Bipolar plate with long service life as well as preparation method and application thereof

Abstract

The invention provides a long-life bipolar plate as well as a preparation method and application thereof. The long-life bipolar plate comprises self-repairing material matrix microspheres and self-repairing initiator microspheres, wherein the self-repairing material matrix microspheres and the self-repairing initiator microspheres are pre-buried in the long-life bipolar plate; the self-repairing material matrix microsphere is a compound containing a self-repairing matrix material and polyvinylidene fluoride; the self-repairing initiator microsphere is a compound containing a self-repairing initiator, polyvinylidene fluoride and a high-molecular polymerization catalyst; when the bipolar plate is broken, the self-repairing material matrix microspheres and the self-repairing initiator microspheres are released and contacted, and cracks of the bipolar plate are cured and repaired through polymerization reaction. Self-repairing base material microspheres and initiator microspheres are pre-buried in the long-life bipolar plate, when the bipolar plate cracks, the microspheres are broken to release a repairing material and are polymerized and cured, so that self-repairing of the bipolar plate is realized, the mechanical strength is remarkably improved, the service life is remarkably prolonged, and the maintenance cost is further reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to bipolar plate technology, in particular to a long-life bipolar plate, a preparation method and application thereof. BACKGROUND

[0002] The bipolar plate is one of the core components of an electrochemical device such as a fuel cell or an electrolytic cell, and its performance directly affects the stability and service life of the equipment.

[0003] The traditional bipolar plate uses a single polymer material as a reinforcing agent to provide air tightness and structural strength. During long-term use, the traditional bipolar plate is prone to structural aging, cracking or damage due to factors such as mechanical stress, chemical corrosion or thermal cycling, thereby causing problems such as gas leakage and reduced electrical conductivity, which seriously affect the reliability and durability of the equipment. The bipolar plate is a long-term structural component of the stack, and after assembly, it cannot be completely disassembled and replaced with spare parts. When the component is aged and damaged, it can only be scrapped.

[0004] Therefore, there is an urgent need for a bipolar plate solution that has self-repairing ability, high electrical conductivity and process feasibility. SUMMARY

[0005] The purpose of the present application is to solve the problem of short service life of the traditional bipolar plate, and to provide a preparation method of a long-life bipolar plate. The long-life bipolar plate prepared by the method has self-repairing matrix material microspheres and initiator microspheres embedded inside. When the bipolar plate cracks, the microspheres break and release repair materials and polymerize and solidify, achieving self-repairing of the bipolar plate, significantly improving the mechanical strength and service life, and thereby reducing maintenance costs.

[0006] It should be noted that in the present application, unless otherwise specified, the specific meaning of "including" involved in the composition limitation and description includes both the open-ended "including", "containing" and the like, and the closed "consisting of", "consisting of" and the like.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the present application is: a long-life bipolar plate, comprising:

[0008] Self-repairing material matrix microspheres and self-repairing initiator microspheres embedded in the long-life bipolar plate;

[0009] The self-repairing material matrix microspheres are a composite containing self-repairing matrix material and polyvinylidene fluoride;

[0010] The self-repairing initiator microspheres are a composite containing self-repairing initiator, polyvinylidene fluoride and high molecular polymerization catalyst;

[0011] When the bipolar plate is broken, the self-repairing material matrix microspheres and the self-repairing initiator microspheres are released and contacted, and the crack of the bipolar plate is repaired by solidification through polymerization.

[0012] Further, in the long-life bipolar plate, the total content of the embedded self-repairing material matrix microspheres and self-repairing initiator microspheres is 1.5-2.15% (preferably 1.65-2%) of the total mass of the long-life bipolar plate, and the balance is polyvinylidene fluoride, spherical graphite and graphite worms.

[0013] Further, the mass ratio of the self-repairing material matrix microspheres to the self-repairing initiator microspheres is 1:0.05-0.1.

[0014] Further, the mass ratio of the self-repairing matrix material to polyvinylidene fluoride in the self-repairing material matrix microspheres is 10-15:2-5.

[0015] Further, the self-repairing matrix material is one or more of acrylic acid, aniline and epoxy resin.

[0016] Further, the particle size of the self-repairing matrix material microspheres is 300-800 mesh.

[0017] Further, in the self-repairing initiator microspheres, the mass ratio of the self-repairing initiator, polyvinylidene fluoride and high molecular polymerization catalyst is 10-15:2-5:1-5.

[0018] Further, the self-repairing initiator is one or more of benzoyl peroxide, tetra(3-mercaptopropionic acid) pentaerythritol ester and azobis cyanovaleric acid.

[0019] Further, the high molecular polymerization catalyst is one or more of azobis isobutyronitrile and hexanediamine.

[0020] Further, the particle size of the self-repairing initiator microspheres is 300-800 mesh.

[0021] When the bipolar plate is cracked or broken due to mechanical stress, chemical corrosion or thermal cycling during long-term use, the self-repairing material matrix microspheres and the self-repairing initiator microspheres embedded in the bipolar plate will be broken along with the crack and release the internal functional components. The self-repairing material matrix microspheres contain a composite of self-repairing matrix material and polyvinylidene fluoride, and the self-repairing initiator microspheres contain a composite of self-repairing initiator, polyvinylidene fluoride and high molecular polymerization catalyst. After the two types of components are released, they quickly contact and start the polymerization reaction under the action of the high molecular polymerization catalyst.

[0022] The self-repairing process belongs to the microcapsule self-repairing technology in exogenous self-repairing, and is realized through the following mechanism: micron (300-800 mesh) microsphere materials are uniformly dispersed in the coating resin system of the bipolar plate, and are fully mixed with the curing related components in the system; when a microcrack appears in the bipolar plate and extends to the position of the microspheres, the microsphere shell is broken, and the internal self-repairing components rapidly penetrate to each part of the microcrack under the capillary action; then, the self-repairing matrix material and the initiator complete polymerization and curing under the mediation of the catalyst, to form a dense repair layer, thereby realizing efficient plugging and structure repair of the bipolar plate crack, and restoring the mechanical strength, air tightness and conductivity of the bipolar plate.

[0023] Another object of the present application also discloses a preparation method of the long-life bipolar plate, comprising the following steps:

[0024] Step 1, preparing self-repairing matrix material microspheres

[0025] The self-repairing matrix material and polyvinylidene fluoride are dissolved in an organic solvent, an anionic active agent is added for emulsification, and washing and drying are performed to prepare the self-repairing matrix material microspheres;

[0026] Step 2, preparing self-repairing initiator microspheres

[0027] The self-repairing initiator, polyvinylidene fluoride and a catalyst are dissolved in an organic solvent, an anionic active agent is added for emulsification, and washing and drying are performed to prepare the self-repairing initiator microspheres;

[0028] Step 3, preparing bipolar plate raw materials

[0029] The self-repairing matrix material microspheres, the self-repairing initiator microspheres, polyvinylidene fluoride powder and spherical graphite are blended to prepare a spraying raw material, and the spraying raw material is sprayed onto graphite worms to prepare the bipolar plate raw materials; the spraying raw material is in a powder form, the length of the graphite worms is about 2-6 mm, and the volume of different graphite worms is greatly different, so that it is difficult to realize uniform dispersion if the graphite worms are directly mixed. The spraying process is needed to uniformly attach the powder to the surface of the graphite worms by electrostatic action, so that the uniformity is improved.

[0030] Step 4, pressing the bipolar plate

[0031] The long-life bipolar plate is obtained after roller pressing and high-temperature hot die pressing.

[0032] Further, step 1 of preparing self-repairing matrix material microspheres

[0033] The self-repairing matrix material and polyvinylidene fluoride are dissolved in an organic solvent, and are fully dissolved and stirred until uniform and without solid suspension to prepare a self-repairing matrix organic liquid;

[0034] adding deionized water to the self-repairing matrix organic liquid, then adding cationic active agent for emulsification, and fully stirring to obtain a self-repairing matrix suspension liquid;

[0035] The self-repairing matrix suspension liquid is dried once, then washed with ethanol and deionized water respectively, filtered after washing, and dried twice to obtain self-repairing matrix material microspheres.

[0036] Further, the mass ratio of the self-repairing matrix material, polyvinylidene fluoride, and cationic active agent in step 1 is 10-15:2-5:0.2-0.5.

[0037] Further, the mass ratio of the self-repairing matrix material, polyvinylidene fluoride, organic solvent, cationic active agent, and deionized water in step 1 is 10-15:2-5:150-200:0.2-0.5:200-300. The deionized water acts as a dispersant, and the emulsion is an organic substance that is not soluble in water but dispersed into small droplets with the help of water.

[0038] Further, the self-repairing matrix material in step 1 is one or more of acrylic acid, aniline, and epoxy resin.

[0039] Further, the cationic active agent is sodium chloride hexadecyl trimethyl and / or triethanolamine stearate. The cationic active agent is an additive for preparing self-repairing matrix material microspheres and has the function of emulsifying the self-repairing matrix material, which will not ultimately remain in the finished bipolar plate.

[0040] Further, the organic solvent in step 1 is one or more of N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMF), and tetrahydrofuran (THF).

[0041] Further, the water content after the first drying in step 1 is 3-10%, and the water content after the second drying is below 3%.

[0042] Further, the particle size of the self-repairing matrix material microspheres in step 1 is 300-800 mesh.

[0043] Further, the self-repairing initiator microspheres are prepared in step 2

[0044] The self-repairing initiator is mixed with polyvinylidene fluoride and added to an organic solvent for full dissolution, then a high-molecular polymerization catalyst is added and stirred uniformly to prepare a self-repairing initiator organic liquid;

[0045] Deionized water is added to the self-repairing initiator organic liquid, then anionic active agent is added for emulsification, and fully stirred to obtain a self-repairing initiator suspension liquid;

[0046] The self-repairing initiator suspension is dried once, then washed with ethanol and deionized water respectively, filtered after washing, and dried twice to obtain self-repairing initiator microspheres.

[0047] Further, the mass ratio of the self-repairing initiator, polyvinylidene fluoride, high polymer polymerization catalyst, and anionic active agent in step 2 is 10-15:2-5:1-5:7-10.

[0048] Further, the mass ratio of the self-repairing initiator, polyvinylidene fluoride, high polymer polymerization catalyst, organic solvent, anionic active agent, and deionized water in step 2 is 10-15:2-5:1-5:150-200:7-10:200-300. Deionized water is used as a dispersant, and the emulsion is an organic substance that is not soluble in water but dispersed into small droplets with the help of water.

[0049] Further, the self-repairing initiator in step 2 is one or more of benzoyl peroxide, tetra(3-mercaptopropionic acid) pentaerythritol ester, and azobis cyanovaleric acid.

[0050] Further, the high polymer polymerization catalyst in step 2 is one or more of azobis isobutyronitrile and hexanediamine.

[0051] Further, the anionic active agent in step 2 is sodium dodecyl sulfate and / or ammonium dodecylbenzenesulfonate.

[0052] Further, the organic solvent in step 2 is one or more of N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMF), and tetrahydrofuran (THF).

[0053] Further, the particle size of the self-repairing initiator microspheres in step 2 is 300-800 mesh.

[0054] Further, the mass ratio of the self-repairing matrix material microspheres, self-repairing initiator microspheres, polyvinylidene fluoride, and spherical graphite in the spraying raw material in step 3 is 1:0.05-0.1:40-50:10-12.

[0055] Further, the mass ratio of the spraying raw material to the sprayed graphite worm in step 3 is 1:5.5-6.5.

[0056] Further, the preparation steps of the bipolar plate raw material in step 3 are as follows: the self-repairing matrix material microspheres, self-repairing initiator microspheres, polyvinylidene fluoride powder, and graphite worm are blended to form a spraying raw material; the flake graphite is expanded into graphite worm at high temperature, and the expanded graphite worm is introduced into a cyclone tower using a blower, and the spraying raw material is sprayed into the front end of the cyclone tower according to the mass ratio to make the graphite worm and the spraying raw material fully mixed and fall into the bin.

[0057] Further, the high-temperature temperature in step 3 is 800-950 DEG C.

[0058] Further, the pressing bipolar plate in step 4 is as follows: adjusting the discharge height of the stock bin according to the required density of the bipolar plate to be prepared, and pressing into a bipolar plate green plate by using a multi-stage roller, and then cutting the bipolar plate green plate after high-temperature hot pressing to obtain the long-life bipolar plate.

[0059] Further, the high-temperature hot pressing temperature in step 4 is 130-180 DEG C.

[0060] Another object of the present application also discloses an application of the long-life bipolar plate in the field of liquid flow batteries and fuel cells.

[0061] The working principle of the long-life bipolar plate of the present application is that the self-repairing matrix material microspheres and the self-repairing initiator microspheres are pre-embedded in the bipolar plate.

[0062] The self-repairing matrix material microspheres comprise a composite of self-repairing matrix material and polyvinylidene fluoride.

[0063] The self-repairing initiator microspheres comprise a composite of self-repairing initiator, polyvinylidene fluoride and high-molecular polymerization catalyst.

[0064] When the bipolar plate is broken, the self-repairing matrix material microspheres and the self-repairing initiator microspheres are released and contacted, and the cracks are repaired by polymerization reaction.

[0065] The long-life bipolar plate, the preparation method and the application thereof have the following advantages compared with the prior art:

[0066] 1) The long-life bipolar plate of the present application has the self-repairing matrix material microspheres and the self-repairing initiator microspheres pre-embedded therein, when cracks or aging rupture occurs in the bipolar plate during long-term use, the microspheres are broken to release the repair materials, which are rapidly polymerized and solidified under the action of the catalyst, so that the cracks can be effectively repaired, the service life of the bipolar plate is significantly improved, and the replacement and maintenance costs are reduced.

[0067] 2) The microsphere structure formed by the self-repairing material (such as acrylic acid, epoxy resin, etc.) and polyvinylidene fluoride not only provides the repair function, but also enhances the mechanical strength and corrosion resistance of the bipolar plate, so that the bipolar plate can maintain stable performance under harsh working conditions of the fuel cell.

[0068] 3) The preparation process of the long-life bipolar plate of the present application adopts conventional methods such as solution mixing, emulsification and blending, and the equipment requirement is low, so that the industrial production is easy. The types of the self-repairing matrix material and the initiator can be flexibly adjusted according to the requirements, so that the present application can be easily expanded to the self-repairing field of other types of bipolar plates or composite materials, and has wide technical adaptability.

[0069] 4) The emulsification-drying method for preparing the microspheres is simple and controllable, the microspheres are uniform in size, and the microspheres are easy to combine with other materials (such as graphite worms, polyvinylidene fluoride) to ensure the consistency of the overall performance of the bipolar plate.

[0070] The materials (such as graphite worms, polyvinylidene fluoride) are uniformly mixed to ensure the consistency of the overall performance of the bipolar plate. The spraying combined with the rolling forming process can be adapted to large-scale production, and the preparation efficiency is improved.

[0071] The long-life bipolar plate has good application prospect and large-scale popularization potential in the fields of flow batteries and fuel cells. BRIEF DESCRIPTION OF DRAWINGS

[0072] Figure 1 Scanning electron micrograph of free radical matrix particles;

[0073] Figure 2 Scanning electron micrograph of self-repairing initiator particles. DETAILED DESCRIPTION

[0074] Hereinafter, the present application will be further described with reference to examples. The description of the technical features described below is based on representative embodiments, specific examples of the present application, but the present application is not limited to these embodiments, specific examples. It should be noted that:

[0075] Unless otherwise specified, the units used in the specification are international standard units, and the numerical values and numerical value ranges appearing in the present application should be understood to include systematic errors that are inevitable in industrial production.

[0076] In the specification, the numerical range represented by "numerical value A to numerical value B" means a range including the end point values A and B.

[0077] In the specification, the numerical range represented by "above" or "below" means a numerical range including the number.

[0078] In the specification, the meaning represented by "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0079] In the specification, "optional" or "optionally" means that some substances, components, steps, applied conditions, etc. are used or not used.

[0080] In the specification, when "room temperature" or "room temperature" is used, the temperature can be 15-25 DEG C.

[0081] In the specification, the reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained by purchase.

[0082] Example 1

[0083] The embodiment provides a preparation method of a long-life bipolar plate, comprising the following steps:

[0084] Step 1, preparation of self-repairing matrix material microspheres

[0085] After mixing acrylic acid and polyvinylidene fluoride, the mixture is added into N-methyl pyrrolidone (NMP) to be fully dissolved and stirred to be uniform without solid suspension to prepare self-repairing matrix organic liquid.

[0086] Deionized water is added into the self-repairing matrix organic liquid, and sodium chloride emulsion is further added to fully stir to obtain self-repairing matrix suspension liquid.

[0087] The mass ratio of the self-repairing matrix material (acrylic acid), polyvinylidene fluoride, organic solvent (N-methyl pyrrolidone), cationic active agent (sodium chloride emulsion) and deionized water is 15:5:180:0.5:200.

[0088] The self-repairing matrix suspension liquid is preliminarily dried at 45 DEG C for 2 hours to reduce the water content to 10%, and then washed and filtered by using ethanol and deionized water respectively, and the filtered sample is dried at 70 DEG C again for 3 hours to obtain self-repairing matrix material microspheres with water content less than 0.5%.

[0089] Step 2, preparation of self-repairing initiator microspheres

[0090] After mixing tetra (3-mercaptopropionic acid) pentaerythritol ester and polyvinylidene fluoride, the mixture is added into N,N-dimethylamide (DMF) to be fully dissolved, and then azobisisobutyronitrile is added into the organic solution to be stirred to be uniform to prepare self-repairing initiator organic liquid.

[0091] Deionized water and sodium dodecyl sulfate emulsion are added into the self-repairing initiator organic liquid, and then fully stirred to obtain self-repairing initiator suspension liquid.

[0092] The mass ratio of the self-repairing initiator (tetra (3-mercaptopropionic acid) pentaerythritol ester), polyvinylidene fluoride, high polymerization catalyst (azobisisobutyronitrile), organic solvent (N,N-dimethylamide), anion active agent (sodium dodecyl sulfate) and deionized water is 12:2:1:200:7:200. The self-repairing initiator suspension liquid is preliminarily dried at 45 DEG C for 2 hours to reduce the water content to 10%, and then washed and filtered by using ethanol and deionized water respectively, and the filtered sample is dried at 70 DEG C again for 3 hours to obtain self-repairing initiator microspheres with water content less than 0.5%.

[0093] Step 3, the self-repairing matrix material microspheres and the self-repairing initiator microspheres are added to the polyvinylidene fluoride powder. The mixed polyvinylidene fluoride powder and the spherical graphite are blended to prepare a spraying raw material. The mass ratio of the self-repairing matrix material microspheres, the self-repairing initiator microspheres, the polyvinylidene fluoride and the spherical graphite is 1:0.1:40:10.

[0094] The flake graphite is expanded into graphite worms at high temperature, the expanded graphite worms are introduced into a cyclone tower by using a blower, and the spraying raw material is sprayed into the front end of the cyclone tower at a mass ratio of 1:5.8 to make the graphite worms and the spraying raw material fully mixed and fall into a bin.

[0095] Step 4, the discharge height of the bin is adjusted according to the required density of the prepared bipolar plate, and the bipolar plate green plate is pressed by using a multi-stage roller to obtain the long-life bipolar plate.

[0096] Figure 1 It is a scanning electron microscope image of the free radical matrix particles. The free radical matrix material is completely wrapped inside the PVDF particles, and the excess components are completely removed by organic solvents and deionized water.

[0097] Figure 2 It is a scanning electron microscope image of the self-repairing initiator particles. The self-repairing initiator particles are completely wrapped inside the PVDF particles, and the excess components are completely removed by organic solvents and deionized water.

[0098] Example 2

[0099] The embodiment provides a preparation method of a long-life bipolar plate, including the following steps:

[0100] Step 1, preparation of self-repairing matrix material microspheres

[0101] After the aniline and the polyvinylidene fluoride are mixed, they are added to N,N-dimethylformamide (DMF) to be fully dissolved and stirred until uniform and no solid suspension is formed to prepare a self-repairing matrix organic liquid.

[0102] Deionized water is added to the self-repairing matrix organic liquid, and sodium chloride hexadecyl trimethyl emulsion is added, and the self-repairing matrix suspension liquid is obtained by fully stirring.

[0103] The self-repairing matrix suspension liquid is initially dried at 45°C for 2 hours to reduce the water content to 10%, and then washed and filtered by using ethanol and deionized water, respectively. The sample after filtration is dried at 70°C for 3 hours again to obtain self-repairing matrix material microspheres with a water content of less than 0.5%.

[0104] The mass ratio of the self-repairing base material (aniline), polyvinylidene fluoride, organic solvent (N, N-dimethylamide), cationic active agent (sodium chloride hexadecyl trimethyl), and deionized water is 15:5:200:0.5:200

[0105] Step 2, preparation of self-repairing initiator microspheres

[0106] After mixing azobis cyanovaleric acid with polyvinylidene fluoride, N, N-dimethylamide (DMF) is added to fully dissolve the mixture, and azobis isobutyronitrile is then added to the dissolved organic solution and stirred until uniform to prepare a self-repairing initiator organic liquid.

[0107] Deionized water and sodium dodecyl sulfate are added to the self-repairing initiator organic liquid for emulsification. After sufficient stirring, a self-repairing initiator suspension is obtained.

[0108] The self-repairing initiator suspension is initially dried at 45°C for 2 hours to reduce the water content to 10%, and then washed and filtered using ethanol and deionized water. The filtered sample is then dried at 70°C for 3 hours to obtain self-repairing initiator microspheres with a water content of less than 0.5%.

[0109] The mass ratio of the self-repairing initiator (azobis cyanovaleric acid), polyvinylidene fluoride, high molecular polymerization catalyst (azobis isobutyronitrile), organic solvent (N, N-dimethylamide), anionic active agent (sodium dodecyl sulfate), and deionized water is 10:2:1:200:8:200.

[0110] Step 3, the self-repairing base material microspheres and the self-repairing initiator microspheres are added to polyvinylidene fluoride powder. The mixed microspheres and polyvinylidene fluoride powder are blended with spherical graphite to prepare a spraying raw material. The mass ratio of the self-repairing base material microspheres, the self-repairing initiator microspheres, polyvinylidene fluoride, and spherical graphite is 1:0.1:40:10.

[0111] The flake graphite is expanded into graphite worms at high temperature, and the expanded graphite worms are introduced into a cyclone tower using a blower. The spraying raw material is sprayed into the front end of the cyclone tower according to the required mass ratio to fully mix the graphite worms and the spraying raw material and fall into the hopper.

[0112] Step 4, the hopper discharge height is adjusted according to the required density of the prepared bipolar plate, and a bipolar plate green sheet is pressed using multiple rollers. The bipolar plate green sheet is cut after hot molding at 150°C to obtain the long-life bipolar plate.

[0113] Example 3

[0114] The present embodiment provides a preparation method of a long-life bipolar plate, including the following steps:

[0115] Step 1, preparation of self-repairing base material microspheres

[0116] The epoxy resin and polyvinylidene fluoride are mixed and added to N-methyl pyrrolidone (NMP) to fully dissolve and stir to uniformity without solid suspension to prepare a self-repairing matrix organic liquid.

[0117] Deionized water is added to the self-repairing matrix organic liquid, and triethanolamine stearate is emulsified to fully stir to obtain a self-repairing matrix suspension liquid.

[0118] The self-repairing matrix suspension liquid is initially dried at 45°C for 2 hours to reduce the water content to 10%, and is washed and filtered using ethanol and deionized water, respectively. The filtered sample is again dried at 70°C for 3 hours to obtain self-repairing matrix material microspheres with a water content of less than 0.5%.

[0119] The mass ratio of the self-repairing matrix material (epoxy resin), polyvinylidene fluoride, organic solvent (N-methyl pyrrolidone), cationic active agent (triethanolamine stearate), and deionized water is 15:5:200:0.5:200.

[0120] Step 2, preparation of self-repairing initiator microspheres

[0121] Tetra(3-mercaptopropionic acid) pentaerythritol ester and polyvinylidene fluoride are mixed and added to N-methyl pyrrolidone (NMP) to fully dissolve, and hexamethylenediamine is added to the dissolved organic solution and stirred to uniformity to prepare a self-repairing initiator organic liquid.

[0122] Deionized water and sodium dodecyl sulfate are added to the self-repairing initiator organic liquid to emulsify. The self-repairing initiator suspension liquid is fully stirred to obtain a self-repairing initiator suspension liquid.

[0123] The self-repairing initiator suspension liquid is initially dried at 45°C for 2 hours to reduce the water content to 10%, and is washed and filtered using ethanol and deionized water, respectively. The filtered sample is again dried at 70°C for 3 hours to obtain self-repairing initiator microspheres with a water content of less than 0.5%.

[0124] The mass ratio of the self-repairing initiator (tetra(3-mercaptopropionic acid) pentaerythritol ester), polyvinylidene fluoride, high molecular polymerization catalyst (hexamethylenediamine), organic solvent (N-methyl pyrrolidone), anionic active agent (sodium dodecyl sulfate), and deionized water is 10:5:1:200:7:200.

[0125] Step 3, the self-repairing matrix material microspheres and the self-repairing initiator microspheres are added to polyvinylidene fluoride powder. The mixed microspheres and polyvinylidene fluoride powder are blended with spherical graphite to prepare a spray coating raw material. The mass ratio of the self-repairing matrix material microspheres, the self-repairing initiator microspheres, polyvinylidene fluoride, and spherical graphite is 1:0.1:40:10.

[0126] The flake graphite is expanded into graphite worms at high temperature, the expanded graphite worms are introduced into a cyclone tower by using a blower, and the spraying raw material is sprayed into the front end of the cyclone tower according to the required mass ratio, so that the graphite worms and the spraying raw material are fully mixed and fall into the bin.

[0127] Step 4, adjust the discharge height of the bin according to the required density of the prepared bipolar plate, and press the bipolar plate green plate into the bipolar plate by using multi-stage rolling.

[0128] Comparative Example 1

[0129] The present comparative example provides a preparation method of a long-life bipolar plate, comprising the following steps:

[0130] Step 1, add graphite worms to polyvinylidene fluoride powder, and the mass ratio of polyvinylidene fluoride to graphite worms is 4:1. The mixed polyvinylidene fluoride powder and graphite worms are blended to form a spraying raw material.

[0131] The flake graphite is expanded into graphite worms at high temperature, the expanded graphite worms are introduced into a cyclone tower by using a blower, and the spraying raw material is sprayed into the front end of the cyclone tower according to the required mass ratio, so that the graphite worms and the spraying raw material are fully mixed and fall into the bin.

[0132] Step 2, adjust the discharge height of the bin according to the required density of the prepared bipolar plate, and press the bipolar plate green plate into the bipolar plate by using multi-stage rolling.

[0133] The long-life bipolar plate of Example 1 and the bipolar plate of Comparative Example 1 are respectively tested, and the test method and test results are as follows: the sample of Example 1 and the sample of Comparative Example 1 are cut into 10*100mm strip samples and placed in a hydrochloric acid system full vanadium liquid flow battery electrolyte (electrolyte pH range 1.4-1.6, V ion concentration 1.5-1.6mol / L, temperature 45℃) for 36h. The above soaked samples are taken out, first washed with secondary water, then the surface is wiped with alcohol, then a 70℃ oven is used for drying for 30min, then the temperature is reduced to room temperature to make a tensile strength test sample.

[0134] The tensile test results are shown in Tables 1-4:

[0135] Table 1, tensile strength of Example 1 before soaking

[0136] Sample width Sample thickness Maximum force Tensile strength mm mm N Mpa 1st 10.31 0.797 255.23 31.06 2nd 10.31 0.799 226.08 27.45 3rd 10.36 0.8 250.18 30.18 4th 10.31 0.799 243.25 29.53 5th 10.28 0.799 240.51 29.28 6th 10.44 0.809 296.65 35.12 7th 10.26 0.808 287.67 34.7 8th 10.34 0.812 276.83 32.97 9th 10.44 0.812 247.55 29.2 10th 10.26 0.807 282.38 34.1

[0137] Table 2, tensile strength of Example 1 after soaking

[0138] Sample width Sample thickness Maximum force Tensile strength mm mm N Mpa 1st 10.34 0.82 231.33 27.28 2nd 10.35 0.818 247.45 29.23 3rd 10.44 0.81 247.94 29.32 4th 10.35 0.821 243 28.6 5th 10.45 0.814 227.55 26.75 6th 10.4 0.824 250.75 29.26 7th 10.38 0.82 230.85 27.12 8th 10.45 0.824 252.1 29.28 9th 10.43 0.821 242.56 28.33 10th 10.35 0.822 241.71 28.41

[0139] Table 3, tensile strength of Comparative Example 1 before soaking

[0140] Sample width Sample thickness Maximum force Tensile strength mm mm N Mpa 1st 10.16 0.819 255.8 30.74 2nd 10.17 0.819 233.94 28.09 3rd 10.2 0.82 261.95 31.32 4th 10.15 0.82 264.39 31.77 5th 10.25 0.82 267.86 31.87 6th 10.21 0.831 236.48 27.87 7th 10.2 0.827 225.34 26.71 8th 10.21 0.827 217.2 25.72 9th 10.26 0.826 238 28.08 10th 10.23 0.829 230.07 27.13

[0141] Table 4, tensile strength after immersion of Comparative Example 1

[0142] Sample width Sample thickness Maximum force Tensile strength mm mm N Mpa 1st 10.25 0.788 215.29 26.65 2nd 10.21 0.789 212.42 26.37 3rd 10.28 0.792 204.21 25.08 4th 10.28 0.792 188.56 23.16 5th 10.21 0.79 190.17 23.58 6th 10.31 0.796 200 24.37 7th 10.24 0.797 192.91 23.64 8th 10.2 0.797 200.93 24.72 9th 10.2 0.798 179.44 22.04 10th Sample width Sample thickness Maximum force Tensile strength mm mm Mpa 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 10.22 0.8 169.67 20.75

[0143] As can be seen from Tables 1-4, the tensile strength of the bipolar plate of Example 1, to which the self-repairing material is added, decreases less after long-term electrolyte corrosion, while part of the electrolyte penetrates into the layered structure of the bipolar plate after immersion of the bipolar plate of Comparative Example 1, and the linking ability of the bipolar plate decreases.

[0144] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A long-life bipolar plate, characterized in that, include: Self-healing material matrix microspheres and self-healing initiator microspheres pre-embedded in long-life bipolar plates; The self-healing material matrix microspheres are a composite containing a self-healing matrix material and polyvinylidene fluoride; The self-healing initiator microspheres are a composite containing a self-healing initiator, polyvinylidene fluoride, and a polymer polymerization catalyst; When the bipolar plate breaks, the self-healing material matrix microspheres and the self-healing initiator microspheres are released and come into contact, and the bipolar plate cracks are repaired through polymerization reaction.

2. The long-life bipolar plate according to claim 1, characterized in that, The total content of the pre-embedded self-healing material matrix microspheres and self-healing initiator microspheres is 1.5% to 2.15% of the total mass of the long-life bipolar plate; And / or, the mass ratio of the self-healing material matrix microspheres to the self-healing initiator microspheres is 1:0.05 to 0.

1.

3. The long-life bipolar plate according to claim 1, characterized in that, The mass ratio of the self-healing matrix material to polyvinylidene fluoride in the self-healing matrix microspheres is 10-15:2-5; And / or, the self-healing matrix material is one or more of acrylic acid, aniline, and epoxy resin.

4. The long-life bipolar plate according to claim 1, characterized in that, In the self-healing initiator microspheres, the mass ratio of the self-healing initiator, polyvinylidene fluoride, and polymer polymerization catalyst is 10-15:2-5:1-5; And / or, the self-healing initiator is one or more of benzoyl peroxide, pentaerythritol tetrakis(3-mercaptopropionic acid) and azodicyanovalerate; And / or, the polymer polymerization catalyst is one or more of azobisisobutyronitrile and hexamethylenediamine.

5. A method for preparing a long-life bipolar plate according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Preparation of self-healing matrix material microspheres: Self-healing matrix material and polyvinylidene fluoride were dissolved in an organic solvent, emulsified with a cationic surfactant, and then washed and dried to prepare self-healing matrix material microspheres. Step 2: Preparation of self-healing initiator microspheres: Self-healing initiator, polyvinylidene fluoride and catalyst were dissolved in an organic solvent, emulsified with an anionic surfactant, washed and dried to prepare self-healing initiator microspheres; Step 3: Preparation of bipolar plate raw materials: Self-healing matrix material microspheres, self-healing initiator microspheres, polyvinylidene fluoride powder and spherical graphite are blended to prepare a spraying material, and the spraying material is sprayed onto graphite worms to prepare bipolar plate material. Step 4: Press the bipolar plate: The long-life bipolar plate is obtained by roller pressing and high-temperature hot molding.

6. The method for preparing a long-life bipolar plate according to claim 5, characterized in that, The mass ratio of the self-healing matrix material, polyvinylidene fluoride, and cationic surfactant mentioned in step 1 is 10-15: 2-5: 0.2-0.

5. And / or, the self-healing matrix material described in step 1 is one or more of acrylic acid, aniline and epoxy resin; And / or, the cationic surfactant is sodium hexadecyltrimethyl chloride and / or triethanolamine stearate; And / or, the organic solvent in step 1 is one or more of N-methylpyrrolidone, N,N-dimethylamide and tetrahydrofuran.

7. The method for preparing a long-life bipolar plate according to claim 5, characterized in that, The mass ratio of the self-healing initiator, polyvinylidene fluoride, polymer polymerization catalyst, and anionic surfactant in step 2 is 10-15:2-5:1-5:7-10; And / or, the self-healing initiator in step 2 is one or more of benzoyl peroxide, pentaerythritol tetrakis(3-mercaptopropionic acid) and azodicyanovalerate; And / or, the polymer polymerization catalyst in step 2 is one or more of azobisisobutyronitrile and hexamethylenediamine; And / or, the anionic surfactant in step 2 is sodium dodecyl sulfate and / or ammonium dodecylbenzenesulfonate; And / or, the organic solvent in step 2 is one or more of N-methylpyrrolidone, N,N-dimethylamide and tetrahydrofuran.

8. The method for preparing a long-life bipolar plate according to claim 5, characterized in that, In step 3, the mass ratio of the self-healing matrix material microspheres, self-healing initiator microspheres, polyvinylidene fluoride and spherical graphite in the spraying material is 1:0.05-0.1:40-50:10-12; And / or, the mass ratio of the spraying material to the graphite worm to be sprayed in step 3 is 1:5.5 to 6.

5.

9. The method for preparing a long-life bipolar plate according to claim 5, characterized in that, The high-temperature hot molding temperature in step 4 is 130-180℃.

10. The application of the long-life bipolar plate according to any one of claims 1-4 in the field of flow batteries and fuel cells.

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