JP2002015769A - Non-aqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a non-aqueous electrolyte battery which has an excellent high-temperature preservation property, high reliability and high energy density by suppressing the dissolution of the electrolyte inside the battery even in the case of being disposed to the high temperature in the square battery. SOLUTION: This battery comprises a negative electrode and a non-aqueous electrolyte which are sealed in a square battery can, and the non-aqueous electrolyte contains unsaturated cyclic carbonate and halogenate methoxybenzene group compound, in particular, vinylenecarbonate and 2,4-fluoroanisole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode, a negative electrode,
The present invention relates to a non-aqueous electrolyte battery provided with a non-aqueous electrolyte, and more particularly to a non-aqueous electrolyte battery in which a positive electrode, a negative electrode, and a non-aqueous electrolyte are sealed in a rectangular battery can.

[0002]

2. Description of the Related Art In recent years, new portable electronic devices such as camera-integrated video tape recorders, mobile phones, and laptop computers have appeared one after another, and their size and weight have been reduced. A secondary battery has been spotlighted as a power source, and active research and development are being carried out to obtain a higher energy density.

Under such circumstances, as a secondary battery having a higher energy density than an aqueous electrolyte secondary battery such as a lead battery and a nickel cadmium battery, a lithium ion secondary battery using a non-aqueous electrolyte has been proposed and put into practical use. Began.

[0004] As the battery form of the lithium ion secondary battery, a cylindrical battery in which an electrode element wound in a spiral shape is inserted into a cylindrical case, a folded electrode, a rectangular laminated electrode element, or a strip-like positive and negative electrode There is a prismatic battery in which a wound electrode element formed by winding is wound into a rectangular case. The latter is more space-efficient than the cylindrical battery, and has been increasingly demanded in recent years as devices become thinner.

[0005]

The above-mentioned small secondary battery is used not only in normal use but also in a car in the middle of summer, so that high reliability is required. In particular, a rectangular battery can has a lower strength than a cylindrical battery can, and thus easily deforms with an increase in battery internal pressure. Therefore, in the case of a battery of a type that can be housed inside a device, exposure to a high temperature may cause the battery to expand due to decomposition of the electrolytic solution inside the battery, which may result in damage to the battery can and damage to the device.

The present invention has been proposed in view of such a conventional situation. For a rectangular battery, even if it is exposed to a high temperature, the decomposition of the electrolytic solution inside the battery is suppressed so that the battery can be stored at a high temperature. An object of the present invention is to provide a non-aqueous electrolyte battery having excellent characteristics, high reliability and high energy density.

[0007]

A non-aqueous electrolyte battery according to the present invention comprises a positive electrode, a negative electrode, and a non-aqueous electrolyte sealed in a rectangular battery can. It is characterized by containing a carbonate and a halogenated methoxybenzene compound.

In the non-aqueous electrolyte battery according to the present invention as described above, since the non-aqueous electrolyte contains an unsaturated cyclic carbonate and a halogenated methoxybenzene compound, the battery is exposed to high temperatures. Even in this case, gas generation due to the decomposition of the non-aqueous electrolyte is suppressed. Particularly, vinylene carbonate is used as the unsaturated cyclic carbonate and 2,4-vinylene is used as the halogenated methoxybenzene-based compound.
It is effective when it contains fluoroanisole.

[0009]

Embodiments of the present invention will be described below.

FIGS. 1 and 2 show a configuration example of a nonaqueous electrolyte battery 1 according to the present invention. As shown in FIG. 2 which is a longitudinal sectional view, this non-aqueous electrolyte battery 1 has an electrode in which a film-shaped positive electrode 2 and a film-shaped negative electrode 3 are wound in close contact with a separator 4 interposed therebetween. The element 5 is mounted inside the battery can 7 via the insulating film 6 on the upper and lower end surfaces.

The battery can 7 has a flat rectangular shape and is made of, for example, iron and nickel-plated inside. The opening of the battery can 7 in which the electrode element 5 is stored is sealed by a battery lid 9 via a case 8 made of, for example, polypropylene. This battery cover 9 has a gasket 1
0 and the positive terminal 11 are attached, and the positive terminal 1
1 is connected to the positive electrode 2 by a positive electrode lead 12.

The positive electrode 2 is manufactured by applying a positive electrode mixture containing a positive electrode active material and a binder on a positive electrode current collector and drying the mixture. A metal foil such as an aluminum foil is used as the positive electrode current collector.

As the positive electrode active material, for example, a lithium composite oxide represented by a general formula of Li _x MO ₂ or an intercalation compound containing Li can be used. Here, M is one or more transition metals, and x is usually a value in the range of 0.05 ≦ x ≦ 1.10.

As the transition metal M constituting the lithium composite oxide, cobalt (Co), nickel, (Ni)
Alternatively, at least one of manganese (Mn) is preferable. Specific examples of the lithium composite oxide include L
iCoO ₂ , LiNiO ₂ , Li _x Ni _y Co _{1 -y} O ₂ (The values of x and y vary depending on the charge / discharge state of the battery.
0 <x <1, 0.7 <y <1.0. ) Or L
iMn ₂ O _{4 and the} like.

Further, in addition to the above-described lithium composite oxide, a second lithium-containing compound can be used as a mixture as a positive electrode active material. As the second lithium-containing compound, for example, LiMoS ₂ , LiTiS ₂ , L
iP ₂ O ₅ , Li _x FePO _{4 and the} like.

It is preferable that these positive electrode active materials have an average particle size of about 3 μm or more and about 7 μm or less.

As the binder for the above-mentioned positive electrode mixture, a known binder which is usually used for a positive electrode mixture of this type of battery can be used. And other known additives can be added.

The negative electrode 3 is manufactured by applying a negative electrode mixture containing a negative electrode active material and a binder on a negative electrode current collector and drying the mixture. A metal foil such as a copper foil is used for the negative electrode current collector, for example.

Examples of the negative electrode active material include oxides having a relatively low potential such as iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, and silicon compounds, and other oxides; and lithium and lithium alloys. A carbon material capable of doping and undoping lithium ions can be used.

As the carbon material, phenol resin,
Acrylic resin, vinyl halide resin, polyimide resin, polyamide imide resin, polyamide resin, conjugated resin such as polyacetylene, poly (p-phenylene), cellulose or its derivative, any organic polymer compound, and especially furfuryl Furan resins made of homopolymers or copolymers of alcohol or furfural, organic materials such as petroleum pitch, and carbonaceous materials obtained by carbonizing plants such as coffee beans and bamboo by using a method such as firing. Can be Further, carbon materials such as natural graphite, artificial graphite, pyrolytic carbons, cokes, acetylene black and the like, glassy carbon, activated carbon and carbon fiber can also be preferably used.

As the binder for the negative electrode mixture, a known binder used for a negative electrode mixture of this type of battery can be used, and a known binder for the negative electrode mixture can be used. Additives and the like can be added.

The non-aqueous electrolyte is prepared by dissolving an electrolyte in a non-aqueous solvent.

As the non-aqueous solvent, various non-aqueous solvents conventionally used for non-aqueous electrolytes can be used. For example, propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxymethane, γ-butyrolactone, valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-
Dioxolan, 4-methyl-1,3-dioxolan, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like are used alone or in combination of two or more.

As the electrolyte, a known electrolyte usually used for a battery electrolyte can be used. Specifically, LiPF ₆ , LiClO ₄ , LiAsF ₆ , Li
BF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ S
O ₃ Li, LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ S
O ₂ ) ₃ , LiCl, LiBr and the like.

Here, in the non-aqueous electrolyte battery according to the present invention, the non-aqueous electrolyte contains an unsaturated cyclic carbonate and a halogenated methoxybenzene compound.

Examples of the unsaturated cyclic carbonate include alkyl phenyl carbonates such as methyl phenyl carbonate, ethyl phenyl carbonate and propyl phenyl carbonate, and vinylene carbonate. Among them, vinylene carbonate shown in Chemical formula 1 is used. Is particularly preferred.

[0027]

Embedded image

Examples of the halogenated methoxybenzene compound include 4-fluoroanisole, 2-bromoanisole, tetrafluoroanisole, 2,4-difluoroanisole, and alkyl-substituted compounds thereof. However, among them, 2,4-
It is particularly preferred to use difluoroanisole.

[0029]

Embedded image

An unsaturated cyclic carbonate and a halogenated methoxybenzene compound, particularly vinylene carbonate,
By using a non-aqueous electrolyte containing 2,4-difluoroanisole, gas generation due to decomposition of the non-aqueous electrolyte can be suppressed even when exposed to high temperatures.
Thereby, in the flat battery can 7 having a rectangular shape or the like, even when the battery is stored at a high temperature, the expansion of the battery can 7 due to gas generation inside can be suppressed.

Generally, in a non-aqueous electrolyte battery in which vinylene carbonate is added to a non-aqueous electrolyte, low-temperature characteristics are improved, but high-temperature storage characteristics are very poor. It has been confirmed by the present inventors that this is remarkable. That is, the nonaqueous electrolyte containing vinylene carbonate was very easily decomposed by oxygen radicals generated inside the battery when stored in a high-temperature environment.

Therefore, in the present invention, 2,4-difluoroanisole, which is a halogenated methoxybenzene compound, is added to the non-aqueous electrolyte together with vinylene carbonate. This 2,4-difluoroanisole captures oxygen radicals and suppresses the reaction between the non-aqueous electrolyte, particularly vinylene carbonate, and oxygen radicals.

Therefore, in the non-aqueous electrolyte battery 1 according to the present invention, even when stored in a high-temperature environment, the generated oxygen radicals are supplemented by 2,4-difluoroanisole, so that vinylene carbonate is obtained. As a result, decomposition of the non-aqueous electrolyte can be suppressed, and gas generation can be prevented.

Here, even when only 2,4-difluoroanisole is added to the non-aqueous electrolyte, the irreversible reaction in the positive electrode and the negative electrode in a severe oxidizing and reducing atmosphere in the battery caused by charging is suppressed. Thus, an effect of preventing deactivation of the active material can be obtained.

However, when vinylene carbonate is added together with the methoxybenzene compound, the vinylene carbonate reacts with the active material, and the reactant generated on the surface of the active material undergoes a degradation suppression reaction due to the methoxybenzene compound. It is considered that vinylene carbonate also reacts at the same time and exhibits a higher inhibitory effect.

The vinylene carbonate content of the non-aqueous electrolyte is preferably in the range of 0.3% by weight to 1.2% by weight, and the content of 2,4-difluoroanisole is 0.05 mol. / L or more and 0.3 mol / l or less.

When the content of vinylene carbonate is less than 0.3% by weight, the effect of suppressing gas generation in a high temperature environment and suppressing the expansion of the battery can 7 cannot be sufficiently obtained. On the other hand, if the content of 2,4-difluoroanisole is less than 0.05 mol / l, the effect of capturing oxygen radicals in a high-temperature environment and preventing the decomposition of vinylene carbonate cannot be sufficiently obtained. When the content of vinylene carbonate exceeds 1.2% by weight or the content of 2,4-difluoroanisole exceeds 0.3 mol / l, the battery characteristics of the nonaqueous electrolyte battery 1 are reduced. On the contrary, it lowers.

Therefore, the vinylene carbonate content of the non-aqueous electrolyte is in the range of 0.3% by weight or more and 1.2% by weight or less, and the content of 2,4-difluoroanisole is 0.05 mol /%. 1 to 0.3 mol / l, even when the battery is stored at a high temperature,
Decomposition of the non-aqueous electrolyte can be suppressed, and gas generation due to decomposition of the non-aqueous electrolyte can be prevented. Further, a more preferable content of the compound is such that the vinylene carbonate content is in the range of 0.6% by weight to 1.0% by weight and the content of 2,4-difluoroanisole is 0.1 m
ol / l or more and 0.3 mol / l or less.

In the non-aqueous electrolyte battery 1 according to the present embodiment as described above, the non-aqueous electrolyte contains unsaturated cyclic carbonate and a halogenated methoxybenzene compound, particularly vinylene carbonate and 2,4-difluoroanisole. Therefore, even when the battery is stored at a high temperature, decomposition of the non-aqueous electrolyte can be suppressed, and gas generation due to decomposition of the non-aqueous electrolyte can be prevented. This allows
This nonaqueous electrolyte battery 1 has excellent reliability because the expansion of the battery can 7 due to gas generation inside the battery is suppressed.

In the above embodiment, the non-aqueous electrolyte battery 1 using the non-aqueous electrolyte has been described as an example.
The present invention is not limited to this, and is also applicable to a gel electrolyte battery using a gel electrolyte in which a non-aqueous electrolyte is made into a gel by a matrix polymer.

The rectangular nonaqueous electrolyte battery according to the present embodiment as described above can be formed in various sizes. Further, the present invention is applicable to both primary batteries and secondary batteries.

[0042]

EXAMPLES Next, examples will be described in which the effects of the present invention are confirmed, but the present invention is not limited to these examples.

First, a square nonaqueous electrolyte secondary battery as a sample was prepared as follows.

<Sample 1> First, the H / C atomic ratio was set to 0.1.
A petroleum pitch appropriately selected from the range of 6 to 0.8 was pulverized and oxidized in an air stream to obtain a carbon precursor. Quinoline-insoluble matter of this carbon precursor (JIS centrifugation: K242
5-1983) was 80% and the oxygen content (by organic elemental analysis) was 15.4% by weight.

The carbon precursor was heated at 1000 ° C. in a nitrogen stream.
And heat-treated, and then pulverized to obtain a carbon material powder having an average particle size of 10 μm. In addition, as a result of performing X-ray diffraction measurement on the non-graphitizable carbon material obtained at this time, (00
2) The plane spacing is 0.381 nm, and the true specific gravity is 1.
It was 54 g / cm ³ .

90 parts by weight of this carbon material and 10 parts by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture, and this negative electrode mixture was mixed with N-methyl-
A negative electrode slurry was prepared by dispersing in 2-pyrrolidone to form a slurry.

The negative electrode slurry thus obtained is uniformly coated on both sides of a 15 μm-thick strip-shaped copper foil serving as a negative electrode current collector, dried, and then compression-molded by a roll press to form a strip. The negative electrode 3 was produced.

Next, the positive electrode 2 was produced as follows.

Lithium carbonate and cobalt carbonate were mixed at a ratio of 0.5 mol: 1.0 mol and calcined at 900 ° C. for 5 hours in air to obtain LiCoO ₂ having a particle size of 5.0 ± 2.0 μm.
I got

The LiCoO ₂ obtained in this manner was converted to 9
1 part by weight, 6 parts by weight of graphite as a conductive agent,
A positive electrode mixture was prepared by mixing 3 parts by weight of polyvinylidene fluoride as a binder, and this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a slurry to prepare a positive electrode slurry.

The positive electrode slurry thus obtained is uniformly applied to both sides of a 20 μm-thick strip-shaped aluminum foil serving as a positive electrode current collector, dried, and then compression-molded by a roll press to form a strip. Of positive electrode 2 was produced.

The strip-shaped negative electrode 3 and the positive electrode 2 manufactured as described above are laminated in order of the negative electrode 3, the separator 4, the positive electrode 2, and the separator 4 via the separator 4 made of microporous polypropylene having a thickness of 20 μm. , Wound many times. Then, the electrode element 5 was manufactured by fixing the final end portion of the copper foil as the negative electrode current collector located at the outermost periphery with the element adhesive tape 13 having a width of 40 mm.

The electrode element 5 manufactured as described above was housed in a nickel-plated iron flat battery can 7 as shown in FIG. 2, and an insulating sheet 6 was placed on the upper and lower end surfaces of the electrode element 5.

Next, the positive electrode lead 12 made of aluminum was led out of the positive electrode current collector, and was welded to the positive electrode terminal 11 previously attached to the battery cover 9 via the gasket 10, and the battery can 7 and the battery cover were laser-welded. And fixed.

Then, LiPF ₆ was added to an equal volume mixed solvent of ethylene carbonate and dimethyl carbonate in an amount of 1.0%.
dissolving at a rate of 0.1 mol / l, further adding 2,4-difluoroanisole at a rate of 0.1 mol / l, and injecting the prepared electrolyte from the electrolyte inlet, and welding the electrolyte inlet. To maintain the airtightness inside the battery, and as shown in FIGS. 1 and 2, a height (H) of 48 mm and a width (W) of 34 m
A square nonaqueous electrolyte secondary battery having a thickness of m and a thickness (T) of 6 mm was produced.

<Sample 2> Sample 2 was identical to Sample 1 except that vinylene carbonate was added at a ratio of 0.6% by weight and 2,4-difluoroanisole at a ratio of 0.1 mol / l in the non-aqueous electrolyte. Similarly, a prismatic nonaqueous electrolyte secondary battery was produced.

<Sample 3> Sample 3 was identical to Sample 1 except that vinylene carbonate was added to the nonaqueous electrolyte at a ratio of 1.0% by weight and 2,4-difluoroanisole at a ratio of 0.1 mol / l. Similarly, a prismatic nonaqueous electrolyte secondary battery was produced.

<Sample 4> Sample 4 was prepared in the same manner as in Sample 1, except that vinylene carbonate was added at a ratio of 1.5% by weight and 2,4-difluoroanisole at a ratio of 0.1 mol / l. Similarly, a prismatic nonaqueous electrolyte secondary battery was produced.

<Sample 5> Sample 5 was prepared in the same manner as in Sample 1 except that vinylene carbonate was added at a ratio of 2.0% by weight and 2,4-difluoroanisole at a ratio of 0.1 mol / l in the non-aqueous electrolyte. Similarly, a prismatic nonaqueous electrolyte secondary battery was produced.

<Sample 6> A rectangular non-aqueous electrolyte secondary battery was fabricated in the same manner as in Sample 1, except that nothing was added to the non-aqueous electrolyte.

<Sample 7> A prismatic non-aqueous electrolyte secondary battery was manufactured in the same manner as in Sample 1, except that vinylene carbonate was added to the non-aqueous electrolyte at a ratio of 0.3% by weight.

<Sample 8> A prismatic non-aqueous electrolyte secondary battery was fabricated in the same manner as in Sample 1, except that vinylene carbonate was added to the non-aqueous electrolyte at a ratio of 0.6% by weight.

<Sample 9> A rectangular non-aqueous electrolyte secondary battery was fabricated in the same manner as in Sample 1, except that vinylene carbonate was added at a ratio of 0.9% by weight to the non-aqueous electrolyte.

<Sample 10> A rectangular non-aqueous electrolyte secondary battery was manufactured in the same manner as in Sample 1, except that vinylene carbonate was added to the non-aqueous electrolyte at a ratio of 1.0% by weight.

<Sample 11> A rectangular non-aqueous electrolyte secondary battery was manufactured in the same manner as in Sample 1, except that vinylene carbonate was added to the non-aqueous electrolyte at a ratio of 1.2% by weight.

<Sample 12> A square non-aqueous electrolyte secondary battery was produced in the same manner as in Sample 1, except that vinylene carbonate was added to the non-aqueous electrolyte at a ratio of 2.0% by weight.

<Sample 13> A square nonaqueous electrolyte secondary battery was produced in the same manner as in Sample 1, except that vinylene carbonate was added to the nonaqueous electrolyte at a ratio of 3.0% by weight.

<Sample 14> Sample 14 was prepared in the same manner as in Sample 1 except that vinylene carbonate was added at a ratio of 0.6% by weight and 2,4-difluoroanisole at a ratio of 0.05 mol / l in the non-aqueous electrolyte. Similarly, a prismatic nonaqueous electrolyte secondary battery was produced.

<Sample 15> Sample 15 was prepared in the same manner as in Sample 1 except that vinylene carbonate was added at a ratio of 0.6% by weight and 2,4-difluoroanisole at a ratio of 0.1 mol / l. Similarly, a prismatic nonaqueous electrolyte secondary battery was produced.

<Sample 16> Sample 16 was identical to Sample 1 except that vinylene carbonate was added at a ratio of 0.6% by weight and 2,4-difluoroanisole at a ratio of 0.2 mol / l in the nonaqueous electrolyte. Similarly, a prismatic nonaqueous electrolyte secondary battery was produced.

<Sample 17> Sample 17 was identical to Sample 1 except that vinylene carbonate was added at a ratio of 0.6% by weight and 2,4-difluoroanisole was added at a ratio of 0.3 mol / l in the non-aqueous electrolyte. Similarly, a prismatic nonaqueous electrolyte secondary battery was produced.

<Sample 18> 2,4-
A rectangular non-aqueous electrolyte secondary battery was fabricated in the same manner as in Sample 1, except that difluoroanisole was added at a rate of 0.05 mol / l.

<Sample 19> 2,4-
A square nonaqueous electrolyte secondary battery was produced in the same manner as in Sample 1, except that difluoroanisole was added at a rate of 0.2 mol / l.

<Sample 20> 2,4-
A square nonaqueous electrolyte secondary battery was produced in the same manner as in Sample 1, except that difluoroanisole was added at a rate of 0.3 mol / l.

The thickness (T ₁ ) of the battery can 7 after charging the battery prepared as described above at a constant voltage of 4.2 V and a constant current of 280 mA for 5 hours was measured. In addition,
The thickness of the battery can 7 was the maximum thickness measured at the center of the side surface of the battery can 7, that is, at the portion A indicated by x in FIG. Further, the thickness (T ₂ ) of the battery can 7 after being charged at 4.2 V and stored at 80 ° C. for 168 hours was measured. And (T ₂ −
The rate of increase in battery can thickness (%) was calculated from T ₁ ) / T ₂ × 100.

First, while changing the amount of vinylene carbonate to be added, samples 1 to 5 containing both vinylene carbonate and 2,4-difluoroanisole were added.
FIG. 3 shows the relationship between the amount of vinylene carbonate added and the rate of increase in the thickness of the battery can for the battery No. 1.

From FIG. 3, it was found that vinylene carbonate was 0.1% higher than that of sample 1 to which vinylene carbonate was not added.
It can be seen that the rate of increase in the thickness of the battery can is reduced in Samples 2 and 3 in which the content is in the range of 3% by weight or more and 1.2% by weight or less.

This is because vinylene carbonate is decomposed in the initial charge and the decomposition product covers the negative electrode surface, thereby preventing decomposition of the electrolytic solution at a high temperature and gas generation due to decomposition of the electrolytic solution. It is presumed to be due to

However, in Samples 4 and 5 to which vinylene carbonate was added in an amount of 1.2% by weight or more, vinylene carbonate remaining without being decomposed by the initial charge continued to decompose at a high temperature, and the battery can swelled. Is increasing.

Therefore, there is an optimum value for the amount of vinylene carbonate to be added, and the amount of vinylene carbonate to be added should be in the range of 0.
When the range is 3% by weight or more and 1.2% by weight or less,
It can be seen that the rate of increase in the thickness of the battery can is small, and the expansion of the battery can is suppressed. It can be seen that particularly favorable effects are obtained when the amount of vinylene carbonate is in the range of 0.6% by weight or more and 1.0% by weight or less.

Further, for the batteries of Samples 6 to 13 to which only vinylene carbonate was added while changing the amount of vinylene carbonate, the relationship between the amount of vinylene carbonate added and the rate of increase in the thickness of the battery can was also shown in FIG.
Shown in

FIG. 4 shows that even when only vinylene carbonate is added, a favorable effect is obtained when the amount of vinylene carbonate is in the range of 0.3% by weight or more and 1.2% by weight or less. You can see that.

However, as is apparent from a comparison between FIG. 3 and FIG. 4, when the amount of vinylene carbonate added is the same, FIG. 3 obtained by adding both vinylene carbonate and 2,4-difluoroanisole The effect of suppressing the increase in the thickness of the battery can is more pronounced.

This is because vinylene carbonate and 2,4-difluoroanisole are both decomposed in the initial charge, and the decomposition products cover the negative electrode surface, thereby preventing the decomposition of the electrolytic solution at a high temperature. It is presumed that.
It is also considered that the surface coating of both vinylene carbonate and 2,4-difluoroanisole prevents the decomposition of the electrolyte at a high temperature more than the surface coating of vinylene carbonate alone.

Therefore, vinylene carbonate and 2,4-
It is understood that by adding both difluoroanisole, gas generation due to decomposition of the electrolytic solution can be prevented, and the expansion of the battery can can be more effectively suppressed.

Next, vinylene carbonate and 2,4-difluoroanisole were added while changing the amount of 2,4-difluoroanisole added.
For the batteries of Sample 8 and Samples 14 to 17 to which both difluoroanisole were added, 2, 4
FIG. 5 shows the relationship between the amount of difluoroanisole added and the rate of increase in the thickness of the battery can.

As shown in FIG. 5, 2,4-difluoroanisole was more than 0.05 mol / l and 0.3 mol / l more than Sample 8, to which 2,4-difluoroanisole was not added.
It can be seen that in the samples 14 to 17 added in the range of 1 or less, the rate of increase in the thickness of the battery can is reduced. On the other hand, 0.3 mol / l of 2,4-difluoroanisole
It has been confirmed that the addition of the above also increases the swelling of the battery can.

Accordingly, there is an optimum value for the amount of 2,4-difluoroanisole added, and the amount of 2,4-difluoroanisole added is 0.05 mol / l or more and 0.3 mol / l or more.
It can be seen that when the range is 1 or less, the rate of increase in the thickness of the battery can is small and the expansion of the battery can is suppressed. And, the added amount of 2,4-difluoroanisole is 0.1 m
ol / l or more and 0.3 mol / l or less,
It can be seen that a particularly favorable effect has been obtained.

Further, the batteries of Sample 1, Sample 6, and Samples 18 to 20 to which the added amount of 2,4-difluoroanisole was added while changing the added amount of 2,4-difluoroanisole were also used. , 2, 4
FIG. 6 shows the relationship between the amount of difluoroanisole added and the rate of increase in the battery can thickness.

FIG. 6 shows that, even when only 2,4-difluoroanisole was added, the amount of 2,4-difluoroanisole added was 0.05 mol / l or more and 0.3 mol / l or more.
It can be seen that a favorable effect is obtained when the ratio is not more than / l.

However, as is apparent from a comparison between FIG. 5 and FIG. 6, when the added amount of 2,4-difluoroanisole is the same, both vinylene carbonate and 2,4-difluoroanisole are used. In FIG. 5, the effect of suppressing the increase in the thickness of the battery can is more remarkably exhibited.

This is because vinylene carbonate is decomposed at the initial charge and the decomposition product covers the negative electrode surface, thereby preventing decomposition of the electrolytic solution at a high temperature and gas generation due to decomposition of the electrolytic solution. It is presumed to be due to
Furthermore, vinylene carbonate and 2,4-
It is presumed that both difluoroanisole decomposed, and the decomposition products covered the negative electrode surface, thereby preventing the decomposition of the electrolytic solution at high temperatures. It is also considered that the surface coating of both vinylene carbonate and 2,4-difluoroanisole is more likely to prevent the decomposition of the electrolyte at high temperatures than the surface coating of vinylene carbonate alone.

Therefore, vinylene carbonate and 2,4-
It is understood that by adding both difluoroanisole, gas generation due to decomposition of the electrolytic solution can be prevented, and the expansion of the battery can can be more effectively suppressed.

[0094]

According to the present invention, an unsaturated cyclic carbonate and a halogenated methoxybenzene compound, particularly, both vinylene carbonate and 2,4-difluoroanisole, are added to a nonaqueous electrolyte in a nonaqueous electrolyte. By
Even when exposed to a high temperature, gas generation due to decomposition of the electrolytic solution can be prevented, and expansion of the battery can can be suppressed. Thereby, in the present invention, a highly reliable nonaqueous electrolyte battery can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a non-aqueous electrolyte battery according to the present invention.

FIG. 2 is a longitudinal sectional view of the nonaqueous electrolyte battery shown in FIG.

FIG. 3 shows vinylene carbonate and 2,4 in a non-aqueous electrolyte.
FIG. 4 is a diagram showing the relationship between the amount of vinylene carbonate added and the rate of increase in the battery can thickness for a battery to which both difluoroanisole were added.

FIG. 4 is a graph showing the relationship between the amount of vinylene carbonate added and the rate of increase in the thickness of a battery can for a battery in which only vinylene carbonate is added to a non-aqueous electrolyte.

FIG. 5 shows vinylene carbonate and 2,4 in a non-aqueous electrolyte.
FIG. 6 is a graph showing the relationship between the amount of 2,4-difluoroanisole added and the rate of increase in battery can thickness for a battery to which both -difluoroanisole are added.

FIG. 6 is a graph showing the relationship between the amount of 2,4-difluoroanisole added and the rate of increase in the thickness of a battery can for a battery in which only 2,4-difluoroanisole is added to a nonaqueous electrolyte.

[Explanation of symbols]

1 Non-aqueous electrolyte battery, 2 Positive electrode, 3 Negative electrode, 4
Separator, 5 electrode element, 6 insulating film,
7 Battery can, 8 Case, 9 Battery cover, 10 Gasket

Claims (4)

[Claims] 1. A non-aqueous electrolyte battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte sealed in a rectangular battery can, wherein the non-aqueous electrolyte comprises an unsaturated cyclic carbonate and a halogenated methoxybenzene. A non-aqueous electrolyte battery characterized by containing a base compound. 2. The non-aqueous electrolyte battery according to claim 1, wherein the unsaturated cyclic carbonate is vinylene carbonate, and the halogenated methoxybenzene compound is 2,4-fluoroanisole. 3. The non-aqueous electrolyte contains the vinylene carbonate in a range of 0.3% by weight or more and 1.2% by weight or less, and 0.05 mol / l of the 2,4-difluoroanisole. The non-aqueous electrolyte battery according to claim 2, wherein the content is in the range of 1 to 0.3 mol / l. 4. The positive electrode contains a lithium composite oxide or a lithium-containing interlayer compound as a positive electrode active material, and the negative electrode contains a material capable of doping / dedoping lithium ions as a negative electrode active material. The non-aqueous electrolyte battery according to claim 1, wherein: