given that there is more concern about the stability of
electrolytes at high temperatures, the V 5 + mixed solutions
were further investigated at 50 ° C. After 10 days, no precipitation
was observable in a mixture of 2.7 M V 5 + and 0.3 M V 4 +
(corresponding to 90% of state-of-charge of a 3 M VRB system),
indicating excellent V 5 + stability in the mixed electrolytes. The
extension of operational temperatures from 10 to 40 ° C to −5 to 50 ° C would signifi cantly ease or potentially eliminate the need for the electrolyte temperature control in most areas in the
world, leading to much improved energy storage efficiency and
reduced energy storage cost. The related stability test results are
given in Table 1 and 2