Flow battery balancing cells having a bipolar membrane for simultaneous modification of a negative electrolyte solution and a positive electrolyte solution

A method comprising:

• providing an electrochemical balancing cell comprising:
• a first chamber containing a first electrode;
• a second chamber containing a second electrode;
• a third chamber disposed between the first chamber and the second chamber;
• an ion-selective membrane forming a first interface between the first chamber and the third chamber;
• and
• a bipolar membrane forming a second interface between the second chamber and the third chamber;
• introducing a first electrolyte solution comprising a first active material into the third chamber;
• introducing a second electrolyte solution comprising a second active material into the first chamber and the second chamber:
• wherein at least one of the first electrolyte solution and the second electrolyte solution comprises an aqueous electrolyte solution;
• applying a potential across the electrochemical balancing cell so as to induce a current therein, such that the second electrode is a positive electrode and the first electrode is a negative electrode;
• and
• converting water into protons and hydroxide ions at the bipolar membrane;
• wherein the protons migrate into the first electrolyte solution in the third chamber and the hydroxide ions migrate into the second electrolyte solution in the second chamber;
• placing the electrochemical balancing cell in fluid communication with a first half-cell and a second half-cell of a flow battery;
• and
• transferring the first electrolyte solution and the second electrolyte solution between the electrochemical balancing cell and the flow battery.