Electrolyte flow configuration for a metal-halogen flow battery

1. A flow battery, comprising:

horizontal flow cells disposed in a vertical stack, electrically connected in series, and separated by flow channels, each flow cell comprising:

a permeable first electrode that serves as a positive electrode in a discharge mode;

a second electrode comprising an impermeable, oxidizable metal and that serves as a negative electrode in the discharge mode;

a reaction zone located between the first electrode and the second electrode;

an inlet configured to provide electrolyte to the reaction zone;

a first outlet configured to receive electrolyte from the reaction zone during a charge mode and the discharge mode; and

a second outlet configured to receive electrolyte from the flow channels during the charge mode, such that an electrolyte flow path during the charge mode is at least partially different from an electrolyte flow path during the discharge mode; and

frames supporting the first and second electrodes, wherein,

the flow channels are configured to receive a portion of the electrotype that passes through the first electrodes during the charge mode, and

the frames comprise:

discharge mode outlet channels formed in first surfaces of the frames and configured to receive the electrolyte from the first outlets; and

charge mode outlet channels formed in opposing second surfaces of the frames and configured to received the electrolyte from the second outlets.

2. The flow battery of claim 1 , wherein:

the charge mode outlet channels are connected to a charge mode outlet manifold formed in the frames; and

the discharge mode outlet channels are connected to a discharge mode outlet manifold formed in frames.

3. The flow battery of claim 1 , wherein:

each first outlet is configured to provide a liquefied halogen reactant poor first portion of the electrolyte to a reservoir in the charge mode;

each second outlet is configured to provide a liquefied halogen reactant rich second portion of the electrolyte to the reservoir in the charge mode;

each second outlet is configured to receive no electrolyte from the reaction zone in the discharge mode and each first outlet is configured to provide all of the electrolyte which comprises a liquefied halogen reactant poor electrolyte from the reaction zone to the at least one reservoir in the discharge mode;

the first electrode comprises a porous ruthenized titanium;

the second electrode comprises titanium that is coated with zinc during the charge mode;

the electrolyte comprises an aqueous zinc chloride electrolyte; and

the liquefied halogen reactant comprises a liquefied chlorine reactant.

4. A method of operating a flow battery comprising a stack of flow cells that are separated by flow channels, and frames supporting the flow cells, the flow cells each including a permeable first electrode that serves as a positive electrode in a discharge mode, a second electrode comprising an impermeable, oxidizable metal and that serves as a negative electrode in the discharge mode, a reaction zone disposed between the first electrode and the second electrode, an inlet configured to provide electrolyte to the reaction zone, a first outlet configured to receive electrolyte from the reaction zone during a charge mode and the discharge mode, and a second outlet configured to receive electrolyte from the flow channels during the charge mode, the method comprising:

in a charge mode, flowing electrolyte through the first inlets and into the reaction zones, such that a first portion of the electrolyte flows through the reaction zones and into the first outlets, and a second portion of the electrolyte flows through the first electrodes, into the flow channels, and then into the second outlets; and

in a discharge mode, flowing the electrolyte through the first inlets, through the reaction zones, and into the first outlets, such that the electrolyte does not flow through the second outlets,

wherein a flowpath of the electrolyte in the charge mode is at least partially different from a flowpath of the electrolyte in the discharge mode, and

wherein the frames comprise:

discharge mode outlet channels formed in first surfaces of the frames and configured to receive the first portion of the electrolyte from the first outlets; and

charge mode outlet channels formed in opposing second surfaces of the frames and configured to received the second portion of the electrolyte from the second outlets.

5. The method of claim 4 , wherein the flow channels are disposed between conductive spacers that electrically connect first and second electrodes of adjacent flow cells.

6. The method of claim 5 , wherein each of the flow channels has a non-uniform gap height.

7. The flow battery of claim 1 , further comprising an outlet valve configured to prevent electrolyte from flowing through the second outlet during the discharge mode and to allow electrolyte to flow through the second outlet during the charge mode.

8. The flow battery of claim 7 , further comprising at least one conduit fluidly connecting the first and second outlets to an electrolyte reservoir,

wherein the outlet valve is disposed on one of the at least one conduits.

9. The flow battery of claim 1 , wherein:

the first outlets are configured to receive electrolyte directly from the reaction zones; and

the second outlets are configured to receive electrolyte directly from the flow channels.

10. The method of claim 4 , wherein:

in the charge mode, the first portion of the electrolyte flows from the first outlets and into the discharge mode outlets, and the second portion of the electrolyte flows from the second outlets and into the charge mode outlets; and

in the discharge mode, the electrolyte flows from the first outlets and into the discharge mode outlets.

11. The method of claim 4 , wherein:

in the charge mode, an outlet valve is opened to allow the second portion of the electrolyte to flow through the second outlets; and

in the discharge mode, the outlet valve is closed to prevent the electrolyte from flowing through the second outlets.