JP3457462B2 - Non-aqueous electrolyte secondary battery - 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 having high safety and high weight energy density.

[0002]

2. Description of the Related Art In recent years, electronic devices have become smaller and more portable, and as a power source for driving these devices, they have become small-sized, lightweight, high energy density, long-life secondary batteries with excellent charge / discharge cycle characteristics. Is highly demanded. Therefore, recently, a material capable of doping / dedoping lithium ions such as lithium, a lithium alloy, or a carbon material is used as a negative electrode active material,
Research on non-aqueous electrolyte secondary batteries using lithium composite oxides such as lithium cobalt composite oxides as positive electrode active materials
Some are under development and some are already in practical use.

Conventionally, such a non-aqueous electrolyte secondary battery has been
Generally, one spiral electrode is housed in a cylindrical can.

By the way, since the non-aqueous electrolyte secondary battery has a high energy density and uses an organic solvent as an electrolytic solution as described above, when a short circuit occurs inside the battery, it generates heat due to an excessive current, which is the worst case. In this case, the battery may burst. The risk of rupture increases as the capacity per battery increases, because the energy flowing into the short circuit increases. For this reason, a plurality of batteries housed in a battery can having a relatively small capacity are connected to ensure safety. However, this method has a problem that the weight of the battery can becomes relatively large with respect to the total weight of the battery. Alternatively, there is also a method of providing an explosion-proof valve or the like that releases the pressure and shuts off the current when the pressure inside the battery increases, but the structure is complicated and the cost increases.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a non-aqueous electrolyte secondary battery having a simple structure, high safety and high weight energy density.

[0006]

In order to solve the above-mentioned problems, a non-aqueous electrolyte secondary battery of the present invention is provided with a strip-shaped electrode in which a strip-shaped positive electrode and a strip-shaped negative electrode are laminated with a separator interposed between them. a plurality of spiral <br/> can-shaped electrode formed by winding an electrode spirally arranged, are assembled by closely these, accommodating the electrode group and the set in regular hexagonal cylindrical battery can, between the electrodes Connected in parallel via leads , and each lead
It is characterized by having an overcurrent interruption function . Here, the lead has a constriction in a part thereof, or a part thereof.
It is preferable to have an overcurrent cutoff function by using different materials .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the non-aqueous electrolyte secondary battery of the present invention will be described below. 1 is a fragmentary plan view of the non-aqueous electrolyte secondary battery of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG.
[Fig. 3] is an explanatory diagram of a case where an assembled battery is used.

In the non-aqueous electrolyte secondary battery 1 of the present invention, a spiral electrode having the same diameter is formed by spirally winding a strip electrode in which a strip positive electrode 2 and a strip negative electrode 3 are laminated via a separator 4. 5) Providing 7 electrodes, and centering on one of these electrodes, the remaining 6 electrodes are assembled in an annular and intimate contact,
The assembled electrode group is housed in a bottomed regular hexagonal tubular battery can 6, and the electrodes 5 and 5 are connected in parallel via leads 7 and 8. In FIG. 2, reference numeral 9 is a positive electrode cap, and 10 is a packing for insulating the battery can 6 and the positive electrode cap 9 and maintaining airtightness. In addition,
A non-aqueous electrolytic solution is injected into the battery can 6. In the above description, “through a lead” includes not only a case where the electrodes are directly connected to each other through a lead, but also a case where the electrodes are further connected through a positive electrode cap 9 and a battery can 6 which have electrical continuity.

The housing of the plurality of electrodes 5 in the battery can 6 is
This is to reduce the capacity of each electrode 5 and to reduce the energy that flows into the electrode 5 even when a short circuit occurs, thereby improving safety. The reason why the battery can 6 has a regular hexagonal cylindrical shape is that the volume efficiency is the best for accommodating an electrode group in which seven spiral electrodes 5 having the same diameter are assembled, and a plurality of single cells are used. This is because when the cells are assembled into a battery pack, the gaps 11 can be reduced as shown in FIG. 3 and the energy density can be increased. The reason why the electrodes are connected in parallel is that the voltage may become too high and the electrolytic solution may be decomposed in series connection.

Here, it is preferable in order to ensure safety that the leads 7 and 8 connecting the spiral electrodes 5 and 5 have an overcurrent blocking function. A lead having an overcurrent cutoff function is, for example, one in which a part of the lead has a constriction to increase the resistance so that it melts down due to an overcurrent. There is a method in which the material of the leads is partially different (for example, the resistance is high, the melting point is low, etc.), and the leads are blown by an overcurrent. Among these, those in which a part of the lead has a constriction and those in which the material of the lead is partly different are preferable because the structure is simple and the cost is advantageous. Further, the lead having the overcurrent interruption function can be used for the positive electrode 2, the negative electrode 3, or the both electrodes 2, 3. The material of the positive electrode lead 7 is aluminum, and the material of the negative electrode lead 8 is
Copper or nickel is generally used as the material of the material, but is not limited to such material.

The non-aqueous electrolyte secondary battery in the present invention is not particularly limited as long as it is a secondary battery using a non-aqueous electrolyte solution in which an electrolyte such as a lithium salt is dissolved in an organic solvent. Specific examples of the positive electrode active material, the organic solvent and the electrolyte include the following.

The negative electrode active material is preferably a carbon material capable of being doped or dedoped with lithium ions, and examples of such a carbon material include pyrolytic carbons, cokes, calcined organic polymer compounds, graphite and glassy carbons. Etc.
The positive electrode active material is not particularly limited as long as it is a material that can be doped with lithium and dedoped, but a lithium transition metal composite oxide is preferable, and specifically, LiCoO ₂ , LiM
nO ₂ , LiNiO ₂ , LiCrO ₂ , LiMn ₂ O ₄
Etc.

The organic solvent is not particularly limited, and examples thereof include ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, dipropyl carbonate, γ-butyrolactone and the like. One kind or a mixed solvent of two or more kinds can be used. Further, as the electrolyte, LiPF ₆ , LiBF ₄ , LiC
lO ₄ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO
₃ , LiC (CF ₃ SO ₂ ) _{3, and the} like, and one or more of these may be used in combination.

[0014]

EXAMPLES The present invention will be described more specifically below with reference to examples. The examples are illustrative of the invention and are not intended to limit the invention. Example 1 A spiral electrode 5 in FIG. 1 is obtained by disposing a polypropylene separator 4 between a strip-shaped positive electrode 2 and a strip-shaped negative electrode 3 and spirally winding the same. Here, the positive electrode 2 has a thickness of 20 μm.
A mixture of 90 parts by weight of lithium cobalt composite oxide, 5 parts by weight of graphite powder, 5 parts by weight of polyvinylidene fluoride resin, and 50 parts by weight of N-methylpyrrolidone was applied, dried and rolled on both sides of the aluminum foil of m. Is. The negative electrode 3 was obtained by applying a mixture of 90 parts by weight of graphite powder, 10 parts by weight of polyvinylidene fluoride resin and 100 parts by weight of N-methylpyrrolidone on both surfaces of a copper foil having a thickness of 15 μm,
It is dried and rolled. A positive electrode lead 7 is welded to the positive electrode 2 and a negative electrode lead 8 is welded to the negative electrode 3. In addition, the positive electrode lead 7 used has a thickness capable of being fused by a current of 20A. The battery group in which seven spiral electrodes (5) are assembled is loaded into a regular hexagonal tubular battery can 6, and then, between the positive electrode lead 7 and the positive electrode cap 9, and between the negative electrode lead 8 and the battery can 6.
Welded between. Next, ethylene carbonate 50vol
% Lithium and 50% by volume of diethyl carbonate, lithium hexafluorophosphate was dissolved at a concentration of 1 mol / L, the adjusted non-aqueous electrolyte was injected into the battery can 6, and the battery can 6 was charged through the packing 10. The positive electrode cap 9 was fixed and the battery can 6 was sealed by caulking the upper part of the above to obtain the non-aqueous electrolyte secondary battery 1. Table 1 shows the charge / discharge test results and the nail penetration test results of the non-aqueous electrolyte secondary battery 1 thus manufactured.
Shown in. The charge / discharge test was conducted in the voltage range of 2.5 to 4.1.
V and the charge / discharge current was 1000 mA. In addition, the nail penetration test was conducted on a battery 1 charged to 4.1V with a diameter of 3 m.
It was performed by pushing in (penetrating) the nail 12 of m at a constant speed of 5 cm per minute.

COMPARATIVE EXAMPLE 1 One spiral electrode produced by increasing the length of the positive electrode and the negative electrode in Example 1 to 7 was loaded into a cylindrical battery can.
Next, the same electrolytic solution as in Example 1 was injected into the battery can, and the upper part of the battery can was caulked to seal the battery can, thereby forming a non-aqueous electrolyte secondary battery. Table 1 shows the charge / discharge test results and the nail penetration test results of the non-aqueous electrolyte secondary battery thus manufactured.

Comparative Example 2 One spiral electrode made of a positive electrode and a negative electrode having the same length and width as in Example 1 was loaded into a cylindrical battery can. Next, the same electrolytic solution as in Example 1 was injected into the battery can, and the upper part of the battery can was caulked to seal the battery can, and the non-aqueous electrolyte secondary battery (diameter 18 mm, length 65 mm). And Table 1 shows the charge / discharge test results and the nail penetration test results of the non-aqueous electrolyte secondary battery thus manufactured.

Comparative Example 3 Seven non-aqueous electrolyte secondary batteries produced in the same manner as in Comparative Example 2 were combined and connected in parallel to form an assembled battery. Table 1 shows the charge / discharge test results of the non-aqueous electrolyte secondary battery thus produced.

[0018]

[Table 1] Table 1 Discharge capacity Weight energy tight nail penetration test (MAh) degree (Wh / kg) Battery of Example 1 4620 123 * 1 Battery of Comparative Example 1 4630 125 Explosion from positive electrode cap part Battery of Comparative Example 2 660 125 * 2 Battery of Comparative Example 3 4590 100 Not implemented * 1: Temperature and internal pressure increased Although a part of the positive electrode lead was fused, it did not burst. * 2: Although the temperature and internal pressure increased, it did not burst.

As can be seen from Table 1, battery 1 of Example 1
Shows a high weight energy density similar to Comparative Example 1,
Moreover, the nail puncture test did not result in rupture, and the safety was high. Although the battery of Comparative Example 2 has no problem in safety, Comparative Example 3 in which a plurality of batteries are combined in order to increase the capacity.
In the assembled battery of (1), the weight of the battery can was relatively large with respect to the entire battery, so that a sufficiently high weight energy density could not be obtained.

[0020]

As described above, according to the non-aqueous electrolyte secondary battery of the present invention, the battery can has a plurality of electrodes.
Therefore, reduce the capacitance of each electrode, and
The energy that flows into this unit can be reduced to improve safety.
You can In addition, each lead connecting the electrodes is
Since it has a flow blocking function, it can be
Is preferred. Also, there is a constriction in a part of the lead, or
Has an overcurrent cutoff function by changing some materials.
Therefore, the structure is simple and the cost is advantageous.

[Brief description of drawings]

FIG. 1 is a fragmentary plan view of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an explanatory diagram of a case where an assembled battery is used.

[Explanation of symbols]

1 Non-aqueous electrolyte secondary battery 2 positive electrode 3 Negative electrode 4 separator 5 spiral electrode 6 regular hexagonal battery cans 7,8 leads

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Claims (2)

(57) [Claims] 1. A provided strip-shaped cathode and a strip-shaped anode and the strip electrodes laminated via a separator, the strip electrodes provided with a plurality of spiral electrodes formed by winding spirally, these
Were assembled by closely accommodates the electrode group was the aggregate in regular hexagonal cylindrical battery can, it becomes connected in parallel between the electrodes through the lead, each lead having an overcurrent interrupting function <br /> A non-aqueous electrolyte secondary battery characterized by the following. 2. The lead has a constriction in a part thereof,
Or overcurrent cutoff function by changing some materials
The non-aqueous electrolyte electrolyte according to claim 1, characterized in that
Next battery.