CN1320679C

CN1320679C - Inner wetting proton exchanging film fuel battery

Info

Publication number: CN1320679C
Application number: CNB021604975A
Authority: CN
Inventors: 胡里清
Original assignee: Shanghai Shen Li High Tech Co Ltd
Current assignee: State Grid Corp of China SGCC; Shanghai Municipal Electric Power Co; Shanghai Shenli Technology Co Ltd
Priority date: 2002-12-27
Filing date: 2002-12-27
Publication date: 2007-06-06
Anticipated expiration: 2022-12-27
Also published as: CN1512614A

Abstract

The present invention relates to an internal humidification proton exchange membrane fuel battery which comprises a humidifying section and an electricity generating section, wherein the humidifying section comprises an air inlet, a hydrogen inlet, a cooling water outlet, a humidified air outlet, a humidified hydrogen outlet and a humidified cooling water inlet, and the electricity generating section comprises a humidified air inlet, a humidified hydrogen inlet, a humidified cooling water outlet, an air outlet, a hydrogen outlet and a cooling water inlet. The humidified air outlet, the humidified hydrogen outlet and the humidified cooling water inlet of the humidifying section respectively correspond to the humidified air inlet, the humidified hydrogen inlet and the humidified cooling water outlet of the electricity generating section, and the air outlet, the hydrogen outlet and the cooling water inlet of the electricity generating section are arranged on a panel at the back end of the electricity generating section. Compared with the prior art, the present invention has the advantages of increase of effective working area, compact structure, etc.

Description

Internal humidifying proton exchange membrane fuel cell

Technical Field

The invention relates to a fuel cell, in particular to a proton exchange membrane fuel cell with an internal humidifying device.

Background

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 hydrogen ions 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 guiding plate in contact with the MEA is die-cast, stamped, or mechanically milled to form at least one or more guiding grooves. The guide electrode plates can be plates made of metal materials or plates made of graphite materials. The diversion pore canals and the diversion grooves on the diversion electrode 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 arranged, and a flow guide polar plate of anode fuel and a flow guide polar plate of cathode oxidant are respectively arranged on two sides of the membrane electrode. The flow guide polar plates are used as a current flow collection mother plate and mechanical supports at two sides of the membrane electrode, and flow guide grooves on the flow guide polar 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 proton exchange membrane fuel cell can be used as a power system of all vehicles, ships and other vehicles, and can also be used as a portable, movable and fixed power generation device. The core component of the proton exchange membrane fuel cell is a membrane electrode, and the proton exchange membrane is the core component of the membrane electrode.

At present, a proton exchange membrane used in a membrane electrode of a proton exchange membrane fuel cell needs water molecules to keep moisture in the running process of the cell. Because only hydrated protons can freely pass through the proton exchange membrane and reach the electrode cathode end from the electrode anode end to participate in electrochemical reaction, otherwise, when a large amount of dry fuel hydrogen or air passes through the two sides of the membrane electrode, water molecules in the proton exchange membrane are easy to be carried away, at the moment, the proton exchange membrane is in a dry state, protons cannot pass through the proton exchange membrane, so that the internal resistance of the electrode is increased rapidly, and the performance of the cell is reduced rapidly. Therefore, the fuel hydrogen or air supplied to the fuel cell generally needs to be humidified to increase the relative humidity of the fuel hydrogen or air entering the fuel cell so as not to cause water loss from the proton exchange membrane.

Currently, the methods applied to humidification of proton exchange membrane fuel cells are mainly classified into two types:

(1) external humidification: the humidifying device is separated from the fuel cell stack and is independent from the outside of the fuel cell stack. The fuel hydrogen gas or air gas directly collides with water molecules in the external humidifying device through sufficient mixing to promote the gas to absorb vaporized water molecules.

(2) Internal humidification: the internal humidification apparatus is part of the fuel cell stack assembly. The fuel cell group is divided into two parts, one part is called internal humidifying section, and the other part is called active working section of cell. The internal humidifying section consists of humidifying guide plate and humidifying electrode, and the active cell section consists of guide plate and membrane electrode. The humidifying electrode is usually composed of a membrane capable of freely exchanging water molecules, for example, a DuPont ion exchange membrane named Nafion, which allows deionized water to flow on one side of the membrane and allows fuel gas or oxidant gas, such as air, to flow on the other side of the membrane, and the membrane can separate the fuel gas or air from liquid water molecules, but the water molecules can freely pass through the membrane to enter the fuel gas or air, thereby achieving the purpose of humidifying.

The internal humidification mode is often more advantageous than the external humidification mode in view of the overall compactness of the fuel cell and the volume saving of the fuel cell system. The current art of internal humidification has the following two engineering designs and manufacturing methods and has been reported in US patent5,382,478.

The method comprises the following steps: the internal humidification section is placed at the rear end of the fuel cell stack, and as shown in fig. 1a, 1b and 1c, an air inlet 1, an air outlet 2, a hydrogen inlet 3, a hydrogen outlet 4, a cooling water inlet 5, a cooling water outlet 6, a fuel cell power generation section 7, a fuel cell humidification section 8, a humidification air inlet section 9, a humidification hydrogen inlet section 10 and a cooling water inlet section 11 are arranged.

The second method comprises the following steps: the design method is that the fuel hydrogen and oxidant air or pure oxygen pass through the humidifying section of the battery pack to reach certain relative humidity, then enter the battery section for reaction, and the cooled deionized water enters the battery section to take out the reaction heat of the battery section, and then carry out water and heat exchange with the fuel hydrogen, oxidant air or pure oxygen at the humidifying section of the battery pack to achieve the purpose of improving the energy efficiency, as shown in fig. 2a, 2b and 2 c.

Although the above design method can achieve the purpose of humidification, it has the following disadvantages:

① the guide plate and the electrode of the fuel cell power generation section are provided with six guide holes, which are the inlet and outlet of the fuel hydrogen, the inlet and outlet of the oxidant air and the inlet and outlet of the cooling water, so that no matter the humidification section is arranged at the back or front of the whole cell group, the guide holes on the humidification guide plate and the humidification diaphragm spacer must be more than six.

As shown in fig. 2a, 2b, and 2c, the positions of the six diversion holes of the fuel cell stack power generation section (rear section) are: an air outlet 1, a humidifying air inlet section 9, a humidifying hydrogen inlet section 10, a hydrogen outlet 4, a cooling water inlet 5 and a cooling water outlet 11. And the guide holes which are positioned at the same position with the guide plate on the power generation section and the guide holes on the electrode on the humidification guide plate and the humidification membrane spacer of the humidification section (front section) of the fuel cell group are respectively provided with: an air outlet 1, a humidifying air inlet section 9, a humidifying hydrogen outlet section 10, a hydrogen inlet 4, a cooling water inlet 5 and a cooling water outlet 11. The humidifying guide plate and the humidifying diaphragm spacer are also provided with an air inlet 2, a hydrogen inlet 3 and a cooling water outlet 6, and the positions of the three guide holes can not be the same as those of the guide plate on the power generation section and the guide holes on the electrodes.

The situation is more severe when the humidification section of the fuel cell stack is placed behind the power generation section of the fuel cell stack. Besides six diversion holes, three additional diversion holes are added on the diversion plate and the electrode of the rear power generation section, and the diversion holes are respectively as follows: the air enters 1, the air enters 9 after entering the humidifying section, the hydrogen enters 4, the hydrogen enters 10 after entering the humidifying section, the cooling water enters 5, the air exits 2, the hydrogen exits 3, the cooling water exits 11 and enters the humidifying section, and the cooling water exits 6 from the humidifying section, and the number of the flow guide holes is nine, as shown in figure 2 d.

Therefore, the humidifying section is arranged at the back or the front of the whole battery pack, and the humidifying plate (flow guide plate) and the humidifying membrane spacer or the flow guide plate and the electrode of the power generation section cause that a plurality of flow guide holes are additionally added. The existence of the diversion holes greatly occupies the effective working area of the diversion guide plate, the diversion diaphragm or the diversion pole plate and the electrode of the power generation section. Thereby increasing the length of the entire humidification section or the power generation section and thus decreasing the power density of the entire battery pack.

② the extra irregular diversion holes make the processing of the diversion plate and the humidification diaphragm of the humidification section of the battery pack or the diversion pole plate and the electrode of the power generation section need special design and consideration, because the shapes of the diversion plate and the humidification diaphragm of the humidification section are completely different from those of the diversion plate and the electrode of the battery section, many materials such as a sealing ring and the like can not be manufactured and used uniformly, thereby wasting many materials.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the internal humidification proton exchange membrane fuel cell which can enable the fluid holes of the humidification section and the power generation section to be consistent, thereby improving the effective working areas of a guide plate and a diaphragm of the humidification section.

The purpose of the invention can be realized by the following technical scheme: an internal humidification proton exchange membrane fuel cell comprises a humidification section and a power generation section, and is characterized in that the humidification section is provided with an air inlet, a hydrogen inlet, a cooling water outlet, a humidification air outlet, a humidification hydrogen outlet and a humidification cooling water inlet, and the power generation section is provided with a humidification air inlet, a humidification hydrogen inlet, a cooling water outlet, an air outlet, a hydrogen outlet and a cooling water inlet; the humidifying air outlet, the humidifying hydrogen outlet and the humidifying cooling water inlet of the humidifying section correspond to the humidifying air inlet, the humidifying hydrogen inlet and the cooling water outlet of the power generation section respectively, and the air outlet, the hydrogen outlet and the cooling water inlet of the power generation section are arranged on the rear end panel of the power generation section.

And an air inlet, a hydrogen inlet and a cooling water outlet of the humidifying section are arranged on a front panel of the humidifying section.

The air inlet, the hydrogen inlet and the cooling water outlet of the humidifying section are arranged on the side end face of the flow collecting panel.

The air inlet and the hydrogen inlet of the humidifying section are arranged on one side end face of the flow collecting panel, and the cooling water outlet is arranged on the other side end face of the flow collecting panel.

Compared with the prior art, the invention can eliminate redundant flow guide holes adopted in the prior art, so that the sizes, the number and the positions of the flow guide holes on the humidifying flow guide plate and the humidifying diaphragm sheet can be completely the same as those of the flow guide plates in a battery section (namely a power generation section) and the humidifying diaphragm sheet, thereby not only improving the effective working areas of the flow guide plates and the humidifying diaphragms in the humidifying section, but also keeping the same with the flow guide plates and the electrodes on the battery section in design, and ensuring that certain materials (such as sealing rings and the like) can be commonly used. The invention has the following characteristics:

①, the humidifying section and the power generation section have the same area and the same size and position of all the diversion holes, as shown in fig. 3a, 3b and 3 c;

② instead of having six inlets and outlets for all of the inlet and outlet fluids, the three inlets and three outlets for fuel hydrogen, oxidant air and cooling water may be separately located on the front and rear panels of the stack as shown in figures 3a, 3b and 3 c.

③ the effective areas of the electrodes, polar plates, humidifying guide electrodes and humidifying membranes of the battery are greatly increased.

④ the three inlets and three outlets of fuel hydrogen, oxidant air and cooling water can also be collected on the collecting panel and the rear panel in the middle of the battery pack (the junction of the humidifying section and the battery section), and can respectively enter and exit from the side of the boundary panel, thus greatly improving the integration compactness of the fuel battery pack and increasing the power density.

Drawings

FIG. 1a is a schematic air flow diagram of a conventional internal rear humidification fuel cell;

FIG. 1b is a schematic diagram of the hydrogen flow direction of a conventional internal humidification fuel cell;

FIG. 1c is a schematic flow diagram of cooling water for a conventional post internal humidification fuel cell;

FIG. 2a is a schematic air flow diagram of a prior art front internal humidification fuel cell;

FIG. 2b is a schematic diagram of a prior art front internal humidification fuel cell hydrogen flow;

FIG. 2c is a schematic flow diagram of cooling water for a conventional front internal humidification fuel cell;

FIG. 2d is a schematic diagram of the structure of the current baffle and electrode in the power generation section of the internal humidification fuel cell;

figure 3a is a schematic air flow diagram of an internal humidification fuel cell of the present invention;

FIG. 3b is a schematic hydrogen flow diagram of an internal humidification fuel cell of the present invention;

figure 3c is a schematic flow diagram of the cooling water for an internally humidified fuel cell in accordance with the present invention;

FIG. 4 is a schematic view of the structure of an internal humidification fuel cell electrode and humidification membrane of the present invention;

FIG. 5a is a schematic structural view of an air deflector of a power generation section of a fuel cell according to the present invention;

FIG. 5b is a schematic diagram of a hydrogen baffle structure of a power generation section of a fuel cell according to the present invention;

FIG. 5c is a schematic view of a cooling water deflector of the power generation section of the fuel cell of the present invention;

FIG. 5d is a schematic view of an air humidifier plate structure of a humidification stage of a fuel cell of the present invention;

FIG. 5e is a schematic diagram of a hydrogen gas humidifying plate structure of a humidifying section of a fuel cell according to the present invention;

FIG. 5f is a schematic view of the structure of a cooling water humidifying plate of the humidifying section of a fuel cell according to the present invention;

FIG. 6a is a schematic air flow diagram of a fuel cell in accordance with example 1 of the present invention;

FIG. 6b is a schematic flow diagram of hydrogen gas in accordance with example 1 of the fuel cell of the present invention;

FIG. 6c is a schematic flow diagram of cooling water in accordance with example 1 of the fuel cell of the present invention;

FIG. 7 is a schematic structural view of a fuel cell of example 2 of the invention;

FIG. 7a is a schematic air flow diagram of a fuel cell of example 2 of the present invention;

FIG. 7b is a schematic flow diagram of hydrogen gas flow in example 2 of a fuel cell according to the present invention;

fig. 7c is a schematic flow diagram of cooling water in example 2 of the fuel cell of the present invention.

Detailed Description

The invention will be further explained with reference to the drawings and the specific embodiments.

Example 1

The fuel cell has six flow guide holes for the fuel hydrogen, oxidant air and cooling water to enter and exit, which are distributed separately on the flow guide plate and the electrode.

Wherein, the electrode and the humidifying membrane are shown in figure 4, and are provided with an air inlet 1, an air outlet 2, a hydrogen inlet 3, a hydrogen outlet 4, a cooling water inlet 5 and a cooling water outlet 6.

Wherein, the air guide plate of the power generation section is shown in figure 5a and is provided with an air inlet 1 and an air outlet 2, the hydrogen guide plate is shown in figure 5b and is provided with a hydrogen inlet 3 and a hydrogen outlet 4, and the water guide plate is shown in figure 5c and is provided with a cooling water inlet 5 and a cooling water outlet 6.

Wherein, the air humidifying plate of the humidifying section is shown as figure 5d and is provided with an air inlet 1 'and an air outlet 2', the hydrogen humidifying plate is shown as figure 5e and is provided with a hydrogen inlet 3 'and a hydrogen outlet 4', and the water humidifying plate is shown as figure 5f and is provided with a cooling water inlet 5 'and a cooling water outlet 6'.

The fuel cell stack assembled according to the new method of the present invention is designed, as shown in fig. 6a, 6b and 6c, oxidant air enters from the inlet 1 ' of the humidification section of the front end panel of the stack, passes through the diversion field of the humidification diversion plate, and is converged to the outlet 2 ' of the humidification section, the outlet 2 ' is exactly corresponding to the inlet 1 of the air of the power generation section in the stack (the position and the size are the same), and the humidified air enters the power generation section, undergoes electrochemical reaction, and then comes out from the outlet 2 of the back end panel of the stack.

Fuel hydrogen enters from the inlet 3 ' of the humidification section of the front end panel of the cell stack, the guide flow field of the humidification guide plate is converged to the outlet 4 ' of the humidification section, the outlet 4 ' is exactly corresponding to the inlet 3 of the hydrogen of the power generation section in the cell stack (the position and the size are the same), and after the humidified hydrogen enters the power generation section for power generation and electrochemical reaction, redundant hydrogen comes out from the outlet 4 of the rear end panel of the cell stack.

The cooling water enters the power generation section of the cell stack from the rear end panel 5 of the cell stack, takes out the heat generated by the cells, and then exits from the outlet 6, and enters the humidification section 5 'of the cell stack and exits from the outlet of the humidification section 6'.

Example 2

As shown in fig. 7, another fuel cell stack designed and assembled according to the new method of the present invention, the humidification baffles and humidification membranes, and the flow guide plates and electrodes of the cell segment are the same as in example 1, except that a thicker collector plate is used to separate the humidification segment from the power generation segment, so that the air inlet 1 ', the fuel hydrogen inlet 3 ', and the cooling water outlet 6 ' of the fuel cell are provided on the collector plate, and the air outlet 2, the hydrogen outlet 4, and the cooling water inlet 5 of the fuel cell are provided on the rear end plate of the fuel cell, and the principles of fluid flow guidance, as shown in fig. 7a, 7b, and 7c, are the same as in example 1.

Claims

1. An internal humidification proton exchange membrane fuel cell comprises a humidification section and a power generation section, and is characterized in that the humidification section is provided with an air inlet, a hydrogen inlet, a cooling water outlet, a humidification air outlet, a humidification hydrogen outlet and a humidification cooling water inlet, and the power generation section is provided with a humidification air inlet, a humidification hydrogen inlet, a cooling water outlet, an air outlet, a hydrogen outlet and a cooling water inlet; the humidifying air outlet, the humidifying hydrogen outlet and the humidifying cooling water inlet of the humidifying section correspond to the humidifying air inlet, the humidifying hydrogen inlet and the cooling water outlet of the power generation section respectively, the air outlet, the hydrogen outlet and the cooling water inlet of the power generation section are arranged on the rear end panel of the power generation section, and the air inlet, the hydrogen inlet and the cooling water outlet of the humidifying section are arranged on the front end panel of the power generation section.

2. The internally humidified proton exchange membrane fuel cell according to claim 1, further comprising a current collecting panel sandwiched between the humidifying section and the power generating section, wherein the air inlet, the hydrogen inlet, and the cooling water outlet of the humidifying section are provided on a side end surface of the current collecting panel.

3. The proton exchange membrane fuel cell as claimed in claim 1, wherein the air inlet and the hydrogen inlet of the humidification stage are disposed on one side end surface of the current collecting panel, and the cooling water outlet is disposed on the other side end surface of the current collecting panel.