Reservoir for multiphase electrolyte flow control

1. A flow battery reservoir, comprising:

a reservoir housing;

an electrolyte inlet located in an upper portion of the reservoir and configured to provide an electrolyte mixture comprising a liquid metal-halide electrolyte solution and a complexed halogen phase at or toward a stagnant zone in a lower portion of the reservoir;

an electrolyte outlet configured to outlet the liquid metal-halide electrolyte solution from the reservoir, wherein the electrolyte outlet is positioned such that in use the liquid metal-halide solution flows upward against the force of gravity to reach the electrolyte outlet while the complexed halogen phase settles in the stagnant zone;

a secondary electrolyte inlet located in an upper portion of the reservoir;

a first diffuser fluidly connected to the electrolyte inlet of the reservoir; and

a second diffuser fluidly connected to the secondary electrolyte inlet of the reservoir.

2. The reservoir of claim 1 , further comprising an outlet conduit that extends from the electrolyte outlet in the lower portion of the reservoir through the lower portion of the reservoir into a middle portion of the reservoir, wherein an inlet of the outlet conduit is located in the middle portion of the reservoir.

3. The reservoir of claim 2 , wherein in use the liquid metal-halide solution flows upward against the force of gravity into the inlet of the outlet conduit using suction from a pump while the complexed halogen phase settles in the stagnant zone.

4. The reservoir of claim 1 , further comprising a secondary electrolyte outlet located in the stagnant zone in the lower portion of the reservoir, the secondary electrolyte outlet configured to remove complexed halogen phase from the stagnant zone.

5. The reservoir of claim 1 , wherein the first diffuser comprises a first porous pipe comprising a non-horizontal segment connected to a first non-vertical extension segment, and wherein the second diffuser comprises a second porous pipe comprising a non-horizontal segment connected to a second non-vertical extension segment.

6. The reservoir of claim 5 , further comprising at least one conduit connecting the first non-vertical extension segment and the second non-vertical extension segment.

7. The reservoir of claim 1 , further comprising an outlet conduit that extends from the electrolyte outlet in the lower portion of the reservoir through the lower portion of the reservoir into a middle portion of the reservoir, wherein an inlet of the outlet conduit is located in the middle portion of the reservoir and an outlet of the outlet conduit is located in a sidewall of the reservoir.

8. The reservoir of claim 1 , wherein the first diffuser comprises a plurality of first porous conduits and the second diffuser comprises a plurality of second porous conduits.

9. The reservoir of claim 8 , wherein the plurality of first porous conduits comprise a plurality of first vertically oriented conduits which are fluidly connected to one or more first horizontally oriented conduits which are fluidly connected to a first vertically oriented conduit which is connected to the electrolyte inlet in a top of the reservoir and the plurality of second porous conduits comprise a plurality of second vertically oriented conduits which are fluidly connected to one or more second horizontally oriented conduits which are fluidly connected to a second vertically oriented conduit which is connected to the secondary electrolyte inlet in a top of the reservoir.

10. A flow battery system, comprising:

the reservoir of claim 1 ;

a stack of flow battery cells;

a first stack outlet comprising complexed halogen phase poor electrolyte outlet in the stack;

a second stack outlet comprising complexed halogen phase rich electrolyte outlet in the stack;

a first outlet conduit fluidly connecting the first stack outlet to the electrolyte inlet of the reservoir; and

a second outlet conduit fluidly connecting the second stack outlet to the secondary electrolyte inlet of the reservoir.

11. The system of claim 10 , further comprising:

a first pump;

a second pump or valve;

a second electrolyte outlet located in the stagnant zone in the lower portion of the reservoir; and

a single loop flow circuit between the stack and the reservoir.

12. The system of claim 11 , wherein:

a reaction zone between positive and negative electrodes of each flow battery cell in the stack lacks a separator, such that the electrolyte mixture circulates through the single flow loop circuit without a separation between the positive and negative electrodes in each flow battery cell;

the second pump or valve is connected to the second electrolyte outlet; and

the electrolyte outlet is configured to outlet the liquid metal-halide electrolyte solution; and

the second electrolyte outlet is configured to outlet the complexed halogen phase.

13. A method of operating a flow battery, comprising:

providing an electrolyte mixture comprising a liquid metal-halide electrolyte solution and a complexed halogen phase from a flow battery stack at or toward a stagnant zone in a lower portion of a reservoir;

providing the liquid metal-halide solution from the reservoir to the flow battery stack such that the liquid metal-halide solution flows upward against the force of gravity in the reservoir while the complexed halogen phase settles in the stagnant zone;

using a pump in a single flow loop to pump the liquid metal-halide electrolyte solution from the reservoir to the flow battery stack during a charge mode, and to pump the liquid metal-halide electrolyte solution and the complexed halogen phase from the reservoir to the flow battery stack during a discharge mode;

closing a valve or stopping a second pump, to minimize providing of the complexed halogen phase to the flow battery stack during the charge mode; and

opening the valve or operating the second pump, to provide the complexed halogen phase to the flow battery stack during the discharge mode.

14. The method of claim 13 , wherein the electrolyte mixture is provided from above the lower portion of the reservoir toward the stagnant zone.

15. The method of claim 13 , further comprising providing the electrolyte mixture from the middle portion of the reservoir through an outlet conduit into an electrolyte outlet located in the lower portion of the reservoir.

16. The method of claim 15 , further comprising removing the complexed halogen phase from the stagnant zone through a secondary electrolyte outlet located in the stagnant zone in the lower portion of the reservoir.

17. The method of claim 16 , further comprising:

combining electrolyte mixture from the outlet conduit and complexed halogen phase from the secondary electrolyte outlet to form an enriched complexed halogen phase electrolyte mixture after removal from the reservoir; and

providing the enriched complexed halogen phase electrolyte mixture to the flow battery stack.

18. The method of claim 17 , wherein the enriched complexed halogen phase electrolyte mixture is provided to the flow battery stack with the pump and the enriched complexed halogen phase is formed outside of the reservoir prior to being provided to the pump.

19. The method of claim 16 , further comprising providing the electrolyte mixture to the stagnant zone through a secondary electrolyte inlet.

20. The method of claim 13 , further comprising removing a portion of a gas from an upper portion of the reservoir through a gas outlet.

21. The method of claim 13 , wherein the liquid metal-halide electrolyte solution flows upward against the force of gravity into the inlet of an outlet conduit located above the stagnant zone and then flows through the conduit and out of the reservoir through an outlet located in the stagnant zone using suction from the pump, while the complexed halogen phase settles in the stagnant zone.

22. The method of claim 13 , further comprising:

splitting the electrolyte mixture in the flow battery stack into a first portion having a first concentration of complexed halogen phase and a second portion having a second concentration of complexed halogen phase, wherein the first concentration is smaller than the second concentration; and

providing both the first and second portions of the electrolyte mixture to the lower portion of the reservoir.

23. The method of claim 22 , wherein the first portion of the electrolyte mixture is provided through a first diffuser into the lower portion of the reservoir and the second portion of the electrolyte is provided through a second diffuser into the lower portion of the reservoir.

24. The method of claim 23 , wherein:

the first portion of the electrolyte mixture passes through a reaction zone between a negative, impermeable electrode and a positive, permeable electrode in the stack and then through a first stack outlet into a first inlet on top of the reservoir; and

the second portion of the electrolyte mixture passes through the positive, permeable electrode to a flow channel below the positive, permeable electrode and then through a second stack outlet into a second inlet on top of the reservoir.