Principle of operation

A redox flow battery consists of two storage containers and an electrochemical cell in which the reactions take place.

The two electrolytes – catholyte and anolyte – are separated from one another in the electrochemical cell by a membrane. This prevents the electrolytes from mixing. However, the ions are able to move unimpeded through the membrane from one electrolyte solution to the other.

When the battery is being charged, the charging current ensures that electrons are added to the polymers of the anolyte (REDuction). At the same time, the catholyte releases its electrons (OXidation).

The catholyte and anolyte molecules charged in this way are pumped from the cell into the storage container and replaced by uncharged molecules. The reaction is reversed when the battery discharges. The anolyte molecules release their electrons which are then available as electric current.

The maximum storage capacity of this redox flow battery is limited only by the size of the storage container for the electrolyte liquids.

Both charged electrolytes can then be stored for several months.