JP2000164197A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent internal shortage between electrodes in manufacturing of a nonaqueous electrolyte secondary battery. SOLUTION: This secondary battery is provided with a wound electrode body 12 wound as spiral along a direction longitudinally of a first and second band-like electrodes 14 laminated via a band-like separator, nonaqueous electrolyte, a electrode lead 4 bonded with the first electrode 14 or the second electrode 14 along the width direction thereof and posited on the outer periphery of the wound electrode body and a battery can 6 containing the wound electrode body. An opening arranged at an one end of the battery can 6 is sealed to form the secondary battery. An one end 4a longitudinal of the electrode 4 is displaced from an end portion 14a in the width direction of the electrodes 14 and from an end portion 14b along the direction longitudinally of the electrodes 14.

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 a wound electrode body formed in a battery can by laminating a strip-shaped electrode and a strip-shaped separator and then spirally winding them. Things.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable increase in performance and miniaturization of electronic devices such as video cameras and headphone stereos, and improvement of heavy load characteristics and high capacity of secondary batteries serving as power supplies for these electronic devices have been remarkable. The demand for conversion is also increasing. As a secondary battery, a lead secondary battery or a nickel cadmium battery has been conventionally used.

Further, recently, a non-aqueous electrolyte secondary battery using a material capable of doping and undoping lithium ions, such as a lithium metal, a lithium alloy, or a carbon material such as coke or an organic fired body, as a negative electrode material has been developed. Is also being actively conducted.

In such a non-aqueous electrolyte secondary battery, a spirally wound electrode body is used to improve the heavy load characteristics.

A conventional cylindrical non-aqueous electrolyte secondary battery using such a wound electrode body will be described with reference to FIGS.

The non-aqueous electrolyte secondary battery shown in FIG. 4 can be manufactured as follows.

In the negative electrode 2, for example, ground pitch coke, which is a carbon material, can be used as the negative electrode active material carrier. 90 parts by weight of this pitch coke is mixed with 10 parts by weight of polyvinylidene fluoride to form a negative electrode mixture. Dispersing this negative electrode mixture in N-methylpyrrolidone as a solvent,
Make a slurry (paste). Next, this negative electrode mixture slurry is formed into a negative electrode current collector 14 having a thickness of, for example, 10 μm.
m and uniformly dried on both sides of a strip-shaped copper foil. After drying, compression molding and cutting, width 41.5mm, length 2
A 90 mm strip-shaped negative electrode 2 is obtained.

As shown in FIG. 3, the strip-shaped negative electrode 2 is provided with a negative electrode mixture layer 2 a on both surfaces of a negative electrode current collector 14.
The negative electrode mixture layer 2a is not formed in a certain range near the end 14a along the width direction of No. 4.

Near the end portion 14a of the negative electrode current collector 14 in the width direction, a long and narrow plate-shaped negative electrode lead 4 made of nickel is provided along the width direction and joined to the negative electrode current collector 14.

In this case, one end 4a of the negative electrode lead 4 in the longitudinal direction has an end 1a along the longitudinal direction of the negative electrode current collector 14.
Attach by welding so as to coincide with 4b. This is because the contact area between the negative electrode current collector 14 and the negative electrode lead 4 is increased,
This is to increase the welding strength with the steel as much as possible.

Next, in the positive electrode 1, for example, 0.5 mol of carbon lithium and 1 mol of carbon cobalt are mixed,
LiCoO ₂ obtained by baking in air for 5 hours can be used as the positive electrode active material. This LiCoO ₂ 9
1 part by weight, 6 parts by weight of graphite as a conductive agent,
3 parts by weight of polyvinylidene fluoride as a binder is mixed to prepare a positive electrode mixture. This positive electrode mixture is dispersed in N-methylpyrrolidone as a solvent to form a slurry (paste). Next, this positive electrode mixture slurry was mixed with the positive electrode current collector 15.
Is uniformly applied to both sides of a belt-shaped aluminum foil having a thickness of, for example, 20 μm and dried. After drying and compression molding, a strip-shaped positive electrode 1 having a width of 39.5 mm and a length of 270 mm
Get. The positive electrode lead 5 made of aluminum is welded to the positive electrode current collector 15.

Using the above-mentioned strip-shaped negative electrode 2, strip-shaped positive electrode 1 and a pair of separators 3a, 3b made of a microporous polypropylene film having a thickness of, for example, 25 μm, the negative electrode 2, the separator 3b, the positive electrode 1, and the separator 3a are formed. After laminating in order, the spirally wound electrode body 12 can be obtained by spirally winding this laminated body many times in the longitudinal direction.

FIG. 5 shows a partial cross section of the outer peripheral portion of such a wound electrode body 12.

As shown in FIG. 5, the negative electrode current collector 1 of the negative electrode 2
Negative electrode lead 4 attached near the end 14a of the negative electrode 4
Are located on the outer peripheral surface 13 side of the wound electrode body 12.

As shown in FIG. 4, one end 4a of the negative electrode lead 4 coincides with the tip M of the negative electrode 1 in the spirally wound electrode body 12.

In the wound electrode body 12, the negative electrode 2 protrudes from the upper and lower ends of the positive electrode 1 at the upper and lower ends thereof.
In the example shown in (1), each of the upper and lower ends protrudes by 1 mm. The width of the separators 3a and 3b is wider than the width of the negative electrode 2. The positive electrode lead 5 is located on the innermost peripheral side of the spirally wound electrode body 12.

According to the structure of the spirally wound electrode body 12 described above, the electrode area can be made relatively large and the current per unit area becomes small even when a large current flows, so that excellent heavy load characteristics can be obtained. . The negative electrode current collector 14 and the positive electrode current collector 1
5 is preferably as thin as possible in order to increase the capacity of the battery (fill the active material or active material carrier as much as possible).

Next, the spirally wound electrode body 12 shown in FIG.
As shown in the figure, a nickel-plated iron battery can 6
Housed inside.

At this time, insulating plates 4a and 4b are respectively provided on the upper and lower surfaces of the wound electrode body 12, and the other end 4b side (see FIG. 3) of the negative electrode lead 4 attached to the negative electrode current collector 9 is connected to the battery. Can 6
And the positive electrode lead 5 attached to the positive electrode current collector 15 is welded to the projection 10a of the metal safety valve 10.

A non-aqueous electrolyte as a non-aqueous electrolyte is obtained by dissolving LiPF ₆ at a ratio of 1 mol / l in a mixed solvent of, for example, propylene carbonate and 1,2-dimethoxyethane in the same volume. Inject.

Thereafter, the upper end portion 20 of the battery can 6 is swaged through the safety valve 10 and the metal cover 9 made of metal and the insulating sealing gasket 8 which are in close contact with each other to seal the battery can 6. I do. Thereby, the battery lid 9 and the safety valve 10 can be fixed, and the airtightness in the battery can 6 can be maintained.

FIG. 6 is a sectional view showing the vicinity of the upper end 20 of the battery can 6 before the battery can 6 is sealed. Insulating sealing gasket material 8 and safety valve 10 from opening 6a of battery can 6
After the battery lid 9 is fitted into the inner peripheral surface of the upper end 20 of the battery can 6, the upper end 20 of the battery can 6 and the insulating sealing gasket material 8 are deformed by deforming the battery can 6 from the direction of arrow a in the figure. The battery can 6 is sealed.

At this time, the annular extension 8a of the gasket 8 comes into contact with the outer peripheral surface of the insulating plate 4a, so that the insulating plate 4a comes into close contact with the upper surface of the spirally wound electrode body 12.

In the battery manufactured as described above, as shown in FIG. 4, at the deformed portion L of the battery can 6 corresponding to the upper end portion 20 of the battery can 6 shown in FIG. The outer peripheral surface is deformed into an annular concave shape.

As described above, a cylindrical non-aqueous electrolyte secondary battery having a diameter of 14 mm and a height of 50 mm can be manufactured. The cylindrical non-aqueous electrolyte secondary battery has a safety valve 10, a stripper 36, and an intermediate fitting made of an insulating material for integrating the safety valve 10 and the stripper 36 in order to constitute a double safety device. A combination 35 is provided. Although not shown, the safety valve 10 is provided with a cleaving portion which is cleaved when the safety valve 10 is deformed, and the battery lid 9 is provided with a hole.

In the event that the internal pressure of the battery rises for some reason, the safety valve 10 is turned around the projection 10a as shown in FIG.
So that the connection between the positive electrode lead 12 and the protruding portion 34a is cut off to cut off the battery current, or the gas generated in the battery is opened by the rupture of the safety valve 10 being opened. Each is configured.

[0027]

However, a battery using the above-mentioned wound electrode body has a problem that an internal short-circuit is likely to occur during the manufacture of the battery.

This is because the negative electrode lead 4 is present inside the portion L where the battery can 6 is deformed by caulking as shown in FIG. This is because the inner peripheral surface of the battery can 6 is pressed. The vicinity of the front end M of the negative electrode 2 adjacent to the negative electrode lead 4 via the negative electrode current collector 14 and the separator 3a is pressed, so that the vicinity of the front end M of the negative electrode 2 penetrates through the separator 3b and the positive electrode 1 In contact with the vicinity of the front end N. As a result, the battery causes an internal short circuit.

When the negative electrode lead 4 is pressed and deformed because the negative electrode current collector 14 is thin due to high capacity and the separators 3a and 3b are easily deformed because of the microporous polypropylene film, The adjacent negative electrode 2 via the negative electrode current collector 14 and the separator 3a is deformed and comes into contact with the positive electrode 1.

An object of the present invention is to provide a battery that prevents the above-described internal short circuit.

[0031]

SUMMARY OF THE INVENTION The present invention provides first and second embodiments.
A spirally wound electrode body 12 formed by spirally winding the strip electrodes 1 and 2 in a state of being stacked via the strip separators 3a and 3b along the longitudinal direction thereof, and the first or second strip electrode The outer peripheral surface 1 of the spirally wound electrode body 12 is provided along the width direction of the electrode 2 (1) so as to be joined to the electrode 2 (1).
A battery can 6 comprising an electrode lead 4 located at 3 and a battery can 6 accommodating the wound electrode body 12 and configured to close an opening 6a provided at one end of the battery can 6; One end 4a in the length direction of the electrode lead 4 is preferably shifted at least 1 mm from the end portion 14a along the length direction of the strip electrode 2.

When the first and / or second electrodes 1 and 2 include the band-shaped current collectors 14 and 15, it is preferable that the electrode lead 4 is provided on the band-shaped current collector 14.

Further, the first electrode can form the positive electrode 1 or the negative electrode 2, and the second electrode can form the negative electrode 2 or the positive electrode 1.

[0034]

According to the present invention, one end 4a in the longitudinal direction of the electrode lead 4 is shifted away from the end 14a along the longitudinal direction of the current collector 14, so that when the battery can 6 is sealed, Even when the battery can 6 is deformed, the electrode lead 4 does not exist at the end of the outer peripheral surface 13 of the wound electrode body 12 corresponding to the deformed portion L. Therefore, in the step of closing the battery can 6, the electrode lead 4 is not pressed by the battery can 6, so that the tip M of one electrode 2 in the wound electrode body 12 penetrates through the separator 3a and the other end. Contact with the tip N of the electrode 1 can be prevented.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to FIGS. The same parts as those in the conventional example described with reference to FIGS. 3 to 6 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 is a perspective view showing the strip-shaped negative electrode 2 in which the negative electrode lead 4 is attached to the strip-shaped negative electrode current collector 14.

As shown in FIG. 1, a negative electrode lead 4 is provided near an end portion 14a along the width direction of the negative electrode current collector 14, and one end 4a of the negative electrode current collector 14 in the length direction thereof is disposed in the length direction of the negative electrode current collector 14. It was attached by welding so as to be shifted by 1 mm from the end 14b along the edge. Accordingly, the distance l ₁ between the end portion 14b along the length of the end 4a in the longitudinal direction of the negative electrode lead 4 and the negative electrode current collector 14 is 1 mm.

Since the width of the negative electrode is 41.5 mm,
Length of the portion negative electrode lead 4 are polymerized or bonded to the negative electrode current collector 14 (welding length) l ₂ is 40.5 mm.

The negative electrode lead 4 has a thickness of 50 μm and a width of 4 mm. The thickness of the negative electrode lead 4 is preferably about 40 to 100 μm from the viewpoint of securing strength.

The welding for attaching the negative electrode lead 4 to the current collector 14 can be performed by ultrasonic welding, spot welding, laser welding, or the like.

Except for using the strip-shaped negative electrode 1 as described above,
A cylindrical non-aqueous electrolyte secondary battery having a diameter of 14 mm and a height of 50 mm was produced in the same manner as the battery shown in FIG. This battery is referred to as A for convenience.

FIG. 2 shows a schematic longitudinal section of the non-aqueous electrolyte secondary battery produced as described above.

As shown in FIG. 2, the outer periphery of the wound electrode body 12
One end 4a of the negative electrode lead 4 located on the surface 13 is
1 mm from the tip M of the adjacent negative electrode 2 via the parator 3a
(L ₁).

Therefore, even if the upper end 20 of the battery can 6 is deformed in order to seal the opening 6a of the battery can 6 by caulking, the upper end of the outer peripheral surface 13 of the spirally wound electrode body 12 corresponding to the deformed portion L is formed. The negative electrode lead 4 does not exist. Therefore, in the step of sealing the battery can 6, the negative electrode lead 4 is
Therefore, it is possible to prevent a portion near the tip M of the negative electrode 2 from penetrating through the separator 3a and coming into contact with a portion near the tip N of the positive electrode 1.

Next, l ₁ in FIG.
Cylindrical non-aqueous electrolyte secondary batteries B, C, and D similar to FIG. 2 except that they were 10 mm and 38 mm, respectively, were produced.

[0046] As a comparative example for confirming the effect of the present invention, except that the l ₁ in FIG. 1 and 0mm are
A cylindrical nonaqueous electrolyte secondary battery E (battery substantially the same as the conventional battery shown in FIG. 4) similar to that of FIG. 2 was produced.

[0047] In the above-described battery D (the l ₁ is 38mm Figure 1), the negative electrode lead 4 will be taken from the current collector 14 during cell fabrication, it was not possible to complete the battery.

Accordingly, 50 batteries were prepared for each of the four types of batteries A, B, C, and E, and the occurrence rate of internal short-circuit products in each of these batteries was examined.

The results are shown in Table 1 below.

[0050]

[Table 1]

As can be seen from Table 1 above, in the batteries A, B and C in which the value of l ₁ is 1 mm, 5 mm and 10 mm, the occurrence rate of the internal short circuit is 0%, and the occurrence of the internal short circuit is not recognized. ,
The effect of the present invention has appeared.

Meanwhile, in the battery E value of _{l 1} is 0 mm 3
% Of internal short-circuit products have occurred. When the battery in which the internal short circuit occurred was disassembled and observed, the portion near one end 4a of the negative electrode lead 4 was deformed together with the upper end portion of the negative electrode current collector 14 to which the negative electrode lead 4 was attached. And the deformed portion of the negative electrode current collector 14 is the separator 3a.
Was breaking. Then, the negative electrode 2 was deformed in the vicinity of the tip M, and the deformed portion of the tip M was broken by the separator 3b and was in contact with the vicinity of the tip N of the positive electrode 1.

As described above, in the cylindrical non-aqueous electrolyte secondary battery having the wound electrode body, in order to prevent an internal short circuit, the length of the electrode lead located on the outer peripheral surface of the wound electrode body is reduced. Distance l between one end and end along the length of current collector
_It can be seen that 1 must be at least 1 mm apart.

[0054] Further, when the end distance l ₁ of the above increases, the contact area between the electrode lead and the current collector is reduced,
It is not preferable because the welding strength is reduced and the electrode lead is separated from the current collector or the electric resistance is increased.

Therefore, the distance l ₁ between the ends and the welding length l
_As for the relationship with ₂ , it is desirable that l ₂ / (l ₁ + l ₂ ) be 0.1 or more.

In the non-aqueous electrolyte secondary battery of this embodiment, a material capable of doping and undoping lithium can be used for the negative electrode. Such materials include:
Examples thereof include conductive polymers such as lithium metal, lithium alloy, and polyacetylene, and carbon materials such as coke.

Further, a transition metal compound such as manganese dioxide or vanadium pentoxide, a transition metal chalcogen compound such as iron sulfide, or a composite compound of these compounds and lithium (lithium-cobalt composite oxide, Lithium-cobalt-nickel composite oxide) can be used.

As the non-aqueous electrolyte, for example, a non-aqueous electrolyte obtained by dissolving a lithium salt in an organic solvent (non-aqueous solvent) can be used.

Here, the organic solvent is not particularly limited. For example, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-
Diequitocietane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolan, 4-methyl-1,3-
Dioxolan, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like can be used alone or in combination of two or more. As the electrolyte, any of conventionally known electrolytes can be used.
ClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , L
iB (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO
₃ Li, CF ₃ SO ₃ Li, and the like.

The non-aqueous electrolyte may be solid, for example, a polymer complex solid electrolyte.

[0061]

As described above, according to the present invention, in a battery having a spirally wound electrode body, it is possible to prevent an internal short circuit caused by an electrode lead which is likely to occur during a step of sealing a battery can. it can. Therefore, the yield in battery manufacture is increased, and the productivity of the battery is improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a strip-shaped negative electrode used in a cylindrical nonaqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of a non-aqueous electrolyte secondary battery using the negative electrode shown in FIG.

FIG. 3 is a perspective view of a strip-shaped negative electrode used in a conventional non-aqueous electrolyte secondary battery.

4 is a schematic longitudinal sectional view of a conventional nonaqueous electrolyte secondary battery using the negative electrode shown in FIG.

5 is a partial cross-sectional view of the wound electrode body before being housed in the battery shown in FIGS. 2 and 4. FIG.

FIG. 6 is a longitudinal sectional view of an upper end portion of the battery before the battery shown in FIGS. 2 and 4 is sealed.

[Explanation of symbols]

2 strip-shaped negative electrode (first or second electrode) 3a strip-shaped separator 3b strip-shaped separator 4 negative electrode lead (electrode lead) 4a one end in the length direction of the negative electrode lead 6 battery can 6a opening 12 wound electrode body 13 outer peripheral surface 14 negative electrode collection Current collector (strip current collector) 14a End portion along width direction of negative electrode current collector or strip electrode 14b End portion along length direction of negative electrode current collector or strip electrode

Claims (8)

[Claims] A non-aqueous electrolyte comprising: a spirally wound electrode body formed by spirally winding a first and a second strip-shaped electrode along a longitudinal direction thereof in a state of being stacked via a strip-shaped separator; An electrode lead provided along the width direction of the first or second strip-shaped electrode and joined to the electrode and located on the outer peripheral surface of the wound electrode body; and a battery can housing the wound electrode body In a battery configured to seal an opening provided at one end of the battery can, one end in a length direction of the electrode lead is shifted from an end in a width direction of the electrode, and A non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte secondary battery is displaced from an end along a length direction of the strip electrode. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein said negative electrode is made of a material which can be doped with lithium and de-dove. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein a carbon material is used for the negative electrode. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein a transition metal compound or a lithium / transition metal compound is used for the positive electrode. 5. A first and a second strip-shaped electrode formed by applying an electrode mixture of a positive electrode and a negative electrode to both sides of a strip-shaped current collector and laminated along a strip-shaped separator along a length direction thereof. And a spirally wound spirally wound electrode body, a non-aqueous electrolyte, and a spirally wound electrode provided along with the first or second strip-shaped electrode in a width direction thereof. Comprising an electrode lead located on the outer peripheral surface of the body, and a battery can housing the wound electrode body,
In a battery configured to seal an opening provided at one end of the battery can, one end in a length direction of the electrode lead is shifted from an end in a width direction of the electrode, and a length of the strip-shaped electrode. A non-aqueous electrolyte secondary battery which is shifted from an end along a direction. 6. The non-aqueous electrolyte secondary battery according to claim 5, wherein a material capable of doping and undoping lithium is used for the negative electrode. 7. The non-aqueous electrolyte secondary battery according to claim 5, wherein a carbon material is used for the negative electrode. 8. The non-aqueous electrolyte secondary battery according to claim 5, wherein a transition metal compound or a lithium / transition metal compound is used for the positive electrode.