REDOX FLOW BATTERY WITH RAMAN SPECTROMETER

1 . A redox flow battery comprising:

a cell having first and second electrodes and an ion-exchange layer arranged there between;

first and second circulation loops fluidly connected with, respectively, the first and second electrodes;

first and second electrolyte storage tanks in, respectively, the first and second circulation loops;

first and second electrolytes contained in, respectively, the first and second circulation loops; and

a Raman spectrometer on at least one of the first or second circulation loops for determining a state-of-charge of at least one of the first or second electrolytes, the Raman spectrometer including a laser source that is rated to emit a laser of a wavelength of 694 nanometers to 1444 nanometers.

2 . The redox flow battery as recited in claim 1 , wherein the first electrolyte is a manganese electrolyte, the second electrolyte is a polysulfide electrolyte, and the Raman spectrometer is on the first circulation loop.

3 . The redox flow battery as recited in claim 2 , wherein the wavelength is 1064 nanometers +/−1 nanometers.

4 . The redox flow battery as recited in claim 1 , wherein the Raman spectrometer includes a probe on at least one of the first or second circulation loops.

5 . The redox flow battery as recited in claim 1 , wherein the Raman spectrometer includes a control module that is configured to collect spectrometer data and determine from the spectrometer data the state-of-charge of at least one of the first or second electrolytes.

6 . The redox flow battery as recited in claim 5 , wherein the control module is configured with calibration data that provides a correlation between the spectrometer data and concentration and state-of-charge.

7 . The redox flow battery as recited in claim 1 , wherein the cell has an inlet side where the first and second circulation loops feed, respectively, the first and second electrolytes into the cell, an outlet side where the first and second electrolytes discharge from the cell into, respectively, the first and second circulation loops feed, and the Raman spectrometer is located on the outlet side of the cell.

8 . The redox flow battery as recited in claim 1 , wherein the first electrolyte is a manganese electrolyte, the second electrolyte is a polysulfide electrolyte, the Raman spectrometer is on the first circulation loop, the Raman spectrometer includes a probe on the first circulation loop, the Raman spectrometer includes a laser source that is rated to emit a laser of a wavelength of 1064 nanometers +/−1 nanometers, the cell has an inlet side where the first and second circulation loops feed, respectively, the first and second electrolytes into the cell, the cell has an outlet side where the first and second electrolytes discharge from the cell into, respectively, the first and second circulation loops feed, and the probe is located on the outlet side of the cell.

9 . A method comprising:

during operation of a redox flow battery (RFB) to charge or discharge electrical energy, using a Raman spectrometer to collect spectrometer data from an electrolyte in the RFB, the Raman spectrometer includes a laser source that is rated to emit a laser of a wavelength of 694 nanometers to 1444 nanometers;

comparing the spectrometer data to calibration data to determine a state-of-charge of the electrolyte; and

based on the state-of-charge, determining whether to perform a rebalance on the RFB.

10 . The method as recited in claim 9 , wherein the RFB includes:

a cell that has first and second electrodes and an ion-exchange layer arranged there between,

first and second circulation loops fluidly connected with, respectively, the first and second electrodes,

first and second electrolyte storage tanks in, respectively, the first and second circulation loops,

the electrolyte is contained in the first circulation loop, and

the Raman spectrometer is on the first circulation loop.

11 . The method as recited in claim 10 , wherein the Raman spectrometer includes a probe on at least one of the first or second circulation loops.

12 . The redox flow battery as recited in claim 11 , wherein the cell has an inlet side where the first and second circulation loops feed, respectively, the first and second electrolytes into the cell, an outlet side where the first and second electrolytes discharge from the cell into, respectively, the first and second circulation loops feed, and the Raman spectrometer is located on the outlet side of the cell.

13 . The method as recited in claim 10 , wherein the electrolyte is a manganese electrolyte.

14 . The method as recited in claim 10 , wherein the wavelength is 1064 nanometers +/−1 nanometers.