JP2000277088A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the safety while restraining the heat generation even if overcharge and internal short-circuit is generated by fitting a positive electrode lead terminal and a negative electrode lead terminal to the inner peripheral part of a positive plate and a negative plate provided in a power generation element with a separator. SOLUTION: An elliptic winding type power generating element is housed in a case so that the winding center axis thereof is arranged nearly vertical to an opening part of the bag-like battery case having the airtight structure formed of a metal laminated resin film capable of being manufactured at a low cost and capable of reducing the weight. A positive electrode lead terminal 4 and a negative electrode lead terminal 5 are respectively fitted to the ends of the most inner peripheral part of a positive plate 6 and a negative plate 7 forming the power generating element with a separator. In the case where heat is generated in the abnormal condition, heat is radiated from the positive electrode lead terminal 4 and the negative electrode lead terminal 5 having the predetermined thickness and made of Cu, Al, Ni, Ti or stainless steel having excellent heat conductivity and fitted to the inner peripheral part of the power generating element, of which temperature is easy to be raised due to the bad heat radiating property. With this structure, lowering of battery characteristic can be prevented without complicating a manufacturing process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery.

[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 l04 and LiPF6 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] Each of the positive electrode plate and the negative electrode plate is formed into a thin sheet or foil shape, and is a power generating element formed by sequentially laminating or spirally winding through a separator. Then, the power generating element is housed in a battery container made of a metal such as stainless steel, nickel-plated iron, or aluminum, and after injecting the electrolytic solution, hermetically sealed with a lid plate to assemble the battery.

However, when a metal battery container is used,
Although it is highly airtight and has excellent mechanical strength,
There are great restrictions on battery weight, battery container material and design.

In order to solve the problem, a method has been proposed in which a power generating element is housed in a bag-shaped unit cell case.
In particular, by using a metal laminated resin film having an airtight structure as a material of the bag-shaped unit cell case,
There is no leakage of electrolyte or intrusion of moisture or the like from the outside of the battery, and the battery can be reduced in weight.

[0007] The shape of the power generating element is a wound type,
In particular, when the cross section is non-circular or oval, the electrode surface area can be increased and the manufacturing process can be simplified.

When such a non-aqueous electrolyte secondary battery is used in electronic equipment, a predetermined voltage is obtained as a unit cell or a plurality of cells connected in series. 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.

[0009]

However, if the battery enters an overcharged state due to a malfunction of the charge / discharge control circuit or an abnormal state such as an internal short circuit, the battery generates heat and becomes the worst. In the case of, there was a problem that the heat escaped and burst or ignited.

[0010] Therefore, an object of the present invention is to provide a battery which suppresses heat generation of a battery and has excellent safety even if the battery is in an abnormal state such as an overcharged state or an internal short circuit. It aims to supply a water electrolyte battery.

[0011]

SUMMARY OF THE INVENTION A non-aqueous electrolyte secondary battery according to the present invention has been made in view of the above problems, and has a power generating element having a positive electrode plate, a separator and a negative electrode plate, and a positive electrode lead. The terminal and the negative electrode lead terminal are both attached to the positive electrode plate and the negative electrode plate on the inner periphery of the power generating element.

Further, in the nonaqueous electrolyte secondary battery according to the present invention, an elliptical wound type power generating element is provided in an airtightly sealed bag-shaped unit cell case, the winding center axis of which is the opening surface of the bag-shaped unit cell case. In a vertical direction. It should be noted that the vertical direction does not only mean a completely vertical direction but also a substantially vertical direction.

Further, the present invention is characterized in that the material of the bag-shaped unit cell case is a metal laminated resin film.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings, taking a battery provided with an elliptical winding type power generating element as an example. The external appearance of the nonaqueous electrolyte secondary battery according to the present invention is shown in FIG. 1, and the winding center axis of the elliptical wound type power generation element is substantially perpendicular to the opening surface of the bag-shaped unit cell case. Thus, it is housed in a bag-shaped unit cell case.
In FIG. 1, 1 is a bag-shaped single cell case, 2 is a power generation element,
Reference numeral 3 denotes a winding center axis of the winding element, 4 denotes a positive lead terminal, and 5 denotes a negative lead terminal.

FIGS. 2 and 3 show a cross section of the non-aqueous electrolyte secondary battery according to the present invention, taken along a plane perpendicular to the winding center axis of the power generating element (cross section taken along the line AA 'in FIG. 1). Things.
2 and 3, symbols 4 and 5 indicate the same components as in FIG. 1, 6 is a positive electrode plate, 7 is a negative electrode plate, and 8 is a separator. In the non-aqueous electrolyte secondary battery according to the present invention,
As shown in FIGS. 2 and 3, the positive electrode lead terminal and the negative electrode lead terminal are both attached to the positive electrode plate and the negative electrode plate on the inner peripheral portion of the elliptical wound power generating element.

The mounting position of the lead terminal on the electrode plate is not limited to the position shown in FIGS. 2 and 3, but may be any position on the inner periphery of the elliptical wound power generating element. The innermost peripheral portion shown in FIG. 2 is more preferably attached to the end of the electrode plate in the innermost peripheral portion as shown in FIG.

The shape of the power generating element used in the present invention is not limited to an elliptical wound type in cross section, but may be a circular wound type, a non-circular wound type in cross section, or a flat plate-shaped electrode plate. A power generating element having any shape can be used, such as a stack type in which the sheet-shaped electrode plate is folded and a type in which the sheet-shaped electrode plate is folded and stacked through a separator.

Further, in the present invention, a bag-shaped unit cell case having an airtight structure can be used, and a metal laminated resin film is preferably used as a material of the bag-shaped unit cell case.

In the present invention, when the elliptical wound type power generating element is stored in the bag-shaped unit cell case, the winding center axis of the elliptical wound type power generating element is set at the opening surface of the bag-shaped unit cell case. Preferably it is vertical. The vertical direction is
It does not only mean completely vertical, but also generally vertical.

As the metal material of the metal laminated resin film, aluminum, aluminum alloy, titanium foil and the like can be used.

As the material of the heat-welded portion of the metal laminated resin film, any material may be used as long as it is a thermoplastic polymer material such as polyethylene, polypropylene, polyethylene terephthalate and the like.

Further, the resin layer and the metal foil layer of the metal laminated resin film are not limited to one layer each, but may be two or more layers.

The electrolyte solvent used for the nonaqueous electrolyte secondary battery according to the present invention includes ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide. , 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran,
A polar solvent such as 2-methyltetrahydrofuran, dioxolan, methyl acetate, or a mixture thereof may be used.

The lithium salts dissolved in the organic solvent include LiPF6, LiClO4, LiBF4, LiAs
F6, LiCF3CO2, LiCF3SO3, LiN
(SO2CF3) 2, LiN (SO2CF2CF3)
2, LiN (COCF3) 2 and LiN (COCF2)
A salt such as CF3) 2 or a mixture thereof may be used.

The separator of the non-aqueous electrolyte secondary battery according to the present invention may be an insulating polyethylene microporous membrane impregnated with an electrolyte, a solid polymer electrolyte, or a solid polymer electrolyte. A gel electrolyte or the like may be used. Further, an insulating microporous film and a solid polymer electrolyte may be used in combination. Further, when a porous solid polymer electrolyte membrane is used as the solid polymer electrolyte, the electrolyte contained in the polymer and the electrolyte contained in the pores may be different.

Further, as a compound capable of inserting and extracting lithium as a positive electrode material, an inorganic compound is represented by a composition formula L
ixMO2 or LiyM2O4 (where M is a transition metal, 0 ≦ x ≦ 1, 0 ≦ y ≦ 2), a composite oxide, an oxide having tunnel-like vacancies, or a metal chalcogenide having a layered structure is used. be able to. Specific examples thereof include LiCoO2, LiNiO2, and LiMn2O.
4, Li2Mn2O4, MnO2, FeO2, V2O
5, V6O13, TiO2, TiS2 and the like.
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, as a compound as a negative electrode material, Al, S
alloy of lithium with i, Pb, Sn, Zn, Cd, etc., L
transition metal oxides such as iFe2O3, WO2, MoO2,
Carbonaceous materials such as graphite and carbon, Li5 (Li
Lithium nitride such as 3N) or metallic lithium foil, or a mixture thereof may be used. Further, as a material of the positive and negative electrode lead terminals, a thickness of 50 to 150 μm
Can be used. Specific examples thereof include aluminum, copper, nickel, titanium, stainless steel, and alloys thereof.

[0027]

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

Embodiment 1 In a non-aqueous electrolyte secondary battery according to the present invention, an elliptical wound-type power generating element comprising a positive electrode plate, a separator and a negative electrode plate is made of metal together with a non-aqueous electrolyte (not shown). It is housed in a metal laminated resin film case formed by heat welding a laminated resin film, and its appearance is shown in FIG.

As the positive electrode active material, a lithium cobalt composite oxide was used. The positive electrode plate is obtained by holding the above-mentioned lithium cobalt composite oxide as an active material on a current collector. As the current collector, an aluminum foil having a thickness of 20 μm was used. The positive electrode plate is
After 6 parts of polyvinylidene fluoride as a binder and 3 parts of acetylene black as a conductive agent are mixed together with 91 parts of an active material, N-methylpyrrolidone is added to prepare a paste, and then both sides of the current collector material are prepared. And dried.

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 on both sides of a current collector, and adding N-methylpyrrolidone to form a paste. It was manufactured by applying and drying the prepared product. The current collector of the negative electrode plate has a thickness of 14
A μm copper foil was used.

The separator was a microporous polyethylene membrane, and the electrolyte was a mixed solution of ethylene carbonate: diethyl carbonate = 4: 6 (volume ratio) containing 1 mol / l of LiPF6.

The dimensions of the electrode plate are as follows.
Width 49mm, separator thickness 25μm, width 53mm,
The negative electrode plate had a thickness of 170 μm and a width of 51 mm. Lead terminals are welded to the ends of the positive electrode plate and the negative electrode plate, respectively, and the positive and negative electrode lead terminals are overlapped so as to form a winding start portion. It is wound in an elliptical spiral around the power generation element so as to be parallel to the winding center axis of the power generation element.
The power generating element had a size of 4 mm. By winding as described above, a power generating element in which both the positive electrode lead terminal and the negative electrode lead terminal were attached to the positive and negative electrode plates on the inner peripheral portion of the power generating element was prepared.

FIG. 2 is a sectional view of a power generating element in which both a positive electrode lead terminal and a negative electrode lead terminal are attached to a positive electrode plate and a negative electrode plate at an inner peripheral portion of the power generating element. Note that a 100 μm thick aluminum piece was used for the positive electrode lead terminal, and a 100 μm thick nickel piece was used for the negative electrode lead terminal.

Then, the insulating portion of the electrode is covered with an electrode width (length of the power generation element parallel to the winding center axis of the power generation element) by a tape for stopping winding made of polypropylene (here, an adhesive is applied on one side). Was attached to the side wall of the power generation element parallel to the winding center axis, and the power generation element was stopped and fixed.

This is housed in a metal-laminated resin film case, and the elliptical wound-type power generating element is housed such that the winding center axis is substantially perpendicular to the opening surface of the bag-shaped metal-laminated resin film case, and the lead terminals are placed. The electrolyte was fixed and sealed, and the electrolyte was vacuum-injected in such an amount that each electrode and the separator were sufficiently wetted and no free electrolyte was present outside the power generating element.

FIG. 4 shows a cross section taken along line BB 'of the battery shown in FIG. In FIG. 4, symbols 4 and 5
Shows the same thing as FIG. 1, 11 is a 12 μm PET film for surface protection of the outermost layer, and 12 is 9
μm aluminum foil, 13 is 100 μm as a heat welding layer
m is an acid-modified low-density polyethylene layer. A metal-laminated resin film case as a bag-shaped unit cell case for an airtight opening is composed of 11, 12, and 13. The outermost surface protective PET film 11 and an aluminum foil 12 as a barrier layer are bonded with a urethane-based adhesive. are doing.

Finally, sealing welding is performed to obtain a nominal capacity of 50 mm.
A prototype of a 0 mAh laminated cell was made.

Example 2 A negative electrode lead terminal having a thickness of 100
A laminated unit cell similar to that of Example 1 was produced as a trial except that a copper piece of μm was used.

Comparative Example 1 A laminated cell similar to that of Example 1 was produced as a trial except that both the positive electrode lead terminal and the negative electrode lead terminal were attached to the outer periphery of the wound power generating element. A cross section taken along a plane perpendicular to the winding center axis of the power generating element (A in FIG. 1).
FIG. Symbols 4 to 8 in FIG.
Shows the same thing as FIG.

[Comparative Example 2] A laminated unit cell similar to that of Example 1 except that the positive electrode lead terminal was attached to the inner peripheral portion of the wound power generating element and the negative electrode lead terminal was attached to the outer peripheral portion of the wound power generating element. Was prototyped. FIG. 6 shows a cross section (AA ′ cross section in FIG. 1) cut along a plane perpendicular to the winding center axis of the power generating element. Symbols 4 to 8 in FIG. 6 indicate the same as those in FIG.

COMPARATIVE EXAMPLE 3 Comparative Example 3 was performed in the same manner as in Example 1 except that the negative electrode lead terminal was attached to the inner peripheral portion of the wound power generating element and the positive electrode lead terminal was attached to the outer peripheral portion of the wound power generating element.
A prototype of the same laminated unit cell was manufactured. FIG. 7 shows a cross section (AA ′ cross section in FIG. 1) cut along a plane perpendicular to the winding center axis of the power generating element. Symbols 4 to 8 in FIG. 7 indicate the same as those in FIG.

Here, the batteries of Examples 1 and 2 and Comparative Examples 1 to 3 having a nominal capacity of 500 mAh were charged to a voltage of 10 V at a temperature of 25 ° C. and a current of 500 mA at a temperature of 25 ° C., thereby securing the overcharged state. A sex test was performed.

After charging each battery for 20 cells at a constant current / constant voltage for 3 hours under the conditions of current 500 mA / voltage 4.4 V, φ0.
A test was performed for safety when a needle of 56 mm was inserted into the battery.

Table 1 shows the results of the overcharge test and the needle stick test.
Shown in The numbers in the table indicate the number of batteries that burst or fired out of the 20-cell batteries tested.

[0045]

[Table 1]

As is clear from Table 1, all of the comparative examples fell into a dangerous state involving rupture and ignition, while the examples showed safe results without causing rupture and ignition. Obtained. In addition, the battery surface temperature when the overcharge test was performed was also up to 500 ° C. in the comparative example.
While there were batteries that rose up to the above, the maximum temperature was 125 ° C. in Example 1 and 104 ° C. in Example 2.

When the nonaqueous electrolyte secondary battery generates heat due to an abnormal state such as overcharge or internal short circuit, an abnormal temperature rise occurs in the inner peripheral portion of the power generating element due to poor heat dissipation of the inner peripheral portion of the power generating element. , Causing heat escape and rupture, leading to fire. In the battery of Example 2 using a copper piece having excellent heat conductivity for the negative electrode lead terminal, the maximum temperature of the battery surface temperature in the overcharge test was lower than the battery of Example 1 using the nickel piece for the negative electrode lead terminal. Therefore, in the embodiment, since the metal having excellent thermal conductivity such as Al, Ni, and Cu is disposed in the inner peripheral portion of the power generating element, the inner peripheral portion of the power generating element is sufficiently dissipated and the heat escape is suppressed. It is considered possible.

From the above results, by using the power generating element in which both the positive electrode lead terminal and the negative electrode lead terminal are attached to the positive electrode plate and the negative electrode plate on the inner peripheral portion of the power generating element, it is safe even in an abnormal state involving heat generation. Battery can be supplied.

In the embodiment, an aluminum piece is used for the positive electrode lead terminal and a nickel piece or copper piece is used for the negative electrode lead terminal. However, stainless steel, titanium or the like may be used. Although the thickness of the lead terminal is not particularly limited here, it is more preferably 50 because the heat radiation is excellent and the thickness of the battery can be suppressed.
It is additionally noted that the range of μm to 150 μm is suitable.

[0050]

According to the present invention, the battery characteristics are high, the safety is high even in an abnormal state involving heat generation, and the production process is not complicated without causing deterioration in battery characteristics.
It is possible to provide a non-aqueous electrolyte battery in which an oval wound-type power generating element is housed in a metal laminated resin film case as a bag-shaped unit cell case.

Further, according to the present invention, since the power generation element is housed in, for example, a thin sheet-shaped soft case, it is excellent in airtightness and can eliminate the complexity of the sealing process. Becomes possible.

In addition, since the cells have excellent airtightness, the airtightness of the hard case itself does not matter as in the conventional case. 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 container, it is possible to further simplify the manufacturing process and reduce the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is an external view of a nonaqueous electrolyte secondary battery.

FIG. 2 is a cross-sectional view of the non-aqueous electrolyte secondary battery according to the present invention, taken along a plane perpendicular to the winding center axis of the power generating element (A-
The figure which shows an example of A 'cross section).

FIG. 3 is a cross-sectional view of the non-aqueous electrolyte secondary battery according to the present invention, taken along a plane perpendicular to the winding central axis of the power generating element (A- FIG. 1);
The figure which shows the other example (A 'cross section).

FIG. 4 is a diagram showing a cross section (BB ′ cross section in FIG. 1) of a lead terminal take-out portion of the nonaqueous electrolyte secondary battery according to the present invention.

5 is a cross-sectional view of the non-aqueous electrolyte secondary battery according to Comparative Example 1 taken along a plane perpendicular to the winding center axis of the power generating element (A-
FIG.

6 is a cross-sectional view of the nonaqueous electrolyte secondary battery according to Comparative Example 2 taken along a plane perpendicular to the winding center axis of the power generating element (A-
FIG.

7 is a cross section of the nonaqueous electrolyte secondary battery according to Comparative Example 3 taken along a plane perpendicular to the winding center axis of the power generating element (A-
FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bag-shaped cell case 2 Power generation element 3 Center axis of winding of power generation element 4 Positive electrode lead terminal 5 Negative electrode lead terminal 6 Positive electrode plate 7 Negative electrode plate 8 Separator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuya Murai 1st institution, Nishinosho Nishinosho-machi, Minami-ku, Kyoto, Kyoto Prefecture Inside of Nippon Battery Co., Ltd. (72) Inventor Shinya Kitano, Kichijoin-nishi, Minami-ku, Kyoto, Kyoto No. 1 Inohomaba-cho, No. 1, Japan Battery Co., Ltd. (72) Inventor Hiroyuki Yumoto No. 1 Nishinosho Inomaba-cho, Kisho-in, Minami-ku, Kyoto, Kyoto Prefecture, Japan No. 1, Japan Battery Co., Ltd. (72) Mikio Okada, Kyoto Prefecture 1F, Nippon Battery Co., Ltd. F term (Reference) 5K01A AA13 CC02 CC06 CC10 DD13 EE04 FF02 GG09 HH13 JJ25 5H022 AA09 CC02 CC12 5H029 AJ12 AK02 AK03 AK05 AK16 AL02 AL03 AL06 AL12 AM03 AM04 AM05 AM07 BJ01 BJ14 DJ02 DJ05 EJ01 EJ11

Claims (3)

[Claims] 1. A non-aqueous electrolyte secondary battery provided with a power generating element having a positive electrode plate, a separator, and a negative electrode plate, wherein both the positive electrode lead terminal and the negative electrode lead terminal are a positive electrode plate and a negative electrode plate on the inner periphery of the power generating element. A non-aqueous electrolyte secondary battery attached to a battery. 2. A bag-shaped cell case having an airtight structure,
2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the elliptical wound-type power generating element is housed such that a winding central axis thereof is perpendicular to an opening surface of the bag-shaped unit cell case. . 3. The non-aqueous electrolyte battery according to claim 1, wherein the material of the bag-shaped unit cell case is a metal laminated resin film.