JP2007095477A - Battery and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery in which two battery cans are fitted together, in which a power generating element is housed inside, in which adhesion strength of the fitted battery cans is large, and which is high in anti-liquid leakage characteristics. <P>SOLUTION: This is the battery provided with the power generating element, the battery can 1, the battery can 2 of which the bottom area is larger than that of the battery can 1, and a sealing material 3. The battery can 1 and the battery can 2 are opposed and fitted together, they are sealed and adhered between the outside face of the batter can 1 and the inside face of the battery can 2 by the sealing material 3, the power generating element is arranged between the bottom face of the battery can 1 and the bottom face of the battery can 2, and the sealing material 3 includes a thermally expansible microcapsule 3b and a resin 3a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery in which a power generation element is housed in a battery can and a method for manufacturing the same.

  In recent years, with the development of portable devices such as small mobile devices due to the progress of wireless communication technology such as Bluetooth and the high integration of integrated circuits (IC), batteries having characteristics suitable for these devices have been developed. Is demanded by the market. That is, the battery has a large electric capacity, a small size and a light weight, and high reliability such as leakage resistance.

Conventionally, coin-type batteries and laminate-type batteries are mainly used as such batteries. However, neither battery is necessarily sufficient to satisfy the market demands as described above. In particular, the difference between the demand for electric capacity and the reality is large. For example, a coin-type battery uses a caulking structure, and as the battery is downsized, the influence of the volume occupied by the caulking portion that cannot accommodate the power generation element increases. Similarly, in the laminate type battery, the laminated sealing portion of the laminate film is lost. Therefore, in order to solve these problems, a thin battery in which two battery cans having different bottom sizes are fitted and a power generation element is housed therein has been proposed (see, for example, Patent Documents 1 and 2). .)
JP 55-1111060 A Japanese Utility Model Publication No. 58-139668

  In general, the adhesive strength when metals are bonded to each other with a sealing material is determined by the state of the metal deposition surface and the bonding surface of the sealing material, and the temperature, pressure and time during bonding. That is, at the time of bonding, heating at a temperature and time sufficient to uniformly dissolve the encapsulant, and bonding while applying high pressure in a direction perpendicular to the adherend surface, the gap between the metal and the encapsulant A large adhesive strength can be obtained without air entering. However, in the case of manufacturing a battery, if it is heated for a long time at a temperature necessary for melting the sealing material, for example, 150 to 200 ° C., the power generation element inside the battery is adversely affected. Therefore, the adhesive strength is maintained by applying heat and pressure simultaneously in a short time of about several seconds. For example, for the production of the laminate type battery, a method of applying high heat and a constant pressure from both outer surfaces of two exterior laminate films sandwiching a sealing material is used.

  However, since the battery as disclosed in Patent Documents 1 and 2 described above has a configuration in which one battery can is fitted over the other battery can, the attachment surface (side surface) of the battery can. Sufficient pressure cannot be applied from the direction perpendicular to. Therefore, a method is used in which only the temperature is applied from the outer surface of one of the battery cans for adhesion. However, this bonding method has a problem that sufficient adhesive strength cannot be obtained, and the battery has insufficient liquid resistance.

  The present invention provides a battery in which two battery cans are fitted and a power generation element is housed therein, and the battery can have high adhesion strength and high leakage resistance.

  The battery of the present invention is a battery comprising a power generation element, a battery can a, a battery can b having a larger bottom area than the battery can a, and a sealing material, the battery can a and the battery can b is fitted oppositely, and the outer surface of the battery can a and the inner surface of the battery can b are sealed and bonded by the sealing material, and the power generation element is the battery can It is arrange | positioned between the bottom face of a, and the bottom face of the said battery can b, The said sealing material contains a thermally expansible microcapsule and resin, It is characterized by the above-mentioned.

  The battery manufacturing method of the present invention includes a power generation element, a battery can a, and a battery can b having a larger bottom area than the battery can a. The battery can a and the battery can b face each other. And the power generation element is disposed between the bottom surface of the battery can a and the bottom surface of the battery can b, and (A) the outer surface of the battery can a and the battery A step of disposing a sealing material including a thermally expandable microcapsule and a resin between the inner surface of the can b; and (B) heating or sealing the sealing material to dissolve or soften the resin. The step of expanding the thermally expandable microcapsule, and (C) by curing the sealing material after the step (B), the outer surface of the battery can a and the inner surface of the battery can b, And a step of adhering the sealing material.

  According to the battery of the present invention, it is possible to provide a battery having high adhesive strength between the fitted battery cans and high leakage resistance.

  Moreover, according to the battery manufacturing method of the present invention, it is possible to manufacture a battery having high adhesion strength between the battery cans fitted together and high leakage resistance.

  The battery of the present invention is a battery including a power generation element, a battery can a, a battery can b having a larger bottom area than the battery can a, and a sealing material. Further, the battery can a and the battery can b are fitted to face each other, and the outer surface of the battery can a and the inner surface of the battery can b are sealed and bonded by the sealing material. Has been. Furthermore, the power generation element is disposed between the bottom surface of the battery can a and the bottom surface of the battery can b, and the sealing material includes a thermally expandable microcapsule and a resin. With such a configuration, a battery having high adhesive strength between the battery can a and the battery can b and having high leakage resistance can be obtained. In other words, if the encapsulant includes a thermally expandable microcapsule, the battery can have high leakage resistance by increasing the adhesive strength between the battery cans by expanding the thermally expandable microcapsule by heating at the time of manufacturing the battery. Can be.

  The thermally expandable microcapsule is composed of a microsphere having a shell wall made of a thermoplastic resin, and a volatile expansion agent having a boiling point of 80 ° C. or higher and 250 ° C. or lower is included in the microsphere. preferable. Thereby, at the time of manufacture of a battery, a thermally expansible microcapsule can be expanded more efficiently.

  The content of the thermally expandable microcapsule in the sealing material is preferably 5% by volume or more and 20% by volume or less. If the content rate of a thermally expansible microcapsule exists in this range, the adhesive strength of battery cans can be kept moderate.

  The resin contained in the sealing material preferably contains at least one thermoplastic resin selected from polypropylene, polyethylene, polyamideimide, and fluororesin. This is because such a thermoplastic resin has better adhesion to the battery can.

  The battery manufacturing method of the present invention includes a power generation element, a battery can a, and a battery can b having a larger bottom area than the battery can a, and the battery can a and the battery can b face each other. The battery generating method is a method of manufacturing a battery that is fitted between the bottom surface of the battery can a and the bottom surface of the battery can b, the outer surface of the battery can a and the inner surface of the battery can b And (A) the step of disposing a sealing material containing thermally expandable microcapsules and a resin, and heating the sealing material to dissolve or soften the resin, and The step (B) of expanding the microcapsules and the step of curing the sealing material after the step (B) allow the sealing material to be applied to the outer surface of the battery can a and the inner surface of the battery can b. (C) making it adhere | attach. With such a manufacturing method, a battery having high adhesion strength between battery cans and high leakage resistance can be manufactured.

  If the expansion start temperature of the thermally expandable microcapsule is higher than the temperature of the encapsulant in the step (A) and is equal to or lower than the heating temperature of the encapsulant in the step (B), the thermal expandability It is more preferable because the microcapsules can be expanded more efficiently.

  The thermally expandable microcapsule is composed of a microsphere having a shell wall made of a thermoplastic resin, and a volatile expansion agent is included inside the microsphere, and the boiling point of the volatile expansion agent is the above (A). It is preferable that the temperature is higher than the temperature of the sealing material in the step and not more than the heating temperature of the sealing material in the step (B). Thereby, a thermally expansible microcapsule can be expanded more efficiently.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example of the battery of the present invention. A method for manufacturing the battery shown in FIG. 1 will be described below.

  First, the power generation element is arranged on the bottom surface inside the battery can 1 and / or the battery can 2, and the battery can 1 and the battery can 2 are opposed and fitted. At this time, the sealing material 3 including the thermally expandable microcapsule 3b and the resin 3a is disposed on the outer surface of the battery can 1 and / or the inner surface of the battery can 2 (hereinafter referred to as the step (A)). The battery can 2 is a battery can having a larger bottom area than the battery can 1.

  The step (A) will be described more specifically. For example, the negative electrode 4 is disposed on the bottom surface inside the battery can 1, the positive electrode 6 and the insulating plate 7 are disposed on the bottom surface inside the battery can 2, and the positive electrode 6 The separator 5 is arranged on the top. Further, the sealing material 3 is disposed on the inner surface of the battery can 2. Then, the battery can 1 and the battery can 2 are fitted to face each other so that the negative electrode 4 and the separator 5 are in contact with each other.

  Next, the sealing material 3 is heated to dissolve or soften the resin 3a and expand the thermally expandable microcapsule 3b (hereinafter referred to as (B) step). Finally, the sealing material 3 is cured to adhere the sealing material 3 to the outer surface of the battery can 1 and the inner surface of the battery can 2 (hereinafter referred to as (C) step). The battery is complete.

  In such a manufacturing method, since the battery can is pressurized by the sealing material due to the expansion of the thermally expandable microcapsule, it is difficult for air to enter between the battery can and the sealing material. That is, it is possible to manufacture a battery having high adhesion strength between battery cans and high leakage resistance.

  The battery can 1 and the battery can 2 may be fitted to face each other so that the battery can 2 covers the opening of the battery can 1. The battery can 2 is a battery can having a larger bottom area than the battery can 1, and the shape of the bottom surface thereof is preferably similar to the shape of the bottom surface of the battery can 1. The shape of the bottom surfaces of the battery cans 1 and 2 can be, for example, circular, rectangular, or the like. The material, size, etc. of the battery cans 1 and 2 are not particularly limited. Materials generally used for batteries, for example, metals such as stainless steel, nickel, iron, and aluminum can be used.

  The negative electrode 4, the separator 5, the positive electrode 6, and the insulating plate 7 are generally used for batteries, and are not particularly limited by the material, configuration, or the like. Moreover, although not shown in figure, the negative electrode 4, the separator 5, and the positive electrode 6 contain the liquid electrolyte.

  The sealing material 3 includes the thermally expandable microcapsule 3b and the resin 3a, and may be bonded to the battery can. Specifically, 3 parts by weight or more and 12 parts by weight or less, preferably 5 parts by weight or more and 10 parts by weight or less, more preferably 6 parts by weight or more and 8 parts by weight or less with respect to 100 parts by weight of the resin 3a. A sealing material including the microcapsule 3b can be used. The form of the sealing material 3 before heating is not particularly limited, and can be, for example, liquid, sheet-like, block-like, or film-like. Moreover, the sealing material 3 may further contain an additive, an organic solvent, or the like. When the sealing material 3 is in the form of a sheet, a film, or the like, the surface treatment is performed on the adhesive surface with the battery can. It may be given.

  The resin 3a can disperse the heat-expandable microcapsules 3b and is a solid resin at the use environment temperature of the battery, and is generally a thermoplastic resin. In particular, the inclusion of at least one resin selected from polypropylene, polyethylene, polyamideimide, and fluororesin is more preferable because the adhesiveness between the sealing material and the battery can is increased.

  The heat-expandable microcapsule 3b includes a substance that is liquid at normal temperature and a shell wall that contains the substance, and can be microspheres that expand when heated. In general, it is a microsphere having a particle diameter of about 1 μm to 30 μm and expands up to about 200 times the volume when heated. Furthermore, if the expansion start temperature of the thermally expandable microcapsule is higher than the temperature of the sealing material in the step (A) and is equal to or lower than the heating temperature of the sealing material in the step (B), It is more preferable because the expandable microcapsule can be expanded more efficiently.

  In particular, the thermally expandable microcapsule 3b is composed of microspheres having a shell wall made of a thermoplastic resin, encapsulating a volatile expansion agent inside the microsphere, and the boiling point of the volatile expansion agent is: It is preferable that the temperature is higher than the temperature of the sealing material in the step (A) and not higher than the heating temperature of the sealing material in the step (B). Thereby, the thermally expandable microcapsule 3b can be expanded more efficiently, and a battery with higher leakage resistance can be manufactured.

  Here, the microsphere provided with the shell wall made of the thermoplastic resin will be described more specifically.

  The thermoplastic resin constituting the shell wall is, for example, a copolymer synthesized using 15% by weight or more of a nitrile monomer, a non-nitrile monomer, a crosslinking agent, and a polymerization initiator as necessary. It is.

  Examples of the nitrile monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile, any mixture of these compounds, and the like. In particular, it is preferable to use acrylonitrile and / or methacrylonitrile.

  As the non-nitrile monomer, for example, vinylidene chloride, methacrylic acid esters, acrylic acid esters and the like can be used. In particular, it is preferable to use vinylidene chloride, methyl methacrylate, ethyl methacrylate, or methyl acrylate.

  Examples of the crosslinking agent include divinylbenzene, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, triacryl formal, trimethylolpropane trimethacrylate, allyl methacrylate, 1,3-butyl glycol dimethacrylate, Allyl isocyanate and the like can be used. In particular, it is preferable to use a trifunctional crosslinking agent such as triacryl formal or trimethylolpropane trimethacrylate. Moreover, what is necessary is just to let the usage-amount of the said crosslinking agent be 0.1 to 3 weight% with respect to the total weight of a raw material.

  Examples of the polymerization initiator include azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide, diisopropyl peroxydicarbonate, t-butyl peroxide, 2,2′-azobis (2,4-dimethylvalero). Nitrile) or the like can be used.

Examples of the volatile swelling agent encapsulated in the microspheres include propane, propylene, butene, normal butane, isobutane, isopentane, neopentane, normal pentane, hexane, heptane, ethers, and methane halides (for example, Low boiling point liquid such as methyl chloride, methylene chloride, CCl ₃ F, CCl ₂ F _2, etc.), tetraalkylsilane (eg, tetramethylsilane, trimethylethylsilane, etc.), etc. A compound such as AIBN can be used. In particular, it is preferable to use hydrocarbons such as isobutane, normal butane, normal pentane, isopentane, and ethers.

  Moreover, the manufacturing method of the microsphere provided with the said shell wall and including the said volatile swelling agent is not specifically limited, What is necessary is just to follow a conventional method. For example, the nitrile monomer, the non-nitrile monomer, the crosslinking agent, the volatile swelling agent and the polymerization initiator are mixed, and the mixture is subjected to suspension polymerization in an aqueous medium containing an emulsifying dispersion aid and the like. Can be formed. The aqueous medium is not particularly limited. For example, in addition to silica, calcium phosphate, calcium carbonate, sodium chloride, sodium sulfate and the like, organic additives (for example, diethanolamine-adipic acid condensate, gelatin, methylcellulose, polyvinyl alcohol, polyethylene) Oxide, dioctylsulfosuccinate, sorbitan ester, etc.) may be appropriately blended in deionized water and the pH adjusted to about 3-4.

  The thermally expandable microcapsules 3b are preferably uniformly dispersed in the sealing material 3. In the step (B), a part of the force that expands the thermally expandable microcapsule 3 b becomes a force that presses the sealing material 3 against the adherend surface of the battery can 1 or 2. Therefore, with such a sealing material 3, the pressure is evenly applied to the adherend surface. In the steps (B) and (C), it is preferable to hold the battery can 2 from the outside toward the inside of the battery because the battery can is prevented from being distorted and formed by the expanding force.

  The power generation element is a means for converting chemical energy into electrical energy, and generally includes a positive electrode, a negative electrode, an electrolyte, and a separator. However, depending on the type of battery, the power generation element may further contain an additive or the like, or the separator may not be included by using a solid electrolyte. That is, the battery manufacturing method of the present invention has a main feature in the step of sealing the power generation element with a battery can. The battery manufactured by this method may be a primary battery or a secondary battery. Good. For example, a battery such as a silver oxide primary battery, a lithium ion secondary battery, a lithium primary battery, or an alkaline battery can be manufactured.

  The battery of the present embodiment manufactured as described above is a battery having high adhesive strength between battery cans and high leakage resistance.

  The content of the thermally expandable microcapsule 3b in the sealing material 3 is 5% by volume or more and 20% by volume or less, preferably 8% by volume or more and 17% by volume or less. If the content of the heat-expandable microcapsules is too low, sufficient adhesive strength cannot be obtained, and if the content of the heat-expandable microcapsules is too high, the expansion force becomes too large, which may cause distortion of the battery. However, if such a sealing material is used, the battery can have a high bond strength between battery cans and no distortion.

  The battery of the present invention is mainly characterized by the sealing material for sealing the battery can, and the battery is not particularly limited by the power generation element, the shape of the battery, and the like. Specifically, it may be a primary battery or a secondary battery, and may be a flat battery or a thin battery. In particular, a thin battery of a lithium ion secondary battery is more preferable because it has a high market demand, and can provide a thin, high-capacity battery with excellent leakage resistance.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples.

Example 1
A positive electrode mixture was prepared by mixing LiCoO _{2 as a} positive electrode active material and carbon black as a conductive additive at a weight ratio of 83:10. Next, the positive electrode mixture was mixed with an N-methyl-2-pyrrolidone (NMP) solution containing 7% by weight of polyvinylidene fluoride (PVDF), and the mixture was sufficiently stirred to prepare a coating material. The paint was dried to remove the solvent, pulverized in a mortar, and then molded into a pellet having a diameter of 15 mm and a thickness of 0.9 mm to obtain a positive electrode. Moreover, graphite and PVDF were mixed as a negative electrode by weight ratio 93: 7, and the negative mix was produced. Similarly to the positive electrode described above, this negative electrode mixture was used to form a negative electrode by molding into a pellet having a diameter of 16 mm and a thickness of 0.7 mm.

  Next, the positive electrode was fixed to a positive electrode battery can (stainless steel (SUS) can having an outer diameter of 20 mm), and the negative electrode was fixed to a negative electrode battery can (SUS can having an outer diameter of 16.5 mm). A sealing material having a thickness of 100 μm was disposed on the outer surface of the negative battery can. The sealing material is polyethylene (PE), thermally expandable microcapsule “thermally expandable microsphere H850” (manufactured by Dainichi Seika Kogyo Co., Ltd., particle size: 10-30 μm, shell wall softening point: 155 ° C., A volume expansion coefficient at 155 ° C .: 120) was mixed by 25% by weight and formed into a film shape.

Next, an electrolyte solution in which 1 M of LiPF ₆ was dissolved in a solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a weight ratio of 1: 4 was injected into the positive electrode and the negative electrode. Then, the said positive electrode battery can and the said negative electrode battery can were fitted so that a positive electrode and a negative electrode might pass through a 25-micrometer-thick polyimide separator.

  Finally, the outer surface of the positive electrode battery can was fixed, heated at 170 ° C. for 4 seconds using a high-frequency induction heater, and then allowed to cool, thereby bonding the battery cans together.

  The battery of this example was found to have a capacity of about 20% larger than that of a conventional caulking structure battery having the same outer diameter and the same thickness.

(Example 2)
A battery of this example was fabricated in the same manner as in Example 1 except for the sealing material and the heating temperature and time for bonding the battery can.

  As a sealing material of this example, a thermally expandable microcapsule “Matsumoto Microsphere F30” (Matsumoto Yushi) against a modified olefin hot melt adhesive “1501SG30” (manufactured by Toa Gosei Co., Ltd., softening point: 150 ° C.). A mixture of 30% by weight of a particle size of 10 to 20 μm, a softening point of shell wall: 85 ° C., and a volume expansion coefficient at 200 ° C. of 200 ° C. at 200 ° C. was applied to the outer surface of the negative electrode battery can.

  The heating temperature and time for bonding the battery can of this example were 150 ° C. and 5 seconds.

(Comparative Example 1)
A battery of this comparative example was fabricated in the same manner as in Example 1 except that the heat-expandable microcapsules were not mixed in the sealing material.

(Comparative Example 2)
A battery of this comparative example was fabricated in the same manner as in Example 2 except that the heat-expandable microcapsules were not mixed in the sealing material.

Regarding the batteries of Examples 1 and 2 and Comparative Examples 1 and 2, 30 batteries were produced. These batteries were charged at a charge voltage of 4.0 V, a discharge voltage of 2.0 V, a charge current density of 1 mA / cm ² and charged and discharged for 2 cycles, and then charged to 4.0 V at a temperature of 60 ° C., relative Stored in an atmosphere of 90% humidity. The number of batteries that leaked every 20 days was visually examined using an optical microscope, and the results are shown in Table 1. In general, this test is an accelerated test that can be judged to have a leak resistance of 1 year at room temperature if the liquid does not leak for 20 days.

  As is clear from Table 1, the batteries of Comparative Examples 1 and 2 leaked after 20 days, whereas the batteries of Examples 1 and 2 did not leak even after 100 days. It was. Therefore, it can be seen that the battery of this example using the sealing material including the thermally expandable microcapsule has a high adhesive strength between the battery cans and a high leakage resistance.

  As described above, the present invention relates to a battery in which two battery cans having different bottom sizes are fitted to face each other, a battery having high adhesive strength between the battery cans and high leakage resistance, and a method for manufacturing the same. And its industrial value is great.

It is sectional drawing which shows an example of the battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Battery can 3 Sealing material 3a Resin 3b Thermal expansion microcapsule 4 Negative electrode 5 Separator 6 Positive electrode 7 Insulation board

Claims (8)

A battery comprising a power generation element, a battery can a, a battery can b having a larger bottom area than the battery can a, and a sealing material,
The battery can a and the battery can b are fitted to face each other,
Between the outer surface of the battery can a and the inner surface of the battery can b is sealed and bonded by the sealing material,
The power generation element is disposed between the bottom surface of the battery can a and the bottom surface of the battery can b,
The battery, wherein the sealing material includes a thermally expandable microcapsule and a resin.   The heat-expandable microcapsule comprises microspheres having a shell wall made of a thermoplastic resin, and a volatile expansion agent having a boiling point of 80 ° C. or higher and 250 ° C. or lower is encapsulated inside the microsphere. 1. The battery according to 1.   The battery according to claim 1, wherein the content of the thermally expandable microcapsule in the sealing material is 5% by volume or more and 20% by volume or less.   The battery according to claim 1, wherein the resin includes at least one thermoplastic resin selected from polypropylene, polyethylene, polyamideimide, and fluororesin. A power generation element, a battery can a, and a battery can b having a larger bottom area than the battery can a, wherein the battery can a and the battery can b are fitted to face each other, and the power generation element is the battery A method of manufacturing a battery disposed between a bottom surface of a can a and a bottom surface of the battery can b,
(A) Disposing a sealing material including a thermally expandable microcapsule and a resin between the outer surface of the battery can a and the inner surface of the battery can b;
(B) heating the sealing material to dissolve or soften the resin and expand the thermally expandable microcapsule;
(C) including the step of adhering the sealing material to the outer side surface of the battery can a and the inner side surface of the battery can b by curing the sealing material after the step (B). A battery manufacturing method.   The expansion start temperature of the thermally expandable microcapsule is higher than the temperature of the encapsulant in the step (A) and is equal to or lower than the heating temperature of the encapsulant in the step (B). Battery manufacturing method.   The thermally expandable microcapsule is composed of a microsphere having a shell wall made of a thermoplastic resin, and a volatile expansion agent is included inside the microsphere, and the boiling point of the volatile expansion agent is (A) The battery manufacturing method according to claim 5, wherein the temperature is higher than a temperature of the sealing material in the step and is equal to or lower than a heating temperature of the sealing material in the step (B).   The battery according to claim 5, wherein the resin includes at least one thermoplastic resin selected from polypropylene, polyethylene, polyamideimide, and fluororesin.

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