Electrochemical device with electrical manifold

Abstract

An electrochemical device comprising at least two insulating layers each having at least one component provided on or in the insulating layer; each insulating layer comprising a first conductive through via, in electrical connection with a first conductive through via of the other insulating layer, the electrical connection between the first conductive through vias providing a first conductive bus through the insulating layers; each insulating layer further comprising a second conductive through via, in electrical connection with a second conductive through via of the other insulating layer, the electrical connection between the second conductive through vias providing a second conductive bus through the insulating layers; wherein a component located on or in one insulating layer is connected to the first conductive bus and a component located on or in the other insulating layer is connected to the second conductive bus.

Description

[0001] ELECTROCHEMICAL DEVICE WITH ELECTRICAL MANIFOLD

[0002] The present disclosure relates to an electrochemical device manufactured with an electrical manifold. The electrical manifold takes the form of a plurality of conductive bus lines formed through insulating layers of the device. The conductive bus lines can be connected to one or more components forming part of the electrochemical device. A component may be an active part of the electrochemical device such as the electrodes or electrolyte, and may also be a reference electrode, passive or active sensor or actuator used in the electrochemical device for carrying out some intended application or design.

[0003] The electrical manifold may be used for monitoring various parameters of the electrochemical device, such as electrical or physical properties; for diagnostic purposes, for control of the device, for performance enhancement and may be used for fault management or heating, for example.

[0004] BACKGROUND

[0005] An electrochemical device is a generic term to refer to a device that can convert chemical energy into electrical energy, or vice versa, through electrochemical reactions. Examples of electrochemical devices include batteries, fuel cells, sensors and electrolysers.

[0006] A fuel cell (e.g., a solid-polymer-electrolyte 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, indeed most applications where power is required, particularly portable power generation.

[0007] An electrolyser is an electrochemical device that uses power to split water into its constituent elements, hydrogen (H2) and oxygen (02) using a process called electrolysis. Electrolyser technology finds application in hydrogen production for fuel cell operation and other industrial processes. An example of electrolyser technology is described in WO2023099877. Typically, taking a fuel cell as an example of an electrochemical device, such as that described in W02024201082, a fuel cell comprises two electrodes, an anode and a cathode, separated by an electrolyte that allows ions (e.g., hydrogen ions), but not free electrons, to pass through from one electrode to the other. A catalyst on the electrodes facilitates a reaction with the fuel on the anode to separate electrons and protons / cations, and oxidant on the cathode to undergo a reduction reaction to produce water. A circuit can then be formed between the anode and the cathode where current can be drawn to power a load e.g., an electrical device. A reactant fluid, e.g., oxygen or reactant air, is supplied to the cathode and a fuel, e.g., hydrogen, is supplied to the anodes.

[0008] A single pair of electrodes separated by an electrolyte membrane is called a membrane electrode assembly (MEA). A fuel cell MEA operating on hydrogen and air under a moderate load produces an output voltage of about 0.7 V, which is often too low for many practical considerations. In order to increase this voltage, MEAs are typically assembled into a stack, as shown in FIG. 1. Each MEA has a layer of electrolyte membrane la (such as a Nation™ membrane), which comprises an ion-permeable membrane sandwiched between two electrode layers, and an anode 2 and a cathode 3 on either side of the electrolyte membrane. Adjacent MEAs can be separated by an electrically conducting bipolar separator plate 4, and a fuel (e.g., hydrogen) 6 and an oxidant 5 (e.g., oxygen gas or 'reactant air') flow through the channels provided on opposing sides of the bipolar plate. End plates 9 are connected to an external circuit via an electrical connector 7, 8. The number of these MEAs in a stack in a fuel cell determines the total voltage that can be output, and the surface area of each membrane electrode determines the total current that can be drawn / output. Catalyst layers adjacent to the electrodes increase the rate of and efficiency of the reactions at the electrodes.

[0009] FIG. 2 shows an exemplary fuel cell of the prior art (see e.gWO 2012 / 117035) in which a plurality of fuel cell boards 22 are stacked between two endplates 21 in order to provide increased voltage and power. Electrode pairs are arranged in a series along either side of a single layer of polymer electrolyte 10, such as a Nation™ membrane. Anodes 11 are disposed on one surface of these membranes and cathodes 12, separated by gaps are disposed on the other, opposite, surface of these membranes. The anode and cathode respectively of two adjacent electrode pairs may partially overlap. Through-membrane electrical connectors 13 connect the electrodes across the membrane in the overlapping region and may be produced by a homogeneous chemical deposition process. A catalyst on the electrodes encourages the reactions at the electrodes. A fuel 17, such as hydrogen gas, flows along the face of the fuel cell board 22 supplying the anodes 11 and a reactant or oxidant 16, such as oxygen gas or air, flows along the surface of the fuel cell board 22 supplying the cathodes 12. One electrode at the edge of the upper surface and one electrode at another edge of the lower surface of the fuel cell board are connected to an external circuit via an electrical connection 18, 19. In this series arrangement, the surface area of an electrode pair determines the size of the current for a fuel cell board 22, but the voltage accumulates in proportion to the number of electrode pairs on that fuel cell board 22.

[0010] Electrically insulating spacers 20 can be integrated into the stack between each of the fuel cell boards each comprising a spacer composed of electrically insulating material (such as plastic).

[0011] The size of an individual cell (the surface area of a pair of electrodes) determines the size of the current for a fuel cell board. The total number of individual cells on a fuel cell board determines the voltage produced. The number of fuel cell boards in a stack determines the size of the total power of the fuel cell stack.

[0012] The end cathodes 12 and anodes 11 on each fuel cell board are connected to respective first and second output lines via electrical connections 18, 19. The connection between each fuel cell board in the stack and the second output line can be controlled by a switch mechanism such as a field-effect transistor (FET) switch providing power handling and control directly at the cell. Each of these switches can be controlled by individual control lines.

[0013] There are a number of factors that determine the power and efficiency of an electrochemical device. In the case of a fuel cell, such factors affect the performance and determine the consistency of voltage output / current output of the fuel cell. Consistency of voltage output / current of a fuel cell is important for most fuel cell applications. Unless specifically desired, too great a voltage variance can affect performance of the operations downstream of the fuel cell.

[0014] Particularly, temperature of a fuel cell or fuel cell stack is important. The temperature variance across fuel cells, cells or MEAs or individual fuel cell boards can affect the performance of a fuel cell and consistency of voltage output / current of a fuel cell or subsequent fuel cell stack. If used, heat exchange fluid (e.g., coolant in coolant channels) can affect fuel cell performance and affect the consistency of voltage output / current of a fuel cell.

[0015] In a fuel cell stack it is useful to monitor electrical and physical properties; for diagnostic purposes and to use this monitoring for fault management or heating, for example.

[0016] Prior art arrangements of monitoring such as may be used for cell voltage measurement in a fuel cell results in a high density of electrical measurements throughout the stack. Typically, electrical measurements are made by electrical connections to the edge of a stack and a tab is required in order to solder an electrical connection to the edge of the stack or physically connect an electrical connection using a bolt. Soldering individual cables for external wiring on each stack can be error prone due to broken connections, is time consuming and may cause damage to the fuel cell itself because heat is applied to the fuel cell using a soldering iron. Prior art arrangements are not best suited for high chloride or highly corrosive environments such as marine environments.

[0017] In view of the foregoing, there is a need to provide an improved structural arrangement for monitoring of various properties of an electrochemical device for control purposes and so that pre-emptive or remedial action can be taken to ensure that the electrochemical device is operating close to its rated efficiency and power rating.

[0018] SUMMARY

[0019] According to a first aspect of the present invention, there is provided an electrochemical device comprising at least two insulating layers each having at least one component provided on or in the insulating layer; each insulating layer comprising a first conductive through via, in electrical connection with a first conductive through via of the other insulating layer, the electrical connection between the first conductive through vias providing a first conductive bus through the insulating layers; each insulating layer further comprising a second conductive through via, in electrical connection with a second conductive through via of the other insulating layer, the electrical connection between the second conductive through vias providing a second conductive bus through the insulating layers; wherein a component located on or in one insulating layer is connected to the first conductive bus and a component located on or in the other insulating layer is connected to the second conductive bus.

[0020] In embodiments, electrical connection between vias is provided by physical contact between conductive through vias of preferably adjacent insulating layers. The physical contact may be a press contact, that is under some kind of stress formed over the entire stack. In other embodiments, the electrical connection is provided by an additional conductive coupling between conductive vias. For example, an intermediate conductive via, metal trace or other conductive connection between conductive vias of adjacent insulating layers.

[0021] The present invention takes the 'external' wiring arrangements in electrochemical devices and replaces it with an 'internal' electrically conductive bus. The conductive bus is constructed in a self-assembled manner because adjacent insulating layers align with each other. The arrangement leads to electrical connection being made between each conductive through via of an adjacent layer. There may be mechanical compression between each layer in the electrochemical device, to aid the electrical connection. The conductive through vias may be individual plated through hole (PTH) vias, such as ones used in printed circuit boards or any vias, such as staggered or stepped vias, so long as a conductive path, herein referred to as a conductive bus is formed through an insulating layer. For example, silicon wafers may be fabricated with conductive through vias formed through doping of conductive paths through the wafer. This arrangement allows for an electrical connection to extend through at least part of the entire depth of the stack. Multiple conductive buses formed through a stack formed of a plurality of insulating layers create the electrical manifold. Multiple arrays of conductive buses can each address a different type of component on each insulating layer.

[0022] In order for each layer, cell or module in the stack to have a unique connection to one of the multi-layer conductive buses, an electrical connection is made between one conductive bus and a component of the cell so that each component has an individual connection to one conductive bus line. This can be achieved by designing it as part of the electrical connections within the board, or by adding an electrical connection to just one of the conductive paths, or starting with electrical connections between all of the conductive paths and an electrical component and cutting the connection with all but one of the conductive through vias. If an insulating layer does not have a component present, then the conductive through via passes through the insulating layer without any connection to a component.

[0023] A conductive bus formed in this way through the stack may be a single bus connected between a conductive pad and a component or may be multiple buses connected between a conductive pad and a component. Multiple buses can be used, for example, where there is a need to carry more current than a single bus is able to do through the conductive path between the conductive pad and the component.

[0024] Preferably, the at least one component is connected to the first conductive bus by a conductive trace.

[0025] Preferably, there are one or more components on both of the at least two insulating layers.

[0026] Preferably, the one or more components are selected from an electrical component, an electronic component, an electrode, an electrolyte a sensor, a heat trace or an actuator.

[0027] Preferably, the one or more components are individually connected to one or more electrically isolated conductive buses.

[0028] Preferably, the electrically isolated conductive buses are formed of a single conductive bus or multiple conductive buses. Preferably the component is a working electrode, which in operation has a voltage change due to electrochemical reactions in the electrochemical device.

[0029] Preferably, the component is a reference electrode, separate from a working electrode.

[0030] Preferably, the working electrode is an anode electrode or cathode electrode and the reference electrode is in contact with an electrolyte.

[0031] Preferably, a voltage measuring device is connected across two conductive buses, wherein each conductive bus is connected to at least one component.

[0032] Preferably, at least one conductive bus is a voltage bus channel connected to a voltage measuring device and to at least one component for carrying out voltage measurement.

[0033] Preferably, at least one conductive bus is a current carrying bus channel connected to a current source and connected to at least one component for carrying a current to the component.

[0034] Preferably, the current carrying bus channel is configured to carry a current to the component for heating.

[0035] Preferably, on at least one insulating layer, two conductive buses are connected respectively to two components, wherein the connection is under the control of a switch or relay; optionally wherein at least two conductive buses are connected to one component or one conductive bus is connected to two components, preferably under the control of a switch or relay.

[0036] Preferably, the components are a first and second electrode, optionally an anode and a cathode electrode.

[0037] In embodiments, the electrochemical device preferably comprises further insulating layers each having at least one component provided on or in the insulating layer; each insulating layer comprising a further conductive through via, in electrical connection with a further conductive through via on an adjacent insulating layer, the electrical connection between the further conductive through vias providing further conductive buses through the insulating layers; wherein there is one further conductive bus through the insulating layers for each insulating layer, wherein a component is located on or in each further insulating layer, the connected to one further conductive bus.

[0038] In embodiments, the electrochemical device further comprises at least two further insulating layers separate from the first two insulating layers, each of the further insulating layer having at least one component provided on or in the insulating layer; each insulating layer comprising a first conductive through via, in electrical connection with a first conductive through via of the other insulating layer, the electrical connection between the first conductive through vias providing a first conductive bus through the insulating layers; each insulating layer further comprising a second conductive through via, in electrical connection with a second conductive through via of the other insulating layer, the electrical connection between the second conductive through vias providing a second conductive bus through the insulating layers; wherein a component located on or in one insulating layer is connected to the first conductive bus and a component located on or in the other insulating layer is connected to the second conductive bus.

[0039] According to a second aspect of the present invention, there is provided an electrochemical device comprising a plurality of insulating layers, all of the plurality of insulating layers comprising a conductive through via in electrical connection with the conductive through via of at least one adjacent insulating layer, the electrical connection between the conductive through vias providing a first conductive bus through the plurality of insulating layers, wherein the conductive through vias are aligned with one another and in series electrical contact, so that in use an electrical continuity measurement can be made through the first conductive bus.

[0040] Preferably, the device also comprises at least two insulating layers each having at least one component provided on or in the insulating layer; each insulating layer comprising a first conductive through via, in electrical connection with a first conductive through via of the other insulating layer, the electrical connection between the first conductive through vias providing a first conductive bus through the insulating layers; each insulating layer further comprising a second conductive through via, in electrical connection with a second conductive through via of the other insulating layer, the electrical connection between the second conductive through vias providing a second conductive bus through the insulating layers; wherein a component located on or in one insulating layer is connected to the first conductive bus and a component located on or in the other insulating layer is connected to the second conductive bus.

[0041] Preferably, the insulating layer is a printed circuit board and preferably the vias are solid electrical connectors, annular plated through holes, fully filled plated through holes or annular plated through holes that have been filled with an electrically conducting material.

[0042] Preferably, the vias comprise an electrically conductive pad.

[0043] Preferably, the electrically conductive pad is connected to a single conductive bus or to multiple conductive buses.

[0044] Preferably, the electrochemical device is a battery, capacitor, fuel cell, electrolyser or sensor.

[0045] There are many uses of the present invention. In embodiments, the present invention is used to measure a characteristic of the electrochemical device, preferably wherein that characteristic is cell voltage or activity / performance of a component of the electrochemical device or a physical attribute. Preferably, use of at least one conductive bus to measure the temperature or humidity of a part of the electrochemical device. Preferably, use of at least one of the conductive buses to measure the mechanical alignment or orientation of the insulating layers. Preferably, use of at least one of the conductive buses (single or multiple) to supply current to the component, preferably wherein current is supplied to restore performance of that component, or preferably wherein current is supplied to electrically short one or more components. Preferably, use of at least one of the conductive buses to supply current to at least part of an insulating layer, preferably to a heat trace located on or in the insulating layer.

[0046] Preferably, the conductive vias are connected to a heat trace on one or more of the insulating layers. Preferably, the heat traces are tracks of heat conductive material. Preferably, the heat trace is connected to a means to transfer heat or energy capable of generating heat to one or more of the layers. Preferably, the means to transfer heat to the fuel cell board is a source of electrical energy. Preferably, this is a battery, or the device itself, for example when it is a fuel cell the energy may come from the fuel cell itself.

[0047] Preferably, any conductive material described herein is a metal. Preferably, the conductive material is copper, nickel, a copper alloy, a nickel alloy, carbon-based conductive material such as graphite or an ink, resin or a conductive polymer.

[0048] Preferably, one or more of the insulating layers also comprises heat conductive vias. Preferably, the heat conductive vias are selected from the group consisting of through holes, buried vias, blind vias, or any combination of these, optionally wherein the holes or vias are plated or filled with a conductive material.

[0049] In preferred embodiments, the internal electrical bus can be connected at either end of the stack, at multiple points in the stack, (or both ends of the stack for enhanced reliability I fault tolerance). This electrical array is in a form conducive to parallel connection to a conventional cell voltage measurement using parallel connected ribbon cable. Alternatively, the analogue signals can undergo analogue- to-digital conversion on-board and the entire array of voltage measurements translated from the stack via a digital bus such as a Universal Serial Bus (USB), I2C cable or wireless connectivity. In embodiments, signals, voltage and current can be carried by the internal electrical bus from an external source into the electrochemical device.

[0050] Such an internal, self-assembled, electrical bus cannot be implemented in a conventional bipolar plate arrangement that uses electrically conducting materials, e.g., metal or graphite fuel cell bipolar plates. Further differentiating the presently described insulating layer approach.

[0051] In embodiments, the conductive through vias forming the internal electrical bus may be formed through an insulating layer in a staggered arrangement such that the first conductive through via through one insulating layer is formed of a two part conductive through via such as may be described as an upper conductive through via offset in position relative to a lower conductive through via, the upper and lower conductive through vias connected to form a conductive path and in effect a single yet staggered or stepped first conductive through via.

[0052] Forming the conductive through vias in staggered arrangement provides several advantages for the design and functionality of an electrochemical device, such as a fuel cell or an electrolyser.

[0053] A staggered configuration makes more efficient use of space within the stack. Instead of running the buses vertically, a staggered configuration or stepped configuration can provide more vias.

[0054] As described in embodiments of the invention, multiple conductive buses can take on a staggered or step-wise configuration through the multiple insulating layers of a stack.

[0055] Accordingly, according to a further aspect of the invention, an insulating layer comprises a first conductive through via through one insulating layer formed of a first portion conductive through via offset in position relative to a second portion conductive through via, the first and second portion conductive through vias connected to form a conductive path.

[0056] Arranged in this configuration provides that the two portions are connected to form a conductive path by a conductive material electrically connecting the first and second portion; optionally wherein the conductive material is a metal trace or a conductive polymer or exposed metal etch.

[0057] The conductive through via may take many preferable configurations within individual insulating layers such as the via may be one substantially aligned structure within the insulating layer, yet offset still from a conductive via in an adjacent insulating layer. The first conductive through via of one insulating layer may be connected via a conductive path to the corresponding first conductive through via on the adjacent insulating layer to form a conductive bus to maintain the staggered conductive bus configuration across the entire stack without having a staggered via within individual insulating layers.

[0058] When formed across or through more than one insulating layer and stacked to form an electrochemical device such as a fuel cell or electrolyser, the first conductive through via of one insulating layer is offset in position with respect to the first conductive through via of the other insulating layer, and any second, third or fourth conductive through vias is / are offset in position with respect to the second, third or fourth conductive through via(s) of the other insulating layer.

[0059] Preferably, the offset is such that the first portion of the first conductive through via of one insulating layer does not overlap with the first portion of the first conductive through via of the other insulating layer, as also applies respectively to the second, third of fourth conductive through vias.

[0060] When arranged across a stack the offset provides a first and second conductive bus plus where applicable a third, fourth, fifth conductive buses arranged in a staggered configuration across adjacent and / or multiple stacked insulating layers.

[0061] Preferably, multiple conductive buses are formed in an offset configuration and very preferably each bus independently monitors a corresponding property of a component on or in an insulating layer. Preferably, a conductive path is created to the first conductive through via between the first conductive bus and the component and optionally the conductive path is a metal trace.

[0062] A staggered configuration makes for error prevention and provides repeatability and production simplification in a poka-yoke design where the electrical connection between a busbar and a component in an insulating layer can be manufactured always in the same position (for example, a metal trace is created in correspondence of the first via between the first busbar and the component to be measured). Stacking insulating layers upon each other in an electrochemical device with busbars in a staggered configuration will automatically enable the first busbar to be connected to the component in the first insulating layer, the second busbar to be connected to the component in the second insulating layers and so on, without having to rely on the operator during the assembly of the stack to correctly place each insulant layer in specific order in the stack in relation to the location of the electrical connection, therefore actively preventing human errors, allowing for greater assembly repeatability and manufacturing simplification.

[0063] Diagonal spacing which is an outcome of the staggering makes for more efficient use of space around the edge of the board which can be used for connections or other purposes. The efficiency arises because for the same amount of real estate on the board we can fit almost double the amount of staggered busbars than busbars that are vertically aligned.

[0064] The insulating layers may be any suitable insulating layers, for example dielectric layers.

[0065] When used, an actuator may provide both monitoring and a follow-up action in a feed-back loop.

[0066] The present invention provides a number of technical advantages over the prior art:

[0067] • Wiring is protected within the body of the stack.

[0068] • No need for slow and error-prone external wire solder connections.

[0069] • Electrical connection throughout the stack is generated at the same time as the stack assembly process.

[0070] • Allows rapid read-out diagnostics based on cell / stack measurements.

[0071] • Improved safety as there are no exposed electrical contact points throughout the external body of the stack with no need to electrically seal / insulate the stack body.

[0072] • Tamper-proof.

[0073] • Standard fabrication routes can be used and minimal design changes are required to implement it.

[0074] • No need for an individual wires to be externally connected to each cell / module in the stack using individual external wired connections.

[0075] • Such an internal bus can also be used for other / multiple in situ sensing scenarios (e.g., temperature, humidity, pressure, resistance), and can measure both the anode and cathode of each cell, and / or it can be connected to an internal reference electrode.

[0076] • Such an internal bus can be used to control mechanical, pneumatic or hydraulic actuators, such as valves, for example.

[0077] • Such a mechanically connected multi-layer plated through hole assembly can also be used for quality control to ensure suitable module alignment and orientation during stack assembly. • Provides a route to furnish current to cells and / or electrically short cells to improve or restore the performance of the electrochemical cell.

[0078] • Provides a route to selectively provide current to heating elements located within the device to ensure effective thermal management and start-up.

[0079] • Lends itself to single-wire data pull off (e.g., USB) or wireless connectivity. It is also an advantage of using an electrochemical device that we can readily connect electrical components - connectors, integrated circuits, FETs, and so on.

[0080] • An operator can readily manage the stack while limiting downtime and / or perturbing the stack. E.g., highly corrosive off-shore electrolyser maintenance no longer involves extracting the stack and performing diagnostics / repair in a more controlled environment.

[0081] • A cheaper and simplified production of the insulant layers and a poka-yoke assembly of the electrochemical device stack.

[0082] BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Embodiments of the present invention will now be described by example only and with reference to the accompanying drawings, in which:

[0084] FIG. 1 shows a schematic side view of a stacked fuel cell of the prior art;

[0085] FIG. 2 shows a cross-section of a fuel cell of the prior art comprising a stack of fuel cell boards;

[0086] FIG. 3a and FIG. 3b shows a plated through hole according to an embodiment of the present invention;

[0087] FIG. 4 shows a stacked electrical connection arrangement according to an embodiment of the present invention;

[0088] FIG. 5 shows a working electrode and reference electrode according to a voltage monitoring embodiment of the present invention;

[0089] FIG. 6a, FIG. 6b and FIG 6c show a voltage monitoring device according to embodiments of the present invention; FIG. 7 shows vias connected to a reference electrode according to an embodiment of the present invention;

[0090] FIG. 8 shows a graph of current density vs cell potential for a measured fuel cell operated on hydrogen and air;

[0091] FIG.9 shows location vias for alignment and an electrical component for measurement according to an embodiment of the present invention;

[0092] FIG. 10 shows an arrangement for determining alignment between boards in a stack according to an embodiment of the present invention;

[0093] FIG. 11A, 11B and 11C show arrangements of stacked electrochemical devices according to various embodiments of the present invention;

[0094] FIG. 12 shows part of a module of an electrochemical device in perspective view, top view and side view illustrating a staggered electrical connection according to an embodiment of the present invention;

[0095] FIG. 13 shows a side view of multiple layers forming part of a module of an electrochemical device illustrating a staggered electrical connection through multiple layers according to an embodiment of the present invention; and

[0096] FIG. 14 shows an electrochemical device comprising multiple layers and output electronics according to an embodiment of the present invention.

[0097] DETAILED DESCRIPTION

[0098] 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.

[0099] Referring to Figure 3a, two plated through holes 30 according to embodiments of the present invention are shown fabricated through an insulation board 32. On the left is one type of plated through hole, on the right a second type. As best seen in Figure 3b, individual plated through holes 30 are placed outside a component (e.g., the electrolyte) towards the edge of the board 32 so that the individual plated through holes 30 do not penetrate the component. Such plated through holes 30 align with each other on consecutive boards in a stack of electrically insulating layers in an electrochemical device.

[0100] Each plated through hole 30 is electrically isolated from the board around it and also electrically isolated from other plated through holes. There is a wide range of conductive materials to choose from to make the plated through hole and a conductive material such as a copper cladding 34 is used in the present example. In the present embodiment, the copper surface is etched to make the cladding on the insulation board 32, either an annular copper circuit around the PTH outer diameter or the copper square outside the outer diameter of the PTH. PTHs described herein may have a pad of conductive material extending around one or both sides of the plated hole, which may be a continuation of the plating material. The pad 36 provides a larger surface area to give increased overlapping surface areas between adjacent in-line plated through holes 30 on neighbouring boards. Such an arrangement provides better tolerance in alignment of boards whilst maintaining physical contact between in-line plated through holes 30.

[0101] A plated through hole 30 is a specific example of a via. To operate, the via needs to form an electrical connection from one side of the board to the other. This can occur via a straight through linear connection, such as a plated through hole (PTH) in a PCB introduced using electroplating. The via can be a single connection or made up of smaller discrete vias in electrical connection that can be staggered, stacked, or connected through the use of internal planes, embedded or blind vias.

[0102] Alternatively, holes can be drilled through the insulating board layer from one side to the other and conducting elements inserted into the holes. For example, the use of copper rivets, provided the heads do not protrude excessively or are recessed into the board.

[0103] Interconnected vias can be solid electrical connectors, annular PTHs, fully filled PTHs via electroplating or annular PTHs that have been filled with an electrically conducting (e.g., metal, carbon) loaded resin (e.g., DuPont CB100 or Tatsuto AE3030 the 'silver coated copper particle' filled epoxy matrix).

[0104] Figure 4 shows a stacked electrical connection arrangement 40 according to an embodiment of the present invention. Each board 42a, 42b, 42c and 42d contains all the plated through holes 30 corresponding to the number of the boards 42a- 42d in the stack. For example, for a 50 fuel cell board fuel cell stack, there are 50 plated through holes on each board forming the electrical bus, aligned with each other on successive boards. Other vias or PTHs may be present in or through the layer, for other purposes.

[0105] Each plated through hole 30 is isolated from other plated through holes 30 on the same board 42a-42d. On each board 42a-42d there is one contact between one plated through hole 44a on board 42a with a plated through hole 44b on board 42b, with a plated through hole 44c on board 42c and with a plated through hole 44d with board 42d. By making all the plated through holes 30, 44a-44d in line and connected to each other by way of mechanical compression or adhesion between boards to form an electrical connection with each other, the present invention provides an internal electrical bus 46. Additionally, the internal electrical bus 46 may be referred to as a busbar or conductive bus.

[0106] The internal electrical bus 46 is fabricated all the way through the stack of insulating layers 42a-42d and is achieved by placing individual printed circuit board layers aligned with each other. Different types of layers may be present in the stack. For example, fuel cell boards that generate power may be next to liquid cooling plates or plates which are added to the stack to carry monitoring, diagnostic, controlling and or performance enhancement equipment. In such electrically insulating layers some plated through holes 30 can be embedded as required to form or continue the electrical bus. The internal electrical bus 46 is operational when the plated through holes 30 are in registry and when the printed circuit boards are aligned the internal electrical bus 46 will automatically align also creating electrical connection between the layers; therefore, the internal electrical bus 46 is automatically formed when a stack of electrically insulating layers is built. The plated through holes 30 are designed according to their function. For example, an internal electrical bus 46 used for voltage measurement can be smaller in terms of its volume (via diameter) than one used to carry current. The area of a plated through hole 30 can also be chosen for its function and can be as large or as small as required. For those holes which use a pad, a larger pad may ensure contact to allow a certain tolerance for alignment. The electrical connection provided by the internal electrical bus 42 provides a way of monitoring various parameters of the fuel cell, such as electrical or physical properties; for diagnostic purposes and may be used for fault management or heating, for example. In order to address the required monitoring, there is a connection from the internal electrical bus 42 to the point where the electrical measurement is made.

[0107] As is discussed in more detail below, electrical buses allow electrical measurements and each board has its own connection via a different conductive track to measure electrically a characteristic of the fuel cell module. Cell voltage measurement can be performed and with placement of plated through holes in pre-determined positions on the board, the present invention provides for buses for a range of applications such as thermistors to measure the temperature in each board, measuring relative humidity and the location of plated through holes can be used to check the alignment of consecutive boards in a stack amongst many applications.

[0108] One such application is a cell voltage measurement. Cell voltage monitoring is an important part of fuel cell and other electrochemical device measurement and control. Generally speaking, in order for each cell in the stack to have a unique connection to one of the multi-layer internal electrical buses 42, an electrical connection is made between the bus line and the current carrying part of the cell to give a cell voltage. These connections can be achieved as a step in the manufacturing of the PCBs during, for example, copper imaging and etching of the copper. The connections may be carried out during the PCB design stage, or by adding an electrical connection to one of the lines or starting with electrical connections between all of the plated through holes 30 and the electrode and cutting the connection with all but one of the plated through holes 30. Therefore, imaging and etching has made the connection required at the design stage, or a post-production step can make a connection to only the specific component on the board by adding a track of conductive matter. Alternatively, as a post-production step, connections to all components on the board are made at the imaging and etching stage and all connections but the one needed to the specific board are removed.

[0109] Referring to Figure 5, a fuel cell 50 voltage measurement arrangement comprises a working electrode 52 and reference electrode 54. A single board 56 formed of insulating material comprises electrical vias 58, 60 formed from plated though holes (not shown in Figure 5). The active part of the fuel cell 50 is described in detail in Figures 1 and 2 and is represented in Figure 5 as an electrolyte membrane 62 sandwiched between a cathode electrode 64 and an anode electrode 66. Other features include thermal vias 68, external copper surfaces communicating with other modules 70 and internal copper surfaces in contact with the electrolyte membrane 62 such as a membrane electrode assembly (MEA).

[0110] In operation, the polarisation of the working electrode 52 is determined by measuring the delta voltage between it and the reference electrode 54.

[0111] The reference electrode 54 is used for checking electrochemical activity of the fuel cell 50 and is to separate the electrochemical performance of the cathode electrode 64 and / or the anode 66 in the board 56. Such a measurement can determine if an individual electrode is performing as expected and identify the individual performance losses associated with the anode and cathode of each cell. The reference electrode must maintain a constant electrochemical potential throughout operation and not change when loaded due to polarisation losses. This can be achieved by using an isolated area of electrode, disconnected from the main electrode, that is exposed to a constant composition of hydrogen (associated with the feed of hydrogen to the cell, for example). A dedicated internal bus is then associated with each reference electrode on each board of the stack.

[0112] The reference electrode 54 is used for checking electrochemical activity of the fuel cell 50 and is able to locate electrochemical performance of the cathode electrode 64 and / or the anode 66 in the board 56. Such checking can determine if an individual electrode is performing as expected. Figures 6A, 6B and 6C illustrate a voltage measurement arrangement as a stack. In this way cell voltage measurement can measure a delta voltage between two fuel cell electrodes on the same board or different fuel cell boards, which is a differential measurement between two electrodes on the same board or different fuel cell boards, each connected to its own internal electrical bus 46 via a conductive track or trace 90.

[0113] Referring to Figure 6A, a voltage monitoring device 80 is connected across each internal electrical bus 46 with each internal electrical bus 46 connecting to an electrode of a fuel cell module 82, 84, 86, 88 by way of a conductive track 90.

[0114] Referring to Figure 6B, a voltage monitoring device 100 is on board, this is fabricated as part of a board and is not a separate, external device, as in Figure 6A. The voltage monitoring device 100 is connected to a management system by way of a Universal Serial Bus (USB) 102 or alternatively by a wireless connection 104 such as Wi-Fi, Bluetooth ™ or other wireless connection.

[0115] Referring to Figure 6C, a voltage monitoring device 110 is also shown fabricated as part of a board 112 and is not a separate, external device, as in Figure 6B.

[0116] The board 112 in Figure 6c comprising the voltage monitoring device 110 is an electrochemical board such as may be multi-layered and formed of conductive and insulating material. A printed circuit board may be used for the mounting and interconnection of components in electronic equipment, comprising conductive connections between the busbars and any processing units.

[0117] The embodiment is illustrated as two adjacent boards 112, 114. The voltage monitoring device 110 is connected to a management system by way of a Universal Serial Bus (USB) 102 or alternatively by a wireless connection 104 such as Wi-Fi, Bluetooth ™ or other wireless connection. In Figure 6c, each internal electrical bus 46 is connected to an electrode 52 of each board 112, 114 to measure the delta voltage between electrodes and boards. The voltage monitoring device 110 is connected to an Analogue to Digital Converter (ADC) 116. Each ADC 116 has four general purpose connectors on the top of the voltage measuring device 110 to be used in other measurement sensors such as thermistor and another device like a pressure sensor. In Figure 6c, there are two internal electrical buses 46 going through the stack and each is connected to an electrode 52 of an adjacent fuel cell to measure the delta voltage between the two. Each delta voltage is measured on an individual circuit in the ADC 116 and each ADC monitors multiple fuel cells. The ADC 116 can output a digital signal to an external electronic board (not shown in Figure 6c). Additional ADCs 116 can be connected together to monitor more cells for larger stacks. For example, an ADC 116 can be placed on each board every 30 or more cells and all ADCs 116 can be chained together.

[0118] FIG. 7 shows more detail with respect to the electrical connection of an internal electrical bus 46 to a reference electrode 54 according to an embodiment of the present invention, as described in Figure 5. The internal electrical bus 46 is connected to the reference electrode 54 which is on the electrolyte 120 but not connected to the electrode 122.

[0119] The reference electrode 54 can be on the cathode and / or the anode side to measure the internal losses of the electrode when polarization occurs, reaction happens and the current starts flowing. With reference to Figure 8, a graph 150 of current density against cell potential illustrates the electrical behaviour of a fuel cell. Initially when the circuit is open there is no current flowing and the cathode is at approx. 1.23 V and the anode is at 0 V with respect to the standard hydrogen electrode (if operating on hydrogen and air). When current flows, there is initially a rapid drop in voltage from an open circuit voltage due to activation losses followed by a linear drop in voltage due to Ohmic losses.

[0120] Taking 0.9 V as an example of the operating potential of a fuel cell under load where both the cathode and anode are polarised, this is the difference in voltage between the anode and the cathode where the cathode comes down and anode goes up in potential from the open circuit potential case. If we have a reference electrode 54 that is always at a constant potential, we can pinpoint the polarisation of each electrode with respect to the reference electrode potential. On the anode side the reference electrode 54 is not connected to the anode working electrode; the reference electrode 54 will experience the H2 coming in and therefore it would be at 0 V (with respect to the hydrogen potential). This reference electrode 54 is connected to an internal electrical bus via a plated through hole, a carbon coated copper or electroless nickel immersion gold (ENIG) coated copper track can be used to avoid corrosion. Integration of a reference electrode 54 will confer a level of insight that is difficult to achieve using conventional stack architecture and would have with very little additional cost, and no external wiring to create this measuring ability. All will go via an electrical internal bus 42 to measure a characteristic of a layer in the electrochemical device such as a fuel cell, as described herein.

[0121] Figure 9 shows location vias 130 for alignment and orientation and an internal electrical bus 132 for measurement according to an embodiment of the present invention. Referring to Figure 9, different arrays of vias are used for measuring different physical characteristics of the fuel cell. Vias can be connected to sensors to measure the temperature and humidity, for internal reference and as locators or location vias for aligning the fuel cell modules in the stack. Sensors can be thermistors or even capacitors to measure the thickness of the fuel cell board itself.

[0122] Location vias 130 used for alignment are used for quality control purposes to ensure the stack is built with all the modules in suitable alignment and orientation.

[0123] In a further embodiment, Figure 10 shows an arrangement that can determine if all layers of the device are in series electrical contact by performing an electrical continuity measurement through an internal bus composed of a series of connected vias that run through the full extent of the device.

[0124] Such a connection continuity bus can be located at specific points across the board (distributed around the edge of each board or in diagonally opposite corners, for example), to ensure that the full extent of each board is in electrical contact throughout the device.

[0125] This approach allows the user to know that electrical contact has been made throughout the device (stack) and that sufficient mechanical compression or adhesion between boards has been exerted to deform internal gaskets, such that electrical connection between all layers (boards) has occurred. The nature of the continuity measurement is one of "connected" or "not-connected" and does not provide a measure of the quality of the connection in terms of its contact resistance. This is particularly useful during device (stack) assembly where knowledge that each board throughout the stack is in electrical contact is desirable.

[0126] To make the continuity measurement, two electrical connection points are required, these can be at the top and bottom of the stack (the two ends of the interconnected via bus). Alternatively, the terminus of two buses can be connected together at one end of the stack and the electrical connections can both occur at the same opposite end of the stack.

[0127] Within electrochemical power systems that have cells connected in electrical series, multiple electrically conducting layers exist that are in physical contact. The nature of the physical contact between the layers defines the electrical contact resistance between the layers, this includes the material, presence of surface layers such as oxides and sulfides, surface roughness, planarity, extent of physical contact across each surface, physical compression pressure between layers, etc. The ability to measure this resistance in situ is of value to ensure suitable contact resistance at the beginning of device life, after assembly and during operation.

[0128] Contact resistance between electrically conducting components can be determined through a measurement of the voltage on each layer and knowledge of the current passing between the layers. The application of Ohms Law providing the resistance from knowledge of current and voltage difference. The provision of an internal bus allows for facile connection of different layers in the electrochemical device to allow for voltage measurement on each adjacent layer. When the device is operational, the current between layers is known, as this is constant for each layer in the stack connected in electrical series and can be measured at the device level. Alternatively, for a device that is not operational and passing current, a separate current carrying bus can be used to pass a known current between the layers. The result of this approach is that the contact resistance of adjacent layers throughout the device (stack if referring to a fuel cell) can be monitored. This is a valuable diagnostic of device performance and can be used to optimize mechanical compression of the device to ensure suitable pressure is applied. The vias 132 can be small and packed in a high density area and such an arrangement lends itself well to a high density cable to take measurements.

[0129] Figures 11A, 11B and 11C show simplified arrangements of some stacked electrochemical devices according to various embodiments of the present invention. The electrochemical device 160 can be a fuel cell, electrolyser or battery, for example. The precise form and function of the electrochemical device 160 is not important in the context of Figures 11A, 11B and 11C and so only the exemplary stacked arrangement of the layers and the conductive through bus is illustrated.

[0130] Referring to FIG 11A, an electrochemical device 160 comprises stacked insulating layers 162, 164, 166 and 168. Each insulating layer 162, 164, 166 and 168 has a number of conductive through vias 170 passing through the insulating layer, in this case each insulating layer 162, 164, 166 and 168 has four conductive through vias 170, but in practice each insulating layer 162, 164, 166 and 168 could have many more, as described above. When the insulating layers 162, 164, 166 and 168 are sandwiched together it will be appreciated that the four assembled conductive through vias 170 will form four conductive through buses through the stacked electrochemical device 160. Each insulating layer 162, 164, 166 and 168 has a component 162A, 164A, 166A and 168A on or in the respective insulating layer 162, 164, 166 and 168, with each component connected to only one conductive through via.

[0131] Referring to FIG 11B, two insulating layers 162 and 164 are shown with an additional insulating layer 172 located between the insulating layers 162 and 164. Additional insulating layer 172 has two conductive through vias 170 which form two conductive through buses through its layer, and in a first embodiment additional insulating layer 172 does not comprise a component in or on insulating layer 172 since not all layers in a stack necessarily have components connected to the electrical bus or have the same kinds of component. They may not have such components, or they may have components which are not connected to the electrical bus. In a second embodiment additional insulating layer 172 is an electronic board such as described in respect of Figure 6c, the external electronic board, but in respect of Figure 11B, the electronic board 172 is not external and is within the stack. In the second embodiment, the additional insulating layer 172 has busbars running through it, so that electrical connections can be made within layer 172. One example of an electronic board is known as a "Rigid-Flex" board. The Rigid-Flex type of electronic board is a hybrid circuit board combining elements of both flexible circuit boards and rigid circuit boards, with an end result of a board that is able to be folded or continuously flexed.

[0132] When assembled according to the second embodiment, the insulating layer 172 acting as an electronic board can be located at any point in the stack, but preferably located at one end, or at both either ends of the stack before the current collector and the end plate. When multiple sets of busbars are considered, one or more electronic boards contain the connections between the busbars and any processing units. Further details are described with reference to Figure 14.

[0133] Referring to Figure 11C, the electrochemical device 160 is formed using a modular approach. Insulating layers 160, 164 and 166 are stacked as shown in Figure 11A but are separated from additional layers 168, 174 and 176 by a featureless layer 178. As noted in Figure 11C, there is no conductive through via through the featureless layer 178.

[0134] The nature of the connection from the plated through holes to the point that is being measured can be physically different depending on if the measurement is a potential (e.g., no current), a small current to retrieve a signal, or to measure compression or a high current; this is summarised in TABLE 1.

[0135] TABLE 1

[0136] All the embodiments described above are an effective way of making a voltage measurement, passing current in the stack and taking readings out of an electrochemical device. The electrical connection may vary between: a connection just to measure voltage, carrying small current and carrying high current depending on the functionality required, but the medium will be the same, an internal electrical manifold of vias / plated through holes engineered for specific purposes.

[0137] Another useful measurement is to be able to identify when a fuel cell is malfunctioning such as when an electrode is poisoned with CO, because its potential would be low. Being all modules in series, having one module with low performance does affect the overall fuel cell stack, lowering the stack potential. The cell voltage measure allows a user to identify the module with the low potential among the other modules. As a result, action can be taken such as shorting the cell and / or load the fuel cell module individually to remove the CO and restore the catalyst activity, for example.

[0138] Heat management of electrochemical devices made of insulating materials, such as PCBs is beneficial to their operation. Heat transfer can be provided by, for example, solid heat transfer means such as heat traces, thermally conductive vias or conductive material plating to transfer heat within a fuel cell stack. Heat transfer and a circuit to remove the CO may need to be powered by an independent source of power as to not affect the performance of the fuel cell stack. Being independent the mode of furnishing the current can vary, such as using pulse width modulation.

[0139] The internal electrical manifold will provide an internal, self-assembled and addressable arrays of vias, positioned in non-active (no electrode) areas of the board (around the perimeter, for example). Suitable locations may be near an edge of a board that does not cover the electrolyte (eg MEA), membrane, manifolds, or is blocked / obstructed by any stack architecture, e.g. endplates, current collectors, cowls, and fan controllers. Connection between the electrical manifold and the component on the board can be made by a trace of copper, dab of conductive carbon paint silver ink, etc. Whatever connection we may choose it must be not be proud of the board, at least not to exceed the height where it will interfere with the compression homogeneity of the fuel cell stack.

[0140] Cell shorting is a strategy commonly employed for fuel cells (and particularly polymer electrolyte membrane fuel cells) to regenerate cell performance following a period of degradation. The process involves making an electrical contact between the anode and cathode of a cell, or collection of cells, such that the cell(s) are short circuited. The result of this is that maximum current flows between the electrodes and the voltage of the cell tends to zero volts. The consequence of this includes: (i) increase in the amount of water generated and available to the membrane electrode assembly to hydrate the membrane and reduce its ionic resistance; (ii) increased heat generation, sufficient to evaporate the excess generated water from the gas diffusion layers; (iii) stripping of oxygen species from the cathode as the voltage of the cathode is reduced; and (iv) oxidizing poisons from the anode (e.g. CO impurity present in the hydrogen supply gas) as the voltage on the anode is increased. Each of these factors can act to improve the performance of the fuel cell either in unison or a combined effect.

[0141] The time over which a short circuit can take place varies, typical examples include 500 ms short applied every minute or a 100 ms short applied every 10 s.

[0142] Short circuiting of an entire stacks of cells connected in series can lead to improved performance; however, this does not ensure that the same effect is experienced by each cell in the stack as each cell can have a different internal resistance that leads to a different short circuit current. Shorting will require the transitory passage of high current through the stack which requires an appropriately sized conductive track to carry the high current. This non-uniform effect can lead to the reversal of cell voltage that can damage cells and cause irreversible performance loss. This also means that the power delivered by the stack is interrupted as it affects all cells in the stack. Rather, ideally, shorting should be applied to each cell in a stack individually. However, this approach has the challenge of connecting high current carrying cables to each side of every cell in a stack which is difficult to achieve in practice using cables connected external to the stack.

[0143] The ability to contact each cell in a stack to an individual current carrier, that is connected to a switch capable of carrying the short-circuit current, is a requirement of individual cell short-circuiting.

[0144] The arrangements and embodiments of the present invention provide a means of achieving an ability to contact each cell in a stack to an individual current carrier. The key requirement is that the interconnect between each cell is capable of carrying the short circuit current. To achieve this, individual electrical vias (PTHs) can be fabricated with higher loadings of conducting material (e.g., copper or any suitable conducting material e.g., a metal containing PTFE, a resin filled with copper or silver, for example). And / or, individual vias (PTHs) can be connected together in parallel to share the current carrying requirement of the short circuit condition.

[0145] Connected between each connector achieving the short circuit is a switch such as a field effect transistor (FET) or relay specified to be able to handle the short- circuit current. Each cell is connected to a switch via the electrical manifold. A multitude of switches can be used in a bank such that the shorting of each cell in the stack can be scheduled to occur as required. This scheduling could be imposed based on a defined schedule or as a response to the condition of an individual cell. For example, the voltage or temperature of the cell.

[0146] Excessive shorting of cells can lead to net negative performance degradation if over-used and / or performed in an unoptimized way. The ability to control the shorting conditions of each cell in a stack individually limits the potential negative effect of shorting.

[0147] The act of shorting typically leads to heat generation in the shorting circuit I switch and is lost electrical power not available to the load application. This is another reason to minimize the time that the cells in a stack spend in shorted mode. However, capacitors (typically supercapacitors) can be used to store the electrical current discharged during the shorting event / s. Again, the ability to control the scheduling of the shorting of individual cells is essential in order to minimize the electrical energy lost in the shorting and that captured by the capacitor.

[0148] Single MOSFETs on a control board are used to short a fuel cell board in a stack.

[0149] An embodiment may comprise a FET associated with each board, located on the board (e.g., protruding from the side of a board) and trigger the FET to close by a separate signal that comes in via the electrical manifold. In that way, high current carrying going all the way through the stack would not be required, just the signal that goes to trigger the FET. Each FET requires a gate signal.

[0150] A person skilled in the art will determine that there are a number of ways to manufacture an electrical manifold of the type described herein. At least two ways of manufacture will now be described:

[0151] To address / connect each electrical element using the electrical manifold, each board must be associated with a given channel within a bus or multiple buses (e.g., current carrying, voltage only, sensor, etc.). This involves having an electrical connection between a given channel in a bus and the electrical element on the board associated with that channel, i.e., voltage bus channel 1 connects to electrical element requiring voltage measurement on board 1; current carrying bus channel 5 connects to electrical element requiring current carrying connection on board 5.

[0152] The nature of the electrical connection (referred to as the track) between the bus channel and the component is determined by at least two factors including: 1) relative location of the bus channel and the component; and 2) the amount of current that the track is required to carry.

[0153] 1) Relative location of bus channel and electrical component and the connection between them.

[0154] The track connecting the bus channel and the component can be composed of:

[0155] A surface electrical track such as used on the outer surface of PCBs.

[0156] Internal connections within a multi-layered non-electrically conducting substrate (e.g., a PCB) that can use through-board vias, blind vias, buried vias, etc. such that connection can be made within the structure of the board and can also access components throughout the thickness of the board (e.g., buried sensors, catalyst layers, gas diffusion layers).

[0157] A wire making suitable electrical connection between the bus channel and the component being of sufficiently low profile not to affect adjacent board electrical contact when brought into physical contact.

[0158] Where there is the requirement to avoid the exposure of internal electrical connections and the external surface of the stack, the track route should be designed to avoid extending to the edge of the board.

[0159] The conductive track, as well as the conductive bus should avoid contact with any electrolyte material as this could introduce unwanted shunt currents through the stack.

[0160] The track should be routed to avoid compromising sealing adjacent boards, or if etched from the outer copper surface, it will not protrude from the surface and not jeopardize either sealing and / or compression of the fuel cell stack. The minimum distance between bus channel and component is a function of the potential difference [AV between the two; and any other busbar and the component and other factors, such environmental conditions] between the two and should be designed for appropriately (see next point - 2 below).

[0161] 2) Current carrying requirement

[0162] Different types of internal electrical buses may require different current carrying capabilities (e.g., a cell voltage monitoring (CVM) bus requires no current; current shorting bus requires a high current for a short period of time (typically of the order of 15 ms); board heating bus requires current provision for extended period of time; board diagnostics bus may require an alternating current to be carried at varying frequencies for extended periods of time). In each case, the track must be designed to be suitable for the amount and nature (AC or DC) of current it is required to carry. This requires sufficient electrically carrying material to be available (e.g., the thickness, width and lengths of a copper track on a PCB) so as not to present an excessively large electrical impedance that could lead to overheating or efficiency losses. Electrical clearance and creepage between conductive buses within the same insulating board and between the connected insulating boards within the electrochemical device stack needs to be considered and different applications may require different spacing, and a person skilled in the art is aware of design requirements.

[0163] There are multiple ways to make the electrical connection between the conductive bus and the electrical component. These can be separated into four categories: 1) standard connection engineered in the insulant layer, 2) bespoke board manufacture; 3) selective additive connection; 4) selective subtractive disconnection.

[0164] The standard connection is engineered during the manufacturing of all the insulant layer and does not differ from insulant layer to insulant layer. When the insulant layer is a PCB the standard connection is created during the imaging, development and etching of the PCB manufacturing. Bespoke board manufacture has the advantage that the electrical connection is specifically designed for the task. The advantage is that no additive and subtractive step post etching of the copper phase will need to be carried out: such as 1) adding the specific connection from a specific busbar to the electrical component on the board, or 2) severing all connections but one from the busbar to the electrical component on the specific board. However, each of the boards need to be designed specifically for their location in the stack. The additive and subtractive methods have the advantage that every module can be fabricated to be the same, with all the connection necessary on each board created at the etching state -here connections of different characteristics -thin and or large would be designed depending on the amount of current they need to carry, simplifying the manufacturing process; however, each module needs subsequentially to be modified leaving only the connections required for the specific board, on the board, before assembly into the stack.

[0165] 1) Standard connection

[0166] This involves designing each board placing the electrical connection between the bus channel and the relevant electrical element always in the same location. It does not require subsequent configuration during assembly. Each board can be simply stacked upon each other and the busbar forming during the assembly of the electrochemical device automatically connects to a component in the insulant layer relative to its position in the stack, without requiring each board to be numbered / categorized in the manufacturing stage.

[0167] 2) Bespoke board manufacture

[0168] This involves designing each board to have a specific electrical connection between the bus channel and the relevant electrical element on each board such that it does not require subsequent configuration. This requires each board to be associated with a specific location in the stack at the point of manufacture, i.e., each board would be numbered / categorized in the manufacturing stage. Specific board labelling to identify position in the stack (e.g., adhesive labels, silkscreen, engraving, integrated RFID) can occur as part of the manufacturing process as each board will have been electrically hard connected during manufacture.

[0169] 3) Additive electrical connection Additive electrical connection is based on none of the bus channels having any initial connection to a component or track to the component. To address any given bus channel to a component on a given board, an electrical connection is made between the bus channel and the component on the board or the track to the component. This can be done by forming a connection between the bus channel direct to the component or to the track leading to the component. This connection can be made via any means that allows for electrical connection that does not compromise the ability to make an electrical contact or ensure sealing between the boards. For example, by excessively protruding from the board. The additive connection can take place via a surface connection or within a recess in the board surface.

[0170] Examples of methods to achieve an additive connection include:

[0171] Use of low profile conductive metallic tape, (for example, RS PRO conductive metal tape made from copper material with a thermosetting adhesive on one side with a foil thickness of 0.035 mm).

[0172] Conducting metal paint (for example, RS PRO Conductive Lacquer, a silver conductive paint used to repair PCB tracks, manually draw circuits or make electrical connections on non-solderable surfaces).

[0173] A solder bridge jumper between a pair of pads on a PCB that can be bridged by adding solder between the pads.

[0174] A foil that can be placed in position and maintained in place when the boards are compressed together. Or soldered or glued into place.

[0175] A metallic jumper thicker than a foil and capable of carrying greater current that can be recessed into the board to make electrical connection but not protrude from the board.

[0176] The action of additive connection can be a manual, semi-automated or fully automated and occur during board manufacture, following board manufacture, or at point of stack assembly.

[0177] 4) Subtractive Subtractive electrical disconnection is based on all of the internal bus connections having initial connection to a component or track to a component. Disconnection of all of the channels in the bus that are not associated with that board then takes place leaving only the relevant bus channel / s associated with that board and component connected.

[0178] The action of disconnection can be a manual, semi-automated or fully automated process and occur during board manufacture, directly following board manufacture, or at point of stack assembly.

[0179] The action of disconnection of bus channel to track or component can include:

[0180] Mechanical cutting via a rotating drill piece either directly into a connecting track or cutting across one or more adjacent tracks.

[0181] Mechanical cutting via a scoring action.

[0182] Laser cutting I ablation either directly into a connecting track or cutting across one or more adjacent tracks.

[0183] With reference to Figure 12, part of a module of an electrochemical device 1200 is shown in perspective view 1202, top view 1204 and side view 1206 to illustrate one example of a staggered electrical connection according to an embodiment of the present invention.

[0184] Perspective view 1202 comprises insulating layer 1208 having a top copper layer 1210, internal copper layer 1212 and bottom copper layer 1214. Copper is an example of a conductive material used for the conductive pad and conductive traces discussed throughout the description.

[0185] The copper layers 1210, 1212 and 1214 are etched during manufacturing of the insulating layer 1208 to form the required patterns provided by conductive vias; for example, conductive via 1216 and 1218. A conductive via 1220 etched on the top copper layer 1210 is formed to provide an electrical connection through the insulating layer 1208 and is connected to another conductive via 1216 by way of a metal trace 1222 which thereby forms an offset in location between upper conductive via 1220 and in this case lower conductive via 1216. Together and with the conductive pad 1228 and the metal trace 1229, metal trace 1222 connecting the two conductive vias 1220 and 1216 forms a first staggered conductive bus 1224 through the insulating layer 1208.

[0186] Metal trace 1230 is an electrical connection between the conductive via and an insulating layer and a component to measure a property of the insulating layer 1208.

[0187] As best seen in perspective view, an integral part of the conductive via 1224 is connection 1229, being a metal trace on the top copper layer 1210 connecting a copper pad 1228 permitting the connection with an adjacent staggered via.

[0188] Disposed adjacent to the first staggered conductive bus 1224 is a second staggered conductive bus 1226 spaced from the first conductive bus 1226 by a predetermined distance, for example, but not limiting 1 mm.

[0189] Shown from a top view 1204, it will be appreciated that the top copper layer 1210 comprises conductive via 1220 connected to conductive via 1216 by way of metal trace 1222 in the insulating layer 1208. As also seen from the side view 1206, the top copper layer 1210 comprises conductive via 1220 connected to conductive via 1216 by way of metal trace 1222 through the insulating layer 1208.

[0190] Figure 13 shows a side view of multiple layers 1300 forming part of a module of an electrochemical device illustrating a staggered electrical connection through the multiple layers 1300 according to an embodiment of the present invention. A first insulating layer 1302 comprises an arrangement as described in respect of Figure 12 in that the first staggered conductive bus 1220 is formed in the insulating layer connected to the conductive via 1216 by way of the metal trace 1222 through the insulating layer 1302.

[0191] The first staggered conductive bus 1224 may terminate at the first insulating layer 1302 or may be connected to a further conductive via 1304 formed on a top layer 1306 of a second insulating layer 1308, which in turn may continue the electrical path of the first staggered conductive bus 1224 through the second insulating layer 1308 by way of metal trace 1311 to conductive via 1310, where the first staggered conductive bus 1224 may terminate. As will be appreciated by a person of skill in the art, the terminating layer of any staggered conductive bus is a matter of design choice at the manufacturing stage and chosen depending upon which insulating layer is to be monitored. Any conductive bus could travel through to a third insulating layer 1312 or multiple N layers. Also shown in Figure 13 is the second staggered conductive bus 1226 spaced from the first conductive bus 1224 by a predetermined distance.

[0192] Figure 14 shows an electrochemical device 1400 comprising multiple layers LI, L2, L3, L4, L5, L6 and L7 with output electronic boards, Area 1 and Area 2 according to an embodiment of the present invention.

[0193] Conductive buses VI, V2, V3, V4, V5, V6 and V7 are formed in the manner described in Figures 12 and 13 such that conductive bus VI is a first conductive bus connected through the entire stack from LI to terminate at L7 and any data or signal can be taken out at electronic board Area 1 connected to electronic board Area 2 at the top of the stack.

[0194] Conductive bus V2 is connected through part of the stack from L7 to terminate at L2, conductive bus V3 from L7 to terminate at L2, conductive bus V3 from L7 to terminate at L3, conductive bus V4 from L7 to terminate at L4, conductive bus V5 from L7 to terminate at L5, conductive bus V6 from L7 to terminate at L6 and conductive bus V7 is connected to L7 only. The output of each conductive bus V2 to V7 is connected to electronic board Area 1 and Area 2 at the bottom of the stack to bring any signals to a management system.

[0195] Additional connections can be provided onto each layer LI to L7. As can be seen in Figure 14, L6 comprises two conductive buses, one connecting bus 1402 and a second connecting bus 1404 with an arrangement so that signals can be taken out from the top or bottom of the stack.

[0196] The electronic boards Area 1 and Area 2 can be located at any point of the stack before any current collector or plate. When multiple sets of conductive buses are present then one or more electronic boards can contain the connections between the conductive buses and any processing units.

[0197] According to Figure 14, each conductive bus allows for the measurement of a characteristic of a layer, being connected to at least one component in one layer. All the conductive buses are then connected to an electronic board where the traces from the conductive buses are taken off the board within the stack to a processing unit. The stack is then topped with the current collector and the endplate.

[0198] One outcome of the stacking arrangement, some of the connecting electrical paths whilst are not connected to the insulating layer at the top of the stack, they are connected to the insulating layer at the bottom of the stack, which could be connected to another electronic board. This allows for the taking of much more measurements of the characteristics of the stack, then would be the case if all the conductive buses would cross through all layers as discussed in respect of the arrangement of Figure 4. The staggered arrangement also allows for the creation of many more conductive buses using the same amount of conductive vias per board, as buses can be taken from the top and the bottom of the stack. For example, for a stack of 7 layers as illustrated in Figure 14, we have at least 7 conductive buses taking two measurements. So, for n layers, we have (2n-l) measurements which can be double the amount compared to Figure 4.

[0199] An increase in conductive buses will require consideration of creepage and clearance electronic rules. The taking of signals using copper traces, for example, can be helped by using electronic boards so that the plurality of copper traces can be split from top to bottom.

[0200] The electronic board to collect the conductive buses can be a "Rigid- Flex" printed circuit board combining elements of both flexible circuit boards and rigid circuit boards, with an end result of a board that is able to be folded or continuously flexed and is normally formed by flexible materials during manufacturing process and flexed into physical position during installation. This provides an advantage of being able to process the information and measurements outside of the stack, but in close proximity to the stack. Depending on the size of the processing units, these can be located in Area 1 within the volume of the stack or Area 2 outside of the stack via the Flexible part of the board. In addition, Area 1, interface board that connects to the conductive buses also has to carry the stack current from the top or bottom of the stack to the current collector plates. This current is independent of from the conducting activity of the conductive buses to measure the performance of the stack. The current is connected to the ability of the electrochemical device to, in the case of a fuel cell, power a load, to the operation of the fuel cell itself.

[0201] The present embodiment provides further advantages for the data collection and processing. Using a "Rigid-Flex" electronic board is that Area 1 in the electronic board, located within the stack can be used to collect data from connected conductive buses and can also host some of the processing equipment. This can be embedded in the board and does not stand proud outside the height of the board as not to create any preferential uneven compression area within, for example a fuel cell board with the stack.

[0202] Other processing units, either too bulky to be within the electronic board in the stack or sensitive to pressure or stack environment can be located in Area 2, outside of the stack, as the copper traces can be taken off the board from Area 1 to Area 2 using a connecting zone made of flexible polymer on which such copper trace have been etched; so that the data collected from some of the conductive buses can be processed in Area 2 outside of the stack.

[0203] As described throughout the specification, one example of a particularly suited insulating layer for the manufacture of electrochemical devices is a Printed Circuit Board.

[0204] Boards of insulating materials, such as FR-4 epoxy resin boards, have the advantage of enabling the elements to be manufactured in large quantities and at low cost. For example, multiple flow field boards can be manufactured at the same time, by using thin laminate boards which are stacked and then simultaneously routed or drilled. Individually routed boards are then stacked and laminated together. PCBs have a high mechanical strength, whilst being light, and when laminated together provide a solid structure, with good contact between the individual layers. Accordingly, a monolithic, light, and completely sealed structure is produced.

[0205] Use of insulating materials to construct a device also enables the present devices to be constructed without a mass or size penalty which may be present using other materials such as metal. These insulating material plates can be plated with copper and / or have plated through holes or other means to conduct electrical current through or across the plates. This allows improved control of current through stacks, as not all of the plates, spacers etc. need be conductive, like when prior art bipolar plates or conductive metal components are utilised in prior art devices.

[0206] In an electrochemical device such as in a fuel cell then preferably, a Membrane Electrode Assembly (MEA) further comprises at least one gas diffusion layer. The one or more gas diffusion layer(s) may be between the at least one cathode or all of the cathodes and the first insulating layer and at least one or all of the first fluid path(s). The one or more gas diffusion layer(s) may be between the at least one anode or all of the anodes and the second insulating layer and at least one or all of the second fluid path(s). The MEA may comprise multiple gas diffusion layers as described herein.

[0207] Preferably, the oxidisable fluid described in any aspect of the invention described herein is air and the reducible fluid is hydrogen gas.

[0208] Preferably, when the device is a fuel cell, each fuel cell board may have a power rating of at least 1W. Preferably, each fuel cell board may have a power rating of at least 10W. 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, each fuel cell comprising multiple fuel cell boards may have a power rating of up to lOOOkW. Preferably, each fuel cell comprising multiple fuel cell boards may have a power rating of 2W to lOOOkW.

[0209] Preferably, one or more of the layers described herein are laminated together. This lamination may be achieved by chemical bonding by heating layers of prepreg between the insulating layers under pressure and an increased temperature, as described herein. Use of an epoxy resin prepreg also maintains compression of the gas diffusion layer of the MEAs, a critical component in maintaining fuel cell performance as it provides a sufficiently low resistance electrical path without compromising distribution of reactant fluids.

[0210] Preferably, the oxidisable fluid, the reducible fluid and / or the one or more heat exchange fluids enter and leave the relevant fluid paths described herein via inlets and outlets. These inlets and outlets may connect the fluid paths to manifolds which supply the relevant fluids to the fluid paths. These manifolds are those described herein, but may be apertures in the insulating layers.

[0211] The fuel cell boards as disclosed herein may comprise single or multiple anodes and single or multiple cathodes. All cathodes are arranged across a first surface of the ion permeable membrane and all anodes are arranged across a second surface opposing the first surface of the ion permeable membrane.

[0212] A fuel cell disclosed herein may comprise at least one fuel cell board. Each fuel cell board comprises at least one first insulating layer, at least one ion permeable membrane, and at least one or multiple anodes and at least one or multiple cathodes. All cathodes are arranged across a first surface of the ion permeable membrane and all anodes are arranged across a second surface opposing the first surface of the ion permeable membrane. These are arranged such that each anode overlaps with at least one cathode through the ion permeable membrane and / or such that each cathode overlaps with at least one anode through the ion permeable membrane. If more than one of each, pairs of anodes and cathodes across the at least one ion permeable membrane are electrically connected in parallel with adjacent pairs of pairs of anodes and cathodes. Individual cells comprise at least one anode and at least one cathode on opposite faces of at least one ion permeable membrane such that the anode and cathode can exchange ions across the at least one ion permeable membrane. Each individual cell is connected in parallel across the fuel cell board.

[0213] Pairs of anodes of cathodes across the at least one ion permeable membrane, sometimes referred to herein as individual cells on a fuel cell board or individual MEAs on a fuel cell board, may be electrically connected so that they are connected in parallel with the other (i.e., adjacent) pairs of pairs of anodes and cathodes on the same fuel cell board. They may be connected by any means known in the art, as described here.

[0214] Having the pairs of anodes and cathodes, individual cells on a fuel cell board or individual MEAs on a fuel cell board connected in parallel, rather than in series, will lower the overall voltage of the fuel cell and will increase the amount of current drawn from the fuel cell board, it can be termed "flattening" the polarisation / potential curve of the fuel cell. Operating in this method can be used to flatten the polarization curve.

[0215] Operating the individual MEAs on a fuel cell board in series may produce a higher voltage (than when operated in parallel), which can be advantageous in certain circumstances. So, fuel cell boards connected to be switchable between series and parallel may advantageous, offering advantages over those just operable in series or operable in parallel.

[0216] 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 at least two insulating layers each having at least one component provided on or in the insulating layer; each insulating layer comprising a first conductive through via, in electrical connection with a first conductive through via of the other insulating layer, the electrical connection between the first conductive through vias providing a first conductive bus through the insulating layers; each insulating layer further comprising a second conductive through via, in electrical connection with a second conductive through via of the other insulating layer, the electrical connection between the second conductive through vias providing a second conductive bus through the insulating layers; wherein a component located on or in one insulating layer is connected to the first conductive bus and a component located on or in the other insulating layer is connected to the second conductive bus.

2. An electrochemical device wherein the at least one component is connected to the first conductive bus by a conductive trace.

3. An electrochemical device as claimed in claim 1 or claim 2, wherein there are one or more components on both of the at least two insulating layers.

4. An electrochemical device as claimed in claim 3, wherein the one or more components are selected from an electrical component, an electronic component, an electrode, an electrolyte a sensor, a heat trace or an actuator.

5. An electrochemical device as claimed in claim 3 or 4, wherein the one or more components are individually connected to one or more electrically isolated conductive buses.

6. An electrochemical device as claimed in claim 5, wherein the electrically isolated conductive buses are formed of a single conductive bus or multiple conductive buses.

7. An electrochemical device as claimed in any preceding claim, wherein the component is a working electrode, which in operation has a voltage change due to electrochemical reactions in the electrochemical device.

8. An electrochemical device as claimed in any one of claims 1 to 6, wherein the component is a reference electrode, separate from a working electrode.

9. An electrochemical device as claimed in claim 7, wherein the working electrode is an anode electrode or cathode electrode and the reference electrode is in contact with an electrolyte.

10. An electrochemical device as claimed in any preceding claim, wherein a voltage measuring device is connected across two conductive buses, wherein each conductive bus is connected to at least one component.

11. An electrochemical device as claimed in any preceding claim, wherein at least one conductive bus is a voltage bus channel connected to a voltage measuring device and to at least one component for carrying out voltage measurement.

12. An electrochemical device as claimed in any preceding claim, wherein at least one conductive bus is a current carrying bus channel connected to a current source and connected to at least one component for carrying a current to the component.

13. An electrochemical device as claimed in claim 12, wherein the current carrying bus channel is configured to carry a current to the component for heating.

14. An electrochemical device as claimed in any preceding claim, wherein on at least one insulating layer, two conductive buses are connected respectively to two components, wherein the connection is under the control of a switch or relay; optionally wherein at least two conductive buses are connected to one component or one conductive bus is connected to two components, preferably under the control of a switch or relay.

15. An electrochemical device as claimed in claim 14, wherein the components are a first and second electrode, optionally an anode and a cathode electrode.

16. An electrochemical device as claimed in any preceding claim, wherein the device comprises further insulating layers each having at least one component provided on or in the insulating layer; each insulating layer comprising a further conductive through via, in electrical connection with a further conductive through via on an adjacent insulating layer, the electrical connection between the further conductive through vias providing further conductive buses through the insulating layers; wherein there is one further conductive bus through the insulating layers for each insulating layer, wherein a component is located on or in each further insulating layer, the connected to one further conductive bus.

17. An electrochemical device as claimed in any preceding claim, wherein the an electrochemical device further comprises at least two further insulating layers separate from the first two insulating layers, each of the further insulating layer having at least one component provided on or in the insulating layer; each insulating layer comprising a first conductive through via, in electrical connection with a first conductive through via of the other insulating layer, the electrical connection between the first conductive through vias providing a first conductive bus through the insulating layers; each insulating layer further comprising a second conductive through via,in electrical connection with a second conductive through via of the other insulating layer, the electrical connection between the second conductive through vias providing a second conductive bus through the insulating layers; wherein a component located on or in one insulating layer is connected to the first conductive bus and a component located on or in the other insulating layer is connected to the second conductive bus.

18. An electrochemical device comprising a plurality of insulating layers, all of the plurality of insulating layers comprising a conductive through via in electrical connection with the conductive through via of at least one adjacent insulating layer, the electrical connection between the conductive through vias providing a first conductive bus through the plurality of insulating layers, wherein the conductive through vias are aligned with one another and in series electrical contact, so that in use an electrical continuity measurement can be made through the first conductive bus.

19. The electrochemical device of claim 18, wherein the device also comprises at least two insulating layers each having at least one component provided on or in the insulating layer; each insulating layer comprising a first conductive through via, in electrical connection with a first conductive through via of the other insulating layer, the electrical connection between the first conductive through vias providing a first conductive bus through the insulating layers; each insulating layer further comprising a second conductive through via, in electrical connection with a second conductive through via of the other insulating layer, the electrical connection between the second conductive through vias providing a second conductive bus through the insulating layers; wherein a component located on or in one insulating layer is connected to the first conductive bus and a component located on or in the other insulating layer is connected to the second conductive bus.

20. The electrochemical device of any preceding claim, wherein the insulating layer is a printed circuit board.

21. The electrochemical device of any preceding claim, wherein the vias are solid electrical connectors, annular plated through holes, fully filled plated through holes or annular plated through holes that have been filled with an electrically conducting material.

22. The electrochemical device of any preceding claim, wherein the vias comprise an electrically conductive pad.

23. The electrochemical device as claimed in claim 22, wherein the electrically conductive pad is connected to a single conductive bus or to multiple conductive buses.

24. The electrochemical device of any preceding claim, wherein the first conductive through via through one insulating layer is formed of a first portion conductive through via offset in position relative to a second portion conductive through via, the first and second portion conductive through vias connected to form a conductive path.

25. The electrochemical device as claimed in claim 24, wherein the connection to form a conductive path is formed by a conductive material electrically connecting the first and second portion; optionally wherein the conductive material is a metal trace or a conductive polymer or exposed metal etch.

26. The electrochemical device of any preceding claim, wherein the first conductive through via of one insulating layer is offset in position with respect to the first conductive through via of the other insulating layer, and the second conductive through via is offset in position with respect to the second conductive through via of the other insulating layer.

27. The electrochemical device as claimed in claim 24, 25 or 26, wherein the offset is such that the first portion of the first conductive through via of one insulating layer does not overlap with the first portion of the first conductive through via of the other insulating layer.

28. The electrochemical device of claim 24 to 27, wherein the offset provides a first and second conductive bus arranged in a staggered configuration across adjacent insulating layers.

29. The electrochemical device of claim 28, wherein multiple conductive buses are formed in a stepped or staggered configuration across multiple insulating layers of the stack.

30. The electrochemical device of claim 29, wherein each conductive bus independently monitors a corresponding property of a component on or in an insulating layer.

31. The electrochemical device as claimed in any of claims 24 to 30, wherein a conductive path is created to the first conductive through via between the first conductive bus and the component.

32. The electrochemical device as claimed in claim 31, wherein the conductive path is a metal trace.

33. The electrochemical device of any preceding claim, wherein the electrochemical device is a battery, capacitor, fuel cell, electrolyser or sensor.

34. Use of at least one of the conductive buses of any of the preceding claims to measure a characteristic of the electrochemical device, preferably wherein that characteristic is cell voltage or activity / performance of a component of the electrochemical device or a physical attribute.

35. Use of at least one of the conductive buses of any of the preceding claims to measure the temperature or humidity of a part of the electrochemical device.

36. Use of at least one of the conductive buses of any of the preceding claims to measure the mechanical alignment or orientation of the insulating layers.

37. Use of at least one of the conductive buses of any of the preceding claims to supply current to the component, preferably wherein current is supplied to restore performance of that component, or preferably wherein current is supplied to electrically short one or more components.

38. Use of at least one of the conductive buses of any of the preceding claims to supply current to at least part of an insulating layer, preferably to a heat trace located on or in the insulating layer.

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