Distribution of electrolytes in a flow battery

Patent metadata

Field	Value
Publication number	US-2016315339-A1
Application number	US-201315107499-A
Country	US
Kind code	A1
Filing date	Dec 23, 2013
Priority date	Dec 23, 2013
Publication date	Oct 27, 2016
Grant date	—

Abstract

A method of determining a distribution of electrolytes in a flow battery includes providing a flow battery with a fixed amount of fluid electrolyte having a common electrochemically active specie, a portion of the fluid electrolyte serving as an anolyte and a remainder of the fluid electrolyte serving as a catholyte. An average oxidation state of the common electrochemically active specie is determined in the anolyte and the catholyte and, responsive to the determined average oxidation state, a molar ratio of the common electrochemically active specie between the anolyte and the catholyte is adjusted to increase an energy discharge capacity of the flow battery for the determined average oxidation state.

First claim

What is claimed is:

1 . A method of determining a distribution of electrolytes in a flow battery, the method comprising:
(a) providing a flow battery with a fixed amount of fluid electrolyte having a common electrochemically active specie, a portion of the fluid electrolyte serving as an anolyte and a remainder of the fluid electrolyte serving as a catholyte; (b) determining an average oxidation state of the common electrochemically active specie in the anolyte and the catholyte; and (c) responsive to the determined average oxidation state, adjusting a molar ratio of the common electrochemically active specie between the anolyte and the catholyte to increase an energy discharge capacity of the flow battery for the determined average oxidation state.

2 . The method as recited in claim 1 , wherein the anolyte and the catholyte define a fully balanced average oxidation state with respect to equal molar ratios of the anolyte and the catholyte, and the determined average oxidation state is different than the fully balanced average oxidation state.

3 . The method as recited in claim 2 , wherein the molar ratio is represented by N − /(N − +N + ), where N − is moles of the common electrochemically active specie in the anolyte and N + is moles of the common electrochemically active specie in the catholyte, and the adjusted molar ratio is less than or greater than 0.5.

4 . The method as recited in claim 1 , wherein the adjusting of the molar ratio includes adjusting to non-equal volumes of the anolyte and the catholyte in the flow battery.

5 . The method as recited in claim 1 , wherein said step (b) is conducted at a 100% state of charge of the anolyte and the catholyte.

6 . The method as recited in claim 1 , wherein said step (c) includes adjusting the molar ratio such that the increased energy discharge capacity of the flow battery is less than a full energy discharge capacity of the flow battery at the fully balanced average oxidation state with respect to equal molar ratio of the anolyte and the catholyte.

7 . The method as recited in claim 1 , wherein said step (c) includes partially mixing the anolyte and the catholyte together.

8 . The method as recited in claim 7 , including mixing less than 50 vol % of the anolyte with the catholyte and then mixing less than 50 vol % of the catholyte with the anolyte.

9 . The method as recited in claim 1 , wherein the common electrochemically active elemental specie is selected from the group consisting of vanadium, iron, and chromium.

10 . The method as recited in claim 1 , wherein said step (b) includes directly determining the average oxidation state from concentrations of different oxidation states of the common electrochemically active elemental specie in the anolyte and the catholyte.

11 . The method as recited in claim 1 , wherein said step (b) includes determining the average oxidation state as a function of molar concentrations of different oxidation states of the common electrochemically active elemental specie in the anolyte and the catholyte divided by a total molar amount of the common electrochemically active elemental specie.

12 . The method as recited in claim 1 , wherein said step (b) includes collecting measurements representing volumes of the anolyte and the catholyte and concentrations of different oxidation states of the common electrochemically active specie in the anolyte and the catholyte.

13 . The method as recited in claim 12 , wherein the measurements are selected from the group consisting of optical measurements, conductivity measurements, density measurements, viscosity measurements, and combinations thereof.

14 . The method as recited in claim 1 , further including adjusting the molar ratio in response to a concentration of the common electrochemically active specie in one of the anolyte and the catholyte exceeding a defined threshold.

15 . The method as recited in claim 1 , further including adjusting the molar ratio in response to an external environmental air temperature of the flow battery being below a defined threshold.

16 . The method as recited in claim 1 , wherein said step (c) includes partially mixing the anolyte and the catholyte together as a function of an external environmental air temperature of the flow battery such that volumes that are mixed are inversely related to the external environmental air temperature.

17 . The method as recited in claim 1 , further including adjusting the volume ratio of the anolyte according to the chart shown in FIG. 5 .

18 . The method as recited in claim 1 , wherein the flow battery includes a supply/storage system external of the at least one electrochemical cell, the supply/storage system including first and second vessels fluidly connected with the at least one electrochemical cell, the first and second vessel having respective volumetric sizes, wherein at least one of the volumetric sizes is selected, at least in part, according to a state of charge range of the flow battery.

19 . The method as recited in claim 18 , wherein the state of charge range of the flow battery is from a first value that is less than 100% charge to a second value that is greater than 0% discharge.

20 . The method as recited in claim 18 , wherein the state of charge range of the flow battery is 80% charge to 20% discharge.

Assignees

• United Technologies Corp

Inventors

• Darling Robert Mason
• Smeltz Andrew
• Junker Sven Tobias
• Perry Michael L

Classifications

• H01M8/20

  Indirect fuel cells, e.g. fuel cells with redox couple being irreversible (H01M8/18 takes precedence) · CPC title

• H01M8/04276 Primary

  Arrangements for managing the electrolyte stream, e.g. heat exchange · CPC title

• H01M8/0444

  Concentration; Density (H01M8/04492 takes precedence) · CPC title

• H01M8/188

  by recharging of redox couples containing fluids; Redox flow type batteries · CPC title

• H01M8/04791

  Concentration; Density (H01M8/04828 takes precedence) · CPC title