HK1130570A

HK1130570A - Direct liquid fuel cell and method of preventing fuel decomposition in a direct liquid fuel cell

Info

Publication number: HK1130570A
Application number: HK09109476.5A
Authority: HK
Inventors: 盖纳蒂‧芬克尔斯坦; 尤利‧卡茨曼; 伊兰‧撒顿; 马克‧埃斯特林; 亚历山大‧里特维诺夫; 波里斯‧艾予新; 亚历山大‧史奈克; 亚历山大‧布卢夫斯坦; 迈克尔‧冷诺
Original assignee: 摩尔能源有限公司
Priority date: 2004-09-15
Filing date: 2005-09-15
Publication date: 2009-12-31

Description

Direct liquid fuel cell and method for preventing fuel decomposition in direct liquid fuel cell

Technical Field

The present invention relates to a Direct Liquid Fuel Cell (DLFC) using a hydride fuel (hydride fuel) and to the particular prevention or at least substantial reduction of hydrogen generation caused by decomposition of the hydride fuel at the fuel cell anode when the DLFC is under no load or only low load.

During periods when the fuel cell is in a no-load or only low-load condition, the hydride fuel decomposition reaction at the anode of the fuel cell produces hydrogen. The invention therefore also provides a method of providing a separation layer between the anode and the liquid fuel using the generated hydrogen. In this way, fuel is substantially prevented from contacting the anode, thereby preventing decomposition of the fuel, at least to a substantial extent.

One way in which this can be accomplished is by arranging a special membrane close to or in contact with the surface of the anode facing the fuel chamber. The initially generated hydrogen gas accumulates between the membrane and the anode and pushes or forces the liquid fuel out of the space between the anode and the membrane. This separates the liquid fuel from the anode.

Background

The most common liquid fuel for DLFC is methanol. The main drawbacks of the Direct Methanol Fuel Cell (DMFC) are the toxicity of methanol and the very poor discharge characteristics at room temperature. As a result, the DMFC is not generally used for portable electronic products and the like.

Fuels based on (metal) hydrides and borohydride compounds, such as sodium borohydride, have a very high chemical and electrochemical activity. Therefore, the DLFC using the fuel has very good discharge characteristics (current density, specific energy, etc.) even at room temperature.

For example, the electroplating oxidation of borohydride fuel on the surface of the fuel cell anode proceeds according to the following formula:

the main problem associated with hydride and borohydride fuels is the spontaneous decomposition of the fuel on the (active layer of the) anode surface, which is accompanied by the generation of hydrogen gas, typically in the form of micro-bubbles, such as bubbles from about 0.01 to about 2mm in size. This process is particularly pronounced in the open state and standby (low current) state of the DLFC.

The decomposition of borohydride compounds is carried out according to the following formula:

the decomposition of hydrides and borohydrides at DLFC anodes leads to several technical problems, in particular, energy loss, destruction of the anode active layer and reduction of safety performance. As a result, there is a need to develop methods to substantially prevent fuel decomposition when DLFC is under no load or no significant load.

Disclosure of Invention

The present invention provides a liquid fuel cell using a liquid fuel that tends to decompose on the surface of an anode and to generate a gas during the decomposition. The fuel cell includes a cathode; an anode; an electrolyte chamber disposed between the cathode and the anode; a fuel chamber disposed on a side of the anode opposite to a side facing the electrolyte chamber; and at least one membrane arranged on a side of the anode facing the fuel chamber. The at least one layer of membrane is constructed and arranged to allow gas formed on or near a surface of the anode facing the fuel chamber due to fuel decomposition to accumulate adjacent the anode, at least to an extent that the accumulated gas substantially prevents direct contact between the anode and the liquid fuel when present in the fuel chamber.

According to one aspect of the fuel cell of the present invention, the fuel may comprise a metal hydride and/or borohydride compound and/or the gas may comprise hydrogen.

In another aspect, at least one of the membranes may comprise a single layer of material and/or at least one of the membranes may comprise a hydrophilic material. The hydrophilic material may include a metal and/or a metal alloy. As a non-limiting example, the hydrophilic material may include stainless steel.

In another aspect, at least one of the films can include a hydrophobic material, for example, organic polymers such as polyolefins (e.g., homopolymers and copolymers of ethylene and propylene), polyamides, and polyacrylonitriles.

In another aspect, the at least one layer of film may comprise one or more of a nonwoven material, a composite material, a laminate material, a composite/laminate material, a foam material, a porous paper material, a textile material, a carbon material (e.g., graphite), a sintered metal material, a ceramic material, and a polymeric material.

In another aspect of the fuel cell of the present invention, at least one of the membranes may comprise a foam and/or a screen, for example, a stainless steel microsieve. For example, the microsieves may include mesh having a size of up to about 0.5mm, such as from about 0.06 μm to about 0.05 mm. In yet another aspect, the at least one layer of film (screen) may have a thickness of from about 0.01mm to about 5mm, for example, from about 0.03mm to about 3mm, or from about 0.05mm to about 0.3 mm.

In yet another aspect, the at least one membrane may include a polymer screen and/or a porous polymer layer. For example, the polymer screen or porous polymer layer has a thickness of from about 0.02mm to about 2mm and/or a mesh size of from about 0.01mm to about 0.1mm or a pore size of from about 0.01 μm to about 0.1 mm.

In another aspect of the fuel cell of the present invention, at least one membrane may be in contact with a surface of the anode facing the fuel chamber. For example, at least one of the films may be joined and/or bonded to a surface of the anode (e.g., rolled onto the anode).

In another aspect, the fuel cell may further include a free space and/or spacer structure disposed between the at least one membrane and the anode. As a non-limiting example, the spacer structure may comprise a spacer material having free space therein.

In one aspect, the spacer structure may comprise a layer of spacer material having a thickness of up to about 3mm and/or at least about 0.1 mm. For example, the spacer material layer has a thickness of from about 0.5mm to about 1.5 mm.

In another aspect, the spacer material may comprise a hydrophobic material (e.g., in combination with a membrane comprising a hydrophilic material), such as a polymeric material. By way of non-limiting example, the hydrophobic material may include one or more of olefin homopolymers (e.g., polyethylene, polypropylene, polytetrafluoroethylene), olefin copolymers, ABS, polymethyl methacrylate, polyvinyl chloride, and polysulfone.

In yet another aspect, the spacer material may comprise a mesh, such as a fence-like mesh. For example, the mesh includes openings from about 1mm to about 50 mm.

On the other hand, instead of or in addition to the spacer material with free space therein, the spacer structure may comprise a frame seal arranged on the surface of the anode facing the fuel chamber. The frame seal comprises a hydrophobic material, such as a polymer, for example a fluorinated polymer (e.g. polytetrafluoroethylene). Further, the frame seal preferably has a thickness of up to about 0.1mm, for example, from about 0.02mm to about 0.05 mm.

The fuel cell of the invention may further comprise pressure relief means arranged to allow gas to escape from the space between the anode and the at least one membrane, in particular in case the at least one membrane is not connected to or in contact with the surface of the anode. In one aspect, the pressure relief device may be arranged to allow gas to enter the fuel chamber. In another aspect, the pressure relief device may comprise a small diameter tube

In another aspect of the fuel cell of the present invention, the at least one membrane and the spacer structure together may form a unitary structure.

In yet another aspect, a fuel cell may include at least a first membrane adjacent to an anode and a second membrane on a side of the first membrane facing a fuel chamber, at least the first membrane being constructed and arranged to allow gas formed on or near a surface of the anode facing the fuel chamber to accumulate adjacent to the anode, at least to an extent that the accumulated gas substantially prevents direct contact between the anode and a liquid fuel.

In another aspect, the second membrane may be constructed and arranged to filter solids from the liquid fuel and/or to protect the first membrane. In another aspect, the first membrane and the second membrane form a unitary structure.

In yet another aspect, the second membrane may comprise a different material and/or may have a different thickness and/or may have a different pore or mesh size than the first membrane.

In yet another aspect, the second membrane may comprise substantially the same material and/or may have substantially the same thickness and/or may have substantially the same pore or mesh size as the first membrane.

The fuel cell may be the same as the fuel cell having (at least) one membrane described above, except that at least two membranes are present. For example, at least the first membrane may comprise a polymeric screen or a porous polymeric layer having a thickness of between about 0.02mm and 2mm and a mesh size of from about 0.01mm to about 0.1mm or a pore size of from about 0.01 μm to about 0.1mm, or at least the first membrane comprises a stainless steel screen having a thickness of from about 0.01mm to about 5 mm. Furthermore, the first membrane may be bonded to and/or in contact with a surface of the anode facing the fuel chamber. Furthermore, the fuel cell comprises a free space and/or spacing structure arranged between the first membrane and the anode. The spacing structure may be the same as the spacing structure described above, including various aspects thereof.

In another aspect of the fuel cell of the present invention, the anode may be secured within and/or sealingly engaged with the fuel cell (housing).

In another aspect of the fuel cell of the present invention, the fuel chamber may include at least a first portion adjacent to the at least one membrane and at least one second portion connected to the first portion by one or more liquid channels. For example, at least one second part of the fuel chamber may comprise (optionally replacing) a liquid fuel cartridge.

In another aspect, a fuel cell of the present invention may include a case that houses at least an anode, at least a portion of the fuel chamber being disposed outside the case, and the case being connected to at least a portion of the fuel chamber disposed outside the case by one or more liquid passages. At least a portion of the fuel chamber disposed outside the tank may comprise an (optionally replaceable) cartridge body. For example, in this case, the at least one layer of film may be disposed at least one of: (a) at or near one or more locations of the tank where at least the fuel chamber is disposed outside the tank, where liquid fuel can enter the tank, (b) at least a portion of the fuel chamber is disposed outside the tank, where at or near one or more locations where at least the fuel chamber is disposed outside the tank, where liquid fuel can exit the tank, and (c) at one or more locations within the one or more liquid passages.

The invention further provides a method of reducing or substantially preventing decomposition of a fuel in a direct liquid fuel cell at an anode of the fuel cell when the fuel cell is in a substantially unloaded state, wherein the decomposition of the fuel produces a gas. The method includes allowing the gas produced by the decomposition of the initial fuel to form a barrier layer that limits or substantially prevents further contact between the fuel and the anode.

In one aspect, the barrier layer can comprise a substantially continuous gas layer across substantially the entire surface of the anode facing the fuel chamber of the fuel cell.

In another aspect, the gas can include hydrogen gas and/or the fuel can include at least one of a hydride compound and a borohydride compound, e.g., an alkali metal (e.g., sodium) borohydride dissolved and/or suspended in a liquid carrier.

In yet another aspect of the method, the fuel decomposition is substantially stopped within no more than about 5 minutes, e.g., no more than about 3 minutes, after the fuel cell is placed in a substantially unloaded state.

In yet another aspect, the method may limit or substantially prevent the ability of gases produced by the decomposition of the initial fuel to flow away from the anode. For example, limited or substantially prevented. This may be done by at least one membrane arranged on the side of the anode facing the fuel chamber of the fuel cell.

In addition, the present invention also provides a method of reducing or substantially preventing fuel decomposition at the anode of a direct liquid fuel cell that uses a fuel that generates a gas when subjected to decomposition. The method comprises the following steps: one or more of the following structures are disposed between a fuel chamber and an anode of a fuel cell: at least one porous structure; at least one screen structure; and at least one film; and forming a gas in the fuel cell during initial decomposition of the fuel, whereby the gas limits or substantially prevents contact between the fuel and the anode.

In one aspect, the forming of the gas may further include substantially preventing the fuel from contacting the anode with the gas. In another aspect, it may further comprise forming a substantially continuous gas layer across substantially the entire surface of the anode facing the fuel chamber of the fuel cell. In yet another aspect, it may further comprise a gas substantially confining between the anode and the at least one porous structure, the at least one sieve structure, and/or the at least one membrane.

In another aspect of the invention, the gas may comprise hydrogen.

In yet another aspect, the method may further comprise placing the fuel cell in a substantially no-load condition to cause decomposition of the fuel.

In yet another aspect, the method may further comprise substantially ceasing the initial decomposition of the fuel in no more than about 3 minutes.

In another aspect, the method may further comprise providing a space between the anode and the at least one porous structure, the at least one sieve structure, or the at least one membrane, which space may be substantially filled with a gas.

The present invention also provides a method of preventing or reducing fuel decomposition in the above-described fuel cell, including aspects thereof. The method includes generating electrical energy with a fuel cell; substantially preventing further generation of electrical energy by the fuel cell thereby causing decomposition of the fuel at the anode of the fuel cell with concomitant generation of gas; and (a) promoting accumulation of gas produced at the anode adjacent the anode by at least one membrane, at least to the extent that the accumulated gas restricts or substantially prevents contact between the anode and the liquid fuel; or (b) allowing gas generated at the anode to accumulate adjacent the anode, at least to the extent that the accumulated gas substantially prevents contact between the anode and the liquid fuel; or (c) allowing gas generated at the anode to accumulate between the at least one membrane and the anode, at least to the extent that the accumulated gas substantially prevents contact between the anode and the liquid fuel.

The present invention also provides a fuel cell comprising a cathode, an anode, and an electrolyte chamber disposed between the cathode and the anode. The cartridge body containing the fuel chamber may be attached and/or removably attached to a fuel cell housing (case) having a cathode, an anode, and an electrolyte chamber. When the cartridge body is connected to the housing, the fuel chamber is arranged on the side of the anode opposite to the side facing the electrolyte chamber. At least one membrane (and also a spacer material) is disposed between the gas accumulation space adjacent the anode and the fuel chamber. The at least one layer of membrane is constructed and arranged to allow gases formed on or near a surface of the anode facing the fuel chamber due to fuel decomposition to accumulate adjacent the anode, at least to an extent that the accumulated gases substantially prevent direct contact between the anode and the liquid fuel.

Other exemplary embodiments and advantages of the present invention can be ascertained from the present disclosure and the accompanying drawings.

Drawings

The present invention will be further explained in the detailed description which follows, with reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

fig. 1 shows a schematic cross-sectional view of a prior art fuel cell;

FIG. 2 shows a cross section of a fuel cell according to an embodiment of the invention;

FIG. 3 shows an enlarged portion of FIG. 2;

FIG. 4 is a graph illustrating hydrogen gas production in a fuel cell of the type shown in FIG. 1;

FIG. 5 is a graph illustrating hydrogen gas production in a fuel cell of the type shown in FIG. 2;

FIG. 6 shows a partial view of a non-limiting weave pattern of a picket spacer material;

FIG. 7 shows a partial view of another boundless weave pattern of a picket spacer material;

fig. 8 shows a cross section of a fuel cell according to another embodiment of the invention;

fig. 9 shows a cross section of a fuel cell according to a further embodiment of the invention;

fig. 10 shows a cross section of a fuel cell according to a further embodiment of the invention;

fig. 11 shows a cross section of a fuel cell according to a further embodiment of the present invention. This embodiment uses a cartridge containing a fuel chamber (or at least a portion thereof) that is attachable and/or removably mounted to the fuel cell housing;

fig. 12 shows an enlarged view of the embodiment of fig. 11 and illustrates how the membrane and/or spacer material can have a small screen-type filter member shape. This figure also illustrates how the channel (tube) of the cartridge is sealed against the opening in the housing wall by an O-ring; and

figure 13 shows a cross section of a fuel cell according to the embodiment of figure 11 with a cartridge that is separate and/or unconnected to the housing of the fuel cell.

Detailed Description

The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

As shown in fig. 1, the conventional DLFC uses a case or container body 1 containing a fuel chamber 2 and an electrolyte chamber 5 therein. The tank 1 is typically formed of a plastic material, for example. The fuel chamber 2 contains a liquid fuel, for example in the form of a hydride or borohydride fuel. The electrolyte chamber 5 contains a liquid electrolyte in the form of, for example, an aqueous alkali metal hydroxide solution. An anode 3 is arranged within the housing 1 and separates the two chambers 2 and 5. The anode 3 is typically composed of a porous material that is permeable to gaseous and liquid substances. A cathode 4 is also disposed in the case 1 and defines an electrolyte chamber 5 together with the anode 3. Oxidation of the liquid fuel takes place at the anode 3. At the cathode 4, the species (typically oxygen in ambient air) is reduced.

As shown in fig. 2, a DLFC according to at least one non-limiting embodiment of the present invention differs from the fuel cell shown in fig. 1at least in that it additionally includes a frame seal 6 disposed within the case 1, a special membrane 8, a spacer material 9, and optionally a pressure vent 7 having, for example, a capillary needle shape.

In the DLFC according to the present invention, the generated gas, typically hydrogen gas and typically in the form of microbubbles ranging in size from about 0.01mm to about 2mm, accumulates in the space between the surface of the anode 3 and the special membrane 8. The gas bubbles will typically coalesce and/or coalesce to form a gas layer filling substantially all of the volume between the anode 3 and the particular membrane 8. This in turn causes the liquid fuel to separate from the anode 3. The special membrane 8 substantially prevents any further contact of the liquid fuel with the anode 3. The space between the anode 3 and the membrane 8 will typically be about 0.1mm to about 3.0mm thick, preferably having a thickness of about 0.5mm to about 1.5mm, most preferably about 0.5 mm.

Any additional gas that exceeds the volume of the space between the anode 3 and the particular membrane 8 leaks or vents out and enters the fuel chamber 2 through the optional capillary needle 7. The discharge process is substantially automatically stopped when the pressure in the volume between the anode 3 and the special membrane 8 equals the pressure in the fuel chamber 2.

The frame seal 6 extends around the periphery of the anode 3 and is arranged between the anode 3 and the special membrane 8. The frame seal 6 is preferably in the form of a thin (non-porous) membrane and is used to prevent fuel leakage from the border or peripheral region of the anode periphery. The material of the frame seal 6, which is typically hydrophobic (at least on its surface facing the fuel chamber), may be formed from a material such as polytetrafluoroethylene, although other hydrophobic materials such as olefin polymers like polyethylene and polypropylene may also be used for this purpose. Typically, the frame seal 6 is made of or at least comprises a fluorinated polymer, such as a fluorinated or perfluorinated polyolefin. It should be noted that the frame seal 6 may also be made of a non-hydrophobic material, but its surface is rendered hydrophobic by, for example, coating with a hydrophobic material or other procedure of imparting hydrophobicity. Preferably, the frame seal 6 has a thickness of no more than about 0.1 mm. Typically it will have a thickness of at least about 0.02 mm. A thickness of about 0.05mm is particularly preferred for the frame seal 6 used in the present invention. The frame seal 6 may be mounted on the anode 3 in various ways, for example, using pressure and/or using an adhesive. A preferred way of mounting frame seal 6 comprises insert moulding. The frame seal 6 may also be replaced by fixing and/or sealing the perimeter frame of the anode 3 to the anode 3 by, for example, friction welding (replace).

A spacer material 9 is arranged between the anode 3 and the special membrane 8. The spacer material 9 also extends into the periphery of the cabinet 1, and in the peripheral area the spacer material 9 is also arranged between the frame seal 6 and the special membrane 8. The purpose of the spacer material 9 is to create a space between the special membrane 8 and the surface of the anode 3. This spacing forms a gas layer space or volume. As gas is generated, it accumulates within and fills the space. The spacer material 9 allows the gas to flow substantially freely over the surface of the anode 3 and may be in the form of a mesh, for example a fence-like mesh material. The spacer material 9 must be able to withstand chemical attack by the liquid fuel component and is generally hydrophobic, at least on its outer surface. In other words, the spacer material 9 may also be a hydrophilic material rendered hydrophobic on its other surface by any suitable treatment, such as coating with a hydrophobic material. The spacer material used in the present invention preferably comprises organic polymers such as olefin homopolymers and olefin copolymers. Specific examples thereof include materials that can also be used for the frame seal 6, such as homopolymers and copolymers of ethylene and propylene, polytetrafluoroethylene, and the like. The spacer material 9 may also be made of other materials such as ABS, polymethylmethacrylate, polyvinyl chloride, polysulfone and similar organic polymers. The spacer material 9 typically has a thickness of no greater than about 5mm, preferably no greater than about 3mm, and more typically no greater than about 1.5 mm. The spacer material 9 typically has a thickness of at least about 0.1mm, preferably at least about 0.5 mm. In a preferred embodiment of the invention, the spacer material 9 has a thickness of about 0.5 mm. Of course, in other embodiments, which will be described below, the spacer material 9 can also be dispensed with (its function being performed by other structures and/or the special membrane 8 itself). As mentioned above, the frame seal 6 may also be dispensed with.

As described above, the special membrane 8 separates the gas layer formed on the anode surface from the liquid fuel in the fuel chamber 2. The special membrane 8 is made of a material that can withstand chemical attack by the liquid fuel components and does not catalyse the decomposition of the fuel or its components to any appreciable extent. The material may be hydrophilic or hydrophobic. The hydrophilic material may also be a hydrophobic material on the outer surface of which hydrophilicity is obtained by any suitable treatment such as coating, surface treatment (e.g., oxidation), and the like. Non-limiting examples of hydrophilic materials that are preferably suitable for use in the particular membrane 8 include metals or alloys. Particularly preferred materials include corrosion resistant metals (e.g., nickel) and corrosion resistant alloys such as steel, particularly stainless steel, and the like.

Non-limiting examples of hydrophobic materials that are preferably suitable for use in the particular membrane 8 include organic polymers such as polyolefins (e.g., homopolymers and copolymers of ethylene or propylene), polyamides, and polyacrylonitriles. The hydrophilic or hydrophobic material is preferably present in the form of a foam, a mesh, or the like.

By way of non-limiting example, the special membrane 8 may comprise or at least comprise a metal mesh such as a stainless steel micro-mesh. The mesh (cells of the mesh) may have a size of, for example, up to about 0.5mm, for example, up to about 0.1mm or up to about 0.06 mm. Preferred mesh sizes are from about 0.05 μm to about 0.06mm, with a size of about 0.05mm being especially preferred. The metal screen preferably has a thickness of from about 0.01mm to about 5mm, for example from about 0.03mm to about 3 mm.

Other non-limiting examples of special membranes 8 include polymer screens or porous polymer layers. Preferably, the polymer screen or porous polymer layer has a thickness of from about 0.02mm to about 2 mm. Preferably, the mesh size or pore size is from about 0.01mm to about 0.1mm and from about 0.01 μm to about 0.1mm, respectively.

The membrane 8 may also comprise other hydrophilic and/or hydrophobic materials, such as composites and/or laminates of hydrophilic and hydrophobic materials and combinations of hydrophilic and hydrophobic materials. The membrane 8 may also comprise, for example, non-woven materials, foamed materials (polymeric or metallic), and other porous materials such as porous papers, fabrics, carbon (e.g. in the form of graphite), sintered metals, and ceramic materials.

The capillary needles 7 are fastened to the particular membrane 8 and may be arranged at a convenient location thereon, such as a central location (and preferably substantially perpendicular to the membrane 8). As mentioned above, the purpose of the needle 7 is to equalize the pressure between the gas layer and the liquid fuel in the fuel chamber 2. Typically, the equilibrium pressure ranges from about 1atm to about 1.5atm (absolute). The needle 7 is made of a material that can withstand the chemical attack of the components of the liquid fuel and does not catalyse the decomposition of the fuel to any appreciable extent. The material is generally selected from materials suitable for use in making the particular membrane 8, but may be made of other materials, such as polymeric materials. Non-limiting examples of polymeric materials include polyolefins such as polytetrafluoroethylene and polypropylene. Preferably, the needle 7 is a stainless steel needle. Although the suitable length of the needle 7 may vary over a wide range (depending in part on the spacing 9, the size of the membrane 8, etc.), the needle 7 often has a length of up to about 2cm or even more. The inner diameter of the needle 7 is generally not more than about 2mm, preferably not more than about 1mm, or not more than about 0.5 mm. The needles 7 may be attached to the membrane 8 by any suitable method, for example by thermal bonding, welding and mechanical attachment (the latter being the preferred method). Of course, in the case of the other embodiments described below, the operation of the fuel cell of the present invention with respect to 7 is not essential and can be dispensed with.

Fig. 8 shows another non-limiting embodiment of the fuel cell of the present invention which differs from the fuel cell shown in fig. 1at least in that: it additionally comprises an anode 3 with a frame, arranged inside the tank 1, a special membrane 8a, an optional second membrane 8b and an optional spacer material 9. This embodiment does not require a frame seal 6 nor does it include a capillary needle 7. The peripheral frame of the anode 3 may be fixed to the anode 3 by, for example, friction welding. The materials and thicknesses of the devices 3, 4, 9, 8a and 8b are the same as for the corresponding devices described above for the embodiment shown in fig. 2. The membranes 8a and 8b may be of the same material, type and/or thickness as described above, or may differ in any one or more of these respects.

Fig. 9 shows yet another non-limiting embodiment of the fuel cell of the present invention, which differs from the fuel cell shown in fig. 1at least in that: it additionally comprises an anode 3, a special membrane 8a, an optional second membrane 8b, an optional spacer material 9 and an optional frame seal 6 arranged within the tank 1. This embodiment also does not comprise capillary needles 7. The materials and thicknesses of the devices 3, 4, 6, 9, 8a and 8b are the same as for the corresponding devices described above for the embodiment shown in fig. 2. The membranes 8a and 8b may be of the same material, type and/or thickness as described above, or may differ in any one or more of these respects.

Fig. 10 shows yet another non-limiting embodiment of the fuel cell of the present invention that differs from the fuel cell shown in fig. 1at least in that: it additionally comprises an anode 3, a special membrane 8a and an optional second membrane 8b arranged inside the tank 1. This embodiment does not require the spacer material 9 and the frame seal 6, nor does it include the capillary needles 7. The materials and thicknesses of the devices 3, 4, 8a and 8b are the same as for the corresponding devices described above for the embodiment shown in fig. 2. The membranes 8a and 8b may be of the same material, type and/or thickness as described above, or may differ in any one or more of these respects. In this embodiment, the membrane 8a is preferably in contact with the anode 3. As a non-limiting example, the membrane 8a may be rolled or connected or bonded to the surface of the anode 3. In this case, the voids and/or free spaces in the membrane 8a provide empty spaces that may be occupied by the generated gas, thereby forming a barrier that substantially prevents the fuel from contacting the anode.

In particular, in embodiments using more than one particular membrane 8a, such as membranes 8a and 8b, a first membrane 8a may function in the manner described above depending on the space and/or spacing material, while a second membrane 8b may serve a different purpose, such as to protect the first membrane 8a and/or substantially prevent clogging thereof, filter solids from the fuel in the fuel chamber 2, and the like.

Those skilled in the art will appreciate that not every one of the various components of the fuel cell of the present invention need be present as a single component, and need not be disposed entirely within a single housing. By way of non-limiting example, the fuel chamber 2 may include a portion adjacent to at least one membrane 8 (e.g., adjacent to membrane 8 b) and a portion or more other portions (e.g., one or more cartridges) disposed outside of the fuel cell housing or tank and connected to the tank by one or more liquid passages. The volume of the fuel chamber, if any, disposed within the housing is small relative to the volume of the portion or portions disposed outside the housing (e.g., no greater than about 20%, such as no greater than about 10%, no greater than about 5%, or no greater than about 2%, of the latter volume). Furthermore, the fuel chamber 2 may be arranged substantially completely outside the tank and may be connected to the tank by one or more liquid channels (e.g. in the form of small diameter pipes or the like). By way of non-limiting example, the fuel chamber may be in the form of an (optionally replaceable) cartridge connected to the tank. Examples of methods of attaching the cassette to the cassette are disclosed in, for example, pending U.S. patent application nos. 10/824,443 and 10/849,503, which are incorporated herein by reference in their entirety.

In this case, the at least one membrane 8 may be included in the tank (e.g., at or near one or more points where liquid fuel may enter the tank), and/or may be included in the fuel chamber 2 (e.g., a cartridge) (e.g., at or near one or more points where liquid fuel may exit the fuel chamber 2), and/or may be disposed somewhere between the tank and the fuel chamber 2 (e.g., within one or more liquid passages connecting the fuel chamber 2 and the tank). Of course, in this case, the details regarding the various components of the fuel chamber may also be the same as previously described. For example, the at least one film 8 may include at least a first film 8a and a second film 8 b.

Fig. 11-13 show one non-limiting embodiment of a fuel cell 1 having a cathode 4, an anode 3, an electrolyte chamber 5 disposed between the cathode 4 and the anode 3. The cartridge CA with the fuel chamber 2 is attached and/or detachably attached to a fuel cell housing with a cathode 4, an anode 3 and an electrolyte chamber 5. When the cartridge CA is attached to the housing (fig. 11), the fuel chamber 2 is arranged on the side of the anode 3 opposite to the side facing the electrolyte chamber 5. At least one membrane 8 is arranged between the gas accumulation space adjacent to the anode 3 and the fuel chamber 2. By way of non-limiting example, the width of the space may be about 1mm, but may also be considerably larger or smaller. The at least one membrane 8 is constructed and arranged to allow gas formed by the decomposition of the fuel to accumulate adjacent the anode 3 on or near the surface of the anode 3 facing the fuel chamber 2, at least to an extent that the gas substantially prevents direct contact between the anode 3 and the liquid fuel in the fuel chamber 2. As shown in fig. 12, the membrane 8 (which may also include an additional layer of spacer material 9) may be in the form of a small screen filter member secured to the inner surface of the housing wall. Of course, the filtering means can also be arranged on the opposite ends of the duct and can thus be arranged in the cartridge CA without going beyond the scope of the present invention. Furthermore, the filter member may also be arranged on both sides of the duct. Still further, the interior of the tube may include a membrane/spacer material in the form of a cigarette filter of sufficient length. As shown in fig. 13, the tubes of the cassette CA (which may vary in number and size as desired and may be similar to the tubes 7) are sealed against the opening in the housing wall by one or more O-rings. Of course, any number of sealing techniques or methods may be employed in providing a seal between the conduit and the wall opening. In addition, it is contemplated that the conduit may also be connected to the fuel cell housing, with the opening being disposed in the wall of the cartridge CA. Fig. 13 shows the cartridge CA detached and/or not attached from the housing of the fuel cell 1. Although not shown, valves may be used to stop and/or regulate flow to and from the cartridge CA and the housing of the fuel cell 1.

By way of non-limiting illustration, when the fuel cell is in or placed in an unloaded or substantially unloaded state, the liquid fuel initially decomposes and generates a gas (e.g., hydrogen) near the anode 3, thereby pushing the liquid fuel away from the anode 3 and preventing the fuel from further contacting the anode 3, which in turn terminates the generation of gas. When the fuel cell is then placed under load (closed circuit), the gas is consumed by oxidation on the anode surface to create a vacuum that draws back the liquid fuel and comes into direct contact with the surface of the anode 3 where it is oxidized to produce electrical power. When the circuit is again broken (no load), gas is initially generated by decomposition of the liquid fuel and the process starts from the beginning.

Example 1

The experiment was carried out using a conventional DLFC of the type shown in figure 1 with the following parameters:

the areas of the anode and cathode are 45cm each²(62mm×73mm)；

The thickness or width of the electrolyte chamber is 4 mm;

the volume of the electrolyte in the electrolyte chamber is 18cm³；

The thickness or width of the fuel chamber is 20 mm; and

fuel volume of the fuel chamber is 90cm³。

DLFC was filled with borohydride fuel and tested under the following conditions:

the total test time is 20 hours;

an unloaded state is an open circuit.

In this test, the maximum gas yield was 15cm³And/min. As shown in fig. 4, hydrogen production began to decline after about 60 minutes, but continued for 20 hours throughout the experiment.

Example 2

Experiments were carried out with a DLFC according to the invention of the type shown in fig. 2 with the following parameters:

the areas of the anode and cathode are 45cm each²(62mm×73mm)；

The thickness or width of the electrolyte chamber is 4 mm;

the volume of the electrolyte in the electrolyte chamber is 18cm³；

The thickness or width of the fuel chamber is 20 mm; and

fuel volume of the fuel chamber is 90cm³；

The thickness of the thin film Teflon (Teflon) frame seal is 50 μm;

the length of the stainless steel capillary needle is 7mm, and the inner diameter is 320 mu m;

the special membrane mesh of the stainless steel micro-pore sieve is 53 mu m;

polypropylene mesh net (net) like spacer material mesh 2mm x 3mm and thickness 1 mm.

the total test time is 20 hours;

an unloaded state is an open circuit.

In this test, the time until the space between the anode 3 and the special membrane 8 was filled was 45 seconds. As shown in fig. 5, the hydrogen gas generation starts to decrease after about 45 seconds and stops after about 3 minutes, i.e., the fuel decomposition stops after about 3 minutes.

It should be noted that the exemplary and preferred dimensions of the elements of the DLFC described above apply particularly to fuel cells for portable devices, e.g., fuel cells having dimensions on the order of magnitude suitable for portable devices (e.g., laptop computers, cell phones, etc.). Examples of corresponding parameters are given in these examples. For those fuel cells that are considerably smaller or larger than those suitable for portable devices, the preferred dimensions given herein may not always provide the desired results to the greatest extent possible. However, one skilled in the art can readily determine the most appropriate size for any given size of fuel cell.

Here, the "hydrophilic" material refers to a material having an affinity for water. The term includes materials that can be wetted, have large surface tension values, and have a tendency to form hydrogen bonds with water. It also includes materials with high water vapor permeability.

Here, the "hydrophobic" material refers to a material that repels water. The term includes materials that allow gas to pass therethrough but substantially prevent the flow of water and similar protons and/or polar liquids therethrough.

It should be noted that the above examples are provided for illustrative purposes only and are not intended to limit the present invention. While the invention has been described with reference to exemplary embodiments, it is understood that the words which have been used are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, without departing from the scope and spirit of the invention in its aspects. Although the invention has been described with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein. Rather, the invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

This application is a continuation-in-part application of U.S. patent application No.10/941,020 filed on 9, 15, 2004, the entire contents of which are incorporated herein by reference.

Claims

1. A direct liquid fuel cell that uses a liquid fuel that tends to decompose to produce a gas, the fuel cell comprising:

a cathode;

an anode;

an electrolyte chamber disposed between the cathode and the anode;

a fuel chamber disposed on a side of the anode opposite to a side facing the electrolyte chamber; and

at least one membrane arranged on a side of the anode facing the fuel chamber,

wherein the at least one layer of membrane is constructed and arranged to allow gases formed on or near a surface of the anode facing the fuel chamber to accumulate adjacent the anode, at least to an extent that the accumulated gases substantially prevent direct contact between the anode and liquid fuel from the fuel chamber.

2. The fuel cell of claim 1, wherein the gas comprises hydrogen.

3. A fuel cell according to claim 1 or 2, wherein the fuel comprises one or more of a metal hydride compound and a metal borohydride compound.

4. The fuel cell of any one of claims 1 to 3, wherein the at least one membrane comprises a single layer of material.

5. The fuel cell of any one of claims 1 to 4, wherein the at least one membrane comprises a hydrophilic material.

6. The fuel cell of claim 5, wherein the hydrophilic material comprises one or more of a metal and a metal alloy.

7. The fuel cell of claim 6, wherein the hydrophilic material comprises stainless steel.

8. The fuel cell of any one of claims 1 to 7, wherein the at least one membrane comprises a hydrophobic material.

9. The fuel cell of claim 8, wherein the hydrophobic material comprises an organic polymer.

10. The fuel cell of claim 8, wherein the hydrophobic material comprises one or more of a polyolefin, a polyamide, and a polyacrylonitrile.

11. The fuel cell of any one of claims 1 to 10, wherein the at least one membrane comprises one or more of a non-woven material, a composite material, a laminate material, a composite/laminate material, a foam material, a porous paper material, a textile material, a carbon/graphite material, a sintered metal material, a ceramic material, and a polymer material.

12. The fuel cell of any one of claims 1 to 11, wherein the at least one membrane comprises one or more of a mesh and a foam.

13. The fuel cell of any one of claims 1 to 12, wherein the at least one membrane comprises a stainless steel microsieve.

14. The fuel cell of claim 13, wherein the microsieve comprises a mesh having a size of up to about 0.5 mm.

15. The fuel cell of claim 14, wherein the mesh has a size of from about 0.06 μ ι η to about 0.05 mm.

16. The fuel cell of any one of claims 13 to 15, wherein the screen has a thickness of from about 0.01mm to about 5 mm.

17. The fuel cell of any one of claims 1 to 16, wherein the at least one membrane comprises one or more of a polymer screen and a porous polymer layer.

18. The fuel cell of claim 17, wherein the polymer screen or porous polymer layer has a thickness of from about 0.02mm to about 2 mm.

19. The fuel cell of claim 17 or 18, wherein the polymer mesh has a mesh size of from about 0.01mm to about 0.1mm and the porous polymer layer has a pore size of from about 0.01 μ ι η to about 0.1 mm.

20. The fuel cell of any one of claims 1 to 19, wherein the at least one membrane is in contact with a surface of the anode facing the fuel chamber.

21. The fuel cell of claim 20, wherein the at least one membrane is one or more of attached and bonded to the surface of the anode.

22. The fuel cell of any one of claims 1 to 19, further comprising one or more of a free space and a spacing structure disposed between the at least one membrane and the anode.

23. The fuel cell of claim 22, comprising a spacer structure comprised of a spacer material having free space therein.

24. The fuel cell of claim 23, wherein the spacing structure comprises a layer of spacing material having a thickness of up to about 3 mm.

25. The fuel cell of claim 24, wherein the spacer material layer has a thickness of at least about 0.1 mm.

26. The fuel cell of claim 25, wherein the spacer material layer has a thickness from about 0.5mm to about 1.5 mm.

27. The fuel cell of any one of claims 23 to 26, wherein the spacer material comprises a hydrophobic material.

28. The fuel cell of claim 27, wherein the hydrophobic material comprises a polymeric material.

29. The fuel cell of claim 27, wherein the hydrophobic material comprises one or more of an olefin homopolymer, an olefin copolymer, ABS, polymethylmethacrylate, polyvinyl chloride, and polysulfone.

30. The fuel cell of claim 29, wherein the hydrophobic material comprises one or more of polyethylene, polypropylene, polytetrafluoroethylene, and ABS.

31. The fuel cell of any one of claims 27 to 30, wherein the at least one membrane comprises a hydrophilic material.

32. The fuel cell of any one of claims 23 to 31, wherein the spacing structure comprises a mesh.

33. The fuel cell of claim 32, wherein the mesh comprises a fence-like mesh.

34. The fuel cell of claim 32 or 33, wherein the mesh comprises openings from about 1mm to about 50 mm.

35. The fuel cell of any one of claims 21 to 34, comprising a spacer structure constituted by a frame seal arranged on a surface of the anode facing the fuel chamber.

36. The fuel cell of claim 35, wherein the frame seal comprises a hydrophobic material.

37. The fuel cell of claim 36, wherein the hydrophobic material comprises a polymer.

38. The fuel cell of claim 37, wherein the polymer comprises a fluorinated polymer.

39. The fuel cell of any one of claims 35 to 38, wherein the frame seal has a thickness of up to about 0.1 mm.

40. The fuel cell of claim 39, wherein the frame seal has a thickness from about 0.02mm to about 0.05 mm.

41. The fuel cell of claim 23 wherein the spacer structure comprises a spacer material having free space therein and a frame seal disposed on a surface of the anode facing the fuel chamber.

42. The fuel cell of any one of claims 22 to 41, further comprising a pressure relief device arranged to allow gas to escape from a space between the anode and the at least one membrane.

43. A fuel cell according to claim 42, wherein the pressure relief device is arranged to allow the gas to escape into the fuel chamber.

44. The fuel cell of claim 42 or 43, wherein the pressure relief device comprises a conduit.

45. The fuel cell of any one of claims 23 to 44, wherein the at least one layer of film and the spacing structure form a unitary structure.

46. The fuel cell of any one of claims 1 to 45, comprising at least a first membrane adjacent to the anode and a second membrane on a side of the first membrane facing the fuel chamber, at least the first membrane being constructed and arranged to allow gas formed on or near a surface of the anode facing the fuel chamber to accumulate adjacent the anode, at least to an extent that the accumulated gas substantially prevents direct contact between the anode and the liquid fuel.

47. The fuel cell of claim 46, wherein the second membrane is constructed and arranged to filter solids from the liquid fuel or to protect the first membrane, or both.

48. The fuel cell of claim 46 or 47, wherein the first membrane and the second membrane form a unitary structure.

49. The fuel cell of any one of claims 46 to 48, wherein the second membrane comprises one or more of a different material than the first membrane, a different thickness than the first membrane, a different pore size or mesh size than the first membrane.

50. The fuel cell of any one of claims 46 to 49, wherein the second membrane comprises one or more of substantially the same material as the first membrane, substantially the same thickness as the first membrane, substantially the same pore size or mesh size as the first membrane.

51. The fuel cell of any one of claims 46 to 50, wherein at least the first membrane comprises a polymer sieve or porous polymer layer having a thickness of between about 0.02mm and 2mm and a mesh size of from about 0.01mm to about 0.1mm or a pore size of from about 0.01 μm to about 0.1 mm.

52. The fuel cell of any one of claims 46 to 51, wherein at least the first membrane comprises a stainless steel screen having a thickness of from about 0.01mm to about 5 mm.

53. The fuel cell of any one of claims 46 to 52, wherein the first membrane is one or more of bonded to and in contact with a surface of the anode facing the fuel chamber.

54. The fuel cell of any one of claims 46 to 52, further comprising one or more of a free space and a spacing structure disposed between the first membrane and the anode.

55. The fuel cell of claim 54, wherein the fuel cell comprises a spacer structure comprised of a spacer material having free space therein.

56. The fuel cell of claim 55, wherein the spacer material comprises a hydrophobic material.

57. The fuel cell of claim 55 or 56, wherein the spacing structure comprises a fence-like mesh.

58. The fuel cell of any one of claims 55 to 57, wherein the spacing structure comprises a frame seal arranged on a surface of the anode facing the fuel chamber.

59. The fuel cell of claim 58, wherein the frame seal has a thickness of from about 0.02mm to about 0.05 mm.

60. The fuel cell of any one of claims 1 to 59, wherein the anode is one or more of secured within and in sealing engagement with the fuel cell housing.

61. A method of reducing or substantially preventing decomposition of a fuel at an anode of a fuel cell in a direct liquid fuel cell when the fuel cell is in a substantially unloaded state, wherein the fuel decomposes to produce a gas, the method comprising causing the gas produced by the initial fuel decomposition to form a barrier which limits or substantially prevents further contact between the fuel and the anode.

62. The method of claim 61, wherein the barrier layer comprises a substantially continuous gas layer across substantially an entire surface of the anode facing a fuel chamber of the fuel cell.

63. The method of claim 61 or 62, wherein the gas comprises hydrogen.

64. The method of any one of claims 61 to 63, wherein the fuel comprises one or more of a hydride compound and a borohydride compound.

65. The method of any one of claims 61 to 64, wherein the fuel comprises an alkali metal borohydride one or more of dissolved and suspended in a liquid carrier.

66. The method of any one of claims 61-65, wherein the fuel decomposition substantially stops in no more than about 5 minutes after the fuel cell is placed in a substantially no-load state.

67. The method of claim 66, wherein the fuel decomposition substantially stops in no more than about 3 minutes.

68. The method of any one of claims 61 to 67, comprising the ability to limit or substantially prevent gas produced by decomposition of the initial fuel from flowing away from the anode.

69. The method of claim 68, wherein the ability of the gas to flow away from the anode is limited or substantially prevented by at least one membrane disposed on a side of the anode facing a fuel chamber of the fuel cell.

70. A method of reducing or substantially preventing decomposition of a fuel at an anode of a direct liquid fuel cell using a fuel that produces a gas when subjected to said decomposition, wherein said method comprises:

disposing one or more of the following structures between a fuel chamber of the fuel cell and the anode:

at least one porous structure;

at least one screen structure; and

at least one film; and

gas is formed in the fuel cell during the initial decomposition of the fuel,

whereby the gas limits or substantially prevents contact between the fuel and the anode.

71. The method of claim 70, wherein the forming comprises substantially preventing the fuel from contacting the anode with the gas.

72. The method of claim 70 or 71, wherein the forming comprises forming a substantially continuous gas layer across substantially an entire surface of the anode facing the fuel chamber of the fuel cell.

73. The method of any one of claims 70 to 72, wherein said forming comprises substantially confining said gas between said anode and said at least one porous structure, said at least one sieve structure, or said at least one membrane.

74. The method of any one of claims 70 to 73, wherein the gas comprises hydrogen.

75. The method of any one of claims 70 to 74, further comprising placing the fuel cell in a substantially no-load condition so as to cause fuel decomposition.

76. The method of any one of claims 70 to 75, further comprising substantially stopping initial fuel decomposition in no more than about 3 minutes.

77. The method of any one of claims 70 to 76, further comprising providing a space between said anode and said at least one porous structure, said at least one sieve structure or said at least one membrane, wherein said space can be substantially filled with said gas.

78. A method of preventing or reducing fuel decomposition in a fuel cell according to any one of claims 1 to 60, wherein the method comprises:

generating electrical energy with the fuel cell;

substantially preventing further electrical energy production by the fuel cell thereby causing decomposition of fuel accompanied by gas production at the anode of the fuel cell; and

by the at least one membrane, accumulation of gas generated at the anode adjacent to the anode is facilitated, at least to the extent that the accumulated gas restricts or substantially prevents contact between the anode and the liquid fuel.

79. A method of preventing or reducing fuel decomposition in a fuel cell according to any one of claims 1 to 60, wherein the method comprises:

generating electrical energy with the fuel cell;

such that the gas produced at the anode accumulates adjacent the anode, at least to an extent that the accumulated gas substantially prevents contact between the anode and the liquid fuel.

80. A method of preventing or reducing fuel decomposition in a fuel cell according to any one of claims 1 to 60, wherein the method comprises:

generating electrical energy with the fuel cell;

allowing the gas produced at the anode to accumulate between the at least one membrane and the anode, at least to an extent that the accumulated gas substantially prevents contact between the anode and the liquid fuel.

81. The fuel cell of any one of claims 1 to 60, wherein the fuel chamber is arranged in a cartridge that is at least one of connected to and detachably mounted to a housing of the fuel cell.

82. The fuel cell of claim 81 further comprising at least one member that permits liquid fuel to flow from the fuel chamber of the cartridge body to the anode-adjacent region.

83. The fuel cell of any one of claims 1 to 60, comprising a tank containing at least the anode, at least a portion of the fuel chamber being arranged outside the tank, and the tank being connected to the at least a portion of the fuel chamber arranged outside the tank by one or more liquid channels.

84. The fuel cell of claim 83, wherein the at least a portion of the fuel chamber disposed outside the tank comprises a canister.

85. The fuel cell of claim 83 or 84, wherein the at least one membrane is disposed in at least one of: (a) at or near one or more locations of the tank where the at least a portion of liquid fuel disposed outside of the tank from the fuel chamber may enter the tank; (b) at or near one or more locations of the at least a portion of the fuel chamber disposed outside the tank at which liquid fuel may exit the at least a portion of the fuel chamber disposed outside the tank; and (c) at one or more locations within the one or more liquid channels.