RU2795048C1 - Composite material for manufacturing of bipolar and monopolar plates of electrochemical cells and method for their manufacture - Google Patents

Abstract

FIELD: electrochemical industry.

SUBSTANCE: method for manufacturing bipolar and monopolar plates for electrochemical cells from highly filled polymer composite materials. The composite material for manufacturing of bipolar and monopolar plates of electrochemical cells contains an elastomer polymer matrix and a functional filler with an auxiliary component distributed in the polymer matrix at the following ratio per 100 parts by weight including polymer matrix components, in parts by weight: functional filler – 100-600; auxiliary component – 0.5-20.

EFFECT: production of bipolar and monopolar plates of electrochemical cells from highly filled polymer composite materials with improved performance characteristics, such as: tensile strength up to 60 MPa, compressive strength up to 150 MPa, chemical resistance in acids and alkalis, electrolytes within pH 1-14, change in mass over 45 days not more than 1%, electrical conductivity up to 50 S/cm, thermal conductivity up to 15 W/(m×K), operating heat resistance up to 300°C, total porosity 2-30%, including open porosity less than 1%.

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Description

FIELD OF TECHNOLOGY

The invention relates to the electrochemical industry, in particular, to a method for manufacturing bipolar and monopolar plates for electrochemical cells from highly filled polymer composite materials.

BACKGROUND OF THE INVENTION

A known method for producing plates of electrochemical cells (fuel cells), disclosed in RU 2333575 C1, publ. 09/10/2008. The method includes manufacturing a base layer and depositing carbon layers on it and assembling a stack of layers. At the same time, an intermediate layer of a mixture of low-density graphite powder and 0.5-2.0 wt. % polytetrafluoroethylene (PTFE), on top of which is placed a sheet extruded from a mixture of porous graphite powder and 10-20 wt. % PTFE, and the package is heated to a temperature of 120-170°C at a pressure of 200-300 kg/cm ² .

The disadvantage of the technical solution disclosed above is the low strength and interlayer strength of the formed package, due to low pressing temperatures and the low content of the polymer binder in the intermediate layer, as well as the instability of the electrical properties due to the heterogeneity of the material structure.

In addition, the prior art method for producing plates of electrochemical cells (fuel cells), disclosed in RU 2316851 C2, publ. 02/10/2008, prototype. The method includes creating a structure containing electrically conductive carbonized or graphitized reinforcing fibers, then mechanically orienting these fibers by needling in the first direction corresponding to the preferred conductive channels to increase the electrical conductivity of the product in the specified first direction, in which the carbonized or graphitized reinforcing fibers is a porous structure saturated thermoplastic polymer, resulting in a matrix of a certain thickness, while the specified first direction is parallel to the specified thickness.

The disadvantage of the technical solution disclosed above is damage to the formed package and a decrease in its electrical conductivity in the direction perpendicular to the punching direction, distortion of the stacking structure of the functional fibrous filler as a whole, which leads to a large inhomogeneity of the electrical properties of the material.

Also, the disadvantages of both technical solutions disclosed above include the fact that the polymer matrix used in them is not electrically conductive.

DISCLOSURE OF THE INVENTION

The technical problem solved in the claimed invention is a method for manufacturing bipolar and monopolar plates for electrochemical cells from highly filled polymer composite materials with high manufacturability, high physical and mechanical properties, chemical resistance, increased electrical conductivity.

The technical result, to which the present invention is directed, is the production of bipolar and monopolar plates of electrochemical cells from materials capable of replacing high-density artificial graphites and filled polymer materials based on fluoroplasts and fluoropolymers used in electrochemical cells, the manufacture of bipolar and monopolar plates of electrochemical cells from highly filled polymer composite materials with improved performance characteristics, such as: tensile strength up to 60 MPa, compressive strength up to 150 MPa, chemical resistance in acids and alkalis, electrolytes within pH 1-14, - weight change for 45 days is not more than 1 %, electrical conductivity up to 50 S/cm, thermal conductivity up to 15 W/(m×K), operational heat resistance up to 300°C, total porosity 2-30%, including open porosity less than 1%.

This technical result is achieved due to the fact that the composite material for the manufacture of bipolar and monopolar plates of electrochemical cells contains a matrix of elastomer subjected to thermal aging and low-temperature carbonization, and a functional filler and an auxiliary component distributed in the specified matrix, with the following ratio distributed in 100 wt. including polymer matrix components, wt. h:

functional filler 100-600 auxiliary component 0.5-20

As an elastomer, at least one elastomer is used, selected from the group: nitrile butadiene, styrene butadiene rubbers.

As a functional filler, at least one component is used, selected from the group: carbon or other inorganic electrically conductive fillers, selected from the group: discrete particles - boron nitride, boron carbide, high-strength or high-modulus carbon fiber, carbon nanotubes, artificial crushed graphite, natural graphite , thermally expanded intercalated graphite, graphene, fullerenes, carbon black, mesophase carbon.

As an auxiliary component, at least one component selected from the group is used: cross-linking agents selected from the group: organic peroxides - dicumyl peroxide, benzoyl peroxide; curing resins - octyl-phenol resole resins, butyl-phenol resole resins, bromine-modified octyl-phenol resole resins.

As an auxiliary component, at least one agent is additionally used that controls the course of thermal destruction of the elastomeric matrix, selected from the group: sodium tetraborate, phosphorus (V) oxide, boron (III) oxide.

The polymer matrix additionally contains at least one component selected from the group: phenol-formaldehyde resins, petroleum and coal tar pitches, in an amount of from 0.1 to 50 wt. % by weight of the polymer matrix.

This technical result is achieved due to the fact that the method of manufacturing bipolar and monopolar plates of electrochemical cells from a composite polymer material includes the following steps:

a) preparation of initial components;

b) obtaining a homogeneous elastomeric mixture by sequentially adding the specified functional fillers and auxiliary components to the elastomeric matrix and subsequent mixing and homogenization;

c) forming a blank using molded or moldless technology and subsequent curing of the blank at a temperature of 120-220°C and a pressure of 0.1-10 MPa or forming a blank at a temperature of 120-220°C and a pressure of 0.1-10 MPa using a molded or formless technology, providing simultaneous molding and vulcanization of the workpiece;

d) heat treatment of the workpiece in a controlled gas environment, including heating the workpiece to a temperature of 320-360°C for 6-24 hours;

e) cooling the billet to room temperature, while the billet is cooled to a temperature of 80°C at a rate of 0.001-2.5°C/min.

In step b), phenol-formaldehyde resins and/or petroleum and/or coal tar pitches are additionally introduced into the polymer matrix.

Between steps c) and d), if necessary, the workpiece is machined.

At stage d) heating to a temperature of 200°C is carried out at a rate of 0.5-2°C/min, to a temperature from the range of 200-320°C at a rate of 0.05-0.6°C/min, to a temperature from the range 320-360°C at a rate of 0.03-0.25°C/min.

At stage d) additionally carry out at least one isothermal exposure at a temperature of 320-360°C for 0.5-6 hours.

Step d) is carried out in a free, unloaded state of the workpiece.

Step d) is carried out with a pressure of 0.1 to 10 MPa applied to the preform.

Step d) is carried out in a flowing gas atmosphere of an inert gas with a supply of 0.01 to 50 ml/min per 1 g of composite material.

Step d) is carried out in a flowing gas atmosphere of an inert gas with a supply of 0.01 to 50 ml/min per 1 g of composite material with dynamic stirring of the atmosphere in an oven.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the description, which is not restrictive and given with reference to the accompanying drawings, which show:

Fig. 1 - Microstructure of the proposed composite materials: a, c - composite material EK-TE-1; b, d - composite material EK-TE-3.

IMPLEMENTATION OF THE INVENTION

The claimed composite material for the manufacture of bipolar and monopolar plates of electrochemical cells contains a matrix of elastomer subjected to thermal aging and low-temperature carbonization, and a functional filler and an auxiliary component distributed in the specified matrix, with the following ratio distributed in 100 wt. including polymer matrix components, wt. h:

functional filler 100-600 auxiliary component 0.5-20

As an elastomer, at least one elastomer is used, selected from the group: nitrile butadiene, styrene butadiene rubbers.

As a functional filler, at least one component is used, selected from the group: high-strength or high-modulus carbon fiber 0.01-100 mm long; carbon nanotubes with a length of 10 nm to 5 mm, discrete particles with a particle size of 10 nm to 0.5 mm, selected from the group: boron nitride, boron carbide, artificial crushed graphite, natural graphite, thermally expanded intercalated graphite, graphene, fullerenes, technical carbon, mesophase carbon.

As an auxiliary component, at least one component selected from the group is used: cross-linking agents selected from the group: organic peroxides - dicumyl peroxide, benzoyl peroxide; curing resins - octyl-phenol resole resins, butyl-phenol resole resins, bromine-modified octyl-phenol resole resins.

As an auxiliary component, at least one agent is additionally used that controls the course of thermal destruction of the elastomeric matrix, selected from the group: sodium tetraborate, phosphorus (V) oxide, boron (III) oxide.

The polymer matrix additionally contains at least one component selected from the group: phenol-formaldehyde resins, petroleum and coal tar pitches, in an amount of from 0.1 to 50 wt. % by weight of the polymer matrix.

The method for manufacturing bipolar and monopolar plates of electrochemical cells from the composite material disclosed above includes the following steps.

At the first stage, the initial components are prepared, which includes:

- removal of the sizing agent or lubricant from the surface of the carbon fiber when the fiber is heated in a thermal chamber at a temperature of 350-400°C for 10-15 minutes in an air atmosphere in order to increase the adhesive interaction between the fiber and the matrix;

- removal of a fraction with a particle size of more than 200 microns from artificial graphite using standard technological equipment (sieve screening, classifiers) in order to increase the homogeneity of the mixture;

- drying of the functional filler and auxiliary component at a temperature of 50-120°C for 4-8 hours. The drying process is completed 30 minutes before the use of materials for the production of the mixture.

After preparing the initial components, a homogeneous elastomeric mixture is obtained by successively introducing a functional filler and an auxiliary component into the polymer matrix, followed by mixing the polymer matrix with the components introduced into it using standard devices: rollers, closed-type rubber mixers, intermixes, etc.

After obtaining a homogeneous mixture, the workpiece is formed using a molded or moldless technology, followed by vulcanization of the workpiece at a temperature of 120-220°C and a pressure of 0.1-10 MPa or the formation of a workpiece at a temperature of 120-220°C and a pressure of 0.1-10 MPa using molded or moldless technology, providing simultaneous molding and vulcanization of the workpiece.

In molding technology, molding of the workpiece is carried out in a mold, for example, by casting the resulting homogeneous mixture into a mold. With shapeless technology, the shape of the product is given by the mouthpiece of the extruder, through which the molded product of the required shape exits and is subsequently cut to the required length.

After fixing the mold, the final heat treatment of the workpiece is carried out in a controlled gas environment (argon, nitrogen, air, etc.), which includes heating the workpiece to a temperature of 320-360°C for 6-24 hours and leading to processes of thermal aging and low-temperature carbonization of the workpiece. To implement the final heat treatment, standard furnaces with a controlled gas atmosphere are used, equipped with control systems that ensure heating at specified rates for a specified time and ensure a given uniformity of the thermal field inside the furnace. Heat treatment is carried out in order to form the final structure and material properties of products. Heating is carried out in a flowing gas atmosphere in order to remove gaseous pyrolysis products from the reaction zone; argon, nitrogen, air, etc. can be used as gases to create a flowing atmosphere.

At the last stage, the finished product is cooled to room temperature, while the product is cooled to a temperature of 80°C at a rate of 0.001 -2.5°C/min. As a result, the final product is obtained - a finished product from the claimed composite material, which can be machined to give the final geometry, followed by quality control. Cooling is carried out by known methods, for example together with the furnace in which the heat treatment takes place, or in air after leaving the furnace, or in a separate cooling device.

Between the stages of vulcanization and final heat treatment, if necessary, mechanical processing of the workpiece is carried out: milling to a given profile of the channels of the flow field, drilling of flow channels, etc.

Upon receipt of a homogeneous mixture, phenol-formaldehyde resins and/or oil and/or coal tar pitches are additionally introduced into the polymer matrix.

Heating at the final heat treatment stage is carried out as follows: to a temperature of 200°C at a rate of 0.5-2°C/min, to a temperature in the range of 200-320°C at a rate of 0.05-0.6°C/min, to a temperature in the range of 320-360°C at a rate of 0.03-0.25°C/min.

At the final heat treatment stage, at least one isothermal holding at a temperature of 320-360°C for 0.5-6 hours can additionally be performed.

Heat treatment is carried out in a free, unloaded state of the workpiece.

Heat treatment is carried out at pressure applied to the workpiece from 0.1 to 10 MPa.

Heat treatment is carried out in a flowing gas atmosphere of an inert gas with a flow rate of 0.01 to 50 ml/min per 1 g of composite material.

Heat treatment is carried out in a flowing gas atmosphere of an inert gas with a supply of 0.01 to 50 ml/min per 1 g of composite material with dynamic stirring of the atmosphere in the furnace.

Example 1

For the manufacture of bipolar and monopolar plates of electrochemical cells from a composite material, nitrile butadiene rubber, crushed artificial graphite with a particle size distribution of D10 = 18 μm, D50 = 43 μm, D90 = 86 μm, and dicumyl peroxide are used as initial components.

The nitrile butadiene rubber was dried in a vacuum oven at 50° C. for 6 hours, weight loss 0.7%.

Artificial crushed graphite is dried in an oven for 6 hours at a temperature of 115°C, weight loss 1.2-1.7%.

After drying the initial components, a homogeneous mixture is obtained. To do this, 100 mass parts of nitrile butadiene rubber are added to the rubber mixing rollers, and then 300 mass parts of crushed artificial graphite, 1 mass part of dicumyl peroxide are sequentially added from the content of the specified rubber and mixing of the initial components is carried out at a ratio of shaft speeds of 1: 1.25 for 40 minutes.

Then the workpiece is molded in the form of plates 210x290x5 mm, for this a homogeneous mixture is placed in a steel tooling and the elastomer blanks are vulcanized in a steel tooling at a temperature of 170°C for 5 minutes, on a vulcanization press at a constant mold closing force of 5 MPa.

The resulting plates are subjected to heat treatment in an inert atmosphere (argon) when heated from room temperature to a temperature of 200°C at a rate of 2.0°C/min, to a temperature of 320°C at a rate of 0.33°C/min, to a temperature 340°C at a rate of 0.133°C/min in a muffle ashing furnace. Heat treatment leads to thermal aging and low-temperature carbonization of the workpiece.

Further, the heat-treated billet is cooled to a temperature of 80°C at a rate of 0.5°C/min in the furnace, and then it is unloaded from the furnace and cooled to room temperature in air.

As a result, a bipolar or monopolar plate is obtained from a composite material, the properties of which are presented in table 1.

Example 2

Example 2 is similar to example 1, except that with stirring in 100 wt. including butadiene-nitrile rubber add 300 mass parts of crushed artificial graphite, 50 mass parts of high-strength carbon fiber, 10 mass parts of Elaztobond C 650 butyl-phenol resole resin. Vulcanization of the workpiece is carried out at a temperature of 170°C and a pressure of 7 MPa for 30 minutes; heat treatment leading to thermal aging and low-temperature carbonization of the workpiece is carried out from room temperature to a temperature of 200°C at a rate of 1.5°C/min, to a temperature of 320°C at a rate of 0.33°C/min, to a temperature of 340° C at a rate of 0.111°C/min; cooling the billet to a temperature of 80°C at a rate of 0.25°C/min in the furnace.

As a result, a bipolar or monopolar plate is obtained from a composite material, the properties of which are presented in table 1.

Example 3

Example 3 is similar to example 1, except that with stirring in 100 wt. including butadiene-nitrile rubber add 600 mass parts of crushed artificial graphite, 15 wt. including modified alkylphenol resin Elaztobond T 6000, 5 wt. including butyl-phenol resole resin Elaztobond C 650. Vulcanization of the workpiece is carried out at a temperature of 200°C and a pressure of 10 MPa for 60 minutes; heat treatment leading to thermal aging and low-temperature carbonization of the workpiece, from room temperature to a temperature of 200°C at a rate of 1.0°C/min, to a temperature of 320°C at a rate of 0.152°C/min, to a temperature of 360°C at a rate of 0.067°C/min; cooling the billet to a temperature of 80°C at a rate of 0.25°C/min in the furnace.

As a result, a bipolar or monopolar plate is obtained from a composite material, the properties of which are presented in table 1.

Example 4

Example 4 is similar to example 1, except that with stirring in 100 wt. including butadiene-nitrile rubber add 250 mass parts of crushed artificial graphite, 50 mass parts of carbon black P234, 1 mass part of dicumyl peroxide. The final heat treatment is carried out in a dilute air atmosphere with an additional supply of 40 ml/min of argon per 1 g of composite material.

As a result, a bipolar or monopolar plate is obtained from a composite material, the properties of which are presented in table 1.

Example 5

Example 5 is similar to example 2, except that in the manufacture of a homogeneous mixture, a polymer matrix is used in the form of styrene-butadiene rubber SKS 30 ARK.

As a result, bipolar and monopolar plates are obtained from a composite material, the properties of which are presented in table 1.

Example 6

Example 6 is similar to example 2, except that with stirring in 100 wt. including butadiene-nitrile rubber add 250 mass parts of crushed artificial graphite, 50 mass parts of carbon black P-234, 50 mass parts of carbon fiber, 2 mass parts of dicumyl peroxide.

As a result, a bipolar or monopolar plate is obtained from a composite material, the properties of which are presented in table 1.

Example 7

Example 7 is similar to example 3, except that with stirring in 100 wt. including butadiene-nitrile rubber add 340 mass parts of crushed artificial graphite, 50 mass parts of carbon black P-234, 10 mass parts of graphene, 5 wt. h. butyl-phenol resole resin Elaztobond C 650.

As a result, a bipolar or monopolar plate is obtained from a composite material, the properties of which are presented in table 1.

Example 8

Example 8 is similar to example 2, except that with stirring in 100 wt. hours of nitrile butadiene rubber add 250 mass parts of crushed artificial graphite, 50 mass parts of carbon black P-234, 5 mass parts of octyl-phenol resole resin SP 1045 N.

As a result, a bipolar or monopolar plate is obtained from a composite material, the properties of which are presented in table 1.

Example 9

Example 9 is similar to example 2, except that in the manufacture of a homogeneous mixture, a polymer matrix is used in the form of styrene-butadiene rubber, in which 25 wt. % phenol-formaldehyde resin.

As a result, a bipolar or monopolar plate is obtained from a composite material, the properties of which are presented in table 1.

Example 10

Example 10 is similar to example 2, except that the final heat treatment is carried out in a dilute air atmosphere with an additional supply of 40 ml/min of argon per 1 g of composite material with dynamic stirring of the atmosphere in the furnace (supply of air flow into the furnace using a fan).

As a result, a bipolar or monopolar plate is obtained from a composite material, the properties of which are presented in table 1.

Example 11

Example 11 is similar to example 2, except that the vulcanization is carried out at a pressure of 5 MPa applied to the workpiece, 1 mass part of B ₂ O ₃ is additionally used as an auxiliary component.

As a result, a bipolar or monopolar plate is obtained from a composite material, the properties of which are presented in table 1.

The invention has been described above with reference to a specific embodiment. For specialists, other embodiments of the invention may be obvious, without changing its essence, as it is disclosed in the present description. Accordingly, the invention is to be considered limited in scope by the following claims only.

Claims (21)

1. A composite material for the manufacture of bipolar and monopolar plates of electrochemical cells, containing a matrix of elastomer subjected to thermal aging and low-temperature carbonization, and a functional filler and an auxiliary component distributed in the specified matrix in the following ratio distributed in 100 wt. including polymer matrix components, wt. h: functional filler 100-600 auxiliary component 0.5-20 2. Composite material according to claim 1, characterized in that at least one elastomer is used as an elastomer, selected from the group: nitrile butadiene, styrene butadiene rubbers. 3. Composite material according to claim 1, characterized in that at least one component selected from the group is used as a functional filler: high-strength or high-modulus carbon fiber, carbon nanotubes; discrete particles selected from the group: boron nitride, boron carbide, artificial crushed graphite, natural graphite, thermally expanded intercalated graphite, graphene, fullerenes, carbon black, mesophase carbon. 4. Composite material according to claim 1, characterized in that at least one component selected from the group is used as an auxiliary component: cross-linking agents selected from the group: organic peroxides - dicumyl peroxide, benzoyl peroxide; curing resins - octyl-phenol resole resins, butyl-phenol resole resins, bromine-modified octyl-phenol resole resins. 5. Composite material according to claim 4, characterized in that at least one agent is additionally used as an auxiliary component, which controls the processes of thermal destruction of the elastomeric matrix, selected from the group: sodium tetraborate, phosphorus (V) oxide, boron (III) oxide ). 6. Composite material according to claim 1, characterized in that the polymer matrix additionally contains at least one component selected from the group: phenol-formaldehyde resins, petroleum and coal tar pitches, in an amount of from 0.1 to 50 wt. % by weight of the polymer matrix. 7. A method of manufacturing bipolar and monopolar plates of electrochemical cells from a composite material according to any one of paragraphs. 1-6, including the following steps: a) preparation of initial components; b) obtaining a homogeneous elastomeric mixture by sequentially adding the specified functional fillers and auxiliary components to the elastomeric matrix and subsequent mixing; c) forming a blank using molded or moldless technology and subsequent curing of the blank at a temperature of 120-220°C and a pressure of 0.1-10 MPa or forming a blank at a temperature of 120-220°C and a pressure of 0.1-10 MPa using a molded or formless technology, providing simultaneous molding and vulcanization of the workpiece; d) heat treatment of the workpiece in a controlled gas environment, including heating the workpiece to a temperature of 320-360°C for 6-24 hours; e) cooling the billet to room temperature, while the billet is cooled to a temperature of 80°C at a rate of 0.001-2.5°C/min. 8. Method according to claim 7, characterized in that between steps c) and d) the workpiece is machined. 9. The method according to p. 7, characterized in that in step b) phenol-formaldehyde resins and/or petroleum and/or coal tar pitches are additionally introduced into the polymer matrix. 10. The method according to p. 7, characterized in that in step d) heating to a temperature of 200°C is carried out at a rate of 0.5-2°C/min, to a temperature in the range of 200-320°C at a rate of 0.05- 0.6°C/min, up to a temperature in the range of 320-360°C at a rate of 0.03-0.25°C/min. 11. The method according to p. 7, characterized in that at step d) additionally carry out at least one isothermal exposure at a temperature of 320-360°C for 0.5-6 hours. 12. The method according to claim 7, characterized in that step d) is carried out in a free, unloaded state of the workpiece. 13. The method according to p. 7, characterized in that step d) is carried out at a pressure applied to the workpiece from 0.1 to 10 MPa. 14. The method according to p. 7, characterized in that step d) is carried out in a flowing gas atmosphere of an inert gas with a supply of 0.01 to 50 ml/min per 1 g of composite material. 15. The method according to p. 7, characterized in that step d) is carried out in a flowing gas atmosphere of an inert gas with a supply of 0.01 to 50 ml/min per 1 g of composite material with dynamic stirring of the atmosphere in the furnace.

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