TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The second electrode comprises zinc. The electrolyte further comprises zinc chloride, and sodium chloride and/or potassium chloride.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The flow circuit: comprises an outlet of a return conduit that is curved along an upper surface and a lower surface of the curved sheet, a feed conduit that extends vertically down a central axis of the curved sheet, a feed manifold (115) to deliver the metal-halide electrolyte component and the chlorine reactant from the first and second volumes respectively to the cell, an upward flowing return manifold (120) to deliver the chlorine reactant and the metal-halide electrolyte component from the cell to the reservoir, and a first circulation pump and a second circulation pump configured to convey a flow through the flow circuit in a first direction and a second direction that is opposite to the first direction respectively; and is a loop circuit configured to deliver the metal-halide electrolyte component and the chlorine reactant from the first and second volumes respectively to the cell and from the cell to the reservoir. A bottom part of the feed conduit extends through and below the second opening of the curved sheet into the second volume to function as a halogen reactant feed line. The feed manifold comprises and a first inlet and a second inlet located in the first and second volumes respectively, and a first intake line and a second intake line that is separate from the first intake line. The first intake line is configured to intake the metal-halide electrolyte. The second intake line is configured to intake the chlorine reactant, and extends below the first intake line in the reservoir. A pressure in an inner volume of the vessel is present above a liquefication pressure for the chlorine reactant. The reservoir contains baffle plates to reduce eddy currents in the reservoir, and is located below the cell. The first electrode comprises a porous carbonaceous material. The cell comprises a vertical stack (103) of horizontal cells connected in series. The stack is located above the reservoir in the vessel. The chlorine reactant is partially separated by gravity below the metal-halide electrolyte in the reservoir. An inlet of the circulation pump is a horizontal inlet protruding a wall of the reservoir. The sealed vessel has a first pressure zone that contains the reservoir and the cell, and a second pressure zone enveloping the first pressure zone. A pressure in the first pressure zone is 75-400 psi. The pressure in the second pressure zone is 100-600 psi. The second pressure zone contains an inert gas and/or a neutralizer for the chloride reactant. An inlet for the halogen reactant and the electrolyte is located above the first electrode. An outlet for the halogen reactant and the electrolyte is located below the first electrode. The first electrode comprises electrically conductive spacers electrically contact the porous electrode of the first cell and the metal electrode of the second cell. The electrically conductive spacers are configured such that the halogen reactant and the metal-halide electrolyte flow in a space between the electrically conductive spacers through the porous electrode of the first cell and into the reaction zone of the first cell. A cell to cell distance between the first cell and the second cell is three times greater than an interelectrode distance between the porous electrode of the first cell and the metal electrode of the first cell.