Bipolar plate for an electro-energy or electro-synthetic cell

Abstract

Disclosed is a bipolar plate for an electro-energy or electro-synthetic cell. The bipolar plate comprises an internal channel and can increase in thickness. The bipolar plate is adapted to apply a pressure or a force to an adjacent object when a fluid contained in the internal channel is pressurised. When provided as part of a stack of multiple adjacent electro-energy or electro-synthetic cells, the increase in thickness of the bipolar plate is adapted to create and thereafter maintain a compression force across the stack of multiple cells. Also disclosed is a cell stack, and method of forming the cell stack, comprising more than one individual cells, wherein bipolar plates are positioned between adjacent cells in the cell stack. The more than one individual cells are stacked in electrical series between a first endplate and a second endplate.

Description

BIPOLAR PLATE FOR AN ELECTRO-ENERGYOR ELECTRO-SYNTHETIC CELLTECHNICAL FIELD

[0001] The present invention broadly relates to bipolar plate devices with internal channels, for compressing individual electro-synthetic or electro-energy cells within a cell stack, such as an industrial cell stack. The architecture of each individual cell is such that more than one cell can be stacked together to effectively constitute a single electrosynthetic or electro-energy apparatus.BACKGROUND

[0002] An electro- energy cell is an electrochemical cell that generates electrical power over sustained periods of time, for use outside of the cell. Electro-energy cells are distinguished from other galvanic cells in that they require a constant external supply of reactants. The products of the electrochemical reaction must also be constantly removed from such cells. Unlike a battery, an electro-energy cell does not store chemical or electrical energy within the electro-energy cell.

[0003] Examples of electro-energy cells include but are not limited to hydrogen-oxygen Polymer Electrolyte Membrane (PEM) fuel cells, hydrogen-oxygen alkaline fuel cells, ammonia fuel cells, and the like.

[0004] An electro-synthetic cell may be similarly considered to be an electrochemical cell that manufactures one or more chemical materials over sustained periods of time, for use outside of the cell. The chemical materials may be in the form of a gas, liquid, or solid. Like an electro-energy cell, an electro-synthetic cell also requires a constant supply of reactants and a constant removal of products. Electro-synthetic cells may generally further require a constant input of electrical energy.

[0005] Examples of electro-synthetic cells include but are not limited to: water electrolysis cells, chlor-alkali cells, and cells for manufacturing hydrogen peroxide, ammonia, and the like.

[0006] Another feature of electro-synthetic or electro-energy cells is the large quantities of reactants and products that are typically involved in their operation. Such cells need to be constantly fed with substantial amounts of reactants, whilst significant volumes of products must be, simultaneously, constantly removed.

[0007] Large quantities of electrical energy are also involved in operating electro-energy and electro-synthetic cells. Therefore, a key challenge in the development of these cells is to make them as energy efficient as possible during operation. This may be achieved, in part, by minimizing their electrical impedance. Impedance is the opposition that a cell circuit presents to an electrical current. One well-known method of minimizing impedance is to employ a cell architecture in which the anode and cathode electrodes of the cell are placed facing each other, as close as possible to each other, without touching (which would create a short circuit). The gap between the two electrodes should then, ideally, also be occupied by an electrolyte having the highest possible conductivity. In general, liquid electrolytes, as a class, have the highest conductivities of any electrolyte. An inter-electrode membrane / ionomer / diaphragm (also called a ‘separator’) may typically also be placed between the electrodes to prevent the electrodes from touching each other, and to maintain the reactants consumed by and / or the products generated by each electrode separate from each other. The electrodes may, in many electro-energy and electro-synthetic cells, be sandwiched closely (tightly) against opposite sides of the membrane / ionomer / diaphragm separator to minimise the gap between them. This may be achieved by applying a suitable clamping force to the two electrodes, to thereby push them and hold them closely (tightly) against opposite sides of the separator. Such a clamping force is termed herein, the ‘electrode clamping force’.

[0008] In industrial form, individual electro-synthetic and electro-energy liquid-gas cells may often be ‘stacked’ in electrical series with other individual cells to thereby create a ‘cell stack’. This is commonly achieved within a so-called ‘filter-press’ arrangement (alsoknown as a ‘plate-and- frame’ arrangement). In such a configuration, individual cells having a substantially flat architecture, may be stacked between two endplates that are compressed toward each other. This causes the intervening, stacked individual cells to: (a) make and maintain electrical contact with each other (in electrical series), (b) be securely held within the stack, with the necessary clamping force applied to the electrodes of each individual cell, to thereby: (c) form a single electro-synthetic or electro-energy device, namely, a filter-press-type cell stack. The resulting cell stack is then, effectively, a single device that has the product output from all the incorporated cells, as well as their combined reactant consumption. In this way, large quantities of reactants and products may be accumulated into single, external, product and / or reactant streams, that are more easily managed than multiple smaller streams. Such a single device, or even a combination of multiple such single devices, may also be said to be components within an electro-synthetic or an electro-energy ‘cell’ (in the singular), despite the fact that they formally comprise multiple individual electro-synthetic or electro-energy cells. For example, such a single device may be said to be part of a single electro-synthetic or electro-energy ‘cell’, despite formally comprising of multiple individual electro-synthetic or electro-energy cells. This terminology may be routinely used when referring to an industrial electro-synthetic or electro- energy ‘cell’; i.e. an industrial electro-synthetic or electro- energy cell (in the singular) may comprise many individual electro-synthetic or electro-energy cells.

[0009] The challenges involved in fabricating and maintaining filter-press-type cell stacks of this type are well known. Assembling and simultaneously combining multiple individual cells into a filter-press-type cell stack often requires that a very particular and / or high, overall level of compression be applied across or between the endplates on either end of the cell stack. This very particular and / or high overall level of compression is termed herein the ‘stack compression’. Moreover, this overall stack compression may need to be very evenly and uniformly distributed across each of the individual cells present within the cell stack. This may be required, in part, to afford a relatively uniform clamping force to the electrodes in each individual cell within the stack. Additionally, the compression applied across the stack may need to be very evenly and uniformly spread over each face of each individual cell, so that there are no locations of excessive or insufficient compression onthe front or back face of any of the individual cells in the stack. Each individual cell may further need to be very precisely positioned relative to the other individual cells prior to and during the application of the compression. Achieving these requirements is often difficult, especially in high-volume, mass production environments where such precision must be achieved at speed, in the minimum of time.

[0010] Furthermore, after assembly of the cell stack, the often very high and / or very particular stack compression required may typically have to be precisely maintained to ensure the integrity of the individual cells (e.g. against unwanted leaks), and the application of the correct electrode clamping force in each individual cell in the stack during electrochemical operation. However, cell stacks may be subject to cycling between low and high temperatures (‘thermal cycling’) and low and high pressures (‘pressure-cycling’) during operation, causing thermal and / or pressure-induced expansion and contraction of the individual cells in the stack. The resulting dimensional changes may alter the lateral and facial compression experienced by each individual cell, inducing changes in the net compressive force experienced by each individual cell (and therefore also in the clamping force applied to the electrodes in each individual cell). Such changes may, in extreme cases, lead to leaks of liquid and / or gases within one or more individual cells in the stack, or unwanted mixing of liquids and / or gases within one or more individual cells in the stack, or to the application of an incorrect clamping force on the electrodes within one or more individual cells in the stack. For this reason, the rate of thermal or pressure-induced expansion of each of the cell components needs to be carefully considered and matched wherever possible, for example by using disk springs, also known as Belleville washers, on the tie rods that link and hold the endplates of the cell stack together.

[0011] Many electrochemical cell stacks also employ metallic plates, known as ‘bipolar plates’, that lie between the individual cells in a stack. Such bipolar plates may be held in position by the compression applied to the stack as a whole, via the tie-rods and associated Belleville washers. A bipolar plate is a conductive plate, for example a metallic plate, in an electro- energy or electro-synthetic cell stack, whose one side or face (the ‘anode face’) connects to an anode of one individual cell in the stack and whose other side or face (the‘cathode face’) connects to the cathode in the adjacent cell in the stack. The primary function of the bipolar plate is to uniformly transmit and distribute the electrical current from one cell to the next. A secondary function may be to correctly and uniformly apply the required clamping force on the electrodes in the individual cells. The electrode clamping force is usually applied via an intermediate springed or sprung structure that is located between the bipolar plate and its associated electrode. Such an intermediate springed or sprung structure may be commonly termed a ‘porous transport layer’, or a ‘spring layer’. The dimensional changes that occur during thermal or pressure cycling may affect the physical dimensions and tolerances of the bipolar plate, changing the lateral and facial compression experienced by the individual cells within cell stacks (and thereby also changing the magnitude and / or the uniformity of the clamping force that is applied to the electrodes in the individual cells). A major challenge in the industrialisation of cell stack production is to develop reliable and successful cell stack assembly and maintenance techniques that avoid or mitigate unwanted changes in the lateral, facial and overall compression experienced by the individual cells in cell stacks. A need exists to address or ameliorate this problem.

[0012] International Patent Publication No. WO2023 / 215605 to Electric Hydrogen Co. discloses a system and a method of actively managing electrolyser stack compression. The method includes actively managing electrolyser stack compression. The method includes receiving, by a data acquisition unit, stack data from an electrolyser stack in real time; providing, by the data acquisition unit, the stack data to a compression force controller; and controlling, by the compression force controller, how much force is applied by a force generating mechanism to the electrolyser stack based on the stack data. The compression force controller is configured to control a plurality of hydraulic nuts, pneumatic nuts, or bolt tensioners together such that a same force is applied to each hydraulic nut, pneumatic nut, or bolt tensioner of the plurality of hydraulic nuts, pneumatic nuts, or bolt tensioners. The compression force controller is configured to independently control each hydraulic nut, pneumatic nut, or bolt tensioner such that a same force or a different force is configured to be applied to each hydraulic nut, pneumatic nut, or bolt tensioner of the plurality of hydraulic nuts, pneumatic nuts, or bolt tensioners. Although this method is designed toapply independent forces on hydraulic nuts, pneumatic nuts or bolt tensioners in the electrolyser stack compression, this method does not address the challenge of avoiding or mitigating unwanted changes in the lateral, facial and overall compression experienced by each individual cell in the cell stacks.

[0013] International Patent Publication No. WO2024 / 105252 to Green Hydrogen Systems A / S seeks to address problems that can be associated with electrolyser stack compression including ensuring leak tight enclosures for the half-cell processes and ensuring that anolyte and catholyte are not mixed in cells during electrolysis by fluid flow from one half cell to the next via flow paths around the rim of diaphragms and or bipolar plates in an electrolyser stack. The disclosure of WO2024 / 105252 provides a cell frame adapted for use in a pressurised electrolyser cell stack. From an inner circumferential rim of the cell frame, a circumferential radial shelf with inwardly tapering thickness is provided, such that an annular space between a circumferential radial shelf and a neighbouring circumferential radial shelf is provided when cell frames are stacked in alignment with each other, and that outwardly of the circumferential radial shelf, a mobility link is provided which connects the radial shelf to the remaining cell frame. The combined effect of the radial shelf and the mobility link ensures that the radial shelf may pivot and or translate slightly with respect to the remaining cell frame, and thus elements inserted in the annular space shall allow transfer of movement and thus pressurisation between the two opposed sides of the radial shelf. This movement of the radial shelf allows the radial shelf to compensate for possible deviations in tolerances in a member inserted in the annular space. In a stack comprising a multitude of cell frames, this construction ensures a more even distribution of force between the individual radial shelves and inserted elements in the annular spaces throughout the entire stack. The radial shelf is adapted to pivot and / or translate in the axial direction of a cell stack when two cell frames with a bipolar plate between them are urged against each other. However, the cell frame is an additional component to be applied externally to the cell stack during compression and there is a high potential for failure and damage in a stack when each individual cell can be pivoted and translated against the cell frame.

[0014] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.SUMMARY

[0015] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify all of the key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0016] The inventors have developed a bipolar plate provided with one or more internal channels that is expandable, meaning that the overall thickness of the bipolar plate can increase when the fluid in the one or more internal channels of the bipolar plate is pressurised to a higher pressure than the surrounding environment. The inventors have further discovered that the use of such an ‘expandable internal channel bipolar plate’ between the individual cells in an electro-synthetic or electro-energy cell stack has several unexpected and surprising benefits. One benefit is that the individual cells may be assembled into a cell stack with a notably lower stack assembly compression force between the stack endplates than is normally required. For example, the cells may be assembled into a stack using a stack assembly compression force of less than 3 bar, less than 2 bar, or less than 1 bar; this may be substantially lower than the 10-30 bar compression force that may be needed to assemble, for example, modern commercial alkaline or PEM water electrolyser cell stacks. Further compression may then be applied to the cell stack postassembly, by pressurising the fluid within the one or more internal channels of the bipolar plate above the pressure of the surrounding environment. Such application of pressure may occur with or without physical expansion of the internal channel bipolar plate. That is, the use of expandable, pressure-tolerant internal channel bipolar plates allows for a two-step process of cell stack assembly in which the individual cells are first assembled into the cellstack under less demanding cell stack assembly compression conditions that are more amenable to high-speed, high-volume, mass production environments. In the context of the production of commercial electro-energy or electro-synthetic cell stacks, a high-speed, high-volume, mass production environment may involve continuous or continual production of stack assemblies, with each stack assembly complete in less than 20 minutes, less than 10 minutes, less than 5 minutes, less than 3 minutes, less than 2 minutes, less than 1 minute, or less than 30 seconds. In the second step, further compression may be applied within the cell stack by pressurising the fluid in the internal channels of the expandable, pressure-tolerant bipolar plate. An added advantage is that the compression applied using the second step may be mostly manifested as clamping force applied to the electrodes. Thus, the second step provides a means of ensuring that a uniform and even electrode clamping force is applied to each of the individual cells after the cell stack has been assembled. The fluid in the one or more internal channels of the bipolar plate may be a liquid fluid or a gaseous fluid. The pressure of the fluid in the one or more internal channels of the expandable, pressure-tolerant bipolar plate may be maintained or adjusted as required, during or after electrochemical operation of the cell stack to thereby maintain an even and uniform compression of the individual cells within the cell stack and / or an even and uniform electrode clamping force in the individual cells within the cell stack. Such ‘in-situ’ management of the compression applied to the individual cells in a cell stack, or their electrode clamping force, is not available in conventional electro-energy or electrosynthetic cell stacks.

[0017] According to a first aspect the invention provides a bipolar plate for an electroenergy or electro-synthetic cell, the bipolar plate comprising an internal channel wherein the bipolar plate is adapted to increase a thickness of the bipolar plate, and / or wherein the bipolar plate is adapted to apply a pressure or a force on an adjacent object, when a fluid contained in the internal channel is pressurised such that a pressure inside the internal channel is greater than a pressure external to the bipolar plate. Preferably, but not exclusively, the increase in thickness of the bipolar plate is adapted to create and thereafter maintain a compression force across a stack of multiple adjacent cells, for example across a stack of multiple adjacent electro-energy or electro-synthetic cells. Preferably, but notexclusively, the adjacent object is an adjacent cell and / or an electrode in the adjacent cell and the bipolar plate is adapted to apply the pressure or the force on the adjacent cell and / or the electrode in the adjacent cell.

[0018] Preferably but not exclusively, a cross-section of the internal channel expands when the fluid is pressurised, such that the thickness of the bipolar plate increases in accordance with the cross-section of the internal channel expanding. An expansion of the cross-section of the internal channel may substantially correspond to the increase in thickness of the bipolar plate.

[0019] Preferably but not exclusively, a cathode face wall and / or an anode face wall of the bipolar plate apply the pressure or the force on the adjacent object when the fluid is pressurised, such that the pressure or the force increases in accordance with the pressure of the fluid in the internal channel. In some example embodiments, the cross-section of the internal channel expanding, thus applied, may substantially correspond to an increase in the thickness of the bipolar plate. In other examples, the cross-section of the internal channel expanding, thus applied, may not involve an increase in the thickness of the bipolar plate, or does not substantially correspond to an increase in the thickness of the bipolar plate. Preferably, but not exclusively, the force is a clamping force. Preferably, but not exclusively, the adjacent object is an adjacent cell and / or an electrode in the adjacent cell.

[0020] In one embodiment, the bipolar plate comprises two or more internal channels.

[0021] Preferably, but not exclusively, a maximum increase in the thickness of the bipolar plate is less than 1 mm. The maximum increase in the thickness of the bipolar plate may be less than 0.9 mm, less than 0.8 mm, less than 0.7 mm, less than 0.6 mm, less than 0.5 mm, less than 0.4 mm, less than 0.3 mm, less than 0.2 mm, less than 0.1 mm, less than 0.09 mm, less than 0.08 mm, less than 0.07 mm, less than 0.06 mm, less than 0.05 mm, less than 0.04 mm, less than 0.03 mm, less than 0.02 mm, or less than 0.01 mm.

[0022] The maximum increase in the thickness of the bipolar plate may be less than 10 mm, less than 9 mm, less than 8 mm, less than 7 mm, less than 6 mm, less than 5 mm, less than 4 mm, less than 3 mm, or less than 2 mm.

[0023] Preferably, but not exclusively, the cathode face wall is a conductive metallic wall and the anode face wall is a conductive metallic wall. Optionally, the cathode face wall and the anode face wall are at least partially flexible.

[0024] According to a second aspect, the invention provides a cell stack comprising more than one individual electro-synthetic or electro-energy cells wherein the bipolar plate of any one of the preceding claims is positioned between adjacent cells in the cell stack; wherein the more than one individual electro-synthetic or electro- energy cells are stacked in electrical series between a first endplate and a second endplate. Preferably, but not exclusively, the increase in thickness of the bipolar plate creates and thereafter maintains a stack compression force across the first endplate and the second endplate.

[0025] Preferably, but not exclusively, the internal channel, or the internal channels, of each of the bipolar plates are filled with a fluid, wherein the fluid is a gaseous fluid or a liquid fluid. Preferably, but not exclusively, the fluid is pressurised. The fluid may be pressurised such that a pressure inside the internal channel is greater than a pressure external to the bipolar plate.

[0026] An excess pressure applied to the fluid above the pressure external to the bipolar plate, is preferably but not exclusively, substantially similar or equal to an electrode clamping force applied to one or more electrodes in each cell in the cell stack. Preferably, but not exclusively, the excess pressure applied to the fluid above the pressure external to the bipolar plate applies a calibrated electrode clamping force to the cells adjacent to the bipolar plate.

[0027] Preferably, but not exclusively, the excess pressure applied to the fluid above the pressure external to the bipolar plate, may be greater than or equal to 2 bar. The excess pressure applied to the fluid above the pressure external to the bipolar plate, may be greaterthan or equal to 3 bar, greater than or equal to 4 bar, greater than or equal to 5 bar, greater than or equal to 6 bar, greater than or equal to 7 bar, greater than or equal to 8 bar, greater than or equal to 9 bar, greater than or equal to 10 bar, greater than or equal to 15 bar, or greater than or equal to 20 bar

[0028] Preferably, but not exclusively, the excess pressure applied to the fluid above the pressure external to the bipolar plate, may be greater than or equal to 1 bar, greater than or equal to 0.9 bar, greater than or equal to 0.8 bar, greater than or equal to 0.7 bar, greater than or equal to 0.6 bar, greater than or equal to 0.5 bar, greater than or equal to 0.4 bar, greater than or equal to 0.3 bar, greater than or equal to 0.2 bar, or greater than or equal to 0.1 bar, greater than or equal to 0.05 bar, greater than or equal to 0.02 bar, greater than or equal to 0.01 bar, or greater than or equal to 0.05 bar.

[0029] Preferably, but not exclusively the pressure of the fluid is managed and / or controlled. The pressure of the fluid may be managed and / or controlled during periods of operation of the cell stack.

[0030] According to a third aspect, the invention provides a method for assembling a cell stack comprising more than one individual electro-synthetic or electro-energy cells, the method comprising: stacking the cells such that the bipolar plate of the first aspect is positioned adjacent each cell, wherein the cells are stacked in electrical series between a first endplate and a second endplate; and applying and thereafter maintaining a stack compression force across the first endplate and the second endplate to thereby form the cell stack such that the cell stack comprises a single electrochemical device.

[0031] According to a fourth aspect, the invention provides a method for assembling the cell stack of the second aspect comprising more than one individual electro-synthetic or electro- energy cells, the method comprising: stacking the individual cells such that the bipolar plate of the first aspect is positioned adjacent each cell, wherein the cells are stacked in electrical series between a first endplate and a second endplate; and applying and thereafter maintaining a stack compression force across the first endplate and the secondendplate to thereby form the cell stack such that the cell stack comprises a single electrochemical device.

[0032] Preferably, but not exclusively, the stack assembly compression force applied across the first endplate and the second endplate is substantially lower than a force required to assemble a comparable stack containing bipolar plates that are not adapted to increase in thickness when a fluid contained in an internal channel of the bipolar plate is pressurised. In some examples, the cells may be assembled into a stack using a stack assembly compression force of less than 3 bar, less than 2 bar, or less than 1 bar. This may be substantially lower than the 10-30 bar compression force that may be needed, for example, to assemble modern commercial alkaline or PEM water electrolyser stacks.

[0033] Preferably, but not exclusively, the stack assembly compression force applied across the first endplate and the second endplate is substantially lower than a force required to assemble a comparable stack containing bipolar plates that are not adapted to apply a pressure or force on an adjacent object (for example on an adjacent cell and / or an electrode in an adjacent cell) when a fluid contained in an internal channel of the bipolar plate is pressurised. In some examples, the cells may be assembled into a stack using a stack assembly compression force of less than 3 bar, less than 2 bar, or less than 1 bar. This may be substantially lower than the 10-30 bar compression force that may be needed to assemble modern commercial alkaline or PEM water electrolysis stacks.

[0034] Preferably, but not exclusively, the method for assembling a cell stack is suitable for high-speed, high-volume, mass production. In the context of the production of commercial electro-energy or electro-synthetic cell stacks, a high-speed, high-volume, mass production environment may involve continuous or continual production of stack assemblies, with each stack assembly complete in less than 20 minutes, less than 10 minutes, less than 5 minutes, less than 3 minutes, less than 2 minutes, less than 1 minute, or less than 30 seconds.

[0035] Preferably, but not exclusively the method further comprises the steps of: filling one or more internal channels of the bipolar plates with a fluid; and pressurising the fluid to thereby increase a compression force applied to the cell stack.

[0036] According to a fifth aspect, the invention provides a cell stack assembled according to the method of the third aspect or the fourth aspect.

[0037] According to a sixth aspect, the invention provides the cell stack of the second aspect, wherein the cell stack comprises more than one individual water electrolysis cells stacked in electrical series between two endplates.

[0038] According to a seventh aspect, the invention provides the cell stack of the second aspect, wherein the cell stack comprises more than one individual hydrogen-oxygen fuel cells stacked in electrical series between two endplates.

[0039] In a still further aspect, there is provided a method for assembling a filter-press-type (or plate-and-frame-type) cell stack comprising more than one, or at least two individual electro-synthetic or electro-energy cells, the method involving:stacking the individual cells, with expandable internal channel bipolar plates between them, in electrical series between two endplates; and thenapplying and thereafter maintaining an overall stack compression across the two endplates to thereby form the cell stack as a single electrochemical device.

[0040] Preferably but not exclusively, the compression applied across the two endplates (the ‘stack compression’), is lower than that normally required to assemble a comparable stack containing bipolar plates that are not expandable. Preferably but not exclusively, due to the lower compression requirement, the stack assembly process is more amenable to high-speed, high- volume, mass production than stack assembly processes involving bipolar plates that are not expandable.

[0041] In another aspect, the abovementioned method further involves the additional steps of:filling the internal channel(s) of each of the bipolar plates with a fluid; and thenpressurising the fluid to thereby increase the compression applied in the stack.

[0042] Preferably but not exclusively, the fluid is pressurised to a pressure greater than the pressure of the surrounding environment. Preferably but not exclusively, the excess pressure applied to the fluid above the pressure of the surrounding environment, is equal to or similar to the clamping force that must be applied to the electrodes in each cell in the stack. Preferably but not exclusively, the excess pressure applied to the fluid above the pressure of the surrounding environment, manifests as a uniform and / or even a calibrated electrode clamping force to all of the individual cells in the cell stack. Preferably but not exclusively, the excess pressure applied to the fluid above the pressure of the surrounding environment, is of the magnitudes described in a paragraph above. Preferably but not exclusively, the pressure of the fluid is managed and / or controlled. Preferably but not exclusively, the pressure of the fluid is managed and / or controlled during periods of operation of the cell stack. Such ‘in-situ’ management of the compression applied to the individual cells in a cell stack, or their electrode clamping force, is not available in conventional electro-energy or electro-synthetic cell stacks.

[0043] In a further aspect, the filter-press-type (or plate-and-frame-type) cell stack referred to above, comprises two or more, or at least two, individual water electrolysis cells stacked in electrical series between two endplates.

[0044] In a still further aspect, the filter-press-type (or plate-and-frame-type) cell stack referred to above, comprises two or more, or at least two, individual hydrogen-oxygen fuel cells stacked in electrical series between two endplates.

[0045] In the context of the present invention, the words “comprise”, “comprising” and the like are to be construed in their inclusive, as opposed to their exclusive, sense, that is in the sense of “including, but not limited to”.

[0046] The invention is to be interpreted with reference to the at least one of the technical problems described or affiliated with the background art. The present invention aims to solve or ameliorate at least one of the technical problems and this may result in one or more advantageous effects as defined by this specification and described in detail with reference to the preferred embodiments of the present invention.BRIEF DESCRIPTION OF THE FIGURES

[0047] Figure 1 schematically depicts a cross-section of: (a) an example bipolar plate, the bipolar plate comprising an internal channel (i.e. an internal channel bipolar plate), and (b) an example bipolar plate, the bipolar plate comprising an internal channel (i.e. an internal channel bipolar plate), with two individual electro-synthetic or electro-energy cells directly adjacent to the internal channel bipolar plate, on either side of the internal channel bipolar plate.

[0048] Figure 2 depicts an example cell stack.

[0049] Figure 3 depicts a cross-sectional view of the example cell stack in Figure 2.

[0050] Figure 4 depicts an alternative cross-sectional view of the example cell stack in Figure 2.DESCRIPTION OF THE INVENTION

[0051] Preferred embodiments of the invention will now be described with reference to the accompanying drawings and non-limiting examples.Definitions

[0052] An ‘electro-energy cell’, as discussed herein, is an electrochemical cell that generates electrical power continually or continuously, over indefinite periods of time, for use outside of the cell. Electro-energy cells may require a constant external supply of reactants during operation. The products of the electrochemical reaction may be also constantly removed from such cells during operation. An electro-energy cell may be a liquid-gas cell. An example of an electro-energy cell is a hydrogen-oxygen fuel cell. This example is also a liquid-gas cell.

[0053] An ‘electro-synthetic cell’, as discussed herein, is an electrochemical cell that manufactures one or more chemical materials continually or continuously, over indefinite periods of time, for use outside the cell. The chemical materials may be in the form of a gas, liquid, or solid. Like an electro-energy cell, an electro-synthetic cell may also require a constant supply of reactants and a constant removal of products during operation. Electrosynthetic cells may generally further require a constant input of electrical energy during operation. An electro-synthetic cell may be a liquid-gas cell. An example of an electrosynthetic cell is a water electrolysis cell. This example is also a liquid-gas cell.

[0054] Electro-energy and electro-synthetic cells, as discussed herein, differ from other types of electrochemical cells, such as batteries, sensors and the like, in that they do not incorporate within the cell body all / some of the reactants they require to operate, nor all / some of the products they generate during operation. These may, instead, be constantly brought in from, or removed to the outside of the cell during operation. For example, electro- energy cells are distinguished from galvanic cells in that galvanic cells store their reactants and products within the cell body. Unlike a battery, an electro- energy cell does not store chemical or electrical energy within it. Similarly, while some electrochemical sensors may consume reactants and generate products in limited quantities during the sensing operation, all / some of these are stored within the cell body itself.

[0055] A ‘liquid electrolyte’ is a liquid used in an electro-synthetic or electro-energy cell. Some liquid electrolytes contain dissolved ions that impart the liquid electrolyte with anenhanced capacity to conduct electricity (such as, for example, 1 M KOH, 6 M NaOH, 1 M H2SO4, or 4.5 M HC1). In other cells the liquid electrolyte may not contain significant quantities of ions making them, effectively, non- conductive (such as, for example, the deionized water that is used in Polymer Electrolyte Membrane electrolysis cells or fuel cells).

[0056] A ‘separator’ (also referred to as an ‘inter-electrode separator’) is defined to be a sheet-like material that is placed between the electrodes in an individual electro-synthetic or electro-energy cell to prevent them from touching and short-circuiting with each other. Separators must generally be permeable to ions flowing between the electrodes during operation of the individual electro-synthetic or electro-energy cell. Some separators are also largely impermeable to gas, to thereby minimise gas from one of the component half cells crossing over into the other half-cell. Examples of ‘inter-electrode separators’ include ion-permeable membranes or ionomers (e.g. Nafion 117 and Nafion 115, manufactured by the Du Pont Nemours company), diaphragms (e.g. Zirfon PERL, manufactured by Agfa), fabrics (e.g. various asbestos fabrics used in the past), or similar structures. The term ‘separator’ or ‘inter-electrode separator’ includes an inter-electrode porous capillary separator, as described in International Patent Publication Nos. W02022056603, W02022056604, W02022056605, and W02022056606, which are hereby incorporated by reference.

[0057] ‘Electrode clamping force’ is defined herein as the clamping force that is applied to the two electrodes in an individual electro-synthetic or electro-energy cell that causes them to be (tightly) sandwiched against opposite sides of the inter-electrode separator.

[0058] The term ‘cell’ as used herein refers to an electrochemical cell, for example an electro- energy or electro-synthetic cell. The word ‘cell’ may refer to an individual electrochemical cell in the singular, or to a device containing a collection of individual electrochemical cells in the plural. For example, an electro-energy or electro-synthetic ‘cell’ may refer to a single, individual electro-energy or electro-synthetic cell, or it may refer to a plurality of individual electro-energy or electro-synthetic cells combined into a single cell stack or multiple cell stacks within a single device.

[0059] A ‘cell stack’ or a ‘stack’ is defined as an assembly of two or more electro-synthetic or electro-energy cells, wherein the cells are stacked adjacent to or abutting each other along a single dimensional axis. That is, a cell stack or a stack is a collection of individual electro- energy or electro-synthetic cells stacked laterally, one after the other, such that they are connected in electrical series. A cell stack may be designed to accumulate the reactants and products involved in their constituent individual cells into single, external product and / or reactant streams, that are more easily managed than multiple smaller streams.

[0060] A ‘filter- press’ or ‘plate-and-frame’ cell stack is defined as a cell stack wherein the individual cells have a substantially flat profile and are stacked adjacent to or abutting each other along a single dimensional axis, wherein the cells are compressed against each other between endplates during its assembly and / or operation.

[0061] An ‘endplate’ is defined as a rigid, essentially incompressible, essentially flat structure that is used at the ends of a ‘filter-press’ cell stack and between which the cells in the cell stack are compressed.

[0062] The term ‘stack assembly compression’ or ‘stack assembly compression force’ is herein defined as the compression or compressive force that is applied across the two endplates of a filter-press cell stack during the assembly of a cell stack, which comprises more than one individual electro-synthetic or electro-energy cells stacked in electrical series. In some examples, the cells may be assembled into a stack using a stack assembly compression force of less than 3 bar, less than 2 bar, or less than 1 bar. This may be substantially lower than the 10-30 bar compression force that may be needed to assemble, for example, modern commercial alkaline or PEM water electrolyser stacks.

[0063] The term ‘stack compression’ or ‘overall stack compression’ or ‘stack compression force’ or ‘overall stack compression force’ is herein defined as the overall compression or compressive force that is applied across the two endplates of a filter-press cell stack during operation of a cell stack, which comprises more than one individual electro-synthetic or electro- energy cells stacked in electrical series. In some non-limiting examples, the stack compression force may be 4-30 bar.

[0064] The term ‘high-speed, high-volume, mass production environment’ is defined herein in the context of the production of commercial electro-energy or electro-synthetic cell stacks. A ‘high-speed, high-volume, mass production environment’ is defined as involving the continuous or continual production of stack assemblies, with each stack assembly complete in less than 20 minutes, less than 10 minutes, less than 5 minutes, less than 3 minutes, less than 2 minutes, less than 1 minute, or less than 30 seconds.

[0065] ‘Thermal cycling’ is the process wherein the cells in a cell stack are progressively and repeatedly heated and cooled, as may occur during and after repeated cycles of electrochemical operation.

[0066] ‘Pressure cycling’ is the process wherein the cells in a cell stack are progressively and repeatedly pressurised and de-pressurised, as may occur during and after repeated cycles of electrochemical operation.

[0067] A ‘bipolar plate’ is a conducting plate, that may be metallic, that is located on the outside of an individual electro-synthetic or electro-energy cell, or between individual electro-synthetic or electro-energy cells in a cell stack. The term ‘bipolar’ refers to the fact that, within a cell stack, the voltage applied to a bipolar plate may be used on its one side or face in an anode half-reaction in one individual cell, and on the other side or face in a cathode half-reaction in the adjacent individual cell in the stack. The primary functi on of a bipolar plate is to accumulate and uniformly distribute an electrical current from one cell to the next in a cell stack.

[0068] The ‘anode face’ of a bipolar plate is the side or face of a bipolar plate that is associated with the anode electrode in an individual cell to which it is attached. The ‘cathode face’ is the side or face of a bipolar plate that is associated with the cathode electrode in an individual cell to which it is attached. Typically, the bipolar plate will he between two adjacent individual cells in a cell stack, with its anode face connected to the anode electrode of one of the individual cells and its cathode face connected to the cathode electrode in the other individual cell.

[0069] A ‘porous transport layer’ or a ‘spring layer’ is a compressive or a spring ed or a sprung structure that, when positioned between a bipolar plate and its associated electrode (either anode or cathode) within an assembled individual cell, exerts a clamping force on the associated electrode, compressing it against the inter-electrode separator.

[0070] In the context of the present specification, the term ‘join’, 'joined' or ‘joins’ refers to a secure physical attachment, such as a weld, a fusion, a bonding, an adhesion, a blending, a melding, or a merging of two structures. For example, a metal plate representing the anode face of a bipolar plate, may be joined with a second metal plate representing the cathode face of a bipolar plate, to thereby enclose an internal channel structure within a bipolar plate.

[0071] An ‘internal channel bipolar plate’ is a bipolar plate that contains an internal channel structure within the bipolar plate.

[0072] An ‘expandable internal channel bipolar plate’, or an ‘expandable, pressure-tolerant internal channel bipolar plate’, or a ‘pressure-tolerant internal channel bipolar plate’, is an internal channel bipolar plate that, when the channels are filled with a gaseous or liquid fluid and the fluid is pressurised to a pressure greater than the pressure of the surrounding environment, is capable of: (i) increasing its thickness in some measure (i.e. it is capable of ‘expanding’ or ‘ballooning’ at least somewhat), and / or (ii) placing a pressure or a force on an adjacent object (for example an adjacent cell and / or an electrode in an adjacent cell). Typically, this requires the use of construction materials in the bipolar plate that can bend, flex, or expand in some way.

[0073] The phrase “pressure outside of the bipolar plate”, or “pressure external to the bipolar plate”, or “pressure external of the bipolar plate”, or “pressure of the environment about the bipolar plate”, refers to the pressure that is applied to or experienced by the bipolar plate due to other materials around it. For example, it may refer to the pressure that is applied to the bipolar plate due to the assembly of the cell stack and / or the compression of the cell stack between the two endplates during its assembly.

[0074] An ‘electrolyser’ or ‘water electrolyser’ as discussed herein, is a type of electrosynthetic cell, or an assembly of individual electro-synthetic cells, or a stack of multiple individual electro-synthetic cells, or a combination of stacks, that each comprise of more than one individual electro-synthetic cells, that employs electrical energy in the form of a direct current (DC) to electrochemically drive a non-spontaneous chemical reaction that results in the separation of the chemical bonds in water to produce hydrogen and oxygen gas. The word "lysis" means to separate or break, so electrolysis means "breakdown via electricity". An ‘electrolyser’ may typically further incorporate an engineering system, known as a balance-of-plant, that supports, manages and / or controls the individual cells present. An example of an industrial electrolyser is a water electrolyser of greater than or equal to 50 kW power that splits water into hydrogen gas and oxygen gas. Two types of water electrolysers are widely used industrially, namely, alkaline electrolysers and polymer electrolyte membrane (PEM) electrolysers.

[0075] A ‘header’ is a channel, a tube, a chamber, or a trough formed within the frame of an individual electro-synthetic or electro-energy cell, for conveying a liquid or gas fluid into or out of a cell, and thereby into or out of the full thickness of a cell stack. A header is typically designed to form a tube through the full length of the stack when the headers of multiple cells line up and seal when the cells are compressed together to form the cell stack.Example embodiments

[0076] Figure 1 (a) depicts a cross-section of a bipolar plate for an electro-energy or electro-synthetic cell, the bipolar plate comprising an internal channel and referred to herein as internal channel bipolar plate 100 or simply bipolar plate 100. The internal channel bipolar plate 100 comprises two conductive walls, preferably two conductive metallic walls, namely a cathode face wall 110 and an anode face wall 120. The cathode face wall 110 and the anode face wall 120 are sealed to each other around the periphery of the bipolar plate 100, as depicted at join 130. Between the cathode face wall 110 and the anode face wall 120 is an internal channel 140 that is created by the cathode face wall 110 and the anode face wall 120. The bipolar plate 100 is therefore an ‘internal channel bipolar plate’. The internal channel 140 may be occupied by a gaseous or liquid fluid, a mixture ofgaseous fluids, a mixture of liquid fluids, or a mixture of gaseous fluid(s) and liquid fluid(s). When the fluid in internal channel 140 is pressurised to a higher pressure than the pressure outside of the bipolar plate 100, then the thickness 150 of the bipolar plate 100 may increase. The bipolar plate 100 is thereby an ‘expandable bipolar plate’. In one example, the cathode face wall 110 and the anode face wall 120 are at least partially flexible. Alternatively, or additionally, if the fluid in internal channel 140 is pressurised to a higher pressure than the pressure outside of the bipolar plate 100, the cathode face wall 110 and / or the anode face wall 120 may exert a pressure or a force on an adjacent object to the bipolar plate 100. The bipolar plate 100 is thereby a ‘pressure-tolerant bipolar plate’. For the case where the thickness 150 of the bipolar plate 100 increases and the cathode face wall 110 and / or the anode face wall 120 exert a pressure or force on an adjacent object to the bipolar plate 100, the bipolar plate 100 may be termed an ‘expandable, pressure-tolerant bipolar plate’.

[0077] The cross-section in Figure 1(b) depicts an example embodiment, in which individual electro-synthetic or electro-energy cells 195a and 195b are located adjacent to the bipolar plate 100, on each side. In this example, each of the cells 195a and 195b are an adjacent object to the bipolar plate 100. Each individual cell 195a or 195b comprises a cell frame 196 to which the membrane-electrode assembly is attached, and through which headers 197 pass. The headers 197 allow fluid to be passed into and out of the internal channel 140 of the bipolar plate 100. The membrane-electrode assembly of each of cells 195a and 195b is depicted in the inset in Figure 1(b). The membrane-electrode assembly of each of cells 195a and 195b has the same structure, comprising an inter-electrode separator 160 that is sandwiched on either side by a cathode electrode 170 and an anode electrode 180. On the outside of the cathode electrode 170 and the anode electrode 180 are spring-loaded ‘porous transport layers’ (also termed herein a ‘spring layer’) 190. The spring-loaded porous transport layers 190 lie between their respective electrode, being the cathode electrode 170 or the anode electrode 180, and their respective bipolar plate wall, being the cathode face wall 110 or the anode face wall 120.

[0078] When the fluid in internal channel 140 of the bipolar plate 100 is pressurised to a higher pressure than the external pressure outside of the bipolar plate 100, the thickness 150 of the bipolar plate 100 may increase, thereby compressing the adjacent cells 195a and 195b. Alternatively or additionally, when the fluid in internal channel 140 is pressurised to a higher pressure than the pressure outside of the bipolar plate 100, the cathode face wall 110 and the anode face wall 120 may exert a pressure or a force on the respective adjacent cells 195a and 195b; this may occur without the thickness 150 of the bipolar plate 100 increasing. Such pressure or force may be directed onto the adjacent spring-loaded porous transport layers 190, which then exert a compressive, clamping force on the cathode electrode 170 or the anode electrode 180, sandwiching and compressing them more closely against the separator 160. In the case of cell 195b, the cathode face wall 110 of the bipolar plate 100 may exert a pressure or a force on the adjoining spring-loaded porous transport layer 190, causing the spring-loaded porous transport layer 190 to exert a compressive, clamping force on the cathode electrode 170 of cell 195b, sandwiching and compressing the cathode electrode 170 more closely against the separator 160 of cell 195b. In the case of cell 195a, the anode face wall 120 of the bipolar plate 100 may exert a pressure or a force on the adjoining spring-loaded porous transport layer 190, causing the spring-loaded porous transport layer 190 to exert a compressive, clamping force on the anode electrode 180 of cell 195a, sandwiching and compressing the anode electrode 180 more closely against the separator 160 of cell 195a.

[0079] Thus, there is provided a bipolar plate 100 for an electro- energy or electro-synthetic cell with the bipolar plate 100 comprising an internal channel 140. In one example, the bipolar plate 100 is adapted to increase the thickness 150 of the bipolar plate 100. In another example, additionally or alternatively, the bipolar plate 100 is adapted to apply a pressure or a force to an adjacent object or adjacent objects. The increase in the thickness 150 of the bipolar plate 100 and / or the bipolar plate 100 applying the pressure or the force to the adjacent object or adjacent objects occurs when the fluid contained in the internal channel is pressurised such that the pressure inside the internal channel is greater than the pressure external to the bipolar plate 100. In one example, the cells 195a and / or 195b, and / or theelectrodes in the cells 195a and 195b, are the adjacent object or the adjacent objects to the bipolar plate 100.

[0080] Figure 2 depicts an example cell stack 200 comprising: a first endplate 210 and a second endplate 220, as well as three individual electro-energy or electro-synthetic cells 195a, 195b, and 195c, separated by four expandable, pressure-tolerant, internal channel bipolar plates 100a, 100b, 100c, and lOOd. The first endplate 210 and the second endplate 220 are secured to each other by tie-rods (not shown in Figure 2), making them, essentially, unmovable. The number of individual electro-energy or electro-synthetic cells and the number of expandable, pressure-tolerant, internal channel bipolar plates illustrated is by way of example only. Any number of individual electro-energy or electro-synthetic cells and corresponding adjacent expandable, pressure-tolerant, internal channel bipolar plates could be used. The bipolar plates 100a, 100b, 100c, and lOOd are provided as part of the stack 200 of multiple adjacent electro-energy or electro-synthetic cells 195a, 195b, and 195c. The increase in thickness of the bipolar plates 100a, 100b, 100c, and lOOd is adapted to create and thereafter maintain a stack compression force across the first endplate 210 and the second endplate 220.

[0081] Figure 3(a)-(b) depicts a cross-section of the cell stack 200, viewed along the BC plane shown in Figure 2.

[0082] Figure 3(b) shows that each of the three individual electro- energy or electrosynthetic cells 195a, 195b, and 195c, comprise the same structure as that shown in the inset in Figure 1(b), namely: a separator 160 lying between a cathode electrode 170, and an anode electrode 180, with porous transport layers 190 between the electrodes and the walls of the bipolar plates 100a, 100b, 100c, and lOOd.

[0083] Figure 3(a) shows the internal channels 140a, 140b, 140c, and 140d, within the bipolar plates 100a, 100b, 100c, and lOOd respectively. Arrows 230 and 240 show the pathway that may be followed by a fluid within the internal channels 140a, 140b, 140c, and 140d, within bipolar plates 100a, 100b, 100c, and lOOd. The fluid may be, for example, a cooling fluid, for maintaining the operating temperature of the cell stack 200.

[0084] As will be apparent, if the fluid passing through the internal channels 140a, 140b, 140c, and 140d, is pressurised to a pressure greater than the external pressure of the bipolar plates 100a, 100b, 100c, and lOOd, and the bipolar plates 100a, 100b, 100c, and lOOd, are expandable bipolar plates, or pressure-tolerant bipolar plates, or expandable, pressure-tolerant bipolar plates, then the cathode face walls 110 belonging to bipolar plates 100a, 100b, and 100c will apply a pressure or force, via the intervening porous transport layers 190, on the cathode electrodes 170 belonging to cells 195a, 195b, and 195c, respectively. Simultaneously, the anode face walls 120 belonging to bipolar plates 100b, 100c, and lOOd will apply a pressure or force, via the intervening porous transport layers 190, on the anode electrodes 180 belonging to cells 195a, 195b, and 195c, respectively. Anode wall 120 belonging to bipolar plate 110a will apply a pressure or force upon the first endplate 210, while cathode wall 110 belonging to bipolar plate lOOd will apply a pressure or force on the second endplate 220.

[0085] If the areas over which each of the above pressures or forces are applied are equal, then the pressure or force that is applied in each case must necessarily also be equal. That is, application of the principles of hydraulics (in the case of a liquid fluid) or pneumatics (in the case of a gaseous fluid) means that all of the above forces or pressures must be equal to each other if the areas over which they are applied are equal.

[0086] Accordingly, embodiments of the invention provide a means to apply a uniform clamping force on the electrodes 170 and 180 in each of the cells within cell stack 200, such that the electrodes 170 and 180 are sandwiched against their respective separator 160 with equal force.

[0087] Moreover, the clamping force that is uniformly applied to the electrodes 170 and 180 in each of the cells within cell stack 200, may be uniformly changed by changing the internal pressure in an internal channel 140a, 140b, 140c, and 140d, above the external pressure, of the fluid passing through the bipolar plates 100a, 100b, 100c, and lOOd in the directions 230 and 240 shown in Figure 3.

[0088] Additionally, while the cell stack 200 was assembled with a particular stack assembly compression force (i.e. with a certain compression between the first endplate 210 and the second endplate 220), the overall compression applied to the cell stack 200 may be controlled, varied or increased, post assembly, by adjusting the pressure of the fluid in the internal channels 140a, 140b, 140c, and 140d of the bipolar plates 100a, 100b, 100c, and lOOd. For example, during operational temperature or pressure cycling, the overall compression applied to the cell stack 200 may be controlled by adjusting the pressure of the fluid in the internal channels 140a, 140b, 140c, and 140d of the bipolar plates 100a, 100b, 100c, and lOOd. Moreover, the cell stack 200 may be assembled with a lesser compression than is conventionally applied, allowing for more rapid and reliable assembly in a high-volume, mass-manufacturing industrial assembly process, with further compression applied via the fluid in the bipolar plates 100a, 100b, 100c, and lOOd in a second step.

[0089] Figure 4 depicts a cross section of the cell stack 200, viewed along the intersection of the A plane and the BC plane in Figure 2. Figure 4 depicts the presence of multiple internal channels 420 within each of the bipolar plates 100a, 100b, 100c, and 1 OOd, by the inclusion of conductive pattern- repeating plates 410, for example sinusoidal (wave-shaped) conductive, metallic plates 410 between the cathode face walls 110 and the anode face walls 120 of the bipolar plates 100a, 100b, 100c, and lOOd. (It should be noted that only the multiple internal channels 420 in bipolar plate 100a are labelled with numbers in Figure 4 for clarity). The sinusoidal (wave-shaped) conductive, metallic plates 410 may be fused / joined to the inside of the cathode face walls 110 and the anode face walls 120 of the bipolar plates 100a, 100b, 100c, and lOOd, at the points that touch the cathode face walls 110 and the anode face walls 120, by welding for example. The primary purpose of the sinusoidal conductive metallic plates 410 may be to facilitate electron conduction between the cathode face walls 110 and the anode face walls 120 of the bipolar plates 100a, 100b, 100c, and lOOd; this is the main requirement of a bipolar plate. However, their sinusoidal shape is such that it also allows the bipolar plate 100 to increase its overall thickness if the fluid inside of the bipolar plate 100 is pressurised to a higher than external pressure.

[0090] In non-limiting examples, the cathode face wall 110 and the anode face wall 120 of the bipolar plate 100 are formed of: a conducting material, a composite including a conducting material, a metal, a metallic alloy, graphite, a graphite polymeric material, a coated metal, a carbon composite material, stainless steel, aluminium, titanium, nickel, or combinations thereof. In another example, the cathode face wall 110 and the anode face wall 120 of the bipolar plate 100 are not formed of a uniform material and are formed of a partial conductive section and a partial non-conductive section of different materials.

[0091] In further non-limiting examples, the conductive pattern-repeating plates 410 are formed of: a conducting material, a composite including a conducting material, a metal, a metallic alloy, graphite, a graphite polymeric material, a coated metal, a carbon composite material, stainless steel, aluminium, titanium, nickel, or combinations thereof.

[0092] In non-limiting examples, a maximum increase in the thickness of the bipolar plate is less than 1 mm. The maximum increase in the thickness of the bipolar plate may be less than 0.9 mm, less than 0.8 mm, less than 0.7 mm, less than 0.6 mm, less than 0.5 mm, less than 0.4 mm, less than 0.3 mm, less than 0.2 mm, less than 0.1 mm, less than 0.09 mm, less than 0.08 mm, less than 0.07 mm, less than 0.06 mm, less than 0.05 mm, less than 0.04 mm, less than 0.03 mm, less than 0.02 mm, or less than 0.01 mm.

[0093] In non-limiting examples, the maximum increase in the thickness of the bipolar plate may be less than 10 mm, less than 9 mm, less than 8 mm, less than 7 mm, less than 6 mm, less than 5 mm, less than 4 mm, less than 3 mm, or less than 2 mm.

[0094] In non-limiting examples, the excess pressure applied to the fluid above the pressure external to the bipolar plate, may be greater than or equal to 2 bar. The excess pressure applied to the fluid above the pressure external to the bipolar plate, may be greater than or equal to 3 bar, greater than or equal to 4 bar, greater than or equal to 5 bar, greater than or equal to 6 bar, greater than or equal to 7 bar, greater than or equal to 8 bar, greater than or equal to 9 bar, greater than or equal to 10 bar, greater than or equal to 15 bar, or greater than or equal to 20 bar.

[0095] In non-limiting examples, the excess pressure applied to the fluid above the pressure external to the bipolar plate, may be greater than or equal to 1 bar, greater than or equal to 0.9 bar, greater than or equal to 0.8 bar, greater than or equal to 0.7 bar, greater than or equal to 0.6 bar, greater than or equal to 0.5 bar, greater than or equal to 0.4 bar, greater than or equal to 0.3 bar, greater than or equal to 0.2 bar, or greater than or equal to 0.1 bar, greater than or equal to 0.05 bar, greater than or equal to 0.02 bar, greater than or equal to 0.01 bar, or greater than or equal to 0.05 bar.

[0096] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms, in keeping with the broad principles and the spirit of the invention described herein.

[0097] The present invention and the described preferred embodiments specifically include at least one feature that is industrially applicable.

Claims

THE CLAIMS1. A bipolar plate for an electro-energy or electro-synthetic cell, the bipolar plate comprising an internal channel, wherein the bipolar plate is adapted to increase a thickness of the bipolar plate, and / or wherein the bipolar plate is adapted to apply a pressure or a force to an adjacent object, when a fluid contained in the internal channel is pressurised such that a pressure inside the internal channel is greater than a pressure external to the bipolar plate.

2. The bipolar plate of claim 1, wherein, when provided as part of a stack of multiple adjacent electro-energy or electro-synthetic cells, the increase in thickness of the bipolar plate is adapted to create and thereafter maintain a compression force across the stack of multiple adjacent electro-energy or electro-synthetic cells.

3. The bipolar plate of claim 1 or claim 2, wherein the adjacent object is an adjacent cell and / or an electrode in the adjacent cell, and the bipolar plate is adapted to apply the pressure or the force on the adjacent cell and / or the electrode in the adjacent cell.

4. The bipolar plate of any one of claims 1 to 3, wherein a cross-section of the internal channel expands when the fluid is pressurised, such that the thickness of the bipolar plate increases in accordance with the cross-section of the internal channel expanding.

5. The bipolar plate of any one of claims 1 to 3, wherein a cathode face wall and / or an anode face wall of the bipolar plate apply the pressure or the force on the adjacent object when the fluid is pressurised, such that the pressure or the force increases in accordance with the pressure of the fluid in the internal channel.

6. The bipolar plate of claim 4, wherein the cross-section of the internal channel expanding substantially corresponds to the increase in the thickness of the bipolar plate.

7. The bipolar plate of claim 4, wherein the cross-section of the internal channel expanding does not substantially correspond to the increase in the thickness of the bipolar plate.

8. The bipolar plate of any one of the preceding claims, wherein the force is a clamping force.

9. The bipolar plate of any one of the preceding claims, comprising two or more internal channels.

10. The bipolar plate of any one of the preceding claims, wherein a maximum increase in the thickness of the bipolar plate is less than 1 mm.

11. The bipolar plate of any one of claims 1 to 9, wherein a maximum increase in the thickness of the bipolar plate is less than 0.9 mm, less than 0.8 mm, less than 0.7 mm, less than 0.6 mm, less than 0.5 mm, less than 0.4 mm, less than 0.3 mm, less than 0.2 mm, less than 0.1 mm, less than 0.09 mm, less than 0.08 mm, less than 0.07 mm, less than 0.06 mm, less than 0.05 mm, less than 0.04 mm, less than 0.03 mm, less than 0.02 mm, or less than 0.01 mm.

12. The bipolar plate of any one of claims 1 to 9, wherein a maximum increase in the thickness of the bipolar plate is less than 10 mm, less than 9 mm, less than 8 mm, less than 7 mm, less than 6 mm, less than 5 mm, less than 4 mm, less than 3 mm, or less than 2 mm.

13. The bipolar plate of claim 5, wherein the cathode face wall is a conductive metallic wall and the anode face wall is a conductive metallic wall.

14. The bipolar plate of claim 13, wherein the cathode face wall and the anode face wall are at least partially flexible.

15. A cell stack comprising more than one individual electro-synthetic or electroenergy cells, wherein the bipolar plate of any one of the preceding claims is positioned between adjacent cells in the cell stack, wherein the more than one individual electrosynthetic or electro-energy cells are stacked in electrical series between a first endplate and a second endplate.

16. The cell stack of claim 15, wherein the increase in thickness of the bipolar plate creates and thereafter maintains a stack compression force across the first endplate and the second endplate.

17. The cell stack of claim 16, wherein more than one bipolar plate is provided and the internal channel of each of the more than one bipolar plate is filled with the fluid, wherein the fluid is a gaseous fluid or a liquid fluid.

18. The cell stack of claim 17, wherein an excess pressure applied to the fluid above the pressure external to the more than one bipolar plate is substantially similar or equal to an electrode clamping force applied to one or more electrodes in each cell in the cell stack.

19. The cell stack of claim 18, wherein the excess pressure applied to the fluid above the pressure external to the more than one bipolar plate applies a calibrated electrode clamping force to the cells adjacent to each of the more than one bipolar plate.

20. The cell stack of claim 18 or claim 19, wherein the excess pressure applied to the fluid above the pressure external to the more than one bipolar plate is greater than or equal to 2 bar.

21. The cell stack of claim 18 or claim 19, wherein the excess pressure applied to the fluid above the pressure external to the more than one bipolar plate is greater than or equal to 3 bar, greater than or equal to 4 bar, greater than or equal to 5 bar, greater than or equalto 6 bar, greater than or equal to 7 bar, greater than or equal to 8 bar, greater than or equal to 9 bar, greater than or equal to 10 bar, greater than or equal to 15 bar, or greater than or equal to 20 bar.

22. The cell stack of claim 18 or claim 19, wherein the excess pressure applied to the fluid above the pressure external to the more than one bipolar plate is greater than or equal to 1 bar, greater than or equal to 0.9 bar, greater than or equal to 0.8 bar, greater than or equal to 0.7 bar, greater than or equal to 0.6 bar, greater than or equal to 0.5 bar, greater than or equal to 0.4 bar, greater than or equal to 0.3 bar, greater than or equal to 0.2 bar, or greater than or equal to 0.1 bar, greater than or equal to 0.05 bar, greater than or equal to 0.02 bar, greater than or equal to 0.01 bar, or greater than or equal to 0.05 bar.

23. The cell stack of any one of claims 15 to 22, wherein the pressure of the fluid is managed and / or controlled.

24. The cell stack of any one of claims 15 to 23, wherein the pressure of the fluid is managed and / or controlled during periods of operation of the cell stack.

25. The cell stack of any one of claims 15 to 24, wherein the cell stack comprises two or more individual water electrolysis cells stacked in electrical series between the first endplate and the second endplate.

26. The cell stack of any one of claims 15 to 24, wherein the cell stack comprises two or more individual hydrogen-oxygen fuel cells stacked in electrical series between the first endplate and the second endplate.

27. A method for assembling a cell stack comprising more than one electro-synthetic or electro-energy cells, the method comprising:stacking the cells such that the bipolar plate of any one of claims 1 to 14 is positioned adjacent each cell, wherein the cells are stacked in electrical series between a first endplate and a second endplate; andapplying and thereafter maintaining a stack compression force across the first endplate and the second endplate to thereby form the cell stack such that the cell stack comprises a single electrochemical device.

28. A method for assembling the cell stack of any one of claims 15 to 26, comprising more than one electro-synthetic or electro-energy cells, the method comprising:stacking the cells such that the bipolar plate of any one of claims 1 to 14 is positioned adjacent each cell, wherein the cells are stacked in electrical series between the first endplate and the second endplate; andapplying and thereafter maintaining a stack compression force across the first endplate and the second endplate to thereby form the cell stack such that the cell stack comprises a single electrochemical device.

29. The method for assembling the cell stack of claim 27 or claim 28, wherein the stack assembly compression force applied across the first endplate and the second endplate is less than 3 bar, less than 2 bar, or less than 1 bar.

30. The method for assembling the cell stack of claim 27 or claim 28, wherein the method for assembling the cell stack is suitable for high-speed, high-volume, mass production.

31. The method for assembling the cell stack of any one of claims 27 to 30, wherein more than one bipolar plate is provided, further comprising the steps of:filling the internal channel of each of the more than one bipolar plate with a fluid; andpressurising the fluid to thereby increase the stack compression force applied to the cell stack.

32. A cell stack assembled according to the method of any one of claims 27 to 31.

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