JP3263182B2 - Non-aqueous electrolyte secondary battery and manufacturing method thereof - Google Patents

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 secondary battery and a method for producing the same.

[0002]

2. Description of the Related Art Non-aqueous electrolyte secondary batteries using lithium or a lithium compound as a negative electrode are expected to have a high voltage and a high energy density, and are being actively studied. So far,
V ₂ O ₅ , Cr ₂ as a positive electrode active material of a nonaqueous electrolyte secondary battery
O ₅ , MnO ₂ , TiS _{2 and the} like are known. In recent years, LiMn ₂ O ₄ , LiC has been used as a positive electrode active material to provide a 4 volt class non-aqueous electrolyte secondary battery having a higher energy density.
oO2, such as LiNiO _2, LiFeO ₂ has been attracting attention. In particular, LiMn ₂ O ₄ , LiNiO ₂ and LiFeO
_{As for} No. ₂ , due to its low cost and stable supply of raw materials, active research is being conducted as an active material for providing a large-capacity secondary battery. On the other hand, as the negative electrode active material,
Carbon materials have attracted attention instead of lithium metal in terms of safety and rate characteristics. In particular, graphite powder with a high degree of graphitization has the characteristics that it has a high capacity, has a discharge potential of about 0.1 V noble compared to lithium metal, and has a small decrease in battery voltage, and has been actively studied. I have.

[0003]

The electrode plate using graphite powder for the negative electrode repeats expansion and contraction of the electrode plate while absorbing and releasing lithium during charging and discharging of the battery. Thereby, the electrode plate is loosened, and the contact between the carbon materials of the negative electrode active material is deteriorated. As a result, the current collecting ability of the electrode plate is reduced, and the capacity is reduced due to the charge / discharge cycle of the battery. As a countermeasure, fibrous graphite and the like are added to the negative electrode to form a current collecting network of the electrode plate to improve the current collecting ability of the electrode plate. In the case of adding, it is necessary to increase the amount of the binder in order to increase the strength of the electrode plate, and there remains a problem that the absolute capacity of the battery is reduced. Further, even if fibrous graphite or the like is added, expansion and shrinkage of the negative electrode plate are not suppressed, and a long charge / discharge cycle still has a problem. Therefore, an object of the present invention is to improve the charge / discharge cycle characteristics of a non-aqueous electrolyte secondary battery using a carbon material for the negative electrode.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an axial space of an electrode plate group in which a positive electrode plate and a negative electrode plate made of a carbon material as an active material are spirally wound via a separator. The part is filled with a heat-expandable material and a thermosetting resin . The thermally expandable material is expanded by heating after sealing the battery.

[0005] Examples of the thermally expandable material include those shown in the examples.
Acrylonitrile-vinylidene chloride copolymer tree
Fatty, acrylonitrile-methyl methacrylate copolymer tree
The core is made of various thermoplastic resins such as fats,
Substances that generate gas at temperatures below the softening point of fats, e.g.
A bag containing a low boiling point liquid such as lopan, butane, pentane, etc.
Microcapsules and the like can be used.

A thermosetting resin is filled in the axial space of the electrode group together with the above-mentioned heat-expandable resin, and when the former is expanded and the latter is cured by heating, the pressure state of the electrodes by the expanded resin is reduced. This is advantageous because it can be maintained regardless of environmental changes. It is preferable that the inflation material filled in the shaft space of the electrode group expands to about 1.05 to 5 times the diameter of the shaft space.

[0007]

According to the present invention, after the electrode group in which the axial space of the cylindrical battery is filled with the expanding material is inserted into the battery case, the expanding material is expanded and the electrode group is pressed from the center of the battery. Thereby, the electrode plate can be mechanically pressed. Therefore, loosening of the electrode plate due to expansion and contraction due to charge and discharge of the battery can be suppressed, and a decrease in capacity due to a charge and discharge cycle can be suppressed. Furthermore, since the compression of the electrode plate lasts semipermanently from the time when the filler is expanded, it is effective for a long time.

[0008]

Embodiments of the present invention will be described below. Example 1 LiMn _1.8 Co _0.2 O _{4 as} a positive electrode active material
Is to convert Li ₂ CO ₃ , Mn ₃ O ₄ and CoCO ₃ to 5: 6: 2.
And the mixture is heated at 900 ° C. to synthesize. This is classified into 100 mesh or less, and 10
10 g of carbon powder as a conductive agent and 8 g of an aqueous dispersion of polytetrafluoroethylene as a binder are added to 0 g to form a paste, which is then applied to a titanium core material, dried and rolled to form a positive electrode. Board. On the other hand, a negative electrode plate is prepared by adding 10 g of polyvinylidene fluoride and dimethylformamide to 100 g of graphite powder as an active material to form a paste, applying the paste to a nickel core material, drying and rolling.

FIG. 1 shows a sectional view of the battery used in this embodiment. The electrode body includes a band-shaped porous polypropylene separator 3 wider than the two electrode plates between a positive electrode plate 1 having a positive electrode lead 4 and a negative electrode plate 2 having a negative electrode lead 5 of the same material as the core material attached by spot welding. And the whole is spirally wound. Further, insulating plates 6 and 7 made of polypropylene are arranged on the upper and lower sides of the electrode body, respectively, and inserted into the battery case 8, and polyacrylamide, which is a liquid absorbing and expanding resin, is inserted as a filler 11 into the shaft space. Next, after forming a step on the upper part of the battery case 8, 1 mol /
Then, a mixed solution of propylene carbonate and ethylene carbonate in which 1 l of lithium perchlorate is dissolved is injected at an equal specific volume, and the mixture is sealed with a sealing plate 9 having a positive electrode terminal 10. In addition,
The outer diameter of the battery is 20 mm and the height is 32 mm, and the diameter of the axial space of the electrode plate group is 2 mm and the height is 30 mm. The battery fabricated in this manner is designated as A.

[Comparative Example 1] A battery manufactured in the battery manufacturing process of Example 1 without inserting the liquid-absorbing expander is designated as D. [Comparative Example 2] A negative electrode obtained by adding 5 g of fibrous graphite and 10 g of polyvinylidene fluoride to 100 g of graphite powder, forming a paste using dimethylformamide, applying the paste to a nickel core material, drying and rolling. Is used. The positive electrode is manufactured in the same manner as in Example 1. As in Comparative Example 1, the battery manufactured without filling the axial space with the expanding material is designated as E.

For these batteries, a charge / discharge current of 100
A charge / discharge cycle test was performed at mA and a charge / discharge voltage range of 4.3 V to 3.0 V. The result is shown in FIG. In the battery D of the comparative example, the capacity greatly decreased due to the charge / discharge cycle.
The value is less than half of the initial capacity in about a cycle.
Further, the battery E of the comparative example is different from the battery D in the cyclability.
Although the capacity is not so reduced, the initial capacity is about 20 mAh.
The capacity after 100 cycles is reduced to 75% of the capacity in the first cycle. On the other hand, the battery A of this example has a very good cyclability as compared with the batteries D and E, and the capacity after 100 cycles is 9 times the capacity of the first cycle.
Maintain 3%.

Embodiment 2 An example in which a heat-expandable resin is used as a filler in a shaft space portion of a battery will be described. As the thermal expansion material, microcapsules having an acrylonitrile-vinyl acetate copolymer resin as a core and propane sealed therein were used.
The volume of this microcapsule is 3 ~ by heating.
It increases by about 5%. When a microcapsule having a volume expansion coefficient exceeding 10% is used, the battery is damaged by the expansion of the microcapsule, and thus the battery performance cannot be improved. The battery was manufactured in the same manner as in Example 1, and the above-mentioned heat-expandable microcapsules were filled in place of polyacrylamide which is a liquid-swelling resin. After sealing the battery, the battery is heated at a temperature between 80C and 90C for at least 20 minutes. The battery fabricated in this manner is designated as B. However, heating at this temperature may decrease the performance of the battery itself, so it is better to be as short as possible.

Battery B was also subjected to a charge / discharge cycle test under the conditions of a charge / discharge current of 100 mA and a charge / discharge voltage range of 4.3 V to 3.0 V, as in Example 1. The result is also shown in FIG. Battery B maintains about 96% of the capacity in the first cycle after 100 cycles. Battery B of this example
It can be seen that the cyclability of the battery A was even better than that of the battery A of Example 1. This is due to the difference in the filler in the axial space. That is, since the filler of the present example has a higher hardness than the filler of Example 1, it is considered that loosening of the electrode due to expansion and contraction of the negative electrode can be more effectively suppressed.

[Embodiment 3] An example will be described in which a mixture of a thermosetting resin and a heat-expandable resin is used as a filler for a shaft space portion of a battery. An epoxy resin was used as the thermosetting resin, and microcapsules having an acrylonitrile-vinyl acetate copolymer resin as a nucleus and propane encapsulated therein were used as the thermally expandable resin as in Example 2. A battery was prepared in the same manner as in Example 2, and a mixture of microcapsules, which are thermal expansion spheres, and epoxy resin at a volume ratio of 50:50 was filled in the battery shaft space. After closing the battery,
The battery is heated at a temperature between 80C and 90C for at least 20 minutes. The battery fabricated in this manner is designated as C.

FIG. 2 shows the results of the charge / discharge cycle test of the battery C under the same conditions as in the first embodiment. Battery C is 1
About 96% of the capacity of the first cycle after 00 cycles
Has been maintained. Next, the battery B and the battery C were subjected to a high-temperature cycle test. The test conditions were a temperature atmosphere of 60 ° C., a charge / discharge current of 100 mA, and a charge / discharge voltage range of 4.3 V to
3.0V. The result is shown in FIG. As shown in FIG. 3, it can be seen that the capacity of the battery B is larger than that of the battery C due to the charge / discharge cycle. This is considered to be a result of the fact that the microcapsules filled in the axial space at the temperature of 60 ° C. in the battery B softened slightly, so that the electrodes could not be pressed. That is, since the battery C is also filled with the thermosetting resin at the same time, unlike the battery B, the electrodes cannot be pressed even in the high-temperature cycle.
It is considered that a battery having good high-temperature cycle characteristics was obtained.

In the above embodiments, specific non-aqueous electrolytes and positive electrode active materials were used, but it goes without saying that the effects of the present invention are not limited to these.

[0017]

As described above, according to the present invention, the charge / discharge cycle characteristics of a nonaqueous electrolyte secondary battery using a carbon material as a negative electrode can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylindrical nonaqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 2 is a view showing cycle characteristics of a battery of an example.

FIG. 3 is a diagram showing high-temperature cycle characteristics of a battery of an example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 positive electrode plate 2 negative electrode plate 3 separator 4 positive electrode lead 5 negative electrode lead 6 insulating plate 7 insulating plate 8 battery case 9 sealing plate 10 positive electrode terminal 11 expansion material

Continuing on the front page (72) Inventor Yasuhiko Mito 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-5-121101 (JP, A) JP-A-4-294,071 (JP, A) JP-A 52-134615 (JP, U) (58) Fields investigated (Int. . ^7, DB name) H01M 10/40

Claims (2)

(57) [Claims] 1. An electrode plate group in which a positive electrode plate having reversibility to charge and discharge and a negative electrode plate made of a carbon material as an active material are spirally wound via a separator, a non-aqueous electrolyte, and the electrode plate A non-aqueous electrolyte secondary battery comprising a heat-expandable material and a thermosetting resin filled in a shaft space of a group. A positive electrode plate and a carbon material having a reversible relative wherein the charge and discharge negative electrode plate and the electrode group was wound spirally with the separator to an active material, and a nonaqueous electrolyte battery jar Income
And a heat-expandable material in the axial space of the electrode group.
A method for producing a non-aqueous electrolyte secondary battery, comprising a step of filling a filler and a thermosetting resin , heating after sealing.