JP2001313009A - Sealed battery with convection promoting film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat radiating property of a battery in a simple and easy way without having effect on energy volume density of the battery and improve safety of the battery. SOLUTION: The sealed battery with convection promoting film has a convection promoting film for activating air convection bonded on an outermost surface of the battery. As the convection promoting film, a film selected from a group of a polyethylene terephthalate film, a polytetrafluoroethylene film, a polypropylene film, or a cellophane film is used with film thickness of 300 μm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a sealed battery,
More specifically, the present invention relates to a sealed battery having improved heat dissipation on the outer surface of the battery.

[0002]

2. Description of the Related Art In a sealed battery, if the internal pressure of the battery rises due to gas generation due to improper handling such as heating or overcharging of the battery, the battery may explode or catch fire. For this reason, a safety valve mechanism is incorporated in the sealed battery, and when the internal pressure of the battery becomes equal to or higher than a predetermined pressure, the safety valve operates so that no further pressure increase occurs.

However, in the non-return type safety valve, the operation of the safety valve is directly linked to the end of the battery life. On the other hand, even in the case of a return-type safety valve, when the internal pressure of the battery rises rapidly, the electrolytic solution blows out of the battery together with heat and gas together with the operation of the safety valve, so that the battery life substantially ends.
In addition, the strongly blown gas and the electrolyte itself are dangerous, and the blown battery contents contaminate the periphery of the battery.
Further, when the battery temperature exceeds about 135 ° C., a thermal runaway reaction occurs, the temperature rise does not stop, and the risk of battery rupture or ignition increases. Therefore, in order to further enhance the reliability and safety of the battery, it is necessary to suppress a rapid rise in battery temperature.

[0004] Incidentally, as a method for simply suppressing the rise in battery temperature, a method of increasing the outer surface area of the battery and increasing the amount of heat dissipation can be considered. However, if the outer surface area of the battery is increased by enlarging the outer shape of the battery or disposing a radiation fin on the battery can, a larger mounting volume is required, and the power generation density per unit volume of the battery is reduced. Therefore, such a measure goes against the current situation where a battery having a smaller size and a higher energy density is required.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above,
It is an object of the present invention to provide a means for easily improving the heat radiation characteristics of a battery without affecting the energy density per unit volume of the battery, thereby further improving the safety of the battery.

[0006]

In order to achieve the above object, the invention of claim 1 is a sealed battery with a convection promoting film in which a convection promoting film for promoting air convection is attached to the outermost surface of the battery. It is characterized by the following.

The present inventors have conducted intensive studies on means for improving the heat dissipation of a battery. As a result, it has been found that, when a specific coating is applied to the outermost surface of the battery, convection between the battery surface and the outside air becomes active, and as a result, a rise in battery temperature is suppressed. Claim 1 is an invention completed based on this finding. That is, with the above configuration, the heat dissipation of the battery can be improved by simple means,
The heat generated inside the battery can be quickly radiated to the outside of the battery. Therefore, according to the above configuration, it is possible to suppress the explosion of the battery and the explosion of the battery content due to the rapid rise in the battery temperature due to an internal short circuit, etc., and to significantly improve the reliability and safety of the battery. it can.

[0008] Here, "adhesion" means that the convection promoting film is attached in a state of being in contact with the battery body (unit cell), and the degree of contact only needs to be at least enough to ensure heat conduction. Further, the improvement of the heat radiation property in the present invention does not mean the improvement of the heat radiation property grasped by the thermal conductivity, but means the one based on the effect of convection being activated. In other words, the convection-promoting membrane of the present invention comprises a battery body (or battery can)
The material does not need to have a higher thermal conductivity than that of the battery body, and may be a material having a lower thermal conductivity than the battery body as long as it has a function of activating convection. In the present invention, a convection promoting film having a smaller thermal conductivity than the battery body is assumed.

According to a second aspect of the present invention, in the sealed battery with the convection enhancing film according to the first aspect, the convection enhancing film is a polymer film.

[0010] Since the polymer film can effectively function as a convection promoting film and easily adheres to the battery body, this configuration can easily constitute a sealed battery excellent in heat dissipation.

According to a third aspect of the present invention, in the sealed battery with the convection enhancing film according to the second aspect, the convection enhancing film is selected from a polyethylene terephthalate film, a polytetrafluoroethylene film, a polypropylene film, and a cellophane film. It is characterized by being a film to be formed.

A membrane selected from a polyethylene terephthalate membrane, a polytetrafluoroethylene membrane, a polypropylene membrane, and a cellophane membrane is excellent in promoting convection and is inexpensive. Can be configured without increasing the cost.

According to a fourth aspect of the present invention, in the sealed battery with the convection enhancing film according to the third aspect, the thickness of the convection enhancing film is 300 μm or less.

With a convection promoting film having a thickness of 300 μm or less, the improvement in heat dissipation due to the promotion of convection exceeds the heat storage effect (insulation effect) due to the attachment of the convection promoting film. Can be suppressed.

[0015] The invention according to claim 5 is the invention according to claims 1, 2,
5. The sealed battery with a convection-promoting membrane according to 3 or 4, wherein a thickness of a battery can, which is a component of the battery, is 0.1 m.
m or more metal cans.

The thickness of the metal battery can is closely related to the heat storage in the battery. When the thickness is 0.1 mm or more, the heat dissipation effect of the convection promoting film is sufficiently exhibited. Therefore, with the above configuration, a highly reliable sealed battery with a low possibility of battery rupture or the like can be configured.

[0017] The invention according to claim 6 is the invention according to claims 1 to 5.
The sealed battery with a convection promoting membrane according to any one of the above, wherein the sealed battery includes a lithium-containing oxide capable of inserting and extracting lithium ions in a positive electrode, and a lithium ion including a carbon material capable of inserting and extracting lithium ions in a negative electrode. It is a battery.

A lithium ion battery generates a large amount of heat due to an internal short circuit, and the battery temperature tends to be high, and the possibility of thermal runaway increases. However, by attaching a convection promoting film, thermal runaway can be caused. It is possible to construct a highly safe battery that does not occur.

According to a seventh aspect of the present invention, in the sealed battery with a convection promoting film according to the sixth aspect, the lithium-containing oxide is lithium cobaltate and the carbon material is graphite. .

In the lithium ion battery having this configuration,
The function and effect of the convection promoting film are remarkably exhibited.

[0021] The invention described in claim 8 is the invention according to claims 1 to 7.
5. The sealed battery with a convection promoting film according to any one of the above, wherein the sealed battery has a spiral electrode body formed by winding a strip-shaped positive electrode and a strip-shaped negative electrode via a separator.

Since the spiral electrode body has a large facing area of the positive and negative electrodes and a large mass energy density, when an internal short circuit occurs, the calorific value tends to be large, the battery temperature tends to be high, and thermal runaway may occur. Increase. Therefore, in the battery using such a spiral electrode body, the effect of the convection promoting film is particularly remarkably exhibited.

According to the ninth aspect of the present invention, there is provided an image processing apparatus comprising:
Or the sealed battery with a convection promoting membrane according to 8, wherein the sealed battery has a mass energy density of greater than 129 Wh / Kg.

When the mass energy density is greater than 129 Wh / Kg, heat generation due to an internal short circuit increases, and the possibility of thermal runaway further increases. Therefore, in a battery having a mass energy density of more than 129 Wh / Kg, the effect of the convection promoting film is remarkably exhibited.

[0025]

Embodiments of the present invention will be described. FIG. 1 is a diagram for explaining the relationship between a unit cell (battery main body) and a convection promoting film. In the figure, reference numeral 1 denotes a unit cell in which a power generation element is accommodated in a battery can, and reference numeral 2 denotes a convection promoting film. Reference numeral 3 denotes an external terminal for extracting a generated current to the outside, and reference numeral 4 denotes a direction in which the convection promoting film 2 is brought into contact with the unit cell.

Here, in the present invention, the convection promoting film is brought into contact with the outermost surface of the unit cell (to the extent that heat conduction occurs).
Thus, since the heat dissipation of the battery is to be improved, a sealed battery in which heat is easily trapped in the battery is targeted. On the other hand, there is no particular limitation on the size of the battery, the type of battery, the material of the battery can, and the like, and a wide range of sealed batteries can be applied to the present invention. In addition, as the material of the battery can, generally, metal cans such as iron, stainless steel, copper, aluminum, and aluminum alloys are used. However, the present invention has a remarkable effect on sealed batteries using these metal cans. Demonstrate the effect (improve heat dissipation).

The convection promoting film according to the present invention is a functional film having a function of activating convection at a contact surface with outside air to promote heat radiation. Therefore, the convection promoting film needs to be disposed on the outermost surface of the battery, and the convection promoting film itself needs to be disposed on the surface of the battery body in a state of directly contacting the outside air. However, the convection promoting film does not need to cover the entire surface of the battery body, and may be attached to only a part thereof.

For example, in FIG. 1, any one of the convection promoting films A to D only needs to be attached to any surface of the unit cell, and another coating is provided between the convection promoting film and the unit cell. And other members may be interposed. If the convection promoting film is in direct contact with the outside air, the convection promoting effect can be exhibited. However, in order to efficiently radiate heat from the surface of the convection promoting film, it is preferable that the convection promoting film is directly attached to the surface of the battery can. Note that the number of convection promoting films need not be one, and a plurality of convection promoting films may be stacked and used.

On the other hand, in the present invention, the convection promoting film is adhered to the surface of the unit cell, but this does not include a state in which another film is further adhered to the surface of the convection promoting film. This is because, if another film is further adhered to the surface of the convection promoting film, the convection promoting effect is impaired, and a sufficient effect cannot be obtained. In addition, examples of the other film disposed on the surface of the convection promoting film include a printing ink film, a varnish film, and a packaging film other than the convection promoting film. When a part of the surface of the convection promoting film is covered with these films, the portion not covered with these films corresponds to the “convection promoting film in contact with the outermost surface of the battery” in the present invention. Will do.

The degree of contact of the convection promoting film with the battery body may be such that heat conduction occurs between the surface of the battery body and the convection promoting film. However, in order to ensure heat conduction and facilitate handling of the battery, the convection promoting film adheres to the surface of the unit cell.
More preferably, it is in a fixed state.

As the convection promoting film, a polymer film can be used, and specifically, a polyethylene terephthalate film, a polytetrafluoroethylene film, a polypropylene film, a cellophane film and the like can be used. In particular, a polyethylene terephthalate film (PET film) can be suitably used among these films.

In general, a polymer film has a smaller thermal conductivity than a metal constituting a battery can. Therefore, the polymer film attached to the battery surface functions as a heat insulating film in terms of thermal conductivity, and in order to enhance the heat dissipation of the battery, the heat storage effect (heat insulating effect) due to the small thermal conductivity is required. Effect),
It is important to balance with the heat radiation effect resulting from activating convection on the battery surface. In other words, it is necessary to use a convection promoting film in which the heat radiation effect is superior to the heat storage effect,
This requirement can be satisfied by setting the thickness of the polymer film to 300 μm or less.

The battery may cause a thermal runaway reaction when the temperature becomes higher than about 135 ° C., and the outside air temperature is usually 35 ° C. or less. The polymer film such as a PET film attached to the battery surface activates convection, promotes heat exchange between the battery body and the outside air, and acts to suppress a rise in battery temperature. Even if an internal short circuit occurs, it is possible to prevent the battery temperature from being equal to or higher than the battery burst temperature. The mechanism by which convection is activated on the surface of the polymer membrane has not been sufficiently clarified at present.

(Experimental Section) Various sealed batteries and comparative batteries according to the present invention were produced. Then, the technical significance of the present invention was clarified by experimentally generating an internal short circuit for each battery and measuring the battery temperature.

(Experiment 1) Battery can 10 mm × 34
A test battery was prepared as follows using a rectangular aluminum alloy (JIS A3003) battery can having a height of 50 mm, a height of 50 mm, and a thickness of 0.6 mm. A current collector made of aluminum foil is prepared by mixing a slurry obtained by mixing lithium cobaltate as a positive electrode active material, a conductive agent made of graphite, and a binder made of polyvinylidene fluoride in N-methylpyrrolidone (NMP). , Dried, rolled to a predetermined thickness, and then cut to a predetermined size to produce a band-shaped positive electrode. A slurry obtained by mixing graphite (anode active material) capable of inserting and extracting lithium ions and a binder made of polyvinylidene fluoride in NMP is applied to a current collector made of copper foil, dried, and dried. After rolling to a thickness of, a strip-shaped negative electrode was produced by a method of cutting into a predetermined size. After attaching a current collecting tab to each of the positive and negative electrodes, it was wound through a polyethylene separator to form a spiral electrode body.

The positive electrode current collecting tab was welded to the inside of the battery can, and the negative electrode current collecting tab was welded to the inner end of the negative electrode external terminal provided on the sealing lid. Then, the spirally wound electrode body in this state was housed in a battery can, the battery sealing lid was fitted into the opening of the battery can, and the periphery thereof was laser-welded. Thereafter, a non-aqueous electrolyte is injected from the electrolyte injection port provided in the sealing lid, the injection port is closed, and the design capacity is 1400 mAh.
Was manufactured.

Next, 50 μm, 20 μm
A polyethylene terephthalate film (PET film) having four thicknesses of 0 μm, 300 μm, and 350 μm was prepared, and the state of attachment to the battery can (see FIG. 1) was changed to A only, B only,
A total of 17 batteries were prepared, in which A + B + C + D (applied on the entire surface) and A + B + C + D formed a varnish layer on the entire surface and did not attach a PET film at all. The PET film was adhered by a method of attaching the PET film to the surface of the battery can using a paste.

In each of the above batteries, an internal short circuit is generated by applying a force to the battery from the outside to dent a part of the battery and bringing the positive electrode into contact with the negative electrode, while taking care not to break the airtightness of the battery. Was. Then, the maximum battery temperature after the internal short circuit was measured. Specifically, when an internal short circuit occurs, the battery energy is exhausted in about 5 to 15 minutes. During this time, the battery temperature was monitored and the maximum battery temperature was measured.

FIG. 2 shows the measurement results in relation to the thickness of the convection promoting film (PET film). From FIG. 2, it can be seen that the batteries (●-●, Δ- △, ○-○) in which the convection promoting film was attached to the outermost surface of the battery were compared with the battery (----) in which no convection promoting film was attached. Even the battery maximum temperature was low. On the other hand, as for the battery having the convection promoting film bonded thereto, the battery having the varnish layer formed on the outer surface of the convection promoting film (× − ×) is the battery without bonding (−−).
The maximum temperature was equal to or higher than the maximum battery temperature of-). Further, even in a battery (●-●, Δ- △, ○-○) in which a convection promoting film is adhered to the outermost surface of the battery, the film thickness is 30%.
When it exceeds 0 μm, a tendency was observed that the maximum battery temperature suddenly increased.

When the film thickness exceeds 300 μm, the reason why the maximum temperature of the battery rises is that the heat retaining effect by wrapping the battery surface with a PET film having a small thermal conductivity is more than the heat radiation effect by the convection promoting action. Is thought to be superior. Further, in the battery (× − ×) in which the varnish layer was formed on the outer surface of the convection promoting film (PET film), the highest battery temperature was considered to be because the varnish layer inhibited the convection promoting action of the PET film. . For this reason, it is necessary that the convection promoting film is disposed on the outermost surface of the battery and that the surface is in direct contact with the atmosphere.

(Experiment 2) In Experiment 2, four types of polymer films having a thickness of 50 μm such as a polyethylene terephthalate film (PET film), a polytetrafluoroethylene film (PTFE film), a polypropylene film (PP film), and a cellophane film were prepared. Using each of them, five types of batteries, that is, a sealed battery of the bonding mode A in FIG. 1 and a battery in which the polymer membrane was not bonded, were prepared. The relationship between the type difference and the maximum battery temperature was examined. The results are shown in Table 1.

[0042]

[Table 1]

As is clear from Table 1, the maximum temperature of the battery (No. 1-5) without the convection promoting membrane was 137 ° C. On the other hand, the battery (No. 1
-1 to 1-4), the battery temperature was lower than the above temperature, and in particular, the temperature of the battery (No. 1-1) using the PET film was lower. From these results, as the convection promoting film, PET film, PT film
It has been found that an FE film, a PP film, and a cellophane film can be used, and it is more preferable to use a PET film. In addition, Table 1 shows the results when the convection promoting film is adhered only to the surface A. As is clear, the convection promoting film does not necessarily have to adhere to the entire surface of the outermost surface of the battery.
Even when the convection promoting film is attached to a part of the outermost surface of the battery, a sufficient heat radiation promoting effect can be obtained.

(Experiment 3) In Experiment 3, the thickness was 0.05 m.
m, 0.07 mm, 0.1 mm, 0.15 mm, 0.2
A battery can made of seven kinds of aluminum alloys (JISA3003) of mm, 0.3 mm, and 0.6 mm, a polyethylene terephthalate film (PET film) having a thickness of 50 μm as a convection promoting film, and a bonding mode is A + B + C + D. Seven types of batteries were produced. Regarding other items, the relationship between the thickness of the battery can and the maximum battery temperature was examined in the same manner as in Experiment 1. The results are shown in Table 2.

[0045]

[Table 2]

As is clear from Table 2, as the thickness of the battery can decreases, the maximum temperature of the battery increases, and the thickness of the battery can decreases to 0.1.
When the thickness was less than 0.07 mm (that is, 0.07 mm, 0.05 mm), the maximum battery temperature significantly increased. On the other hand, even when the thickness of the can was 0.6 mm, the battery without the convection promoting film (No. 2-8) exhibited a maximum battery temperature of 140 ° C. or higher.
From these results, it became clear that it is more effective to apply the convection promoting film to a battery having a battery can having a thickness of 0.1 mm or more.

(Experiment 4) In Experiment 4, using aluminum alloy (A3003) prismatic battery cans S1 to S3 having the dimensions shown in Table 3, the battery mass, battery capacity,
In addition, four types of unit cells having different mass energy densities of the cells were manufactured in two ways, one of which was left as a unit cell, and the other was provided with a 50 μm PET film (convection promoting film) on the surface of the unit cell in FIG. The contact was made in the contact mode A. Then, each battery was internally short-circuited by the method described above, and the maximum temperature of the battery was measured. The results are shown in Tables 4, 5 and 6. In addition, about the manufacturing method of the unit cell, it carried out similarly to the said experiment 1 except having adjusted so that the positive-negative active material amount and the positive-negative electrode dimension might satisfy the conditions of Tables 4-6.

The mass energy density of these batteries was measured as follows. First, set the battery capacity to 1
Current value equal to discharging in time (this value is I)
After the battery was charged at a constant current until the battery voltage reached 4.2 V, the battery was immediately charged at a constant voltage of 4.2 V, and the charging was terminated when the charging current value reached I / 20. This battery was used as a fully charged battery. Next, the fully charged battery was discharged at a constant current of I / 5 to 3.0 V at a constant current, and the voltage V from the start of discharge to the end of discharge was measured over time. Then, the value (Wh) obtained by integrating the product of the voltage V and the current value (I / 5) over time with time h is divided by the unit cell mass (Kg), and this value is referred to as mass energy density (Wh / Kg). And

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

[Table 5]

[0052]

[Table 6]

As is clear from Tables 4 to 6, in all the batteries, the maximum temperature of the battery caused by the internal short circuit was significantly lowered by attaching the convection promoting film. Then, the convection promoting film No. 1-3, No. 5-7, No. 9
The maximum battery temperatures in all of the samples No. to No. 11 were 140 ° C. or higher, but the maximum temperatures in these batteries with the convection promoting film attached were 104 ° C. to 126 ° C.

However, the mass energy density is 129 Wh /
In the case of batteries (Nos. 4, 8, and 12) having a temperature of not more than Kg, the temperature is 133 ° C. to 134 ° C. even in a battery without the convection promoting film, and the temperature rise is within a range where thermal runaway does not occur (about 135 ° C. or less). Was.

From these results, it was found that when a convection promoting film was attached to a battery having a mass energy density of more than 129 Wh / Kg, a remarkable effect of preventing thermal runaway due to an internal short circuit was obtained.

In the above embodiment, lithium cobalt oxide (LiCoO ₂ ) was used as the positive electrode active material, but instead of LiNiO ₂ , LiMn ₂ O ₄ , cobalt in these compounds,
Various lithium-containing composite oxides such as those obtained by partially replacing nickel or manganese with another element, and those obtained by mixing a plurality of these compounds can be used. In the above embodiment, graphite is used as the negative electrode active material. However, the present invention is not limited to this, and various carbon materials capable of inserting and extracting lithium ions can be used.

[0057]

As is clear from the above, according to the present invention, the heat dissipation of the battery can be enhanced by the extremely simple means of attaching the convection promoting film to the outermost surface of the battery, thereby improving the safety of the battery. Dramatically increase.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram for explaining a contact state of a convection promoting film.

FIG. 2 is a diagram showing the relationship between the thickness of a convection promoting film and the maximum battery temperature.

 ──────────────────────────────────────────────────の Continued on the front page (72) Nobuaki Sugita 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Hiroshi Munemura 2-chome Keihanhondori, Moriguchi-shi, Osaka No. 5-5 Sanyo Electric Co., Ltd. (72) Inventor Michihiro Kurokawa 2-5-5 Sanyo Electric Co., Ltd., Moriguchi-shi, Osaka (72) Inventor Kenji Nasako Keihan Moriguchi-shi, Osaka 2-5-5 Hondori Sanyo Electric Co., Ltd. (72) Inventor Naoki Hiro 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Yoshisaku Yasutake Osaka Moriguchi, Osaka 2-5-5, Keihan Hondori, Ichigo F-term (reference) in Sanyo Electric Co., Ltd. 5H011 AA02 BB03 CC02 DD09 DD12 KK01 5H029 AJ12 AK03 AL07 AM01 BJ14 CJ05 DJ02 EJ01 EJ12 HJ00 HJ04

Claims (9)

[Claims] 1. A sealed battery with a convection promoting film having a convection promoting film attached to the outermost surface of the battery to promote air convection. 2. The sealed battery with a convection promoting film according to claim 1, wherein the convection promoting film is a polymer film. 3. The sealed battery with a convection promoting film according to claim 2, wherein the convection promoting film is a film selected from a polyethylene terephthalate film, a polytetrafluoroethylene film, a polypropylene film, and a cellophane film. 4. The sealed battery with a convection promoting film according to claim 3, wherein the thickness of the convection promoting film is 300 μm or less. 5. The sealed battery with a convection promoting film according to claim 1, wherein the battery can, which is a component of the battery, is a metal can having a thickness of 0.1 mm or more. . 6. The sealed battery with a convection-promoting membrane is a lithium ion battery including a lithium-containing oxide capable of inserting and extracting lithium ions in a positive electrode and a carbon material capable of inserting and extracting lithium ions in a negative electrode. Item 6. A sealed battery with a convection promoting film according to any one of Items 1 to 5. 7. The sealed battery with a convection promoting film according to claim 6, wherein the lithium-containing oxide is lithium cobalt oxide, and the carbon material is graphite. 8. The sealed battery with a convection promoting film according to any one of claims 1 to 7, wherein the sealed battery with a convection promoting film has a spiral electrode body formed by winding a strip-shaped positive electrode and a strip-shaped negative electrode via a separator. Sealed battery. 9. The sealed battery with a convection promoting film according to claim 6, wherein the sealed battery with a convection promoting film has a mass energy density of more than 129 Wh / Kg.