Vanadium redox battery
The vanadium redox battery ( vanadium redox flow battery, VRFB ) is a rechargeable type of Flussakkumulators. Since it operates with one - vanadium redox couple in each half cell, the problem of cross-contamination due to diffusion effects is prevented by the membrane. Although the use of Vanadiumredoxpaaren in flow batteries already in 1978 by Pissoort, NASA employees, Pellegri and Spaziante was suggested that a successful demonstration and commercial development only in the 1980s at the University of New South Wales through Mary Skyllas - Kazacos and her staff took place. The vanadium redox battery in its current form ( with sulfuric acid electrolytes ) was patented in 1986 by the University of New South Wales in Australia. The original patents expired in 2006, which allowed a free market and led to commercial developments.
The vanadium redox battery utilizes the ability of vanadium to be able to assume four different oxidation states in the solution, so that instead of two only one electro- active element for the rechargeable battery is required. The nominal voltage per cell is no load in the range of 1.15 V to 1.55 V. At 25 ° C it is 1.41 V.
The main advantage of the vanadium redox battery is that the power and energy, in contrast to conventional secondary cells are independent. This allows a battery through modular design arbitrarily high performance and capacity. The performance is V.A. regulated by the electrode area, the storage capacity by the amount of vanadium in the electrolyte. The battery may be discharged completely for a long time without this resulting in significant aging effects. Also a deep discharge is easy. It can be re- loaded as needed by replacing the electrolytes quickly ( refuel ), which also makes him the option for mobile applications. In case of accidental mixing of the electrolytes with the other half-cell or vanadium diffusion through the separating membrane ( self-discharge ) occurs no permanent damage, because the different oxidation states can be restored.
The main disadvantage of the vanadium redox battery technology are still poor volume energy storage ratio and the complex in comparison with standard batteries overall system consisting of pumps and storage tanks.
The few currently available commercial batteries are especially used in renewable energy sources for covering peak load, load balancing, and uninterruptible power supplies in the field in the stationary sector. Be further explored currently cost membranes as an alternative to Nafion and highly concentrated electrolytes stable over wide temperature ranges. Also be catalysts for increasing the exchange current density and thus developed to increase efficiency.