Catalyst device for lead-acid battery, and lead-acid battery

Abstract

A catalyst device for a lead acid battery, and a lead acid battery comprising the catalyst device are disclosed. A catalyst layer (120) is mounted in a cavity (112) of the device, and a porous layer (140) comprising a thermoplastic material is mounted in the cavity so as to cover a face of the catalyst layer and is configured to prevent thermal runaway of the catalyst device. And the plane size of the porous layer is larger than that of the catalyst layer. The catalyst layer is mounted in a cavity within a maintenance means (130) configured to maintain the position of the catalyst layer within the cavity, and wherein at least one face is covered by the porous layer, thereby ensuring alignment of the catalyst layer and the porous layer in use.

Description

Technical Field

[0001] The present invention relates to a catalyst device for a lead-acid battery, and more preferably to a catalyst device for reducing gas accumulation in a lead-acid battery and loss of electrolyte solution from the lead-acid battery, thereby improving battery safety and life. Background Art

[0002] Lead-acid batteries, particularly those used in automotive applications, generally employ an open structure in which an electrolyte solution (such as dilute sulfuric acid) can flow freely. These batteries generate oxygen and hydrogen gases during charging and therefore incorporate vents (air holes) to release these gases. Otherwise, the gas pressure within the battery would increase, potentially causing deformation and rupture of the battery.

[0003] The gas leakage through the vent hole causes a decrease in electrolyte solution, which leads to insufficient chemical reactions in the battery, resulting in a decrease in charge and discharge capacity.

[0004] To address these problems, it is known to provide a catalyst device exposed to an enclosure containing the electrolyte, thereby promoting the recombination of hydrogen and oxygen.

[0005] JP 2017-201594 (Nihon Gore Co Ltd) discloses a catalyst component for a lead-acid battery. The catalyst component comprises a catalyst layer containing a catalyst for accelerating the reaction of oxygen and hydrogen to produce water or water vapor, and a device by which at least a portion of the water or water vapor condenses and / or flows back into the interior of the battery. The catalyst component can reduce gas release from the electrolyte solution and electrolyte solution reduction due to leakage, thereby providing a lead-acid battery with a long life.

[0006] US Pat. No. 7,326,489 (Philadelphia Scientific) discloses a catalyst device for recombining gases from the decomposition of an electrolyte solution. The catalyst material is housed within a container and separated from the battery enclosure at the open end of the chamber by a microporous membrane. The microporous membrane allows the passage of gases but not liquids. Hydrogen and oxygen can pass through the microporous membrane to the catalyst, where they recombine, and the resulting water vapor can return to the battery via the microporous membrane.

[0007] CN102800831A and CN202977567U (Zhejiang Narada Power Co., Ltd., etc.) disclose battery vent plugs, each having a housing with a lower member containing catalyst material, and a porous hydrophobic filter layer separating the catalyst from the battery electrolyte enclosure.

[0008] As mentioned above, when charging, conventional lead-acid batteries release oxygen and hydrogen through the vents, causing a decrease in the electrolyte solution within the lead-acid battery. This decrease ultimately leads to a decrease in both charge and discharge capacity. Increased concentrations of dilute sulfuric acid in the electrolyte solution can cause corrosion of the positive plates, and the reduced electrolyte level can expose the plates, further reducing charge and discharge capacity. Increased acid concentrations can also lead to corrosion within the battery, such as between the negative plates and gaskets.

[0009] Furthermore, the reduction in electrolyte solution can also lead to sulfation, as well as penetrating short circuits. Sulfation is a phenomenon in which the lead sulfate produced by discharge cannot be fully decomposed into lead dioxide and lead by charging, thereby forming large crystals of lead sulfate. Such large crystals are difficult to reduce to metallic lead, which reduces battery performance and shortens battery life. In addition, such large crystals also contribute to penetrating short circuits. The large crystals grow into needle-shaped crystals on the electrode, called "dendrites." If the dendrites continue to grow, they can reach the other electrode, causing a short circuit. This is a penetrating short circuit, making it impossible to charge and discharge the battery.

[0010] In recent years, in particular, the use of motor vehicles equipped with idling stop systems has increased in order to improve fuel economy. The lead-acid batteries used in idling stop vehicles provide energy for all devices, such as air conditioners and fans, during the idling stop period. Consequently, compared to conventional starting lead-acid batteries, these lead-acid batteries tend to be undercharged and used in a low state of charge, exacerbating sulfation and through-current shorts.

[0011] The risk of sulfation and through-current shorts can be reduced by reducing or preventing the reduction of electrolyte solution. This leads to the use of catalyst devices, such as those described above.

[0012] The recombination of hydrogen and oxygen is a highly exothermic reaction (-286 kJ mol -1 ), and H2+1 / 2O caused by overheating or overcharging of the battery 2-> A rapid HO recombination reaction can cause the catalyst to overheat. Generally speaking, increased catalyst temperature leads to increased catalyst activity, which in turn further increases the reaction rate and can lead to thermal runaway. This thermal runaway can create the risk of igniting gases within the battery, leading to explosion or fire.

[0013] US 7326489 discloses that a catalyst device can be provided with a shutdown function. Specifically, the container surrounding the catalyst material can be melted, thereby physically covering the catalyst and quenching the recombination reaction. A disadvantage of the disclosed device is that the melting of the container material creates a risk of losing containment of the catalyst material in the container. Subsequently, the catalyst material may be exposed and continue to overheat, or fragments may be released into the electrolyte, causing a short circuit and potentially dangerous release of electrical energy. In addition, in order for the shutdown to occur, sufficient heat must be transferred from the catalyst material to the container to melt the container, which consumes time and allows thermal runaway to develop further.

[0014] PCT / JP2018 / 043437 (WL Gore & Associates GK) discloses a catalyst having a porous thermoplastic membrane in contact with the catalyst material. The membrane has a melting point of 160°C or less, so that the membrane can melt and reduce porosity, thereby reducing the rate of the recombination reaction or quenching the recombination reaction entirely. However, for some applications (such as certain automotive applications), the registration of the thermoplastic membrane relative to the catalyst (i.e., its position on the entire catalyst surface) may vary, resulting in the risk that some catalyst surface remains exposed to the catalyst encapsulation. Summary of the Invention

[0015] A first aspect of the present invention relates to a catalyst device for a lead-acid battery, the catalyst device comprising;

[0016] a housing defining a cavity;

[0017] a catalyst layer installed in the cavity, wherein the catalyst layer includes a catalyst for accelerating a reaction of generating water or water vapor from oxygen and hydrogen; and

[0018] a porous layer comprising a thermoplastic material, mounted in the cavity, wherein a planar dimension of the porous membrane is larger than a planar dimension of the catalyst layer, and wherein a face of the catalyst layer contacts the porous layer and covers at least one face of the catalyst layer;

[0019] The catalyst layer is mounted in a cavity within a retaining device, the retaining device is configured to maintain the position of the catalyst layer within the cavity, and the at least one face is covered by the porous layer.

[0020] A porous layer comprising a thermoplastic material (hereinafter referred to as the "porous layer") is disposed between the electrolyte enclosure and the catalyst layer of a lead-acid battery during use. Hydrogen and oxygen generated within the battery can permeate through the porous layer and travel to the catalyst layer, reacting in a recombination reaction and forming water vapor. The water vapor permeates the enclosure and condenses, thereby maintaining the electrolyte level in the battery. If the temperature of the catalyst layer rises above the melting point or glass transition temperature of the thermoplastic material, the porosity of the porous layer decreases, thereby controlling the rate of the recombination reaction and regulating the temperature of the catalyst layer.

[0021] Due to manufacturing tolerances, the relative movement of the catalyst layer and the porous layer relative to each other and relative to the shell cannot be completely eliminated. In addition, some gaps between the shell and the layers can help simplify the manufacture of the device. The retaining arrangement maintains the position of the catalyst layer so that within any range of movement of the intracavitary catalyst layer or polymer layer, the face of the catalyst layer in contact with the porous layer remains covered. Therefore, the possibility of misalignment of the catalyst layer and the porous layer (we mean that the portion of the face of the catalyst layer adjacent to the face of the porous layer is not covered by the porous layer) is reduced or eliminated.

[0022] In some embodiments, when the thermoplastic material is heated above its glass transition temperature or melting point, the porous layer undergoes some shrinkage. The larger area of ​​the porous layer accommodates this shrinkage, while the surface of the catalyst layer remains covered. Contact with the catalyst layer can generate friction with the porous layer and resist shrinkage.

[0023] "Layer" means a structure having parallel or substantially parallel, opposing faces, each dimension of which is greater than the thickness of the layer between the faces. A layer may have one or more circumferential surfaces around its circumference and between its faces. When installed in a cavity, the layers disclosed herein will generally be planar.

[0024] "Cavity" includes a depression or opening sized to receive and maintain the catalyst layer and the porous layer. The cavity may be of any shape or configuration, but is conveniently circular in cross-section.

[0025] The retaining means may comprise one or more retaining structures to prevent or substantially prevent lateral movement of the catalyst layer.

[0026] The retaining means may extend around the circumference of the catalyst layer.The one or more retaining structures of the retaining means may extend around at least a portion of the catalyst layer.

[0027] The inner contour of the retaining means may comprise one or more of the retaining structures.

[0028] The housing may contain the retaining means. For example, the retaining means may comprise one or more retaining structures defined by the housing, and wherein the one or more retaining structures extend into the cavity.

[0029] The retaining means may comprise a retainer, wherein the retainer is mounted within the cavity in a substantially fixed relationship to the housing.The one or more retaining structures may be defined by the retainer.

[0030] The retaining means may extend around the circumference of the catalyst layer. The inner contour of the retaining means may contain one or more retaining structures.

[0031] For example, the retaining means may comprise a retainer in the form of a ring having a shape roughly similar to that of the catalyst layer. The inner contour of the ring may serve as a retaining structure. That is, the catalyst layer may fit tightly within the ring.

[0032] A "ring" includes any structure that extends around the circumference of the catalyst layer and may be circular, square, polygonal, etc. The catalyst layer may have a shape corresponding to that of the ring, or may have a different shape sized to fit within and be maintained by the ring.

[0033] It will be appreciated that a lateral gap may be provided between the catalyst layer and the retaining means, for example to accommodate manufacturing tolerances or to facilitate assembly; such that the catalyst layer and the porous layer may each be able to move laterally within the cavity relative to the housing to a certain extent.

[0034] However, in some embodiments, the lateral movement range of the porous layer and all catalyst layers within the cavity is desirably minimized, such as less than 1 mm, less than 0.5 mm, or less than 0.1 mm.

[0035] The porous layer may include a circumferential surface region that extends beyond the extent of lateral movement of the porous layer relative to the catalyst layer around the entire circumference of the catalyst layer. For example, when the cavity, catalyst layer, and porous layer are generally circular, the centers of the catalyst layer and porous layer may be axially offset by at most a first lateral distance. The radius of the porous layer may be greater than the radius of the catalyst layer by a greater extent than the first lateral distance, thereby preventing misalignment of the porous layer and the catalyst layer.

[0036] The circumferential surface area may at least partially cover the retaining means.

[0037] That is, one or more faces of the retention device may be oriented toward a circumferential surface region of the porous layer, while the porous layer may extend laterally so as to cover at least a portion or all of the faces of the retention device.

[0038] As disclosed herein, in some embodiments, the porous layer can be bonded to, adhered to, welded to, or otherwise connected to the retaining device. In use, the porous layer can at least partially seal the retaining device below.

[0039] It will be appreciated that the shell, cavity, porous layer and catalyst layer may each have any suitable shape. For convenience, the catalyst layer, porous layer and cavity (and typically the shell) are coaxial and / or circular.

[0040] The catalyst layer may have a catalyst layer thickness. The retaining device may have a depth (wherein the depth is the distance in a direction between faces of the catalyst layer when the catalyst layer is mounted in the cavity).

[0041] The depth of the retaining device may be greater than, equal to, or less than the thickness of the catalyst layer.

[0042] The present inventors have found that the depth of the retaining means is advantageously similar to, or less than, the thickness of the catalyst layer.

[0043] In some circumstances, the depth of the retaining device is greater than the thickness of the catalyst layer, wherein the depth of the retaining device is less than 0.5 mm, or less than 0.2 mm greater than the thickness of the catalyst layer.

[0044] In some embodiments, the depth of the retaining device is less than the thickness of the catalyst layer, wherein the depth of the retaining device is at least about 0.2 mm, or 0.5 mm less than the thickness of the catalyst layer.

[0045] Without wishing to be bound by theory, we believe that making the depth of the maintaining device similar to or less than the thickness of the catalyst layer helps maintain the porous layer in contact with at least one surface of the catalyst layer, so that the porous layer can more effectively regulate the reaction rate on the catalyst layer when the temperature becomes too high during use.

[0046] The thermoplastic material itself has a melting point or glass transition temperature, referred to herein as a first temperature. At or above this first temperature, the thermoplastic material begins to lose its elastic modulus, and the porosity of the porous layer decreases. In fact, when the thermoplastic material begins to deform or melt, the pores of the porous material coalesce or become blocked.

[0047] In some preferred embodiments, the maintenance device is dimensionally stable up to a second temperature higher than the first temperature, whereby in the event of thermal runaway, the maintenance device remains dimensionally stable while the porous material modulates or quenches the recombination reaction.

[0048] By "dimensionally stable" is meant that the maintenance device does not melt, deform or decompose below the second temperature. For example, the maintenance device may comprise a polymeric material having a melting point, glass transition temperature or decomposition temperature that is higher than the first temperature. For the avoidance of doubt, thermal expansion does not cause a loss of dimensional stability. Where the maintenance device comprises a thermoplastic material and the second temperature is the melting point or glass transition temperature of the maintenance device thermoplastic material, in some embodiments, the second temperature may be the same or substantially the same as the first temperature. For example, the maintenance device thermoplastic material may be the same thermoplastic material as the porous layer. In this case, although the first and second temperatures may be the same, the bulk material of the maintenance device may remain substantially dimensionally stable while the porosity of the porous layer is reduced. This may help the porous layer adhere to the maintenance device where the first and second temperatures are the same or similar.

[0049] In a preferred embodiment, the housing is dimensionally stable up to a third temperature. The third temperature may be higher than the first temperature. In some embodiments, the second and third temperatures may be the same.

[0050] The porous layer may comprise a porous membrane.The porous layer or the porous membrane may be perforated.

[0051] In some embodiments, the porous layer may comprise an expanded thermoplastic polymer film, such as expanded polyethylene, polyurethane, and the like.

[0052] The glass transition temperature or melting point of the thermoplastic polymer material of the porous layer may be 200° C. or less, or 180° C. or less, or 160° C. or less, or 140° C. or less. The glass transition temperature or melting point of the thermoplastic polymer material of the porous layer may be in the range of 50° C. to 200° C., or in the range of 60° C. to 180° C., in the range of 100° C. to 180° C., in the range of 100° C. to 160° C., or in the range of 100° C. to 140° C. The glass transition temperature may be in the range of 50° C. to 180° C., or in the range of 60° C. to 160° C., or in the range of 80° C. to 140° C.

[0053] Those skilled in the art will understand that the thermoplastic material may comprise one thermoplastic polymer, or in some embodiments, more than one thermoplastic polymer. Those skilled in the art will further understand that near all of the above-mentioned glass transition temperatures (in the case of amorphous or semi-crystalline polymers) and / or melting points (in the case of crystalline or semi-crystalline thermoplastic polymers), the thermoplastic polymer begins to lose its elastic modulus and becomes dimensionally unstable. Typically, above the glass transition temperature or melting point, the polymer becomes flowable. In addition, for a given type of polymer material, the glass transition temperature or melting point may depend on a variety of factors, such as the molecular weight or molecular weight range of the polymer, the ratio of the monomers present in the copolymer, and the like. Therefore, the technician will be able to select the desired melting point or glass transition temperature for a particular purpose (e.g., the highest temperature allowable for a specific battery encapsulation or catalyst material) by appropriately selecting the thermoplastic material composition.

[0054] The catalyst device may include a porous layer in contact with both sides of the catalyst layer. The catalyst device may include at least two porous layers, wherein a first porous layer is in contact with a first side of the catalyst layer, and a second porous layer is in contact with a second, opposite side of the catalyst layer, and the planar dimensions of each porous layer are larger than the planar dimensions of the catalyst layer.

[0055] The catalyst device may comprise at least two porous membranes.Each porous layer may comprise more than one porous membrane.

[0056] The or each porous layer may be laminated to and in contact with a corresponding face of the catalyst layer.

[0057] "Laminated to" or "laminate" refers to a structure formed by applying forces between and through the thickness of each layer to bond the layers together. The laminated structure will typically be formed by applying pressure (e.g., by nip rollers, etc.) and heat. Lamination can result in melting or flow between the laminated materials, or in some cases, can result in a chemical reaction, such as a chemical reaction of adhesive materials therebetween.

[0058] Each porous layer can be bonded to a corresponding surface of the catalyst layer and in contact therewith. For example, in some embodiments, an adhesive (such as a contact adhesive) can be used to bond the porous layer to the catalyst layer. The adhesive can be applied in a discontinuous manner, for example in a dotted pattern, to reduce the risk of clogging the pores of the porous layer or covering an excessive area of ​​the surface of the catalyst layer. Alternatively, bonding can include melting or heat welding.

[0059] In some embodiments, alternatively or additionally, some or all of the circumferential regions of at least two of the porous membranes are bonded to one another. For example, the porous membranes may extend over and around the retainer and the catalyst layer therein and be bonded to one another.

[0060] In some embodiments, the at least two porous membranes may form a bag or capsule around the catalyst layer.

[0061] The or each porous layer may be laminated to, or associated with, the retaining means. For example, the porous layer may be laminated to the catalyst layer and the retainer surrounding the catalyst layer, on one or both sides thereof.

[0062] The catalyst device may include a diffusion limiting layer adapted to regulate the diffusion or flow rate of gas to the catalyst layer.

[0063] The diffusion-limiting layer may be adjacent to (in a gas diffusion direction toward the catalyst layer) the porous layer. The porous layer may be located between the diffusion-limiting layer and the catalyst layer.

[0064] The diffusion-limiting layer may be in contact with the porous layer on a surface opposite to a surface of the porous layer in contact with the catalyst layer.The diffusion-limiting layer may be laminated to the porous layer or bonded to the porous layer.

[0065] The skilled artisan will appreciate that, during use, gases in a lead-acid battery will diffuse from the electrolyte enclosure to the catalyst layer of the device according to the present invention, which is in fluid communication therewith. Under certain operating conditions, such as at elevated temperatures, the pressure within the battery enclosure may exceed ambient pressure. In embodiments where the device further includes a vent to vent this excess pressure from the battery, gases may flow from the enclosure, wherein the catalyst device may be positioned through a flow channel from the battery enclosure to the external environment.

[0066] The diffusion or flow-restricting effect of the diffusion-restricting layer may be reflected by a relatively high Gurley Flow Number, such as a Gurley Flow Number of 50 seconds or greater, or 100 seconds or greater.

[0067] The diffusion limiting layer may comprise a porous fluoropolymer layer.

[0068] The porous fluoropolymer layer may be hydrophobic.

[0069] The porous fluoropolymer layer may comprise a fluoropolymer membrane. The fluoropolymer membrane may be an expanded fluoropolymer membrane, such as expanded polytetrafluoroethylene.

[0070] Expanded polymeric membranes, such as the expanded polyethylene or expanded polytetrafluoroethylene membranes described herein, comprise a microstructure of fibrils, typically nodes interconnected by the fibrils, with pores extending therebetween.

[0071] The porous fluoropolymer layer may have a Gurley number of 100 seconds or greater. The porous fluoropolymer layer may have a Gurley number of 200, 300, 400, 700, or 1000 seconds or greater.

[0072] The expanded porous polytetrafluoroethylene may have a Gurley number of 100 seconds or greater. The porous fluoropolymer layer may have a Gurley number of 200, 300, 400, 700, or 1000 seconds or greater.

[0073] The catalyst device may include a porous anti-poisoning layer capable of absorbing or decomposing catalytic poisons.

[0074] The anti-poisoning layer may be adjacent to the porous layer (in the direction of gas diffusion toward the catalyst layer).The anti-poisoning layer may contact a face of the porous layer, and optionally be laminated to or bonded to a face of the porous layer.

[0075] When an anti-poisoning layer is present, the anti-poisoning layer may be adjacent to, in contact with, laminated to, or bonded to the diffusion-limiting layer. The anti-poisoning layer may contact a face of the porous layer, and optionally be laminated to or bonded to a face of the porous layer.

[0076] That is, the anti-poisoning layer may be located between the porous layer and the diffusion-limiting layer, or vice versa.

[0077] Examples of components that act as catalyst poisons include dilute sulfuric acid in the electrolyte solution, or sulfides generated from dilute sulfuric acid, such as H2S. Materials such as antimony and arsenic may also be present and function as catalyst poisons in lead-acid batteries. These catalyst poisons, when in contact with the catalyst, reduce its catalytic performance. Materials capable of absorbing or decomposing catalyst poisons include activated carbon, ZnO, potassium carbonate, and the like, and these materials can absorb or decompose the catalyst poison.

[0078] The anti-poisoning layer may comprise a membrane. The membrane may be an expanded polymer membrane. The porous anti-poisoning layer or membrane may comprise a fluoropolymer. The porous anti-poisoning layer or membrane may comprise polytetrafluoroethylene, such as ePTFE. Woven fabrics, nonwoven fabrics, or knitted fabrics may also be used.

[0079] The anti-poisoning layer may be hydrophilic. For example, the anti-poisoning layer may comprise a membrane that has been subjected to a hydrophilization treatment so that catalytic poisons can be more easily adsorbed. In an exemplary hydrophilization treatment, a metal oxide gel may be used. Specifically, a hydrophilic metal oxide sol is provided, and the porous component is immersed in the sol, which is then gelled. As a result, the inner surface of the pores of the porous component can be modified by the hydrophilic oxide gel. For example, based on a sol-gel process, the surface of the component can be coated with a silica material to perform hydrophilization. Hydrophilization can also be performed by using a surface treatment such as plasma, as known to those skilled in the art.

[0080] The anti-poisoning layer may include a substance capable of absorbing or decomposing the catalytic poison inside the porous layer capable of absorbing or decomposing the catalytic poison.

[0081] The term "inside the porous layer" (or membrane, as the case may be) means that the substance capable of absorbing or decomposing the catalytic poison may be present in or disposed in the cavity, or on or embedded in the pore surfaces of the porous layer. This is similar to, for example, Figure 8 The case where the catalyst is shown to be located within a catalyst layer is similar and will be discussed in more detail below.

[0082] The catalyst device may include an outer hydrophobic porous layer having a Gurley number lower than that of the diffusion-limiting layer, for example, a Gurley number lower than 20 seconds.

[0083] During use, the outer hydrophobic porous layer can inhibit or prevent sulfuric acid mist and / or electrolyte solution (typically a dilute aqueous sulfuric acid solution) from directly contacting the catalyst layer, thereby extending the life of the catalyst device.

[0084] The outer hydrophobic porous layer may comprise a fluoropolymer. The outer hydrophobic porous layer may comprise a membrane. The membrane may be an expanded polymer membrane, such as an expanded fluoropolymer membrane. The membrane may comprise an ePTFE membrane.

[0085] In use, the outer hydrophobic porous layer may be positioned so as to be closer to the electrolyte enclosure of the battery.

[0086] For example, in some circumstances, the cavity has an open end (which, in use, is oriented toward, or is in fluid communication with, the electrolyte enclosure), and the outer hydrophobic porous layer is closer to, or in some circumstances, extends through, the open end of the cavity.

[0087] The catalyst layer may be porous.

[0088] The catalyst layer may include a hydrophobic porous member. In the catalyst layer, the hydrogen and oxygen generated by the battery reaction are recombined to form water or water vapor, and the environment in or around the catalyst layer tends to become humid. When the catalyst is covered with water or water vapor, hydrogen and oxygen are less likely to contact the catalyst, and the catalyst reaction (recombination reaction) tends to be less efficient. Providing a catalyst layer with a hydrophobic porous member is beneficial for releasing the generated water or water vapor from the catalyst layer, and thus improving efficiency. In some embodiments, when using the catalyst device, hydrophobicity is also beneficial for returning water or water vapor to the electrolyte package of the battery.

[0089] The catalyst, or the catalyst support supporting the catalyst, may be disposed in the cavity, or on the pore surface of the catalyst layer (or on a hydrophobic porous member thereof). In this case, the catalyst support, especially the catalyst, is exposed in the cavity of the catalyst layer so that hydrogen and oxygen can contact the catalyst.

[0090] Alternatively, the catalyst layer may comprise a powder that has been molded, granulated, or sintered. The catalyst layer may comprise a powdered catalyst support that has been molded, granulated, or sintered. The catalyst layer may comprise a polymer powder mixed with a powdered catalyst support, wherein the mixture is molded, granulated, or sintered to form the catalyst layer.

[0091] Preferably, the catalyst layer (or its hydrophobic porous component) does not react with other materials (such as sulfates) inside the battery. In fact, other layers of the catalyst device, such as the outer hydrophobic porous layer, the diffusion-limiting layer and / or the anti-poisoning layer, may further comprise materials or membranes that preferably do not react with other materials (such as sulfates) inside the battery.

[0092] For example, polypropylene and PTFE may be used, and woven fabrics, nonwoven fabrics, knitted fabrics, and porous membranes thereof may also be used. The catalyst layer may comprise an expanded polymer membrane.

[0093] The catalyst layer (or hydrophobic porous member) may include porous polytetrafluoroethylene (PTFE), such as ePTFE.

[0094] Polytetrafluoroethylene itself has excellent properties, such as hydrophobicity, chemical tolerance, UV tolerance, oxidation resistance, heat resistance, and is suitable for use as a building material for batteries. Polytetrafluoroethylene can be made porous by expanding the PTFE sheet with a controlled expansion ratio and temperature conditions, optionally biaxially expanding, to form a porous ePTFE layer, as known to those skilled in the art. More specifically, the expanded porous polytetrafluoroethylene comprises knots (nodes) and fibrils (small fibers). The catalyst or catalyst carrier is retained in the microcavity (micropores) defined by the knots and / or the fibrils. Both the knots and the fibrils are made of polytetrafluoroethylene, and it is believed that the difference between the two is due to the difference in the aggregation or crystallization state of polytetrafluoroethylene molecules. In general, it is believed that knots are aggregates of polytetrafluoroethylene primary particles, while fibrils are formed by crystalline ribbons expanded by the knots (i.e., the primary particles).

[0095] Figure 8 Schematic diagram of catalyst particles supported on the surface of a catalytically inert powdered support. The catalyst material, comprising the catalyst and support, is located within the ePTFE membrane, between its filaments and knots. Such a material can be made in the same manner as other expanded polymeric materials, by mixing its powdered components, then extruding (e.g., into a tape), and expanding under controlled temperature and expansion ratio conditions to form an expanded membrane.

[0096] The catalyst may be any catalyst for recombining hydrogen and oxygen to form water, examples of which include Pd, Pt, and Au. The carrier on which the catalyst is loaded may be any carrier having a specific surface area sufficient to load the catalyst in a desired dispersed state. The carrier may be selected from the group consisting of: silica, alumina, zeolite, carbon, oxides and carbides of transition metals of Groups IVB, VB, VIB, VIIB, and VIII, and combinations thereof. Alternatively, the carrier may be a carbon material. It is not preferred that the carrier material undergo a chemical reaction different from the desired reaction, or that the substance constituting the carrier material is washed out when in contact with condensed water. In this regard, carbon materials are chemically stable and preferred carrier materials. Examples of carbon materials include carbon black (e.g., oil furnace black, channel black, lamp black, thermal black, and acetylene black), activated carbon, coke, natural graphite, and artificial graphite. They may be used in combination.

[0097] The catalyst layer may further include a substance capable of absorbing or decomposing catalytic poisons, for example as an alternative to a device comprising a separate anti-poisoning layer. The substance capable of absorbing or decomposing catalytic poisons may be mixed with the catalyst material, or a support comprising the catalyst material, and / or may be dispersed within the catalyst layer (e.g., dispersed within a porous membrane, as described herein).

[0098] In a further aspect, a lead-acid battery is provided, comprising an electrolyte enclosure and one or more catalyst devices according to the first aspect, wherein the cavity of each catalyst device is in fluid communication with the electrolyte enclosure. In use, the cavity of each device may be located above the nominal liquid level of the electrolyte liquid (or isolated from the electrolyte liquid). The housing of the or each device may extend into the enclosure. The open end of each cavity may extend into the enclosure.

[0099] The lead-acid battery may comprise two or more or more unit cells, each having an electrolyte enclosure. Each electrolyte enclosure may be provided with one or more catalyst devices according to the present invention.

[0100] When multiple unit cells are present, the electrolyte solution, catalytically generated water, or water vapor from one unit cell can migrate to other unit cells. In this case, the amount of electrolyte solution can vary between unit cells. At least one catalyst device in each unit cell can help hydrogen and oxygen generated in each unit cell recombine within the catalyst layer within each unit cell and help generated water or water vapor flow back to the unit cell (from which the water or water vapor originated). This can be used to avoid differences in the amount of electrolyte solution between unit cells.

[0101] Unless otherwise indicated, the term "comprising" as applied to a structural feature, material, component, or method herein means that the structural feature, material, component, or method is included in addition to other structural features, materials, compositions, or method steps, or consists of the structural feature, material, component, or method step. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] Exemplary embodiments will now be described with reference to the following drawings, in which:

[0103] Figure 1 is an exploded perspective view of one embodiment of a catalyst device;

[0104] Figure 2 yes Figure 1 A schematic plan view of a catalyst device;

[0105] Figure 3 yes Figure 1 A schematic cross-sectional view of a catalyst device;

[0106] Figure 4-6 is a schematic cross-sectional view of an alternative catalyst device;

[0107] Figure 7 (a)-(e) are schematic plan views of exemplary catalyst devices;

[0108] Figure 8is a schematic diagram of the microstructure of a porous layer with granular materials within the layer;

[0109] Figure 9 shows (A) a test package; (B) a schematic diagram of supplying feed gas to the test package; and (C) a schematic cross-sectional view of a catalytic test apparatus; and

[0110] Figure 10-12 Test data for Examples 1-3 are shown. DETAILED DESCRIPTION

[0111] Figure 1 An exploded view of a catalyst device 100 for a lead-acid battery is shown. Figure 2 and Figure 3 Schematic plan and cross-sectional views of the device 100 are shown in FIG.

[0112] The catalyst device has a housing 110, which is typically molded from a plastic material such as polypropylene. The housing defines a cavity 112 (a cylindrical cavity in the illustrated embodiment) having an open end (generally indicated at 114). In use, the device is configured to be inserted into an opening in a battery housing such that the open end 114 of the cavity 112 faces into the enclosure.

[0113] The catalyst device 100 includes a catalyst layer 120. In the embodiment shown, the catalyst layer is formed from two sheets or sub-layers 120a, 120b to form a catalyst layer of desired thickness. The catalyst layer 120 is mounted within the cavity 112 and is surrounded by a retaining member in the form of a ring 130. The ring 130 is also typically formed from a plastic material, such as polypropylene.

[0114] A porous layer 140 is mounted in the cavity. The porous layer has an area greater than the area of ​​the upper surface 122 (as viewed in the figure) of the catalyst layer 120. The porous layer 140 contacts and covers the upper surface 122. Thus, a circumferential region 144 of the surface 142 adjacent to the catalyst layer 140 partially covers the distal end 132 of the ring 130.

[0115] The porous layer 140 comprises a thermoplastic material. A porous polyethylene material, such as, in particular, an expanded polyethylene film, can be used, wherein the polyethylene has a melting point lower than the melting point of the polypropylene shell 110 and the ring 130.

[0116] The catalyst layer 120 is mounted in the cavity 110, and within the ring 130, a porous layer 140 is also mounted in the cavity in contact with the face 122 of the catalyst layer 120. The ring 130 restricts lateral movement (i.e., generally parallel to the faces 122, 142) so that the surface 122 remains covered by the porous layer 140 throughout the range of possible movement.

[0117] This is Figure 2To aid in assembly of the device layers, and due to manufacturing tolerances, a small gap is provided between the inner profile 133 of the ring 130 and the outer edge 124 of the catalyst layer 120, which provides a maximum lateral displacement L1 between the center of the catalyst layer 126 and the center of the housing 116 before the catalyst layer abuts the ring. Similarly, the porous layer 140 has a gap such that it moves laterally to a maximum lateral displacement L2 between the center of the porous layer 146 and the center of the housing 116 before abutting the inner wall 113 of the cavity 112.

[0118] Therefore, if Figure 2 As shown in the enlarged view of region A of FIG, the maximum possible lateral offset between the centers 126, 146 of the layers 120, 140 is L1 + L2. Advantageously, the radial thickness of the ring 130 can be made equal to, or more preferably, greater than, L1 + L2 to ensure that the face 122 of the catalyst layer 120 is not uncovered by the porous layer 140 due to such lateral movement (e.g., as may occur during vibrations during use).

[0119] It will be appreciated that typically the maximum lateral displacement is small, ranging in size from less than 1 mm, less than 0.5 mm, or less than 0.1 mm.

[0120] During use, when porous layer 140 is exposed to the electrolyte enclosure of a lead-acid battery, hydrogen and oxygen generated within the battery can permeate through the porous layer and travel to catalyst layer 120, where they react in a recombination reaction and form water vapor, which can then return to the enclosure. If the temperature of catalyst layer 120 rises above the melting point or glass transition temperature of the thermoplastic material, the porosity of the porous layer decreases, thereby controlling the rate of the recombination reaction and regulating the temperature of the catalyst layer. The surface area of ​​porous layer 140 is larger than that of catalyst layer 120, and the circumferential region 144 of porous layer 140 extends sufficiently beyond the surface 122 of catalyst layer 120 to prevent any portion of surface 122 from being exposed by porous layer 140 within cavity 122 and catalyst layer 120 within retaining member 130. The material selection for the housing 110, the retaining device, the ring 130 (in the embodiment shown, polypropylene), and the porous layer 140 (in the embodiment shown, polyethylene thermoplastic) ensures that when the thermoplastic material of the porous layer 140 begins to melt, the housing and the retaining device remain dimensionally stable so that misalignment does not occur.

[0121] like Figure 3 As best shown in the cross-sectional view of FIG, the depth d of the catalyst layer 120 is 120 Greater than the depth d of the ring 130 130 A porous layer 140 covers the catalyst layer 120 (a flexible polyethylene film in the illustrated embodiment), effectively wrapping over and around the catalyst layer 120 and regulating the rate of the recombination reaction.

[0122] In other embodiments (not shown), the depths of the porous layer and the retention device are substantially the same, or in some cases, the depth of the retention device may be greater.

[0123] The catalyst device 100 also includes a diffusion limiting layer 150, which in the illustrated embodiment is in the form of an ePTFE membrane having a Gurley gas flow number of approximately 100 seconds. The diffusion limiting layer 150a is positioned adjacent to the porous layer 140 and between the catalyst layer 120 and the open end 114 of the cavity 112, such that, in use, it is positioned between the electrolyte enclosure and the catalyst layer 120 to control the diffusion or flow rate of gas from the enclosure to the catalyst layer 120.

[0124] In the illustrated embodiment, an additional diffusion limiting layer 150b is positioned adjacent to and overlying the lower surface 123 of the catalyst layer 120 (in the orientation shown in the figures) to regulate the diffusion or flow of any gas around the catalyst layer 120 and the ring 130 toward the lower surface 123 .

[0125] The catalyst device 100 further includes a porous anti-poisoning layer 160 adjacent to the diffusion limiting layer 150b. The anti-poisoning layer 160 includes a material capable of absorbing or decomposing catalyst poisons (such as hydrogen sulfide). An example of a suitable anti-poisoning layer 160 is a porous membrane, typically an ePTFE membrane, which contains zinc oxide powder inside the porous membrane.

[0126] In the illustrated embodiment, the outer hydrophobic porous layer 170 is formed of an ePTFE membrane and is positioned across the open end 114 of the cavity 112, and seals the cavity 112 or is bonded to a housing circumferentially surrounding the cavity 112. Compared to the diffusion-limiting layers 150a and 150b, the outer hydrophobic porous layer 170 has a relatively low Gurley airflow number, conveniently in the range of approximately 20 Gurley seconds. In use, the outer hydrophobic porous layer 170 prevents liquid electrolyte solution from entering the cavity 112.

[0127] Although the layers are positioned adjacent to one another in the illustrated embodiment, in alternative embodiments, one or more of the layers may be stacked or otherwise combined with one another, as described herein. Furthermore, in some cases, more than one of each type of layer may be used adjacent to one another, such as two porous layers. Some embodiments may omit one or more of the layers of device 100. For example, in some cases, an outer layer may function as a diffusion-limiting layer, eliminating the need for a separate diffusion-limiting layer. Optionally, for some applications of the catalyst devices described herein, the anti-poisoning layer may also be omitted.

[0128] As described above, the melting point or glass transition temperature of the thermoplastic material of porous layer 140 can be appropriately selected depending on the amount of gas generated in a particular battery application, catalytic performance, and the like. For example, the melting point can be in the range of 100°C to 180°C, or approximately 160°C. Although porous layer 140 of device 100 comprises polyethylene, in other embodiments, the thermoplastic material can be, for example, polyethylene, polypropylene, polyvinyl chloride, polymethyl methacrylate, polystyrene, or polyvinylidene fluoride, which have higher or lower melting points. Table 1 shows the melting points and glass transition temperatures of a range of exemplary thermoplastic materials that can be used.

[0129] Table 1: Melting points and glass transition temperatures of thermoplastic resins

[0130] Thermoplastic materials Glass transition temperature (℃) Melting point (℃) Polyethylene (PE) - 130 Polypropylene (PP) - 160 Polyvinyl chloride (PVC) 60 100 Polymethyl methacrylate (PMMA) 80 115 Polystyrene (PS) 100 - Polyvinylidene fluoride (PVDF) 160 180

[0131] Figure 4 A cross-sectional view of an alternative catalyst device 100A is shown. Features common to the devices 100 are indicated with like reference numerals.

[0132] The device 100A comprises a housing 110 defining a cavity 112. The catalyst device 100A comprises a catalyst layer 120, each of which is covered on each side 122, 123 by a porous layer 140 and an adjacent diffusion limiting layer 150. An anti-poisoning layer 160 and an outer porous hydrophobic layer 170 are also provided. The device 100A further comprises a retaining member 130 in the form of a ring 130 within the cavity 112.

[0133] Figure 5 , another catalyst device 100B is shown, wherein the housing 110B has an open end 114B and a closed end 115B. The catalyst layer 120 is mounted in a recess 130B in the closed end 115B of the housing 110B. The inner wall 133B of the recess limits the lateral movement of the catalyst layer 120, so that the recess 130 serves to maintain the device.

[0134] The anti-poisoning layer 160 is adjacent to, but spaced apart from, the diffusion-limiting layer 150. The anti-poisoning layer 160 and the porous hydrophobic outer layer 170 extend onto the open end 114 of the housing 110B.

[0135] Figure 6 100C is shown in FIG. Catalyst device 100C is similar to catalyst device 100, except that porous layers 140a, 140b cover respective sides 122, 123 of catalyst layer 120. Porous layers 140a, 140b are connected to each other (e.g., by heat welding or bonding with an adhesive) around the outside of ring 130 in region 148, thereby completely encapsulating catalyst layer 120 and ring 130.

[0136] In further embodiments (not shown), each porous layer may be connected to a retaining means, for example around the circumference of a retainer, so as to encapsulate the catalyst layer.

[0137] like Figure 7 As shown in the schematic plan view of FIG, various relationships between the catalyst layer shape and the shape of the holding device are possible. The outer edge 124 of the catalyst layer 120 can have a shape and size that matches the inner contour 133 of the holding device 130 as closely as possible ( Figure 7 (a) and 7(e)). Alternatively, a space may be provided between the catalyst layer 120 and the maintaining device 130 ( Figure 7 (b) and 7(d)) ​​or between the catalyst layer 120 and the inner wall 113 of the cavity 112 ( Figure 7 (c)) One or more gaps C1 are provided. The inner profile 133 of the maintaining device 130 may include a cavity 112 ( Figure 7 (c)) or the inner contour 133 of the retainer 130 ( Figure 7 (d)) A plurality of retaining structures 136 extending therefrom. The inner profile 133 of the retaining device may have a lock-and-key relationship ( Figure 7 (e)). Furthermore, while the examples shown have a generally circularly symmetrical housing and / or maintain device symmetry, the present invention is not limited thereto, and other shapes and configurations are contemplated.

[0138] experiment

[0139] Provide a test package 200 ( Figure 9 (A)) and connected to a controlled flow of feed gas consisting of a stoichiometric mixture of hydrogen and oxygen feed gases (molar ratio 2:1). The feed gases were provided from separate gas tanks via mass flow controllers 210, 220, which were connected to a common feed line 230 extending to the enclosure 200. The catalyst test device 100T was inserted into an opening in the test enclosure wall, with the open end of the device housing cavity oriented toward the interior of the enclosure 200.

[0140] Roughly based on Figure 1-3 The device components of the embodiment catalyst testing device 100T shown in Figure 1 are the same as those shown in Figure 1, but the retaining ring 30 is omitted. Each device has a K-type thermocouple 190 that is manually placed through a small opening in the housing and in thermal contact with the ePTFE layer adjacent to the inner wall of the housing, as shown in Figure 1. Figure 9 (C) Schematic view of the device. The housing, cavity, retaining ring, and all layers are circular in cross-section.

[0141] The catalyst material used was palladium supported on alumina, 5 wt% Pd / alumina (manufacturer: NECC). The catalyst layer consisted of two catalyst sheets, each filled with PTFE, 565 μm thick, with a composition of Pd / alumina / PTFE = 1.2 / 68.8 / 30 (wt%). Therefore, the total mass of palladium in the catalyst layer was approximately 0.7 mg.

[0142] The porous layer used was expanded polyethylene (ePE), manufactured by Shenzhen Senior Technology Material Co., Ltd., with a melting point of 130°C. Each ePE layer had a thickness of 16 μm, a Gurley number of 200 seconds, and a basis weight (mass / area) of 8.9 gm. -2 .

[0143] The flow rates of the 2H2 / O2 feed gases were controlled at the following flow rates, each lasting 5 minutes, and the flow rates were gradually increased according to Table 2.

[0144] The experiments were conducted in the laboratory at ambient temperature, which was varied between tests.

[0145] Table 2: Feed gas flow rates and durations

[0146]

[0147]

[0148] The temperature of the entire catalyst layer was measured.

[0149] During normal use of automotive lead-acid batteries, the gas flow rate of gases emitted from the electrolyte enclosure is typically in the range of 2-4 ml / min. Therefore, the test enclosure and feed gas flow rates significantly exceed those typically found in lead-acid batteries and are believed to represent an extreme condition that could lead to thermal runaway of the catalyst device.

[0150] The Gurley value of the porous layer or film described herein is evaluated based on JIS P 8117: 1998. The Gurley value refers to the value of the porous layer or film at 100 cm 3 Air flows vertically through a tube with an area of ​​6.45 cm at a pressure of 1.29 kPa. 2 The Gurley value is an index of air permeability.

[0151] Example 1

[0152] A first test device (Device 1) was constructed in which a catalyst layer 120 was placed in alignment with a porous layer covering the inner and outer surfaces of the catalyst layer.

[0153] The apparatus was exposed to feed gas flow rates according to Table 2, and the temperature was monitored.

[0154] Two embodiments of the device 1 were tested and the results were Figure 10 Displayed in.

[0155] The catalyst layer temperature changes over time were identical for both runs and were within the experimental error.

[0156] In both runs, the maximum temperature of the catalyst layer measured by the thermocouple was below 100°C, indicating that the polyethylene porous layer played a role in regulating the recombination reaction rate, and after about 10 minutes, the porosity of the polyethylene layer decreased, so that the recombination reaction rate and thus the catalyst layer temperature did not continue to increase with the increase in feed gas flow rate during steps 3-5 of each run. The maximum measured temperature at the contact point between the thermocouple and the catalyst sheet was below the melting point of the porous layer, which is understood to reflect the relative thermal conductivity of the catalyst layer. The changes in the observed temperature curve (also in Figure 12 , discussed below) are caused by variations in the relative positions of the thermocouples with respect to the catalyst sheet during manual construction of the test apparatus.

[0157] Example 2

[0158] A second test device (Device 2) was constructed in which the catalyst layer 120 was intentionally placed out of alignment with the porous layer so that small areas in the catalyst layer surface were not covered by the porous layer.

[0159] Figure 11 The results of the tests performed on device 2 are shown in FIG, together with the results from the first test device 1 for comparison.

[0160] In experiments conducted on Test Device 2, ignition of the feed gas within the test enclosure occurred after approximately 9 minutes.

[0161] Ignition indicates that the temperature of the exposed areas in the catalyst layer surface was high enough to ignite the feed gas. Likewise, the lower temperatures measured at the thermocouples are understood to not reflect the higher temperature areas in the catalyst layer that caused the ignition.

[0162] Example 3

[0163] Roughly based on Figure 3 Two additional test devices, Test Device 4, were constructed that included a polypropylene retention ring 130 and two ePE layers covering both the catalyst layer and the retention ring.

[0164] Two additional test apparatuses, Test Apparatus 5, were constructed in which the two polypropylene retaining rings were omitted.

[0165] Test runs were performed on all four devices, as follows Figure 12 The results are shown in Table 3.

[0166] Table 3

[0167] Temperature rise rate Maximum temperature With PP ring 10.8 105 No PP ring 12.4 148

[0168] (No PE sheet)

[0169] The runs performed on Test Device 5 (labeled (3) and (4), "without PP ring" in the figures and tables) were raised to a maximum temperature of approximately 150°C. This temperature was high enough that the polypropylene housing could begin to deform and risk contaminating the catalyst layer and other layers from the device cavity. Note that at the high flow rates used in the test protocol, the thermocouple cooled slightly.

[0170] Runs performed on Test Device 4 (labeled (1) and (2), “with PP ring”) again show that near the end of step 2, the polyethylene porous layer acts to regulate the rate of the recombination reaction by melting and reducing porosity, but indicate that the presence of the PP ring 130 improves the effectiveness of the shutdown effect of the ePE layer.

[0171] Examples 4 and 5 demonstrate the effect of the catalyst layer and polypropylene in maintaining the relative dimensions of the rings.

[0172] Example 4

[0173] Additional test apparatus were constructed similar to apparatus 4. Two additional apparatus were constructed in which the catalyst layer area was smaller to provide "edge separation" between the circumference of the catalyst and the polypropylene retaining ring. The thickness of both the catalyst layer and the retaining ring was 0.75 mm.

[0174] The results are shown in Table 4 below.

[0175] Table 4

[0176]

[0177]

[0178] Thickness: 0.75mm

[0179] These data indicate that both the recorded maximum rate of catalyst layer temperature rise and the recorded peak temperature are correlated with the size of the spacing or gap between the catalyst layer and the retainer.

[0180] These results indicate that a minimum gap can therefore be expected when applying the apparatus of the present invention where suppressing the catalyst temperature is more advantageous relative to the overall rate of known recombination rates.

[0181] Example 5

[0182] An additional test apparatus was constructed similar to apparatus 4. The thickness of both the catalyst layer and the retaining ring was 0.75 mm.

[0183] Two additional devices were constructed with increasing maintenance ring thickness (0.95 mm and 1.20 mm thick rings). The results are summarized in Table 5 and show the correlation between increasing maintenance ring thickness or depth (compared to catalyst layer thickness / depth) and the maximum heating rate and maximum temperature of the catalyst layer.

[0184] Table 5

[0185]

[0186] ID / OD: 8 / 9

[0187] These results indicate that when using the apparatus of the present invention where suppressing the catalyst temperature is more favorable relative to the overall rate of recombination given the recombination rate, a reduction in the minimum thickness separation or indeed the ring depth can be expected.

[0188] While exemplary embodiments are described herein, they should not be considered limiting as possible modifications and variations within the scope of the invention as described herein and in the appended claims.

Claims

1. A catalyst device for a lead-acid battery, comprising: a housing defining a cavity; a catalyst layer mounted in the cavity, wherein the catalyst layer comprises a catalyst that accelerates a reaction that produces water or water vapor from oxygen and hydrogen; as well as a porous layer installed in the cavity and comprising a thermoplastic material, wherein a planar dimension of the porous membrane is larger than a planar dimension of the catalyst layer, and wherein a face of the catalyst layer contacts the porous layer and covers at least one face of the catalyst layer; The catalyst layer is mounted in a cavity within a retaining device, the retaining device is configured to maintain the position of the catalyst layer within the cavity, and the at least one surface is covered by the porous layer.

2. A catalyst device as described in claim 1, wherein the maintenance device comprises one or more maintenance structures to prevent or substantially prevent lateral movement of the catalyst layer; or comprises a maintainer, wherein the maintainer is mounted in the cavity and is in a substantially fixed relationship with the housing.

3. The catalyst device of claim 2, wherein the retaining means comprises a retainer having the following characteristics: the retainer is in the form of a ring, the shape of the ring being substantially the same as the shape of the catalyst layer.

4. A catalyst device as claimed in any preceding claim, wherein a lateral gap provided between the catalyst layer and the retaining device allows lateral movement of the shell relative to the catalyst layer and the porous layer within the cavity, wherein the porous layer includes a circumferential surface area that extends beyond the range of lateral movement of the porous layer relative to the catalyst layer around the entire circumference of the catalyst layer.

5. The catalyst device of any preceding claim, wherein the catalyst layer has a catalyst layer thickness and the retaining means has a depth, and wherein the depth of the retaining means is equal to or less than the catalyst layer thickness.

6. The catalyst device of any preceding claim, wherein the thermoplastic material has a melting point or glass transition temperature as a first temperature, and the retaining means is dimensionally stable up to a second temperature higher than the first temperature.

7. A catalyst device as claimed in any preceding claim, wherein the porous layer comprises an expanded thermoplastic film.

8. The catalyst device of claim 7, wherein the thermoplastic material of the expanded thermoplastic polymer membrane is polyethylene or polyurethane.

9. A catalyst device as described in any of the preceding claims, wherein the catalyst device comprises at least two porous layers, wherein the first porous layer contacts the first side of the catalyst layer and the second porous layer contacts the second side opposite to the catalyst layer, and the planar size of each porous layer is larger than the planar size of the catalyst layer.

10. The catalyst device of claim 9, wherein circumferential regions of at least two porous membranes are bonded to each other.

11. A catalyst device according to any preceding claim, comprising one or more of the following: a diffusion limiting layer adapted to regulate a diffusion rate or flow rate of gas to the catalyst layer; a porous anti-poisoning layer capable of absorbing or decomposing catalytic poisons; Outer hydrophobic porous layer.

12. The catalyst device of claim 11, wherein one or more of the diffusion limiting layer, the anti-poisoning layer, or the outer hydrophobic porous layer comprises: Expanded polymer membrane; expanded fluoropolymer membrane; or Expanded PTFE membrane.

13. The catalyst device of claim 12, wherein the catalyst device comprises an anti-poisoning layer, and wherein the anti-poisoning layer comprises an expanded polymer membrane and a substance capable of absorbing or decomposing catalytic poisons within the membrane.

14. The catalyst device of any one of claims 11 to 13, wherein the catalyst device comprises a diffusion limiting layer and an outer hydrophobic porous layer, and wherein the outer hydrophobic porous layer has a Gurley number lower than that of the diffusion limiting layer.

15. The catalyst device according to any one of claims 11 to 14, wherein the catalyst device comprises a diffusion-limiting layer, and wherein the diffusion-limiting layer has a Gurley Flow Number of 50 seconds or greater, or 100 seconds or greater.

16. A catalyst device as claimed in any preceding claim, wherein the catalyst layer is porous.

17. The catalyst device according to any preceding claim, wherein the catalyst layer comprises a hydrophobic porous member, a catalyst, or a catalyst carrier supporting the catalyst, the catalyst carrier being disposed in the cavity or on a pore surface of the catalyst layer.

18. The catalyst device of claim 17, wherein the hydrophilic porous member comprises ePTFE.

19. A lead acid battery comprising an electrolyte enclosure and one or more catalyst devices according to any preceding claim, wherein the cavity of the or each catalyst device is in fluid communication with the electrolyte enclosure.

20. The lead-acid battery of claim 19, comprising a plurality of unit cells, each of the unit cells having an electrolyte enclosure, wherein each electrolyte enclosure is provided with one or more catalyst devices according to any one of claims 1 to 18.

Images