JP2932498B2 - Battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a structure of a battery in which an internal short circuit is effectively prevented, and is applied to a secondary battery using lithium as a charge carrier. The best thing to do.

[Summary of the Invention]

The battery of the present invention has a battery outer can containing a laminated electrode body formed by interposing a separator between a negative electrode and a positive electrode, and a cover for closing an opening provided at one end of the battery outer can. A lid, a plate-shaped safety valve arranged inside the lid, a lead stripper attached to the plate-shaped safety valve inside the plate-shaped safety valve, and an end surface of the laminated electrode body on the lid side. And a sealing gasket interposed between the outer periphery of each of the lid and the plate-shaped safety valve and the one end of the battery outer can, respectively. An extension for pressing the separator in order to make the plate abut on the end face of the laminated electrode body is connected to the sealing gasket, so that the opening of the battery outer can is normally closed between the lid and the plate-shaped safety valve. Closed by both, and Even if the battery becomes abnormal and its internal pressure rises, there is almost no damage to the outside.In addition, the separator is always in good contact with the end face of the laminated electrode body, and the internal short circuit of the battery is effective. In addition, the structure can be simplified without particularly complicating the operation of assembling the battery.

[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.
At the same time, demands for improving the heavy load characteristics and increasing the capacity of secondary batteries serving as power supplies for these electronic devices have been increasing.
As a secondary battery, a lead secondary battery or a nickel cadmium battery has been conventionally used. Furthermore, recently, a non-aqueous electrolyte secondary battery using a material capable of doping and undoping lithium ions, such as lithium metal, a lithium alloy, or a carbonaceous material such as coke or an organic fired body, as a negative electrode active material, The development of lithium secondary batteries is being actively pursued.

The configuration of a conventional example of such a lithium secondary battery will be described with reference to FIGS. 5 and 6. FIG.

In FIG. 5, a spirally wound electrode body 12 includes a strip-shaped positive electrode 1 made of a lithium-cobalt composite oxide (LiCoO ₂ ) and a strip-shaped negative electrode 2 made of a carbonaceous material such as coke. It is configured by spirally winding around the core 11 with the separators 3a and 3b interposed. The width of the strip-shaped separators 3a and 3b is slightly wider than that of the strip-shaped positive electrode 1 and the strip-shaped negative electrode 2. Therefore, as shown in FIG. 5, the upper end and the lower end of the separators 3a and 3b constitute the projecting portions 4 slightly projecting from the positive electrode 1 and the negative electrode 2 on the upper end surface 12a and the lower end surface 12b of the spirally wound electrode body 12. doing. A positive electrode lead plate 9 made of aluminum is attached to the band-shaped positive electrode 1, and a negative electrode lead plate 10 made of nickel is attached to the band-shaped negative electrode 2 for current collection of the respective electrodes.

The wound electrode body 12 is formed by an upper end surface 12a of the wound electrode body 12.
It is housed in a nickel-plated iron battery outer can 5 together with disk-shaped separators 13 and 14 arranged on the lower end surface 12b. The separators 13 and 14 are annularly formed of an insulating material such as a synthetic resin, and have a center hole 13 at the center thereof.
a and 14a, respectively. The separator 13 separates the spirally wound electrode body 12 from the lid 7 and the safety valve 8, and electrically insulates them. The separator 14 separates the spirally wound electrode body 12 from the bottom plate of the battery outer can 5 and electrically insulates them.

Since the upper end surface of the battery outer can 5 is open,
15 has an upper opening. Then, the lid 7 and the safety valve 8 constituting the first and second sealing plates are closed by the upper end 15 of the battery outer can 5 so as to close the upper opening.
Mounted on That is, the outer periphery of the lid 7 and the safety valve 8
Are overlapped with each other, and a sealing gasket 26 is fitted in the overlapped portion. The upper portion of the battery outer can 5 is caulked by the upper end portion 15 of the battery outer can 5 via the sealing gasket 26 to seal the battery outer can 5.

FIG. 6 shows the sealing gasket material 26 before being sealed.
It shows. The sealing gasket material 26 has a flange portion 26a on the inner peripheral surface at the lower end. On the upper surface of the flange portion 26a, as shown by a dashed line in FIG.
The safety valve 8 and the lid 7 are held. The sealing gasket material 26 is inserted into the inner peripheral surface of the upper end portion 15 of the battery outer can 5 as shown by a dashed line in FIG. By caulking, the battery outer can 5 is sealed.

The safety valve 8 is provided with a thin groove (not shown) that is opened when gas or the like is generated in the battery and the internal pressure of the battery rises to a predetermined value or more. The lid 7 is provided with a vent hole (not shown) for allowing the gas to escape. The positive electrode lead plate 9 extends to the safety valve 9 through the center hole 13a of the separator plate 13, and the negative electrode lead plate 10 extends to the bottom surface of the battery outer can 5, and is welded there.

[Problems to be solved by the invention]

However, the lithium secondary battery as described above has a problem that the battery is short-circuited internally during repeated charging and discharging. This is mainly because during the charging of the battery, lithium that is originally deposited uniformly on the surface of the negative electrode or that is to be doped in the negative electrode grows in a dendritic manner as metallic lithium on the upper and lower end surfaces of the negative electrode 2. The dendrite-shaped metallic lithium gets over the protrusions 4 of the separators 3a and 3b on the upper end surface 12a and the lower end surface 12b of the spirally wound electrode body shown in FIG. 5 and comes into contact with the positive electrode 1. As a result, an internal short circuit occurs. Because it causes.

Separator plates are provided on the upper end surface 12a and the lower end surface 12b of the wound electrode body 12.
13 and 14 are arranged. However, even in this case, since the upper separator 13 does not always surely adhere to the upper end surface 12a of the spirally wound electrode body 12, the above-mentioned dendritic lithium metal is provided on the separator 13 side. Separator 3a,
In some cases, the vehicle may get over the protrusion 4 of 3b.

According to the present invention, normally, the opening of the battery outer can is closed by both the lid and the plate-shaped safety valve, and even when the battery is in an abnormal state and its internal pressure is increased, the battery can be damaged externally. In addition, it effectively prevents foreign substances such as deposits from crossing the separator from one electrode side and reaching the other electrode side at the end face on the lid side of the laminated electrode body, effectively preventing the internal short circuit of the battery. It is an object of the present invention to provide a battery that can be prevented in terms of safety and that can simplify the structure without particularly complicating the operation of assembling the battery.

[Means for solving the problem]

The battery of the present invention for achieving the above object has a laminated electrode body configured by interposing a separator between a negative electrode and a positive electrode, a battery outer can containing the laminated electrode body, and a battery outer can. A lid for closing an opening provided at one end, and a plate-shaped safety valve disposed inside the lid to close the opening provided at the one end of the battery outer can. A lead stripper mounted inside the plate-shaped safety valve and attached to the plate-shaped safety valve to constitute a current cut-off device for cutting off the current when the internal pressure of the battery rises to a predetermined value, together with the plate-shaped safety valve. A separator disposed near an end face of the laminated electrode body on the lid side to isolate the laminated electrode body from the lid, the plate-shaped safety valve, and the lead stripper; and And the above plate When connecting the outer periphery of each of the valves to the one end of the battery outer can, the outer periphery of the lid and the plate-shaped safety valve is interposed between the one end of the battery outer can. A sealing gasket, and an extension for pressing the separator in order to bring the separator into contact with the end face of the laminated electrode body is connected to the sealing gasket.

The present invention, as the above-mentioned laminated electrode body, by winding a number of turns in a state where a band-shaped negative electrode and a band-shaped positive electrode using a material capable of doping and undoping lithium as a negative electrode active material with a band-shaped separator interposed therebetween. It is optimally applied to a non-aqueous electrolyte secondary battery using a wound electrode body constituted by interposing the separator between the strip-shaped negative electrode and the strip-shaped positive electrode, that is, a so-called lithium secondary battery. in this case,
As the negative electrode active material, metallic lithium, a lithium alloy, a conductive polymer such as polyacetylene, a carbonaceous material such as coke, or the like can be used, and any of these can be doped and dedoped with lithium. . As the positive electrode active material, transition metal compounds such as manganese dioxide and vanadium pentoxide, transition metal chalcogen compounds such as iron sulfide, and alkali transition metal oxides such as LiCoO ₂ 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) as an electrolyte can be used.

Here, as the organic solvent, for example, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolan, 4-methyl-1,3 -A single solvent such as dioxolan, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile or a mixture of two or more solvents can be used. As the electrolyte, any of conventionally known electrolytes can be used, and specifically,
LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiC
l, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, or the like can be used.

[Action]

Normally, the opening provided at one end of the battery outer can is very effectively closed by both the lid and the plate-shaped safety valve, and when the internal pressure of the battery rises to a predetermined value, the plate-shaped The safety valve operates to release the gas inside the battery outer can to the outside, and the current is cut off by the lead stripper. Further, a plate-shaped safety valve to which the lead stripper is attached and an extension connected to a sealing gasket interposed between the outer periphery of the lid and one end of the battery outer can include a lid, a plate-shaped safety valve. And, in order to isolate the laminated electrode assembly from the lead stripper, a separator disposed near the end face on the lid side of the laminated electrode assembly is pressed, and the separator is brought into contact with the end surface of the laminated electrode assembly. Accordingly, it is possible to extremely effectively prevent foreign substances such as deposits from crossing over the separator from one electrode side and reaching the other electrode side on the end face on the lid side of the laminated electrode body. Moreover, the sealing gasket not only has a function of preventing the internal short circuit of the battery by pressing the separator, but also has a plate-shaped safety valve to which the lead stripper is attached, the outer periphery of the lid, and the one end of the battery outer can. Since the sealing gasket also has a function as a seal material between the cover and the parts, the sealing gasket contributes to maintaining the positions of the lid, the plate-shaped safety valve, the lead stripper, and the separator.

〔Example〕

Hereinafter, an embodiment to which the present invention is applied will be described with reference to FIG. 1 to FIG. The same parts as those in the conventional example shown in FIGS. 5 and 6 are denoted by the same reference numerals, and description thereof will be omitted.

First, the negative electrode 2 was prepared as follows. Using ground pitch coke as a negative electrode active material, 90 parts by weight of this pitch coke and polyvinylidene fluoride 10 as a binder were used.
Parts by weight with each other to obtain a negative electrode mixture. This negative electrode mixture was dispersed in a solvent N-methylpyrrolidone to form a slurry (paste). Next, this negative electrode mixture slurry was uniformly applied on both sides of a strip-shaped copper foil having a thickness of, for example, 10 μm as the negative electrode current collector 19 and dried. After drying, compression molding was performed using a roller press machine to form a belt-shaped negative electrode 2 having a width of, for example, 35 mm. In the strip-shaped negative electrode 2, the negative electrode active material layers 18 a and 18 b were formed on both surfaces of the negative electrode current collector 19 with substantially the same thickness.

Next, the positive electrode 1 was prepared as follows. One mole of lithium carbonate and one mole of cobalt carbonate were mixed and fired in air at 900 ° C. for 5 hours to obtain LiCoO ₂ . This was used as a positive electrode active material, and 91 parts by weight of LiCoO ₂ was mixed with 6 parts by weight of graphite as a conductive material and 3 parts by weight of polyvinylidene fluoride as a binder to prepare a positive electrode mixture. This positive electrode mixture was dispersed in a solvent N-methylpyrrolidone to form a slurry (paste). Next, this positive electrode mixture slurry was uniformly applied on both sides of a belt-shaped aluminum foil having a thickness of, for example, 20 μm as the positive electrode current collector 17, and dried. After drying, compression molding with a roller press machine,
A belt-shaped positive electrode 2 was prepared. In this strip-shaped positive electrode 1, the positive electrode active material layers 16 a and 16 b were formed on both surfaces of the positive electrode current collector 17 with substantially the same thickness.

Next, by using the strip-shaped positive electrode 1 and the strip-shaped negative electrode 2 and further using a pair of strip-shaped separators 3a and 3b, these are stacked on each other and then wound a number of times to form a second strip.
A spiral wound electrode body 12 shown in the figure was produced.

FIG. 2 shows a detailed cross section of a part of the spirally wound electrode body 12 used in the battery shown in FIG. The wound electrode body 12 includes a pair of strip-shaped positive electrodes 1, a strip-shaped negative electrode 2, and a pair of strip-shaped separators 3a and 3b made of a microporous polypropylene film having a thickness of, for example, 25 μm.
After the separator 3b and the positive electrode 1 were laminated in this order, the laminate was spirally wound around the hollow core 11 a number of times.

The above-mentioned wound electrode body 12 was housed in a battery outer can 5 having an inner diameter of, for example, 13.3 mm as shown in FIG. A non-aqueous electrolyte obtained by mixing propylene carbonate in which 1 mol / mol of lithium hexafluorophosphate was dissolved and 1,2-dimethoxyethane was further injected into the battery outer can 5.

FIG. 3 shows an annular sealing gasket material 6. The sealing gasket material 6 is composed of an upper annular portion 6a having a cylindrical shape and a relatively large diameter, and a cylindrical annular upper portion 6a.
A lower annular portion 6b having a diameter slightly smaller than that of the lower annular portion 6b, and a flange-shaped intermediate annular portion connecting the upper and lower annular portions 6a and 6b.
6c. The lower annular portion 6b is used to make the separator 13 contact the upper end surface 12a of the wound electrode body 12.
It constitutes an extension for pressing 3, and its axial length may be, for example, 1.2 mm.

Using the sealing gasket material 6 described above, the lid 7 and the safety valve 8 are caulked by the upper end 15 of the battery outer can 5 via the sealing gasket material 6 in the same manner as in the case of FIG. 5 was sealed. At this time, the projecting portions 4 of the separators 3a and 3b are connected to the separator 13 as shown in FIG.
Through the sealing gasket, and is slightly inclined. The separator 13 is fixed in close contact with the upper end surface 12a of the spirally wound electrode body 12. at the same time,
Also on the lower end surface 12b of the wound electrode body 12, the separator 14 is fixed in close contact with the lower end surface 12b.

In this embodiment, a safety valve having a projection 8a at the center thereof and a disc-shaped lead stripper 21 having a center hole are provided.
There is provided a current interrupting device including a safety valve 8 and an intermediate fitting body 22 made of an insulating material for integrally connecting the lead stripper 21 with the safety valve 8. A positive electrode lead plate 9 is welded to the protrusion 8a, and when the internal pressure of the battery rises to a predetermined value, the lead plate 9 peels or breaks at this welded portion to cut off the current. .

As described above, a cylindrical lithium secondary battery having a diameter of, for example, 13.8 mm and a height of, for example, 42 mm was produced.

In addition, as a comparative example, a lithium secondary battery having exactly the same configuration as the above secondary battery was prepared except that the conventional sealing gasket material 26 shown in FIG. 6 was used.

Twenty pieces of the above-described lithium secondary batteries of the present example and 20 pieces of the lithium secondary batteries of the comparative example were produced. Then, these secondary batteries were charged at a current of 190 mA at an upper limit voltage of 4.1 V for 3 hours, followed by 10 charge / discharge cycles of discharging to a discharge end voltage of 2.9 V with a load of 16Ω, and again under the above-described conditions. After charging, it was left at room temperature for 10 days. As a result, a rechargeable battery whose circuit voltage has dropped to 3.9 V or less is regarded as an internal short-circuit product.
The incidence was investigated. The results are shown in the following table.

From the above table, it can be seen that the internal short circuit of the battery generated in the secondary battery of the comparative example did not occur at all in the secondary battery of the present example. This is because, even when dendrite-like metallic lithium is deposited on the negative electrode 2 during charging of the battery, it grows and cannot reach the positive electrode 1 through the protrusions 4 of the separators 3a and 3b.

In the present invention, the sealing gasket 6 can be modified. For example, as shown in FIG. 4, a flange portion 6d may be further provided on the inner peripheral surface at the upper end of the sealing gasket 6. Further, an annular extension 22a similar to the annular extension 6b connected to the sealing gasket 6 may be further provided at the lower end of the outer periphery of the above-mentioned intermediate fitting body 22. In this case, the separator 13 is wound. It is possible to more reliably contact the upper end surface 12a of the electrode body 12. Further, the shape of the battery in the present embodiment is not necessarily required to be a cylindrical shape, but may be a rectangular tube type or the like. The non-aqueous electrolyte may be a solid, and in this case, a conventionally known solid electrolyte can be used.

Furthermore, the present invention can be applied to various types of batteries including a laminated electrode body in which a separator is interposed between a negative electrode and a positive electrode, and is not necessarily a secondary battery. The laminated electrode body does not necessarily need to be a wound electrode body in which a negative electrode, a positive electrode, and a separator are laminated and then wound in a large number, and may be a structure in which these are simply laminated. Further, the extension 6b connected to the sealing gasket 6 for pressing the separator 13 does not necessarily have to be completely annular, but may be an intermittently interrupted annular.

〔The invention's effect〕

The present invention, as described above, a current interrupting device that interrupts the current when the internal pressure of the battery rises to a predetermined value, and a lid for closing an opening provided at one end of the battery outer can, respectively The current interrupting device includes a plate-shaped safety valve disposed inside a lid so as to close the opening provided at the one end of the battery outer can, and a plate-shaped safety valve disposed inside the plate-shaped safety valve. And a reed stripper mounted on the safety valve. Therefore, at normal times, the opening provided at the one end of the battery outer can is very effectively closed by both the lid and the plate-shaped safety valve, and the internal pressure of the battery has increased to a predetermined value. Occasionally, the plate-shaped safety valve operates to release the gas inside the battery outer can to the outside, and the current is cut off by the lead stripper. Therefore, even if the battery is in an abnormal state, there is almost no damage to the outside.

Further, an extension is connected to the plate-shaped safety valve to which the lead stripper is attached and a sealing gasket interposed between the outer periphery of the lid and one end of the battery outer can. Pressing a separator disposed near an end face on the lid side of the laminated electrode body to isolate the laminated electrode body from the plate-shaped safety valve and the lead stripper, and pressing the separator against the end face of the laminated electrode body Is in contact with Therefore, it is possible to extremely effectively prevent foreign substances such as deposits from crossing the separator from one electrode side and reaching the other electrode side on the end face of the laminated electrode body on the lid side, thereby preventing an internal short circuit of the battery. It can be prevented very effectively. Further, the sealing gasket not only has a function of preventing the internal short circuit of the battery by pressing the separator, but also has a plate-shaped safety valve to which the lead stripper is attached, the outer periphery of the lid, and the one end of the battery outer can. Since it also has a function as a seal material between the
The sealing gasket contributes to maintaining the positions of the lid, the plate-shaped safety valve, the lead stripper and the separator, thereby simplifying the structure without particularly complicating the battery assembly operation. it can.

[Brief description of the drawings]

1 to 4 show an embodiment in which the present invention is applied to a lithium secondary battery. FIG. 1 is a schematic longitudinal sectional view of a lithium secondary battery, and FIG. 2 is FIG. 3 is a detailed cross-sectional view of a part of the spirally wound electrode body shown in FIG. 3, FIG. 3 is a longitudinal sectional view of a sealing gasket material used in the lithium secondary battery shown in FIG. 1, and FIG. It is a longitudinal cross-sectional view of a material. FIG. 5 is a schematic longitudinal sectional view of a conventional lithium secondary battery, and FIG. 6 is a longitudinal sectional view of a sealing gasket material used for the lithium secondary battery shown in FIG. In addition, in the code | symbol used for drawing, 1 ... belt-shaped positive electrode 2 ... band-shaped negative electrode 3a, 3b ... band-shaped separator 5 ... battery outer can 6 ... sealing gasket 6b ... extension part 7 ... lid 8 ... Safety valve 12… Wound electrode body 13, 14… Separator plate 15… Upper end of battery outer can 21… Lead stripper 22… Intermediate fitting body 22 a… Extension part.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 2/08 H01M 10/04 H01M 10/40

Claims (3)

(57) [Claims] 1. A laminated electrode body having a separator interposed between a negative electrode and a positive electrode, a battery outer can containing the laminated electrode body, and an opening provided at one end of the battery outer can. A lid for closing, a plate-shaped safety valve disposed inside the lid so as to close the opening provided at the one end of the battery outer can, and an internal pressure of the battery up to a predetermined value. A lead stripper attached to the plate-shaped safety valve and arranged inside the plate-shaped safety valve to constitute a current cut-off device that cuts off the current when it rises, together with the plate-shaped safety valve; A separator disposed in the vicinity of the lid-side end surface of the laminated electrode body to isolate the laminated electrode body from the valve-shaped safety valve and the lead stripper; and a lid and the plate-shaped safety valve, respectively. Outside When connecting to the one end of the battery outer can, the lid and the plate-shaped safety valve are respectively provided with a sealing gasket interposed between the outer periphery of the safety valve and the one end of the battery outer can. An extended portion for pressing the separator in order to contact the separator with the end face of the laminated electrode body is connected to the sealing gasket. 2. The battery according to claim 1, wherein said battery is a lithium secondary battery. 3. The apparatus according to claim 1, further comprising an intermediate connector interposed between said plate-shaped safety valve and said lead stripper for integrally connecting said plate-shaped safety valve and said lead stripper. 3. The battery according to claim 1, wherein a second extension for pressing the separator in order to contact the end face of the laminated electrode body is connected to the intermediate connector.