JP3203517B2 - Battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of forming a spirally wound electrode body in a battery can by laminating a strip-shaped electrode and a strip-shaped separator and then winding them in a spiral shape. The present invention relates to a battery provided in a battery.

[Summary of the Invention]

The present invention relates to a wound electrode body formed by spirally winding a band-shaped electrode and a band-shaped separator in which an electrode mixture is formed on both surfaces of a band-shaped current collector, and along a width direction of the band-shaped electrode. In a battery including a provided electrode lead and a battery can accommodating the wound electrode body, by displacing one end of the electrode lead from an end along the width direction and an end along the length direction of the electrode. This prevents the occurrence of an internal short circuit in the battery assembly process.

[Conventional technology]

In recent years, there has been a remarkable increase in the performance and miniaturization of electronic devices such as video cameras and headphone stereos, and there is also a demand for improving the heavy load characteristics and increasing the capacity of secondary batteries that power these electronic devices. It is getting stronger. As a secondary battery, a lead secondary battery or a nickel cadmium battery has been conventionally used.

Furthermore, recently, active development of non-aqueous electrolyte secondary batteries using lithium ion-doped and undoped substances as negative electrode materials, such as carbon materials such as lithium metal and lithium alloys or coke and fired organic materials, has also been active. It is being done.

In such a nonaqueous 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, pulverized 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 polyvinylidene fluoride 10
The parts by weight are mixed to form a negative electrode mixture. This negative electrode mixture is dispersed in N-methylpyrrolidone as a solvent to form a slurry (paste). Next, the negative electrode mixture slurry is uniformly applied to both surfaces of a strip-shaped copper foil having a thickness of, for example, 10 μm as the negative electrode current collector 14 and dried. After drying, compression molding and cutting are performed to obtain a strip-shaped negative electrode 2 having a width of 41.5 mm and a length of 290 mm.

As shown in FIG. 3, the strip-shaped negative electrode 2 is a negative electrode current collector 14.
A negative electrode mixture layer 2a is provided on both surfaces of the negative electrode current collector 14, and the negative electrode mixture layer 2
does not form a.

Near the end portion 14a of the negative electrode current collector 14 in the width direction, an elongated plate-shaped negative electrode lead 4 made of nickel is provided along the width direction so as to overlap the negative electrode current collector 14.

In this case, the negative electrode lead 4 is attached by welding so that one end 4a in the length direction thereof coincides with the end 14b along the length direction of the negative electrode current collector 14. This is the negative electrode current collector
This is because the welding strength between the negative electrode current collector 14 and the negative electrode lead 4 is increased as much as possible by increasing the contact area between the negative electrode current collector 14 and the negative electrode lead 4.

Next, in the positive electrode 1, for example, LiCoO ₂ obtained by mixing 0.5 mol of carbon lithium and 1 mol of carbon cobalt and calcining the mixture in air at 900 ° C. for 5 hours can be used as the positive electrode active material. To 91 parts by weight of LiCoO _2, 6 parts by weight of graphite as a conductive agent and 3 parts by weight of polyvinylidene fluoride as a binder are 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, the positive electrode mixture slurry is uniformly applied to both sides of a belt-shaped aluminum foil having a thickness of, for example, 20 μm as the positive electrode current collector 15, and dried. Compression molding after drying, width 39.5mm, length 270mm
Is obtained. The positive electrode lead 5 made of aluminum is welded to the positive electrode current collector 15.

A negative electrode 2 and a separator were formed by using a pair of separators 3a and 3b made of a strip-shaped negative electrode 2, a strip-shaped positive electrode 1 and a microporous polypropylene film having a thickness of, for example, 25 μm as described above.
After laminating 3b, the positive electrode 1, and the separator 3a in this order, the laminated body is spirally wound many times in the longitudinal direction to obtain the wound electrode body 12.

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 end portion 14 of the negative electrode current collector 14 of the negative electrode 2
The negative electrode lead 4 attached near the a
2 is located on the outer peripheral surface 13 side.

Further, as shown in FIG.
Corresponds to the tip M of the negative electrode 1 in the wound electrode body 12.

In the spirally 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, and in the example shown in FIG. 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 wound electrode body 12 as described above, the electrode area can be made relatively large, and even if a large current flows, the current per unit area becomes small, so that excellent heavy load characteristics can be obtained. Note that the thickness of the negative electrode current collector 14 and the positive electrode current collector 15 is preferably as small as possible in order to increase the capacity of the battery (fill the active material or the active material carrier as much as possible).

Next, as shown in FIG. 4, the wound electrode body 12 shown in FIG. 5 is housed in a nickel-plated iron battery can 6.

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

In this battery can 6, for example, propylene carbonate
A non-aqueous electrolyte as a non-aqueous electrolyte in which LiPF ₆ is dissolved at a ratio of 1 mol / in a mixed solvent of equal volume with 1,2-dimethoxyethane is injected.

Thereafter, the battery can 6 is sealed by caulking the upper end portion 20 of the battery can 6 through the safety valve 10 and the metal cover 9 and the insulating sealing gasket 8 whose outer circumferences are in close contact with each other. 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 portion 20 of the battery can 6 before the battery can 6 is sealed. After the insulating sealing gasket material 8 and the safety valve 10 and the battery lid 9 are fitted into the inner peripheral surface of the upper end portion 20 of the battery can 6 from the opening 6a of the battery can 6, the upper end portion 20 of the battery can 6 and the insulating sealing gasket material 8 The battery can 6 is crimped by deforming the battery can 6 from the direction of arrow a in the drawing, whereby 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 is in 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 by caulking of the battery can 6 corresponding to the upper end portion 20 of the battery can 6 in FIG. The surface is deformed into a ring-shaped recess.

As described above, for example, a cylindrical nonaqueous 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 includes 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 to constitute a double safety device. It has a coalescence 35. Although not shown in the drawings, the safety valve 10 is provided with a cleavage portion that is cleaved when the safety valve 10 is deformed, and the battery lid 9 is provided with a hole.

If the internal pressure of the battery rises for some reason, the safety valve 10 is deformed upward in FIG. 4 around the projection 10a, and the connection between the positive electrode lead 12 and the projection 34a is cut off. To shut off the current or use a safety valve
Each of the ten cleavage parts is configured to cleave and exhaust gas generated in the battery.

[Problems to be solved by the invention]

However, the battery using the wound electrode body as described above is
There has been a problem that an internal short circuit is likely to occur during battery production.

This is because the negative electrode lead 4 exists inside the portion L where the battery can 6 is deformed by caulking as shown in FIG.
This is because the vicinity of 4a is pressed against the inner peripheral surface of the battery can 6. 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 to increase the capacity and the separators 3a and 3b are easily deformed due to the microporous polypropylene film, the negative electrode current collector 14 The adjacent negative electrode 2 via the conductor 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 which prevents the above-mentioned internal short circuit.

[Means for solving the problem]

The battery according to the present invention is obtained by laminating first and second strip-shaped electrodes 2 and 1 each having an electrode mixture formed on both sides of strip-shaped current collectors 14 and 15 via strip-shaped separators 3a and 3b. A spirally wound electrode body 12 formed by spirally winding along the length direction
And an outer peripheral surface of the spirally wound electrode body 12 which is provided at the spirally wound end portion of the spirally wound electrode body 12 along the width direction of the first strip-shaped electrode 2 and is joined to the spirally wound electrode body 12. And one end 4a in the length direction is shifted from the end portion 14a along the width direction of the first strip-shaped electrode 2 and along the length direction of the first strip-shaped electrode 2. A first electrode lead 4 shifted from an end portion 14b and a second electrode provided at the inner peripheral side of the spirally wound electrode body 11 at the spirally wound end portion and joined to the second strip-shaped electrode 1; An electrode lead 5 and a battery can 6 containing the wound electrode body 12;
One of the second strip-shaped electrodes 2, 1 is wider than the other electrode 1, and is configured to seal an opening 6 a provided at one end of the battery can 6. ing. It is preferable that both the deviation from the end 14a along the width direction and the deviation from the end 14b along the length direction are at least 1 mm.

A current collector in which the first and / or second electrodes 1 and 2 are band-shaped;
In the case where the electrode lead 4 is provided, it is preferable that the electrode lead 4 be provided on the strip-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.

[Action]

According to the present invention, one end 4a in the length direction of the electrode lead 4 is offset from the end 14a along the width direction and the end 14b along the length direction of the strip-shaped electrode 2, so that the battery can Even when the battery can 6 is deformed when the battery case 6 is sealed, the electrode lead 4 is attached to the end of the outer peripheral surface 13 of the wound electrode body 12 corresponding to the deformed portion L.
Is configured not to exist. Therefore, in the step of sealing 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 passes through the separator 3a and the other end. Contact with the tip N of the electrode 1 can be prevented.

〔Example〕

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS. The same parts as those of 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 a strip-shaped negative electrode 2 in which a negative electrode lead 4 is attached to a strip-shaped negative electrode current collector 14.

As shown in FIG. 1, the negative electrode lead 4 is disposed near the end 14a of the negative electrode current collector 14 in the width direction, and the one end 4a of the negative electrode current collector 14 is disposed along the length direction of the negative electrode current collector 14. 1mm from end 14b
It was attached by welding so that it only shifted. 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, the length (weld length) l ₂ of the portion where the negative electrode lead 4 overlaps the negative electrode current collector 14 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 40 to 100 μm for securing strength.
m is preferable.

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

A cylindrical nonaqueous 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. 4 except that the strip-shaped negative electrode 1 as described above was used. This battery is referred to as A for convenience.

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

As shown in FIG. 2, one end 4a of the negative electrode lead 4 located on the outer peripheral surface 13 of the spirally wound electrode body 12 is shifted by ₁ mm (l ₁ ) from the tip M of the adjacent negative electrode 2 via the separator 3a. ing.

Therefore, even if the upper end portion 20 of the battery can 6 is deformed in order to close the opening 6a of the battery can 6 by caulking, the negative electrode lead 4 is attached to the upper end of the outer peripheral surface 13 of the wound electrode body 12 corresponding to the deformed portion L. Does not exist. Therefore, in the step of closing the battery can 6, the negative electrode lead 4 is not pressed by the battery can 6, so that a portion near the tip M of the negative electrode 2 penetrates through the separator 3 a and a portion near the tip N of the positive electrode 1. Can be prevented.

Next, l ₁ in FIG. ₁ was changed to 5 mm, 10 mm, and 38 mm, respectively.
2, except that the same cylindrical nonaqueous electrolyte secondary batteries B, C, and D as in FIG. 2 were produced.

Further, as a comparative example for confirming the effect of the present invention, except that the l ₁ in Fig. 1 was 0 mm, Fig. 2 and similar cylindrical non-aqueous electrolyte secondary battery E (prior art shown in FIG. 4 (Battery substantially the same as the above battery).

In the above-mentioned battery D (l 1 in FIG. ₁ is 38 mm), the negative electrode lead 4 was removed from the current collector 14 during battery production, and the battery could not be completed.

Therefore, for each of the above four types of batteries A, B, C, and E, 50 batteries were produced, and the occurrence rate of internal short-circuit products of each of these batteries was investigated.

 The results are shown in Table 1 below.

As can be seen from Table 1 above, the value of l ₁ is 1 mm, 5 mm, 10 mm
In batteries A, B, and C, the rate of occurrence of an internal short circuit was 0%, and no occurrence of an internal short circuit was observed. Thus, the effects of the present invention appeared.

On the other hand, in the battery E value of l ₁ is 0 mm 3% of the internal short-circuit article is generated. 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. The deformed portion of the negative electrode current collector 14 has broken the separator 3a. 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 including the wound electrode body, in order to prevent an internal short circuit, the electrode lead located on the outer peripheral surface of the wound electrode body is gathered with one end in the length direction of the electrode lead. It can be seen that the distance l _{1 from} the end along the length of the conductor must be at least 1 mm.

Further, when the distance l ₁ between the ends is increased, the contact area between the electrode lead and the current collector is reduced, the welding strength is reduced, the electrode lead is separated from the current collector, or the electric resistance is increased. It is not preferable because it becomes.

Therefore, the relationship between the edge distance l ₁ between the weld length l ₂ is l ₂
It is desirable that / (l ₁ + l ₂ ) be 0.1 or more.

In the non-aqueous electrolyte secondary battery of this embodiment, a material that can be doped with lithium and undoped can be used for the negative electrode. Examples of such a material include a conductive polymer such as lithium metal, a lithium alloy, and polyacetylene, and a carbon material such as coke.

In addition, 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 with lithium (lithium-cobalt composite oxide, lithium-cobalt composite oxide) A nickel composite oxide).

Further, 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, but, for example, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxytoshiethane, γ-butyrolactone, terolahydrofuran, 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. Any known electrolyte can be used as the electrolyte.LiClO ₄ , LiAsF ₆ , LiPF
_{6, LiBF 4, LiB (C} 6 H 5) 4, LiCl, LiBr, CH 3 SO 3 Li, CF 3
SO ₃ Li and others.

Further, the non-aqueous electrolyte may be a solid, such as a polymer complex solid electrolyte.

〔The invention's effect〕

Since the present invention is configured as described above, in a battery provided with a wound electrode body, it is possible to prevent an internal short circuit due to an electrode lead which is likely to occur during a step of sealing a battery 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 non-aqueous electrolyte secondary battery according to an embodiment of the present invention, and FIG.
FIG. 3 is a schematic vertical sectional view of a non-aqueous electrolyte secondary battery using the negative electrode shown in FIG. 3, FIG. 3 is a perspective view of a strip-shaped negative electrode used in a conventional non-aqueous electrolyte secondary battery, and FIG. FIG. 5 is a schematic longitudinal sectional view of a conventional nonaqueous electrolyte secondary battery using the negative electrode shown in FIG. 5, and FIG. 5 is a partial view of a wound electrode body before being housed in the battery shown in FIG. 2 and FIG. FIG. 6 is a longitudinal sectional view of the upper end of the battery showing a state before the battery shown in FIGS. 2 and 4 is sealed. In the reference numerals used in the drawings, 2 ... a strip-shaped negative electrode (first or second electrode) 3a, 3b ... a strip-shaped separator 4 ... a negative electrode lead (electrode lead) 4a ... a lengthwise direction of the negative electrode lead One end 6 Battery can 6a Opening 12 Wound electrode 13 Outer peripheral surface 14 Negative electrode current collector (strip-shaped current collector) 14b Along the length direction of negative electrode current collector The end (the end along the length direction of the strip-shaped electrode).

Continuation of the front page (56) References JP-A-1-143140 (JP, A) JP-A-2-92662 (JP, U) JP-A-1-106070 (JP, U) JP-A-1-106071 (JP) , U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01M 2/26 H01M 10/40

Claims (1)

(57) [Claims] 1. A state in which first and second strip-shaped electrodes having an electrode mixture formed on both sides of a strip-shaped current collector are laminated via a strip-shaped separator and spirally wound along the length direction. A wound electrode body formed by being wound; and a winding end provided on the outer peripheral side of the wound electrode body along the width direction of the first strip-shaped electrode and provided with the electrode. Located on the outer peripheral surface of the electrode body,
A first electrode whose one end in the length direction is shifted from the end along the width direction of the first strip-shaped electrode and which is shifted from the end along the length direction of the first strip-shaped electrode A lead, a second electrode lead provided at the inner circumferential end of the wound electrode body at a winding end thereof and joined to the second strip-shaped electrode, and a battery can containing the wound electrode body And wherein the width of one of the first and second strip-shaped electrodes is wider than the width of the other electrode, and the opening provided at one end of the battery can is sealed. Composed battery.