JPH07192775A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To provide a nonaqueous secondary battery where the rise of inner pressure can be opened safely and moreover the noxious matter contained in ejected gas reduced and besides the ejection of solid substance such as fireworks, etc., suppressed by arranging a gas adsorber between a relief valve and a battery cover. CONSTITUTION:In an nonaqueous electrolyte secondary battery being equipped with a relief valve 7 inside a battery cover 6, a gas adsorber 11 is arranged between the relief valve 7 and the battery cover 6. As the gas adsorber, for example, synthetic zeolite, activated carbon, activated alumina, etc., can be cited. It is desirable that a film 8 (example: stainless net) having a mesh-shaped opening should be arranged between the relief valve 7 and the battery cover 6.

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, and more particularly to a non-aqueous electrolyte secondary battery having a safety valve.

[0002]

2. Description of the Related Art In recent years, advances in electronic technology have led to advances in performance, miniaturization, and portability of electronic equipment, and the demand for high energy density secondary batteries used in these electronic equipment is increasing. Conventionally, secondary batteries used in these electronic devices include nickel-cadmium batteries and lead batteries, but these batteries still have low discharge potential and high energy density. Is insufficient.

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. Non-aqueous electrolyte secondary batteries are being researched and developed. This battery has a high battery voltage, a high energy density, little self-discharge, and excellent cycle characteristics.

However, in a battery using an organic solvent as an electrolytic solution, such as the non-aqueous electrolytic solution secondary battery, if the internal temperature rises, the internal pressure is likely to rise, which may cause rupture or the like. Therefore, in this type of battery, in order to prevent rupture or the like, a safety valve that opens at a predetermined internal pressure and releases the internal pressure is provided.

[0005]

However, if a safety valve is simply provided, when the safety valve is actuated to release the internal pressure, a gas containing harmful organic matter or solid matter (in some cases, sparks are generated). (Solid matter) may gush out,
It has a large effect on the surroundings and may damage peripheral devices.

In view of such conventional circumstances, the present invention can safely release the rise in internal pressure, reduce harmful components contained in the jet gas, and suppress the jet of solid matter such as sparks. It is an object to provide a water electrolyte secondary battery.

[0007]

In order to achieve the above-mentioned object, the present invention provides a non-aqueous electrolyte secondary battery having a safety valve inside a battery lid, wherein a gas adsorbent is provided between the safety valve and the battery lid. When the gas is blown out from the inside of the battery, it has a mechanism for reducing the harmful substances contained in the gas and preventing the blowout of solid matter. To do.

In the non-aqueous electrolyte secondary battery of the present invention, the material of the gas adsorbent may be any material as long as it adsorbs gas, for example, synthetic fluorite having a uniform pore size (eg Linde Co. ．Molecular sieve),
Examples thereof include activated alumina, oxide powder (iron oxide powder and the like), activated carbon and the like.

[0009]

[Function] In a non-aqueous electrolyte secondary battery equipped with a safety valve,
When the internal pressure rises due to an abnormality, the safety valve operates (opens), and this internal pressure rise is released. At this time, a gas containing a harmful organic substance or a solid substance (a solid substance which becomes a spark in some cases) is ejected, but in the battery of the present invention, the gas adsorbent acts as a kind of filter, Organic substances and solids (sparks) in the gas are captured.

[0010]

EXAMPLES Specific examples to which the present invention is applied will be described below with reference to the drawings and experimental results.

Example 1 First, a negative electrode was prepared as follows. Pitch coke was crushed to obtain a carbon material powder having an average particle size of 30 μm. 90 parts by weight of the carbon material powder thus obtained was combined with 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and this negative electrode mixture was dispersed in a solvent N-methyl-2pyrrolidone to form a slurry. Negative electrode current collector thickness 10
The above negative electrode slurry was uniformly applied to both surfaces of a strip-shaped copper foil having a thickness of μm, dried and then compression-molded with a roll press machine to prepare a strip-shaped negative electrode 1.

Next, a positive electrode was prepared as follows. Lithium carbonate and cobalt carbonate were mixed in the positive electrode active material so that Li / Co (molar ratio) = 1, and the mixture was heated in air at 900 ° C. for 5
Using LiCoO ₂ obtained in time firing, LiCoO ₂
91 parts by weight of a mixture of 99.5 parts by weight and 0.5 part by weight of lithium carbonate, 6 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride (PVDF) as a binder were mixed. The positive electrode mixture was mixed with the solvent N-methyl 2
It was dispersed in pyrrolidone to form a slurry. Then, the positive electrode slurry is uniformly applied to both surfaces of a strip-shaped aluminum foil having a thickness of 20 μm as a positive electrode current collector and dried,
The strip positive electrode 2 was produced by compression molding with a roll press.

A microporous polypropylene film was prepared as a separator. When the strip-shaped negative electrode 1, the strip-shaped positive electrode 2, and the separator 3 are spirally wound electrode elements, the length and width thereof are adjusted in advance so that they can be appropriately accommodated in the battery can 5 having an outer diameter of 20 mm and a height of 51 mm. And first
A spiral electrode as shown in the figure was produced.

The spiral electrode thus produced was housed in the battery can 5, and the nickel negative electrode lead was led out from the negative electrode current collector and welded to the battery can 5. Similarly, the aluminum positive electrode lead 4 was led out from the positive electrode current collector and welded to the aluminum safety valve 7. Next, 50 parts by volume of propylene carbonate and 5 parts of diethyl carbonate were placed in the battery can 5.
An electrolyte solution in which 1 mol / l of LiPF ₆ was dissolved in 0 volume part mixed solvent was injected.

As the gas adsorbent 11, a 2 mm-thick sheet in which powdered activated carbon was carried on a non-woven fabric and pressure-bonded to the stainless net 8 was arranged between the battery lid 6 and the aluminum safety valve 7.

Finally, the battery can 5 was caulked via an insulating sealing gasket coated with asphalt to fix the battery lid 6, and a cylindrical nonaqueous electrolyte battery having a diameter of 20 mm and a height of 50 mm was produced.

The safety valve 7 is a notch made in aluminum, and when the internal pressure of the battery exceeds a certain level, the notch portion is split to release the internal pressure, and at the same time, between the positive electrode lead 4 and the battery lid 6. Is cut off and the current is cut off.

Comparative Example 1 A battery was prepared in the same manner as in Example 1. However, the battery lid 6 was placed directly on the aluminum safety valve 7, and no gas adsorbent was used. Others are exactly the same as in the first embodiment.

In the batteries produced as in the above-mentioned Examples and Comparative Examples, up to 4.2 V, which is the normally used maximum voltage, 4
Charge at 00mA, then to 2.75V, 4
It was discharged at 00 mA and the capacity was confirmed.

Next, a heating test was conducted to confirm the safety of these batteries. The temperature of these batteries was raised in air at 10 ° C./min on a hot plate at 25 ° C.
Heated to 0 ° C. As a result, in both Examples and Comparative Examples, no gas was ejected up to 200 ° C., and all were ejected at 250 ° C. The results are shown in Table 1.

[0021]

[Table 1]

Compared to the comparative example, the content of the organic solvent in the gas of the example is reduced to about 2/3. Also, the sparks have disappeared. This is because when the gas adsorbent 11 is present as in the embodiment, the gas adsorbent 11 acts as a kind of filter when the safety valve 7 is activated (opens) to release the internal pressure and adsorbs the organic solvent in the gas. This is because the sparks are prevented from being emitted.

Further, in the above embodiment, the gas adsorbent 11
Was used by pressing it onto the stainless steel net 8, but as shown in FIG. 2, the stainless steel net was not used and the gas adsorbent 1 was directly used.
The same effect can be obtained by disposing 1 between the battery lid 6 and the aluminum safety valve 7.

[0024]

As described above, in the non-aqueous electrolyte secondary battery having the safety valve inside the battery lid, by providing the gas adsorbent between the safety valve and the battery lid, gas ejection from the inside of the battery is prevented. If so, it is possible to reduce harmful organic substances contained in the jet gas and prevent the jetting of solid substances, and to provide a highly safe battery.

[0025]

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a main part showing a configuration example of a non-aqueous electrolyte secondary battery to which the present invention has been applied.

FIG. 2 is a schematic cross-sectional view of a main part showing another configuration example of a non-aqueous electrolyte secondary battery to which the present invention has been applied.

[Explanation of symbols]

 1 ・ ・ ・ ・ ・ ・ ・ ・ Negative electrode 2 ・ ・ ・ ・ ・ ・ ・ ・ Positive electrode 3 ・ ・ ・ ・ ・ ・ ・ ・ Separator 4 ・ ・ ・ ・ ・ ・ ・ ・ Positive electrode lead 5 --- Battery can 6 --- Battery lid 7 --- Safety valve 8 --- Stainless steel net 9: Gas opening 11: Gas adsorbent

Claims (3)

[Claims] 1. A non-aqueous electrolyte secondary battery having a safety valve inside a battery lid, wherein a gas adsorbent is provided between the safety valve and the battery lid. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein activated carbon is used as the gas adsorbent. 3. The non-aqueous electrolyte secondary battery according to claim 1, further comprising a membrane having a mesh opening between the safety valve and the battery lid.