JP2003217674A - Non-aqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte battery having excellent safety by preventing contact between a positive electrode and a negative electrode even if a separator causes thermal contraction. <P>SOLUTION: This non-aqueous electrolyte battery is formed of rectangular positive electrode and negative electrode, a non-aqueous electrolyte interposed between the positive electrode and the negative electrode, and a rectangular separator containing thermoplastic resin and disposed between the positive electrode and the negative electrode. When the length of the long side of the negative electrode is taken as Aa, the length of the short side is taken as Ab, the length of the long side of the positive electrode is taken as Ca, the length of the short side is taken as Cb, the length of the long-side direction of the separator is taken as SLa, the heat contraction rate is taken as Ra, the length in the short-side direction of the separator is taken as SLb, and the heat contraction rate is taken as Rb, they satisfy the following expressions: Aa>Ca, and Ab>Cb, SLa>Ca/(1-Ra), and SLb>Cb/(1-Rb). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery used as a power source for portable electronic devices and the like, and has an appropriate size and characteristics even when the temperature of the battery or the surroundings becomes abnormally high. The present invention relates to a non-aqueous electrolyte battery with improved safety by adopting a special structure for the separator.

[0002]

2. Description of the Related Art Batteries have occupy an important position in industry as a power source for portable electronic devices. In order to reduce the size and weight of the device, it is required that the battery is light and the storage space inside the device is used efficiently. Lithium batteries with high energy density and high output density are the most suitable for this.

The fact that a lithium battery has a high energy density means that a large amount of energy is released in the unlikely event that the energy is released at a dash due to a short circuit or the like, and the battery heats up at that time. Is concerned. In order to prevent this, various safety mechanisms are prepared for the battery, and one of the typical mechanisms is a separator.

Polyolefin films such as porous polyethylene and polypropylene are mainly used as separators for lithium batteries. Since these materials are thermoplastic, the pores shrink and close when the battery heats up and the temperature rises, and acts as a fuse by blocking the passage of ions in the electrolyte.

[0005]

However, if the temperature is further increased, the separator film may be further shrunk, and the positive electrode and the negative electrode may come into contact with each other. If this happens, a short-circuit current will flow at the contact point and the battery will generate heat. If the amount of heat generated is large, the battery may be in a dangerous state.

The present invention has been proposed in view of such conventional circumstances, and provides a non-aqueous electrolyte battery having excellent safety by preventing contact between the positive electrode and the negative electrode even when the separator thermally contracts. The purpose is to

[0007]

A non-aqueous electrolyte battery of the present invention contains a rectangular positive electrode and a negative electrode, a non-aqueous electrolyte interposed between the positive electrode and the negative electrode, and a thermoplastic resin. In a non-aqueous electrolyte battery composed of a rectangular separator arranged between the negative electrode and the negative electrode, the length of the long side of the negative electrode is A
a, the length of the short side is Ab, the length of the long side of the positive electrode is Ca,
When the length of the short side is Cb, the length of the separator in the long side direction is SLa, the heat shrinkage is Ra, and the length of the separator in the short side direction is SLb and the heat shrinkage is Rb, Aa >
Ca and Ab> Cb and SLa> Ca / (1-R
a) and satisfying SLb> Cb / (1-Rb).

In the non-aqueous electrolyte battery of the present invention as described above, since the lengths of the positive electrode, the negative electrode, and the separator in the long side and short side directions are specified, the separator is always the positive electrode even if the separator thermally contracts. A larger area can be maintained and contact between the positive electrode and the negative electrode can be prevented.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment Hereinafter, a gel electrolyte battery to which the present invention is applied will be described in detail with reference to the embodiments.

An example of the structure of the gel electrolyte battery 1 according to this embodiment is shown in FIGS. This gel electrolyte battery 1
As shown in FIG. 3, the strip-shaped positive electrode 2, the strip-shaped negative electrode 3 arranged to face the positive electrode 2, the gel electrolyte layer 4 formed on the positive electrode 2 and the negative electrode 3, and the gel electrolyte layer 4 are The separator 5 is provided between the formed positive electrode 2 and the negative electrode 3 on which the gel electrolyte layer 4 is formed.

In this gel electrolyte battery 1, as shown in FIG. 3, a positive electrode 2 having a gel electrolyte layer 4 and a negative electrode 3 having a gel electrolyte layer 4 are laminated via a separator 5. At the same time, the electrode winding body 6 wound in the longitudinal direction is covered and hermetically sealed with an exterior film 7 made of an insulating material as shown in FIGS. 1 and 2. A positive electrode terminal 8 is connected to the positive electrode 2 and a negative electrode terminal 9 is connected to the negative electrode 3, and the positive electrode terminal 8 and the negative electrode terminal 9 are sandwiched by a sealing portion which is a peripheral edge portion of the exterior film 7. ing. Further, a resin film 10 is arranged at a portion where the positive electrode terminal 8 and the negative electrode terminal 9 are in contact with the exterior film 7.

In a structure in which the negative electrode 3 is smaller than the positive electrode 2, that is, the end face of the negative electrode is located on the positive electrode surface, the current density at the edge portion of the negative electrode becomes large, and metallic lithium may be deposited and short circuit may occur. Therefore, in this gel electrolyte battery 1, the negative electrode 3 is larger than the positive electrode 2 and protrudes to the outside, and the separator 5 further protrudes to the outside of the negative electrode 3.

As shown in FIG. 4, the positive electrode 2 has a positive electrode active material layer 2a containing a positive electrode active material formed on both surfaces of a positive electrode current collector 2b. As the positive electrode current collector 2b, for example, a metal foil such as an aluminum foil is used.

The positive electrode active material layer 2a is prepared by, for example, uniformly mixing a positive electrode active material, a conductive material, and a binder into a positive electrode mixture, and dispersing this positive electrode mixture in a solvent to form a slurry. To Next, this slurry is uniformly applied on the positive electrode current collector 2b by a doctor blade method or the like, dried at high temperature, and the solvent is removed to form the slurry. Here, the positive electrode active material, the conductive material, the binder, and the solvent only need to be uniformly dispersed, and the mixing ratio thereof does not matter.

A composite oxide of lithium and a transition metal is used as the positive electrode active material. Specifically, examples of the positive electrode active material include LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ . Also, a solid solution in which a part of the transition metal element is replaced with another element can be used. LiNi _0.5 Co
Examples thereof include _0.5 O ₂ and LiNi _0.8 Co _0.2 O ₂ .

As the conductive material, for example, a carbon material or the like is used. Further, as the binder, for example, polyvinylidene fluoride or the like is used. Further, as the solvent, for example, N-methylpyrrolidone or the like is used.

Further, the positive electrode 2 has a positive electrode terminal 8 connected to the other end portion in the length direction by spot welding or ultrasonic welding. The positive electrode terminal 8 is preferably a metal foil or a metal mesh, but it does not matter if it is not metal as long as it is electrochemically and chemically stable and can conduct electricity. Examples of the material of the positive electrode terminal 8 include aluminum.

The positive electrode terminal 8 preferably extends in the same direction as the negative electrode terminal 7. However, as long as a short circuit does not occur and battery performance does not occur, it does not matter which direction the positive electrode terminal 8 extends. Further, the connection location of the positive electrode terminal 8 is not limited to the above example as long as it is electrically connected to the location.

As shown in FIG. 5, the negative electrode 3 has a negative electrode active material layer 3a containing a negative electrode active material, and a negative electrode current collector 3b.
Are formed on both sides of. As the negative electrode current collector 3b, a metal foil such as a copper foil is used.

For the negative electrode active material layer 3a, for example, a negative electrode active material, a conductive material if necessary, and a binder are uniformly mixed to form a negative electrode mixture, and this negative electrode mixture is dispersed in a solvent. To make a slurry. Next, this slurry is uniformly applied on the negative electrode current collector 3b by a doctor blade method or the like, dried at a high temperature, and the solvent is removed to form the slurry. Here, the negative electrode active material, the conductive material, the binder, and the solvent only need to be uniformly dispersed, and the mixing ratio thereof does not matter.

As the negative electrode active material, a lithium metal, a lithium alloy, or a carbon material capable of being doped / dedoped with lithium is used. Specifically, examples of carbon materials that can be doped / dedoped with lithium include graphite, non-graphitizable carbon, and easily graphitizable carbon, and examples of graphites include mesophase carbon microbeads, carbon fibers,
Artificial graphite such as coke or natural graphite can be used.

Further, as the binder, for example, polyvinylidene fluoride, styrene-butadiene rubber or the like is used.
Further, as the solvent, for example, N-methylpyrrolidone, methyl ethyl ketone, water or the like is used.

Further, the negative electrode 3 has a negative electrode terminal 9 connected to the other end portion in the length direction by spot welding, ultrasonic welding or a conductive adhesive. The negative electrode terminal 9 is preferably a metal foil or a mesh-like one, but there is no problem even if it is not a metal as long as it is electrochemically and chemically stable and can conduct electricity. Examples of the material of the negative electrode terminal 9 include copper and nickel.

It is preferable that the negative electrode terminal 9 extends in the same direction as the positive electrode terminal 8. However, as long as a short circuit or the like does not occur and battery performance does not occur, there is no problem in any direction. Further, the connection location of the negative electrode terminal 7 is not limited to the above example as long as it is electrically connected to the connection location.

The gel electrolyte is obtained by gelling an electrolytic solution containing a non-aqueous solvent and an electrolyte salt with a matrix polymer.

As the non-aqueous solvent, a known solvent used as the non-aqueous solvent of the non-aqueous electrolytic solution can be used. Specifically, hydrogen of ethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, ethyl propyl carbonate, or carbonic acid esters thereof is converted into halogen. A substituted solvent and the like can be mentioned. One type of these solvents may be used alone, or a plurality of types may be mixed with a predetermined composition.

The electrolyte salt is soluble in the above non-aqueous solvent.
One can be used. For example LiPF₆, Li
BF_Four, LiN (CF_ThreeSO_Two)_Two, LiN (C_TwoF₅
SO _Two)_Two, LiClO_FourEtc. Note that electrolysis
As the salt concentration, the concentration that can be dissolved in the above solvent
However, if the lithium ion concentration is a non-aqueous solvent,
0.4 mol / kg or more, 1.5 mol / kg
The following range is preferable.

Examples of the matrix polymer include polymers containing polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polyacrylonitrile, and polymethacrylonitrile as repeating units. Such polymers may be used alone or in combination of two or more.

The separator 5 has ion permeability in pores and the like, on the other hand, the electrodes do not physically come into contact with each other, and powder such as an active material and a conductive auxiliary agent does not pass through, so that the potential of the positive electrode or the negative electrode may be changed. It should be electrochemically stable even when exposed, chemically stable to a solvent or an electrode active material, and not electronically conductive. To meet this requirement, a polymeric non-woven fabric, a porous film, or a paper-like glass or ceramic fiber can be used. However, the porous polyolefin film is most effective because it melts at a high temperature and blocks the ion permeation path. It is also possible to combine such a film with a heat-resistant material such as polyimide, glass, or ceramic fiber.

The inventors of the present invention have made extensive studies as to the problem of internal short circuit due to heat shrinkage of the separator 5 as described above, and as a result, reduce the heat shrinkage rate of the separator 5 or reduce the heat shrinkage rate of the separator 5. It was found that the problem can be solved by determining the size of the separator 5 based on the numerical value calculated from the size of the positive electrode 2. That is, the dimension of the positive electrode 2 is made larger than the value divided by (1-heat shrinkage rate) so that the separator 5 does not become smaller than the positive electrode 2 even if the separator 5 shrinks.

The margin of the separator 5 protruding from the positive electrode 2 controls the short circuit between the positive electrode 2 and the negative electrode 3. Therefore, it is sufficient to prevent the positive and negative electrodes from coming into contact with each other even if the protruding portion shrinks due to thermal contraction.
Since the contraction occurs toward the center of the separator 5, the margin on one side may be larger than half the contraction amount of the separator 5.

That is, in this gel electrolyte battery 1, as shown in FIG. 6, the long side length of the negative electrode 3 is Aa, the short side length is Ab, and the long side length of the positive electrode 2 is Ca. The length of the short side is Cb, and the length of the separator 5 in the long side direction is SL.
a, the heat shrinkage is Ra, the length of the separator 5 in the short side direction is SLb, and the heat shrinkage is Rb, Aa> Ca, Ab> Cb, and SLa> Ca / (1- Ra) and SLb> Cb /
(1-Rb) is satisfied. In order to satisfy the above relational expression, the positive electrode 2,
By defining the lengths of the negative electrode 3 and the separator 5 in the long side direction and the short side direction, the separator 5 always maintains a larger area than the positive electrode 2 even when the separator 5 is thermally contracted.
Can be prevented from coming into contact with the negative electrode 3. This makes the gel electrolyte battery excellent in safety without causing an internal short circuit.

The thermal contraction rate is 500 kgf in the cross-sectional area of a separator obtained by cutting out a rectangular separator having the same direction as the long side / short side when actually used in a battery.
It is determined from the contracted length when the sample is left in a constant temperature bath at 150 ° C. for 30 minutes while applying a tension multiplied by / cm ² . That is, Ra = 1- (long side length of separator after 30 minutes in 150 ° C. constant temperature bath) / (long side length at room temperature) Rb = 1- (after 30 minutes in 150 ° C. constant temperature bath) (Length of short side of separator) / (length of short side at room temperature) In the gel electrolyte battery 1, the separator 5
Has a larger area than the positive electrode 2, and when the separator 5 is arranged so as to protrude from the positive electrode 2 as shown in FIG.
The protruding widths of the separators 5 parallel to the long sides in the portions of the opposite short sides are ma1 and ma2, and the protruding widths of the separators 5 parallel to the short sides in the portions of the opposite long sides are mb1 and mb2. Then, when ma1 <ma2 and mb1 <mb2, ma1> SLa × Ra / 2 and mb1> SLb × R
b / 2 is satisfied. By defining the protruding width of the separator 5 from the positive electrode 2 so as to satisfy the above relational expression, even if the separator 5 is thermally contracted, the separator 5 always keeps a larger area than the positive electrode 2, and the separator and the positive electrode Even if the arrangement is uneven, it is possible to prevent the positive electrode from protruding from the separator and coming into contact with the negative electrode during thermal contraction of the separator. As a result, the gel electrolyte battery 1 becomes excellent in safety without causing an internal short circuit.

The package film 9 is a hermetically sealed pack of the electrode winding body 8 in which the positive electrode 2 and the negative electrode 3 are laminated via the gel electrolyte layer 4 and are wound in the longitudinal direction. This exterior film is made of, for example, a moisture-proof and insulating multilayer film in which an aluminum foil is sandwiched between a pair of resin films.

In such a gel electrolyte battery 1, the lengths of the positive electrode 2, the negative electrode 3, the separator 5 in the long side and short side directions,
Alternatively, since the width of protrusion of the separator 5 from the positive electrode 2 is defined, the separator 5 can always maintain a larger area than the positive electrode 2 even if the separator 5 thermally contracts. As a result, the gel electrolyte battery 1 becomes excellent in safety because contact between the positive electrode 2 and the negative electrode 3 is prevented and an internal short circuit does not occur.

Further, in the above-described embodiment, the gel electrolyte battery 1 is formed by laminating the belt-shaped positive electrode 2 and the belt-shaped negative electrode 3 with the gel-shaped electrolyte layer 4 interposed therebetween, and further winding in the longitudinal direction. The case where the electrode winding body 5 is used has been described as an example, but the present invention is not limited to this, and a laminated electrode body obtained by laminating a positive electrode and a negative electrode via a gel electrolyte layer. The present invention is also applicable to the case of using, and the case of using a so-called zigzag-folded electrode body that is so-called zigzag without winding.

In the above-described embodiment, the case where a gel electrolyte is used as the non-aqueous electrolyte battery has been described as an example, but the present invention is not limited to this.
It is also applicable to the case of using a liquid non-aqueous electrolyte solution and the case of using a solid electrolyte containing no solvent.

Battery 1 according to the present embodiment as described above
There is no particular limitation on the shape, such as a cylindrical shape, a rectangular parallelepiped shape, and a thin flat plate shape, and the area can be various sizes.

[0039]

EXAMPLE An example carried out to confirm the effects of the present invention will be described. In the following description, specific compound names, numerical values, and the like are given for explanation, but it goes without saying that the present invention is not limited thereto.

First Experiment In the following experiment, a gel electrolyte battery was produced and its characteristics were evaluated in order to confirm the effect of the present invention.

<Sample 1> A positive electrode was prepared as follows.

First, lithium cobalt oxide (LiCo
92% by weight of O ₂ ) and 3% of powdered polyvinylidene fluoride
% By weight and 5% by weight of powdery graphite were dispersed in N-methylpyrrolidone to prepare a slurry-like positive electrode mixture. Next, this positive electrode material mixture was uniformly applied to both surfaces of an aluminum foil serving as a positive electrode current collector, and dried under reduced pressure at 100 ° C. for 24 hours to form a positive electrode active material layer. Then, this was pressure-molded with a roll press machine to obtain a positive electrode sheet, and the positive electrode sheet was cut into a strip of 48 mm × 300 mm to obtain a positive electrode. An aluminum ribbon lead was welded to the end of the electrode.

A negative electrode was manufactured as follows.

First, 91% by weight of artificial graphite and 9% by weight of powdery polyvinylidene fluoride were dispersed in N-methylpyrrolidone to prepare a slurry negative electrode mixture. Next, this negative electrode mixture was uniformly applied to both surfaces of a copper foil which was a negative electrode current collector, and dried under reduced pressure at 120 ° C. for 24 hours to form a negative electrode active material layer. Then, this was pressure-molded with a roll press machine to obtain a negative electrode sheet, and the negative electrode sheet was cut into a strip of 50 mm × 310 mm to obtain a negative electrode. The lead of the nickel ribbon was welded to the non-coated portion of the negative electrode mixture.

Then, a gel electrolyte layer was formed on the positive electrode and the negative electrode produced as described above. In order to form a gel electrolyte layer, first, polyvinylidene fluoride copolymerized with hexafluoropropylene at a ratio of 6%, a non-aqueous electrolyte solution, and dimethyl carbonate are mixed and stirred.
It was made to melt | dissolve and the sol-like electrolyte solution was obtained. Here, the non-aqueous electrolyte was prepared by dissolving LiPF ₆ at a ratio of 1 mol / kg in a mixed solvent in which ethylene carbonate (EC) and propylene carbonate (PC) were mixed at a weight ratio of 4: 6.

Next, the obtained sol-like electrolyte solution was uniformly applied to both surfaces of the positive electrode and the negative electrode. Then, it was made to dry and the solvent was removed. Thus, gel electrolyte layers were formed on both surfaces of the positive electrode and the negative electrode.

Next, the strip-shaped positive electrode having the gel-like electrolyte layer formed on both sides and the strip-shaped negative electrode having the gel-like electrolyte layer formed on both sides, which were produced as described above, were formed to a thickness of 10 μm.
The electrode winding body was obtained by winding in the longitudinal direction while laminating the porous polyethylene separator of m. The negative electrode protrudes outside the positive electrode and the separator protrudes outside the positive electrode. It was assembled so that the protruding width is evenly protruded on both sides.

The separator had a width of 52 mm. The length direction is 360 mm, which is sufficiently longer than the negative electrode and the positive electrode, and the relationship of SLa> Ca is satisfied. Since there are separators between the positive and negative electrodes coated on both sides, there are four separators in total. As the separator, a film having a heat shrinkage ratio Rb = 5% in the width direction (perpendicular to the length direction) was used.

Finally, the wound body is sandwiched by an exterior film made of an aluminum foil sandwiched between a pair of resin films, and the outer peripheral edge of the exterior film is heat-sealed under reduced pressure to seal and wind. The revolving body was sealed in an exterior film.
At this time, the portions where the resin pieces were applied to the positive electrode terminal and the negative electrode terminal were sandwiched between the sealing portions of the exterior film. Thus, the gel electrolyte battery was completed.

<Sample 2 to Sample 20> A gel electrolyte battery was prepared in the same manner as in Sample 1, except that the width of the separator and the heat shrinkage ratio were changed as shown in Table 1.

In Samples 2 to 20, the contraction rate in the width direction of the used separator was changed in the range of 5 to 9%,
The width of the separator was changed and examined. Further, an example in which the margin of the separator protruding from the positive electrode was intentionally made nonuniform (Samples 16 to 20) <Samples 21 to 60> Samples 21 to 60 were flat batteries. The positive electrode and the negative electrode were manufactured in the same manner as in Sample 1. However, the electrode active material was applied to only one surface of the current collector and cut into a rectangular shape. The negative electrode is 2
06 mm x 156 mm, positive electrode is 200 mm x 150 mm
Is.

Then, a flat gel electrolyte battery was prepared by changing the width and heat shrinkage ratio of the separator as shown in Table 2. The heat shrinkage rate of the separator is considered to be 5 to 9%, and in the samples 21 to 35, the long side length S of the separator is
La, and in Samples 36 to 50, the short side SLb is examined,
For samples 51 to 60, the margins ma1 and mb1 were examined.

Then, the batteries of Sample 1 to Sample 60 produced as described above were subjected to a heating test, a nailing test and an overcharge test as follows, and safety was evaluated.

The heating test was carried out at 150 ° C. at which the shrinkage ratio of the separator was measured. After overcharging with constant current and constant voltage up to 4.5V at 1C (current value that discharges the battery in 1 hour) at room temperature, put it in a constant temperature bath at room temperature and raise the temperature at 5 ° C / min.
A constant temperature was maintained when the temperature reached ℃, and the temperature was maintained for 1 hour.

The nail insertion test was carried out at 60 ° C. and 1 C in 4.
After overcharging with constant current and constant voltage up to 5V, take it out and 60
It was carried out by penetrating a nail having a diameter of 2.5 mm under a temperature environment.

The overcharge test was carried out in a room temperature environment by overcharging the discharged battery with a large current of 5 C at an upper limit of 24 V for 1 hour.

As a result, it was judged that nothing happened was OK, the swelling of the exterior film by heat generation was 1, mild smoke was 2, and gas ejection was 3.

The safety evaluation results of the batteries of Sample 1 to Sample 20 are shown in Table 1 and Sample 21 to Sample 6 are shown.
Table 2 shows the results of the safety evaluation for the No. 0 battery, together with the respective conditions.

[0059]

[Table 1]

[0060]

[Table 2]

Further, FIG. 8 shows changes with time of the battery surface temperature and the battery voltage in the heating test for the batteries of Samples 6 and 10, and the battery surface temperature and the battery voltage of the nailing test for the batteries of Samples 6 and 10 are shown in FIG. Fig. 9 shows the changes over time of the batteries of Samples 6, 7, 9, and 10
FIG. 10 shows the change over time in the battery surface temperature during C overcharge.

As is clear from these results, in order to prevent the separator from becoming smaller than the positive electrode even when it is heat-shrinked, a separator having a small heat shrinkage ratio or a sample having a separator width wider than the positive electrode width was used. It has been found that, even when the separator sometimes undergoes thermal contraction, the separator can maintain a larger area than the positive electrode. Further, in such a battery, it is possible to prevent contact between the positive and negative electrodes and enhance the safety of the battery, and it is possible to reduce the dead volume and increase the energy density while maintaining the safety. I understood.

Second Experiment In the following experiment, in order to confirm the effect of the present invention, a prismatic non-aqueous electrolyte battery was manufactured and its characteristics were evaluated.

<Sample 61> First, a positive electrode was prepared as follows.

First, lithium cobalt oxide (LiCo
92% by weight of O ₂ ) and 3% of powdered polyvinylidene fluoride
% By weight and 5% by weight of powdery graphite were dispersed in N-methylpyrrolidone to prepare a slurry-like positive electrode mixture. Next, this positive electrode material mixture was uniformly applied to both surfaces of an aluminum foil serving as a positive electrode current collector, and dried under reduced pressure at 100 ° C. for 24 hours to form a positive electrode active material layer. Then, this was pressure-molded with a roll press machine to obtain a positive electrode sheet, and the positive electrode sheet was cut into a strip of 48 mm × 300 mm to obtain a positive electrode. An aluminum ribbon lead was welded to the end of the electrode.

A negative electrode was prepared as follows.

First, 91% by weight of artificial graphite and 9% by weight of powdery polyvinylidene fluoride were dispersed in N-methylpyrrolidone to prepare a slurry negative electrode mixture. Next, this negative electrode mixture was uniformly applied to both surfaces of a copper foil which was a negative electrode current collector, and dried under reduced pressure at 120 ° C. for 24 hours to form a negative electrode active material layer. Then, this was pressure-molded with a roll press machine to obtain a negative electrode sheet, and the negative electrode sheet was cut into a strip of 50 mm × 310 mm to obtain a negative electrode. The lead of the nickel ribbon was welded to the non-coated portion of the negative electrode mixture.

Next, the strip-shaped positive electrode and negative electrode produced as described above were laminated in a porous polyethylene separator having a thickness of 25 μm and wound in the longitudinal direction thereof to wind the electrode. Got the body The negative electrode protrudes outside the positive electrode and the separator protrudes outside the positive electrode. The outermost periphery was used as a negative electrode current collector.

The separator had a width of 52 mm. The length direction was made sufficiently longer than the negative electrode. As the separator, a film having a heat shrinkage ratio Rb = 5% in the width direction (perpendicular to the length direction) was used.

Place the wound body in a stainless steel can
Insert, weld the positive terminal and the lid, then weld the lid to the outer can.
It was In addition, inject the electrolyte, seal the inlet and
An ion secondary battery was produced. In addition, this electrolyte is
Ren carbonate (EC) and diethyl carbonate (D
EC) was mixed in a weight ratio of 1: 1 and LiPF was added to the mixed solvent.
₆Was dissolved at a ratio of 1 mol / kg to prepare.

<Sample 62 to Sample 75> A rectangular nonaqueous electrolyte battery was produced in the same manner as in Sample 61, except that the width of the separator and the shrinkage ratio in the width direction were changed as shown in Table 3.

Then, the batteries of Sample 61 to Sample 75 manufactured as described above were subjected to a heating test, a nailing test and an overcharge test to evaluate the safety. The heating test, the nail insertion test, and the overcharge test were performed by the same methods as the tests performed in the first experiment described above.

Table 3 shows the safety evaluation results of the batteries of Samples 60 to 75.

[0074]

[Table 3]

As is clear from these results, in order to prevent the separator from becoming smaller than the positive electrode even if it contracts due to heat, a sample having a small heat shrinkage ratio or a sample having a separator width wider than the positive electrode width is used. It has been found that, even when the separator sometimes undergoes thermal contraction, the separator can maintain a larger area than the positive electrode. Further, in such a battery, it is possible to prevent contact between the positive and negative electrodes and enhance the safety of the battery, and it is possible to reduce the dead volume and increase the energy density while maintaining the safety. I understood.

[0076]

According to the present invention, the lengths of the positive electrode, the negative electrode, and the separator in the long side and short side directions, or the width of protrusion of the separator from the positive electrode are regulated so that the separator is always contracted even if the separator is thermally contracted. It is possible to maintain a larger area than the positive electrode. Thus, in the present invention, it is possible to realize a non-aqueous electrolyte battery that prevents contact between the positive electrode and the negative electrode, does not cause an internal short circuit, and is excellent in safety.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration example of a gel electrolyte battery of the present invention.

FIG. 2 is a perspective view showing a state in which a battery element is housed in an exterior film.

FIG. 3 is a cross-sectional view taken along the line AB in FIG.

FIG. 4 is a perspective view showing a configuration of a positive electrode.

FIG. 5 is a perspective view showing a configuration of a negative electrode.

FIG. 6 is a diagram showing lengths and contraction rates of a positive electrode and a separator.

FIG. 7 is a diagram showing a state in which a separator is arranged so as to protrude from a positive electrode.

FIG. 8 is a diagram showing changes with time of battery surface temperature and battery voltage in a heating test for batteries of Samples 6 and 10.

FIG. 9 is a diagram showing changes with time of battery surface temperature and battery voltage in a nailing test for batteries of Samples 6 and 10;

FIG. 10 is a diagram showing changes over time in battery surface temperature during 5 C overcharge for batteries of Samples 6, 7, 9, and 10.

[Explanation of Codes] 1 gel electrolyte battery, 2 positive electrode, 3 negative electrode, 4
Gel electrolyte layer, 5 separator, 6 electrode winding body, 7 exterior film, 8 positive electrode lead, 9 negative electrode lead, 10 resin film

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuharu Ujiie             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F term (reference) 5H029 AJ12 AK03 AL06 AL07 AL12                       AM03 AM05 AM07 AM16 BJ04                       BJ14 BJ27 CJ06 CJ07 DJ04                       HJ00 HJ04 HJ07

Claims (4)

[Claims] 1. A rectangular positive electrode and a negative electrode, a non-aqueous electrolyte interposed between the positive electrode and the negative electrode, and a rectangular separator containing a thermoplastic resin and arranged between the positive electrode and the negative electrode. In the constructed non-aqueous electrolyte battery, the long side length of the negative electrode is Aa, the short side length is Ab, the long side length of the positive electrode is Ca, the short side length is Cb, and the separator length is The length in the side direction is SLa and the heat shrinkage is Ra
Let SLb be the length of the separator in the short side direction and Rb be the heat shrinkage ratio.
Then, Aa> Ca and Ab> Cb SLa> Ca / (1-Ra) and SLb> Cb /
A non-aqueous electrolyte battery satisfying (1-Rb). 2. The separator has a larger area than the positive electrode, and when the separator is arranged so as to protrude from the positive electrode, the protruding width of the separator, which is parallel to the long side, between the short sides facing each other is set. ma1 and ma2, and the protruding widths of the separators parallel to the short side in the portions of the long sides facing each other are mb1 and mb2, when ma1 <ma2 and mb1 <mb2, ma1> SLa × Ra / 2, And mb1> SLb × R
The non-aqueous electrolyte battery according to claim 1, wherein b / 2 is satisfied. 3. The negative electrode contains carbon, a lithium alloy or lithium metal as a negative electrode active material, the positive electrode contains a substance capable of reversibly inserting and removing lithium as a positive electrode active material, and the non-aqueous electrolyte comprises: The non-aqueous electrolyte battery according to claim 1, wherein a salt containing Li is dissolved in a non-aqueous solvent, and the separator is a porous polyolefin thin film. 4. The non-aqueous electrolyte battery according to claim 1, wherein the non-aqueous electrolyte is in a gel state by a matrix polymer.