Additives for redox mediated flow batteries

A battery system comprising:

• an electrochemical half-cell comprising an electrode, a liquid containing a first reactive substance dissolved therein which is able to undergo an electrochemical reaction at the electrode, and structure defining a flow path to carry flow of the liquid into contact with the electrode;
• a vessel containing a porous mass comprising a reactive substance which is a solid and is insoluble in the liquid, the vessel and the porous mass defining a flow path to carry flow of the liquid through the porous mass;
• at least one pump;
• and
• piping connecting the pump, the vessel and the half-cell for the pump to circulate the liquid from the vessel to the half-cell, through the half-cell and back to the vessel, wherein the dissolved and insoluble reactive substances are such that when electric current is supplied to charge the battery system while the pump is circulating the liquid, a first dissolved reactive substance is converted at the electrode to a second dissolved reactive substance which subsequently reacts in the vessel with the insoluble solid reactive substance in which reaction the insoluble solid reactive substance is converted from a first state to a second state and the second dissolved reactive substance is converted back to the first dissolved reactive substance,
• and during discharge of electric current from the battery system while the pump is circulating the liquid, the insoluble solid reactive substance in the vessel undergoes reaction with a reactive substance dissolved in the liquid, in which reaction the insoluble solid reactive substance reverts from its second state to its first state and the dissolved reactive substance is converted to another dissolved reactive substance and subsequently that conversion is reversed by electrochemical reaction at the electrode;
• and further wherein;
• the liquid contains a solute enabling the liquid to display elastic turbulence;
• and
• the flow path through the porous mass in the vessel is configured to compel changes in the direction of liquid flow, to cause elastic turbulence of the liquid in contact with the insoluble solid reactive substance in the porous mass within the vessel.