JP2003132951A - Manufacturing method of lithium polymer secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a lithium polymer secondary battery which integrates a separator, a cathode plate and an anode plate even if a thin laminate sheet is used for an exterior case. SOLUTION: An electrode group, which winds around the separator having a cathode an anode, and an adhesive layer on its surface, is integrated by gelating the adhesive layer by injecting and warming organic electrolytic solution to keep a certain distance between the cathode and the anode.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing an organic electrolyte battery such as a lithium polymer secondary battery, and more particularly to a method for manufacturing a positive electrode plate and a negative electrode plate through a separator. .

[0002]

2. Description of the Related Art In response to the demand for smaller, lighter and thinner portable devices, the batteries used therein are required to be smaller and thinner. As one of means for achieving a thinner battery, there is a method of using a laminate sheet using a metal foil of aluminum or the like as an intermediate layer instead of a metal case made of aluminum or iron for the outer case.

However, since the laminated sheet has a lower pressure for pressing the electrode group than a metal case made of aluminum or iron, the distance between the positive and negative electrodes becomes large due to charge / discharge cycles and high temperature storage, resulting in a decrease in capacity.

Therefore, by integrating the positive and negative electrodes and the separator,
Many batteries have been proposed that have excellent cycle characteristics and storage characteristics by maintaining a constant distance between the positive and negative electrodes.

As an example of such a battery, US Pat.
No. 607485 discloses a positive electrode plate having a positive electrode active material layer formed on a positive electrode current collector, a negative electrode plate having a negative electrode active material layer formed on a negative electrode current collector, and a polymer material such as vinylidene fluoride. In this method, a separator made of a copolymer of propylene and hexafluoropropylene is produced, and the positive electrode plate and the negative electrode plate are heated and pressed through the separator to integrate them. In this manufacturing method, in order to reduce the heating temperature at the time of integration, all of the positive electrode plate, the negative electrode plate, and the separator contain a plasticizer such as n-dibutyl phthalate (DBP), and xylene is used after integration. It is characterized by extracting the plasticizer with a solvent such as.

Further, in WO99 / 26307,
One of the positive electrode plate and the negative electrode plate is sandwiched between two separators, and an electrode group with a separator is prepared in advance by adhering with polyvinylidene fluoride, and then the other electrode is wound to form an integrated electrode group. A method of making has been proposed.

[0007]

By integrating the positive and negative electrodes and the separator and maintaining the distance between the positive and negative electrodes constant, it is possible to achieve high cycle characteristics and storage characteristics even when a thin laminated sheet is used as an outer case. Can, but
The manufacturing method is more complicated than the conventional lithium-ion batteries, and the material cost and the manufacturing cost are unavoidably increased.

For example, in the case of the manufacturing method of the above-mentioned US Pat. No. 5,607,485, the plasticizer must be extracted with a solvent such as xylene after the electrode group is manufactured. Further, in order to uniformly permeate the entire extraction electrode group with this extraction solvent to extract the plasticizer, either or both of the positive and negative electrode metal current collectors have through holes instead of inexpensive metal foils. For example, it must be expanded metal, lath metal, etc.

[0009] In WO99 / 26307, for example, a separator is preliminarily adhered to both surfaces of a negative electrode by using polyvinylidene fluoride, and then wound together with a positive electrode to prepare an integrated electrode group. In this method, the separator is adhered to both sides of the negative electrode. When the above separator is wound, a difference in inner and outer circumferences occurs, and particularly, the separator outside the negative electrode is stretched, and in an extreme case, the separator is broken and the yield in the process is reduced.

Further, a problem common to the above two manufacturing methods is that it takes an extremely long time to permeate the organic electrolytic solution into the entire electrode group because the organic electrolytic solution is injected after the electrode groups are integrated. is there.

[0011]

In order to achieve the above object, the invention of claim 1 is a positive electrode plate having a positive electrode active material layer formed on a positive electrode current collector, and a negative electrode active material on a negative electrode current collector. The negative electrode plate on which the material layer is formed and the electrode group wound via a porous polyolefin separator having an adhesive layer on the surface are housed in an outer case, and then an organic electrolyte is injected and sealed lithium In the method for producing a polymer secondary battery, by gelling the adhesive layer on the separator surface by injecting and heating an organic electrolyte solution into the electrode group,
In the method for manufacturing a lithium polymer secondary battery, the separator is integrated with the positive electrode plate and the negative electrode plate.

According to the first aspect of the invention, since the organic electrolytic solution is injected without integrating the electrode group, the time required for permeation into the entire electrode group can be greatly shortened. Further, when the wound electrode group is manufactured, neither of the separators is integrated with the positive and negative electrode plates, so that it is possible to obtain a battery in which the yield is not reduced due to the breakage of the separator due to the difference between the inner and outer circumferences.

According to a second aspect of the present invention, a vinylidene fluoride / hexafluoropropylene copolymer (hereinafter referred to as P
(Abbreviated as VdF-HFP)), and by heating in the presence of an organic electrolyte, the adhesive layer is gelled,
The positive and negative electrode plates and the separator are bonded together. Thus, it is not necessary to use a plasticizer such as DBP, and it is not necessary to use a plasticizer extraction step or a metal current collector having a through hole such as expanded metal, so that an inexpensive battery can be obtained.

The inventions of claims 3 and 4 are characterized in that the adhesive layer is gelated by heating while pressurizing and pressing, and then the electrode group is cooled in the pressurized state. .

As a result, the adhesive layer which has been gelled by heating is not lost due to the flow between the separator and the positive electrode or the negative electrode, so that a uniform and strong gel layer can be produced.

The invention of claim 5 is an invention in which all of claims 1 to 4 are combined.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of a wound electrode group of the battery of the present invention.

Reference numeral 1b is a collector made of aluminum foil, on one or both sides of which a positive electrode active material and a binder, and if necessary, a paste prepared by kneading and dispersing a conductive agent in a solvent,
It is the positive electrode plate 1 that is dried and rolled to form the active material layer 1a.

As the positive electrode active material, for example, a lithium-containing transition metal compound capable of accepting lithium ions as a guest is used. For example, a composite metal oxide of at least one metal selected from cobalt, manganese, nickel, chromium, iron and vanadium and lithium, L
iCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiCo _x Ni
_(1-x) O ₂ (0 <x <1), LiCrO ₂ , αLiFe
O ₂ , LiVO _{2 and the} like are preferable.

Examples of the binder include a fluororesin material that maintains the adhesion between the active materials, a polymer material having a polyalkylene oxide skeleton, and a styrene-butadiene copolymer. As the fluorine-based resin material, polyvinylidene fluoride (PVdF), a copolymer P (Vd) of vinylidene fluoride (VdF) and hexafluoropropylene (HFP) is used.
F-HFP) is preferred.

As the conductive agent added as required, carbon-based conductive agents such as acetylene black, graphite and carbon fiber are preferable.

As the solvent, a solvent capable of dissolving the binder is suitable. In the case of an organic binder, an organic solvent such as acetone, cyclohexanone, N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone (MEK), etc. A single solvent or a mixed solvent obtained by mixing these is preferable, and water is preferable in the case of an aqueous binder.

Reference numeral 2b is a collector made of a copper foil, on one side or both sides of which a negative electrode active material and a binder, and if necessary, a paste prepared by kneading and dispersing a conductive agent in a solvent, dried and rolled. It is the negative electrode plate 2 that the active material layer 2 a is produced by the above.

Here, as the negative electrode active material, for example, a material containing graphite having a graphite type crystal structure capable of inserting and extracting lithium ions, such as natural graphite or artificial graphite is used. In particular, it is preferable to use a carbon material having a graphite type crystal structure in which the lattice spacing (d ₀₀₂ ) of the lattice plane (002) is 3.350 to 3.400 Å.

As the binder, the solvent, and the conductive agent which can be added if necessary, the same materials as those for the positive electrode plate can be used.

Reference numeral 4 denotes a separator, which is preferably a microporous polyolefin resin such as polyethylene resin or polypropylene resin.

The polymer material used for the adhesive layer 3 is a copolymer P (VdF) of vinylidene fluoride and hexafluoropropylene which swells in an organic electrolyte and easily gels.
-HFP) is preferable, and the weight% of hexafluoropropylene is preferably in the range of 2% to 15% from the viewpoint of swelling property with respect to organic electrolyte and adhesiveness between positive and negative electrodes.

A preferred manufacturing method for integrating the wound electrode group is as follows. First, the polymer material is dissolved in an organic solvent such as acetone, cyclohexanone, N-methyl-2-pyrrolidone (NMP), or methyl ethyl ketone (MEK) alone or in a mixed solvent thereof, and this solution is applied to both surfaces of the separator. After coating and drying, an adhesive layer is provided on the separator in advance.

The thickness of the adhesive layer at this time is 1 μm to 8 μm.
A range of m is preferred.

The positive electrode and the negative electrode are wound with this separator interposed therebetween to produce an electrode group. At this stage, the adhesive layer of the separator does not adhere to either the positive electrode or the negative electrode. Further, this wound electrode group is inserted into an outer case made of a laminate sheet using a metal foil such as aluminum in the middle layer, and after pouring a predetermined amount of the organic electrolytic solution, it is sealed by heat sealing or the like. In this state, it is preferable that the entire battery is heated while being pressed and pressed to swell the adhesive layer on the surface of the separator with the organic electrolytic solution and gelate the same to integrate them. In order to promote gelation, it is preferable to heat to 60 ° C. or higher, preferably in the range of 60 ° C. to 90 ° C.,
The time at that time is preferably in the range of 3 hours to 30 minutes.

The pressure for pressurizing is 0.
The pressure range of 01 MPa to 20 MPa is preferable in order to uniformly weld the adhesive layer to the positive electrode and the negative electrode. Further, the pressure-pressed state is cooled to room temperature to prevent the gelled adhesive layer from being lost due to flow between the separator and the positive electrode or the negative electrode.

Since the outer case is required to have a barrier property and a light blocking property for an electrolytic solution and water, a metal foil layer made of an aluminum foil having a thickness of 20 to 50 μm is arranged in the center, and an outer side is provided with an electrolytic resistance. Polyethylene terephthalate having a thickness of 10 μm to 50 μm, because liquidity and mechanical strength are required,
Resin such as heat-welding polyimide, polymethylmethacrylate, and stretch-treated polyamide (nylon), or a resin layer obtained by copolymerizing two or more kinds of these resins, heat-welding property inside and short-circuit preventing property with leads. Thickness 2 to be required
An outer case made of a polyolefin resin such as a polyethylene resin or a polypropylene resin having a thickness of 0 μm to 50 μm, a copolymer thereof, or an acid-modified resin layer is preferable.

The organic electrolyte used here is
It is composed of a non-aqueous solvent and an electrolyte. As the non-aqueous solvent, a cyclic carbonate and a chain carbonate are contained as main components. Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC),
And at least one selected from butylene carbonate (BC). The chain carbonate may be dimethyl carbonate (DMC),
It is preferably at least one selected from diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and the like.

As the electrolyte, for example, a lithium salt having a strong electron-withdrawing property is used. For example, LiPF ₆ or LiB is used.
F ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , L
iN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , Li
C (SO ₂ CF _{3) 3} and the like. These electrolytes may be used alone or in combination of two or more. These electrolytes are preferably dissolved in the non-aqueous solvent at a concentration of 0.5 to 1.5M.

[0036]

EXAMPLES The present invention will be described in detail with reference to Examples and Comparative Examples, but these do not limit the present invention in any way.

Example 1 First, 100 parts by weight of lithium cobalt oxide as a positive electrode active material, 3 parts by weight of acetylene black as a conductive agent, and N-methyl-2-pyrrolidone (NMP) of polyvinylidene fluoride as a binder. 33 parts by weight of solution (solid content 12%), 1 NMP as organic solvent
3 parts by weight were each used and kneaded and dispersed to prepare a pasty mixture. After applying this paste mixture to the current collector 1b made of a strip-shaped aluminum foil having a thickness of 20 μm,
By drying, the positive electrode plate 1 having the positive electrode active material layer 1a was produced.

Next, flake graphite was used as the negative electrode active material 10 times.
0 parts by weight, N-methyl-2-pyrrolidone (NMP) solution of polyvinylidene fluoride as a binder (solid content 12%)
And 66 parts by weight of NMP and 13 parts by weight of NMP as an organic solvent were kneaded and dispersed to prepare a paste mixture. The paste mixture was applied to a current collector 2b made of a strip-shaped copper foil having a thickness of 14 μm and then dried to prepare a negative electrode plate 2 having a negative electrode active material layer 2a.

Then, a 10 wt% solution of P (VdF-HFP) dissolved in a mixed solvent of acetone and cyclohexanone in a weight ratio of 3: 1 was coated with a separator 4 made of porous polyethylene resin having a thickness of 25 μm. Then, the adhesive layers 3 having a thickness of 3 μm were provided on both surfaces of the separator by drying.

The positive electrode plate 1 and the negative electrode plate 2 thus produced were wound into an elliptical shape with a separator 4 having an adhesive layer 3 on the surface, and the non-integrated electrode group was housed in an outer case. The outer case has a thickness of 40
A metal foil layer made of aluminum foil having a thickness of μm was arranged in the center, and an outer case made of a polyamide resin layer having a thickness of 20 μm on the outer side and a maleic acid-modified polypropylene resin layer having a thickness of 30 μm on the inner side was used.

Next, ethylene carbonate and ethyl methyl carbonate were mixed in a volume ratio of 1: from the opening of the outer case 1.
After injecting a predetermined amount of an electrolyte solution in which 1.0 mol / l of LiPF ₆ was dissolved in the mixed solvent of No. 3, the temperature was 200 ° C. and the pressure was 0.1.
The state in which MPa was added was maintained for 30 seconds and sealed.

Further, in a state of being pressure-pressed at a pressure of 1.0 MPa, by heating at a temperature of 90 ° C. for 30 minutes, the adhesive layer on the surface of the separator was gelated with an organic electrolytic solution, and this pressure-pressed. By cooling to 20 ° C. (room temperature) in this state, a lithium polymer secondary battery in which a positive electrode plate, a negative electrode plate, and a separator were integrated was produced, and was named battery A.

Example 2 A lithium polymer produced in the same manner as in Example 1 except that the thickness of the adhesive layer 3, the pressure applied, the gelling temperature and the time were set as shown in Table 1. The secondary batteries were batteries B to G.

[0044]

[Table 1]

Comparative Example 1 A positive electrode plate 1 produced in the same manner as in Example 1 was provided with a separator 4 having no adhesive layer on both sides and a thickness of 20 μm, a polyvinylidene fluoride, acetone and cyclohexanone mixed solvent in a weight ratio of 3: 1. In the same manner as in Example 1 except that a positive electrode plate with a separator adhered using a 10 wt% solution dissolved in and a negative electrode plate prepared in the same manner as in Example 1 were wound into an elliptical shape. The prepared lithium polymer secondary battery was used as a battery L.

(Comparative Example 2) A lithium polymer secondary battery manufactured in the same manner as in Example 1 was used as a battery M except that it was cooled without applying pressure.

[0047]

As described above, according to the present invention,
The electrode group can be integrated by winding a separator having a positive electrode, a negative electrode, and an adhesive layer on the surface and producing an electrode group that is not integrated, and then pouring an organic electrolyte solution and heating to gel the adhesive layer. A highly reliable and highly productive method for manufacturing a lithium polymer secondary battery can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

[Explanation of symbols]

1 Positive plate 1a Positive electrode active material layer 1b Positive electrode current collector 2 Negative electrode plate 2a Negative electrode active material layer 2b Negative electrode current collector 3 adhesive layer 4 separator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshibayashi Furubayashi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5H021 AA06 BB01 BB02 BB12 BB17                       CC04 CC08 EE04 EE10 EE15                       EE25 EE32 EE33                 5H029 AJ14 AK03 AL07 AM03 AM05                       AM07 BJ02 BJ14 CJ02 CJ03                       CJ06 CJ07 CJ13 HJ12

Claims (5)

[Claims] 1. A positive electrode plate having a positive electrode active material layer formed on a positive electrode current collector and a negative electrode plate having a negative electrode active material layer formed on a negative electrode current collector are porous having an adhesive layer on the surface. In a method for manufacturing a lithium polymer secondary battery, in which an electrode group wound through a transparent polyolefin separator is housed in an outer case, an organic electrolytic solution is then injected, and an organic electrolytic solution is injected into the electrode group. A method for manufacturing a lithium polymer secondary battery, characterized in that the separator is integrated with the positive electrode plate and the negative electrode plate by gelling the adhesive layer on the surface of the separator by liquefying and heating. 2. The method for producing a lithium polymer secondary battery according to claim 1, wherein the adhesive layer is a copolymer of vinylidene fluoride and hexafluoropropylene. 3. The separator according to claim 1, wherein the separator is uniformly integrated with the positive electrode plate and the negative electrode plate by heating while pressurizing and pressing. Manufacturing method of lithium polymer secondary battery of. 4. The pressure press is a pressure press that cools in a pressure-pressed state.
The method for producing the lithium polymer secondary battery according to 1. 5. A positive electrode plate having a positive electrode active material layer formed on a positive electrode current collector and a negative electrode plate having a negative electrode active material layer formed on a negative electrode current collector are porous having an adhesive layer on the surface. In a method for manufacturing a lithium polymer secondary battery in which an electrode group wound through a hydrophilic polyolefin separator is housed in an outer case, an organic electrolytic solution is injected and sealed, the organic electrolytic solution is injected into the electrode group. Liquid, after gelling the adhesive layer made of a copolymer of vinylidene fluoride and hexafluoropropylene on the surface of the separator by heating while heating under pressure, by cooling in a pressed state, A method for producing a lithium polymer secondary battery, wherein the separator, the positive electrode plate and the negative electrode plate are uniformly integrated.