MXPA98003614A - Separating plate of prote exchange membrane fuel cells - Google Patents

Abstract

A bipolar, gas-impermeable separator plate for a proton exchange membrane fuel cell, having at least one electronically conductive material, in an amount in the range of approximately 50 to 95% by weight of the separator plate, when less a resin, in an amount of at least about 5% by weight of the separator plate, and at least one hydrophilic agent, wherein the electronically conductive material, the resin, and the hydrophilic agent are dispersed substantially uniformly throughout the the separate plate

Description

SEPARATOR PLATE OF FUEL CELLS OF MEMBRANE OF EXCHANGE OF PROTONS BACKGROUND OF THE INVENTION This invention relates to a bipolar separator plate, for use in fuel cell stacks of proton exchange membranes. The separator plate is hydrophilic and has a controlled porosity, which facilitates the internal humidification of the fuel cell, as well as the removal of the product water from this fuel cell, all while providing resources to control the temperature of the cell stack. gas. Generally, the fuel cell electrical output units are comprised of a multiplicity of stacked individual cells, separated by electronically conductive, bipolar separator plates. The individual cells are walled together and secured in a single-stage unit to achieve the desired energy output from the fuel cell. Each individual cell generally includes anode and cathode electrodes, a common electrolyte and a source of fuel and oxidant gases. Both gases, fuel and oxidant, are introduced through collectors, internal or external, to the fuel cell stack, to the respective reactive chambers, between the separator plate and the electrolyte.

DESCRIPTION OF THE PREVIOUS TECHNIQUE There are currently a number of fuel cell systems in existence and / or in development, which are designed for use in a variety of applications, including power generation, automobiles, and other applications, where will avoid environmental pollution. They include molten carbonate fuel cells, solid oxide fuel cells, phosphoric acid fuel cells and proton exchange membrane fuel cells. A consequence associated with the successful operation of each of these types of fuel cell is the control of the temperature of the fuel cell and the removal of the products generated by the electrochemical reactions from within the fuel cell. Commercially viable fuel cell stacks can contain up to 600 individual units of fuel cells, each with a flat area of up to 111.5 dm2. In the stacking of such individual cells, the separator plates divide the individual cells, with the fuel and oxidant being introduced between a set of separator plates, this fuel is introduced between a face of the separator plate and the side of the anode of an electrolyte and the oxidant is introduced between the other face of the separator plate and the cathode side of a second electrolyte. The cell stacks, which contain 600 cells, can be up to 6.10 meters high, presenting serious problems with respect to maintaining the integrity of the cell during heating and the operation of the fuel cell stack. Due to the thermal gradients between the cell assembly and the operating conditions of the cell, differential thermal expansions and the required strength of the materials, required for the various components, narrow tolerance and very difficult engineering problems are presented. In this aspect, the control of the temperature of the cell is highly significant and,. if it is not achieved with a minimum temperature gradient, the uniform density of current can not be maintained, and degradation of the cell will occur. In a fuel cell of a proton exchange membrane ("PEM"), the electrolyte is an organic polymer in the form of a proton conductive membrane, such as a perfluorosulfonic acid polymer. This type of fuel cell works best when the electrolyte membrane is kept wet with water, because the membrane will not operate efficiently when it is dry. During the operation of the cell, water is drawn through the membrane from the side of the anode to the side of the cathode, along with the movement of protons through the membrane. This tends to dry the anode side of the membrane, and also tends to create a film of water on the side of the cathode of the membrane. The surface of the cathode is further wetted by the product water, which is formed in the electrochemical reaction. Thus, it is critical in the operation of the PEM fuel cell that the product water be continuously removed from the side of the cathode of the membrane, while keeping the anode side of the membrane moist to facilitate the electrochemical reaction and the conductivity of the membrane. membrane. The sequel to water management in a proton exchange membrane fuel cell is addressed by a number of US patents. US Patent No. 4,769,297 teaches the use of a fuel cell of a solid polymer, in which the water is supplied with the anode gas on the side of the anode of the membrane. Some of the water migrates through the cell from one cell to another, the water migration is the result of that water being dragged from the anode through the membrane to the cathode and through the use of a porous hydrophilic separator plate, interposed between units of adjacent cells. The water is forced through the porous separator plate, by means of a reagent pressure differential, maintained between the cathode and the anode. The anode support plates provide a large surface area from which the water evaporates to perform the cooling function. The separating plate indicated is made of graphite. U.A. Patent No. 4,824,741 teaches a fuel cell system using a porous graphite anode plate. The water supplied to the porous plate and the reactant gas of the anode are evaporated from the surface of the plate. The proton exchange membrane is wetted by contact with the porous plate of the anode. A non-porous, gas-impermeable separating plate adjacent to the cathode plate is used to prevent gas crossing from the anode to the cathode. See also U.A. Patent No. 4,826,741, U.A. Patent No. 4,826,742, U.A. Patent No. 5,503,944, and PCT Application No. WO 94/15377. Bipolar separator plates, for use in proton exchange membrane cells, constructed of graphite or graphite carbon composite materials bonded to resin, and having gas flow channels, are taught in US Patent No. 4,175,165. This patent also teaches the treatment of bipolar separator plates by coating the surfaces with a wetting agent, such as colloidal silica sols, to make their hydrophilic surfaces. In this way, the water generated in the fuel cell is kept away from the electrodes for subsequent storage. However, coating the surfaces with a wetting agent inconveniently increases the electrical resistance across the plate, resulting in reduced conductivity. The patent of E. U. A., No. 3,634,569 teaches a method of producing dense plates of graphite from a mixture of graphite powder and a thermosetting resin, for use in acid fuel cells. The method employs a mixture, by weight, of 5 to 25% of a binder of the thermosetting phenolic resin and 75 to 95% of powdered graphite of a certain size. Bipolar graphite and resin plates are also taught by US Patent No. 4,339,322 (a bipolar plate comprised of a molded thermoplastic fluoropolymer, graphite and carbon fibers), US Patent No. 4,738,872 (Separating plates comprising 50 percent by weight graphite and 50 percent by weight thermoset phenolic resin, U.S. Patent No. 5,208,849 (coil flow panels in a fuel cell separator lacquer, non-porous graphite compounds or other powders) corrosion-resistant metal and a thermoplastic resin, such as polyvinylidene fluoride, in a composition of 10 to 30 weight percent resin and 70 to 90 weight percent graphite powder), EU Patent No., No. 4,670,300 (a plate of cells) of fuel comprising 20 to 80% graphite and the remainder being cellulose fibers or cellulose fibers and a thermosetting resin, in equal proportions), U.S. Patent No. 4,592,968 (separating plate comprised of graphite, coke and a carbonizable thermostable phenolic resin, which is then gratified at 26502C), US Patent No. 4,737,421. { carbon or graphite fuel cell plate, in the range of 5 to 45%, thermosetting resin in the range of 40 to 80%, with the remainder being cellulose fibers), U.S. Patent No. 4,627,944 (plate of carbon or graphite fuel cells, a thermosetting resin and cellulose fibers), U.S. Patent No. 4,652,502 (fuel cell plate made of 50% graphite and 50% thermosetting resin), the USA, No. 4,301,222 (separator plate made of a mixture of 40 to 65% graphite and 35 to 55% resin), and US patent, No. 4,360,485 (separator plate made of a mixture of 45 to 65% of graphite and from 35 to 55% of resin). We have found that there are numerous features for a bipolar separator plate for use in proton exchange membrane fuel cells, which are important from the point of view of manufacturing, as well as operation, which are not solved by the prior art. . They include the water permeability of the plate in relation to the electronic conductivity of this plate; the resistance to crushing of the plate; the functionality of the plate with respect to its ability to maintain its water absorption capacity and the capacity of the plate to undergo thermal cycling, between frozen and melted conditions, as will probably be found in, for example, the application of automobiles of the fuel cell. In addition, the separator plate should be able to be constructed from cheap starting materials, materials that are easily formed in any configuration of the plate, with the use preferably of a one-stage molding process, materials that are resistant to corrosion in fuel cells of low temperature and which do not require a further process, such as thermal treatments at high temperature, and which use a method to produce the plates in which the hydrophilicity and the porosity of the plate can be controlled.

SUMMARY OF THE INVENTION Therefore, it is an object of this invention to provide a bipolar spacer plate for use in a proton exchange membrane fuel cell, which is relatively inexpensive to produce. It is another object of this invention to provide a bipolar spacer plate having improved properties for water removal from, and internal humidification of, a proton exchange membrane fuel cell. It is yet another object of this invention to provide a bipolar separator plate for a proton exchange membrane fuel cell, having a crush resistance greater than about 14 kg / cm2. It is yet another object of this invention to provide a bipolar separator plate for a proton exchange membrane fuel cell, which is suitable for use in a stack of fuel cells, internally diversified in a complete manner. It is still another object of this invention to provide a method for producing a bipolar spacer plate, suitable for use in a proton exchange membrane fuel cell. These and other objects of this invention are achieved by a bipolar spacer plate, comprising at least one electronically conductive material, in an amount ranging from about 50 to 95% by weight of the spacer plate, at least one resin, in an amount of at least 5% by weight of the separator plate, and at least one hydrophilic agent, for use in a proton exchange membrane fuel cell, to attract water into the separator plate. The electronically conductive material, the resin and the hydrophilic agent are dispersed substantially uniformly through the separator plate. According to a particularly preferred embodiment of this invention, the electronically conductive material is an electronically conductive carbonaceous material and the hydrophilic agent is a hydrophilic resin. The bipolar separator plate, according to this invention, is produced by mixing at least one electronically conductive material, preferably a carbonaceous material, at least one resin and at least one hydrophilic agent, to form a substantially homogeneous mixture, comprising the conductive material electronically in an amount ranging from about 50 to 90% by weight of the mixture, at least one resin in an amount of at least 5% by weight of the mixture, and at least one hydrophilic agent. The mixture is then molded into a desired configuration at a temperature in the range of 121 to 427sc, this temperature is a function of the resin used, and a pressure in the range of 35 to 280 kg / cm2, which results in the formation of the bipolar plate. The bipolar spacer plate, produced according to this method, has a porosity in the range of about 0 to 25% of the volume of the plate and preferably forms a plurality of pores having an average pore size in the approximate range of 0.25 to 2.0 microns.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and features of the invention will be better understood from the following detailed description taken in conjunction with the drawings, in which: Figure 1 is a side view of a PEM fuel cell stack, with one piece separator plates, according to one embodiment of this invention; Figure Ib is a side view of a PEM fuel cell stack with two-piece separator plates, according to one embodiment of this invention; Figure 2 is a graphic representation of the ratio of the percentage of the silica, as a wetting agent, in the separator plate versus the conductivity of the separator plate; Figure 3 is a graphic representation of the relationship between the percentage of the silica in the separator plate and the water absorbed by this separator plate; and Figure 4 is a diagram showing the internal diversification configuration of a fuel cell stack.

DESCRIPTION OF THE PREFERRED MODALITIES The invention relates to a bipolar gas-impermeable separator plate for a proton exchange membrane fuel cell, comprising at least one electronically conductive material, at least one resin and at least one hydrophilic agent , in which this electronically conductive material, the resin and the hydrophilic agent are dispersed substantially uniformly through the separator plate. This bipolar spacer plate of the invention eliminates the need for external humidification of the proton exchange membrane fuel cells and provides thermal management and removal of the product water in the fuel cell stack system. The preferred composition of the bipolar separator plate comprises a mixture of resin and graphite which, when molded under moderate conditions of pressure and temperature, provides a conductive bipolar plate, light in weight, suitable for use in low temperature electrochemical systems such as proton exchange membrane fuel cells.

The plate can be produced with passage for the flow of the reactive fluids for the desired electrochemical system. The plate can be produced with various degrees of conductivity, for use in a desired electrochemical system. This plate can be produced with various degrees of porosity for the water management of electrochemical systems. And finally, the plate can be produced with various degrees of hydrophilicity for use in the water and thermal management of electrochemical systems. According to a particularly preferred embodiment of this invention, the bipolar separator plate comprises at least one electronically conductive material in an amount ranging from about 50 to 95% by weight of the separator plate, at least one resin in an approximate amount of 5% by weight of the separating plate, and at least one hydrophilic agent. According to a particularly preferred embodiment of this invention, the separating plate is formed of a composition comprising a mixture of about 50 to 95 weight percent graphitic material, graphite, about 5 to 30 weight percent of a type of thermosetting resin, 0 to 45 weight percent carbon fibers, and 0 to 25 weight percent silica. This composition is then molded at an elevated temperature in the range of about 121 to 42 ° C and a pressure in the range of about 35 to 280 kg / cm. The conductivity of the molded material, produced in this way, is at least 5 S / cm, which represents the minimum nominal conductivity required for use in a proton exchange membrane fuel cells. The porosity of the molded material can be up to 25% voids in volume. The bubble pressure of the molded material, which increases with the decrease in the void volume of the plate is at least about 0.35 kg / cm2. As previously noted, the proton exchange membrane fuel cells that employ these polymer electrolyte membranes, operate best when the electrolytic membrane is moistened with water. During the operation of the proton exchange membrane fuel cells, water is drawn through the membrane, from the side of the anode to the side of the cathode, along with the movement of protons through the membrane. This phenomenon tends to dry the anode side of the membrane, all the while creating water droplets on the surface facing the cathode of the membrane. This surface facing the cathode is also wetted by the product water, which is formed in the electrochemical reaction and which appears on the surface facing the cathode. Unless handled properly, water on the surface that faces the cathode, particularly if it is in the form of droplets, it can clog the oxidant channels, thus inhibiting the oxidizing gas's access to the catalyst and reducing the electrochemical reaction. Therefore, it is important that the water be supplied to the side of the anode of the membrane in the fuel cell, to prevent drying and that the water be continuously removed from the side of the cathode to prevent water droplets forming on the side of the cathode. surface of the membrane. Thus, the separator plate of this invention must have sufficient hydrophilicity not only to prevent the accumulation of water on the side of the cathode, but also to promote the distribution of water through the separator plate. By the presence of water through the separator plate, the potential for mixing the reactive gases through the separator plate is substantially reduced. Therefore, the bipolar spacer plate of this invention comprises at least one hydrophilic agent dispersed in substantially uniform form through the plate, suitable for use in a proton exchange membrane fuel cells to attract water into the separator plate. According to a preferred embodiment of this invention, the at least one resin of the separating plate is hydrophilic. According to a particularly preferred embodiment of this invention, the hydrophilic resin is a phenolic-formaldehyde thermoset resin. According to another embodiment of this invention, the at least one hydrophilic agent is a wetting agent, preferably selected from the group consisting of the oxides of Ti, Al, Si, and mixtures thereof. By virtue of the dispersion of the hydrophilic agent through the separating plate, this plate of the invention has sufficient water permeability to remove at least 5.5 cc per minute of the product water with a current density of 107.64 amps per square decimeter, at a differential pressure of less than about 0.7 kg / cm2. An application of the proton exchange membrane fuel cells is for the generation of energy in a car. In this application, the fuel cell is exposed to a wide temperature range and can undergo numerous freeze / melt cycles during its lifetime. One would expect that the retention of water within the separator plate, as a result of the absorption of water by the plate, due to the dispersion of the hydrophilic agent through the plate, would result in the fracture of the plate, after the cycles to Freezing and melting temperature conditions. Surprisingly, the bipolar separating plate of the invention, with water absorption of 18 weight percent, did not exhibit fractures after undergoing 12 freeze / melt cycles. The patent of E. U. A., No. 4,175,165 teaches the use of various wetting agents, such as colloidal silica sols or alumina alumina-silica compositions of high surface area, which are deposited on the surfaces of the separating plate described herein. However, alumina and silica, like other wetting agents, are generally electrical insulators. Thus, the application of the wetting agents to the surface of the separating plates makes the hydrophilic surface, and also increases the resistance of the surface contact of the plates, thus increasing the internal resistance of the cell units, which, in turn, decrease the power of the cell. Surprisingly, the separator plate of this invention employs a wetting agent which is uniformly dispersed through the separator plate and still capable of maintaining sufficient electrical conductivity. According to a preferred embodiment, the wetting agent is added as fine particles to the mixture of the electronically conductive material and the resin and intimately mixed with it to produce a uniform dispersion of that wetting agent. However, it can also be added as a dispersed solution which, when it is completely mixed with the electronically conductive material and the resin, it produces the same molding compound uniformly mixed. We believe that the wetting agent promotes the formation of pores in the molded product, preventing the resin and other components from forming a continuous phase. The affinity of these wetting agents to water reduces the surface tension between the water and the molded product. As a result, the water in contact with the molded plate has a tendency to form a film on the surface of the molded plate rather than forming droplets. Because the molded plate can contain pores, these pores become filled with water easier, due to the hydrophilic nature of the plate. If a sufficient pressure differential is applied across the plate, the water can be transported from one side of the plate to the other. Another consequence of the separator plate of this invention is the stability of the plate. We have found that the plate of this invention retains 99% of its original weight after more than 1,200 hours in water at 90 ° C. During this period, the water absorption of the plate also remains constant at 18 weight percent. The conductivity of the separator plate of this invention, as a function of the content of the silica, is shown in Figure 2, in which a variety of plates with different amounts of silica dispersed uniformly therein are manufactured. The separator plates, from which these data are derived, comprise a thermosetting resin in an amount of about 12.5% by weight of the separator plate, silica in an amount between 0 and 10% by weight of the separator plate, and the graphite in an amount between 77.5 and 87.5% by weight of the separator plate. Separating plates suitable for use in the proton exchange membrane fuel cells, must have an electrical conductivity of not less than about 5S / cm and preferably not less than about 75S / cm. The plates of this invention can be porous or non-porous, but, in any case, they should not be gas permeable. According to a particularly preferred embodiment of this invention, the plates are porous, have a porosity of less than 25% by volume. The pore diameters of the separator plate, according to this invention, are preferably in the approximate range of 0.25 to 2 microns, with median pore diameter preferably in the approximate range of 0.5 to 1.5 microns. In addition to the hydrophilic agent, the separator plate of this invention comprises at least one electronically conductive material and at least one resin, this electronically conductive material is present in an amount of about 50 to 95% by weight of the separator plate and at least one resin is present in an amount of at least 5% by weight of the separator plate. Electronically conductive materials suitable for use in the separator plate of this invention are selected from the group consisting of carbonaceous materials, metals, alloys, metal carbides, metal nitrides and mixtures thereof. Suitable metals include titanium, niobium, tantalum and alloys, such as Hastalloy. According to a particularly preferred embodiment of this invention, the electronically conductive material is a carbonaceous material selected from the group consisting of graphite, carbon black, carbon fibers, and mixtures thereof. Graphite, or various electrically conductive, available compounds of carbon, such as electrically conductive carbon blacks, are particularly preferred. The use of carbon-based materials reduces the costs associated with manufacturing as well as simplifies the manufacture of gas flow control elements, such as channels in the plates and the molding of these plates. According to a preferred embodiment of this invention, the separator plate comprises up to 10% by weight of carbon fibers. The addition of carbon fibers not only strengthens the plate, but also promotes the absorption of water and the conductivity of the plate. The separator plate of this invention also comprises more than 5% of a resin. The resin functions as a binder for the molded separator plate and, as previously discussed, may also increase the hydrophilicity of the plate. Suitable resins include thermosetting resins, thermoplastic resins and mixtures thereof. Suitable thermoplastic resins for use in the separator plate of this invention, include polyvinylidene fluorides, polycarbonates, nylons, polytetrafluoroethylenes, polyurethanes, polyesters, polypropylenes and HDPE. Preferred thermosetting resins are selected from the group consisting of phenolic resins, aldehydes, epoxides and vinyls. The following examples are presented to show the relationship between the various compositions of the separator plate of this invention and the resulting properties of this separator plate. In each case, 10.16 x 10.16 cm porous separator plates were molded from various mixtures of the phenolic resin Varcum 29338, having a particle size of less than 200 mesh, obtained from Occidental Chemical Corporation of Dallas, Texas, silica particles of 40 nanometers in size, carbon fibers having a length of 150 microns and graphite powder having a particle size of less than 200 mesh. The powders were completely mixed and molded into a plate at 70 kg / cm2 and at 204GC. Examples I to IV show the effect of silica, as a wetting agent, on the conductivity and hydrophilicity of the separating plates at room temperature. Conductivity and hydrophilicity, as a function of the silica content, are also shown in Figures 2 and 3, respectively. Example V shows the properties of a separator plate, according to an embodiment of this invention, having 10 percent by weight graphite, replaced with carbon fibers. Based on the results of Examples I to IV, it can be seen that as the silica is added to the composition, the hydrophilicity of the plates, indicated by the amount of water absorption, increases as the electrical conductivity decreases. However, substituting up to 10 weight percent carbon fibers for a portion of the electronically conductive graphite material used in the composition increases the porosity of the plate, the amount of the wetting agent (silica) required to achieve absorption Substantial water (18%) is reduced and the conductivity of the plate at a reduced level of silica is maintained on a plate having a corresponding amount of silica and no carbon fibers (Example II).

EXAMPLE I A plate was molded at 70 kg / cm2 and at 2042c, with the following composition and properties: Degussa Corp. of Richfield Park, New York 'Dixon-Ticonderoga Company, Lake Hurst, New Jersey EXAMPLE II A plate was molded at 70 kg / cm2 and at 2042C with the following composition and properties: EXAMPLE III A plate was molded at 70 kg / cm2 and at 204oc with the following composition and properties: EXAMPLE IV A plate was molded at 70 kg / cm2 and at 204sc with the following composition and properties: EXAMPLE IV A plate was molded at 70 kg / cm2 and at 204sc with the following composition and properties: Zoltek Coforation of St. Louis, Missouri Resilience is the ability of a deformed body to recover its size and configuration after this deformation, caused, for example, by a compressive force. The resilience of the graphite used in the separator plate of this invention is about 26%. That is, after undergoing a compression force, the graphite expands to approximately 126% of its configuration and compressed form. In contrast, carbon fiber has a significantly higher resilience. A separating plate having a greater resilience due to the resilience of the individual components comprising it is inconvenient since it limits the size of pores that can be achieved. In particular, the use of materials having greater resilience results in plates having larger pore sizes, while the use of materials having low resilience results in a plate having smaller pore sizes. Larger pore sizes generally reduce the pressure required for reactive gases to pass from one side of the separator plate to the other and result in a reduction in the conductivity of the plate. Plates that use low resilience materials are generally stronger and more conductive. Surprisingly, we have found that a mixture of graphite and carbon fibers, as used in Example V, results in a plate having a resilience corresponding to the resilience of the graphite alone. This is surprising to what one skilled in the art expects from the addition of carbon fibers, which have a substantially higher resilience than that of graphite, would result in a plate with a significantly higher resilience. Thus, according to a preferred embodiment of this invention, the amount of carbon fibers present in the separator plate of this invention is less than about 10% by weight. The bubble pressure of a separator plate refers to the ability to prevent the crossing of reactive gases from one side of the separator plate to the other. The bubble pressure is a positive pressure of the water in a pore of the separator plate, which is inversely proportional to the pore size in the plate. That is, the smaller the median pore size, the greater the pressure exerted by the water absorbed in the plate. Thus, the bubble pressure is the pressure at which the reactive gases are forced through the water-saturated plate, which results in a disadvantageous mixing of the two reactants as well as the entry of reactive gases into the water passages of cooling of the separator plate, we have found that the separator plates of this invention have a bubble pressure greater than 0.35 kg / cm2. Preferred embodiments of the separator plate of this invention have bubble pressures greater than 0.7 kg / cm2 and more preferably, greater than 1.4 kg / cm2. Figures la and Ib show a cell 15 of fuel cells, having a plurality of fuel cell units 20, each unit comprising a proton exchange membrane 25, an anode electrode 30 on one side and a cathode electrode. 35 on the other side. Arranged between the anode electrode 30 and the membrane 25 is an anode catalyst layer 31 and disposed between the cathode electrode 35 and the membrane 25., there is a suitable cathode catalyst layer 36. The separation of the anode electrode 30 from a fuel cell unit from the cathode electrode 35 of an adjacent fuel cell unit is by the bipolar separator plate 39. According to a embodiment of this invention, as shown in Figure la, the separator plate 39 of this invention is a one piece spacer plate, comprising a surface 40 facing the cathode and a surface 45 facing the anode, the surface 40 which the cathode forms a plurality of channels 41 of the oxidant gas flow, which extend therethrough, so as to provide contact between the oxidant in the cathode channels with the cathode electrode 35. Similarly, the surface 45 facing the anode forms suitable fuel gas flow channels 46, for supplying the contact between the fuel gas and the anode electrode 30. According to another embodiment of this invention, as e shows in Figure Ib, the separator plate 39 is constructed of two plates, the plate 39a facing the cathode and the plate 39b facing the anode. To provide water cooling of the stack, the interface of the plate 38a facing the cathode and the plate 39b facing the anode forms a plurality of channels 34 of the cooling water. The fuel cell stack further includes an end plate 50 of the cathode spacer and an end plate 60 of the anode spacer. The end plates, 50 and 60, are waterproof or sealed otherwise to prevent leakage. Suitable tension mechanisms and gaskets (not shown) are provided to secure the battery components together. In this aspect, the separator plate of this invention must be strong enough to withstand crushing under the forces applied during the assembly of the fuel cell stack. The resistance to crushing of the separating plate must be greater than 14 kg / cm2. The separating plate, produced according to cor? Example 5, has a crush resistance greater than 147 kg / cm2. In addition to the crush resistance, the spacer plate of this invention must have some degree of flexibility to allow it to conform to the other components of the cell stack assembly. According to a particularly preferred embodiment of this invention, the separator plate has a minimum flexibility of 3.5% or about 0.03583 cm per linear centimeter, without breaking. As previously discussed, carbon fibers can be added to the separator plates of this invention and are preferably distributed substantially uniformly across the plate, in an amount of up to 20% by weight of the separator plate, but more preferably less than 10% by weight of the separator plate. Because carbon fibers are expensive, their use is optional, but advantageous, because they provide porosity and structural reinforcement without sacrificing much conductivity, using a corresponding amount of the wetting agent. As can be seen from the examples, there is a balance which must be achieved in the composition of the separator plate to supply a plate having the desired conductivity and hydrophilicity. The examples show that the amount of the wetting agent in the form of SiO 2 is increased in order to increase the hydrophilicity, the conductivity of the plate is reduced. Figure 3 shows the increase in the amount of water absorbed in the plate with the increasing content of SIO2, while Figure 2 shows a decreased conductivity with an increase in the content of SIO2. The data points cross at a silica content of about 5% by weight. Therefore, the preferred range of the silica used in the separator plate of this invention is in the range of approximately 1 to 10% by weight, and more preferably in the range of approximately 2 to 4% by weight. The addition of carbon fibers, as previously discussed, up to 20% by weight, provides additional porosity without loss of conductivity. However, carbon fibers are expensive and so, it is convenient to minimize the amount used. The separator plate of this invention is suitable for use in a stack of externally diversified fuel cells or an internally diversified fuel cell stack. In the externally diversified fuel cell stack, reactive gases are provided from external collectors connected to the edge regions of the fuel cell stack, while, in the internally diversified fuel cell stack, reactive gases are provided through collectors formed by the perforations in the components of the cell to the reaction sites. A stack of internally diversified fuel cells, utilizing a bipolar separator plate, according to one embodiment of this invention, is shown in Figure 4. As shown in Figure 4, the ion exchange membranes 25 and the plates separators 39 of the fuel cell stack extend to the peripheral edge of the stack. The separator plates 39 are provided with flattened peripheral seal structures 43, which extend from each surface for contact with the ion exchange membranes, completely around its periphery, thus forming a peripheral seal. The ion exchange membranes and the separator plates each form a plurality of fuel manifold holes 54, ones for delivery and others for removal, and a plurality of collector holes 55 of the oxidant, some for supply and others. for removal. The collector holes 54, 55 in the separator plates are surrounded by flattened collector seal sources 56, 57, which extend from each surface of the separator plate for contact with the ion exchange membrane, thereby forming a seal of collectors, thus forming a plurality of fuel and oxidizing gas collectors, which extend through the stack of cells. The conduits, 47, 47 'are provided through the flattened seal structures of manifolds, which surround the holes 54 of the fuel manifold on the surface facing the anode of the separator plate, so as to provide communication of the combustible gas between a set of manifolds and reactive regions of the anode gas formed between the anodes and the surfaces facing the anode of the separator plates and conduits 48, 48 'are provided through the seal structure of the flattened manifold surrounding the holes 55 of the oxidant collector on the surface facing the cathode of the separator plate, which supplies the communication of the oxidizing gas between a second set of collectors and the reaction regions of the cathode, formed between the cathodes and the surfaces facing the cathode of the separator plates, thus providing the completely internal diversification of the fuel and oxidant gases to and from each cell unit d e fuel in the fuel cell stack. The bipolar separator plates, according to this invention, are produced by mixing at least one carbonaceous material, preferably electronically conductive, at least one resin and at least one hydrophilic agent, so as to form a substantially homogeneous mixture comprising from 50 to 96% by weight of the electronically conductive material, at least 5% by weight of the resin and the hydrophilic agent. The mixture is then molded in a desired configuration at a temperature in the range of about 121 to 427 ° C and a pressure in the range of about 35 to 280 kg / cm 2, thus forming a bipolar plate. According to one embodiment of this invention, the PEM fuel cell stack and thus the separator plate of this invention comprise elements for water supply and removal., for circulation and removal of cooling water from inside the fuel cell stack. As shown in Figure Ib, the separator plate 39, comprising the plate 39a facing the cathode and the plate 39b facing the anode, form a plurality of channels 34 of the cooling water at its interface. In a stack of diversified fuel cells in the interior, as shown in Figure 4, water is provided from the manifold holes 58, which are provided with the collector seal structures extended to seal against adjacent cell components and which they form conduits for communication between the holes 58 of the water collector and the channels 34 of the cooling water, and the water is removed through the holes 58 'of the water collector. While in the above specification this invention has been described in relation to certain of its preferred embodiments, and many details have been pointed out for purposes of illustration, it will be apparent to those skilled in the art that the invention is amenable to additional modalities and that certain of the details described herein can be varied considerably, without departing from the basic principles of the invention.

Claims (51)

1. CLAIMS 1. A gas-insulated, bipolar separator plate for a proton exchange membrane fuel cell, this plate comprises: at least one electronically conductive material, in an amount in the range of approximately 50 to 95% by weight of the separating plate; at least one resin, in an amount of at least about 5% of the weight of the separator plate; and at least one hydrophilic agent, suitable for use in a proton exchange membrane fuel cell, to attract water into the separator plate, and at least one electronically conductive material, is at least one resin, and at least A hydrophilic agent is dispersed substantially uniformly through the separating plate.
2. 2. A bipolar separating plate, according to claim 1, wherein said at least one resin is hydrophilic.
3. 3. A bipolar spacer plate according to claim 1, wherein this at least one electronically conductive material is selected from the group consisting of carbonaceous materials, metals, metal alloys, metal carbides, metal nitrides, and mixtures thereof.
4. 4. A bipolar spacer plate according to claim 3, wherein this at least one electronically conductive material comprises at least one carbonaceous material.
5. 5. A bipolar separating plate, according to claim 1, wherein the hydrophilic agent is a wetting agent.
6. 6. A bipolar spacer plate according to claim 1, which further comprises carbon fibers up to about 45% by weight of the spacer plate, substantially uniformly disperse through the spacer plate.
7. 7. A bipolar separating plate, according to claim 5, wherein the wetting agent is selected from the group consisting of Ti, Al, Si, and mixtures thereof.
8. 8. A bipolar separating plate, according to claim 1, wherein said at least one resin is selected from the group consisting of thermosetting resins, thermoplastic resins, and mixtures thereof.
9. 9. A bipolar separator plate, according to claim 1, wherein this at least one electronically conductive material is selected from the group consisting of graphite, carbon black, carbon fibers, and mixtures thereof.
10. 10. A bipolar separating plate, according to claim 1, in which this plate is porous.
11. 11. A bipolar separating plate, according to claim 10, wherein the porosity of the plate is less than about 25% by volume of the plate.
12. 12. A bipolar separating plate, according to claim 10, in which the median diameter of the pores is in the approximate range of 0.25 to 2.0 microns.
13. 13. A bipolar separating plate, according to claim 10, wherein the bubble pressure of the plate is greater than about 0.35 kg / cm2.
14. 14. A bipolar separator plate, according to claim 1, wherein the electrical conductivity of the plate is at least about 5S / cm.
15. 15. A bipolar separating plate, according to claim 1, comprising, in an approximate range of 70 to 90% by weight of the electronically conductive material, in an approximate range of 8 to 15% by weight of a thermosetting resin, of about 0 to 10% by weight of carbon fibers and approximately 0.01 to 5.0% by weight of the silica.
16. 16. A bipolar separator plate, according to claim 1, further comprising a resource for circulating the water through the separator plate, between the surface facing the anode and the surface facing the cathode of the separator plate.
17. 17. In a bipolar separator plate, comprising a conductive, electronically conductive material, in an approximate range of 50 to 90% by weight of the separator plate, and a resin in an amount in the range of at least about 5% by weight of the separating plate, the improvement comprising: that the bipolar separating plate includes a hydrophilic agent, suitable for use in a proton exchange membrane fuel cell, uniformly dispersed through this separating plate, whereby the water is able to be absorbed in and pass through the separator plate.
18. 18. A bipolar separating plate, according to claim 17, wherein the hydrophilic agent is a hydrophilic resin.
19. 19. A bipolar separating plate, according to claim 17, wherein the hydrophilic agent is a wetting agent.
20. 20. A bipolar separator plate, according to claim 17, further comprising carbon fibers up to about 45% by weight of the separator plate, dispersed substantially uniformly through the separator plate.
21. 21. A bipolar separating plate, according to claim 19, wherein the wetting agent is selected from the group consisting of the oxides of Ti, Al, Si, and mixtures thereof.
22. 22. A bipolar separating plate, according to claim 17, wherein said at least one resin is selected from the group consisting of thermosetting resins, thermoplastic resins, and mixtures thereof.
23. 23. A bipolar spacer plate according to claim 17, wherein said at least one carbonaceous, electrically conductive material is selected from the group consisting of graphite, carbon black, carbon fibers, and mixtures thereof.
24. 24. A bipolar spacer plate, according to claim 17, wherein the plate is porous.
25. 25. A bipolar separating plate, according to claim 24, wherein the porosity of the plate is less than about 25% by volume of the plate.
26. 26. A bipolar separating plate, according to claim 24, wherein the median diameter of the pores is in the range of about 0.25 to 2.0 microns.
27. 27. A bipolar separating plate, according to claim 24, wherein the bubble pressure of the plate is greater than about 0.35 kg / cm2.
28. 28. A bipolar spacer plate, according to claim 17, wherein the electrical conductivity of the plate is at least about 5S / cm.
29. 29. A bipolar separator plate, according to claim 17, wherein the central region of the separator plate forms a flow guide element for the distribution of the gases from the fuel cell.
30. 30. A bipolar spacer plate, according to claim 29, wherein the crush resistance of the central region is greater than about 14 kg / cm2.
31. 31. In a proton exchange membrane fuel cell stack, comprising a plurality of individual fuel cell units, each fuel cell unit comprises an anode, a cathode, an ion exchange membrane, disposed between the anode and the cathode, and a separator plate, having a surface facing the anode and a surface facing the cathode, this separator plate divides the fuel cell units between an anode of a fuel cell unit and a cathode of a adjacent unit of fuel cell, the improvement comprising: that the separating plate comprises at least one electronically conductive carbonaceous material, in an amount ranging from approximately 50 to 95% by weight of the separator plate, at least one resin, in an amount of at least about 5% by weight of the separator plate, and at least one hydrophilic agent, suitable for use in a fuel cell e) of proton exchange membrane, to attract water into the separator plate, this at least one electronically conductive carbonaceous material, this at least one resin and this at least one hydrophilic agent, are dispersed in substantially uniform form, through the separating plate.
32. 32. A fuel cell stack, according to claim 31, wherein said at least one resin is hydrophilic.
33. 33. A fuel cell stack, according to claim 31, wherein the hydrophilic agent is a wetting agent.
34. 34. A fuel cell stack, according to claim 31, wherein the separator plate further comprises carbon fibers up to about 45% by weight of the separator plate, dispersed substantially uniformly through this separator plate.
35. 35. A fuel cell stack, according to claim 33, wherein the wetting agent is selected from the group consisting of the oxides of Ti, Al, Si, and mixtures thereof.
36. 36. A fuel cell stack, according to claim 31, wherein said at least one resin is selected from the group consisting of thermosetting resins, thermoplastic resins, and mixtures thereof.
37. 37. A fuel cell stack, according to claim 31, wherein this at least one electrically conductive carbonaceous material is selected from the group consisting of graphite, carbon black, carbon fibers, and mixtures thereof.
38. 38. A fuel cell stack, according to claim 31, wherein the plate is porous.
39. 39. A fuel cell stack, according to claim 38, wherein the porosity of the plate is less than about 25% by volume of the plate.
40. 40. A fuel cell stack, according to claim 38, wherein the median diameter of the pores is in the range of about 0.25 to 2.0 microns.
41. 41. A fuel cell stack, according to claim 38, wherein the bubble pressure of the plate is greater than about 0.35 kg / cm2.
42. 42. A fuel cell stack, according to claim 31, wherein the electrical conductivity of the plate is at least about 5S / cm.
43. 43. A fuel cell stack, according to claim 31, in which the ion exchange membranes and the separator plates extend to a peripheral edge of the fuel cell stack, and the separator plates have a seal structure flattened peripheral, extending from each surface for contacting the ion exchange membranes completely around its periphery, which forms a peripheral seal, these ion exchange membranes and the separator plates each have a plurality of aligned perforations, these perforations in the separator plates are surrounded by a flattened seal structure of the collector, which extends from each surface for contacting the ion exchange membrane, which forms a collector seal, thus forming a plurality of gas collectors, which extend through the stack of cells, and conduits through the flattened structure of the manifold seal, which provides the communication of the fuel gas between a set of collectors and the anode chambers, formed between the anodes and the surfaces facing the anode of the separator plates and the conduits through the flattened structure of the collector seal, which supplies the communication of the oxidizing gas between a second set of collectors and the cathode chambers, formed between the cathodes and the surfaces facing the cathode of the separator plates, thus providing the completely internal diversification of the fuel and oxidizing gases to and from each unit fuel cell in the fuel cell stack.
44. 44. A stack of fuel cells, according to claim 31, wherein the central region of the separator plate forms a flow guide element, for the distribution of the fuel cell gases within each fuel cell unit .
45. 45. A fuel cell stack, according to claim 31, further comprising a water circulation resource, for circulating and removing the water from the fuel cell stack.
46. 46. A method for producing a bipolar separator plate, this method comprises: mixing at least one electronically conductive material, at least one resin and at least one hydrophilic agent, suitable for use in a proton exchange membrane fuel cell, forming a substantially homogeneous mixture, which includes this at least one electronically conductive material, in an amount in an approximate range of 50 to 95% by weight of the mixture, this at least one resin, in an amount of at least about 5% by weight weight of the mixture, and this at least one hydrophilic agent; and molding the mixture in a desired configuration, at a temperature in the approximate range of 121 to 2600C and a pressure in the approximate range of 35 to 280 kg / cm2, forming a bipolar plate.
47. 47. A method, according to claim 46, wherein the plate has a porosity of less than about 25% of the plate volume.
48. 48. A method, according to claim 47, wherein the plate forms a plurality of pores, which have a medium size in the range of about 0.25 to 2.0 microns.
49. 49. A method, according to claim 46, wherein said at least one resin is hydrophilic.
50. 50. A method, according to claim 46, wherein the hydrophilic agent is a wetting agent.
51. 51. A method, according to claim 46, further comprising mixing carbon fibers up to about 45% by weight of the mixture, within said mixture. 53. A method, according to claim 50, wherein the wetting agent is selected from the group consisting of the oxides of Ti, Al, Si, and mixtures thereof. 54. A method, according to claim 46, wherein said at least one resin is selected from the group consisting of thermosetting resins, thermoplastic resins, and mixtures thereof. 55. A method, according to claim 51, wherein this at least one carbonaceous, electrically conductive material is selected from the group consisting of graphite, carbon black, carbon fibers, and mixtures thereof.