REFERENCE OPEN-CIRCUIT-VOLTAGE CELL FOR REDOX FLOW BATTERY
In one embodiment, a redox flow battery includes an electrochemical cell in fluid communication with anolyte and catholyte working electrolytes, and a primary OCV cell to measure the potential difference between the positive and negative working electrolyte, and a reference OCV cell to measure the potential difference between the reference cell working electrolyte, which is one of the anolyte and catholyte working electrolytes, and a reference electrolyte, wherein the reference electrolyte has a known potential. In another embodiment, a method of operating a redox flow battery includes calculating the potential values of the anolyte and catholyte working electrolytes based on the known potential values of the reference electrolyte and the first and second potential difference values obtained from the primary OCV cell and the reference OCV cell.
1 . A redox flow battery, comprising:
an electrochemical cell in fluid communication with anolyte and catholyte working electrolytes, and a primary OCV cell to measure the potential difference between the positive and negative working electrolyte; and
a reference OCV cell to measure the potential difference between the reference cell working electrolyte, which is one of the anolyte and catholyte working electrolytes, and a reference electrolyte, wherein the reference electrolyte has a known potential.
2 . The redox flow battery of claim 1 , wherein the reference electrolyte has ions of the same metal as the reference cell working electrolyte.
3 . The redox flow battery of claim 1 , wherein the reference electrolyte and the reference cell working electrolyte include an initial electrolyte mixture of V 3+ and V 4+ ions or one of V 3+ and V 4+ ions.
4 . The redox flow battery of claim 1 , wherein the reference electrolyte and the reference cell working electrolyte are both catholytes or both anolytes.
5 . The redox flow battery of claim 1 , wherein one of the reference electrolyte and the reference cell working electrolyte is a catholyte and the other is an anolyte.
6 . The redox flow battery of claim 1 , wherein the state of charge of the reference electrolyte is between 0% and 100%.
7 . The redox flow battery of claim 1 , wherein the state of charge of the reference electrolyte is between 30% and 60%.
8 . The redox flow battery of claim 1 , wherein the state of charge of the reference electrolyte is between 40% and 50%.
9 . The redox flow battery of claim 1 , wherein the reference OCV cell includes at least one ion exchange separator.
10 . The redox flow battery of claim 9 , wherein the reference OCV cell includes an electrode for measuring the potential of the reference electrolyte, wherein the electrode is spaced from the ion exchange separator by a distance of more than 0.1 m.
11 . The redox flow battery of claim 9 , wherein the reference OCV cell includes an electrode for measuring the potential of the reference electrolyte, wherein the electrode is spaced from the ion exchange separator with a distance range of more than 0.1 m to 1.0 m.
12 . The redox flow battery of claim 9 , wherein the reference OCV cell includes an electrode for measuring the potential of the reference electrolyte, wherein the electrode is spaced from the ion exchange separator by a distance of 0.1 m or less.
13 . The redox flow battery of claim 1 , wherein the electrolyte system in the redox flow battery is selected from the group consisting of a V-sulfate system, a V-chloride system, a V-mixed sulfate and chloride system, a zinc-bromine system, a zinc-cerium system, a V-bromide system, a sodium polysulfide-bromide system, a V—Fe system, and a Fe—Cr system.
14 . A method of operating a redox flow battery, the method comprising:
providing an electrochemical cell in fluid communication with anolyte and catholyte working electrolytes, and a primary OCV cell to measure a first potential difference between the positive and negative working electrolyte, and a reference OCV cell to measure a second potential difference between the reference cell working electrolyte, which is one of the anolyte and catholyte working electrolytes, and a reference electrolyte, wherein the reference electrolyte has a known potential; and
calculating the potential values of the anolyte and catholyte working electrolytes based on the known potential values of the reference electrolyte and the first and second potential difference values obtained from the primary OCV cell and the reference OCV cell.
15 . The method of claim 14 , further comprising determining the state of charge values of the anolyte and catholyte working electrolytes based on the calculated potential values of the anolyte and catholyte working electrolytes.
16 . The method of claim 15 , further comprising detecting a difference in the calculated state of charge values of the anolyte and catholyte working electrolytes.
17 . The method of claim 15 , wherein the state of charge values of the anolyte and catholyte working electrolytes are determined from pre-measured state of charge and potential values.
18 . The method of claim 15 , further comprising controlling the operation of the redox flow battery based on the state of charge values of the anolyte and catholyte working electrolytes.
19 . The method of claim 16 , wherein the difference between the calculated state of charge values of the anolyte and the catholyte is selected from the group consisting of less than 20%, less than 10%, and less than 5%.