JP2009266402A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack absorbing heat in abnormal heat generation a secondary battery and suppressing temperature rising of a battery pack outside wall surface while keeping the shape of the battery pack. <P>SOLUTION: The battery pack 1 has structure forming a heat absorbing layer 12 coming in contact with the inside of a resin molded body 11 composing the battery pack 1, that is, the inside wall surface of the battery pack, and a gap 13 for diffusing heat to the inside of the battery pack. By the structure, heat in abnormal heat generation of secondary batteries housed inside can be absorbed while suppressing the concentration to the periphery of the secondary batteries 2. In order to furthermore effectively absorb heat of the secondary batteries and suppress temperature rising on the outside wall surface of the battery pack 1, the heat absorbing layer is formed on the outside of the secondary batteries in addition to the inside wall surface of the battery pack. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery pack that houses a battery that may generate heat in the event of an abnormality.

  In recent years, with the widespread use of portable devices such as notebook computers and mobile phones, the demand for batteries as power sources is increasing. In particular, there is an increasing demand for secondary batteries that are small and lightweight, have high energy density, and can be repeatedly charged and discharged. As such a battery, research and development of a lithium ion secondary battery using a non-aqueous solvent as an electrolyte is being actively conducted.

  These lithium-ion secondary batteries have come to hold more energy as the functionality of portable devices increases, and the amount of heat generated at the time of potential abnormalities is proportionally larger. .

  As a battery pack for storing such a battery, a styrene resin is added to a molded polycarbonate resin mixed with a halogen-based flame retardant (see, for example, Patent Document 1) or polyphenylene ether mixed with a phosphate ester-based flame retardant. What molded the blended resin composition was used (for example, refer patent document 2).

In order to further enhance the flame retardancy, inorganic hydrates such as magnesium hydroxide (Mg (OH) ₂ ), aluminum hydroxide (Al (OH) ₃ ), and dawsonite (NaAl (OH) ₂ CO ₃ ) are used as resin. Mixing in a composition has also been proposed (see, for example, paragraph 23 of Patent Document 2).

When magnesium hydroxide or aluminum hydroxide is heated, it uses an endothermic reaction when water (H 2 O) is released to reduce the heat of combustion and produce a flame retardant effect. As a method using such an endothermic reaction, a method using latent heat of fusion when the polymer material constituting the covering of the unit cell melts when the battery generates heat has been proposed (for example, Patent Document 3). .
Japanese Patent Laid-Open No. 10-46015 Japanese Patent No. 3408676 JP 2004-228047 A

  However, halogen-based flame retardants are not used because halogen-based flame retardants may generate substances with a large environmental load, such as dioxins, depending on combustion conditions. On the other hand, it is considered that the phosphoric acid ester is often used as a non-halogenated flame retardant for this problem, and the problem of environmental burden is considered to be small. However, the resin composition in which these halogen-based and non-halogen-based flame retardants are mixed, when the battery abnormally generates heat, the flammability is remarkably reduced, but the resin softens and exhibits fluidity, and the shape of the battery pack May be damaged, and the battery that has become hot may be exposed.

  Therefore, there is a method of absorbing the heat of the secondary battery using an endothermic agent, but if a method of filling the endothermic agent between the secondary battery and the molded body is used as in the past, the periphery of the secondary battery There is a problem that heat is accumulated inside and heat is concentrated locally.

  In addition, when inorganic hydrates such as magnesium hydroxide and aluminum hydroxide are mixed in the resin composition, it is necessary to maintain flowability and moldability when molding the resin in the subsequent process, so that a large amount There is also a problem that sufficient endothermic characteristics cannot be obtained because it cannot be contained in the resin or an endothermic reaction is caused in the temperature range of injection molding.

  Therefore, the present invention provides a battery pack that has sufficient heat absorption performance without impairing the shape of the battery pack and suppresses heat from being generated inside the secondary battery.

  In order to solve the above-described conventional problems, the present invention includes a molded body that houses a secondary battery therein, a first heat absorbing layer formed on the inner wall of the molded body, and a void inside the molded body. The battery pack accommodates a chargeable / dischargeable secondary battery.

  With such a configuration, the heat radiated from the secondary battery is diffused by the air gap and then absorbed by the first heat absorbing layer. Therefore, it is possible to suppress heat from staying around the secondary battery, and thus it is possible to suppress the concentration of heat around the secondary battery.

  Furthermore, an endothermic layer having an endothermic agent can be formed at a higher density on the surface of the molded body that houses the secondary battery than when the molded body or the like contains an endothermic agent. Furthermore, the heat absorption layer can be formed while having sufficient heat absorption characteristics without requiring a heating step such as injection molding.

  That is, as compared with the prior art, heat at the time of abnormal heat generation of the secondary battery accommodated therein can be absorbed while suppressing concentration on the periphery of the secondary battery. Therefore, the temperature rise of the battery pack outer wall surface can be suppressed while maintaining the shape of the battery pack.

  Further, in order to absorb the heat of the secondary battery more effectively and suppress the temperature rise of the outer wall surface of the battery pack, an endothermic layer is provided on the outer side of the secondary battery in addition to the inner wall surface of the battery pack. Is this.

  According to the battery pack of the present invention, when the secondary battery is abnormally heated, heat is absorbed by the endothermic layer while suppressing concentration around the secondary battery. Therefore, the temperature rise of the battery pack outer wall surface can be suppressed while maintaining the shape of the battery pack.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram of a battery pack 1 according to Embodiment 1 of the present invention. The battery pack 1 has a configuration in which the outermost side is formed of a resin molded body 11 and a first heat absorbing layer 12 is provided in contact with the inner wall. A chargeable / dischargeable secondary battery 2 is accommodated in the battery pack 1 having the two-layer structure. A gap 13 is formed between the first endothermic layer 12 and the secondary battery surface. The heat generated in the secondary battery by the gap 13 diffuses in the battery pack and absorbs heat in the first heat absorbing layer 12 provided on the inner wall of the molded body 11.

  Furthermore, the endothermic layer preferably has a flame retardant binder and an endothermic agent. By using a flame retardant binder, the endothermic agent can absorb heat while suppressing melting of the binder. That is, softening of the endothermic layer caused by melting of the polymer material can be suppressed as compared with the case where the latent heat of fusion of the polymer material is used as the endothermic reaction. That is, the polymer material is softened and exhibits fluidity, and at the same time, the secondary battery that has generated heat due to volume shrinkage can suppress exposure. Therefore, it is possible to form an endothermic layer having durability up to a higher temperature.

  Such a battery pack 1 containing the secondary battery 2 was produced as follows.

(A) a step of forming a molded body 11 that houses a chargeable / dischargeable secondary battery 2;
(B) Calcium sulfate dihydrate (CaSO ₄ .2H ₂ O), sodium hydrogen carbonate (NaHCO ₃ ), aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), calcium carbonate At least one endothermic agent of (CaCO ₃ );
Mixing with at least one solution of polyvinylidene chloride or polyvinylidene fluoride in N-methylpyrrolidone (1-methyl-2-pyrrolidone), or calcium sulfate dihydrate (CaSO ₄ .0.5H ₂ O) and Mixing water with a kneaded product to make a paste,
(C) applying the paste to the inner wall of the molded body 11 and drying the paste.

  First, in the step (A), the molded body 11 that houses the secondary battery 2 is formed using a resin. The resin molded body 11 is preferably a flame retardant resin of V-0 or higher of UL-94 standard, and this is referred to as “Guide for Safe Use of Lithium Ion Secondary Batteries in Notebook PCs” (Corporation). Japan Electronics and Information Technology Industries Association, Battery Industry Association). Therefore, also in the embodiment of the present invention, the resin molded body 11 is made of a polymer material that is made flame retardant. As the polymer material, polycarbonate (PC), polypropylene (PP), polyethylene terephthalate (PET), or the like subjected to flame retardant treatment is used.

Subsequently, in step (B), calcium sulfate dihydrate (CaSO ₄ .2H ₂ O), sodium hydrogen carbonate (NaHCO ₃ ), aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (which is an endothermic agent) An N-methylpyrrolidone (1-methyl-2-pyrrolidone) solution of at least one of Mg (OH) ₂ ) and calcium carbonate (CaCO ₃ ) and a flame retardant binder of polyvinylidene chloride or polyvinylidene fluoride Alternatively, a paste was prepared by kneading calcium sulfate half hydrate (CaSO ₄ .0.5H ₂ O) and water.

  In step (C), the endothermic layer 12 was formed by applying the above paste to the inner wall of the molded body.

By such a production method, the endothermic agent is calcium sulfate dihydrate (CaSO ₄ .2H ₂ O), sodium hydrogen carbonate (NaHCO ₃ ), aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), an endothermic layer 12 containing at least one of calcium carbonate (CaCO ₃ ), and the binder containing at least one of polyvinylidene chloride, polyvinylidene fluoride, and calcium sulfate dihydrate. It can be formed on the surface of the molded body 11.

  The endothermic reaction temperature of each endothermic agent is as follows: calcium sulfate dihydrate 80-150 ° C, sodium bicarbonate 100-230 ° C, aluminum hydroxide 230-350 ° C, magnesium hydroxide 350-450 ° C, carbonic acid Calcium is 690-850 ° C. It is also possible to maintain an endothermic reaction continuously by appropriately combining these.

  Polyvinylidene chloride and polyvinylidene fluoride used in this embodiment are themselves flame retardant resins and are preferable materials as a binder. In addition, calcium sulfate half hydrate is so-called “calcined gypsum”. Gypsum as a treatment tool at the time of fracture, mold gypsum was made by reacting powdered calcined gypsum with water and hardening it. As is clear from the fact that the material is kneaded with water, it can be bound by drying. At the same time, since it becomes calcium sulfate dihydrate after drying, it can also be said to be a preferable binder because it acts as an endothermic agent. The ratio between the endothermic agent and the binder should be changed according to the moldability and shape retention, the calorific value of the secondary battery 2 to be included, the heat capacity, and the combination of the materials of the endothermic agent and the binder. Therefore, it should be blended according to the desired characteristics.

  Furthermore, as shown in FIG. 2, the 2nd heat absorption layer 21 can also be provided in the outer wall of a secondary battery. As described above, by providing the second heat absorbing layer 21 also on the outside of the secondary battery 2, heat absorption can be started before the heat is transferred to the battery pack 1, so that the heat of the secondary battery 2 can be more effectively reduced. It absorbs heat and can suppress the temperature rise of the outer wall surface of the battery pack 1.

(Embodiment 2)
The second embodiment is the same as the first embodiment except for the method of manufacturing the endothermic layer. Here, only differences from the second embodiment will be described, and the same parts will be omitted.

First, (A) a molded body 11 that houses a chargeable / dischargeable secondary battery 2 is formed. Subsequently, (B ′) calcium sulfate half hydrate (CaSO ₄ .0.5H ₂ O) and water are kneaded to prepare a paste, and finally (C) the paste is applied to the molded body 11. And dry. Since step (A) and step (C) are the same as those in the first embodiment, description thereof is omitted here.

The step (B ′) is a step of kneading calcium sulfate half hydrate (CaSO ₄ .0.5H ₂ O) and water to produce a paste. It is so-called “calcined gypsum”, and casts and cast gypsum as a treatment tool at the time of fracture are obtained by reacting powdered calcined gypsum with water and hardening it. Can be bound by kneading and drying.

That is, in this way, by using a paste in which calcium sulfate half hydrate (CaSO ₄ .0.5H ₂ O) and water are mixed, an adsorbent is applied to the surface of the resin molded body 11. Can be painted. Therefore, in Embodiment 2, calcium sulfate dihydrate can serve as both a binder and an adsorbent. That is, the adsorbent density can be increased as compared with the endothermic layer using the endothermic agent and the binder. Furthermore, it is possible to form the endothermic layer more easily without the need to mix the adsorbent and the binder.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited at all by the following Example, In the range which does not change the summary, it can change suitably and can implement.

Example 1
12 g of sodium bicarbonate (special grade reagent manufactured by Wako Pure Chemical Industries) and 10 g of KF polymer # 1120 (polyvinylidene fluoride 12% N-methylpyrrolidone solution, manufactured by Kureha Co., Ltd.) were mixed and stirred, and then placed on a polycarbonate plate (thickness 1 mm). It was applied and dried at room temperature in the air.

  The endothermic layer thickness obtained was 1 mm. The sample was cut into a 10 mm square, a ceramic heater (MS-1000, manufactured by Sakaguchi Electric Heat Co., Ltd.) was placed on the endothermic layer side, a voltage was applied, the temperature was raised at 100 ° C./min, and the temperature on the polycarbonate plate side The temperature plateau accompanying the endotherm and its duration were confirmed, and the degree of deformation of the polycarbonate plate at the end of the temperature plateau observation was visually observed.

(Comparative Example 1)
The same test as in Example 1 was performed except that the ceramic heater was directly brought into contact with the polycarbonate plate except for the endothermic layer of Example 1.

(Example 2)
6 g of aluminum hydroxide (special grade reagent manufactured by Wako Pure Chemical Industries) and 10 g of KF polymer # 1120 were mixed and stirred, then applied to a polycarbonate plate (thickness 1 mm), and dried in the atmosphere at room temperature. Thereafter, the same test as in Example 1 was performed.

(Example 3)
6 g of magnesium hydroxide (special grade reagent manufactured by Wako Pure Chemical Industries) and 10 g of KF polymer # 1120 were mixed and stirred, then applied to a polycarbonate plate (thickness 1 mm), and dried in the atmosphere at room temperature. Thereafter, the same test as in Example 1 was performed.

Example 4
6 g of calcium sulfate dihydrate (special grade reagent manufactured by Wako Pure Chemical Industries) and 10 g of KF polymer # 1120 are mixed and stirred, and then applied to a polycarbonate plate (thickness 1 mm) and dried in the air at room temperature. It was. Thereafter, the same test as in Example 1 was performed.

(Example 5)
Calcium sulfate half hydrate (manufactured by Kojundo Chemical Laboratory Co., Ltd.) and pure water were kneaded so as to have a volume ratio of 1: 1, applied to a polycarbonate plate (thickness 1 mm), Dry at room temperature. Thereafter, the same test as in Example 1 was performed.

(Example 6)
6 g of calcium carbonate (special grade reagent manufactured by Wako Pure Chemical Industries) and 10 g of KF polymer # 1120 were mixed and stirred, and then applied to a polycarbonate plate (thickness 1 mm) and dried at room temperature in the atmosphere. Thereafter, the same test as in Example 1 was performed.

(Example 7)
6 g of polyvinylidene chloride (saran wrap (R) Asahi Kasei) was dissolved in 50 g of N-methylpyrrolidone (special grade reagent manufactured by Wako Pure Chemical) to prepare a 12% N-methylpyrrolidone solution of polyvinylidene chloride. A sample similar to Example 2 was prepared and tested except that the solution was used.

(Example 8)
After mixing and stirring the calcium sulfate paste and magnesium hydroxide obtained in Example 5 so as to have a volume ratio of 1: 1, the mixture was applied to a polycarbonate plate (thickness 1 mm) and dried at room temperature in the air. . Thereafter, the same test as in Example 1 was performed.

Example 9
4 g of sodium bicarbonate, 2 g of aluminum hydroxide and magnesium hydroxide, and 10 g of KF polymer # 1120 were mixed and stirred, and then applied to a polycarbonate plate (thickness 1 mm) and dried in the atmosphere at room temperature. . Thereafter, the same test as in Example 1 was performed.

  The results of the above examples are summarized in Table 1.

  By providing the endothermic layer, a temperature difference of about 20 ° C. to 200 ° C. can be secured between the heater temperature and the resin side temperature. Even if the battery pack 1 exterior resin is softened, the endothermic layer functions as a structural material. I did not want to transform. Therefore, providing the heat absorption layer on the inner wall of the battery pack 1 can suppress heat transfer to the outside even when the secondary battery 2 generates heat in the battery pack 1.

(Example 10)
The paste produced in Example 3 was applied to the outside of a rectangular battery case (5.2 mm × 34 mm × 50 mm), and a ceramic heater (MS-M5, manufactured by Sakaguchi Denki Co., Ltd.) was disposed in the battery case. The battery case was sealed in a battery pack 1 made of polycarbonate in which the paste produced in Example 2 was applied to the inner wall. Energize the ceramic heater from the outside, raise the temperature at 100 ° C / min, measure the temperature outside the battery pack 1, check the temperature plateau accompanying the endotherm and its duration, and deform the polycarbonate plate at the end of the temperature plateau observation The degree was visually observed.

  As a result, the temperature outside the battery pack 1 was maintained at 220-240 ° C. between the heater temperatures of 300-700 ° C., and no deformation of the battery pack 1 exterior resin was observed.

  From the above, heat transfer to the outside of the battery pack 1 can be more effectively suppressed by providing heat absorption layers on both the inner wall of the battery pack 1 and the outer wall of the secondary battery 2.

  In the examples, the polycarbonate most often used as the resin molded body 11 constituting the battery pack 1 was used, but it is obvious that the same effect can be obtained even if propylene carbonate or polyethylene terephthalate is used. It is not limited.

  The battery pack according to the present invention has a function of absorbing heat at the time of abnormal heat generation of the secondary battery and suppressing the temperature rise of the outer wall surface of the battery pack while maintaining the shape of the battery pack. Useful as a pack material. It can also be applied to exterior materials that have improved the safety of large secondary batteries such as electric vehicles.

Sectional drawing of the battery pack in Embodiment 1 of this invention Sectional drawing of the battery pack in Embodiment 2 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery pack 2 Secondary battery 11 Resin molding 12 1st heat absorption layer 13 Cavity 21 2nd heat absorption layer

Claims (6)

A molded body containing a secondary battery inside;
A first endothermic layer formed on the inner wall of the molded body;
A battery pack that houses a chargeable / dischargeable secondary battery having a void inside the molded body. A battery pack for storing a chargeable / dischargeable secondary battery, further comprising a second heat absorbing layer on an outer wall of the secondary battery. 3. The battery pack containing the chargeable / dischargeable secondary battery according to claim 1, wherein the endothermic layer has a flame retardant binder and an endothermic agent. The endothermic agent is calcium sulfate dihydrate (CaSO ₄ .2H ₂ O), sodium hydrogen carbonate (NaHCO ₃ ), aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), Including at least one of calcium carbonate (CaCO ₃ ),
The battery pack according to any one of claims 1 to 3, wherein the flame retardant binder includes at least one of polyvinylidene chloride, polyvinylidene fluoride, and calcium sulfate dihydrate. (A) forming a molded body that houses a chargeable / dischargeable secondary battery;
(B) Calcium sulfate dihydrate (CaSO ₄ .2H ₂ O), sodium hydrogen carbonate (NaHCO ₃ ), aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), calcium carbonate At least one endothermic agent of (CaCO ₃ );
Mixed with at least one of polyvinylidene chloride or polyvinylidene fluoride in N-methylpyrrolidone (1-methyl-2-pyrrolidone) solution, or calcium sulfate half hydrate (CaSO ₄ .0.5H ₂ O) and water And mixing with a kneaded product to make a paste,
(C) applying the paste to the inner wall of the molded body and drying;
The manufacturing method of the battery pack which accommodates the secondary battery which can be charged / discharged. (A) forming a molded body that houses a chargeable / dischargeable secondary battery;
(B ′) a step of kneading calcium sulfate half hydrate (CaSO ₄ .0.5H ₂ O) and water to prepare a paste;
(C) applying the paste to the inner wall of the molded body and drying;
The manufacturing method of the battery pack which accommodates the secondary battery which can be charged / discharged.

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