CN107039658B - A low-cost method for mass production of metal plates - Google Patents

Abstract

The invention relates to a method for producing metal pole plates in batches at low cost, which comprises the following steps: (1) taking a metal plate to be processed for surface pretreatment; (2) printing the anti-corrosion layer ink on the metal plate which is obtained in the step (1) and is cleaned, and drying; (3) covering the metal plate with a graphic film with a designed processing pattern, and exposing and developing the ink of the anti-corrosion layer on the metal plate to expose the part to be etched; (4) processing the part to be etched by using an etching solution to etch a corresponding pattern; (5) removing the ink of the anti-corrosion layer, and drying to obtain the metal polar plate processed at one time; (6) and (5) repeating the steps (2) to (5) for 0 time or more than 1 time to obtain the final product metal pole plate. Compared with the prior art, the metal polar plate processed by the method has the advantages of high processing precision, smooth surface, almost no residual stress, short development period, low cost and the like.

Description

A low-cost method for mass production of metal plates

technical field

The invention relates to the development and manufacture of a metal electrode plate of a liquid flow battery and a fuel cell, in particular to a low-cost mass production method of the metal electrode plate.

Background technique

Power generation devices that require fluid participation, such as flow batteries and fuel cells, all include positive and negative electrode materials, electrolyte membranes, and plates for supplying reactive substances and cooling fluids. The cost, performance and durability of the electrode plate greatly affect the commercialization and application of flow batteries and fuel cells.

According to the different valence element systems, flow batteries can be divided into various types such as all-vanadium, all-chromium, all-iron, titanium-iron, chromium-iron, vanadium-cerium, and vanadium-bromine, etc. The solutions of anions and cations with different valence states are respectively introduced into the positive electrode and the negative electrode through the flow channel on the electrode plate, and an electrochemical reaction occurs to charge and discharge. Flow batteries have large positive/negative potential difference, good reversibility, small side reactions, high and stable solubility, easy preparation, low price, environmental friendliness, and low corrosiveness. If the manufacturing cost of key materials and components such as ion exchange membranes and polar plates can be greatly reduced, it will have broad application prospects in the field of energy storage, and is very suitable for large-scale development of renewable energy such as wind energy, solar energy, and tidal energy. and use. It is of great significance in the promotion and application of new energy and the realization of stable power supply.

Fuel cells include direct methanol fuel cells (DMFC), hydrogen/air (oxygen) fuel cells (PEFC), solid oxide fuel cells (SOFC), molten carbonate fuel cells (MCFC), phosphoric acid fuel cells (PAFC), etc. Many types. The fuel cell uses air or pure oxygen as the oxidant and methanol, hydrogen, methane and hydrazine as the fuel. Because of its high energy conversion efficiency, cleanliness and pollution-free, and high power density, it has attracted more and more attention from governments, energy companies and automobile manufacturers in various countries. car engine.

Flow batteries and fuel cells also require the introduction of liquid or gaseous reaction substances into the plates, and in some low-temperature fuel cells, cooling medium is also required. As an important component of flow batteries and fuel cells, the electrode plate occupies more than 60% of its weight and more than 30% of the cost of the entire stack. Therefore, reducing the cost of the electrode plate also has far-reaching significance for the commercialization and application of flow batteries and fuel cells.

The main functions of the plate are: (1) collect the current generated by the reaction and conduct it from the anode of one single cell to the cathode of the next single cell; (2) separate the oxidant and the reducing agent, and evenly distribute it on the surface of the positive and negative electrodes. Distribute the reactants; (3) Discharge the generated products; (4) If necessary, introduce a cooling medium to ensure that the temperature of the stack is stable and evenly distributed; (5) Separate and support each group of electrolytes in a flow battery or fuel cell and catalyst.

In order to meet the above requirements, the plates of flow batteries and fuel cells must have the following requirements: (1) high electrical conductivity to conduct electrons more efficiently; (2) good sealing to block adjacent cells (3) Corrosion resistance; (4) Better flexural strength and compressive strength; (5) Low manufacturing cost. Therefore, the research progress of the electrode plate plays a significant role in improving the specific power density of the power generation device and reducing its manufacturing cost, and has an important impact on the industrialization of the entire flow battery and fuel cell, which makes the material and processing technology of the electrode plate. Research has become a hot spot at home and abroad.

Plate material Bipolar plate materials can be roughly divided into the following categories: pure graphite materials, polymer/conductive filler composite materials, carbon/carbon composite materials, metal materials, etc. Graphite has excellent electrical conductivity and corrosion resistance, but the cost of pure graphite material itself is high, and its brittleness makes it difficult to process, which limits its large-scale application.

Metals are traditionally used as electrode materials due to their good electrical conductivity, high electrochemical activity, and excellent mechanical properties. Bipolar plate metal materials that can be used as flow batteries and fuel cells include: gold, lead, titanium, titanium-based platinum, stainless steel, aluminum, and nickel-based alloys.

Since the distribution of the cathode and anode reactants and the pressure drop have a great influence on the battery, these two factors have become important considerations in the design and processing of the plate flow channel. Generally, the flow channel can be divided into the following four forms: single-channel serpentine flow channel, parallel flow channel, multi-channel snake-shaped flow channel, compound flow channel, etc. The pressure drop of the serpentine flow channel is large, and the dispersion of the fluid is better. The pressure drop of the parallel channel is smaller, but the dispersion of the fluid is not as good as that of the serpentine channel. Multi-serpentine runners and composite runners can combine the advantages of the above two.

Traditional sheet metal forming processes include rolling, stamping, etc. The rolling and stamping process can realize the rolling forming of the plate flow channel, continuous manufacturing, and high production efficiency. In mass production, the mold development cost can be diluted and the comprehensive manufacturing cost can be reduced. However, when rolling, the contact area becomes smaller and the pressure is uneven, which will inevitably cause deformation of the plate surface; the manufacturing accuracy of the roller will affect the final forming accuracy of the pole plate.

The stamping process relies on one or more stampings of a thin sheet of metal from a flat die. Sheet metal stamping has high production efficiency, is easy to realize automation, and can significantly reduce costs in mass production, so it has attracted the attention of many researchers.

In addition to the high precision requirements of the mold and the high manufacturing cost, the rolling and stamping forming process also has other shortcomings, such as: the front and back sides are symmetrical, and cannot be independently designed; it is not suitable for the processing of complex design runners; through holes need secondary processing , cannot be formed at one time; the stress distribution is uneven, and the surface is easily deformed, which causes inconvenience to the subsequent treatment of dense surface corrosion resistance, seal production and assembly.

On the other hand, the forming of metal plates belongs to the category of micro forming technology. When rolling and stamping are used, the ductility of metal is extremely large, the range of deformation area is extremely wide, and the size and details of deformation are relatively small but numerous. Therefore, during the finite element simulation and design of the entire plate forming, a large number of meshes need to be divided, which often takes a long time or even cannot be simulated. Before plate processing, there is still a lot of work to be done in the selection of modeling scheme, the optimization of process parameters, and the design of forming molds, which results in high mold development costs. Therefore, it can be said that in today's increasingly urgent society's demand for new energy, the high time and economic cost of metal plate mold development has become a major bottleneck restricting the development of flow batteries and fuel cells.

In view of the limitations of the above two processes, it is extremely necessary to develop a simple and efficient metal plate forming process with low development and manufacturing costs.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for mass production of metal electrode plates at low cost in order to overcome the above-mentioned defects of the prior art.

The object of the present invention can be realized through the following technical solutions:

A method for mass production of metal electrode plates at low cost, comprising the following steps:

(1) Take the metal plate to be processed for surface pretreatment;

(2) printing the anti-corrosion layer ink on the cleaned metal plate obtained in step (1), and drying;

(3) Take the graphic film with the designed processing pattern to cover the metal plate, and expose and develop the ink of the anti-corrosion layer on the metal plate to expose the part that needs to be etched;

(4) use etching solution to process the part that needs to be etched, and etch out the corresponding graphics;

(5) remove the ink of the anti-corrosion layer, and dry it to obtain the metal pole plate processed at one time;

(6) Repeat steps (2) to (5) 0 or more times to obtain the final product metal electrode plate.

As a preferred embodiment, the material of the metal plate is aluminum, stainless steel, nickel or titanium.

As a preferred embodiment, the process of metal plate pretreatment in step (1) includes brushing, degreasing, descaling, water washing and drying, wherein, for descaling, rolling, vibrating, shot blasting, polishing, chemical Either polished or mechanically polished.

As a preferred embodiment, in step (2), the anti-corrosion layer ink is screen printed on the metal plate, wherein, the screen printing environment is a clean and dust-free space, and the screen is a single wire screen with a mesh number of 100-200, It is available in stainless steel, nylon or polyester.

As a preferred embodiment, the etching solution described in step (4) is an alkaline etching solution or an acidic etching solution, wherein, the alkaline etching solution is mainly sodium hydroxide etchant, and the acidic etching solution The main etchant is one or more of hydrochloric acid, nitric acid, phosphoric acid, hydrofluoric acid, ferric chloride, chromic acid, sulfuric acid, oxalic acid and acetic acid.

As a more preferred embodiment, the etching solution described in the step (4) is an acidic etching solution, and its formula is: hydrochloric acid 65g/L, nitric acid 190g/L, ammonium nitrate 135g/L, phosphoric acid 80g/L, and the rest are to remove Ionized water.

As a preferred embodiment, the etching method in step (4) is vertical etching, the residence time of the etching solution on the metal plate is 5-15min, and the temperature during etching is 45-55°C. In order to ensure the depth of etching and reduce side corrosion, vertical etching can be used, so that the etching solution is evenly distributed on the surface of the metal plate, and the flow rate is consistent everywhere.

As a preferred embodiment, after removing the ink on the anti-corrosion layer in step (5), bake at 50°C to 150°C for 0.5 to 2 hours. After etching, it is also necessary to remove the anti-corrosion protective layer ink. For alkali-resistant ink, use dilute sulfuric acid solution to remove; for acid-resistant ink, use sodium hydroxide solution to remove.

As a preferred embodiment, the groove depth of the electrode plate flow channel on the obtained metal electrode plate is more than 0.4 mm, and the groove depth: groove width=0.7-0.9:1. In order to reduce the flow resistance of fluids such as fuel, oxidant and cooling medium during the electrochemical reaction, the electrode plate flow channel obtained by etching must be deep enough, and generally the groove depth should reach more than 0.4mm. At the same time, in order to ensure a good contact area, a sufficient groove width must also be ensured. Therefore, the ratio of groove depth to width needs to be controlled within a reasonable range. Generally, groove depth: groove width = 0.7 to 0.9:1.

As a preferred embodiment, in step (3), the lines of the ink on the anti-corrosion layer on the graphic film are reserved for the anti-corrosion width compensation. The side etching rate during the etching process also needs to be kept at a very low level. The side etching process is shown in Figure 4. The smaller the side erosion width, the higher the precision of the processed flow channel. Therefore, the width of side etching is a factor that needs to be controlled in the process of metal plate processing. The side etching width is directly related to the etching conditions such as the formula of the etching solution, the flow rate, the spray method of the etching machine, the concentration of the main etching solution, the operating temperature and the use time. The relationship between the width and depth of side etching is shown in Figure 4, the metal plate is marked as 8, and the anti-corrosion layer is marked as 9. If the etching depth obtained through experiments is h and the side etching width is a, then the undercut factor F=a/h can be calculated. If the above etching solution formulation, flow rate, temperature and other etching conditions and etching factor F are fixed, the width of the undercut depends entirely on the etching depth of the metal plate; the deeper the etching depth, the greater the amount of undercut. On the contrary, in order to ensure a high etching depth and flow channel (or ridge) width, it is necessary to reduce the side etching factor F as much as possible, which requires adjustment of various etching conditions, the most important of which is to optimize the etching solution. formula. On the other hand, the line width of the resist layer can be compensated in advance during etching. For example, if the ridge width obtained by etching is L ₁ , the width L ₂ of the resist line must be enlarged and compensated, and its value can be calculated by the following formula:

L ₂ =L ₁ +h×F×2.

Compared with the prior art, the present invention adopts the processing method of photochemical etching, and combines the processes of mechanical drawing, screen printing, exposure, development and chemical etching to manufacture metal plates. Through the corrosion effect of the etching solution on the metal substrate, common channels, positioning holes and flow channels are formed, so as to abandon any mechanical processing process that may produce deformation and internal stress, so the development cycle is short, and the manufacturing cost is extremely high regardless of large or small batches. Low, front and back flow channels can be independently designed, with high machining accuracy, smooth surface, and almost no residual stress; it can realize rapid development and low-cost manufacturing of flow battery and fuel cell plates.

Description of drawings

Fig. 1 is the processing technology flow chart of the present invention;

Fig. 2 is the side sectional view of metal pole plate;

Fig. 3 is the ridge and groove schematic diagram of metal pole plate;

FIG. 4 is a schematic diagram of the occurrence of side erosion during the processing of the metal electrode plate.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

This embodiment provides an example of a metal bipolar plate processing process for the processing of a bipolar plate with air on one side and cooling water on the other side in a hydrogen/air proton exchange membrane fuel cell stack. Those skilled in the art should understand that the present invention can be used for other types of fuel cells and various flow batteries besides hydrogen/air proton exchange membrane fuel cells; in addition to 304 stainless steel, it can also be used for Various other types of stainless steel and nickel, aluminum, titanium and other metals and their alloys.

The anti-corrosion layer ink in the following examples adopts acid-resistant mask ink.

Fig. 1 is the processing technology flow chart of the metal electrode plate of the present invention, according to the structures such as the shared channel etched on the metal electrode plate, the positioning hole and the flow channel, can adopt the etching processing method twice, namely first process the shared channel and the positioning Hole and other through-hole structures, and then process the flow channel, which specifically includes the following steps:

(1) Surface treatment of metal plate

The 304 stainless steel plate is placed on the pretreatment production line, and the steps of brushing, degreasing, descaling, and water washing are carried out according to the steps.

(2) The first screen printing

Use 150 mesh monofilament nylon mesh to print the acid-resistant mask ink on the surface-treated stainless steel plate, and then bake it in an oven at 150°C for 30 minutes until it is completely dry;

(3) First exposure

The stainless steel plate is covered with a pre-prepared transparent film with a common channel, positioning holes and other through-hole patterns, and the ink is exposed in an exposure machine. The ink in the light-transmitting part of the film is exposed, and the rest is masked.

(4) The first development

Immerse the exposed stainless steel plate in the developer solution, and after 10 minutes, the parts of the through holes that need to be etched are exposed, and the parts that do not need to be etched are protected by the unexposed ink (ie, the anti-corrosion layer). .

(5) The first etching

In a vertical etcher, the corresponding metal plate through holes are etched with an etching solution. During the etching process, the operating speed of the etching machine was adjusted to 1 m/min, the temperature was 50 ± 5 °C, and the injection pressure was controlled at 3 bar. The etching time was 15 minutes to obtain the desired vias.

The main formula of this etching solution is as follows: hydrochloric acid 65g/L, nitric acid 190g/L, ammonium nitrate 135g/L, phosphoric acid 80g/L, and the rest are deionized water.

(6) Remove the anti-corrosion layer for the first time

The resist ink was removed with 20% NaOH aqueous solution and dried.

(7) Second screen printing

Similarly, using a 150-mesh monofilament nylon mesh, the acid-resistant masking ink was printed on the stainless steel plate with the through holes etched, and then baked in an oven at 150 °C for 30 minutes until it was completely dry;

(8) Second exposure

A transparent film with patterns such as flow fields is covered on a stainless steel plate to expose the ink.

(9) Second development

The stainless steel plate after the ink has been exposed is immersed in the developing solution, and after 10 minutes, the flow channel that needs to be etched is revealed.

(10) Second etching

In the vertical etching machine, the same process parameters and etching solution as the first etching are used to etch the corresponding flow channels (as shown in Figure 2, it can be seen that the formed metal plate includes ridge a1, ridge b2, flow channel a2 , flow channel b4, sealing groove 5, through hole a6 and through hole b7, etc.). Etching time 8 minutes.

(11) The second time to remove the anti-corrosion layer

The resist ink was removed with 20% NaOH aqueous solution and dried.

(12) Drying

The etched stainless steel plate was placed in an oven and baked at 150 °C for 30 minutes until it was completely dry, and the hydrogen that might have entered the metal lattice was excluded.

As shown in Fig. 3, the stainless steel plate obtained by etching has a thickness of 1.0±0.01mm. The air side flow channel groove depth is 0.5±0.05mm, the groove width is 0.6±0.05mm, and the ridge width is 0.5±0.05mm. The groove depth of the water side channel is 0.3±0.05mm, the groove width is 1.5±0.05mm, and the ridge width is 1.0±0.05mm. After measurement, the air side erosion rate is 0.20, and the water side is 0.33.

The foregoing description of the embodiments is provided to facilitate understanding and use of the invention by those of ordinary skill in the art. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made, and the generic principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should all fall within the protection scope of the present invention.

Claims (1)

1. a method for low-cost mass production of metal pole plate, is characterized in that, comprises the following steps: (1) Take the metal plate to be processed for surface pretreatment; (2) printing the anti-corrosion layer ink on the cleaned metal plate obtained in step (1), and drying; (3) Take the graphic film with the designed processing pattern to cover the metal plate, and expose and develop the ink of the anti-corrosion layer on the metal plate to expose the part that needs to be etched; (4) use etching solution to process the part that needs to be etched, and etch out the corresponding graphics; (5) remove the ink of the anti-corrosion layer, and dry it to obtain the metal pole plate processed at one time; (6) Repeat steps (2) to (5) 0 or more times to obtain the final product metal plate; The etching solution described in the step (4) is an acidic etching solution, and its formula is: hydrochloric acid 65g/L, nitric acid 190g/L, ammonium nitrate 135g/L, phosphoric acid 80g/L, and the rest are deionized water; The etching method in step (4) is vertical etching, the residence time of the etching solution on the metal plate is 5-15min, and the temperature during etching is 45-55°C; The groove depth of the electrode plate flow channel on the obtained metal electrode plate is more than 0.4mm, and the groove depth: groove width=0.7～0.9:1; The material of the metal plate is aluminum, stainless steel, nickel or titanium; The process of metal plate pretreatment in step (1) includes brushing, degreasing, descaling, water washing and drying, wherein the descaling is selected from one of roller polishing, vibrating light, shot peening, polishing, chemical polishing or mechanical polishing. kind; In step (2), the anti-corrosion layer ink is screen printed on the metal plate, wherein the screen printing environment is a clean and dust-free space, and the screen is a single wire screen with a mesh number of 100-200, and its material is stainless steel, nylon or polyester; In step (5), after removing the ink on the anti-corrosion layer, bake at 50°C to 150°C for 0.5 to 2 hours; In step (3), the lines of the anti-corrosion layer ink on the graphic film are reserved for anti-corrosion width compensation.

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