JP2000277091A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the safety while restraining the heat generation of a battery even if overcharge and internal short-circuit is generated by using aluminum having a specified purity or more for a positive electrode lead terminal of a positive plate provided in a power generating element with a separator and a negative plate. SOLUTION: An elliptic winding type power generating element is housed in a case so that a winding center axis is arranged nearly vertical to an opening part of the bag-like battery case having the airtight structure formed of a metal laminate resin film capable of preventing leakage of the electrolyte, intrusion of water from outside and capable of reducing the weight. Purity of the aluminum having the predetermined thickness and to be used for positive electrode lead terminal is set at 99.50% or more so as to prevent the generation of breakdown and ignition of a battery under the internal short-circuit condition, and surface temperature of the battery at the time of overcharge test is restrained to 120 deg.C or less. With this structure, excellent discharge characteristic can be obtained because of a small polarization without generating the lowering of battery characteristic and without complicating the manufacturing process. As a negative electrode terminal, a nickel alloy plate or a copper plate is used in usual.

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, a battery using a metal-laminated resin film having an airtight structure as a material for a bag-shaped unit cell case does not have the pressure resistance of a metal battery container, and thus is not suitable for use in a high-temperature environment. Left alone,
When the internal pressure rises, there is a problem that it is difficult to radiate heat generated inside the battery to the outside of the battery. In particular, if the battery is placed in an abnormal state such as an overcharged state or an internal short circuit due to a malfunction of the charge / discharge control circuit, the battery will generate heat, and in the worst case, it will lead to thermal runaway and may burst or ignite. there were.

Accordingly, the present invention provides a non-aqueous electrolyte battery excellent in safety by suppressing heat generation of the battery even when the battery is in an abnormal state such as an overcharged state or an internal short circuit. Aim. Still another object of the present invention is to provide a non-aqueous electrolyte battery having excellent discharge characteristics.

[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 is characterized by using aluminum having a purity of 99.50% or more.

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 central axis of the power generating element, 4 denotes a positive lead terminal, and 5 denotes a negative lead terminal.

The non-aqueous electrolyte secondary battery according to the present invention is characterized in that aluminum having a purity of 99.50% or more is used for the positive electrode lead terminal.

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-type 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.

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

The material of the heat-welded portion of the metal laminated resin film may be any material 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.

Examples of the bag-shaped unit cell case include a laminated case formed into an envelope by heat-welding a metal-laminated resin film, a case in which four sides of two metal-laminated resin sheets are heat-sealed, and a single case. Use a metal-laminated resin film case of any shape, such as one obtained by folding the sheet in two and heat-welding the three sides, or a laminating case in which a power-generating element is placed in a cup-shaped metal-laminated resin sheet. be able to.

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, A
Alloys of lithium with l, Si, Pb, Sn, Zn, Cd, etc., transition metal oxides such as LiFe2O3, WO2, MoO2, carbonaceous materials such as graphite, carbon, Li5
Lithium nitride such as (Li3N) or metallic lithium foil, or a mixture thereof may be used.

[0028]

Next, the present invention will be described based on preferred embodiments. [Example 1] In a nonaqueous electrolyte secondary battery according to the present invention, an elliptical wound-type power generating element including a positive electrode plate, an isolator, and a negative electrode plate heat welds a metal laminated resin film together with a nonaqueous electrolytic solution. FIG. 1 shows the external appearance of a metal-laminated resin film case.

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
6 parts of polyvinylidene fluoride as a binder and 3 parts of acetylene black as a conductive agent were mixed together with 91 parts of an active material, and N-methylpyrrolidone was appropriately added to prepare a paste. It was manufactured by coating and drying on both sides.

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 as appropriate. Was prepared by coating and drying. A 14 μm thick copper foil was used as the current collector of the negative electrode plate.

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 has a thickness of 170 μm and a width of 51 mm, and the lead terminals are welded to the positive electrode plate and the negative electrode plate, respectively, and superimposed in order, with a rectangular core of polyethylene as a center, and a long side having a winding center axis of a power generating element. Was wound in an elliptical spiral shape so as to be parallel to the above, thereby forming a power generating element having a size of 50 × 35 × 4 mm. The positive electrode lead terminal used here is 100 μm thick aluminum having a purity of 99.50% or more. A nickel alloy plate having a thickness of 100 μm was used for the negative electrode lead terminal. A copper plate or the like can be used for the negative electrode lead terminal.

Then, the insulating portion of the electrode is covered with a tape for winding made of polyethylene (adhesive is applied on one side in this case) and the width of the electrode (the length of the power generating element parallel to the winding central axis of the power generating element). 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 accommodated in a metal laminated resin film case, and the elliptical wound type power generating element is housed so that the winding center axis is perpendicular to the opening surface of the bag-shaped metal laminated resin film case, and the lead terminals are fixed. And seal the electrolyte.
Each electrode and the separator were sufficiently wetted, and vacuum injection was performed in such an amount that no free electrolyte solution was present outside the power generating element.

FIG. 2 shows a cross section taken along the line AA 'of the battery shown in FIG. In FIG. 2, reference numeral 11 denotes a 12 μm PET film for protecting the surface of the outermost layer, 12 denotes a 9 μm aluminum foil as a barrier layer, and 13 denotes a 100 μm acid-modified low density polyethylene layer as a heat welding 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.
Also, the positive lead terminal 14 and the negative lead terminal 15
Is a metal conductor of copper, aluminum, nickel or the like having a thickness of 50 to 100 μm.

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

COMPARATIVE EXAMPLE 1 A positive electrode having a purity of 9
Thickness 100 which is not less than 9.00% and less than 99.50%
A laminated unit cell was prototyped with the same components and manufacturing method as in Example 1 except that μm of aluminum was used.

[Comparative Example 2] The purity of the positive electrode lead terminal was 9
100 μm thick aluminum less than 9.00%
Except for using a manganese alloy, a laminated unit cell was prototyped with the same components and manufacturing method as in Example 1.

[Discharge Test Example] The 500 mAh laminated single cells according to Comparative Examples 1 and 2 and Example were subjected to an ambient temperature of 25.
FIG. 3 shows discharge characteristics obtained when a constant current / constant voltage charge was performed at 500 ° C. and a voltage of 4.1 V for 3 hours and then discharged at a current of 1000 mA.

As is clear from FIG. 3, Comparative Examples 1 and 2 had a large polarization at the time of discharge, while Examples had a small polarization and showed good discharge characteristics.

[Safety Test Examples] The laminated cells of 500 mAh according to Comparative Examples 1 and 2 and Examples were subjected to an ambient temperature of 2
Table 1 shows the results of tests performed on the safety of the battery in an overcharged state by charging the battery to a voltage of 10 V at a current of 500 mA at 5 ° C.

After performing constant-current / constant-voltage charging for 3 hours under the conditions of a current of 500 mA and a voltage of 4.3 V, a test was performed for safety when a needle of φ1 mm was inserted into the battery to simulate an internal short circuit. The results are shown in Table 1. The numbers in the table indicate the number of batteries that burst and ignited for each of the 20 test batteries.

[0043]

[Table 1]

As is clear from Table 1, the batteries of Comparative Examples 1 and 2 all fell into a dangerous state involving rupture and ignition, while the batteries of Examples caused rupture and ignition. And very safe results were obtained. In addition, the battery surface temperature at the time of performing the overcharge test was also measured in Comparative Example 1.
In the batteries of Examples 2 and 3, some batteries had a maximum temperature of 500 ° C. or higher, while in the batteries of Examples,
The battery surface temperature was able to be suppressed to below ℃.

[0045]

According to the present invention, the battery characteristics are high, the safety is high, and the manufacturing process is not complicated even under abnormal conditions involving heat generation, without deteriorating the battery characteristics.
A non-aqueous electrolyte battery can be provided. Furthermore, a non-aqueous electrolyte battery with small polarization and excellent discharge characteristics can be provided, and the industrial value of the present invention is extremely large.

[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-
FIG.

FIG. 3 is a diagram showing discharge characteristics at the time of 2C discharge of the nonaqueous electrolyte secondary battery according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bag-shaped unit 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

Continuation of the front page (72) Inventor Tetsuya Murai 1 Inosibabacho, Nishinosho, Kichijoin, Kyoto, Kyoto, Japan Inside of Nippon Battery Co., Ltd. (72) Shinya Kitano Nishinosho, Nishinosho, Kyoto, Kyoto Nobabacho No. 1 Japan Battery Co., Ltd. (72) Hiroyuki Yumoto Inventor Hiroyuki Yumoto Kinoshoin Nishinosho Ino Babacho, Minami-ku, Kyoto, Kyoto 1 Japan Battery Co., Ltd. (72) Inventor Mikio Okada Kyoto, Minami Kyoto 1F, Nishinosho-Inomabacho, Kichijo-ku, Tokyo F-term (reference) in Nihon Batteries Co., Ltd. AM05 AM07 BJ01 BJ14 DJ02 DJ05 EJ01 EJ11 HJ02

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 aluminum having a purity of 99.50% or more is used for a positive electrode lead terminal. Non-aqueous electrolyte secondary battery. 2. An oval wound type power generating element is housed in a bag-shaped unit cell case having an airtight structure such that a winding central axis thereof is perpendicular to an opening surface of the bag-shaped unit cell case. The non-aqueous electrolyte secondary battery according to claim 1, wherein: 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.