CN1564360A - Self-breathing portable power supply - Google Patents

Abstract

The invention discloses a self-breathing air portable power supply of a self-breathing air polymer electrolyte fuel cell based on an integrated fuel device and belongs to the technical field of fuel cells. The hydrogen fuel device of the energy unit is connected in series with the power unit of the fuel cell stack consisting of bipolar plates, membrane electrodes, fuel flow field plates, air flow field plates, collector plates, end plates and gaskets with fastening bolts. The metal separator is replaced by an annular bipolar plate with gas distribution grooves on both sides, the complex exhaust valve and simplified fasteners are removed, and the hydrogen source device is organically combined with the self-breathing fuel cell stack. Good airtightness, reduced volume, weight and cost, can be used as a portable power source in remote places far away from high-pressure hydrogen cylinders, without the need to use AC grid charging, as long as fuel is added, it will breathe oxygen from the air for a quiet electrochemical reaction without manual labor Intervention, which continuously outputs electrical energy, is a very convenient portable power source.

Description

Self-breathing air portable power

field of invention

The invention belongs to the technical field of fuel cells, and mainly relates to a self-breathing air portable power source of a polymer electrolyte fuel cell based on an integrated fuel device.

Background technique

The invention relates to an air-breathing portable power supply, which has the characteristics of light weight, no noise and zero pollution. This kind of portable power supply can be used for many purposes, for example, it can be used as a clean energy source for outdoor activities, vehicles, household electronic equipment, personal electronic equipment, etc. This portable power supply is mainly composed of the energy unit of the hydrogen fuel device and the fuel cell stack The power unit consists of two parts, the hydrogen fuel device can be a hydrogen storage device or a hydrogen generator, and the fuel cell stack is a self-suction air-adaptive solid polymer cell stack. Compared with the usual fuel cell stacks that are pressurized, heated and equipped with management systems such as water heat, the self-breathing fuel cell stack is a completely passive operation (passive operation), which is very suitable for portable power applications. During the power generation process of the self-breathing fuel cell stack, the fuel flows from the fuel device into the cell stack, and electrochemically reacts with the breathed ambient air on the membrane electrode, releasing electric energy and reacting to generate water. The self-breathing air fuel The stack does not require pump power to circulate or remove reactants or generate water. The ideal fuel for fuel cell stacks is hydrogen. Polymer fuel cell has the characteristics of low operating temperature and high output power, and is a type of fuel cell.

An example of a portable fuel cell stack is described in U.S. Patent No. 5,595,834 and No. 5,514,486, in which the anode (fuel electrode) and cathode (oxygen electrode) of a unit cell are arranged on both sides of a solid polymer electrolyte membrane, The fuel flow field plate and the oxygen flow field plate are arranged on the sides of the anode (fuel electrode) and the cathode (oxygen electrode) respectively; the two unit cells are separated by a separation plate. The unit cells are integrated with each other to form a battery stack in which a plurality of unit cells are stacked to form an overall structure. Since these fuel cell stacks are suitable for low-power fuel cells, they can be designed as a fuel cell stack with small size and light weight. Chinese Patent No.02106940.9 has made several improvements on this basis: (1) removed the fuel flow field plate, because there is no flow field plate set on the anode side of each battery unit in the fuel cell stack, to a certain extent reduced The amount of contact between the two surfaces; (2) The way the fuel is supplied from the side hole is changed, that is, the fuel supply flow field plate and the end plate opening for fuel supply are abandoned. Instead, a fuel supply fine hole is opened on the fixing nut, and the fine hole communicates with the fuel distribution manifold for supplying fuel from the center of the end plate. In this way, the fuel is directly supplied to the fuel distribution main pipe without flowing through the fuel flow field, the flow resistance will be reduced, and a stable fuel supply can be realized; in the traditional self-breathing battery stack discharge process, when the hydrogen fuel is distributed from the hydrogen device to the After the fuel flow field plate of the battery stack undergoes an electrochemical reaction, if there is no outlet for exhaust gas, water may slowly accumulate in the fuel flow channel, which will cause the battery to accumulate water and cause a drop in voltage and current, affecting the output performance of the battery stack. . The traditional method is to install a purge valve at the end of the hydrogen fuel main pipe, and its structure is described in detail in Patent No. 5,595,834 and Patent No. 02106940.9.

However, in the above traditional air-breathing battery stack design, there are still big problems: first, in the above-mentioned patents, more or less metal separators are used, which increases the weight and volume of the battery stack, and further The important thing is to increase the contact interface in the battery stack, resulting in an increase in internal resistance, and the metal surface is easily corroded, and the internal resistance will increase as the discharge progresses, thereby reducing the output power of the entire battery stack. In Patent No. 02106940.9, although the fuel flow field plate is removed, the internal resistance of the battery stack can be reduced on the surface, but because the metal surface is directly in contact with the fuel cell membrane electrode, the membrane electrode is a weakly acidic environment, so the metal separation The corrosion effect on the surface of the plate will be strengthened, which may not only increase the internal resistance, but also release metal impurity ions, making the core components of the membrane electrode of the battery stack invalid. On the other hand, the lack of a fuel flow field plate negatively impacts the uniform distribution of the fuel, as water, the product of the electrochemical reaction, tends to lodge in the electrode, forming a 'dead zone' where hydrogen cannot reach, leading to performance degradation. Secondly, the fuel cell stack is not integrated with the hydrogen fuel device, it is only a power unit for energy conversion, and cannot be a portable power source. Thirdly, there are many unfavorable factors to install the exhaust valve at the end of the hydrogen fuel distribution main pipe, because under the pressure difference between the inside of the battery stack and the ambient air pressure, the accumulated water and waste gas will be discharged through the exhaust valve, which requires the exhaust valve to be regularly adjusted. is opened so that it is in the discharge state. In this way, the normal operation of the self-breathing fuel cell stack requires manual intervention. If the discharge time of the exhaust valve is insufficient, the electrical performance will decrease; but if the exhaust valve discharges frequently, a large amount of fuel hydrogen will be wasted. On the other hand, although the exhaust valve can also be operated by an automatic device, and the exhausted hydrogen fuel can also be recovered by a hydrogen pump, this will greatly reduce the passive operation of the battery stack. In addition, because hydrogen is flammable and explosive, the intermittent direct discharge of the exhaust valve has a negative impact on the safety of the application. Of course, there are many problems such as heavy maintenance work, complicated shape and large size.

Contents of the invention

The purpose of the present invention is to provide a portable power supply of self-breathing air, the energy unit fuel device 9 of the portable power supply of self-breathing air is composed of bipolar plate 1, membrane electrode 2, fuel flow field plate 3, air flow field plate 4. The power unit of the fuel cell stack composed of the current collecting plate 10, the end plate 7 and the gasket 8 is connected in series with the fastening bolts 5 and 6; it is characterized in that it adopts an annular structure with gas distribution grooves on both sides. The integrated graphite bipolar plate replaces the fuel flow field plate, the air flow field plate and the metal separator plate. The outer and inner circumferences of the bipolar plate are provided with sealing grooves 17, and holes 14 or bridges are formed on the outer peripheral edge of the bipolar plate. The way is connected with the outside air, and the fuel hydrogen in the fuel device enters the fuel central distribution pipe 13 through the fuel connection hole 12 through the hole 14 or the bridging method of the inner peripheral edge part, and the hydrogen fuel and the air are separated by the bipolar plate 1 isolated on both sides.

The air flow field distribution side of the bipolar plate has diversion grooves 16 connected to each other to form a diversion network, providing holes 14 around the substrate 15 to directly communicate with the outside air; the air flow inlet and outlet holes 14 are square, circular or trapezoidal.

The groove width of the diversion groove 16 can be changed continuously or discontinuously, and the shape of the diversion groove 16 is a straight line, a curve, a broken line or a network shape. The depth of the diversion groove can be changed continuously or discontinuously, and the bottom of the groove is in the shape of plane, step, wave or curved surface.

On the hydrogen distribution side of the bipolar plate, there are interpenetrating diversion grooves 16 similar to those on the air flow field distribution side to form a hydrogen diversion network.

The membrane electrode 2 is composed of a hydrophobic carbon paper 19, an anode hydrophobic carbon powder layer 20, an anode catalytic layer 21, a cathode catalytic layer 22, and a solid polymer electrolyte membrane 18; Hydrophobic treatment of vinyl fluoride plastic.

The beneficial effects of the present invention are: 1. In addition to automatically distributing the reaction gas, the bipolar plate used also has a good heat dissipation effect, because the air distribution flow field is completely communicated with the outside air, and with the natural convection and diffusion of the air Or with the evaporation and discharge of the water produced by the electrochemical reaction, it naturally plays a good role in heat dissipation. 2. The metal separator is removed, which is conducive to the automatic breathing of air and the uniform distribution of fuel hydrogen, and will not produce a "dead zone" where fuel cannot reach; greatly reducing the number of components and the difficulty of installation, reducing the two surfaces The number of contacts and the resistance of the contact parts also prevent the corrosion phenomenon caused by the use of metals, thereby effectively reducing the internal resistance of the stack, improving the operating life of the battery, and realizing high-efficiency portable power generation.

3. Through the special distribution of through-type air guide grooves, a good heat dissipation method of natural air air cooling is realized, the fuel cell system is simplified, the number of components is reduced, and the cost is reduced. 4. Integrate the fuel device with the air-breathing polymer fuel cell stack, and remove the metal separator of the fuel cell stack. By integrating a special bipolar plate to reduce the interface contact part, the internal resistance of the cell stack is reduced. This improves electrical performance.

5. The exhaust valve with complex structure is removed, and the accumulated water in the anode is discharged through the synergistic effect of the membrane electrode and the air flow field plate, so as to realize the operation of the self-breathing battery stack without manual intervention, and enhance the adaptability of its power generation. Thereby reducing the complexity and safety of the operation and further reducing the size and weight. The invention has broad market prospect.

Description of drawings

Figure 1 is a schematic diagram of the structure of a portable power supply for self-breathing air.

Fig. 2A is a schematic diagram of the hydrogen fuel flow field of the bipolar plate.

Fig. 2B is a schematic diagram of the air flow field of the bipolar plate.

FIG. 2C is a schematic front view of a double plate.

Fig. 3 is a schematic diagram of a membrane electrode assembly.

Fig. 4 is a perspective view of a portable power supply for self-breathing air.

Detailed ways

The present invention is a self-breathing air portable power source. In the structure of the self-breathing air portable power supply shown in Figure 1, the energy unit hydrogen fuel device 9 is connected with a bipolar plate 1, a membrane electrode 2, a fuel flow field plate 3, an air flow field plate 4, a current collector plate 10, a terminal The plate 7 and the washer 8 constitute the power unit of the fuel cell stack, which is formed by connecting the fastening bolts 5 and 6 in series. The invention adopts an annular integrated graphite bipolar plate with gas distribution grooves on both sides to replace the fuel flow field plate, the air flow field plate and the metal separation plate. The outer circumference and inner circumference of the bipolar plate are provided with a sealing groove 17, and the outer peripheral edge of the bipolar plate is connected with the outside air through a hole 14 or a bridging method, and the inner peripheral edge is connected with the outside air through a hole 14 or a bridging method. The fuel hydrogen in the fuel device enters the fuel central distribution pipe 13 through the fuel connection hole 12, and the hydrogen fuel and the air are separated on both sides by the bipolar plate. On the distribution side of the air flow field of the bipolar plate, there are diversion grooves 16 connected to each other to form a diversion network, providing the holes 14 around the substrate 15 to directly communicate with the outside air; the air flow inlet and outlet holes 14 are square, circular or trapezoidal ; The groove width of the diversion groove 16 can be changed continuously or discontinuously, and the shape of the diversion groove 16 is a straight line, a curve, a broken line or a network shape. The depth of the diversion groove can be changed continuously or discontinuously, and the bottom of the groove is in the shape of plane, step, wave or curved surface. On the hydrogen distribution side of the bipolar plate, there are interpenetrating diversion grooves 16 similar to those on the air flow field distribution side to form a hydrogen diversion network (as shown in FIGS. 2A-2C ).

Above-mentioned membrane electrode 2 (as shown in Figure 3) uses highly hydrophobic porous carbon paper 19 to make anode base, distributes on its one side surface the hydrophobic carbon powder layer that has micropore (equivalent pore diameter is less than the equivalent pore diameter of carbon paper) 20, prepare the anode catalytic layer 21 substrate like this; Use highly hydrophobic porous carbon paper 19 as the cathode substrate, but there is no hydrophobic carbon powder layer 20 above, directly used as the substrate of the cathode catalytic layer 22. They are then prepared together with the solid polymer electrolyte membrane 18 to form a membrane electrode 2 assembly. In the stack, the air flow field groove of the bipolar plate (or air flow field plate) is treated with hydrophobic functionalization, which is beneficial to drainage of the cathode, prevents the accumulation of water generated by the electrochemical reaction, and reduces the water activity on the cathode side.

In the present invention, the complex exhaust valve is eliminated and the fasteners of the battery stack are simplified. In order to maintain good hydrogen sealing, the use of nuts for movable parts is reduced, and only two bolts are used to fasten and form hydrogen fuel distribution pipes. One of the bolts has a fuel connection hole 12 in both the axial and radial directions, and a hole 11 with an internal thread is formed on its fixed head to connect with the fuel device to realize the hydrogen connection between the fuel device and the battery stack. The fastening of the battery stack is to connect the front end of the screw rod of one bolt with the front end of the screw rod of the other bolt under the occlusion of the thread, and the end plate of the battery stack is pressed tightly through the transmission of the pressure of the gasket, so that the connection head is placed on the battery pack. The new design inside the stack is beneficial to reduce volume, weight and cost, so that the portable power supply can be placed horizontally or vertically relative to the direction of the axis. The fastening parts are simplified, the airtightness is good, and because there is no connector outside the battery stack, the battery stack is beautiful, and no manual intervention is required in the power generation process, which enhances its practicability, can enhance public acceptance, and is conducive to popularization and use

In addition, the present invention organically combines the on-site hydrogen source device with the self-breathing fuel cell stack, and truly realizes a portable power supply with both an energy unit and a power unit. It can be used as a portable power source in remote places far away from high-pressure hydrogen cylinders. It does not need to be charged by an AC grid. As long as fuel is added, it will breathe oxygen from the air for a quiet electrochemical reaction and continuously output electric energy. It is a very convenient portable power source. .

Solid polymer electrolyte membranes include proton exchange membranes using fluorinated or aromatic ring structures or their organic and inorganic composite proton exchange membranes. In this implementation, a perfluorosulfonic acid proton exchange membrane is used, the thickness of which is between 25 μm and μ180 m, and the EW value thereof is between 600 and 1300. The solid polymer electrolyte membrane generally needs to be treated with a dilute solution of H ₂ O ₂ and H ₂ SO ₄ to remove organic impurities and protonize them. In this embodiment, the surface is also roughened. Finally, the electrode is cut into a ring-shaped electrode according to the shape of the bipolar plate 1 , and combined with a solid polymer electrolyte membrane to prepare a membrane electrode assembly 2 .

FIG. 4 is a three-dimensional appearance view of the self-breathing air portable power supply with the above structure. It works as follows.

The fuel device is the portable power source and energy unit, and the storage or production of the fuel determines the energy density of the power source; the self-breathing fuel cell stack is the power unit of the power source, and the electrochemical reaction between them determines the output power. After the power is turned on, the fuel hydrogen in the fuel device enters the fuel central distribution pipe 13 through the fuel connection hole 12, and then the fuel central distribution pipe 13 delivers the hydrogen fuel to The fuel flow field surface of each cell unit, and the hydrogen gas is evenly distributed on the anode side of the membrane electrode 2 by the guide groove 16 in the fuel flow field. On the other hand, the ambient air enters the air flow field surface of each battery cell from the outside through the peripheral holes 14 of the bipolar plate 1 and the air distribution plate 4 through convection, diffusion, etc., and is evenly distributed by the guide grooves in the air flow field. Oxygen in the air is distributed on the cathode side of the membrane electrode 2 efficiently. In this way, hydrogen fuel gas and oxygen are respectively distributed on both sides of the membrane electrode 2, the core component of the battery stack, where the electrochemical reaction takes place. Hydrogen dissociates into protons and negatively charged electrons under the action of the anode catalyst, and the protons are transferred from one sulfonic acid group (-SO 3 H) to another sulfonic acid group (-SO ₃ H) in the solid electrolyte membrane in the form of hydration H ⁺ .(nH ₂ O) The acid group finally reaches the cathode to realize proton conduction. This migration of protons results in a buildup of negatively charged electrons at the anode, which becomes a negatively charged terminal (cathode). At the same time, the oxygen molecules at the cathode react with the electrons generated under the action of the catalyst to become oxygen ions, making the cathode a positively charged terminal (positive electrode), which results in negatively charged terminals at the anode and positively charged terminals at the cathode. A voltage is developed between the electrical terminals. The voltage superposition can be obtained by connecting the battery back units in series. If the two poles are connected through an external circuit at this time, electrons will flow from the anode to the cathode through the loop, thereby generating electricity.

Claims (5)

1. compact power from breathe air, the energy unit fuel-device (9) of described compact power from breathe air is connected in series with fastening bolt (5) and fastening bolt (6) with the power cell by bipolar plates (1), membrane electrode (2), fuel flow field plate (3), air flow field plate (4), collector plate (10), end plate (7) and packing ring (8) formation fuel cell pack; It is characterized in that: adopt two sides all to have the circular integration graphite bi-polar plate of gas distribution groove to replace fuel flow field plate, air flow field plate and metal demarcation strip, the periphery of this bipolar plates and interior week are provided with seal groove (17), connect at the mode and the outside air of bipolar plates neighboring part by hole (14) or bridge formation, and partly entering fuel central dispense pipe (13) by the fuel connecting hole (12) on the fastening bolt (5) by the mode and the fuel hydrogen in the fuel-device of hole (14) or bridge formation in inner periphery, hydrogen fuel and air are isolated in both sides respectively by bipolar plates.

2. according to the described compact power of claim 1 from breathe air, it is characterized in that: the air flow field distribution side of described bipolar plates, have the guiding gutter (16) that interpenetrates to form the water conservancy diversion network, the hole (14) of matrix (15) periphery directly communicates with outside air; Air flow inlet and outlet hole (14) is square, circular or trapezoidal.

3. according to claim 1 or 2 described compact powers from breathe air, it is characterized in that: the groove width of described guiding gutter (16) can be continuously or is changed discontinuously, guiding gutter (16) be shaped as straight line, curve, broken line or network shape; The degree of depth of guiding gutter can change continuously or discontinuously, and bottom land is plane, step, wave or curve form.

4. according to the described compact power from breathe air of claim 1, it is characterized in that: the hydrogen distribution side of described bipolar plates has the guiding gutter that interpenetrate (16) similar to air flow field distribution side to form the hydrogen flow guide network.

5. according to the described compact power from breathe air of claim 1, it is characterized in that: described membrane electrode (2) is made of hydrophobic carbon paper (19), anode hydrophobic carbon bisque (20), anode catalyst layer (21), cathode catalysis layer (22), solid polymer electrolyte membrane sheet (18); Used carbon paper is composited by carbon fiber, and adopts poly-fluoroplastics to carry out hydrophobic treatment.

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