An electrochemical cell comprising: an ionically conductive separator disposed between a first half-cell and a second half-cell; and a first bipolar plate in the first half-cell and a second bipolar plate in the second half-cell, at least one of the first bipolar plate and the second bipolar plate being a porous composite comprising a porous conductive material and a blocking material; wherein the blocking material comprises a thermoplastic polymer; wherein the blocking material defines a plurality of flow channels (320 a-f) that are spaced apart from one another and extend laterally through the porous composite with respect to the ionically conductive separator; wherein the plurality of flow channels (320 a-f) are in fluid communication with one another through the porous composite; the electrochemical cell further comprising: a fluid inlet manifold configured to provide a first electrolyte solution to the first bipolar plate and a second electrolyte solution to the second bipolar plate; and a fluid outlet manifold configured to withdraw the first electrolyte solution from the first bipolar plate and the second electrolyte solution from the second bipolar plate; wherein the fluid inlet manifold and the fluid outlet manifold are configured to provide and to withdraw the first electrolyte solution and the second electrolyte solution from alternating flow channels within the porous composite, preferably wherein the fluid inlet manifold and the fluid outlet manifold are configured to provide and to withdraw the first electrolyte solution and the second electrolyte solution on opposing lateral faces of the first bipolar plate and the second bipolar plate; and wherein the plurality of flow channels (320 a-f) forms interdigitated first and second flow channels with first flow channels having an inlet but no outlet and second flow channels having an outlet but no inlet; and wherein at least some of the plurality of flow channels (320 a-f) optionally contain the porous conductive material. an ionically conductive separator disposed between a first half-cell and a second half-cell; and a first bipolar plate in the first half-cell and a second bipolar plate in the second half-cell, at least one of the first bipolar plate and the second bipolar plate being a porous composite comprising a porous conductive material and a blocking material; wherein the blocking material comprises a thermoplastic polymer; wherein the blocking material defines a plurality of flow channels (320 a-f) that are spaced apart from one another and extend laterally through the porous composite with respect to the ionically conductive separator; wherein the plurality of flow channels (320 a-f) are in fluid communication with one another through the porous composite; a fluid inlet manifold configured to provide a first electrolyte solution to the first bipolar plate and a second electrolyte solution to the second bipolar plate; and a fluid outlet manifold configured to withdraw the first electrolyte solution from the first bipolar plate and the second electrolyte solution from the second bipolar plate; wherein the fluid inlet manifold and the fluid outlet manifold are configured to provide and to withdraw the first electrolyte solution and the second electrolyte solution from alternating flow channels within the porous composite, preferably wherein the fluid inlet manifold and the fluid outlet manifold are configured to provide and to withdraw the first electrolyte solution and the second electrolyte solution on opposing lateral faces of the first bipolar plate and the second bipolar plate; and wherein the plurality of flow channels (320 a-f) forms interdigitated first and second flow channels with first flow channels having an inlet but no outlet and second flow channels having an outlet but no inlet; and wherein at least some of the plurality of flow channels (320 a-f) optionally contain the porous conductive material.