Abstract: A multicell assembly for a redox flow electrolyzer is constituted by alternately stacking pre-assembled elements, typically an electrode subassembly including porous mat electrodes on opposite faces of a conductive plate and a permionic membrane subassembly. Pressure drops in circulating the electrolyte solutions through respective cell compartments, in contact with fluid permeable three-dimensional electrodes in the form of porous mats, are reduced while enhancing evenness of electrolyte refreshing over the whole geometrical cell-area, by defining cooperatively interleaved flow channels in the porous mat electrode. Two interleaved orders of parallel flow channels are defined. All the parallel spaced channels of each order extend from a common orthogonal base channel formed along the respective inlet or outlet side of the electrolyte flow chamber, and terminate short of reaching the base channel of the other.

Abstract: A multicell assembly is constituted by alternately stacking two types of pre-assembled elements: a bipolar electrode holding subassembly and a membrane holding subassembly. The alternate stack of elements is piled over a bottom end element and the stack is terminated by placing over the last membrane holding element a top end electrode element.

Abstract: A redox flow battery composed of a plurality of cells in electrical series defined by a stacked and repetitive arrangement of a conductive intercell separator having a generally bipolar function, a positive electrode, an ion exchange membrane, a negative electrode and another conductive intercell separator, is operated by flowing a positive half-cell electrolyte containing reducible and oxidizable ions of a first redox couple through the compartments containing the positive electrodes and a negative half-cell electrolyte containing reducible and oxidizable ions of a second redox couple through the compartments containing the negative electrodes in cascade in a counter or equi-current mode. The difference of cell voltage between the first and the last cell of the stack is sensibly reduced and by-pass currents are substantially eliminated thus resulting in an increased overall faradic efficiency.

Abstract: Carbon-base bipolar electrode for electrochemical redox reactions in an acid electrolyte in the form of a fluid impervious and electrically conductive septum, at least a face of which consists, at least partially, of a fluid previous woven or unwoven electrodically active fabric of carbon fibers or of yarns of carbon fibers, has an electrically conductive fluid impervious septum consisting of a composite of a matrix fabric in the form of a tightly knit or woven fabric of carbon fibers or of yarns of carbon fibers the pores of which are hydraulically sealed by an electrically conductive carbon containing material at least partly filling the pores of said matrix fabric.