JP2000021368A - Battery and battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent swelling of a battery by avoiding an increase of battery internal pressure, and to restrain damage to an apparatus for installing the battery and the human body by using a material having a softening point lower than a resin film thermally welded by constituting a laminate film, at least in a part of the thermally welding sealing part of the laminate film. SOLUTION: An organic electrolyte secondary battery 1 uses a laminate film case 2. A positive electrode terminal 3 and a negative electrode terminal 4 are taken out of the thermally welding part 7, and the terminals are not taken out of the thermally welding parts 8 to 10. When battery internal pressure abnormally increases at a high temperature since a material having a low softening point is made to partically exist in a laminate film, the laminate film case 2 opens in the low softening point part to release generated gas so as to restrain swelling of an organic electrolyte secondary battery 1 by abnormal high pressure. Even if the laminate film case 2 opens when using the material having a low softening point as the thermally welding parts 8 to 10, corrosion by the battery contents is prevented to avoid a danger such as overcharge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a battery and a battery pack.

[0002]

2. Description of the Related Art In recent years, electronic devices such as a portable radio telephone, a portable personal computer, and a portable video camera have been developed, and various electronic devices have been reduced in size to be portable. Along with this, a battery having a high energy density and a light weight is also adopted as a built-in battery. A typical battery that satisfies such a requirement is an active material such as lithium metal or lithium alloy, or a host material containing lithium ions (here, a host material refers to a material that can occlude and release lithium ions). Lithium intercalation compound occluded in a certain carbon is used as a negative electrode material, and LiC
This is a non-aqueous electrolyte secondary battery using an aprotic organic solvent in which a lithium salt such as 10 ₄ or LiPF ₆ is dissolved as an electrolyte.

This non-aqueous electrolyte secondary battery has a negative electrode plate in which the above-mentioned negative electrode material is held on a negative electrode current collector as a support, and a reversible electrochemical reaction with lithium ions such as a lithium-cobalt composite oxide. The positive electrode plate, which holds the positive electrode active material that reacts on the positive electrode current collector that is the support, from the separator that holds the electrolytic solution and intervenes between the negative electrode plate and the positive electrode plate to prevent a short circuit between the two electrodes Has become.

[0004] A battery case made of a metal laminated resin film having an airtight structure is obtained by laminating or spirally winding the above-mentioned positive electrode plate, separator and negative electrode plate each formed into a thin sheet or foil shape. Is stored in.

When this non-aqueous electrolyte secondary battery is used in electronic equipment, a single battery or a plurality of batteries connected in series is used to obtain a voltage according to the application. The single or plural batteries are housed in a housing made of resin or metal and resin together with the charge / discharge control circuit, and sealed so that the contents cannot be taken out, and used as a battery pack.

[0006]

In a secondary battery using a metal laminated resin film or its molded body for a case, the laminated resin is heat-sealed to seal the battery. If the internal pressure of the battery rises abnormally due to abnormal heat generation, reverse charging, heating, etc., the thickness of the battery will increase, and part of the case made of this laminated resin will be ruptured, causing the contents such as the electrolyte to flow out of the battery. Spurts out.

At this time, the abnormally high pressure in the battery is instantaneously released at a high temperature, and the contents such as the electrolytic solution squirt out of the battery with a considerable force, so that the battery-equipped device and Using it could cause injury to the human body.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems.

That is, a first invention is directed to a unit cell having an air-tight structure, in which a power generation element is housed by heat-sealing a laminated film made of metal and resin as constituent materials.
A battery and a battery pack, wherein a material having a softening point lower than the softening point of the heat-sealed resin film constituting the laminate film is used in at least a part of the heat-sealing sealing portion of the laminate film.

[0010] A second invention is characterized in that the material having a low softening point is used in a heat-sealing sealing portion other than the heat-sealing sealing portion to which a terminal portion of a battery and a protection circuit are attached.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a view showing the appearance of a battery according to the present invention. In the figure, reference numeral 1 denotes a unit cell, which uses a laminated film 2 having metal and resin as constituent elements as a battery case. Reference numeral 3 denotes a positive electrode terminal, and 4 denotes a negative electrode terminal. Portions of the laminate film 2 taken out of the sealing portion 7 are covered with a positive electrode terminal protective film 5 and a negative terminal protective film 6, respectively. Numerals 8, 9 and 10 are sealing portions from which no terminals are taken out.

It is not always necessary to use two laminated films as shown in FIG. 1 as the battery case, but as shown in FIGS. It may be a case. FIG.
3 and FIG. 3, symbols 1 to 10 indicate the same as those in FIG. In FIG. 2, the laminated film is 7,
In FIG. 3, the heat-welded portion 10 of the laminate film is located at the upper center of the battery.

FIG. 4 shows a cross-sectional structure of the laminated film. The laminated film is composed of four layers.
11 is an outermost surface protection film, 12 is an adhesive layer,
Reference numeral 13 denotes a metal barrier layer, and reference numeral 14 denotes a resin film layer to be thermally welded.

FIG. 5 is a sectional view of the unit cell 1 shown in FIG.
In the figure, reference numerals 11 to 14 indicate the same components as those in FIG. 2, 15 is a metal terminal, 16 is a metal interface adhesive layer, 17 is a seal layer as an electrolyte barrier layer, and 16 And 17 constitute a terminal protection film.

FIG. 6 shows BB 'of the cell 1 shown in FIG.
It shows a cross section, in which 3 is a positive electrode terminal,
The periphery is covered with a positive terminal protection film 5, the reference numeral 4 is a negative terminal, and the periphery is covered with a negative terminal protection film 6. Two laminated sheets are stacked so that the resin film layers 14 to be thermally welded face each other, the positive electrode terminal 3 and the negative electrode terminal 4 are interposed therebetween, and the resin film layer 14 of the laminate sheet is welded by thermal welding. .

FIG. 7 is a cross-sectional view of the unit cell 1 shown in FIG.
In a cross section, two laminated sheets are stacked so that the resin film layers 14 to be heat-welded face each other,
In the meantime, a material 18 having a softening point lower than the softening point of the resin film layer 14 to be thermally welded of the laminate sheet is sandwiched therebetween, and the resin film layer 14 of the laminate sheet is welded by thermal welding.

[0017]

Next, the present invention will be described based on preferred embodiments.

Example 1 A non-aqueous electrolyte secondary battery in which an electrode group consisting of a positive electrode plate, a negative electrode plate, and a separator and a non-aqueous electrolyte were both housed in a laminate film case was manufactured. The laminate film case is obtained by heat-sealing a laminate film composed of metal and resin as constituent materials.
FIG. 1 shows the appearance of the produced non-aqueous electrolyte secondary battery, wherein 1 is a non-aqueous electrolyte secondary battery, and 2 is a laminate film case.

The positive electrode plate is prepared by mixing 91 parts of lithium-cobalt composite oxide (LiCoO 2) as an active material, 6 parts of polyvinylidene fluoride as a binder, and 3 parts of acetylene black as a conductive agent, and appropriately mixing N-methyl A paste prepared by adding pyrrolidone was prepared by applying and drying both sides of a current collector made of an aluminum foil having a thickness of 10 μm.

The negative electrode plate was prepared by mixing 92 parts of graphite (graphite) as a host substance and 8 parts of polyvinylidene fluoride as a binder, and adding N-methylpyrrolidone as appropriate. It was prepared by applying and drying both sides of a current collector made of copper foil.

The separator uses a polyethylene microporous membrane, and the electrolyte is a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1 mol / l of LiPF ₆ at a volume ratio of 4: 6.

Each dimension is such that the positive electrode plate has a thickness of 180 μm.
m, width 49 mm, separator thickness 25 μm, width 53
mm, the negative electrode plate had a thickness of 170 μm and a width of 51 mm. The negative electrode plate was superposed in order, wound around an elliptical core around a rectangular core of polyethylene, and then housed in a laminate film case.

FIG. 4 shows a cross-sectional structure of a laminated film using metal and resin as constituent materials. In FIG. 4, the outermost surface protection film 11 is a PET film having a thickness of 12 μm, and the surface protection film 11 and an aluminum foil having a thickness of 9 μm as a barrier layer 13 are bonded together by a urethane-based adhesive layer 12. Further, an acid-modified polyethylene layer having a thickness of 100 μm is provided as a resin film layer 14 which is thermally welded below the barrier layer 13. Here, the acid-modified polyethylene layer has a melting point of 115 ° C. and a softening point of 10
The one at 4 ° C. was used.

The lead terminal take-out portions of the positive electrode and the negative electrode are formed as shown in FIG.
A 50 μm acid-modified PE layer for forming an adhesive layer 16 with a metal is adhered to a metal conductor 15 made of copper, aluminum, nickel or the like having a thickness of 0 to 100 μm. (Ethylene-vinyl alcohol copolymer resin) layer. As shown in FIG.
Good airtightness can be obtained by overlapping and bonding as shown in FIG.

The size of the battery is 33 (mm) × 60 (mm)
The heat-welded portion of the laminate case was provided with a width of 5 mm. At the sealing portion (sealing portion 8 in FIG. 1) opposite to the sealing portion (sealing portion 7 in FIG. 1) to which the lead terminals of this battery were attached, when the sealing portion was thermally welded, 5 mm × 3 mm
Was sandwiched between the sealing portions and heat-sealed simultaneously with the sealing. This polyethylene piece had a melting point of 107 ° C. and a softening point of 96 ° C.

The structure of the sealing portion will be described with reference to FIGS. FIG. 6 shows the structure of the sealing portion of the cross section BB 'shown in FIG.
4 shows the same thing as FIG. 4, and these constitute a laminated film. 3 is a positive terminal, 4 is a negative terminal,
Each is covered with an acid-modified PE layer 16 and an Eval resin layer 17. FIG. 7 shows a structure of a sealing portion where a polyethylene piece having a cross section taken along the line CC ′ shown in FIG. 1 is sandwiched. In the drawing, symbols 11 to 14 are the same as those in FIG.
18 is a polyethylene piece. 100 cells of this battery were produced. This battery has a nominal capacity of 550 mAh.

Example 2 The size of a polyethylene piece was 5
The same battery as in Example 1 except that the
0 cells were produced.

Example 3 The size of a polyethylene piece was 5
The same battery as in Example 1 except that the
00 cells were produced. FIG. 8 shows the battery according to Example 3 in FIG.
Shows the structure of the sealing portion in which the polyethylene piece of the CC ′ cross section shown in FIG.
Shows the same thing as FIG. 4, and 18 is a piece of polyethylene. FIG. 9 shows the structure of the sealing portion of the battery according to the third embodiment in which the polyethylene piece having the DD ′ cross section shown in FIG. 1 is sandwiched. The same thing as 4 is shown.

Example 4 The size of a polyethylene piece was 5
The same battery as in Example 1 except that the
00 cells were produced.

Example 5 The size of a polyethylene piece was 5
The same battery as in Example 1 except that the
00 cells were produced.

Example 6 The size of a polyethylene piece was 5
The same battery as in Example 1 except that the
00 cells were produced.

Example 7 100 cells were manufactured in the same manner as in Example 1 except that the size of the polyethylene piece was set to 2.5 mm × 10 mm and heat-welded as shown in FIG. FIG. 10 shows the structure of the cross section taken along the line DD ′ of the sealing portion where the polyethylene piece shown in FIG. 1 is sandwiched, in which the symbols 11 to 14 and 18 are those of FIG. The same thing is shown, and a polyethylene piece is used in a part in contact with the battery internal space in the heat-welded portion of the laminate film.

[Comparative Example 1] 100 cells were manufactured in the same manner as in Example 1 except that the heat sealing was performed without using the polyethylene piece.

[Comparative Example 2] Fifteen cells were manufactured in the same manner as in Example 1 except that an iron hard case was used instead of the laminate film as the battery case.

First, the battery of Comparative Example 2 was left in a charged state (charging conditions: 1 CmA / 4.2 V-3 hours) at 60, 85 and 100 ° C. for 30 days. At this time, the internal pressure of the battery was measured using a pressure sensor. The result is shown in FIG.

FIG. 11 shows that the longer the number of days left for each temperature, the higher the internal pressure of the battery. 85 ° C and 100 ° C
In the case of leaving at 0 ° C., the internal pressure of the battery increased significantly immediately after the start of the leaving. After 15 days, the degree of increase in the internal pressure of the battery was small.

Further, from the above result and the fact that the increase in the thickness (volume) of the battery was small, it is considered that an increase in the internal pressure of the battery indicates that the amount of gas generated in the battery was large. Here, when the metal hard case in Comparative Example 2 is replaced with a case using a laminated film, the laminated film case expands in volume to relieve the pressure of gas generated in the battery. It is presumed that this leads to significant deformation and expansion.

On the other hand, the batteries of Examples 1 to 7 and Comparative Example 1 using a laminate film containing metal and resin as constituent materials for the battery cases were 30 cells each, 60, 85 and 1 respectively.
Charged at 00 ° C. for 30 days (Charging condition: 1 Cm
A / 4.2 V-3 hours). FIG. 1 shows the number of days until opening of the laminate film case at this time.
It is shown in FIG.

As shown in FIG. 12, at 85 and 100 ° C., the example of the present invention opened in a shorter number of days than Comparative Example 1. Further, comparing Examples 1 to 7, the larger the size of the polyethylene piece used for the heat-welded portion of the laminate film case, the shorter the number of days required to open.
In addition, as a result of examining the heat-welded portion of the laminated film case of the battery where the storage temperature was 85 ° C. and the storage days were changed, it was found that the opening of the laminated film case started from the portion using the material having a low softening point.

This is because when the battery internal pressure rises due to gas generated in the battery while the battery is left at a high temperature,
This is considered to be a phenomenon that occurred because the portion of the material having a low softening point used for part or all of the heat-welded portion has lower strength against deformation than other heat-welded portions. That is, by appropriately setting the size of the resin piece of a material having a lower melting point or softening point than the material used for the heat-welded portion of the laminate film case, the temperature at which the laminate film case opens and / or the battery It is possible to set the internal pressure to a desired point. Further, as seen in the case of Example 7, if a material lower than the softening point of the heat-welded portion is present even in a part of the heat-sealed portion of the laminated film case in contact with the battery internal space, the laminating is performed. The opening of the film case can be limited to that portion, and the temperature at the opening and / or the internal pressure of the battery can be set to a desired value.

That is, the greatest effect of the present invention is as follows.
If a safety valve is required, that is, if the battery temperature becomes abnormally high, the laminated film case itself is reduced to the appropriate pressure resistance to ensure safety, and the opening is intentionally limited. Where you can.

Materials having a softening point lower than the softening point of the heat-sealed resin film constituting the laminated film (hereinafter, this material is referred to as "low softening point material") are shown in Examples 1 to 7. As described above, it may be attached to at least a part of the heat-sealing sealing portion of the laminate film.

For example, four places (7, 8, 9, 1 in FIG. 1) around two laminated films as shown in FIG.
In the case of using a battery case in which 0) is heat-sealed, the low softening point material can be attached to any of the positions 7, 8, 9, and 10 in FIG. However, when the internal pressure of the battery rises abnormally and the place where the low softening point material is attached is torn and the contents such as the electrolytic solution squirt, the contents adhere to the terminals and the protection circuit and damage them. However, in these batteries, the protection circuit is usually mounted near the terminal, so the material with a low softening point is not heat-sealed except for the terminal and the heat-sealed sealing part to which the protection circuit is mounted. It is desirable to attach it to the welding opening (8, 9, 10 in FIG. 1).

Similarly, when using a battery case in which one laminated film is bent and heat-welded at three places as shown in FIGS. 2 and 3, the low softening point material is used in the case of FIG. It can be attached to any of the locations 7, 8, and 10, and in the case of FIG. 3, it can be attached to any of the locations 7 and 10. But also in these cases,
When the internal pressure of the battery rises abnormally and the place where the low softening point material is attached is torn, and the contents such as the electrolytic solution squirt, the contents adhere to the terminals and protection circuits and damage them. In order to prevent this, a low softening point material is used for the heat-sealing sealing portion other than the heat-sealing sealing portion to which the terminal portion and the protection circuit are attached (FIG.
8 and 10 in FIG. 3 and 8) in FIG.

According to the present invention, since the power generating element is housed in a soft case formed of, for example, a thin sheet, it is excellent in airtightness and can eliminate the complexity of the sealing process. Is possible. In addition, by storing the single cell or a plurality of single cells in a hard case made of, for example, hard plastic, it is possible to supplement mechanical strength not provided in the single cell. In addition, since the cells have excellent airtightness, the airtightness of the hard case itself does not matter as in the related art.
Therefore, since a one-touch assembly structure can be provided, the manufacture of the battery pack can be extremely facilitated. Furthermore, since the terminal for connecting external equipment formed by insert molding is formed in the battery housing, the manufacturing process can be further simplified and the manufacturing cost can be further reduced.

In the examples, polyethylene was described as an example of the material of the heat-welded portion of the laminated film composed of metal and resin. However, the material may be any of thermoplastic polymer materials such as polypropylene and polyethylene terephthalate. Any substance may be used. Also, at the time of heat sealing of the film, a method of sandwiching a polyethylene piece between films as a material having a lower softening point than the heat-welded portion of the laminated film case has been described as an example, but is not limited thereto. As a material, if the softening point is substantially lower than the heat-welded portion of the laminate film case, a material different from the heat-welded portion of the laminate film may be used, or a part of the heat-welded portion of the laminate film itself. A method of heat sealing with a material having a low softening point may be used.

In the above embodiment, EC and DE were used as electrolytes.
Although a mixed solution of C is used, the present invention is not limited to this, and ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ
-Polar solvents such as butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolan, methyl acetate, or a polar solvent thereof; Mixtures may be used.
It is also possible to use a lithium ion conductive polymer electrolyte membrane. In this case, the electrolytic solution contained in the polymer electrolyte and the electrolytic solution contained in the pores may be the same or different.

Further, in the above embodiment, LiCoO 2 was used as the compound capable of inserting and extracting lithium as the positive electrode material.
₂ is used, but is not limited to this.
In addition, as the inorganic compound, the composition formula LixMO
₂ or LiyM ₂ O ₄ (where M is a transition metal, 0 ≦
A composite oxide, an oxide having tunnel-like vacancies, and a metal chalcogenide having a layered structure represented by x ≦ 1, 0 ≦ y ≦ 2) can be used. As a specific example, L
iCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , Li ₂ Mn
₂ O ₄ , MnO ₂ , FeO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , Ti
O ₂ and TiS ₂ are mentioned. Examples of the organic compound include a conductive polymer such as polyaniline. Further, the above-mentioned various active materials may be mixed and used regardless of an inorganic compound or an organic compound.

Further, in the above embodiment, graphite is used as the compound as the negative electrode material. In addition, alloys of lithium with Al, Si, Pb, Sn, Zn, Cd, etc., LiFe ₂ O ₃ , Transition metal oxides such as WO ₂ and MoO ₂ , graphite, carbonaceous materials such as carbon,
Lithium nitride such as Li ₅ (Li ₃ N), or metallic lithium foil, or a mixture thereof may be used.

[0050]

According to the present invention, a material having a softening point lower than the softening point of the heat-sealed resin film constituting the laminated film in the heat-sealed portion of the laminated film comprising the metal and the resin is provided. When the internal pressure of the battery is abnormally increased at a high temperature, the battery case is opened at the low softening point. Thereby, when the internal pressure of the battery is increased at a high temperature, the gas generated in the battery is released to prevent the internal pressure of the battery from becoming abnormally high, and it is possible to suppress the swelling of the battery. Also, by the above method,
It is possible to specify the location where the laminate film case opens.

Further, when a material having a low softening point is used in a heat-sealing sealing portion other than the heat-sealing sealing portion to which the terminal portion of the battery and the protection circuit are attached, in the event that the laminate film case is opened, In addition, it is possible to prevent the corrosion of the lead terminals and the protection circuit due to the battery contents. As a result, even if the user starts charging without knowing the opening of the battery, the function of the protection circuit is not lost, so that danger such as large current charging and overcharging can be avoided.

According to the present invention, it is possible to avoid an abnormal increase in the internal pressure of the battery at high temperatures, and at the same time, it is possible to prevent the battery from bulging, thereby suppressing damage to equipment to which the battery is mounted and the human body using the same. can do.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the appearance of a battery according to the present invention.

FIG. 2 is a view showing another example of the appearance of the battery according to the present invention.

FIG. 3 is a diagram showing still another example of the appearance of the battery according to the present invention.

FIG. 4 is a diagram showing a cross-sectional structure of a laminate film used for a battery according to the present invention.

FIG. 5 is a view showing a cross section AA ′ of the battery according to the first embodiment of the present invention.

FIG. 6 is a view showing a BB ′ cross section of the battery according to the first embodiment of the present invention.

FIG. 7 is a view showing a cross section taken along line CC ′ of the battery according to the first embodiment of the present invention.

FIG. 8 is a view showing a cross section taken along the line CC ′ of a battery according to a third embodiment of the present invention.

FIG. 9 is a diagram showing a cross section taken along line DD ′ of a battery according to a third embodiment of the present invention.

FIG. 10 shows DD ′ of the battery according to Example 7 of the present invention.
It is a figure showing a section.

FIG. 11 is a diagram showing the relationship between the number of days left and the battery internal pressure when the battery of Comparative Example 2 was left standing at each temperature.

FIG. 12 is a diagram showing the number of days required for the laminated film case to open when the batteries of Examples 1 to 7 and Comparative Example 1 were left at each temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic electrolyte secondary battery 2 Laminated film case 3 Positive electrode terminal 4 Negative electrode terminal 7, 8, 9, 10 Heat welding part 16 Polyethylene piece

Claims (2)

[Claims] In a unit cell having an airtight structure and a power generation element housed by sealing a laminated film made of metal and resin as a constituent material by heat sealing, at least a part of the heat sealed sealing portion of the laminated film. A battery and a battery pack using a material having a softening point lower than the softening point of a resin film to be thermally welded constituting a laminate film. 2. The battery according to claim 1, wherein the material having a low softening point is used for a heat-sealing sealing portion other than the heat-sealing sealing portion to which the terminal portion and the protection circuit of the battery are attached. And battery pack.