Vanadium redox flow battery - membrane selection and characterization

Conference Dates

September 11-16, 2016


The increasing share of renewable energy sources in the total energy production emphasizes the need for a reliable and cheap stationary energy storage. Such a tool allows to baffle hardly predictable non-stabilities in output power of photovoltaics or wind turbines on the power transmission level. Vanadium redox flow battery (VRFB) appears as a promising solution for the stationary energy storage as it offers high efficiency (80% DC-DC), foolproof arrangement of decoupled power (kW) to capacity (kWh), extended durability and fast demand response. However, the broader commercialization of the technology is still obstructed by relatively high investment costs.

In redox flow batteries, electrolytes are not stored in the battery construction but in an external tank and are continuously pumped through the battery stack where electrical energy is transformed on inert electrodes into chemical during charging and conversely during discharging. Battery stack is composed of several serially connected cells. Each cell consists of positive and negative half-cells which are mutually separated typically by ion-exchange membrane. In VRFB, both electrolytes comprises vanadium salts dissolved in diluted sulfuric acid (i.e., (VO2)2SO4 and VOSO4 in positive electrolyte and VSO4 and V2(SO4)3 in negative electrolyte). Price of the ion-exchange membrane, one of the key components of the battery stack, represents 5 - 15 % of the overall costs typically. Long term durability of membrane in acidic electrolytes is vitally necessary for VRFB function.

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