JPH10340708A - Polymer packaged lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery with a light weight and high performance packaged with an outer jacket material with light weight and a low water penetration amount by specifying the water penetration amount of the outer jacket made of polyvinylidene chloride sheet laminate to a specified value or lower. SOLUTION: A polyethylene terephthalate sheet, a polyvinylidene chloride sheet, an aluminum sheet, and a polyethylene sheet are stacked in order, to form a laminate sheet, and a water penetration amount of an outer jacket body made of the laminate sheet is limited to 1 g/m<2> .24 hr or lower. In the process of lamination, the laminate sheet having a part containing no aluminum at both ends of a roll film is produced. The sheet is suitably cut, bent, heat- bonded to form an envelope, having an opening part where parts having no aluminum are mutually faced. A battery stacked body formed by stacking electrode sheets and a hybrid electrolyte sheet is put into the envelope, and the envelope is sealed and packaged so that positive and negative electrode terminals are exposed to the outside of the envelope for forming a battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lithium ion battery packaged with a polymer material.

[0002]

2. Description of the Related Art High-density batteries such as lithium ion batteries are used for power supplies of portable devices such as personal computers, mobile phones, and video cameras, and their capacity and weight have been reduced.
These batteries use an electrolytic solution as an ion transfer medium between the electrodes, and a metal can is used for a package to prevent liquid leakage. However, due to the weight of the metal can package, the battery as a whole became heavy and it was difficult to reduce the weight.

On the other hand, a battery using a solid polymer electrolyte as an ion transfer medium is a laminate in which a sheet-like electrode and a solid polymer electrolyte are laminated, or a solid polymer electrolyte layer is formed by coating a solid polymer electrolyte layer on an electrode surface. The stacked pair can be manufactured by processing it into a predetermined shape. As described above, since a method such as sheet lamination or coating can be adopted, it is expected that the production process is excellent in mass productivity. Further, since the liquid leakage which can occur in the conventional electrolyte battery does not substantially occur, the production process can be easily controlled, and a higher voltage is expected by the series connection lamination of the electrode / polymer solid electrolyte / electrode laminate. I have.

For the package of the polymer solid electrolyte battery, a polymer sheet / aluminum sheet laminate that can be heat-sealed because of substantially no liquid leakage and light weight is used. Since the polymer sheet / aluminum sheet laminate is made of, for example, polyethylene / aluminum, polyethylene / aluminum / polyester, etc., the water permeability barrier property depends on the barrier property of the aluminum layer. For this reason, if a pinhole is present in the aluminum layer, there is a problem that the watertight barrier property is lost due to the pinhole, and the battery performance is reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a light-weight lithium ion battery which is packaged with a light-weight and low-permeability package material and has excellent battery performance.

[0006]

Means for Solving the Problems As a result of investigations in view of the above problems, the present inventors have found that a lithium ion battery sealed with an outer package material containing a polyvinylidene chloride-based polymer as a component has excellent performance. And completed the present invention.
That is, the present invention is as follows. (1) A lithium ion nonaqueous battery packaged with an exterior body made of a polyvinylidene chloride-based sheet laminate, wherein the exterior body made of the laminate has a water permeability of 1 g / m ^2.
-A lithium ion battery characterized by being 24 hours or less. (2) The exterior body made of the polyvinylidene chloride-based sheet laminate is an exterior body made of the polyvinylidene chloride-based sheet laminate having a metal layer, and at least the electrode terminal taking-out opening does not include the metal layer. The lithium ion battery according to 1 above, which is an exterior body formed of a vinylidene chloride-based sheet laminate.

The present invention relates to a lithium ion nonaqueous battery packaged with an outer package made of a polyvinylidene chloride-based sheet laminate, and a unit cell constituting the battery,
An outer package made of a polyvinylidene chloride-based sheet laminate will be sequentially described. First, the unit cell in the lithium ion battery of the present invention is a non-aqueous battery and is a non-aqueous organic solvent or a non-solvent lithium ion battery. Lithium-ion batteries can be composed of various electrode materials as primary batteries or secondary batteries. For example, lithium cobalt oxide, lithium nickel oxide, lithium manganate, and the like are used as positive electrode materials, carbon materials such as graphite and coke, oxide materials, alloys with lithium metal, and materials that can form intermetallic compounds are used as negative electrode materials. Can be used. Usually, a form in which these electrode materials are applied together with a binder in a powder form, or a continuous form produced by a method such as sintering, rolling, vapor deposition, or sputtering can be used, and a current collector can be provided on this electrode.

Further, as an ion transfer medium between the electrodes, a non-aqueous solvent-based electrolyte, a material in which a non-aqueous solvent-based electrolyte is impregnated or swelled uniformly or non-uniformly with a polymer material, an ion-coordinating polymer or ceramic material A material containing ions that can move to the substrate can be used. As the configuration of the unit cell, an element structure composed of a positive electrode / an ion transfer medium / anode alone or a structure in which this element structure is laminated in series or in parallel can be used. Further, an electrode terminal for extracting a current from the electrode can be connected to the electrode to form a battery structure. As the shape of the unit cell, a sheet shape, a rectangular parallelepiped shape, a roll shape, or the like can be used. As described above, the battery component, structure, and form of the present invention can be selected according to the intended use.

Next, an outer package made of the polyvinylidene chloride-based sheet laminate of the present invention will be described. The polyvinylidene chloride-based sheet laminate used for the outer package of the present invention is characterized in that the laminate structure includes a vinylidene chloride-based polymer in the form of a sheet, and the sheet made of the vinylidene chloride-based polymer has a water-permeable barrier property. Due to the excellent flame retardancy, the performance and safety of the packaged non-aqueous battery are superior to the battery packaged with conventional materials. The vinylidene chloride-based polymer contains 70 to 98% by weight of a vinylidene chloride component as a main component and a monomer polymerizable with the vinylidene chloride component, for example, a vinyl chloride, an acrylonitrile, an acrylic acid, a carbon of an alkyl methacrylate group. A copolymer of 30 to 2% by weight of at least one unsaturated monomer such as alkyl acrylate, maleic anhydride, alkyl maleate, itaconic acid, alkyl itaconate and vinyl acetate having a number of 1 to 18; Coalescing is used.

Among them, when extruding into a sheet shape, one of vinyl chloride, methyl acrylate, butyl acrylate and 2-ethylhexyl acrylate is contained in an amount of 30 to 2% by weight and the vinylidene chloride component is 70 in terms of extrusion processability. ~ 98% by weight of the copolymer is desirable,
Since both water permeability and gas barrier properties are excellent, methyl acrylate is 8 to 2% by weight and vinylidene chloride is 9%.
More preferred is 2-98% by weight of the copolymer. The range of the weight average molecular weight of the polyvinylidene chloride-based material to be processed into a sheet is 10,000 to 1,000,000, preferably 50,000 to 30.
Range of ten thousand. More preferably, a copolymer in the range of 70,000 to 150,000 is used.

The polyvinylidene chloride-based sheet laminate according to the present invention is characterized in that the vinylidene chloride-based polymer sheet includes a polymer sheet such as polyethylene, polypropylene, nylon, ionomer resin, polyester, aromatic polyamide, vinylidene fluoride-based polymer, or aluminum. ,
It can be formed by laminating inorganic material sheets of stainless steel, nickel, ceramic, carbon, and the like. As a lamination method, a method in which sheets are laminated by heating and laminating, a general name "K-coated film" in which an emulsion of the above vinylidene chloride polymer is coated on polyethylene (PET), nylon (Ny), or polypropylene (PP) is used. And the like.

The structure of the polyvinylidene chloride-based sheet laminate has a water-permeable barrier property required for a package, a sealing method,
It is formed in consideration of the adhesiveness of the electrode terminals, for example, vinylidene chloride-based polymer / aluminum / polyethylene,
Examples thereof include polyethylene terephthalate / polyvinylidene chloride, vinylidene chloride-based polymer / polyethylene terephthalate / aluminum / polyethylene, and among them, vinylidene chloride-based polymer / aluminum / polyethylene is preferable.

In particular, regarding the water permeability barrier property, as described in the section of the prior art, a polymer sheet laminate in which polyethylene, polyethylene terephthalate, etc. and aluminum are laminated is used in the conventional material, and the water permeability barrier property is used. Depended on barrier properties such as an aluminum layer.
For this reason, the water-permeable barrier property was lost due to the pinholes in the aluminum layer, and the battery performance was sometimes reduced. On the other hand, since the laminate material used for the exterior body of the present invention includes a vinylidene chloride-based polymer sheet having a high water-permeable barrier property, even if there is a defect in the water-permeable barrier layer such as an aluminum layer such as a pinhole, the defect is caused by the defect. Performance degradation is unlikely to occur. Therefore, the reliability and productivity of the battery can be improved, and the battery is industrially useful.

The water permeation amount of the exterior body made of the polyvinylidene chloride-based sheet laminate of the present invention is 1 g / m ² · 24 h.
r or less. This water permeability is preferably low for a non-aqueous battery, preferably 0.2 g / m ² · 24 hr or less, more preferably 0.1 g / m ² · 24 hr or less. A battery using an outer package having a water permeability of more than 1 g / m ² · 24 hr is not preferable because the battery structural elements inside the outer package are deteriorated by water absorption and the battery capacity is reduced. Further, the electrolyte material inside the unit cell is decomposed by the water absorption, and gas generation may be accompanied. The amount of water permeation can be determined by sealing a water-absorbing material such as anhydrous calcium chloride in the interior of the outer package, maintaining the sample in a predetermined atmosphere, and measuring the weight increase.

The vinylidene chloride-based polymer sheet is characterized by having a high gas barrier property such as oxygen gas, and also has an effect of suppressing leakage of gas generated inside the battery to the outside. Further, since the vinylidene chloride-based polymer is more flame-retardant than a polymer used for an ordinary exterior body, the battery of the present invention is provided with flame retardancy. The flame retardancy of the material is determined by its oxygen index (ASTM-2863-70), ignition temperature,
It can be evaluated by the flash temperature. Since the vinylidene chloride-based sheet laminate, which is the outer package material of the present invention, has a higher oxygen index and flame retardancy as compared with a normal polymer sheet for a package, the safety during abnormal operation of the battery is enhanced. preferable.

As a method for sealing the polyvinylidene chloride sheet laminate of the lithium ion battery of the present invention, a method using friction heat such as heat sealing, impulse sealing, spin welding, external heating such as laser, infrared ray, hot jet, and high frequency sealing. And an internal heating method such as an ultrasonic seal. This sealing method may be considered depending on the type and structure of the laminated material constituting the polyvinylidene chloride-based sheet laminate. In addition, the sheets can be bonded together with an adhesive, a pressure-sensitive adhesive, or the like to be packaged.

The lithium ion battery of the present invention is a battery packaged with an outer package made of a polyvinylidene chloride-based sheet laminate. As described above, since the polyvinylidene chloride-based polymer sheet of the polyvinylidene chloride-based sheet laminate has excellent water-permeable barrier properties, the laminate does not necessarily need a water-permeable barrier layer such as an aluminum layer and does not include a metal layer such as aluminum. However, it is possible to use as a package material of a non-aqueous battery, but it is preferable to use a polyvinylidene chloride-based sheet laminate having a metal layer such as aluminum from the viewpoint of water permeability barrier properties. Examples of the metal used for the metal layer used in the present invention include aluminum, an aluminum alloy, nickel, copper, and iron.

When a unit cell is packaged with an outer package, it is necessary to enclose the electrode terminals for extracting a current from the electrodes to the outside into the outer package. May cause contact with the electrode terminals at the time of fusion, resulting in a problem that the performance of the battery is reduced and the battery becomes inoperable. From this,
When a unit cell is packaged with an outer package made of a polyvinylidene chloride-based sheet laminate having a metal layer such as aluminum, an opening for taking out an electrode terminal is provided with a polyvinylidene chloride-based sheet laminate having no aluminum or other metal layer. It is preferable to form with.

The electrode terminal take-out opening formed of a polyvinylidene chloride-based sheet laminate having no metal layer such as aluminum has an opening of 0.5 mm or more from the tip of the opening.
mm or less, preferably a width equal to or more than the circumference of the electrode terminal x 1/2 or more.
mm or less, and more preferably the circumference of the electrode terminal × １ ／ + the thickness of the polyvinylidene chloride-based sheet laminate × 5 or more. Within these ranges, the short circuit between the electrode terminals is reduced, and the effect of preventing short circuit can be sufficiently improved. In particular, it is preferable that a portion of the electrode terminal protruding from the exterior body to the outside (sealing end) does not have a metal layer such as aluminum or the like, and this structure can prevent short circuit.

Since the vinylidene chloride-based polymer sheet has an excellent water-permeable barrier property, a polyvinylidene chloride-based polymer sheet in which a metal layer is removed from portions requiring insulating and light-transmitting properties such as an electrode terminal sealing portion and a display portion of an electrochromic element. A lithium ion battery having a sufficient water-permeable barrier property can be produced even by using an outer package made of a sheet laminate. In this way, the outer body structure can be selected depending on the application and the water permeability barrier property. As a method for removing the metal layer of the exterior body material,
It can be produced by a method of etching a part of the metal layer at the time of forming the laminate, a method of laminating strip-shaped metal sheets to form a metal sheet non-laminated portion, or the like.

As described above, the battery of the present invention is industrially preferable because it is lightweight, has excellent battery performance stability and safety, and can reduce the failure rate in production. Hereinafter, the battery of the present invention will be further described with reference to Examples.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

1. Fabrication example of lithium ion secondary battery Polyvinylidene fluoride as a binder using needle coke as a negative electrode active material (the amount of binder is 7% by weight of the active material)
A slurry dispersed in an N-methylpyrrolidone solvent was applied on a metal copper sheet and dried to form a coating film.
By hot pressing at a temperature of 0 ° C., an electrode thickness of 133 μm was obtained. In addition, lithium cobalt oxide is used as a positive electrode active material, polyvinylidene fluoride is used as a binder (the amount of the binder is 10% by weight of the positive electrode active material), and carbon black (3% by weight of the positive electrode active material) is used as a conductive aid on an aluminum sheet in the same manner as the negative electrode. And heat-press it to form a positive electrode sheet (film thickness 110
μm). After cutting the electrode sheet into a predetermined shape, ultrasonic welding was performed on the exposed surface of the current collector (the surface opposite to the electrode application surface) using a stainless steel sheet strip as an electrode terminal. A poly (vinylidene fluoride-hexafluoropropylene) copolymer (hexafluoropropylene weight 3%) was heated and extruded at a temperature of 190 ° C. to produce a 50 μm-thick polymer sheet. Electron beam (irradiation amount 15
Mrad) to crosslink the polymer. After the sheet was heated and impregnated with Freon HFC134a, it was introduced into a heating furnace and foamed and stretched to prepare a foamed sheet (foaming ratio 4 times, film thickness 70 μm). Then, the foamed sheet was subjected to an electrolytic solution (ethylene carbonate (EC) / propylene carbonate (PC) / γ-butyl lactone (BL) = 1/1 /
(A solution in which LiBF ₄ was dissolved at 1.5 mol / liter in a mixed solvent of No. 2) and heated at a temperature of 90 C for 3 hours to prepare a hybrid electrolyte impregnated with an electrolyte. next,
A positive electrode sheet, a hybrid electrolyte, and a negative electrode sheet having a predetermined shape were laminated and heated and pressed to prepare a laminate (thickness of the laminate was 340 μm). 2. Production Example of Vinylidene Chloride Sheet 2% by weight of epoxidized vegetable oil was added to and mixed with a vinylidene chloride copolymer having a component ratio of a vinylidene chloride component to a methyl acrylate component of 96: 4. This resin composition is extruded, formed into a film by an inflation method, and wound at a speed of 3
Wound on a bobbin at a rate of 0m / min, width 1000m
m, a film having a thickness of 25 μm was obtained. The oxygen gas permeability of this film is 0.7 cc / m ² · 24 hr · 20 ° C.
・ Atm, water vapor permeability is 0.8 g / m ²・ 24 hr ・
It was 40 ° C and 90% RH. 3. Evaluation of Charge / Discharge Characteristics of Battery The charge / discharge characteristics of the battery were evaluated at a temperature of 25 ° C. at a constant current (current density of 1 mA / cm ² ) followed by a 4.2 V constant potential charge and a discharge at a 2.7 V cut constant current (current density of 1 mA / cm ² ). cm ² )
I went in.

[0023]

Example 1 Polyethylene terephthalate (film thickness 12 μm)
m), a polyvinylidene chloride sheet (thickness: 25 μm), an aluminum sheet (thickness: 7 μm), and polyethylene (thickness: 50 μm) were sequentially laminated to prepare a laminate sheet. In the lamination process, the width of the aluminum sheet was adjusted to produce a laminate sheet (total width 220 mm) having a structure having aluminum-free portions (width 20 mm) at both ends of the roll film. The sheet is stretched 110
The sheet was cut at a width of 1 mm, the center portion was bent, and two sides were heat-sealed at a width of 5 mm to produce a 110 mm square envelope having openings facing each other without aluminum. A battery stack in which a 9 cm square electrode sheet and a 95 mm square hybrid electrolyte sheet are stacked is placed inside the envelope, and the strip electrode terminals of the positive and negative electrodes having a width of 10 mm protrude outside the envelope. Was performed to produce a battery. As a result of evaluating the charge / discharge characteristics, the initial discharge amount was 253 mAh, and charge / discharge was possible repeatedly. 40 when charged
The discharge amount after leaving for one month (30 days) in an atmosphere at 90 ° C. and a humidity of 90% was 211 mAh. The water permeability of the outer package made of the laminate sheet is 0.08 g / m ² · 24 h
r or less. The amount of water permeation was determined by enclosing anhydrous calcium chloride in a separately prepared envelope and leaving it for one month in an atmosphere of 40 ° C. and 90% humidity to find the weight increased.

[0024]

Comparative Example 1 A laminate sheet was produced in the same manner as in Example 1, except that the polyvinylidene chloride sheet of the laminate sheet was changed to a polyethylene sheet. The sheet was cut and heat-sealed to produce an 11 cm square envelope. Using this envelope, a battery was produced in the same manner as in Example 1. As a result of performing the same evaluation as in Example 1, the initial charge amount was 240 mAh,
The amount of discharge after leaving the charged state for one month is 203 mAh,
The package was swollen during the standing period. The water permeability of the outer package made of the laminate sheet is 2.1 g / m ² · 2.
It was 4 hours.

[0025]

Example 2 Polyethylene terephthalate sheet (film thickness 12 μm), polyvinylidene chloride sheet (film thickness 25 μm)
m) were alternately laminated to form a laminate sheet. The sheet was high-frequency sealed to produce an envelope,
A battery was prepared by stacking 10 layers of a battery stack in which an m-square positive electrode and a negative electrode and a 55-mm square hybrid electrolyte were stacked, placed in an envelope, and then sealed with high frequency to produce a battery. The initial discharge amount of this battery was 762 mAh, and 4
The discharge amount evaluated after being left for one month in an atmosphere of 0 ° C. and 90% was 716 mAh. No deformation of the battery structure due to this standing was observed. Further, anhydrous calcium chloride was sealed in a separately prepared envelope, left for one month in an atmosphere of 40 ° C. and 90% humidity, and the weight increase was evaluated.
m ² · 24 hr or less.

[0026]

Comparative Example 2 The polyvinylidene chloride sheet of the laminate sheet of Example 2 was replaced with a polyethylene sheet (25 μm thick).
A laminate sheet was prepared in the same manner except that the above was changed. A battery was produced using an envelope obtained by processing the sheet in the same manner as in Example 2. As a result of performing the same evaluation as in Example 1, the initial charge amount was 610 mAh, the discharge amount after leaving the battery in the charged state for one month was 92 mAh, and the package swelled and the electrode was deformed during the leaving period. Anhydrous calcium chloride is sealed in a separately prepared envelope, and dried in an atmosphere of 40 ° C. and 90% humidity.
5 g / m ² · 24
hr.

[0027]

Example 3 Oriented nylon sheet (film thickness 12 μm), polyvinylidene chloride sheet (film thickness 25 μm), aluminum foil (7 μm), polyethylene (film thickness 50 μm)
Were sequentially laminated to produce a laminated sheet. The sheet was cut and heat-sealed to produce a 10 cm square envelope. A battery laminate in which a 9 cm square electrode sheet and a 95 mm square hybrid electrolyte sheet were laminated was placed in the envelope, and the width was 10 m.
The strip electrode terminals of each of the positive and negative electrodes of m protruded outside the envelope, and were sealed and packaged to produce a battery. As a result of charging and discharging the battery, the initial discharge amount was 251 mAh.
And repeated charge / discharge was possible. After leaving this battery in a charged state for one month (40 ° C., humidity 90%), the discharge amount was 235 mAh. The water permeability of the outer package made of the laminate sheet was 0.1 g / m ² · 24 hr.

[0028]

As described above, the polymer package battery of the present invention is packaged with a material having a high water barrier property, and thus has excellent battery performance stability as a lithium ion secondary battery. Further, since the exterior body material is a flame-retardant material, the risk of ignition and combustion in abnormal operation of the battery is low, and the safety of the battery is enhanced.

Claims (2)

[Claims] 1. A non-aqueous lithium-ion battery packaged with an outer package made of a polyvinylidene chloride-based sheet laminate, wherein the outer package made of the laminate has a water permeability of 1 g / g.
m ² · 24 hr or less. 2. The exterior body made of a polyvinylidene chloride-based sheet laminate is an exterior body made of a polyvinylidene chloride-based sheet laminate having a metal layer, and at least an opening for extracting an electrode terminal includes a metal layer. 2. The lithium ion battery according to claim 1, wherein the exterior body is formed of a polyvinylidene chloride-based sheet laminate.