CN1198352C

CN1198352C - Fuel battery with higher output power

Info

Publication number: CN1198352C
Application number: CNB011059737A
Authority: CN
Inventors: 胡里清
Original assignee: Shanghai Shen Li High Tech Co Ltd
Current assignee: Shanghai Shenli Technology Co Ltd
Priority date: 2001-04-13
Filing date: 2001-04-13
Publication date: 2005-04-20
Anticipated expiration: 2021-04-13
Also published as: CN1381917A

Abstract

The present invention relates to a fuel cell with high output power, which comprises a membrane electrode composed of two parallel independent polar plates, guide polar plates, a front end plate, a rear end plate, a pull rod, a cooling unit and a monitoring unit, wherein two guide polar plates clamp a membrane electrode to form a single cell; a plurality of single cells are connected in series to form the fuel cell. Compared with the prior art, the fuel cell increases the active area of the membrane electrode in multiples; thus, the power of the membrane electrode is improved in multiples; simultaneously, the distribution of fuel gas and oxidant gas is even, and the operation of the fuel cell is stable.

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 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 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 largenumber 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. At present, the proton exchange membrane fuel cell used as a high-power movable power supply is designed, and the following measures are mainly adopted to improve the power density.

(1) Increasing the effective area of the membrane electrode to increase the output current;

(2) the thickness of the flow guide polar plate is reduced, the weight of the whole battery pack is reduced, and the volume is reduced;

(3) the fuel gas for intensifying the operation and the oxidant are operated under the conditions of pressure, concentration, temperature and the like so as to output larger power.

The first method for increasing the output power of the battery pack often has great limitations, mainly because the fuel gas and the oxidant gas are difficult to be uniformly distributed along with the increase of the area to a certain degree, and the electrochemical reaction speeds of all parts of the effective area are different, so that the current density is different, and the rate of the product water generated by all parts is different, thereby increasing the difficulty of water, heat management and control of the fuel cell with large area, often causing the local overhigh temperature, increasing the risk of pore burning of the membrane electrode, or causing the local low power generation efficiency and the expected power to be far different.

The second method for increasing the output power density of the battery pack has a great limitation because the guide plate is thin to a certain extent, and thus, the guide plate is liable to have insufficient mechanical strength, and if a graphite material is used, the guide plate is liable to cause a risk of leakage of fuel gas and oxidant gas, and is liable to be broken.

The third method has great limitations to increase the output power of the battery pack, such as increasing the operating air pressure of the fuel cell, increasing the power consumption of the air compressor of the peripheral auxiliary system, and increasing the volume and weight of the air compressor.

The present invention is directed to overcome the above-mentioned drawbacks of the prior art, and to provide a fuel cell which can increase the power by times and operate stably.

The purpose of the invention can be realized by the following technical scheme: a fuel cell comprises a membrane electrode capable of conducting protons, a flow guide polar plate capable of respectively leading in fuel and oxidant, a front end plate, a rear end plate, a 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 front end plate and the rear end plate clamp a plurality of single cells and are connected in series through the pull rod to form a fuel cell, the cooling unit cools the heat generated by the process, the monitoring unit monitors the process data, it is characterized in that the membrane electrode is formed by connecting two independent pole pieces in parallel, the flow guide pole plate is formed by connecting two independent pole pieces in parallel, the front end plate, the rear end plate, the membrane electrodes and the flow guide polar plate are provided with a common air inlet channel and a common air outlet channel at corresponding positions; the membrane electrode is integrally formed; the flow guide polar plate is integrally formed.

The invention adopts the technical proposal, the effective area of the membrane electrode is multiplied, so the power is multiplied, simultaneously, the fuel gas and the oxidant gas are uniformly distributed, the electrochemical reaction speed of each part of the effective area of the membrane electrode is the same,the current density of the membrane electrode is uniform, and the cell runs stably. At present, for large and medium fuel cell stacks with power of 5 to 10 kilowatts or more than 10 kilowatts, the effective area of the membrane electrode of a single cell is about 200 to 400cm²The area of the flow guide polar plate is about 20cm multiplied by 20cm, if the flow guide polar plate and the membrane electrode are designed in parallel, the power can be doubled or multiplied, and the battery pack can achieve the same maturity and stability in operation. If the guide plate and the membrane electrode are respectively designed into a whole, the power density of the fuel cell set is much higher than that of two fuel cell sets which are put together and run in parallel. In addition, the invention also combines the inlet and outlet channels of fuel hydrogen, oxidant air and cooling fluid (deionized water) to carry out common air intake and common air exhaust, thereby leading the fuel cell of the invention to have compact structure and reducing the product cost.

FIG. 1 is a schematic structural diagram of an embodiment of the present invention;

FIG. 2 is a front view of a membrane electrode assembly according to one embodiment of the present invention;

FIG. 3 is a front view of a baffle plate according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a flow guide channel according to an embodiment of the present invention.

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

As shown in the figure, the embodiment of the fuel cell with higher power of the present invention comprises a membrane electrode 1 which is formed by connecting two single pole pieces in parallel and is formed integrally and can conduct protons, a flow guide pole plate 2 which is formed by connecting two single pole pieces in parallel and is formed integrally, a cooling water clamping plate 3, a front end plate 4, a rear end plate 5, a pull rod 6 and an auxiliary monitoring device; the membrane electrode 1 is adhered with catalyst 7 on both sides, the outside of the catalyst is provided with porous carbon paper 8, the guide polar plate 2 is provided with guide grooves 9 which can respectively guide fuel and oxidant, the membrane electrode 1 is clamped by the two guide polar plates 2 to form a single cell, a plurality of single cells are connected in series and are arranged in each single cellA cooling water clamping plate 3 is arranged between the tanks, and a front end plate 4 and a rear end plate 5 are respectively arranged at the front and the rear and are fastened together by a pull rod 6 to form a fuel cell. The corresponding positions of the front end plate, the rear end plate, each membrane electrode and each flow guide polar plate of the fuel cell are respectively provided with a common fuel inlet channel 10J for feeding fuel, oxidant and cooling water, a common oxidant inlet channel 11J, a common cooling water inlet channel 12J, a common fuel outlet channel 10C for feeding fuel, oxidant and cooling water, a common oxidant outlet channel 11C and a common cooling water outlet channel 12C. The effective area of the single cell membrane electrode of the present example was 600cm²The area of the flow guide polar plate is 800cm²The power of the fuel cell is 20 kilowatts, which is higher than that of the existing single-pole plate direct stacked cellThe power is doubled.

Of course, if three, four or even more single-membrane electrode plates are connected in parallel and integrally formed to form the membrane electrode, and three, four or even more single-pole plates are connected in parallel and integrally formed to form the flow guide polar plate, the power of the battery of the invention is improved by three times, four times or even more times than that of the existing single-pole plate direct-stacked battery.

Claims

1. A fuel cell comprises a membrane electrode capable of conducting protons, a flow guide polar plate capable of respectively leading in fuel and oxidant, a front end plate, a rear end plate, a 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 front end plate and the rear end plate clamp a plurality of single cells and are connected in series through the pull rod to form a fuel cell, the cooling unit cools the heat generated by the process, the monitoring unit monitors the process data, it is characterized in that the membrane electrode is formed by connecting two independent pole pieces in parallel, the flow guide pole plate is formed by connecting two independent pole pieces in parallel, the front end plate, the rear end plate, the membrane electrodes and the flow guide polar plate are provided with a common air inlet channel and a common air outlet channel at corresponding positions; the membrane electrode is integrally formed; the flow guide polar plate is integrally formed.