Note: Descriptions are shown in the official language in which they were submitted.
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WO 97/27260 PCT/EP97100313
Speci~ication
METHOD FOR THE ADHESION OF FLUORINATED RESINS TO METALS
TEC~NICAL FIELD OF THE INVENTION
The present invention relates to a method for the adhesion/lamination of
5 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(JP43-12012 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
polyimides (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 eiastomers
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 of
fluorinated resins to metal materials, and of offering a method for obtaining
composite materials of metal materials and fluorinated resins.
CONFIF~MATION COPY
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WO 97/27260 PCT/EP97/00313
MEANS FOR RESOLVING THE PROBLEM
The present inventors have found that a fluorinated composition comprising at
least 2 of the 3 following components:
(a) at least a PVDF resin,
(b) at least a acrylic an/or methacrylic polymer having functional groups with
bonding properties or affinity in respect of metalsl
(c) at least a vinylidene fluoride copolymer resin
exhibits good adhesion properties on metal materials, and they have
discovered that such characteristics are effective in the production of composite
10 materials comprising such compositions and metals.
The PVDF resins (a) referred to here can be selected from polyvinylidene
fluoride homopolymers and have preferably a melt flow rate (MFR) of 0.01 to 300
9/1 Omin at 230 ~C under a load of 2.16 kg.
The vinylidene fluoride copolymers (c) are copolymers of vinylidene fluoride
15 (VF2) and other monomer(s) which can copolymerize with VF2, and the percentage
VF2 component in these copolymers should be from 50 to 95 wt%, more preferdbly
from 75 to 95 wt%. As the copolymerizable other monomer here, fluoro-monomers
such as tetrafluoroethylene, hexafluoropro~.ylene, tri-fluoroethylene and
trifluorochloroethylene, etc, are prefe~ed, and it is possible to use one or more of
20 these. It is desirable that the copolymers (c) have a room temperature flexural
modulus of no more than 1.000 MPa and that they exhibit a breaking elongation of at
least 50% and preferably a melt flow rate (MFR) at 230~C under a 2.16kg load in the
range from 0.01 to 3009/10 min.
The fluorinated resins (a) and (c) may be obtained by the polymerization of
25 vinylidene fluoride monomer or vinylidene fluoride monomer and other monomer(s)
by the suspension polymerization method or emulsion polymerization method, etc,
The acrylic and/or methacrylic polymers (b) are polymers in which the chief
component is an alkyl acrylate andlor alkyl methacrylate and which has, in the main
chain, in the side chains or at the terminals, functional groups which exhibit bonding
30 properties or affinity in terms of metals. As examples of such polymers, there are the
random copolymers, block copolymers and graft polymers produced by methods
such as radical polymerization, ionic polymerization or co-ordination polymerization
from at least one type of monomer selected from alkyl acrylates and alkyl
methacrylates, plus monomer with a functional group which exhibits bonding
35 properties or affinity in respect of metals.
As examples of functional groups which exhibit bonding properties or affinity inrespect of metals, there can be cited carLoxylic acid groups or carboxylic acid
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WO 97127260 PCT/EP97/00313
anhydride groups epoxy groups ~glycidyl 9roups)l mercapto groups, sulphide
groups, oxazoline groups, phenolic groups, ester groups, and the like.
One example of the aforesaid acrylic and/or methacrylic polymer comprises the
copolymer of monomer with a carboxylic acid group or carboxylic acid anhydride
5 group and an alkyl acrylate andlor alkyl methacrylate. In such circumstances,
specific examples of the alkyl (meth)acrylate are methyl acrylate, ethyl acrylate,
methyl methacrylate, ethyl methacrylate and butyl methacrylate. Further~ as specific
examples of the monomer with a carboxylic acid group or carboxylic acid anhydride
group, there are acrylic acid7 methacrylic acid, crotonic acid, maleic acid, fumaric
10 acid, alkenylsuccinic acid, acrylamido-glycolic acid, allyl 1,2-
cyclohexanedicarboxylate and other such unsaturated carboxylic acids, and maleicanhydride, alkenylsuccinic anhydride and other such unsaturated carboxylic acid
anhydrides, etc.
Further, it is preferred that at least 50 wt%, and more desirably at least 70 wt%,
15 of this acrylic and/or methacrylic polymer be composed of at least one type of
monomer selected from acrylate and/or methacrylate esters. The amount of the
contained functional groups which exhibit bonding properties or affinity in respect of
metals will preferably be from 0.01 to 2 mole per 1 kg of the acrylic andlor
methacrylic polymer. In the case where this polymer component is a copolymer of at
20 least one monomer selected from acrylate and/or methacrylate esters and monomer
having a carboxylic acid group or carboxylic acid anhydride group, the proportion of
the monomer with a carboxylic acid group or carboxylic acid anhydride group willpreferably be from 0.2 to 30 wt% of the said copolymer, and more preferably from 1
to 20 wt%. Further, as a constituent component, there may also be included in the
25 molecular chain, besides the above, vinyl monomer such as styrene or modifiedunits such as imides, but the amount of these will not be more than 50 wt%, and
prefer~bly not more than 30 wt% of the said polymer.
- When the metal-adhesive composition contains (a), (b) and (c) components, it
contains from 0.5 to 100 parts by weight of an acrylic and/or methacrylic polymer (b),
30 from 1 to 200 parts by weight of vinylidene fluoride copolymer resin (c) per 100 parts
by weight of polyvinylidene fluoride resin (a).
The metal-adhesive composition of the present invention can be prepared by a
solution process or melt process. In the case of a solution process, the aforesaid
components (a), (b) and (c) may be dissolved in the prescribed proportions in a
35 solvent such as N-methylpyrrolidone, N, N-dimethylrur" ,amide, tetrahydrofuran,
dimethyl-acetamide, dimethylsulphoxide, hexamethylphosphoramide,
tetramethylurea, acetone, methyl ethyl ketone or the like, at a temperature lower
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than the boiling point of the solvent used in the case of a melt process, production
can be carried out by a conventional method, i-e. heating and mixing the
components (a), (b), (c) in the prescribed proportions using a screw mixing machine.
Here, conventionally-known methods can be used as the method of melting and
mixing, such as a Banbury mixer, rubber mill or single or twin-screw extruder, etc,
and normally the resin composition is obtained by melting and mixing at 100 to
300~C and preferably, although it will also depend on the composition, 150 to 260~C.
In the present invention, if the amount of the vinylidene fluoride copolymer
10 added per 100 parts by weight of the vinylidene fluoride resin is from 1 to 10 parts by
weight, and preferably from 1 to 5 parts by weight, and, similarly, if the amount of the
acrylic or methacrylic polymer is from O.S to 10 parts by weight, preferably from 1 to
S parts by weight, then it is possible to improve the adhesion to metals withoutgreatly altering the properties of the vinylidene fluoride resin. This method is15 especially effective where the adhesion process is a solution application method.
Further, this fluorinated composition of the present invention, the metal
adhesion properties of which are improved by the aforesaid method, can be
employed as the adhesive agent when sticking fluorinated resins to metals. In
20 particular, in the case where the adhesion process is a melt process, it is preferred
that the three component-composition is composed of 5 to 100 parts by weight of the
acrylic or methacrylic polymer (b) with bonding properties or affinity in terms of
metals and from 10 to 200 parts by weight of vinylidene fluoride copolymer (c) per.
100 parts by weight of PVDF resin (a).
In the present invention, the fluorinated composition with improved metal
adhesion can be used as an adhesive agent when sticking a fluorinated resin to ametal, the said fluorinated resin does not necessarily have to be composed of the
same fluorinated resin as fluorinated resin which constitutes the surface layer.There can be selected, as the fluorinated resin employed in the adhesive layer, a
30 resin having an appropriate melt flow rate (MFR), copolymer composition and
melting point, according to the adhesion/processing operation.
As examples of the metal materials employed as the adhered base material 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
35 is not particularly restricted.
EFFECTS OF THE INVENTION
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As explained above, by means of the present invention it becomes possible to
easily improve the adhesion of fluorinated resins (and of fluorinated resin-containing
materials) and metal materials, and to easily obtain metai-adhesive fluorinated
composite materials. The metal-adhesive fluorinated composite materials obtainedby this method consist of fluorinated resin such as an extrusion moulded article (film,
sheet, plate, pipe, rod, profile extruded article, strand, monofilament, fibre, etc),
injection moulded article or press moulded article, etc, part or the entire face of
which comprises a layer of the aforesaid metal-adhesive composition, and it is not
especially restricted. Means for the preparation thereof include calendering,
10 coextrusion, extrusion lamination, multi-layer injection, fluid immersion coating,
dipping, spraying and coating the surface of a moulded body, etc. Here, the
polyvinylidene fluoride resin used as the base material and the polyvinylidene resin
used in the metal-adhesive composition may be the same or dir~aren~.
- The method of the present invention can be used for fluoro-coating materials
15 employing fluorinated resin dissolved or dispersed in a solvent or for electric wire
coating by means of fluorinated resin. Moreover, it can be used for the binders for
the electrodes of lithium batteries, etc, and in such circumstar,ces it is useful in
improving the adhesion between the metal substrate (in the case of a battery, the
current collector) and the electrode active material layer.
The method of the present invention for sticking fluorinated resins and
particularly PVDF resins andlor VF2 copolymer resins to metals can be employed in
various products, and it is valuable in many fields such as structural components of
equipment where chemical inactivity is demanded in the chemical, pharmaceutical
and foodstuffs industries, and exterior building materials and industrial materials
25 where weatherability over a prolonged period is required, and also for the binders for
electrodes in lithium batteries, etc.
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 layer.
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 seNices, hand-held and laptop computers, video games, cam recorders, etc, electric vehicles. The
lithium-ion batteries (LlBs) are an excellent solution because they are thin and35 iightweight, 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.
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The lithium-ion battery's laminate structure is generally as follows:
- a meta~ 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
10 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
15 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
20 chemicals so as their high solubility in methylpyrolidone 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.~ wt% are also preferred.
An usuai 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
30 transition metals as manganese oxide and vanadium oxide, sulfides of transition
metals such as iron sulfide and titanium sulfide, or composite compounds betweenthese 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,
35 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.
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The btnders for cathodes can be the same than dlsclosed 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
5 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 cottectors to
10 increase the anchoring effect of the fluorinated resins. However, sufficient adhesion
cannot be achieved by this technique.
The present invention provides improved binders consisting of the above
metal-adhesive compositions
1/ which contains(a) and (b) only, the amount of (b) corresponding to 0.5 to 20
15 wt% of the total composition
2/ which contains(a) and (c) only, the amount of (c) corresponding to 0.5 to 50
wt% of the total composition,
3/ which contains(a) (b) and (c) only, the amount of (b) corresponding to 0.5 to20 wt% of the total composition and the amount of (c) corresponding to 0.5 to 5020 wt%.
The electrode can be produced by the steps of kneading predetermined
amounts of electrode active substance and binder in the presence of solvent to
obtain a slurry, coating the resulting slurry onto a collector of an electrode and
drying the slurry, optionally followed by press-molding. The coated slurry is
25 preferably subjected to heat-treatment at 60 to 250 ~C, preferably 80 to 200 DC for 1
minute to 10 hours. The resulting band-shaped electrode can be wound together
with separator sheet to produce a spirally wound cylindrical electrode.
The solvent used to prepare the slurry to be coated on a metal collector can be
water and/or an organic solvent as N-methylpyrolidone, N, N-dimethylformamide,
30 tetrahydrofuran, dimethyl acetoamide, dimethyl sulfoxide, hexar"etl1ylsulfonamide,
tetramethylurea, acetone and/or methylethyl ketone. Among these solvents, N-
methylpyrolidone is preferably used. If necessary, a dispersant can also be used,
and prefer~bly an nonionic dispersant.
Below, the present invention is explained by means of examples, but the
3~ invention is not to be restricted in any way by the said examples.
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WO 97n7260 PCT/EP97/00313
Example 1
100 parts by weight of PVDF resin pellets consisting of Kynar~) 710, (sold by
the applicant, melting point 170~C, MFR at 230~C/2.16kg load = 12g/10min), 30
parts by weight of polymethylmethacrylate in which maleic anhydride had been
introduced as a copolymer component (Sumipex TR, made by Sumitomo Chemical
Co.) and 70 parts by weight of hexafluoropropylene/vinyiidene fluoride copolymer(Kynar(~) 2800 sold by the applicant, MFR at 230~C/12.5kg load = 6g/10min, melting
point 142~C) were introduced into a blender and, after mixing, pellets were produced
from the composition comprising these three components using a twin-screw
10 extruder with the cylinder temperature set at 170-240~C.
Using a film (A) of thickness about 0.2mm produced from these pellets using a
single-screw extruder, a separately-produced Kynar~) 710 film (B) (of thickness
0.3mm), and a steel sheet (C) of thickness 1mm, these were superimposed in the
order BIA/C and then pressing carried out for 10 minutes at 180~C at a maximum
15 pressure of about 10kglcm2. After cooling to room temperature, a 2cm wide layer of
B/A was stripped away from the steel sheet at 23~C using a tensile testing machine,
at a rate of 100mmlmin. When the force was measured, the adhesive strength was
found to be 2.0kglcm.
Example 2
Except for changing the proportions of Example 1 to 2 parts by weight of the
Sumipex TR and 5 parts by weight of the Kynar 2800 per 100 parts by weight of the
Kynar 710, pellets of the composition comprising these three components were
produced by the same method as in Example 1. When the adhesive strength
between the steel sheet and the PVDF resin layer was measured in the same way as25 in Example 1, it was 310g/cm.
Example 3
100 parts by weight of PVDF resin powder sold by the applicant under Kynar
(~)310F, melting point 160~C, MFR at 230~C/12.5kg load = 1.2g/10min), 1 part by
weight of Sumipex TR and 1 part by weight of Kynar(~) 2800 were introduced int
30 1000ml of N-methylpyrrolidone, and a uniform solution obtained by stirring for about
24 hours at 30~C.
This solution was coated onto 1mm thickness copper sheet and aluminium
sheet which had been degreased with toluene, and then the solution dried for 2
hours at 120~C. The thickness of the PVDF resin layer was about 50 ~um. When the35 PVDF resin layer was cut at spacings of 1mm and a cross-cut adhesion test (based
on Japanese standard JIS K5400, 6.15) and a tape peeling test carried out, in
neither test was any separation of the PVDF resin layer noted.
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Example 4
Excepting that, as the acrylic polymer with functional groups which exhibit goodbonding properties or affinity in respect of metals in Example 3, there was used a
copolymer of maleic anhydride, N-methyl-dimethylglutarimide, carboxylic-acid-
5 containing monomer and methyl methacrylate (Paraloid(~) EXL4151 sold by Rohmand Haas), a solution of metal-adhesive composition was prepared in the same way
as in Example 3. When the adhesive strength was measured in the same way as in
Example 3, no peeling of the PVDF resin layer was noted and the adhesive strength
was excellent.
ExamPle 5
Excepting that, as the acrylic polymer with functional groups which exhibit
bonding properties or affinity in respect of metals in Example 3, there was usedpolymethyl methacrylate to which epoxy-modified polymethyl methacrylate had beengrafted (made by Toagosei Chemical Industry Co., Rezeda GP-301), a solution of
metal-adhesive composition was prepared in the same way as in Example 3.
When the adhesive strength was measured in the same way as in Example 3,
no peeling of the PVDF resin layer was noted and the adhesive strength was
excellent.
Example 6
Using a co-extruder comprising a co-extrusion head for obtaining a two-layer
thermoplastic structure and two extruders for supplying molten resin thereto
(extruder A having a screw of co~pression ratio 3.5 and LID = 15 and extruder B
having a screw of compression ratio 4 and L/D = 20), PVDF resin sold by the
applicant under Kynar(E~)740) was extruded from extruder A and the adhesive
composition obtained in Example 1 was extruded from extruder B, to produce a
composite film comprising a 0.3mm PVDF resin layer and a 0.1mm adhesive layer.
The cylinder temperatures of extruders A and B at this time were 170-240~C and
1 50-220~C respectively.
When the adhesive strength between the film obtained and steel sheet was
measured by the same method as in Example 1, it was 1 .9kg/cm.
Comparative ExamPle 1
100 parts by weight of PVDF resin pellets Kynar (~)710) and 30 parts by weight
of a copolymer of maleic anhydride and methyl methacrylate (Sumipex TR sold by
Sumitomo Chemical Co.,) were introduced into a blender and, after mixing together,
there was produced a film of thickness about 0.1mm using a twin-screw extruder set
at a cylinder temperature of 1 70-240~C.
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When the adhesive strength in terms of steel sheet was measured by the
above method, using this film and a separately-prepared Kynar~710 film (of
thickness 0.3mm), the value was no more than 1 kg/cm.
Comparative ExamRle 2
100 parts by weight of PVDF resin powder (Kynar(3301F) was dissolved in
1000ml of N-methylpyrrolidone and a solution produced. Then, in the same way as
in Example 3, a PVDF resin layer was formed on metal sheet. When the adhesion
properties were evaluated by means of a cross-cut adhesion test in the same way as
in Example 3, it was found that, in the case of copper sheet, about 80% of the PVDF
layer, and in the case of the aluminium sheet, all of the PVDF layer separated away
due to the cutting at spacings of 1 mm.
ComParative ExamPle 3
100 parts by weight of Kynar(~301F and 1 part by weight of Sumipex TR were
dissolved in 1000ml of N-methylpyrrolidone, to produce a solution. When a PVDF
resin layer was formed on aluminium sheet in the same way as in Example 3, and
the adhesive strength measured, it was found that whereas in the cross-cut
adhesion test about 80% of the PVDF layer remained without peeling, in the tape
peeling test all the PVDF layer separated away.
Example 7
A binder solution was made by dissolving 10 parts by weight of
polyvinylidenefluoride Kynar@)500 and 0.1 part by weight of a methacrylate
copolymer (MFR at 230 ~C/3.8 kg: 2 4 9/10 min ) comprising 100 parts by weight of
methylmethacrylate and 10 parts by weight of maleic anhydride in N-
methylpyrolidone. Then, 90 parts by weight of coal pitch coke crushed in a ball mill
as anode activ substance was added to the solution to obtain a slurry (paste). The
slurry was coated on both sides of a copper foil of thickness 20 ,um, heated at 120
~C for 1 hour, dried under reduced pressure and then press-molded to obtain a
cathode of thickness of 140 ,um and of 20 mm.
A cathode was prepared as follows:
90 parts by weight of LiCoO2 as cathode active substance, 6 parts of graphite
as electro-conductive additive, 10 parts by weight of PVDF as binder and 0.1 part by
weight of the above-mentioned methyl"lelhacr~rlate-maleic anhydride copolymer
were mixed and dispersed in N-methylpyrolidone to obtain a slurry (paste). The
slurry was coated on both sides of an aluminum foil of thickness 20 ~m, heated at
120 ~C for 1 hour, dried under reduced pressure and tl-en press-molded to obtainanode having a thickness of 170 ,um and of width 20 mm.
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11
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 polypropyleneof thickness of 25 ,um as separator to form a laminate of
separator/cathode/separator/anode/separator which was wound up spirally to obtain
a cylindrical electrode assembly. 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 solution of LiPF6 dissolved in a
10 equivolumic mixture of propylene carbonate and 1, 2-dimethoxyethane.
A charge-discharge test was effected: the battery was charged with a current
density of 30 mA / 1 9 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 to evaluate
the capacity of discharge. The capacity of discharge after 100 cycles was 90 % of a
15 value of 10th cycle.
Example 8
The procedure of Example 7 was repeated but and the methacrylate copolymer
was changed to a block copolymer consisting of methymethacrylate block and a
copolymer block comprising methylmethacryate and acrylic acid (acrylic acid
20 contents 5 % by weight) and as the PVDF type resin, a copolymer of
vinylidenefluoride and hexafluoropropylene sold by the applicant under Kynar
2800) was used to prepare both anode and 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
25 with a cutter-knife.
A cell was manufactured by the same method as Example 1 and the same
charge-discharge test was effected. The capacity of discharge after 100 cycles was
85 % of a value of 10th cycle.
comParative ExamPle 4
The same procedure as Example 7 was repeated but no methacrylate
copolymer was added to the slurry during the preparation of both anode and
cathode.
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 7 and the same
charge-discharge test was effected. After 100 cycles the ca,uacily of discharge was
50 % of a value of 10th cycle.
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WO 97n7260 PCT/EP97/00313
12
Example 9
A binder soiution was made by dissolving 10 parts by weight of
polyvinytidenefluoride Kynar ~3500 and 0. 3 parts by weight of a copolymer of
vinylidenefluoride and hexafluoropropylene (contents of hexafluoropropylene: 10 %
by weight, a product of Elf Atochem, Kynar ~)2820, MFR of 1.0 9/10 min at 230 ~Cunder a load of 2.16 kg) in N-methylpyrolidone. Then 90 parts by weight of coal
pitch coke crushed in a ball mill as anode active substance was added to the
solution to obtain a slurry (paste). The slurry was coated on both sides of a copper
foil of thickness 20 I~m and whose surfaces have been roughened previously by
Emery paper No. 1000, heated at 120 ~C for 1 hour, dried under reduced pressure
and then press-molded to obtain a cathode of thickness of 140 ~m and of width 20mm.
A cathode was prepared as follows: 90 parts by weight of LiCoO2 as cathode
active substance, 6 parts of graphite as electro-conductive additive and 10 parts by
weight of the same PVDF and 0.3 % by weight of the same fluorinated copolymer asbinder were mixed and dispersed in N-methylpyrolidone to obtain a slurry (paste).
The slurry was coated on both sides of the aluminum foil whose surface have beenroughened previously by Emery paper No. 1000, heated at 120 ~C for 1 hour, driedunder reduced pressure and then press-molded to obtain anode of thickness 165 I~m
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 of 25 ~m as separator to form a laminate of
separa~or/cathode/separatorlanode/separator which was wound spirally to obtain acylindrical electrode assembly. 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 LiPF6 solution dissolved in anequivolumic 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 9 of carbon to 4.1 V and then was discharged with the same current to 2.5
V. The same charge-disc'narge operation was repeated to evaluate the capacity ofdischarge. The capacity of discharge after 100 cycles was 90 % of a value of 10th
cycle.
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WO 97/27260 PCT/EP97100313
13
Example 10
The procedure of Example 9 was repeated but the vinylidenefluoride copolymer
was changed to a copolymer of vinylidenefluoride and tetrafluoroethylene (Kynar
2820, weight contents of tetrafluoroethylene: 27 %, MFR of 3 g/10 min at 230 ~C
under a load of 2.16 kg) 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 Example 9 and the same
10 charge-discharge test was effected. The capacity of discharge after 100 cycles was
85 % of a value of 1 0th cycle.
ComParalive ExamPle 5
The procedure of Example 9 was repeated but no vinylidenefluoride copolymer
was~added to the slurry for electrodes.
No part of both collectors remains on both 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. After 100 cycles the capacity of discharge was
60%ofavalueof10thcycle.
ExamPle 1 1
A binder solution was made by dissolving 10 parts by weight of PVDF Kynar
500, 0.1 part by weight of a methacrylate copolymer (melt flow index of 2.4 g/10 min
at 230 ~C under a load of 3.8 kg) comprising 100 parts by weight of
methylmethacrylate and 10 parts by weight of maleic anhydride, and 0.1 part by
25 weight of a copolymer of vinylidenefluoride and hexafluoropropylene Kynar~2800
MFR of 0.2 g/10 min at 230 ~C under a load of 2.16 kg) in N-methylpyrolidone. Then,
90 parts by weight of coal pitch coke crushed in a ball mill as anode active carrier
was added to the solution to obtain a slurry (paste). The slurry was coated on both
sides of a copper foil of thickness 20 IJm, heated at 120 ~C for 1 hour, dried under
30 reduced pressure and then press-molded to obtain an anode of thickness 145 ,um
and of width 20 mm.
A cathode was prepared as follows: 90 parts by weight of LiCoO2 as cathode
active substance, 6 parts of graphite as electro-conductive additive, 10 parts by
weight of PVDF, 0.1 part by weight of the above-mentioned methacrylate copolymer35 and 0.1 part by weight of the above copolymer of vinylidenefluoride and
hexafluoropropylene as binder were mixed and dispersed in N-methylpyrolidone to
obtain a slurry (paste). The slurry was coated on both sides of an aluminum foil of
CA 022433~4 1998-07-17
WO 97/27260 PCT/EP97100313
14
thickness 20 ~m, heated at 120 ~C for 1 hour, dried under reduced pressure and
then press-molded to obtain an anode of thickness 175 ~m 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 IJm as separator to form a laminate of
separator/cathode/separator/anodelseparato~ which was wound up spirally to obtain
a cylindrical electrode assembly. After lead wires were attached to respective
10 electrodes, the electrode assembly was packed in a stainless container into which
an electrolyte was poured. The electrolyte is 1 M solution of LiPF6 dissolved in an
equivolumic mixture of propylene carbonaté 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
15 V. The same charge-discharge operation was repeated to evaluate the capacity of
discharge. The capacity of discharge after 100 cycles was 95 % of a value of 10th
cycle.
Example 12
The procedure of Example 11 was repeated but the methacrylate copolymer
20 was replaced to a block copolymer consisting of methylmethacrylate block and a
copolymer block comprising methylmethacrylate and acrylic acid (weight contents of
acrylic acid: 5 %) and the fluorinated copolymer was replaced by a copolymer of
vinylidenefluoride and tetrafluoroethylene (weight contents of tetrafluoroethylene:
27 %, MFR of 3 g/10 min at 230 ~C under a load of 2.16 kg) to prepare an anode
25 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 Example 11 and the same
30 charge-discharge test was effected. The capacity of discharge after 100 cycles was
92 % of a value of 1 0th cycle.
Comparative ExamPle 6
The same procedure as Example 1 was repeated but the methacrylate
copolymer and the fluorinated copolymere were not added to the slurry in
35 preparation of both anode and cathode.
No part of both collectors remains on both electrodes when peeled off with a
cutter-knife.
CA 02243354 1998-07-17
WO 97/27260 PCT/EP97/00313
A cell was manufactured by the same method as in Example 11 and the same
charge-dischar~e test was effected. After 100 cycles the capacity of discharge was
50%ofavalueof 10thcycle.
