RU2216826C2 - Sealing unit of fuel element - Google Patents

Abstract

FIELD: electrical engineering, specifically, sealing units for fuel elements with proton-conducting polymer electrolyte. SUBSTANCE: in correspondence with invention sealing unit includes proton- conducting polymer membrane perforated over outline and installed between two semigaskets produced from elastic material. Alternating holes and puckers are made over internal outline of semi-gaskets in zone of membrane sealing. Membrane is put on puckers of one semi-gasket, then second semi-gasket is linked to first one. Puckers of one semi- gasket enter holes in another semi-gasket and vice versa. To raise sealing reliability there is proposed ultrasonic welding of membrane to semi-gaskets or usage of polymerizing or non-hardening sealing compounds. Unit sealing semi-gaskets to bipolar cooling chambers is based on protrusions made in semi-gaskets over their external and internal outlines as well as over surfaces located between collector-forming holes. EFFECT: raised sealing reliability. 4 cl, 2 dwg

Description

 The invention relates to the field of electrical engineering, in particular to fuel cells (FCs) with proton-conducting polymer membranes and other chemical current sources that use membrane or matrix electrolyte structures.

 Known designs of batteries TE with proton-conducting polymer membranes containing a package of sequentially assembled membranes, electrodes and bipolar cooling chambers installed in rubber frames, along the contour of which are collector-forming holes and channels for supplying and discharging working reagents and coolant. The walls of the bipolar cooling chambers have corrugations that form gas channels in the spaces between the electrode and the walls of the chambers (see Lidorenko N.S., Muchnik G.F. Electrochemical Generators, pp. 318, 320, 329, Moscow: Energoizdat, 1982 ) Sealing the edge of the membrane is done by compressing the bag between two flanges. At the same time, collectors are sealed, gas chambers are formed and electrical contact between the membrane, electrodes and walls of the bipolar cooling chambers is ensured.

 According to a similar design scheme, the Siemens company in the 90s developed a 40 kW power plant for underwater vehicles.

 This design has the following disadvantages. When assembling a package of many elements during the compression process, in particular of moistened membranes, due to the lack of a clear fixation of the membranes relative to the rubber frames, the membrane edge may partially slip out of the sealing zone. This leads to a loss of internal tightness. In addition, the assembly is complicated by the fact that at the same time it is necessary to provide internal and external tightness and a given current collector between the membrane, electrodes and the bipolar cooling chamber.

 Such polymer electrolyte fuel cell batteries are known in which the membrane-electrode block is sealed between two flat gaskets that simultaneously seal adjacent cooling chambers or plates and are provided with collector-shaped openings around the perimeter (see US Pat. No. 5,491,980, class H 01 M 8 / 10, published on 05/30/1995).

 A similar technical solution is proposed in Japanese patent 4-11985, class. H 01 M 8/02, publ. 04/04/1992, the Sealing unit according to this invention includes a three-layer gasket formed from green sintered fluoropolymer with various elastic moduli. Moreover, the elastic modulus of the middle gasket is higher than the elastic moduli of the extreme gaskets.

 Recent inventions are adopted as a prototype.

 Flat gaskets do not provide reliable sealing of membranes and bipolar cooling chambers or plates. Assembly of packages of elements is difficult because There is no constructive mutual fixation of the parts assembled in the package.

 More reliable sealing with simultaneous mutual fixation of the components of the package of parts is done by mating protrusions made on gaskets - separators located between adjacent cooling plates, in which there are corresponding recesses (see US patent 5521018, CL N 01 M 8/4, publ. May 28, 1996). However, in this technical solution the issue of reliable fixation and sealing of the membrane with respect to the sealing gaskets is not resolved.

 The aim of the present invention is to increase the reliability of sealing the membrane-electrode block, as well as the sealing site of adjacent bipolar cooling chambers or plates, simplifying the process of assembling a battery of fuel cells by fixing the membrane-electrode block with respect to the sealing gaskets and the latter relative to bipolar cooling chambers or plates beyond due to the introduction of special structural elements in the construction of gaskets, membranes and chambers according to the invention.

 This goal is achieved by the fact that the sealing unit with proton-conducting polymer membranes containing a membrane-electrode block, sealing gaskets of elastic material, along the perimeter of which collector-forming holes are made, and bipolar cooling chambers with flat walls and with similar collector-forming holes, are made as follows. According to the invention, the membrane of the membrane-electrode block is perforated along the sealing circuit. Sealing gaskets made of elastic material located between the bipolar cooling chambers are made of two half-gaskets equipped with alternating holes and beads corresponding to the membrane sealing perforation, which, when assembling the half-gaskets and the membrane-electrode block between them, form a joint by pairing the holes of one of the half-gaskets with puklami other half-laying and vice versa. In this case, the membrane-electrode membrane is preliminarily installed on the convexes of one of the half-strips, and the height of the convexes of each of the half-strips does not exceed the thickness of the other half-strips in the sealing zone. The sealing of adjacent bipolar cooling chambers is ensured by the protrusions made along the external and internal sealing contours of the seals, as well as the protrusions around the collector holes of the seals.

 This goal is also achieved by the fact that the connection of the seals between themselves and with the membrane is performed using ultrasonic welding, and the membrane-electrode block is pre-dehydrated.

 This goal is also achieved by the fact that the connection of semi-gaskets with each other, with bipolar cooling chambers and with the membrane is made through polymerizable or non-hardening sealants.

 It is preferable to introduce electrodes up to 2 mm in the sealing zone of the membrane between the half-pads along the sealing contour of the membrane-electrode block.

 It is advisable that the bipolar cooling chamber be provided with external and internal sealing along the contour, as well as grooves around the collector-forming holes, which in their profile correspond to the protrusions in the sealing half-gaskets.

 Preferably, the half-pads contained projections of only linear size in the plan, while sealing between the collector-forming holes was also carried out by linear projections in the plan, orthogonal to the protrusions of the external and internal sealing contours of the half-pads.

 The proposed technical solutions provide reliable fixation and mutual orientation of the membrane-electrode block, sealing half-gaskets and bipolar cooling chambers or plates when assembling fuel cell batteries, as well as reliable sealing of mating surfaces. The battery assembly process is simplified.

 Ultrasonic welding or the introduction of sealants in the sealing zone increases the reliability of the joints for tightness.

 The introduction of the edges of the electrodes into the sealing zone of semi-gaskets to a depth of 2 mm ensures that there is no direct contact of the open membrane with the working gases, which eliminates the possibility of overdrying the membrane and reduces the diffusion of the working components into the adjacent gas cavity.

 The implementation of the protrusions in the gaskets only linear in terms of plan allows you to reduce the cost of equipment.

 The analysis of the prior art showed that the claimed combination of features set forth in the formula is unknown. This allows us to conclude that the claimed device meets the criterion of "novelty."

 To verify the conformity of the claimed invention to the criterion of "inventive step", a search was made for technical solutions in order to identify features that match the distinctive features of the prototype of the claimed invention.

 It is established that the claimed invention does not follow for a person skilled in the art explicitly from the prior art. Therefore, the claimed invention meets the criterion of "inventive step".

 The invention is illustrated in the drawing and description.

 In FIG. 1 shows a fragment of a fuel cell battery in plan (from the half-gasket side), FIG. 2 shows a section along the axis of the reagent supply manifold.

 The membrane-electrode block 1, consisting of a membrane 2 and electrodes 3, 4, is installed between two half-strips 5, 6, which, in turn, are crimped by bipolar cooling chambers or plates 7, 8. The membrane 2 is perforated along the contour, and the half-strips are equipped with alternating the holes 9 and the bulges 10. On the outer contour of the gasket protrusions 11 are formed, and on the inner contour - protrusions 12. To seal the collector-forming holes 13, the half-gaskets are equipped with linear protrusions 14 located orthogonally to the protrusions 11 and 12. For When sealing the half-gaskets with bipolar cooling chambers or plates 7, 8, the linear grooves 15, 16 corresponding to the protrusions in the gaskets are made during sealing. The working reagents enter the gas spaces 17, 18 through the channels 19, 20. The assembly is sealed by crimping the protrusions 11, 12, 14 in semi-gaskets, as well as by applying polymerizable or liquid sealants to mutually mating surfaces of parts 1, 5, 6, 7, 8. Ultrasonic welding of parts 2, 5, 6 is possible before battery assembly. Holes 21 are for mounting tie rods.

 The device is assembled as follows. The membrane-electrode unit 1 with a perforated membrane 2 is put on the convexes 10 of one of the half-strips, for example 6, then the second half-strip 5 is installed. In this case, the convexes 10 of one of the half-strips enter the holes 9 of the other half-strip and vice versa. For a more reliable sealing of the surfaces of the parts to be absorbed in the sealing zone, they are pre-coated with a sealant prior to assembly. A variant of ultrasonic welding of half-gaskets between themselves and with the membrane is also possible. After that, the assembled assembly is installed between two adjacent bipolar refrigeration chambers 7, 8, a sequential set of fuel cells is assembled into the battery, and the packet is compressed between the end flanges and fixed with studs installed in the holes 21.

 The battery generates current after the supply of working components through the collectors 22 and channels 19, 20 to the gas cavities 17, 18. The membrane-electrode block provides a cold combustion reaction, i.e. direct conversion of the chemical energy of the fuel and oxidizer into electricity. Heat is removed by plates 7, 8.

The claimed sealing unit was implemented on a prototype battery TE with an active surface of 10 • 10 cm ² with a sealing option based on a liquid sealant - a solution of polyisobutylene in gasoline. Sealing gaskets were made of fluororubber SKF-26. When assembling a TE battery, the membrane-electrode blocks were previously dehydrated. The bipolar cooling chambers were solid brazed structures with flat walls. The internal separator was made of a volumetric perforated corrugation with a height of 1.2 mm and pitch 2.5 mm. A metal frame was installed around the perimeter of the chamber with collector-forming holes and channels for supplying and discharging H ₂ , O ₂ , coolant and reaction water. The current collector-separators in the gas chambers of the TE consisted of three-layer grids - a woven mesh of 0.16 mm, a perforated mesh with a diamond-shaped cell of 3 mm and a perforated mesh with a diamond-shaped cell of 5 mm (from a sheet 0.2 mm thick), located cells orthogonally to a grid with 3 mm cell. The compression force of the FC between the end flanges is 50 kgf / cm ² . Working pressures of H ₂ and O ₂ 2-2.5 kgf / cm ² , coolant - 1.0 kgf / cm ² . The test pressure on the internal tightness (H ₂ - O ₂ ) is 1.5 kgf / cm ² , the external tightness is 3.0 kgf / cm ² .

After assembling and checking the internal and external tightness, the TE battery was filled with distilled water (H ₂ and O ₂ cavities) and kept at room temperature for 24 hours. Before the functional tests, the distillate merged and the H ₂ and O ₂ cavities were purged with an inert gas for ~ 2 min.

The breadboard battery of the fuel cell worked for 500 hours at current densities of up to 350 mA / cm ² and a voltage on the fuel cell of at least 0.7 ... 0.8 V.

 Based on the foregoing, we can conclude that the claimed invention can be used in practice to achieve the specified result and, therefore, meets the criterion of "industrial applicability".

Claims (5)

 1. The sealing unit of fuel cells with proton-conducting polymer membranes, containing a membrane-electrode block, sealing gaskets of elastic material, along the perimeter of which collector-forming holes are made, and bipolar cooling chambers with flat walls and similar collector-forming holes, characterized in that the membrane is membrane the electrode block is perforated along the sealing circuit, and the sealing gaskets of elastic material located between the bipolar cooling chambers are made of two half-pads equipped with alternating holes and beads corresponding to the membrane perforation along the membrane sealing circuit, which, when assembling the half-pads and the membrane-electrode block between them, form a connection by pairing the holes of one of the half-pads with the other half-beads, the height of each of half-gaskets does not exceed the thickness of the other half-gaskets in the sealing zone, and the sealing of adjacent bipolar cooling chambers is ensured by t protrusions made along the external and internal sealing contours of the seals, as well as linear protrusions located orthogonal to the above protrusions.  2. The sealing unit according to claim 1, characterized in that the connection by interfacing the half-gaskets with each other and with the membrane is performed using ultrasonic welding, the membrane-electrode block being previously dehydrated.  3. The sealing unit according to claim 1, characterized in that the connection by interfacing the semi-gaskets with each other, with bipolar cooling chambers and with the membrane is through polymerizable or non-hardening sealants.  4. The sealing unit according to claim 1, characterized in that electrodes are introduced into the sealing zone of the membrane between the half-gaskets at a size of up to 2 mm along the sealing loop of the membrane-electrode block.  5. The sealing unit according to claim 1, characterized in that the bipolar cooling chamber is provided with grooves along the external and internal sealing contour, as well as along the linear protrusions located orthogonally to the protrusions along the external and internal sealing contours.

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