JP2009087875A - High heat radiation electrochemical element and power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical element superior in heat radiation characteristics having a high safety even at the time of abnormality. <P>SOLUTION: The electrochemical element has a coated layer having as a main component at least one kind of particles selected from a group of oxide and a silicate compound. In the extreme-infrared emission spectrum which has measured the coated layer at 100°C, it has a point in which the value of extreme-infrared emissivity exceeds 0.85 in the wavelength range 4-15 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrochemical element and a power supply device that have a high heat radiation characteristic by including a coating layer having a high far-infrared emissivity, and that can efficiently release heat in response to heat generated in an abnormal state.

Electrochemical elements such as lithium ion secondary batteries, nickel metal hydride secondary batteries, and electric double layer capacitors have been widely used as small portable power sources, and energy density and output characteristics have been dramatically improved. Along with this, heat generation when an abnormal situation such as a short circuit occurs in these electrochemical elements or a power supply device using the same is a big problem. Furthermore, in recent years, new applications such as a power source for hybrid electric vehicles and an energy storage power source are being opened in addition to a small portable power source, and the problem of heat generation due to the increase in size has become more serious.
Conventionally, there have been many proposals for solving the problem of heat generation occurring in these electrochemical elements or power supply devices.

  For example, Patent Document 1 proposes to release generated heat by providing an electrochemical element or a power supply device with a heat pipe. Heat pipes, heat sinks, and the like are those in which a solvent is enclosed in a metal pipe or metal case, and the solvent evaporates due to the generated heat and dissipates heat by its convection phenomenon. In fact, this heat pipe and heat sink have a very high apparent thermal conductivity and excellent heat dissipation characteristics, but unfortunately they are extremely expensive and require extra weight and volume by incorporating these parts. Therefore, it is not suitable for an electrochemical element and / or a power supply device in which miniaturization and weight reduction are important.

  In patent document 2, there exists a proposal of making it thermally radiate by interposing a high heat conductive member between a battery surface and a battery accommodating part inner surface. A metal material having a high thermal conductivity and being inexpensive is a metal material, but cannot be used in the case of an electrochemical element or a power supply device that requires electrical insulation. As materials having electrical insulation properties and high thermal conductivity, materials such as diamond, sapphire, aluminum nitride and boron nitride are known, but they are expensive and are not used for general purposes. . Furthermore, the method of radiating heat based on the principle of heat conduction has a fatal problem that a sufficient heat radiation effect cannot be exerted unless the heat generating portion and the heat receiving portion (portion where heat is released to the outside) are not completely adhered. . It is practically impossible to completely bring electrochemical elements having various shapes into close contact with the heat conducting material, and it is not an appropriate method even in the case of a power supply device in which a space must be present.

  Patent Document 3 proposes that a heat-dissipating sheet containing a silicone gel as a matrix and blended with a high thermal conductivity material is attached to a battery. According to this method, it is possible to attach a heat radiating sheet according to the shape of the battery. However, when it is intended to be used for a power supply device, the heat radiating sheet attached to the battery is further replaced with a heat receiving portion (heat is transferred to the outside A common problem remains when heat is dissipated by a heat conduction mechanism that must be in close contact with the part to be released.

  Patent Document 4 proposes a method based on thermal radiation (thermal radiation), which is a new heat radiation mechanism different from conventional heat transfer and convection. That is, it is said that by forming a high emissivity layer having a thermal emissivity of 0.6 or more in the battery, particularly the battery terminal portion, the heat dissipation characteristics are improved and the safety of the battery is enhanced. In the case of a heat dissipation mechanism based on this heat radiation, unlike heat conduction, the heat is dissipated through the space, so the heat generating part and the heat receiving part (the part that releases heat to the outside) must be in close contact. It has attracted attention as an optimal heat dissipation method for electrochemical devices and power supply devices. However, the heat dissipation effect is still not sufficient, and there remains a problem particularly with respect to the phenomenon of internal short circuit in which large heat is generated locally in electrochemical devices, which has become a problem in recent years.

Patent Document 5 proposes a method in which the thermal emissivity (radiation rate) is set to 0.6 or more by coloring the battery exterior member (mainly polymer heat-shrinkable tube), and the function of thermal radiation is exhibited. ing. Although attention is paid to the fact that a heat radiation function is incorporated in a conventionally used exterior member, the effect is insufficient for an internal short-circuit phenomenon in which a large amount of heat is generated locally.
JP 09-245845 A JP 2002-216726 A JP 2007-042362 A JP 2002-231192 A JP 2007-134308 A

As described above, the thermal problems related to electrochemical elements and power supply devices are serious, and not only the problem of deterioration of power supply characteristics due to heat generation, but also the safety as a power supply due to heat generation in the event of an abnormality. However, at present, no means for solving the problem has been found.
The present invention was made in order to solve these problems. Focusing on a heat radiation mechanism called heat radiation, the improvement provides a sufficient heat radiation effect even in the case of an internal short-circuit accompanied by a large amount of heat locally. The present invention provides an electrochemical element and a power supply device with high performance.

The present inventors have intensively studied to solve the above problems. As a result, the present inventors have found that the above problem can be solved by forming a coating layer having a high far-infrared emissivity in a specific wavelength range, and have reached the present invention. That is, this invention is the following electrochemical element and power supply device.
1. An electrochemical element having a coating layer mainly composed of at least one kind of particles selected from the group consisting of inorganic oxides and silicate compounds, wherein the coating layer is measured in a far infrared radiation spectrum measured at 100 ° C An electrochemical element having a point where the value of far-infrared emissivity exceeds 0.85 in a wavelength range of 4 to 15 µm.
2. The electrochemical element as described in 1 above, wherein a coating layer having a point where the far-infrared emissivity measured at 100 ° C. exceeds 0.95 is formed in a wavelength range of 4 to 15 μm.
3. The electrochemical device as described in 1 above, wherein the far infrared emissivity measured at 100 ° C. has a point where the wavelength exceeds 0.85 in a wavelength range of 5 to 10 μm.
4. The electrochemical element according to 2 above, wherein the far infrared emissivity measured at 100 ° C. has a point where the wavelength exceeds 0.95 in a wavelength range of 5 to 10 μm.
5). A power supply device including an electrochemical element having a coating layer mainly composed of at least one kind of particles selected from the group consisting of an inorganic oxide and a silicate compound, and a container case for storing the electrochemical element. The power supply device is characterized in that the electrochemical element is the one described in any one of 1 to 4 above.
6). A power supply device including a container case having a coating layer mainly composed of at least one kind of particles selected from the group consisting of an inorganic oxide and a silicate compound, and an electrochemical element housed in the container case. A far-infrared radiation spectrum measured at 100 ° C. of the coating layer has a far-infrared emissivity value exceeding 0.85 in a wavelength range of 4 to 15 μm.

  The electrochemical element and the power supply device of the present invention have a high heat dissipation effect based on a heat dissipation mechanism called heat radiation, and have an effect of improving reliability and safety when the electrochemical element and the power supply device are abnormal.

The present invention will be described in detail below.
The electrochemical element of the present invention is an element that electrochemically generates electric energy, and an example thereof is shown below. Lithium primary battery with metallic lithium as negative electrode and manganese dioxide, carbon fluoride as positive electrode; carbon material, metal oxide, lithium alloy, etc. as negative electrode, lithium cobaltate, lithium nickelate, lithium manganate, iron phosphate Lithium ion secondary battery with lithium as positive electrode; Electric double layer capacitor with activated carbon as positive electrode and negative electrode; Lithium-transition metal composite oxide such as vanadium, titanium and iron as negative electrode, cobalt, manganese, iron, etc. Water-based ion battery using lithium-transition metal composite oxide as a positive electrode; alkaline secondary battery using cadmium, hydrogen storage alloy, etc. as negative electrode, nickel oxyhydroxide, etc. as positive electrode; reaction using hydrogen as a fuel source and oxygen For example, a fuel cell that extracts energy.

A power supply device is composed of at least one or a plurality of the aforementioned electrochemical elements and a container case for storing the electrochemical elements, and if necessary, as a power supply by incorporating other components such as a control system circuit board. A functioning device.
The far-infrared emission spectrum is a diagram in which the far-infrared emissivity of a substance measured by a spectrometer described later is plotted for each wavelength. The present invention is based on the finding that when the coating layer has a specific far-infrared emissivity in a specific wavelength range, the actual heat dissipation effect of the electrochemical element and the power supply device is remarkably exhibited. That is, it is necessary that the coating layer has a point where the far-infrared emissivity value measured at 100 ° C. in the wavelength range of 4 to 15 μm is at least 0.85, preferably exceeding 0.95. In the following description, the far-infrared emissivity value is a value measured at 100 ° C. unless otherwise specified. When there is no point where the far-infrared emissivity value exceeds 0.85 in the wavelength range of 4 to 15 μm, it is sufficient for the heat dissipation effect, particularly when large heat generation such as internal short circuit occurs. The heat dissipation effect cannot be demonstrated. Furthermore, it is preferred that the coating layer has a far infrared emissivity value of at least 0.85, preferably exceeding 0.95 in the wavelength range of 5 to 10 μm.

  The coating layer in the present invention is a layer containing a substance having a thermal radiation function exhibiting far-infrared emissivity in the above range (hereinafter also simply referred to as “emissivity”). Preferable examples of the substance having such a heat radiation function include inorganic oxides such as titanium oxide, aluminum oxide, silicon dioxide, zirconium oxide, tin oxide, magnesium oxide, zinc oxide, indium oxide, and antimony oxide, and kaolin. And silicate compounds such as zeolite, perlite, talc, dolomite, and tourmaline can be used, and can be used in the present invention by blending one or more of these groups. Since these materials have a difference in emissivity with respect to each wavelength, the coating layer has an average high emissivity in a wavelength range of 4 to 15 μm and an emissivity of 0.85 or more at a specific wavelength. It is more preferable to mix seeds or more. In addition to containing the above-mentioned substance having a heat radiation function as a main component, the coating layer may contain a binder, for example, a silicone resin.

The following method is exemplified for forming the coating layer using the substance having the heat radiation function on the electrochemical element and / or the power supply device.
As a first method, there is a method in which a sheet containing a substance having a heat radiation function is prepared, and this is attached to an electrochemical element and / or a power supply device to form a coating layer. In this case, a composition composed of a substance having a heat radiation function and a binder resin or a solution or dispersion thereof is applied or impregnated on a substrate such as a glass cloth, a resin film, a metal plate, or a metal foil, and dried. Make a sheet. If necessary, an adhesive layer can be formed on one side of the sheet to form an adhesive sheet.

  The binder resin is not particularly limited, and examples thereof include styrene / butadiene resin, butyl rubber, acrylic resin, epoxy resin, and silicone resin. In the sheet, the binder resin is preferably 5 to 75 parts by weight with respect to 100 parts by weight of the substance having a heat radiation function. Moreover, as resin which comprises an adhesion layer, a rubber adhesive, an acrylic adhesive, a silicone adhesive, etc. are mentioned, Thickness is preferable 1-25 micrometers.

  As the second method, a composition comprising a substance having a heat radiation function and a binder resin or a solution or dispersion thereof is used as a paint, and applied directly to an electrochemical element and / or a power supply device and dried to form a coating layer. There is a way. The binder resin that can be used in this method is not particularly limited, and examples thereof include styrene / butadiene resin, butyl rubber, acrylic resin, epoxy resin, and silicone resin.

As a third method, there is a method in which a material having a heat radiation function is directly formed on an electrochemical element and / or a power supply device by a method such as thermal spraying, vapor deposition, or CVD to form a coating layer.
Among the methods of forming the coating layer, the method of forming the first sheet is preferable because it is simple and provides a high heat dissipation effect. Further, it is preferable to use a glass cloth as the base material at that time from the viewpoint of heat resistance, durability, and the like. Although the thickness of this coating layer is not specifically limited, The range of 5 micrometers-200 micrometers is preferable. If the thickness is 5 μm or more, a sufficient heat dissipation effect is exhibited, and if it is 200 μm or less, the space efficiency is excellent.
When the coating layer is formed on the electrochemical device, it is preferably formed on the whole or a part of the side surface, bottom surface, and / or upper end portion of the outer surface of the container of the electrochemical device. Moreover, when forming a coating layer in a power supply device, it is preferable to form it in the whole surface or a part of container case inner surface or outer surface of a power supply device. Of course, a coating layer may be formed on the outer surface of the container of the electrochemical element and the inner and outer surfaces of the container case of the power supply device.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.
FIG. 1 shows an example of an electrochemical element and a coating layer of the present invention. In FIG. 1, 1 is a battery container, 2 is a long side surface of the battery container (meaning a side surface having the largest area), 3 is a short side surface of the battery container, 4 is a positive electrode terminal, 5 is a negative electrode terminal, 6 is a safety valve, 7 is a coating layer. FIG. 2 shows the far-infrared emission spectrum. FIG. 3 shows changes in the surface temperature of the battery container during the external short circuit test. FIG. 4 shows changes in the surface temperature of the battery container during the nail penetration test. FIG. 5 shows an assembled battery in which two batteries are connected in series. FIG. 6 shows a power supply device comprising the assembled battery and a container case.
The far-infrared radiation spectrum was measured using a Fourier transform infrared spectrophotometer (manufactured by JASCO Corporation, FT-IR660) at 100 ° C. The measured far-infrared emissivity values were calibrated with a reference material with known far-infrared emissivity (Pyromark, Tempil Inc.).

[Reference Example 1]
With respect to 100 parts by mass of LiCoO ₂ , 2.5 parts by mass of graphite, 2.5 parts by mass of acetylene black, 8 parts by mass of polyvinylidene fluoride as a binder were added, and N-methylpyrrolidone parts by mass were used as a solvent to make a paste. This was applied to both sides of an aluminum foil having a thickness of 18 μm and dried to prepare a positive electrode having a total thickness of 220 μm. Next, 8 parts by mass of polyvinylidene fluoride as a binder is added to 100 parts by mass of graphite, and a paste formed using N-methylpyrrolidone parts by mass as a solvent is applied to both sides of a copper foil having a thickness of 12 μm. A dried negative electrode having a total thickness of 150 μm was produced. A separator made of polyethylene and having a thickness of 24 μm was interposed between the positive electrode and the negative electrode, wound around many times to produce a spiral electrode body, and then the side surface of the electrode body was pressed and flattened. After this electrode body was accommodated in a container made of an aluminum battery can (length: 48 mm, width: 34 mm, thickness: 6 mm), 1 mol of LiPF ₆ was added as an electrolyte in a mixed solvent of ethylene carbonate / methyl ethyl carbonate in a volume ratio of 1: 2. -A solution dissolved at a concentration of dm- ³ was injected. A positive electrode terminal, a negative electrode terminal, and a metal thin film type safety valve were incorporated and sealed to produce a square lithium ion secondary battery shown in FIG.

[Example 1]
Silicon dioxide powder (average particle size 3.5 μm) 35 as a powder of a substance having a heat radiation function (hereinafter referred to as “heat radiation powder”) in 100 parts by weight of an aqueous dispersion of silicone resin (silicone resin content 54% by weight) Part by weight, 25 parts by weight of aluminum oxide powder (average particle size 8.3 μm), and 15 parts by weight of zirconium oxide powder (average particle size 1.5 μm) were dispersed and mixed with a mixer. After impregnating this dispersion into a glass cloth having a thickness of 30 μm (1037 manufactured by Asahi Kasei Electronics Co., Ltd.), drying was performed at 120 ° C. to obtain a sheet having an average thickness of 60 μm. A heat radiation powder layer having a thickness of 15 μm is formed on both sides of the cloth.) An adhesive layer made of butyl rubber having a thickness of 10 μm is formed on one side of this sheet by applying a hexane solution, cut to a length of 40 mm and 30 mm, and adhered to the long side surfaces on both sides of the prismatic battery of Reference Example 1. It was set as the coating layer.
The result of measuring the far-infrared emission spectrum of this coating layer is shown in FIG. It has a maximum value of emissivity at a wavelength of 8.5 μm, and its value was 0.98. An external short-circuit test was performed in a state where this square battery was overcharged to 4.35 V, and the change in the battery can surface temperature at that time is shown in FIG. Next, a nail penetration test was performed as an internal short-circuit test in a state where a square battery prepared in the same manner was overcharged to 4.35 V, and the change in the battery can surface temperature at that time is shown in FIG. Table 1 summarizes these results.

The external short circuit test and the nail penetration test were performed according to the following procedure.
[External short circuit test]
A thermocouple was placed on the short side surface of the battery can, and the positive electrode terminal and the negative electrode terminal were connected with a copper wire having a diameter of 3 mm to externally short-circuit. The time of short-circuiting was set to 0, and the subsequent temperature change was measured with a thermocouple.
[Nail penetration test]
A thermocouple is placed on the short side of the battery can, and a 3 mmφ nail is inserted into the center of the long side of the battery can. The puncture time was set to 0 and the subsequent temperature change was measured with a thermocouple.

[Example 2]
In Example 1, 35 parts by weight of silicon dioxide powder (average particle size 3.5 μm), 25 parts by weight of aluminum oxide powder (average particle size 8.3 μm), tin oxide powder (average particle size 0.5 μm) The same operation was performed except that the amount was changed to 15 parts by weight to obtain a sheet having an average thickness of 60 μm. As a result of measuring the far-infrared radiation spectrum of this coating layer, it had a maximum value of emissivity at a wavelength of 6.5 μm, and its value was 0.96. An external short circuit test and a nail penetration test were performed under the same conditions as in Example 1. The results are shown in Table 1.

[Example 3]
In Example 1, the heat radiation powder was 35 parts by weight of silicon dioxide powder (average particle size 3.5 μm), 30 parts by weight of kaolin powder (average particle size 0.3 μm), magnesium oxide powder (average particle size 3.5 μm) 5 A sheet having an average thickness of 60 μm was obtained by performing the same operation except that the weight part was used. As a result of measuring the far-infrared radiation spectrum of this coating layer, it had a maximum value of emissivity at a wavelength of 11.5 μm, and its value was 0.88. An external short circuit test and a nail penetration test were performed under the same conditions as in Example 1. The results are shown in Table 1.

[Example 4]
In Example 1, 35 parts by weight of aluminum oxide powder (average particle size 8.3 μm), 30 parts by weight of kaolin powder (average particle size 0.3 μm), calcium phosphate powder (average particle size 3.5 μm) 5 A sheet having an average thickness of 60 μm was obtained by performing the same operation except that the weight part was used. As a result of measuring the far-infrared radiation spectrum of this coating layer, it had a maximum emissivity at a wavelength of 4.5 μm, and its value was 0.87. An external short circuit test and a nail penetration test were performed under the same conditions as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, the same operation was performed except that the heat radiation powder was replaced with 35 parts by weight of activated clay powder (average particle size 0.3 μm) and 35 parts by weight of kaolin powder (average particle size 0.3 μm), and the average thickness 60 μm. Got the sheet. The measurement result of the far-infrared radiation spectrum of this coating layer is shown in FIG. It has a maximum value of emissivity at a wavelength of 8.5 μm, and the value was 0.81. An external short circuit test and a nail penetration test were performed under the same conditions as in Example 1. The results are shown in FIGS. 3 and 4, respectively. Table 1 summarizes these results.

[Comparative Example 2]
In Example 1, the same operation was performed except that the heat radiation powder was replaced with 35 parts by weight of activated clay powder (average particle size 8.3 μm) and 35 parts by weight of calcium oxide powder (average particle size 2.3 μm), and the average thickness was changed. A 60 μm sheet was obtained. As a result of measuring the far-infrared radiation spectrum of this coating layer, it had a maximum value of emissivity at a wavelength of 15.5 μm, and its value was 0.79. An external short circuit test and a nail penetration test were performed under the same conditions as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
An external short circuit test and a nail penetration test were performed under the same conditions as in Example 1 without using the battery prepared in Reference Example 1 and forming a coating layer. The results are shown in Table 1.

[Example 5]
Two batteries having the coating layer prepared in Example 1 were connected in series to prepare an assembled battery shown in FIG. This assembled battery was placed in a polycarbonate resin power supply container case shown in FIG. The same coating layer as that prepared in Example 1 was also formed inside the long side surface of the power supply device case. An external short circuit test and a nail penetration test were performed under the same conditions as in Example 1 with this power supply device overcharged to 8.7V.
The results are shown in Table 1. Even when the battery was sealed in the power supply container case, excellent safety was maintained.

[Example 6]
A commercially available cylindrical nickel-metal hydride battery (Sanyo Electric N-TG1S diameter 14 mm, height 50 mm) was peeled off and the same 10 μm adhesive layer was formed on the 60 μm thick sheet prepared in Example 1 Was pasted on the side for one lap. The nickel-metal hydride battery was charged with a commercially available charger (NC-TG1 manufactured by Sanyo Electric) for 7 hours, and then an external short-circuit test and a nail penetration test were performed under the same conditions as in Example 1. However, in the nail penetration test, a nail was inserted in the center of the side. The results are shown in Table 1.

[Comparative Example 4]
The external heat-shrink film of the same commercially available cylindrical nickel-metal hydride battery (N-TG1S diameter 14 mm, height 50 mm) as in Example 6 was peeled off for 7 hours with a commercially available charger (NC-TG1 manufactured by Sanyo Electric). After charging, an external short circuit test and a nail penetration test were performed under the same conditions as in Example 1. However, in the nail penetration test, a nail was inserted in the center of the side. The results are shown in Table 1. In addition, a far-infrared emissivity shows the value of the battery can surface without a coating layer.

  The electrochemical element and the power supply device of the present invention are excellent in heat dissipation, can maintain excellent reliability and safety even in abnormal situations such as external short-circuit and internal short-circuit, and are usefully used as a small portable power source and a large power source. be able to.

It is an external view of the electrochemical element used in Examples 1 to 5 and Comparative Examples 1 to 3 of the present invention. It is a far-infrared radiation spectrum figure of the coating layer used in Example 1 or Comparative Example 1 of the present invention. It is a figure which shows the temperature change of the battery can surface at the time of the external short circuit test done in Example 1 or Comparative Example 1 of this invention. It is a figure which shows the temperature change of the battery can surface at the time of the nail penetration test performed in Example 1 or Comparative Example 1 of the present invention. FIG. 6 is an external view of a battery pack created in Example 5. It is a perspective view of the power supply device (however, an assembled battery is abbreviate | omitted) created in Example 5. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery container 2 Long side surface 3 Battery container short side surface 4 Positive electrode terminal 5 Negative electrode terminal 6 Safety valve 7 Cover layer 9 Positive electrode lead wire 10 Negative electrode lead wire 11 Power supply container case 12 Long side surface 13 Positive electrode lead wire port 14 Negative electrode lead wire

Claims (6)

  An electrochemical element having a coating layer mainly composed of at least one kind of particles selected from the group consisting of inorganic oxides and silicate compounds, wherein the coating layer is measured in a far infrared radiation spectrum measured at 100 ° C An electrochemical element having a point where the value of far-infrared emissivity exceeds 0.85 in a wavelength range of 4 to 15 µm.   2. The electrochemical element according to claim 1, wherein a coating layer having a point where the far-infrared emissivity measured at 100 [deg.] C. exceeds 0.95 in a wavelength range of 4 to 15 [mu] m is formed.   2. The electrochemical device according to claim 1, wherein the far-infrared emissivity value measured at 100 ° C. has a point where the wavelength exceeds 0.85 in a wavelength range of 5 to 10 μm.   The electrochemical device according to claim 2, wherein the far infrared emissivity value measured at 100 ° C has a point where the wavelength exceeds 0.95 in a wavelength range of 5 to 10 µm.   A power supply device including an electrochemical element having a coating layer mainly composed of at least one kind of particles selected from the group consisting of an inorganic oxide and a silicate compound, and a container case for storing the electrochemical element. The power supply device is characterized in that the electrochemical element is the one according to any one of claims 1 to 4.   A power supply device including a container case having a coating layer mainly composed of at least one kind of particles selected from the group consisting of an inorganic oxide and a silicate compound, and an electrochemical element housed in the container case. A far-infrared radiation spectrum measured at 100 ° C. of the coating layer has a far-infrared emissivity value exceeding 0.85 in a wavelength range of 4 to 15 μm.

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