Operating a redox flow battery with a negative electrolyte imbalance

A method of operating a flow battery, comprising:

• controlling one or more of:
• an operating characteristic;
• and a physical characteristic of at least one component of the flow battery having a positive liquid electrolyte arranged to flow through a positive half-cell of a flow-through reaction cell and a negative liquid electrolyte arranged to flow through a negative half-cell of the flow-through reaction cell, wherein the negative liquid electrolyte in the negative half-cell of the flow-through reaction cell contains a first quantity of a negative reactant in an oxidized ionic state and a second quantity of the negative reactant in a reduced ionic state, and the positive liquid electrolyte in the positive half-cell of the flow-through reaction cell contains a first quantity of a positive reactant in a reduced ionic state and a second quantity of the positive reactant in an oxidized ionic state;
• and
• maintaining a negative imbalance in which the second quantity of the negative reactant in the reduced ionic state in the negative liquid electrolyte in the negative half-cell is greater than the second quantity of the positive reactant in the oxidized ionic state in the positive liquid electrolyte in the positive half-cell,
• wherein:
• maintaining the negative imbalance is based on controlling the at least one of:
• the operating characteristic;
• and the physical characteristic of the at least one component;
• the negative imbalance is a difference obtained by subtracting the second quantity of the negative reactant in the reduced ionic state from the second quantity of the positive reactant in the oxidized ionic state;
• and
• when charging the flow battery by applying an electric current to the cell;
• a portion of the first quantity of the negative reactant is reduced from the oxidized ionic state to the reduced ionic state and a portion of the first quantity of the positive reactant is oxidized from the reduced ionic state to the oxidized ionic state;
• determining that the obtained difference of the negative imbalance is less negative than a threshold negative imbalance;
• and
• processing at least one of the positive electrolyte and the negative electrolyte to cause the negative imbalance to become more negative;
• wherein the second quantity of the negative reactant in the reduced ionic state in the negative liquid electrolyte, the second quantity of the positive reactant in the oxidized ionic state in the positive liquid electrolyte, and the negative imbalance are molar concentrations, and wherein the threshold negative imbalance is between −0.01M and −0.05M;
• and
• wherein processing at least one of the positive electrolyte and the negative electrolyte to cause the negative imbalance to become more negative proceeds until the negative imbalance is between −0.05M and −0.20M.