HK1012128B - Electrochemical cell with a polymer electrolyte and process for producing these polymer electrolytes - Google Patents

Description

The invention relates to an electrochemical cell with: a pair of electrodes with an electrode body of porous support material, each consisting essentially of carbon particles held together by a binder, and having pores allowing fluid to percolate through the electrode body, in which the electrode body is charged with a catalyst deposited on the support material, one placed between the electrodes, the electrode bodies electrochemically contacting, acting as an electrolyte and separator of the electrochemical cell, a membrane film of a hydrophilic, proton-conducting, polymeric material, providing an intermediate flow between the membrane film and the support material with the electrode catalyst deposited on it, the introduction of an electrode into at least one of the electrodes, and at least one of the means of extraction of the electrode material, is a method for the production of the electrode material, and the detection of the electrode is a process involving the extraction of the electrode from the electrode.

An electrochemical cell of the above-mentioned type is known from US-A-4876115. This known cell uses as electrolyte and separator a membrane whose material is a polymer material of substituted poly (perfluoroalkyl), with part of the substitutes being completely sulphonated. A preferred membrane material according to US-A-4876115 is Nafion (a trademark of DuPont), which is documented, inter alia, in Römpp's Chemie Lexikon and is there referred to as membrane material based on poly (perfluoroalkyl) sulfonic acids. Reference is made to other membrane materials in US-A-4876115 at US-A-4337137

Such perfluorinated membrane materials of US-A-4876115 have the long-term stability required for the operation of the electrochemical cell at temperatures up to 100°C due to their chemical composition, but are very expensive and it is very difficult and expensive to establish a satisfactory contact between such perfluorinated membrane materials and the electrodes.

No other membrane materials are known to have the desired long-term stability for the operation of electrochemical cells at significantly lower manufacturing costs than the perfluorinated membrane materials according to US-A-4876115.

Err1:Expecting ',' delimiter: line 1 column 265 (char 264)

In this context, long-term stability is defined as follows: The membrane of an electrochemical cell is said to be stable if the ohmic loss in the cell due to membrane resistance increases by less than 100 mV in 1000 hours at a current density of 1 A/cm2.

On the other hand, although the membrane materials known from, for example, US-A-4469579, US-A-4506035 or US-A-4605685 show the desired long-term stability, they are very expensive and therefore not widely used.

Err1:Expecting ',' delimiter: line 1 column 167 (char 166)

Err1:Expecting ',' delimiter: line 1 column 47 (char 46)

It is also known from EP-A-0483085 that the electrodes or their support material with the catalyst deposited on them are impregnated with a solution of the ion-exchanging sulphonated material Nafion (a DuPont trademark).

Err1:Expecting ',' delimiter: line 1 column 47 (char 46)

The object of the invention is therefore to propose an electrochemical cell of the type mentioned at the outset which, when operating above room temperature in particular, allows sufficient long-term stability to be achieved by using more cost-effective membrane materials than hitherto.

To solve this problem, an electrochemical cell of the type mentioned at the beginning is characterised by the fact that the membrane film material is a base polymer beamed with finely sulphonated vinyl residues, whereby the base polymer is selected from the group consisting of substituted and unsubstituted polyolefins, substituted and unsubstituted vinyl polymers and their copolymers and the vinyl residues are derived from vinyl monomers selected from the group consisting of substituted and unsubstituted vinyl monomers and furthermore the intermediate layer consists of a proton-conducting hydrophilic copolymer of polyperfluoralkyls substituted with ion exchange groups and polyperfluoralkyls substituted with non-ion exchange groups.

The intermediate layer is applied to the membrane film on at least one side and can envelop the carrier material with the catalyst deposited on one of the electrode bodies by impregnating the electrode body with the proton-conducting hydrophilic copolymer in its pores.

The base polymer is preferably a polyolefin selected from the group formed by polyethylene, polypropylene, polytetrafluoroethylene, copolymer of polytetrafluoroethylene and polyethylene and copolymer of polytetrafluoroethylene and polyhexafluoropropylene or a vinyl polymer selected from the group formed by polyvinyl fluoride, polyvinyl chloride and polyvinyl difluoride, while the vinyl monomer is preferably selected from the group formed by styrene, alpha-fluorstyrene, alpha-methylstyrene and para-chloromethylstyrene.

Preferably, the vinyl residues beamed onto the base polymer are interlinked by residues derived from a binding agent, the binding agent being preferably selected from the group formed by divinylbenzole and triallyl cyanurate and mixtures thereof, the membrane film material preferably containing beamed vinyl monomer residues and binding agent residues in a relative weight ratio up to approximately 60:40.

Preferably, the membrane film material contains 15 to 45% by weight of radially grafted vinyl monomer residues.

Preferably, the membrane film shall have a thickness of more than about 50 μm, in particular between 80 and 170 μm.

The electrochemical cell is preferably either a fuel cell, where: one of the means of introducing a fluid as a means of introducing a gaseous fuel into an electrode which is formed,another of the means of introducing a fluid as a means of introducing a gaseous oxidizing agent into the other electrode which is formed,another of the means of introducing a fluid as a means of introducing reaction products from the combustion reaction between the fuel and the oxidizing agent from one electrode which is formed,and,if applicable,another of the means of introducing a fluid as a means of introducing gases supplied with the gaseous oxidizing agent from the other electrode which is formed,or an electrolytic cell, 'Fluid' means a substance which is designed to initiate a fluid as a means of initiating a starting material to be electrolysed, and 'Fluid' means a substance which is designed to extract a fluid as a means of extracting reaction products from the electrochemical decomposition of the starting material.

The electrochemical cell may also be operated as a fuel cell or electrolysis cell.

A process to produce the membrane film material of this electrochemical cell is characterised by the process steps of: selecting a base polymer to be modified from the group formed by substituted and unsubstituted polyolefins, substituted and unsubstituted vinyl polymers and their copolymers; selecting a vinyl monomer from the group formed by substituted and unsubstituted vinyl monomers; performing a p-p-p reaction of the base polymer with the vinyl monomer in a mixture by applying electromagnetic radiation to the polymer to form the p-p-p-p mixture; and sulphonizing the polymer to form the p-p-p-p-p.

A first preferred embodiment of this process involves the addition and mixing of the vinyl monomer into the base polymer to form the mixture and the conduct of the grafting reaction in the mixture by exposure of electromagnetic radiation to the mixture as process steps.

A second preferred embodiment of this process includes as process steps irradiation of the base polymer with electromagnetic radiation to form a clotting intermediate polymer, cooling of the intermediate polymer to a temperature below 0°C, addition and mixing of the vinyl monomer into the cool clotting intermediate polymer to form a cool mixture and carrying out the clotting reaction in the mixture by raising the mixture temperature to at least 20°C.

A third preferred embodiment of this process involves, as process steps, the addition and mixing of the vinyl monomer and the binding agent into the base polymer to form a mixture and the execution of the grafting reaction by exposure of electromagnetic radiation to the mixture, while a grafting reaction of the vinyl residue radially grafted onto the base polymer passes through the binding agent to form the interlinked radially grafted polymer.

A fourth preferred embodiment of this process includes as process steps irradiation of the base polymer with electromagnetic radiation to form a grafting intermediate polymer, cooling of the intermediate polymer to a temperature below 0°C, addition and mixing of the vinyl monomer and the binding agent into the cool grafting intermediate polymer to form a cool mixture, and carrying out the grafting reaction in the mixture by raising the temperature of the mixture to at least 20°C, while a grafting reaction of the grafted vinyl residues tightly bound to the base polymer through the binding agent to form the grafted copper polymer is carried out.

The electrochemical cells of the invention are surprisingly stable for a long time. The ohmic loss due to membrane resistance in the electrochemical cells of the invention increases by 100 mV over a period of about 1000 hours at a current density of about 1 A/cm2 and an operating temperature of about 80°C. This result is, as I said, completely surprising because not only the membrane film material of the electrochemical cells defined in the invention was used in electrochemical cells, but also its use in electrochemical cells, and it was not known that this material achieved sufficient long-term stability of the electrochemical cells.

In this connection, it should be noted that the publication by F.N. Büchi et al. mentioned above emphasizes very strongly (in italics and bold) that no special treatment and, in particular, no impregnation of the electrodes took place in the studies and experiments described therein.

It was therefore not to be expected and is therefore surprising that the use of this material, which is known in itself, in an electrochemical cell equipped with specially trained electrodes, whereby not only this electrochemical cell but also this special training of its electrodes was known in itself, would lead to a sufficient long-term stability of the electrochemical cell of the invention.

The invention enables electrochemical cells to be manufactured where the membrane film acting as an electrolyte and separator of the electrochemical cell is significantly less expensive than the current electrochemical cells, e.g. Nafion (DuPont trademark), which results in a significant reduction in the cost of the electrochemical cells at approximately the same power under approximately the same operating conditions. Typically, under the same operating conditions and at a cell voltage of approximately 0,5 V, an invention-conform electrochemical cell produces an output of 205 mW/cm2 and a conventional cell according to US-A-4876115 and the membrane material Na 117 (DuPont trademark) produces an output of 225 mW/cm2, which are thus essentially comparable.

The method known from US-A-4605685 is much easier and cheaper and therefore particularly advantageous, in which the mixture to be grafted is first moulded into a film and the grafting reaction is then carried out, where appropriate, together with the networking reaction in the film.

The manufacture of the membrane film material of the electrochemical cell according to the invention can also be carried out as described in US-A-4605685 by using, for example, a mixture containing as the base polymer a copolymer of polytetrafluoroethylene and polyhexafluorpropylene, as the vinyl monomer styrene and as the binding agent divinylbenzene, which is made into a film of about 50 μm thickness and irradiated with gamma radiation from a Co60 source to graft the copolymer with the styrene and bind it to the divinylbenzene. The penalty is carried out with a radiation dose of, for example, 2 to 10 M, when the binding is carried out before the welding, or from 60 to 80 °C, for example, when the welding is carried out at a temperature of 40 to 80 °C.

The resulting beam-grafted and cross-linked intermediate material is then finally sulphonated as described in US-A-4605685 for example at a temperature of 40°C to 90°C for 1 to 10 hours.

The resulting material is used as an electrolyte and separator in an electrochemical cell, which may be constructed, for example, as described in US-A-4876115.

Err1:Expecting ',' delimiter: line 1 column 504 (char 503)

The following are examples of training of the invention by drawing. Figure 1 shows a schematic, not scale-relevant and partly average formation of an electrochemical cell according to the invention.

As shown in Figure 1, 1 is the generic designation for an electrochemical cell with a pair of electrodes 2a, 2b. The electrodes 2a, 2b are shaped as essentially flat electrode bodies 3a, 3b. Between the electrodes 2a, 2b and electrode bodies 3a, 3b, a film- or film-like membrane 4 is sandwiched in and arranged so that it electrochemically contacts the two electrode bodies 3a, 3b. The sandwich structure consisting of the electrode body 3a, 3b and membrane 4 is divided between two globe-shaped housing parts 5a, 5b, with these housing parts 5a, 5b together with the electrode bodies 3a, 3b, 6a, 6a, 6b, defining each chamber.

The electrode bodies 3a, 3b are composed of porous support material, which in turn consists essentially of carbon particles held together by a binder and has pores which allow fluid to percolate through the electrode body and in which the electrode body is charged with a catalyst deposited on the support material, as is known, for example, from US-A-4876115.

The housing parts 5a, 5b are connected to conduits 7a, 7b, which are intended to supply fluid, if necessary, under pressure, to the respective chambers 6a, 6b, as shown in arrows 8a, 8b. The fluid is thus introduced into the electrodes 2a, 2b and passes through the porous electrode bodies 3a, 3b to the membrane 4, which thus acts as an electrolyte and separator of the electrochemical cell 1.

Finally, electrical wires 11a and 11b are provided for the electrical contact of electrodes 2a and 2b, which are inserted into or otherwise attached to the electrode bodies 3a and 3b, for example to switch electrode 2a as anode and electrode 2b as cathode.

In this case, line 7a is used to introduce a gaseous fuel such as hydrogen, methane, natural gas and the like via anode side chamber 6a into an electrode or anode 2a, while line 7b is used to introduce a gaseous oxidizer such as oxygen or air via the cathodic chamber 6b into the other electrode or cathode 2b. In addition, line 9a is used to remove reaction products from the combustion reaction between the fuel and the oxidizer, e.g. carbon dioxide, an electrode or an electrode 2a from the bottom of the chamber 6a, while line 9 is used to remove the nitrogen from the catalyst and the other gases from the main oxygen source in the cathode side chamber 6a, respectively.

The electrochemical cell 1 may also be operated as an electrolysis cell, in which case one or both of the conduits 7a, 7b are used to introduce an input material to be electrolysed, such as water, aqueous hydrochloric acid solution and the like, via the corresponding chamber 6a, 6b, into one or both of the electrodes 2a, 2b, while the conduit 9a is used to extract reaction products from the electrochemical decomposition of the input material, such as oxygen, ozone, chlorine and the like, from one electrode or anode 2a via the anode side chamber 6a and the conduit 9b is used to extract reaction products from the electrode side chamber 6a and the main hydrogen from the other electrode base, the hydrogen, via the cathode side chamber 2 or 6b.

Finally, the electrochemical cell 1 can be operated as either a fuel cell or an electrolysis cell, as a combination of the two options mentioned above.

The interlayer is applied to the membrane film and may cover it on one or both sides.

In this case, the electrode bodies 2a, 3a or at least one of them may be impregnated in the pores in a manner substantially similar to that of US-A-4876115 with a material which improves the efficiency of the electrochemical cell and is a proton-conducting hydrophilic copolymer of polyperfluoralkylen substituted with ion exchange groups and polyperfluoralkylen substituted with non-ion exchange groups, while the membrane is in turn composed of a hydrophilic, proton-conducting polymeric material which is a basic polymer, as defined above, strapped, if necessary interlaced, with a vinyl residue of definite sulphony, so that in at least one of the electrode polymers 2a and 3a the catalyst is discharged into the porous electrode ring of the catalyst by a copper catalyst.

The following are examples of the invention, which are not limited to the invention or to the examples of the invention.

Furthermore, the relative weight ratio between vinyl monomer residues and binding agent residues resulting from examples 8 to 14 is very difficult to determine and has therefore not been reported directly by weight ratio in the examples but indirectly by volume ratio in the propelling solution.

Example 1

50 μm thick films of a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP) were irradiated in a 2 Mrad Co60 chamber and then stored in a polyethylene bag at approximately -60°C in a refrigerator for several days or weeks.

The film was placed in a glass vessel filled with a mixture of 60% vol. styrene and 40% vol. benzene, and the glass vessel was degassed by several freezing and thawing cycles, and then kept in a thermostat at 60°C for 8 hours. The glass vessel was then opened and the film was removed and extracted with toluene in a socket extractor for 5 hours. The film was then dried and weighed under vacuum.

The film was then removed, washed and dried, and the film thickness was now 57 μm. After a soaking process in water, where the thickness of the membrane film after soaking was about 80 μm, the film was titrated to the neutral point with dilute basefonate. A sulphurisation rate of 93% was calculated from the base consumption.

Example 2

A 125 μm thick FEP film was irradiated and grafted as in Example 1 and then sulphonated as in Example 1 and then grafted to a sulphonation rate of 96%.

Example 3

A 75 μm thick FEP film was irradiated as in example 1 but at a dose of 6 Mrad and then grafted with pure styrene as in example 1 and a grafting rate of 45%; the grafted film was then sulphonated as in example 1 and a sulphonation rate of 99% was calculated.

Example 4

A 75 μm thick FEP film was irradiated at a dose of 7 Mrad and then grafted at -20 °C into a mixture of 40% vol. alpha-methylstyrol and 60% vol. toluene for 50 hours. After further treatment as in example 1, a grafting rate of 19% was calculated. The grafted film was then sulphonated as in example 1, resulting in a sulphonation rate of 88%.

Example 5

A 150 μm thick polyethylene (PE) film was irradiated as in example 1 but at a dose of 2 Mrad and then grafted for 10 hours in a mixture of 60% vol. styrene and 40% vol. benzene, calculating a grafting rate of 31%, as in example 1, and then sulphonated as in example 1, calculating a sulphonation rate of 87.

Example 6

A 100 μm thick polyvinyl fluoride (PVF) film was irradiated as in example 1 but at a dose of 4 Mrad and then grafted for 10 hours as in example 1 but with a grafting rate of 29%.

Example 7

A 100 μm thick PVF film was irradiated as in example 4 but at a dose of 10 Mrad and then grafted for 60 hours as in example 4 and then sulphonated as in example 1 and then grafted for 86%.

Example 8

A 50 μm thick FEP film was irradiated as in example 1 but at a dose of 6 Mrad and then grafted as in example 1 but in a mixture of 48 vol. % styrene, 32 vol. % divinylbenzene and 20 vol. % benzene, with a grafting rate of 19%, and the grafted film was sulphonated as in example 1 with a sulphonation rate of 92%.

Example 9

A 75 μm thick FEP film was irradiated as in example 1 but at a dose of 6 Mrad and then grafted as in example 1 but in a mixture of 68 vol. % styrene, 12 vol. % divinylbenzene and 20 vol. % benzene, with a grafting rate of 25%, and the grafted film was sulphonated as in example 1 with a sulphonation rate of 94%.

Example 10

A 75 μm thick FEP film was irradiated and grafted as in Example 8 to obtain a grafting rate of 19%, and then sulphonated as in Example 1 to obtain a sulphonation rate of 91%.

Example 11

A 75 μm thick FEP film was irradiated as in example 1 but at a dose of 6 Mrad and then grafted for 4 hours as in example 1 but in a mixture of 31 vol. % styrene and 70 vol. % divinylbenzene, with a grafting rate of 15%, and then sulphonated as in example 1 with a sulphonation rate of 90%.

Example 12

A 125 μm thick FEP film was irradiated as in example 1 but at a dose of 6 Mrad and then grafted as in example 1 but in a mixture of 60% vol. styrene and 40% vol. divinylbenzene, with a grafting rate of 19%, and then sulphonated as in example 1 with a sulphonation rate of 94%.

Example 13

A 75 μm thick FEP film was irradiated as in example 1 but at a dose of 6 Mrad and then grafted as in example 1 but in a 17.5% by weight solution of triallyl cyanate in pure styrene, with a grafting rate of 29%, and the grafted film was sulphonated as in example 1 with a sulphonation rate of 88%.

Example 14

A 75 μm thick FEP film was irradiated as in example 1 but at a dose of 6 Mrad and then grafted as in example 1 but in a solution of 7.5% by weight of triallyl cyanate in a mixture of 10% by volume of divinylbenzene and 90% by volume of styrene, with a grafting rate of 40%, and the grafted film was then sulphonated as in example 1 with a sulphonation rate of 90%.

Example 15

A 75 μm thick FEP film was placed in a glass vessel filled with a mixture of 90% vol. styrene and 10% vol. divinylbenzene, which was then degassed through several freezing and thawing cycles, and then irradiated in a thermostatic Co60 chamber for about 10 hours at about 60°C at a dose of 0.03 Mrad. The glass vessel was then opened, and the film was removed and extracted with toluene in a sox elevator for 5 hours. The film was then vacuum dried and weighed. The weight gain was measured at a rate of 18%, which is the weight of the FEP film, calculated on the basis of the initial film.

The grafted film was placed in a glass vessel containing a mixture of 70% vol. 1,1,2,2-tetrachlorethan and 30% vol. chlorosulfonic acid. The film was sulphonated at 80°C for 5 hours in this mixture, stirred, then removed, washed and dried. After a spraying process in water, the film was titrated to neutral with a diluted base.

Example 16

Err1:Expecting ',' delimiter: line 1 column 361 (char 360)

Betriebsdauer (h)	20	250	500	750	1000
Ohmscher Verlust (mV)	471	474	477	479	483

Example 17

A membrane film produced in accordance with Example 14 was coated with Nafion on both sides and tested in a fuel cell in accordance with Example 16. Other

Betriebsdauer (h)	20	250	500	750	1000
Ohmscher Verlust (mV)	93	99	115	136	169

Claims (19)

1. Electrochemical cell comprising

   • a pair of electrodes each having one electrode body made of porous base material which essentially consists of carbon particles held together by a binder and has pores which permit percolation of fluid through the electrode body, and in which the electrode body is charged with a catalyst deposited on the base material,

   • a membrane film which is arranged between the electrodes, contacts the two electrode bodies electrochemically, acts as an electrolyte and separator of the electrochemical cell and is made of a hydrophilic, proton-conducting polymer material, an interlayer being provided between the membrane film and the base material with the catalyst deposited thereon,

   • means for introducing a fluid into at least one of the electrodes,

   • means for passing out a fluid from at least one of the electrodes, and

   • means for making electrical contact with the electrodes,

   characterized in that the material of the membrane film is a base polymer radiation-grafted with terminally sulphonated vinyl radicals,

   • the base polymer being selected from the group formed by substituted and unsubstituted polyolefins, substituted and unsubstituted vinyl polymers and their copolymers and

   • the vinyl radicals being derived from vinyl monomers which are selected from the group formed by substituted and unsubstituted vinyl monomers,

   and in that the interlayer comprises a proton-conducting hydrophilic copolymer of poly(perfluoroalkylene) which is substituted with ion-exchanging groups, and poly(perfluoroalkylene) which is substituted with non-ion-exchanging groups, and has been applied to the membrane film at least on one side.
2. Electrochemical cell according to Claim 1, characterized in that in the case of one of the electrode bodies the interlayer envelops the base material with the catalyst deposited thereon, the electrode body being impregnated in its pores with the proton-conducting hydrophilic copolymer.
3. Electrochemical cell according to Claim 1, characterized in that the base polymer is a polyolefin selected from the group formed by polyethylene, polypropylene, poly(tetrafluoroethylene), copolymer of poly(tetrafluoroethylene) and polyethylene, and copolymer of poly(tetrafluoroethylene) and poly(hexafluoropropylene).
4. Electrochemical cell according to Claim 1, characterized in that the base polymer is a vinyl polymer selected from the group formed by poly(vinyl fluoride), poly(vinyl chloride) and poly(vinylidene difluoride).
5. Electrochemical cell according to Claim 1, characterized in that the vinyl monomer is selected from the group formed by styrene, α-fluorostyrene, α-methylstyrene and para-chloromethylstyrene.
6. Electrochemical cell according to Claim 1, characterized in that the vinyl radicals radiation-grafted to the base polymer are cross-linked by radicals derived from a cross-linking agent.
7. Electrochemical cell according to Claim 6, characterized in that the cross-linking agent is selected from the group formed by divinylbenzene and triallyl cyanurate and mixtures thereof.
8. Electrochemical cell according to either Claim 6 or 7, characterized in that the material of the membrane film contains radiation-grafted vinyl monomer radicals and cross-linking agent radicals in a relative weight ratio with respect to one another of up to approximately 60:40.
9. Electrochemical cell according to any one of Claims 1 to 8, characterized in that the material of the membrane film contains from 15 to 45% by weight of radiation-grafted vinyl monomer radicals.
10. Electrochemical cell according to any one of Claims 1 to 9, characterized in that the membrane film has a thickness of more than approximately 50 µm.
11. Electrochemical cell according to Claim 10, characterized in that the membrane film has a thickness of from 80 to 170 µm.
12. Electrochemical cell according to any one of Claims 1 to 11, characterized in that it is a fuel cell,

    • one of the means for introducing a fluid being designed as a means for introducing a gaseous fuel into the one electrode,

    • another of the means for introducing a fluid being designed as a means for introducing a gaseous oxidant into the other electrode,

    • one of the means for passing out a fluid being designed as a means for passing out reaction products from the combustion reaction between the fuel and the oxidant from the one electrode,

    • and optionally another of the means for passing out a fluid being designed as a means for passing out inert gases, which have been supplied with the gaseous oxidant, from the other electrode.
13. Electrochemical cell according to any one of Claims 1 to 11, characterized in that it is an electrolytic cell,

    • the means for introducing a fluid being designed as a means for introducing a starting material to be electrolysed,

    • and the means for passing out a fluid being designed as a means for passing out reaction products from the electrochemical decomposition of the starting material.
14. Electrochemical cell according to Claims 12 and 13, characterized in that it is an electrochemical cell which can optionally be operated as a fuel cell or an electrolytic cell.
15. Process for preparing the electrochemical cell according to Claim 1, comprising

    • a pair of electrodes each having one electrode body made of porous base material which essentially consists of carbon particles held together by a binder and has pores which permit percolation of fluid through the electrode body, and in which the electrode body is charged with a catalyst deposited on the base material,

    • a membrane film which is arranged between the electrodes, contacts the two electrode bodies electrochemically, acts as an electrolyte and separator of the electrochemical cell and is made of a hydrophilic, proton-conducting polymer material, an interlayer being provided between the membrane film and the base material with the catalyst deposited thereon,

    • means for introducing a fluid into at least one of the electrodes,

    • means for passing out a fluid from at least one of the electrodes, and

    • means for making electrical contact with the electrodes,

    characterized by the process steps of:

    • selecting a base polymer to be modified, from the group formed by substituted and unsubstituted polyolefins, substituted and unsubstituted vinyl polymers and their copolymers,

    • selecting a vinyl monomer from the group formed by substituted and unsubstituted vinyl monomers,

    • carrying out a grafting reaction of the base polymer with the vinyl monomer in a mixture thereof by exposing the mixture to electromagnetic radiation to form the radiation-grafted polymer, and

    • sulphonating the radiation-grafted polymer.
16. Process according to Claim 15, characterized by

    • adding and blending the vinyl monomer into the base polymer to form the mixture, and

    • carrying out the grafting reaction in the mixture by exposing the mixture to electromagnetic radiation.
17. Process according to Claim 15, characterized by

    • irradiating the base polymer with electromagnetic radiation to form a graftable intermediate polymer,

    • cooling the intermediate polymer to a temperature below 0°C,

    • adding and blending the vinyl monomer into the cool graftable intermediate polymer to form a cool mixture, and

    • carrying out the grafting reaction in the mixture by raising the temperature of the mixture to at least 20°C.
18. Process according to Claim 15 for preparing the material of the membrane film of the electrochemical cell according to Claim 4, characterized by

    • adding and blending the vinyl monomer and the cross-linking agent into the base polymer to form a mixture,

    • carrying out the grafting reaction by exposing the mixture to electromagnetic radiation while at the same time a cross-linking reaction of the vinyl radicals radiation-grafted onto the base polymer takes place by means of the cross-linking agent to form the cross-linked radiation-grafted polymer.
19. Process according to Claim 15 for preparing the material of the membrane film of the electrochemical cell according to Claim 4, characterized by

    • irradiating the base polymer with electromagnetic radiation to form a graftable intermediate polymer,

    • cooling the intermediate polymer to a temperature below 0°C,

    • adding and blending the vinyl monomer and the cross-linking agent into the cool graftable intermediate polymer to form a cool mixture, and

    • carrying out the grafting reaction in the mixture by raising the temperature of the mixture to at least 20°C while at the same time a cross-linking reaction of the vinyl radicals radiation-grafted onto the base polymer takes place by means of the cross-linking agent to form the cross-linked radiation-grafted polymer.