CN1416184A - Metal compound bipolar plate of fuel cell with proton exchange film - Google Patents

Abstract

The present invention proposes a metal composite bipolar plate for a proton exchange membrane fuel cell. The bipolar plate is composed of two parts, one part is a strip-shaped groove part corresponding to the three-in-one electrode, and two completely symmetrical thin It is made of metal welding, the boss of the strip groove is snake-shaped, and the other part is the metal frame, which is used to support and fix the strip groove part and form the air channel and water channel. The frame and the strip groove part pass through Bonded or welded into one. The invention has the following advantages: 1. The gas channel can ensure the uniform distribution of fuel gas and oxidant gas; 2. The boss with strip groove can ensure the uniform distribution of current and minimize the contact resistance; 3. The water cooling function can ensure Uniform distribution of stack temperature; 4. The bipolar plate is composed of two parts, a strip groove part and a metal frame, which can not only make it have multiple functions but also have sufficient mechanical strength.

Description

Metal Composite Bipolar Plates for Proton Exchange Membrane Fuel Cells

Technical field:

The invention provides a metal composite bipolar plate of a proton exchange membrane fuel cell, which belongs to the technical field of fuel cells.

Background technique:

A fuel cell is a power generating device that can continuously and directly convert chemical energy into electrical energy. When the battery is working, it is necessary to continuously deliver fuel and oxidant to the battery to obtain electrical energy continuously, and at the same time, it is necessary to continuously remove the water produced by the chemical reaction and the heat generated by the chemical reaction. Because proton exchange membrane fuel cells have the characteristics of low operating temperature, fast start-up, high energy conversion efficiency, and environmental friendliness, the development of proton exchange membrane fuel cells has become one of the hotspots of modern scientific and technological research. However, proton exchange membrane fuel cells cannot be commercialized at the current technical level, and one of the most important factors is the bipolar plate. The material of the bipolar plate, the structure of the flow field, and especially its processing cost (at the current technical level, the cost of the bipolar plate accounts for more than 40% to 60% of the cost of the entire fuel cell) all have many technical problems to be solved urgently. At present, there are many researches in this field in the world. The main research directions are: carbon-polymer composite materials and metal-based materials. The research of carbon-polymer composite materials is mainly to mix graphite and polymer materials in a certain way, and then press them into shape. Among them, the graphite material plays a conductive role, while the polymer plays a bonding role. This method can reduce the production cost to a large extent, but the amount of graphite added should not be too large, otherwise it will reduce the stampability of the material, and cause uneven distribution of graphite, which is prone to gas leakage, and makes the conductivity of the material lower than Graphite, which is inherently inferior to metals, is lower. The metal-based bipolar plate has become a research hotspot due to its good electrical conductivity, mechanical strength and low cost. The research on metal-based bipolar plate materials focuses on the simple substitution of materials on the one hand, and on the other hand focuses on the development of new High efficiency and low cost structure. In the prior art, one is to use a titanium metal plate with a thickness of only a few tenths of a millimeter as a base material to prepare a new type of bipolar plate with the function of a cooling plate. First, the thin titanium plate is processed into a groove structure by stamping and other methods, and then the two metal thin plates are welded directly or through an intermediate metal partition by brazing. Grooves on the surface of the metal plates act as gas channels, while the cavity in the middle of the two metal plates forms the channel for the liquid coolant. This method can make the bipolar plate very light and has good heat dissipation. However, the cost of using titanium materials is still relatively high. The other is to use a thin metal plate with a thickness of only 0.2 to 0.3 mm, such as stainless steel (steel grade 310 or 316, of which 310 bipolar plates have better polarization characteristics than 316 bipolar plates) to make bipolar plates Material, the flow field plate is made of square stainless steel and other metal screens, and the air inlet and outlet holes are located on the diagonal of the flow field plate, which can ensure a relatively uniform air flow distribution. The form of the cooling plate is similar to that of a bipolar plate. A metal mesh is sandwiched between two thinner metal plates (thickness is about 0.25mm). The liquid coolant flows through the metal mesh to ensure good fluid distribution. The entire cooling plate The thickness is 3 mm. The third type is a fuel cell bipolar plate composed of three layers of thin metal plates, with a separator in the middle and deflectors with strip grooves on both sides. The grooves on the deflector are continuous from the inlet to the outlet; and the grooves are gradually joined together, so that the cross-sectional area of the grooves gradually decreases from the gas inlet to the outlet, and the strip grooves account for 1% of the entire working area. /2～4/5. The above technologies all improve the performance of the bipolar plate from a certain side, but none of them will reduce the volume and weight of the bipolar plate, improve the utilization rate of the reaction gas, increase the cooling function of the bipolar plate, and improve the stability of the bipolar plate material. Conductivity, reduction of material and production costs, and good assembly are comprehensively considered and included. Therefore, their improvements to the performance and cost of bipolar plates are not comprehensive, and they are only improved in one aspect.

Invention content:

The invention consists of two parts, one part is the strip groove part corresponding to the three-in-one electrode. This part is welded by two thin metal plates with completely symmetrical shapes. The main points are: the boss of the strip groove is in the shape of a snake, and has two characteristics: one is to divide the gas diversion groove into two different parts. Comb-shaped air passages that communicate with each other, one of the two comb-shaped air passages that are not connected to each other is the intake passage and the other is the exhaust passage; the other feature is the serpentine strip grooves on two thin metal plates that are completely symmetrical in shape The boss of the groove forms a snake-shaped cooling water channel; the other part is a metal frame, which is used to support and fix the strip groove part and form an air channel and a water channel. The frame and the strip groove part are integrated by bonding or welding. Elaborate the principle of the present invention and structure below in conjunction with accompanying drawing: in the middle of metal frame 1, be inlaid with two thin metal plates 2 of structure, shape complete symmetry, upper thin metal plate is anode plate, lower thin metal plate is cathode plate, anode plate It is welded into a whole with the cathode plate, round holes 3, 4 are drilled at the two lower corners of the metal frame 1, square holes 7, 8 and round holes 5, 6 are respectively drilled at the two upper corners of the metal frame 1, and round holes 4 , 6 processing grooves and snake-shaped strip grooves form gas channels, square holes 7 and 8 processing grooves are connected with snake-shaped coolant channels between the two pole plates, and are stamped on the anode plate to form a snake The boss with strip-shaped grooves forms a serpentine coolant channel inside the boss with snake-shaped strip grooves, which can strictly control the internal temperature of the fuel cell by controlling the flow and velocity of the coolant, which is beneficial to The temperature and current density of the reaction area are evenly distributed, which improves the performance of the fuel cell. In the present invention, the snake-shaped strip-shaped groove boss divides the gas guide groove into two comb-shaped air passages that are not connected to each other, and the fuel gas and oxidant gas reach one of the bosses through their respective comb-shaped inlet passages. side, and then flow through the diffusion layer to the exhaust channel in the direction perpendicular to the boss. This structure can fully ensure that the gas reaches every corner of the electrode uniformly, and improves the utilization rate of the reaction gas. Since the oxidant gas must pass through the boss of the serpentine channel from the inlet hole to reach the outlet hole on the diagonal side, this gas flow mode is conducive to the discharge of product water on the cathode side of the fuel cell. Metals such as Ag and Au are plated on the raised surfaces of the positive and negative plates, which can effectively improve the anti-corrosion, electrical conductivity or exhaust performance of the two plates. The metal frame 1 can be made of Al, stainless steel and other metals. The role of the metal frame can support and fix the strip-shaped groove part, which improves the shortcoming of the poor mechanical strength of the thin stainless steel plate, can realize the smooth installation of the fuel cell stack, and can form easy-to-process air passages and coolant passages . The present invention will give full play to the following functions of the bipolar plate: 1. The air channel can ensure the uniform distribution of fuel gas and oxidant gas; 2. The boss of the strip groove can ensure the uniform distribution of current and reduce the contact resistance to the greatest extent ; 3. The water cooling function can ensure the uniform distribution of the stack temperature; 4. The bipolar plate is composed of a strip groove part and a metal frame, which can not only make it have multiple functions but also have sufficient mechanical strength.

Fig. 1 is a schematic structural diagram of the anode plate of the present invention.

Fig. 2 is a schematic structural diagram of the cathode plate of the present invention.

Fig. 3 is a sectional view of A-A in Fig. 2 of the present invention.

Example 1:

Austenitic stainless steel with a thickness of 0.15 to 0.5 mm is used to stamp the strip-shaped groove part, and its geometric shape is rectangular. The side length of the rectangle is determined according to the working current of the battery. The larger the current, the larger the area. The method of electric welding is used to weld the two completely symmetrical strip groove parts together, and its thickness can be 1.5-3.5mm according to the needs. The structure is shown in Figure 1. The stamped strip groove structure is also shown in FIG. 1 . Its structural feature is that the start and end of the boss part are located on one side of the short side of the rectangle, that is, the start and end of the coolant channel are located on one side of the short side of the rectangle. The structure is shown in Figure 1. The width of the boss part is 2.0-6.0 mm, and the width of the groove part is 0.5-3.0 mm. Part of the part where the boss of the serpentine groove is in contact with the diffusion layer is partially electroplated or electroless plated with multi-layer plating of Ag and Au. The Ag layer is the bottom layer and the surface layer is Au. The thickness of the silver layer is about 5-10 μm based on the standard of no holes. The gold plating layer is 0.1-05 μm. The other part is a rectangular metal frame as shown in Figure 1. It can be stamped or cast with Al, Ti, Mg and their alloys. The structural feature is that the gas and liquid passages are located on the short sides of the rectangle. The rectangular metal frame and the strip groove part are formed into one by bonding or welding.

Example 2:

Al, Ti and their alloys with a thickness of 0.15-0.5 mm are used to stamp the strip-shaped groove part. Its geometric shape is a rectangle, and the side length of the rectangle is determined according to the working current of the battery. The larger the current, the larger the area. The method of electric welding is used to weld the two completely symmetrical strip groove parts together, and its thickness can be 1.5-3.5mm according to the needs. The structure is shown in Figure 1. The structure of the stamped strip groove part is shown in Figure 1. Its structural feature is that the start and end of the boss part are located on one side of the short side of the rectangle, that is, the start and end of the coolant channel are located on one side of the short side of the rectangle. The structure is shown in Figure 1. The width of the boss part is 2.0-6.0 mm, and the width of the groove part is 0.5-3.0 mm. Part of the part where the boss of the serpentine groove is in contact with the diffusion layer is partially electroplated or chemically plated with multilayer plating of Ag and Au. The Ag layer is the bottom layer and the surface layer is Au, the thickness of the silver layer is about 5-10 μm based on the standard of non-porous, and the gold plating layer is 0.1-05 μm. The other part is a rectangular metal frame, as shown in Figure 1. It can be stamped or cast with Al, Ti, Mg and their alloys. The structural feature is that the gas and liquid passages are arranged on the short side of the rectangle, and the rectangular metal frame and the strip groove part are formed into one by bonding or welding.

Claims (1)

1. the metal compound bipolar plate of a proton exchanging film fuel battery, it is characterized in that: in the middle of the metal edge frame [1], stud with two block structures, shape is the metal sheet [2] of symmetry fully, last metal sheet is a positive plate, following metal sheet is a minus plate, positive plate and minus plate are welded into an integral body, [1] two inferior horn place is drilled with circular hole [3] at metal edge frame, [4], the place, angle is drilled with square hole [7] respectively on metal edge frame [1] two, [8] and circular hole [5], [6], in circular hole [4], [6] locate machined grooves and snake type strip-shaped grooves and constitute gas passage, square hole [7], [8] locating to process groove links to each other with snake type coolant channel between two-plate, on positive plate through punching press, make the strip-shaped grooves boss that is the snake type, constituted the coolant channel of a snake type in the boss inside that is snake type strip-shaped grooves.

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