JP2001060453A - Battery - Google Patents

Abstract

(57) [Problem] To improve the reliability of a battery by preventing moisture from entering through a sealing portion of the battery sealed by a laminate exterior body. SOLUTION: In a battery sealed in a laminate outer package composed of at least a metal thin film and a heat-fusible resin film, at least one side of a sealing portion is heat-fused in a state bent at least once. With such a configuration, a battery with high energy density with improved hermetic reliability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery sealed by a laminate casing. More specifically, the present invention relates to a battery having a sealing portion having an improved structure, and the structure can prevent moisture from entering the inside of the battery, and as a result, the reliability of the battery can be improved.

[0002]

2. Description of the Related Art There are various types of batteries. Among them, with the spread of lithium ion batteries, the size and weight of batteries as power sources for portable devices have been dramatically reduced. However, there is a strong demand for further miniaturization and thinning of portable devices, and accordingly, there is a strong demand for miniaturization and thinning of batteries. 2. Description of the Related Art Conventionally, a battery can and a lid formed by molding a metal plate into a cylindrical shape, a square shape, a coin shape, or the like, depending on the application, have been used as an exterior body of a battery. In this case, the battery can and the lid
It has the function of both positive and negative terminals. In addition, the airtightness of the battery is determined by the method of crimping the battery can and lid with resin packing, the method of hermetic sealing between them using a sealing material such as glass, the method of laser welding, etc. It is kept closed.

[0003] However, in a battery using such a battery can, there is a limit in weight reduction and thickness reduction. In particular, regarding a thickness reduction, the thickness limit is usually about 4 mm. In order to further reduce the weight and thickness of the battery, Japanese Patent Application Laid-Open No. 60-100362 discloses a battery that does not use a battery can.
Japanese Patent Application Laid-Open No. Sho 60-65442 proposes a battery in which a battery element comprising a positive electrode, a negative electrode and an ionic conductor is enclosed in a laminate outer package comprising a metal foil and a heat-fusible resin film. Further, Japanese Patent Application Laid-Open No. 10-214606 proposes a thin battery in which a sealing portion of a laminate outer package is adhered to the surface of a battery element.

[0004]

The laminate exterior body is
Basically, it is composed of a metal thin film for preventing gas from entering, particularly preventing moisture from entering, and a heat-fusible resin film layer for imparting heat-fusibility. The resin film does not have a sufficient gas barrier property, particularly a barrier effect against water vapor, and therefore, a metal thin film is indispensable.

[0005] However, Japanese Patent Application Laid-Open No. 60-100362 discloses a method.
In Japanese Patent Application Laid-Open No. 60-65442 and Japanese Patent Application Laid-Open No. 60-65442, when the sealing portion is viewed from the cross-sectional direction, there is no metal foil layer between the inside of the battery and the outside air. Is blocked. Therefore, it was necessary to increase the width of the sealing portion in order to increase the airtightness. In particular, a portion where a metal tab is taken out for taking out electricity from the battery tends to be a factor for lowering the airtightness.

[0006] Japanese Patent Application Laid-Open No. 10-214606 proposes to increase the width of the sealing portion by providing a sealing portion of the laminate exterior body on the surface of the battery element (see FIG. 6). . However, it is impossible to provide all sides of the sealing portion on the surface of the battery element, and it is necessary to increase the width of the sealing portion to some extent other than the surface of the battery element.

As described above, when the width of the sealing portion is increased in order to increase the reliability of the sealing portion, there is a problem that the size of the battery increases. That is,
In order to improve the airtight reliability, the width of the sealing portion is desired to be sufficiently large, but in order to improve the energy density, the width of the sealing portion is required to be as narrow as possible. It is also conceivable to reduce the projected area of the battery by increasing the width of the sealing portion and folding the sealing portion on the back surface (or the front surface) of the battery. Features will be faded.

[0008] In order to improve the airtight reliability of the tab pull-out portion, it is conceivable to use a metal porous body for the tab. Has a problem that a tab is cut because stress is easily applied. An object of the present invention is to provide a battery sealed with a laminate outer package that is kept airtight without increasing the size or thickness of the battery.

[0009]

Thus, according to the present invention, at least a battery comprising a positive electrode, a negative electrode and an ionic conductor encapsulated in a laminate outer package comprising at least a metal thin film and a heat-fusible resin film. A battery is provided, wherein one side of the portion is heat-sealed with at least one bend.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A battery according to the present invention is a battery in which a battery element is sealed in a laminate outer package comprising at least a metal thin film and a heat-fusible resin film, wherein at least one side of a sealing portion is at least once. It is characterized by having a configuration in which it is thermally fused in a folded state. With such a structure, it is possible to increase the substantial width of the sealing portion without increasing the size of the battery, and it is possible to improve the hermetic reliability.

The laminate package comprises at least a metal thin film and a heat-fusible resin film, and has a structure in which a metal thin film is sandwiched between a heat-fusible resin film and two layers of a metal thin film and a heat-fusible resin film. It may have a laminated structure of three layers or more. Further, if necessary, a protective layer of a metal thin film made of a polyester film or the like may be provided.
Of these, it is preferable that the heat-fusible resin film is located in the outermost layer of the laminate exterior body. Since the heat-fusible resin film is located in the outermost layer, sealing by heat fusion can be easily performed.

The metal thin film that can be used in the present invention is not particularly limited as long as water can be prevented from entering the battery, and any film made of a known material can be used. Aluminum, stainless steel,
A film made of a material such as nickel and copper is used. The thickness of the metal thin film is preferably about 5 to 50 μm, and more preferably about 10 to 30 μm. If the metal thin film is too thin, it is not preferable because the penetration of moisture cannot be sufficiently prevented. On the other hand, if the thickness is too large, heat cannot be sufficiently transmitted to the resin film at the time of heat fusion, so that the hermetic reliability after the heat fusion decreases. Further, since the thickness of the laminate outer package itself is increased, the energy density of the battery is reduced, which is not preferable.

On the other hand, the heat-fusible resin film is not particularly limited as long as the battery can be sealed by heat fusion, and any film made of a known material can be used. Examples of the heat-fusible resin film include films made of polypropylene, polyethylene, ionomer resin, and the like having excellent heat-fusibility. The thickness of the heat-fusible resin film is preferably about 20 to 250 μm, and varies depending on the type thereof.
The range of 80 to 200 μm is more preferable from the viewpoint of film physical properties.

In the present invention, the width of the sealed portion is 30% of the width of the battery in a direction perpendicular to the sealed portion in a folded state.
Or less, more preferably 20% or less, and still more preferably 10% or less. Note that it is preferable to make the width of the sealing portion as narrow as possible from the viewpoint of energy density. Further, the width of the sealing portion can be appropriately adjusted by increasing the number of times of bending. The number of bends is
Although not particularly limited, it is preferable that the thickness of the folded sealing portion is set within a range not exceeding the thickness of the thickest portion of the battery. When the width of the sealing portion is smaller than the thickness of the battery, the folded sealing portion can be further vertically bent. By bending vertically, the projected area of the battery can be further reduced.

According to the present invention, when the tab is located at the sealing portion,
Especially effective. Although the sealing portion where the tab is located is a portion where airtight failure is most likely to occur, the present invention makes it possible to improve the airtight reliability. When a tab is located at the sealing portion, one or more heat-fusible layers may be further laminated on the sealing portion of the laminate exterior body in order to further improve the sealing property. As the heat-fusible layer, the same material as the heat-fusible resin film or a modified resin layer thereof can be used. Further, as shown in FIGS. 7 and 8, it is also possible to shift and close the laminate exterior body at the sealing portion where the tab is located to protect the tab. 7 and 8, 1
Reference numerals 6 and 18 denote a laminate outer package, and reference numerals 17 and 19 denote positive electrode tabs, respectively.

The tab that can be used in the present invention is not particularly limited, and is made of a known metal thin film. Here, the thickness of the tab is 3
It is preferably from 20 to 20 μm. Furthermore, the width of the tab
Although it depends on the size of the battery, it is preferably as narrow as possible in consideration of the airtightness of the battery, and in view of the efficiency of extracting electricity to the outside, the ratio of the tab extraction portion to the width of the battery is 5 to 40%. And more preferably 5 to 20%. Further, the tab may be a porous body in order to improve airtight reliability. As the porous body, a punching metal having a hole in a metal film, an expanded metal obtained by cutting a metal film, forming a hole by stretching, and pressing the metal film, or the like can be used. In the present invention, stress is less likely to be applied to the boundary between the tab and the sealing portion, so that the problem of tab breakage can be solved. In particular, when a tab having holes such as expanded metal or punching metal is used, the mechanical strength is smaller than that of a foil tab, but in the present invention, even if such a tab is used, it is possible to prevent the tab from being cut. it can. The tab can be fixed by welding to each of the positive electrode and the negative electrode (or a current collector described below). As a method for welding the tab, known ultrasonic welding, resistance welding, laser welding, or the like can be appropriately used.

If the side orthogonal to the side which is bent at least once and sealed is sealed by heat-sealing the back and front sides of the laminated exterior film (see FIG. 6), the sealing portion is formed. Can be further improved in the location where the airtightness is orthogonal. In FIG. 6, reference numeral 14 denotes a laminate exterior body, and reference numeral 15 denotes a battery element. The battery element sealed by the laminate outer package is not particularly limited, and any primary or secondary battery element can be used as long as it has at least a positive electrode, an ion conductor, and a negative electrode. In particular, it is preferable to use a non-aqueous lithium-ion secondary battery element, which is strongly required to be reduced in size and thickness. Hereinafter, the non-aqueous lithium ion secondary battery element will be described, but the present invention is not limited to this description.

The positive electrode generally comprises a positive electrode active material, a conductive material and
And a binder. As the positive electrode active material, LiCoO
_Two, LiNiO_TwoLi represented by_xM1_yM2_{1 -y}O2 (this
Here, M1 is any of Fe, Co, and Ni, and M2 is
0 <x ≦, representing a transition metal, a Group 4B or Group 5B metal
1, y = 0-1), LiMn_TwoO_FourAnd LiMn_2-ZM2_Z
O4 (where M2 is the same as above, 0 ≦ z ≦ 2)
And a chalcogen compound containing chromium. After this
Outside, lithium-free, MnO_Two, MoO_Three, V_TwoO_Five, V₆O
₁₃And the like can also be used.

When an oxide containing no lithium is used, the negative electrode or the positive electrode must contain lithium in advance. On the other hand, when a lithium-containing chalcogen compound is used, considering the safety during the manufacturing process and the simplification of the manufacturing process because the battery element is completed in a discharged state,
It is preferable to use such a compound. As the conductive material, carbons such as carbon black (acetylene black, thermal black, channel black, etc.), graphite powder, metal powder, and the like can be used, but are not limited thereto. As the binder, a fluorine-based polymer such as polytetrafluoroethylene or polyvinylidene fluoride, a polyolefin-based polymer such as polyethylene or polypropylene, or a synthetic rubber can be used, but is not limited thereto.

The mixing ratio of the positive electrode active material, the conductive material and the binder is preferably 1 to 50 parts by weight of the conductive material and 1 to 30 parts by weight of the binder with respect to 100 parts by weight of the active material. .
More preferably, the conductive material is 1 to 10 parts by weight, and the binder is 3 to 10 parts by weight. When the conductive material is less than 5 parts by weight or the binder is more than 30 parts by weight, the internal resistance or polarization of the electrode is increased, and the discharge capacity of the electrode is reduced, so that a practical lithium secondary battery element is manufactured. It is not preferable because it cannot be done. If the amount of the conductive material is more than 50 parts by weight, the amount of the active material contained in the electrode is relatively reduced, and the discharge capacity as a positive electrode is undesirably reduced. If the amount of the binder is not less than 1 part by weight, the binding ability of the active material is lost, and it is difficult to manufacture the battery element due to the fall of the active material and the decrease in mechanical strength, which is not preferable. When the amount of the binder is more than 30 parts by weight, the amount of the active material contained in the electrode is reduced as in the case of the conductive material. Therefore, it is not preferable.

In general, a positive electrode is prepared by mixing a positive electrode active material and a conductive material with a binder dissolved or dispersed in a solvent to form a slurry, and applying the slurry on a current collector or collecting the slurry. After filling in an electric body, it can be manufactured by removing a solvent. In addition, during the preparation of the positive electrode, in order to improve the binding property of the positive electrode active material and the conductive material to the current collector,
The heat treatment is preferably performed at a temperature around the melting point of the binder and at least the boiling point of the solvent.

The negative electrode generally comprises a negative electrode active material and optionally a conductive material and a binder. As the negative electrode active material, a lithium metal, a lithium alloy, a carbon material capable of inserting and extracting lithium, a metal oxide, and the like can be used.

Among the above-mentioned negative electrode active materials, carbon materials are promising in terms of safety and cycle characteristics. Known materials can be used as the carbon material, for example, natural graphite, petroleum coke, cresol resin fired carbon, furan resin fired carbon, polyacrylonitrile fired carbon, vapor grown carbon, mesophase pitch fired carbon, high crystallinity A graphite material having an amorphous carbon layer formed on the surface of graphite particles can be used.
Among these carbon materials, a graphite material with improved crystallinity is preferable because the voltage of the battery can be flattened and the energy density can be increased. Further, among graphite materials, a graphite material having an amorphous carbon layer on the surface of graphite particles has few side reactions with an electrolytic solution and is weak against an internal pressure like a battery sealed by a laminate outer package. Particularly preferable is a battery having a shape.

When the above-described carbon material is used as a negative electrode active material, a negative electrode is formed by mixing carbon particles and a binder. At this time, a conductive material may be mixed to improve conductivity. As the binder, a fluorine-based polymer such as polyvinylidene fluoride and polytetrafluoroethylene, a polyolefin-based polymer such as polyethylene and polypropylene, and synthetic rubbers can be used, but are not limited thereto.

The mixing ratio of the carbon material and the binder is 9 by weight.
It is preferably from 9: 1 to 70:30. When the weight ratio of the binder is more than 30, the internal resistance or polarization of the electrode becomes large, and as a result, the discharge capacity becomes low, so that a practical lithium secondary battery cannot be produced, which is not preferable. If the weight ratio of the binder is less than 1, the binding ability between the carbon material itself or the carbon material and the current collector becomes insufficient, and the carbon material falls off or the mechanical strength decreases. It is not preferable because the production of the element becomes difficult.

The conductive material is not particularly limited, and carbons such as carbon black (acetylene black, thermal black, channel black, etc.), metal powder, and the like can be used. When a carbon material is used as a negative electrode active material, a negative electrode active material is generally prepared by mixing a negative electrode active material, a binder dissolved or dispersed in a solvent, and a conductive material as necessary to form a slurry. . A negative electrode can be manufactured by applying or filling this slurry on a current collector and removing the solvent. In this case, in order to improve the binding property and remove the solvent of the binder, heat treatment in a vacuum, an inert gas atmosphere or air at a temperature not lower than the boiling point of the solvent and around the melting point of the binder. Is preferably performed.

As the current collector for the positive electrode and the negative electrode, a metal simple substance, an alloy or the like can be used. For example, copper, nickel, titanium, aluminum, stainless steel and the like can be mentioned. Further, copper, aluminum, or stainless steel having titanium and silver coated on the surface thereof, and those obtained by oxidizing these materials can also be used. The shape of the current collector is foil,
A film, a sheet, a net, a punched shape, a lath, a porous body, a foam, a molded article of a fiber group, and the like are used. The thickness of the current collector is not particularly limited, but may be 1 from the viewpoint of strength, conductivity, and energy density when a battery is manufactured.
It is preferably from 1 μm to 1 mm, more preferably from 1 μm to 100 μm.

Although the ionic conductor is not particularly limited,
For example, an organic electrolyte (consisting of an electrolyte salt and an organic solvent), a polymer solid electrolyte, an inorganic solid electrolyte, a molten salt, and the like can be used, and among them, a polymer solid electrolyte can be suitably used. As a polymer solid electrolyte,
Examples include a substance composed of a polymer that dissociates an electrolyte salt and an electrolyte, and a substance in which a polymer has an ion dissociating group.

In the present specification, a polymer solid electrolyte is used to distinguish it from a liquid electrolyte generally used for a battery element, and a polymer and an organic solvent are used in the range. It contains a gelled electrolyte. The gel electrolyte is very promising because it has the characteristics of a solid electrolyte without fear of liquid leakage and the ionic conductivity close to that of a liquid.

The organic compound serving as the skeleton of the gel electrolyte is not particularly limited as long as it has a compatibility with the solvent solution of the electrolyte and has a polymerizable functional group. Examples thereof include those having a polyether structure and an unsaturated double bond group, oligoester acrylates, polyesters, polyimines, polythioethers, polysulfans, phosphate polymers, and the like, alone or in combination of two or more. Incidentally, those having a polyether structure and an unsaturated double bond group are preferred from the viewpoint of affinity with a solvent. Examples of the polyether structural unit include ethylene oxide, propylene oxide, butylene oxide, glycidyl ethers and the like, and a single or a combination of two or more thereof is suitably used. In the case of a combination of two or more, the form can be appropriately selected irrespective of block or random. Further, examples of the unsaturated double bond group include allyl, methallyl, vinyl, acroyl, and metalloyl groups.

Examples of the organic solvent used for the gel electrolyte include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC) and butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate and the like. Chain carbonates, γ-butyrolactone,
lactones such as γ-valerolactone, furans such as tetrahydrofuran and 2-methyltetrahydrofuran, ethers such as diethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, dioxane, and dimethyl sulfoxide , Sulfolane,
Examples include methylsulfolane, acetonitrile, methyl formate, methyl acetate and the like.

As the electrolyte salt, lithium perchlorate (LiClO
_Four), Lithium borofluoride (LiBF_Four), Lithium phosphofluoride
(LiPF₆), Lithium hexafluoroarsenate (LiAsF₆), Hexafluoride
Lithium thimonate (LiSbF₆), Trifluoromethanesulfo
Lithium phosphate (LiCF_ThreeSO_Three), Lithium trifluoroacetate (L
iCF_ThreeCOO), lithium halide, lithium aluminate chloride
(LiAlCl_Four), Trifluoromethanesulfonic acid imidori
Titanium (LiN (CF_ThreeSO_Two) _Two)), And the like.
One or more of these can be used as a mixture.

The gel-like solid electrolyte is prepared by dissolving an electrolyte salt in the solvent selected above to prepare an electrolyte.
It is obtained by mixing with the above organic compound and polymerizing. Examples of the polymerization method include thermal polymerization, photopolymerization, and radiation polymerization. As the thermal polymerization initiator and the photopolymerization initiator, those known to those skilled in the art can be used. The amount of the polymerization initiator can be appropriately selected depending on the composition and the like.

As another method of producing a gel electrolyte, the gel electrolyte is expanded with an electrolyte.
Create an electrode in which the moisturizing polymer is premixed in the electrode.
By swelling with an electrolyte later.
It is also possible to produce a solid electrolyte. In addition, Io
The electrolyte conductor contains an organic solvent in which an electrolyte salt is dissolved in an organic solvent.
It is also possible to use a lysing solution. Furthermore, inorganic solid electrolyte
May be used as the electrolyte, a nitride of Li,
Halides, oxyacid salts and the like are known. Specifically
Is Li _ThreeN, LiI, Li_ThreeN-LiI-LiOH, LiSiO_Four, LiSiO_Four-LiI-L
iOH, Li_ThreePO_Four-Li_FourSiO_Four, Phosphorus sulfide compound, Li_TwoSiS_ThreeEtc.
You. In addition, using inorganic solid electrolyte and organic solid electrolyte together
Is also good.

[0035]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not affected at all. In the following examples, the average interplanar spacing d ₍₀₀₂₎ by the X-ray wide-angle diffraction method or the crystallite size (Lc, Lc
The method for measuring a) is described in “Carbon Materials Experimental Technique 1, p.5.
5 to 63, edited by the Society of Carbon Materials, Japan (Science and Technology Corporation). The shape factor K for obtaining Lc and La was 0.9. The specific surface area of the particles was determined by the BET method. The particle size and the particle size distribution were measured using a laser diffraction type particle size distribution analyzer, and the peak in the particle size distribution was taken as the average particle size.The R value was measured by Raman spectroscopy using an argon laser of 514.5 nm. Peak intensity I136 around 1360 cm ^-1 from the two peaks observed by the method
The intensity ratio of peak intensity I1580 around 0 and 1580 cm ⁻¹ , that is, R value = I1360 / I1580 was determined.

In Raman spectroscopy, 1580 cm ^-1
The peak in the vicinity is due to the graphite structure, the peak in the vicinity of 1360 cm ^-1 is due to the disorder in the graphite structure, and the crystallinity of the graphite can be evaluated by the intensity ratio of the peaks. Since the peak position slightly shifts depending on the crystallinity of the graphite, the raw material, the firing conditions, and the like, in the case of this evaluation method, the peak intensity ratio was calculated using the peak top intensity of the peak appearing in the vicinity.

Example 1 Preparation of Electrode Preparation of Positive Electrode Lithium cobaltate (LiCoO ₂ ) was used as a positive electrode active material. Polyvinylidene fluoride as a binder was temporarily dissolved in N-methyl-2-pyrrolidone as a solvent in a mortar to obtain a binder solution. The above-mentioned positive electrode active material and acetylene black (conductive material) were mixed, and this was dispersed in a binder solution to prepare a paste. The obtained paste was applied on a current collector made of aluminum foil, which was temporarily dried at 60 ° C., heat-treated at 150 ° C., and pressed. 3.5 electrode size
× 3 cm (coated part 3 × 3 cm), and a tab made of aluminum foil (50 μm) was welded to the uncoated part. Further, drying was performed at 180 ° C. under reduced pressure to remove water, and this was used as a positive electrode for testing. Coating density is 2.9g / cm ³ , coating thickness is 64μm
Met.

Preparation of negative electrode As the negative electrode active material, artificial graphite MCMB (particle size: 12 μm, d ₍₀₀₂₎ =
0.337 nm, R value = 0.4). Polyvinylidene fluoride as a binder was temporarily dissolved in N-methyl-2-pyrrolidone as a solvent in a mortar to obtain a binder solution. The negative electrode active material was dispersed in a binder solution to prepare a paste. The obtained paste was applied on a current collector made of a copper foil having a thickness of 20 μm, and this was provisionally dried at 60 ° C. and 240 ° C.
And then pressed. The electrode size was 3.5 × 3 cm (coated portion 3 × 3 cm), and a nickel foil (50 μm) tab was welded to the uncoated portion. Further, it was vacuum-dried at 200 ° C. to remove water, and used as a negative electrode for testing. The coating density is
The coating thickness was 1.4 g / cm ³ and the coating thickness was 59 μm.

Preparation of Battery-Battery using gel electrolyte as ion conductor 1M LiPF ₆ dissolved ethylene carbonate (hereinafter referred to as EC)
50 g of a 1: 1 (volume ratio) solution of ethylene oxide and diethyl carbonate (hereinafter referred to as DEC) was added to an ethylene oxide / propylene oxide / diacrylate copolymer (molecular weight: 200
0) 10 g was dissolved, and 0.06 g of a polymerization initiator was further added. This solution is applied to a polypropylene nonwoven fabric (thickness: 20μ).
m) was impregnated, sandwiched between glass plates, and gelled by irradiating ultraviolet rays to obtain a gel electrolyte. After the above solution was impregnated into the positive electrode and the negative electrode, the solution was sandwiched between glass plates and gelled by irradiating ultraviolet rays to obtain a composite electrode containing a gel electrolyte. A battery element was produced by overlapping the electrode and the electrolyte layer thus obtained.

As shown in FIG. 1, the obtained battery was sealed on two sides (shaded portions on the left and right sides with respect to the paper surface) (sealing width).
5 mm) It was inserted into a laminate pack, and the side having the tab lead-out portion was sealed as shown in FIG. 2 (projected sealing width 5 mm, actual sealing width 1 cm) to obtain a sealed battery for testing.
The laminate package used in the laminate pack used here was an aluminum foil sandwiched between heat-fusible resin films made of polyethylene. FIG.
Among them, 1 indicates a positive electrode tab, 2 indicates a negative electrode tab, and 3 indicates a sealing portion. FIG. 2 is a cross-sectional view taken along line XX of FIG. 1. In FIG. 2, reference numeral 4 denotes a positive electrode tab, and reference numeral 5 denotes a laminate exterior body.

A battery using an electrolytic solution as an ion conductor A separator (25 μm made of polypropylene) was sandwiched between the positive electrode and the negative electrode, and this battery element was inserted into a laminate pack shown in FIG. 1 and sealed on two sides. . After injecting 1 M LiPF ₆ / EC: DEC as an electrolyte into the laminate pack, the tab lead-out portion was sealed as shown in FIG. 2 to obtain a test battery. Three batteries using the gel electrolyte and three batteries using the electrolytic solution were produced by the above manufacturing method. The charging conditions are constant current and constant voltage charging (voltage value 4.1V, current value 1.8m
A, charging for 125 hours), the battery was subjected to a charge / discharge cycle test under the conditions of a current value of 1.8 mA and a cutoff voltage of 2.75 V. Table 1 shows the battery capacity (first cycle, 100th cycle) and the cycle deterioration rate (100th cycle capacity / initial capacity).

Comparative Example 1 As shown in FIGS. 3 and 4, a gel electrolyte was used in the same manner as in Example 1 except that the side having the tab lead-out portion was sealed without bending the sealing portion (sealing width 5 mm). Three batteries used and three batteries using the electrolyte were prepared and subjected to a cycle test. Battery capacity (first time, 100th cycle), and cycle deterioration rate (100th cycle capacity /
Table 1 shows the initial capacity. In FIG. 3, 6 indicates a positive electrode tab, 7 indicates a negative electrode tab, and 8 indicates a sealing portion. FIG.
FIG. 4 is a cross-sectional view taken along the line XX of FIG. 3, in which 9 denotes a laminate exterior body, and 10 denotes a positive electrode tab.

[0043]

[Table 1]

From the above results, it is possible to double the width of the sealing portion even with the same sealing width by bending the sealing portion from which the tab is led out, thereby improving the airtight reliability and improving the cycle. It can be seen that characteristics can be obtained.
Moreover, in the comparative example manufactured without bending the sealing portion, a battery having extremely poor cycle characteristics was observed, and it was found that the reliability of sealing was low. This is considered to be because the airtight reliability was not sufficient, and moisture in the air entered the battery.

Example 2 A punching metal of aluminum (50 μm, opening ratio 50%) was used on the positive electrode side and a punching metal of nickel (50 μm, opening ratio 50%) was used on the negative electrode side as a tab for extracting current from the electrodes. Was. As a solution of gel electrolyte, 1
EC dissolved in M LiBF ₄ and γ-butyrolactone (GB
A 1: 1 (volume ratio) solution of L) was used. A battery using a gel electrolyte was produced in the same manner as in Example 1 except that the sealing portion was changed as shown in FIG. Table 2 shows the results of the same test as in Example 1 performed on the manufactured batteries. In FIG. 7, reference numeral 16 denotes a laminate exterior body, and reference numeral 17 denotes a positive electrode tab.

Comparative Example 2 A punching metal of aluminum (50 μm, opening ratio: 50%) was used on the positive electrode side and a punching metal of nickel (50 μm, opening ratio: 50%) was used on the negative electrode side as a tab for extracting current from the electrode. Was. Further, as a solution of the gel electrolyte, a 1: 1 (volume ratio) solution of EC and GBL in which 1 M LiBF ₄ was dissolved was used. Otherwise, the procedure of Comparative Example 1 was repeated to prepare a battery using the gel electrolyte. Table 2 shows the results of the same test as in Example 1 performed on the manufactured batteries. One of the batteries of Comparative Example 2 could not be evaluated because the positive electrode tab was broken.

[0047]

[Table 2]

From the above results, when a tab such as punched metal is used, the hermetic reliability is improved to some extent and the cycle characteristics are improved by the conventional method. However, as in the present invention, the airtight reliability is further improved by bending the sealing portion, and good cycle characteristics can be obtained. Also,
By bending the sealing portion, the tab is overlapped with the sealing portion or the battery surface, so that direct stress is less likely to be applied to the base of the tab. As a result, the problem of tab breakage can be solved.

Example 3 As a carbon material, a graphite material ((particle diameter: 15 μm, d ₍₀₀₂₎ = 0.336 nm, R value = 0.38)
A negative electrode was produced in the same manner as in Example 1 except that PCG) was used. In addition, LiPF ₆ was added to the gel electrolyte solution at 1M concentration.
Propylene carbonate (PC) with GBL dissolved and GBL
1: 4 (volume ratio) was used. Otherwise in the same manner as in Example 1, a battery element using the gel electrolyte was produced. The battery element thus obtained is sealed in a state where the long sides are overlapped as shown in FIGS. 5 and 6, the end is bent, and inserted into a sealed bag. A battery was fabricated in the same manner as in Example 1 except that the battery was manufactured.

In FIG. 5, reference numeral 11 denotes a positive electrode tab, 12 denotes a negative electrode tab, and 13 denotes a sealing portion. FIG. 6 is a cross-sectional view of FIG.
FIG. 14 is a cross-sectional view taken along the line Y, in which 14 is a laminate exterior body,
5 means a battery element. FIG. 8 is a cross-sectional view taken along the line XX of FIG. 5, in which 18 denotes a laminate exterior body and 19 denotes a positive electrode tab. A battery test was performed on the obtained battery in the same manner as in Example 1. Table 3 shows the results. Further, the low temperature characteristics (−20 ° C.) of the batteries of Example 1 and Example 3 were measured. Table 4 shows the results.

Comparative Example 3 As a carbon material, artificial graphite (KS-25 manufactured by TIMCAL, particle size: 12)
A battery was produced in the same manner as in Example 1, except that μm, d ₍₀₀₂₎ = 0.336 nm, R value = 0.15). A battery was manufactured in the same manner as in Example 3, except that the both ends (portions 16 and 17 in FIG. 7) of the laminate outer package were sealed without bending.
The battery thus manufactured was subjected to a charge / discharge test in the same manner as in Example 1. Table 3 shows the results. One of the three batteries could not be evaluated because the sealing portion was open at the tab.

[0052]

[Table 3]

[0053]

[Table 4]

From the above comparison, when graphite having an amorphous carbon layer formed on the surface of the graphite material is used, the decomposition of PC which occurs when the conventional graphite material is used is suppressed.
It turns out that the PC can be used. Furthermore, by applying the sealing method of the present invention to the combination of graphite and PC, the airtight reliability was improved, and a highly reliable battery was obtained.

On the other hand, when a conventional graphite material was used as the negative electrode material, if PC was present in the electrolytic solution, the charge / discharge efficiency was extremely low, lithium of the positive electrode was consumed, and sufficient capacity could not be obtained. This is considered to be because the solid-solid interface was broken by the gas generation due to the decomposition of PC, and the characteristics of the battery deteriorated. In addition, since the melting point of propylene carbonate is lower than that of ethylene carbonate, the battery obtained in Example 3 had good low-temperature characteristics.

[0056]

According to the present invention, the width of the sealing portion can be increased without increasing the area of the battery by bending the sealing portion, and the hermeticity is improved. Can be improved. As a result, the reliability of the battery, particularly, the cycle characteristics can be improved. By applying the folded sealing portion to the tab lead-out portion, the sealing effect is greatly improved. Furthermore, if the side orthogonal to the side that is bent and sealed at least once is sealed by heat-sealing the back and front of the laminate exterior body, there is no portion bent twice and reliability is improved. Get nervous.

Further, considering the projected area, the area of the sealing portion can be reduced, and the material of the laminate pack is sufficiently thinner than the battery element. Never become
The capacity per projection area can be increased without increasing the thickness. Furthermore, by using PCG for the negative electrode material, decomposition of the electrolyte solution can be suppressed, thereby improving the airtight reliability. In the case of a gel electrolyte, the solid-solid interface between the gel electrolyte and the negative electrode active material can be prevented from being broken, so that the reliability of the battery, particularly the cycle characteristics, can be improved. When the sealing method and the surface amorphous graphite (PCG) in the present invention are used for the negative electrode,
Even if the battery is used, sufficient airtight reliability can be ensured, so that excellent low-temperature characteristics can be obtained even in a battery using a gel electrolyte, which was conventionally considered to have low low-temperature characteristics.

[Brief description of the drawings]

FIG. 1 is an external view of a battery according to Examples 1 and 2 of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is an external view of a battery in Comparative Examples 1 and 2.

FIG. 4 is a sectional view taken along line XX of FIG. 3;

FIG. 5 is an external view of a battery according to a third embodiment of the present invention.

FIG. 6 is a sectional view taken along line YY of FIG. 5;

FIG. 7 is a sectional view taken along line XX of FIG. 5;

FIG. 8 is a cross-sectional view when the sealing portion is bent twice in the present invention.

[Explanation of symbols]

 1, 4, 6, 10, 11, 17, 19 Positive electrode tab 2, 7, 12 Negative electrode tab 3, 8, 13 Sealing part 5, 9, 14, 16, 18 Laminate package 15 Battery element

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Nishijima Chiaki 22-22, Nagaikecho, Abeno-ku, Osaka, Osaka Inside Sharp Corporation (72) Inventor Naoto Nishimura 22-22, Nagaikecho, Abeno-ku, Osaka, Osaka Within Sharp Corporation (72) Inventor Naoto Kota 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term within Sharp Corporation (reference) 5H011 AA10 CC02 CC06 CC10 DD06 EE04 FF04 GG01 HH02 JJ12

Claims (5)

[Claims] 1. A battery comprising a positive electrode, a negative electrode and an ionic conductor enclosed in a laminate package comprising at least a metal thin film and a heat-fusible resin film, wherein at least one side of a sealing portion is bent at least once. A battery characterized in that the battery is heat-sealed. 2. The battery according to claim 1, wherein the sealing portion is bent by the number of times such that the thickness is equal to or less than the thickness of the thickest portion of the battery. 3. The battery according to claim 1, wherein each of the positive electrode and the negative electrode has a tab for extracting a current to the outside, and the tab is bent at least once together with the laminate exterior body at the sealing portion. 4. The laminate according to claim 1, wherein a side orthogonal to the side formed by being bent and sealed at least once is sealed by heat-sealing the back and front sides of the laminate exterior body. The battery according to one. 5. The battery according to claim 1, wherein the battery is a non-aqueous secondary battery.
5. The battery according to any one of items 4 to 4.