JPH05335011A - Non-aqueous electrolyte secondary battery and its manufacture - Google Patents

Abstract

PURPOSE:To prevent a battery from breakage certainly with actuation of an anti- explosion valve by furnishing an electric isulative layer on that surface of valve, at least a part thereof, on the side which receives the battery internal pressure besides the lead connection part. CONSTITUTION:A negative electrode 1 formed by coating a negative electrode current collector 9 with a negative electrode active material and a positive electrode 2 prepared by coating a positive electrode current collector 10 with a positive electrode active material are wound round while a separator 3 is interposed and accommodated in a battery can 5 in the condition that an insulative substance 4 is laid on and under this roll obtained. A positive electrode lead 12 is installed as welded fast to an anti- explosive valve 8 made in aluminum and connected electrically with a battery lid 7 through this valve 8. When the battery internal pressure rises, the valve 8 is heaved to make deformation, and the lead 12 is cut while the part welded to the valve 8 is left. An insulative layer 13 is formed on the surface of valve 8 other than the lead connection part, at least a part thereof, on the side which receives the battery internal pressure. This prevents the battery certainly from temp. rise and breakage.

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 provided with an explosion-proof valve for interrupting current and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, due to advances in electronic technology, high performance, miniaturization, and portability of electronic devices have advanced, and secondary batteries used in these electronic devices are also required to have high energy density. It is like this. Conventionally, nickel-cadmium batteries and lead batteries have been used as secondary batteries used in these electronic devices, but these batteries are still insufficient in terms of low discharge potential and high energy density. Is.

Therefore, recently, a material capable of doping and dedoping lithium ions such as lithium, a lithium alloy or a carbon material is used as a negative electrode, and a lithium composite oxide such as a lithium cobalt composite oxide is used as a positive electrode. Research and development of water electrolyte secondary batteries are being conducted. This battery has a high battery voltage, a high energy density, little self-discharge, and excellent cycle characteristics.

By the way, in general, when a battery has a closed structure, a battery voltage increases when an electric current of a predetermined amount or more flows during charging and the battery is overcharged, and an electrolyte solution is decomposed to generate gas. The battery internal pressure rises. Furthermore, if this overcharged state continues, an abnormal reaction such as rapid decomposition of the electrolyte or active material may occur, and the battery temperature may rise rapidly. When such an abnormality occurs, the battery is rapidly damaged, the battery loses its function, and peripheral devices are damaged.

As a measure against such a problem, Japanese Patent Application No. 63-265783 proposes an explosion-proof sealed battery provided with an explosion-proof valve that operates in response to an increase in battery internal pressure. That is, as shown in FIG. 7, the battery has an electrode 22 housed in a battery can 21 that also serves as a negative electrode terminal, and a battery lid 23 that also serves as a positive electrode terminal is attached to the upper side of the battery can 21. .. The battery can 21 has a negative electrode lead 2
6, the battery lid 23 is electrically connected to the electrode 22 through an aluminum explosion-proof valve 24 and a positive electrode lead 25 attached to the explosion-proof valve 24 by welding.

In the battery having such a structure, when the pressure inside the battery rises, the explosion-proof valve 24 is pushed up and deformed. Then, the positive electrode lead 25 becomes the explosion-proof valve 24.
The current is cut off by cutting with the welded part left. This stops the progress of abnormal reactions inside the battery,
A rapid increase in battery temperature and an increase in battery internal pressure are prevented.

[0007]

However, in such an explosion-proof sealed battery, the temperature continues to rise despite the deformation of the explosion-proof valve and the disconnection of the positive electrode lead.
Some things can lead to battery damage. Such an abnormal phenomenon is likely to occur especially when the power supply voltage is high, and it is difficult to ensure safety during high voltage charging.

Therefore, the present invention has been proposed in view of such conventional circumstances, and a non-aqueous electrolyte secondary battery capable of reliably preventing damage to the battery by the operation of the explosion-proof valve and the same. It is intended to provide a manufacturing method.

[0009]

In order to achieve the above-mentioned object, the inventors of the present invention have conducted extensive studies, and as a result, the temperature rise that continues after the explosion-proof valve is deformed is increased on the side receiving the battery internal pressure of the explosion-proof valve. It has been found that this can be prevented by providing an insulating layer on the surface. The non-aqueous electrolyte secondary battery of the present invention has been completed based on such findings, and has a conductor explosion-proof valve that deforms with an increase in battery internal pressure, and the explosion-proof valve is an electrode lead. In a non-aqueous electrolyte secondary battery that is electrically connected and the electrical connection between the explosion-proof valve and the electrode lead is broken due to deformation of the explosion-proof valve, a surface of the explosion-proof valve on the side that receives the battery internal pressure and a lead connecting portion. An electrically insulating layer is provided on at least a part of the other parts.

The electrically insulating layer is made of an organic polymer compound. Further, the present invention is characterized in that an electrically insulating layer made of an organic polymer compound is fixed to the explosion-proof valve via an adhesive. Also,
The method for producing a non-aqueous electrolyte secondary battery of the present invention, when providing an electrically insulating layer made of an organic polymer compound in the explosion-proof valve,
Prior to connecting the electrode lead to the explosion-proof valve, the part excluding the electrode lead attachment part of the explosion-proof valve is previously coated with an organic polymer compound paint to form an electrically insulating layer. It is a thing.

Further, in providing an electrically insulating layer made of an organic polymer compound on the explosion-proof valve, prior to connecting the electrode lead to the explosion-proof valve, the electrode lead-attaching portion of the explosion-proof valve is preliminarily adhered to the portion. This is characterized in that an organic polymer compound film is fixed by applying an agent to form an electrically insulating layer.

[0012]

[Function] In a non-aqueous electrolyte secondary battery, which has a conductor explosion-proof valve that deforms as the battery internal pressure increases, and the electrical connection between the explosion-proof valve and the electrode lead is broken by the deformation of the explosion-proof valve, When an electrically insulating layer is provided on at least a part of the surface other than the lead connection portion on the surface receiving the battery internal pressure,
Even if the battery is overcharged when the power supply voltage is high, the explosion-proof valve is deformed to reliably prevent damage to the battery.

The reason for this is not clear, but it is presumed as follows.

That is, in a battery having no insulating layer, when the explosion-proof valve is deformed due to overcharging, the distance between the cut electrode lead and the explosion-proof valve is short even if the electrode lead is cut due to the deformation of the explosion-proof valve. Current leaks to the explosion proof valve. As a result, the abnormal reaction continues, causing the temperature to rise, resulting in battery damage. In a battery in which the explosion-proof valve is provided with an insulating layer, the current leakage to the explosion-proof valve is blocked by the insulating layer, so that damage to the battery is reliably prevented.

[0015]

EXAMPLES The present invention will be described below based on concrete experimental results.

As shown in FIG. 1, the non-aqueous electrolyte secondary battery has a negative electrode 1 formed by coating a negative electrode current collector 9 with a negative electrode active material.
And a positive electrode 2 formed by applying a positive electrode active material to the positive electrode current collector 10.
Are wound via the separator 3, and the insulator 4 is placed on the upper and lower sides of the wound body and housed in the battery can 5.

A battery lid 7 is attached to the battery can 5 by caulking with a sealing gasket 6, and is electrically connected to the negative electrode 1 or the positive electrode 2 via a negative electrode lead 11 and a positive electrode lead 12, respectively, It is configured to function as a negative electrode or a positive electrode.

In the above battery, the positive electrode lead 1
2 is welded and attached to the aluminum explosion-proof valve 8,
Electrical connection is made with the battery lid 7 via the explosion-proof valve 8. As shown in FIG. 2, the explosion-proof valve 8 is pushed up and deformed when the battery internal pressure rises, and the positive electrode lead 12 is welded to the explosion-proof valve 8 by the deformation of the explosion-proof valve 8. It is designed to be cut with the remaining part left.

According to the present invention, as shown in FIGS. 3 and 4, in such a battery, an insulating layer is formed on at least a part of the surface of the explosion-proof valve 8 on the side receiving the battery internal pressure and other than the lead connecting portion. 13 is formed. As a result, it is possible to prevent abnormal reactions and temperature rise that continue after the explosion-proof valve changes and to reliably prevent battery damage.

Here, in order to obtain a sufficient effect by the insulating layer, its thickness is preferably 1 to 50 μm.

The material of the insulating layer 13 may be either an organic polymer compound or an inorganic insulating material. In the case of an inorganic insulating material, it is formed as an insulating layer by, for example, a sputtering method, an anodic oxidation method or the like. In the case of an organic polymer compound, it is formed as an insulating layer by applying an organic polymer compound coating or fixing a tape-shaped organic polymer compound film with an adhesive. For example, polyimide resin, fluorine resin,
There is silicone resin, and polyimide tape, fluororesin tape, etc. are used as an insulating layer when fixed with an adhesive.

In order to form the insulating layer with these materials, in any case, it is easier to perform the manufacturing operation if the insulating layer is formed in advance except for the lead welding portion prior to the lead welding. is there. Further, in the case of fixing a tape-shaped object with an adhesive, when the adhesive surface has a step, for example, the outer tape 13 corresponding to each step as shown in FIG.
Alternatively, the inner tape 13a and the inner tape 13b may be prepared and fixed in stages as shown in FIG.

In the above non-aqueous electrolyte secondary battery,
As the positive electrode active material, Li _X MO ₂ (where M represents at least one transition metal, preferably at least one of Co or Ni, and 0.05 ≦ X ≦ 1.10) is included. Active material is used. Examples of such active materials include LiCoO ₂ , LiNiO ₂ , and LiNi _y Co.
_(1-y) O ₂ (however, 0.05 ≦ X ≦ 1.10, 0 <
The compound oxide represented by y <1) is mentioned. The composite oxide is obtained by, for example, using carbonates of lithium, cobalt, and nickel as starting materials, mixing these carbonates according to the composition, and firing in a temperature range of 600 ° C. to 1000 ° C. in an oxygen-present atmosphere. .. Further, the starting material is not limited to carbonate, and it can be similarly synthesized from hydroxide or oxide.

On the other hand, the negative electrode may be any one that can be doped or dedoped with lithium, such as pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, Organic polymer compound fired body (phenolic resin, furan resin, etc. fired at an appropriate temperature to carbonize), carbon fiber, activated carbon, etc., or metallic lithium, lithium alloy (for example, lithium-aluminum alloy), Polymers such as polyacetylene and polypyrrole can also be used.

As the electrolytic solution, for example, an electrolytic solution in which a lithium salt is used as an electrolyte and this is dissolved in an organic solvent is used. Here, the organic solvent is not particularly limited, but propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, γ-butyl lactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, sulfolane, acetonitrile. A single solvent or a mixed solvent of two or more kinds such as diethyl carbonate and dipropyl carbonate can be used.

As the electrolyte, LiClO ₄ , LiAs
F ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ ,
LiCl, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃
Li or the like can be used.

The explosion-proof valve is not limited to the explosion-proof valve, but may be any one as long as it can interrupt the current according to the internal pressure of the battery.

Next, a non-aqueous electrolyte secondary battery was actually manufactured and the occurrence rate of battery damage was examined.

Example 1 First, the positive electrode 2 was manufactured as follows. Lithium carbonate and cobalt carbonate were mixed so that Li / Co (molar ratio) = 1 and fired in air at 900 ° C. for 5 hours to synthesize a positive electrode active material (LiCoO ₂ ). X-ray diffraction measurement was performed on the positive electrode active material. LiC of JCPDS card
It was in good agreement with oO ₂ . Moreover, when the amount of lithium carbonate in the positive electrode active material was quantified, it was hardly detected and was 0%. Incidentally, lithium carbonate content in the positive electrode active material, after the CO ₂ that samples were generated decomposed with sulfuric acid is absorbed by introducing into the sodium hydroxide and barium chloride solution, CO ₂ by titration with hydrochloric acid standard solution Was quantified and calculated from the amount of CO ₂ . This positive electrode active material was crushed using an automatic mortar to obtain LiCoO ₂ powder.

91% by weight of a mixture obtained by mixing 95% by weight of the LiCoO ₂ powder thus obtained and 5% by weight of lithium carbonate, 6% by weight of graphite as a conductor material, and polyfluoride as a binder. Vinylidene chloride was mixed at a ratio of 3% by weight to prepare a positive electrode mixture, which was mixed with N-methyl-2.
-Disperse in pyrrolidone to make a slurry. Then, the positive electrode mixture slurry was applied to both sides of a strip-shaped aluminum foil that is the positive electrode current collector 10, dried and then compression-molded with a roller press to form a positive electrode 2.

The negative electrode 1 was manufactured as follows. Petroleum pitch was used as a starting material, and a functional group containing oxygen was added thereto.
After introducing about 20% (so-called oxygen crosslinking), it was fired at 1000 ° C. in an inert gas to obtain a non-graphitizable carbon material having properties close to those of glassy carbon. As a result of X-ray diffraction measurement of this carbon material, the interplanar spacing of the (002) plane is 3.76Å
And the true specific gravity was 1.58.

90% by weight of this carbon material and 10% by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture, which was dispersed in N-methyl-2-pyrrolidone to form a slurry. did. The negative electrode mixture slurry was applied on both sides of a strip-shaped copper foil as a negative electrode current collector, dried and then compression-molded with a roller press machine to prepare a negative electrode 1.

The strip-shaped positive electrode 2, negative electrode 1 and separator 3 made of a 25 μm microporous polypropylene film
Then, a spirally-wound electrode was prepared by stacking the layers in sequence and then winding the layers in a spiral shape.

Next, the insulating plate 4 was inserted into the bottom of the nickel-plated iron battery can 5 to house the spiral electrode. Then, in order to collect current from the negative electrode, one end of a negative electrode lead 11 made of nickel was pressure-bonded to the negative electrode 1, and the other end was welded to the battery can 5. Further, one end of a positive electrode lead 12 made of aluminum was attached to the positive electrode 2 in order to collect current from the positive electrode, and the other end was welded to a battery lid 7 having an explosion-proof valve 8 for shutting off current according to the internal pressure of the battery.

However, in the explosion-proof valve 8, a polyimide resin (trade name: Kelimide 10 manufactured by Nippon Polyimide Co., Ltd., which is a surface to be preliminarily subjected to internal pressure and other than the lead welded portion) is used.
50) was applied to form the insulating layer 13. Then, in the battery can 5, 50% by volume of propylene carbonate and 50% by volume of diethyl carbonate were mixed in a mixed solvent of LiPF ₆
An electrolytic solution prepared by dissolving 1 mol / l was injected. Then, the battery can 5 was caulked through the insulating sealing gasket 6 coated with asphalt to fix the battery lid 7, and a cylindrical battery (Example battery 1) having a diameter of 14 mm and a height of 50 mm was prepared.

Example 2 A fluororesin (made by Asahi Glass Co., Ltd., trade name LF-10) was used for the explosion-proof valve 8.
0) was applied to form the insulating layer 13, and a cylindrical battery (Example battery 2) was prepared in the same manner as in Example 1.

Example 3 Silicon resin (made by Toshiba Silicon Co., trade name T
A cylindrical battery (Example battery 3) was prepared in the same manner as in Example 1 except that SE389-C) was applied to form the insulating layer 13.

Example 4 A cylindrical battery (as in Example 1) except that a circular polyimide tape (manufactured by Nitto Denko Corp., trade name No360UL) was fixed to the explosion-proof valve 8 with an adhesive to form the insulating layer 13. Example battery 4) was prepared.

Example 5 A circular fluororesin adhesive tape (made by Nitto Denko Corporation,
A cylindrical battery (Example battery 5) was prepared in the same manner as in Example 1 except that the insulating layer 13 was formed by fixing the product name No. 453) with an adhesive.

Comparative Example 1 A cylindrical battery (Comparative Example Battery 1) was prepared in the same manner as in Example 1 except that the insulating layer was not formed on the explosion-proof valve 8.

For each of the 20 batteries thus produced, the current was set to 2.0 A and the power supply voltage was 20 V.
Overcharging was performed while changing the voltage to 25V and 30V, and the generation of heat and damage after deformation of the explosion-proof valve was examined, and the incidence of battery-damaged products was investigated. The results are shown in Table 1.

[0042]

[Table 1]

As can be seen from Table 1, in Example battery 1 to Example battery 5, even if the power supply voltage was raised to 30 V, the occurrence of battery damage is reliably prevented by the deformation of the explosion-proof valve. On the other hand, in Comparative Example Battery 1, when the voltage is low, damage is prevented by deformation of the explosion-proof valve, but when the power supply voltage is 25 V or higher, abnormal reaction and temperature rise continue even after deformation of the explosion-proof valve. Things come out.

Therefore, it has been found that providing the explosion-proof valve with an insulating layer is effective in obtaining a non-aqueous electrolyte secondary battery having a low battery damage rate and high safety.

[0045]

As is apparent from the above description, in the non-aqueous electrolyte secondary battery of the present invention, the explosion-proof valve has the insulating layer, so that overcharge occurs when the power supply voltage is high. Even if it does, it is possible to reliably prevent the battery temperature from rising and the battery from being damaged by operating the explosion-proof valve.

Therefore, according to the present invention, it is possible to obtain a non-aqueous electrolyte secondary battery having high energy density, low self-discharge rate, long cycle life and extremely high safety.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an example of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a schematic vertical sectional view showing a non-aqueous electrolyte secondary battery after deformation of an explosion-proof valve.

FIG. 3 is a schematic plan view showing an explosion-proof valve having an insulating layer formed thereon.

FIG. 4 is a schematic sectional view showing an explosion-proof valve having an insulating layer formed thereon.

FIG. 5 is a schematic plan view showing an example of shapes of an inner tape and an outer tape.

FIG. 6 is a schematic sectional view showing an explosion-proof valve to which a tape-shaped organic polymer compound film is fixed.

FIG. 7 is a schematic vertical sectional view showing a conventional non-aqueous electrolyte secondary battery.

[Explanation of symbols]

 1 ... Negative electrode 2 ... Positive electrode 3 ... Separator 4 ... Insulating plate 5 ... Battery can 6 ... Seal gasket 7 ... Battery lid 8 ... Explosion-proof valve 9 ... Negative electrode Current collector 10 ... Positive electrode current collector 11 ... Negative electrode lead 12 ... Positive electrode lead 13 ... Insulating layer

Claims (5)

[Claims] 1. An explosion-proof valve made of a conductor that deforms as the internal pressure of a battery increases, the explosion-proof valve is electrically connected to an electrode lead, and the explosion-proof valve and the electrode lead are electrically connected by deformation of the explosion-proof valve. In a non-aqueous electrolyte secondary battery to be broken, an electrical insulating layer is provided on at least a part of the surface of the explosion-proof valve on the side receiving the battery internal pressure and other than the lead connecting portion. Non-aqueous electrolyte secondary battery. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrically insulating layer is made of an organic polymer compound. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrically insulating layer made of an organic polymer compound is fixed to the explosion-proof valve via an adhesive. 4. When providing an electrically insulating layer made of an organic polymer compound on the explosion-proof valve, prior to connecting the electrode lead to the explosion-proof valve, a portion of the explosion-proof valve excluding the electrode lead attachment portion is preliminarily formed with an organic material. A method for producing a non-aqueous electrolyte secondary battery, which comprises applying a polymer compound coating to form an electrically insulating layer. 5. When providing an electrically insulating layer made of an organic polymer compound on the explosion-proof valve, prior to connecting the electrode lead to the explosion-proof valve, the electrode lead of the explosion-proof valve is preliminarily adhered to the part excluding the electrode lead attachment portion. A method for producing a non-aqueous electrolyte secondary battery, which comprises applying an agent to fix an organic polymer compound film and forming an electrically insulating layer in advance.