Ultra-thin bipolar plate for fuel cell and fuel cell stack

Abstract

The present invention relates to an ultra-thin bipolar plate for a fuel cell and a fuel cell stack. The ultra-thin bipolar plate for a fuel cell comprises an anode plate and a cathode plate. A fuel gas flow channel is provided on the front of the anode plate, and an oxidizing gas flow channel is provided on the front of the cathode plate. The fuel gas flow channel comprises grooves of at least two different groove depths, and the oxidizing gas flow channel comprises grooves of at least one groove depth. In the power generation active area, when the backs of the anode plate and the cathode plate are interlocked, the grooves of the fuel gas flow channel and the grooves of the oxidizing gas flow channel are completely staggered. The backs of the anode plate and the cathode plate form electrical contact through dispersed conductive support points, and the positions where the two do not contact each other form cavities for the flow of coolant, and the cavities form coolant flow channels of different groove depths. The fuel cell stack comprises the above-mentioned ultra-thin bipolar plates and membrane electrode assemblies stacked in series. Compared with the prior art, the total thickness of the bipolar plates of the present invention is reduced, and the volume power density of the fuel cell is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to an ultra-thin bipolar plate for a fuel cell and a fuel cell stack. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) use clean energy hydrogen as fuel, have high conversion efficiency, and non-polluting reaction products, making them an ideal new energy carrier for the transportation sector. However, due to certain technical bottlenecks in fuel cells, such as insufficient power density and insufficient lifespan, the cost of using fuel cell stacks remains high. In the early days of commercialization of fuel cell vehicles, fuel cell heavy trucks, container logistics vehicles, locomotives, and ships that can achieve fixed-point refueling and are suitable for long-distance transportation have received increasing attention; this has put forward an urgent need for the design, development, and processing and manufacturing of fuel cell stacks with large power generation and high energy conversion efficiency.

[0003] At present, fuel cells used in the domestic transportation sector are in the small-scale application stage, and commercial promotion has just started. Since the volume-to-power density of fuel cells is not high enough, in order to save the limited space on the car, the stacks configured by automobile factories are currently mainly based on the power level of 30-60kW, and must be supplemented with high-power lithium-ion batteries to provide the energy required for the power system to work at high power. This type of fuel cell stack is mainly for application markets such as urban transportation buses, company commuter buses and light logistics vehicles. If, like automobile manufacturers such as Toyota, Honda and Hyundai, high-power fuel cells are used to assemble passenger cars with more cramped space, while keeping costs under control, it is necessary to increase the volume-to-power density of the stack, that is, while improving the power generation performance of the core power generation unit "membrane electrode (MEA)", the volume of the main unit "bipolar plate" that occupies the largest weight and volume in the stack is greatly reduced. Therefore, under the condition that the power generation performance and life of the stack are not affected, effectively reducing the thickness of the bipolar plate will be one of the best ways to increase the volume-to-power density of the stack.

[0004] The volume power density is a key indicator to highlight the technical content of the fuel cell stack. At present, the volume power density of passenger cars of foreign automobile manufacturers such as Toyota, Honda and Hyundai has reached 3.1kW / L, which has certain commercial value. In order to reach the level of 6.0kW / L comparable to traditional internal combustion engines, the work on improving the performance and reducing the volume of fuel cells cannot be stopped at all. Only in this way can fuel cells truly have competitive advantages in power density, unit power cost and other aspects.

[0005] In the existing technology, there are a large number of patents on the preparation of fuel cell bipolar plates using graphite and metal, but there are fewer patents on ultra-thin metal plate stacks.

[0006] CN209016193 invented a hybrid bipolar plate of metal material + non-metallic material. It consists of a stamped anode half plate nested in a preformed cathode half plate. Among them, the anode half plate is a metal plate, and the cathode half plate is a non-metallic material. In this invention, the cathode half plate is very easy to leak after thinning, and the metal half plate can act as a gas barrier to prevent the cathode and anode reaction gases from mutual leakage. Under the nested design of the two half plates and the gas barrier effect of the metal plate, this structure plays a role in reducing the volume of the battery stack. However, the design is relatively complicated, and the combination of two non-similar materials is prone to problems such as increased interface resistance and uneven stress affecting the mechanical strength of non-metallic materials.

[0007] CN201911301960.0 provides a method for preparing an ultra-thin carbon / carbon composite bipolar plate, which uses an ultra-fine carbon fiber mesh as a substrate, injects a composite high carbon residue slurry into the substrate through hot dipping and chemical vapor infiltration, and then undergoes rough rolling, fine rolling, printing and trimming to finally obtain a low-cost ultra-thin high-strength and high-conductivity C / C composite bipolar plate. The bipolar plate is 0.16mm thick (without flow channel), has a bending strength of more than 150MPa, and a bulk conductivity of 300S / cm.

[0008] CN201910260443.7 provides an ultra-thin bipolar plate for vanadium batteries and a preparation method thereof. The invention uses a resin material film as a substrate, sprays a solution made of a conductive functional material onto the double-sided surface of the substrate, and then solidifies it through a hot pressing process to prepare a flow channel. The thickness of the prepared bipolar plate can reach 30-1000μm, the longitudinal conductivity is greater than 80S / cm, and the flexibility is also very good. The substrate film is a polyethylene, polypropylene or polystyrene material with a thickness of 15-115μm. This type of material has high insulation and is a factor that restricts conductivity.

[0009] CN201710931665.8 also uses a similar process to CN201910260443.7 to prepare ultra-thin bipolar plates. However, the substrate plate uses 20-400μm thick metals, such as stainless steel foil, gold foil, silver foil, copper foil and titanium foil. A polymer-based conductive adhesive layer is coated on the metal substrate by screen printing to form an ultra-fine flow channel flow field. The total thickness of the bipolar plate can be reduced to 400μm, the thickness of the conductive coating can reach 100μm, the flow channel ridge width is 100μm, and the groove width is 50μm.

[0010] The ultra-thin bipolar plates of the above inventions all reduce the thickness of the bipolar plates from the material perspective, and none of them leave the application of non-metallic materials. However, due to the demand for mechanical strength, the use of non-metallic materials to achieve the purpose of reducing the thickness of the bipolar plates will affect their vibration resistance, bending resistance and air tightness, and even sacrifice electrical conductivity and thermal conductivity, which is not worth the loss. In addition, the function of the flow field is to transmit cationic and cation reactants and coolants to meet the demand for fluids during normal power generation, especially high current power generation. The depth of the fluid groove cannot be too shallow, which also limits the further thinning of the bipolar plates. Summary of the invention

[0011] The purpose of the present invention is to provide an ultra-thin bipolar plate for a fuel cell and a fuel cell stack in order to overcome the defects of the prior art.

[0012] The purpose of the present invention can be achieved by the following technical solutions:

[0013] A fuel cell ultra-thin bipolar plate comprises an anode plate and a cathode plate, wherein a fuel gas flow channel is provided on the front side of the anode plate, and an oxidizing gas flow channel is provided on the front side of the cathode plate, wherein the fuel gas flow channel comprises grooves of at least two different depths, wherein in a power generation active area, the oxidizing gas flow channel comprises grooves of at least one depth, wherein when the back sides of the anode plate and the cathode plate are interlocked, the grooves of the fuel gas flow channel and the grooves of the oxidizing gas flow channel are completely staggered, wherein the back sides of the anode plate and the cathode plate form electrical contact through dispersed conductive support points, and a cavity for coolant flow is formed at a position where the two do not contact each other, wherein the cavity forms coolant flow channels of different depths.

[0014] Preferably, the conductive support points include horizontal conductive support points and oblique conductive support points, the horizontal conductive support points are parallel to the overall plane of the bipolar plate, and the oblique conductive support points are at a set inclination angle to the overall plane of the bipolar plate.

[0015] Preferably, the horizontal conductive support point is formed at the bottom of the groove with the largest groove depth on the anode plate, and at this position, the bottom of the groove of the anode plate is in contact with the back of the cathode plate to form electrical contact.

[0016] Preferably, the oblique conductive support point is formed at the side wall position of a part of the groove on the anode plate, and the groove side wall of the anode plate at this position is an inclined surface. Correspondingly, the cathode plate is provided with an inclined surface with the same slope. When the cathode plate and the anode plate are buckled together, the inclined surfaces at corresponding positions of the anode plate and the cathode plate fit each other.

[0017] Preferably, the fuel gas flow channel includes a fuel gas distribution area and a fuel gas active area, the fuel gas distribution area connects the fuel gas main inlet hole and the fuel gas active area, the fuel gas distribution area includes a fuel gas guide structure arranged between the anode plate and the cathode plate and a fuel gas distribution structure arranged on the front side of the anode plate, the fuel gas guide structure guides the fuel gas from the fuel gas main inlet hole to the front side of the anode plate, and the fuel gas distribution structure diverts the fuel gas led out of the fuel gas guide structure to the front side of the anode plate and inputs it into the fuel gas active area.

[0018] Preferably, the fuel gas guiding structure includes a fuel gas interlayer flow channel arranged between the anode plate and the cathode plate and a fuel gas guiding hole arranged on the anode plate for guiding the fuel gas to the front side of the anode plate, the gas input end of the fuel gas interlayer flow channel is connected to the fuel gas inlet main hole, the output end of the fuel gas interlayer flow channel is connected to the fuel gas guiding hole, and the fuel gas distribution structure includes a plurality of first zigzag flow channels, and the inlet of the first zigzag flow channel faces the fuel gas guiding hole.

[0019] Preferably, the oxidation gas flow channel includes an oxidation gas distribution area and an oxidation gas active area, the oxidation gas distribution area connects the oxidation gas main inlet hole and the oxidation gas active area, the oxidation gas distribution area includes an oxidation gas guide structure arranged between the anode plate and the cathode plate and an oxidation gas distribution structure arranged on the front side of the cathode plate, the oxidation gas guide structure guides the oxidation gas from the oxidation gas main inlet hole to the front side of the cathode plate, and the oxidation gas distribution structure diverts the oxidation gas led out of the oxidation gas guide structure to the front side of the cathode plate and inputs it into the oxidation gas active area.

[0020] Preferably, the oxidation gas guide structure includes an oxidation gas interlayer flow channel arranged between the anode plate and the cathode plate and an oxidation gas guide hole arranged on the cathode plate for guiding the oxidation gas to the front side of the cathode plate, the gas input end of the oxidation gas interlayer flow channel is connected to the oxidation gas inlet main hole, the output end of the oxidation gas interlayer flow channel is connected to the oxidation gas guide hole, and the oxidation gas distribution structure includes a plurality of second zigzag flow channels, and the inlet of the second zigzag flow channel faces the oxidation gas guide hole.

[0021] Preferably, the groove depth of the coolant flow channel decreases in a step-by-step manner along the coolant flow direction.

[0022] A fuel cell stack comprises bipolar plates and membrane electrode assemblies stacked in series, wherein the bipolar plates are the above-mentioned ultra-thin bipolar plates for fuel cells.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The fuel gas flow channel of the present invention includes grooves of at least two different groove depths, and the oxidizing gas flow channel includes grooves of at least one groove depth. When the back surfaces of the anode plate and the cathode plate are interlocked with each other, the grooves of the fuel gas flow channel and the grooves of the oxidizing gas flow channel are completely staggered to form a tooth-embedded combination, thereby reducing the total thickness of the bipolar plate, thereby greatly improving the volume power density of the fuel cell manufactured using the bipolar plate;

[0025] (2) The anode plate and cathode plate of the present invention are connected by horizontal conductive support points and oblique conductive support points, which reduces the thickness of the bipolar plate while maintaining good functions of circulating coolant, conducting electricity and transferring heat. Unlike the traditional bipolar plate design in which the anode plate and cathode plate are in vertical contact in the stacking direction of the battery, the contact effect of the present invention can also occur on the side wall (i.e., at the conductive support point). Compared with the traditional bipolar plate design, the design of the present invention increases the lateral contact between the cathode and anode plates, strengthens the electrical and thermal conduction capabilities in all directions, and is beneficial to the conduction and heat transfer of the battery stack;

[0026] (3) The fuel gas flow channel and the oxidizing gas flow channel of the present invention are respectively guided to the fuel gas distribution structure and the oxidizing gas distribution structure on the front side of the anode plate and the cathode plate through the fuel gas interlayer flow channel and the oxidizing gas interlayer flow channel between the cathode plate and the anode plate, and this design reduces the thickness of the bipolar plate and makes the gas distribution more uniform;

[0027] (4) The coolant flow channel of the present invention is composed of a cavity for the flow of coolant formed by the anode plate and the cathode plate. The height of the coolant cavity also changes, and the flow of coolant in the coolant cavity is also diverted and staggered, forming a turbulent effect. In this way, it can not only ensure good contact between the coolant and the metal plate, but also allow it to be evenly distributed in various areas of the anode and cathode plates; while improving the heat dissipation effect of the battery stack, it also improves the uniformity of the temperature within the surface. This is particularly effective during high-power power generation. Because the electrical efficiency of the fuel cell decreases during high-power power generation, more waste heat is generated, and at the same time, the problem of uneven heat distribution will become more significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of the anode single plate structure;

[0029] Figure 2 Schematic diagram of cathode single plate structure;

[0030] Figure 3 is a cross-sectional view of a bipolar plate;

[0031] Figure 4 This is a schematic diagram of the direction of the oxidation gas flow path of the anode plate;

[0032] Figure 5 for Figure 4 A partial enlarged view of the middle area A;

[0033] Figure 6 is the conductive support point on the anode channel ( Figure 4 (B) in the middle area;

[0034] Figure 7 This is a schematic diagram of the direction of the oxidation gas flow path of the cathode plate;

[0035] Figure 8 for Figure 7 A partial enlarged view of the middle area C;

[0036] Fig. 9 It is a schematic diagram of the coolant flow channel structure;

[0037] Fig.10 It is a partial enlarged view of the coolant flow channel;

[0038] Fig.11 is a schematic cross-sectional view of a coolant flow channel;

[0039] Fig.12 It is a schematic diagram of the structure of the fuel cell stack of the present invention.

[0040] In the figure, 1 is a fuel cell stack, 2 is a bipolar plate, 3 is an anode plate, 4 is a cathode plate, 5 is a membrane electrode assembly, 6 is a fuel gas inlet hole, 7 is a coolant inlet hole, 8 is an oxidizing gas near hole, 9 is a fuel gas outlet hole, 10 is a positioning hole, 11 is a coolant outlet hole, 12 is an oxidizing gas outlet hole, 13 is a fuel gas distribution area, 14 is a fuel gas sealing groove, 15 is an oxidizing gas distribution area, 16 is an oxidizing gas sealing groove, and 17 is a sealing member , 3-1 is a fuel gas intake boss, 3-2 is a local area of ​​a fuel gas sealing groove, 3-3 is a fuel gas intake branch channel, 3-4 is a fuel gas guide hole, 3-5 is a fuel gas distribution structure, 3-6 is a horizontal conductive support point, 3-7 is an oblique conductive support point, 4-1 is an oxidation gas intake boss, 4-2 is a local area of ​​a oxidation gas sealing groove, 4-3 is an oxidation gas intake branch channel, 4-4 is an oxidation gas guide hole, and 4-5 is an oxidation gas distribution structure. DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Note that the following embodiments are merely illustrative in nature, and the present invention is not intended to limit its applicable objects or uses, and the present invention is not limited to the following embodiments.

[0042] A fuel cell ultra-thin bipolar plate, comprising an anode plate 3 and a cathode plate 4, such as Figure 1 As shown, Figure 2As shown, a fuel gas flow channel is provided on the front side of the anode plate 3, and an oxidizing gas flow channel is provided on the front side of the cathode plate 4. The fuel gas flow channel includes grooves of at least two different depths, and the oxidizing gas flow channel includes grooves of at least one depth. In the power generation active area, when the back sides of the anode plate 3 and the cathode plate 4 are buckled together, the grooves of the fuel gas flow channel and the grooves of the oxidizing gas flow channel are completely staggered, and the back sides of the anode plate 3 and the cathode plate 4 form electrical contact through dispersed conductive support points, and a cavity for the flow of coolant is formed at a position where the two are not in contact, and the cavity forms a coolant flow channel with different groove depths. The anode plate 3 and the cathode plate 4 are respectively provided with a fuel gas inlet main hole 6, a fuel gas outlet main hole 9, an oxidation gas inlet main hole 8, an oxidation gas outlet main hole 12, a coolant inlet main hole 7, and a coolant outlet main hole 11. The fuel gas inlet main hole 6 and the fuel gas outlet main hole 9 are diagonally distributed and connected to the fuel gas flow channel. The oxidation gas inlet main hole 8 and the oxidation gas outlet main hole 12 are diagonally distributed and connected to the oxidation gas flow channel. The fuel gas flow channel is close to the fuel gas inlet main hole 6 as a fuel gas distribution area 13. The fuel gas active area is located in the entire anode plate. 3, the oxidation gas flow channel is close to the oxidation gas inlet main hole 8 as the oxidation gas distribution area 15, the oxidation gas active area is located in the central part of the entire cathode plate 4, the coolant inlet main hole 7 and the coolant outlet main hole 11 are symmetrically distributed at the long side of the gas active area (oxidation gas active area and fuel gas active area), a circle of fuel gas sealing grooves 14 are provided around the anode plate 3, a circle of oxidation gas sealing grooves 16 are provided around the cathode plate 4, and positioning holes 10 are respectively provided at the four corners of the anode plate 3 and the cathode plate 4, and the positioning holes 10 are used for positioning when assembling the battery stack. The oxidation gas reaches the anode side of the membrane electrode assembly 5 through the anode plate 3, and the oxidation gas reaches the cathode side of the membrane electrode assembly 5 through the cathode plate 4; the oxidation gas reaching the membrane electrode assembly 5 and the oxidation gas generate electricity through electrochemical reaction and do work externally. In the present invention, the oxidation gas is hydrogen and the oxidation gas is air.

[0043] Figure 3 The depth of the grooves through which each fluid flows in the bipolar plate 2 is clearly shown. The coolant flows in the cavity formed by the combination of the coolant side of the anode plate 3 and the coolant side of the cathode plate 4, taking away the waste heat generated during the electrochemical reaction, thereby maintaining a stable and efficient working state for the battery stack. Ta is the thickness of the anode plate 3 (including the depth of the oxidizing gas flow channel); Tb is the thickness of the cathode plate 4 (including the depth of the oxidizing gas flow channel); unlike conventional designs, the ingenuity of the present invention lies in that the total thickness T of the bipolar plate 2 satisfies the following formula: T<(Ta+Tb). Figure 4It can be seen that in the embodiment of the present invention, the oxidizing gas flow channel includes at least two grooves with different groove depths, so that the oxidizing gas flow channel has two different groove depths, namely Ha1 and Ha2; the oxidizing gas flow channel is provided with a groove with one groove depth, and then the oxidizing gas flow channel has only one groove depth, namely Hb; the coolant flow channel through which the coolant flows has three depths, namely Hc1, Hc2 and Hc3.

[0044] like Figure 4 and Figure 5 As shown, the fuel gas flow channel includes a fuel gas distribution area 13 and a fuel gas active area. The fuel gas distribution area 13 connects the fuel gas main inlet hole 6 and the fuel gas active area. The fuel gas distribution area 13 includes a fuel gas guide structure arranged between the anode plate 3 and the cathode plate 4 and a fuel gas distribution structure 3-5 arranged on the front of the anode plate 3. The fuel gas guide structure guides the fuel gas from the fuel gas main inlet hole 6 to the front of the anode plate 3. The fuel gas distribution structure 3-5 diverts the fuel gas led out of the fuel gas guide structure to the front of the anode plate 3 and inputs it into the fuel gas active area. Among them, the fuel gas guiding structure includes a fuel gas interlayer flow channel arranged between the anode plate 3 and the cathode plate 4, and a fuel gas guiding hole 3-4 arranged on the anode plate 3 for guiding the fuel gas to the front side of the anode plate 3, the gas input end of the fuel gas interlayer flow channel is connected to the fuel gas inlet main hole 6, the output end of the fuel gas interlayer flow channel is connected to the fuel gas guiding hole 3-4, and the fuel gas distribution structure 3-5 includes a plurality of first zigzag bend flow channels, and the inlet of the first zigzag bend flow channel faces the fuel gas guiding hole 3-4.

[0045] The fuel gas flows in the following way: the fuel gas (hydrogen) enters through the fuel gas inlet main hole 6, and the hydrogen first flows in the irregular cavity between the anode plate and the cathode plate, that is, through the gaps between the multiple fuel gas inlet bosses 3-1 on the coolant side of the anode plate 3 and the gap (fuel gas inlet branch channel 3-3) on the back of the local area 3-2 of the fuel gas sealing groove; then it enters the regular fuel gas distribution structure through several parallel fuel gas guide holes 3-53-4; the fuel gas is diverted into the fuel gas active area after turning two right-angle turns in the fuel gas distribution structure to participate in the electrochemical reaction. The fuel gas flowing out of each fuel gas guide hole 3-53-4 can be diverted into 3 to 4 streams to make the distribution of the fuel gas in its active area more uniform.

[0046] The conductive support points in the present invention include horizontal conductive support points 3-6 and oblique conductive support points 3-7. The horizontal conductive support points 3-6 are parallel to the overall plane of the bipolar plate 2, and the oblique conductive support points 3-7 are at a set inclination angle to the overall plane of the bipolar plate 2. The horizontal conductive support points 3-6 are formed at the bottom of the groove with the largest groove depth in the upper part of the anode plate 3. At this position, the bottom of the groove of the anode plate 3 is bonded to the back of the cathode plate 4 to form an electrical contact. The oblique conductive support points 3-7 are formed at the side wall position of the groove of the upper part of the anode plate 3. At this position, the side wall of the groove of the anode plate 3 is an inclined surface. Correspondingly, the cathode plate 4 is provided with an inclined surface with the same slope. When the cathode plate 4 and the anode plate 3 are buckled, the inclined surfaces at the corresponding positions of the anode plate 3 and the cathode plate 4 are bonded to each other.

[0047] like Figure 6 As shown, in the flow channel of the fuel gas active zone of the anode plate 33, a large number of bottom bosses and side bosses, i.e., conductive support points, are uniformly formed by processes such as stamping and molding. They are further divided into horizontal conductive support points 3-6 perpendicular to the stacking direction of the battery stack and oblique conductive support points 3-7 at a certain angle to the stacking direction of the battery stack. The anode plate 3 is connected to the cathode plate 4 through the above-mentioned conductive support points, which can increase the contact surface in terms of electricity, maintain the operation of the battery stack, especially ensure good electrical conductivity and heat transfer when working under high current density; and in places where the two cathode plates 4 and the anode plate 3 are not in contact, a good cavity for coolant flow can be formed. In terms of mechanics, the conductive support points can enhance the structural strength and thickness stability of the battery stack after assembly, and can also effectively prevent the occurrence of plate misalignment problems during the assembly process and the operation of the battery stack under a vibration environment. It greatly guarantees the stability of the single cell structure, the consistency of performance and the long life.

[0048] like Figure 7 , Figure 8As shown, the oxidation gas flow channel includes an oxidation gas distribution area 15 and an oxidation gas active area. The oxidation gas distribution area 15 connects the oxidation gas main inlet hole 8 and the oxidation gas active area. The oxidation gas distribution area 15 includes an oxidation gas guide structure arranged between the anode plate 3 and the cathode plate 4 and an oxidation gas distribution structure 4-5 arranged on the front side of the cathode plate 4. The oxidation gas guide structure guides the oxidation gas from the oxidation gas main inlet hole 8 to the front side of the cathode plate 4. The oxidation gas distribution structure 4-5 diverts the oxidation gas led out of the oxidation gas guide structure to the front side of the cathode plate 4 and inputs it into the oxidation gas active area. Among them, the oxidizing gas guiding structure includes an oxidizing gas interlayer flow channel arranged between the anode plate 3 and the cathode plate 4, and an oxidizing gas guiding hole 4-4 arranged on the cathode plate 4 for guiding the oxidizing gas to the front side of the cathode plate 4, the gas input end of the oxidizing gas interlayer flow channel is connected to the oxidizing gas inlet main hole 8, the output end of the oxidizing gas interlayer flow channel is connected to the oxidizing gas guiding hole 4-4, and the oxidizing gas distribution structure 4-5 includes a plurality of second zigzag flow channels, and the inlet of the second zigzag flow channel faces the oxidizing gas guiding hole 4-4.

[0049] The oxidizing gas flows in the following manner: the oxidizing gas (oxygen) enters through the oxidizing gas main inlet hole 8, and the oxygen first flows in the irregular cavity between the anode plate and the cathode plate, that is, through the gaps between the multiple oxidizing gas inlet bosses 4-1 on the coolant side of the cathode plate 4 and the gaps (oxidizing gas inlet branch channels 4-3) on the back of the oxidizing gas sealing groove local area 4-2; then it enters the regular oxidizing gas distribution structure 4-5 through several parallel oxidizing gas guide holes 4-4; the oxidizing gas is diverted into the oxidizing gas active area after turning two right-angle turns in the oxidizing gas distribution structure 4-5 to participate in the electrochemical reaction. The oxidizing gas flowing out of each oxidizing gas guide hole 4-4 can be diverted into 3 to 4 streams to make the distribution of the oxidizing gas in its active area more uniform.

[0050] like Fig. 9 , Fig.10 The figure shows a schematic diagram of the flow of the coolant in the bipolar plate 2. The length of the coolant inlet total hole 7 and the coolant outlet total hole 11 covers one side of the active area to make the distribution of the coolant more uniform. After the coolant inlet total hole 7 enters the single cell, it flows along the gap between the fuel gas intake boss 3-1 and the oxidation gas intake boss 4-1, then passes through the area corresponding to the back of the fuel gas sealing groove local area 3-2 and the oxidation gas sealing groove local area 4-2, and finally enters the back of the active area of ​​the cathode plate 4 and the anode plate 3. On the coolant side of the cathode and anode plates 3, the flow channel form of the coolant is inconsistent, the height of the groove also changes, and the flow of the coolant in the coolant cavity is also diverted and staggered, forming a turbulent effect.

[0051] Fig.11 A clearer view of the coolant flow, Fig.11 for Fig.10 A cross-sectional view of area D in the middle. In the figure, the thick black arrow indicates the flow direction of the coolant. It can be seen that after the coolant enters from the coolant inlet main hole 7, it first flows through the cavity with a height of Hc1 formed by the cathode plate 4 and the anode plate 3, then reaches the cavity with a height of Hc2, and finally passes through the cavity with a height of Hc3. Among them, the cross-sectional area of ​​the coolant flow channel gradually increases, while the groove depth of the flow field gradually decreases, satisfying Hc1>Hc2>Hc3.

[0052] like Fig.12 As shown, a fuel cell stack, an oxidation cell stack 1 includes bipolar plates 2 and membrane electrode assemblies 5 stacked in series, the bipolar plates 2 are the above-mentioned oxidation cell ultra-thin bipolar plates 2, and seals 17 are respectively arranged on both sides of the membrane electrode assembly 5. The function of the seals 17 is to prevent the reaction gas (hydrogen and air) from leaking out of the stack (external leakage), and also to prevent hydrogen, air and coolant from leaking into each other (internal leakage).

[0053] In summary, the ultra-thin bipolar plate of the fuel cell of the present invention and the fuel cell stack constituted therefrom mainly include the following components:

[0054] Bipolar plate 2: It is composed of an anode plate 3 and a cathode plate 4 combined by bonding, welding, etc.

[0055] Anode single: A unique structure groove is formed by stamping a metal foil plate, one side of which provides a flow channel for the fuel gas (hydrogen) to enter and exit; the opposite side and a specific side of the cathode plate 4 together form a flow channel for the coolant to enter and exit; and the size and shape of the groove are designed to ensure uniform distribution of the fuel gas and coolant.

[0056] Cathode single: A unique structure groove is formed by stamping a metal foil plate, one side of which provides a flow channel for the entry and exit of the oxidizing gas (air); the opposite side and a specific side of the anode plate 3 together form a flow channel for the entry and exit of the coolant; and the size and shape of the groove are designed to ensure the uniform distribution of the oxidizing gas and the coolant.

[0057] Any conductive metal plate, metal foil, pure graphite plate, expanded graphite plate, metal / graphite composite plate, C / C composite plate, conductive plastic plate, etc. made of iron, stainless steel, nickel, aluminum, gold, platinum and base alloy can be used as the material of the anode plate 3 and cathode plate 4 of this patent. In order to reduce the thickness of the battery stack and improve the power density of the battery stack, the material is selected according to needs, and the thickness range is 0.01mm to 0.1mm.

[0058] Membrane electrode assembly 5: It is composed of a proton exchange membrane and an anode catalyst layer and a cathode catalyst layer coated on both sides, forming a three-in-one power generation unit. The proton exchange membrane separates hydrogen and air, and uses the hydrogen oxidation reaction on the anode side and the oxygen reduction reaction on the cathode side as the negative electrode and positive electrode of the fuel cell, respectively, to generate current and perform electrical work externally.

[0059] Working principle of proton exchange membrane fuel cell:

[0060] Under the action of the anode catalyst, hydrogen undergoes the following reactions:

[0061] H2→2H + +2e -

[0062] The hydrogen ions reach the cathode through the electrolyte, and the electrons reach the cathode through the external circuit. Under the action of the cathode catalyst, they react with oxygen to generate water. The reaction formula is as follows:

[0063] 2H + +2e - +1 / 2O2→H2O

[0064] In summary, the overall reaction in a hydrogen fuel cell is:

[0065] 2H2+O2→H2O

[0066] It is through this cell reaction that the cell outputs electrical energy. As long as the supply of hydrogen and air or oxygen is guaranteed, the fuel cell can continuously generate electrical energy. For proton exchange membrane fuel cells, since they are not constrained by the Carnot cycle, the ideal maximum conversion efficiency under standard conditions is 83%. However, in actual applications, due to various conditions, the actual efficiency of the fuel cell system is about 45% to 60%. Specific embodiment 1

[0068] In this embodiment, the bipolar plate 2 is designed using the scheme in the above specific implementation method and constitutes a fuel cell stack. Specifically, the anode plate 3 and the cathode plate 4 are both made of 0.1mm thick 316L stainless steel plates, which are formed by stamping process. The fuel gas flow channel groove depth Ha1 is 0.3mm, Ha2 is 0.4mm, the oxidation gas flow channel groove depth Hb is 0.3mm, and the total thickness T of the bipolar plate 2 is 0.6mm. Compared with the thickness of the traditional metal bipolar plate 2 of about 1.0mm, the plate thickness of the present invention is reduced by 40%. The stacking thickness of the bipolar plate 2 usually accounts for 40-50% of the total length of the stack; this means that under the performance conditions and test conditions of the same membrane electrode assembly 5 (MEA), the volume power density of the fuel cell will be increased by 15%-20% when the thickness of all components except the bipolar plate 2 (including the front and rear end plates, the current collecting plate, the MEA, etc.) remains unchanged. Specific embodiment 2

[0070] In this embodiment, the bipolar plate 2 is designed using the scheme in the above specific implementation method and constitutes a fuel cell stack. Specifically, the anode plate 3 and the cathode plate 4 are both 0.15mm thick graphite / resin composite plates, which are formed by molding process. The fuel gas flow channel groove depth Ha1 is 0.3mm, Ha2 is 0.4mm, the oxidation gas flow channel groove depth Hb is 0.3mm, and the total thickness T of the bipolar plate 2 is 0.7mm. Compared with the thickness of the traditional graphite composite bipolar plate 2 of about 1.4mm, the plate thickness of the present invention is reduced by 50%. The stacking thickness of the bipolar plate 2 usually accounts for 40-50% of the total length of the stack; this means that under the performance conditions and test conditions of the same membrane electrode assembly 5 (MEA), the volume power density of the fuel cell will be increased by 20%-30% when the thickness of all components (including front and rear end plates, current collecting plates, MEA, etc.) except the bipolar plate 2 remains unchanged.

[0071] The above embodiments are merely examples and do not limit the scope of the present invention. These embodiments can also be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the technical concept of the present invention.

Claims

1. A fuel cell ultra-thin bipolar plate, comprising an anode plate (3) and a cathode plate (4), wherein the front surface of the anode plate (3) is provided with a fuel gas flow channel, and the front surface of the cathode plate (4) is provided with an oxidizing gas flow channel, characterized in that: In the power generation active area, the fuel gas flow channel includes grooves of at least two different groove depths, and the oxidation gas flow channel includes grooves of at least one groove depth. In the power generation active area, when the back sides of the anode plate (3) and the cathode plate (4) are engaged with each other, the grooves of the fuel gas flow channel and the grooves of the oxidation gas flow channel are completely staggered. The back sides of the anode plate (3) and the cathode plate (4) form electrical contact through dispersed conductive support points, and the positions where the two are not in contact form cavities for the flow of coolant, and the cavities form coolant flow channels of different groove depths. The conductive support points include horizontal conductive support points (3-6) and oblique conductive support points (3-7), the horizontal conductive support points (3-6) are parallel to the overall plane of the bipolar plate (2), and the oblique conductive support points (3-7) are at a set inclination angle with the overall plane of the bipolar plate (2); The horizontal conductive support point (3-6) is formed at the bottom of the groove with the largest groove depth in the upper part of the anode plate (3), and at this position, the bottom of the groove of the anode plate (3) is attached to the back side of the cathode plate (4) to form electrical contact; The oblique conductive support point (3-7) is formed at the side wall position of the groove of the upper part of the anode plate (3), and the groove side wall of the anode plate (3) at this position is an inclined surface. Correspondingly, an inclined surface with the same slope is provided on the cathode plate (4). When the cathode plate (4) and the anode plate (3) are buckled, the inclined surfaces at corresponding positions of the anode plate (3) and the cathode plate (4) are in contact with each other. The groove depth of the coolant flow channel decreases in a step-by-step manner along the coolant flow direction.

2. The ultra-thin bipolar plate for a fuel cell according to claim 1, characterized in that: The fuel gas flow channel includes a fuel gas distribution area (13) and a fuel gas active area. The fuel gas distribution area (13) is connected to the fuel gas main inlet hole (6) and the fuel gas active area. The fuel gas distribution area (13) includes a fuel gas guide structure arranged between the anode plate (3) and the cathode plate (4) and a fuel gas distribution structure (3-5) arranged on the front of the anode plate (3). The fuel gas guide structure guides the fuel gas from the fuel gas main inlet hole (6) to the front of the anode plate (3). The fuel gas distribution structure (3-5) diverts the fuel gas led out of the fuel gas guide structure to the front of the anode plate (3) and inputs it into the fuel gas active area.

3. The ultra-thin bipolar plate for a fuel cell according to claim 2, characterized in that: The fuel gas guiding structure comprises a fuel gas interlayer flow channel arranged between the anode plate (3) and the cathode plate (4) and a fuel gas guiding hole (3-4) arranged on the anode plate (3) for guiding the fuel gas to the front of the anode plate (3); the gas input end of the fuel gas interlayer flow channel is connected to the fuel gas inlet main hole (6); the output end of the fuel gas interlayer flow channel is connected to the fuel gas guiding hole (3-4); the fuel gas distribution structure (3-5) comprises a plurality of first zigzag bend flow channels; the inlet of the first zigzag bend flow channel faces the fuel gas guiding hole (3-4).

4. The ultra-thin bipolar plate for a fuel cell according to claim 1, characterized in that: The oxidizing gas flow channel comprises an oxidizing gas distribution area (15) and an oxidizing gas active area. The oxidizing gas distribution area (15) is connected to the oxidizing gas inlet main hole (8) and the oxidizing gas active area. The oxidizing gas distribution area (15) comprises an oxidizing gas guiding structure arranged between the anode plate (3) and the cathode plate (4) and an oxidizing gas distribution structure (4-5) arranged on the front side of the cathode plate (4). The oxidizing gas guiding structure guides the oxidizing gas from the oxidizing gas inlet main hole (8) to the front side of the cathode plate (4). The oxidizing gas distribution structure (4-5) diverts the oxidizing gas led out of the oxidizing gas guiding structure to the front side of the cathode plate (4) and inputs it into the oxidizing gas active area.

5. The ultra-thin bipolar plate for a fuel cell according to claim 4, characterized in that: The oxidation gas guiding structure comprises an oxidation gas sandwich flow channel arranged between the anode plate (3) and the cathode plate (4) and an oxidation gas guiding hole (4-4) arranged on the cathode plate (4) for guiding the oxidation gas to the front side of the cathode plate (4); the gas input end of the oxidation gas sandwich flow channel is connected to the oxidation gas inlet main hole (8); the output end of the oxidation material gas sandwich flow channel is connected to the oxidation gas guiding hole (4-4); the oxidation gas distribution structure (4-5) comprises a plurality of second zigzag flow channels; the inlet of the second zigzag flow channel faces the oxidation gas guiding hole (4-4).

6. A fuel cell stack, comprising bipolar plates (2) and membrane electrode assemblies (5) stacked in series, characterized in that: The bipolar plate (2) is the ultra-thin bipolar plate for a fuel cell as claimed in any one of claims 1 to 5.

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