WO1997027003A1

WO1997027003A1 - Method for the adhesion of fluorinated resins to metals

Info

Publication number: WO1997027003A1
Application number: PCT/EP1997/000314
Authority: WO
Inventors: Yoshiyuki Miyaki; Kazuyoshi Ohashi; Takatoshi Kuratsuji; Yoshiyuki Shimonishi
Original assignee: Elf Atochem S.A.
Priority date: 1996-01-22
Filing date: 1997-01-22
Publication date: 1997-07-31
Also published as: AU1544997A

Abstract

The objective of the present invention is to offer a simple method for improving the adhesion of fluorinated resins to metal materials, and for obtaining composite materials of metal materials and fluorinated resins and composite materials of metal materials and fluorinated resins-containing materials. The method consists of treating the surface of the metal with a (metha)crylate copolymer prior to the adhesion of metal and fluorinated resins or fluorinated resins-containing materials.

Description

Specification

METHOD FOR THE ADHESION OF FLUORINATED RESINS TO METALS TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for the adhesion/lamination of fluorinated resins and metals which are inherently non-adhesive thereto, and the invention can be applied to steel pipe linings, chemical plant components, and binders for the electrodes of batteries, etc, where corrosion resistance, weathering resistance or chemical resistance is demanded. PRIOR ART As a fluoropolymer of outstanding weatherability and chemical resistance, etc, which can be melted and moulded, polyvinylidene fluoride (hereinafter abbreviated to PVDF) resin is used for coating materials and for electrical/electronic components, steel pipe linings, chemical plant components and weather-resistant/stain-resistant film, etc. However, since it has practically no adhesion properties in terms of other materials, it suffers from the problem that it is difficult to modify or composite with other materials.

Hence, the mixing of other polymers with PVDF has been attempted in order to overcome this disadvantage, but there are few polymers having adhesion properties or compatibility in respect of PVDF, and because of adverse effects on the physical properties of the PVDF, etc, the application range is extremely restricted. For example, polymethyl methacrylate resin (hereinafter abbreviated to

PMMA) is known to be a material with good compatibility for PVDF (JP 43-12012 and JP51-18197), but the glass transition temperature of PMMA is very high when compared to that of PVDF, so mixtures of these lack flexibility and they have poor adhesion to metals. On the other hand, composites with polycarbonate (JP57-

8244), composites with modified polyolefins having functional groups (JP62-

57448), and composites with poiyimides (JP2-308856), and the like, have also been proposed, but these combinations are lacking in compatibility and they are inferior in terms of their adhesion to metals. In addition, composites with acrylate or methacrylate elastomers have also been proposed (JP4-218552), but nothing is known of the adhesion to metals system.

PROBLEM TO BE RESOLVED BY THE INVENTION

The present invention has the objective of improving the adhesion between fluorinated resins and metal materials, and of offering a simple method for obtaining composite materials of metal materials and fluorinated resins and composite materials of metal materials and fluorinated resins-containing materials. MEANS FOR RESOLVING THE PROBLEM

The present inventors have found that add a metal surface with an acrylate and/or methacrylate polymer to fluorinated resins, so that traces of such resin adhere to the said metal surface, there is a considerable improvement in the adhesion between the metal material and fluorinated resin, and they have discovered that this method is effective in the production of composite materials comprising fluorinated resins and metals. Specifically, the present invention relates to a method for the adhesion of fluorinated resin to metals which is characterized in that, at the time of the adhesion of fluorinated resin to metals, the surface of the metal is treated beforehand with an acrylate and/or methacrylate polymer.

The fluorinated resins referred to here can be selected from vinylidene fluoride homopolymers and the copolymers of vinylidene fluoride with other fluorinated monomers, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene, copolymers of ethylene and tetrafluoroethylene, copolymers of tetrafluoroethylene and hexafluoropropylene, polyvinylfluoπde (PVF), polyaikylvinylethers. These resins can be used on their own or as mixtures of two or more types

Among them, the vinylidene fluoride homo- and/or copolymers (briefly the PVDF resins) with at least 50 wt% and preferably at least 75 wt% of vinylidene fluoride (VF2) are preferred, alone or in combination. As examples of copolymerizable other monomers, there can be cited fluoro-monomers such as tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trifluorochloroethylene and vinyl fluoride, etc, and one or more than one of these can be used. These PVDF resins are generally obtained by the polymerization of vinylidene fluoride monomer, or vinylidene fluoride monomer and other monomer(s), by the suspension polymerization method or emulsion polymerization method, etc, and a melt flow rate (MFR) at 230°C under a 2.16 kg load in the range from 0.01 to 300g/10 min is preferred.

The acrylate and/or methacrylate polymer employed in the present invention is a polymer in which the main component is an alkyl acrylate and/or an alkyl methacrylate. Here, examples of the alkyl (meth)acrylates are methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate and butyl methacrylate, etc. In the present invention, the (meth)acrylate polymer preferably has, in the main chain, side chains or at the chain ends, functional groups which exhibit bonding properties or affinity in terms of metals. As examples of such polymers, there are the random copolymers, block copolymers and graft polymers obtained by the polymerization of at least one monomer selected from alkyl acrylates and alkyl methacrylates, and monomer with a functional group which displays bonding properties or affinity in respect of metals, by the radical polymerization, ionic polymerization or co-ordination polymerization methods, etc

As examples of the functional group which exhibits bonding properties or affinity in respect of metals, there can be cited the carboxylic acid or carboxylic acid anhydride group, epoxy group (glycidyl group), mercapto group, sulphide group, oxazoline group, phenolic group, ester group, or the like.

As examples of monomer with a carboxylic acid group or carboxylic acid anhydride group, there are acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, alkenylsuccinic acid, acrylamidoglycolic acid, allyl 1 ,2- cyclohexanedicarboxylate and other such unsaturated carboxylic acids, and maleic anhydride, alkenylsuccinic anhydride and other such unsaturated carboxylic acid anhydrides, etc. As an example of a monomer containing an epoxy group, there is glycidyl methacrylate.

In such a (meth)acrylate polymer, it is preferred that at least 50 wt% of the said polymer be composed of one or more than one monomer selected from acrylic acid esters and/or methacrylic acid esters, with at least 70 wt% being further preferred. The amount of contained functional groups with bonding properties or affinity in terms of metals will preferably be from 0.01 to 2 mmol per

1g of the (meth)acrylate polymer. Hence, in the case of a copolymer of at least one monomer selected from acrylate esters and/or methacrylate esters, and monomer with a carboxylic acid group or carboxylic acid anhydride group, the proportion of this monomer with a carboxylic acid group or carboxylic acid anhydride group will desirably lie in the range from 0.2 to 30 wt%, more preferably in the range from 1 to 20 wt%. Further, as a constituent component, there may also be included in the molecular chain, besides the above, vinyl monomer such as styrene or modified units such as imides, but the amount of these will not be more than 50 wt%, and preferably not more than 30 wt% of the acrylic polymer.

As the method of treating the metal surface with the (meth)acrylate copolymer, there is the method of bringing the metal surface into contact with a solution formed by dissolving the copolymer in a solvent. An appropriate concentration for this copolymer solution is typically from 0.02 to 10 wt%, and after treating the metal surface with this solution, following optional washing with solvent, the surface should be dried.

In the case where the concentration of the aforesaid (meth)acrylate copolymer solution is low i-e from 0.02 to 1 wt%, following the contacting of the metal surface with this solution there is no necessity to perform washing using solvent, and the surface may be dried as it is. On the other hand, in the case where the concentration of the copolymer solution is high i-e exceeds 1 wt%, then, following the contacting of the metal surface with this solution, it is preferred that washing be conducted using solvent, after which drying is performed In cases where a PVDF Iayer is coated onto a metal which has been covered with a thick acrylate and/or methacrylate copolymer Iayer, when there is prolonged contact with a solvent the adhesive Iayer is swollen by the solvent and the affixed Iayer tends to separate away Hence, the preferred thickness of the (meth)acrylate copolymer Iayer coated onto the metal is no more than 2 μm, and more preferably no more than 0 5 μm

As examples of the metal materials employed in the present invention, there are iron, stainless steel, aluminium, copper, nickel, titanium, lead, silver, chromium, and alloys of various kinds, etc, and the form thereof is not particularly restricted

EFFECTS OF THE INVENTION

As explained above, by means of the present invention it becomes possible to perform the adhesion of fluorinated resins , and preferably PVDF resins and metal materials easily This method can be applied to the case of the melt adhesion of a metal material and a fluorinated resin film or sheet by the extrusion lamination method, or the like, or it can be applied to the coating of a fluorinated resin or a fluorinated resin-containing material onto a metal surface by means of the fluid dip coating, dipping, coil coating or spray coating method, etc, using a fluoro-coating material formed by dissolving or dispersing fluorinated resin in a solvent The method of the present invention can be applied to various products, and it is valuable in many fields such as the structural components of equipment where chemical inactivity is demanded in the chemical, pharmaceutical and foodstuffs industries, and exterior building materials and industrial materials where weatherability over a prolonged period is required, and also for the binders for electrodes in lithium-ion batteries. For the electrode production process of lithium- ion batteries, it is useful to strengthen the adhesion between the metal substrate of the current collector and the electrodes' active material Iayer There is a great demand for smaller rechargeable batteries possessing high capacity and long life in portable electronic products (cellular phones, pagers, personal digital assistants, equipment for personal communication services, hand¬ held and laptop computers, video games, cam recorders, etc, electric vehicles. The lithium-ion batteries (LIBs) are an excellent solution because they are thin and lightweight, do not contain heavy metals than cause environmental problems and they provide higher energy density than existing nickel-cadmium, nickel-metal hydride, and lead-acid batteries. The lithium-ion battery's laminate structure is generally as follows ^'

- a metal collector

- a lithium/metal oxide-based positive electrode or cathode,

- an electrolyte, - a carbon-based negative electrode or anode ,

- a metal collector

The anode active substance can be made of any material which permits doping and releasing of lithium ions and is generally made of carbonaceous materials including cokes such as petroleum cokes and carbon cokes, carbon blacks such as acetylene black, graphite, fibrous carbon, activated carbon, carbon fibers and sintered articles obtained from organic high polymers by burning the organic high polymer in non-oxidation atmosphere. Copper oxide or other electro¬ conductive materials also can be incorporated or added to the cathode active substance. The binder which must possess high resistance to solvents and chemicals is generally based on fluorinated resins, polyolefins, synthetic rubbers but fluorinated resins are preferred. The contents of fluorinated resins in the binder is preferably more than 90 wt%.

The PVDF resins are preferably used and more particularly these ones with more than 75 wt% VF2 because of their high resistance to solvents and to active chemicals so as their high solubility in methyipyrolidone which is a common solvent of lithium-ion batteries. Among PVDF resins, these ones consisting of mixtures of homopolymer of vinylidenefluoride and fluorinated copolymer(s), the contents of VF2 of the fluorinated copolymer(s) is 50 to 95 wt% and whose amount of homopolymer of vinylidenefluoride in the mixture is 50 to 99.5 wt% are also preferred.

An usual process for making the anode consists of mixing the carbonaceous material in powder form with a suitable amount of binder and is kneaded with a solvent to prepare a paste or slurry. Then a collector (generally copper) is coated onto the paste and is then dried and compacted to obtain the anode.

The lithium-ion battery cathode is generally made of lithium and oxide of transition metals as manganese oxide and vanadium oxide, sulfides of transition metals such as iron sulfide and titanium sulfide, or composite compounds between these substances as composite oxides of lithium and cobalt, composite oxides of lithium, cobalt and nickel, composite oxides of lithium and manganese. The cathode active substance can also be mixed with electroconductive substances (usually, carbon) and a suitable amount of binder and is kneaded with a solvent to prepare a paste which is then applied to a collector (generally an aluminum collector) and is then dried and compacted to obtain the cathode

The binders for cathodes can be the same than disclosed for the anodes and are preferably based on fluorinated resins. For both types of electrodes, the amount of binder is generally of 1 to 30 parts, preferably 3 to 15 parts by weight, with respect to 100 parts by weight of electrode active substance.

But, as mentioned above, fluorinated resins, having inherently poor adhesion to metals, the electrode (active substance + binder) separate easily from the collector for both types of electrodes i-e cathode and anode, resulting in inferior cycle property of cells. JP5-6766 has proposed to roughen a surface of collectors to increase the anchoring effect of the fluorinated resins. However, sufficient adhesion cannot be achieved by this technique.

The adhesion method of the present invention provides lithium-ion batteries and cells whose collectors' adhesion to electrodes is dramatically improved.

The method is characterized in that the surface of the metallic collector is treated with a (meth)acrylate copolymer as mentioned above prior to be coated onto the electrode (active substance + binder), preferably in the form of a slurry. The treatment method of collector with a (met)acrylate copolymer can be carried out by the following steps comprising contacting the collector with a solution of (meth)acrylate copolymer (concentration from 0.02 to 10 wt%, and preferably from 0.05 to 2 % by weight) as disclosed above, washing with a solvent and drying, preferably when the concentration of (meth)acrylate copolymer in the solution is higher than 1 wt%.

The (meth)acrylate copolymer can be chosen among those disclosed above and preferably contains at least 0.5 to 20 parts by weight of a monomer having carboxyl group or carboxyl anhydride group and more preferably 2 to 15 parts by weight. Then the treated collector is coated with a slurry comprising the electrode active and the binder in a solvent which can be water and/or an organic solvent as N-methylpyrolidone, N, N-dimethylformamide, tetrahydrofuran, dimethyl acetoamide, dimethyl sulfoxide, hexamethylsulfonamide, tetramethylurea, acetone and/or methylethyl ketone. Among these solvents, N-methylpyrolidone is preferably used. If necessary, a dispersant can also be used, and preferably an nonionic dispersant. The present invention relates also to electrodes which can be produced by the steps of

- kneading the electrode active substance and the binder based on PVDF resins, in the presence of a solvent to obtain a slurry, - coating the-said slurry onto a collector pre-treated with a (meth)acrylate copolymer,

- and drying the slurry, optionally followed by press-molding. The resulting band-shaped electrode can be bound together via an electrolyte or an electrolyte plus separator sheet to produce a complete battery cell. The collector for electrode may be metal foil, metal mesh, three-dimensional porous block or the like and is made preferably of a metal which does not produce easily an alloy with lithium (in the case of the cathode) such as iron, nickel, cobalt, copper, titanium, vanadium, chromium and manganese alone or of their alloy. EXAMPLES The present invention is explained by means of examples, but the invention is not to be restricted in any way by the said following examples.

Example 1

Polymethyl methacrylate in which maleic anhydride had been introduced as a copolymer component (Sumipex TR, made by Sumitomo Chemical Co.) was dissolved in tetrahydrofuran, to give a polymer concentration of 0.2 wt%. Copper sheet of thickness 1.0 mm, which had been degreased with toluene, was immersed in this solution for 3 min, and then dried for 10 min at 50 °C in dry air. Further, there was also obtained aluminium sheet of thickness 1.0 mm, surface- treated with Sumipex TR in the same manner. The thickness of the Sumipex TR Iayer formed on the metal surface at this time was about 0.1 μm.

A solution formed by dissolving 10 g of PVDF resin powder (Kynar® 301 F, soldby the applicant; melting point = 160°C; MFR at 230°C/12.5 kg load = 1.2g/10min) in 100ml of N-methylpyrolidone was applied onto the aforesaid copper and aluminium sheets, then dried for 2 hours at 120°C, and an approximately 50 μm PVDF resin Iayer coating formed on these metal sheets. When cutting of the PVDF resin Iayer was carried out at 1 mm spacings and a cross-cut adhesion test (based on the Japanese standard JIS K5400 6.15) and also a tape peeling test carried out, in neither test was there any observed separation of the PVDF resin Iayer at all. Furthermore, even when these test- pieces were immersed for 2 hours in ethylene carbonate at 80°C, absolutely no separation of the PVDF resin Iayer was noted. Example 2

Metal sheets coated with a PVDF resm Iayer were prepared in the same way as in Example 1 except that the PVDF of Example 1 was replaced by Kynar® 2821 (sold by the applicant, melting point = 142°C, melt flow rate (MFR) at 230°C/2 16kg load = 1g/10mιn), which is a copolymer of vinylidene fluoride and hexafluoropropylene When a cross-cut adhesion test and tape peeling test were carried out in the same way, in neither test was any separation of the PVDF resin Iayer observed Example 3 Metal sheets coated with a PVDF resin Iayer were prepared in the same way as in Example 1 except that, as the methacrylate polymer with functional groups having bonding properties or affinity in terms of metal in Example 1 , there was used a copolymer comprising 11 wt% maleic anhydride, 74 wt% methyl methacrylate and 15 wt% styrene (sold by Degussa, Plexiglas ® HW55) When a cross-cut adhesion test and tape peeling test were carried out in the same way, in neither test was any separation of the PVDF resin layer observed. Example

A copper sheet coated with a PVDF resin Iayer was prepared in the same way as in Example 1 except that, instead of the methacrylate copolymer Sumipex TR in Example 1 , there was used methyl methacrylate homopolymer (Acrypet MF made by Mitsubishi Rayon). When a cross-cut adhesion test and tape peeling test were carried out in the same way, no separation of the PVDF resin layer was observed in the cross-cut adhesion test but in the tape peeling test about 30% of the PVDF resin Iayer came away Example 5

At the time of the dissolution of the Sumipex TR in tetrahydrofuran in Example 1, a polymer concentration of 5 wt% was produced. After immersing, in this solution, copper sheet and aluminium sheet of thickness 1.0 mm for 3 min respectively, washing was performed with tetrahydrofuran which did not contain polymer, and then drying carried out for 10 minutes at 30 °C in dry air. Metal sheets coated with PVDF resin Iayer were then prepared using a PVDF solution in the same way as in Example 1. When the same cross-cut adhesion test and tape peeling test were carried out, absolutely no separation of the PVDF resin Iayer was noted in either test. Further, even when, following the cross-cut adhesion test, the test pieces were immersed for 2 hours in ethylene carbonate at 80°C, absolutely no separation of the PVDF resin Iayer was observed. Example 6

After the immersion of the copper sheet in the 5 wt% solution of Sumipex TR in Example 5, the said copper sheet was directly dried for 10 mm at 30°C in dry air without first washing with the tetrahydrofuran which did not contain any polymer. This copper sheet was then coated with a PVDF resin Iayer in the same way, and when the same cross-cut adhesion test and tape peeling test were carried out, in neither test was there any observed separation of the PVDF resin Iayer. However, when, following the cross-cut adhesion test, the test piece was immersed for 2 hours in ethylene carbonate at 80 °C, about 50 % of the PVDF resin Iayer came away.

Example 7

Metal sheets coated with a PVDF resin Iayer were prepared in the same way as in Example 1 except that, as the methacrylate polymer with functional groups which display bonding properties or affinity in terms of metals, there was used polymethyl methacrylate to which epoxy-modified polymethyl methacrylate had been grafted (Rezeda® GP-301 , sold by Toagosei Chemical Industry). When a cross-cut adhesion test and tape peeling test were carried out in the same way, in neither test was any separation of the PVDF resin Iayer observed. Example 8 The tetrahydrofuran solution containing 0.2 wt% Sumipex TR produced in

Example 1 was coated onto one face of copper foil of thickness 20 μm which had been degreased with toluene, and then drying carried out for 10 mm at 50 °C in dry air. Next, a sheet of thickness 300 μm produced from Kynar® 710 (sold by ELF ATOCHEM S.A.; melting point = 170°C, MFR at 230°C/2.16kg load = 12g/10 min), which is a PVDF homopolymer, was superimposed on the face of the aforesaid foil which had been coated with Sumipex TR, and then pressing conducted for 5 min at 180 °C and at a maximum pressure of 3 kg/cm². When the sheet obtained was cut to a 2cm width and the adhesive strength measured by means of a tensile testing machine, it was found that the copper foil broke during the test so that an accurate value could not be obtained. Nevertheless, it was clear that the adhesive strength was over 100 g/cm. Comparative Example 1

Using the copper and aluminium sheets of thickness 1.0 mm in Example 1, but which had only been subjected to degreasing with toluene and had not been treated with the Sumipex TR, there was applied thereto a Kynar® 301 F solution identical to that in Example 1, then drying carried out for 2 hours at 120 °C, to form an approximately 50 μm PVDF resin Iayer coating on these metal sheets. In the evaluation of the adhesion by means of a cross-cut adhesion test, as a result of the cutting at spacings of 1mm, about 80% of PVDF Iayer came away in the case of the copper sheet, and all the PVDF Iayer came away in the case of the aluminium sheet.

Comparative Example ? An aluminium sheet coated with a PVDF resin Iayer was prepared in the same way as in Comparative Example 1, except that instead of the Kynar® 301 F in Comparative Example 1 there was used Kynar® 2821. When a cross-cut adhesion test and a tape peeling test were carried out in the same way, it was found that, while in the cross-cut adhesion test there was 0% separation of the PVDF resin Iayer, in the tape peeling test about 60% of the PVDF Iayer came away.

Comparative Example 3

Using the same copper foil that in Example 8, but which had only been subjected to degreasing with toluene and which had not been treated with Sumipex TR, this copper foil and a sheet of thickness 300 μm prepared from Kynar 710 were stuck together by pressing in the same way as in Example 1. When the sheet obtained was cut to a width of 2 cm, and the adhesive strength measured by means of a tensile testing machine, the value was low, at 20 g/cm. Example 9 A methacrylate copolymer comprising 100 parts by weight of methylmethacrylate and 10 wt % of maleic anhydride (MFR at 230 °C/3.8 kg load = 2.4 g/10 min) was dissolved in tetrahydrofuran to prepare a 0.2 wt % solution of this copolymer.

A copper foil of thickness 20 μm was dipped in the solution for 3 min and dried in heated air at 30 °C for 10 min. An aluminum foil of thickness 20 μm was treated in the same manner with the same copolymer.

90 parts by weight of coal pitch coke crushed in a ball mill as anode activ substance was added to a solution of N-methylpyrolidone in which homopolymer of polyvinylidenefluoride (Kynar® 461 sold by the applicant, MFR at 230°C/2.16 kg load = 0.03 g/10min ) as binder was dissolved to prepare a slurry. Then, the slurry was coated on both sides of the copper foil treated with the methacrylate copolymer previously left at 120 °C for one hour, dried under reduced pressure and then press-molded at 150 °C to obtain an anode of thickness 140 μm and of width 20 mm. A cathode was prepared according to the following procedure :

90 parts by weight of L1C0O2 as cathode active substance, 6 parts of graphite as electroconductive additive and 10 parts by weight of the same PVDF as binder were mixed and dispersed in N-methylpyrolidone to obtain a slurry. The slurry was coated on both sides of the pre-treated aluminum foil heated at 120 °C for 1 hour, dried under reduced pressure and then press-molded to obtain a cathode of thickness 170 μm and of width 20 mm.

A good adhesion between the electrodes and the collectors was noted : the collectors cannot be removed from the surface of the electrodes when peeled off with a cutter-knife.

The resulting cathode and anode were laminated alternately through a film of porous polypropylene of thickness 25 μm as separator to form a laminate cell consisting of separator/cathode/separator/anode/separator which was wound up spirally to obtain a cylindrical cell. After lead wires were attached to respective electrodes, the electrode assembly was packed in a stainless container into which an electrolyte was poured. The electrolyte is 1 M LiPFβ solution dissolved in an equivolumic mixture of propylene carbonate and 1, 2-dimethoxyethane.

In the charge-discharge test, the battery was charged with a current density of 30 mA/1 g of carbon to 4 1 V and then was discharged with the same current to 2.5 V. The same charge-discharge operation was repeated in order to evaluate the capacity of discharge. The capacity of discharge after 100 cycles was 90 % of a value of 10 th cycle. Example 10 The procedure of Example 9 was repeated but the collector was treated with a methylmethacryate and acrylic acid block copolymer whose acrylic acid content is 5 % by weight. A copolymer of vinylidenefluoride and hexafluoropropylene (Kynar® 2800 sold by ELF ATOCHEM S.A., MFR at 230°C/2.16 kg load = 0.2 g/10 min) was used as binder to prepare an anode and a cathode. A good adhesion between the electrodes and the collectors was noted : the collectors cannot be removed from the surface of the electrodes when peeled off with a cutter-knife.

A cell was manufactured according to the same method as in Example 1 and the same charge-discharge test was effected. The capacity of discharge after 100 cycles was 86 % of a value of 10th cycle. Example 11

The procedure of Example 9 was repeated but the binder was a mixture of 98 wt% of polyvinylidenefluoride (Kynar® 461 sold by the applicant) and of 2 wt% of a copolymer of vinylidenefluoride and hexafluoropropylene (10 wt% of HFP ; MFR at 230°C/2.16 kg load = 1.0 g/10min) to prepare an anode and a cathode.

A good adhesion between the electrodes and the collectors was noted : the collectors cannot be removed from the surface of the electrodes when peeled off with a cutter-knife. A cell was manufactured by the same method as in Example 9 and the same charge-discharge test was effected. The capacity of discharge after 100 cycles was 93 % of a value of 10th cycle.

Comparative Example 4 The procedure of Example 9 was repeated but both collectors (copper foil and aluminum foil) were not treated with a methacrylate copolymer.

No part of collector remains on the electrode when peeled off with a cutter- knife.

A cell was manufactured by the same method as in Example 9 and the same charge-discharge test was effected. After 100 cycles the capacity of discharge was 50 % of a value of 10th cycle.

Claims

1_. Method for the adhesion of fluorinated resins and fluorinated resins- containing materials to metals which is characterized in that, at the time of the adhesion of a polyvinylidene fluoride resin to a metal, the surface of the said metal is treated beforehand with an acrylate/or methacrylate polymer.

2. Method according to claim 1 , characterized in that the metal surface is brought into contact with a solution formed by dissolving the (meth)acrylate copolymer in a solvent at a concentration of 0.02 to 1.0 wt%, after which drying is carried out.

3. Method according to claim 1 , characterized in that the metal surface is brought into contact with a solution formed by dissolving the (meth)acrylate copolymer in a solvent at a concentration of 1.0 to 10 wt%, after which washing is performed with a solvent and then drying is carried out.

4. Method for the adhesion of fluorinated resins and fluorinated resins- containing materials to metals according to Claims 1 to 3, where the

(meth)acrylate copolymer has functional groups which display bonding properties or affinity in terms of metals, which are preferably carboxylic acid groups and/or carboxylic acid anhydride groups and/or epoxy groups.

5. Method according to any of claims 1 to 4, characterized in that the fluorinated resin is polyvinylidene fluoride homopolymer and/or a copolymer of vinylidene fluoride and at least one monomer selected from tetrafluoroethylene, hexafluoropropylene, trifluoro-ethylene and trifluorochloroethylene, whose vinylidene fluoride contents is at least 50 wt%.

6. Method for the adhesion of an metal collector to an fluorinated resin- containing electrode characterized in that the surface of the metallic collector is treated with a (meth)acrylate copolymer as defined in any of claims 1 to 3, prior to be coated onto the electrode (active substance + binder), preferably in the form of a slurry.

7. Electrode comprising a metallic collector coated on the electrode active substance and binder , characterized in that the surface of the collector is pre¬ treated according to the method of claim 6.

8. Battery and/or cell comprising at least one electrode as defined in claim 7, and preferably lithium-ion battery and/or cell.