CN1200473C - Fuel battery with higher power density - Google Patents

Abstract

The present invention relates to a fuel cell with high power density, which comprises a membrane electrode, guide polar plates, a positive plate, a negative plate, a connecting pull rod, a cooling unit and a monitoring unit, wherein the guide polar plates clamp the membrane electrode to form a single cell; the positive plate and the negative plate clamp a plurality of single cells and are connected in series by the connecting pull rod to form a fuel cell pack; the cooling unit is a peripheral water tank filled with deionized water; the fuel cell pack is arranged in the peripheral water tank. Compared with the prior art, the present invention has the advantages of high power density, compact structure, etc.

Description

Fuel cell

The present invention relates to batteries, and more particularly to electrochemical fuel cells.

An electrochemical fuel cell is a device that is capable of converting hydrogen fuel and an oxidant into electrical energy and reaction products. The inner core component of the device is a Membrane Electrode (MEA), which is composed of a proton exchange Membrane and two porous conductive materials sandwiched between two surfaces of the Membrane, such as carbon paper. The membrane contains a uniform and finely dispersed catalyst, such as a platinum metal catalyst, for initiating an electrochemical reaction at the interface between the membrane and the carbon paper. The electrons generated in the electrochemical reaction process can be led out by conductive objects at two sides of the membrane electrode through an external circuit to form a current loop.

At the anode end of the membrane electrode, fuel can permeate through a porous diffusion material (carbon paper) and undergo electrochemical reaction on the surface of a catalyst to lose electrons to form positive ions, and the positive ions can pass through a proton exchange membrane through migration to reach the cathode end at the other end of the membrane electrode. At the cathode end of the membrane electrode, a gas containing an oxidant (e.g., oxygen), such as air, forms negative ions by permeating through a porous diffusion material (carbon paper) and electrochemically reacting on the surface of the catalyst to give electrons. The anions formed at the cathode end react with the positive ions transferred from the anode end to form reaction products.

In a pem fuel cell using hydrogen as the fuel and oxygen-containing air as the oxidant (or pure oxygen as the oxidant), the catalytic electrochemical reaction of the fuel hydrogen in the anode region produces hydrogen cations (or protons). The proton exchange membrane assists the migration of positive hydrogenions from the anode region to the cathode region. In addition, the proton exchange membrane separates the hydrogen-containing fuel gas stream from the oxygen-containing gas stream so that they do not mix with each other to cause explosive reactions.

In the cathode region, oxygen gains electrons on the catalyst surface, forming negative ions, which react with the hydrogen positive ions transported from the anode region to produce water as a reaction product. In a proton exchange membrane fuel cell using hydrogen, air (oxygen), the anode reaction and the cathode reaction can be expressed by the following equations:

and (3) anode reaction:

and (3) cathode reaction:

in a typical pem fuel cell, a Membrane Electrode (MEA) is generally placed between two conductive plates, and the surface of each conductive plate in contact with the MEA is die-cast, stamped, or mechanically milled to form at least one or more channels. The conductive plates can be plates made of metal materials or plates made of graphite materials. The flow guide pore canals and the flow guide grooves on the conductive polar plates respectively guide the fuel and the oxidant into the anode area and the cathode area on two sides of the membrane electrode. In the structure of a single proton exchange membrane fuel cell, only one membrane electrode is present, and a guide plate of anode fuel and a guide plate of cathode oxidant are respectively arranged on two sides of the membrane electrode. The guide plates are used as current collector plates and mechanical supports at two sides of the membrane electrode, and the guide grooves on the guide plates are also used as channels for fuel and oxidant to enter the surfaces of the anode and the cathode and as channels for taking away water generated in the operation process of the fuel cell.

In order to increase the total power of the whole proton exchange membrane fuel cell, two or more single cells can be connected in series to form a battery pack in a straight-stacked manner or connected in a flat-laid manner to form a battery pack. In the direct-stacking and serial-type battery pack, two surfaces of one polar plate can be provided with flow guide grooves, wherein one surface can be used as an anode flow guide surface of one membrane electrode, and the other surface can be used as a cathode flow guide surface of another adjacent membrane electrode, and the polar plate is called a bipolar plate. A series of cells are connected together in a manner to form a battery pack. The battery pack is generally fastened together into one body by a front end plate, a rear end plate and a tie rod.

A typical battery pack generally includes: (1) the fuel (such as hydrogen, methanol or hydrogen-rich gas obtained by reforming methanol, natural gas and gasoline) and the oxidant (mainly oxygen or air) are uniformly distributed in the diversion trenches of the anode surface and the cathode surface; (2) cooling fluid (such as water) is uniformly distributed into cooling channels in each battery pack through an inlet and an outlet of the cooling fluid and a flow guide channel, and heat generated by electrochemical exothermic reaction of hydrogen and oxygen in the fuel cell is absorbed and taken out of the battery pack for heat dissipation; (3) the outlets of the fuel gas and the oxidant gas and the corresponding flow guide channels can carry out liquid and vapor water generated in the fuel cell when the fuel gas and the oxidant gas are discharged. Typically, all fuel, oxidant, and cooling fluid inlets and outlets are provided in one or both end plates of the fuel cell stack.

The positive hydrogen ions in the anode region migrate through the proton exchange membrane and usually need to carry a large number of water molecules to pass through together, so that the water molecules must be kept on the two side surfaces of the membrane to ensure that the migration conductance of the positive hydrogen ions is not affected. Therefore, the fuel and oxidant gases must be humidified before they enter the active region of the fuel cell to react in order to ensure that the membrane in the membrane electrode is saturated with water.

The overall design of a pem fuel cell varies greatly depending on the intended use of the cell. When used as a low-power mobile power supply or a mobile power supply, the proton exchange membrane fuel cell is designed to operate at a pressure close to normal atmospheric pressure, because such a power supply usually requires a simple structure, light weight and small size of the whole system.

There are a number of patents reporting such low Power portable Power sources or fuel cells usable as portable Power sources, such as H-Power and the like. These types of low power (less than 1 kw) fuel cells have the disadvantage of low power density, which means the ratio of the output power of the fuel cell to the weight and volume of the system, which is generally less than 200W/kg. The main reasons are:

1. the fuel cell adopts a self-heat dissipation design, mainly depends on exhausted air and water carried by the air to dissipate heat, but the specific heat of the air is limited, so the heat dissipation amount is also limited. Therefore, additional heat dissipation and heat dissipation fins are required, thereby increasing the volume of the battery.

2. Because of the improper heat dissipation method, the improper design structure leads to the fuel cell being able to operate only under the condition of low current density (low power output) to prevent the heat dissipation of the cell from reaching, so thepower output of the fuel cell is hindered.

3. The insufficient design of membrane electrodes and flow-guiding plates, which are internal key components in the fuel cell, and the combined design relationship between them, lead to the increase of volume, weight and power density of the fuel cell.

It is an object of the present invention to overcome the above-mentioned drawbacks of the prior art by providing a fuel cell having a higher power density.

The purpose of the invention can be realized by the following technical scheme: a fuel cell with high power density is prepared as setting guide slot on guide plate, clamping a membrane electrode by two guide plates to form a single cell, connecting multiple single cells by positive plate and negative plate and connecting them in series to form a fuel cell set, cooling heat generated in course by cooling unit and monitoring course data by monitoring unit.

The temperature of the deionized water in the peripheral water tank is 40-80 ℃.

The peripheral water tank is provided with an external circulation deionized water pipeline, and the pipeline is provided with a heat exchanger and a circulation pump.

The heat exchanger may preheat or transfer heat to the fuel.

The conductive polar plate is a bipolar plate, and the front surface and the back surface of the bipolar plate are respectively provided with a diversion trench for guiding fuel and oxidant.

The water plate is arranged at the pipe orifice of the deionized water circulating pipe.

The peripheral water tank is made of stainless steel or plastic.

And the peripheral water tank is provided with radiatingfins.

Compared with the prior art, the invention has the following advantages:

1. the whole fuel cell is put into a deionized water tank, the heat generated by the fuel cell can be quickly absorbed and taken out by peripheral deionized water, the fuel cell can work under high current density, and the general temperature (the peripheral water tank) can be controlled between 40 ℃ and 80 ℃.

2. The peripheral deionized water can take out the heat of the fuel cell through pump circulation and enter the heat exchanger in the peripheral hydrogen storage bottle, because a large amount of hydrogen is absorbed in the metal powder hydrogen storage bottle, when the hydrogen is discharged and supplied to the fuel cell, a large amount of heat needs to be absorbed, and the method for circulating hot water is safe and effective.

3. The design of internal cooling water inlet and outlet is not required in the fuel carrying-out interior, and bipolar plates can be used as guide plates for the fuel carrying-out without internally clamping cooling clamping plates. Thus, in effect, there is one membrane electrode per bipolar plate on average, increasing the power density.

4. If the fuel cell adopts the design of internal humidification, additional water supply is not needed, the water plate can be specially designed and processed, deionized water can freely and quickly enter the water plate, the pipe orifice of the deionized water circulating pipe is opposite to the water plate, and water can quickly enter the water plate.

FIG. 1 is a schematic structural view of example 1 of the present invention;

FIG. 2 is a front view of a bipolar plate of example 2 of the present invention;

figure 3 is a rear view of a bipolar plate of example 2 of the present invention;

FIG. 4 is a front view of a membrane electrode of example 2 of the invention;

fig. 5 is a front view of a water plate of embodiment 3 of the present invention;

fig. 6 is a rear view of a water plate of embodiment 3 of the present invention;

FIG. 7 is a front view of the gas-water humidification exchange membrane of embodiment 3 of the present invention.

The invention is further described with reference to the following figures and specific embodiments.

Example 1

As shown in fig. 1, an embodiment of a fuel cell with a higher power density according to the present invention includes a membrane electrode 1 capable of conducting protons, a flow guide plate 2 capable of guiding hydrogen, a flow guide plate 3 capable of guiding air, a positive plate 4, a negative plate 5, a connecting pull rod (not shown), a peripheral water tank 6, deionized water 7, and a monitoring unit (not shown), wherein catalysts and porous carbon paper are attached to two sides of the membrane electrode 1, the flow guide plate 2 and the flow guide plate 3 sandwich one membrane electrode 1 to form a single cell, the positive plate 4 and the negative plate 5 clamp a plurality of single cells and connect them in series through the connecting pull rod to form a fuel cell stack, and the fuel cell stack is disposed in the peripheral water tank 6; the peripheral water tank is made of stainless steel or plastic materials, the temperature of deionized water in the water tank is controlled to be 40-80 ℃, the peripheral water tank 6 is provided with an external circulation deionized water pipeline 8, and a heat exchanger 9 and a circulation pump 10 are arrangedon the pipeline; the fuel hydrogen is preheated by passing through a heat exchanger 9 before entering the cell, which is economical and safe.

Example 2

As shown in fig. 2, 3 and 4, a fuel cell having a higher power density is characterized in that a conductive plate is changed into a bipolar plate, and the front and back surfaces of the bipolar plate are respectively provided with a channel 11 for guiding hydrogen and a channel 12 for guiding air, so that in practice, one membrane electrode 13 is provided on average for each bipolar plate, thereby increasing the power density; the rest of the structure is the same as in example 1.

Example 3

As shown in fig. 5, 6 and 7, a fuel cell with higher power density is characterized in that an internal humidification design is adopted, no additional water supply is needed, a water plate 14 is arranged at the pipe orifice of the deionized water circulating pipe of the embodiment 2, and a gas-water humidification exchange membrane 15 is arranged in the water plate; the rest of the structure is the same as in example 2.

Claims (3)

1. A fuel cell comprises a membrane electrode capable of conducting protons, a flow guide polar plate capable of respectively introducing fuel and oxidant, a positive plate, a negative plate, a connecting pull rod, a cooling unit and a monitoring unit, catalyst and porous carbon paper are adhered to two sides of the membrane electrode, the flow guide polar plates are provided with flow guide grooves, one membrane electrode is clamped between the two flow guide polar plates to form a single cell, the positive plate and the negative plate clamp a plurality of monocells and are connected in series through connecting pull rods to form a fuel cell stack, the cooling unit cools the heatgenerated by the process, the monitoring unit monitors the process data, the fuel cell system is characterized in that the cooling unit is a peripheral water tank filled with deionized water, the peripheral water tank is provided with an external circulation deionized water pipe, and the fuel cell stack is arranged in the peripheral water tank; the water plate is arranged in the fuel cell and faces the pipe orifice of the external circulation deionized water pipe, and a gas-water humidifying exchange membrane is arranged in the water plate.

2. The fuel cell of claim 1, wherein the external circulation deionized water pipe is provided with a heat exchanger and a circulation pump on the pipe; the heat exchanger may preheat or transfer heat to the fuel.

3. The fuel cell of claim 1 wherein said peripheral water tank is provided with fins.

Images