Membranes and electrochemical cells incorporating such membranes

The present invention relates to an electrochemical cell such as a fuel cell or an electrolytic cell incorporating an ionic conductive membrane. Certain embodiments of the invention provide an ionic conductive membrane for use in such cells.

Ionomer membranes, including ionomer membranes such as Nafion®, are important components in membrane separation processes and electrochemical reaction systems, including chlorine-alkali batteries, electrolytic cells and fuel cells. Such membranes act as ionic conductors and avoid mixing of reactants. In some applications, the ion conducted by such a membrane is a proton. The use of solid, proton-conducting materials has made great strides in the production of simple and durable fuel cell devices.

In a typical conventional fuel cell, the ionic conductive membrane is structurally capable of providing ionic conductivity, providing a barrier between reactants, and withstanding the gripping force required to seal the fuel cell. An ionic membrane that performs multiple functions, including providing spacers.

The design of ionic conductive membranes used in electrochemical cells typically requires a balance between two incompatible design objectives. First, it is generally desirable to maximize the conductivity of the ionic conductive film in order to minimize loss during use. In order to achieve this primary purpose, ionic conductive materials having a high water content and therefore in a state close to a liquid tend to be adopted. Secondly, since different pressure differences exist via the membrane, it is possible to provide a membrane that is strong as a structural material in the cell and suitable for use in order to maintain the integrity of the cell. desirable. In order to achieve this second purpose, ionic conductive materials that are solid and have high strength tend to be adopted. It will be understood that these two design objectives are often incompatible with each other. The current practice of designing electrochemical cells involves compromising these design objectives.

An example of an ionic conductive material is Nafion®, which is typically provided as a sheet with a thinness of 25 microns. FIG. 1 is a schematic cross-sectional view of the Nafion® membrane 8. Membrane 8 is a continuous sheet of ionic conductive material. Nafion® membranes tend to be mechanically defective and difficult to handle, especially if the membrane is very thin. Another problem with materials such as Nafion® is that they are dimensionally unstable when used to conduct protons. Inevitable fluctuations in the water content of the membrane during proton conduction cause considerable contraction and swelling. Electrochemical cells containing Nafion® membranes need to be designed to adapt to such shrinkage and swelling.

Gore-Select® is a composite perfluoromaterial composed of a homogeneous porous substrate filled with an ionic conductive material. Patent Document 1 describes this type of film. FIG. 2 is a schematic representation of a GoreSelect® membrane 10 having a homogeneous substrate 12 filled with an ionic conductive material 14. The porous substrate 12 provides some structural integrity and dimensional stability to the membrane 10, while the ionic conductive filler 14 provides proton conductivity.<patcit num="1"><text>U.S. Pat. No. 6613203</text></patcit>

<p> There is a need for ionic conductive membranes for use in electrochemical applications such as fuel cells, electrolytic cells, chlorine-alkali plants, etc., which combine excellent mechanical properties with the desired high ionic conductivity.</p>

<p> A first aspect of the present invention provides an ionic conductive membrane comprising an ionic conductive region. The ionic conductive region comprises a substrate, which has one or more ionic conductive passages extending through it. Each passage contains an ionic conductive material that is relatively more ionic than the substrate.</p><p> Another aspect of the invention provides an ionic conductive membrane, which provides a substrate penetrated by a plurality of pores in its porous region and a plurality of ionic conductive passages penetrating the substrate. Includes an ionic conductive material that fills the pores. Ion conductive materials are richer in ionic conductivity than substrates.</p><p> Another aspect of the invention provides an ionic conductive membrane, which is pierced by at least one pore and at least one to provide an ionic conductive passage through the substrate. It contains an ionic conductive material that fills the pores and provides a first surface film layer on the first side of the substrate, which extends laterally beyond the periphery of the pores. Ion conductive materials are richer in ionic conductivity than substrates.</p><p> Another aspect of the invention provides an ionic conductive membrane comprising an ionic conductive region. The ionic conductive region comprises a substrate, which has one or more ionic conductive passages extending through it. The ionic conductive passage is formed by selectively converting the substrate into a state having high ionic conductivity at a position corresponding to the ionic conductive passage.</p><p> Another aspect of the invention provides an electrochemical cell comprising an ionic conductive membrane according to the invention. Another aspect of the invention provides a method of making an ionic conductive membrane for use in an electrochemical cell. The method is for forming a plurality of pores penetrating the sheet-like substrate material at selected positions for the purpose of forming a porous region, and for forming a plurality of ion conductive passages penetrating the substrate material. Includes a step of filling the pores with an ionic conductive material.</p><p> Another aspect of the invention provides a method of making an ionic conductive membrane for use in an electrochemical cell. In the same method, the sheet-like substrate material is relatively ionic-conducting at multiple positions in order to form multiple ionic conductive passages penetrating the sheet-like substrate and to form an ionic conductive region on the sheet. Includes the step of selectively converting to a large state.</p><p> Another aspect of the invention provides a method of making an ionic conductive membrane for use in an electrochemical cell. The method involves filling at least one pore with an ionic conductive material in order to form at least one pore that penetrates the sheet-like substrate material and an ionic conductive passage that penetrates the substrate material. The step includes a step of forming a surface film layer which is a first surface film layer and extends laterally beyond the peripheral edge of the pores on the first side of the substrate.</p><p> Further features and uses of the particular embodiments of the invention are described below.</p>

Through the following description, a specific detailed description will be provided for a more complete understanding of the present invention. However, the present invention may be practiced in addition to these special ones. In other examples, well-known elements are not shown or described in detail in order to avoid unnecessarily obscuring the invention. Therefore, the specification and drawings should be regarded as having an exemplary meaning rather than a limited meaning.

Membranes suitable for use in electrochemical cells can be made by providing a sheet-like substrate material and forming one or more ionic conductive passages through the sheet-like substrate material. The ionic conductive passage has greater ionic conductivity than the substrate material surrounding the passage. The ionic conductive passage is a step of forming a hole penetrating the substrate material and filling the pore with the ionic conductive material, and selecting the substrate material for a larger ionic conductive state at the position of the ionic conductive passage. It can be formed by at least one of the steps of converting the target. The mechanical and ionic conductive properties of the membrane can be in different states in different regions by providing the ionic conductive passages with at least one of different sizes, shapes, densities and arrangements. it can.

FIG. 3A shows a schematic cross-sectional view of the ionic conductive film 20 according to a particular embodiment of the present invention. Membrane 20 includes one or more ionic conductive regions 33 and one or more non-ionic conductive regions 35A, 35B (collectively 35). FIG. 3A shows a membrane 20 having one ionic conductive region 33 bounded by a pair of non-ionic conductive regions 35A, 35B. The film 20 contains the substrate 21 of the substrate material 22, and selectively contains at least one of the first and second surface films 28,29 on the corresponding sides 32,37 of the substrate 21.

The ionic conductive region 33 of the membrane 20 includes an ionic conductive passage 27 extending from the first side 32 of the substrate 21 to the second side 37 of the substrate 21. The ionic conductive passage 27 includes an ionic conductive material 26 that has greater ionic conductivity than the surrounding material (ie, the material outside the ionic conductive passage 27). In some embodiments, the ionic conductive material 26 is an ionic material. The selective surface films 28,29 can also be an ionic conductive material 26.

The ionic conductive passage 27 is a step of forming a hole 24 penetrating the substrate material 22 and filling the hole 24 with the ionic conductive material 26, and the substrate material 22 is ionic conductive at the position of the ionic conductive passage. It can be formed by at least one of the steps of selectively converting to a larger state. Each of these manufacturing techniques is described in more detail below.

According to one embodiment of the invention, the membrane 20 comprises a substrate 21 formed from the substrate material 22. The pores 24 can be formed through the substrate 21 at selected positions. The hole 24 can be a microstructure. In this disclosure, the "microstructure" is a structure that can be viewed with a microscope having a magnification of 5x or higher. The hole 24 does not have to be a microstructure. In some embodiments, the hole 24 is larger.

The pores 24 provide one or more porous regions 30 to the substrate 21, which is more porous than the surrounding regions 31A, 31B. Each porous region 30 of the substrate 21 contains a plurality of pores 24 and coincides with the ionic conductive region 33 of the membrane 20. The non-porous regions 31A and 31B (collectively 31) correspond to the non-ionic conductive regions 35A and 35B of the membrane 20, respectively. In the embodiment of FIG. 3A, no pores 24 are formed in the non-porous regions 31A, 31B of substrate 21.

Substrate material 22 may include any suitable material or combination of materials that provides a substantial barrier to the reactants used with the membrane 20. For example, membranes for use in hydrogen / air fuel cells are preferably substantially impermeable to hydrogen and oxygen gases. Substrate material 22 includes, for example, polyamide films, polyimide films such as Kapton®, polyethylene films, Teflon® films, films containing other polymers, hydrolyzed Nafion®. Includes materials selected from resin precursors, non-polymeric materials such as silicon or glass. Substrate material 22 is selected to be suitable for the desired application. In some embodiments, it is advantageous that the substrate material 22 is reasonably flexible.

In the porous region 30 of substrate 21, the pores 24 are ions to form an ionic conductive passage 27 that extends through the membrane 20 from the first side 32 of the substrate 21 to the second side 37 of the substrate 21. It is filled with conductive material 26. The ionic conductive material 26 has a higher ionic conductivity than the surrounding substrate material 22. In the illustrated embodiment, each passage 27 has a thickness L of substrate 21._coreHas a passage length equal to. That is, the passage 27 has a tortuosity of 1, and the tortuosity is the thickness of the substrate 21 (L)._core) Is equal to the distance that the particle must travel through the substrate 21.

Pore 24 can be formed on substrate 21 using any suitable method. By a non-limiting example, the hole 24 is formed by chemical etching, laser micromachining, laser drilling, mechanical drilling, milling, punching, calendering, printed circuit board manufacturing technology, lithograph manufacturing technology, mechanical dies, etc. Can be formed through substrate 21. As mentioned above, the passage also changes the material of substrate 21 from one state to another, for example, selectively hydrolyzing the Nafion® precursor resin, without forming and filling the pores 24. It can also be formed by selectively converting to.

The dimensions of the passage 27, the gaps in the passage 27, the shape of the passage 27 and the arrangement of the passage 27 will be selected to suit the particular application and will also be influenced by cost factors. In one particular embodiment, the passage 27 is formed in the shape of a slit in the hole 24 formed using the conventional sheet conversion method. The passage 27 can be circular or has other shapes such as cross, hexagon, oval, oval or star.

In a preferred embodiment, the passages 27 are formed in an aligned arrangement, as opposed to those arranged at random positions. Any suitable pattern can be used. For example, the passage 27 may be located at the node of a square or rectangular array, a triangular array, a hexagonal array, or any other suitable array.

FIG. 3B is a partial cross-sectional view of the ionic conductive region 33 of membrane 20 along line 3-3 (see FIG. 3A) according to a particular embodiment of the invention. In this embodiment, the ionic conductive passages 27 have a circular cross section and are arranged in a rectangular array.

Parameter D is used to indicate the widest cross-sectional dimension of the ionic conductive passage 27. In the embodiment of FIG. 3B, the passages 27 are all the same size, and parameter D is equal to the diameter of the hole 24 in which the passage 27 is formed. Parameter L indicates the transverse gap between the centers of the closest adjacent ionic conductive passages 27.

FIG. 3C shows a partial cross-sectional view of the ionic conductive region 33 of membrane 20 along line 3-3 (see FIG. 3A) according to another embodiment of the invention. In the embodiment of FIG. 3C, the ionic conductive passage 27 has a hexagonal cross section and is arranged in a hexagonal packing array. Parameter D (ie, the widest dimension of passage 27) and parameter L (the gap between the centers of both passages between the closest adjacent passages 27) are also shown in FIG. 3C.

In some embodiments, the parameter D of passage 27 is less than or equal to 200 microns. In other embodiments, the parameter D of passage 27 is 2500 microns or less. In some embodiments, the passage 27 is 5x10.^-8m²It has a cross-sectional area that does not exceed. In other embodiments, passage 27 is 1x10.^-5m²It has a cross-sectional area that does not exceed. In some embodiments, the ionic conductive passage 27 has a minimum transverse dimension of at least 25 microns. In other embodiments, the ionic conductive passage 27 has a minimum transverse dimension of at least 50 microns. In some embodiments, the parameter L of the passage 27 is less than or equal to 500 microns in at least some of the porous regions 30. In other embodiments, the parameter L of the passage 27 is less than or equal to 5000 microns in at least some of the porous regions 30.

In order to maximize the conductivity through the membrane 20, it is desirable to match the parameter ratios L / D as much as possible. In some embodiments, the membrane according to the invention is configured to have a parameter ratio L / D not exceeding 2.5 in one or more ionic conductive regions. In other embodiments, the membrane according to the invention is configured to have a parameter ratio L / D not exceeding 1.5.

Other parameter ratios γ can be used to characterize the conductive regions of the membrane according to the present invention. The parameter ratio γ can be defined as the ratio of the total cross-sectional area of the ionic conductive region to the total cross-sectional area of the ionic conductive passage 27 within the ionic conductive region. In some embodiments, the membrane according to the invention is configured to have a parameter ratio γ not exceeding 2.5 in one or more ionic conductive regions. In other embodiments, the membrane according to the invention is configured to have a parameter ratio γ not exceeding 1.5.

Substrate 21 provides a structural support for the ionic conductive material 26 and an overall structural support for the membrane 20 (see Figure 3A). The mechanical properties of substrate 21 are selected to match the mechanical properties desired for a particular application. For example, by changing at least one of the densities, sizes, shapes and arrangements of the pores 24 in different regions of substrate 21, of different mechanical and ionic conductive properties in those different regions. At least one can be provided.

FIG. 4 shows a flat sheet 34 of substrate material 22 according to a particular embodiment of the invention. Sheet 34 can be used as substrate 21 for the type of ionic conductive film 20 shown in FIG. 3A for use in electrochemical cells such as fuel cells. In the embodiment of FIG. 4, the sheet 34 is made from a thin sheet of substrate material 22 and is divided into a peripheral (non-porous) sealing region 31 that surrounds the porous region 30. The porous region 30 has a hole 24 that penetrates the sheet 34. When the fuel cell having the ionic conductive film 20 is constructed using the sheet 34 as the substrate 21, the ions are conducted through the pores 24 of the porous region 30, while the peripheral seal region 31 of the fuel cell. Provides structural strength near the compression seal.

The porous region 30 does not necessarily have to be uniformly porous. In some cases, the characteristics of the hole 24 (eg, at least one of the size, shape, density and arrangement of the hole 24) and the parameters associated with the hole 24 over the porous region such as the region 30 (eg L, It would also be advantageous to change at least one of (at least one of D, L / D and γ). In some cases, it is advantageous to provide the substrate 21 with multiple porous regions. The properties of the pores 24 and the parameters associated with the pores 24 may be different for each porous region.

In regions that are expected to be exposed to relatively large local mechanical stresses, the holes 24 are either formed relatively small or the density of the holes 24 is relatively low, at least one of them. In the region where exposure to relatively large local mechanical stresses is expected, at least one of the parameter ratio L / D and the parameter γ can be relatively large. For example, in such a region, at least one of the parameter ratio L / D and the parameter γ is greater than 5. Such regions have relatively low proton conductivity but can provide relatively high mechanical strength.

In regions that are expected to be exposed to relatively small local mechanical stresses, the holes 24 are either formed relatively large or the density of the holes 24 is relatively high, at least one of them. In the region expected to be exposed to relatively small local mechanical stresses, at least one of the parameter ratio L / D and the parameter γ can be relatively small. For example, in such a region, at least one of the parameter ratio L / D and the parameter γ is less than 3. Such regions can provide relatively large proton conductivity at the expense of mechanical strength. By using these techniques, it is possible to adjust the performance (eg, mechanical strength and proton conductivity) over the spatial dimensions of the fuel cell membrane.

FIG. 5 shows a flat sheet 40 of substrate material 22 according to another exemplary embodiment of the invention. Sheet 40 can be used as substrate 21 for the type of ionic conductive film 20 shown in FIG. 3A for use in fuel cells. The sheet 40 is formed from the substrate material 22 and includes a non-porous peripheral region 44, a first porous region 46, a second porous region 48, and a third porous region 49. Each of the porous regions 46, 48 and 49 has a hole 24. At least one of the properties of the pores 24 in the porous regions 46,48,49 and the parameters associated with the pores 24 is different from each other. For example, at least one of the size of the holes 24, the density of the holes 24, the shape of the holes 24 and the arrangement of the holes 24 is varied between the porous regions 46,48,49. In the embodiment of FIG. 5, the size and shape of the holes 24 differ between the porous regions 46,48,49.

In other embodiments (not shown), the properties of the hole 24 (eg, at least one of size, shape, density and arrangement) and the parameters of the hole 24 (eg, L, D, L / D and γ). At least one of (at least one) is smoothly modified over the porous region of the substrate. For example, at least one of the parameter ratio L / D of the hole 24 and the parameter γ of the hole 24 can be changed according to a smooth function such as a bell curve. In yet another embodiment (not shown), the sheet of substrate material 22 can be made to have holes 24 having at least one of uniform properties and parameters throughout the sheet of substrate material 22. In the present specification, the holes 24 are described as having various properties such as size, shape, density, arrangement and various parameters such as L, D, minimum cross-sectional dimensions L / D and γ. Any of at least one of these properties and parameters can be used to generally describe the ionic conductive passage.

Each of the above embodiments consists of a sheet of substrate material in which an ionic conductive passage 27 is formed to provide one or more ionic conductive regions. In some embodiments of the invention, the ionic conductive membrane consists of a composite substrate formed from multiple layers of different materials. Some layers of the composite substrate can be porous. For example, one or more layers of the composite substrate may include a mesh material. Other layers of such a composite substrate may include ionic and non-ionic conductive regions that follow a suitable one of the constructs described herein. The composite substrate produced by this method may have excellent mechanical strength.

FIG. 6 is an exploded view of the composite substrate 50 according to a particular embodiment of the present invention. The composite substrate 50 comprises a first layer 52. Layer 52 may include, for example, a substrate layer similar to any of those described above. In the illustrated embodiment, layer 52 includes a non-porous region 31 that surrounds a porous region 30 having pores 24 therein. The intermediate layer 54 includes a mesh-like structure bonded to the first layer 52 to provide a structural reinforcement. The selective lining layer 56 can be formed in layers such that the intermediate layer 54 is enclosed by the layers 52 and 56. The composite substrate may include more than two or three layers of substrate precursor material.

The above discussion deals primarily with the properties and formation of substrates containing porous regions formed in the substrate material. Ionic conductive materials such as ionomers can be deposited in the porous regions of such substrates to form ionic conductive membranes with ionic conductive passages for use in fuel cells, electrolytic cells and the like. The ionic conductive material can be deposited in various arrangements of such substrates to form an ionic conductive membrane according to the present invention.

7A, 7B, 7C and 7D show cross-sectional views of many exemplary ionic conductive films according to various embodiments of the present invention. The ionic conductive materials are arranged differently in each of the membranes shown in FIGS. 7A, 7B, 7C and 7D. FIG. 7A shows a membrane 60A containing substrate 21 formed from substrate material 22. Substrate 21 has pores 24 formed in the substrate 21. The pores 24 of the membrane 60A are filled with an ionic conductive material 26 to form an ionic conductive passage 27 penetrating the membrane 60A. The ionic conductive material 26 has a relatively large ionic conductivity as compared with the substrate material 22. In the membrane 60A, the thickness of the ionic conductive material 26 and the length of the ionic conductive passage 27 are the thickness L of the substrate 21._coreAlmost similar to. In other embodiments, the thickness of the ionic conductive material 26 (and the ionic conductive passage 27) is the thickness of substrate 21 L._coreIs different.

FIG. 7B shows the membrane 60B according to another embodiment of the present invention. Membrane 60B has pores 24 filled with ionic conductive material 26 to form ionic conductive passages 27. Membrane 60B also includes ionic conductive surface films 62, 64 covering either side of substrate material 22. The ionic conductive material in each of the surface films 62 and 64 may be the same or different, and may be the same as or different from the ionic conductive material 26 in the pores 24. The ionic conductive material in each of the surface films 62 and 64 has higher ionic conductivity than the substrate material 22. In the embodiment of FIG. 7B, the thickness L of each surface film 62,64_skinAre substantially the same. In other embodiments, the surface films 62, 64 have different thicknesses.

Coating substrate 21 with surface films 62,64 is optional. Providing the surface membranes 62,64 means that the surface membranes 62,64 are between the non-porous and porous regions of substrate 21 (ie, between the ionic and non-porous regions of the membrane 60B). It is advantageous because it provides an ionic conductive passage between the non-porous regions on the opposite sides of the substrate 21 (ie, between the non-ionic conductive regions on either side of the membrane 60B).

FIG. 7C includes a substrate 21 having pores 24 filled with an ionic conductive material 26 to form an ionic conductive passage 27. Substrate 21 is coated with ionic conductive surface films 62,64. In the embodiment of FIG. 7C, the surface films 62,64 extend laterally over the porous region of substrate 21 and slightly extend into the non-porous region of substrate 21. In other embodiments, the surface films 62,64 extend laterally over only a portion of the porous region of substrate 21. In yet other embodiments, the surface films 62,64 extend laterally only over the porous region of substrate 21 and do not extend into the non-porous region of substrate 21.

FIG. 7D shows a substrate material 22 having pores 24 filled with an ionic conductive material 26 to form an ionic conductive passage 27 and a single ionic conductive surface covering only one side of the substrate 21. A film 62 and a film 60D composed of the film 62 are shown. The surface film 62 may have different lateral extension properties, as described above.

FIG. 8A shows an ionic conductive film 70A according to another embodiment of the present invention. Membrane 70A comprises substrate 21 formed from substrate material 22, which comprises pores 24 formed at selected positions, as described above. Substrate 21 supports multiple ionic conductive materials of different compositions. In the embodiment of FIG. 8A, the membrane 70A comprises three layers of ionic conductive material, i.e., a surface membrane layer 62 of the first ionic conductive material 72 and a first on the first side 73 of the membrane 70A. The intermediate layer of the second ionic conductive material 26 which is different from the material 72 and the second material 26 which is different from the second material 26 on the second side 77 of the membrane 70A (and selectively the first material 72 and the second Includes a surface film layer 64 of a third ionic conductive material 76 (different from any of the materials 26). The ionic conductive materials 72,26,76 have higher ionic conductivity than the substrate material 22. In the embodiment shown in FIG. 8A, the surface films 62 and 64 have almost the same thickness (L)._skin), But this is not always necessary.

FIG. 8B shows an ionic conductive film 70B according to another embodiment of the present invention. Membrane 70B has two ionic conductive layers 78,79 of different ionic conductive materials. Layers 78 and 79 of the ionic conductive material have greater ionic conductivity than the substrate material 22.

The ionic conductive material is on and in the substrate to form an ionic conductive film according to the invention by any of a variety of methods including casting, dipping, printing, syringe injection, molding. Can be deposited. Further, when one or more surface membranes are used, by binding a substrate having a porous region to a preformed sheet of the ionic conductive material (ie, the surface membrane), or by preforming the ionic conductive material. A membrane can be produced by binding a substrate having a porous region between the two sheets. Membranes can also be formed by binding an ionic conductive sheet (surface membrane) to a liquid precursor.

9A and 9B show the production of ionic conductive membranes according to specific embodiments of the present invention. FIG. 9A shows the formation of substrate 80. Substrate 80 comprises substrate material 22, which has pores 24 at selected positions to provide porous regions 30 and non-porous regions 31A, 31B on either side, as described above. It is formed.

In the embodiment of FIG. 9A, each of the non-porous regions 31A, 31B comprises one or more selectively manufactured vias 82A, 82B. The manufactured vias 82A, 82B can be formed in the same manner as the holes 24. The manufactured vias 82A, 82B are preferably separated from the porous region 30. In some embodiments, the manufactured via 82 is formed laterally spaced from the corresponding porous region 30 by at least (1 + 1/2) L, where L corresponds. A lateral gap from center to center of both pores between the closest adjacent pores in the perforated region 30. In other embodiments, the manufactured via 82A is formed laterally separated from the corresponding porous region 30 by a distance of at least 3 L.

FIG. 9B shows substrate 80 plus ionic conductive material 26 to form an ionic conductive film 84 with ionic conductive passages 27. The ionic conductive material 26 has a higher ionic conductivity than the substrate material 22. In the embodiment of FIG. 9B, the ionic conductive material 26 is the substrate 80, the filled pores 24, and the filled selectively manufactured vias 82A, 82B (shown in 86A, 86B). Is applied (eg, by casting) to form an ionic conductive surface film 62,64. The selectively manufactured vias 82A, 82B offer the advantage that they can be in a liquid state when the ionic conductive material 26 is applied. The ionic conductive materials 86A, 86B in the manufactured vias 82A, 82B act like anchors that provide tensile strength to the ionic conductive material 26, thereby deforming the ionic conductive material 26 during drying. To avoid. In particular, the manufactured vias 82A, 82B can improve the uniformity of the surface films 62,64. The bond between the surface films 62,64 and the substrate 80 (eg, at positions 83,85) adds tensile strength to the ionic conductive material 26, thereby reducing the deformation of the ionic conductive material 26 during drying. To.

9C and 9D schematically show different cross-sectional views of an ionic conductive film manufactured according to another embodiment of the present invention. Substrate 120 comprises substrate material 22 in which pores 122 are formed. Hole 122 preferably includes a smooth curved perimeter as shown in FIG. 9D to avoid stress concentration. The non-porous region 31 adjacent to the hole 122 is provided with one or more selectively manufactured vias 82A, 82B (collectively described as 82). The manufactured via 82 is formed by any suitable method as described above, and is preferably separated from the hole 122. In some embodiments, the manufactured via 82 is formed laterally spaced from the corresponding hole 122 by a distance of at least 100 microns. In other embodiments, the manufactured via 82 is formed laterally spaced from the corresponding hole 122 by a distance of at least 200 microns.

The ionic conductive material 26 is added to the substrate 120 to form an ionic conductive film 124 having an ionic conductive passage 27. The ionic conductive material 26 has a higher ionic conductivity than the substrate material 22. In the embodiment of FIG. 9C, the ionic conductive material 26 is shown by the substrate 120, the filled pores 122, and the filled selectively manufactured vias 82 (86A, 86B) (collectively). Is applied (eg by casting) to coat with 86)) to form ionic conductive surface films 62,64. As already mentioned, if the manufactured vias 82 are present, they act like anchors that anchor the ionic conductive material 26 around the edges of the holes 122. By providing such an anchor, the ionic conductive material 26 is prevented from being deformed during drying, making the overall structure more undulating. The bond between the surface film 62,64 and the non-porous region 31 of the substrate 120 (eg, at positions 83,85), with or without the presence of the produced via 82, is at the edge of the hole 122. It allows the adhesion of the ionic conductive material 26 in the periphery, which makes it suitable for some applications.

The above-mentioned film is formed by applying the ionic conductive material 26 to the substrate 21 in which the pores 24 are formed. The ionic conductive material 26 fills the pores 24, thereby providing the ionic conductive passages 27, and the ionic conductive surface films 62,64 may be selectively provided. In some alternative embodiments, the ionic conductive membrane provides a sheet-like substrate material and selectively transforms the substrate material into a relatively ionic conductive state at selected positions to ionize. By forming a conductive passage, or by providing a sheet-like ionic conductive substrate material and selectively converting the ionic conductive material to a relatively non-ionic conductive state at a selected position. Manufactured by forming a non-ionic conductive passage.

10A-10C schematically show the manufacture of an ionic conductive membrane according to another embodiment of the present invention. FIG. 10A shows Sheet 90 of Substrate Material 92. The substrate material 92 is preferably one that can be melt-processed. In one particular embodiment, the substrate material 92 is a resin precursor to Nafion® that can be a copolymer of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octenesulfonyl fluoride. including. Substrate material 92 can be transformed into a relatively ionic conductive state at selected regions. For example, a resin precursor of Nafion® can be converted to ion-conducting Nafion® at a selected position.

FIG. 10B shows the conversion of substrate material 92 to a relatively ionic conductive state 94 at a position selected to form the ionic conductive passage 96. The ionic conductive passage 96 provides an ionic conductive passage that penetrates the substrate sheet 90. The ionic conductive passages 96 are arranged in any suitable arrangement. For example, the ionic conductive passage 96 is configured and arranged in connection with the passage 27 by any of the methods described above. Sheet 90 is described as having one or more ionic conductive regions 33 (ie, near the ionic conductive passage 96) and one or more non-ionic conductive regions 35. Each of the ionic conductive regions 33 consists of an array of ionic conductive passages 96. In the embodiment of FIG. 10B, the non-ionic conductive regions 35A and 35B are arranged on either side of the ionic conductive region 33.

Substrate material 92 can be transformed into a relatively ionic conductive state to form the ionic conductive passage 96 using any suitable technique. By a non-limiting example, the ionic conductive passage 96 can be formed by selectively exposing the region of the substrate sheet 90 to chemicals, radiation, heat, etc. A mask can be used to selectively expose the area of substrate sheet 90 to chemicals, radiation, heat and the like. Other lithograph, etching, and printed circuit board manufacturing techniques are also available.

In one particular embodiment, where the non-ionic conductive material 92 is a resin precursor of Nafion®, the ionic conductive material of the non-ionic conductive material 92 at a selected location in the ionic conductive passage 96. The conversion to 94 comprises a mask sheet 90 and a selective hydrolysis region of the sheet 90 by exposing the sheet 90 to water.

Ion-conducting membranes formed by selective conversion of substrate materials have different spatial membrane regions with at least one of different ionic conductivity and mechanical properties to suit a particular application. Can be formed to provide. For example, the ionic conductive passage 96 formed by selective transformation has properties (eg, size, shape, density) similar to those of the holes 24 (and at least one of the ionic conductive passages 27), as described above. And at least one of the arrangements) and parameters (eg, L, D, L / D, γ) can be formed to have at least one of them. The ionic conductive passage 96 may have at least one of different properties and parameters in different regions of the sheet 90. At least one of such different properties and parameters can be changed smoothly or individually. Sheet 90 can be made from multiple layers according to the embodiments described above. As mentioned above, one or more layers can be added to the sheet 90.

FIG. 10C shows the application of selective surface films 62,64 of ionic conductive materials to Sheet 90. Surface films 62,64 can be applied using, for example, any of the techniques already described.

Those skilled in the art will appreciate that there is a loss of energy associated with the conduction of ions through the membrane as described above. In some cases, it may be desirable to minimize the loss associated with the conduction of ions through the membrane (or part of the membrane). As an example, with reference to the embodiment of FIG. 7B, a predetermined core thickness L_coreAnd the optimum surface film thickness L to provide the minimum loss across the film for the parameter ratio L / D._skinThe inventors of the present application have found that there is. Temporarily the thickness of the surface film L_skinIf is below the optimum level, the overall film loss is relatively large and the surface film thickness L_skinThe loss will increase as the value falls below the optimum level and further decreases. On the other hand, the thickness of the surface film L_skinIf is above the optimum level, the overall film loss is relatively large and the surface film thickness L_skinThe loss will increase as the value increases beyond the optimum level.

Optimal surface film layer thickness L in some embodiments of the present invention_skinIs in the range of 5 to 50 microns. Optimal surface film layer thickness L in some embodiments_skinIs the thickness of the core layer L_coreIt is in the range of 0.25 to 5 times.

The previously disclosed ionic conductive membranes can provide the desired conductivity, gas permeability and mechanical strength properties, which can be modified at the designer's discretion over the spatial range of the membrane. obtain. This gives designers a great deal of design flexibility while locally adjusting mechanical and electrical parameters that optimally meet the conflicting needs of ionic conductivity and mechanical strength in fuel cells or similar systems. Allows you to.

The present invention may be provided in the form of any suitable type of electrochemical cell incorporating a membrane according to the present invention. Some embodiments of the present invention provide a fuel cell or a membrane electrode assembly for a fuel cell.

As will be appreciated by those skilled in the art in light of the above disclosure, many modifications and modifications are possible in the practice of the invention without departing from the spirit and scope of the invention. Therefore, the scope of the present invention may be constructed according to the subject matter defined by the following claims.

<figref num="1">It is the schematic sectional drawing of the sheet-like ion conductive material of the type generally used for the fuel cell of the prior art.</figref><figref num="2">FIG. 6 is a schematic cross-sectional view of a prior art composite membrane having a homogeneous porous substrate filled with an ionic conductive material.</figref><figref num="3A">FIG. 6 is a schematic cross-sectional view of an ionic conductive membrane according to a particular embodiment of the present invention.</figref><figref num="3B">FIG. 3 is a partial cross-sectional view along line 3-3 of the ionic conductive region of the membrane of FIG. 3A, according to a particular embodiment of the invention.</figref><figref num="3C">FIG. 3 is a partial cross-sectional view along line 3-3 of the ionic conductive region of the membrane of FIG. 3A, according to another embodiment of the present invention.</figref><figref num="4">FIG. 3 is a perspective view of a sheet-like substrate material that can be used for the type of membrane shown in FIG. 3A, according to a particular embodiment of the invention.</figref><figref num="5">FIG. 3 is a perspective view of a sheet-like substrate material that can be used for the type of membrane shown in FIG. 3A, according to another embodiment of the present invention.</figref><figref num="6">FIG. 3 is a exploded perspective view of a substrate formed from layers of a plurality of sheets of precursor material, which can be used for the type of membrane shown in FIG. 3A, according to another embodiment of the present invention.</figref><figref num="7A">FIG. 3 is a schematic cross-sectional view of an ion conductive membrane according to various embodiments of the present invention.</figref><figref num="7B">FIG. 3 is a schematic cross-sectional view of an ion conductive membrane according to various embodiments of the present invention.</figref><figref num="7C">FIG. 3 is a schematic cross-sectional view of an ion conductive membrane according to various embodiments of the present invention.</figref><figref num="7D">FIG. 3 is a schematic cross-sectional view of an ion conductive membrane according to various embodiments of the present invention.</figref><figref num="8A">FIG. 5 is a schematic cross-sectional view of an ionic conductive membrane in which a plurality of different ionic conductive materials are applied in layers to form a composite membrane structure.</figref><figref num="8B">FIG. 5 is a schematic cross-sectional view of an ionic conductive membrane in which a plurality of different ionic conductive materials are applied in layers to form a composite membrane structure.</figref><figref num="9A">The production of an ionic conductive membrane according to a particular embodiment of the present invention is schematically shown.</figref><figref num="9B">The production of an ionic conductive membrane according to a particular embodiment of the present invention is schematically shown.</figref><figref num="9C">FIG. 6 is a schematic representation of different cross-sectional views of an ionic conductive membrane manufactured according to another embodiment of the present invention.</figref><figref num="9D">FIG. 6 is a schematic representation of different cross-sectional views of an ionic conductive membrane manufactured according to another embodiment of the present invention.</figref><figref num="10A">The production of an ionic conductive membrane according to another embodiment of the present invention is schematically shown.</figref><figref num="10B">The production of an ionic conductive membrane according to another embodiment of the present invention is schematically shown.</figref><figref num="10C">The production of an ionic conductive membrane according to another embodiment of the present invention is schematically shown.</figref>