CN114744230A - Flexible graphite bipolar plate and preparation method thereof - Google Patents

Abstract

The invention discloses a flexible graphite bipolar plate and a preparation method thereof, belonging to the field of fuel cell bipolar plate manufacture. The preparation method of the flexible graphite bipolar plate comprises the steps of taking a graphite sponge cake plate and reinforced resin as raw materials; immersing the graphite sponge cake plate into reinforced resin, and filling graphite pores; removing the solvent, pressing by a mould, and curing at high temperature to obtain the product; wherein the reinforcing resin comprises: a resin mixed with diacetone alcohol and propylene glycol methyl ether; or a resin. The preparation method of the invention can ensure that the reinforced resin is uniformly distributed in the graphite sponge cake plate, and the prepared flexible graphite bipolar plate has good conductivity, bending resistance and lower gas leakage rate.

Description

Flexible graphite bipolar plate and preparation method thereof

Technical Field

The invention relates to the field of manufacturing of fuel cell bipolar plates, in particular to a flexible graphite bipolar plate and a preparation method thereof.

Background

The fuel cell has wide development prospect and can be widely applied to the fields of distributed power generation systems, electric automobiles and the like. The fuel cell bipolar plate is composed of a polar plate and a flow field, mainly has the functions of gas distribution, current collection, heat conduction and sealing, the performance of the bipolar plate determines the volume specific power and the mass specific power of a fuel cell stack, the bipolar plate is a core component of a fuel cell, and the weight of the bipolar plate accounts for 70-80% of the whole fuel cell stack. The bipolar plate has great influence on the performance and the cost of the fuel cell, and is one of the problems that the commercialization of the fuel cell must solve. The bipolar plate made of flexible graphite has the advantages of low cost and corrosion resistance, and is one of the research directions of the bipolar plate of the fuel cell.

In the prior art, solid resin powder and graphite powder are mainly uniformly mixed and are subjected to hot pressing to prepare the graphite bipolar plate, wherein the resin powder mainly plays a role in binding graphite, and thermoplastic resin is mainly used. In addition, there is another method of forming a flow field by molding a low-density flexible graphite sheet at one time, then performing resin impregnation, and finally heating and curing for molding, for example, patent CN102569834A discloses a high-strength flexible graphite bipolar plate and a preparation method thereof, CN1225049C discloses a preparation method of a flexible graphite bipolar plate, and the like. Although the bipolar plate prepared by the method in the prior art is easy to form, the resin impregnation effect is not ideal, the gas permeability and the mechanical property of the material can be influenced, the thickness of the bipolar plate is large, and the assembly and the practical application of the battery are limited to a certain extent.

Disclosure of Invention

The invention aims to provide a flexible graphite bipolar plate with uniform resin distribution, high conductivity and strong bending resistance and a preparation method thereof.

In order to achieve the purpose of the invention, the following technical scheme is adopted.

The invention discloses a preparation method of a flexible graphite bipolar plate, which comprises the steps of taking a graphite sponge cake plate and reinforced resin as raw materials; immersing the graphite sponge cake plate into a reinforced resin diluent for soaking; removing the solvent, pressing by a mould, and curing at high temperature to obtain the product; wherein the reinforcing resin comprises:

(1) a resin mixed with diacetone alcohol and propylene glycol methyl ether; or

(2) And (3) resin.

The diacetone alcohol and propylene glycol methyl ether are mixed into the resin, so that the mechanical property of the flexible graphite bipolar plate can be optimized, and the prepared flexible graphite bipolar plate has better bending resistance. In addition, the conductivity and the air tightness of the flexible graphite bipolar plate can be improved.

Preferably, the weight ratio of diacetone alcohol, propylene glycol methyl ether to resin is 5-10:1-3: 80-90.

Preferably, the resin comprises:

(1) a phenolic resin; or

(2) An epoxy resin; or

(3) A mixture of phenolic resin and epoxy resin; or

(4) Polyvinylidene fluoride; or

(5) A mixture of phenolic resin, epoxy resin and polyvinylidene fluoride.

Preferably, the condition for immersing the graphite sponge cake plate in the reinforcing resin is normal temperature and pressure.

Preferably, the graphite sponge cake plate is immersed in the reinforcing resin for 1 to 15 min.

Preferably, the pressure of the die pressing is 25-100 MPa.

Preferably, the temperature of the high-temperature curing is 100-130 ℃, and the pressure of the high-temperature curing is 3-5 MPa.

Preferably, the preparation method of the graphite sponge cake plate comprises the following steps: and (3) expanding expandable graphite to obtain graphite worms, and pressing the graphite worms in multiple sections to obtain the graphite sponge cake plate.

Preferably, the density of the graphite sponge cake board is 0.08-0.15g/cm³。

The graphite sponge cake board prepared by the invention has low density, and is beneficial to simplifying the subsequent resin soaking operation. Soaking in a low-density state, without a vacuum environment, and after short-time soaking, the resin can be uniformly distributed, and the uniform distribution of the resin is further promoted in the subsequent pressing process; the resin which is uniformly distributed can improve the air tightness of the flexible graphite bipolar plate and reduce the gas leakage.

Preferably, the preparation method of the expandable graphite comprises the following steps: mixing nitric acid and itaconic acid, adding the mixture into a mixture of natural graphite and potassium permanganate for constant-temperature reaction, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

Preferably, the weight ratio of nitric acid to itaconic acid is 0.1-0.3: 0.1-0.2.

Preferably, the weight ratio of the natural graphite to the potassium permanganate is 1: 0.1-0.5.

More preferably, the weight ratio of the natural graphite to the potassium permanganate to the nitric acid to the itaconic acid is 1:0.1-0.5:0.1-0.3: 0.1-0.2.

Preferably, the reaction temperature for preparing the expandable graphite is 25-35 ℃ and the reaction time is 30-90 min.

More preferably, the method of preparing expandable graphite comprises: mixing nitric acid, methyl thioglycolate and itaconic acid, adding the mixture into a mixture of natural graphite and potassium permanganate for constant-temperature reaction, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

More preferably, the amount ratio of nitric acid, methyl thioglycolate and itaconic acid is 0.1-0.3:0.1-0.2: 0.1-0.3.

The graphite is subjected to strong acid intercalation by nitric acid, methyl thioglycolate and itaconic acid, so that the prepared expandable graphite has better expansion performance, larger expansion volume and less generated slag.

More preferably, the method for preparing the flexible graphite bipolar plate comprises the following steps:

1. preparation of expandable graphite

Mixing nitric acid and itaconic acid, adding the mixture of natural graphite and potassium permanganate into the mixture, reacting at constant temperature, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

2. Preparation of graphite sponge cake plate

And taking expandable graphite, expanding to obtain graphite worms, and pressing the graphite worms into the low-density graphite sponge cake boards in multiple sections.

3. Preparation of flexible graphite bipolar plate

(1) Taking a graphite sponge cake plate and reinforced resin as raw materials; (2) preparing a reinforced resin diluent; (3) soaking the graphite sponge cake plate in a reinforced resin diluent, and wiping residual resin on the surface after soaking; (4) putting the graphite sponge cake plate filled with the reinforced resin diluent into an oven to remove solvent water until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by using a mould; (6) and curing to obtain the flexible graphite bipolar plate.

More preferably, the reinforcing resin diluent comprises 10 to 40 wt% of a diluent.

Even more preferably, the diluent is water or MIBK or DMF or NMP.

Still further preferably, the method for preparing the flexible graphite bipolar plate comprises the following steps:

1. preparation of expandable graphite

According to the weight portion, 0.1-0.3 portion of nitric acid and 0.1-0.2 portion of itaconic acid are mixed and added into the mixture of 1 portion of natural graphite and 0.1-0.5 portion of potassium permanganate, the mixture is reacted for 30-90min at the constant temperature of 25-35 ℃, and after the reaction is finished, the mixture is filtered and washed by clean water, and the expandable graphite is obtained after vacuum drying.

2. Preparation of graphite sponge cake plate

According to the weight portion, expandable graphite is taken, expanded for 20-30s at the temperature of 900-1200 ℃, and then graphite worms are obtained, and the graphite worms are pressed into low-density graphite sponge cake plates with the density of 0.08-0.15g/cm³。

3. Preparation of flexible graphite bipolar plate

(1) Taking the density of 0.08-0.15g/cm³The graphite sponge cake plate and the reinforced resin are used as raw materials; (2) preparing a reinforced resin diluent; (3) soaking the graphite sponge cake plate in the reinforced resin diluent for 1-15min, and wiping residual resin on the surface after soaking; (4) putting the graphite sponge cake plate filled with the reinforced resin diluent into a 70-90 ℃ oven to remove solvent water until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by using a mould under 25-100 MPa; (6) curing at 100-130 deg.C under 3-5Mpa to obtain the flexible graphite bipolar plate.

The invention also discloses the flexible graphite bipolar plate prepared by the preparation method.

The invention also discloses application of the reinforced resin in improving the bending resistance of the flexible graphite bipolar plate.

Compared with the prior art, the invention has the beneficial effects that:

the flexible graphite bipolar plate prepared by the method uses the low-density graphite sponge cake plate, and is soaked in resinThe resin can be more uniformly distributed, the soaking time is shortened, and the vacuum environment is not needed in the soaking process. In addition, the expandable graphite for preparing the graphite sponge cake plate is prepared by carrying out strong acid intercalation on graphite simultaneously by nitric acid, methyl thioglycolate and itaconic acid; the expandable graphite prepared by the method has better expansibility and larger expansion volume which can reach more than 500 ml/g. In addition, the flexible graphite bipolar plate prepared by the invention has good conductivity, bending resistance and air tightness, wherein the conductivity can reach more than 400S/cm; the bending resistance can reach more than 25 MPa; gas leakage rate lower than 1.5X 10^-6mbarl/s。

Drawings

FIG. 1 is an electron micrograph of a cross section of a graphite sponge cake plate.

Detailed Description

The exemplary embodiments will be described herein in detail, and the embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Rather, they are merely examples of methods consistent with certain aspects of the present disclosure, as detailed in the appended claims.

The experimental procedures in the following examples are, unless otherwise specified, either conventional or according to the manufacturer's recommendations. Materials, reagents and the like used in the following examples are commercially available unless otherwise specified. Wherein, the natural graphite is purchased from trace graphite company Limited in cigarette tai city.

Example 1

Preparation of flexible graphite bipolar plate

1. Preparation of expandable graphite

And (3) mixing 20g of nitric acid and 10g of itaconic acid, adding the mixture into a mixture of 100g of natural graphite and 10g of potassium permanganate, reacting at the constant temperature of 28 ℃ for 40min, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

2. Preparation of graphite sponge cake plate

Taking expandable graphite, expanding at 1000 deg.C for 30s to obtain graphite worm, and pressing the graphite worm in multiple stages to obtain low-density graphite sponge cake board with density of 0.1g/cm³。

3. Preparation of flexible graphite bipolar plate

(1) Selecting 0.1g/cm³The graphite sponge cake board takes phenolic resin as a raw material; (2) preparing phenolic resin diluent, wherein the phenolic resin diluent is water, and the diluent accounts for 25 wt% of the diluent; (3) soaking the graphite sponge cake plate in the resin diluent for 5min, taking out, and wiping residual resin on the surface; (4) putting the graphite sponge cake plate filled with the resin diluent into an oven at 80 ℃ to remove solvent water until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by a mould under the pressure of 100 MPa; (6) curing at 130 ℃ under the pressure of 5 MPa.

Example 2

Preparation of flexible graphite bipolar plate

The present embodiment is different from embodiment 1 in that:

3. preparation of flexible graphite bipolar plate

(1) Selecting 0.1g/cm³The graphite sponge cake board takes phenolic resin as a raw material; (2) preparing phenolic resin diluent, wherein the phenolic resin diluent is water, and the diluent accounts for 25 wt% of the diluent; (3) soaking the graphite sponge cake plate in the resin diluent for 10min, taking out, and wiping residual resin on the surface; (4) putting the graphite sponge cake plate filled with the resin diluent into an oven at 80 ℃ to remove solvent water until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by a mould under the pressure of 100 MPa; (6) curing at 130 ℃ under the pressure of 5 MPa.

Example 3

Preparation of flexible graphite bipolar plate

The present embodiment is different from embodiment 1 in that:

3. preparation of flexible graphite bipolar plate

(1) Selecting 0.1g/cm³The graphite sponge cake board takes epoxy resin as a raw material; (2) preparing an epoxy resin diluent, wherein the epoxy resin diluent is MIBK and accounts for 25 wt% of the diluent; (3) soaking the graphite sponge cake plate in the resin diluent for 5min, taking out, and wiping residual resin on the surface; (4) placing the graphite sponge cake plate filled with the resin diluent into an oven at 80 ℃ to remove the solvent MIBK, wherein the baking time is determined by that the weight of the graphite sponge cake plate does not change any moreUntil the end; (5) pressing the sponge cake plate by a mould under the pressure of 100 MPa; (6) curing at 130 ℃ under the pressure of 5 MPa.

Example 4

Preparation of flexible graphite bipolar plate

1. Preparation of expandable graphite

And (3) mixing 20g of nitric acid and 10g of itaconic acid, adding the mixture into a mixture of 100g of natural graphite and 10g of potassium permanganate, reacting at the constant temperature of 28 ℃ for 40min, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

2. Preparation of graphite sponge cake plate

Taking expandable graphite, expanding for 30s at 1000 deg.C to obtain graphite worm, and pressing the graphite worm into low-density graphite sponge cake plate with density of 0.15g/cm³。

3. Preparation of flexible graphite bipolar plate

(1) Selecting 0.15g/cm³The graphite sponge cake board takes epoxy resin as a raw material; (2) preparing an epoxy resin diluent, wherein the epoxy resin diluent is MIBK, and the diluent accounts for 25 wt% of the diluent; (3) soaking the graphite sponge cake plate in the resin diluent for 15min, taking out, and wiping residual resin on the surface; (4) putting the graphite sponge cake plate filled with the resin diluent into an oven at 80 ℃ to remove the solvent MIBK, wherein the baking time is determined until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by a mould under the pressure of 100 MPa; (6) curing at 130 ℃ under the pressure of 5 MPa.

Example 5

Preparation of flexible graphite bipolar plate

1. Preparation of expandable graphite

And (3) mixing 20g of nitric acid and 10g of itaconic acid, adding the mixture into a mixture of 100g of natural graphite and 10g of potassium permanganate, reacting at the constant temperature of 28 ℃ for 40min, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

2. Preparation of graphite sponge cake plate

Taking expandable graphite, expanding at 1000 deg.C for 30s to obtain graphite worm, and pressing the graphite worm in multiple stages to obtain low-density graphite sponge cake plate with density of 0.08g/cm³。

3. Preparation of flexible graphite bipolar plate

(1) Selecting 0.08g/cm³The graphite sponge cake board takes phenolic resin as a raw material; (2) preparing phenolic resin diluent, wherein the phenolic resin diluent is water, and the diluent accounts for 25 wt% of the diluent; (3) immersing the graphite sponge cake plate in the resin diluent for 1min, fishing out, and wiping residual resin on the surface; (4) putting the graphite sponge cake plate filled with the resin diluent into an oven at 80 ℃ to remove solvent water until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by a mould under the pressure of 100 MPa; (6) curing at 130 ℃ under the pressure of 5 MPa.

Example 6

Preparation of flexible graphite bipolar plate

The present embodiment is different from embodiment 1 in that:

1. preparation of expandable graphite

And (3) mixing 20g of nitric acid, 10g of methyl thioglycolate and 10g of itaconic acid, adding the mixture into a mixture of 100g of natural graphite and 10g of potassium permanganate, reacting at the constant temperature of 28 ℃ for 40min, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

Example 7

The present embodiment is different from embodiment 3 in that:

1. preparation of expandable graphite

And (3) mixing 20g of nitric acid, 20g of methyl thioglycolate and 10g of itaconic acid, adding the mixture into a mixture of 100g of natural graphite and 30g of potassium permanganate, reacting at the constant temperature of 25 ℃ for 70min, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

Example 8

This embodiment is different from embodiment 5 in that:

1. preparation of expandable graphite

And (3) mixing 20g of nitric acid, 10g of methyl thioglycolate and 10g of itaconic acid, adding the mixture into a mixture of 100g of natural graphite and 10g of potassium permanganate, reacting at the constant temperature of 28 ℃ for 40min, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

Example 9

1. Preparation of expandable graphite

And (3) mixing 20g of nitric acid, 10g of methyl thioglycolate and 10g of itaconic acid, adding the mixture into a mixture of 100g of natural graphite and 10g of potassium permanganate, reacting at the constant temperature of 28 ℃ for 40min, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

2. Preparation of graphite sponge cake plate

Taking expandable graphite, expanding at 1000 deg.C for 30s to obtain graphite worm, and pressing the graphite worm in multiple stages to obtain low-density graphite sponge cake plate with density of 0.08g/cm³。

3. Preparation of flexible graphite bipolar plate

(1) Selecting 0.08g/cm³The graphite sponge cake board takes epoxy resin as a raw material; (2) preparing an epoxy resin diluent, wherein the epoxy resin diluent is MIBK, and the diluent accounts for 25 wt% of the diluent; (3) immersing the graphite sponge cake plate in the resin diluent for 1min, fishing out, and wiping residual resin on the surface; (4) putting the graphite sponge cake plate filled with the resin diluent into an oven at 80 ℃ to remove solvent water until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by a mould under the pressure of 100 MPa; (6) curing at 130 ℃ under the pressure of 5 MPa.

Example 10

The present embodiment is different from embodiment 1 in that:

3. preparation of flexible graphite bipolar plate

(1) Selecting 0.1g/cm³The graphite sponge cake plate takes phenolic resin mixed with diacetone alcohol and propylene glycol methyl ether as a raw material, wherein the weight ratio of the acetone alcohol, the propylene glycol methyl ether and the phenolic resin is 5:1: 86; (2) preparing phenolic resin diluent mixed with diacetone alcohol and propylene glycol methyl ether, wherein the diluent is water and accounts for 25 wt% of the diluent; (3) soaking the graphite sponge cake plate in the resin diluent for 5min, taking out, and wiping residual resin on the surface; (4) putting the graphite sponge cake plate filled with the resin diluent into an oven at 80 ℃ to remove solvent water until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by a mould under the pressure of 100 MPa; (6) curing at 130 ℃ under the pressure of 5 MPa.

Example 11

The present embodiment is different from embodiment 3 in that:

3. preparation of flexible graphite bipolar plate

(1) Selecting 0.1g/cm³The graphite sponge cake plate takes epoxy resin mixed with diacetone alcohol and propylene glycol methyl ether as a raw material, wherein the weight ratio of the acetone alcohol, the propylene glycol methyl ether and the epoxy resin is 5:1: 86; (2) preparing epoxy resin diluent mixed with diacetone alcohol and propylene glycol methyl ether, wherein the diluent is MIBK and accounts for 25 wt% of the diluent; (3) soaking the graphite sponge cake plate in the resin diluent for 5min, taking out, and wiping residual resin on the surface; (4) putting the graphite sponge cake plate filled with the resin diluent into an oven at 80 ℃ to remove the solvent MIBK, wherein the baking time is determined until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by a mould under the pressure of 100 MPa; (6) curing at 130 ℃ under the pressure of 5 MPa.

Example 12

This embodiment is different from embodiment 5 in that:

3. preparation of flexible graphite bipolar plate

(1) Selecting 0.08g/cm³The graphite sponge cake plate takes phenolic resin mixed with diacetone alcohol and propylene glycol methyl ether as a raw material, wherein the weight ratio of the acetone alcohol, the propylene glycol methyl ether and the phenolic resin is 5:1: 86; (2) preparing phenolic resin diluent mixed with diacetone alcohol and propylene glycol methyl ether, wherein the diluent is water and accounts for 25 wt% of the diluent; (3) soaking the graphite sponge cake plate in the resin diluent for 5min, taking out, and wiping residual resin on the surface; (4) putting the graphite sponge cake plate filled with the resin diluent into an oven at 80 ℃ to remove solvent water until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by a mould under the pressure of 100 MPa; (6) curing at 130 ℃ under the pressure of 5 MPa.

Example 13

1. Preparation of expandable graphite

And (3) mixing 20g of nitric acid, 10g of methyl thioglycolate and 10g of itaconic acid, adding the mixture into a mixture of 100g of natural graphite and 10g of potassium permanganate, reacting at the constant temperature of 28 ℃ for 40min, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

2. Preparation of graphite sponge cake plate

Taking expandable graphite, expanding for 30s at 1000 deg.C to obtain graphite worm, and pressing the graphite worm into low-density graphite sponge cake plate with density of 0.08g/cm³。

3. Preparation of flexible graphite bipolar plate

(1) Selecting 0.08g/cm³The graphite sponge cake plate takes epoxy resin mixed with diacetone alcohol and propylene glycol methyl ether as a raw material, wherein the weight ratio of the acetone alcohol, the propylene glycol methyl ether and the epoxy resin is 5:1: 86; (2) preparing epoxy resin diluent mixed with diacetone alcohol and propylene glycol methyl ether, wherein the diluent is MIBK and accounts for 25 wt% of the diluent; (3) soaking the graphite sponge cake plate in the resin diluent for 5min, taking out, and wiping residual resin on the surface; (4) putting the graphite sponge cake plate filled with the resin diluent into an oven at 80 ℃ to remove the solvent MIBK, wherein the baking time is determined until the weight of the graphite sponge cake plate is not changed any more; (5) pressing the sponge cake plate by a mould under the pressure of 100 MPa; (6) curing at 130 ℃ under the pressure of 5 MPa.

Test example 1

Measurement of expansion volume of expandable graphite

The expandable graphite obtained in examples 1, 6 and 7 was used, and the expanded volume was measured by the method described in GB/T10698-1989 Expandable graphite.

The expandable graphite prepared in example 1 had an expanded volume of 407mL/g at 1000 deg.C; the expandable graphite prepared in example 6 had an expanded volume of 495mL/g at 1000 ℃; the expandable graphite obtained in example 7 had an expanded volume of 507mL/g at 1000 ℃.

From the measurement results, it is understood that the expanded graphite obtained in examples 6 and 7 has a larger expansion volume and a better expansion effect than the expanded graphite obtained in example 1; the effect of increasing the expansion volume of the graphite is shown by adding nitric acid, methyl thioglycolate and itaconic acid when preparing the expandable graphite.

Test example 2

Graphite sponge cake plate appearance observation

The graphite sponge cake plate obtained in example 6 was cut and the cross section was analyzed by scanning electron microscopy, and the results are shown in FIG. 1.

As can be seen, the expandable graphite has a lamellar structure, obvious interlayer spacing, a loose and porous structure and no obvious fracture. Therefore, the resin is uniformly distributed when the resin is soaked in the solution.

Test example 3

Determination of flexible graphite bipolar plate performance

Measurement of conductivity

The electrical resistivity of the flexible graphite bipolar plates obtained in examples 1 to 9 was measured according to the method for measuring electrical resistivity of carbon material YB/T120-1997, and the results of the measurement were recorded after converting the electrical resistivity into the electrical conductivity, as shown in the table.

Second, measurement of bending resistance

The flexural strength of the flexible graphite bipolar plates produced in examples 1 to 9 was measured according to the method for measuring flexural strength of graphite electrode described in GB/T3074.1-2008, and the measurement results are shown in the table.

Third, measuring gas leakage rate

The gas leakage rate of the flexible graphite bipolar plates prepared in examples 1 to 9 was measured using an airtight tester at a test pressure of 1bar and with a test gas of hydrogen, and the test results are shown in table 1.

Table 1 flexible graphite bipolar plate performance measurement results

As can be seen from table 1, the electrical conductivity in comparison with each example is generally better when using phenol resin than when using epoxy resin; the flexible graphite bipolar plate prepared in example 2 had the best conductivity, followed by the flexible graphite bipolar plate prepared in example 8; comparative examples 1, 10 were grouped; examples 5 and 12 show that the use of a phenol resin mixed with diacetone alcohol and propylene glycol methyl ether can improve the electrical conductivity of a graphite bipolar plate to a small extent when producing a flexible graphite bipolar plate. In the preparation process, the phenolic resin or the epoxy resin is used, and the electric conductivity indexes are greatly different, so that the bending resistance and the gas leakage rate have no obvious relationship with the types of the used resins; the conductivity index is in negative correlation with the density, and the effect of improving the conductivity after mixing the diacetone alcohol, the propylene glycol methyl ether and the phenolic resin is better than that of mixing the diacetone alcohol, the propylene glycol methyl ether and the epoxy resin.

Comparing the bending resistance of the examples, it can be seen that the flexible graphite bipolar plate prepared in example 4 has the best bending resistance, probably due to the longer soaking time; comparative examples 1, 10 were grouped; examples 5, 12; examples 3, 11; examples 9 and 13 show that, when preparing a flexible graphite bipolar plate, the use of a phenolic resin mixed with diacetone alcohol and propylene glycol methyl ether can significantly improve the bending resistance of the graphite bipolar plate; and can reach higher bending resistance when the soaking time is shorter (1min), which is beneficial to shortening the time for preparing the flexible graphite bipolar plate.

Comparing the gas leakage rates of the examples, the flexible graphite bipolar plate prepared in example 4 has the lowest gas leakage rate; comparative examples 1, 10 were grouped; examples 5, 12; examples 3 and 11 show that the use of a phenol resin mixed with diacetone alcohol and propylene glycol methyl ether can reduce the gas leakage rate to a small extent when producing a flexible graphite bipolar plate.

Conventional operations in the operation steps of the present invention are well known to those skilled in the art and will not be described herein.

The embodiments described above are intended to illustrate the technical solutions of the present invention in detail, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modification, supplement or similar substitution made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A method for preparing flexible graphite bipolar plate comprises using graphite sponge cake plate and reinforced resin as raw materials; immersing the graphite sponge cake plate into a reinforced resin diluent for soaking; removing the solvent, pressing by a mould, and curing at high temperature to obtain the product; wherein the reinforcing resin comprises:

(1) a resin mixed with diacetone alcohol and propylene glycol methyl ether; or

(2) And (3) resin.

2. The method according to claim 1, wherein the weight ratio of diacetone alcohol, propylene glycol methyl ether to resin is 5-10:1-3: 80-90.

3. The method of claim 1, wherein the resin comprises:

(1) a phenolic resin; or

(2) An epoxy resin; or

(3) A mixture of phenolic resin and epoxy resin; or

(4) Polyvinylidene fluoride; or

(5) A mixture of phenolic resin, epoxy resin and polyvinylidene fluoride.

4. The method of manufacturing according to claim 1, wherein the method of manufacturing the graphite sponge cake board comprises: and (3) taking expandable graphite, expanding to obtain graphite worms, and pressing the graphite worms in multiple sections to obtain the graphite sponge cake plate.

5. The method for preparing as claimed in claim 4, wherein the graphite sponge cake board has a density of 0.08 to 0.15g/cm³。

6. The method of claim 4, wherein the expandable graphite is prepared by a method comprising: mixing nitric acid and itaconic acid, adding the mixture of natural graphite and potassium permanganate into the mixture, reacting at constant temperature, filtering after the reaction is finished, washing with clear water, and drying in vacuum to obtain the expandable graphite.

7. The method according to claim 6, wherein the ratio of nitric acid to itaconic acid is 0.1-0.3: 0.1-0.2.

8. Flexible graphite bipolar plate produced by the production method as claimed in claims 1 to 7.

9. Use of the reinforced resin in the production method of claim 1 for increasing the bending resistance of a flexible graphite bipolar plate.

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