An electrochemical device

Abstract

The present disclosure provides an electrochemical device The electrochemical device comprises a first and a second electrochemical board 200. Each of the electrochemical boards comprises a first electrically insulating layer and a planar array of membrane electrode assemblies (MEAs) connected in series. A last MEA in the planar array of MEAs of the first electrochemical board is electrically connected to the first MEA in the planar array of MEAs of the second electrochemical board below the first electrochemical board by a first electrically conductive means aligned vertically with the last MEA in the planar array of MEAs of the first electrochemical board and the first MEA in the planar array of MEAs of the second electrochemical board. A first MEA in the planar array of MEAs of the first electrochemical board is electrically insulated from a last MEA in the planar array of MEAs of the second electrochemical board by a first electrically insulating means at least partially aligned vertically with the first MEA in the planar array of MEAs of the first electrochemical board and the last MEA in the planar array of MEAs of the second electrochemical board.

Description

[0001] AN ELECTROCHEMICAL DEVICE

[0002] The present disclosure relates to electrochemical devices, boards for electrochemical devices and uses of electrochemical devices.

[0003] BACKGROUND

[0004] An example of electrochemical device is a solid-polymer-electrolyte fuel cell. A fuel cell is an electrochemical device which generates electrical energy and heat from a reactant or oxidant (e.g. pure oxygen or air) and a fuel (e.g. hydrogen or a hydrogen-containing mixture, or a hydrocarbon or hydrocarbon derivative). Fuel cell technology finds application in stationary and mobile applications, such as power stations, vehicles and laptop computers. Electrochemical devices such a fuel cells and electrolysers are well known throughout the art. Those utilising insulating boards, for example printed circuit boards (PCBs) have found particular utility in the art. The construction of electrochemical device cells from PCBs and their advantages are outlined for example in WO2012 / 117035, WO2013 / 164639, WO 2022 / 106818, WO2023 / 099877 WO 2023 / 052789 which are incorporated herein by reference. Electrolysers utilising insulating boards are described for example in WO 2023 / 099877, which is incorporated herein by reference. These describe reactant and if present heat exchange fluid flow paths as part of the insulating layers of those designs. The size of an individual cell, or a collection of co-planar cells in a board connected in series (the surface area of a pair of electrodes) determines the current output of a fuel cell board. The total number of individual cells on a fuel cell board determines the voltage produced by the board. The number of fuel cell boards in a stack determines the size of the total current of the fuel cell stack and the overall number of cells in the stack connected in series, determine the overall voltage of the stack.

[0005] The ability to have a system which, whilst providing the same power output can vary the current and voltage to match the needs of the application it also desirable for fuel cell designs.

[0006] Being able to increase cell density (i.e. the number of cells within the same available volume) is desirable for a range of electrochemical devices, to provide improved electrochemical devices, uses of such devices, methods of controlling the ability to match the incoming current and voltage to power the device or the outcoming current and voltage to power the load, boards for such devices.Engineers seek to balance electrochemical device power or output with weight / volume of the device, driving towards increasing density whilst reducing the weight. For example, applications for fuel cells would benefit from powerful but lightweight fuel cells. Reducing board pitch, increasing electrochemical performance and control of the current and voltage distribution within the stack allows fuel cell engineers to increase power density of fuel cells. Electrochemical devices such as electrolysers, can benefit from the ability to take power with different voltage and current characteristics, making them a versatile solution which can be deployed in several applications. Weight reduction, power density increases and versatility to adapt to the requirement of different applications is desirable.

[0007] In view of the foregoing, it is desirable to provide improved electrochemical devices and electrochemical device boards.

[0008] SUMMARY

[0009] An aspect of the invention provides an electrochemical device. The device comprising at least two electrochemical boards, a first electrochemical board and a second electrochemical board. Each of the multiple or first and second electrochemical boards comprising: a first electrically insulating layer and a planar array of membrane electrode assemblies (MEAs) connected in series. A last MEA in the planar array of MEAs of the first electrochemical board is electrically connected to the first MEA in the planar array of MEAs of the second electrochemical board below the first electrochemical board by a first electrically conductive means aligned vertically with the last MEA in the planar array of MEAs of the first electrochemical board and the first MEA in the planar array of MEAs of the second electrochemical board. A first MEA in the planar array of MEAs of the first electrochemical board is electrically insulated from a last MEA in the planar array of MEAs of the second electrochemical board by a first electrically insulating means at least partially aligned vertically with the first MEA in the planar array of MEAs of the first electrochemical board and the last MEA in the planar array of MEAs of the second electrochemical board. Preferably, in the electrochemical device the second electrochemical board is below the first board.

[0010] The planar array of MEAs is connected in series so that current may move laterally across the series of MEAs in the electrochemical device board. The upwards and downwards electrical connections are above or below the non-central, end or last MEAs of the planar array of MEAs. This arrangement provides a lateral conductive path across a single board, with an electrically insulating layer present.Preferably, the device comprises at least three electrochemical boards, or multiple electrochemical boards. Each of the multiple electrochemical boards comprising: an electrically insulating layer (the first board a first electrically insulating layer, the second board a second electrically insulating layer and the third board a electrically insulating layer) and a planar array of MEAs connected in series. The second electrochemical board may be located between the first and third electrochemical boards in the electrochemical device. A last MEA in the planar array of MEAs of the second electrochemical board may be electrically connected to the first MEA in the planar array of MEAs of the third electrochemical board by a second electrically conductive means aligned vertically with the last MEA in the planar array of MEAs of the second electrochemical board and the first MEA in the planar array of MEAs of the third electrochemical board. A first MEA in the planar array of MEAs of the second electrochemical board may be electrically insulated from a last MEA in the planar array of MEAs of the third electrochemical board by a second electrically insulating means at least partially aligned vertically with the first MEA in the planar array of MEAs of the second electrochemical board and the a last MEA in the planar array of MEAs of the third electrochemical board.

[0011] Preferably, each planar array of MEAs connected in series comprises a first MEA, at least one central MEA and a last MEA connected. All MEAs on the board are connected in series. The first electrically insulating means may be also at least partially aligned vertically with the central MEAs of the first electrochemical board and the second electrochemical board. The second electrically insulating means may be also at least partially aligned vertically with the central MEAs of the second electrochemical board and third electrochemical board. The first and second electrically insulating means vertically insulates the central MEAs of each board from the adjacent boards. The planar array of MEAs comprises at least two MEAs, a first MEA at one end of the planar array of MEAs and a last MEA at the other end of the planar array of MEAs. Where more than two MEAs may be present in an electrochemical board the planar array of MEAs comprises also central MEAs in between the first and last MEA.

[0012] In this arrangement, the cathode side of one MEA may be electrically connected to the anode side of the other MEA. A cathode of adjacent boards is electrically connected to an anode of adjacent boards. This provides a conductive path across boards then across the stacks. This has not previously been described. Previously described arrangement utilised connections outside of the footprint with the MEAs and the flow-fields, for example edge of board connectors, or via external connecting wires.Preferably, the cells of the board are located on the insulating layer. Preferably, cells of the board are located between two insulating layers. The insulating layer or two insulating layers may further comprise two conductive layers either side of the insulating layer. The insulating layer or two insulating layers may be PCBs as described herein. The insulating layer or insulating layers may be an anode plate and / or a cathode plate as described herein.

[0013] Preferably, each MEA of the planar array of MEAs comprises at least one anode and at least one cathode arranged on opposite sides of a single ion permeable membrane for all MEAs in the planar array, or each MEA comprising at least one anode and at least one cathode arranged on the opposite side of a single ion permeable membrane for each MEA. All anodes may be arranged on one face of each of the planar array of MEAs and all cathodes may be arranged on the other face of each of the planar array of MEAs, wherein anodes on one electrochemical board face cathodes on an adjacent electrochemical board.

[0014] Preferably, the first electrically conductive means and the first electrically insulating means between the first electrochemical board and the second electrochemical board are a single layer or component between the two adjacent electrochemical boards. The second electrically conductive means and the second electrically insulating means may also be between the second electrochemical board and the third electrochemical board and are a single layer or component between the two adjacent electrochemical boards.

[0015] Preferably, the means to vertically insulate any part of one electrochemical board from another electrochemical board above or below that electrochemical board comprises: an electrically insulating coating layer, a layer of at least partially electrically insulating material and / or wherein the means to vertically insulate any part of one electrochemical board from another electrochemical board above or below that electrochemical board comprises the electrically insulating layer acting to insulate any part of one electrochemical board from another electrochemical board above or below that electrochemical board.

[0016] Preferably, each electrochemical board comprises: a cathode plate comprising the first electrically insulating layer between a first conductive layer and a second conductive layer, arranged so that the first conductive layer faces the cathodes of the planar array of MEAs and so the first conductive layer is electrically connected to the cathodes of the planar array of MEAs, an anode plate comprising a second electrically insulating layer between a third conductive layer and a fourth conductive layer, arranged so that the third conductive layer faces the anodes of the planar array of MEAs and so the third conductive layer is electrically connected to the anodes of the planar array of MEA; wherein one or more of the first,second, third and fourth conductive layers each comprise multiple fluid flow paths separated by multiple electrically conductive lands.

[0017] Preferably, the second and fourth conductive layers comprise multiple fluid flow paths separated by multiple electrically conductive lands. Preferably, upwards and downwards electrical connections between the MEAs of adjacent electrochemical boards are formed between vertically aligned electrically conductive lands of the second conductive layers of the cathode plates with vertically aligned electrically conductive lands of the fourth conductive layers of anode plates of adjacent boards contacting each other. Preferably, lands of conductive layers facing each other are vertically aligned, and lands of adjacent boards contact each other to form electrical connections between the lands and consequently between the boards, plates and MEAs.

[0018] Further, placement of fluid pathways within just the conductive layers allows for the use of a thinner insulating core compared to previous designs, within an electrochemical device stack. An increased amount of conductive material, coupled with a thinner insulating core, allows for a great control of the thermal properties of the fuel cell boards and fuel cell stacks overall. Any conductive layer may just be a partial layer or multiple partial layers on an insulating layer, some of each of those parts of the conductive layer comprising the fluid paths described herein. These may be conductive material “lands”. Areas between the conductive material (lands) may form the fluid paths described herein. Those paths may form only in the conductive material and only have a base or floor of insulating material, or may have a base or floor also of conductive material, they may be solely contained in one or more areas of conductive material on an insulating layer. This may apply to any conductive material described herein.

[0019] Preferably, the majority of one of the one or more of the fluid flow paths in one or more of the conductive layers is the full depth of the conductive layer. Preferably, the majority of one of the one or more of the fluid flow paths in one or more of the conductive layers is shallower or less than the full depth or thickness of the conductive layer, so for at least part of the fluid path all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within. One, two, three, or four of conductive layers comprising fluid flow paths may have one or more of these arrangements for all fluid flow paths in that layer. The first and third conductive layer may have different flow path arrangements to the second and fourth conductive layers. The second and fourth conductive layers may not comprise fluid flow paths when the first andthird conductive layers do.

[0020] Fluid flow paths may be formed in a structured field flow pattern defined in the outer surface of the conductive layer. These may be through the body of the conductive layer, or may not be. The structured flow field pattern or flow path pattern defines one or more fluid channels. Preferably, the first, second, third and / or fourth fluid flow path is a structured field flow pattern defined in the outer surface of the first, second, third and / or fourth conductive layer. Preferably, there are multiple first, second, third and / or fourth fluid flow paths in the structured field flow pattern defined in the outer surface of the first, second, third and / or fourth conductive layer. Preferably the first, second, third and / or fourth fluid flow paths are within the body of the first, second, third and / or fourth conductive layer.

[0021] Preferably, the majority of the length of one or more of the fluid flow paths in the first conductive layer and / or the third conductive layer are the full depth of the first conductive layer and / or the third conductive layer, and wherein the majority of the length of one or more of the fluid flow paths in second conductive layer and / or the fourth conductive layer are the full depth of the second conductive layer and / or the fourth conductive layer. Or preferably, the majority of the length of one or more of the fluid flow paths in the first conductive layer and / or the third conductive layer are the full depth of the first conductive layer and / or the third conductive layer, and wherein the majority of the length of one or more of the fluid flow paths in second conductive layer and / or the fourth conductive layer are shallower or smaller than the full depth or thickness of the second and / or fourth conductive layer, so all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within. Or preferably, the majority of the length of one or more of the fluid flow paths in the second conductive layer and / or the fourth conductive layer are the full depth of the second conductive layer and / or the fourth conductive layer, and wherein the majority of the length of one or more of the fluid flow paths in first conductive layer and / or the third conductive layer are shallower or smaller than the full depth or thickness of the second and / or fourth conductive layer, so all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within. Or preferably, the majority of the length of one or more of the fluid flow paths in the first conductive layer and / or the third conductive layer are shallower or smaller than the full depth or thickness of the first and / or third conductive layer, so all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within, and wherein themajority of the length of one or more of the fluid flow paths in second conductive layer and / or the fourth conductive layer are shallower or smaller than the full depth or thickness of the second and / or fourth conductive layer, so all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within.

[0022] Preferably, the fluid paths in the second conductive layer and fourth conductive layer are for heat exchange fluid and the fluid paths in the first conductive layer and the third conductive layer are for anode and cathode reactant fluids. Reactant and heat exchange fluid may be any fluid as described herein.

[0023] Preferably, the gaps between adjacent MEAs in series in the planar array of MEAs are parallel to the reactant fluid paths in the first conductive layer and wherein the gaps between adjacent MEAs in series in the planar array of MEAs are parallel to the reactant fluid paths in the third conductive layer. Or, preferably the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the reactant fluid paths in the first conductive layers and wherein the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the reactant fluid paths in the third conductive layer. Or, preferably the gaps between adjacent MEAs in the planar array of MEAs in series are parallel to the reactant fluid paths in the first conductive layer and wherein the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the reactant fluid paths in the third conductive layer. Or, preferably the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the reactant fluid paths in the first conductive layer and wherein the gaps between adjacent MEAs in the planar array of MEAs in series are parallel to the reactant fluid paths in the third conductive layer. Or, preferably the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the reactant fluid paths in the first conductive layer and wherein the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the reactant fluid paths in the third conductive layer. Or preferably any combination of these.

[0024] Preferably the conductive path between MEAs in the planar array of MEAs is perpendicular to the reactant fluid paths in the first conductive layer and wherein the conductive path between adjacent MEAs in series in the planar array of MEAs is perpendicular to the reactant fluid paths in the third conductive layer. Or, preferably the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the reactant fluid paths in the first conductive layer and wherein the conductive path between adjacent MEAs in series in theplanar array of MEAs is perpendicular to the reactant fluid paths in the third conductive layer. Or, preferably the conductive path between adjacent MEAs in series in the planar array of MEAs is perpendicular to the reactant fluid paths in the first conductive layer and wherein the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the reactant fluid paths in the third conductive layer. Or preferably any combination of these.

[0025] Preferably, the heat exchange fluid flow paths in the second and / or fourth conductive layers are parallel to the reactant fluid paths in the first and / or third conductive layers. Or preferably, the heat exchange fluid flow paths in the second and / or fourth conductive layers are perpendicular to the reactant flow paths in the first and / or third conductive layers. Or preferably, the heat exchange fluid flow paths in the second and / or fourth conductive layers are parallel to the conductive path between adjacent MEAs in series in the planar array of MEAs. Or preferably, the heat exchange fluid flow paths in the second and / or fourth conductive layers are perpendicular to the conductive path between adjacent MEAs in series in the planar array of MEAs.

[0026] Preferably, at least part of the heat exchange fluid path of one electrochemical board and at least part of the heat exchange fluid path of an adjacent electrochemical board at least partially align with each other so as to form part of a single heat exchange fluid path between the two adjacent electrochemical boards.

[0027] Preferably, the electrically insulating layers comprises electrically conductive means located through them to connect the two electrically conductive layers on opposite sides of the electrically insulating layers, preferably wherein the electrically conductive means to provide a conductive path through the electrically insulating layer are plated through holes or filled through holes.

[0028] Preferably, each of the electrochemical boards of the multiple electrochemical boards comprises means to provide a conductive path laterally across the electrochemical board, providing a conductive path between an electrochemical board above the electrochemical board and an electrochemical board below the electrochemical board along the planar array of MEAs connected in series. Preferably, the means to provide a conductive path comprises the first, second, third and fourth conductive layers, and the second conductive layer is electrically connected to the fourth conductive layer by a first through electrochemical board electrically conductive means, the first through electrochemical board electrically conductive means passing through the first electrically insulating layer, through the second electricallyinsulating layer and if present through the membrane to provide a conductive path from the second conductive layer to the fourth conductive layer, or the first conductive layer is electrically connected to the third conductive layer by a first through electrochemical board electrically conductive means, the first through electrochemical board electrically conductive means passing through the membrane if present to provide a conductive path from the first conductive layer to the third conductive layer

[0029] Preferably, the first, second, third and fourth conductive layers all comprise multiple fluid flow paths separated by multiple electrically conductive lands, the means to provide a conductive path comprises a first electrically conductive land of the second conductive layer electrically connected to a first electrically conductive land of the fourth conductive layer by the first through electrochemical board electrically conductive means, the first through electrochemical board electrically conductive means passing through the first electrically insulating layer, through the second electrically insulating layer and if present through the membrane to the first electrically conductive land of the fourth conductive layer to provide a conductive path from the second conductive layer to the fourth conductive layer, and the conductive path is provided laterally along the planar array of MEAs from the first MEA to the second MEA via the conductive layers and through the first electrochemical board electrically conductive means.

[0030] Preferably, the means to provide a conductive path comprises multiple of the electrically conductive lands in the first conductive layer, the second conductive layer, the third conductive layer and the fourth conductive layer. Preferably, multiple of the electrically conductive lands in the first conductive layer and multiple of the electrically conductive lands in the second conductive layer partially align on opposite sides of the first electrically insulating layer and wherein the same multiple electrically conductive lands in the first conductive layer and the same multiple electrically conductive lands in the second conductive layer partially do not align on opposite sides of the first electrically insulating layer. Preferably, the multiple of the electrically conductive lands in the third conductive layer and multiple of the electrically conductive lands in the fourth conductive layer partially align on opposite sides of the second electrically insulating layer and wherein the same multiple electrically conductive lands in the third conductive layer and the same multiple electrically conductive lands in the fourth conductive layer partially do not align on opposite sides of the second electrically insulating layer. Preferably, a first of the aligning electrically conductive lands in the first conductive layer and a first of the aligning electrically conductive lands in the second conductive layer are electrically connected by a first electrically conductivemeans through the first electrically insulating layer at a point of those electrically conductive lands aligning. Preferably, a first of the aligning electrically conductive lands in the third conductive layer and a first of the aligning electrically conductive lands in the fourth conductive layer are electrically connected by a first electrically conductive means through the second electrically insulating layer at a point of those electrically conductive lands aligning. Preferably, the electrically conductive lands and the electrically conductive means through the first electrically insulating layer arranged so that the conductive path is provided laterally across the electrochemical board.

[0031] Preferably, a first electrically conductive land of the second conductive layer is electrically connected to a first electrically conductive land of the fourth conductive layer by a first through electrochemical board electrically conductive means, the through electrochemical board electrically conductive means passing through the first electrically insulating layer, through the second electrically insulating layer and if present through the membrane to the first electrically conductive land of the fourth conductive layer to provide a conductive path from the second conductive layer to the fourth conductive layer.

[0032] Preferably, the region of the second conductive layer above the first MEA of the planar array of MEAs is planarly insulated from the region of the second conductive layer above the adjacent MEA, and / or the region of the fourth conductive layer below the first MEA of the planar array of MEAs is planarly insulated from the region of the fourth conductive layer below the adjacent MEA. Preferably, the regions are planarly insulated by a gap in the conductive layer, a gap in the lands forming the conductive layer, a line of electrically insulating material or any means to electrically isolate one region of the conductive layer from another region of the conductive layer, and / or the region of the first conductive layer above the first MEA of the planar array of MEAs is planarly insulated from the region of the first conductive layer above the adjacent MEA, and / or the region of the third conductive layer below the first MEA of the planar array of MEAs is planarly insulated from the region of the third conductive layer below the adjacent MEA. Preferably, the regions are planarly insulated by a gap in the conductive layer, a gap in the lands forming the conductive layer, a line of electrically insulating material or any means to electrically isolate one region of the conductive layer from another region of the conductive layer.

[0033] Preferably, there are multiple through board electrically conductive means to connect the electrically conductive land of the second conductive layer to the first electrically conductive land of the fourth conductive layer. Preferably and / or the electrically conductive meanscomprise plated or conductive filled through holes, a strip of metal / metal alloy, a portion of copper wires, a metal foam (porous metal) or solder paste.

[0034] Preferably, two electrically conductive lands of the second conductive layer align with two of the electrically conductive lands of the fourth conductive layer and multiple through board electrically conductive means electrically connect a first electrically conductive land of the second conductive layer with a first of the electrically conductive lands of the fourth conductive layer and multiple through board electrically conductive means electrically connect a second electrically conductive land of the second conductive layer with a second of the electrically conductive lands of the fourth conductive layer.

[0035] Preferably, the majority of one or more of the fluid flow paths in one or more of the conductive layers is shallower or less than the full depth or thickness of the conductive layer, so for at least part of the fluid path all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within, and the conductive layer provides the conductive path laterally across the electrochemical board. Preferably, the first insulating layer of one electrochemical board and the second insulating layer of an adjacent electrochemical board provides the first electrically insulating means. Preferably, the first insulating layer of one electrochemical board and the second insulating layer of an adjacent electrochemical board provides the second electrically insulating means.

[0036] Preferably, the board comprises a PCB and wherein the electrically insulating layer comprises one or more dielectric substrates, preferably an epoxy resin, preferably one or more of FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5, polytetrafluoroethylene, G-10 or polyimide, preferably the electrically insulating layer comprises FR-4. Preferably, the insulating layer and conductive layer are a PCB, preferably wherein the insulating core is FR-4 and the conductive layer is copper. Preferably, the insulating layer and conductive layer together are a PCB. Preferably the method comprises electrochemical machining, chemical etching, or any other method of removing material from a PCB to create a fluid flow path. The board may also comprise a passivation layer on the conductive layer. The conductive layer may be metal. Preferably, the one or more insulating layers can comprise PCB layers.

[0037] Preferably, at least two boards in the device are laminated together. Preferably, the boards in the device are mechanically pressed or compressed together, preferably with a sealant. Use of an epoxy resin prepreg may maintain compression of the gas diffusion layer of theMEAs, a critical component in maintaining device performance as it provides a sufficiently low resistance electrical path without compromising distribution of reactant fluids.

[0038] Preferably, the electrochemical device is a fuel cell, an electrolyser, a hydrogen sensor or a redox flow battery.

[0039] Preferably, when the electrochemical device is a fuel cell, each fuel cell board may have a power rating of at least 1 W. Preferably, each fuel cell board may have a power rating of up to 1000W. Preferably, each fuel cell board may have a power rating of 1W to 1000W. Preferably, a fuel cell comprising multiple fuel cell boards may have a power rating of at least 2W. Preferably, a fuel cell comprising multiple fuel cell boards may have a power rating of up to 1000kW. Preferably, each fuel cell a fuel cell comprising multiple fuel cell boards may have a power rating of 2W to 1000kW. Preferably, when a fuel cell the oxidant fluid described in any aspect of the invention described herein is air and / or the reductant fluid is hydrogen gas.

[0040] Preferably, when the electrochemical device is an electrolyser, each electrolyser component may have a power rating of at least 20W. Preferably, each electrolyser component may have a power rating of up to 5kW. Preferably, each electrolyser component may have a power rating of 20W to 5kW. Preferably, an electrolyser comprising multiple electrolyser components may have a power rating of at least 10kW. Preferably, an electrolyser comprising multiple components may have a power rating of up to 1MW. Preferably, each electrolyser comprising multiple components may have a power rating of 5kW to 1 MW. Preferably, when an electrolyser, water or an electrolyte is used as input fluid. On the anode, oxygen generated and on the cathode hydrogen is produced. Thus, there may be fluids both flowing towards and away from the electrodes in a component or device.

[0041] Preferably, there are multiple membranes on the board.

[0042] Preferably, the MEA comprises one or more catalyst components. Preferably, the board comprises one or more gas diffusion layers (GDLs).

[0043] Preferably, the one or more fluid paths is formed by electrochemical machining or chemical etching or any other method of removing material from the conductive layer.

[0044] Electrochemical machining, chemical etching or any other method of removing material from a conductive layer allows the decoupling of the fluid path geometry on opposite sides of the same plate (cathode and / or anode plate), allowing for different fluid pathways on different faces of boards. These methods allow independent creation of flow paths on the same platebut different sides or different parts of a plate. One of the fluid paths may be independently created from one or more of the other fluid paths. Any fluid path may be independently created from another fluid path on the same or another face / side of the same plate.

[0045] Preferably, each conductive layer has multiple flow paths. Preferably, the flow paths are serpentine, substantially linear, or substantially parallel to other flow paths in the same layer. Preferably, one or more of the flow paths comprise flow restrictions or flow directional changes to perturbate fluid flow at defined intervals and / or to increase mass flow velocity and / or a change in pressure drop. Preferably, one or more flow paths are convergent flow fields with tapered channels dimensions. These can introduce a useful pressure drop between inlet and outlet to maximise the efficiency of the electrochemical device / board. Preferably, one or more of the flow paths have cascade-type fractal designs, where the flow is split down a number of levels before it reaches the electrodes. These can help maintaining a fixed pressure throughout the surface of the MEA and could promote a uniform fuel utilisation relative to more traditional designs.

[0046] Preferably, the flow paths the flow path geometry of the first fluid path is different to the flow path geometry of the second fluid path; and / or preferably, the flow path geometry of the first fluid path is different to the flow path geometry of the third fluid path, and / or the flow path geometry of the second fluid path is different to the flow path geometry of the fourth fluid path, wherein the flow path geometry of a fluid path on one face of the anode plate and / or the cathode plate is different to the flow path geometry of fluid path on the opposing face of the same anode plate or cathode plate.

[0047] A further aspect of the invention is a board for an electrochemical device. The electrochemical board comprising a planar array of membrane electrode assemblies (MEAs) connected in series, each MEA comprising at least one anode and at least one cathode arranged on opposite sides of a single ion permeable membrane for all MEAs in the planar array, or each MEA comprising at least one anode and at least one cathode arranged on the opposite side of an ion permeable membrane. All anodes are arranged on one face of the planar array of MEAs and all cathodes arranged on the other face of the planar array of MEAs. The electrochemical board comprises a cathode plate comprising a first electrically insulating layer between a first conductive layer and a second conductive layer, arranged so that the first conductive layer faces the cathodes of the planar array of MEAs and so the first conductive layer is electrically connected to the cathodes of the planar array of MEAs. The electrochemical board comprises an anode plate comprising a second electricallyinsulating layer between a third conductive layer and a fourth conductive layer, arranged so that the third conductive layer faces the anodes of the planar array of MEAs and so the third conductive layer is electrically connected to the anodes of the planar array of MEAs. The first, second, third and fourth conductive layers each comprise multiple fluid flow paths separated by multiple electrically conductive lands. A first electrically conductive land of the second conductive layer is electrically connected to a first electrically conductive land of the fourth conductive layer by a through board electrically conductive means, the electrically conductive means passing through the first electrically insulating layer, through the second electrically insulating layer and if present through the membrane to the first electrically conductive land of the fourth conductive layer. A lateral electrically conductive path is provided along the planar array of MEAs from the first MEA to the second MEA.

[0048] A further aspect of the invention is a board for an electrochemical device. The board for an electrochemical device comprises a first electrically insulating layer between a first conductive layer and a second conductive layer, the first conductive layer and the second conductive layer each comprising multiple fluid flow paths separated by multiple electrically conductive lands laterally spaced across the first electrically insulating layer. A first of the electrically conductive lands in the first conductive layer and a first of the electrically conductive lands in the second conductive layer at least partially align on opposite sides of the first electrically insulating layer, and wherein a first of the electrically conductive lands in the second conductive layer and a second of the electrically conductive lands in the first conductive layer at least partially align on opposite sides of the first electrically insulating layer. The first of the electrically conductive lands in the first conductive layer and the first of the electrically conductive lands in the second conductive layer are electrically connected by a first electrically conductive means through the first electrically insulating layer at a point of these two electrically conductive lands aligning. A first of the electrically conductive lands in the second conductive layer and a second of the electrically conductive lands in the first conductive layer are electrically connected by a second electrically conductive means through the first electrically insulating layer at a point of these two electrically conductive lands aligning. The electrically conductive lands and the electrically conductive means through the first electrically insulating layer arranged to provide a lateral electrically conductive path across the electrical board.

[0049] Preferably, the second of the electrically conductive lands in the first conductive layer and a second of the electrically conductive lands in the second conductive layer are electrically connected by a third electrically conductive means through the first electrically insulatinglayer at a point of these two electrically conductive lands aligning. Preferably, a second of the electrically conductive lands in the second conductive layer and a third of the electrically conductive lands in the first conductive layer are electrically connected by a fourth electrically conductive means through the first electrically insulating layer at a point of these two electrically conductive lands aligning.

[0050] Preferably, multiple of the electrically conductive lands in the first conductive layer and multiple of the electrically conductive lands in the second conductive layer are electrically connected by electrically conductive means through the first electrically insulating layer at points of the electrically conductive lands aligning electrically through the electrically insulating layer. Preferably, the electrically conductive lands and the electrically conductive means through the first electrically insulating layer have a staggered arrangement so that a lateral electrically conductive path is provided across the electrochemical board.

[0051] Preferably, the electrochemical board further comprises a second electrically insulating layer between a third conductive layer and a fourth conductive layer. The third conductive layer and the fourth conductive layer each comprising multiple fluid flow paths separated by multiple electrically conductive lands laterally spaced across the second electrically insulating layer. Preferably, a first of the electrically conductive lands in the third conductive layer and a first of the electrically conductive lands in the fourth conductive layer at least partially align on opposite sides of the second electrically insulating layer, and wherein a first of the electrically conductive lands in the fourth conductive layer and a second of the electrically conductive lands in the third conductive layer at least partially align on opposite sides of the second electrically insulating layer. Preferably, the first of the electrically conductive lands in the third conductive layer and the first of the electrically conductive lands in the fourth conductive layer are electrically connected by a first electrically conductive means through the second electrically insulating layer at a point of these two electrically conductive lands aligning. Preferably, a first of the electrically conductive lands in the fourth conductive layer and a second of the electrically conductive lands in the third conductive layer are electrically connected by a second electrically conductive means through the second electrically insulating layer at a point of these two electrically conductive lands aligning, the electrically conductive lands and the electrically conductive means through the second electrically insulating layer arranged so that a lateral electrically conductive path is provided across the second electrically insulating layer.Preferably, the electrochemical board further comprises a plurality of MEAs between the first conductive layer of the first electrically insulating layer and the third conductive layer of the second electrically insulating layer.

[0052] Preferably, at least part of the first electrically conductive land of the first conductive layer is not aligned with at least part of the first electrically conductive land of the second conductive layer, optionally wherein at least part of the first electrically conductive land has a different angle of direction across the electrically insulating layer to the first electrically conductive land of the second conductive layer to cause the portion of the lands to not align.

[0053] Preferably, the means to provide a conductive path through the electrically insulating layer are plated through holes or filled through holes

[0054] Preferably, the board comprises a PCB and wherein the electrically insulating layer comprises one or more dielectric substrates, preferably an epoxy resin, preferably one or more of FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5, polytetrafluoroethylene, G-10 or polyimide, preferably the electrically insulating layer comprises FR-4. Preferably, the insulating layer and conductive layer are a PCB, preferably wherein the insulating core is FR-4 and the conductive layer is copper. Preferably, the insulating layer and conductive layer together are a PCB. Preferably the method comprises electrochemical machining, chemical etching, or any other method of removing material from a PCB to create a fluid flow path. The board may also comprise a passivation layer on the conductive layer. The conductive layer may be metal. Preferably, the one or more insulating layers can comprise PCB layers.

[0055] An aspect of the invention is an electrochemical device comprises one of or multiple of the boards of the second or third aspects of the invention.

[0056] The electrochemical device of the first aspect may comprise one of or multiple of the boards of either or both of the second and third aspects, along with any preferable features.

[0057] An aspect of the present invention is the use of an electrochemical device or board for an electrochemical device of any embodiment or aspect described herein. An aspect of the present invention is the manufacture of any embodiment or aspect described herein.

[0058] BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Embodiments of the present disclosure will now be described with reference to the accompanying drawings, in which:FIG. 1 shows an arrangement of two electrochemical boards and conductive path arrangements;

[0060] FIG. 2a and FIG. 2b show a schematic of conductive path arrangements between three electrochemical boards;

[0061] FIG. 3 shows lateral conductive path architecture;

[0062] FIG. 4, FIG. 5 and FIG. 6 show arrangements of conductive and insulating layers with an MEA layer;

[0063] FIG. 7 shows how adjacent MEAs may be connected and FIG. 8 shows the conductive path from one cell through an adjacent co-planar cell via the Inter cells Lands (ICL);

[0064] FIG. 8 and 9 shows lateral conductive path architecture in further detail;

[0065] FIG. 10a, 10b, 10c and 10d show flow path and MEA arrangements;

[0066] FIG. 11a shows an expanded embodiment of a fuel cell board of the present invention, FIG. 11 b shows an alternative view of the same expanded embodiment of a fuel cell board of the present invention;

[0067] FIG 12a shows the outer face of cathode plate of an embodiment, FIG 12b shows the inner face of a cathode plate of an embodiment and FIG 12c shows an inner face of an anode plate of an embodiment;

[0068] FIG. 13 shows a prior art flow path arrangement; and

[0069] FIG. 14 shows a schematic representation of how fluid paths may be in the present embodiments.

[0070] DETAIL DESCRIPTION

[0071] Embodiments will now be described in detail with reference to the accompanying drawings. The same reference signs indicate the same or similar features in different figures and embodiment of the invention, although this is only for reference and is not limiting on the invention. In the following detailed description numerous specific details are set forth by way of examples, in order to provide a thorough understanding of the relevant teachings. However, it will be apparent to one of ordinary skill in the art that the present teachings may be practiced without these specific details.

[0072] The boards and electrochemical devices described herein represent a development in howconductive paths can be arranged across and throughout boards for electrochemical devices and throughout electrochemical devices.

[0073] As used herein, “across a board”, “across an electrochemical board”, “across an electrochemical device board”, “across a component”, “across an electrolyser board” or “across a fuel cell board” refers to from one side of the component to the opposite side of that board, perhaps along the length of the board, or along the breadth of the board. This may be referred to as laterally across. Board and component may be used herein interchangeable to refer to a board or component for an electrochemical device. Reference herein to “active area” refers to the areas of a board or component which in, above or below, an electrochemical reaction may take place, for example the MEA or cell area.

[0074] As an example of electrochemical device which can benefit from the herein described inventions is a fuel cell equipped with PEMs, including HTPEMs. This design can also benefit electrolysers, for example AEM electrolysers.

[0075] Multiple electrochemical components or boards may be connected in series in a stack of boards. For example, fuel cell or electrolyser boards may be stacked up and connected in series.

[0076] Herein are described planar arrays of MEAs connected in series so that the conductive path may be arranged laterally across the series of MEAs in the electrochemical device board. These electrochemical devices contain boards which are engineered to comprise a defined number of individual co-planar MEAs connected in series to achieve an increased voltage compared to previous designs.

[0077] In the planar series of MEAs / cells across an electrochemical board, MEAs / cells can be isolated from each other by removal of conductive material, so gaps, or / and by utilising insulating material such as pre-preg, or other insulant polymers or composites to achieve intra-board (within the same board) isolation. There is intra- board isolation of MEAs, aside from the connections described above to connect one MEA or cell to the next in series. Increasing the number of MEAs connected in series within the electrochemical device alters the overall current and voltage output, so that the fuel cell can match the current and voltage requirement of the load it is connected to, or an electrolyser can match the current and voltage profile of the source of its power.

[0078] This can obviate the need for a DC / DC, rendering the balance of plant simpler and cheaper, as the fuel cell stack can be tuned to provide the same power output whilst targeting specificcurrent and voltage to match the needs of the application is powering. Similarly for an electrolyser, engineering the device to be able to receive power with specific current and voltage characteristics allow the device to match the current and voltage profile of the source of power, such as renewable energy like solar and wind predominantly at low voltage, but also from batteries or the grid which operate at much higher voltage, reducing the need of a DC / DC to modulate the current and voltage intake.

[0079] These arrangements provide the lateral conductive path across a single board, with an electrically insulating layer present. Upwards and downwards electrical connections above or below the first and last (or end, or not central / in-between in the event three or more MEAs in series are envisaged) MEAs of the planar array of MEAs are also described. As described herein, MEAs / cells can be electrically isolated vertically from the MEA / cells of adjacent boards, i.e. those boards above and below a component, in a z direction. When there are multiple cells in series in a board, the end cells are not isolated from the cells of adjacent boards upwards or downwards in the stack, so that these end cells can be utilised to arrange the conductive path through the stack. This is inter- board isolation, isolation of adjacent boards. This arrangement of MEAs insulated from adjacent boards, but electrically connected in certain places, ensures the provision of a conductive path up and down a stack of electrochemical boards combined with lateral movement across a board. This could be used for example to provide power to electrolyser boards or for fuel cell boards to power a load.

[0080] As used here, “vertically aligned” and “partially vertically aligned” refers to something found above or below an area or region, e.g. an MEA or a cell. There may be full or partial alignment. This may be something positioned along the vertical axis, or arranged in a straight vertical formation or stacked above or below. The whole means may be above or below the area in question, or the alignment may only be partial, and part of the means is not above or below the area in question whilst part is.

[0081] This arrangement provides a conductive path laterally across a board, and upwards or downwards in a stack within a portion of the active area of the board in a zone in at least partial alignment with the first and last MEAs of the planar arrangement of MEAs. In previously described arrangements, conductive path has been provided from the MEA via PTHs, to a contiguous external copper surface, then to the perimeter of the board, and then to adjacent electrochemical boards through inter-board connectors allocated within spacers, or external electrical connectors such as cables. This maybe be possible when the currentis small, but the larger the current the larger the interconnecting conductive region has to be to minimise resistance. Board designs are driven by the constant demand to increase power density, which requires the maximum possible area, within a board, to be used for the electrochemical reaction. Therefore, the board edge is often very narrow. Previous designs adopted longer travelling conductive paths to connect adjacent boards in a stack. If this was used in the present arrangement the resistance would result in a large voltage drop. The present arrangement reduces voltage drop across the boards / boards within the stack by eliminating the need for additional connectors, or further PTH architectures outside the active areas, greatly improving designs. Less connectors equates to a gain in the total active area of the boards, eliminating the need for inter- board aligned plated through holes within spacers.

[0082] Providing a large active area, whilst simultaneously building-up the voltage without increasing the size of the stack is important to achieve the required power density.

[0083] The conductive path may be described in terms of axis or x, y or z directions. The conductive path can be in the Z direction up and down a stack via the first and last MEAs in the series of planar MEAs, whilst also being able to move in the x or y direction (depending on MEA arrangement) across an insulating electrochemical device board, from one MEA in series to the next. This may represent a conductive path, as would be understood by a person of skill in the art. A conductive path may refer to an average of the multiple conductive paths across a whole board, representing an overall conductive path or current flow.

[0084] Benefits of utilising insulating layer, such as FR-4, in electrochemical device boards or components have been described previously for example WO 2023 / 052789 and WO 2023 / 099877, incorporated by reference herein. But, due to the nature of the insulating layer, management of how the conductive path can be arranged through electrochemical devices utilising stacks of boards / components can be a challenge.

[0085] In an electrochemical device stack, all boards will have all anodes on one side of the membrane or the multiple membranes, and all cathodes on one side of the membrane or the multiple membranes. Each membrane can be in itself made up of several layers or membranes. Then, the boards will be stacked so that cathodes face anodes of adjacent boards. They do not touch, multiple layers are placed between them. But the stack is arranged in a cathode-anode-cathode-anode configuration, all the way up or down the stack. The inter-board connectors require the use of insulating means between the cells within the boards, to ensure that the electrical connection between the boards when stacked is aligned.Misaligned connections could result in higher resistance within the board, shorting and stack failure. Insulating means are also required between boards within the stack, in a cathode facing anode configuration, otherwise there could be alternative and undesirable conductive paths in the z direction through the stack and in the y direction through the boards and then through the stack via the last cell in series within the board, potentially shorting the system. The MEAs may be described as central MEAs and first and last MEAs, or central and end MEAs. There could be at least two MEAs connected in series on a single board. There may be multiple MEAs connected in series on a single board, with a first MEA, a last MEA and multiple central MEAs. The first and last MEAs may be described as the end MEAs, compared to the central or in-between MEAs. First, last end etc refer to in the series of MEAs, regardless of how the MEAs are physically arranged on a board.

[0086] This can be seen in Figure 1 , where two boards for an electrochemical device are stacked on each other and aligned. Each component has three cells, Cells 1 to 3 are highlighted for the upper component. Conductive lands and fluid flow paths between them as described above are present in the conductive layers either side of the insulant core. As used therein “insulant core” has the same meaning of “insulant layer”

[0087] Here, a planar array of membrane electron assemblies (MEAs) is connected in series, each MEA comprising at least one anode and at least one cathode arranged on opposite sides of a single ion permeable membrane for all MEAs in the planar array. A single ion permeable membrane can comprise several layers and / or several membranes. All anodes are arranged on one face of the planar array of MEAs and all cathodes arranged on the other face of the planar array of MEAs. Here the planar array of MEAs comprises three MEAs, a central MEA - cell 2 - a first MEA at one end of the planar array of MEAs - cell 1 - and a last MEA at the other end of the planar array of MEAs - cell 3.

[0088] Also shown are boards above the MEA - anode and cathode plates or boards (two boards within a board) comprising insulating core / layers, opposing conductive layers and fluid paths between electrically conductive lands as described for boards herein.

[0089] Here, the anode plate and the cathode plate comprise an insulating coating to vertically electrically insulate the central MEAs -cell 2- of the planar array of MEAs from anything above or below the MEA, i.e. from any vertically adjacent boards above and below the boards in the stack. The insulating coating stops any conductive paths vertically directly from the central MEAs shown in Figure 1. Here just one central MEA is shown, but there may be multiple, and all central MEAs of the planar array of MEAs should be electrically insulatedfrom the vertically adjacent boards above and below the board in the stack. An inter-boards isolation between cells is achieved via the use of an insulant material coating or barrier such as a solder-mask. This might also be achieved by other insulating means, such as a further insulating layer, or in certain embodiments the insulating core of the anode and / or cathode plates may act to insulate the MEAs / cells vertically from MEAs in other electrochemical boards . Whilst this layer would isolate the lands of one board from the adjacent one in the stack, the lands would still be electrically conducting within the board and lateral conductive paths would be provided across a board, thanks to the means providing a conductive path through the insulating layers which act to connect multiple lands, as described above.

[0090] As an example, looking at the top of the two boards shown, the anode of cell 3 at one end of the planar array of MEAs can be electrically connected to a cathode of a downwards vertically adjacent boards in the stack. There is no insulating coating on those specific lands of that (fourth) conductive layer, and non on the equivalent below lands of the (second) conductive layer of that board, so there an electrical connection can form between the two lands / boards / last and first MEAs. The arrows 7Z shows the conductive path down from one board to another.

[0091] Equivalent lands of the top (second) conductive layer of cell 1 of the same top board also do not have the insulating coating, so there an electrical connection can form between the equivalent aligned lands on an above board (not shown). The arrow 7Z shows the conductive path down from the above board to this board.

[0092] The horizontal arrows 7Y represent the lateral conductive path across the two boards shown, which would move as described for the above embodiment: lateral movement via the architecture of conductive lands and conductive means through the insulating layer. Arrow 7Y is shown across the membrane, but this is just representative of overall lateral movement, there would not actually be a current laterally across the whole board through the membrane. The inter-boards isolation between cells combined with specific conductive means provided between specific parts of the electrochemical boards provides a conductive path from the first MEA in the series along the board to the last MEA in the series.

[0093] The first and last MEAs of the planar array of MEAs cannot be uninsulated in both directions, there must be a conductive path in one direction for each MEA to ensure a conductive path through a stack of boards; there must be a directional insulation of the MEAs. The first and last MEAs must be insulated in a different plane to each other. Figures 2a and 2b show this simplified with 900 representing boards, insulating areas 902 and 904 and conductive areas910 and 912, arrows 930 representing the conductive path upwards or downwards and arrows 940 representing the conductive path laterally across boards. The conductive path 940 is arranged horizontally along the planar array of MEAs, and vertically up and down 930 the multiply stacked boards but only upwards or downwards via the end MEAs of the planar arrangement of MEAs. Therefore, there is a conductive path from one board to another within the active area of the board, with the above noted benefits.

[0094] These boards are engineered to comprise a defined number of individual co-planar MEAs connected in series to achieve an increased voltage compared to previous designs. Two are shown represented in FIG 2a by two squares, representing a first and last MEA, or a first and second MEA, but there may be more and in various arrangements as described herein. Figure 2b shows three squares, representing a first, a central and a last MEA in series. Or central and end MEAs, or first, second and third MEAs, various nomenclature may be used. The insulating means may be an electrically insulating coating, which may be solder masks, etch-resist, photo-resist, conformal coating, other coatings, such as resins normally used in the PCB industry in various manufacturing stages to protect and / or isolate exposed conductive surfaces form harmful operating conditions such as water or other environmental agents. Examples of such coatings are solder masks such as Imagecure®, Carapace® EMP110 or TAIYO PSR-4000 CC01 SE, conformal coatings may comprise acrylic polymers, epoxy resin or silicon resin dependent on the physical-chemical environment to which they will be exposed in the electrochemical device. Coating available in the PCB industry are normally well above the requirement necessary, both for insulation resistance and for the Dielectric Withstanding Voltage (DWV). Such material may be 3-100 pm thick - the range will depend on the insulant coating utilised.

[0095] If an electrically insulating coating is used, to ensure thickness conformity of boards, if needed, further conductive material may be located in the portions of the board to provide the conductive path. This might be a sheet or layer of material, the same thickness as the insulating coating, material or layer. This might be a further electrically conductive coating, solder conductive paste, carbon paste, conductive lacquer or the electrically conductive layer in that part of the board may just be thicker to compensate for the additional insulating material or layers between the adjacent boards in the stack. This further conductive material might be additional copper plating, a sheet of carbon, copper, or other such conductive material.

[0096] There may be a single layer or component between adjacent boards which comprises boththe means to electrically connect MEAs of one board to MEAs of an adjacent board and the means to vertically insulate the MEAs from the adjacent board. In a stack of boards, any pair of “adjacent boards” may have such a layer or component between them. The layer will have correctly aligned conductive regions and correctly aligned insulating regions. So instead of using a coating i.e. a solder-mask to isolate a portion of the board, the means to isolate portions of a board may be a layer of or other such shaped nonconductive or insulating material layer between the relevant conductive areas of adjacent boards. For this purpose, for example, Kapton®, Mylar® or PEN films can be used, depending on the application and the temperature ranges experienced by the electrochemical device. The layer may have conductive regions vertically aligned with the end MEAs of the planar array of MEAs, so the first and last MEAs may be electrically connected within the active area of the first and last MEAs to equivalent MEAs above and below the board in question. The layer may be a porous transport layer, comprising a conductive transport layer and an insulating transport layer. Such transport layer could provide a flow field for the Heat exchange fluid, and the conductive part of the transport layer being actively part of the conductive layer on a side of the insulating layer. The porous transport layer may be for example a mesh, felt, foam or sinter layer.

[0097] The electrochemical boards may comprise a cathode plate and an anode plate which sandwich one or more MEAs. Both of those anode and cathode plates comprise an insulating layer between two conductive layers.

[0098] In previous designs, the insulating layers of the cathode plate and anode plate had fluid flow paths for reactant fluids within. But, in the designs described herein, the fluid paths for reactant fluids may be within or part of the conductive layers on the boards. Other than for the apertures in the insulant core to allow the reactants to flow from the manifold to the fluid path, all, or substantially all, or the majority of the fluid flow paths may be in located only in the conductive material, not in the insulating / dielectric core.

[0099] As described herein, boards have fluid paths in the conductive layers on the insulating layers. These could be reactant fluid paths to supply reactant to an MEA. The boards may also comprise heat exchange fluid paths at least partially located in the conductive layer on the opposite face of each insulating layer to the conductive layer where the reactant fluids are located. Or the heat exchange fluid paths may partially be in an additional component or spacer between the boards.

[0100] Any reference to a conductive layer herein does not necessarily mean a contiguous layercovering the whole face of an insulating layer, those may just be a partial layer or multiple partial layers on an insulating layer. These conductive layers may have fluid paths through their full depth, so down to the insulating layer. These paths are gaps between the conductive material “lands” and these gaps maybe arranged to create fluid paths geometries. The conductive material may not extend to the edge of the insulating layer, and therefore the conductive layers may just be partial layers across an insulating layer. The fluid pathways in the conductive material may only be partially through the conductive layer, so that the walls and the floor of the fluid path are all made of conductive material. This may be wholly or partially along the fluid flow path. A structured field flow pattern may be defined in the outer surface of the conductive layer, the structured flow field pattern or flow path pattern defining one or more fluid channels.

[0101] Referred to herein are “lands”, which are the material between those fluid paths found in the conductive material. These lands are the remaining conductive material after the conductive material has had the fluid paths formed in it, for example etched in it. Or the lands may be deposited, so fluid paths are formed around or between such lands. These lands may be partially or fully conductive material, preferably heat and electrically conductive. Lands may be, but are not necessarily, planarly electrically insulated from each other. These lands may be electrically isolated from each other unless further means to connect them are added, for example an architecture of conductive means through the insulating layer, and a means on the other side of the insulating layer to provide the conductive path laterally. Lands may have conductive material between them and may not be electrically insulated from each other, a conductive path may form across the whole conductive layer with lands in. This may be when the fluid flow paths in the conductive layer are not through the whole conductive layer or are shallower / less than the full depth of the conductive layer.

[0102] Another way to define fluid flow paths in conductive layers may be to say that a structured field flow pattern is defined in the outer surface of the conductive layer, the structured flow field pattern or flow path pattern defining one or more fluid channels. Any fluid flow path as noted herein may be defined in this way.

[0103] The insulating layers described herein may have no reactant or heat exchange fluid paths in the main body of the insulating core. Or, the majority of the flow path may be in the conductive layer, with a lesser portion in the insulating core This referred to other than possibly means i.e. manifolds and inlet / outlet holes / apertures for the reactant and heat exchange fluids to enter or leave the boards. Those means are outside the active area ofthe electrodes, and do not supply reactant directly to any possibly adjacent electrodes or a diffusion layer adjacent to the electrodes. This represents a design change from the previously described designs, where the reactant and heat exchange fluid paths were described as being present in the insulating core of the fuel cell boards, or were only in the insulating core of the fuel cell boards, for example fully and / or depth routed into those, through both the conductive material and the insulating core.

[0104] The plate, e.g. the anode plate and / or cathode plates (consisting of insulating layers and conductive layers) can be printed circuit boards (PCB), as described herein. PCBs comprising an insulating layer of dielectric material (such as FR-4 epoxy resin) and a conductive material layer (such as copper) plating on one or more of the outside faces, have the advantage of enabling the boards to be manufactured in large quantities and at low cost. A PCB insulating layer of the present invention may comprise multiple PCB layers, referred to as a single insulating layer. Use of insulating materials to construct boards for electrochemical devices also enables these boards and devices to be constructed without a mass or size penalty which may be present using other materials such as metal. They may also have conductive material plated or filled through holes or other means to provide a conductive path through or across the plates. This allows improved control of the conductive path through stacks, as not all of the plates, any present spacers etc need be conductive, like when prior art bipolar plates or conductive metal boards are utilised in prior art stacks. Conductive features, such as through holes, e.g. copper plated or conductive resin filled though holes can be focused in specific areas to allow a high level of control of the current through or across boards or stacks of boards / devices.

[0105] The conductive layer may comprise a conductive material such as copper, nickel, graphite and optionally a conductive coating such as a passivation layer, as described herein. This may also be considered part of the conductive layers, i.e. the conductive material layer comprises a conductive material and a passivation layer on top, which is also conductive. As used herein, conductive material refers to heat and electrically conductive, insulating and / or dielectric refers to heat and electrically insulating. As used herein, ‘board’ may refer to a ‘component’ of an electrochemical device, and vice versa. ‘Insulating core’ may be used herein to describe the insulating layer between the conductive layers. This may be a PCB, or it may be a composite resin layer such as FR4, or a polyimide or any other insulating materials.

[0106] These designs obviate the need for cap layers on individual boards, or between individualboards in a device, to close off fluid flow paths. Cap layers may still be present at the end of stacks to close those end fluid paths. Cap layers were previously required to seal external fluid paths. Here, part of an adjacent board will act to cap or seal adjacent heat exchange fluid paths (when present); or when boards are adjacent to other boards with heat exchange fluid paths in the conductive material layer the adjacent boards may at least partially align with each other so as to form a combined heat exchange fluid path between the boards. Any additional insulating material layers present here between boards in a stack may be utilised as part of the lateral conductive path across a board, not necessarily to close off fluid paths as previously described.

[0107] Joint, aligned, negative space fluid paths formed between two boards to host the heat exchange fluid may be referred to as negative space layers or paths, where the heat exchange pathway is formed in the negative space between two boards. These may offer space saving over other arrangements, because the fluid path is formed in the conductive layer comprising a metal rather than in the insulating layers themselves. Boards and devices may be thinner as a result, particularly because the insulating core can be much thinner not containing any fluid paths and no cap layers may be needed to contain the fluid. The conductive areas may have a thin layer insulating material on top of them. The layer or coating of insulant material on the top of the lands insulates the lands of one area of one board from the lands of the corresponding area of the adjacent board in the stack. This layer may also act to protect the conductive layer underneath, often metal, from corrosion, and to bestow to the flow paths walls and floors a smoother hydrophobic surface which can improve the removal of unwanted residual water, which could block the fluid paths. Or, if electrical conduction between these two areas may be beneficial, it is left.

[0108] The boards and electrochemical device designs utilising these boards described herein represent a development of the previous designs which utilise insulating layers. These may be in comparison to the designs described for example in WO 2023 / 052789, which is incorporated herein by reference. Electrolysers utilising insulating layer boards are described for example in WO 2023 / 099877, which is incorporated herein by reference, but not with flow paths contained in the conductive layers. The present designs represent a development of those electrolyte designs. Now, fluid paths are within the conductive layers on the insulating cores, rather than having some or all of the fluid paths in the insulating core of a fuel cell boards.

[0109] A thinner electrochemical board pitch, (defined as the thickness of an individualelectrochemical cell, e.g. from the top surface of a cathode plate to the top surface of the adjacent cell cathode plate, including any heat exchange medium, or defined as a repeating unit within a stack / electrochemical device, or defined as the distance between two bipolar plates (cathode and anode plates, heat exchange fluid space, and MEA and any sealant / gasket in between), resulting from the use of fewer layers and / or thinner layers increases the power density of the individual board and of the electrochemical device overall. The designs described herein thus offer an increased efficiency.

[0110] Fluid paths in the conductive layers allows for the use of a thinner insulating core compared to previous designs, there is no need for fluid paths to be located (e.g. routed) within the insulating core, unless a deeper fluid path than what provided by the thickness of the conductive layer is required, in which case additional thickness can be obtained by routing the insulating core. The conductive layer may be comparatively thicker compared to previous designs. An increased amount of conductive material, coupled with a thinner insulating core, allows for a great control of the thermal properties of the boards and device stacks overall. Greater heat management e.g. a more homogenous temperature allows better understanding and prediction of the temperature across boards and stacks. A higher % of conductive material in contact with the heat exchange fluid path allows for a faster equalisation of the temperature and a further improved design.

[0111] A more efficient heat removal mechanism means a fuel cell stack can be operated at higher overall power density, when it is required to operate at higher current / cm2A higher operating current will increase heat generated within a board, but a more efficient heat management can counter that. A more efficiently regulated MEA prevents or reduces the risk of a thermal runaway and permanent damage to the MEA and to the stack.

[0112] Additionally, having a fluid path formed within the conductive material means the surfaces of the fluid path will be hotter reducing the formation of liquid water droplets resulting from the condensation of water touching cooler surfaces then the temperature of the gas-stream, making the displacement of any water within a reactant fluid path easier. Displacement of water is advantageous because the accumulation of water in the fluid path may cause mass transfer issues when the reactants cannot reach the MEA to perform the electrochemical reaction, resulting in a drop in the performance of the overall fuel cell.

[0113] Previously described fuel cell reactant and heat exchange paths, for example those in WO 2023 / 052789, were created by routing or drilling insulating material layers of the fuel cell boards, fluid paths were not solely or majorly in the conductive layers either side of theinsulating core layer.

[0114] In the present invention the formation of the fluid path in the conductive layers can be achieved by etching the metal layer in a specific design, to favour the diffusion of the fluid within a chosen geometric pattern to achieve a specific pressure drop, reactant fluid distribution, product fluid and heat removal within the electrochemical board and or the electrochemical stack, ensuring all parts of the board are serviced. Copper etching is used in the PCB industry to create circuitry on an electric board, making sure rules of creepage and clearance are respected to avoid any shorting. Here, metal etching is instead used to engineer a geometrical pattern of voids, flow-altering obstructions and distribution features to enhance the thermomechanical properties of the fluid. Such features are tailored to the requirements of the reactant or heat exchange fluid. Alternatively, conductive material may be deposited on the insulating material to form the desired path patterns.

[0115] Having the fluid pathways in the conductive layers means that varying path thicknesses can be also created, for example part of all of the fluid path may be defined by three conductive surfaces, where the pathway floor comprise some metal or any other conductive material which alters the depth of the fluid path in specific locations, comprising have a conductive material floor / bottom.

[0116] Having the fluid pathways in the conductive layers means introduction of in-path features without the limitation of having a mirror-negative feature on the opposite side of the board (as in prior art metal stamped-out plates) in the fluid path. These designs are made possible by the present invention because the two conductive layers are independent from each other, as they are separated by the insulating core, and therefore can be treated independently. Metal fuel cell boards are typically stamped to produce flow field designs, which results in negative / positive flow pathways design on the sides of a metal board. When flow paths are stamped in metal plates the pathways must mirror, repeat or complement each other as a result of the manufacturing process. Further, in the designs described herein, the flow pathways on opposite faces of the same boards can have different pathways, e.g. different pathway depths or flow field designs. The fluid paths on different faces of the layers described herein can have a different depth or pathway direction and ramification than those on the other face of the same board.

[0117] Because PCBs comprise insulating material, unlike metal or graphite-based fuel cell boards of the prior art where the whole board is conductive, the fuel cell boards described herein can be designed to ensure the conductive path is only provided in specific locations, forexample via plated through holes, conductive material (e.g. copper plating or connective zones between cells) in selective areas of the PCB board, or electrical connection tabs at the edges of the MEAs. These may be designed to maintain a desired current and voltage range, providing a consistent output if desired. This is not technically possible in, for example, metal fuel cell boards. In the present design the use of insulant layers within the electrochemical boards also allows for multiple cells or MEAs in a single board, which would not be possible in metal fuel cell boards or metal fuel cell boards utilising insulating spacers between metal fuel cell boards. Metal boards have no means to insulate individual cells within the board and therefore cannot increase the boards’ voltage by connecting the cells in series within the board itself. Multiple cells on a single board have the advantages as described herein.

[0118] Conductivity across an insulating layer can be achieved within a board by a specific architecture of the conductive lands between fluid flow paths etched into a conductive layer, or conductive regions, found on an insulating layer. This combined with means to provide a conductive path through the insulating layer, such as plated through holes (PTHs), provides the lateral conductive path via the overlapping or crossing of the electrically conductive lands or regions on opposite sides of the insulating layers. These features combined may be a means to provide the lateral conductive path across the electrochemical board. The conductive path does not rely on other means, such as the lateral conductivity of a gas diffusion layer if present, or edge of board conductive traces.

[0119] The two conductive layers either side of the insulating layer, being independent from each other permit the design of an architecture to provide lateral or horizontal conductive path across a board which comprises an insulating layer. Due to the nature of the insulating layer, management of the conductive paths through electrochemical devices utilising stacks of boards / components can be challenging. But, by having fluid paths in the conductive layers, previous designs can be improved.

[0120] Previously described are electrochemical device boards and individual plates (e.g. cathode and anode plates) forming such boards having means to provide electrical connections from one surface of a plate or board to the other. These may for example be “plated through holes” (PTHs) or conductive material filled through holes. An electrically insulating material core may require such a means, so that copper faces either side of an insulating layer can be electrically conductive, so that a conductive path can be formed from the MEAs via electrical connections through the electrochemical device stack, and electrical power isoutputted from the electrochemical device. But now, the arrangement of these conductive means through the insulating layer in combination with the conductive lands between fluid paths of the conductive layers can be utilised to improve the lateral conductive path along electrochemical device boards. This has not been described previously.

[0121] Figure 3 shows how conductive lands on electrically insulating core can provide a conductive path laterally across a board for an electrochemical device.

[0122] Here, lands 50, 51 have fluid paths 52, 53 between them. Two lands 50 with two fluid paths 52 between them in a first conductive layer are labelled, but multiple are visible across the board. Further lands 51 with fluid paths 53 between them in a second conductive layer are labelled, but multiple are visible across the board. An insulant core layer 160 with two conductive layers either side is shown. Both conductive layers have lands 50, 51 and fluid paths 52, 53 between those lands 50, 51. Fluid flow paths 52, 53 are formed or found in the conductive material of the conductive layers. The fluid paths 52, 53 may be through the whole body of the conductive layer. The lands 50, 51 and paths 52, 53 are laterally spaced across the insulating layer 160. If the board is for use with an MEA 1001 as shown here, fluid paths 53 will be for a reactant at the MEA, i.e. a fuel or oxidant fluid, and fluid paths 52 will be for a coolant on the opposite side of the board. A single (cathode or anode) plate is shown above the MEA 1001 layer is shown here, an equivalent (cathode or anode) plate will also be below in operation.

[0123] Electrically conductive lands 51 located above an MEA layer 1001 will provide a conductive path / transport current from the MEA 1001 on the anode side of the MEA 1001. This conductive path can continue along the lands 51.

[0124] Lands 50, 51 are connected to lands on the other side of insulating layer 160 by means to provide a conductive path through the insulating layer 160, here shown as PTHs 120, 122. The cutaway of the board makes these visible, they otherwise would be hidden from view. Cutaway 1C shows a such a connecting means as a filled through hole, but this may be any means to carry current through an insulating layer as described herein.

[0125] Multiple electrically conductive lands 51 in the first conductive layer and multiple electrically conductive lands 50 in the second conductive layer partially align or overlap on opposite sides of the first insulating layer, or through the first insulating layer. As is also visible in FIG 3, the same multiple lands in the first conductive layer 51 and the same multiple lands 50 in the second conductive layer also partially do not overlap or align on opposite sides of the first insulating layer, due to the flow path or land geometry / design.Cutaway 1A shows possible conductive path from the MEA 1001 through PTHs 120 from one land to another, aligned through the insulating layer 160. Arrows on each land 50 show conductive path along these lands 50.

[0126] PTHs 122 connect the same land of one conductive layer with a different land through the insulating layer 160, due to the now different alignment or overlap of the lands through the insulating layer 160. Two of those are labelled in FIG 3. This is shown more closely in cutaway 1B, showing conductive paths from the MEA 1001 through PTHs 122 from one land to another, unaligned through the insulating layer 160, land on the opposing side of the insulating layer 160.

[0127] Those means 120, 122 provide conductive paths through the insulating layer may be the same type of means (e.g. PTHs, filled through holes), but just positioned to connect different lands 50 through insulating layer 160.

[0128] Herein, at least a first of the overlapping electrically conductive lands 51 in the first conductive layer and a second of the overlapping electrically conductive lands 50 in the second conductive layer are electrically connected by a first electrically conductive means 120 through the first insulating layer 160 at a point of the electrically conductive lands 50, 51 aligning / overlapping. Further, at least a second electrically conductive land 50 in the second conductive layer is electrically connected by a second electrically conductive means 122 through the first insulating layer 160 to a further electrically conductive land 51 in the first conductive layer which partially overlaps with the second electrically conductive land 50 in the second conductive layer on opposite sides of the first insulating layer 160. This is a different land to the first land in the opposing conductive layer.

[0129] Thus, the electrically conductive lands and the electrically conductive means through the first insulating layer are arranged to provide conductive paths laterally or horizontally across the electrical board. Here, the large horizontal arrow labelled 1 D shows conductive paths across one side of an MEA of this electrochemical board.

[0130] The electrically conductive lands 50, 51 in the conductive layers are separate and horizontally insulated from each other, or insulated from each other than by the conductive means through the insulating layer. The lands may be described herein as offset / separate / electrically insulated from each other. Lands may be described as regions, zones or areas and may be of varying thicknesses of widths. They may be of a conductive material such as copper described herein. They may have protective coatings such as passivation layers, as described herein.Conductivity across an insulating layer can be achieved by a specific architecture of the conductive lands between fluid flow paths etched into a conductive layer found on an insulating layer. This combined with means to provide conductive paths through the insulating layer allows for lateral conductive paths via the overlapping or crossing of the reactant lands through the insulating layer. The conductive paths do not rely on the lateral conductivity of a gas diffusion layer if present. Lateral conductive paths are provided across the first insulating layer and board from the one electrically conductive land of the first conductive layer to the second / further electrically conductive land of the first conductive layer via the lands of the opposite / second / other electrically conductive layer.

[0131] Whilst electrically conductive lands overlapping or running parallel may have been previously described, not previous described is a specific architecture to ensure the lateral conductive paths across a board. In previously described arrangements, any arrangement of PTHs and copper surfaces would not act in a coordinated manner to provide lateral conductive paths across a board. Conductive paths may be provided from the MEA via PTHs up to a contiguous external copper surface and then, to the perimeter of the board and may reach the adjacent MEAs via cross-board PTHs. This maybe be possible when the current is small, but the larger the current the larger the interconnecting region have to be to minimize resistance. Board designs are driven by the constant demand to increase power density, which requires the maximum possible area for the electrochemical reaction. Therefore, the board edge is often very narrow. A longer conductive path to interconnect two adjacent co-planar MEAs is needed in previous designs, resulting in a voltage drop due to the resistance encountered. Also, relying on using solely the GDL for lateral conduction is not desirable because of the much lower conductivity of carbon or other GDL materials, compared to the materials which can be used for the conductive layers described herein, such as copper. This further allows a voltage increase compared to any designs which might rely on GDL conductivity.

[0132] Because of the use of insulating materials combined with conductive regions (e.g., lands), a greater level of control over the conductive paths across boards and through a wider stack of boards can be achieved. Preferential conductive paths can then be designed.

[0133] To provide lateral conductive paths, at least one land or conductive region can have two different points along its path overlap with two different, otherwise electrically insulated from each other, lands on the opposing side of the insulating layer. A conductive path will be formed at those overlap points through the insulating layer. The conductive regions or landson the opposite sides of the insulating layer may be offset from one another, for example by using wavy land designs, “out of phase” designs, “asymmetric” designs of lands on opposant faces, non-straight designs, non-parallel designs, angled designs. Ensuring one land or conductive region overlaps with two or more lands positioned further toward the edge of board, combined with means to conduct through the insulating layer at that point, provides lateral conductive paths. This can be seen for example in Figure 4 and is described in more detail later related to that.

[0134] Or, lands of one conductive layer can overlap with conductive regions or just the conductive layer on the other opposite conductive layer, i.e. a contiguous copper surface or embodiments when the fluid flow paths do not go through the whole conductive layer. This can be seen in for example in Figures 5 and 6 and is described in more detail later related to that.

[0135] Flow paths and thus lands may have different designs, as long as regions overlapped in a manner to allow the herein described lateral conduction. Various number of lands and fluid flow paths are visible in the figures. However, any number could be utilised to provide lateral conductive paths across the insulating layer / board / component. For example, there could be 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20 or more separate conductive lands and fluid flow paths in each conductive layer.

[0136] There may be different numbers of flow paths in the two different conductive layers of the same board. It may be that it is that difference in number of paths or lands which creates the asymmetry which results in lands overlapping though the insulating layers at different points, allowing the lateral conduction across the insulating layer / board.

[0137] Various channels / fluids paths / flow field patterns and entry and exit points on a plate to the plate will be known to those of skill in the art. For example, fluid paths can be serpentine, circular, wavy or linear substantially straight (linear) across a plate. There herein described fluid paths can have more advance designs and complicated geometries. Among these for example are serpentine and parallel flow fields where narrow channels could be used to deploy high velocity mass flows to effectively remove water accumulation; these can be with or without the addition of 3-D features, introducing flow restrictions or flow directional changes, using different radii, to further perturbate the flow at defined intervals, to alternate an increase in mass flow velocity with a change in pressure drop. Convergent flow fields, with tapered channels dimensions have also been used in industry to introduce a useful pressure drop between inlet and outlet to maximise the efficiency of the electrochemicaldevice board.

[0138] These herein arrangements of paths, lands and conductive regions so that there is lateral conduction through these conductive layers has the particular advantages of not needing to rely on other means to provide lateral conductive paths across a board, for example adjacent GDL conductivity, potentially allowing the use of better / alternative GDLs (the conductivity of the GDL is not sufficient to provide efficient conductive paths through a stack of electrochemical boards). This is as described herein.

[0139] This permits exploration of the most beneficial fluid paths and cell designs in an electrochemical component, widening as much as possible the active area to have the highest current production, whilst simultaneously building-up the voltage, allowing a higher number of co-planar cells connected in series, without increasing the size of the stack, which in the case of a fuel cell, would otherwise penalize the power density.

[0140] Figure 4 shows an example of how lands may overlap on the other side of insulating FR4 core / layer (exemplary material) with PTHs 120 through the insulating layer 160. Here a lateral electrically conductive path is shown from the membrane, anode and GLD to the lands adjacent to the GDL, across insulating layer 160, from position 1 to position 4 across the plate.

[0141] The lateral conductive path across a board / insulating layer / plate may use lands between reactant channels on the side adjacent to the MEA (the anode or cathode side, conductive layers facing the MEA), to just a layer with no flow paths on the other side of the insulating layer. This conductive layer may just be a layer of conductive material with no flow paths in it, a contiguous layer. This is represented in Figure 5. This represents an alternative conductive path laterally across the electrochemical board. If present, flow paths such as for a heat exchange fluid may be in a further layer, i.e. a further insulating layer or a combined insulating and conductive layer as described herein. This is further to the anode and cathode plates as described herein. This may comprise conductive regions to form part of the conductive path laterally across the board. These conductive regions may be part of a conductive layer on the insulating layer and that conductive layer may have the heat exchange fluid paths formed in that conductive layer. This may be when there are no fluid flow paths formed in the outer conductive layer of the anode or cathode plate, where just a conductive layer forms part of the conductive path across the board, but does not comprise heat exchange fluid paths. This may be for the anode plate, cathode plate, or both.

[0142] Figure 6 shows an alternative arrangement. Here, the fluid pathways are in the conductivematerial but are only partially through the conductive layer, so that the walls and the floor of the fluid path are all made of conductive material. This may be wholly or partially along the fluid flow paths. A structured field flow pattern is defined in the outer surface of the conductive layer, the structured flow field pattern or flow path pattern defining one or more fluid channels, here 3 are visible in the outer conductive layer. These flow paths would be for a heat exchange fluid. The “floor” or inner surface of the conductive layer, closest to the MEA, provides the conductive path across the board. This represents an alternative conductive path laterally across the electrochemical board. This is similar to the layer of conductive material with no flow paths in it seen in FIG. 5.

[0143] Two conductive layers on opposite sides of an insulating layer being independent from each other allows for design of an architecture to provide lateral or horizontal conductive paths across a board. This also allows for improved connection between adjacent co-planar MEAs or cells with improved designs to manage a higher voltage output from a fuel cell, or input for an electrolyser.

[0144] Here are described multiple electrochemical cells or MEAs connected in series, planarly in one single board. This may be for example an electrolyser, a board for an electrolyser or a fuel cell. If required, paths for a heat exchange fluid can be provided on the outer layers of the boards, in the outer conductive layers (the inner conductive layers comprising the reactant fluid paths, adjacent the anodes and cathodes).

[0145] The conductive paths described above can be also synergistically utilised to provide conductive paths to the adjacent co-planar MEA. Co-planar MEAs can be isolated from each other by removal of any conductive material, so creating gaps, and by utilising insulating material such as pre-preg to achieve intra-board (within the same board) isolation. These may be found in any of the conductive layers described herein. Regions of the conductive layers above and below each MEA are then planarly insulated from adjacent regions of the conductive layers. This means that adjacent MEAs are electrically insulated from each other, except for very specific connections made between the adjacent MEAs. This allows the herein described increased voltage of such boards.

[0146] Figure 7 shows how conductive lands on electrically insulating core 160 can provide conductive paths laterally across a board for an electrochemical device. Here, lands overlap on the other side of insulating FR4 core layer (exemplary material) with PTHs 120 through the insulating layer 160. Here conductive paths are shown from the membrane, anode and GLD to the lands adjacent to the GDL. Lateral conductive paths can be provided acrossinsulating layer 160, from position 1 to position 4 across the board. Then further, a means to connect the outer lands of one board to the outer lands of another board are shown -125, FIG. 8. This allows connection between the adjacent MEAs represented here. The electrically conductive layers above and below each MEA are planarly insulated from each other, preventing lateral conductive paths at the edges of the MEAs and regions above / below those MEAs. Lateral movement from one cell or MEA to another may be via the lands shown in FIG 7., equivalent to the arrangement shown in FIG. 4, or the outer conductive layers may look like the arrangements shown in FIG. 5 and FIG. 6, with flow paths (or not) arranged like those.

[0147] Figure 8 shows how conductive lands on electrically insulating core can provide lateral conductive paths across a board for an electrochemical device, conductive paths can also be provided between two adjacent cells, CELL 1 and CELL 2, on a single board.

[0148] The same arrangement in CELL 1 as Figure 1 can be seen; for CELL 1 lands 50, 51 have fluid paths 52, 53 between them in two conductive layers either side of an insulating core 160. The lands 50, 51 and paths 52, 53 are laterally spaced across the insulating layer 160. The first insulating layer, the layer adjacent MEA with lands 51 is electrically connected to the MEA.

[0149] CELL 2 is also present here, where lands 60, 61 have fluid paths 62, 63 between them in two conductive layers either side of the same insulating core 160. The lands 60, 61 and paths 62, 63 are laterally spaced across the insulating layer 160. There are two insulating core 160 layers which CELL 1 and CELL 2 are arranged across; they are just shown cut away in this figure. These plus the lands and flow paths may be cathode and anode plates as described herein.

[0150] MEA 1001 is shown here as layer, as these boards are for use with or for arrangement with an MEA. Here, fluid paths 53 and 63 will be for a reactant at the MEA, i.e. a fuel or oxidant fluid, and fluid paths 52, 62 will be for a Heat Exchange Fluid in the other conductive layer(s) on the opposite side of the insulating core.

[0151] On the other side of MEAs 1001 there is also a further equivalent board comprising two conductive layers either side of an insulating core. Equivalent flow paths 62, 63 are located between lands 60, 61 either side of the insulating core. This will have further, third and fourth, conductive layers, with the third conductive layer electrically connected to the MEA. Each cell comprises two insulating core layer areas and four conductive layer areas (two conductive layer areas for each plate, one plate above and one plate below the MEA). Theymay be considered together on a single board as a single insulating core layer and two electrically conductive layers for two cells or considered separately.

[0152] Electrically conductive lands 51 are in electrical connection with the MEA 1001. Conductive paths are arranged along the lands 51. Lands 51 with lands 50 on the other side of insulating layer 160 by means to conduct electrical current through the insulating layer 160, here shown as PTHs 120, 122. The cutaway of the board makes these visible, they otherwise would be hidden from view. Equivalent also happens in CELL 2, where electrically conductive lands 61 are in electrical contact with the MEA 1001. Conductive paths are arranged along the lands 61. Lands 61 are connected to lands 60 on the other side of insulating layer 160 by means to provide electrically conductive path through the insulating layer 160, here shown as PTHs 120, 122.

[0153] Herein, at the overlapping electrically conductive lands 51 , 61 in the first and third conductive layers and the overlapping electrically conductive lands 50, 60 in the second and fourth conductive layers are electrically connected by electrically conductive means 120 through the first insulating layer 160 at points of the electrically conductive lands 50, 51 and 60, 61 aligning / overlapping. A further electrically conductive land 50, 60 in the second and fourth conductive layer is electrically connected by electrically conductive means 122 through the first insulating layer 160 to further electrically conductive lands 51 , 61 in the first conductive layer which partially overlaps with a further electrically conductive land 50, 60 in the second and fourth conductive layers on opposite sides of the first insulating layer 160.

[0154] The arrangement in CELL 1 and CELL 2 individually is the same as for the embodiment shown in Figure 1 , with aligned and not aligned lands to ensure lateral conduction across the board. Thus, the electrically conductive lands and the electrically conductive means through the first insulating layer are arranged so that conductive paths are arranged laterally or horizontally across the electrochemical board, and across both CELL 1 and CELL 2. Here, the large horizontal arrow labelled 5C shows lateral conductive paths across this electrochemical board. This is x-direction where the conductive paths are arranged laterally across the cells of the board.

[0155] In the further insulating layer and conductive layers, the other side of the MEA for each cell, the same lands 60, 61 , fluid paths 62, 63 and conductive means are arranged to provide lateral conductive path across this electrochemical board.

[0156] The MEA layer 1001 may comprise a single membrane spanning the whole board, where electrodes are arranged either side of it to create CELL 1 and CELL 2. Or, there may bemultiple membranes present and each cell present would have its own membrane.

[0157] Co-planar MEAs, comprising at least an anode and cathode pair on opposite side of the membrane, are separate from each other, or referred to “segmented” throughout. One ion permeable membrane can be shared by multiple anode-cathode pairs, or each pair can comprise its own separate membrane. MEAs may also be referred to as ‘cells’ herein. The anodes and the cathodes have a gap between the adjacent anodes or cathodes on the same fuel cell board. The membrane of the first electrode pairs may be divided from the adjacent membrane by a gap or an isolation break, described here. This gap may be filled by an insulating material, for example pre-preg.

[0158] Further shown in Figure 8 are conductive paths from one cell adjacent on a board to another cell.

[0159] Lateral conductive paths via lands adjacent to the MEA, here lands 51 and 61 across the board are described above. Then, through board electrically conductive means 125 can electrically connect the two outer conductive layers of the board, the second and fourth conductive layers. A third type of electrically conductive means, 125, passing through the first insulating layer, through the second insulating layer and if present at this point, the membrane. Effectively, so that the first conductive layer is electrically connected to the third conductive layer via the through board electrically conductive means 125, as illustrated in the cutout 5A and 5B. The outer conductive layers of the two plates are connected by these through board electrically conductive means.

[0160] Here, the through board electrically conductive means 125 are shown through the two insulating layers and the membrane. In some embodiments, the first conductive layer is electrically connected to the third conductive layer by a first through electrochemical board electrically conductive means. This may not need to pass through the insulating layers and would just pass through the membrane if present. Because the electrochemical boards comprise insulating layer components, these allow the design of specific conductive paths across the board.

[0161] The conductive path between two adjacent co-planar cells from the cathode of one electrode pair to the anode of the adjacent electrode pair is provided by intra-cell conductive means such as PTHs, or a strip of metal, a portion of copper wires, or metal sponge / foam, a porous sintered element or solder conductive paste, or silver lacquer for example. This may be any conductive material that is malleable enough to ensure as much contact as possible between the copper surfaces of the HEF lands to guarantee good conductivity betweenanode and cathode of adjacent electrodes pairs. This conductive path is as arranged in the z-direction, in contrast to the x-direction lateral conductive path across the MEAs / cells of the board.

[0162] To create the combination of lateral, x (or y depending on perspective / orientation) direction, and between cell, z, direction conductive paths, isolation breaks can be utilised in the design of these boards. The lands on each layer may be horizontally electrically isolated from each other so that the conductive paths may be arranged in the x and z direction. This isolation means may be a gap in the lands, a line of insulating material or any means to electrically isolate lands in the conductive layer of one cell from adjacent lands which are part of a second cell. These isolation breaks may be flow paths / channels cutting through a wave or acting to interrupt a wave front of flow channels in correspondence of intra-cell within the board creating isolation gaps to ensure isolation of the cells within the board and minimize shorting. An isolation break in both of the conductive layers, in the coolant lands and in the reactant lands, isolates the lands of adjacent cells from each other. This ensures selective conductive paths in both an X and a Z direction are arranged in the electrochemical stack. This is visible in Figure 9, where the isolation breaks 71 and 72 are highlighted. Here insulating cores 160 have electrically conductive layers either side, comprising flow paths 52, 53, 62, 63 and lands 50, 51, 60, 61 as described in the earlier embodiments. Conductive means 125 connect lands on the outer layers to each other. Arrows show conductive paths direction. MEA is not shown here. Means to connect lands are also visible through the insulating layers, as these are cut away for the figure. Break 71 is in the upper layer and break 72 is in the lower layer.

[0163] Here, breaks 71 and 72 are flow paths cutting through any flow path design on the board, to or interrupt lands which might have otherwise provided lateral conductive paths across the same electrode plate, rather than to the opposite electrode plate in the adjacent co-planar MEAs. The interruption / isolation of the adjacent MEAs but for the through board interconnection provides only conductive paths down the means 125 to connect the two outer layers.

[0164] In the planar series of MEAs / cells, MEAs / cells can be isolated from each other by removal of any conductive material, so gaps, or / and by utilising insulating material such as pre-preg to achieve intra- board (within the same board) isolation. To achieve this, the region of the conductive layer above the first MEA of the planar array of MEAs is planarly insulated from the region of the equivalent conductive layer above the adjacent or next MEA. The same forthe equivalent conductive layers on the other side of the insulating layer for the plate above MEA, i.e. the layers the other side of the insulating core. The same arrangement will be found for the plate below the MEA, where the equivalent conductive regions of that plate above one MEA are also planarly isolated from adjacent regions. This may be achieved by a gap in the conductive layer, a gap in the lands forming the conductive layer, a line of electrically insulating material or any means to electrically isolate one region of the conductive layer from another region of the conductive layer.

[0165] In previous designs utilising insulating layers, conductive paths would be arranged via plated through holes located at the edge of the cells or active areas of the cells, or edge of the board. Conductive paths would be provided from the MEA to the edge of the board via contiguous conductive material layers, via PTHs. Those conductive paths had limited capacity. The present arrangement instead, using connections in the space between cells, provides a conductive path within the board without the risk of damaging the electrochemical board, where a PTH arrangement at the edge of a board could not. Resistivity is decreased with these conductive path arrangements.

[0166] Co-planar-MEAs or cells in a single board could be arranged in multiple different configurations relative to reactant and heat exchange fluid flow paths, or relative to the conductive paths across the boards. Examples of these can be seen in Figures 10a, 10b, 10c and 10d all show three cells or active areas, representing MEAs. Here some flow paths are shown, which could represent reactant or heat exchange fluid flow paths.

[0167] The reactant and heat exchange fluid paths in the conductive layers on opposite sides of the same insulating layer can have fluid flow directed across the board parallel to each other. This is represented by Figures 10a and 10b. The arrows in 10a and 10b show flow paths for both reactant and heat exchange fluids. Conductive paths are created across adjacent MEAs in the X direction across the board for FIG. 10a, and conductive paths are created across adjacent MEAs in the Y direction across the board for FIG. 10b. Heat exchange fluid may be provided by alternative means so may not necessarily be present in the second and fourth conductive layers, but if present those would be on in the conductive layers on the opposite face of the insulating layer providing the reactant flow paths in the conductive layer facing the MEA. These represented by paths shown and arrows in these figures, but may be in multiple different layers not shown in these simple schematic diagrams.

[0168] Conductive paths between MEAs, laterally across the fuel cell boards, may be provided by various means described herein: combinations of conductive layers or regions of those,lands providing conductive paths across the boards, conductive layers with flow paths formed therein and the floors of those paths providing the conductive path, and connections between adjacent MEAs such as through board conductive means.

[0169] The gaps between adjacent MEAs or cells in the planar array of MEAs may be parallel to the direction of reactant flow in the fluid paths for the reactant and / or the direction of heat exchange fluid flow in the fluid paths for the heat exchange fluid. The gaps between adjacent MEAs or cells in the planar array of MEAs may be perpendicular to the direction of reactant flow in the fluid paths for the reactant and / or the direction of heat exchange fluid flow in the fluid paths for the heat exchange fluid. Or there may be a combination or one of reactant or heat exchange flow direction being parallel and the other reactant being perpendicular to the gaps between the MEAs.

[0170] This may also be described in terms of the direction of the electrically conductive paths between adjacent MEAs in the planar array of MEAs. The direction of the conductive path between adjacent MEAs in the planar array of MEAs may be parallel to the direction of reactant flow in the fluid paths for the reactant and / or the direction of heat exchange fluid flow in the fluid paths for the heat exchange fluid. The direction of the conductive paths between adjacent MEAs in the planar array of MEAs may be perpendicular to the direction of reactant flow in the fluid paths for the reactant and / or the direction of heat exchange fluid flow in the fluid paths for the heat exchange fluid. Or there may be a combination or one of reactant or heat exchange flow direction being parallel and the other being perpendicular to the conductive paths.

[0171] In FIG. 10a the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the reactant fluid paths (which would be in the first and / or third conductive layers) and if present, the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the heat exchange fluid paths (which would be in the second and / or fourth conductive layers). The conductive layers will be providing a conductive path laterally across the board, in the X direction, and here the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the reactant fluid paths in the first and / or third conductive layers and if present, the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the heat exchange fluid paths (which would be in the second and / or fourth conductive layers).

[0172] In FIG. 10b the gaps between adjacent MEAs in the planar array of MEAs in series are parallel to the reactant fluid paths (which would be in the first and / or third conductive layers)and if present, the gaps between adjacent MEAs in the planar array of MEAs in series are parallel to the heat exchange fluid paths (which would be in the second and / or fourth conductive layers). The conductive layers will be providing a conductive path laterally across the board, in the Y direction, and here the conductive path between adjacent MEAs in series in the planar array of MEAs is perpendicular to the reactant fluid paths in the first and / or third conductive layers and if present, the conductive path between adjacent MEAs in series in the planar array of MEAs is perpendicular to the heat exchange fluid paths (which would be in the second and / or fourth conductive layers).

[0173] The reactant and heat exchange fluid paths in the conductive layers on opposite sides of the same insulating layer can have fluid flow directed across the board perpendicular to each other. This is represented by Figures 10c and 10d. The arrows in 10c and 10d show flow paths for both reactant and heat exchange fluids, either could be the reactant or the heat exchange fluid, preferably the flow paths in the X direction are reactant flow fields and the flow paths in the Y direction are heat exchange flow fields, or one of the reactants flow field, for example the oxidant flow field. Conductive paths are created across adjacent MEAs in the Y direction across the board for FIG. 10c, and conductive paths are created across adjacent MEAs in the X direction across the board for FIG. 10d.

[0174] In FIG. 10c the gaps between adjacent MEAs in the planar array of MEAs in series are parallel to the X direction reactant fluid paths (which would be in the first and / or third conductive layers) and the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the heat exchange fluid paths (which would be in the second and / or fourth conductive layers). The conductive layers will be providing a conductive path laterally across the board, in the Y direction, and here the conductive path between adjacent MEAs in series in the planar array of MEAs is perpendicular to the reactant fluid paths in the first and / or third conductive layers and the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the heat exchange fluid paths (which would be in the second and / or fourth conductive layers).

[0175] In FIG. 10d the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the reactant fluid paths (which would be in the first and / or third conductive layers) and the gaps between adjacent MEAs in the planar array of MEAs in series are parallel to the heat exchange fluid paths (which would be in the second and / or fourth conductive layers). The conductive layers will be providing a conductive path laterally across the board, in the X direction, and here the conductive path between adjacent MEAs in seriesin the planar array of MEAs is perpendicular to the reactant fluid paths in the first and / or third conductive layers and the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the heat exchange fluid paths (which would be in the second and / or fourth conductive layers).

[0176] The direction of heat exchange fluid flow in the fluid paths may be parallel to the direction of reactant flow in the fluid paths. The direction of heat exchange fluid flow in the fluid paths may be perpendicular to the direction of reactant flow in the fluid paths. The direction of heat exchange fluid flow in the fluid paths may be perpendicular to the direction of one reactant flow in the fluid paths, for example the oxidant fluid flow, and parallel to the other flow in the fluid path, for example the reductant fluid flow. The direction of heat exchange fluid flow in the fluid paths may be parallel to the direction of the conductive paths between adjacent MEAs in the planar array of MEAs. The direction of heat exchange fluid flow in the fluid paths may be perpendicular to the direction of the conductive paths between adjacent MEAs in the planar array of MEAs.

[0177] The MEAs or cells do not need to be the same size, as described herein, the individual physical characteristics of the different cells or sub-MEAs can be tailored to account for the changes across the board in reactant concentration, pressure etc. Segmentation can allow tailoring of the properties of the MEAs to account for various factors, such as variation across a board. For example, catalyst loading can be adjusted to account for different reactant concentration / consumption moving across a fuel cell board. This can help account for gradient between inlet and outlet reactant concentration or pressure.

[0178] Furthermore, the herein described tailored varied segmentation can reduce the impact of transient events such as those which occur at fuel cell start up and / or fuel cell shut down. Properties of the cells vary across the board for example corrosion resistance catalysts can be used in areas where high potentials are likely to be experienced, or reversal tolerant material could be used where this may occur. Further, segmenting the MEAs on fuel cell boards with varying properties reduces parts of the fuel cell ending up at a relatively low potential during operation. This is beneficial because large variance in potential can accelerate degradation of fuel cell boards. Thus, the fuel cell boards described herein have improved degradation resistance / longer lifespans.

[0179] Embodiments described herein may combine:

[0180] • all flow fields (reactant and coolant) parallel with each other and lands creating these flow fields in conductive layers overlapping in places to create the lateral conductivepaths, for example as visible in FIG. 3, combined with fluid flow fields parallel to the gaps between the MEAs, for example as visible in FIG. 10b;

[0181] • all flow fields formed in the conductive layers but not going through the conductive layers, for example as visible in FIG. 6 and 14, so the conductive path is provided through the body of the conductive layer, combined with fluid flow fields (either just reactant, or both reactant and heat exchange fluid) parallel to the gaps between the MEAs, for example as visible in FIG. 10b; or

[0182] • reactant flow fields formed in the conductive layers but not going through the conductive layers, combined with a heat exchange fluid flow paths in a further layer, i.e. a further insulating layer / insulating and conductive layer as described herein. Further, the first and last MEAs in the planar array of MEAs may have different through insulating layer / plate connections to the central / other MEAs in the planar array of MEAs. When either side of the MEA are plates (anode and cathode plate), each comprising an insulating layer and two conductive layers either side of the insulating layer. The first MEA may have through the outer plate / insulating layer electrically conductive means (e.g. PTHs) to provide a conductive path from the outer conductive layer to the inner conductive layer adjacent the MEA. So, there is a conductive path from the first MEA to an equivalent MEA on an adjacent electrochemical board above. Similarly, but in the opposite way, the end MEA may have through inner plate / insulating layer electrically conductive means (e.g. PTHs) to provide a conductive path from the inner conductive layer adjacent the MEA to the outer conductive layer. So, there is a conductive path from the last MEA to an equivalent MEA on an adjacent electrochemical board below.

[0183] Through board connections, as described herein, provide a lateral conductive path between adjacent MEAs, across the electrochemical board, i.e. from the first MEA to a central MEA and from the central / last central MEA to the last MEA. The whole conductive path would be from an above electrochemical board, along the electrochemical board and to a below electrochemical board. As noted herein, the through board connections to provide the conductive path from one MEA to an adjacent MEA may just be between the two inner conductive layers of the two plates (first and third conductive layers). This would pass through the membrane if present but would not need to pass through the insulating layers of the plate. This provides the lateral conductive path across the board. In these embodiments, the central MEAs would not need connections between the inner and outer conductive layers of the insulating layers, because they are not necessary. The outerconductive layers above the central MEAs are not necessary to provide a lateral conductive path. These regions (vertically aligned with the central MEAs) of the outer conductive layers and inner conductive layers may not need to be electrically connected. In these embodiments, the insulating layers of the anode and cathode plates would act to electrically insulate the central MEAs from the MEAs of adjacent electrochemical boards, because there is no vertical conductive path from the central MEAs provided by electrically conductive means through the insulating layers.

[0184] This may be combined with, for example, all flow fields formed in the conductive layers but not going through the conductive layers, for example as visible in FIG. 6 and 14, so the conductive path is provided through the body of the conductive layer, combined with fluid flow fields (either just reactant, or both reactant and heat exchange fluid) parallel to the gaps between the MEAs, for example as visible in FIG. 10b. The conductive layers above the first MEA and below the last MEA will act to provide a conductive path to electrochemical boards above and below this board. But, conductive layers above and below the central MEAs will not provide any conductive path laterally, it is not needed. FIG.11a is a schematic diagram of one view of an expanded board 200 of an embodiment. A fuel cell board 200 is shown to represent the board, but boards for other electrochemical devices would follow the same structural principles. Fuel cell board 200 is shown expanded for the purposes of this figure, to show the membrane electrode assembly (MEA) layer 103 separated from cathode plate 101 and anode plate 102. The cathode plate may be the first insulating layer between a first conductive layer and a second conductive layer as described herein. The anode plate may be the second insulating layer between a third conductive layer and a fourth conductive layer as described herein. In fuel cell board 201 the cathode plate 101 and anode plate 102 are laminated together with the MEA layer 103, the MEA between the cathode plate 101 and anode plate 102 to form a fuel cell board 200.

[0185] MEA layer 103 shown here, used in this example, comprises three planar MEAs as described in the earlier embodiments. The cathode(s) on the MEA layer 103 face the cathode plate 101a and the anode(s) face the anode plate 102a. In this embodiment the MEA layer 103 is laminated between the cathode plate 101 and anode plate 102, but shown separated / expanded in this figure just to show their presence. The MEA may also include a gas diffusion layer, not shown. This shows just one embodiment of an MEA suitable for use for the embodiments described here. Other MEA designs, shapes, orientations would be known to a person of skill in the art and understood to be suitable with the present embodiments.Cathode plate 101 and anode plate 102 may be printed circuit boards (PCBs), but in embodiments herein could be layers of any insulating material with a conductive layer either side as described herein

[0186] The inner faces of both anode plate 102 and cathode plate 102 (101 a and 102a respectively) have conductive layers comprising the fluid paths between conductive lands, as described in the earlier embodiment. Such layers are coated with a passivation layer to prevent the corrosion of the conductive layer (e.g. the metal) and prevent the poisoning of the MEA. Here, the fluid paths are not located in the insulating layer, but in the conductive layer. Other than for the apertures in the insulant core to allow the reactants and heat exchange fluids to flow from their respective manifolds to the fluid paths.

[0187] The outer faces 101b, 102b of plates 101, 102 are also partially covered in conductive material comprising copper or other metals such as nickel, and optionally a passivation layer, and both comprise the heat exchange fluid paths. As with the reactant flow paths the heat exchange fluid paths are not located in the insulating core, but they are located in the conductive material. The whole heat exchange fluid path is located only in the conductive material and none of it is in any part of the i nsulating / dielectric core.

[0188] Reactants are carried within the fluid paths (for example air, hydrogen) to be supplied to the cathodes and anodes. Oxidant fluids flow only to all of or one or more of the cathodes and reductant fluids flow only to all of or one or more of the anodes of each fuel cell board. Reference herein to ‘oxidant fluids’ refers to fluids that will react at the cathode, oxidants, for example air or oxygen.

[0189] Reference to ‘reductant fluids’ herein refers to fluids that will react at the anode, cathode or electrodes described herein. The MEA layer 103 is located between the anode plate (first insulating layer) 102 and the cathode plate (second insulating layer) 101 so that when the boards are laminated or mechanically compressed / placed together, the at least one first fluid path 111 of the cathode plate 101 is arranged such that an oxidant fluid can flow to the cathodes of the MEA layer 103 and the anode plate 102 is arranged so that the at least one second fluid path 112 is arranged such that a reductant can flow to the anodes of the MEA layer 103. The present arrangement allows effective separation of the reactants for the anodes and the cathodes. Different reactants or electrolytes might flow to or away from the electrodes in different electrochemical devices, but the principles are the same.‘Fluid path’, ‘fluid channel’, ‘flow path’, ‘fluid flow path’ ‘fluidic path’, ‘flow field’ and ‘channel’ may all be used interchangeably herein and may be substituted for one another herein. They all refer to means by which fluids can flow or travel along, down or through. Fluids may be substantially directed, either with or without assistance, along fluid flow paths, channels, or other alternative geometries or the like.

[0190] Reactants may enter one side or corner of the plate and leave via the opposing or opposite side or corner of the plate. Fluid paths are connected to reactant manifolds 105 and 109. Heat exchange fluid paths are connected to heat exchange fluid manifold 107.

[0191] The etching of the fluid paths with the decoupling of the fluid path geometry on opposite sides of the same plate (cathode and / or anode plate) within the conductive layer on both sides of the insulating layer, allows for different fluid pathways on different surfaces of plates, for example one surface of a plate may display one or more serpentine flow path and one face may display parallel flow paths with the addition of several 3-D perturbating features. This will allow the herein described lands overlapping and not overlapping in the desired locations through the insulating layer, to provide conductive paths across the fuel cell boards.

[0192] Manifolds may be drilled into the plates after lamination, or possibly before lamination or compression. The manifold holes are visible in all layers of the fuel cell stacks and individual layers throughout, but not all holes are labelled in every figure. Equivalent holes line up with equivalent holes when plates are stacked. Generally, for all embodiments herein, manifolds of any appropriate size, dimension and shape supply and collect the reactants and heat exchange fluids, or any other relevant substances, into and out of the inlets and outlets of fuel cell boards. Vertical channels up and down fuel cell stacks are connected to manifolds along the two opposed edges of the stack, which supply and collect the reactants, heat exchange fluids (e.g. coolants) etc. to and from boards. These may be drilled or routed into the individual boards before or after lamination to other boards.

[0193] The plates may also have holes drilled for bolting holes, and / or alignment pins can be inserted into these.

[0194] FIG. 11b is a schematic diagram of an opposing view to FIG. 11a of the same expanded fuel cell board 201. Fuel cell board 201 is shown expanded for the purposes of this figure, to show MEA layer 103 separated from cathode plate 101 and anode plate 102.

[0195] Only inner face 102a of anode plate 102 and outer face 101 b of cathode plate 101 are visiblein FIG. 11b. The anode fluid paths are visible on the inner face 102a of anode plate 102. Anode manifold 105, heat exchange fluid manifold 107 and cathode manifold 105 are also visible in FIG. 11b.

[0196] A second set of heat exchange fluid paths can be seen in FIG 11 b (these specific ones not visible in FIG. 11a) on outer face 102b of anode plate 102 connected to heat exchange fluid manifold 107. These supply a heat exchange fluid to the fluid paths on side 102b of anode plate 102. Heat exchange fluid paths may be the fluid paths for a heat exchange fluid as described herein.

[0197] In embodiments herein, heat exchange fluid paths in the conductive layers of adjacent boards may at least partially align with each other, so as to form a combined heat exchange fluid path between the two fuel cell boards. The conductive layers may comprise any combination of copper, copper with an additional metal coating such as Nickel, ENIG or any conductive polymeric and or carbon based conductive passivating coating.

[0198] Fluid paths formed between two boards may be referred to as negative space fluid paths or a negative space layer, where the heat exchange pathway is formed in the space or void between two or more boards. The utilisation of this space may offer space saving over other arrangements, because the fluid paths are formed in the conductive layers between two boards, normally used only to provide conductive paths through the stack, therefore exploiting a synergic effect of this new cell structure. Symmetrical designs of heat exchange fluid paths on adjacent boards may be used, which can be advantageous because it enables easier alignment of the conductive means such as PTHs, making the electrically conductive paths shorter and therefore reducing the electrical resistance within the structure and the consequential additional heating of the conductive layers.

[0199] While fluid paths may be fully aligned, fluid paths may be partially aligned so not all of the path overlaps. This may vary along the flow paths. Parts of equivalent flow paths on adjacent boards may not align at all. For example, the alignment may only occur within the active area of the MEA. Additionally, or alternatively, flow paths may be partially unaligned or just partially aligned, flow paths on adjacent boards may only partially align with each other. Part of the flow path may overlap with the conductive material between the flow paths on the adjacent board (termed lands herein).

[0200] Figure 12a shows the outer face 102a of cathode plate 102 of this embodiment. Cathode manifold 105, coolant manifold 107, anode manifold 109 are all shown. Also shown is a wavy land 50 and fluid path 52 design. Fluid paths 52 are located between electricallyconductive lands 50. Lands are separated into three zones, areas or for three cells by two isolation breaks 71. These are fluid paths running parallel and horizontally in the x direction so as to break the otherwise wavy path design. PTHs connecting the lands through the insulating layer to equivalent lands the other side of the insulating layer are visible. This allows for the lateral conduction across the plate as described above.

[0201] Figure 12b shows the inner face 102b of the cathode plate 102 of this embodiment. Fluid paths 53 are located between electrically conductive lands 51. PTHs are visible here on the lands 53. The flow paths here are parallel flow paths, complimenting the wavy and offset through the insulating layer flow paths visible in Figure 12a. These flow paths will supply an oxidant fluid to the MEA. There are isolation breaks and the flow-field in between the two central lands, which here can be filled by insulating material such as pre-preg.

[0202] Figure 12c shows an inner face 101a of an anode plate 101 of this embodiment, as visible in FIG. 11b. Fluid paths are located between electrically conductive lands. PTHs are visible here on the lands. The flow paths here are parallel flow paths and will supply a reductant fluid to the MEA. In this example, the other side of this plate, not shown separately but visible as face 101 b of plate 101 in FIG. 11a has an equivalent design to that of FIG. 12a, a wavy design of lands so that lands in part are not completely aligned with the lands of this face 101a. This allows for the lateral conduction across the plate as described above.

[0203] FIG. 13 shows a prior art flow path arrangement, where previously described arrangement of how fluid paths or fluid channels may be in the insulating layer is demonstrated, as described in WO 2023 / 052789. This contrasts with the presently described designs in that the fluid paths are within the insulating core. Fluid paths on the same board may be partially aligned with each other, i.e. fluid paths to supply fluid to the MEA on side of the MEA (e.g. first and second fluid paths as described herein) may be at least partially aligned with each other. This can help sturdiness of boards, as the lands between fluid paths would also partially align. Here, reactant flow paths 111,112 and coolant flow path 302 are shown through the whole body of the insulating core 160 and capping layers may be required for those paths not supplying reactant to a MEA, here capping layer 150 is shown.

[0204] Comparatively, FIG. 14 shows a schematic representation of how fluid paths are in the conductive layers described herein. Here an insulating core layer 160 is shown, which is equivalent to an ‘insulating layer’ as described herein. This is a core of insulating material and has a conductive layer on each face. This could be the cathode plate 101 or anode plate 102 as described above, and each plate may be a PCB. The conductive layers comprise ametal layer 903a / 903b and a passivation layer 904 / 904b either side of the insulating core 160. Four insulating layers with conductive layers on both sides are present, representing two anode and two cathode places. Here, cathode and anode plates are adjacent to each other and contact each other. 1001 represents the GDL layer, structure of this and the MEA is not shown. A whole single board can be seen between two MEA / GDL layers 1001 , and half another board or module can be seen below a MEA / GDL layer 1001.

[0205] FIG. 14 shows heat exchange fluid paths 302 in the conductive material layers 903a / 904a, along with reactant fluid paths 111, 112 also in the opposite conductive material layers 903b / 904b. Reactant fluid paths 111, 112 may carry reactants to the cathodes or the anodes as described herein. No fluid path is present in the insulating core 160 (nor in the pre-preg 900).

[0206] Here, adhesion or gluing between the layers, or just mechanical compression can hold such an arrangement together in operation. Sealant 906 acts to seal, bond or adhere layers together where show. Sealant could be used through such stacks or layers, or just mechanical compression could be used if appropriate.

[0207] FIG. 14 shows a central portion of boards, without the inlet and or the outlet of the fluid paths visible. The figure shows only three heat exchange fluid paths 302 per layer and two of each reactant fluid paths 111, 112 per layer, but in embodiments herein varying numbers of each could be present in each board or device described herein. Or, just one of each may be present in each layer. These flow paths may have varying designs i.e. patterns, fields, geometries or arrangements as described herein.

[0208] As can be seen between the two middle plates heat exchange fluid paths are aligned and thus create a combined fluid path between the previously separate boards. Here they are shown as fully aligned at this point in the cross section. Fluid paths may be partially aligned so not all of the path overlaps, which may vary along the flow paths, or part of equivalent flow paths on adjacent boards may not align algin at all.

[0209] As shown here, when at least part of the heat exchange fluid paths align at least a portion of the lands between those heat exchange fluid paths on the adjacent board also aligns with and is in contact with equivalent adjacent lands between the heat exchange fluid paths on the adjacent board. With alignment of the lands or non-fluid path part of the boards, the electrochemical device stack can be compressed without crashing areas of the MEA which are unsupported (as where a portion of conductive material from one of the cathode or anode facing the MEA is pressed across the MEA, against a void in the opposite conductive layerof the anode or cathode it may collapse into the void causing the crashing of the softer MEA or the GDL). Alignment of these lands also allows alignment of means to provide electrical conductive paths, e.g. PTHs, through these parts of the board or stacks. Reactant lands may align fully, partially or not at all, allowing the compression of MEAs to be optimized for given materials and applications, whilst over compression or crushing can be avoided. Exemplary dimensions of various board of the fuel cell boards can be found in Table 1 , for all embodiments described herein:

[0210] Table 1

[0211]

[0212]

[0213] These dimensions are purely exemplary to illustrate dimensions suitable for use with the presently described inventions.

[0214] Included in Table 1 is a passivation layer. Conductive layers may comprise at least a partial passivation layer, e.g. passivation ink or ENIG, as described herein. This may have a thickness of 3 pm to 100 pm, preferably 15 pm to 90 pm. For example, for a passivation ink layer this may be 15 pm to 90 pm, for a ENIG layer this may be between 3 pm to 10 pm, preferably 3 pm to 6 pm. Any of the herein described fluid flow paths can be formed within the conductive layer as the flow fields. Preferably they are etched into the conductive layer once the conductive layers and the electrical means through the conductive layers and the insulating layer (cathode and anode plates either side of the MEA) have been completed. Heat exchange fluid paths may be located in the conductive layer. Preferably, 80% of the fluid paths (reactant and / or coolant) are in the conductive layer, preferably 90% of the fluid paths (reactant and / or coolant) are in the conductive layer, preferably 95% of the fluid paths (reactant and / or coolant) are in the conductive layer, preferably over 90% of the fluid paths (reactant and / or coolant) are in the conductive layer.

[0215] As can be seen throughout some of the figures herein, a fluid path may provide a fluid path for fluid within a single layer, as opposed to requiring one layer to provide a fluid path, and another layer to provide a sealing face sealing the fluid path (i.e. no cap layers required). The fluid paths may of a depth of up to the thickness or depth of the conductive layer. The fluid paths may be through the whole body of the conductive layer. If in the conductive layer and the thickness of the conductive layer varies, the fluid paths depths will vary with that. When in the conductive layer, the fluid paths may be found of a depth of up to the thickness of the conductive layer. Fluid paths may be around 1mm, 0.9mm, 0.8mm, 0.7mm, 0.6mm, 0.5mm, 0.4mm, 0.3mm, 0.2mm or 0.1mm in depth. Fluid paths may be between 1mm and 0.1mm, or between 1mm and 0.3mm, between 0.9mm and 0.4mm, or between 0.8mm and 0.4mm. Preferably the flow paths are 10%, or 20%, or 30%, or 40%, or 50%, or 60%, or 70%, or 80%, or 90% or up to the entire depth of the layer. Preferably, the flow path if the geometry of the fluid path requires a layer of conductive material to lay on the bottom of thefluid path, this can be of any thickness from 5% to 95% of the conductive layer, preferably 20% to 5% of the conductive layer remains, preferably less than 20% of the conductive layer remains, preferably less than 10% of the conductive layer remains. Preferably 5% of the conductive layer remains. The floor of the channel in the conductive layer may be around 0.1mm thickness. The floor of the channel in the conductive layer may between 0.01 mm and 0.1mm thickness.

[0216] Flow paths may not be the full depth of the conductive layers, i.e. they may be shallower or less than the full depth or thickness of the conductive layer, so for at least part of the fluid path all three walls of the fluid path are of the conductive layer, or not through the whole body of the conductive layer the one or more flow paths is located within.

[0217] These parameters and distances may be applied to embodiments here. These embodiments and features may also apply to the board for an electrochemical device described herein. The conductive layer (e.g. metal 903 and passivation 904 layers) could be deposited / plated / coated / printed or otherwise manufactured using techniques known in the art so as to have the flow paths / fields / channels / gaps, or they could be etched, drilled, machined or routed to have the fluid paths / fields / channels / gaps.

[0218] In certain designs PTHs could be located both in correspondence of the full depth of the conductive material and in the thin layer of conductive material left adjacent to the insulating core constituting a conductive floor of the fluid channel (normally the void forming the fluid path would have the insulating core as a floor surface). Such a thin layer of conductive material on the floor of flow paths is not needed to provide a conductive path to and from the MEA or through the stack via the opposite conductive layers of the electrochemical board to adjacent boards, therefore it can be protected from corrosion with a non-conductive coating. PTHs located on the floor of fluid paths, may also distribute heat to the floor of the paths, which might help keep the water in the gaseous state making its removal from the pathways easier. In the same way these thin surfaces may favour the transfer of heat from the heat conductive material to the reactant fluids, as they are equally efficient in transferring heat to the heat exchange fluid to keep the electrochemical device at optimal operational temperature. An increase in means to provide electrical conductive paths from one face of a plate or board to the other (e.g. PTHs) also decreases the overall electrical resistance of the plate and fuel cell board overall.

[0219] Fewer PTHs may be desired in areas of the board operating normally at lower temperature, and conversely a greater number of PTHs may be desirable in areas of the board operatingat greater efficiency, generating more heat, which will need to be removed faster to avoid any thermal runaway. A higher density of PTHs equates to a faster rate of heat removal. Further, with these designs the thickness of the conductive layer (e.g. metal / s with the optional addition of a passivation coating) can be varied to change the compression over specific areas of the electrochemical boards, once established where compression will be needed most. This can be mapped to take into account areas where the pressure is uneven and more pressure is required.

[0220] Sealant 906 may also be present in this, and any embodiment described herein. Sealant between / at the edges of boards can prevent heat exchange fluid leakage and can act to stabilise the stack against slippage of modules in use, for example from vibrations. Sealant is just representative here, and the boards may be wider to have more flow paths than shown.

[0221] For all Figures herein, flow paths and board sizes / thicknesses are not to scale and are adjusted just to show how they could be arranged, real thicknesses, sizes and numbers of paths may vary. As shown here, there may be multiple flow paths in a single board.

[0222] These embodiments and features, for example flow path arrangements, relative depths etc. may also apply to any board or component for an electrochemical device described herein. By positioning all the fluid paths within the board’s conductive layers and using a very thin insulant core the overall cell pitch can be reduced by 50% and the performance over the entire operational window increased compared to previous generations design.

[0223] The number of anodes, cathodes, cells or MEAs on a single fuel cell board is not limited to the number shown in the examples herein. There may be as few as two MEAs / co-planar cells on a single fuel cell board, preferably there may be 2, 3, 4, 5, 6, 7, 8, 9, 10 or more MEAs on a single fuel cell board. There could be over 10 MEAs on a single fuel cell board, for example 20, 30, 40, 50, 60, 70, 80, 90, 100 or over 100 MEAs on a single fuel cell board, depending on fuel cell board size. Anodes and cathodes can have the same design pattern, geometry size, shapes or material properties on opposing faces of the ion permeable membrane, or anodes and cathodes can have different design pattern, geometry size, shapes or material properties on opposing faces of the ion permeable membrane. This is as long as all anodes and all cathodes overlap with at least one cathode or anode through the ion permeable membrane, so there can be exchange of ions for fuel cell operation. As well as size, MEAs can have their material properties varied across the fuel cell board, asdescribed later herein. MEAs can be designed to account for different limiting factors, for example humidity, temperature or partial pressure of the reactant fluids.

[0224] There herein described embodiments may be applied to both fuel cell boards and electrolyser boards. Electrochemical cells in electrolysers can also be connected in series. Each cell can comprise co-planar sub-cells also connected in series. Depending on the number of the electrochemical cells and their co-planar sub-cells the electrolyser will be able to work at different voltages and currents for a defined power inlet. This will allow the device to utilise power from different sources, such as renewable energy like solar and wind predominantly at low voltage, but also from batteries or the grid which operate at much higher voltage, reducing the need of a DC / DC to modulate current and voltage.

[0225] Thus, there herein described arrangements to provide electrically conductive paths through a board and the stack of electrochemical boards can equally be applied to electrolysers. In terms of manufacture of these, once the PTHs have been allocated as required by the chosen geometry of the fluid path and expected performance of the electrochemical device, a photoresist dry film is applied to the metal surface, usually copper, and the image of the desired fluid path is printed on it to mask the areas of the metal which will constitute the structure of the fluid path, and leave exposed the waste copper sections to be etched. The board is then developed to remove the unwanted metal and the residual photoresist in subsequent alkaline and / or acidic chemical spray treatments to reveal the copper forming the fluid path. Multiple treatments maybe required depending on the fluid paths geometrical patterns and / or the thickness of the conductive material. Other techniques maybe use to create the fluid paths such as electrochemical machining reverse plating (ECM anodic dissolution) depending on what is available during the manufacturing of the boards.

[0226] Either of the techniques described above are more accurate industrial processes than routing; permitting the implementation of complicated fluid path designs with a vast array of radii and other features which are prevented by mechanical drilling, due to the inherent constrains of the material removal process and tolerance limitations associated to routing 3-D areas. Metal etching the fluid path, especially a complicated one, is significantly faster and cheaper than routing. Additionally, the use of geometrical patterns is not restricted by the physical limitations of stamping metal bipolar board, where whichever feature is incorporated in the fluid pathway on one side of the metal is negatively created in the opposite side of the board. Therefore, a greater variety of shapes could be explored to direct the flow at varying angles within the fluid path to achieve, in the case of the heat exchange fluids theincrease / alteration of the heat transfer areas and, in the case of the reactants an optimisation / improvement of the pressure drop, velocity and flow distribution based on the changing concentration of the reactant fluid. After formation of the fluid paths, a further conductive layer, e.g. a passivation layer, can then be applied to the etched conductive layer.

[0227] The location of PTHs is a result of the flow pattern necessary electrical clearance and creepage, and of the thermal profile of electrochemical plate. A greater control of PTH design and placement can be achieved utilising these new designs. These are now used as part of the electrically conductive architecture of the electrochemical boards described herein, allowing for improved control and electrical management of such electrochemical devices.

[0228] The designs described herein bring the thermal conductivity of the electrochemical board (Thermal conductivity (k) refers to the ability of a given material to conduct / transfer heat and it is measured in W / mK -Watts per meter Kelvin-) closer to typical prior art metal boards, whilst having the advantages of utilising an insulating core as middle layer to target heat management rate at different location of the electrochemical board and decoupling the geometry of the reactant fluids from that of the heat exchange fluids. The insulating middle layer core is used chiefly in the present design to be able to create several co-planar cells connected in series, and therefore not only targeting the heat management but specifically the mapping and provision of electrically conductive paths, as appropriate laterally within the board (intra-board) and then vertically within the stack (inter-boards).

[0229] These electrochemical arrangements may require end boards or boards to cap the end of the stacks. These may comprise flow paths for a heat exchange fluid, possible to combine with the outer flow paths for heat exchange fluids in the outer conductive layers of the outermost boards in the stack. There will be means, for example PTHs, in the correct corresponding area of the end plate to provide conductive paths into or out of the stack of boards. This may be in correspondence with the first and last cells of the relevant first and last boards in the stack.

[0230] Reference herein to “heat exchange fluid”, “thermal management fluid” or a “temperature control fluid”, interchangeable herein, refers to a fluid which can be used in an electrochemical device or a board for a fuel cell or other such electrochemical device which can flow near or flow adjacent or flow to contact one or more portions of the fuel cell boards, fuel cells, boards for fuel cells or fuel cell stacks described herein. For example, the systemsand methods herein can allow a heat exchange fluid to flow through a flow path adjacent or near the anodes of a fuel cell board, acting to cool or heat those anodes. These can act to cool boards, for example cool anodes of a fuel cell whilst the fuel cell functions. Or, such heat exchange fluids can act to heat or warm boards, for example to heat up an anode board of a fuel cell at the point of fuel cell start up, early in a fuel cell operation timeline / program or in low temperature environments. Heat exchange fluids can be liquids, gases or other such suitable fluids as described herein. Heat can be added or removed from various parts of the fuel cell boards, fuel cells, components for fuel cells or fuel cell stacks described herein.

[0231] The heat exchange fluid can be used in any electrochemical device where the device temperature regulation is required. In fuel cells for example it may contact one or more portions of the fuel cell boards, fuel cells, components or boards for fuel cells or fuel cell stacks described herein. For example, the systems and methods herein can allow a heat exchange fluid to flow through a flow path adjacent or near the anodes of a fuel cell board, acting to cool those anodes.

[0232] Particularly, heat exchange fluids can be deionised water, water, or a mixture of water or deionised water and glycol to prevent freezing of the water or water / deionized water and benzotriazole to inhibit copper corrosion, can be used. Other suitable heat exchange fluids and specific additives to avoid freezing and or corrosion of any of the elements of the devices are envisioned, and would be known to a person of skill in the art. For example, a fluid with a 1 : 1 , 2: 1 , 3: 1 or 4: 1 ratio of deionised water to glycol (such as ethylene glycol or propylene glycol) may be used. A solution may be up to 10% glycol in deionised water, or 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50% glycol in deionised water. Or, a heat exchange fluid may be a mixture of another type of alcohol (for example, methanol, ethanol, isopropyl alcohol) and deionised water. A solution may be up to 10% alcohol in deionised water, or 1%, 2%, 5%, 10%, 20%, 30%, 40% or 50% alcohol in deionised water. Coolant fluid may also comprise one or more perfluoroamines, such as Fluorinert.

[0233] Electrochemical devices may be constructed by layering up of MEAs arrays, cathode and anode plates, and an epoxy resin pre-preg (herein ‘pre-preg’). In construction of a electrochemical device, the MEAs is sandwiched between two layers of pre-preg, then the cathode and anode plates are laminated either side of those two layers of pre-preg. These layers are laminated all together. Plated through holes are then drilled into the anode andcathode plates. After that, gas manifolding, bolting holes, and alignment pins can be made. Electrochemical boards for those devices may be constructed of insulating layers sandwiched between conductive layers, for example Printed Circuit Boards (PCB). Such layers can be adhered together into a solid structure using an epoxy-containing glass fibre composite (pre-preg). The MEAs may be laser bonded onto an insulating layer, a plurality of boards can then be laminated together. In certain embodiments the gaps between the electrodes, and the sealing achieved in these gaps by the epoxy resin, prevent separate flows from mixing, i.e. prevent air cooling, reactant and fuel flows from mixing.

[0234] Use of a sealing materials such as pre-preg, and the use of the layer aforementioned, such as PCBs ensures that the MEAs are sealed from anything not deliberately directed to the boards of the MEAs by the fluid paths in the conductive layers hosted in the (e.g. anode and cathode plates) directly adjacent to the MEAs. This is an advantage of the herein described technology, it allows quick, simple and cheap construction of such structures. Use of lamination with for example an epoxy resin pre-preg also maintains compression of the gas diffusion layer of the MEAs, an important factor in maintaining device performance, providing a sufficiently low resistance electrical path without compromising distribution of reactant fluids.

[0235] The construction of the boards and the electrochemical devices / stacks is described herein in terms of 'horizontal' and 'vertical' planes, in accordance with the embodiments illustrated in the Figures. However, these terms are used for clarity only and are not limiting on the scope of the invention. It will be clear to the reader that the electrochemical boards can be arranged in any plane, not just the horizontal plane. Further, the term 'directly opposite' is not limited to the electrodes being in register. The anode lies on one face of the polymer electrolyte and lies directly opposite a cathode on the opposite face of the same electrolyte membrane layer.

[0236] Reference herein to “fuel cell boards” or a “fuel cell board”, “board” or “component (for a fuel cell or for an electrolyser)”, “electrolyser”, “electrolyser stack” may refer to a membrane electrode assembly (MEA) 113 sandwiched between and a cathode plate 101 and an anode plate 102. In the present embodiments, the three layers may be laminated together, or compressed together. The use of these terms is not intended to limit the size, shape or arrangement of the MEAs, or other boards. No limitation should be placed on the size, shape or dimensions of the boards.The term ‘insulating layer’ used therein refers to an insulating core alone. The cathode and the anode plates of the present design comprise an insulating layer along with one or more conductive layers on either face of the insulating layer. These may be printed circuit boards (PCBs). PCBs for the embodiments may be produced in the known way. Reference herein to ‘Printed Circuit Board(s)’ or ‘PCB(s)’ refers to one or more layers of insulating material comprise of one or more dielectric substrates such as an epoxy resin, for example FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5, polytetrafluoroethylene, polyimides and G-10, preferably the insulating layer comprises FR-4. Multiple layers or boards may be laminated together, for example with an epoxy resin prepreg. Plates or boards may comprise one or more layers of these insulating materials, or one or more PCB boards may make up a single ‘insulating layer’ as referred to herein. PCB boards comprise areas of conductive material plating.

[0237] Reference herein to a passivating or passivation layer means an additional layer deposited, coated, printed on the metal / s or other conductive material layer. A passivation layer may be a passivation ink, which may refer to a conductive ink, particularly the ink may have a functional conductive element that is carbon based. The ink acts to provide a low through-plane resistance conductive path between the electrode and the conductive layer facing the MEA while protecting the copper from the potentially corrosive environment of the devices. It does this by passivating any migratory copper which would otherwise cause irreversible damage of the electrolyte / membrane. Further, the ink may be a carbon ink, it may be a silver paste and polyurethane based ink with conductive elements dispersed in it such as carbon nanotubes or gold / silver nanoparticles these and other inks will be known to a person of skill in the art. A passivation layer may comprise gold, silver or nickel, and / or may be an electroless nickel immersion gold (ENIG) layer, an organic solderability preservative layer or an immersion silver plating layer, or any other passivation treatment known in the art. When the fluid paths are formed in copper on insulating layers, the manufacturing steps may consist of first etching away the conductive material (e.g. copper), then depositing a passivation layer which will only be deposited on the conductive material (e.g. copper). The “means to conduct electricity” as referred to herein may be plated through holes or conductive material filled through holes. “Plated through holes” (PTHs) are holes that form a conduit through one or more insulating layers, said conduit running substantially perpendicular to the planar surfaces of the boards. These are plated with a conductive material, for example copper, to act as a conduit for electricity. The Plated though holes are necessary because insulating layer (e.g. FR-4) consists of electrically insulative core soPTHs must be introduced so that electricity can pass from one face of a layer to another, if desired. These may be formed by holes being drilled through the layer of insulating material (for example a PCB plate) and then lining with a conductive material. For example, they may be lined with a conductive material by an electroplating dip process such that copper lines the edge of each hole. Optional additional steps can occur after electroplating, wherein i) resin can be used fill the remainder of the hole, which is achieved by forcing resin over the PCB layer such that it flows through any holes present; ii) electroplating dip processing again such that the resin filled holes are capped with copper on both sides; and iii) there may be a mild milling process after this to ensure the surface of the PCB is flat. When these are found through PCB layers they can create continuity between two layers of copper plating on either side of the PCB. PTHs may be formed through only certain areas of the insulating layers described herein, or through the plates of the boards (for example through just the anode and cathode plates, to be able to carry current to / from the anode / cathode to the outer surface of the plate via the insulating layer to the external conductive layer). PTHs may be formed through the whole board (for example through both the anode and cathode plate and MEA framework with the same hole, to be able to carry current to / from one surface of the board to the other surface of the board), or they may be made through only the cathode and / or anode plate connecting the lands with other conductive surfaces. Holes filled with a conductive material such as a conductive paste or copper may be used in place of or in addition to PTHs.

[0238] Any reference to alignment or overlap of electrodes forming an MEA, placed on both sides of an insulating core herein may be partial. Partial overlap or alignment may be in more than one axis through a considered board or device.

[0239] Anodes can be designed to be aid in the hydrogen oxidation reaction (HOR), be robust to degradation (thermal cycling, voltage, acidic environment), and have a high electrochemically active surface area (ECSA). The same applies for cathode but for the oxygen reduction reaction (ORR).

[0240] Anodes and cathodes may comprise platinum with a carbon support. Other platinum group metals can be used (Pt, Ir, Os, Pa, Rh, Ru, Pd) as well as non precious metals (NPMs) which have much lower electrochemical activity such as Ni, Fe, Co, Sn). These could vary by ionomer content, PTFE content, catalyst content, composition of the electrodes of by varying the coatings on the electrodes.

[0241] The materials that the anodes and / or the cathodes themselves are made of may vary. Thiscould be by changing the material the electrodes are made of, i.e. they could be made of graphite, Pt, Ir, a mixture of these or of different mixes or materials across the face of a board. For example, the % of platinum in graphite electrodes might vary across a board to account for variation in condition across the board. The additive materials provided to or with the anodes and / or the cathodes may vary. This could be by addition of IrOx, PTFE, Ru, in varying concentrations across a board for an electrochemical device. Different anodes or cathodes may be used for different electrochemical devices, and would be known to one skilled in the art. Any suitable electrode may be used in any board or device herein, and no limitation should be put on the use of anode or cathode herein.

[0242] In some embodiments of a fuel cell board, a catalyst layer on the electrodes accelerates a reaction with the fuel (on the anode electrode) and oxidant (on the cathode electrode) to create or consume the ions and electrons. This layer may be made of suitable catalytic material for the reactions of interest, as is commonly understood by a person skilled in the art of fuel cell production. For example, the catalyst layer may be composed of platinum nanoparticles deposited on carbon and bound with a proton conducting polymer (e.g. Nation™). Similarly, for an electrolyser different catalysts may be utilised to drive the electrochemical reaction.

[0243] MEAs may also comprise one or more gas diffusion layers (GDLs). These may be porous carbon papers such as Sigracet (SGL Carbon), Avcarb, orToray. These can also be metallic foams or porous metallic materials (e.g. foams or felts). These may comprise aluminium, titanium or stainless steel.

[0244] The electrolyte membrane may be a proton-exchange membrane (PEMFC), also known as polymer electrolyte membrane (PEM). This maybe either for low temperature applications LT PEM or for high temperature application, HT PEM. This may be fluorinated (for example a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, e.g. Nation™) or a not fluorinated membrane (for example a hydrocarbon membrane, e.g. an lonomr PEMION™ membrane). They can be based on polybenzimidazole and phosphoric acid for high temperature application and high tolerance to CO in the fuel feed. The membrane may be lonomr Pemion, GORE-Select membrane or a Fumatech Fumapem membrane. Or, the electrolyte membrane may be an anion exchange membrane (for example a Fumatech Fumasep FAA-3 membrane). Other such suitable membranes known in the art may be used with the embodiments herein. The electrolyte membrane may be an anion exchange membrane (AEM), for example in an electrolyser.The electrochemical devices described herein may comprise a means to supply fuel / reactants to the electrodes / MEAs and may comprise a means to supply a heat exchange fluid to the boards of the device.

[0245] For fuel cell boards, the reactant fluid may be oxygen gas, air or pressurised air or any other suitable fluid which would be reduced at the cathodes. As described above, the reactant fluid for the cathodes may be air draw in from the atmosphere outside the fuel cell by means of a fan or air compression device. Although the invention as exemplified uses hydrogen as the reactant fuel (i.e. the reductant gas for the anodes), the fuel cells could be used with all suitable pressurised fluids. As used herein “fluid” refers to a substance that has no fixed shape and yields easily to external pressure, for example a gas or a liquid. Fuels for use with the systems and methods as described herein are fluids. These fuels can be hydrogen or a hydrogen-containing mixture, or a hydrocarbon or hydrocarbon derivative. Fuels could be other gaseous fuels, such as methane or propane. Fuels could be other gaseous fuels, such as methane or propane and fluids include oxidants such as air and oxygen.

[0246] For electrolysers, an electrolyte may be supplied to one or more of the electrodes and referred to as the ‘reactant’ herein. This may be water or another electrolyte solution such as a 1% potassium hydroxide (KOH) water electrolyte. In an electrolyser, the resultant products (e.g. water and gases produced, H2 and O2) may travel in the fluid channels away from the electrodes. Fluids paths may be used to supply or remove fluids from the electrodes described herein.

[0247] Electrolysers may further comprise cathode transport layers and an anode transport layers. These are porous so are sometimes known as porous transport layers (PTLs). For example, a cathode transport layer may be NiFe on Nickel felt, and the anode transport may be MoCa on Carbon felt. Electrolysers may have a catalyst containing layer or catalyst present somewhere on either side of the ion exchange membrane, then Gas Diffusion Layers (GDLs) or transport layers either side of the ion exchange membrane over or comprising the catalyst containing layers.

[0248] The component, board or device described herein may also be for a redox flow battery or hydrogen sensor electrochemical device, wherein those devices comprise components or boards with insulating layers and conductive layers where flow paths may be located. The electrochemical device as described herein may be a redox flow battery or hydrogen sensor. The hydrogen sensor may be a hydrogen sensor as disclosed in WO 2022 / 167793, the contents of which are incorporated by reference herein.The construction of electrochemical device cells from PCBs and their advantages are further described in WO2012 / 117035, WO2013 / 164639, WO2023 / 099877 WO 2023 / 052789 which are incorporated herein by reference.

[0249] The fuel cells and fuel cell boards / components described herein can be capable of, any envisioned power output for a fuel cell stack. Each fuel cell board may have a power rating of at least 1 W. Each fuel cell board may have a power rating of up to 1000W. Each fuel cell board may have a power rating of 1W to 1000W. A fuel cell comprising multiple fuel cell boards may have a power rating of at least 2W. Preferably, each fuel cell comprising multiple fuel cell boards may have a power rating of up to 1000kW. Preferably, each fuel cell comprising multiple fuel cell boards may have a power rating of 2W to 1000kW. But any power rating is merely representative of current embodiments, and the rating may vary from these described as just exemplary.

[0250] An electrolyser or electrolyser board / cell / component may have a power rating of at least 20W. Each electrolyser board may have a power rating of up to 5kW. Each electrolyser board may have a power rating of 20W to 5kW. An electrolyser comprising multiple electrolyser boards may have a power rating of at least 1kW. An electrolyser comprising multiple boards may have a power rating of up to 1MW. Electrolyser comprising multiple components may have a power rating of 1 kW to 1 MW.

[0251] The systems and methods can be used with pressurised fuel storage units or containers, as are well known in the art. The fuel can be stored in a pressurised storage unit, for example a bottle or canister. These can be, for example at a pressure of between 700 and 300 bar. It will be clear to one skilled in the art that many improvements and modifications can be made to the foregoing exemplary embodiments without departing from the scope of the present disclosure.

Claims

CLAIMS1. An electrochemical device comprising:a first and a second electrochemical board, each of the electrochemical boards comprising:a first electrically insulating layer; anda planar array of membrane electrode assemblies (MEAs) connected in series; wherein a last MEA in the planar array of MEAs of the first electrochemical board is electrically connected to the first MEA in the planar array of MEAs of the second electrochemical board below the first electrochemical board by a first electrically conductive means aligned vertically with the last MEA in the planar array of MEAs of the first electrochemical board and the first MEA in the planar array of MEAs of the second electrochemical board,wherein a first MEA in the planar array of MEAs of the first electrochemical board is electrically insulated from a last MEA in the planar array of MEAs of the second electrochemical board by a first electrically insulating means at least partially aligned vertically with the first MEA in the planar array of MEAs of the first electrochemical board and the last MEA in the planar array of MEAs of the second electrochemical board.

2. The electrochemical device of claim 1 , wherein the device comprises at a third electrochemical board, the third electrochemical board comprising:a third electrically insulating layer; anda planar array of MEAs connected in series; andwherein the second electrochemical board is located between the first and third electrochemical boards in the electrochemical device,wherein a last MEA in the planar array of MEAs of the second electrochemical board is electrically connected to the first MEA in the planar array of MEAs of the third electrochemical board by a second electrically conductive means aligned vertically with the last MEA in the planar array of MEAs of the second electrochemical board and the first MEA in the planar array of MEAs of the third electrochemical board,65wherein a first MEA in the planar array of MEAs of the second electrochemical board is electrically insulated from a last MEA in the planar array of MEAs of the third electrochemical board by a second electrically insulating means at least partially aligned vertically with the first MEA in the planar array of MEAs of the second electrochemical board and the last MEA in the planar array of MEAs of the third electrochemical board.

3. The electrochemical device of any preceding claim, wherein each planar array of MEAs connected in series comprises a first MEA, at least one central MEA and a last MEA connected in series,wherein the first electrically insulating means is also at least partially aligned vertically with the central MEAs of the first electrochemical board and the second electrochemical board;wherein the second electrically insulating means is also at least partially aligned vertically with the central MEAs of the second electrochemical board and third electrochemical board, andwherein the first and second electrically insulating means vertically insulate the central MEAs of each board from the adjacent board.

4. The electrochemical device of any preceding claim, wherein each MEA of the planar array of MEAs comprises at least one anode and at least one cathode arranged on opposite sides of a single ion permeable membrane for all MEAs in the planar array, or each MEA comprises at least one anode and at least one cathode arranged on the opposite side of a single ion permeable membrane for each MEA,wherein all anodes are arranged on one face of each of the planar array of MEAs and all cathodes arranged on the other face of each of the planar array of MEAs,wherein anodes on one electrochemical board face cathodes on an adjacent electrochemical board.

5. The electrochemical device of any preceding claim, wherein the first electrically conductive means and the first electrically insulating means between the first electrochemical board and the second electrochemical board are a single layer or component between the two adjacent electrochemical boards; and / or wherein, if present, the second electrically conductive means and the second electrically insulating means66between the second electrochemical board and the third electrochemical board are a single layer or component between the two adjacent electrochemical boards.

6. The electrochemical device of any preceding claim, wherein the means to vertically insulate any part of one electrochemical board from another electrochemical board above or below that electrochemical board comprises: an electrically insulating coating layer, a layer of at least partially electrically insulating material and / or wherein the means to vertically insulate any part of one electrochemical board from another electrochemical board above or below that electrochemical board comprises the electrically insulating layer acting to insulate any part of one electrochemical board from another electrochemical board above or below that electrochemical board.

7. The electrochemical device of any preceding claim, wherein each electrochemical board comprises:a cathode plate comprising the first electrically insulating layer between a first conductive layer and a second conductive layer, arranged so that the first conductive layer faces the cathodes of the planar array of MEAs and so the first conductive layer is electrically connected to the cathodes of the planar array of MEAs,an anode plate comprising a second electrically insulating layer between a third conductive layer and a fourth conductive layer, arranged so that the third conductive layer faces the anodes of the planar array of MEAs and so the third conductive layer is electrically connected to the anodes of the planar array of MEAs;wherein one or more of the first, second, third and fourth conductive layers each comprise multiple fluid flow paths separated by multiple electrically conductive lands.

8. The electrochemical device of claim 7, wherein the second and fourth conductive layers comprise multiple fluid flow paths separated by multiple electrically conductive lands, wherein upwards and downwards electrical connections between the MEAs of adjacent electrochemical boards are formed between vertically aligned electrically conductive lands of the second conductive layers of the cathode plates with vertically aligned electrically conductive lands of the fourth conductive layers of anode plates of adjacent boards contacting each other.

9. The electrochemical device of claim 7 or claim 8, wherein the majority of one of the one or more of the fluid flow paths in one or more of the conductive layers is:67i) the full depth of the conductive layer; and / orii) shallower or less than the full depth or thickness of the conductive layer, so for at least part of the fluid path all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within.

10. The electrochemical device of claim 9, wherein:i) the majority of the length of one or more of the fluid flow paths in the first conductive layer and / or the third conductive layer are the full depth of the first conductive layer and / or the third conductive layer, and wherein the majority of the length of one or more of the fluid flow paths in second conductive layer and / or the fourth conductive layer are the full depth of the second conductive layer and / or the fourth conductive layer; orii) the majority of the length of one or more of the fluid flow paths in the first conductive layer and / or the third conductive layer are the full depth of the first conductive layer and / or the third conductive layer, and wherein the majority of the length of one or more of the fluid flow paths in second conductive layer and / or the fourth conductive layer are shallower or smaller than the full depth or thickness of the second and / or fourth conductive layer, so all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within, oriii) the majority of the length of one or more of the fluid flow paths in the second conductive layer and / or the fourth conductive layer are the full depth of the second conductive layer and / or the fourth conductive layer, and wherein the majority of the length of one or more of the fluid flow paths in first conductive layer and / or the third conductive layer are shallower or smaller than the full depth or thickness of the second and / or fourth conductive layer, so all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within; oriv) the majority of the length of one or more of the fluid flow paths in the first conductive layer and / or the third conductive layer are shallower or smaller than the full depth or thickness of the first and / or third conductive layer, so all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within, and wherein the68majority of the length of one or more of the fluid flow paths in second conductive layer and / or the fourth conductive layer are shallower or smaller than the full depth or thickness of the second and / or fourth conductive layer, so all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within.

11. The electrochemical device of any one of claims 8 to 10, wherein the fluid paths in the second conductive layer and the fourth conductive layer are for heat exchange fluid and the fluid paths in the first conductive layer and the third conductive layer are for anode and cathode reactant fluids.

12. The electrochemical device of claim 11 , wherein the gaps between adjacent MEAs in series in the planar array of MEAs are parallel to the reactant fluid paths in the first conductive layer and wherein the gaps between adjacent MEAs in series in the planar array of MEAs are parallel to the reactant fluid paths in the third conductive layer, or wherein the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the reactant fluid paths in the first conductive layers and wherein the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the reactant fluid paths in the third conductive layer, orwherein the gaps between adjacent MEAs in the planar array of MEAs in series are parallel to the reactant fluid paths in the first conductive layer and wherein the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the reactant fluid paths in the third conductive layer; orwherein the gaps between adjacent MEAs in the planar array of MEAs in series are perpendicular to the reactant fluid paths in the first conductive layer and wherein the gaps between adjacent MEAs in the planar array of MEAs in series are parallel to the reactant fluid paths in the third conductive layer; and / orwherein the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the reactant fluid paths in the first conductive layer and wherein the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the reactant fluid paths in the third conductive layer, orwherein the conductive path between MEAs in the planar array of MEAs is perpendicular to the reactant fluid paths in the first conductive layer and wherein the69conductive path between adjacent MEAs in series in the planar array of MEAs is perpendicular to the reactant fluid paths in the third conductive layer, orwherein the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the reactant fluid paths in the first conductive layer and wherein the conductive path between adjacent MEAs in series in the planar array of MEAs is perpendicular to the reactant fluid paths in the third conductive layer, orwherein the conductive path between adjacent MEAs in series in the planar array of MEAs is perpendicular to the reactant fluid paths in the first conductive layer and wherein the conductive path between adjacent MEAs in series in the planar array of MEAs is parallel to the reactant fluid paths in the third conductive layer.

13. The electrochemical device of claim 11 or claim 12, wherein the heat exchange fluid flow paths in the second and / or fourth conductive layers are parallel to the reactant fluid paths in the first and / or third conductive layers, orwherein the heat exchange fluid flow paths in the second and / or fourth conductive layers are perpendicular to the reactant flow paths in the first and / or third conductive layers, orwherein the heat exchange fluid flow paths in the second and / or fourth conductive layers are parallel to the conductive path between adjacent MEAs in series in the planar array of MEAs, orwherein the heat exchange fluid flow paths in the second and / or fourth conductive layers are perpendicular to the conductive path between adjacent MEAs in series in the planar array of MEAs.

14. The electrochemical device of any one of claim 11 to 13, wherein at least part of the heat exchange fluid path of one electrochemical board and at least part of the heat exchange fluid path of an adjacent electrochemical board at least partially aligned with each other so as to form part of a single heat exchange fluid path between the two adjacent electrochemical boards.

15. The electrochemical device of any one of claims 7 to 14, wherein the electrically insulating layers comprise electrically conductive means located through them to connect the two electrically conductive layers on opposite sides of the electrically insulating layers,70preferably wherein the electrically conductive means to provide a conductive path through the electrically insulating layer are plated through holes or filled through holes.

16. The electrochemical device of any one of claims 7 to 15, wherein each of the electrochemical boards of the multiple electrochemical boards comprises means to provide a conductive path laterally across the electrochemical board, providing a conductive path between an electrochemical board above the electrochemical board and an electrochemical board below the electrochemical board along the planar array of MEAs connected in series.

17. The electrochemical device of claim 16, wherein the means to provide a conductive path comprises the first, second, third and fourth conductive layers, and wherein:the second conductive layer is electrically connected to the fourth conductive layer by a first through electrochemical board electrically conductive means, the first through electrochemical board electrically conductive means passing through the first electrically insulating layer, through the second electrically insulating layer and if present through the membrane to provide a conductive path from the second conductive layer to the fourth conductive layer, orthe first conductive layer is electrically connected to the third conductive layer by a first through electrochemical board electrically conductive means, the first through electrochemical board electrically conductive means passing through the membrane if present to provide a conductive path from the first conductive layer to the third conductive layer.

18. The electrochemical device of claim 16, wherein the first, second, third and fourth conductive layers all comprise multiple fluid flow paths separated by multiple electrically conductive lands,wherein the means to provide a conductive path comprises a first electrically conductive land of the second conductive layer electrically connected to a first electrically conductive land of the fourth conductive layer by the first through electrochemical board electrically conductive means, the first through electrochemical board electrically conductive means passing through the first electrically insulating layer, through the second electrically insulating layer and if present through the membrane to the first electrically conductive land of the fourth conductive layer to provide a conductive path from the second conductive layer to the fourth conductive layer,wherein the conductive path is provided laterally along the planar array of MEAs from the first MEA to the second MEA via the conductive layers and through the first electrochemical board electrically conductive means.

19. The electrochemical device of any one of claims 16, wherein the means to provide a conductive path comprises multiple of the electrically conductive lands in the first conductive layer, the second conductive layer, the third conductive layer and the fourth conductive layer, wherein multiple of the electrically conductive lands in the first conductive layer and multiple of the electrically conductive lands in the second conductive layer partially align on opposite sides of the first electrically insulating layer and wherein the same multiple electrically conductive lands in the first conductive layer and the same multiple electrically conductive lands in the second conductive layer partially do not align on opposite sides of the first electrically insulating layer,wherein the multiple of the electrically conductive lands in the third conductive layer and multiple of the electrically conductive lands in the fourth conductive layer partially align on opposite sides of the second electrically insulating layer and wherein the same multiple electrically conductive lands in the third conductive layer and the same multiple electrically conductive lands in the fourth conductive layer partially do not align on opposite sides of the second electrically insulating layerwherein a first of the aligning electrically conductive lands in the first conductive layer and a first of the aligning electrically conductive lands in the second conductive layer are electrically connected by a first electrically conductive means through the first electrically insulating layer at a point of those electrically conductive lands aligning,wherein a first of the aligning electrically conductive lands in the third conductive layer and a first of the aligning electrically conductive lands in the fourth conductive layer are electrically connected by a first electrically conductive means through the second electrically insulating layer at a point of those electrically conductive lands aligning,the electrically conductive lands and the electrically conductive means through the first electrically insulating layer arranged so that the conductive path is provided laterally across the electrochemical board.

20. The electrochemical device of claim 19, wherein a first electrically conductive land of the second conductive layer is electrically connected to a first electrically conductive land ofthe fourth conductive layer by a first through electrochemical board electrically conductive means, the through electrochemical board electrically conductive means passing through the first electrically insulating layer, through the second electrically insulating layer and if present through the membrane to the first electrically conductive land of the fourth conductive layer to provide a conductive path from the second conductive layer to the fourth conductive layer21. The electrochemical device of any one of claims 7 to 20, wherein the region of the second conductive layer above the first MEA of the planar array of MEAs is planarly insulated from the region of the second conductive layer above the adjacent MEA, and / or wherein the region of the fourth conductive layer below the first MEA of the planar array of MEAs is planarly insulated from the region of the fourth conductive layer below the adjacent MEA,optionally wherein the regions are planarly insulated by a gap in the conductive layer, a gap in the lands forming the conductive layer, a line of electrically insulating material or any means to electrically isolate one region of the conductive layer from another region of the conductive layer, and / orwherein the region of the first conductive layer above the first MEA of the planar array of MEAs is planarly insulated from the region of the first conductive layer above the adjacent MEA, and / orwherein the region of the third conductive layer below the first MEA of the planar array of MEAs is planarly insulated from the region of the third conductive layer below the adjacent MEA,optionally wherein the regions are planarly insulated by a gap in the conductive layer, a gap in the lands forming the conductive layer, a line of electrically insulating material or any means to electrically isolate one region of the conductive layer from another region of the conductive layer.

22. The electrochemical device claims 20 or claim 21 , wherein there are multiple through board electrically conductive means to connect the electrically conductive land of the second conductive layer to the first electrically conductive land of the fourth conductive layer, and / or wherein the electrically conductive means comprise plated or conductive filled through73holes, a strip of metal / metal alloy, a portion of copper wires, a metal foam (porous metal) or solder paste.

23. The electrochemical device of any one of claims 7 to 22, wherein two electrically conductive lands of the second conductive layer align with two of the electrically conductive lands of the fourth conductive layer and multiple through board electrically conductive means electrically connect a first electrically conductive land of the second conductive layer with a first of the electrically conductive lands of the fourth conductive layer and multiple through board electrically conductive means electrically connect a second electrically conductive land of the second conductive layer with a second of the electrically conductive lands of the fourth conductive layer.

24. The electrochemical device of any one of claims 7 to 23, wherein the majority of one or more of the fluid flow paths in one or more of the conductive layers is shallower or less than the full depth or thickness of the conductive layer, so for at least part of the fluid path all three walls of the fluid path are of the conductive layer or not through the whole body of the conductive layer the one or more flow paths is located within, and the conductive layer provides the conductive path laterally across the electrochemical board,wherein the first insulating layer of one electrochemical board and the second insulating layer of an adjacent electrochemical board provides the first electrically insulating means andwherein the first insulating layer of one electrochemical board and the second insulating layer of an adjacent electrochemical board provides the second electrically insulating means25. The electrochemical device of any one of claims 1 to 24, wherein the board comprises a PCB and wherein the electrically insulating layer comprises one or more dielectric substrates, preferably an epoxy resin, preferably one or more of FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5, polytetrafluoroethylene, G-10 or polyimide, preferably the electrically insulating layer comprises FR-4.

26. The electrochemical device of any one of claims 1 to 25, wherein the electrochemical device is a fuel cell, an electrolyser, a hydrogen sensor or a redox flow battery.

27. A board for an electrochemical device, the electrochemical board comprising:74i) a planar array of membrane electrode assemblies (MEAs) connected in series, each MEA comprising at least one anode and at least one cathode arranged on opposite sides of a single ion permeable membrane for all MEAs in the planar array, or each MEA comprising at least one anode and at least one cathode arranged on the opposite side of an ion permeable membrane,wherein all anodes are arranged on one face of the planar array of MEAs and all cathodes arranged on the other face of the planar array of MEAs;ii) a cathode plate comprising a first electrically insulating layer between a first conductive layer and a second conductive layer, arranged so that the first conductive layer faces the cathodes of the planar array of MEAs and so the first conductive layer is electrically connected to the cathodes of the planar array of MEAs,iii) an anode plate comprising a second electrically insulating layer between a third conductive layer and a fourth conductive layer, arranged so that the third conductive layer faces the anodes of the planar array of MEAs and so the third conductive layer is electrically connected to the anodes of the planar array of MEAs;wherein the first, second, third and fourth conductive layers each comprise multiple fluid flow paths separated by multiple electrically conductive lands,wherein a first electrically conductive land of the second conductive layer is electrically connected to a first electrically conductive land of the fourth conductive layer by a through board electrically conductive means, the electrically conductive means passing through the first electrically insulating layer, through the second electrically insulating layer and if present through the membrane to the first electrically conductive land of the fourth conductive layer,wherein a lateral electrically conductive path is provided along the planar array of MEAs from the first MEA to the second MEA.

28. A board for an electrochemical device, the board for an electrochemical device comprising:a first electrically insulating layer between a first conductive layer and a second conductive layer,75the first conductive layer and the second conductive layer each comprising multiple fluid flow paths separated by multiple electrically conductive lands laterally spaced across the first electrically insulating layer,wherein a first of the electrically conductive lands in the first conductive layer and a first of the electrically conductive lands in the second conductive layer at least partially align on opposite sides of the first electrically insulating layer, and wherein a first of the electrically conductive lands in the second conductive layer and a second of the electrically conductive lands in the first conductive layer at least partially align on opposite sides of the first electrically insulating layer,wherein the first of the electrically conductive lands in the first conductive layer and the first of the electrically conductive lands in the second conductive layer are electrically connected by a first electrically conductive means through the first electrically insulating layer at a point of these two electrically conductive lands aligning,wherein a first of the electrically conductive lands in the second conductive layer and a second of the electrically conductive lands in the first conductive layer are electrically connected by a second electrically conductive means through the first electrically insulating layer at a point of these two electrically conductive lands aligning,the electrically conductive lands and the electrically conductive means through the first electrically insulating layer arranged to provide a lateral electrically conductive path across the electrical board.

29. The board for an electrochemical device of claim 28, wherein the second of the electrically conductive lands in the first conductive layer and a second of the electrically conductive lands in the second conductive layer are electrically connected by a third electrically conductive means through the first electrically insulating layer at a point of these two electrically conductive lands aligning,wherein a second of the electrically conductive lands in the second conductive layer and a third of the electrically conductive lands in the first conductive layer are electrically connected by a fourth electrically conductive means through the first electrically insulating layer at a point of these two electrically conductive lands aligning.

30. The board for an electrochemical device of claim 27 or claim 28, wherein multiple of the electrically conductive lands in the first conductive layer and multiple of the electrically76conductive lands in the second conductive layer are electrically connected by electrically conductive means through the first electrically insulating layer at points of the electrically conductive lands aligning electrically through the electrically insulating layer,wherein the electrically conductive lands and the electrically conductive means through the first electrically insulating layer have a staggered arrangement so that a lateral electrically conductive path is provided across the electrochemical board.

31. The board for an electrochemical device of any one of claims 28 to 30, wherein the electrochemical board further comprises a second electrically insulating layer between a third conductive layer and a fourth conductive layer,the third conductive layer and the fourth conductive layer each comprising multiple fluid flow paths separated by multiple electrically conductive lands laterally spaced across the second electrically insulating layer,wherein a first of the electrically conductive lands in the third conductive layer and a first of the electrically conductive lands in the fourth conductive layer at least partially align on opposite sides of the second electrically insulating layer, and wherein a first of the electrically conductive lands in the fourth conductive layer and a second of the electrically conductive lands in the third conductive layer at least partially align on opposite sides of the second electrically insulating layer,wherein the first of the electrically conductive lands in the third conductive layer and the first of the electrically conductive lands in the fourth conductive layer are electrically connected by a first electrically conductive means through the second electrically insulating layer at a point of these two electrically conductive lands aligning,wherein a first of the electrically conductive lands in the fourth conductive layer and a second of the electrically conductive lands in the third conductive layer are electrically connected by a second electrically conductive means through the second electrically insulating layer at a point of these two electrically conductive lands aligning,the electrically conductive lands and the electrically conductive means through the second electrically insulating layer arranged so that a lateral electrically conductive path is provided across the second electrically insulating layer.

32. The board for an electrochemical device of claim 31, wherein the electrochemical board further comprises a plurality of MEAs between the first conductive layer of the first77electrically insulating layer and the third conductive layer of the second electrically insulating layer.

33. The board for an electrochemical device of any one of claims 28 to 32 wherein at least part of the first electrically conductive land of the first conductive layer is not aligned with at least part of the first electrically conductive land of the second conductive layer, optionally wherein at least part of the first electrically conductive land has a different angle of direction across the electrically insulating layer to the first electrically conductive land of the second conductive layer to cause the portion of the lands to not align.

34. The board for an electrochemical device of any one of claims 28 to 33, wherein the means to provide a conductive path through the electrically insulating layer are plated through holes or filled through holes.

35. The board for an electrochemical device of any one of claims 28 to 34, wherein the board comprises a PCB and wherein the electrically insulating layer comprises one or more dielectric substrates, preferably an epoxy resin, preferably one or more of FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5, polytetrafluoroethylene, G-10 or polyimide, preferably the electrically insulating layer comprises FR-4.

36. An electrochemical device comprising the electrochemical board of any one of claims 28 to 35 or a plurality of the electrochemical boards of any one of claims 28 to 35.78

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